The Experts below are selected from a list of 642 Experts worldwide ranked by ideXlab platform
Jules A Hoffmann - One of the best experts on this subject based on the ideXlab platform.
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Toll-Pathway Activation Is Wild-Type in DaGal4;UAS iPGRP-SC Flies
2013Co-Authors: Vincent Bischoff, Jules A Hoffmann, Cécile Vignal, Bernard Duvic, Ivo G Boneca, Julien RoyetAbstract:Kinetics of Drosomycin mrna induction (Drs/RpL32) after infection by gram-positive (upper panel) and gram-negative (lower panel) bacteria. Each histogram corresponds to the mean value of six independent experiments (± standard deviation). Asterisk indicates that the difference between DaGal4;UAS iPGRP-SC and control UAS iPGRP-SC values is statistically significant (p
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Drosophila MyD88 is required for the response to fungal and Gram-positive bacterial infections.
Nature immunology, 2001Co-Authors: Servane Tauszig-delamasure, Jules A Hoffmann, Hana Bilak, Maria Capovilla, Jean-luc ImlerAbstract:We report here the identification and functional characterization of DmMyD88, a gene encoding the Drosophila homolog of mammalian MyD88. DmMyD88 combines a Toll-IL-1R homology (TIR) domain and a death domain. Overexpression of DmMyD88 was sufficient to induce expression of the antifungal 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 comparison of DmMyD88-mutant flies and MyD88-deficient mice showed essential differences in the control of Gram-negative infection in insects and mammals.
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tissue specific inducible expression of antimicrobial peptide genes in drosophila surface epithelia
Immunity, 2000Co-Authors: Phoebe Tzou, Jules A Hoffmann, Bruno Lemaitre, Jean-marc Reichhart, Maria Capovilla, Dominique Ferrandon, Serge Ohresser, Jean-luc ImlerAbstract: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.
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Toll-related receptors and the control of antimicrobial peptide expression in Drosophila.
Proceedings of the National Academy of Sciences of the United States of America, 2000Co-Authors: Servane Tauszig, Jules A Hoffmann, Emmanuelle Jouanguy, Jean-luc ImlerAbstract: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.
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LPS-induced immune response in Drosophila.
Journal of endotoxin research, 2000Co-Authors: Jean-luc Imler, Servane Tauszig, Emmanuelle Jouanguy, Claire Forestier, Jules A HoffmannAbstract: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 Toll 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.
Bruno Lemaitre - One of the best experts on this subject based on the ideXlab platform.
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Synergy and remarkable specificity of antimicrobial peptides in vivo using a systematic knockout approach
Elife, 2019Co-Authors: Mark Austin Hanson, Mickael Poidevin, Anna Dostálová, Camilla Ceroni, Shu Kondo, Bruno LemaitreAbstract:Antimicrobial peptides (AMPs) are host-encoded antibiotics that combat invading microorganisms. These short, cationic peptides have been implicated in many biological processes, primarily involving innate immunity. In vitro studies have shown AMPs kill bacteria and fungi at physiological concentrations, but little validation has been done in vivo. We utilized CRISPR gene editing to delete all known immune-inducible AMPs of Drosophila, namely: 4 Attacins, 4 Cecropins, 2 Diptericins, Drosocin, Drosomycin, Metchnikowin and Defensin. Using individual and multiple knockouts, including flies lacking all 14 AMP genes, we characterize the in vivo function of individual and groups of AMPs against diverse bacterial and fungal pathogens. We found that Drosophila AMPs act primarily against Gram-negative bacteria and fungi, contributing either additively or synergistically. We also describe remarkable specificity wherein certain AMPs contribute the bulk of microbicidal activity against specific pathogens, providing functional demonstrations of highly specific AMP-pathogen interactions in an in vivo setting.
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École Polytechnique Fédérale de Lausanne 183 PUBLICATIONS 15,857 CITATIONS SEE PROFILE
2016Co-Authors: Bruno Lemaitre, Sandrine Uttenweiler-josephAbstract:Ferrandon, D. et al. A Drosomycin-GFP reporter transgene reveals a local immune response in Drosophila that is not dependent on the Toll pathway. EMBO J. 17, 1217-122
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Melanization is not required for Toll and Imd pathway activities.
