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| Titre, Autheur(s) | Journal, Références | | 325. Essential roles of the Fas ligand in the development of hepatitis.
Abstract : The Fas ligand (FasL) is expressed in activated T cells and induces apoptosis in Fas-bearing cells. A cytotoxic T lymphocyte (CTL) clone specific for hepatitis B surface antigen (HBsAg) causes an acute liver disease in HBsAg transgenic mice. Here we observed that the CTL clone killed hepatocytes expressing HBsAg in a Fas-dependent manner. Administration of the soluble form of Fas into HBsAg transgenic mice prevented the CTL-induced liver disease. In the second model, mice were primed with Propionibacterium acnes. A subsequent challenge with lipopolysaccharide (LPS) killed the mice by inducing liver injury. Neutralization of FasL rescued the mice from LPS-induced mortality, and Fas-null mice were resistant to LPS-induced mortality. These results suggest that FasL has an essential role in the development of hepatitis.
| Nat Med
3, 409-413 | Abstract
Article complet | 324. AP-1/Fos-TGase2 axis mediates wounding-induced Plasmodium falciparum killing in Anopheles gambiae.
Nsango SE, Pompon J, Xie T, Rademacher A, Fraiture M, Thoma M, Awono-Ambene PH, Moyou RS, Morlais I, Levashina EA.
Abstract : Abstract
Anopheline mosquitoes are the only vectors of human malaria worldwide. It is now widely accepted that mosquito immune responses play a crucial role in restricting Plasmodium development within the vector, therefore further dissection of the molecular mechanisms underlying these processes should inform new vector control strategies urgently needed to roll back the disease. Here, using genome-wide transcriptional profiling, bioinformatics and functional gene analysis we identify a new axis of mosquito resistance to monoclonal P. falciparum infections that includes the AP-1 transcription factor Fos and the transglutaminase 2 (TGase2), a cross-linking enzyme with known roles in wound responses. We demonstrate that Fos regulates induction of TGase2 expression after wounding but does not affect expression of the components of the well-characterized complement-like system. Silencing of Fos or of TGase2 aborts the wounding-induced mosquito killing of P. falciparum. These results reveal multiple signaling pathways that are required for efficient Plasmodium killing in A. gambiae.
| J Biol Chem.
2013 Apr 16 | Abstract
Article complet | 323. Broad RNA interference-mediated antiviral immunity and virus-specific inducible responses in Drosophila.
Kemp C, Mueller S, Goto A, Barbier V, Paro S, Bonnay F, Dostert C, Troxler L, Hetru C, Meignin C, Pfeffer S, Hoffmann JA, Imler JL.
Abstract : The fruit fly Drosophila melanogaster is a good model to unravel the molecular mechanisms of innate immunity and has led to some important discoveries about the sensing and signaling of microbial infections. The response of Drosophila to virus infections remains poorly characterized and appears to involve two facets. On the one hand, RNA interference involves the recognition and processing of dsRNA into small interfering RNAs by the host RNase Dicer-2 (Dcr-2), whereas, on the other hand, an inducible response controlled by the evolutionarily conserved JAK-STAT pathway contributes to the antiviral host defense. To clarify the contribution of the small interfering RNA and JAK-STAT pathways to the control of viral infections, we have compared the resistance of flies wild-type and mutant for Dcr-2 or the JAK kinase Hopscotch to infections by seven RNA or DNA viruses belonging to different families. Our results reveal a unique susceptibility of hop mutant flies to infection by Drosophila C virus and cricket paralysis virus, two members of the Dicistroviridae family, which contrasts with the susceptibility of Dcr-2 mutant flies to many viruses, including the DNA virus invertebrate iridescent virus 6. Genome-wide microarray analysis confirmed that different sets of genes were induced following infection by Drosophila C virus or by two unrelated RNA viruses, Flock House virus and Sindbis virus. Overall, our data reveal that RNA interference is an efficient antiviral mechanism, operating against a large range of viruses, including a DNA virus. By contrast, the antiviral contribution of the JAK-STAT pathway appears to be virus specific.
| J Immunol.
2013 Jan 15;190(2):650-8 | Abstract
Article complet | 322. Silencing of genes and alleles by RNAi in Anopheles gambiae.
Lamacchia M, Clayton JR, Wang-Sattler R, Steinmetz LM, Levashina EA, Blandin SA.
Abstract : Anopheles gambiae mosquitoes are the major vectors of human malaria parasites. However, mosquitoes are not passive hosts for parasites, actively limiting their development in vivo. Our current understanding of the mosquito antiparasitic response is mostly based on the phenotypic analysis of gene knockdowns obtained by RNA interference (RNAi), through the injection or transfection of long dsRNAs in adult mosquitoes or cultured cells, respectively. Recently, RNAi has been extended to silence specifically one allele of a given gene in a heterozygous context, thus allowing to compare the contribution of different alleles to a phenotype in the same genetic background.
| Methods Mol Biol.
2013;923:161-76. | Abstract
Article complet | 321. The complementary facets of epithelial host defenses in the genetic model organism Drosophila melanogaster: from resistance to resilience.
Abstract : Significant advances have been made in our understanding of the host defense against microbial infections taking place at frontier epithelia of Drosophila flies. Immune deficiency (IMD), the major NF-κB immune response pathway induced in these epithelia, displays remarkable adaptations in its activation and regulation in the respiratory and digestive tract. The host defense against ingested pathogens is not limited to resistance, that is, the immune response. It also involves resilience, the capacity of the host to endure and repair damages inflicted by pathogens or the host's own immune response. For instance, enterocytes damaged by pathogens, the microbiota of aging flies, or host-derived reactive oxygen species (ROS), are replaced under the control of multiple pathways by the compensatory proliferation of intestinal stem cells (ISCs).
| Curr Opin Immunol
2012 Dec 7. pii: S0952-7915(12)00189-6 | Abstract
Article complet | 320. A negative role for MyD88 in the resistance to starvation as revealed in an intestinal infection of Drosophila melanogaster with the Gram-positive bacterium Staphylococcus xylosus.
Ayyaz A, Giammarinaro P, Li?geois S, Lestradet M, Ferrandon D.
Abstract : Drosophila melanogaster is a useful model to investigate mucosal immunity. The immune response to intestinal infections is mediated partly by the Immune deficiency (IMD) pathway, which only gets activated by a type of peptidoglycan lacking in several medically important Gram-positive bacterial species such as Staphylococcus. Thus, the intestinal host defense against such bacterial strains remains poorly known. Here, we have used Staphylococcus xylosus to develop a model of intestinal infections by Gram-positive bacteria. S. xylosus behaves as an opportunistic pathogen in a septic injury model, being able to kill only flies immunodeficient either for the Toll pathway or the cellular response. When ingested, it is controlled by IMD-independent host intestinal defenses, yet flies eventually die. Having excluded an overreaction of the immune response and the action of toxins, we find that flies actually succumb to starvation, likely as a result of a competition for sucrose between the bacteria and the flies. Fat stores of wild-type flies are severely reduced within a day, a period when sucrose is not yet exhausted in the feeding solution. Interestingly, the Toll pathway mutant MyD88 is more resistant to the ingestion of S. xylosus and to starvation than wild-type flies. MyD88 flies do not rapidly deplete their fat stores when starved, in contrast to wild-type flies. Thus, we have uncovered a novel function of MyD88 in the regulation of metabolism that appears to be independent of its known roles in immunity and development.
| Immunobiology
2012 Sep 13. pii: S0171-2985(12)00191 | Abstract
Article complet | 319. High-throughput sorting of mosquito larvae for laboratory studies and for future vector control interventions
Marois E, Scali C, Soichot J, Kappler C, Levashina EA, Catteruccia F.
Abstract : BACKGROUND:
Mosquito transgenesis offers new promises for the genetic control of vector-borne infectious diseases such as malaria and dengue fever. Genetic control strategies require the release of large number of male mosquitoes into field populations, whether they are based on the use of sterile males (sterile insect technique, SIT) or on introducing genetic traits conferring refractoriness to disease transmission (population replacement). However, the current absence of high-throughput techniques for sorting different mosquito populations impairs the application of these control measures.
METHODS:
A method was developed to generate large mosquito populations of the desired sex and genotype. This method combines flow cytometry and the use of Anopheles gambiae transgenic lines that differentially express fluorescent markers in males and females.
RESULTS:
Fluorescence-assisted sorting allowed single-step isolation of homozygous transgenic mosquitoes from a mixed population. This method was also used to select wild-type males only with high efficiency and accuracy, a highly desirable tool for genetic control strategies where the release of transgenic individuals may be problematic. Importantly, sorted males showed normal mating ability compared to their unsorted brothers.
CONCLUSIONS:
The developed method will greatly facilitate both laboratory studies of mosquito vectorial capacity requiring high-throughput approaches and future field interventions in the fight against infectious disease vectors.
| Malar J
2012 Aug 28;11:302 | Abstract
Article complet | 318. On-bead tryptic proteolysis: an attractive procedure for LC-MS/MS analysis of the Drosophila caspase 8 protein complex during immune response against bacteria.
Fukuyama H, Ndiaye S, Hoffmann J, Rossier J, Liuu S, Vinh J, Verdier Y.
Abstract : This study aims to characterize the immune response against bacteria in Drosophila melanogaster. Obtaining a description of the in vivo state of protein complexes requires their isolation as a snapshot of physiological conditions before their identification. Affinity purification with streptavidin-biotin system is widely used to address this issue. However, because of the extraordinary stability of the interaction between streptavidin and biotin, the release of biotin-labeled bait remains a challenge. We transfected Drosophila cells with a DNA construct encoding a biotin-tagged Dredd protein (ortholog of caspase 8). After affinity purification, different strategies were evaluated, and proteins analyzed by LC-MS/MS mass spectrometry. The on-bead digestion allowed the identification of more proteins associated to the Dredd complex than different protocols using competitive or acid elution. A functional assay showed that a large part of the proteins specifically identified in the Dredd sample are functionally involved in the activation of the Imd pathway. These proteins are immune response proteins (BG4, Q9VP57), stress response proteins (HSP7C, Q9VXQ5), structural proteins (TBB1, CP190), a protein biosynthesis protein (Q9W1B9) and an antioxidant system protein (SODC). Our results clearly show that on-bead digestion of proteins is an attractive procedure for the study of protein complexes by mass spectrometry. This article is part of a Special Issue entitled: Translational Proteomics.
| J Proteomics
2012 Aug 3;75(15):4610-9. | Abstract
Article complet | 317. Conserved cis-regulatory regions in a large genomic landscape control SHH and BMP-regulated Gremlin1 expression in mouse limb buds.
Zuniga A, Laurent F, Lopez-Rios J, Klasen C, Matt N, Zeller R.
Abstract : ABSTRACT:
BACKGROUND: Mouse limb bud is a prime model to study the regulatory interactions that control vertebrate organogenesis. Major aspects of limb bud development are controlled by feedback loops that define a self-regulatory signalling system. The SHH/GREM1/AER-FGF feedback loop forms the core of this signalling system that operates between the posterior mesenchymal organiser and the ectodermal signalling centre. The BMP antagonist Gremlin1 (GREM1) is a critical node in this system, whose dynamic expression is controlled by BMP, SHH, and FGF signalling and key to normal progression of limb bud development. Previous analysis identified a distant cis-regulatory landscape within the neighbouring Formin1 (Fmn1) locus that is required for Grem1 expression, reminiscent of the genomic landscapes controlling HoxD and Shh expression in limb buds.
RESULTS:
Three highly conserved regions (HMCO1-3) were identified within the previously defined critical genomic region and tested for their ability to regulate Grem1 expression in mouse limb buds. Using a combination of BAC and conventional transgenic approaches, a 9 kb region located ~70 kb downstream of the Grem1 transcription unit was identified. This region, termed Grem1 Regulatory Sequence 1 (GRS1), is able to recapitulate major aspects of Grem1 expression, as it drives expression of a LacZ reporter into the posterior and, to a lesser extent, in the distal-anterior mesenchyme. Crossing the GRS1 transgene into embryos with alterations in the SHH and BMP pathways established that GRS1 depends on SHH and is modulated by BMP signalling, i.e. integrates inputs from these pathways. Chromatin immunoprecipitation revealed interaction of endogenous GLI3 proteins with the core cis-regulatory elements in the GRS1 region. As GLI3 is a mediator of SHH signal transduction, these results indicated that SHH directly controls Grem1 expression through the GRS1 region. Finally, all cis-regulatory regions within the Grem1 genomic landscape locate to the DNAse I hypersensitive sites identified in this genomic region by the ENCODE consortium.
CONCLUSIONS:
This study establishes that distant cis-regulatory regions scattered through a larger genomic landscape control the highly dynamic expression of Grem1, which is key to normal progression of mouse limb bud development.
| BMC Dev Biol 2012 Aug 13;12(1):23.
| Abstract
Article complet | 316. Fly culture collapse disorder: detection, prophylaxis and eradication of the microsporidian parasite Tubulinosema ratisbonensis infecting Drosophila melanogaster.
Niehus S, Giammarinaro P, Li?geois S, Quintin J, Ferrandon D.
Abstract : Drosophila melanogaster is a robust model to investigate many biological problems. It is however prone to some infections, which may endanger fly stocks if left unchecked for. One such infection is caused by an obligate fungal intracellular parasite, Tubulinosema ratisbonensis, which can be found in laboratory stocks. Here, we identify and briefly characterize a T. ratisbonensis strain that was infesting our Drosophila cultures and that required intensive measures to contain and eradicate the infection. We describe the phenotypes of infested stocks. We also report PCR-based techniques that allow the detection of infested stocks with a high sensitivity. We have developed a high-throughput qPCR assay that allows the efficient parallel screening of a large number of potentially-infested stocks. We also have investigated several prophylactic measures to prevent the further contamination of stocks, namely UV-exposure, ethanol treatment, bleaching, and desiccation. Bleaching was found to kill all spores. Other treatments were less effective but were found to be sufficient to prevent further contamination of noninfested stocks. Two treatments were efficacious in curing infested stocks (1) bleaching of eggs and subsequent raising of the larvae in clean vials; (2) fumagillin treatment. These cures only work on stocks that have not become too weak to withstand the procedures.
| Fly (Austin)
2012 Jul 1;6(3) | Abstract
Article complet | 315. Midgut Microbiota of the Malaria Mosquito Vector Anopheles gambiae and Interactions with Plasmodium falciparum Infection.
Boissi?re A, Tchioffo MT, Bachar D, Abate L, Marie A, Nsango SE, Shahbazkia HR, Awono-Ambene PH, Levashina EA, Christen R, Morlais I.
Abstract : The susceptibility of Anopheles mosquitoes to Plasmodium infections relies on complex interactions between the insect vector and the malaria parasite. A number of studies have shown that the mosquito innate immune responses play an important role in controlling the malaria infection and that the strength of parasite clearance is under genetic control, but little is known about the influence of environmental factors on the transmission success. We present here evidence that the composition of the vector gut microbiota is one of the major components that determine the outcome of mosquito infections. A. gambiae mosquitoes collected in natural breeding sites from Cameroon were experimentally challenged with a wild P. falciparum isolate, and their gut bacterial content was submitted for pyrosequencing analysis. The meta-taxogenomic approach revealed a broader richness of the midgut bacterial flora than previously described. Unexpectedly, the majority of bacterial species were found in only a small proportion of mosquitoes, and only 20 genera were shared by 80% of individuals. We show that observed differences in gut bacterial flora of adult mosquitoes is a result of breeding in distinct sites, suggesting that the native aquatic source where larvae were grown determines the composition of the midgut microbiota. Importantly, the abundance of Enterobacteriaceae in the mosquito midgut correlates significantly with the Plasmodium infection status. This striking relationship highlights the role of natural gut environment in parasite transmission. Deciphering microbe-pathogen interactions offers new perspectives to control disease transmission.
| PLoS Pathog.
2012 - 8(5) | Abstract
Article complet | 314. Salivary gland-specific P. berghei reporter lines enable rapid evaluation of tissue-specific sporozoite loads in mosquitoes.
Ramakrishnan C, Rademacher A, Soichot J, Costa G, Waters AP, Janse CJ, Ramesar J, Franke-Fayard BM, Levashina EA.
Abstract : Malaria is a life-threatening human infectious disease transmitted by mosquitoes. Levels of the salivary gland sporozoites (sgs), the only mosquito stage infectious to a mammalian host, represent an important cumulative index of Plasmodium development within a mosquito. However, current techniques of sgs quantification are laborious and imprecise. Here, transgenic P. berghei reporter lines that produce the green fluorescent protein fused to luciferase (GFP-LUC) specifically in sgs were generated, verified and characterised. Fluorescence microscopy confirmed the sgs stage specificity of expression of the reporter gene. The luciferase activity of the reporter lines was then exploited to establish a simple and fast biochemical assay to evaluate sgs loads in whole mosquitoes. Using this assay we successfully identified differences in sgs loads in mosquitoes silenced for genes that display opposing effects on P. berghei ookinete/oocyst development. It offers a new powerful tool to study infectivity of P. berghei to the mosquito, including analysis of vector-parasite interactions and evaluation of transmission-blocking vaccines.
| PLoS One.
2012 - 7(5) | Abstract
Article complet | 313. Genetic clonality of Plasmodium falciparum affects the outcome of infection in Anopheles gambiae.
Nsango SE, Abate L, Thoma M, Pompon J, Fraiture M, Rademacher A, Berry A, Awono-Ambene PH, Levashina EA, Morlais I.
Abstract : Mosquito infections with natural isolates of Plasmodium falciparum are notoriously variable and pose a problem for reliable evaluation of efficiency of transmission-blocking agents for malaria control interventions. Here, we show that monoclonal P. falciparum isolates produce higher parasite loads than mixed ones. Induction of the mosquito immune responses by wounding efficiently decreases Plasmodium numbers in monoclonal infections but fails to do so in infections with two or more parasite genotypes. Our results point to the parasites genetic complexity as a potentially crucial component of mosquito-parasite interactions.
| Int J Parasitol.
2012 ? 15;42(6):589-95 | Abstract
Article complet | 312. Specific versus Non-Specific Immune Responses in an Invertebrate Species Evidenced by a Comparative de novo Sequencing Study
Abstract : Our present understanding of the functioning and evolutionary history of invertebrate innate immunity derives mostly from
studies on a few model species belonging to ecdysozoa. In particular, the characterization of signaling pathways dedicated
to specific responses towards fungi and Gram-positive or Gram-negative bacteria in Drosophila melanogaster challenged our
original view of a non-specific immunity in invertebrates. However, much remains to be elucidated from lophotrochozoan
species. To investigate the global specificity of the immune response in the fresh-water snail Biomphalaria glabrata, we used
massive Illumina sequencing of 59-end cDNAs to compare expression profiles after challenge by Gram-positive or Gramnegative
bacteria or after a yeast challenge. 59-end cDNA sequencing of the libraries yielded over 12 millions high quality
reads. To link these short reads to expressed genes, we prepared a reference transcriptomic database through automatic
assembly and annotation of the 758,510 redundant sequences (ESTs, mRNAs) of B. glabrata available in public databases.
Computational analysis of Illumina reads followed by multivariate analyses allowed identification of 1685 candidate
transcripts differentially expressed after an immune challenge, with a two fold ratio between transcripts showing a
challenge-specific expression versus a lower or non-specific differential expression. Differential expression has been
validated using quantitative PCR for a subset of randomly selected candidates. Predicted functions of annotated candidates
(approx. 700 unisequences) belonged to a large extend to similar functional categories or protein types. This work
significantly expands upon previous gene discovery and expression studies on B. glabrata and suggests that responses to
various pathogens may involve similar immune processes or signaling pathways but different genes belonging to
multigenic families. These results raise the question of the importance of gene duplication and acquisition of paralog
functional diversity in the evolution of specific invertebrate immune responses.
| PLoS One
| Abstract
Article complet | 311. Immune cell transdifferentiation: a complex crosstalk between circulating immune cells and the haematopoietic niche
Marie Meister1 and Dominique Ferrandon2
Abstract : ROS sensed in the haematopoietic niche induces the differentiation of circulating plasmatocytes into wasp-egg-fighting lamellocytes in a non-cell-autonomous manner, as described in this issue of EMBO reports.
| EMBO Rep
2012 January; 13(1): 3?4. | Abstract
Article complet | 310. Drosophila EYA regulates the immune response against DNA through an evolutionarily conserved threonine phosphatase motif.
Liu X, Sano T, Guan Y, Nagata S, Hoffmann JA, Fukuyama H
Abstract : Innate immune responses against DNA are essential to counter both pathogen infections and tissue damages. Mammalian EYAs were recently shown to play a role in regulating the innate immune responses against DNA. Here, we demonstrate that the unique Drosophila eya gene is also involved in the response specific to DNA. Haploinsufficiency of eya in mutants deficient for lysosomal DNase activity (DNaseII) reduces antimicrobial peptide gene expression, a hallmark for immune responses in flies. Like the mammalian orthologues, Drosophila EYA features a N-terminal threonine and C-terminal tyrosine phosphatase domain. Through the generation of a series of mutant EYA fly strains, we show that the threonine phosphatase domain, but not the tyrosine phosphatase domain, is responsible for the innate immune response against DNA. A similar role for the threonine phosphatase domain in mammalian EYA4 had been surmised on the basis of in vitro studies. Furthermore EYA associates with IKKβ and full-length RELISH, and the induction of the IMD pathway-dependent antimicrobial peptide gene is independent of SO. Our data provide the first in vivo demonstration for the immune function of EYA and point to their conserved immune function in response to endogenous DNA, throughout evolution.
| PLoS One.
2012;7(8):e42725 | Abstract
Article complet | 309. Pseudomonas aeruginosa RhlR is required to neutralize the cellular immune response in a Drosophila melanogaster oral infection model.
Limmer S, Haller S, Drenkard E, Lee J, Yu S, Kocks C, Ausubel FM, Ferrandon D.
Abstract : An in-depth mechanistic understanding of microbial infection necessitates a molecular dissection of host-pathogen relationships. Both Drosophila melanogaster and Pseudomonas aeruginosa have been intensively studied. Here, we analyze the infection of D. melanogaster by P. aeruginosa by using mutants in both host and pathogen. We show that orally ingested P. aeruginosa crosses the intestinal barrier and then proliferates in the hemolymph, thereby causing the infected flies to die of bacteremia. Host defenses against ingested P. aeruginosa included an immune deficiency (IMD) response in the intestinal epithelium, systemic Toll and IMD pathway responses, and a cellular immune response controlling bacteria in the hemocoel. Although the observed cellular and intestinal immune responses appeared to act throughout the course of the infection, there was a late onset of the systemic IMD and Toll responses. In this oral infection model, P. aeruginosa PA14 did not require its type III secretion system or other well-studied virulence factors such as the two-component response regulator GacA or the protease AprA for virulence. In contrast, the quorum-sensing transcription factor RhlR, but surprisingly not LasR, played a key role in counteracting the cellular immune response against PA14, possibly at an early stage when only a few bacteria are present in the hemocoel. These results illustrate the power of studying infection from the dual perspective of host and pathogen by revealing that RhlR plays a more complex role during pathogenesis than previously appreciated.
| Proc Natl Acad Sci U S A
011 Oct 18;108(42):17378-83 | Abstract
Article complet | 308. Pathogen-Derived Effectors Trigger Protective Immunity via Activation of the Rac2 Enzyme and the IMD or Rip Kinase Signaling Pathway.
Boyer L, Magoc L, Dejardin S, Cappillino M, Paquette N, Hinault C, Charriere GM, Ip WK, Fracchia S, Hennessy E, Erturk-Hasdemir D, Reichhart JM, Silverman N, Lacy-Hulbert A, Stuart LM.
Abstract : Although infections with virulent pathogens often induce a strong inflammatory reaction, what drives the increased immune response to pathogens compared to nonpathogenic microbes is poorly understood. One possibility is that the immune system senses the level of threat from a microorganism and augments the response accordingly. Here, focusing on cytotoxic necrotizing factor 1 (CNF1), an Escherichia coli-derived effector molecule, we showed the host indirectly sensed the pathogen by monitoring for the effector that modified RhoGTPases. CNF1 modified Rac2, which then interacted with the innate immune adaptors IMD and Rip1-Rip2 in flies and mammalian cells, respectively, to drive an immune response. This response was protective and increased the ability of the host to restrict pathogen growth, thus defining a mechanism of effector-triggered immunity that contributes to how metazoans defend against microbes with pathogenic potential.
| Immunity
2011 : Vol 35, 536-549 | Abstract
Article complet | 307. Microbial Sensing by Toll Receptors. A Historical Perspective
Stanislava Chtarbanova and Jean-Luc Imler
Abstract : The family of Toll-like receptors plays an essential role in the induction of the immune response. These
receptors sense the presence of microbial ligands and activate the nuclear factor-KB transcription factor. We review the
key studies that led from the formulation of the concept of pattern recognition receptors to the characterization of
Toll-like receptors, insisting on the important role played by the model organism Drosophila melanogaster and on the
increasing evidence connecting these receptors to cardiovascular disease.
| Journal of the American Heart Association
Arterioscler Thromb Vasc Biol. 2011; 31: 1734-1738 | Abstract
Article complet | 306. Virulence on the fly: Drosophila melanogaster as a model genetic organism to decipher host-pathogen interactions.
Limmer S, Quintin J, Hetru C, Ferrandon D.
Abstract : To gain an in-depth grasp of infectious processes one has to know the specific interactions between the virulence factors of the pathogen and the host defense mechanisms. A thorough understanding is crucial for identifying potential new drug targets and designing drugs against which the pathogens might not develop resistance easily. Model organisms are a useful tool for this endeavor, thanks to the power of their genetics. Drosophila melanogaster is widely used to study host-pathogen interactions. Its basal immune response is well understood and is briefly reviewed here. Considerations relevant to choosing an adequate infection model are discussed. This review then focuses mainly on infections with two categories of pathogens, the well-studied Gram-negative bacterium Pseudomonas aeruginosa and infections by fungi of medical interest. These examples provide an overview over the current knowledge on Drosophila-pathogen interactions and illustrate the approaches that can be used to study those interactions. We also discuss the usefulness and limits of Drosophila infection models for studying specific host-pathogen interactions and high-throughput drug screening.
| Curr Drug Targets
2011 Jun;12(7):978-99. | Abstract
Article complet | 305. The Drosophila serpins multiple functions in immunity and morphogenesis.
Reichhart JM, Gubb D, Leclerc V
Abstract : Members of the serpin superfamily of proteins have been found in all living organisms, although rarely in bacteria or fungi. They have been extensively studied in mammals, where many rapid physiological responses are regulated by inhibitory serpins. In addition to the inhibitory serpins, a large group of noninhibitory proteins with a conserved serpin fold have also been identified in mammals. These noninhibitory proteins have a wide range of functions, from storage proteins to molecular chaperones, hormone transporters, and tumor suppressors. In contrast, until recently, very little was known about insect serpins in general, or Drosophila serpins in particular. In the last decade, however, there has been an increasing interest in the serpin biology of insects. It is becoming clear that, like in mammals, a similar wide range of physiological responses are regulated in insects and that noninhibitory serpin-fold proteins also play key roles in insect biology. Drosophila is also an important model organism that can be used to study human pathologies (among which serpinopathies or other protein conformational diseases) and mechanisms of regulation of proteolytic cascades in health or to develop strategies for control of insect pests and disease vectors. As most of our knowledge on insect serpins comes from studies on the Drosophila immune response, we survey here the Drosophila serpin literature and describe the laboratory techniques that have been developed to study serpin-regulated responses in this model genetic organism.
| Methods in Enzymology
2011: Vol 499, 205-225 | Abstract
Article complet | 304. A tecpr1-dependent selective autophagy pathway targets bacterial pathogens
Michinaga Ogawa, Yuko Yoshikawa, Taira Kobayashi, Hitomi Mimuro, Makoto Fukumatsu, Kotaro Kiga, Zhenzi Piao, Hiroshi Ashida, Mitsutaka Yoshida, Shigeru Kakuta, Tomohiro Koyama, Yoshiyuki Goto, Takahiro Nagatake, Shinya Nagai, Hiroshi Kiyono, Magdalena Kawalec, Jean-Marc Reichhart, Chihiro Sasakawa
Abstract : Selective autophagy of bacterial pathogens represents a host innate immune mechanism. Selective autophagy has been characterized on the basis of distinct cargo receptors but the mechanisms by which different cargo receptors are targeted for autophagic degradation remain unclear. In this study we identified a highly conserved Tectonin domain-containing protein, Tecpr1, as an Atg5 binding partner that colocalized with Atg5 at Shigella-containing phagophores. Tecpr1 activity is necessary for efficient autophagic targeting of bacteria, but has no effect on rapamycin- or starvation-induced canonical autophagy. Tecpr1 interacts with WIPI-2, a yeast Atg18 homolog and PI(3)P-interacting protein required for phagophore formation, and they colocalize to phagophores. Although Tecpr1-deficient mice appear normal, Tecpr1-deficient MEFs were defective for selective autophagy and supported increased intracellular multiplication of Shigella. Further, depolarized mitochondria and misfolded protein aggregates accumulated in the Tecpr1-knockout MEFs. Thus, we identify a Tecpr1-dependent pathway as important in targeting bacterial pathogens for selective autophagy.
| Cell Host Microbe
Vol 9, 376-389 | Abstract
Article complet | 303. Structure-function analysis of grass clip serine protease involved in Drosophila Toll pathway activation
Christine Kellenberger,?,1 Philippe Leone,? Laurent Coquet,? Thierry Jouenne,? Jean-Marc Reichhart,‖ and Alain Roussel?
Abstract : Grass is a clip domain serine protease (SP) involved in a proteolytic cascade triggering the Toll pathway activation of Drosophila during an immune response. Epistasic studies position it downstream of the apical protease ModSP and upstream of the terminal protease Spaetzle-processing enzyme. Here, we report the crystal structure of Grass zymogen. We found that Grass displays a rather deep active site cleft comparable with that of proteases of coagulation and complement cascades. A key distinctive feature is the presence of an additional loop (75-loop) in the proximity of the activation site localized on a protruding loop. All biochemical attempts to hydrolyze the activation site of Grass failed, strongly suggesting restricted access to this region. The 75-loop is thus proposed to constitute an original mechanism to prevent spontaneous activation. A comparison of Grass with clip serine proteases of known function involved in analogous proteolytic cascades allowed us to define two groups, according to the presence of the 75-loop and the conformation of the clip domain. One group (devoid of the 75-loop) contains penultimate proteases whereas the other contains terminal proteases. Using this classification, Grass appears to be a terminal protease. This result is evaluated according to the genetic data documenting Grass function.
| J Biol Chem
2011 : 286(14):12300-7 | Abstract
Article complet | 302. Relative roles of the cellular and humoral responses in the Drosophila host defense against three gram-positive bacterial infections.
Nehme NT, Quintin J, Cho JH, Lee J, Lafarge MC, Kocks C, Ferrandon D
Abstract : BACKGROUND:
Two NF-kappaB signaling pathways, Toll and immune deficiency (imd), are required for survival to bacterial infections in Drosophila. In response to septic injury, these pathways mediate rapid transcriptional activation of distinct sets of effector molecules, including antimicrobial peptides, which are important components of a humoral defense response. However, it is less clear to what extent macrophage-like hemocytes contribute to host defense.
METHODOLOGY/PRINCIPAL FINDINGS:
In order to dissect the relative importance of humoral and cellular defenses after septic injury with three different gram-positive bacteria (Micrococcus luteus, Enterococcus faecalis, Staphylococcus aureus), we used latex bead pre-injection to ablate macrophage function in flies wildtype or mutant for various Toll and imd pathway components. We found that in all three infection models a compromised phagocytic system impaired fly survival--independently of concomitant Toll or imd pathway activation. Our data failed to confirm a role of the PGRP-SA and GNBP1 Pattern Recognition Receptors for phagocytosis of S. aureus. The Drosophila scavenger receptor Eater mediates the phagocytosis by hemocytes or S2 cells of E. faecalis and S. aureus, but not of M. luteus. In the case of M. luteus and E. faecalis, but not S. aureus, decreased survival due to defective phagocytosis could be compensated for by genetically enhancing the humoral immune response.
CONCLUSIONS/SIGNIFICANCE:
Our results underscore the fundamental importance of both cellular and humoral mechanisms in Drosophila immunity and shed light on the balance between these two arms of host defense depending on the invading pathogen.
| PLoS One.
2011 Mar 3;6(3):e14743 | Abstract
Article complet | 301. Negative regulation of immune responses on the fly.
Lee KZ, Ferrandon D.
Abstract : The Toll and the IMD pathways are key regulators of innate immunity in Drosophila. A paper in this issue of the EMBO Journal reports that activation of the Ras/MAPK pathway negatively regulates the IMD pathway and limits the magnitude of the innate immune response during an infection.
| EMBO J.
2011 Mar 16;30(6):988-90 | Abstract
Article complet | 300. Analysis of thioester-containing proteins during the innate immune response of Drosophila melanogaster
Bou Aoun R, Hetru C, Troxler L, Doucet D, Ferrandon D, Matt N.
Abstract : Thioester-containing proteins (TEPs) are conserved proteins among insects that are thought to be involved in innate immunity. In Drosophila, the Tep family is composed of 6 genes named Tep1-Tep6. In this study, we investigated the phylogeny, expression pattern and roles of these genes in the host defense of Drosophila. Protostomian Tep genes are clustered in 3 distinct branches, 1 of which is specific to mosquitoes. Most D. melanogaster Tep genes are expressed in hemocytes, can be induced in the fat body, and are expressed in specific regions of the hypodermis. This expression pattern is consistent with a role in innate immunity. However, we find that TEP1, TEP2, and TEP4 are not strictly required in the body cavity to fight several bacterial and fungal infections. One possibility is that Drosophila TEPs act redundantly or that their absence can be compensated by other components of the immune response. TEPs may thus provide a subtle selective advantage during evolution. Alternatively, they may be required in host defense against specific as yet unidentified natural pathogens of Drosophila.
| J Innate Immun.
2011;3(1):52-64. | Abstract
Article complet | 299. Protease inhibitors and proteolytic signalling cascades in insects
Gubb D, Sanz-Parra A, Barcena L, Troxler L, Fullaondo A
Abstract : Proteolytic signalling cascades control a wide range of physiological responses. In order to respond rapidly, protease activity must be maintained at a basal level: the component zymogens must be sequentially activated and actively degraded. At the same time, signalling cascades must respond precisely: high target specificity is required. The insects have a wide range of trapping- and tight-binding protease inhibitors, which can regulate the activity of individual proteases. In addition, the interactions between component proteases of a signalling cascade can be modified by serine protease homologues. The suicide-inhibition mechanism of serpin family inhibitors gives rapid turnover of both protease and inhibitor, but target specificity is inherently broad. Similarly, the TEP/macroglobulins have extremely broad target specificity, which suits them for roles as hormone transport proteins and sensors of pathogenic virulence factors. The tight-binding inhibitors, on the other hand, have a lock-and-key mechanism capable of high target specificity. In addition, proteins containing multiple tight-binding inhibitory domains may act as scaffolds for the assembly of signalling complexes. Proteolytic cascades regulated by combinations of different types of inhibitor could combine the rapidity of suicide-inhibitors with the specificity lock-and-key inhibitors. This would allow precise control of physiological responses and may turn out to be a general rule.
| Biochimie
2010 Dec;92(12):1749-59 | Abstract
Article complet | 298. RNAi-mediated immunity provides strong protection against the negative-strand RNA vesicular stomatitis virus in Drosophila
Mueller S, Gausson V, Vodovar N, Deddouche S, Troxler L, Perot J, Pfeffer S, Hoffmann JA, Saleh MC, Imler JL
Abstract : Activation of innate antiviral responses in multicellular organisms relies on the recognition of structural differences between viral and cellular RNAs. Double-stranded (ds)RNA, produced during viral replication, is a well-known activator of antiviral defenses and triggers interferon production in vertebrates and RNAi in invertebrates and plants. Previous work in mammalian cells indicates that negative-strand RNA viruses do not appear to generate dsRNA, and that activation of innate immunity is triggered by the recognition of the uncapped 5' ends of viral RNA. This finding raises the question whether antiviral RNAi, which is triggered by the presence of dsRNA in insects, represents an effective host-defense mechanism against negative-strand RNA viruses. Here, we show that the negative-strand RNA virus vesicular stomatitis virus (VSV) does not produce easily detectable amounts of dsRNA in Drosophila cells. Nevertheless, RNAi represents a potent response to VSV infection, as illustrated by the high susceptibility of RNAi-defective mutant flies to this virus. VSV-derived small RNAs produced in infected cells or flies uniformly cover the viral genome, and equally map the genome and antigenome RNAs, indicating that they derive from dsRNA. Our findings reveal that RNAi is not restricted to the defense against positive-strand or dsRNA viruses but can also be highly efficient against a negative-strand RNA virus. This result is of particular interest in view of the frequent transmission of medically relevant negative-strand RNA viruses to humans by insect vectors.
| Proc Natl Acad Sci USA
2010 Nov 9;107(45):19390-5 | Abstract
Article complet | 297. Involvement of the cytokine MIF in the snail host immune response to the parasite Schistosoma mansoni.
