Publications
2013 |
Quintin, Jessica; Asmar, Joelle; Matskevich, Alexey A; Lafarge, Marie-Céline; Ferrandon, Dominique The Drosophila Toll pathway controls but does not clear Candida glabrata infections Article de journal J. Immunol., 190 (6), p. 2818–2827, 2013, ISSN: 1550-6606. Résumé | Liens | BibTeX | Étiquettes: Adaptor Proteins, Animal, Animals, Antigens, Candida glabrata, Candidiasis, Cells, Cultured, Differentiation, Disease Models, ferrandon, Immunologic, M3i, Phagocytosis, Receptors, Signal Transducing, Signal Transduction, Toll-Like Receptors, Virulence @article{quintin_drosophila_2013b, title = {The Drosophila Toll pathway controls but does not clear Candida glabrata infections}, author = {Jessica Quintin and Joelle Asmar and Alexey A Matskevich and Marie-Céline Lafarge and Dominique Ferrandon}, doi = {10.4049/jimmunol.1201861}, issn = {1550-6606}, year = {2013}, date = {2013-03-01}, journal = {J. Immunol.}, volume = {190}, number = {6}, pages = {2818--2827}, abstract = {The pathogenicity of Candida glabrata to patients remains poorly understood for lack of convenient animal models to screen large numbers of mutants for altered virulence. In this study, we explore the minihost model Drosophila melanogaster from the dual perspective of host and pathogen. As in vertebrates, wild-type flies contain C. glabrata systemic infections yet are unable to kill the injected yeasts. As for other fungal infections in Drosophila, the Toll pathway restrains C. glabrata proliferation. Persistent C. glabrata yeasts in wild-type flies do not appear to be able to take shelter in hemocytes from the action of the Toll pathway, the effectors of which remain to be identified. Toll pathway mutant flies succumb to injected C. glabrata. In this immunosuppressed background, cellular defenses provide a residual level of protection. Although both the Gram-negative binding protein 3 pattern recognition receptor and the Persephone protease-dependent detection pathway are required for Toll pathway activation by C. glabrata, only GNBP3, and not psh mutants, are susceptible to the infection. Both Candida albicans and C. glabrata are restrained by the Toll pathway, yet the comparative study of phenoloxidase activation reveals a differential activity of the Toll pathway against these two fungal pathogens. Finally, we establish that the high-osmolarity glycerol pathway and yapsins are required for virulence of C. glabrata in this model. Unexpectedly, yapsins do not appear to be required to counteract the cellular immune response but are needed for the colonization of the wild-type host.}, keywords = {Adaptor Proteins, Animal, Animals, Antigens, Candida glabrata, Candidiasis, Cells, Cultured, Differentiation, Disease Models, ferrandon, Immunologic, M3i, Phagocytosis, Receptors, Signal Transducing, Signal Transduction, Toll-Like Receptors, Virulence}, pubstate = {published}, tppubtype = {article} } The pathogenicity of Candida glabrata to patients remains poorly understood for lack of convenient animal models to screen large numbers of mutants for altered virulence. In this study, we explore the minihost model Drosophila melanogaster from the dual perspective of host and pathogen. As in vertebrates, wild-type flies contain C. glabrata systemic infections yet are unable to kill the injected yeasts. As for other fungal infections in Drosophila, the Toll pathway restrains C. glabrata proliferation. Persistent C. glabrata yeasts in wild-type flies do not appear to be able to take shelter in hemocytes from the action of the Toll pathway, the effectors of which remain to be identified. Toll pathway mutant flies succumb to injected C. glabrata. In this immunosuppressed background, cellular defenses provide a residual level of protection. Although both the Gram-negative binding