2014Co-Authors: Olivier Binggeli, Claudine Neyen, Mickael Poidevin, Bruno LemaitreAbstract:(A) Expression of Diptericin in PPO mutant flies. Total RNA was extracted from animals either uninfected or collected 6 h and 12 h after septic injury with Gram-negative bacteria E. carotovora. Shown are the relative expression levels of Dpt in relation to RpL32. Single and double PPO mutants as well as Bc flies have wild-type Dpt expression levels. The Imd pathway mutant Relish was used as a negative control. (B) Expression of Drosomycin in PPO mutant flies 24 h after septic injury with Gram-positive bacteria M. luteus show that PPO1Δ, PPO2Δ mutant flies (*,p
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The In Vivo Rescuing and In Vitro PG-Binding Activities of Wild-Type rPGRP-SA
2013Co-Authors: Chung-i Chang, Bruno Lemaitre, Sébastien Pili-floury, Mireille Hervé, Claudine Parquet, Yogarany Chelliah, Dominique Mengin-lecreulx, Johann DeisenhoferAbstract:(A–E) Drosomycin-GFP expression in (A) wild-type and (B to E) PGRP-SAseml flies after challenge by M. luteus. (A and B) Water or (C to E) rPGRP-SA at variable concentrations was injected into Drosomycin-GFP flies prior to the challenge with M. luteus. (F) rPGRP-SA binds to both lysine-type (M. luteus and E. faecalis) and DAP-type (E. coli and P. aeruginosa) PGs but not to amidated DAP-type (Bacillus subtilis and Bacillus thuringiensis) PG. The left lane (Input) is loaded with the same amount (20 μg) of protein used for the binding assay.
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Pillars article: the dorsoventral regulatory gene cassette spätzle/Toll/cactus controls the potent antifungal response in Drosophila adults. Cell. 1996. 86: 973-983
Journal of Immunology, 2012Co-Authors: Bruno Lemaitre, Lydia Michaut, Emmanuelle Nicolas, Jean-marc Reichhart, Jules HoffmannAbstract:The cytokine-induced activation cascade of NF-kappaB in mammals and the activation of the morphogen dorsal in Drosophila embryos show striking structural and functional similarities (Toll/IL-1, Cactus/I-kappaB, and dorsal/NF-kappaB). Here we demonstrate that these parallels extend to the immune response of Drosophila. In particular, the intracellular components of the dorsoventral signaling pathway (except for dorsal) and the extracellular Toll ligand, spätzle regulatory gene cassette, control expression of the antifungal peptide gene Drosomycin in adults. We also show that mutations in the Toll signaling pathway dramatically reduce survival after fungal infection. Antibacterial genes are induced either by a distinct pathway involving the immune deficiency gene (imd) or by combined activation of both imd and dorsoventral pathways.
Shunyi Zhu - One of the best experts on this subject based on the ideXlab platform.
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Characterization of bi-domain Drosomycin-type antifungal peptides in nematodes: An example of convergent evolution
Developmental and comparative immunology, 2018Co-Authors: Bin Gao, Shunyi ZhuAbstract:Abstract Drosomycin-type antifungal peptides (DTAFPs) are natural effectors of the innate immune system, which are restrictedly distributed in plants and ecdysozoans. Mehamycin is a bi-domain DTAFP (abbreviated as bDTAFP) firstly found in the Northern root-knot nematode Meloidogyne hapla. Here, we report its structural and functional features and the evolution of bDTAFPs in nematodes. Different from classical DTAFPs, mehamycin contains an insertion, called single Disulfide Bridge-linked Domain (abbreviated as sDBD), located in a loop region of the Drosomycin scaffold. Despite this, recombinant mehamycin likely adopts a similar fold to Drosomycin, as revealed by the circular dichroism spectral analysis. Functionally, it showed some weak activity against three species of fungi but relatively stronger activity against seven species of Gram-positive bacteria, indicative of functional diversification between mehamycin and classical DTAFPs. By computational data mining of the nematode databases, we identified polymorphic genes encoding mehamycin and a new multigene family of bDTAFPs (named roremycins) from Rotylenchulus reniformis. A combination of data suggests that the origination of sDBDs from M. hapla and R. reniformis is a consequence of convergent evolution, in which some probably suffered positive selection during evolution. Our study may be valuable in understanding the role of these unique antimicrobial peptides in the innate immunity of nematodes.
