Role of EspF in host cell death induced by enteropathogenic Escherichia coli

Abstract

Enteropathogenic Escherichia coli (EPEC) causes diarrhoea in children in developing countries. Many EPEC genes involved in virulence are contained within the locus of enterocyte effacement (LEE), a large pathogenicity island. One of the genes at the far righthand end of the LEE encodes EspF, an EPEC secreted protein of unknown function. EspF, like the other Esps, is a substrate for secretion by the type III secretory system. Previous studies found that an espF mutant behaved as wild type in assays of adherence, invasion, actin condensation and tyrosine phosphorylation. As EPEC can kill host cells, we tested esp gene mutants for host cell killing ability. The espF mutant was deficient in host cell killing despite having normal adherence. The addition of purified EspF to tissue culture medium did not cause any damage to host cells, but expression of espF in COS or HeLa cells caused cell death. The mode of cell death in cells transfected with espF appeared to be pure apoptosis. EspF appears to be an effector of host cell death in epithelial cells; its proline‐rich structure suggests that it may act by binding to SH3 domains or EVH1 domains of host cell signalling proteins.

Enteropathogenic Escherichia coli induces modification of the focal adhesions of infected host cells

“…This was observed with several cell lines including epithelial HeLa cells and DU17 fibroblasts (data not shown). Similar observations were reported by Crane et al (2001). In that case, EPEC induced the detachment of T84 polarized epithelial cells.…”

“…We showed that EPEC induced the detachment of all the examined cell lines including epithelial cell lines (HeLa, Caco2) and fibroblasts (DU17). Detachment of other epithelial cell lines including T84 was noticed by others but not quantified (Crane et al, 2001). We demonstrated that detachment of infected cells was initiated early after infection and was particularly dramatic in the DU17 fibroblast cell line.…”

“…Three additional proteins, EspA, EspB and EspD, are required for protein translocation into host cells but not for secretion . Five EPEC effectors were identified that are translocated by TTSS into the host cell: Tir (EspE), EspB, EspF, EspG and Map Deibel et al, 1998;Wolff et al, 1998;Kenny and Jepson, 2000;Crane et al, 2001;Elliott et al, 2001;McNamara et al, 2001). Map appears to interfere with the mitochondria membrane potential (Kenny and Jepson, 2000).…”

“…Tir is involved in the formation of actin-containing protrusions, termed actin pedestals or attaching and effacing (A/E) lesions Deibel et al, 1998). EspF has been implicated in the disruption of tight junction structure and in the induction of apoptosis (Crane et al, 2001;McNamara et al, 2001). No apparent phenotype was identified in espG knock-out (Elliott et al, 2001).…”

Pathogenesis and evolution of virulence in enteropathogenic and enterohemorrhagic Escherichia coli

“…27). In addition, the espF mutant fails to induce apoptosis in host cells, another feature of the EPEC-host cell interaction (28). Application of EspF to the exterior of cells has no effect, but synthesis of EspF in transfected cells results in rapid cell death.…”