Site-Specific Tyrosine Phosphorylation of the Type III Secretion Chaperone CesT Regulates Effector Hierarchy and Promotes Enteropathogenic Escherichia coli Intestinal Disease

Abstract

Enteropathogenic E. coli (EPEC) is a global enteric pathogen that causes serious gastrointestinal disease and inflicts a significant burden on healthcare systems worldwide. Recent phosphoproteomic studies suggest that phosphotyrosine modifications are widespread in bacteria and likely have significant impact on virulence factor regulation. In this study, we provide the first evidence that tyrosine phosphorylation of a multicargo chaperone, CesT, is functionally important for EPEC type III secretion system (T3SS)- mediated pathogenesis. The conserved phosphosites, Y152 and Y153, are located within a unique domain of CesT at the C-terminus. Positional tyrosine to phenylalanine mutations resulted in differential secretion of CesT-dependent type III effectors, and loss of phenotypes associated with disease progression in vitro. These observations were validated in vivo using the closely related mouse pathogen Citrobacter rodentium, which requires CesT, and specifically a CesT phosphosite, for significant intestinal colonization. This study identifies a novel research direction to pursue limitation of EPEC pathogenesis.