Enteropathogenic Escherichia coli translocate Tir and form an intimin-Tir intimate attachment to red blood cell membranes.
Type III secretion allows bacteria to inject effector proteins into host cells. In enteropathogenic Escherichia coli (EPEC) the type III secreted protein, Tir, is translocated to the host-cell plasma membrane where it functions as a receptor for the bacterial adhesin intimin, leading to intimate bacterial attachment and "attaching and effacing" (A/E) lesion formation. To study EPEC type III secretion the interaction of EPEC with monolayers of red blood cells (RBCs) has been exploited and in a recent study [Shaw, R. K., Daniell, S., Ebel, F., Frankel, G. & Knutton, S. (2001 ). Cell Microbiol 3, 213-222] it was shown that EPEC induced haemolysis of RBCs and translocation of EspD, a putative pore-forming type III secreted protein in the RBC membrane. Here it is demonstrated that EPEC are able to translocate and correctly insert Tir into the RBC membrane and produce an intimin-Tir intimate bacterial attachment, identical to that seen in A/E lesions. Following translocation Tir did not undergo any change in apparent molecular mass or become tyrosine-phosphorylated and there was no focusing of RBC cytoskeletal actin beneath intimately adherent bacteria, and no pedestal formation. This study, employing an RBC model of infection, has demonstrated that Tir translocation can be separated from host-cell-mediated Tir modifications; the data show that the EPEC type III protein translocation apparatus is sufficient to deliver and correctly insert Tir into host-cell membranes independent of eukaryotic cell functions.
Shaw
Robert K
RK
Institute of Child Health, University of Birmingham, Birmingham B4 6NH, UK1.
Daniell
Sarah
S
Centre for Molecular Microbiology and Immunology, Department of Biosciences, Imperial College of Science, Technology and Medicine, London SW7 2AZ, UK2.
Frankel
Gad
G
Centre for Molecular Microbiology and Immunology, Department of Biosciences, Imperial College of Science, Technology and Medicine, London SW7 2AZ, UK2.
Knutton
Stuart
S
Institute of Child Health, University of Birmingham, Birmingham B4 6NH, UK1.
D018829:Adhesins, Bacterial / Q000378:metabolism*; D001422:Bacterial Adhesion; D002352:Carrier Proteins / Q000378:metabolism*; D004910:Erythrocyte Membrane / Q000378:metabolism* / Q000382:microbiology* / Q000648:ultrastructure; D004926:Escherichia coli / Q000378:metabolism* / Q000472:pathogenicity* / Q000648:ultrastructure; D029968:Escherichia coli Proteins; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D011485:Protein Binding; D021381:Protein Transport; D011956:Receptors, Cell Surface / Q000378:metabolism*
D018829:Adhesins, Bacterial; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D011956:Receptors, Cell Surface; C109287:Tir protein, E coli; C073819:eaeA protein, E coli