Project description:Traditional treatments for bacterial infection have focused upon directly inhibiting growth of the pathogen. However, an equally important determinant of infection outcome is the host defense response. We previously performed a high-throughput chemical screen to identify small molecules that rescued the nematode Caenorhabditis elegans from infection by Pseudomonas aeruginosa. Over 20 of the hits stimulated host defense gene expression. During in-depth studies of five such molecules using microarray analysis, bioinformatic clustering, and RNAi knockdown of candidate gene targets, we identified PMK-1/p38 MAPK and SKN-1/Nrf2 as two key pathways modulated by these hits. Interestingly, the molecules studied did not depend on a single pathway for ameliorating P. aeruginosa pathogenesis in liquid-based assay, but did rely on the PMK-1/p38 MAPK pathway during a colonization-based infection assay on agar. A subset of these molecules was also protective against Enterococcus faecalis and Staphylococcus aureus. In general, the compounds showed little toxicity against mammalian cells or worms, consistent with their identification in a phenotypic, high-content screen. These molecules possess significant potential for use as tools to study innate immune processes
Project description:C-type lectin-like domain (CTLD) encoding genes are highly diverse in C. elegans, comprising a clec gene family of 283 members. Since vertebrate CTLD proteins have characterized functions in defense responses against pathogens and since expression of C. elegans clec genes is pathogen-dependent, it is generally assumed that clec genes function in C. elegans immune defenses. In this study we challenged this assumption and focused on the C. elegans clec gene clec-4, whose expression is highly upregulated upon infection with various pathogens. We tested the involvement of clec-4 in the defense response to infection with Pseudomonas aeruginosa PA14, Bacillus thuringiensis BT18247, and the natural pathogen Serratia rubidaea MYb237. Contrary to our expectation clec-4(ok2050) mutant worms were not more susceptible to pathogen infection than wildtype worms. To explore potential redundant function between different C. elegans clec genes, we investigated expression of several clec-4 paralogs, finding that clec-4, clec-41, and clec-42 expression shows similar infection-dependent changes and co-localizes to the intestine. We found that only clec-42 is required for the C. elegans defense response to BT18247 infection and that clec-4 genetically interacts with clec-41 and clec-42. The exact role of clec-4 in pathogen defense responses however remains enigmatic. Our results further indicate that a complex interplay between different clec genes regulates C. elegans defense responses.
Project description:Discriminating pathogenic bacteria from energy-harvesting commensals is key to host immunity. Using mutants defective in the enzymes of O-linked N-acetylglucosamine (O-GlcNAc) cycling, we examined the role of this nutrient-sensing pathway in the Caenorhabidits elegans innate immune response. Using whole genome transcriptional profiling, O-GlcNAc cycling mutants exhibited deregulation of unique stress- and immune-responsive genes as well as genes shared with the p38 MAPK/PMK-1 pathway. Moreover, genetic analysis showed that deletion of O-GlcNAc transferase (ogt-1) yielded animals hypersensitive to the human pathogen S. aureus but not to P. aeruginosa. Genetic interaction studies further revealed that nutrient-responsive OGT-1 acts through the conserved ß-catenin (BAR-1) pathway and in concert with p38 MAPK/PMK-1 to modulate the immune response to S. aureus. The participation of the nutrient sensor O-GlcNAc transferase in an immunity module conserved from C. elegans to humans reveals an unexplored nexus between nutrient availability and a pathogen-specific immune response. In C. elegans, three mutant strains(genotypes used: N2 (wild-type), ogt-1 (ok1474), oga-1 (ok1207), and pmk-1 (km25)) were treated with the human pathogen S. aureus (SA) or P. aeruginosa(PA) and OP50 (E. coli control) with three biological replications.
Project description:The Caenorhabditis elegans bus (bacterial unswollen) mutants were isolated by their altered response to the nematode pathogen Microbacterium nematophilum. The bus-2, bus-4 and bus-17 mutants are resistant to infection by this bacterium and to infection by human pathogens Yersinia pestis and Yersinia pseudotuberculosis. Here we extend that list to Staphylococcus aureus. The bus-2, bus-4 and bus-17 mutants each harbors a defect in a different glycosyltransferase involved in O-glycosylation. Glycomics analysis of these strains reveals significant O-glycosylation defects. We further investigated the nature of bus mutant phenotypes in bus-2, bus-4 and bus-17 by gene expression analysis. Three distinct areas of altered expression were identified: 1) N- and O-glycosylation; 2) innate immune response; 3) protein folding and editing control. As expected N- and O-glycosylation gene expression was altered at key enzymatic steps. Innate immune system expression patterns were altered in a way that significantly overlapped with expression patterns seen in wild-type upon exposure to Staphylococuss aureus. Upon infection with S. aureus markers of innate immune activity increased significantly compared to wild-type. The abu/pqn genes, active in the non-canonical unfolded protein response (UPR) pathway were dramatically upregulated in bus when these mutants were exposed to the pathogen. This work demonstrates a genetic link between O-glycosylation and expression of key components of the innate immune response.