protein 3 pattern recognition receptor and the Persephone protease-dependent detection pathway are required for Toll pathway activation by C. glabrata, only GNBP3, and not psh mutants, are susceptible to the infection. Both Candida albicans and C. glabrata are restrained by the Toll pathway, yet the comparative study of phenoloxidase activation reveals a differential activity of the Toll pathway against these two fungal pathogens. Finally, we establish that the high-osmolarity glycerol pathway and yapsins are required for virulence of C. glabrata in this model. Unexpectedly, yapsins do not appear to be required to counteract the cellular immune response but are needed for the colonization of the wild-type host. |
Ayyaz, Arshad; Giammarinaro, Philippe; Liégeois, Samuel; Lestradet, Matthieu; Ferrandon, Dominique Immunobiology, 218 (4), p. 635–644, 2013, ISSN: 1878-3279. Résumé | Liens | BibTeX | Étiquettes: Adaptor Proteins, Animal, Animals, Antigens, Differentiation, Disease Models, ferrandon, Immunity, Immunologic, Innate, Intestinal Diseases, M3i, Mucosal, Mutation, Receptors, Signal Transducing, Staphylococcal Infections, Staphylococcus, Starvation, Toll-Like Receptors @article{ayyaz_negative_2013b, title = {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}, author = {Arshad Ayyaz and Philippe Giammarinaro and Samuel Liégeois and Matthieu Lestradet and Dominique Ferrandon}, doi = {10.1016/j.imbio.2012.07.027}, issn = {1878-3279}, year = {2013}, date = {2013-01-01}, journal = {Immunobiology}, volume = {218}, number = {4}, pages = {635--644}, 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.}, keywords = {Adaptor Proteins, Animal, Animals, Antigens, Differentiation, Disease Models, ferrandon, Immunity, Immunologic, Innate, Intestinal Diseases, M3i, Mucosal, Mutation, Receptors, Signal Transducing, Staphylococcal Infections, Staphylococcus, Starvation, Toll-Like Receptors}, pubstate = {published}, tppubtype = {article} } 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. |
2006 |
Chen, Li-Ying; Wang, Juinn-Chin; Hyvert, Yann; Lin, Hui-Ping; Perrimon, Norbert; Imler, Jean-Luc; Hsu, Jui-Chou Weckle is a zinc finger adaptor of the toll pathway in dorsoventral patterning of the Drosophila embryo Article de journal Current biology: CB, 16 (12), p. 1183–1193, 2006, ISSN: 0960-9822. Résumé | Liens | BibTeX | Étiquettes: Adaptor Proteins, Animals, Antigens, Biological, Body Patterning, Cell Membrane, Differentiation, dimerization, DNA-Binding Proteins, Embryo, Epistasis, Genetic, imler, Immunity, Immunologic, Innate, M3i, Models, Mutation, Nonmammalian, Phenotype, Phosphoproteins, Receptors, Signal Transducing, Toll-Like Receptors, Transcription Factors, Zinc Fingers @article{chen_weckle_2006, title = {Weckle is a zinc finger adaptor of the toll pathway in dorsoventral patterning of the Drosophila embryo}, author = {Li-Ying Chen and Juinn-Chin Wang and Yann Hyvert and Hui-Ping Lin and Norbert Perrimon and Jean-Luc Imler and Jui-Chou Hsu}, doi = {10.1016/j.cub.2006.05.050}, issn = {0960-9822}, year = {2006}, date = {2006-06-01}, journal = {Current biology: CB}, volume = {16}, number = {12}, pages = {1183--1193}, abstract = {BACKGROUND: 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 Spätzle, 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.}, keywords = {Adaptor Proteins, Animals, Antigens, Biological, Body Patterning, Cell Membrane, Differentiation, dimerization, DNA-Binding Proteins, Embryo, Epistasis, Genetic, imler, Immunity, Immunologic, Innate, M3i, Models, Mutation, Nonmammalian, Phenotype, Phosphoproteins, Receptors, Signal Transducing, Toll-Like Receptors, Transcription Factors, Zinc Fingers}, pubstate = {published}, tppubtype = {article} } BACKGROUND: 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 Spätzle, 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. |