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The Drosomycin multigene family: three-disulfide variants from Drosophila takahashii possess antibacterial activity
Scientific reports, 2016Co-Authors: Bin Gao, Shunyi ZhuAbstract:Drosomycin (DRS) is a strictly antifungal peptide in Drosophila melanogaster, which contains four disulfide bridges (DBs) with three buried in molecular interior and one exposed on molecular surface to tie the amino- and carboxyl-termini of the molecule together (called wrapper disulfide bridge, WDB). Based on computational analysis of genomes of Drosophila species belonging to the Oriental lineage, we identified a new multigene family of DRS in Drosphila takahashii that includes a total of 11 DRS-encoding genes (termed DtDRS-1 to DtDRS-11) and a pseudogene. Phylogenetic tree and synteny analyses reveal orthologous relationship between DtDRSs and DRSs, indicating that orthologous genes of DRS-1, DRS-2, DRS-3 and DRS-6 have undergone duplication in D. takahashii and three amplifications (DtDRS-9 to DtDRS-11) of DRS-3 have lost WDB. Among the 11 genes, five are transcriptionally active in adult fruitflies. The ortholog of DRS (DtDRS-1) shows high structural and functional similarity to DRS while two WDB-deficient members display antibacterial activity accompanying complete loss or remarkable reduction of antifungal activity. To the best of our knowledge, this is the first report on the presence of three-disulfide antibacterial DRSs in a specific Drosophila species, suggesting a potential role of DB loss in neofunctionalization of a protein via structural adjustment.
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Nematode-derived Drosomycin-type antifungal peptides provide evidence for plant-to-ecdysozoan horizontal transfer of a disease resistance gene
Nature communications, 2014Co-Authors: Shunyi Zhu, Bin GaoAbstract:Drosomycin-type antifungal peptides (DTAFPs) confer resistance to fungal infections in Drosophila and plants. Here, the authors report the discovery of a family of DTAFPs in the nematode, Caenorhabditis remanei, which provides insight into the origin and evolution of disease resistance genes in animals.
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Drosotoxin, a selective inhibitor of tetrodotoxin-resistant sodium channels.
Biochemical pharmacology, 2010Co-Authors: Shunyi Zhu, Bin Gao, Yuzhe Yuan, Meichun Deng, Lan Luo, Steve Peigneur, Yucheng Xiao, Songping Liang, Jan TytgatAbstract:Abstract The design of animal toxins with high target selectivity has long been a goal in protein engineering. Based on evolutionary relationship between the Drosophila antifungal defensin (Drosomycin) and scorpion depressant Na + channel toxins, we exploited a strategy to create a novel chimeric molecule (named drosotoxin) with high selectivity for channel subtypes, which was achieved by using Drosomycin to substitute the structural core of BmKITc, a depressant toxin acting on both insect and mammalian Na + channels. Recombinant drosotoxin selectively inhibited tetrodotoxin-resistant (TTX-R) Na + channels in rat dorsal root ganglion (DRG) neurons with a 50% inhibitory concentration (IC 50 ) of 2.6 ± 0.5 μM. This chimeric peptide showed no activity on K + , Ca 2+ and TTX-sensitive (TTX-S) Na + channels in rat DRG neurons and Drosophila para/tipE channels at micromolar concentrations. Drosotoxin represents the first chimeric toxin and example of a non-toxic core scaffold with high selectivity on mammalian TTX-R Na + channels.
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Functional role of charged residues in Drosomycin, a Drosophila antifungal peptide.
Developmental and comparative immunology, 2010Co-Authors: Zhenting Zhang, Shunyi ZhuAbstract:The functional importance of positively charged residues in antibacterial peptides (ABPs) has been well documented. However, their role in antifungal peptides (AFPs) has not been extensively evaluated. To address this question, we investigated the functional role of charged residues in Drosomycin, a specific Drosophila antifungal peptide, using site-directed mutagenesis in combination with circular dichroism (CD) analysis and antifungal assays. As a result, we firstly identified five cationic residues (R6, K8, R20, R21 and K38) whose alterations significantly affected the antifungal activity. Intriguingly, two negatively charged residues (D1 and E25) are also recognized as functional determinants of Drosomycin. This indicates that it is the location of these charged residues rather than net charges that is crucial for activity. These functional sites are located in different secondary structure elements, including the N-loop, α-helix and γ-core regions, all highly exposed on the molecular surface, suggesting that Drosomycin may bind to fungal targets through electrostatic interactions. Our work has implications for further modification of Drosomycin to obtain new antifungal peptides with enhanced activity.