Baeza Garcia A, Pierce RJ, Gourbal B, Werkmeister E, Colinet D, Reichhart JM, Dissous C, Coustau C.
Abstract : We have identified and characterized a Macrophage Migration Inhibitory Factor (MIF) family member in the Lophotrochozoan invertebrate, Biomphalaria glabrata, the snail intermediate host of the human blood fluke Schistosoma mansoni. In mammals, MIF is a widely expressed pleiotropic cytokine with potent pro-inflammatory properties that controls cell functions such as gene expression, proliferation or apoptosis. Here we show that the MIF protein from B. glabrata (BgMIF) is expressed in circulating immune defense cells (hemocytes) of the snail as well as in the B. glabrata embryonic (Bge) cell line that has hemocyte-like features. Recombinant BgMIF (rBgMIF) induced cell proliferation and inhibited NO-dependent p53-mediated apoptosis in Bge cells. Moreover, knock-down of BgMIF expression in Bge cells interfered with the in vitro encapsulation of S. mansoni sporocysts. Furthermore, the in vivo knock-down of BgMIF prevented the changes in circulating hemocyte populations that occur in response to an infection by S. mansoni miracidia and led to a significant increase in the parasite burden of the snails. These results provide the first functional evidence that a MIF ortholog is involved in an invertebrate immune response towards a parasitic infection and highlight the importance of cytokines in invertebrate-parasite interactions.
| PLoS Pathog.
2010: Vol 6 | Abstract
Article complet | 296. Serpins flex their muscle: II. Structural insights into target peptidase recognition, polymerization, and transport functions.
Whisstock JC, Silverman GA, Bird PI, Bottomley SP, Kaiserman D, Luke CJ, Pak SC, Reichhart JM, Huntington JA.
Abstract : Inhibitory serpins are metastable proteins that undergo a substantial conformational rearrangement to covalently trap target peptidases. The serpin reactive center loop contributes a majority of the interactions that serpins make during the initial binding to target peptidases. However, structural studies on serpin-peptidase complexes reveal a broader set of contacts on the scaffold of inhibitory serpins that have substantial influence on guiding peptidase recognition. Structural and biophysical studies also reveal how aberrant serpin folding can lead to the formation of domain-swapped serpin multimers rather than the monomeric metastable state. Serpin domain swapping may therefore underlie the polymerization events characteristic of the serpinopathies. Finally, recent structural studies reveal how the serpin fold has been adapted for non-inhibitory functions such as hormone binding.
| J Biol Chem.
2010: Vol 285, 24307-24312 | Abstract
Article complet | 295. Serpins flex their muscle: I. Putting the clamps on proteolysis in diverse biological systems.
Silverman GA, Whisstock JC, Bottomley SP, Huntington JA, Kaiserman D, Luke CJ, Pak SC, Reichhart JM, Bird PI.
Abstract : Serpins compose the largest superfamily of peptidase inhibitors and are well known as regulators of hemostasis and thrombolysis. Studies using model organisms, from plants to vertebrates, now show that serpins and their unique inhibitory mechanism and conformational flexibility are exploited to control proteolysis in molecular pathways associated with cell survival, development, and host defense. In addition, an increasing number of non-inhibitory serpins are emerging as important elements within a diversity of biological systems by serving as chaperones, hormone transporters, or anti-angiogenic factors.
| J Biol Chem.
2010: Vol 285, 24299-24305 | Abstract
Article complet | 294. The major yolk protein vitellogenin interferes with the anti-plasmodium response in the malaria mosquito Anopheles gambiae
Abstract : Abstract : When taking a blood meal on a person infected with malaria, female Anopheles gambiae mosquitoes, the major vector of human malaria, acquire nutrients that will activate egg development (oogenesis) in their ovaries. Simultaneously, they infect themselves with the malaria parasite. On traversing the mosquito midgut epithelium, invading Plasmodium ookinetes are met with a potent innate immune response predominantly controlled by mosquito blood cells. Whether the concomitant processes of mosquito reproduction and immunity affect each other remains controversial. Here, we show that proteins that deliver nutrients to maturing mosquito oocytes interfere with the antiparasitic response. Lipophorin (Lp) and vitellogenin (Vg), two nutrient transport proteins, reduce the parasite-killing efficiency of the antiparasitic factor TEP1. In the absence of either nutrient transport protein, TEP1 binding to the ookinete surface becomes more efficient. We also show that Lp is required for the normal expression of Vg, and for later Plasmodium development at the oocyst stage. Furthermore, our results uncover an inhibitory role of the Cactus/REL1/REL2 signaling cassette in the expression of Vg, but not of Lp. We reveal molecular links that connect reproduction and immunity at several levels and provide a molecular basis for a long-suspected trade-off between these two processes.
| PloS Biology
Vol. 8(7):e1000434 | Abstract
Article complet | 293. Caspase-mediated cleavage, IAP binding, and ubiquitination: linking three mechanisms crucial for Drosophila NF-kappaB signaling.
Paquette N, Broemer M, Aggarwal K, Chen L, Husson M, Erturk-Hasdemir D, Reichhart JM, Meier P, Silverman N.
Abstract : Innate immune responses are critical for the immediate protection against microbial infection. In Drosophila, infection leads to the rapid and robust production of antimicrobial peptides through two NF-κB signaling pathways?IMD and Toll. The IMD pathway is triggered by DAP-type peptidoglycan, common to most Gram-negative bacteria. Signaling downstream from the peptidoglycan receptors is thought to involve K63 ubiquitination and caspase-mediated cleavage, but the molecular mechanisms remain obscure. We now show that PGN stimulation causes caspase-mediated cleavage of the imd protein, exposing a highly conserved IAP-binding motif (IBM) at its neo-N terminus. A functional IBM is required for the association of cleaved IMD with the ubiquitin E3-ligase DIAP2. Through its association with DIAP2, IMD is rapidly conjugated with K63-linked polyubiquitin chains. These results mechanistically connect caspase-mediated cleavage and K63 ubiquitination in immune-induced NF-κB signaling.
| Mol. Cell
2010: Vol 37, 172-82 | Abstract
Article complet | 292. Drosophila Genome-wide Obesity Screen Reveals Hedgehog as a Determinant of Brown versus White Adipose Cell Fate.
Pospisilik JA, Schramek D, Schnidar H, Cronin SJ, Nehme NT, Zhang X, Knauf C, Cani PD, Aumayr K, Todoric J, Bayer M, Haschemi A, Puviindran V, Tar K, Orthofer M, Neely GG, Dietzl G, Manoukian A, Funovics M, Prager G, Wagner O, Ferrandon D, Aberger F, Hui CC, Esterbauer H, Penninger JM.
Abstract : Over 1 billion people are estimated to be overweight, placing them at risk for diabetes, cardiovascular disease, and cancer. We performed a systems-level genetic dissection of adiposity regulation using genome-wide RNAi screening in adult Drosophila. As a follow-up, the resulting approximately 500 candidate obesity genes were functionally classified using muscle-, oenocyte-, fat-body-, and neuronal-specific knockdown in vivo and revealed hedgehog signaling as the top-scoring fat-body-specific pathway. To extrapolate these findings into mammals, we generated fat-specific hedgehog-activation mutant mice. Intriguingly, these mice displayed near total loss of white, but not brown, fat compartments. Mechanistically, activation of hedgehog signaling irreversibly blocked differentiation of white adipocytes through direct, coordinate modulation of early adipogenic factors. These findings identify a role for hedgehog signaling in white/brown adipocyte determination and link in vivo RNAi-based scanning of the Drosophila genome to regulation of adipocyte cell fate in mammals. Copyright ? 2010 Elsevier Inc. All rights reserved.
| Cell
2010: Vol 140, 148-160 | Abstract
Article complet | 291. Toll-dependent antimicrobial responses in Drosophila larval fat body require Spaetzle secreted by haemocytes.
Shia AK, Glittenberg M, Thompson G, Weber AN, Reichhart JM, Ligoxygakis P.
Abstract : n Drosophila, the humoral response characterised by the synthesis of antimicrobial peptides (AMPs) in the fat body (the equivalent of the mammalian liver) and the cellular response mediated by haemocytes (blood cells) engaged in phagocytosis represent two major reactions that counter pathogens. Although considerable analysis has permitted the elucidation of mechanisms pertaining to the two responses individually, the mechanism of their coordination has been unclear. To characterise the signals with which infection might be communicated between blood cells and fat body, we ablated circulating haemocytes and defined the parameters of AMP gene activation in larvae. We found that targeted ablation of blood cells influenced the levels of AMP gene expression in the fat body following both septic injury and oral infection. Expression of the AMP gene drosomycin (a Toll target) was blocked when expression of the Toll ligand Sp?tzle was knocked down in haemocytes. These results show that in larvae, integration of the two responses in a systemic reaction depend on the production of a cytokine (spz), a process that strongly parallels the mammalian immune response.
| J Cell Sci.
2009: Vol 122, 4505-15. | Abstract
Article complet | 290. Identification and analysis of serpin-family genes by homology and synteny across the 12 sequenced Drosophilid genomes
Garrett M, Fullaondo A, Troxler L, Micklem G, Gubb D
Abstract : BACKGROUND:
The Drosophila melanogaster genome contains 29 serpin genes, 12 as single transcripts and 17 within 6 gene clusters. Many of these serpins have a conserved "hinge" motif characteristic of active proteinase inhibitors. However, a substantial proportion (42%) lacks this motif and represents non-inhibitory serpin-fold proteins of unknown function. Currently, it is not known whether orthologous, inhibitory serpin genes retain the same target proteinase specificity within the Drosophilid lineage, nor whether they give rise to non-inhibitory serpin-fold proteins or other, more diverged, proteins.
RESULTS:
We collated 188 orthologues to the D. melanogaster serpins from the other 11 Drosophilid genomes and used synteny to find further family members, raising the total to 226, or 71% of the number of orthologues expected assuming complete conservation across all 12 Drosophilid species. In general the sequence constraints on the serpin-fold itself are loose. The critical Reactive Centre Loop (RCL) sequence, including the target proteinase cleavage site, is strongly conserved in inhibitory serpins, although there are 3 exceptional sets of orthologues in which the evolutionary constraints are looser. Conversely, the RCL of non-inhibitory serpin orthologues is less conserved, with 3 exceptions that presumably bind to conserved partner molecules. We derive a consensus hinge motif, for Drosophilid inhibitory serpins, which differs somewhat from that of the vertebrate consensus. Three gene clusters appear to have originated in the melanogaster subgroup, Spn28D, Spn77B and Spn88E, each containing one inhibitory serpin orthologue that is present in all Drosophilids. In addition, the Spn100A transcript appears to represent a novel serpin-derived fold.
CONCLUSION:
In general, inhibitory serpins rarely change their range of proteinase targets, except by a duplication/divergence mechanism. Non-inhibitory serpins appear to derive from inhibitory serpins, but not the reverse. The conservation of different family members varied widely across the 12 sequenced Drosophilid genomes. An approach considering synteny as well as homology was important to find the largest set of orthologues.
| BMC Genomics
2009 Oct 22;10:489 | Abstract
Article complet | 289. Focusing on complement in the antiparasitic defense of mosquitoes.
Volohonsky G, Steinert S, Levashina EA
Abstract : Malaria is an infectious disease caused by Plasmodium and transmitted to humans by the Anopheles mosquitoes. The mosquito immune system predominantly targets Plasmodium at the ookinete stage, and efficiently eliminates the majority of invading parasites. Identification of the components of the mosquito complement system now provides new focus for studies on the activation and control of this pathway, whose manipulation is expected to block malaria transmission at the vector level.
| Trends Parasitol.
2009: 26(1):1-3 | Abstract
Article complet | 288. Dissecting the genetic basis of resistance to malaria parasites in Anopheles gambiae.
Blandin SA, Wang-Sattler R, Lamacchia M, Gagneur J, Lycett G, Ning Y, Levashina EA, Steinmetz LM.
Abstract : The ability of Anopheles gambiae mosquitoes to transmit Plasmodium parasites is highly variable between individuals. However, the genetic basis of this variability has remained unknown. We combined genome-wide mapping and reciprocal allele-specific RNA interference (rasRNAi) to identify the genomic locus that confers resistance to malaria parasites and demonstrated that polymorphisms in a single gene encoding the antiparasitic thioester-containing protein 1 (TEP1) explain a substantial part of the variability in parasite killing. The link between TEP1 alleles and resistance to malaria may offer new tools for controlling malaria transmission. The successful application of rasRNAi in Anopheles suggests that it could also be applied to other organisms where RNAi is feasible to dissect complex phenotypes to the level of individual quantitative trait alleles.
| Science
2009 Oct 2;326(5949):147-50 | Abstract
Article complet | 287. Host tolerance versus resistance and microbial virulence in the host-pathogen equation.
Ferrandon D.
Abstract : To deal with an infection, the organism resorts to nonmutually exclusive strategies: resistance, that is, neutralization or destruction of the pathogen; or tolerance, the ability to withstand damages inflicted by the pathogen or by host defense. In this issue of Cell Host & Microbe, Shinzawa et al. (2009) identify p38-mediated phagocytic encapsulation as a potential tolerance mechanism.
| Cell Host Microbe.
2009 Sep 17;6(3):203-5. | Abstract
Article complet | 286. The N-terminal domain of drosophila gram-negative binding protein 3 (GNBP3) defines a novel family of fungal pattern recognition receptors.
Mishima Y, Quintin J, Aimanianda V, Kellenberger C, Coste F, Clavaud C, Hetru C, Hoffmann JA, Latgé JP, Ferrandon D, Roussel A.
Abstract : GNBP3, a pattern recognition receptor (PRR) that circulates in the hemolymph of Drosophila, is responsible for sensing fungal infection and triggering Toll pathway activation. Here, we report that GNBP3 N-terminal domain binds to fungi upon identifying long chains of beta-1,3-glucans in the fungal cell wall as a major ligand. Interestingly, this domain fails to interact strongly with short oligosaccharides. The crystal structure of GNBP3-Nter reveals an immunoglobulin-like fold in which the glucan binding site is masked by a loop that is highly conserved among glucan binding proteins identified in several insect orders. Structure-based mutagenesis experiments reveal an essential role for this occluding loop in discriminating between short and long polysaccharides. The displacement of the occluding loop is necessary for binding and could explain the specificity of the interaction with long chain structured polysaccharides. This represents a novel mechanism for beta-glucan recognition.
| Journal of Biological Chemistry.
2009 Oct 16;284(42):28687-97. Epub 2009 Aug 19. | Abstract
Article complet | 285. Genome-wide RNAi screen identifies genes involved in intestinal pathogenic bacterial infection
Cronin, S.J., Nehme, N.T., Limmer, S., Liegeois, S., Pospisilik, J.A., Schramek, D., Leibbrandt, A., Simoes Rde, M., Gruber, S., Puc, U., Ebersberger, I., Zoranovic, T., Neely, G.G., von Haeseler, A., Ferrandon, D., and Penninger, J.M.
Abstract : Innate immunity represents the first line of defense in animals. We report a genome-wide in vivo Drosophila RNA interference screen to uncover genes involved in susceptibility or resistance to intestinal infection with the bacterium Serratia marcescens. We first employed whole-organism gene suppression, followed by tissue-specific silencing in gut epithelium or hemocytes to identify several hundred genes involved in intestinal antibacterial immunity. Among the pathways identified, we showed that the JAK-STAT signaling pathway controls host defense in the gut by regulating stem cell proliferation and thus epithelial cell homeostasis. Therefore, we revealed multiple genes involved in antibacterial defense and the regulation of innate immunity.
| Science
2009: vol. 325, p 340-343 | Abstract
Article complet | 284. Viral suppressors of RNA silencing hinder exogenous and endogenous small RNA pathways in Drosophila.
Berry B, Deddouche S, Kirschner D, Imler JL, Antoniewski C.
Abstract : BACKGROUND: In plants and insects, RNA interference (RNAi) is the main responder against viruses and shapes the basis of antiviral immunity. Viruses counter this defense by expressing viral suppressors of RNAi (VSRs). While VSRs in Drosophila melanogaster were shown to inhibit RNAi through different modes of action, whether they act on other silencing pathways remained unexplored. METHODOLOGY/PRINCIPAL FINDINGS: Here we show that expression of various plant and insect VSRs in transgenic flies does not perturb the Drosophila microRNA (miRNA) pathway; but in contrast, inhibits antiviral RNAi and the RNA silencing response triggered by inverted repeat transcripts, and injection of dsRNA or siRNA. Strikingly, these VSRs also suppressed transposon silencing by endogenous siRNAs (endo-siRNAs). CONCLUSIONS/SIGNIFICANCE: Our findings identify VSRs as tools to unravel small RNA pathways in insects and suggest a cosuppression of antiviral RNAi and endo-siRNA silencing by viruses during fly infections.
| PLoS One.
2009 Jun 10;4(6):e5866. | Abstract
Article complet | 283. RNAi in the malaria vector, Anopheles gambiae.
Catteruccia F, Levashina EA.
Abstract : Malaria is a disease that kills more than a million people each year in tropical and subtropical countries. The disease is caused by Plasmodium parasites and is transmitted to humans exclusively by mosquitoes of the genus Anopheles. The lack of functional approaches has hampered study of the biological networks that determine parasite transmission by the insect vector. The recent discovery of RNA interference and its adaptation to mosquitoes is now providing crucial tools for the dissection of vector-parasite interactions and for the analysis of aspects of mosquito biology influencing the vectorial capacity. Two RNAi approaches have been established in mosquitoes: transient gene silencing by direct injection of double-stranded RNA, and stable expression of hairpin RNAs from transgenes integrated in the genome. Here we describe these methods in detail, providing information about their use and limitations.
| Methods Mol Biol.
2009;555:63-75 | Abstract
Article complet | 282. Viral suppressors of RNA silencing hinder exogenous and endogenous small RNA pathways in Drosophila
Berry B., Deddouche S., Kirchner D., Imler J.L. & Antoniewski C.
Abstract : In plants and insects, RNA interference (RNAi) is the main responder against viruses and shapes the basis of antiviral immunity. Viruses counter this defense by expressing viral suppressors of RNAi (VSRs). While VSRs in Drosophila melanogaster were shown to inhibit RNAi through different modes of action, whether they act on other silencing pathways remained unexplored. METHODOLOGY/PRINCIPAL FINDINGS: Here we show that expression of various plant and insect VSRs in transgenic flies does not perturb the Drosophila microRNA (miRNA) pathway; but in contrast, inhibits antiviral RNAi and the RNA silencing response triggered by inverted repeat transcripts, and injection of dsRNA or siRNA. Strikingly, these VSRs also suppressed transposon silencing by endogenous siRNAs (endo-siRNAs). CONCLUSIONS/SIGNIFICANCE: Our findings identify VSRs as tools to unravel small RNA pathways in insects and suggest a cosuppression of antiviral RNAi and endo-siRNA silencing by viruses during fly infections.
| PLoS ONE
2009: vol. 4(6): e5866, p 1-10 | Abstract
Article complet | 281. Two mosquito LRR proteins function as complement control factors in the TEP1-mediated killing of Plasmodium.
Fraiture M, Baxter RH, Steinert S, Chelliah Y, Frolet C, Quispe-Tintaya W, Hoffmann JA, Blandin SA, Levashina EA.
Abstract : Plasmodium development within Anopheles mosquitoes is a vulnerable step in the parasite transmission cycle, and targeting this step represents a promising strategy for malaria control. The thioester-containing complement-like protein TEP1 and two leucine-rich repeat (LRR) proteins, LRIM1 and APL1, have been identified as major mosquito factors that regulate parasite loads. Here, we show that LRIM1 and APL1 are required for binding of TEP1 to parasites. RNAi silencing of the LRR-encoding genes results in deposition of TEP1 on Anopheles tissues, thereby depleting TEP1 from circulation in the hemolymph and impeding its binding to Plasmodium. LRIM1 and APL1 not only stabilize circulating TEP1, they also stabilize each other prior to their interaction with TEP1. Our results indicate that three major antiparasitic factors in mosquitoes jointly function as a complement-like system in parasite killing, and they reveal a role for LRR proteins as complement control factors.
| Cell Host Microbe.
2009 Mar 19;5(3):273-84 | Abstract
Article complet | 280. Antiviral immunity in drosophila
Kemp, C. & Imler J.L.
Abstract : Genetic analysis of the drosophila antiviral response indicates that RNA interference plays a major role. This contrasts with the situation in mammals, where interferon-induced responses mediate innate antiviral host-defense. An inducible response also contributes to antiviral immunity in drosophila, and similarities in the sensing and signaling of viral infection are becoming apparent between drosophila and mammals. In particular, DExD/H box helicases appear to play a crucial role in the cytosolic detection of viral RNAs in flies and mammals.
| Current Opinion in Immunology
2009: vol. 21, p 3-9 | Abstract
Article complet | 279. Chapter 4 « Drosophila as a model for studying antiviral defenses »
Imler J.L. & Eleftherianos I.
Abstract :
| In « Insect Infection and Immunity : evolution, ecology and mechanisms »
Editors : S. Reynolds and J. Rolff. Published by Oxford university Press. p 49-68. | Abstract
Article complet | 278. 159 : Toll family receptors.
Hyvert, Y. & Imler, J.L.
Abstract :
| In "Handbook of cellular Signaling"
Editors: R.A. Bradshaw and E. Dennis. p 1275-1280. | Abstract
Article complet | 277. Phagocytosis in Drosophila melanogaster Immune Response
Leclerc V, Caldelari I, Veresceaghina N, Reichhart JM
Abstract :
| Phagocyte-Pathogen Interactions
D.G. Russell and S. Gordon, ed. ASM Press Washington DC, p 513-521 | Abstract
Article complet | 276. Drosophila viruses and the study of antiviral host-defense.
Huszar, T. & Imler, J.L.
Abstract : The fruit fly Drosophila melanogaster is a powerful model to study host-pathogen interactions. Most studies so far have focused on extracellular pathogens such as bacteria and fungi. More recently, viruses have come to the front, and RNA interference was shown to play a critical role in the control of viral infections in drosophila. We review here our current knowledge on drosophila viruses. A diverse set of RNA viruses belonging to several families (Rhabdoviridae, Dicistroviridae, Birnaviridae, Reoviridae, Errantiviridae) has been reported in D. melanogaster. By contrast, no DNA virus has been recovered up to now. The drosophila viruses represent powerful tools to study virus-cell interactions in vivo. Analysis of the literature however reveals that for many of them, important gaps exist in our understanding of their replication cycle, genome organization, morphology or pathogenesis. The data obtained in the past few years on antiviral defense mechanisms in drosophila, which point to evolutionary conserved pathways, highlight the potential of the D. melanogaster model to study antiviral innate immunity and to better understand the complex interaction between arthropod-borne viruses and their insect vectors.
| Advances in Virus Research
2008: vol 72, p. 227-265. Academic Press, San Diego. | Abstract
Article complet | 275. Molecular and cellular components of the mating machinery in Anopheles gambiae females.
Rogers DW, Whitten MM, Thailayil J, Soichot J, Levashina EA, Catteruccia F.
Abstract : Anopheles gambiae mosquitoes are the principal vectors of malaria. A major determinant of the capacity of these mosquitoes as disease vectors is their high reproductive rate. Reproduction depends on a single insemination, which profoundly changes the behavior and physiology of females. To identify factors and mechanisms relevant to the fertility of A. gambiae, we performed a comprehensive analysis of the molecular and cellular machinery associated with copulation in females. Initial whole-body microarray experiments comparing virgins with females at 2 h, 6 h, and 24 h after mating detected large transcriptional changes. Analysis of tissue localization identified a subset of genes whose expression was strikingly regulated by mating in the lower reproductive tract and, surprisingly, the gut. In the atrium of virgin females, where the male seminal fluid is received, our studies revealed a "mating machinery" consisting of molecular and structural components that are turned off or collapse after copulation, suggesting that this tissue loses its competence for further insemination. In the sperm storage organ, we detected a number of mating-responsive genes likely to have a role in the maintenance and function of stored sperm. These results identify genes and mechanisms regulating the reproductive biology of A. gambiae females, highlighting considerable differences with Drosophila melanogaster. Our data inform vector control strategies and reveal promising targets for the manipulation of fertility in field populations of these important disease vectors.
| Proc Natl Acad Sci.
2008 Dec 9;105(49):19390-5 | Abstract
Article complet | 274. The DEXD/H-box helicase Dicer-2 mediates induction of an antiviral activity in drosophila
Deddouche S., Matt N., Budd A., Mueller S., Kemp C., Galiana-Arnoux D., Dostert C., Antoniewski C., Hoffmann J.A. & Imler J.L.
Abstract : Drosophila, like other invertebrates and plants, relies mainly on RNA interference for its defense against viruses. In flies, viral infection also triggers the expression of many genes. One of the genes induced, Vago, encodes a 18-kilodalton cysteine-rich polypeptide. Here we provide genetic evidence that the Vago gene product controlled viral load in the fat body after infection with drosophila C virus. Induction of Vago was dependent on the helicase Dicer-2. Dicer-2 belongs to the same DExD/H-box helicase family as do the RIG-I-like receptors, which sense viral infection and mediate interferon induction in mammals. We propose that this family represents an evolutionary conserved set of sensors that detect viral nucleic acids and direct antiviral responses.
| Nature Immunology
2008: Vol. 9, 1425-1432 | Abstract
Article complet | 273. Sensing of 'danger signals' and pathogen-associated molecular patterns defines binary signaling pathways 'upstream' of Toll.
El Chamy L, Leclerc V, Caldelari I, Reichhart JM.
Abstract : In drosophila, molecular determinants from fungi and Gram-positive bacteria are detected by circulating pattern-recognition receptors. Published findings suggest that such pattern-recognition receptors activate as-yet-unidentified serine-protease cascades that culminate in the cleavage of Sp?tzle, the endogenous Toll receptor ligand, and trigger the immune response. We demonstrate here that the protease Grass defines a common activation cascade for the detection of fungi and Gram-positive bacteria mediated by pattern-recognition receptors. The serine protease Persephone, shown before to be specific for fungal detection in a cascade activated by secreted fungal proteases, was also required for the sensing of proteases elicited by bacteria in the hemolymph. Hence, Persephone defines a parallel proteolytic cascade activated by 'danger signals' such as abnormal proteolytic activities.
| Nature Immunology
2008: Vol 10, 1165-70. | Abstract
Article complet | 272. Candida glabrata environmental stress response involves Saccharomyces cerevisiae Msn2/4 orthologous transcription factors.
Roetzer, A. Gregori, C. Jennings, AM. Quintin, J. Ferrandon, D. Butler, G. Kuchler, K. Ammerer, G. Schüller, C.
Abstract : We determined the genome-wide environmental stress response (ESR) expression profile of Candida glabrata, a human pathogen related to Saccharomyces cerevisiae. Despite different habitats, C. glabrata, S. cerevisiae, Schizosaccharomyces pombe and Candida albicans have a qualitatively similar ESR. We investigate the function of the C. glabrata syntenic orthologues to the ESR transcription factor Msn2. The C. glabrata orthologues CgMsn2 and CgMsn4 contain a motif previously referred to as HD1 (homology domain 1) also present in Msn2 orthologues from fungi closely related to S. cerevisiae. We show that regions including this motif confer stress-regulated intracellular localization when expressed in S. cerevisiae. Site-directed mutagenesis confirms that nuclear export of CgMsn2 in C. glabrata requires an intact HD1. Transcript profiles of CgMsn2/4 mutants and CgMsn2 overexpression strains show that they regulate a part of the CgESR. CgMsn2 complements a S. cerevisiae msn2 null mutant and in stressed C. glabrata cells, rapidly translocates from the cytosol to the nucleus. CgMsn2 is required for full resistance against severe osmotic stress and rapid and full induction of trehalose synthesis genes (TPS1, TPS2). Constitutive activation of CgMsn2 is detrimental for C. glabrata. These results establish an Msn2-regulated general stress response in C. glabrata.
| Molecular Microbiology
2008: vol 69(3):603-20 | Abstract
Article complet | 271. Host-parasite interactions: the balance of trade
Levashina EA
Abstract : Living organisms are constantly exposed to microbes. Nevertheless a disease as an outcome of the pathogen attack remains an exception rather than a rule, and most species are remarkably resistant to infectious agents. In some cases, pathogens invade more than one host to complete their complex life cycle. To warrant a successful transmission from one host to another, parasites have developed a number of strategies and tricks, many of which rely on the passive or active participation of the host. This is especially true for parasitic protozoa such as trypanosomes, leishmania and Plasmodium, single cell organisms that are obligatorily transmitted to mammals by insect vectors. Inside their hosts, the parasites change looks and coats and invade a diverse set of cells and tissues, some for a transient passage, whereas others to establish a long-term infection. The past decade has shown an explosion in the field of host?pathogen interactions. The rapid progress was made possible by the availability of sequence information and bioinformatic tools and development of a series of functional assays, including RNAi screens and transgenic technologies relevant for both the host and the pathogen. These efforts, although in their very early days, firmly established an intricate crosstalk between the interacting organisms and have already identified a number of key molecules involved in it. Finally, development of in vivo imaging, high throughput methodologies, and computational techniques has gathered conceptual breakthroughs that infringe on some reputable dogmas. In this issue of the journal, selected contributions summarize new developments and current challenges related to three host?protozoa combinations. Two reviews outline recent progress in the understanding of interactions between flies and Euglenozoa parasites, whereas the third one focuses on the Plasmodium interactions with its mammalian host.
Leishmania parasites are the causative agents of leishmaniasis, a debilitating disease transmitted by female phlebotomine sand flies. Complex interactions that occur between the haemoflagellate parasites and their vectors might be the basis of the narrow host specificity: out of the thousand sand fly species described to date, only 70 are proven or suspected vectors. The review by Bates discusses molecular events required for a successful parasite development within the sand fly midgut. Several molecules and structures have been identified that underlie leishmania motility (flagellum), midgut attachment (a leishmania surface lipophosphoglycan and a sand fly galectin), and regulation of metacyclogenesis, the differentiation process that leads to the accumulation of mammal-infective promastigotes.
The review by Roditi and Lehane describes a fascinating crosstalk between tsetse flies and trypanosomes. African trypanosomes are insect-borne parasites that cause sleeping sickness in humans and nagana, the disease characterized by fever, lethargy, and edema, in domesticated animals. Although the development of transgenic tools to study biology of the trypanosome inside the insect vector is in its very beginning, it has already offered tools for in vivo imaging of parasites within the fly vector to elucidate regulation of gene expression and genetic exchange. On the sand fly side, a series of parameters that affect the infection rates has been established. The current challenge is to identify genes and molecules that underlie these factors and shape tsetse fly's capacity to transmit trypanosomes.
Malaria remains today as one of the most devastating infectious diseases. The life cycle of its causative agent, Plasmodium, is split between the human host (the asexual stage) and the mosquito vector (the sexual stage). Review by Silvie et al. focuses on the asexual stages of the parasite development and highlights the advantages of the rodent in vivo models that continue to play crucial roles in the dissection of the genetic basis of the fine-tuned host?parasite interactions. Application of the high-end intravital imaging to follow fluorescently labeled P. berghei identified novel invasion routes and cryptic forms of parasites, demonstrating how new powerful technologies change our views on what was thought to be an established concept. The general message of this issue is that in spite of a long history, many more fascinating discoveries are awaiting us in the world of host?parasite interactions.
| Curr Opin Microbiol.
2008 Aug;11(4):338-9 | Abstract
Article complet | 270. Antimalarial responses in Anopheles gambiae: from a complement-like protein to a complement-like pathway.
Blandin SA, Marois E, Levashina EA.
Abstract : Malaria transmission between humans depends on the ability of Anopheles mosquitoes to support Plasmodium development. New perspectives in vector control are emerging from understanding the mosquito immune system, which plays critical roles in parasite recognition and killing. A number of factors controlling this process have been recently identified, and key among them is TEP1, a homolog of human complement factor C3 whose binding to the parasite surface targets it for subsequent killing. Here, we review our current knowledge of mosquito factors that respond to Plasmodium infection and elaborate on the activity and mode of action of the TEP1 complement-like pathway.
| Cell Host Microbe
2008 Jun 12;3(6):364-74 | Abstract
Article complet | 269. Impairing retinoic acid signalling in the neural crest cells is sufficient to alter entire eye morphogenesis.
Matt N, Ghyselinck NB, Pellerin I, Dup? V.
Abstract : Retinoic acid (RA) is known to be required at various levels of eye patterning via Retinoic Acid Receptors (RAR); however the molecular and cellular mechanisms triggered by these nuclear receptors are still obscure. The genetic studies performed here enable us to present a new model to study RA action during eye development. By inactivating the three RARs, specifically in the periocular mesenchyme, we discriminate the individual contribution of each RAR during eye development and describe a new function for RARs during the formation of the optic nerve. We demonstrate that RARalpha is the only receptor that mediates RA signalling in the neurectoderm during ocular development. Surprisingly, and despite a sophisticated pattern of RA-activity in the developing retina, we observed that RA signalling is not autonomously required in this tissue for eye formation. We show that the action of RA during eye morphogenesis is occurring specifically in neural crest-derived periocular mesenchyme and is mediated by all three RARs. Furthermore, we point out that Pitx2, which encodes a homeodomain transcription factor, is a key RA-responsive gene in neural crest cells during eye development. Interestingly, we observed that RA is required in the neural crest cells for normal position of the extraocular muscle.
| Dev Biol.
2008 Aug 1;320(1):140-8 | Abstract
Article complet | 268. Immunité antivirale chez la drosophile
Galiana-Arnoux, D., Deddouche, S. & Imler, J.L.
Abstract : Viral diseases represent a constant threat and an important cause of mortality worldwide. We have developed a model to study the response to RNA virus infection in the fruit-fly drosophila. This insect is a good model to study the genetic bases of innate immunity, which constitutes the first level of host-defense in animals. We have shown that viral infection in drosophila triggers a response different from that to bacterial or fungal infections. Our data at this stage point to the existence of at least two types of antiviral defense mechanisms. On one hand, viral infection triggers a JAK-STAT dependent transcriptional response that leads to the expression of antiviral molecules that remain to be characterized. On the other hand, viral RNAs are recognized by Dicer-2 and degraded in siRNAs, thus inducing RNA interference and degradation of viral RNAs. Strikingly, the drosophila antiviral response evokes by some aspects the interferon response in mammals (JAK-STAT pathway) and antiviral defenses in plants (RNA interference).
| J. Soc. Biol.
2007: Vol 201, 359-365 | Abstract
Article complet | 267. Crystal structure of Drosophila PGRP-SD suggests binding to DAP-type but not lysine-type peptidoglycan.
Leone P, Bischoff V, Kellenberger C, Hetru C, Royet J, Roussel A.
Abstract : In Drosophila the synthesis of antimicrobial peptides in response to microbial infections is under the control of the Toll and immune deficiency (Imd) signaling pathways. The Toll signaling pathway responds mainly to Gram-positive bacterial and fungal infection while the Imd pathway mediates the response to Gram-negative bacteria. Microbial recognition upstream of Toll involves, at least in part, peptidoglycan recognition proteins (PGRPs). The sensing of Gram-positive bacteria is mediated by the pattern recognition receptors PGRP-SA and Gram-negative binding protein 1 (GNBP1) that cooperate to detect the presence of lysine-type peptidoglycan in the host. Recently it has been shown that a loss-of-function mutation in peptidoglycan recognition protein SD (PGRP-SD) severely exacerbates the PGRP-SA and GNBP1 mutant phenotypes. Here we have solved the crystal structure of PGRP-SD at 1.5A resolution. Comparison with available structures of PGRPs in complex with their peptidoglycan (PGN) ligand strongly suggests a diaminopimelic acid (DAP) specificity for PGRP-SD. This result is supported by pull-down assays with insoluble PGNs. In addition we show that Toll pathway activation after infection by DAP-type PGN containing bacteria is clearly reduced in PGRP-SD mutant flies. Our hypothesis is that the role of PGRP-SD is the recognition of DAP-type PGNs responsible for the activation of the Toll pathway by Gram-negative bacteria.
| Mol Immunol.
2008 May;45(9):2521-30 | Abstract
Article complet | 266. Reverse genetics analysis of antiparasitic responses in the malaria vector, Anopheles gambiae.
Blandin SA, Levashina EA.