2003 |
Kambris, Zakaria; Bilak, Hana; D'Alessandro, Rosalba; Belvin, Marcia; Imler, Jean-Luc; Capovilla, Maria DmMyD88 controls dorsoventral patterning of the Drosophila embryo Article de journal EMBO reports, 4 (1), p. 64–69, 2003, ISSN: 1469-221X. Résumé | Liens | BibTeX | Étiquettes: Adaptor Proteins, Alleles, Animals, Antigens, Base Sequence, Cell Surface, Complementary, Developmental, Differentiation, DNA, DNA Transposable Elements, Egg Proteins, Embryo, Exons, Female, Gene Expression Regulation, Genetically Modified, Genotype, imler, Immunity, Immunologic, Innate, Insertional, M3i, Male, messenger, Morphogenesis, Mutagenesis, Myeloid Differentiation Factor 88, Nonmammalian, Oocytes, Protein Biosynthesis, Protein Structure, Receptors, Reverse Transcriptase Polymerase Chain Reaction, RNA, Signal Transducing, Tertiary, Toll-Like Receptors, Zygote @article{kambris_dmmyd88_2003, title = {DmMyD88 controls dorsoventral patterning of the Drosophila embryo}, author = {Zakaria Kambris and Hana Bilak and Rosalba D'Alessandro and Marcia Belvin and Jean-Luc Imler and Maria Capovilla}, doi = {10.1038/sj.embor.embor714}, issn = {1469-221X}, year = {2003}, date = {2003-01-01}, journal = {EMBO reports}, volume = {4}, number = {1}, pages = {64--69}, abstract = {MyD88 is an adapter protein in the signal transduction pathway mediated by interleukin-1 (IL-1) and Toll-like receptors. A 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 patterning of the embryo. We found that, like Toll, DmMyD88 messenger 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 carboxy-terminal extension, normally located downstream of the Toll/IL-1 receptor 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 an essential component of the Toll pathway in dorsoventral pattern formation.}, keywords = {Adaptor Proteins, Alleles, Animals, Antigens, Base Sequence, Cell Surface, Complementary, Developmental, Differentiation, DNA, DNA Transposable Elements, Egg Proteins, Embryo, Exons, Female, Gene Expression Regulation, Genetically Modified, Genotype, imler, Immunity, Immunologic, Innate, Insertional, M3i, Male, messenger, Morphogenesis, Mutagenesis, Myeloid Differentiation Factor 88, Nonmammalian, Oocytes, Protein Biosynthesis, Protein Structure, Receptors, Reverse Transcriptase Polymerase Chain Reaction, RNA, Signal Transducing, Tertiary, Toll-Like Receptors, Zygote}, pubstate = {published}, tppubtype = {article} } MyD88 is an adapter protein in the signal transduction pathway mediated by interleukin-1 (IL-1) and Toll-like receptors. A 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 patterning of the embryo. We found that, like Toll, DmMyD88 messenger 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 carboxy-terminal extension, normally located downstream of the Toll/IL-1 receptor 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 an essential component of the Toll pathway in dorsoventral pattern formation. |
2002 |
Tauszig-Delamasure, Servane; Bilak, Hana; Capovilla, Maria; Hoffmann, Jules A; Imler, Jean-Luc Drosophila MyD88 is required for the response to fungal and Gram-positive bacterial infections Article de journal Nature Immunology, 3 (1), p. 91–97, 2002, ISSN: 1529-2908. Résumé | Liens | BibTeX | Étiquettes: Adaptor Proteins, Amino Acid, Animals, Antigens, Antimicrobial Cationic Peptides, Cell Surface, Chromosome Mapping, Differentiation, Disease Susceptibility, Enterococcus faecalis, Epistasis, Escherichia coli, Female, Gene Expression Regulation, Genes, Genetic, Genetically Modified, Gram-Negative Bacteria, hoffmann, Hypocreales, imler, Immunologic, Insect, Insect Proteins, M3i, Membrane Glycoproteins, Micrococcus luteus, Myeloid Differentiation Factor 88, Protein Structure, Protein-Serine-Threonine