Protein translocation into host epithelial cells by infecting enteropathogenic Escherichia coli

Abstract

SummaryEnteropathogenic Escherichia coli (EPEC) causes diarrhoea in young children. EPEC induces the formation of actin pedestal in infected epithelial cells. A type III protein secretion system and several proteins that are secreted by this system, including EspB, are involved in inducing the formation of the actin pedestals. We have demonstrated that contact of EPEC with HeLa cells is associated with the induction of production and secretion of EspB. Shortly after infection, EPEC initiates translocation of EspB, and EspB fused to the CyaA reporter protein (EspB-CyaA), into the host cell. The translocated EspB was distributed between the membrane and the cytoplasm of the host cell. Translocation was strongly promoted by attachment of EPEC to the host cell, and both attachment factors of EPEC, intimin and the bundle-forming pili, were needed for full translocation efficiency. Translocation and secretion of EspB and EspB-CyaA were abolished in mutants deficient in components of the type III protein secretion system, including sepA and sepB mutants. EspB-CyaA was secreted but not translocated by an espB mutant. These results indicate that EspB is both translocated and required for protein translocation by EPEC.

Nck adaptors, besides promoting N-WASP mediated actin-nucleation activity at pedestals, influence the cellular levels of enteropathogenicEscherichia coliTir effector

“…S1A). We also found that the levels of EspB effector, a component of the translocation pore, 36 were not diminished in Nckdeficient cells, as observed with EspF (Fig. S1A).…”

“…37 Moreover, the levels of Tir and that of other effectors detected in the insoluble fraction are an indicator of bacterial attachment to cells. 36 We found that the levels of DnaK in the insoluble fraction of Nck-deficient cells were decreased with respect to control cells (asterisk in Fig. S1B).…”

Infection strategies of enteric pathogenic Escherichia coli

“…115 This filament functions in initial attachment to the host cell before secretion of the translocators, EspB and EspD, which form the translocation pore in the host cell membrane. 116,117 EHEC and EPEC use the T3SS to inject dozens of effector proteins into the eukaryotic cell cytoplasm. Once translocated, these effector proteins are targeted to different subcellular compartments and affect diverse signaling pathways and physiological processes.…”

Suppression of NF-κB Activation and Proinflammatory Cytokine Expression by Shiga Toxin-Producing Escherichia coli

“…It is generally assumed that after initial attachment of EPEC and STEC to the intestinal epithelium, a LEE-encoded type III-secreted protein translocation tube is formed, which connects the pathogen with its target cell (15,16). EspA seems to be a major component of this tube (17,18), whereas EspD (19,20) and EspB (18,21,22) appear to be inserted into the host membrane, forming a pore structure. Thus, additional Esp proteins such as EspE/translocated intimin receptor (23,24) and EspF (25) can be directly injected from the cytoplasm of the bacterium into the host cell to modulate host responses.…”