title: Identifying mechanisms by which Escherichia coli O157:H7 subverts interferon-γ mediated signal transducer and activator of transcription-1 activation.
abstract: Enterohemorrhagic Escherichia coli serotype O157:H7 is a food borne enteric bacterial pathogen that causes significant morbidity and mortality in both developing and industrialized nations. E. coli O157:H7 infection of host epithelial cells inhibits the interferon gamma pro-inflammatory signaling pathway, which is important for host defense against microbial pathogens, through the inhibition of Stat-1 tyrosine phosphorylation. The aim of this study was to determine which bacterial factors are involved in the inhibition of Stat-1 tyrosine phosphorylation. Human epithelial cells were challenged with either live bacteria or bacterial-derived culture supernatants, stimulated with interferon-gamma, and epithelial cell protein extracts were then analyzed by immunoblotting. The results show that Stat-1 tyrosine phosphorylation was inhibited by E. coli O157:H7 secreted proteins. Using sequential anion exchange and size exclusion chromatography, YodA was identified, but not confirmed to mediate subversion of the Stat-1 signaling pathway using isogenic mutants. We conclude that E. coli O157:H7 subverts Stat-1 tyrosine phosphorylation in response to interferon-gamma through a still as yet unidentified secreted bacterial protein.
authors.affiliation: Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Nathan K
authors.initials: NK
authors.lastname: Ho
authors.forename: Ian
authors.initials: I
authors.lastname: Crandall
authors.forename: Philip M
authors.initials: PM
authors.lastname: Sherman
mesh_terms: D002460:Cell Line; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology; D019453:Escherichia coli O157 / Q000187:drug effects / Q000276:immunology*; D029968:Escherichia coli Proteins / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism; D050794:STAT1 Transcription Factor / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology
chemical_list: D029968:Escherichia coli Proteins; D050794:STAT1 Transcription Factor; C470844:ZinT protein, E coli; D019000:Phosphotyrosine; D007371:Interferon-gamma