Abstract : In Drosophila the synthesis of antimicrobial peptides in response to microbial infections is under the control of the Toll and immune deficiency (Imd) signaling pathways. The Toll signaling pathway responds mainly to Gram-positive bacterial and fungal infection while the Imd pathway mediates the response to Gram-negative bacteria. Microbial recognition upstream of Toll involves, at least in part, peptidoglycan recognition proteins (PGRPs). The sensing of Gram-positive bacteria is mediated by the pattern recognition receptors PGRP-SA and Gram-negative binding protein 1 (GNBP1) that cooperate to detect the presence of lysine-type peptidoglycan in the host. Recently it has been shown that a loss-of-function mutation in peptidoglycan recognition protein SD (PGRP-SD) severely exacerbates the PGRP-SA and GNBP1 mutant phenotypes. Here we have solved the crystal structure of PGRP-SD at 1.5 ? resolution. Comparison with available structures of PGRPs in complex with their peptidoglycan (PGN) ligand strongly suggests a diaminopimelic acid (DAP) specificity for PGRP-SD. This result is supported by pull-down assays with insoluble PGNs. In addition we show that Toll pathway activation after infection by DAP-type PGN containing bacteria is clearly reduced in PGRP-SD mutant flies. Our hypothesis is that the role of PGRP-SD is the recognition of DAP-type PGNs responsible for the activation of the Toll pathway by Gram-negative bacteria.
| Methods Mol Biol
2008;415:365-77 | Abstract
Article complet | 265. Akirins are highly conserved nuclear proteins required for NF-kappaB-dependent gene expression in Drosophila and mice
Goto A, Matsushita K, Gesellchen V, El Chamy L, Kuttenkeuler D, Takeuchi O, Hoffmann JA, Akira S, Boutros M, Reichhart JM
Abstract : During a genome-wide screen with RNA-mediated interference, we isolated CG8580 as a gene involved in the innate immune response of Drosophila melanogaster. CG8580, which we called Akirin, encoded a protein that acted in parallel with the NF-kappaB transcription factor downstream of the Imd pathway and was required for defense against Gram-negative bacteria. Akirin is highly conserved, and the human genome contains two homologs, one of which was able to rescue the loss-of-function phenotype in drosophila cells. Akirins were strictly localized to the nucleus. Knockout of both Akirin homologs in mice showed that one had an essential function downstream of the Toll-like receptor, tumor necrosis factor and interleukin (IL)-1beta signaling pathways leading to the production of IL-6. Thus, Akirin is a conserved nuclear factor required for innate immune responses.
| Nature Immunology
2008 : Vol 9, 97-104 | Abstract
Article complet | 264. ATP-sensitive potassium channels mediate survival during infection in mammals and insects
Croker B, Crozat K, Berger M, Xia Y, Sovath S, Schaffer L, Eleftherianos I, Imler JL, Beutler B
Abstract : Specific homeostatic mechanisms confer stability in innate immune responses, preventing injury or death from infection. Here we identify, from a screen of N-ethyl-N-nitrosourea-mutagenized mice, a mutation causing both profound susceptibility to infection by mouse cytomegalovirus and approximately 20,000-fold sensitization to lipopolysaccharide (LPS), poly(I.C) and immunostimulatory (CpG) DNA. The LPS hypersensitivity phenotype is not suppressed by mutations in Myd88, Trif, Tnf, Tnfrsf1a, Ifnb, Ifng or Stat1, genes contributing to LPS responses, and results from an abnormality extrinsic to hematopoietic cells. The phenotype is due to a null allele of Kcnj8, encoding Kir6.1, a protein that combines with SUR2 to form an ATP-sensitive potassium channel (K(ATP)) expressed in coronary artery smooth muscle and endothelial cells. In Drosophila melanogaster, suppression of dSUR by RNA interference similarly causes hypersensitivity to infection by flock house virus. Thus, K(ATP) evolved to serve a homeostatic function during infection, and in mammals it prevents coronary artery vasoconstriction induced by cytokines dependent on TLR and/or MDA5 immunoreceptors.
| Nature Genetics
2007: Vol 39, 1453-1460 | Abstract
Article complet | 263. A Model of Bacterial Intestinal Infections in Drosophila melanogaster
Nehme NT, Liégeois S, Kele B, Giammarinaro P, Pradel E, Hoffmann J, Ewbank JJ, and Ferrandon D
Abstract : Serratia marcescens is an entomopathogenic bacterium that opportunistically infects a wide range of hosts, including humans. In a model of septic injury, if directly introduced into the body cavity of Drosophila, this pathogen is insensitive to the host's systemic immune response and kills flies in a day. We find that S. marcescens resistance to the Drosophila immune deficiency (imd)-mediated humoral response requires the bacterial lipopolysaccharide O-antigen. If ingested by Drosophila, bacteria cross the gut and penetrate the body cavity. During this passage, the bacteria can be observed within the cells of the intestinal epithelium. In such an oral infection model, the flies succumb to infection only after 6 days. We demonstrate that two complementary host defense mechanisms act together against such food-borne infection: an antimicrobial response in the intestine that is regulated by the imd pathway and phagocytosis by hemocytes of bacteria that have escaped into the hemolymph. Interestingly, bacteria present in the hemolymph elicit a systemic immune response only when phagocytosis is blocked. Our observations support a model wherein peptidoglycan fragments released during bacterial growth activate the imd pathway and do not back a proposed role for phagocytosis in the immune activation of the fat body. Thanks to the genetic tools available in both host and pathogen, the molecular dissection of the interactions between S. marcescens and Drosophila will provide a useful paradigm for deciphering intestinal pathogenesis.
| PloS Pathog
2007: | Abstract
Article complet | 262. The Drosophila systemic immune response : sensing and signalling during bactrial and fungal infections
Ferrandon D, Imler JL, Hetru C, Hoffmann JA
Abstract : A hallmark of the potent, multifaceted antimicrobial defence of Drosophila melanogaster is the challenge-induced synthesis of several families of antimicrobial peptides by cells in the fat body. The basic mechanisms of recognition of various types of microbial infections by the adult fly are now understood, often in great detail. We have further gained valuable insight into the infection-induced gene reprogramming by nuclear factor-kappaB (NF-kappaB) family members under the dependence of complex intracellular signalling cascades. The striking parallels between the adult fly response and mammalian innate immune defences described below point to a common ancestry and validate the relevance of the fly defence as a paradigm for innate immunity.
| Nature Reviews of Immunology
2007 : Vol 7, 862-874 | Abstract
Article complet | 261. Ubiquitin-proteasome : pallbeare carries the deceased to the grave
Ferrandon D
Abstract : Phagocytosis is a complex process that involves multiple cellular functions. In this issue of Immunity, Silva et al. (2007) report that a protein ubiquitylation complex and the proteasome are required for the clearance of apoptotic cells in Drosophila.
| Immunity
2007 : Vol 27, 541-544 | Abstract
Article complet | 260. Phagocytosis in mosquito immune responses
Blandin SA, Levashina EA
Abstract : Anopheles mosquitoes are the only vectors of human malaria parasites. Mosquito-parasite interactions are critical for disease transmission and therefore are a potential target for malaria control strategies. Mosquitoes mount potent immune responses that efficiently limit proliferation of a variety of infectious agents, including microbial pathogens and malaria parasites. The recent completion of the Anopheles gambiae genome sequencing project combined with the development of the powerful RNA interference-based gene silencing helped to identify major players of the immune defenses and uncovered evolutionarily conserved mechanisms in the anti-bacterial and anti-Plasmodium responses. The anti-bacterial responses are based on phagocytosis at early steps of infections, followed, several hours later, by the synthesis of anti-microbial peptides. The principal regulators of anti-parasitic responses are predominantly synthesized by the mosquito blood cells; however, the exact molecular mechanisms of parasite killing remain unclear. Several regulators of phagocytosis are also required for efficient parasite killing. Here, we summarize our current knowledge of the anti-bacterial and anti-parasitic responses, with the particular emphasis on the role of phagocytosis in mosquito immunity.
| Immunological Reviews
2007 : Vol 219, 8-16 | Abstract
Article complet | 259. Genetic analysis of resistance to viral infection
Beutler B, Eidenschenk C, Crozat K, Imler JL, Takeuchi O, Hoffmann JA, Akira S
Abstract : As machines that reprogramme eukaryotic cells to suit their own purposes, viruses present a difficult problem for multicellular hosts, and indeed, have become one of the central pre-occupations of the immune system. Unable to permanently outpace individual viruses in an evolutionary footrace, higher eukaryotes have evolved broadly active mechanisms with which to sense viruses and suppress their proliferation. These mechanisms have recently been elucidated by a combination of forward and reverse genetic methods. Some of these mechanisms are clearly ancient, whereas others are relatively new. All are remarkably adept at discriminating self from non-self, and allow the host to cope with what might seem an impossible predicament.
| Nature Reviews of Immunology
2007 : Vol 7, 753-766 | Abstract
Article complet | 258. New mechanism for detection of infections using the innate immune system of animals
Ferrandon D, Gottar M, Gobert V.
Abstract :
| Med Sci (Paris)
2007 Aug-Sep;23(8-9):707-9. | Abstract
Article complet | 257. Dicing with viruses : microRNAs as antiviral factors
Müller, S. & Imler, J.L
Abstract : In plants and invertebrates, Dicer genes play a critical role against infections by RNA viruses. In this issue, Otsuka et al. (2007) report that Dicer mutant mice are hypersusceptible to infection by the RNA virus VSV.
| Immunity
2007: Vol 27, 123-134 | Abstract
Article complet | 256. Structural basis for conserved complement factor-like function in the antimalarial protein TEP1 (2007)
Baxter RH, Chang CI, Chelliah Y, Blandin S, Levashina EA, Deisenhofer J
Abstract : Thioester-containing proteins (TEPs) are a major component of the innate immune response of insects to invasion by bacteria and protozoa. TEPs form a distinct clade of a superfamily that includes the pan-protease inhibitors alpha2-macroglobulins and vertebrate complement factors. The essential feature of these proteins is a sequestered thioester bond that, after cleavage in a protease-sensitive region of the protein, is activated and covalently binds to its target. Recently, TEP1 from the malarial vector Anopheles gambiae was shown to mediate recognition and killing of ookinetes from the malarial parasite Plasmodium berghei, a model for the human malarial parasite Plasmodium falciparum. Here, we present the crystal structure of the TEP1 isoform TEP1r. Although the overall protein fold of TEP1r resembles that of complement factor C3, the TEP1r domains are repositioned to stabilize the inactive conformation of the molecule (containing an intact thioester) in the absence of the anaphylotoxin domain, a central component of complement factors. The structure of TEP1r provides a molecular basis for the differences between TEP1 alleles TEP1r and TEP1s, which correlate with resistance of A. gambiae to infection by P. berghei.
| Proc. Natl. Acad. Sci. USA
2007 : Vol 104, 11615-11620 | Abstract
Article complet | 255. Structural basis for conserved complement factor-like function in the antimalarial protein TEP1
Baxter RH, Chang CI, Chelliah Y, Blandin S, Levashina EA, Deisenhofer J.
Abstract : Thioester-containing proteins (TEPs) are a major component of the innate immune response of insects to invasion by bacteria and protozoa. TEPs form a distinct clade of a superfamily that includes the pan-protease inhibitors α2-macroglobulins and vertebrate complement factors. The essential feature of these proteins is a sequestered thioester bond that, after cleavage in a protease-sensitive region of the protein, is activated and covalently binds to its target. Recently, TEP1 from the malarial vector Anopheles gambiae was shown to mediate recognition and killing of ookinetes from the malarial parasite Plasmodium berghei, a model for the human malarial parasite Plasmodium falciparum. Here, we present the crystal structure of the TEP1 isoform TEP1r. Although the overall protein fold of TEP1r resembles that of complement factor C3, the TEP1r domains are repositioned to stabilize the inactive conformation of the molecule (containing an intact thioester) in the absence of the anaphylotoxin domain, a central component of complement factors. The structure of TEP1r provides a molecular basis for the differences between TEP1 alleles TEP1r and TEP1s, which correlate with resistance of A. gambiae to infection by P. berghei.
| Proc Natl Acad Sci U S A
2007 Jul 10;104(28):11615-20 | Abstract
Article complet | 254. Evolutionary dynamics of immune-related genes and pathways in disease-vector mosquitoes
Waterhouse RM, Kriventseva EV, Meister S, Xi Z, Alvarez KS, Bartholomay LC, Barillas-Mury C, Bian G, Blandin S, Christensen BM, Dong Y, Jiang H, Kanost MR, Koutsos AC, Levashina EA, Li J, Ligoxygakis P, Maccallum RM, Mayhew GF, Mendes A, Michel K, Osta MA, Paskewitz S, Shin SW, Vlachou D, Wang L, Wei W, Zheng L, Zou Z, Severson DW, Raikhel AS, Kafatos FC, Dimopoulos G, Zdobnov EM, Christophides GK
Abstract : Mosquitoes are vectors of parasitic and viral diseases of immense importance for public health. The acquisition of the genome sequence of the yellow fever and Dengue vector, Aedes aegypti (Aa), has enabled a comparative phylogenomic analysis of the insect immune repertoire: in Aa, the malaria vector Anopheles gambiae (Ag), and the fruit fly Drosophila melanogaster (Dm). Analysis of immune signaling pathways and response modules reveals both conservative and rapidly evolving features associated with different functional gene categories and particular aspects of immune reactions. These dynamics reflect in part continuous readjustment between accommodation and rejection of pathogens and suggest how innate immunity may have evolved.
| Science
2007: Vol 316, 1738-1743. | Abstract
Article complet | 253. Antifungal defense in Drosophila
Hoffmann JA
Abstract :
| Nature Immunology
2007 : Vol 8, 543-545 | Abstract
Article complet | 252. Role of the Spatzle Pro-domain in the generation of an active toll receptor ligand
Weber AN, Gangloff M, Moncrieffe MC, Hyvert Y, Imler JL, Gay NJ
Abstract : The cytokine Spätzle is the ligand for Drosophila Toll, the prototype of an important family of membrane receptors that function in embryonic patterning and innate immunity. A dimeric precursor of Spätzle is processed by an endoprotease to produce a form (C-106) that cross-links Toll receptor ectodomains and establishes signaling. Here we show that before processing the pro-domain of Spätzle is required for correct biosynthesis and secretion. We mapped two loss-of-function mutations of Spätzle to a discrete site in the pro-domain and showed that the phenotype arises because of a defect in biosynthesis rather than signaling. We also report that the pro-domain and C-106 remain associated after cleavage and that this processed complex signals with the same characteristics as the C-terminal fragment. These results suggest that before activation the determinants on C-106 that bind specifically to Toll are sequestered by the pro-domain and that proteolytic processing causes conformational rearrangements that expose these determinants and enables binding to Toll. Furthermore, we show that the pro-domain is released when the Toll extracellular domain binds to the complex, a finding that has implications for the generation of a signaling-competent Toll dimer.
| J. Biol. Chem.
2007: Vol 282, 13522-13531 | Abstract
Article complet | 251. The host defense of Drosophila melanogaster
Lemaitre B, Hoffmann JA
Abstract : To combat infection, the fruit fly Drosophila melanogaster relies on multiple innate defense reactions, many of which are shared with higher organisms. These reactions include the use of physical barriers together with local and systemic immune responses. First, epithelia, such as those beneath the cuticle, in the alimentary tract, and in tracheae, act both as a physical barrier and local defense against pathogens by producing antimicrobial peptides and reactive oxygen species. Second, specialized hemocytes participate in phagocytosis and encapsulation of foreign intruders in the hemolymph. Finally, the fat body, a functional equivalent of the mammalian liver, produces humoral response molecules including antimicrobial peptides. Here we review our current knowledge of the molecular mechanisms underlying Drosophila defense reactions together with strategies evolved by pathogens to evade them.
| Annual Review of Immunology
2007 : Vol 25, 697-743 | Abstract
Article complet | 250. Genes required for osmoregulation and apical secretion in Caenorhabditis elegans
Liégeois S, Benedetto A, Michaux G, Belliard G, Labouesse M.
Abstract : Few studies have investigated whether or not there is an interdependence between osmoregulation and vesicular trafficking. We previously showed that in Caenorhabditis elegans che-14 mutations affect osmoregulation, cuticle secretion, and sensory organ development. We report the identification of seven lethal mutations displaying che-14-like phenotypes, which define four new genes, rdy-1–rdy-4 (rod-like larval lethality and dye-filling defective). rdy-1, rdy-2, and rdy-4 mutations affect excretory canal function and cuticle formation. Moreover, rdy-1 and rdy-2 mutations reduce the amount of matrix material normally secreted by sheath cells in the amphid channel. In contrast, rdy-3 mutants have short cystic excretory canals, suggesting that it acts in a different process. rdy-1 encodes the vacuolar H+-ATPase a-subunit VHA-5, whereas rdy-2 encodes a new tetraspan protein. We suggest that RDY-1/VHA-5 acts upstream of RDY-2 and CHE-14 in some tissues, since it is required for their delivery to the epidermal, but not the amphid sheath, apical plasma membrane. Hence, the RDY-1/VHA-5 trafficking function appears essential in some cells and its proton pump function essential in others. Finally, we show that RDY-1/VHA-5 distribution changes prior to molting in parallel with that of actin microfilaments and propose a model for molting whereby actin provides a spatial cue for secretion.
| Genetics
2007 February; 175(2): 709–724 | Abstract
Article complet | 249. Drosophila Serpins: Regulatory Cascades in Innate Immunity and Morphogenesis in
Gubb D, Robertson A, Dafforn T, Troxler L, Reichhart JM
Abstract :
| Ed. by Silverman GA and Lomas DA, World Scientific Pub., London UK
2007, Chapter 8, p 207-227 | Abstract
Article complet | 248. Innate immunity of insects to infection
Dostert, C., Galiana-Arnoux, D. & Imler, J.L.
Abstract :
| in "Virology and the Honey Bee", Editors : M. Aubert, B. Ball, I. Fries, R. Moritz, N. Milani, I. Bernardelli. European Commission.
2007: p. 311-346. | Abstract
Article complet | 247. Dual Detection of Fungal Infections in Drosophila via Recognition of Glucans and Sensing of Virulence Factors
Gottar M, Gobert V, Matskevich AA, Reichhart JM, Wang C, Butt TM, Belvin M, Hoffmann JA, Ferrandon D
Abstract : The Drosophila immune system discriminates between various types of infections and activates appropriate signal transduction pathways to combat the invading microorganisms. The Toll pathway is required for the host response against fungal and most Gram-positive bacterial infections. The sensing of Gram-positive bacteria is mediated by the pattern recognition receptors PGRP-SA and GNBP1 that cooperate to detect the presence of infections in the host. Here, we report that GNBP3 is a pattern recognition receptor that is required for the detection of fungal cell wall components. Strikingly, we find that there is a second, parallel pathway acting jointly with GNBP3. The Drosophila Persephone protease activates the Toll pathway when proteolytically matured by the secreted fungal virulence factor PR1. Thus, the detection of fungal infections in Drosophila relies both on the recognition of invariant microbial patterns and on monitoring the effects of virulence factors on the host.
| Cell
2006: Vol 127, 1425-37. | Abstract
Article complet | 246. Fz2 and cdc42 mediate melanization and actin polymerization but are dispensable for Plasmodium killing in the mosquito midgut
Shiao SH, Whitten MM, Zachary D, Hoffmann JA, Levashina EA
Abstract : The midgut epithelium of the mosquito malaria vector Anopheles is a hostile environment for Plasmodium, with most parasites succumbing to host defenses. This study addresses morphological and ultrastructural features associated with Plasmodium berghei ookinete invasion in Anopheles gambiae midguts to define the sites and possible mechanisms of parasite killing. We show by transmission electron microscopy and immunofluorescence that the majority of ookinetes are killed in the extracellular space. Dead or dying ookinetes are surrounded by a polymerized actin zone formed within the basal cytoplasm of adjacent host epithelial cells. In refractory strain mosquitoes, we found that formation of this zone is strongly linked to prophenoloxidase activation leading to melanization. Furthermore, we identify two factors controlling both phenomena: the transmembrane receptor frizzled-2 and the guanosine triphosphate-binding protein cell division cycle 42. However, the disruption of actin polymerization and melanization by double-stranded RNA inhibition did not affect ookinete survival. Our results separate the mechanisms of parasite killing from subsequent reactions manifested by actin polymerization and prophenoloxidase activation in the A. gambiae-P. berghei model. These latter processes are reminiscent of wound healing in other organisms, and we propose that they represent a form of wound-healing response directed towards a moribund ookinete, which is perceived as damaged tissue.
| PLoS Pathog.
2006: Vol 2, 1152-1164 | Abstract
Article complet | 245. Boosting NF-κB-Dependent Basal Immunity of Anopheles gambiae Aborts Development of Plasmodium berghei
Frolet C, Thoma M, Blandin S, Hoffmann JA, Levashina EA
Abstract : Anopheles gambiae, the major vector for the protozoan malaria parasite Plasmodium falciparum, mounts powerful antiparasitic responses that cause marked parasite loss during midgut invasion. Here, we showed that these antiparasitic defenses were composed of pre- and postinvasion phases and that the preinvasion phase was predominantly regulated by Rel1 and Rel2 members of the NF-kappaB transcription factors. Concurrent silencing of Rel1 and Rel2 decreased the basal expression of the major antiparasitic genes TEP1 and LRIM1 and abolished resistance of Anopheles to the rodent malaria parasite P. berghei. Conversely, depletion of a negative regulator of Rel1, Cactus, prior to infection, enhanced the basal expression of TEP1 and of other immune factors and completely prevented parasite development. Our findings uncover the crucial role of the preinvasion defense in the elimination of parasites, which is at least in part based on circulating blood molecules.
| Immunity
2006: Vol 25, 677-85. | Abstract
Article complet | 244. Immune pathways and defence mechanisms in honey bees Apis mellifera
Evans JD, Aronstein K, Chen YP, Hetru C, Imler JL, Jiang H, Kanost M, Thompson GJ, Zou Z, Hultmark D.
Abstract : Social insects are able to mount both group-level and individual defences against pathogens. Here we focus on individual defences, by presenting a genome-wide analysis of immunity in a social insect, the honey bee Apis mellifera. We present honey bee models for each of four signalling pathways associated with immunity, identifying plausible orthologues for nearly all predicted pathway members. When compared to the sequenced Drosophila and Anopheles genomes, honey bees possess roughly one-third as many genes in 17 gene families implicated in insect immunity. We suggest that an implied reduction in immune flexibility in bees reflects either the strength of social barriers to disease, or a tendency for bees to be attacked by a limited set of highly coevolved pathogens.
| Insect Mol Biol
2006: Vol 15, 645-56. | Abstract
Article complet | 243. Prophenoloxidase activation is not required for survival to microbial infections in Drosophila
Leclerc V, Pelte, N, El Chamy L, Martinelli C, Ligoxygakis P, Hoffmann JA and Reichhart JM
Abstract : he antimicrobial defence of Drosophila relies on cellular and humoral processes, of which the inducible synthesis of antimicrobial peptides has attracted interest in recent years. Another potential line of defence is the activation, by a proteolytic cascade, of phenoloxidase, which leads to the production of quinones and melanin. However, in spite of several publications on this subject, the contribution of phenoloxidase activation to resistance to infections has not been established under appropriate in vivo conditions. Here, we have isolated the first Drosophila mutant for a prophenoloxidase-activating enzyme (PAE1). In contrast to wild-type flies, PAE1 mutants fail to activate phenoloxidase in the haemolymph following microbial challenge. Surprisingly, we find that these mutants are as resistant to infections as wild-type flies, in the total absence of circulating phenoloxidase activity. This raises the question with regard to the precise function of phenoloxidase activation in defence, if any.
| EMBO Rep
2006 : (2):231-5 | Abstract
Article complet | 242. Weckle is a zinc finger adaptor of the toll pathway in dorsoventral patterning of the Drosophila embryo
Chen LY, Wang JC, Hyvert Y, Lin HP, Perrimon N, Imler JL, Hsu JC
Abstract : The Drosophila Toll pathway takes part in both establishment of the embryonic dorsoventral axis and induction of the innate immune response in adults. Upon activation by the cytokine Spatzle, Toll interacts with the adaptor proteins DmMyD88 and Tube and the kinase Pelle and triggers degradation of the inhibitor Cactus, thus allowing the nuclear translocation of the transcription factor Dorsal/Dif. weckle (wek) was previously identified as a new dorsal group gene that encodes a putative zinc finger transcription factor. However, its role in the Toll pathway was unknown. RESULTS: Here, we isolated new wek alleles and demonstrated that cactus is epistatic to wek, which in turn is epistatic to Toll. Consistent with this, Wek localizes to the plasma membrane of embryos, independently of Toll signaling. Wek homodimerizes and associates with Toll. Moreover, Wek binds to and localizes DmMyD88 to the plasma membrane. Thus, Wek acts as an adaptor to assemble/stabilize a Toll/Wek/DmMyD88/Tube complex. Remarkably, unlike the DmMyD88/tube/pelle/cactus gene cassette of the Toll pathway, wek plays a minimal role, if any, in the immune defense against Gram-positive bacteria and fungi. Conclusions: We conclude that Wek is an adaptor to link Toll and DmMyD88 and is required for efficient recruitment of DmMyD88 to Toll. Unexpectedly, wek is dispensable for innate immune response, thus revealing differences in the Toll-mediated activation of Dorsal in the embryo and Dif in the fat body of adult flies.
| Curr. Biol.
2006: Vol 16, 1183-93. | Abstract
Article complet | 241. The V0-ATPase mediates apical secretion of exosomes containing Hedgehog-related proteins in Caenorhabditis elegans
Liégeois S = Benedetto A, Garnier JM, Schwab Y, and Labouesse M
Abstract : Polarized intracellular trafficking in epithelia is critical in development, immunity, and physiology to deliver morphogens, defensins, or ion pumps to the appropriate membrane domain. The mechanisms that control apical trafficking remain poorly defined. Using Caenorhabditis elegans, we characterize a novel apical secretion pathway involving multivesicularbodies and the release of exosomes at the apical plasma membrane. By means of two different genetic approaches, we show that the membrane-bound V0 sector of the vacuolar H+-ATPase (V-ATPase) acts in this pathway, independent of its contribution to the V-ATPase proton pump activity. Specifically, we identified mutations in the V0 “a” subunit VHA-5 that affect either the V0-specific function or the V0+V1 function of the V-ATPase. These mutations allowed us to establish that the V0 sector mediates secretion of Hedgehog-related proteins. Our data raise the possibility that the V0 sector mediates exosome and morphogen release in mammals.
| J Cell Biol
2006 June 19; 173(6): 949–961 | Abstract
Article complet | 240. Toll-like receptors and innate antiviral immunity
Galiana-Arnoux D, Imler JL
Abstract : Abstract Viral infections are first detected by a set of innate immunity receptors that detect primary infections by pathogens, and trigger a transcriptional response. Among the induced target genes, type I interferons (IFNs) are central to the antiviral response of the host. The receptors and signaling pathways that mediate the strong induction of the synthesis of these cytokines have long remained elusive. In the past few years, Toll-like receptors (TLRs) emerged as important sensors of infections. Several TLRs participate in the recognition of virus infection, interacting in particular with viral nucleic acids. Upon activation, TLRs interact with different cytosolic adapter molecules and activate transcription factors of the nuclear factor-kappaB and IFN regulatory factor families that concur to mediate induction of IFN-alpha/beta and other inflammatory cytokines. In addition to the transmembrane TLRs, cytosolic helicases also detect viral nucleic acids, and trigger type I IFN synthesis.
| Tissus Antigens
2006: Vol 4, 267-276 | Abstract
Article complet | 239. Mosquito midguts and malaria: cell biology, compartmentalization and immunology
Whitten MM, Shiao SH, Levashina EA
Abstract : The malaria parasite Plasmodium has an absolute requirement for both a vertebrate and a mosquito host in order to complete its life cycle, and its interactions with the latter provide the focus for this review. The mosquito midgut represents one of the most challenging environments for the survival and development of Plasmodium, and is thus also one of the most attractive sites for novel targeted malaria control strategies. During their attempts to cross the midgut epithelium en route to the salivary glands, motile ookinetes are swiftly detected and labelled by mosquito recognition factors and targeted for destruction by a variety of immune responses that recruit killing factors both from the midgut and from other tissues in the surrounding body cavity. The exact interplay between these factors and the parasite is highly species- and strain-specific, as are the timing and the route of parasite invasion. These features are paramount to determining the success of the infection and the vector competence of the mosquito. Here we discuss recent advances in genomic analyses, coupled with detailed microscopical investigations, which are helping to unravel the identity and roles of the major players of these complex systems.
| Parasite Immunol.
2006: Vol 4, 121-130 | Abstract
Article complet | 238. Immune response of Drosophila
Imler JL
Abstract : Interview.
| Mod. Asp. of Immunobiol
2006: Vol 18, 8 | Abstract
Article complet | 237. Essential function in vivo for Dicer-2 in host defense against RNA viruses in drosophila
Galiana-Arnoux D, Dostert C, Schneemann A, Hoffmann JA, Imler JL
Abstract : The fruit fly Drosophila melanogaster is a model system for studying innate immunity, including antiviral host defense. Infection with drosophila C virus triggers a transcriptional response that is dependent in part on the Jak kinase Hopscotch. Here we show that successful infection and killing of drosophila with the insect nodavirus flock house virus was strictly dependent on expression of the viral protein B2, a potent inhibitor of processing of double-stranded RNA mediated by the essential RNA interference factor Dicer. Conversely, flies with a loss-of-function mutation in the gene encoding Dicer-2 (Dcr-2) showed enhanced susceptibility to infection by flock house virus, drosophila C virus and Sindbis virus, members of three different families of RNA viruses. These data demonstrate the importance of RNA interference for controlling virus replication in vivo and establish Dcr-2 as a host susceptibility locus for virus infections.
| Nature Immunology
2006: Vol 7, 590 - 597 | Abstract
Article complet | 236. The hedgehog-related gene qua-1 is required for molting in Caenorhabditis elegans
Hao L, Liégeois S, Mukherjee K, Baillie D, Labouesse M, Burglin TR
Abstract : The Caenorhabditis elegans genome encodes ten proteins that share similarity with Hedgehog through the C-terminal Hint/Hog domain. While most genes are members of larger gene families, qua-1 is a single copy gene. Here we show that orthologs of qua-1 exist in many nematodes, including Brugia malayi, which shared a common ancestor with C. elegans about 300 million years ago. The QUA-1 proteins contain an N-terminal domain, the Qua domain, that is highly conserved, but whose molecular function is not known. We have studied the expression pattern of qua-1 in C. elegans using a qua-1::GFP transcriptional fusion. qua-1 is mainly expressed in hyp1 to hyp11 hypodermal cells, but not in seam cells. It is also expressed in intestinal and rectal cells, sensilla support cells, and the P cell lineage in L1. The expression of qua-1::GFP undergoes cyclical changes during development in phase with the molting cycle. It accumulates prior to molting and disappears between molts. Disruption of the qua-1 gene function through an internal deletion that causes a frame shift with premature stop in the middle of the gene results in strong lethality. The animals arrest in the early larval stages due to defects in molting. Electron microscopy reveals double cuticles due to defective ecdysis, but no obvious defects are seen in the hypodermis. Qua domain-only::GFP and full-length QUA-1::GFP fusion constructs are secreted and associated with the overlying cuticle, but only QUA-1::GFP rescues the mutant phenotype. Our results suggest that both the Hint/Hog domain and Qua domain are critically required for the function of QUA-1.
| Dev Dyn
2006: Vol 235, Issue 6, p 1469–1481 | Abstract
Article complet | 235. Prophenoloxidase activation is not required for survival to microbial infections in Drosophila
Leclerc V, Pelte N, ElChamy L, Martinelli C, Ligoxygakis P, Hoffmann JA, Reichhart JM
Abstract : The antimicrobial defence of Drosophila relies on cellular and humoral processes, of which the inducible synthesis of antimicrobial peptides has attracted interest in recent years. Another potential line of defence is the activation, by a proteolytic cascade, of phenoloxidase, which leads to the production of quinones and melanin. However, in spite of several publications on this subject, the contribution of phenoloxidase activation to resistance to infections has not been established under appropriate in vivo conditions. Here, we have isolated the first Drosophila mutant for a prophenoloxidase-activating enzyme (PAE1). In contrast to wild-type flies, PAE1 mutants fail to activate phenoloxidase in the haemolymph following microbial challenge. Surprisingly, we find that these mutants are as resistant to infections as wild-type flies, in the total absence of circulating phenoloxidase activity. This raises the question with regard to the precise function of phenoloxidase activation in defence, if any.
| EMBO Reports
2006: Vol 7, 231-235 | Abstract
Article complet | 234. Downregulation of the Drosophila Immune Response by Peptidoglycan-Recognition Proteins SC1 and SC2
Bischoff V, Vignal C, Duvic B, Boneca IG, Hoffmann JA, Royet J
Abstract : Peptidoglycan-recognition proteins (PGRPs) are evolutionarily conserved molecules that are structurally related to bacterial amidases. Several Drosophila PGRPs have lost this enzymatic activity and serve as microbe sensors through peptidoglycan recognition. Other PGRP family members, such as Drosophila PGRP-SC1 or mammalian PGRP-L, have conserved the amidase function and are able to cleave peptidoglycan in vitro. However, the contribution of these amidase PGRPs to host defense in vivo has remained elusive so far. Using an RNA-interference approach, we addressed the function of two PGRPs with amidase activity in the Drosophila immune response. We observed that PGRP-SC1/2-depleted flies present a specific over-activation of the IMD (immune deficiency) signaling pathway after bacterial challenge. Our data suggest that these proteins act in the larval gut to prevent activation of this pathway following bacterial ingestion. We further show that a strict control of IMD-pathway activation is essential to prevent bacteria-induced developmental defects and larval death.
| PLoS Pathog
2006: Vol 2, 139-147 | Abstract
Article complet | 233. Insight into social insects from the genome of the honeybee
The Honeybee Genome Sequencing Consortium
Abstract : Here we report the genome sequence of the honeybee Apis mellifera, a key model for social behaviour and essential to global ecology through pollination. Compared with other sequenced insect genomes, the A. mellifera genome has high A+T and CpG contents, lacks major transposon families, evolves more slowly, and is more similar to vertebrates for circadian rhythm, RNA interference and DNA methylation genes, among others. Furthermore, A. mellifera has fewer genes for innate immunity, detoxification enzymes, cuticle-forming proteins and gustatory receptors, more genes for odorant receptors, and novel genes for nectar and pollen utilization, consistent with its ecology and social organization. Compared to Drosophila, genes in early developmental pathways differ in Apis, whereas similarities exist for functions that differ markedly, such as sex determination, brain function and behaviour. Population genetics suggests a novel African origin for the species A. mellifera and insights into whether Africanized bees spread throughout the New World via hybridization or displacement.
| Nature
2006: Vol 443, 931-949 | Abstract
Article complet | 232. Immune challenge induces N-terminal cleavage of the Drosophila serpin Necrotic
Pelte N, Robertson AS, Zou Z, Belorgey D, Dafforn TR, Jiang H, Lomas D, Reichhart JM, Gubb D
Abstract : The Drosophila Necrotic protein is a serine proteinase inhibitor, which regulates the Toll-mediated innate immune response. Necrotic specifically inhibits an extracellular serine proteinase cascade leading to activation of the Toll ligand, Spatzle. Necrotic carries a polyglutamine extension amino-terminal to the core serpin structure. We show here that cleavage of this N-terminal extension occurs following immune challenge. This modification is blocked in PGRP-SA(semmelweiss) mutants after Gram-positive bacterial challenge and in persephone mutants after fungal or Gram-positive bacterial challenge, indicating that activation of either of the Toll pathway upstream branches induces N-terminal cleavage of the serpin. The absolute requirement of persephone gene product for this cleavage indicates that Gram-positive bacteria activate a redundant set of proteinases upstream of Toll. Both full-length Necrotic and the core serpin are active inhibitors of a range of serine proteinases: the highest affinity being for cathepsin G and elastases. We found a 13-fold increase in the specificity of the core serpin over that of full-length Necrotic for one of the tested proteinases (porcine pancreatic elastase). This finding indicates that cleavage of the Necrotic amino-terminal extension might modulate Toll activation following the initial immune response.
| Insect Biochem. Mol. Biol.