Kinases, Receptors, Recombinant Fusion Proteins, Sequence Alignment, Sequence Homology, Signal Transducing, Tertiary, Toll-Like Receptors, Transfection @article{tauszig-delamasure_drosophila_2002, title = {Drosophila MyD88 is required for the response to fungal and Gram-positive bacterial infections}, author = {Servane Tauszig-Delamasure and Hana Bilak and Maria Capovilla and Jules A Hoffmann and Jean-Luc Imler}, doi = {10.1038/ni747}, issn = {1529-2908}, year = {2002}, date = {2002-01-01}, journal = {Nature Immunology}, volume = {3}, number = {1}, pages = {91--97}, abstract = {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.}, keywords = {Adaptor Proteins, Amino Acid, Animals, Antigens, Antimicrobial Cationic Peptides, Cell Surface, Chromosome Mapping, Differentiation, Disease Susceptibility, Enterococcus faecalis, Epistasis, Escherichia coli, Female, Gene Expression Regulation, Genes, Genetic, Genetically Modified, Gram-Negative Bacteria, hoffmann, Hypocreales, imler, Immunologic, Insect, Insect Proteins, M3i, Membrane Glycoproteins, Micrococcus luteus, Myeloid Differentiation Factor 88, Protein Structure, Protein-Serine-Threonine Kinases, Receptors, Recombinant Fusion Proteins, Sequence Alignment, Sequence Homology, Signal Transducing, Tertiary, Toll-Like Receptors, Transfection}, pubstate = {published}, tppubtype = {article} } 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. |
2000 |
Imler, Jean-Luc; Hoffmann, Jules A Toll and Toll-like proteins: an ancient family of receptors signaling infection Article de journal Reviews in Immunogenetics, 2 (3), p. 294–304, 2000, ISSN: 1398-1714. Résumé | BibTeX | Étiquettes: Adaptor Proteins, Animals, Antigens, Autoantigens, CD14, Cell Adhesion Molecules, Cell Surface, Differentiation, DNA-Binding Proteins, Gene Expression Regulation, hoffmann, I-kappa B Proteins, imler, Immunity, Immunologic, infection, Innate, Insect Proteins, Interleukin-1 Receptor-Associated Kinases, Knockout, Larva, Lipopolysaccharides, M3i, Mammals, MAP Kinase Signaling System, Membrane Glycoproteins, Membrane Proteins, Mice, Multigene Family, Myeloid Differentiation Factor 88, NF-kappa B, peptidoglycan, Phosphorylation, Post-Translational, Protein Kinases, Protein Processing, Protein Structure, Receptors, Recombinant Fusion Proteins, Signal Transducing, Signal Transduction, Teichoic Acids, Tertiary, Toll-Like Receptor 4, Toll-Like Receptor 5, Toll-Like Receptor 6, Toll-Like Receptor 9, Toll-Like Receptors, Ubiquitins @article{imler_toll_2000, title = {Toll and Toll-like proteins: an ancient family of receptors signaling infection}, author = {Jean-Luc Imler and Jules A Hoffmann}, issn = {1398-1714}, year = {2000}, date = {2000-01-01}, journal = {Reviews in Immunogenetics}, volume = {2}, number = {3}, pages = {294--304}, 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.}, keywords = {Adaptor Proteins, Animals, Antigens, Autoantigens, CD14, Cell Adhesion Molecules, Cell Surface, Differentiation, DNA-Binding Proteins, Gene Expression Regulation, hoffmann, I-kappa B Proteins, imler, Immunity, Immunologic, infection, Innate, Insect Proteins, Interleukin-1 Receptor-Associated Kinases, Knockout, Larva, Lipopolysaccharides, M3i, Mammals, MAP Kinase Signaling System, Membrane Glycoproteins, Membrane Proteins, Mice, Multigene Family, Myeloid Differentiation Factor 88, NF-kappa B, peptidoglycan, Phosphorylation, Post-Translational, Protein Kinases, Protein Processing, Protein Structure, Receptors, Recombinant Fusion Proteins, Signal Transducing, Signal Transduction, Teichoic Acids, Tertiary, Toll-Like Receptor 4, Toll-Like Receptor 5, Toll-Like Receptor 6, Toll-Like Receptor 9, Toll-Like Receptors, Ubiquitins}, pubstate = {published}, tppubtype = {article} } 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. |