Signal transduction between enteropathogenic Escherichia coli (EPEC) and epithelial cells: EPEC induces tyrosine phosphorylation of host cell proteins to initiate cytoskeletal rearrangement and bacterial uptake.

Abstract

Upon attachment to cultured HeLa cells, enteropathogenic Escherichia coli (EPEC) induces assembly of a complex cytoskeletal structure within the eucaryotic cell, localized beneath the adherent bacterium. In addition, EPEC induces its own internalization by non‐phagocytic epithelial cells. We found that after binding to the epithelial cell surface, EPEC induces tyrosine phosphorylation of three eucaryotic proteins. The major phosphorylation substrate is a 90 kDa protein (Hp90). In correlation with Hp90 tyrosine phosphorylation, the EPEC‐induced cytoskeletal structure also contained tyrosine phosphorylated proteins. Using tyrosine protein kinase inhibitors and EPEC mutants (cfm) that fail to induce Hp90 phosphorylation, we demonstrate that induction of Hp90 phosphorylation is involved in initiation of the cytoskeletal structure assembly and in bacterial uptake. Other non‐invasive EPEC mutants (eae) are still able to induce Hp90 tyrosine phosphorylation and to initiate aggregation of the tyrosine phosphorylated proteins and some cytoskeleton components. However, eae mutants are deficient in nucleating the aggregates into an organized structure.

Identification of a Bacterial Inhibitor of Protein Kinases

“…1 and 3 h after infection, the phosphotyrosine content of this band decreases in cells infected with both strains, but the decrease is greater in cells infected with EPEC overexpressing UDP-sugar hydrolase. As described earlier by Rosenshine et al (31), infection with EPEC results in the induction of additional phosphotyrosinecontaing bands of host cell origin (approximately 90 and 140 kDa). We also observe a marked reduction in phosphotyrosine content of these bands 3 h after infection with EPEC overexpressing UDP-sugar hydrolase activity.…”

Microaerophilic Conditions Permit to Mimic in VitroEvents Occurring during in Vivo Helicobacter pylori Infection and to Identify Rho/Ras-associated Proteins in Cellular Signaling

“…The perversion of cellular proteins appears as a paradigm of host-pathogen interactions. For example, enteropathogenic Escherichia coli induces tyrosine phosphorylation of three eukaryotic proteins, all apparently cytoskeletal-associated (59). Along the same line, Listeria monocytogenes induces the tyrosine phosphorylation of two isoforms (42 and 44 kDa) of the mitogen-activated protein kinase (60) found downstream of the ras-raf-mitogen-activated protein kinase/extracellular signal-regulated kinase kinase pathway.…”

Enteropathogenic Escherichia coli contains a putative type III secretion system necessary for the export of proteins involved in attaching and effacing lesion formation.

“…These mutants (called cfin, for class four mutants) are noninvasive and are unable to induce Hp9O phosphorylation or trigger inositol phosphate fluxes (3,4,13). Here we identify one of the interrupted genes in cftn 27-3-2(1) and describe three additional open reading frames in the LEE region of the EPEC chromosome.…”

“…The eaeA gene encodes a 94-kDa outer membrane protein, intimin, which has sequence homology to the invasin protein of Yersinia species (8). An eaeA mutant of EPEC is unable to form AE lesions in cultured cells (8,10) but can still induce host cell tyrosine phosphorylation of Hp9O and fluxes in inositol phosphate levels (3,4). When tested in an experimental human model of EPEC infection, the eaeA mutant showed reduced virulence (11).…”