2006: Vol 1, 37-46 | Abstract
Article complet | 231. The Jak-STAT signaling pathway is required but not sufficient for the antiviral response of Drosophila
Dostert C, Jouanguy E, Irving P, Troxler L, Galiana-Arnoux D, Hetru C, Hoffmann JA, Imler JL
Abstract : The response of drosophila to bacterial and fungal infections involves two signaling pathways, Toll and Imd, which both activate members of the transcription factor NF-kappaB family. Here we have studied the global transcriptional response of flies to infection with drosophila C virus. Viral infection induced a set of genes distinct from those regulated by the Toll or Imd pathways and triggered a signal transducer and activator of transcription (STAT) DNA-binding activity. Genetic experiments showed that the Jak kinase Hopscotch was involved in the control of the viral load in infected flies and was required but not sufficient for the induction of some virus-regulated genes. Our results indicate that in addition to Toll and Imd, a third, evolutionary conserved innate immunity pathway functions in drosophila and counters viral infection.
| Nature Immunology
2005: Vol 6, 646-953 | Abstract
Article complet | 230. New insights into Drosophila larval hemocyte functions through genome-wide analysis
Irving P, Ubeda JM, Doucet D, Troxler L, Lagueux M, Zachary D, Hoffmann JA, Hetru C, Meister M
Abstract : Drosophila blood cells or haemocytes comprise three cell lineages, plasmatocytes, crystal cells and lamellocytes, involved in immune functions such as phagocytosis, melanisation and encapsulation. Transcriptional profiling of activities of distinct haemocyte populations and from naive or infected larvae, was performed to find genes contributing to haemocyte functions. Of the 13 000 genes represented on the microarray, over 2500 exhibited significantly enriched transcription in haemocytes. Among these were genes encoding integrins, peptidoglycan recognition proteins (PGRPs), scavenger receptors, lectins, cell adhesion molecules and serine proteases. One relevant outcome of this analysis was the gain of new insights into the lamellocyte encapsulation process. We showed that lamellocytes require betaPS integrin for encapsulation and that they transcribe one prophenoloxidase gene enabling them to produce the enzyme necessary for melanisation of the capsule. A second compelling observation was that following infection, the gene encoding the cytokine Spatzle was uniquely upregulated in haemocytes and not the fat body. This shows that Drosophila haemocytes produce a signal molecule ready to be activated through cleavage after pathogen recognition, informing distant tissues of infection.
| Cellular Microbiology
2005: Vol 7, 335-350 | Abstract
Article complet | 229. Sensing and Signaling during Infection in Drosophila
Royet J, Reichhart JM, Hoffmann JA
Abstract : Most of the progress in dissecting the Drosophila antimicrobial response over the past decade has centered around intracellular signaling pathways in immune response tissues and expression of genes encoding antimicrobial peptide genes. The past few years, however, have witnessed significant advances in our understanding of the recognition of microbial invaders and subsequent activation of signaling cascades. In particular, the roles of peptidoglycan recognition proteins, which have known homologues in mammals, have been recognized and examined at the structural and functional levels.
| Current Opinion in Immunology
2005: Vol 17, 11-17 | Abstract
Article complet | 228. Ligand-receptor and receptor-receptor interactions act in concert to activate the signalling in the Drosophila toll pathway
Weber AN, Moncrieffe MC, Gangloff M, Imler JL, Gay NJ
Abstract : No abstract.
| Journal of Biological Chemistry
2005: Vol 280, 22793-22799. | Abstract
Article complet | 227. Innate Immunity
Aderem A, Levashina EA
Abstract : No abstract.
| Current Opinion in Immunology
2005: Vol 17, 1-3 | Abstract
Article complet | 226. In vivo identification of novel regulators and conserved pathways of phagocytosis in A. gambiae
Moita LF, Wang-Sattler R, Michel K, Zimmermann T, Blandin S, Levashina EA, Kafatos FC
Abstract : Anopheles gambiae uses effective immune responses, including phagocytosis, to fight microbial infection. We have developed a semiquantitative phagocytosis test and used it in conjunction with dsRNA gene silencing to test the in vivo roles of 71 candidate genes in phagocytosis of Escherichia coli and Staphylococcus aureus. Here, we show that inactivation of 26 genes changes the phagocytic activity by more than 45% and that two pathways similar to those that mediate apoptotic cell removal in Caenorhabditis elegans are used in A. gambiae for phagocytosis of microorganisms. Simultaneous inactivation of the identified regulators of phagocytosis and conserved components defining each signaling pathway permitted provisional assignment of the novel regulators to one or the other pathway. Pathway inactivation enhances at least three times the ability of E. coli and S. aureus to proliferate in the mosquito. Interestingly, mosquito survival is not compromised even if both pathways are perturbed simultaneously.
| Immunity
2005: Vol 23, 65-73 | Abstract
Article complet | 225. Antimicrobial peptides in Drosophila: structures, activities and gene regulation
Imler JL, Bulet P
Abstract : The production of antimicrobial peptides (AMPs) is an important aspect of host-defence in multicellular organisms. Biochemical analysis of the hemolymph of the fruit-fly Drosophila melanogaster and other Diptera has led to the discovery of eight classes of AMPs. These peptides can be grouped into three families based on their main biological targets, gram-positive bacteria (defensin), gram-negative bacteria (cecropins, drosocin, attacins, diptericin, MPAC), or fungi (drosomycin, metchnikowin). Drosophila AMPs are synthesized by the fat body in response to infection, and secreted into the blood. Most of them can also be induced in surface epithelia in a tissue-specific manner. Finally, some of them are constitutively expressed in defined tissues, such as the salivary glands or the reproductive tract. We review here the structures and activities of these AMPs, as well as the signalling cascades, which lead to their induction upon detection of infectious non-self.
| Chem. Immunol. Allergy
2005: Vol 86, 1-21. Revue | Abstract
Article complet | 224. Evolution and integration of innate immune systems from fruit flies to man: lessons and questions
Martinelli C, Reichhart JM
Abstract : Despite broad differences in morphology, ecology and behavior, the fruit fly Drosophila melanogaster and humans show a remarkably high degree of conservation for many molecular, cellular, and developmental aspects of their biology. During the last decade, similarities have also been discovered in some of the mechanisms regulating their innate immune system. These parallels regard mainly the Toll-like receptor family and the intracellular signaling pathways involved in the control of the immune response. However, if the overall similarities are important, the detailed pathogen recognition mechanisms differ significantly between fly and humans, highlighting a complicated evolutionary history of the metazoan innate defenses. In this review, we will discuss the main similarities and differences between the two types of organisms. We hope that this current knowledge will be used as a starting point for a more comprehensive view of innate immunity within the broad variety of metazoan phyla.
| Journal of Endotoxin Research
2005: Vol 11, 243-8 | Abstract
Article complet | 223. Eater, a transmembrane protein mediating phagocytosis of bacterial pathogens in Drosophila
Kocks C, Cho JH, Nehme N, Ulvila J, Pearson AM, Meister M, Strom C, Conto SL, Hetru C, Stuart LM, Stehle T, Hoffmann JA, Reichhart JM, Ferrandon D, Ramet M, Ezekowitz RA
Abstract : Phagocytosis is a complex, evolutionarily conserved process that plays a central role in host defense against infection. We have identified a predicted transmembrane protein, Eater, which is involved in phagocytosis in Drosophila. Transcriptional silencing of the eater gene in a macrophage cell line led to a significant reduction in the binding and internalization of bacteria. Moreover, the N terminus of the Eater protein mediated direct microbial binding which could be inhibited with scavenger receptor ligands, acetylated, and oxidized low-density lipoprotein. In vivo, eater expression was restricted to blood cells. Flies lacking the eater gene displayed normal responses in NF-kappaB-like Toll and IMD signaling pathways but showed impaired phagocytosis and decreased survival after bacterial infection. Our results suggest that Eater is a major phagocytic receptor for a broad range of bacterial pathogens in Drosophila and provide a powerful model to address the role of phagocytosis in vivo.
| Cell
2005: Vol 123, 335-346 | Abstract
Article complet | 222. Tip of another iceberg: Drosophila serpins.
Reichhart JM
Abstract : Serpins are serine protease inhibitors with a conserved structure that have been identified in nearly all species and act as suicide substrates by binding covalently to their target proteases. Serpins regulate various physiological processes and defence mechanisms. In humans, several serpin mutations are linked to diseases. The genome of Drosophila melanogaster encodes 29 serpins and even more serine proteases. To date, three serpins have been investigated in detail. Spn27A controls the Toll pathway during early development and is involved in defence reactions in adult flies. SPN42DaA is an inhibitor of furin, a subtilisin-like convertase that is required for pro-protein maturation. Spn43Ac controls the Toll pathway during the immune response. In each case, Drosophila genetics has shed new light on the function of these serine protease inhibitors.
| Trends in Cell Biology
2005: Vol 123, 335-346 | Abstract
Article complet | 221. Is innate enough ? The innate immune response in Drosophila
Irving P, Troxler L, Hetru C
Abstract : In recent years, the innate immune system has emerged from the shadow of adaptive immune responses as a major area of research in its own right. One of the most significant model systems that has been used to investigate this phenomenon has been the fruit fly, Drosophila melanogaster. Exploration of the differential immune response presented by Drosophila led to the discovery of important signalling events and transduction pathways, which were thereafter shown to be specific for the type of infecting pathogen. These factors and pathways were subsequently found to have homologues in many other organisms, including those with adaptive immune responses. In light of the present status of studies in innate immunity, this review describes the current state of understanding of the Drosophila immune response.
| Comptes Rendus Biologies
2004: Vol 327, 557-570 | Abstract
Article complet | 220. Mosquito Immune Response Against Malaria Parasite
Blandin S, Levashina EA
Abstract : Anopheline mosquitoes are the major vectors oh human malaria. Mosquito-parasite interactions are a critical aspect of disease transmission and a potential target for malaria control. Mosquitoes vary in their innate ability to support development of the malaria parasite, but the molecular mechanisms that determine vector competence are poorly understood. This area research has been revolutionized by recent advances I nthe mosquito genome characterization and by the development of new tools for functional gene analysis.
| Current Opinion in Immunology
2004: Vol 16, 1-5 | Abstract
Article complet | 219. Thioester-containing proteins and insect immunity
Blandin S, Levashina EA
Abstract : Here, we discuss the role of thioester-containing proteins in innate immune responses of insects. TEPs are represented by multi-member families both in the fruitfly, Drosophila melanogaster, and in the mosquito, Anopheles gambiae. Phylogenetic analysis of the family suggests that in these two dipteran species evolution of TEPs followed independent scenarios as a result of specific adaptation to distinct ecological environments. Research on these two relatively simple model systems, which lack adaptive immunity, may provide new insights into the evolutionary origins and functions of this important protein family.
| Mol. Immunol.
2004: Vol 40, 903-908 | Abstract
Article complet | 218. Editorial
Reichhart JM
Abstract : No abstract
| Mol. Immunol.
2004: Vol 40, 843 | Abstract
Article complet | 217. Blood cells of Drosophila : cell lineages and role in host defense
Meister M
Abstract : Drosophila haemopoiesis gives rise to three independent cell lineages: plasmatocytes, crystal cells and lamellocytes. The regulation of Drosophila stem cell proliferation and lineage specification involves transactivators and signalling pathways, many of which have mammalian counterparts that control haemopoietic processes. Drosophila plasmatocytes are professional phagocytes that resemble the monocyte/macrophage lineage, crystal cells play a critical role in defence-related melanisation, and lamellocytes encapsulate large invaders. Crystal cells and lamellocytes have no clear mammalian homologues. Research into the molecular mechanisms that underlie the various immune functions of Drosophila blood cells, such as non-self recognition, is now taking wing.
| Current Opinion in Immunology
2004: Vol 16, 10-15 | Abstract
Article complet | 216. Biology of Toll receptors : lessons from insects and mammals
Imler JL, Zheng L
Abstract : Toll receptors are type I transmembrane proteins that play important roles in development and immunity in animals. Comparison of the genomes of mouse and human on one side and of the fruitfly Drosophila and the mosquito Anopheles (two dipteran insects) on the other, revealed that the four species possess a similar number of Toll receptors (approximately 10). However, phylogenetic analyses indicate that the families of Toll receptors expanded independently in insects and mammals. We review recent results on these receptors, which point to differences in the activation and signaling between Tolls in insects and Toll-like receptors (TLRs) in mammals. Whereas mammalian TLRs appear to be solely dedicated to host-defense, insect Tolls may be predominantly linked to other functions, probably developmental.
| J. Leukoc. Biol.
2004: Vol 75, 18-26 | Abstract
Article complet | 215. Sensing infection in Drosophila: Toll and beyond
Ferrandon D, Imler JL, Hoffmann JA
Abstract : Drosophila has evolved a potent immune system that is somewhat adapted to the nature of infections through the selective activation of either one of two NF-kappaB-like signalling pathways, the Toll and IMD (Immune deficiency) pathways. In contrast to the mammalian system, the Toll receptor does not act as a pattern recognition receptor (PRR) but as a cytokine receptor. The sensing of microbial infections is achieved by at least four PRRs that belong to two distinct families: the peptidoglycan recognition proteins (PGRPs) and the Gram-negative binding proteins (GNBPs)/beta-glucan recognition proteins (betaGRPs).
| Semin. Immunol.
2004: Vol 16, 43-53. | Abstract
Article complet | 214. Primary structure and in vitro antibacterial properties of the Drosophila melanogaster attacin C pro-domain
Rabel D, Charlet M, Ehret-Sabatier L, Cavicchioli L, Cudic M, Otvos L, Bulet P
Abstract : In Drosophila melanogaster, seven distinct families of antimicrobial peptides with different structures and specificities are synthesized by the fat body and released into the hemolymph during the immune response. Using microscale-high performance liquid chromatography, matrix-assisted laser desorption/ionization-time of flight mass spectrometry and Edman-degradation, we have isolated and characterized from immune-challenged Drosophila two novel induced molecules, under the control of the Imd pathway, which correspond to post translationally modified antimicrobial peptides or peptide fragments. The first molecule is a doubly glycosylated form of drosocin, an O-glycosylated peptide that kills Gram-negative organisms. The second molecule represents a truncated form of the pro-domain of the Drosophila attacin C carrying two post-translational modifications and has significant structural similarities to prolinerich antibacterial peptides including drosocin. We have synthesized this peptide and found that it is active against Gram-negative bacteria. Furthermore, this activity is potentiated when the peptide is used in combination with the Drosophila antimicrobial peptide cecropin A. The synergistic action observed between these two molecules suggests that the truncated post-translationally modified pro-domain of attacin C by itself may play an important role in the antimicrobial defense of Drosophila.
| J. Biol. Chem.
2004: Vol. 279 (15), 14853-14859. | Abstract
Article complet | 213. Proteomic analysis of the systemic immune reponse of Drosophila
Levy F, Bulet P, Ehret-Sabatier L
Abstract : Improvements in two-dimensional gel electrophoresis, mass spectrometry, and bioinformatics provide new tools to characterize proteins involved in a physiological process, such as the immune response of the insect model Drosophila melanogaster. Profiling of the proteins present in the hemolymph (insect blood) of noninfected flies versus flies infected with bacteria or fungi was performed by two-dimensional gel electrophoresis, silver or Coomassie staining, and image analysis. Through this differential analysis, more than 70 out of 160 spots were up- or down-regulated by at least 5-fold after microbial infection. Coomassie staining, in-gel digestion, and database searches yielded the identity of a series of proteins that are directly involved in the Drosophila immune system. This included proteases, protease inhibitors, and recognition molecules such as prophenoloxydase-activating enzymes, serpins, and Gram-negative binding protein-like. Proteins with a potential function in the immune response were also identified, such as an odorant binding protein, peptidylglycine alpha-hydroxylating monooxygenase, and transferrin, affording new candidates for further investigation of innate immune mechanisms. Moreover, several molecules resulting from the cleavage of proteins were detected after the fungal infection. Altogether, this first differential proteomic analysis of the immune response of Drosophila paves the way for the study of proteins affected during innate immunity.
| Mol. Cell Proteomics
2004: Vol 3, 156-166 | Abstract
Article complet | 212. Primitive Immune Systems
Hoffmann JA
Abstract : This volume of Immunological Reviews is devoted to primitive immune systems. Of course, since what is primitive is in the eye of the beholder, we must first define what constitutes the primitive immune system. The expression ante-antibody immunity, coined by Alan Ezekowitz, describes the present topic well. As antibodies did not appear in evolution before the separation of the ancestors of jawless and jawed fish, that is some 450 million years ago, ante-antibody immunity is indeed the ancient and first (primus) form of immunity, and it will serve as our operating definition for this volume.
| Immunological Reviews
2004: Vol 198, 5-9 | Abstract
Article complet | 211. The Immune Response of Drosophila Melanogaster
Leclerc V, Reichhart JM
Abstract : Abstract: The response of the fruit fly Drosophila melanogaster to various microorganism infections relies on a multilayered defense. The epithelia constitute a first and efficient barrier. Innate immunity is activated when microorganisms succeed in entering the body cavity of the fly. Invading microorganisms are killed by the combined action of cellular and humoral processes. They are phagocytosed by specialized blood cells, surrounded by toxic melanin, or lysed by antibacterial peptides secreted into the hemolymph by fat body cells. During the last few years, research has focused on the mechanisms of microbial recognition by various pattern recognition receptors and of the subsequent induction of antimicrobial peptide expression. The cellular arm of the Drosophila innate immune system, which was somehow neglected, now constitutes the new frontier.
| Immunological Reviews
2004: Vol 198, 59-71. | Abstract
Article complet | 210. Drosophila melanogaster innate immunity: an emerging role for peptidoglycan recognition proteins in bacteria detection
Royet J
Abstract : Over the past years, parallel studies conducted in mammals and flies have emphasized the existence of common mechanisms regulating the vertebrate and invertebrate innate immune systems. This culminated in the discovery of the central role of the Toll pathway in Drosophila immunity and in the implication of Toll-like receptors (TLRs)/interleukin-1(IL-1) in the mammalian innate immune response. In spite of clear similarities, such as shared intracellular pathway components, important divergences are expected between the two groups, whose last common ancestor lived more than half a billion years ago. The most obvious discrepancies lie in the mode of activation of the signalling receptors by microorganisms. In mammals, TLRs are part of protein complexes which directly recognize microbe-associated patterns, whereas Drosophila Toll functions like a classical cytokine receptor rather than a pattern recognition receptor. Recent studies demonstrate that members of the evolutionarily conserved peptidoglycan recognition protein family play an essential role in microbial sensing during immune response of Drosophila.
| Cell Mol. Life Sci.
2004: Vol 61, 537-546 | Abstract
Article complet | 209. Cg-Rel, the first Rel/NF-B homolog characterized in a mollusk, the Pacific oyster Crassostrea gigas
Montagnani C, Kappler C, Reichhart JM, Escoubas JM
Abstract : We report here the identification and functional characterization of Cg-Rel, a gene encoding the Crassostrea gigas homolog of Rel/NF-B transcription factors found in insects and mammals. Sequence and phylogenetic analysis showed that Cg-Rel shares the structural organization of Rel/NF-B transcription factors of class II. It includes a Rel homology domain as well as a C-terminal transactivation domain (TD). Overexpression of Cg-Rel in the Drosophila S2 cell line activated the expression of a NF-B-dependent reporter gene, whereas transfection with a Cg-Rel construct containing a C-terminal deletion of the TD or using a reporter gene with mutated B binding sites failed to activate expression. These results suggest that Cg-Rel is a functional member of the Rel family of transcription factors, making this the sixth structurally homologous component of the Rel/NF-B pathway characterized in C. gigas. Based on homology to other invertebrates' Rel/NF-B cascade, the function of the oyster pathway may serve to regulate genes involved in innate defense and/or development. These findings serve to highlight a potentially important regulatory pathway to the study of oyster immunology, hence allowing comparison of the immune system in vertebrates and invertebrates, an important key issue to understand its evolution.
| FEBS Letters
2004: Vol 561, 75-82 | Abstract
Article complet | 208. Complement-like protein TEP1 is a determinant of vectorial capacity in the malaria vector Anopheles gambiae
Blandin S, Shiao SH, Moita LF, Janse CJ, Waters AP, Kafatos FC, Levashina EA
Abstract : Anopheles mosquitoes are major vectors of human malaria in Africa. Large variation exists in the ability of mosquitoes to serve as vectors and to transmit malaria parasites, but the molecular mechanisms that determine vectorial capacity remain poorly understood. We report that the hemocyte-specific complement-like protein TEP1 from the mosquito Anopheles gambiae binds to and mediates killing of midgut stages of the rodent malaria parasite Plasmodium berghei. The dsRNA knockdown of TEP1 in adults completely abolishes melanotic refractoriness in a genetically selected refractory strain. Moreover, in susceptible mosquitoes this knockdown increases the number of developing parasites. Our results suggest that the TEP1-dependent parasite killing is followed by a TEP1-independent clearance of dead parasites by lysis and/or melanization. Further elucidation of the molecular mechanisms of TEP1-mediated parasite killing will be of great importance for our understanding of the principles of vectorial capacity in insects.
| Cell
2004: Vol 116, 661-670 | Abstract
Article complet | 207. Bacterial a2-macroglobulins: colonization factors acquired by horizontal gene transfer from the metazoan genome ?
Budd A, Blandin S, Levashina EA, Gibson TJ
Abstract : Invasive bacteria are known to have captured and adapted eukaryotic host genes. They also readily acquire colonizing genes from other bacteria by horizontal gene transfer. Closely related species such as Helicobacter pylori and Helicobacter hepaticus, which exploit different host tissues, share almost none of their colonization genes. The protease inhibitor a2-macroglobulin provides a major metazoan defense against invasive bacteria, trapping attacking proteases required by parasites for successful invasion.
| Genome Biology
2004: Vol 5 | Abstract
Article complet | 206. Immune responses in Anopheles gambiae
Levashina EA
Abstract : Transmission of human malaria requires a successful development of Plasmodium parasites in anopheline mosquitoes. Insects have developed efficient immune responses to oppose microbial and eukaryotic invaders. The completion of the sequencing of the Anopheles genome provides a wealth of information on putative immune genes that are homologous to components of the Drosophila and mammalian immune systems. In this review, we will summarize our present knowledge of immune responses in the mosquito Anopheles gambiae and attempt a comparative analysis of insect immune systems.
| Insect Biochem. Mol. Biol.
2004: Vol 34, 673-678 | Abstract
Article complet | 205. TLR-independent control of innate immunity in Caenorhabditis elegans by the TIR domain adaptor protein TIR-1, an ortholog of human SARM
Couillault N, Pujol N, Reboul J, Sabatier L, JF Guichou, Y Kohara, JJ Ewbank
Abstract : Both plants and animals respond to infection by synthesizing compounds that directly inhibit or kill invading pathogens. We report here the identification of infection-inducible antimicrobial peptides in Caenorhabditis elegans. Expression of two of these peptides, NLP-29 and NLP-31, was differentially regulated by fungal and bacterial infection and was controlled in part by tir-1, which encodes an ortholog of SARM, a Toll–interleukin 1 receptor (TIR) domain protein. Inactivation of tir-1 by RNA interference caused increased susceptibility to infection. We identify protein partners for TIR-1 and show that the small GTPase Rab1 and the f subunit of ATP synthase participate specifically in the control of antimicrobial peptide gene expression. As the activity of tir-1 was independent of the single nematode Toll-like receptor, TIR-1 may represent a component of a previously uncharacterized, but conserved, innate immune signaling pathway.
| Nature Immunology
2004: Vol 5, 488-594 | Abstract
Article complet | 204. Identification of an Aspartylglucosaminidase-like protein in the venom of the parasitic wasp Asobara Tabida
Moreau S, Cherqui A, Doury G, Dubois F, Fourdain L, Sabatier L, Bulet P, Saarela J, Prevost G, Giordanengo P
Abstract : This study was designed to identify one of the main components of venomous secretions of the endoparasitic wasp Asobara tabida. By using electrophoretic methods, partial amino acid sequencing and immunostaining, we demonstrated the presence of an aspartylglucosaminidase (AGA)-like protein in the venom of this insect. The enzyme had a polymeric conformation and was formed of 30 and 18 kDa subunits. The relative positions of several amino acids involved in substrate binding and catalytic activity of known AGA-proteins, which are usually lysosomal enzymes, were conserved in the NH2-terminal ends of these subunits. Antibodies raised against human AGA recognized the two subunits of the protein and a 44 kDa protein, suggesting the presence of a precursor molecule of the enzyme in the venom. However, no reliable measurement of the AGA activity could be performed on the venom extracts, which could be explained by the fact the enzyme would be stored in the reservoir of the venom apparatus under an inactive form. These results constitute the first description of an AGA-like protein in an insect venom and are discussed with respect to the knowledge acquired on lysosomal and venom enzymes.
| Insect Biochemistry Molecular Biology
2004: Vol 34, 485-492 | Abstract
Article complet | 203. Cellular immune response to parasitization in Drosophila requires the EBF orthologue Collier
M Crozatier, JM Ubeda, A Vincent and M Meister
Abstract : Drosophila immune response involves three types of hemocytes (‘blood cells’). One cell type, the lamellocyte, is induced to differentiate only under particular conditions, such as parasitization by wasps. Here, we have investigated the mechanisms underlying the specification of lamellocytes. We first show that collier (col), the Drosophila orthologue of the vertebrate gene encoding early B-cell factor (EBF), is expressed very early during ontogeny of the lymph gland, the larval hematopoietic organ. In this organ, Col expression prefigures a specific posterior region recently proposed to act as a signalling centre, the posterior signalling centre (PSC). The complete lack of lamellocytes in parasitized col mutant larvae revealed the critical requirement for Col activity in specification of this cell type. In wild-type larvae, Col expression remains restricted to the PSC following parasitization, despite the massive production of lamellocytes. We therefore propose that Col endows PSC cells with the capacity to relay an instructive signal that orients hematopoietic precursors towards the lamellocyte fate in response to parasitization. Considered together with the role of EBF in lymphopoiesis, these findings suggest new parallels in cellular immunity between Drosophila and vertebrates. Further investigations on Col/EBF expression and function in other phyla should provide fresh insight into the evolutionary origin of lymphoid cells.
| PLoS Biol.
2004: Vol 2, 1107-1113 | Abstract
Article complet | 202. Immune response and parasite transmission in blood-feeding insects
Lehane MJ, Aksoy S, Levashina EA
Abstract : The detailed model of insect immunity being built for Drosophila, allied to mass sequencing programs for blood-feeding insects, has led to advances in our understanding of the interaction between pathogens and insect vectors. An outline of insect immunity is given here based on the Drosophila studies, which is used as a framework to discuss recent work on Plasmodium–mosquito and Trypanosoma–tsetse interactions.
| Trends in Parasitology
2004: Vol 20, 433-439 | Abstract
Article complet | 201. La réponse immunitaire chez la drosophile
Ferrandon D, Royet J
Abstract : No abstract.
| Regards sur la biochimie
2004: Vol 1, 27-33 | Abstract
Article complet | 200. Role of Drosophila pattern recognition receptor, PGRP-SD, in detection of Gram-positive bacteria
Bischoff V, Vignal C, Boneca T, Michel T, Hoffmann JA, Royet J
Abstract : The activation of an immune response requires recognition of microorganisms by host receptors. In drosophila, detection of Gram-positive bacteria is mediated by cooperation between the peptidoglycan-recognition protein-SA (PGRP-SA) and Gram-negative binding protein 1 (GNBP1) proteins. Here we show that some Gram-positive bacterial species activate an immune response in a PGRP-SA- and GNBP1-independent manner, indicating that alternative receptors exist. Consistent with this, we noted that PGRP-SD mutants were susceptible to some Gram-positive bacteria and that a loss-of-function mutation in PGRP-SD severely exacerbated the PGRP-SA and GNBP1 mutant phenotypes. These data indicate that PGRP-SD can function as a receptor for Gram-positive bacteria and shows partial redundancy with the PGRP-SA-GNBP1 complex.
| Nature Immunology
2004: Vol 5, 1175-1180 | Abstract
Article complet | 199. Toll-dependent and Toll-independent immune response in Drosophila
Imler JL, Ferrandon D, Royet J, Reichhart JM, Hetru C, Hoffmann JA
Abstract : The multifaceted response of the fruitfly Drosophila melanogaster to infection by a wide range of microbes is complex and remarkably efficient. Its most prominent aspect is the immune-inducible expression of a set of potent antimicrobial peptides. Genetic analysis of the regulation of the genes encoding these peptides has led to the identification of the receptor Toll as an essential component of the fly's host defense system. In addition, these studies have revealed that the response to Gram-negative bacterial infections involves Toll-independent mechanisms, and that the sensing of infection involves two structurally distinct sets of molecules--the PGRPs and the GNBPs/betaGRPs.
| Journal of Endotoxin Research
2004: Vol 10, 241-246 | Abstract
Article complet | 198. Infectious non-self recognition in invertebrates : lessons from Drosophila and other insect models
Royet J
Abstract : The vertebrate innate immune system recognizes infectious non-self by employing a set of germline-encoded receptors such as nucleotide-binding oligomerisation domain proteins (NODs) or Toll-like receptors (TLRs). These proteins are involved in the recognition of various microbial-derived molecules, including lipopolysaccharide (LPS), peptidoglycan (PGN) and beta1,3-glucan. Drosophila Toll receptors are not directly dedicated to non-self recognition and insect NOD orthologues have not yet been identified. Studies started more than 20 years ago and conducted on different insect models have identified other receptors on which invertebrate innate systems rely to sense invading microorganisms.
| Molecular Immunology
2004: Vol 41, 1063-1075 | Abstract
Article complet | 197. Peptidomic and Proteomic Analyses of the Systemic Immune Response of Drosophila
Levy F, Rabel D, Charlet M, Bulet P, Hoffmann JA, Ehret-Sabatier L
Abstract : Insects have developed an efficient host defense against microorganisms, which involves humoral and cellular mechanisms. Numerous data highlight similarities between defense responses of insects and innate immunity of mammals. The fruit fly, Drosophila melanogaster,isa favorable model system for the analysis of the first line defense against microorganisms. Taking advantages of improvements in mass spectrometry (MS), two-dimensional (2D) gel electrophoresis and bioinformatics, differential analyses of blood content (hemolymph) from immune-challenged versus control Drosophila were performed. Two strategies were developed: (i) peptidomic analyses through matrixassisted laser desorption/ionization time-of-flight (MALDI-TOF) MS and high performance liquid chromatography for molecules below 15 kDa, and (ii) proteomic studies based on 2D gel electrophoresis, MALDI-TOF fingerprinting and database searches, for compounds of greater molecular masses. The peptidomic strategy led to the detection of a large number of peptides induced in the hemolymph of challenged flies as compared to controls. Of these, 28 were characterized, amongst which were antimicrobial peptides. The 2Dgel electrophoresis strategy led to the detection of 70 spots differentially regulated by at least fivefold after microbial infection. This approach yielded the identity of a series of proteins that were related to the Drosophila immune response, such as proteases, protease inhibitors, prophenoloxydase-activating enzymes, serpins and a Gram-negative binding protein-like protein. This strategy also brought to light new candidates with a potential function in the immune response (odorant-binding protein, peptidylglycine a-hydroxylating monooxygenase and transferrin). Interestingly, several molecules resulting from the cleavage of proteins were detected after a fungal infection. Together, peptidomic and proteomic analyses represent new tools to characterize molecules involved in the innate immune reactions of Drosophila.
| Biochimie
2004: Vol 86, 607-616 | Abstract
Article complet | 196. Characterization of a defensin from the sand fly Phlebotomus duboscqi induces by challenge with bacteria or the protozoan parasite Leishmania major
Boulanger N, Lowenberger C, Volf P, Ursic R, Sigutova L, Sabatier L, Svobodova M, Beverley SM, Späth G, Brun R, Pesson B, Bulet P
Abstract : Antimicrobial peptides are major components of the innate immune response of epithelial cells. In insect vectors, these peptides may play a role in the control of gut pathogens. We have analyzed antimicrobial peptides produced by the sand fly Phlebotomus duboscqi, after challenge by injected bacteria or feeding with bacteria or the protozoan parasite Leishmania major. A new hemolymph peptide with antimicrobial activity was identified and shown to be a member of the insect defensin family. Interestingly, this defensin exhibits an antiparasitic activity against the promastigote forms of L. major, which reside normally within the sand fly midgut. P. duboscqi defensin could be induced by both hemolymph or gut infections. Defensin mRNA was induced following infection by wild-type L. major, and this induction was much less following infections with L. major knockout mutants that survive poorly in sand flies, due to specific deficiencies in abundant cell surface glycoconjugates containing phosphoglycans (including lipophosphoglycan). The ability of gut pathogens to induce gut as well as fat body expression of defensin raises the possibility that this antimicrobial peptide might play a key role in the development of parasitic infections.
| Infection and Immunity
2004: Vol 72, 7140-7146 | Abstract
Article complet | 195. Toll signalling: the TIReless quest for specify
Imler JL, Hoffmann J
Abstract : Toll-like receptors (TLRs) have an essential role in the innate immune response against microbial pathogens. These receptors are characterized by an ectodomain composed of leucine-rich repeats, and an intracytoplasmic domain conserved in members of the interleukin-1 receptor (IL-1R) family (Toll/IL or TIR domain). Mammalian TLRs are now recognized as primordial receptors of innate immunity mediating activation by peptidoglycan and bacterial lipopeptides (TLR2), lipopolysaccharide (LPS, TLR4), double-standed (ds) RNA (TLR3), flagellin (TLR5) and unmethylated CpG DNA motifs (TLR9). Upon stimulation, TLRs activate the transcription NF-kB and AP1, leading to production of inflammatory cytokines such as tumor necrosis factor (TNF)-a and up-regulation of the costimulatory molecules CD80 and CD86 on dentritic cells (DCs). The diversity of microbial molecular patterns activating specific TLRs contrasts with the apparent uniformity of the reponses induced by these receptors. However, recent results indicate that signaling by TLRs is more complex that initially anticiped, and that a panel of intracytoplasmic adapter molecules may mirror the diversity of extracellular stimuli for TLRs. In this issue of Nature Immunology and in a recently published article, a new adapter protein involved in TLR signaling has been identified.
| Nature Immunology
2003: Vol 4, 105-106 | Abstract
Article complet | 194. Characterization of three Toll-like genes from mosquito Aedes aegypti
Luna C, Hoa NT, Zhang J, Ka,zok SM, Brownt SE, Imler JL, Knudson DL, Zheng L
Abstract : Three Toll-related genes (AeToll1A, AeToll1B and AeToll5) were cloned and characterized from the yellow fever vector mosquito, Aedes aegypti. All three genes exhibited high levels of amino acid sequence similitary with Drosophila melanogaster (Dm) Toll1 and DmTehoa (Toll5). AeToll1A and AeToll1B are 1124 and 1076 amino acid residues long, respectively. Both contain a carboxyl extension dowstream of the Toll/interleukin-1 receptor (TIR) domain. AeToll5 is 1007 residues long and, like DmTehoa, lacks the carboxyl terminal extension. Expression of these three genes was examined throughout development and after immune challenge. Both AeToll1A and AeToll5, like their Drosophila counterparts, activate transcrption of drosomycin promoter in both Aedes and Drosophila cell lines. Deletion of the carboxyl extension of AeToll1A did not result in a further elevated level of the antifungal response. The intracellular signalling process to be species specific based on two observations. (1) DmToll is completely inactive in an Aedescell line, suggesting a higher specificity requirement for DmToll in the intracellular signalling process. (2) Only one of the three amino acid residues essential for DmToll function is required for AeToll1A function.
| Insect. Molecular Biology
2003: Vol 12, 67-74 | Abstract
Article complet | 193. Drosophila necrotic mutations mirror disease-associated variants of human serpins
Green C, Brown G, Daffoen T, Reichhart JM, Morley T, Lomas D & Gubb D
Abstract : Polymerization of members of the serpin superfamily underlies diseases as diverse as cirrhosis, angioedema, thrombosis and dementia. The Drosophila serpin Necrotic controls the innate immune response and is homologous to human µ1-antirypsin. We show that necrotic mutations that are identical to the Z-deficiency variant of µ1antirypsin form urea-stable polymers in vivo. These necrotic mutations are temperature sensitive, which is in keeping with the temperature-dependent polymerization of serpins in vitro and the role of childhood fevers in exacerbating liver desease Z µ-antitrypsin deficiency. In addition, we identify two nec mutations homologous to an antithrombin point mutation that is responsible for neonatal thrombosis. Transgenic flies carrying an S>F amino-acid substitution equivalent to that found in Siiyama-variant antitrypsin (necS>F.UAS) fail to cmplement nec-null mutations and demonstrate a dominant temperature-dependent inactivation of the wild-type nec allele. Taken together, these data establish Drosophila as a powerful system to study serpin polymerization in vivo.
| Development
2003: Vol 130, 1473-1478 | Abstract
Article complet | 192. The Hexapeptide and Linker Regions of the AbdA Hox Protein Regulate its activating and Repressive Functions
Merabet S, Kambris Z, Capovilla M, Bérenger H, Pradel J, Graba Y
Abstract : The Hox family transcription factors control diversified morphogenesis during develoment and evolution. They function in concert with Pbc cofactor proteins. Pbc proteins bind the Hox hexapeptide (HX) motif and are thereby thought to confer DNA binding specificity. Here we report that mutation of the AbdA HX motif does not alter its binding site selection but does modify its transregulatory properties in a gene-specific manner in vivo. We also show that a short, evolutionarily conserved motif, PPER, in the homeodomain-HX linker region acts together with the HX to control an AbdA activation/repression switch. Our in vivo data thus reveal functions not previously anticipated from in vitro analyses for the hexapeptide motif in the regulation of Hox activity.
| Developemental Cell
2003: Vol 5, 761-768 | Abstract
Article complet | 191. Virulence factors of the human opportunistic pathogen Serratia marcescens identified by in vivo screening
Kurz CL, Chauvet S, Andres E, Aurouze M, Vallet I, Michel GP, UH M, Celli J, Filloux A, DE Bentzmann S, Steinmetz I, Hoffmann JA, Finlay BB, Gorvel JP, Ferrandon D, Ewbank JJ
Abstract : The human opportunistic pathogen Serratia marcescens is a bacterium with a broad host range, and represents a growing problem for public health. Serratia marcescens kills Cenorhabditis elegans after colonizing the nematode’s interstine. We used C. elegans to sreen a bank of transposon-induced S. marcescens mutants and isolated 23 clones with an attenuated virulence. Nine of the selected bacterial clones also showed a reduced virulence in an insect model of infection. Of these, three exhibited a reduced cytotoxicity in vitro, and among them one was also markedly attenuated in its virulence in a murine lung infection model. For 21 of the 23 mutants, the transposon insertion site was identified. This revealed that among the genes necessary for full in vivo virulence are those that function in lipopolysachharide (LPS) biosynthesis , iron uptake and hemolysin production. Using this system we also identified novel conserved virulence factors required for Pseudomonas aeruginosa pathogenicity. This study extends the utility of C. elegans as an in vivo model for the study of basterial virulence and advances the molecular understanding of S. marcescens pathogenicity.
| EMBO J.
