Insertion of EspD into epithelial target cell membranes by infecting enteropathogenic Escherichia coli

Abstract

SummaryDiffusely adhering Escherichia coli (DAEC) strains have been implicated in epidemiological studies as a cause of diarrhoea in children. However, the molecular interactions of these pathogens with target cells have remained largely obscure. We found that some DAEC strains contain homologues of the locus of enterocyte effacement (LEE) pathogenicity island and secrete EspA, EspB and EspD proteins necessary for the formation of the attaching and effacing (A /E) lesions. To characterize the function of the EspD protein further, we cloned and sequenced the espD genes of two DA-EPEC strains and compared their deduced amino-acid sequences with known EspD sequences. A pattern of two conserved transmembrane regions and one conserved coiled-coil region is predicted in EspD and also in the type III system secreted proteins YopB, PopB, IpaB and SipB of Yersinia, Pseudomonas, Shigella and Salmonella respectively. The EspD protein is inserted into a trypsinsensitive location in the HeLa cell membrane at sites of bacterial contact, but is not translocated into the cytoplasm. Secretion of EspD increases upon contact with host cells. We propose that the membrane-located EspD protein is part of the translocation apparatus for Esp proteins into the target host cell performing functions similar to YopB in Yersinia.

α 1 -Antitrypsin Binds to and Interferes with Functionality of EspB from Atypical and Typical Enteropathogenic Escherichia coli Strains

“…AAT is a secreted protease inhibitor that is abundant in human serum but can also be found intracellularly in enterocytes (24). In cells infected with typical LA-EPEC, EspB can be found in the cytosol as well as in the membrane (37,39). EspB of the classical EPEC strain E2348/69 seems to be localized immediately beneath attached bacteria (39).…”

“…EspB and EspD insert into the membrane of infected cells, where they are thought to form a translocation pore. Pore formation correlates with the induction of hemolysis of red blood cells (RBC) (12,32,37,38). Additional type III-secreted proteins include EspF, EspG, EspH, and Map.…”

Pathogenesis and evolution of virulence in enteropathogenic and enterohemorrhagic Escherichia coli

“…There is no evidence that EspA molecules penetrate the host cell cytoplasm or membranes. EspD has several putative transmembrane domains and has been observed in the host cell membrane (23). Because it is required for the translocation of EspB, EspD is also a part of the translocation apparatus.…”

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.…”