Project description:Discriminating pathogenic bacteria from energy-harvesting commensals is key to host immunity. Using mutants defective in the enzymes of O-linked N-acetylglucosamine (O-GlcNAc) cycling, we examined the role of this nutrient-sensing pathway in the Caenorhabidits elegans innate immune response. Using whole genome transcriptional profiling, O-GlcNAc cycling mutants exhibited deregulation of unique stress- and immune-responsive genes as well as genes shared with the p38 MAPK/PMK-1 pathway. Moreover, genetic analysis showed that deletion of O-GlcNAc transferase (ogt-1) yielded animals hypersensitive to the human pathogen S. aureus but not to P. aeruginosa. Genetic interaction studies further revealed that nutrient-responsive OGT-1 acts through the conserved ß-catenin (BAR-1) pathway and in concert with p38 MAPK/PMK-1 to modulate the immune response to S. aureus. The participation of the nutrient sensor O-GlcNAc transferase in an immunity module conserved from C. elegans to humans reveals an unexplored nexus between nutrient availability and a pathogen-specific immune response.
Project description:The nematode Caenorhabditis elegans offers currently untapped potential for carrying out high-throughput, live-animal screens of low molecular weight compound libraries to identify molecules that target a variety of cellular processes. We previously used a bacterial infection assay in C. elegans to identify 119 compounds that affect host-microbe interactions among 37,214 tested. We subsequently found that one of these small molecules, RPW-24, protects C. elegans from bacterial infection by stimulating the host immune response of the nematode. Using transcriptome profiling, epistasis pathway analyses with C. elegans mutants, and an RNAi screen, we showed that RPW-24 promotes resistance to Pseudomonas aeruginosa infection by inducing the transcription of a remarkably small number of C. elegans genes (~1.3% of all genes) in a manner that partially depends on the evolutionarily-conserved p38 MAP kinase pathway and the transcription factor ATF-7. These data demonstrated that the immunostimulatory activity of RPW-24 is required for its efficacy and define a novel C. elegans-based strategy to identify compounds with activity against antibiotic-resistant bacterial pathogens. Here we present the microarray data that were used to define the genes that are differentially regulated in wild-type nematodes following exposure to RPW-24.
Project description:Synchronized C. elegans cultures of three geontypes -- wildype N2, daf-2(e1370) and sma-6(wk7) -- were prepared using standard techniques (http://cmgm.stanford.edu/~kimlab/index_methods.html). Live young adult worms were split between NG plates pre-seeded with the non-pathogenic E. coli strain OP50 or the Pseudomonas aeruginosa clinical isolate PA14 and incubated at 25C for 4 or 24 hours before harvesting. This experiment was repeated at least three times on independent occasions. cDNA probes were prepared from experimental samples and from reference mRNA extracted from mixed stage wild type worms grown at 25C, and were labeled with Cy3 or Cy5, as indicated. A reference experiement design type is where all samples are compared to a common reference. Elapsed Time: Time Infection: Exposure to the non-pathogenic E. coli strain OP50 or to the pathogenic Pseudomonas aeruginosa strain PA14 Strain Name: C. elegans wildtype strain N2 or the immune pathway mutants daf-2(e1370) or sma-6(wk7) Keywords: reference_design Computed
Project description:Young adult fer-15;fem-1 Caenorhabditis elegans were infected with Staphylococcus aureus for 8 h to determine the transcriptional host response to Staphylococcus aureus. Analysis of differential gene expression in C. elegans young adults exposed to two different bacteria: E. coli strain OP50 (control), wild-type Staphylococcus aureus RN6390. Samples were analyzed at 8 hours after exposure to the different bacteria. These studies identified C. elegans genes induced by pathogen infection. Keywords: response to pathogen infection, innate immunity, host-pathogen interactions