2003: Vol 22, 1451-1460 | Abstract
Article complet | 190. Drosophila melanogaster antimicrobial defense. In "J. Infectious Disease:Innate Immunity"
Hetru C, Troxler L, Hoffmann JA
Abstract : The Drosophila melanogaster host defense is complex but remarkably efficient. It is a multifaceted response to a variety of fungal, bacterial, and parasitic invaders. Current knowledge is discussed on recognition of infectious microorganisms and on the activation of intracellular signaling cascades that accur with the expression of numerous immune-responsive genes, among which, to date, the most prominent appear to encode potent antimicrobial peptides.
| Ezekowitz R.A.B. and Hoffmann J.A., eds. Humana Press Inc, Totowa
2003: 187 Suppl 2 :S327-34 | Abstract
Article complet | 189. Binding of the Drosophila cytokine Spaetzle to Toll is direct and establishes signaling
Weber AN, Tauszig-Delamasure S, Hoffmann JA, Lelievre E, Gascan H, Ray KP, Morse MA, Imler JL, Gay NJ
Abstract : The extracellular protein Spatzle is required for activation of the Toll signaling pathway in the embryonic development and innate immune defense of Drosophila. Spatzle is synthetized as a pro-protein and is processed to a functionnal form by a serine protease. We show here that the mature form of Spatzle triggers a Toll-dependent immune response after injection into the hemolymph of flies. Spatzle specifically bound to Drosophila cells and to Cos-7 cells expressing Toll. Furthermore, in vitro experiments showed that the mature form of Spatzle bound to the Toll ectodomain with high affinity and with a stoichiometry of one Spatzle dimer to two receptors. The Spatzle pro-protein was inactive in all these assays, indicating that the pro-domains sequence, which is natively unstructed, acts to prevent interaction of the cytokine and its receptor Toll. These results show that, in contrast to the human Toll-like receptors, Drosophila Toll requires only an endogenous protein ligand for activation and signaling.
| Nature Immunology
2003: Vol 4, 794-800 | Abstract
Article complet | 188. Toll and Toll-like receptors in Drosophila
Bilak H, Tauszig-Delamasure S, Imler JL
Abstract : The Drosophila Toll receptor controls the immune response to Gram-positive bacteria and fungi by activating a signalling pathway partially conserved throughout evolution. The Drosophila genome encodes eight additional Toll-related receptors, most of which appear to carry out developmental rather than immune functions. One exception may be Toll-9, which shares structural and functional similarities with mammalian TLRs.
| Biochem. Soc. Trans.
2003: Vol 31, 648-651 | Abstract
Article complet | 187. Pherokine-2 and –3
Sabatier L, Jouanguy E, Dostert C, Zachary D, Dimarcq JL, Bulet P, Imler JL
Abstract : Drosophila is a powerful model system to study the regulatory and effector mechanisms of innate immunity. To identify molecules induced in the course of viral infection in this insect, we have developed a model based on intrathoracic injection of the picorna-like drosophila C virus (DCV). We have used MALDI-TOF mass spectrometry to compare the hemolymph of DCV infected flies and control flies. By contrast with the strong humoral response triggered by injection of bacteria or fungal spores, we have identified only one molecule induced in the hemolymph of virus infected flies. This molecule, pherokine-2 (Phk-2), is related to OS-D/A10 (Phk-1), which was previously characterized as a putative odor/pheromone binding protein specifically expressed in antennae. The virus-induced molecule is also similar to the product of the gene CG9358 (Phk-3), which is induced by septic injury. Both Phk-2 and Phk-3 are strongly expressed during metamorphosis, suggesting that they may participate in tissue-remodeling.
| Eur. J. Biochem.
2003: Vol 270, 3398-3407 | Abstract
Article complet | 186. Drosophila Blood Cells
Meister M, Lagueux M
Abstract : Drosophila blood cells or haemocytes belong to three lineages: plasmatocytes, crystal cells and lamellocytes. There is no equivalent of a lymphoid lineage in insects which have no adaptive immunity Haematopoiesis is under the control of a number of transcription factors and signalling pathways (such as GATA factors, JAK-SAT or Notch pathways) most of which have homologues which participate in the control of mammalian haematopoiesis. Drosophila plasmatocytes are professional phagocytes reminiscent of the cells from the mammalian monocyte/macrophage lineage. Several receptors responsible for recognition of microorganisms or apoptotic corpses have been identified, which include a Scavenger Receptor, a CD36 homologue and a peptidoglycan recognition protein. Crystal cells contain the enzymes necessary for humoral melanization that accompanies number of immune reactions. The production of melanin generates, as by-products, cytotoxic free radicals that are believed to participate in the killing of pathogens. Finally, lamellocytes represent a cell type that specifically differentiates after parasitism of Drosophila larvae and forms a capsule around the invader. Encapsulation together with melanization eventually kill the parasite within the capsule.
| Cellular Microbiology
2003: Vol 5, 573-580 | Abstract
Article complet | 185. Silencing of Toll pathway components by direct injection of double-stranded RNA into Drosophila
Goto A, Blanbin S, Royet J, Reichhart JM, Levashina EA
Abstract : Double-stranded RNA (dsRNA) gene interference is an efficient method to silence gene expression in a sequence-specific manner. Here we show that the direct injection of dsRNA can be used in adult Drosophila flies to disrupt function of endogenous genes in vivo. As a proof of principle, we habe used this method to silence components of a major signalling cascade, the Toll pathway, which controls fruit fly resistance to fungal and Gram-positive bac terial infections. We demonstrate that the knockout is efficient only if dsRNA is injected in 4- or more day-old flies and that it lasts for at least 1 week. Furthermore, we report dsRNA-based epistatic gene analysis via injection of a mixture of two dsRNAs and propose that injection of dsRNA represents a powerful method for rapid functional analysis of genes in Drosophila melanogaster adults, particularly of those whose mutations are lethal during development.
| Nucleic Acids Research
2003: Vol 31, 6619-6623 | Abstract
Article complet | 184. TLR5 takes aim at bacterial propeller
Reichhart JM
Abstract : The Toll receptor (TLR) familytargets pathogen-derived molecules in regions unlikeky to change under selection pressures. For TLR5, which recognizes the protein flagellin, the function of the targeting motif is key.
| Nature Immunology
2003: Vol 4, 1159-1160 | Abstract
Article complet | 183. The identification of novel genes required for Drosophila anteroposterior axis formation in a germline clone screen using GFP-Staufen
Martin S.G., Leclerc V., Smith-Litiere K., St Johnston D
Abstract : The anteroposterior axis of Drosophila is defined during oogenesis, when the polarisation of the oocyte microtubule cytoskeleton directs the localisation of bicoid and oskar mRNAs to the anterior and posterior poles, respectively. Although maternal-effect lethal and female-sterile screens have identified many mutants that disrupt these processes, these screens could not recover mutations in essential genes. Here we describe a genetic screen in germline clones for mutants that disrupt the localisation of GFP-Staufen in living oocytes, which overcomes this limitation. As Staufen localises to the posterior with oskar mRNA and to the anterior with bicoid mRNA, it acts as a marker for both poles of the oocyte, allowing the identification of mutants that affect the localisation of either mRNA, as well as mutants that disrupt oocyte polarity. Using this approach, we have identified 23 novel complementation groups on chromosome 3R that disrupt anteroposterior axis formation. Analyses of new alleles of spn-E and orb show that both SPN-E and ORB proteins are required to organise the microtubule cytoskeleton at stage 9, and to prevent premature cytoplasmic streaming. Furthermore, yps mutants partially suppress the premature cytoplasmic streaming of orb mutants. As orb, yps and spn-E encode RNA-binding proteins, they may regulate the translation of unidentified RNAs necessary for the polarisation of the microtubule cytoskeleton.
| Development
2003: Vol 130, 4201-4215 | Abstract
Article complet | 182. Hematopoietic development in Drosophila : a parallel with vertebrates. In “ Hematopoietic stem cell development ”.
Meister M and Govind S
Abstract : No abstract
| Godin I. and Cumano A., eds. Landes Bioscience.
2003: | Abstract
Article complet | 181. Thanatin activity on multidrug resistant clinical isolates of Enterobacter aerogenes and Klebsiella pneumoniae
Pages JM, Dimarcq JL, Quenin S, Hetru C
Abstract : Efflux pumps protect bacterial cells by ejecting intracellular toxic molecules such as antibiotics, detergents and defensins that have penetrated the cell envelope. Some of these efflux pumps recognise structurally unrelated compounds (mdr pump) and account for the resistance of some organisms to two or more agents. It would be of interest to identify molecules that are able to circumvent the problems created by multidrug resistance phenotypes during antibiotic therapy. We have studied the activity of thanatin, a 21-residue cationic antimicrobial peptide produced by an insect, against three bacterial species. The antibacterial effect depended on the size of lipopolysaccharide side chains. In clinically resistant isolates of Enterobacter aerogenes and Klebsiella pneumoniae, the biological activity of thanatin is independent of the membrane permeability, possibly controlled by one or more porins, and/or the expression of drug efflux pumps, two mechanisms which confer high level antibiotic resistance. In addition, thanatin was able to improve the activity of structurally unrelated antibiotics (norfloxacin, chloramphenicol, tetracycline) on a multidrug- resistant E. aerogenes clinical isolate.
| Int. J. Antimicrob. Agents
2003: Vol 22, 265-269 | Abstract
Article complet | 180. A Serpin Regulates Dorso-Ventral Axis Formation in the Drosophila Embryo
Ligoxygakis P, Roth S, Reichhart JM
Abstract : Extracellular serine protease cascades have evolved in vertebrates and invertebrates to mediate rapid, local reactions to physiological or pathological cues. The serine protease cascade that triggers the Toll signaling pathway in Drosophila embryogenesis shares several organizational characteristics with those involved in mammalian complement and blood clotting. One of the hallmarks of such cascades in their regulation by serine protease inhibitors (serpins). Serpins act as suicide substrate and are cleaved by their target protease, forming an essentially irreversible 1:1 complex. The biological importance of serpins is highlighted by serpin dysfunction diseases, such as thrombosis caused by a deficiency in antithrombin. Here we describe how a serpin controls the serine protease cascade, leading to Toll pathway activation. Female flies deficient in Serpin-27A produce embryos that lack dorso-ventral polarity and show uniform high levels of Toll signaling. Since this serpin has been recently shown to restrain an immune reaction in the blood of Drosophila, it demonstrates that proteolysis can be regulated by the same serpin in different biological contexts.
| Current Biology
2003: Vol 13, 1-20 | Abstract
Article complet | 179. The Immune Response of Drosophila
Hoffmann JA
Abstract : Drosophila mounts a potent host defence when challenged by various microorganisms. Analysis of this defence by molecular genetics has now provided a global picture of the mechanisms by which this insect senses infection, discriminates between various classes of microorganisms and induces the production of effector molecules, among which antimicrobial peptides are prominent. An unexpected result of these studies was the discovery that most of the genes involved in the Drosophila host defence are homologous or very similar to genes implicated in mammalian innate immune defences. Recent progress in research on Drosophila immune defence provides evidence for similarities and differences between Drosophila immune responses and mammalian innate immunity.
| Nature
2003: Vol 426, 33-38 | Abstract
Article complet | 178. Detection of peptidoglycans by NOD proteins
Royet J and Reichhart JM
Abstract : Mechanisms of innate immune defense are based on the recognition of invariant microbial molecular patterns by specific receptors, followed by the activation of signaling pathways and the expression of effector molecules that will defeat the invading microorganism. Two recent reports add to the growing list of these pattern-recognition receptors by showing that the intracellular nucleotide-binding oligomerization domain 1 (NOD1) protein recognizes a diaminopimelate-containing muropeptide, a cell-wall component of Gram-negative bacteria.
| Trends in cell biology
2003: Vol 12, 610-614 | Abstract
Article complet | 177. Spheniscins : avian b-defensins in preserved stomach contents of the king penguin, Aptenodytes patagonicus
Thouzeau C, Le Maho Y, Froget G, Sabatier L, Le Bohec C, Hoffmann JA, Bulet P
Abstract : During the last part of egg incubation in king penguins, the male can preserve undigested food in the stomach for several weeks. This ensures survival of the newly hatched chick, in cases where the return of the foraging female from the sea is delayed. In accordance with the characterization of stress-induced bacteria, we demonstrate the occurrence of strong antimicrobial activities in preserved stomach contents. We isolated and fully characterized two isoforms of a novel 38-residue antimicrobial peptide (AMP), spheniscin, belonging to the beta-defensin subfamily. Spheniscin concentration was found to strongly increase during the period of food storage. Using a synthetic version of one of the two spheniscin isoforms, we established that this peptide has a broad activity spectrum, affecting the growth of both pathogenic bacteria and fungi. Altogether, our data suggest that spheniscins and other, not yet identified, antimicrobial substances may play a role in the long-term preservation of stored food in the stomach of king penguins.
| J. Biol. Chem.
2003: Vol 278, 51053-51058 | Abstract
Article complet | 176. Dual activation of the Drosophila toll pathway by two pattern recognition receptors
Gobert V, Gottar M, Matskevich AA, Rutschmann S, Royet J, Belvin M, Hoffmann JA, Ferrandon D
Abstract : The Toll-dependent defense against Gram-positive bacterial infections in Drosophila is mediated through the peptidoglycan recognition protein SA (PGRP-SA). A mutation termed osiris disrupts the Gram-negative binding protein 1 (GNBP1) gene and leads to compromised survival of mutant flies after Gram-positive infections, but not after fungal or Gram-negative bacterial challenge. Our results demonstrate that GNBP1 and PGRP-SA can jointly activate the Toll pathway. The potential for a combination of distinct proteins to mediate detection of infectious nonself in the fly will refine the concept of pattern recognition in insects.
| Science
2003: Vol 302, 2126-2130 | Abstract
Article complet | 175. Drosophila innate immunity: an evolutionary perspective
Hoffmann JA, Reichhart JM
Abstract : In response to microbial infections, Drosophila mounts a multifaceted immune response involving humoral reactions that culminate in the destruction of invading organismes by lytic peptides. These defense mechanisms are activated via two distinct signaling pathways. One of these, the Toll pathway controls resistance to fungal and Gram-positive bacterial infections, whereas the Imd pathway is responsible for defense against Gram-negative bacterial infections. Current evidence indicates that recognition of infectious nonself agents results from interactions between microbial wall components and extracellular pattern recognition proteins. We discuss hre evolutionary perspectives on our present understanding of the antimicrobial defenses of Drosophila.
| Nat Immunol.
2002: Vol 3, 121-126. | Abstract
Article complet | 174. Methods for studying infection and immunity in Drosophila
Tzou P, Meister M and Lemaitre B
Abstract : Research on pathogens such as Listeria, Yersinia, Salmonella, Shigella, Escherichia, which are particularly suitable to genetic manipulation, have increased our understanding of the molecular interactions betterave bacterial factors and host cellular components (Finlay and Cossart, 1997). Despite present advances, however, the overall spectrum of interactions between infectious microbesand their hosts remain poorly understood. To date, the model host organism systems used to analyse host/bacteria interaction (cell culture or mouse) have not allowed for a systematic identification by genetic screening of the host factors involved in the infection process and corresponding host immune responses. Nevertheless, many of the mechanism underlying host innate immune response, as well as invasion strategies used by pathogenic microbes, appear to be conserved across phylogeny, pointing to their ancient origin (Hoffmann et al., 1999, Tan and Ausubel, 2000). These results highlight the potential of non-mammalian model organism that are amenable to genetic analysis for studying host-pathogen interactions. During the last century Drosophila melanogaster, the fruit fly, has been widely-used model organism for gentic studies. A facile genetic system, reliable husbrandy techniques, and fully sequenced genome all contribute to the usefulness of this organism. In addition, Drosophila, like other insects, shows efficient constitutive and inducible host defense response that display striking parallels with mammalian innate immune reponses (phagocytosis, by macrophage-like hemocytes, antimicrobial peptides, proteolytic cascades). Consequently, Drosophila is especially suitable for the analysis of the interplay between microbes and the innate immune defense. Flies, like mammals, possess respiratory and digestive tract tissues that are also the target for invading pathogens. Although the physiology of these organs are significantly diffent from their mammalian counterparts they share some basic properties as barriers to microbial infection. Finally, our good understanding of the evolution as well as the ecology of Drosophila in relation to natural pathogens in the wild can be relevant for host-pathogen analysis. In keeping with this idea, it should be pointed out that flies function as vectors in the spread of many human and plant pathogens. In this view, we describe the basic techniques currently used to both infect Drosophila and to monitor corresponding immune responses.
| Methods in Microbiology
2002: Vol 31. | Abstract
Article complet | 173. Drosophila MyD88 is required for the response to fungal and Gram-positive bacterial infections
Tauszig-Delamasure S, Bilak H, Capovilla M, Hoffmann JA, Imler JL
Abstract : We report here the identification and funtional characterization of DmMyD88, a gene encoding the Drosophila homolog of mammalian MyD88. DmMyD88 combines a Toll- IR hology (TIR) domain and death domain. Overexpression of DmMyD88 was sufficient to induce expression of the antifongal peptide Drosomycin, and induction of Drosomycin was markedly reduced in DmMyD88-mutant flies. DmMyD88 interacted with Toll through its TIR domain and required the death domain proteins tube and Pelle to activate expression of Drs, which encodes Drosomycin. DmMyD88-mutant flies were highly susceptible to infection by fungi and Gram-positive bacteria, but resisted Gram-negative bacterial infection much as did wild-type flies. Phenotypic comparaison of DmMyD88-mutant flies and MyD88-deficient mice showed essential differences in the control of Gram-negative infection in insects and mammals.
| Nat Immunol.
2002: Vol 3, 91-97. | Abstract
Article complet | 172. Constitutive expression of a single antimicrobial peptide can restore wild-type resistance to infection in immunodeficient Drosophila mutants
Tzou P, Reichhart JM, Lemaitre B
Abstract : One of the characteristics of the host defense of insects is the rapid synthesis of a variety of potent antibacterial and antifungal peptides. To date, seven types of inducible antimicrobial peptides (AMPs) have been characterized in Drosophila. The importance of these peptides in host defense is supported by the observation that flies deficient for the Toll or Immune deficiency (Imd) pathway, which affects AMP gene expression, are extremely susceptible to microbial infection. Here we have developed a genetic approach to address the functional relevance of a defined antifungal or antibacterial peptide in the host defense of Drosophila adults. We have expressed AMP genes via the control of the UAS/GAL4 system in imd, spätzle double mutants that do not express any known endogenous AMP gene. Our results clearly show that constitutive expression of a single peptide in some cases is sufficient to rescue imd spätzle susceptibility to microbial infection, highlighting the important role of AMPs in Drosophila adult host defense.
| Proc. Natl. Acad. Sci. USA
2002: Vol 99, 2152-2157. | Abstract
Article complet | 171. Cutting edge: the toll pathway is required for resistance to gram-positive bacterial infections in Drosophila
Rutschmann S, Kilinc A, Ferrandon D
Abstract : In Drosophila, the response against various microorganisms involves different recognition and signaling pathways, as well as distinct antimicrobien effectors. On the one hand, the immune deficiency pathway regulates the expression of antimicrobial peptides that are active against Gram-negative bacterial. On the other hand, the Toll pathway is involved in the defense against filamentous fungi and controls the expression of antifungal peptide genes. The gene coding for the only known peptide with high activity against Gram-positive bacteria. Defesin, is regulated by both pathways. So far, survival experiments to Gram-positive bacteria have been performed with Micrococcus luteus and have failed to reveal the involvement of one or the other pathway in host defense against such infections. In this study, we report that the Toll pathway, but not that of immune deficiency, is required for resistance to other Gram-positive bacteria and that this response does not involve Defensin.
| J. Immunol.
2002: Vol 168, 1542-1546. | Abstract
Article complet | 170. The Drosophila response against Gram-negative bacteria is mediated by a peptidoglycan recognition protein
Gottar M, Gobert V, Michel, T Belvin M, Duyk G, Hoffmann JA, Ferrandon D, Royet J
Abstract : The antimicrobial defence of Drosophila relies largely on the challenge-induced symptômes of an array of potent antimicrobial peptides by the fat body. The defence against Gram-positive bacteria and natural fungal infections is mediated by the Toll signalling pathway, whereas defence against Gram-negative bacteria is dépendent on the Immune deficiency (IMD) pathway. Loss-of-function mutations in either pathway reduce the resistance to corresponding infections. The link betterave microbial infections and activation of these two pathways has remained elusive. The Toll pathway is activated by Gram-positive bacteria through a circulating Peptidoglycan recognition protein (PGRP-SA). PGRPs appear to be highly conserved from insects to mammals, and the Drosophila genome contains 13 members. Here we report a mutation in a gene coding for a putative transmembrane protéine, PGRP-LC, which reduces survival to Gram-negative sepsis but has no effect on the response to Gram-positive bacteria or natural fungal infections. By genetic épistasies, we demonstrate that PGRP-LC acts upstream on the imd gene. The data on PGRP-SA with respect to the response to Gram-positive infections, together with the present report, indicate that the PGRP family has a principal role in sensing microbial infections in Drosophila.
| Nature
2002: Vol 416, 640-644. | Abstract
Article complet | 169. Critical evaluation of the role of the Toll-like receptor 18-Wheeler in the host defense of Drosophila
Ligoxygakis P, Bulet P & Reichhart JM
Abstract : Essential aspects of innate immune response to microbial infections appear to be conserved between insects and mammals. In particular, in both group, transmembrane recerptors of the Toll super family play a crucial role in activating immune defenses. The Drosophila Toll family member 18-wheeler had been proposed to sense Gram-negative infection and direct selective expression of peptides active against Gram-negative bacteria. Here we re-examine the role of 18-Wheeler and show that in adults it is indispensable for immune responses. In larvae, 18wheeler is required for normal fat body development, and in mutant larvae induction of all antimicrobial peptide genes, and not only of those directed against Gram-negative bacteria, is compromised. 18-Wheeler does not qualify as a pattern recognition receptor of Gram-negative bacteria.
| EMBO reports
2002: Vol 3, 666-673 | Abstract
Article complet | 168. Toll receptors in Drosophila: a family of molecules regulating development and immunity
Imler JL, Hoffmann JA
Abstract : In recent years, Toll-like receptors (TLRs) have emerged as key receptors which detect microbes and initiate an inflammatory response. The Toll receptor was originally identified and characterized 14 years ago for its role in the embryonic development of the fruit-fly Drosophila melanogaster. Subsequently, it was also shown to be an essential component of the signaling pathway mediating the anti-fungal host defense in this model organism. New factors involved in the activation of the Toll receptor or in intracytoplasmic signaling during the immune response in Drosophila have recently been identified. The existence of significant functional differences between mammalian TLRs and Drosophila Toll receptors is also becoming apparent.
| Current Topic Microbiol. Immunol.
2002: Vol 270, 63-79. | Abstract
Article complet | 167. Activation of Drosophila Toll during fungal infection by a blood serine protease
Ligoxygakis P, Pelte N, Hoffmann J, Reichhart JM
Abstract : Drosophila host defense to fungal and Gram-positive bacterial infection is mediated by the Spaetzle /Toll/cactus gene cassette. It has been proposed that Toll does not function as a pattern recognition receptor per se but is activated through a cleaved form of the cytokine Spaetzle. The upstream events linking infection to the cleavage of Spaetzle have long remained elusive. Here we report the identification of a central component of the fungal activation of Toll. We show that ethylmethane sulfonate-induced mutations in the persephone gene, which endodes a previously unknown serine protease, block induction on the Tollpathway by fungi and resistance to this type of infection.
| Science
2002: Vol 297, 114-116. | Abstract
Article complet | 166. The Drosophila Immune Defense against Gram-Negative Infection Requires the Death Protein dFADD
Naitza S, Rossé C, Kappler C, Georgel P, Belvin M, Gubb D, Camonis J, Hoffmann J, Reichhart JM
Abstract : Drosophila responds to Gram-negative infections by mounting an immune response that depends on components of the IMD pathway. We recently showed that imd encodes a protein with a death domain with high similitary to that of mammalian RIP. Using a two-hybrid screen in yeast, we have isolated the death protein dfADD as a molecule that associates with IMD. Our data show that loss of dfADD function renders flies highly susceptible to Gram-negative infections without affecting resistance to Gram-positive bacteria. By genetic analysis we show that dfADD acts downstream of IMD in the pathway that controls inducibility of the antibacterial peptide genes.
| Immunity
2002: Vol 17, 575-581 | Abstract
Article complet | 165. Notch Signaling Controls Lineage Specification during Drosophila Larval Hematopoiesis
Duvic B, Hoffmann J, Meister M, Royet J
Abstract : Drosophila larval hemocytes originate from a hematopoietic organ called lymph glands, which are composed of paired lobes located along the dorsal vessel. Two nature blood cell populations are found in the circulating hemolymph : the macrophage-like plasmatocytes, and the crystal cells that contain enzymes of the immune-related melanization process. A third class of cells, called lamellocytes, are normally absent in larvae but differentiate after infection by parasites too large to be phagocytosed. Here we present evidence that the Notch signaling pathway plays an instructive role in the differentiation of crystal cells. Loss-of-function mutations in Notch result in severely decreased crystal cell numbers, whereas overexpression of Notch provokes the differentiation of high numbers of these cells. We demonstrate that, in this process, Serrate, not Delta, is the Notch ligand. In addition, Notch function is necessary for lamellocyte proliferation upon parasitization, although Notch overexpression does not result in lamellocyte production. Finally, Notch does not appear to play a role in the differentiation of the plasmatocyte lineage. This study underlines the existence of parallels in the genetic control of hematopoiesis in Drosophila and in mammals.
| Current Biology
2002: Vol 12, 1923-1927. | Abstract
Article complet | 164. Antimicrobial Peptides in Insect Immunity. In "Infectious Disease: Innate Immunity"
Bulet P, Charlet M, Hetru C
Abstract : With around one million named species and probably 8-10 times that number unnamed, insects account for the great majority of animal species on earth. Insects can be found in almost all terrestrial and freshwater habitats, from the driest deserts to freshwater ponds, from the canopy of a tropical rainforest (where their diverstity is unbelievably great) to the artic wastes. They are tremendously successful group. They are a fundamental part of our ecosystem. They are responsible for the pollination of many plants the decomposition of organic materials, facilitating the recycling of carbon, nitrogen, and other essential nutrients, the control of populations of harmful invertebrate species (including other insects), the direct production of certain foods (honey, for example) and the manufacture of useful products such as silk. However, they are often considered as negative, mainly because they are important vectors of animal and human diseases. Important features of their success are their short life cycle and their ability to evolve rapidly to colonize new niches and to mount rapid and efficient immune defenses against pathogens. The response of insects to infection can be divided into three main mechanisms. First, when the size of the foreign body is small enough, particular hemocytes (blood cells) can internalize these foreign bodies by phagocytosis. A second aspect, initiated upon contact of the foreign bodies with the internal cavity of the insect, is the rapid activation of proteolytic cascades leading to (1) melanization and encapsulation of the foreign material within an envelope of highly flattened cells, which become pigmented (melanized), (2) localized clotting of wound, and (3) opsonization. Finally, holometabolous insects respond to infection by a transient transcription of antimicrobial peptides (AMPs) by the fat body tissue (analogous to the mammalian liver). The AMPs are then secreted into hemolymph (bllod), where they accumulate to high concentrations and diffuse throughout the body. Interestingly, local expression of genes coding the AMPs is also observed in various surface epithelia at the site of infection, for an example, see the work of Tzou and co-workers (3) on the tissue-specific expression of AMP genes in Drosophila melanogaster epithelia. However, in insects that undergo an incomplete metamorphosis (heterometabolous). AMPs are produced constitutively by the hemocytes and secreted during infection (4).
| Ezekowitz R.A.B. and Hoffmann J.A., eds. Humana Press Inc
2002: Totowa, NJ, 89-107 | Abstract
Article complet | 163. Innate Immunity. In "Infectious Disease"
Royet J, Meister M, Ferrandon D
Abstract : The immune system of invertebrates has been the object of intense scrutiny ever since Elie Metchnikoo first discovery phagocytosis in starfish embryos in 1884 (1). Not surprisingly, the cellular arm of the insect innate immune response was the first to be investigated at the turn of the 20th century. Glaser and Paillot, followed later on by Metalnikow, uncovered the existence of a humoral arm of the insect host defense (2-5). Hovewer, the nature of the antimicrobial activity found in the hemolymph of immnized insects was not determined until early 1980s, when Hans Boman’s pioneering work ledd to the purification in the moth Hyalophora cecropia of small cationic peptides that were called cecropins (6). Hundreds of peptides with antimicrobial activities were subsequently identified and characterized from insects of most orders (reviewed in ref. 7). Understanding the mechanisms responsible for their production is a major goal of recent research in innate immunity. For the last 10 years, Drosophila has been one major model system successfully used to dissect the molecular cascades controlling innate immunity in invertebrates. We describe here the current knowledge of the humoral and cellular arms of Drosophila immunity and highlight the similitaries and disparities with the mammalian immune system.
| Ezekowitz R.A.B. and Hoffmann J.A., eds. Humana Press Inc
2002: Totowa, NJ, 137-153 | Abstract
Article complet | 162. PVF2, a PDGF/VEGF-like growth factor, induces hemocyte proliferation in Drosophila larvae
Munier A-I, Doucet D, Perrodou E, Zachary D, Meister M, Hoffmann J, Janeway CA, Lagueux M
Abstract : Blood cells play a crucial role in both morphogenetic and immunological processes in Drosophila, yet the factors regulating their proliferation remain largely unknown. In order to address this question, we raised antibodies against a tumorous blood cell line and identified an antigenic determinant that marks the surface of phenotypes and also circulating plasmotocytes in larvae. This antigen was identified as a Drosophila homolog of the mammalian receptor for plateletderived growth factor (PDGF)/vascular endothelial growth factor (VEGF). The Drosophila receptor controls cell proliferation in vitro. By overexpressing in vivo one of its putative ligands, PVF2, we included a dramatic increase in circulating hemocytes. These results identify the PDGF/VEGF receptor homolog and one of its ligands as important player in Drosophila hematopoiesis.
| EMBO Rep.