Jean-marc Reichhart - One of the best experts on this subject based on the ideXlab platform.
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Pillars article: the dorsoventral regulatory gene cassette spätzle/Toll/cactus controls the potent antifungal response in Drosophila adults. Cell. 1996. 86: 973-983
Journal of Immunology, 2012Co-Authors: Bruno Lemaitre, Lydia Michaut, Emmanuelle Nicolas, Jean-marc Reichhart, Jules HoffmannAbstract:The cytokine-induced activation cascade of NF-kappaB in mammals and the activation of the morphogen dorsal in Drosophila embryos show striking structural and functional similarities (Toll/IL-1, Cactus/I-kappaB, and dorsal/NF-kappaB). Here we demonstrate that these parallels extend to the immune response of Drosophila. In particular, the intracellular components of the dorsoventral signaling pathway (except for dorsal) and the extracellular Toll ligand, spätzle regulatory gene cassette, control expression of the antifungal peptide gene Drosomycin in adults. We also show that mutations in the Toll signaling pathway dramatically reduce survival after fungal infection. Antibacterial genes are induced either by a distinct pathway involving the immune deficiency gene (imd) or by combined activation of both imd and dorsoventral pathways.
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tissue specific inducible expression of antimicrobial peptide genes in drosophila surface epithelia
Immunity, 2000Co-Authors: Phoebe Tzou, Jules A Hoffmann, Bruno Lemaitre, Jean-marc Reichhart, Maria Capovilla, Dominique Ferrandon, Serge Ohresser, Jean-luc ImlerAbstract: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.
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The Rel protein DIF mediates the antifungal but not the antibacterial host defense in Drosophila.
Immunity, 2000Co-Authors: Sophie Rutschmann, Jules A Hoffmann, Charles Hetru, Jean-marc Reichhart, Alain C. Jung, Dominique FerrandonAbstract: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.
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Constitutive Activation of Toll-Mediated Antifungal Defense in Serpin-Deficient Drosophila
Science (New York N.Y.), 1999Co-Authors: Elena A. Levashina, Jules A Hoffmann, David Gubb, Emma Langley, Clare Green, Michael Ashburner, Jean-marc ReichhartAbstract: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.
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a mosaic analysis in drosophila fat body cells of the control of antimicrobial peptide genes by the rel proteins dorsal and dif
The EMBO Journal, 1999Co-Authors: Pascal Manfruelli, Jules A Hoffmann, Jean-marc Reichhart, Ruth Steward, Bruno LemaitreAbstract: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.
Jean-luc Imler - One of the best experts on this subject based on the ideXlab platform.
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Antimicrobial peptides in Drosophila: structures, activities and gene regulation.
Chemical Immunology and Allergy, 2005Co-Authors: Jean-luc Imler, Philippe BuletAbstract: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.
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Drosophila MyD88 is required for the response to fungal and Gram-positive bacterial infections.
Nature immunology, 2001Co-Authors: Servane Tauszig-delamasure, Jules A Hoffmann, Hana Bilak, Maria Capovilla, Jean-luc ImlerAbstract:We report here the identification and functional characterization of DmMyD88, a gene encoding the Drosophila homolog of mammalian MyD88. DmMyD88 combines a Toll-IL-1R homology (TIR) domain and a death domain. Overexpression of DmMyD88 was sufficient to induce expression of the antifungal 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 comparison of DmMyD88-mutant flies and MyD88-deficient mice showed essential differences in the control of Gram-negative infection in insects and mammals.
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tissue specific inducible expression of antimicrobial peptide genes in drosophila surface epithelia
Immunity, 2000Co-Authors: Phoebe Tzou, Jules A Hoffmann, Bruno Lemaitre, Jean-marc Reichhart, Maria Capovilla, Dominique Ferrandon, Serge Ohresser, Jean-luc ImlerAbstract: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.
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Toll-related receptors and the control of antimicrobial peptide expression in Drosophila.
Proceedings of the National Academy of Sciences of the United States of America, 2000Co-Authors: Servane Tauszig, Jules A Hoffmann, Emmanuelle Jouanguy, Jean-luc ImlerAbstract: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.
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LPS-induced immune response in Drosophila.
Journal of endotoxin research, 2000Co-Authors: Jean-luc Imler, Servane Tauszig, Emmanuelle Jouanguy, Claire Forestier, Jules A HoffmannAbstract: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 Toll 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.
