The Serine Protease EspC from Enteropathogenic Escherichia coli Regulates Pore Formation and Cytotoxicity Mediated by the Type III Secretion System

摘要: Type III secretion systems (T3SSs) are specialized macromolecular machines critical for bacterial virulence, and allowing the injection of effectors into host cells. The T3SS-dependent process requires prior insertion a protein complex, translocon, cell membranes consisting two-T3SS hydrophobic proteins, associated with pore-forming activity. In all described T3SS to date, hydrophilic connects one component needle, presumably insuring continuum between hollow needle translocon. case Enteropathogenic Escherichia coli (EPEC), EspA polymerizes filament connecting translocon composed EspB EspD proteins. Here, we identify as targets EspC, serine protease autotransporter Enterobacteriaceae (SPATE). We found that in vitro, EspC preferentially EspD, but was less efficient at proteolyzing alone. Consistently, did not regulate filaments surface primed bacteria devoid controlled levels secreted vitro or upon contact. While still proficient T3SS-mediated cytoskeletal reorganization, an espC mutant showed increased cell-associated well pore formation activity cytotoxicity. EspP from enterohaemorrhagic E. (EHEC) also targeted translocator components its interchangeable suggesting common important function these SPATEs. These findings reveal novel regulatory mechanism cytotoxicity control during EPEC/EHEC infection.