2002: Vol 3, 1195-1200. | Abstract
Article complet | 161. Immunity-related genes and gene families in Anopheles gambiae
Christophides GK, Zdobnov E, Barillas-Mury C, Birney E, Blandin S, Blass C, Brey PT, Collins FH, Danielli A, Dimopoulos G, Hetru C, Hoa NT, Hoffmann JA, Kanzok SM, Letunic I, Levashina EA, Loukeris TG, Lycett G, Meister S, Michel K, Moita LF, Muller HM, Osta MA, Paskewitz SM, Reichhart JM, Rzhetsky A, Troxler L, Vernick KD, Vlachou D, Volz J, von Mering C, Xu J, Zheng L, Bork P, Kafatos FC
Abstract : We have identified 242 Anopheles gambiae genes from 18 gene families implicated in innate immunity and have detected marked diversification relative to Drosophila melanogaster. Immune-related gene families involved in recognition, signal modulation, and effector systems show a marked deficit of orthologs and excessive gene expansions, possibly reflecting selection pressures from different pathogens encountered in these insects' very different life-styles. In contrast, the multifunctional Toll signal transduction pathway is substantially conserved, presumably because of counterselection for developmental stability. Representative expression profiles confirm that sequence diversification is accompanied by specific responses to different immune challenges. Alternative RNA splicing may also contribute to expansion of the immune repertoire.
| Science
2002: Vol 298, 159-165. | Abstract
Article complet | 160. Thioester-Containing Proteins of Protostomes. In "Infectious Disease: Innate Immunity"
Levashina EA, Blandin S, Moita LF, Lagueux M, Kafatos FC
Abstract : We characterize a novel hemocyte-specific acute phase glycoprotein from the malaria vector, Anopheles gambiae. It shows substantial structural and functional similarities, including the highly conserved thioester motif, to both a central component of mammalian complement system, factor C3, and to a pan-protease inhibitor, alpha2-macroglobulin. Most importantly, this protein serves as a complement-like opsonin and promotes phagocytosis of some Gram-negative bacteria in a mosquito hemocyte-like cell line. Chemical inactivation by methylamine and depletion by double-stranded RNA knockout demonstrate that this function is dependent on the internal thioester bond. This evidence of a complement-like function in a protostome animal adds substantially to the accumulating evidence of a common ancestry of immune defenses in insects and vertebrates.
| Ezekowitz R.A.B. and Hoffmann J.A., eds. Humana Press Inc
2002: Totowa, NJ, 155-173. | Abstract
Article complet | 159. Tissue and stage-specific expression of the Tolls in Drosophila embryos
Kambris Z, Hoffmann JA, Imler JL, Capovilla M
Abstract : The Drosophila transmembrane receptor Toll play a key role in specifying the dorsoventral axis of the embryo. At later stages of development, it controls the immune response of the fly to fungal and Gram-positive bacterial infections. The Drosophila genome has a total of nine Toll-like genes, including the previously characterizated Toll (Toll-1) and 18-wheller (Toll-2). Here we describe the embryonic expression patterns of the seven Toll-like genes Toll-3 through Toll-9. We find that these genes have distinct expression domains and that their expression is dynamically changing throughout embryonic development. This complex and tissue-specific regulation of Toll-like gene expression strongly suggests a role in embryonic development for most Drosophila Tolls. The evolving picture on the Toll family members in Drosophila contrasts with that of mammalian Toll-like receptors, which are predominantly expressed in immune responsive cells where their activation occurs via microbial structural determinants.
| Gene Expression Patterns
2002: Vol 2, 311-317. | Abstract
Article complet | 158. Immunopeptides in the defense reactions of Glossina morsitans to bacterial and Trypanosoma brucei infections
Boulanger N, Brun R, Ehret-Sabatier L, Kunz C, Bulet P
Abstract : Several dipteran insects are vectors of parasite causing major human infectious diseases. Among these, the tsetse fly, Glossima spp, is responsible for the transmission of trypanosomes, the pathogens responsible for sleeping sickness in Africa. A better understanding of insect-parasite intarctions will help establish new strategies to fight this important often fatal disease. Antimicrobial peptides (AMPs) are part of the humoral immune response in insects during bacterial, fungal and parasitic infections. Here, we studied the immune response of Glossima morsitans to bacteria and to Trypanosoma brucei brucei analysing the synthesis of AMPs as markers of the humoral immune response. By reversed-phase chromatography, mass spectrometry analysis, Edman degradation and in vitro antimicrobial assays of the hemolymph of immune-challenged adults of G. morsitans, we identified three AMPs: a cecropin, an attacin and a defensin. Three AMPs were found to be induced upon systemic bacterial infection and also after per os infections by bacteria and parasites.
| Insect Biochem Mol Biol
2002: Vol 32, 369-375. | Abstract
Article complet | 157. Splice-Activated UAS airpin vector gives complete RNAI knockout of single or double target transcripts in Drosophila melanogaster
Reichhart JM, Ligoxygakis P, Naitza S, Woerfel G, Imler JL, Gubb D
Abstract : A DNA vector giving complete RNAi knockout of nec is described. A stable hairpin–loop is inactive, but introduction of an intronic spacer activates the RNAi response. Similar constructs for the forked, Drs, and BG4 transcripts also give targeted suppression. Furthermore, “splice activation” can affect two trigger sequences, in a double knockout vector. We suggest that the splicing mechanism might cause localized “melting” of RNA followed by reannealing. This process would eliminate mismatched regions expected from hybridation of complementary RNA stands under physiological conditions. Unlike in plants, we show that the RNAi response in Drosophila is cell autonomous and our USA-f::nec-dsRNA strain froms a useful tool to visualize the domain of expression of Gal4 drivers.
| Genesis
2002: Vol 34, 160-164. | Abstract
Article complet | 156. A serpin mutant links Toll activation to melanization in the host defence of Drosophila
Ligoxygakis P, Pelte N, Ji C, Leclerc V, Duvic B, Belvin M, Jiang H, Hoffmann JA, Reichhart JM
Abstract : A prominent response during the Drosophila host defence is the introduction of proteolytic cascades, some of which lead to localized melanization of pathogen surfaces, while others activate one of the major players in the systemic antimicrobial response, the Toll pathway. Despite the fact that gain-of-function mutations in the Toll receptor gene result in melanization, a clear link between Toll activation ant the melanization reaction has not been family established. Here, we present evidence for the coordination of hemolymp-borne melanization with activation of the Toll pathway in the Drosophila host defence. The melanization reaction requires Toll pathway activation and depends on the removal of the Drosophila serine protease inhibitor Serpin27A. Flies deficient for this serpin exhibit spontaneous melanization in larvae and adults. Microbial challenge induces its removal from the hemolymph through Toll-dependent transcription of an acute phase immune reaction component.
| EMBO J
2002: Vol 21, 6330-6337. | Abstract
Article complet | 155. Solution structure of antimicrobial peptides with a b-hairpin fold. Structure-activity relationships. In "Membrane Interacting Peptides and Proteins"
Mandard N, Bulet P, Hetru C, Landon C, Vovelle F
Abstract : Gomesin is the first peptide isolated from spider exhibiting antimicrobial activities. This highly cationic peptide is composed of 18 amino-acid residues including four cysteines forming two disulfide linkages. The solution structure of gomesin has been determined using proton two-dimensional NMR (2D-NMR) and restrained molecular dynamics calculations. The global fold of gomesin consists in a well-resolved two-stranded antiparallel sheet connected by a noncanonical turn. A comparison between the structures of gomesin and protegrin-1 from porcine and androctonin from scorpion outlines several common features in the distribution of hydrophobic and hydrophilic residues. The N- and C-termini, the turn and one face of the sheet are hydrophilic, but the hydrophobicity of the other face depends on the peptide. The similarities suggest that the molecules interact with membranes in an analogous manner. The importance of the intramolecular disulfide bridges in the biological activity of gomesin is being investigated.
| (Ed Heitz) Research Signpost
2002: 155-171. | Abstract
Article complet | 154. DmMyD88 controls dorsoventral patterning of the Drosophila embryo
Kambris Z, Bilak H, D’Alessandro R, Belvin M, Imler JL, Capovilla M
Abstract : MyD88 is an adapter protein in the signal transduction pathway mediated by interleukin-1 (L-1) and Toll-like receptors. Drosophila homologue of MyD88 (DmMyD88) was recently shown to be required for the Toll-mediated immune response. In Drosophila, the Toll pathway was originally characterized for its role in the dorsoventral pattering of the embryo. We found that, like Toll, DmMyD88 messager RNA is maternally supplied to the embryo. Here we report the identification of a new mutant allele of DmMyD88, which generates a protein lacking the carboxyterminal extention, normally located downstream of the Toll/IL-1receptor domain. Homozygous mutant female flies lay dorsalized embryos that are rescued by expression of a transgenic DmMyD88 complementary DNA. The DmMyD88 mutation blocks the ventralizing activity of a gain-of-function Toll mutation. These results show that DmMyD88 encodes a essential component of the Toll pathway in dorsoventral pattern formation.
| EMBO Reports
2003: Vol 4, 64-69 | Abstract
Article complet | 153. Reverse genetics in the mosquito, Anopheles gambiae: targeted disruption of the Defensin gene
Blandin S, Moita LF, Kocher T, Wilm M, Kafatos FC, Levashina EA
Abstract :
| EMBO Reports
2002: 3, 852-856. | Abstract
Article complet | 152. A genome-wide analysis of immune responses in Drosophila
Irving P, Troxler L, Heuer TS, Belvin M, Kopczynski C, Reichhart JM, Hoffmann JA, Hetru C
Abstract : Oligonucleotide DNA microarrays were used for a genome-wide analysis of immune-challenged Drosophila infected with Gram-positive or Gram-negative bacteria, or with fungi. Aside from the expression of an established sef of immune defense genes, a significant number of previously unseen immune-induced genes were found. Genes of particular interest include corin- and Stubble-like genes, both of which have a type II transmembrane domain, easter- and snake-like genes, which may fulfil the roles of easter and snake in the Toll pathway, and a masque rade-like gene, potentially involved in enzyme regulation. The miccroarray data has also helped to greatly reduce the number of target genes in large gene groups, such as the proteases, helping to direct the choices for future mutant studies. Many of the up-regulated genes fit into the current conceptual framework of host defense, whereas others, including the sustantial number of genes with unknown functions, offer new avenues for research.
| Proc. Natl. Acad. Sci. USA
2001: Vol 98, 15119-15224. | Abstract
Article complet | 151. Immune response of Drosophila melanogaster to infection with the flagellate parasite Crithidia spp
Boulanger N, Ehret-Sabatier L, Brun R, Zachary D, Bulet P & Imler JL
Abstract : Insects are able to recognize invading microorganisms and to mount an immune response to bacterial and fungal infections. Recently, the fruitfly Drosophila melanogaster has emerged as a promising invertebrate model to investigate innate immunity because of its well-characterized genetics. Insects are also vectors of numerous parasites which can trigger an immune response. We have investigated the interaction of Drosophila melanogaster with the flagellate protozoan Crithidia spp. We show that a per os parasitic infection triggers the synthesis of several antimicrobial peptides. By reverse phase HPLC and mass spectrometry, peptides were shown to be present in the hemolymph and not in the gut tissue, suggesting the presence of immune messengers between the site of the infection, namely the gut, and the fat body, the main site of synthesis for antimicrobial peptides. Interestingly, we have identified one molecule which is specifically induced in the hemolymph after infection with Crithidia, but not with bacteria, suggesting that Drosophila can discriminate between pathogens. When flagellates were injected into the hemolymph, a low synthesis of antimicrobial peptides was observed together with phagocytosis of parasites by circulating hemocytes. The data presented here suggest that Drosophila-Crithidia spp. represents an interesting model to study host defense against protozoan parasites.
| Insect Biochem. Mol. Biol.
2001: Vol 31, 129-137. | Abstract
Article complet | 150. Insect Immunity. Constitutive expression of a cysteine-rich antifungal and a linear antibacterial peptide in a termite insect
Lamberty M, Zachary D, Lanot R, Bordereau C, Robert A, Hoffmann JA, Bulet P
Abstract : Two novel antimicrobial peptides, which we propose to name termicin and spinigerin, have been isolated from the fungus-growing termite Pseudacanthotermes spiniger (heterometabole insect, Isoptera). Termicin is a 36-amino acid residue antifungal peptide, with six cysteines arranged in a disulfide array similar to that of insect defensins. In contrast to most insect defensins, termicin is C-terminally amidated. Spinigerin consists of 25 amino acids and is devoid of cysteines. It is active against bacteria and fungi. Termicin and spinigerin show no obvious sequence similarities with other peptides. Termicin is constitutively present in hemocyte granules and in salivary glands. The presence of termicin and spinigerin in unchallenged termites contrasts with observations in evolutionary recent insects or insects undergoing complete metamorphosis, in which antimicrobial peptides are induced in the fat body and released into the hemolymph after septic injury.
| J. Biol Chem.
2001: Vol 276, 4085-4092. | Abstract
Article complet | 149. The defensin peptide of the malaria vector mosquito Anopheles gambiae: antimicrobial activities and expression in adult mosquitoes
Vizioli J, Richman AM, Uttenweiler-Joseph S, Blass C, Bulet P
Abstract : A recombinant Anopheles gambiae defensin peptide was used to define the antimicrobial activity spectrum against bacteria, filamentous fungi and yeast. Results showed that most of the Gram-positive bacterial species tested were sensitive to the recombinant peptide in a range of concentrations from 0.1 to 0.75 microM. No activity was detected against Gram-negative bacteria, with the exception of some E. coli strains. Growth inhibitory activity was detected against some species of filamentous fungi. Defensin was not active against yeast. The kinetics of bactericidal and fungicidal effects were determined for Micrococcus luteus and Neurospora crassa, respectively. Differential mass spectrometry analysis was used to demonstrate induction of defensin in the hemolymph of bacteria-infected adult female mosquitoes. Native peptide levels were quantitated in both hemolymph and midgut tissues. The polytene chromosome position of the defensin locus was mapped by in situ hybridization.
| Insect Biochem Mol Biol.
2001: Vol 31, 241-248. | Abstract
Article complet | 148. The domino gene of Drosophila encodes novel members of the SWI2/SNF2 family of DNA-dependent ATPases, which synergistically interact with Polycomb-group proteins
Ruhf ML, Braun A, Papoulas O, Tamkun JW, Randsholt N & Meister M
Abstract : The Drosophila domino gene has been isolated in a screen for mutations that cause hematopoietic disorders. Generation and analysis of loss-of-function domino alleles show that the phenotypes are typical for proliferation gene mutations. Clonal analysis demonstrates that domino is necessary for cell viability and proliferation, as well as for oogenesis. domino encodes two protein isoforms of 3202 and 2498 amino acids, which contain a common N-terminal region but divergent C termini. The common region includes a 500 amino acid DNA-dependent ATPase domain of the SWI2/SNF2 family of proteins, which function via interaction with chromatin. We show that, although domino alleles do not exhibit homeotic phenotypes by themselves, domino mutations enhance Polycomb group mutations and counteract Trithorax group effects. The Domino proteins are present in large complexes in embryo extracts, and one isoform binds to a number of discrete sites on larval polytene chromosomes. Altogether, the data lead us to propose that domino acts as a repressor by interfering with chromatin structure. This activity is likely to be performed as a subunit of a chromatin-remodeling complex.
| Development
2001: Vol 128, 1429-1441. | Abstract
Article complet | 147. Direct regulation of the muscle identity gene apterous by a Hox protein in the somatic mesoderm
Capovilla M, Kambris Z, Botas J
Abstract : Hox genes control segment identity in the mesoderm as well as in other tissues. Most evidence indicates that Hox genes act cell-autonomously in muscle development, although this remains a controversial issue. We show that apterous expression in the somatic mesoderm is under direct Hox control. We have identified a small enhancer element of apterous (apME680) that regulates reporter gene expression in the LT1-4 muscle progenitors. We show that the product of the Hox gene Antennapedia is present in the somatic mesoderm of the second and third thoracic segments. Through complementary alterations in the Antennapedia protein and in its binding sites on apME680, we show that Antennapedia positively regulates apterous in a direct manner, demonstrating unambiguously its cell-autonomous role in muscle development. Finally, we determine that LT1-4 muscles contain more nuclei in the thorax than in the abdomen and we propose that one of the segmental differences under Hox control is the number of myoblasts allocated to the formation of specific muscles in different segments.
| Development
2001: Vol 28, 1221-1230. | Abstract
Article complet | 146. Immunité innée : deux récepteurs pour détecter l'ADN bactérien
Imler JL & Reichhart JM
Abstract : No abstract.
| Médecine/Sciences
2001: Vol 17 | Abstract
Article complet | 145. Conserved role of a complement-like protein in phagocytosis revealed by dsRNA knockout in cultured cells of the mosquito, Anopheles gambiae
Levashina EA, Moita LF, Blandin S, Vriend G, Lagueux M, Kafatos FC
Abstract : We characterize a novel hemocyte-specific acute phase glycoprotein from the malaria vector, Anopheles gambiae. It shows substantial structural and functional similarities, including the highly conserved thioester motif, to both a central component of mammalian complement system, factor C3, and to a pan-protease inhibitor, alpha2-macroglobulin. Most importantly, this protein serves as a complement-like opsonin and promotes phagocytosis of some Gram-negative bacteria in a mosquito hemocyte-like cell line. Chemical inactivation by methylamine and depletion by double-stranded RNA knockout demonstrate that this function is dependent on the internal thioester bond. This evidence of a complement-like function in a protostome animal adds substantially to the accumulating evidence of a common ancestry of immune defenses in insects and vertebrates.
| Cell
2001: Vol 104, 709-718. | Abstract
Article complet | 144. LPS-induced immune response in Drosophila
Imler JL, Tauszig S, Jouanguy E, Forestier C & Hoffmann JA
Abstract : The study of the regulation of the inducible synthesis of antimicrobial peptides in Drosophila melanogaster has established this insect as a powerful model in which to study innate immunity. In particular, the molecular characterization of the regulatory pathway controlling the antifungal peptide drosomycin has revealed the importance of Tool receptors in innate immunity. We report here that injection of LPS into flies induces an immune response, suggesting that LPS receptors are used in Drosophila to detect Gram-negative bacteria infection. We have identified in the recently sequenced genome of Drosophila eight genes coding for Toll-like receptors in addition to Toll, which may function as LPS receptors. However, overexpression of a selection of these genes in tissue-culture cells does not result in up-regulation of the antibacterial peptide genes. These results are discussed in light of the recent data from genetic screens aimed at identifying the genes controlling the antibacterial response in Drosophila.
| J. Endotox. Res.
2001: Vol 6, 459-462 | Abstract
Article complet | 143. Toll receptors in innate immunity
Imler JL & Hoffmann JA
Abstract : Innate immunity is the first-line host defence of multicellular organisms that rapidly operates to limit infection upon exposure to infectious agents. In addition, the cells and molecules operating during this early stage of the immune response in vertebrates have a decisive impact on the shaping of the subsequent adaptive response. Genetic studies initially carried in the fruitfly Drosophila and later in mice have revealed the importance of proteins of the Toll family in the innate immune response. We present here our current understanding of the role of this evolutionary ancient family of proteins which are thought to function as cytokine receptor (Toll in Drosophila) or pattern recognition receptor (TLRs in mammals) and activate similar, albeit non identical, signal transduction pathways in flies and mammals.
| Trends in Cell Biol
2001: Vol 11, 304-310 | Abstract
Article complet | 142. Gambicin: a novel immune responsive antimicrobial peptide from the malaria vector Anopheles gambiae
Vizioli J, Bulet P, Hoffmann JA, Kafatos FC, Muller HM, Dimopoulos G
Abstract : A novel mosquito antimicrobial peptide, gambicin, and the corresponding gene were isolated in parallel through differential display-PCR, an expressed sequence tag (EST) project, and characterization of an antimicrobial activity in a mosquito cell line by reverse-phase chromatography. The 616-bp gambicin ORF encodes an 81-residue protein that is processed and secreted as a 61-aa mature peptide containing eight cysteines engaged in four disulfide bridges. Gambicin lacks sequence homology with other known proteins. Like other Anopheles gambiae antimicrobial peptide genes, gambicin is induced by natural or experimental infection in the midgut, fatbody, and hemocyte-like cell lines. Within the midgut, gambicin is predominantly expressed in the anterior part. Both local and systemic gambicin expression is induced during early and late stages of natural malaria infection. In vitro experiments showed that the 6.8-kDa mature peptide can kill both Gram-positive and Gram-negative bacteria, has a morphogenic effect on a filamentous fungus, and is marginally lethal to Plasmodium berghei ookinetes. An oxidized form of gambicin isolated from the cell line medium was more active against bacteria than the nonoxidized form from the same medium.
| Proc. Natl. Acad. Sci. USA
2001: Vol 98, 12630-12635. | Abstract
Article complet | 141. Drosophila immune deficiency (IMD) is a death domain protein that activates antibacterial defense and can promote apoptosis
Georgel P, Naitza S, Kappler C, Ferrandon D, Zachary D, Swimmer C, Kopczynski C, Duyk G, Reichhart JM, Hoffmann JA
Abstract : We report the molecular characterization of the immune deficiency (imd) gene, which encodes a protein with a death domain similar to that of mammalian RIP (receptor interacting protein), a protéine that plays a role in both NF- B activation and apoptosis. We show that imd functions upstream of the DmIKK signalosome and the caspase DREDD in the control of antibacterial peptides genes. Strikingly, overexpression of imd leads to constitutive transcription of these genes and to apoptosis, and both effects are blocked by coexpression of the caspase inhibitor P35. We also show that imd is involved in the apoptotic response to UV irradiation. These data raise the possibility that antibacterial response and apoptosis share common control eléments in Drosophila.
| Dev. Cell
2001: Vol 1, 503-514 | Abstract
Article complet | 140. Drosophila Toll is activated by Gram-positive bacteria through a circulating peptidoglycan recognition protein
Michel T, Reichhart JM, Hoffmann JA, Royet J
Abstract : Microbial infection activates two distinct intracellular signalling cascades in the immune-responsive fat body of Drosophila. Gram-positive bacteria and fungi predominatly induce the Toll signalling pathway, whereas Gram-negative bacteria activate the Imd pathway. Loss-of-function mutants in either pathway reduce the resistance to corresponding infections. Genetic screens have identified a range of genes involved in these intracellular signalling cascades, but how they are activated by microbial infection is largely unknown. Activation of the transmembrane receptor Toll requires a proteolytically cleaved form of an extracellular cytokine-like polypeptide, Spätzle, suggesting that Toll does not itself function as a bona fide recognition receptor of microbial patterns. This is a apparent contrast with the mammalian Toll-like receptors and raises the question of which host molecules actually rencognize microbial patterns to activate Toll through Spätzle. Here we present a mutation that blocks Toll activation by Gram-positive bacteria and significantly decreases resistance to this type of infection. The mutation semmelweis (seml) inactivates the gene encoding a peptidoglycan recognition protein (PGRP-SA). Interestingly, seml does not affect Toll activation by fungal infection, indicating the existence of a distinct recognition system for fungi to activate the Toll pathway.
| Nature
2001: Vol 414, 756-759. | Abstract
Article complet | 139. JNK signaling pathway is required for efficient wound healing in Drosophila
Rämet M, Lanot R, Zachary D, Manfruelli
Abstract : Efficient wound healing including and subsequent reepithelization is essential for animals ranging from insects to mammals to recover from epithelial injury. It is likely that genes involved in wound healing are conserved through the phylogeny and therefore, Drosophila may be an useful in vivo model to identify genes necessary during this process. Furthermore, epithelial movement during specific developmental precesses, such as dorsal closure, ressembles of those seen in mammalian wound healing. As puckered (puc) gene is a target of the JUN N-terminal kinase signaling pathway during dorsal closure, we investigated puc gene expression during wound healing in Drosophila. We showed that puc gene expression is induced at the edge of the wound in epithelial cells and Jun kinase is phosphorylated in wounded epidermal tissues, suggesting that the JUN N-terminal kinase signaling pathway is activated by a signal produced by an epidermal wound. In the absence of the Drosophila c-Fos homologue, puc gene expression is no longer induced. Finally, impaired epithelial repair in JUN N-terminal kinase deficient flies demonstrates that the JUN N-terminal kinase signaling is required to initiate the cell shape change at the onset of the epithelial wound healing. We conclude that the embryonic JUN N-terminal kinase gene cassette is induced at the edge of the wound. In addition, Drosophila appears as a good in vivo model to study morphogenetic processes requiring ephitelial regeneration such as wound healing in vertebrates.
| Developmental Biology
2001: Vol 241 (1), pp. 145-156 | Abstract
Article complet | 138. Innate immune defence against malaria infection in the mosquito
Dimopoulos G, Muller HM, Levashina EA, Kafatos FC
Abstract :
| Curr Opin Immunol.
2001: 13, 79-88 (Review) | Abstract
Article complet | 137. L'immunité innée : de la drosophile à l'homme
Ferrandon D, Hetru C, Reichhart JM & Hoffmann JA
Abstract : No abstract.
| Pour la Science: "Les défenses de l'organisme 8-12"
Dossier Hors-Série, Octobre 2000 | Abstract
Article complet | 136. The antimicrobial host defense of Drosophila
Meister M, Hetru C & Hoffmann JA
Abstract : No abstract
| Curr. Topics in Microbiol. and Immunol.
2000: 248 17-36 | Abstract
Article complet | 135. Penaeidins, antimicrobial peptides with chitin-binding activity, are produced and stored in shrimp granulocytes and released after microbial challenge
Destoumieux D, Munoz M, Cosseau C, Rodriguez J, Bulet P, Comps M & Bachère E
Abstract : Penaeidins are members of a new family of antimicrobial peptides isolated from a crustacean, which present both Gram-positive antibacterial and antifungal activities. We have studied the localization of synthesis and storage of penaeidins in the shrimp Penaeus vannamei. The distribution of penaeidin transcripts and peptides in various tissues reveals that penaeidins are constitutively synthesized and stored in the shrimp haemocytes. It was shown by immunocytochemistry, at both optical and ultrastructural levels, that the peptides are localized in granulocyte cytoplasmic granules. The expression and localization of penaeidins were further analysed in shrimp subjected to microbial challenge. We found that (1) penaeidin mRNA levels decrease in circulating haemocytes in the first 3 hours following stimulation and (2) an increase in plasma penaeidin concentration occurs after microbial challenge, together with (3) a penaeidin immunoreactivity in cuticular tissue, which can be related to the chitin-binding activity we demonstrate here for penaeidins.
| J. Cell Science.
2000: 113 461-469 | Abstract
Article complet | 134. Antibacterial and antifungal activities of vasostatin-1, the N-terminal fragment of chromogranin A
Lugardon K, Raffner R, Goumon Y, Corti A, Delmas A, Bulet P, Aunis D & Metz-Boutigue MH
Abstract : Vasostatin-1, the natural N-terminal 1-76 chromogranin A (CGA)-derived fragment in bovine sequence, has been purified from chromaffin secretory granules and identified by sequencing and matrix-assisted laser desorption time-of-flight mass spectrometry. This peptide, which displays antibacterial activity against Gram-positive bacteria at micromolar concentrations, is also able to kill a large variety of filamentous fungi and yeast cells in the 1-10 muM range. We have found that the C-terminal moiety of vasostatin-1 is essential for the antifungal activity, and shorter active peptides have been synthesized. In addition, from the comparison with the activity displayed by related peptides (human recombinant and rat synthetic fragments), we could determine that antibacterial and antifungal activities have different structural requirements. To assess for such activities in vivo, CGA and CGA-derived fragments were identified in secretory material released from human polymorphonuclear neutrophils upon stimulation. Vasostatin-1, which is stored in a large variety of cells (endocrine, neuroendocrine, and neurons) and which is liberated from stimulated chromaffin and immune cells upon stress, may represent a new component active in innate immunity.
| J. Biol. Chem.
2000: 275,10745-10753 | Abstract
Article complet | 133. Signaling mechanisms in the antimicrobial host defense of Drosophila
Imler JL & Hoffmann JA
Abstract : Drosophila has appeared in recent years as a powerful model to study innate immunity. Several papers published in the past year shed light on the role of the three Rel proteins Dorsal, Dif and Relish in the regulation of antimicrobial peptide expression. In addition, the discovery that a blood serine protease inhibitor is involved in the control of the antifungal response indicates that Toll is activated upon triggering of a proteolytic cascade and does not function as a Drosophila pattern recognition receptor.
| Curr. Opin. in Microbiol.
2000: 3, 16-22 | Abstract
Article complet | 132. Cloning and analysis of a cecropin gene from the malaria vector mosquito, Anopheles gambiae
Vizioli J, Bulet P, Charlet M, Lowenberger C, Blass C, Müller HM, Dimopoulos G, Hoffmann JA, Kafatos FC & Richman A
Abstract : Parasites of the genus Plasmodium are transmitted to mammalian hosts by anopheline mosquitoes. Within the insect vector, parasite growth and development are potentially limited by antimicrobial defence molecules. Here, we describe the isolation of cDNA and genomic clones encoding a cecropin antibacterial peptide from the malaria vector mosquito Anopheles gambiae. The locus was mapped to polytene division 1C of the X chromosome. Cecropin RNA was induced by infection with bacteria and Plasmodium. RNA levels varied in different body parts of the adult mosquito. During development, cecropin expression was limited to the early pupal stage. The peptide was purified from both adult mosquitoes and cell culture supernatants. Anopheles gambiae synthetic cecropins displayed activity against Gram-negative and Gram-positive bacteria, filamentous fungi and yeasts.
| Insect Mol. Biol.
2000: 9, 75-84 | Abstract
Article complet | 131. Insect peptides with improved protease-resistance protect mice against bacterial infection
Otvos L Jr, Bokonyi K, Varga I, Otvos BI, Hoffmann R, Ertl HCJ, Wade JD, McManus AM, Craik DJ & Bulet P
Abstract : At a time of the emergence of drug-resistant bacterial strains, the development of antimicrobial compounds with novel mechanisms of action is of considerable interest. Perhaps the most promising among these is a family of antibacterial peptides originally isolated from insects. These were shown to act in a stereospecific manner on an as-yet unidentified target bacterial protein. One of these peptides, drosocin, is inactive in vivo due to the rapid decomposition in mammalian sera. However, another family member, pyrrhocoricin, is significantly more stable, has increased in vitro efficacy against gram-negative bacterial strains, and if administered alone, as we show here, is devoid of in vitro or in vivo toxicity. At low doses, pyrrhocoricin protected mice against Escherichia coli infection, but at a higher dose augmented the infection of compromised animals. Analogs of pyrrhocoricin were, therefore, synthesized to further improve protease resistance and reduce toxicity. A linear derivative containing unnatural amino acids at both termini showed high potency and lack of toxicity in vivo and an expanded cyclic analog displayed broad activity spectrum in vitro. The bioactive conformation of native pyrrhocoricin was determined by nuclear magnetic resonance spectroscopy, and similar to drosocin, reverse turns were identified as pharmacologically important elements at the termini, bridged by an extended peptide domain. Knowledge of the primary and secondary structural requirements for in vivo activity of these peptides allows the design of novel antibacterial drug leads.
| Protein Science
2000: 9, 742-749 | Abstract
Article complet | 130. Synthetic glycopeptide and phosphopeptide models of an antibacterial fragment of chromogranin A
Cudic M, Bulet P & Otvos L Jr
Abstract : In order to fully characterize the activity spectrum and additional biochemical properties of native antimicrobial peptides corresponding to chromogranin A, we synthetized glycosylated, phosphorylated and double modified versions of the reportedly antibacterial 173-194 fragment. While no conformational change was detected, the modifications stabilized the peptide from proteolytic cleavage. All peptides remained inactive against a number of Gram-positive and Gram-negative bacterial strains in the experimental conditions used.
| Protein and Peptide Lett.
2000: 7, 143-150 | Abstract
Article complet | 129. The Rel protein DIF mediates the antifungal but not the antibacterial host defense in Drosophila
Rutschmann S, Jung AC, Hetru C, Reichhart JM, Hoffmann JA & Ferrandon D
Abstract : We have isolated two Drosophila lines that carry point mutations in the gene coding for the NF-KB-like factor DIF. Like mutants of the Toll pathway, Dif mutant flies are susceptible to fungal but not to bacterial infections. Genetic epistasis experiments demonstrate that Dif mediates the Toll-dependent control of the inducibility of the antifungal peptide gene Drosomycin. Strikingly, DIF alone is required for the antifungal response in adults, but is redundant in larvae with Dorsal, another Rel family member. In Drosophila, Dif appears to be dedicated to the antifungal defense elicited by fungi and gram-positive bacteria. We discuss in this light the possibility that NF-KB1/p50 might be required more specifically in the innate immune response against gram-positive bacteria in mammals.
| Immunity
2000: 12, 569-580 | Abstract
Article complet | 128. Androctonin, a hydrophilic disulphide-bridged non-haemolytic antimicrobial peptide : a plausible mode of action
Hetru C, Letellier L, Oren Z, Hoffmann JA & Shai Y
Abstract : Androctonin is a 25-residue non-haemolytic anti-microbial peptide isolated from the scorpion Androctonus australis and contains two disulphide bridges. Androctonin is different from known native anti-microbial peptides, being a relatively hydrophilic and non-amphipathic molecule. This raises the possibility that the target of androctonin might not be the bacterial membrane, shown to be a target for most amphipathic lytic peptides. To shed light on its mode of action on bacteria and its non-haemolytic activity, we synthesized androctonin, its fluorescent derivatives and its all-D-amino acid enantiomer. The enantiomer preserved high activity, suggesting a lipid-peptide interaction between androctonin and bacterial membranes. In Gram-positive and (at higher concentrations) Gram-negative bacteria, androctonin induced an immediate perturbation of the permeability properties of the cytoplasmic membrane of the bacterial energetic state, concomitant with perturbation of the morphology of the cell envelope as revealed by electron microscopy. Androctonin binds only to negatively charged lipid vesicles and induces the leakage of markers at high concentrations and with a slow kinetics, in contrast with amphipathic alpha-helical anti-microbial peptides that bind and permeate negatively charged vesicles, and to a smaller extent also zwitterionic ones. This might explain the selective lytic activity of androctonin towards bacteria but not red blood cells. Polarized attenuated total reflection-Fourier transform infrared spectroscopy revealed that androctonin adopts a beta-sheet structure in membranes and did not affect the lipid acyl chain order, which supports a detergent-like effect. The small size of androctonin, its hydrophilic character and its physicochemical properties are favourable features for its potential application as a replacement for commercially available antibiotics to which bacteria have developed resistance.
| Biochem. J.
2000: 345, 653-664 | Abstract
Article complet | 127. The phytopathogenic bacteria Erwinia carotovora infects Drosophila and activates an immune response
Basset A, Khush RS, Braun A, Gardan L, Boccard F, Hoffmann JA & Lemaitre B
Abstract : Although Drosophila possesses potent immune responses, little is known about the microbial pathogens that infect Drosophila. We have identified members of the bacterial genus Erwinia that induce the systemic expression of genes encoding antimicrobial peptides in Drosophila larvae after ingestion. These Erwinia strains are phytopathogens and use flies as vectors, our data suggest that these strains have also evolved mechanisms for exploiting their insect vectors as hosts. Erwinia infections induce an antimicrobial response in Drosophila larvae with a preferential expression of antibacterial versus antifungal peptide-encoding genes. Antibacterial peptide gene expression after Erwinia infection is reduced in two Drosophila mutants that have reduced numbers of hemocytes, suggesting that blood cells play a role in regulating Drosophila antimicrobial responses and also illustrating that this Drosophila-Erwinia interaction provides a powerful model for dissecting host-pathogen relationships.
| Proc. Natl. Acad. Sci. USA
2000: 97, 3376-3381 | Abstract
Article complet | 126. A modular chitin-binding protease associated with hemocytes and hemolymph in the mosquito Anopheles gambiae
Danielli A, Loukeris TG, Lagueux M, Müller H-M, Richman & Kafatos F
Abstract : Sp22D, a modular serine protease encompassing chitin binding, low density lipoprotein receptor, and scavenger receptor cysteine-rich domains, was identified by molecular cloning in the malaria vector, Anopheles gambiae. It is expressed in multiple body parts and during much of development, most intensely in hemocytes. The protein appears to be posttranslationally modified. Its integral, putatively glycosylated form is secreted in the hemolymph, whereas a smaller form potentially generated by proteolytic processing is associated with the tissues. Bacterial challenge or wounding result in low-level RNA induction, but the protein does not bind to bacteria, nor is its processing affected by infection. However, Sp22D binds to chitin with high affinity and undergoes transient changes in processing during pupal to adult metamorphosis, it may respond to exposure to naked chitin during tissue remodeling or damage.
| Proc. Natl. Acad. Sci. USA
2000: 97, 7136-7141 | Abstract
Article complet | 125. Toll-related receptors and the control of antimicrobial peptide expression in Drosophila
Tauszig S, Jouanguy E, Hoffmann JA & Imler JL
Abstract : Insects defend themselves against infectious microorganisms by synthesizing potent antimicrobial peptides. Drosophila has appeared in recent years as a favorable model to study this innate host defense. A genetic analysis of the regulation of the antifungal peptide drosomycin has demonstrated a key role for the transmembrane receptor Toll, which prompted the search for mammalian homologs. Two of these, Toll-like receptor (TLR)2 and TLR4, recently were shown to play a critical role in innate immunity against bacteria. Here we describe six additional Toll-related genes (Toll-3 to Toll-8) in Drosophila in addition to 18-wheeler. Two of these genes, Toll-3 and Toll-4, are expressed at a low level. Toll-6, -7, and -8, on the other hand, are expressed at high levels during embryogenesis and molting, suggesting that, like Toll and 18w, they perform developmental functions. Finally, Toll-5 is expressed only in larvae and adults. By using chimeric constructs, we have tested the capacity of the signaling Toll/IL-1R homology domains of these receptors to activate antimicrobial peptide promoters and found that only Toll and Toll-5 can activate the drosomycin promoter in transfected cells, thus demonstrating specificity at the level of the Toll/IL-1R homology domain. In contrast, none of these constructs activated antibacterial peptide promoters, suggesting that Toll-related receptors are not involved in the regulation of antibacterial peptide expression. This result was independently confirmed by the demonstration that a dominant-negative version of the kinase Pelle can block induction of drosomycin by the cytokine Spaetzle, but does not affect induction of the antibacterial peptide attacin by lipopolysaccharide.
| Proc. Natl. Acad. Sci. USA
2000: 97, 10520-10525 | Abstract
Article complet | 124. Penaeidins, a family of antimicrobial peptides from penaeid shrimp (Crustacea, Decapoda)
Destoumieux D, Munoz M, Bulet P & Bachère E
Abstract : The production of antimicrobial peptides represents a first-line host defense mechanism of innate immunity that is widespread in nature. Only recently such effectors were isolated in crustacean species, whereas numerous antimicrobial peptides have been characterized from other arthropods, both insects and chelicerates. This review presents findings on a family of antimicrobial peptides, named penaeidins, isolated from the shrimp Penaeus vannamei. Their structure and antimicrobial properties as well as their immune function will be discussed through analyses of penaeidin gene expression and peptide distribution upon microbial challenge.
| Cell. Mol. Life Sci.
2000: 57, 1260-1271 | Abstract
Article complet | 123. Role of Drosophila IKKg in a Toll-independent antibacterial immune response
Rutschmann S, Jung AC, Zhou R, Silverman N, Hoffmann JA & Ferrandon D
Abstract : We have generated, by ethylmethane sulfonate mutagenesis, loss-of-function mutants in the Drosophila homolog of the mammalian I-kappa B kinase (IKK) complex component IKK gamma (also called NEMO). Our data show that Drosophila IKK gamma is required for the Relish-dependent immune induction of the genes encoding antibacterial peptides and for resistance to infections by Escherichia coli. However, it is not required for the Toll-DIF-dependent antifungal host defense. The results indicate distinct control mechanisms of the Rel-like transactivators DIF and Relish in the Drosophila innate immune response and show that Drosophila Toll does not signal through a IKK gamma-dependent signaling complex. Thus, in contrast to the vertebrate inflammatory response, IKK gamma is required for the activation of only one immune signaling pathway in Drosophila.
| Nature Immunol.
2000: 1, 342-347 | Abstract
Article complet | 122. Constitutive expression of a complement-like protein in Toll and JAK gain-of-function mutants of Drosophila
Lagueux M, Perrodou E, Levashina EA, Capovilla & Hoffmann JA
Abstract : We show that Drosophila expresses four genes encoding proteins with significant similarities with the thiolester-containing proteins of the complement C3/alpha(2)-macroglobulin superfamily. The genes are transcribed at a low level during all stages of development, and their expression is markedly up-regulated after an immune challenge. For one of these genes, which is predominantly expressed in the larval fat body, we observe a constitutive expression in gain-of-function mutants of the Janus kinase (JAK) hop and a reduced inducibility in loss-of-function hop mutants. We also observe a constitutive expression in gain-of-function Toll mutants. We discuss the possible roles of these novel complement-like proteins in the Drosophila host defense.
| Proc. Natl. Acad. Sci. USA
2000: 97, 11427-11432 | Abstract
Article complet | 121. Tissue-specific inducible expression of antimicrobial peptide genes in Drosophila surface epithelia
Tzou P, Ohresser S, Ferrandon D, Capovilla M, Reichhart JM, Lemaitre B, Hoffmann JA & Imler JL
Abstract : The production of antimicrobial peptides is an important aspect of host defense in multicellular organisms. In Drosophila, seven antimicrobial peptides with different spectra of activities are synthesized by the fat body during the immune response and secreted into the hemolymph. Using GFP reporter transgenes, we show here that all seven Drosophila antimicrobial peptides can be induced in surface epithelia in a tissue-specific manner. The imd gene plays a critical role in the activation of this local response to infection. In particular, drosomycin expression, which is regulated by the Toll pathway during the systemic response, is regulated by imd in the respiratory tract, thus demonstrating the existence of distinct regulatory mechanisms for local and systemic induction of antimicrobial peptide genes in Drosophila.
| Immunity
2000: Vol 13, 737-748 | Abstract
Article complet | 120. Postembryonic hematopoiesis in Drosophila
Lanot R, Zachary D, Holder FC & Meister M
Abstract : We have investigated the blood cell types present in Drosophila at postembryonic stages and have analysed their modifications during development and under immune conditions. The anterior lobes of the larval hematopoietic organ or lymph gland contain numerous active secretory cells, plasmatocytes, few crystal cells, and a number of undifferentiated prohemocytes. The posterior lobes contain essentially prohemocytes. The blood cell population in larval hemolymph differs and consists mainly of plasmatocytes which are phagocytes, and of a low percentage of crystal cells which reportedly play a role in humoral melanisation. We show that the cells in the lymph gland can differentiate into a given blood cell lineage when solicited. Under normal nonimmune conditions, we observe a massive differentiation into active macrophages at the onset of metamorphosis in all lobes. Simultaneously, circulating plasmatocytes modify their adhesion and phagocytic properties to become pupal macrophages. All phagocytic cells participate in metamorphosis by ingesting doomed larval tissues. The most dramatic effect on larval hematopoiesis was observed following infestation by a parasitoid wasp. Cells within all lymph gland lobes, including prohemocytes from posterior lobes, massively differentiate into a new cell type specifically devoted to encapsulation, the lamellocyte.
| Devel. Biol.
