title: Hfq reduces envelope stress by controlling expression of envelope-localized proteins and protein complexes in enteropathogenic Escherichia coli.
abstract: Gram-negative bacteria possess several envelope stress responses that detect and respond to damage to this critical cellular compartment. The σ(E) envelope stress response senses the misfolding of outer membrane proteins (OMPs), while the Cpx two-component system is believed to detect the misfolding of periplasmic and inner membrane proteins. Recent studies in several Gram-negative organisms found that deletion of hfq, encoding a small RNA chaperone protein, activates the σ(E) envelope stress response. In this study, we assessed the effects of deleting hfq upon activity of the σ(E) and Cpx responses in non-pathogenic and enteropathogenic (EPEC) strains of Escherichia coli. We found that the σ(E) response was activated in Δhfq mutants of all E. coli strains tested, resulting from the misregulation of OMPs. The Cpx response was activated by loss of hfq in EPEC, but not in E. coli K-12. Cpx pathway activation resulted in part from overexpression of the bundle-forming pilus (BFP) in EPEC Δhfq. We found that Hfq repressed expression of the BFP via PerA, a master regulator of virulence in EPEC. This study shows that Hfq has a more extensive role in regulating the expression of envelope proteins and horizontally acquired virulence genes in E. coli than previously recognized.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9.
authors.forename: Stefanie L
authors.initials: SL
authors.lastname: Vogt
authors.forename: Tracy L
authors.initials: TL
authors.lastname: Raivio
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D004252:DNA Mutational Analysis; D054308:Enteropathogenic Escherichia coli / Q000235:genetics* / Q000502:physiology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D035001:Host Factor 1 Protein / Q000235:genetics / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D012808:Sigma Factor / Q000378:metabolism*; D013312:Stress, Physiological
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C087373:Hfq protein, E coli; D035001:Host Factor 1 Protein; D012808:Sigma Factor; C063202:sporulation-specific sigma factors; C085504:CpxR protein, Bacteria; D011494:Protein Kinases; C490475:CpxA protein, E coli