2000: Vol 230, 243-257 | Abstract
Article complet | 119. L'hématopoïèse chez la drosophile
Meister M
Abstract : No abstract
| Médecine/Sciences
2000: Vol 16, 1444-1446 | Abstract
Article complet | 118. Médecine/Sciences
Reichhart JM & Imler JL
Abstract : No abstract
| Toll story Mini-Synthèse
2000: Vol 16, 1439-1442 | Abstract
Article complet | 117. Toll and Toll-like proteins : an ancient family of receptors signaling infection
Imler JL & Hoffmann JA
Abstract : Innate immunity is the first-line host defense of multicellular organisms that rapidly operates to limit infection upon exposure to microbes. It involves intracellular signaling pathways in the fruit-fly Drosophila and in mammals that show striking similarities. Recent genetic and biochemical data have revealed, in particular, that proteins of the Toll family play a critical role in the immediate response to infection. We review here the recent developments on the structural and functional characterization of this evolutionary ancient and important family of proteins, which can function as cytokine receptors (Toll in Drosophila) or pattern recognition receptors (TLR4 in mammals) and activate similar, albeit non identical signal transduction pathways, in flies and mammals.
| Reviews in Immunogenetics
2000: Vol 2, 294-304 | Abstract
Article complet | 116. Isolation and characterization of gomesin, an 18-residue cysteine-rich defense peptide from the spider Acanthoscurria gomesiana hemocytes with sequence similarities to horseshoe crab antimicrobial peptides of the tachyplesin family
Silva PI. Jr, Daffre S, Bulet P
Abstract : We have purified a small size antimicrobial peptide, named gomesin, from the hemocytes of the unchallenged tarantula spider Acanthoscurria gomesiana. Gomesin has a molecular mass of 2270.4 Da, with 18 amino acids, including a pyroglutamic acid as the N terminus, a C-terminal arginine alpha-amide, and four cysteine residues forming two disulfide bridges. This peptide shows marked sequence similarities to antimicrobial peptides from other arthropods such as tachyplesin and polyphemusin from horseshoe crabs and androctonin from scorpions. Interestingly, it also shows sequence similarities to protegrins, antimicrobial peptides from porcine leukocytes. Gomesin strongly affects bacterial growth, as well as the development of filamentous fungi and yeast. In addition, we showed that gomesin affects the viability of the parasite Leishmania amazonensis.
| J. Biol Chem.
2000: Vol 275, 33464-33470 | Abstract
Article complet | 115. Interaction between heat shock ptoteins and antimicrobial peptides
Otvos L, Insug O, Rogers M, Consolvo P, Condie B, Lovas S, Bulet P, Blaszczyk-Thurin M
Abstract : Drosocin, pyrrhocoricin, and apidaecin, representing the short (18-20 amino acid residues) proline-rich antibacterial peptide family, originally isolated from insects, were shown to act on a target bacterial protein in a stereospecific manner. Native pyrrhocoricin and one of its analogues designed for this purpose protect mice from bacterial challenge and, therefore, may represent alternatives to existing antimicrobial drugs. Furthermore, this mode of action can be a basis for the design of a completely novel set of antibacterial compounds, peptidic or peptidomimetic, if the interacting bacterial biopolymers are known. Recently, apidaecin was shown to enter Escherichia coli and subsequently kill bacteria through sequential interactions with diverse target macromolecules. In this paper report, we used biotin- and fluorescein-labeled pyrrhocoricin, drosocin, and apidaecin analogues to identify biopolymers that bind to these peptides and are potentially involved in the above-mentioned multistep killing process. Through use of a biotin-labeled pyrrhocoricin analogue, we isolated two interacting proteins from E. coli. According to mass spectrometry, Western blot, and fluorescence polarization, the short, proline-rich peptides bound to DnaK, the 70-kDa bacterial heat shock protein, both in solution and on the solid-phase. GroEL, the 60-kDa chaperonin, also bound in solution. Control experiments with an unrelated labeled peptide showed that while binding to DnaK was specific for the antibacterial peptides, binding to GroEL was not specific for these insect sequences. The killing of bacteria and DnaK binding are related events, as an inactive pyrrhocoricin analogue made of all-D-amino acids failed to bind. The pharmaceutical potential of the insect antibacterial peptides is underscored by the fact that pyrrhocoricin did not bind to Hsp70, the human equivalent of DnaK. Competition assay with unlabeled pyrrhocoricin indicated differences in GroEL and DnaK binding and a probable two-site interaction with DnaK. In addition, all three antibacterial peptides strongly interacted with two bacterial lipopolysaccharide (LPS) preparations in solution, indicating that the initial step of the bacterial killing cascade proceeds through LPS-mediated cell entry.
| Biochemistry
2000: Vol 39 ,14150-14159 | Abstract
Article complet | 114. Identification of genes that modify ataxin-1-induced neurodegeneration
Fernandez-Funez P, Nino-Rosales ML, de Gouyon B, She WC, Luchak JM, Martinez P, Turieganos E, Benito J, Capovilla M, Skinner PJ, McCall A, Canal I, Orr HT, Zoghbi HY, and Botas J
Abstract : A growing number of human neurodegenerative diseases result from the expansion of a glutamine repeat in the protein that causes the disease. Spinocerebellar ataxia type 1 (SCA1) is one such disease-caused by expansion of a polyglutamine tract in the protein ataxin-1. To elucidate the genetic pathways and molecular mechanisms underlying neuronal degeneration in this group of diseases, we have created a model system for SCA1 by expressing the full-length human SCA1 gene in Drosophila. Here we show that high levels of wild-type ataxin-1 can cause degenerative phenotypes similar to those caused by the expanded protein. We conducted genetic screens to identify genes that modify SCA1-induced neurodegeneration. Several modifiers highlight the role of protein folding and protein clearance in the development of SCA1. Furthermore, new mechanisms of polyglutamine pathogenesis were revealed by the discovery of modifiers that are involved in RNA processing, transcriptional regulation and cellular detoxification. These findings may be relevant to the treatment of polyglutamine diseases and, perhaps, to other neurodegenerative diseases, such as Alzheimer's and Parkinson's disease.
| Nature
2000: Vol 408, 101-106 | Abstract
Article complet | 113. The necrotic gene in Drosophila corresponds to one of a cluster of three serpin transcripts mapping at 43A1.2
Green C, Levashina E, McKimmie C, Dafforn T, Reichhart JM, Gubb D
Abstract : Mutants of the necrotic (nec) gene in Drosophila melanogaster die in the late pupal stage as pharate adults, or hatch as weak, but relatively normal-looking, flies. Adults develop black melanized spots on the body and leg joints, the abdomen swells with hemolymph, and flies die within 3 or 4 days of eclosion. The TOLL-mediated immune response to fungal infections is constitutively activated in nec mutants and pleiotropic phenotypes include melanization and cellular necrosis. These changes are consistent with activation of one or more proteolytic cascades. The nec gene corresponds to Spn43Ac, one of a cluster of three putative serine proteinase inhibitors at 43A1.2, on the right arm of chromosome 2. Although serpins have been implicated in the activation of many diverse pathways, lack of an individual serpin rarely causes a detectable phenotype. Absence of Spn43Ac, however, gives a clear phenotype, which will allow a mutational analysis of critical features of the molecular structure of serpins.
| Genetics
2000: Vol 156, 1117-1127. | Abstract
Article complet | 112. A microfluometer assay to measure the expression of b-galactosidase and GFP reporter genes in single Drosophila flies
Jung AC, Criqui MC, Rutschmann S, Hoffmann JA & Ferrandon D
Abstract : beta-galactosidase and green fluorescent protein (GFP) are among the most commonly used reporter genes to monitor gene expression in various organisms including Drosophila melanogaster. Their expression is usually detected in a qualitative way by direct microscopic observations of cells, tissues, or whole animals. To measure in vivo the inducibility of two antimicrobial peptide genes expressed during the Drosophila innate immune response, we have adapted two reporter gene systems based on the beta-galactosidase enzymatic activity and GFP. We have designed a 96-well microplate fluorometric assay sensitive enough to quantify the expression of both reporter genes in single flies. The assay has enabled us to process efficiently and rapidly a large number of individual mutant flies generated during an ethylmethane sulfonate saturation mutagenesis of the Drosophila genome. This method may be used in any screen that requires the quantification of reporter gene activity in individual insects.
| Biotechniques
2000: Vol 30, 594-601. | Abstract
Article complet | 111. Dominant-negative mutants reveal a role for the CDK7 kinase at the midblastula transition in Drosophila embryos
Leclerc V., Tani-Raisin S., Léopold P
Abstract :
| EMBO J.
2000 : 19, 7, 1567-1575. | Abstract
Article complet | 110. Dorsal-B, a splice variant of the Drosophila factor Dorsal, is a novel Rel/NF-kB transcriptional activator
Gross I, Georgel P, Oertel-Buchheit P, Schnarr M & Reichhart JM
Abstract : The Drosophila transcription factor Dorsal, a member of the Rel/NF-kappaB family of proteins, plays a key role in the establishment of dorsoventral polarity in the early embryo and is also involved in the immune response. Here, we present evidence that the primary transcript of dorsal can be alternatively spliced, generating Dorsal-B, a new Rel/NF-kappaB family member. Dorsal and Dorsal-B are identical in the N-terminal region, which comprises both a DNA-binding domain and a dimerization domain. However, Dorsal-B lacks the nuclear localization signal located at the end of the Rel domain of Dorsal and is totally divergent in the C-terminal portion. Although Dorsal-B by itself is not able to induce the expression of a kappaB-controlled Luciferase reporter gene, we demonstrate that its C-terminal portion has transactivating properties. Analysis of the dorsal-B expression pattern indicates that the splicing is tissue-specific and excludes a putative role in early embryogenesis. However, dorsal-B synthesis is enhanced upon septic injury, and this challenge induces a nuclear accumulation of the protein in fat body cells suggesting that it may be involved in the immune response.
| Gene
1999: 228, 233-242 | Abstract
Article complet | 109. Insect immunity : molecular cloning, expression, and characterization of cDNAs and genomic DNA encoding three isoforms of insect defensin in Aedes aegypti.
Lowenberger C, Smartt CT, Bulet P, Ferdig MT, Severson DW, Hoffmann JA & Christensen BM
Abstract : Aedes aegypti were immune activated by injection with bacteria, and the expression of insect defensins was measured over time. Northern analyses indicated that defensin transcriptional activity continued for at least 21 days after bacterial injection, and up to 10 days after saline inoculation. Mature defensin levels in the haemolymph reached approximately 45 microM at 24 h post inoculation. cDNAs encoding the preprodefensins of three previously described mature Ae. aegypti defensins were amplified by PCR, cloned and sequenced. Genomic clones were amplified using primers designed against the cDNA sequence. Sequence comparison indicates that there is significant inter- and intra-isoform variability in the signal peptide and prodefensin sequences of defensin genes. Preprodefensin sequences of isoforms A and B are very similar, consisting of a signal peptide region of twenty amino acids, a prodefensin region of thirty-eight amino acids and a forty amino acid mature peptide domain. The sequence encoding isoform C is significantly different, comprising a signal peptide region of twenty-three amino acids, a prodefensin region of thirty-six amino acids, and the mature protein domain of forty amino acids. Analysis of the genomic clones of each isoform revealed one intron spatially conserved in the prodefensin region of all sequences. The intron in isoforms A and B is 64 nt long, and except for a 4 nt substitution in one clone, these intron sequences are identical. The intron in isoform C is 76 nt long and does not share significant identity with the intron sequences of isoforms A or B. The defensin gene mapped to chromosome 3, between two known loci, blt and LF168.
| Insect Mol. Biol.
1999: 8, 107-118 | Abstract
Article complet | 108. Mosquito-Plasmodium interactions in response to immune activation of the vector
Lowenberger CA, Kamal S, Chiles J, Paskewitz S, Bulet P, Hoffmann JA & Christensen BM
Abstract : During the development of Plasmodium sp. within the mosquito midgut, the parasite undergoes a series of developmental changes. The elongated ookinete migrates through the layers of the midgut where it forms the oocyst under the basal lamina. We demonstrate here that if Aedes aegypti or Anopheles gambiae, normally susceptible to Plasmodium gallinaceum and P. berghei, respectively, are immune activated by the injection of bacteria into the hemocoel, and subsequently are fed on an infectious bloodmeal, there is a significant reduction in the prevalence and mean intensity of infection of oocysts on the midgut. Only those mosquitoes immune activated prior to, or immediately after, parasite ingestion exhibit this reduction in parasite development. Mosquitoes immune activated 2-5 days after bloodfeeding show no differences in parasite burdens compared with naive controls. Northern analyses reveal that transcriptional activity for mosquito defensins is not detected in the whole bodies of Ae. aegypti from 4 h to 10 days after ingesting P. gallinaceum, suggesting that parasite ingestion, passage from the food bolus through the midgut, oocyst formation, and subsequent release of sporozoites into the hemolymph do not induce the production of defensin. However, reverse transcriptase-PCR of RNA isolated solely from the midguts of Ae. aegypti indicates that transcription of mosquito defensins occurs in the midguts of naive mosquitoes and those ingesting an infectious or noninfectious bloodmeal. Bacteria-challenged Ae. aegypti showed high levels of mature defensin in the hemolymph that correlate with a lower prevalence and mean intensity of infection with oocysts. Because few oocysts were found on the midgut of immune-activated mosquitoes, the data suggest that some factor, induced by bacterial challenge, kills the parasite at a preoocyst stage.
| Exp. Parasitol.
1999: 91, 59-69 | Abstract
Article complet | 107. Isolation from the lepidopteran Heliothis virescens of a novel insect defensin with potent antifungal activity
Lamberty M, Ades S, Uttenweiler-Joseph S, Brookhart G, Bushey D, Hoffmann JA & Bulet P
Abstract : Lepidoptera have been reported to produce several antibacterial peptides in response to septic injury. However, in marked contrast to other insect groups, no inducible antifungal molecules had been described so far in this insect order. Surprisingly, also cysteine-rich antimicrobial peptides, which predominate in the antimicrobial defense of other insects, had not been discovered in Lepidoptera. Here we report the isolation from the hemolymph of immune induced larvae of the lepidopteran Heliothis virescens of a cysteine-rich molecule with exclusive antifungal activity. We have fully characterized this antifungal molecule, which has significant homology with the insect defensins, a large family of antibacterial peptides directed against Gram-positive strains. Interestingly, the novel peptide shows also similarities with the antifungal peptide drosomycin from Drosophila. Thus, Lepidoptera appear to have built their humoral immune response against bacteria on cecropins and attacins. In addition, we report that Lepidoptera have conferred antifungal properties to the well conserved structure of antibacterial insect defensins through amino acid replacements.
| J. Biol. Chem.
1999: 274, 9320-9326 | Abstract
Article complet | 106. Les peptides antimicrobiens de la drosophile
Bulet P
Abstract : En réponse à une infection expérimentale, le corps gras des insectes (équivalent fonctionnel du foie des mammifères) synthétise plusieurs peptides antimicrobiens. Chez la drosophile (Drosophila melanogaster, diptère) une approche par biologie moléculaire et biochimie a permis de caractériser sept peptides antimicrobiens qui sont sécrétés dans le sang des insectes à des concentrations variant de 1 µM à 100 µM. Ces molécules appartiennent aux 4 familles de peptides antimicrobiens d'insectes: (1) les peptides constitués d’hélices a, (2) les peptides à ponts disulfure, (3) les peptides riches en résidus proline et (4) les peptides riches en résidus glycine. La réponse immunitaire humorale des insectes présente des similitudes avec la réponse inflammatoire de phase aiguë des mammifères et avec la réponse immunitaire des plantes. En effet, les défensines d’insectes présentent des similitudes structurales avec les défensines des mammifères ainsi qu’avec des peptides antifongiques de plantes. Le corps gras de la drosophile n’est pas le seul site de synthèse des peptides antimicrobiens, il existe également une réponse locale qui est spécifique pour chaque peptide et qui implique des tissus épithéliaux au contact avec l’environnement extérieur. Chez la drosophile, l’importance des peptides antimicrobiens dans la réponse aux agents infectieux a été démontrée grâce à des souches mutantes de drosophile dans lesquelles la synthèse de certains peptides antimicrobiens est affectée.
| Médecine & Sciences
1999: 15, 23-29 | Abstract
Article complet | 105. Range of activity and metabolic stability of synthetic antibacterial glycopeptides from insects
Hoffmann R, Bulet P, Urge L, Otvos L Jr
Abstract : Antibacterial glycopeptides isolated from insects are exciting bio-oligomers because they represent a family of compounds in which the structural and functional effects of incorporating short O-linked sugars to protein fragments can be studied. Additionally, their high activity in vitro warrants detailed further drug development efforts. Due to the limited availability of the isolated material, we used synthetic glycopeptides and some analogs to investigate the range of activity of drosocin and pyrrhocoricin. While addition of the Gal-GalNAc disaccharide to the natural mid-chain position generally increased the antibacterial activity of drosocin, pyrrhocoricin lacking sugar appeared to be more potent, with an IC50 against Escherichia coli D22 of 150 nM. Although glycosylated drosocin was active against E. coli in the low microM range in vitro, this peptide was completely inactive when injected into mice. The lack of in vivo activity of drosocin could be explained by the unusually high degradation rate of the peptides in mammalian sera. The early degradation products were inactive in vitro. In contrast, the peptides were considerably more stable in insect hemolymph, where their natural activity is manifested.
| Biochim Biophys Acta
1999: 1426 (3), 459-67 | Abstract
Article complet | 104. A GFP-drosomycin reporter transgene reveals a local immune response in Drosophila that is not dependent on the Toll pathway
Ferrandon D, Jung AC, Criqui MC, Lemaitre B, Uttenweiler-Joseph S, Michaut L, Reichhart JM & Hoffmann JA
Abstract : A hallmark of the systemic antimicrobial response of Drosophila is the synthesis by the fat body of several antimicrobial peptides which are released into the hemolymph in response to a septic injury. One of these peptides, drosomycin, is active primarily against fungi. Using a drosomycin-green fluorescent protein (GFP) reporter gene, we now show that in addition to the fat body, a variety of epithelial tissues that are in direct contact with the external environment, including those of the respiratory, digestive and reproductive tracts, can express the antifungal peptide, suggesting a local response to infections affecting these barrier tissues. As is the case for vertebrate epithelia, insect epithelia appear to be more than passive physical barriers and are likely to constitute an active component of innate immunity. We also show that, in contrast to the systemic antifungal response, this local immune response is independent of the Toll pathway.
| EMBO J
1998: 17, 1217-1227 | Abstract
Article complet | 103. Phylogenetic perspectives in innate immunity
Hoffmann JA, Kafatos FC, Janeway CA Jr & Ezekowitz RAB
Abstract : The concept of innate immunity refers to the first-line host defense that serves to limit infection in the early hours after exposure to microorganisms. Recent data have highlighted similarities between pathogen recognition, signaling pathways, and effector mechanisms of innate immunity in Drosophila and mammals, pointing to a common ancestry of these defenses. In addition to its role in the early phase of defense, innate immunity in mammals appears to play a key role in stimulating the subsequent, clonal response of adaptive immunity.
| Science
1999: 284, 1313-1318 | Abstract
Article complet | 102. Antimicrobial Peptides in Insects : Structure and Function
Bulet P, Hetru C, Dimarcq JL & Hoffmann D
Abstract : Antimicrobial peptides appear to be ubiquitous and multipotent components of the innate immune defense arsenal used by both prokaryotic and eukaryotic organisms. During the past 15 years a multitude of these peptides have been isolated largely from insects. In spite of great differences in size, amino acid composition and structure, most of the antimicrobial peptides from insects can be grouped into one of three categories. The largest category in number contains peptides with intramolecular disulfide bonds forming hairpin-like beta-sheets or alpha-helical-beta-sheet mixed structures. The second most important group is composed of peptides forming amphipathic alpha-helices. The third group comprises peptides with an overrepresentation in proline and/or glycine residues. In general, the insect antimicrobial peptides have a broad range of activity and are not cytotoxic. Despite a wealth of information on structural requirements for their antimicrobial activity, the mode of action of these peptides is not yet fully understood. However, some data suggest the existence of two types of mode of action: 1. through peptide-lipid interaction or 2. through receptor-mediated recognition processes. This review presents the main results obtained during the last four years in the field of antimicrobial peptides from insects with a special focus on the proline-rich and cysteine-rich peptides.
| Develop. and Comp. Immunol.
1999: 23, 329-344 | Abstract
Article complet | 101. The structure of a glucosylated hormone responsible for sex determination in the isopod, Armadillidium vulgare
Martin G, Sorokine O, Moniatte M, Bulet P, Hetru C, Van Dorsselaer A
Abstract : Two glycoforms (AH1 and AH2) of androgenic hormone, and its corresponding hormone precursor derived from HPLC-purified androgenic gland extract from the woodlouse Armadillidium vulgare were fully characterized by microsequencing and mass spectrometry. The amino-acid sequences of the two glycoforms were identical, they consist of two peptide chains, A and B, of 29 and 44 amino acids, respectively, with chain A carrying one N-glycosylated moiety on Asn18. The two chains are linked by two disulfide bridges. Glycoforms were only differentiated by the size and heterogeneity of the glycan chain. The androgenic hormone precursor (16.5 kDa) was shown to contain the sequence of chains A and B from the androgenic hormone, connected by a C-peptide (50 amino acids). These results were confirmed by matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) analysis performed on a single hypertrophied androgenic gland. When injected into young females, both glycoforms of the androgenic hormone were able to override genetic sex-determination. In invertebrates, there is no other example where sex-differentiation is controlled by a protein hormone that is not synthesized by the gonads but by a special gland. A functional comparison with two other hormones which are believed to play a role in sex determination, i.e. ecdysone in insects and anti-Mullerian hormone in mammals, is presented. Work is in progress to clone and characterize the gene encoding androgenic hormone, moreover special attention is devoted to its regulatory regions, putative targets for the Wolbachia action.
| Eur. J. Biochem.
1999: 262, 727-736. | Abstract
Article complet | 100. A mosaic analysis in Drosophila fat body cells of the control of antimicrobial peptide genes by the Rel proteins Dorsal and DIF
Manfruelli P, Reichhart JM, Steward R, Hoffmann JA & Lemaitre B
Abstract : Expression of the gene encoding the antifungal peptide Drosomycin in Drosophila adults is controlled by the Toll signaling pathway. The Rel proteins Dorsal and DIF (Dorsal-related immunity factor) are possible candidates for the transactivating protein in the Toll pathway that directly regulates the drosomycin gene. We have examined the requirement of Dorsal and DIF for drosomycin expression in larval fat body cells, the predominant immune-responsive tissue, using the yeast site-specific flp/FRT recombination system to generate cell clones homozygous for a deficiency uncovering both the dorsal and the dif genes. Here we show that in the absence of both genes, the immune-inducibility of drosomycin is lost but can be rescued by overexpression of either dorsal or dif under the control of a heat-shock promoter. This result suggests a functional redundancy between both Rel proteins in the control of drosomycin gene expression in the larvae of Drosophila. Interestingly, the gene encoding the antibacterial peptide Diptericin remains fully inducible in the absence of the dorsal and dif genes. Finally, we have used fat body cell clones homozygous for various mutations to show that a linear activation cascade Spaetzle--> Toll-->Cactus-->Dorsal/DIF leads to the induction of the drosomycin gene in larval fat body cells.
| EMBO J.
1999: 18, 3380-3391 | Abstract
Article complet | 99. Constitutive activation of Toll-mediated antifungal defense in serpin-deficient Drosophila
Levashina E, Langley E, Green C, Gubb D, Ashburner M, Hoffmann JA & Reichhart JM
Abstract : The antifungal defense of Drosophila is controlled by the spaetzle/Toll/cactus gene cassette. Here, a loss-of-function mutation in the gene encoding a blood serine protease inhibitor, Spn43Ac, was shown to lead to constitutive expression of the antifungal peptide drosomycin, and this effect was mediated by the spaetzle and Toll gene products. Spaetzle was cleaved by proteolytic enzymes to its active ligand form shortly after immune challenge, and cleaved Spaetzle was constitutively present in Spn43Ac-deficient flies. Hence, Spn43Ac negatively regulates the Toll signaling pathway, and Toll does not function as a pattern recognition receptor in the Drosophila host defense.
| Science
1999: 285 1917-1919 | Abstract
Article complet | 98. The Drosophila homologue of ribosomal protein L8
Ruhf ML & Meister M
Abstract : We have cloned the gene encoding the Drosophila melanogaster homologue of ribosomal protein L8. It contains two introns: one in the 5' untranslated region and the second in the beginning of the ORF, and encodes a 256-residue protein which is highly conserved when compared with RpL8 proteins of other organisms. The gene is present as a single copy in the Drosophila genome and maps at position 62E6-7 on polytene chromosomes. It is expressed ubiquitously at all stages of development. It is located close to the gene encoding RpL12 and both are candidate targets of the Minute mutation, M(3)LS2, mapped in the region 62E-63A.
| Insect Biochem. and Molec. Biol.
1999: 29, 349-353 | Abstract
Article complet | 97. Antimicrobial activity spectrum, cDNA cloning, and mRNA expression of a newly isolated member of the cecropin family from the mosquito Aedes aegypti.
Lowenberger C, Charlet M, Vizioli J, Kamal S, Richman A, Christensen B & Bulet P
Abstract : An antimicrobial peptide belonging to the cecropin family was isolated from the hemolymph of bacteria-challenged adult Aedes aegypti. This new peptide, named cecropin A, was purified to homogeneity and fully characterized after cDNA cloning. The 34-residue A. aegypti cecropin A is different from the majority of reported insect cecropins in that it is devoid of a tryptophan residue and C-terminal amidation. The importance of these two structural features on the activity spectrum was investigated using a chemically synthesized peptide. A comparison of the antimicrobial activity spectrum of A. aegypti and Drosophila cecropin A showed a lower activity for the mosquito molecule. A. aegypti cecropin mRNA expression was not detected by Northern blot or reverse transcription-polymerase chain reaction analysis in any immature stage of the mosquito, nor in naive adults, but it was observed in challenged adults 6 h after bacteria inoculation, and it continued over 7-10 days.
| J. Biol. Chem.
1999: 274, 20092-20097 | Abstract
Article complet | 96. Recombinant expression and range of activity of penaeidins, antimicrobial peptides from penaeid shrimp.
Destoumieux D, Bulet P, Strub JM, Van Dorsselaer A & Bachere E
Abstract : Penaeidins are 5.5- to 6.6-kDa antimicrobial peptides recently isolated from the plasma and haemocytes of the tropical shrimp Penaeus vannamei. These molecules differ from the other classes of antimicrobial peptides in that they are composed of a proline-rich N-terminus and of a C-terminus containing six cysteine residues engaged in three disulfide bridges. In order to gain information on their antimicrobial activity, two penaeidins (Pen-2 and Pen-3a) were expressed in Saccharomyces cerevisiae. The recombinant Pen-2 and -3a were characterized in terms of primary structure by Edman degradation, mass spectrometry and gas chromatography. A protocol was then established to purify the amount of penaeidins required for the determination of their activity spectrum. We demonstrate in this study that expression in yeast is appropriate for the large-scale production of functional penaeidins, whose activities are almost indistinguishable from those of the native molecules. Data on Pen-2 and -3a activity demonstrate that penaeidins have a broad spectrum of antifungal properties associated with a fungicidal activity, and that their antibacterial activities are essentially directed against Gram-positive bacteria, with a strain-specific inhibition mechanism. Despite a better efficiency of Pen-3a on most of the tested strains, similar activity spectra and inhibition mechanisms were observed for both Pen-2 and -3a. Finally, no synergistic effect could be observed between the two molecules.
| Eur. J. Biochem.
1999: 266, 335-346 | Abstract
Article complet | 95. Androctonin, a novel antimicrobial peptide from scorpion Androctonus australis : solution structure and molecular dynamics simulations in the presence of a lipid monolayer
Mandard N, Sy D, Maufrais C, Bonmatin JM, Bulet P, Hetru C & Vovelle F
Abstract : Androctonin is a highly cationic antimicrobial peptide from scorpion exhibiting a broad spectrum of activities against bacteria and fungi. It contains 25 amino acids including four cysteine residues forming two disulfide bridges. We report here on the determination of its solution structure by conventional two-dimensional (2D) 1H-NMR spectroscopy and molecular modelling using distance geometry and molecular dynamics methods. The structure of androctonin involves a well-defined highly twisted anti-parallel beta-sheet with strands connected by a more variable positively charged turn. A comparison with the structure of tachyplesin I (horseshoe crab) reveals that the amphiphilic character of the protein surface of this homologous peptide is not observed in androctonin. We have undertaken a 200-ps molecular dynamics simulation study on a system including one androctonin molecule and a monolayer of DMPG (1,2-dimyristoylphosphatidylglycerol) lipids. On the basis of this simulation, the first steps of the membrane permeabilization process are discussed.
| J. Biomolec. Struct. and Dynamics.
1999: 17, 367-371 | Abstract
Article complet | 94. Chemical synthesis, antibacterial activity and conformation of diptericin, an 82-mer peptide originally isolated from insects
Cudic M, Bulet P, Hoffmann R, Craik DJ & Otvos L Jr
Abstract : The small amounts of antibacterial peptides that can be isolated from insects do not allow detailed studies of their range of activity, side-chain sugar requirements, or their conformation, factors that frequently play roles in the mode of action. In this paper, we report the solid-phase step-by-step synthesis of diptericin, an 82-mer peptide, originally isolated from Phormia terranovae. The unglycosylated peptide was purified to homogeneity by conventional reversed-phase high performance liquid chromatography, and its activity spectrum was compared to that of synthetic unglycosylated drosocin, which shares strong sequence homology with diptericin's N-terminal domain. Diptericin appeared to have antibacterial activity for only a limited number of Gram-negative bacteria. Diptericin's submicromolar potency against Escherichia coli strains indicated that, in a manner similar to drosocin, the presence of the carbohydrate side chain is not necessary to kill bacteria. Neither the N-terminal, drosocin-analog fragment, nor the C-terminal, glycine-rich attacin-analog region was active against any of the bacterial strains studied, regardless of whether the Gal-GalNAc disaccharide units were attached. This suggested that the active site of diptericin fell outside the drosocin or attacin homology domains. In addition, the conformation of diptericin did not seem to play a role in the antibacterial activity, as was demonstrated by the complete lack of ordered structure by two-dimensional nuclear magnetic resonance spectroscopy and circular dichroism. Diptericin completely killed bacteria within 1 h, considerably faster than drosocin and the attacins unlike some other, fast-actin
| Eur. J. Biochem.
1999: 549-558 | Abstract
Article complet | 93. A novel insect defensin from the ant Formica rufa
Taguchi S, Bulet P, Hoffmann JA
Abstract : By combination of size exclusion and reversed-phase chromatography, we have isolated a novel member of insect defensin-type antimicrobial peptides from the entire bodies of bacteria-challenged Formica rufa (hymenoptera, formicidae). The molecular mass of the purified peptide was estimated to be 4120.42 by matrix-assisted laser desorption/ionization-time of flight/mass spectrometry. Sequence analysis revealed that this peptide consisted of 40 amino acid residues with six cysteines engaged in the formation of three intramolecular disulfide bridges. This peptide is unique among the arthropod defensins in terms of the presence of asparatic acid and alanine at position 33 and as C-terminal residue, respectively. In addition, this novel defensin from Formica rufa has the particularity to have no C-terminal extension in contrast to those reported for other hymenoptera defensins.
| Biochimie
1998: 80 (4), 343-6 | Abstract
Article complet | 92. Antimicrobial peptides from insects, In Molecular Mechanisms of Immune Responses in Insects
Hetru C, Hoffmann D & Bulet P
Abstract :
| Eds Brey PT & Hultmark D, Chapman & Hall
1998: pp 40-66 | Abstract
Article complet | 91. In vivo regulation of the IkB homologue cactus during the immune response of Drosophila
Nicolas E, Reichhart JM, Hoffmann JA & Lemaitre B
Abstract : The dorsoventral regulatory gene pathway (spatzle/Toll/cactus) controls the expression of several antimicrobial genes during the immune response of Drosophila. This regulatory cascade shows striking similarities with the cytokine-induced activation cascade of NF-kappaB during the inflammatory response in mammals. Here, we have studied the regulation of the IkappaB homologue Cactus in the fat body during the immune response. We observe that the cactus gene is up-regulated in response to immune challenge. Interestingly, the expression of the cactus gene is controlled by the spatzle/Toll/cactus gene pathway, indicating that the cactus gene is autoregulated. We also show that two Cactus isoforms are expressed in the cytoplasm of fat body cells and that they are rapidly degraded and resynthesized after immune challenge. This degradation is also dependent on the Toll signaling pathway. Altogether, our results underline the striking similarities between the regulation of IkappaB and cactus during the immune response.
| J. Biol. Chem
1998: 273, 10463-10469 | Abstract
Article complet | 90. Plasmodium gallinaceum : differential killing of some mosquito stages of the parasite by insect defensin
Shahabuddin M, Fields I, Bulet P, Hoffmann JA & Miller LH
Abstract : We examined several insect antimicrobial peptides to study their effect on Plasmodium gallinaceum zygotes, ookinetes, oocysts, and sporozoites. Only two insect defensins-Aeschna cyanea (dragon fly) and Phormia terranovae (flesh fly)-had a profound toxic effect on the oocysts in Aedes aegypti and on isolated sporozoites. The defensins affected the oocysts in a time-dependent manner. Injecting the peptide into the hemolymph 1 or 2 days after an infectious blood meal had no significant effect on prevalence of infection or relative oocyst density per mosquito. When injected 3 days after parasite ingestion, the relative oocyst density was significantly reduced. Injection on day 4 or later damaged the developing oocysts, although the oocysts density per mosquito was not significantly different when examined on day 8. The oocysts were swollen or had extensive internal vacuolization. The peptides had no detectable effect on the early stages of the parasite: the zygotes and ookinetes tested in vitro. Both the defensins were highly toxic to isolated sporozoites in vitro as indicated by disruption of the membrane permeability barrier, a change in morphology, and loss of motility. In contrast to the toxicity of cecropin and magainin for mosquitoes, defensin, at concentrations that kill parasites, is not toxic to mosquitoes, suggesting that defensin should be studied further as a potential molecule to block sporogonic development of Plasmodium.
| Exp. parasitol
1998: 89, 103-112 | Abstract
Article complet | 89. Two distinct pathways can control expression of the gene encoding the Drosophila antimicrobial peptide metchnikowin
Levashina E, Ohresser S, Lemaitre B & Imler JL
Abstract : Metchnikowin is a recently discovered proline-rich peptide from Drosophila with antibacterial and antifungal properties. Like most other antimicrobial peptides from insects, its expression is immune-inducible. Here we present evidence that induction of metchnikowin gene expression can be mediated either by the TOLL pathway or by the imd gene product. We show that the gene remains inducible in Toll-deficient mutants, in which the antifungal response is blocked, as well as in imd mutants, which fail to mount an antibacterial response. However, in Toll-deficient, imd double mutants, metchnikowin gene expression can no longer be detected after immune challenge. Our results suggest that expression of this peptide with dual activity can be triggered by signals generated by either bacterial or fungal infection. Cloning of the metchnikowin gene revealed the presence in the 5' flanking region of several putative cis-regulatory motifs characterized in the promoters of insect immune genes: namely, Rel sites, GATA motifs, interferon consensus response elements and NF-IL6 response elements. Establishment of transgenic fly lines in which the GFP reporter gene was placed under the control of 1.5 kb of metchnikowin gene upstream sequences indicates that this fragment is able to confer full immune inducibility and tissue specificity of expression on the transgene.
| J. Mol. Biol
1998: 278, 515-527 | Abstract
Article complet | 88. Differential display of peptides during the immune response of Drosophila : a matrix-assisted laser desorption ionization time-of-flight mass spectrometry study
Uttenweiler-Joseph S, Moniatte M, Van Dorsselaer A, Hoffmann JA & Bulet P
Abstract : We have developed an approach based on a differential mass spectrometric analysis to detect molecules induced during the immune response of Drosophila, regardless of their biological activities. For this, we have applied directly matrix-assisted laser desorption/ionization MS to hemolymph samples from individual flies before and after an immune challenge. This method provided precise information on the molecular masses of immune-induced molecules and allowed the detection, in the molecular range of 1.5-11 kDa, of 24 Drosophila immune-induced molecules (DIMs). These molecules are all peptides, and four correspond to already characterized antimicrobial peptides. We have further analyzed the induction of the various peptides by immune challenge in wild-type flies and in mutants with a compromised antimicrobial response. We also describe a methodology combining matrix-assisted laser desorption ionization time-of-flight MS, HPLC, and Edman degradation, which yielded the peptide sequence of three of the DIMs. Finally, molecular cloning and Northern blot analyses revealed that one of the DIMs is produced as a prepropeptide and is inducible on a bacterial challenge.
| Proc. Natl. Acad Sci. USA
1998: 95, 11342-11347 | Abstract
Article complet | 87. Solution structure of thanatin, a potent bactericidal and fungicidal insect peptide, determined from proton two-dimensional nuclear magnetic resonance data
Mandard N, Sodano P, Labbe H, Bonmatin JM, Bulet P, Hetru C, Ptak M & Vovelle F
Abstract : Thanatin is the first inducible insect peptide that has been found to have, at physiological concentrations, a broad range of activity against bacteria and fungi. Thanatin contains 21 amino acids including two cysteine residues that form a disulfide bridge. Two-dimensional (2D) 1H-NMR spectroscopy and molecular modelling have been used to determine its three-dimensional (3D) structure in water. Thanatin adopts a well-defined anti-parallel beta-sheet structure from residue 8 to the C-terminus, including the disulfide bridge. In spite of the presence of two proline residues, there is a large degree of structural variability in the N-terminal segment. The structure of thanatin is quite different from the known structures of other insect defence peptides, such as antibacterial defensin and antifungal drosomycin. It has more similarities with the structures of various peptides from different origins, such as brevinins, protegrins and tachyplesins, which have a two-stranded beta-sheet stabilized by one or two disulfide bridges. Combined with activity test experiments on several truncated isoforms of thanatin, carried out by Fehlbaum et al. [Fehlbaum, P., Bulet, P., Chernysh, S., Briand, J. P., Roussel, J. P., Letellier, L., Hetru, C. & Hoffmann, J. (1996) Proc. Natl Acad. Sci. USA 93, 1221-1225], our structural study evidences the importance of the beta-sheet structure and also suggests that anti-Gram-negative activity involves a site formed by the Arg20 side-chain embedded in a hydrophobic cluster.
| Eur. J. Biochem
1998: 256, 404-410 | Abstract
Article complet | 86. Analysis of the Drosophila host defense in domino mutant larvae, which are devoid of hemocytes
Braun A, Hoffmann JA & Meister M
Abstract : We have analyzed the Drosophila immune response in domino mutant larvae, which are devoid of blood cells. The domino mutants have a good larval viability, but they die as prepupae. We show that, on immune challenge, induction of the genes encoding antimicrobial peptides in the fat body is not affected significantly in the mutant larvae, indicating that hemocytes are not essential in this process. The hemocoele of domino larvae contains numerous live microorganisms, the presence of which induces a weak antimicrobial response in the fat body. A full response is observed only after septic injury. We propose that the fat body cells are activated both by the presence of microorganisms and by injury and that injury potentiates the effect of microorganisms. Survival experiments after an immune challenge showed that domino mutants devoid of blood cells maintain a wild-type resistance to septic injury. This resistance was also observed in mutant larvae in which the synthesis of antibacterial peptides is impaired (immune deficiency larvae) and in mutants that are deficient for humoral melanization (Black cells larvae). However, if domino was combined with either the immune deficiency or the Black cell mutation, the resistance to septic injury was reduced severely. These results establish the relevance of the three immune reactions: phagocytosis, synthesis of antibacterial peptides, and melanization. By working in synergy, they provide Drosophila a highly effective defense against injury and/or infection.
| Proc. Natl. Acad. Sci. USA
1998: 95, 14337-14342 | Abstract
Article complet | 85. Isolation, characterization and chemical synthesis of a new insect defensin from Chironomus plumosus (Diptera)
Lauth X, Nesin A, Briand JP, Roussel JP & Hetru C
Abstract : Injection of low doses of bacteria into the aquatic larvae of the dipteran insect Chironomus plumosus induces the appearance in their hemolymph of a potent antibacterial activity. We have isolated two 36-residue peptides from this hemolymph which are active against Gram-positive bacteria. The peptides are novel members of the insect defensin family and their sequences present marked differences with those of insect defensins isolated from other dipteran species. We have developed a method for efficient renaturation of this cysteine-rich molecule and obtained a highly pure synthetic Chironomus defensin.
| Insect Biochem. Molec. Biol
1998: 28, 1059-1066 | Abstract
Article complet | 84. Drosophila Information Service
Reichhart JM & Ferrandon D
Abstract :
|
1998: 81, 201-202 | Abstract
Article complet | 83. Cysteine-rich antimicrobial peptides in invertebrates
Dimarcq JL, Bulet P, Hetru C & Hoffmann JA
Abstract : Antimicrobial peptides are pivotal elements of the innate immune defense against bacterial and fungal infections. Within the impressive list of antimicrobial peptides available at present, more than half have been characterized in arthropods. Cysteine-rich antimicrobial peptides represent the most diverse and widely distributed family among arthropods and, to a larger extent, among invertebrates. Proeminent groups of cysteine-rich peptides are peptides with the CS alpha beta motif and peptides forming an hairpin-like beta-sheet structure. Although these substances exhibit a large structural diversity and a wide spectrum of activity, they have in common the ability to permeabilize microbial cytoplasmic membranes. Drosophila has proved a remarkable system for the analysis of the regulation of expression of gene encoding antimicrobial cysteine-rich peptides. These studies have unraveled the striking parallels that exist between insect immunity and innate immunity in mammals that point to a common ancestry of essential aspects of innate immunity.
| Biopolymers (Peptide Science)
1998: 47, 465-477 | Abstract
Article complet | 82. RNA-RNA interaction is required for the formation of specific bicoid mRNA 3'UTR-STAUFEN ribonucleoprotein particles
Ferrandon D, Koch I, Westhof E, Nüsslein-Volhard C.
Abstract : The formation of the anterior pattern of the Drosophila embryo is dependent on the localization of the mRNA of the morphogen Bicoid (bcd) to the anterior pole of the egg cell. Staufen protein (STAU) is required in a late step of the localization to anchor the bcd mRNA in the anterior cytoplasm. We have shown previously that endogenous STAU associates specifically with injected bcd mRNA 3'-untranslated region (UTR), resulting in the formation of characteristic RNA-protein particles that are transported along microtubules of the mitotic spindles in a directed manner. The regions recognized by STAU in this in vivo assay are predicted to form three stem-loop structures involving large double-stranded stretches. Here, we show that the STAU interaction requires a double-stranded conformation of the stems within the RNA localization signal. In addition, base pairing between two single-stranded loops plays a major role in particle formation. This loop-loop interaction is intermolecular, not intramolecular; thus dimers or multimers of the RNA localization signal must be associated with STAU in these particles. The bcd mRNA 3' UTR can also dimerize in vitro in the absence of STAU. Thus, in addition to RNA-protein interactions, RNA-RNA interaction might be involved in the formation of ribonucleoprotein particles for transport and localization.
| EMBO Journal
16, 1751-1758 | Abstract
Article complet | 81. Drosophila immunity.
HOFFMANN JA, REICHHART JM
Abstract :
| Trends in Cell Biology
1997 : 7 309-316 | Abstract
Article complet | 80. Solution structure of drosomycin, the first inducible antifungal protein from insects.
LANDON C, SODANO P, HETRU C, HOFFMANN JA, PTAK M
Abstract :
| Protein Science
1997 : 6 1878-1884 | Abstract
Article complet | 79. Drosophila host defense : differential induction of antimicrobial peptide genes after infection by various classes of microorganisms.
LEMAITRE B, REICHHART JM, HOFFMANN JA
Abstract :
| Proc. Natl. Acad. Sci. USA
1997 : 94 14614-14619 | Abstract
Article complet | 78. Treatment of l(2)mbn Drosophila tumorous blood cells with the steroid hormone ecdysone amplifies the inducibitity of antimicrobial peptide gene expression.
DIMARCQ JL, IMLER JL, LANOT R, EZEKOWITZ A, HOFFMANN JA, JANEWAY C & LAGUEUX M (1997).
Abstract :
| Insect Biochem. & Molec. Biol.
1997 : 27 877-886 | Abstract
Article complet | 77. Similarities between insect and plant host defenses
Levashina EA
Abstract :
| Trends Cell Biol.
1997: 7, 316 (Review) | Abstract
Article complet | 76. Drosophila Cdk8, a kinase partner of cyclin C that interacts with the large subunit of RNA polymerase II
Leclerc V., Tassan J.-P., O'Farrell P. H., Nigg E. A., and Léopold P.
Abstract :
| Mol Biol Cell
1996 : 7, 505-513 | Abstract
Article complet | 75. The cyclin C/Cdk8 pair
Leclerc V. and Léopold P.
Abstract :
| Progress in Cell Cycle Research
1996 : 2, 197-204 | Abstract
Article complet | 74. Drosophila immunity : a comparative analysis of the Rel proteins dorsal and Dif in the induction of the genes encoding diptericin and cecropin.
GROSS I, GEORGEL P, KAPPLER C, REICHHART JM, HOFFMANN JA
Abstract :
| Nucleic Acids Res.
1996 : 24 1238-1245 | Abstract
Article complet | 73. Innate immunity in insects.
HOFFMANN JA, REICHHART JM, HETRU C
Abstract :
| Current Opinion in Immunology
1996 : 8 8-13 | Abstract
Article complet | 72. Inducible immune factors of the vector mosquito Anopheles gambiae : biochemical purification of a defensin antibacterial peptide and molecular cloning of preprodefensin cDNA.
RICHMAN A, BULET P, HETRU C, BARILLAS-MURY C, HOFFMANN JA, KAFATOS F
Abstract :
| Insect Molec. Biol.
1996 : 5 203-210 | Abstract
Article complet | 71. Innate immunity. Isolation of several cystein-rich antimicrobial peptides from the blood of a mollusc, Mytillus edulis.
CHARLET M, CHERNYSH S, PHILIPPE H, HETRU C, HOFFMANN JA, BULET P
Abstract :
| J. Biol. Chem.
1996 : 271 21808-21813 | Abstract
Article complet | 70. The dorsoventral regulatory gene cassette spaetzle/toll/cactus controls the potent antifungal response in Drosophila adults.
LEMAITRE B, NICOLAS E, MICHAUT L, REICHHART JM, HOFFMANN JA
Abstract :
| Cell
1996 : 86 973-983 | Abstract
Article complet | 69. The lytic cycle of Epstein-Barr virus in the nonproducer Raji line can be rescued by the expression of a 135-kilodalton protein encoded by the BALF2 open reading frame.
Decaussin G., Leclerc V., Ooka T.
Abstract :
| J Virol
1995 : 69, 7309-7314 | Abstract
Article complet | 68. Functional analysis and regulation of nuclear import of dorsal during the immune response in Drosophila.
LEMAITRE B, MEISTER M, GOVIND S, GEORGEL P, STEWARD R, REICHHART, HOFFMANN JA
Abstract :
| EMBO J.
1995 : 14 536-545 | Abstract
Article complet | 67. Drosophila immunity. A sequence homologous to mammalian interferon consensus response elements enhances the activity of the diptericin promoter.
GEORGEL P, KAPPLER C, LANGLEY E, GROSS I, NICOLAS E, REICHHART JM, HOFFMANN JA
Abstract :
| Nucleic Acids Res.
1995 : 23 1140-1145 | Abstract
Article complet | 66. Refined three-dimensional solution structure of insect defensin A.
CORNET B, BONMATIN JM, HETRU C, HOFFMANN JA, PTAK M, VOVELLE F
Abstract :
| Structure
1995 : 3 435-448 | Abstract
Article complet | 65. Insect immunity. The inducible antibacterial peptide diptericin carries two O-glycans necessary for biological activity.
BULET P, HEGY G, LAMBERT J, VAN DORSSELAER A, HOFFMANN JA, HETRU C
Abstract :
| Biochemistry
1995 : 34 7394-7400 | Abstract
Article complet | 64. A recessive mutation, immune-deficiency (imd), defines two distinct control pathways in the Drosophila host defense.
LEMAITRE B, KROMER-METZGER E, MICHAUT L, NICOLAS E, MEISTER M, GEORGEL P, REICHHART JM, HOFFMANN JA
Abstract :
| Proc. Natl. Acad. Sci. USA
1995 : 92 9465-9469 | Abstract
Article complet | 63. Metchnikowin, a novel immune-inducible proline-rich peptide from Drosophila with antibacterial and antifungal properties.
LEVASHINA E, OHRESSER S, BULET P, REICHHART JM, HETRU C, HOFFMANN JA
Abstract :
| Eur. J. Biochem.
1995 : 233 694-700 | Abstract
Article complet | 62. Insect Immunity : Isolation of three novel inducible antibacterial defensins from the vector mosquito, Aedes aegypti.
LOWENBERGER C, BULET P, CHARLET M, HETRU C, HODGEMAN B, CHRISTENSEN B, HOFFMANN JA
Abstract :
| Insect Biochem. Molec. Biol.
1995 : 25 867-873 | Abstract
Article complet | 61. Structure-activity analysis of thanatin, a novel 21-residue inducible insect defense peptide with sequence homology to frog skin antimicrobial peptides.
FEHLBAUM P, BULET P, CHERNYSH S, BRIAND JP, ROUSSEL JP, LETELLIER L, HETRU C, HOFFMANN JA
Abstract :
| Proc. Natl. Acad. Sci. USA
1995 : 93 1221-1225 | Abstract
Article complet | 60. Staufen protein associates with the 3'UTR of bicoid mRNA to form particles that move in a microtubule-dependent manner
Ferrandon, D., Elphick, L., Nüsslein-Volhard, C., St Johnston, D.
Abstract : Staufen protein is required in order to anchor bicoid (bcd) mRNA at the anterior pole of the Drosophila egg. Here we show that staufen protein colocalizes with bcd mRNA at the anterior, and that this localization depends upon its association with the mRNA. Upon injection into the embryo, bcd transcripts specifically interact with staufen, and we have mapped the sequences required to three regions of the 3'UTR, each of which is predicted to form a long stem-loop. The resulting staufen-bcd 3'UTR complexes form particles that show a microtubule-dependent localization. Since staufen is also transported with oskar (osk) mRNA during oogenesis, staufen associates specifically with both osk and bcd mRNAs to mediate their localizations, but at two distinct stages of development.
| Cell
79, 1221-1232 | Abstract
Article complet | 59. Insect immunity. A transgenis analysis in Drosophila defines several functional domains in the diptericin promoter
Meister M, Braun A, Kappler C, Reichhart JM and Hoffmann JA.
Abstract :
| EMBO J.
1994: 13, 5958-5966. | Abstract
Article complet | 58. Characterization and transcriptional profiles of a Drosophila gene encoding an insect defensin. A study in insect immunity.
DIMARCQ JL, HOFFMANN D, MEISTER M, BULET P, LANOT R, REICHHART JM, HOFFMANN JA
Abstract :
| Eur. J. Biochem.
1994 : 221 201-209 | Abstract
Article complet | 57. The inducible antibacterial peptides of insects.
COCIANCICH S, BULET P, HETRU C, HOFFMANN JA
Abstract :
| Parasitology Today
1994 : 10 n° 4 132-139 | Abstract
Article complet | 56. Novel inducible antibacterial peptides from a Hemipteran insect, the sap-sucking bug Pyrrhocoris apterus.
COCIANCICH S, DUPONT A, HEGY G, LANOT R, HOLDER F, HETRU C, HOFFMANN JA, BULET P
Abstract :
| Biochem. J.
1994 : 300 567-575 | Abstract
Article complet | 55. Antibacterial peptides/polypeptides in the insect host defense. A comparison with vertebrate antibacterial peptides/polypeptides.
HETRU C, BULET P, COCIANCICH S, DIMARCQ JL, HOFFMANN D, HOFFMANN JA
Abstract :
| Ed. by Hoffmann JA, Janeway Ch, Natori S.R.G. Landes Company.
1994, Austin, Georgetown | Abstract
Article complet | 54. Immune Gene expression in Drosophila. In "Phylogenetic Perspectives in Immunity".
MEISTER M, GEORGEL P, LEMAITRE B, KAPPLER C, LAGUEUX M, REICHHART JM, HOFFMANN JA
Abstract :
| Ed. by Hoffmann JA, Janeway Ch, Natori S.R.G. Landes Company
1994, Austin, Georgetown | Abstract
Article complet | 53. Septic injury of Drosophila induces the synthesis of a potent antifungal peptide with sequence homology to plant antifungal peptides.
FEHLBAUM P, BULET P, MICHAUT L, LAGUEUX M, BROEKAERT W, HETRU C, HOFFMANN JA
Abstract :
| J. Biol. Chem.
1994 : 269 33159-33163 | Abstract
Article complet | 52. The Influence of Plant Phenotype on the Processes of Regeneration
Lutova LA, Bondarenko LV, Buzovkina IS, Levashina EA, Tikhodeev ON, Khodzhaiova LT, Sharova NV, and Shishkova SO
Abstract :
| Russian Journal of Genetics
1994: 30: 1065-1074 | Abstract
Article complet | 51. A novel inducible antibacterial peptide of Drosophila carries an O-glycosylated substitution.
BULET P, DIMARCQ JL, HETRU C, LAGUEUX M, CHARLES M, HEGY G, VAN DORSSELAER A, HOFFMANN JA
Abstract :
| J. Biol. Chem.
1993 : 268 14893-14897 | Abstract
Article complet | 50. The humoral antibacterial response of Drosophila.
HOFFMANN JA, HETRU C, REICHHART JM
Abstract :
| FEBS Lett.
1993 : 325, 63-66 | Abstract
Article complet | 49. Insect defensin, an inducible antibacterial peptide, forms voltage-dependent channels in Micrococcus luteus.
COCIANCICH S, GHAZI A, HETRU C, HOFFMANN JA, LETELLIER L
Abstract :
| J. Biol. Chem.
1993 : 268, 19239-19245 | Abstract
Article complet | 48. Expression and nuclear translocation of the rel/NF-kB-related morphogen dorsal during the immune response of Drosophila.
REICHHART JM, GEORGEL P, MEISTER M, LEMAITRE B, KAPPLER C, HOFFMANN JA
Abstract :
| C.R. Acad. Sci.
1993 : Paris 316, 1218-1224. | Abstract
Article complet | 47. Insect Immunity : the diptericin promoter contains multiple functional regulatory sequences homologous to mammalian acute-phase response elements.
GEORGEL P, MEISTER M, KAPPLER C, LEMAITRE B, REICHHART JM, HOFFMANN JA
Abstract :
| BBRC
1993 : 197 508-517 | Abstract
Article complet | 46. Insect Immunity. Developmental and inducible activity of the Drosophila diptericin promoter.
REICHHART JM, MEISTER M, DIMARCQ JL, ZACHARY D, HOFFMANN D, RUIZ C, RICHARDS G, HOFFMANN JA
Abstract :
| EMBO J.
1992 : 11 n° 4 1469-1477 | Abstract
Article complet | 45. Expression and secretion in yeast of active insect defensin, an inducible antibacterial peptide from the fleshfly Phormia terranovae.
REICHHART JM, PETIT I, LEGRAIN M, DIMARCQ JL, KEPPI E, LECOCQ JP, HOFFMANN JA, ACHSTETTER T
Abstract :
| Inv. Reprod. Develop.
1992 : 21 n° 1 15-24 | Abstract
Article complet | 44. A novel insect defensin mediates the inducible antibacterial activity in larvae of the dragonfly Aeschna cyanea (Paleoptera, Odonata).
BULET P, COCIANCICH S, REULAND M, SAUBER F, BISCHOFF R, HEGY G, VAN DORSSELAER A, HETRU C, HOFFMANN JA
Abstract :
| Eur. J. Biochem.
1992 : 209 977-984 | Abstract
Article complet | 43. Insect defensins, inducible antibacterial peptides of the insect host defence.
HOFFMANN JA, HETRU C
Abstract :
| Immunol. Today
1992 : 13 n° 10 411-415 | Abstract
Article complet | 42. Insect Immunity. Two 17-bp repeats nesting a kB-related sequence confer inducibility to the diptericin gene and bind a polypeptide in bacteria-challenged Drosophila.
KAPPLER C, MEISTER M, LAGUEUX M, GATEFF E, HOFFMANN JA, REICHHART JM
Abstract :
| EMBO J.
1993 : 12 n° 4 1561-1568 | Abstract
Article complet | 41. Sterol Biosynthesis Mutants of Higher Plants
Lutova LA, Levashina EA, Bondarenko LV, Bayramova NL, Andronova EV, Inge-Vechtomov SG
Abstract :
| Genetika
1992: 28: 129-136 | Abstract
Article complet | 40. Synthesis of a tritiated 3-dehydroecdysteroid putative precursor of ecdysteroid biosynthesis in Locusta migratoria.
DOLLE F, HETRU C, ROUSSEL JP, ROUSSEAU B, SOBRIO F, LUU B, HOFFMANN JA
Abstract :
| Tetrahedron
1991 : 47 7067-7080 | Abstract
Article complet | 39. Isolation and structural characterization of an insulin-related molecule, a predominant neuropeptide from Locusta migratoria (Insecta, Orthoptera)
HETRU C, LI KW, BULET P, LAGUEUX M, HOFFMANN JA
Abstract :
| Eur. J. Biochem.
1991 : 201 495-499 | Abstract
Article complet | 38. Determination of disulfide bridges in natural and recombinant insect defensin A.
LEPAGE P, BITSCH F, ROECKLIN D, KEPPI E, DIMARCQ JL, REICHHART JM, HOFFMANN JA, ROITSCH C, VAN DORSSELAER A
Abstract :
| Eur. J. Biochem.
1991 : 196 735-742 | Abstract
Article complet | 37. Insect Immunity. Isolation from a coleopteran insect of a novel inducible antibacterial peptide and of new members of the insect defensin family.
BULET P, COCIANCICH S, DIMARCQ JL, LAMBERT J, REICHHART JM, HOFFMANN D, HETRU C, HOFFMANN JA
Abstract :
| J. Biol. Chem.
1991 : 266 n° 36 24520-24525 | Abstract
Article complet | 36. Two-dimensional 1H-NMR study of recombinant insect defensin A in water. Resonance assignments, secondary structure and global folding.
BONMATIN JM, BONNAT JL, GALLET X, VOVELLE F, REICHHART JM, HOFFMANN JA, PTAK M
Abstract :
| J. Biol. NMR
1991 : 2 235-256 | Abstract
Article complet | 35. Insect Immunity. Expression of the two major inducible antibacterial peptides, defensin and diptericin, in Phormia terranovae.
DIMARCQ JL, ZACHARY D, HOFFMANN JA, HOFFMANN D, REICHHART JM
Abstract :
| EMBO J. 9
1990 : n° 8, 2507-2515 | Abstract
Article complet | 34. Synthesis of high specific activity [3H2-1,2]-7-dehydrocholesterol. Conversion to ecdysone in follicle cells of Locusta (Insects).
DOLLE F, KAPPLER C, HETRU C, ROUSSEAU B, COPPO M, LUU B, HOFFMANN JA
Abstract :
| Tetrahedron 46
1990 : n°15 5305-5316 | Abstract
Article complet | 33. Insect Immunity. Characterization of a Drosophila cDNA encoding a novel member of the diptericin family of immune peptides and expression studies.
WICKER C, REICHHART JM, HOFFMANN D, HULTMARK D, SAMAKOVLIS C, HOFFMANN JA
Abstract :
| J. Biol. Chem.
1990 : 265 n° 36 22493-22498 | Abstract
Article complet | 32. Insect immunity. Isolation from immune blood of the Dipteran Phormia terranovae of two novel antibacterial peptides with sequence homology to rabbit lung macrophage bactericidal peptides
LAMBERT J, KEPPI E, DIMARCQ JL, WICKER, C, REICHHART JM, DUNBAR B, LEPAGE P, VAN DORSSELAER A, HOFFMANN JA, FOTHERGILL J, HOFFMANN D
Abstract :
| Proc. Nat. Acad. Sci.
1989 : USA 86 262-266 | Abstract
Article complet | 31. Enzymes involved in the biosynthesis of ecdysone. In "Ecdysone"
KAPPLER C, HETRU C, DURST F, HOFFMANN JA
Abstract :
| J. Koolman Ed. Thieme Verlag-Berlin.
1989, pp 161-166 | Abstract
Article complet | 30. Allenic cholesteryl derivatives as inhibitors of ecdysone biosynthesis
BURGER A, ROUSSEL JP, HETRU C, HOFFMANN JA, B. LUU B
Abstract :
| Tetrahedron
1989 : 45 155-164 | Abstract
Article complet | 29. Insect Immunity. Isolation of cDNA clones corresponding to diptericin, an inducible antibacterial peptide from Phormia terranovae (Diptera). Transcriptional profiles during immunization
REICHHART JM, ESSRICH M, DIMARCQ JL, HOFFMANN D, HOFFMANN JA, LAGUEUX M
Abstract :
| Eur. J. Biochem.
1989 : 182 423-427 | Abstract
Article complet | 28. L-Canavanine incorporation into vitellogenin and macromolecular conformation.
ROSENTHAL GA, REICHHART JM, HOFFMANN JA
Abstract :
| J. Biol. Chem.
1989 : 264, 13693-13696 | Abstract
Article complet | 27. Characterization of three hydroxylases involded in the final steps of biosynthesis of the steroid hormone ecdysone in Locusta migratoria (Insecta, Orthoptera)
Kappler C, Kabbouh M, Hetru C, Durst F and Hoffmann JA
Abstract :
| J. Steroid Biochem.
1988 : 31, 891-898. | Abstract
Article complet | 26. Insect immunity. Characterization of a family of novel inducible antibacterial proteins from immunized larvae of the dipteran Phormia terranovae and complete amino acid sequence of the predominant member, diptericin A
DIMARCQ JL, KEPPI E, DUNBAR B, LAMBERT J, REICHHART JM, HOFFMANN D, RANKINE SM, FOTHERGILL JE, HOFFMANN JA
Abstract :
| Europ. J. Biochem.
1988 : 171 17-22 | Abstract
Article complet | 25. Study of the biosynthesis of ecdysone. Part IV. Synthesis of high specific activity (3H2-22,23)-2,22-dideoxyecdysone. Tissue distribution of the C-22 hydroxylase in Locusta migratoria
HAAG T, HETRU C, KAPPLER C, MOUSTIER AM, HOFFMANN JA. LUU B
Abstract :
| Tetrahedron
1988 : 44 1397-1408 | Abstract
Article complet | 24. In vitro studies on potential selective and irreversible inhibitors of enzymes involved in the biosynthesis of ecdysone
BURGER A, ROUSSEL JP, COLOBERT F, KAPPLER C, HETRU C, LUU B, HOFFMANN JA
Abstract :
| J. of Pesticide Biochem. and Physiol.
1987 : 29 197-208 | Abstract
Article complet | 23. Studies on the C-2 hydroxylation of 2-deoxyecdysone in Locusta migratoria
KAPPLER C, KABBOUH M, DURST F, HOFFMANN JA
Abstract :
| Insect Biochem.
1986 : 16 25-32 | Abstract
Article complet | 22. Role of the follicle cells and the oocytes in ecdysone biosynthesis and esterification in vitellogenic females of Locusta migratoria.
KAPPLER C, GOLTZENÉ F, LAGUEUX M, HETRU C, HOFFMANN JA
Abstract :
| Int. J. Invert. Reprod. Develop.
1986 : 9 17-34 | Abstract
Article complet | 21. Role of ecdysteroids in reproduction of Insects : a critical analysis. In "Advances in Invertebrate Reproduction"
HOFFMANN JA, LAGUEUX M, HETRU C, KAPPLER C, GOLTZENÉ F, LANOT R, THIEBOLD J
Abstract :
| M. Porchet, J.C. Andries and A. Dhainaut-Eds. Elsevier, Amsterdam, New York.
1986, Oxford, pp 9-22 | Abstract
Article complet | 20. Ecdysone conjugates : isolation and identification. In "Methods in Enzymology".
HETRU C, LUU B, HOFFMANN JA
Abstract :
| J.H. Law and H.C. Rilling Eds. Academic Press Orlando 111.
1985, part B 411-419 | Abstract
Article complet | 19. Recherches sur la conversion in vitro d'un précurseur de biosynthèse d'ecdysone, la 2,22,25-tridésoxyecdysone, par des tissus embryonnaires et larvaires de Locusta migratoria (Insecte Orthoptère)
MEISTER M, DIMARCQ JL, KAPPLER C, LAGUEUX M, HETRU C, LUU B, HOFFMANN JA
Abstract :
|
1985 : Paris 300 347-352 | Abstract
Article complet | 18. Conversion of radiolabelled ecdysone precursor, 2,22,25-tridésoxyecdysone, by embryonic and larval tissues of Locusta migratoria
MEISTER M, DIMARCQ JL, KAPPLER C, HETRU C, LAGUEUX M, LANOT R, LUU B, HOFFMANN JA
Abstract :
| Molec. Cell. Endocrinol.
1985 : 41 27-44 | Abstract
Article complet | 17. Steroid hormones in Invertebrates.
HOFFMANN JA, HETRU C, LAGUEUX M, CHARLET M, HIRN M
Abstract :
| Nova Acta Leopoldina Leipzig
1984 : 255 56-317 | Abstract
Article complet | 16. Ecdysteroids in ovaries and embryos of Locusta migratoria. Biosynthesis metabolism and mode of action of invertebrate hormones
LAGUEUX M, HOFFMANN JA, GOLTZENÉ F, KAPPLER C, TSOUPRAS G, HETRU C, LUU B.
Abstract :
| J.A. Hoffmann and M. Porchet Eds.
Springer Verlag-Heidelberg, 1984, pp 168-180 | Abstract
Article complet | 15. Cycle de mue et ecdystéroïdes chez une sangsue, Hirudo medicinalis.
SAUBER F, REULAND M, BERCHTOLD JP, HETRU C, TSOUPRAS G, LUU B, MORITZ ME, HOFFMANN JA
Abstract :
| C. R. Acad. Sci.
1983 : Paris 296 413-418 | Abstract
Article complet | 14. Conversion in vitro de 20-hydroxyecdysone en métabolites phosphorylés et acétylés par des complexes tube digestif-tubes de Malpighi de larves de Locusta migratoria
TSOUPRAS G, LUU B, HETRU C, MULLER JF, HOFFMANN JA
Abstract :
| C. R. Acad. Sci.
1983 : Paris 296 77-80 | Abstract
Article complet | 13. Identification and metabolic fate of ovarian 22-adenosine-monophosphoric ester of 2-deoxyecdysone in ovaries and eggs of an insect, Locusta migratoria.
TSOUPRAS G, HETRU C, LUU B, CONSTANTIN E, LAGUEUX M, HOFFMANN JA
Abstract :
| Tetrahedron Letters
1983 : 39 1789-1796 | Abstract
Article complet | 12. Synthesis of high specific activity (23,24)3H4-2-deoxyecdysone
HETRU C, NAKATANI Y, LUU B, HOFFMANN JA
Abstract :
| Nouveau J. de Chimie
1983 : 27 587-591 | Abstract
Article complet | 11. Ecdysone. Endocrinology of Insects.
HOFFMANN JA, HETRU C.
Abstract :
| R.G.H. Downer and H. Laufer
Eds. Alan R. Liss New York, 1983: pp 65-88 | Abstract
Article complet | 10. Fate of maternal conjugated ecdysteroids during embryonic development in Locusta migratoria
SALL C, TSOUPRAS G, KAPPLER C, LAGUEUX M, ZACHARY D, LUU B, HOFFMANN JA
Abstract :
| J. Insect Physiol.
1983 : 29 491-507 | Abstract
Article complet | 9. The biosynthetic pathway of ecdysone : studies with vitellogenic ovaries of Locusta migratoria (Orthoptera)
HETRU C, KAPPLER C, HOFFMANN JA, NEARN R, LUU B, HORN DHS
Abstract :
| Molec. Cell. Endocrinol.
1982 : 26 51-80 | Abstract
Article complet | 8. The major conjugates of ecdysteroids in young eggs and in embryos of Locusta migratoria
TSOUPRAS G, HETRU C, LUU B, LAGUEUX M, CONSTANTIN E, HOFFMANN JA
Abstract :
| Tetrahedron Letters
1982 : 23 2045-2048 | Abstract
Article complet | 7. Ecdysteroids and ovarian development in the shore crab, Carcinus maenas.
LACHAISE, F, GOUDEAU M, HETRU C, KAPPLER C, HOFFMANN JA
Abstract :
| Hoppe-Seyler's Z. Physiol. Chem.
1981 : 362 521-529 | Abstract
Article complet | 6. Ecdysone in reproductively competent female adults and in embryos of insects. In "Progress in Ecdysone Research".
HOFFMANN JA, LAGUEUX M, HETRU C, CHARLET M, GOLTZENE F
Abstract :
| Hoffmann JA Ed. Elsevier, North-Holland.
1980, pp 431-465 | Abstract
Article complet | 5. Prothoracic gland activity and blood titres of ecdysone and ecdysterone during the last larval instar of Locusta migratoria
HIRN M, LAGUEUX M, HETRU C, HOFFMANN JA
Abstract :
| J. Insect Physiol.
1979: 25 255-261 | Abstract
Article complet | 4. Ecdysone titre and metabolism in correlation to cuticulogenesis during embryonic development in Locusta migratoria
LAGUEUX M, HETRU C, GOLTZENE F, KAPPLER C, HOFFMANN JA
Abstract :
| J. Insect Physiol.
1979: 25 709-723 | Abstract
Article complet | 3. Adult ovaries of Locusta migratoria contain the sequence of biosynthetic intermediate for ecdysone
LAGUEUX M, HETRU C, LUU B, HOFFMANN JA
Abstract :
| Life Sciences
1978: 22 2141-2154 | Abstract
Article complet | 2. Dicing with viruses : microRNAs as antiviral factors
Muller S, Imler JL
Abstract : In plants and invertebrates, Dicer genes play a critical role against infections by RNA viruses. In this issue, Otsuka et al. (2007) report that Dicer mutant mice are hypersusceptible to infection by the RNA virus VSV.
| Immunity
2007 : Vol 27, 1-3 | Abstract
Article complet | 1. The Drosophila PRR GNBP3 assembles effector complexes involved in antifungal defenses independently of its Toll pathway activation function.
Alexey A. Matskevich, Jessica Quintin, and Dominique Ferrandon
Abstract : The Drosophila Toll signalling pathway controls the systemic antifungal host response. Gram-Negative Binding Protein 3 (GNBP3), a member of the ?-Glucan Recognition Protein (?GRP) family, senses fungal infections and activates this pathway. A second detection system perceives the activity of proteolytic fungal virulence factors and redundantly activates Toll. GNBP3hades mutant flies succumb more rapidly to Candida albicans and to entomopathogenic fungal infections than wild-type flies, even though the Toll pathway is still triggered to normal levels via the virulence detection system. These observations suggest that GNBP3 triggers antifungal defenses that are not dependent on Toll pathway activation. Here, we show that GNBP3 agglutinates fungal cells. Furthermore, it can activate melanization in a Toll-independent manner. Melanization is likely to be an essential defense against some fungal infections since the entomopathogenic fungus B. bassiana inhibits the activity of the main melanization enzymes, the phenol oxidases. Finally, we show that GNBP3 assembles attack complexes, which comprise PO and the serpin NEC. We propose that Drosophila GNBP3 targets fungi immediately at the inception of the infection by bringing effector molecules in direct contact with the invading microorganisms.
| European Journal of Immunology
DOI: 10.1002/eji.200940164 | Abstract
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