Signal transduction responses to enteropathogenic Escherichia coli and Shiga toxin-producing Escherichia coli infections

grantor: University of TorontoEnteropathogenic 'Escherichia coli' (EPEC) and Shiga toxin-producing 'Escherichia coli' (STEC) induce morphological changes in infected epithelial cells. The resulting attaching and effacing lesion is characterized by intimate bacterial adherence to epithelial cells with microvillus destruction, cytoskeletal rearrangement and aggregation of host cytoskeletal proteins, including Ã-actinin. This study was undertaken to further characterize host cytosolic responses to bacterial infection by using a series of specific cell signaling inhibitors of phosphoinositide-specific phospholipase C, phosphoinositide 3-kinase, 5-lipoxygenase, and cyclooxygenase. Inhibitory effects of the enzyme inhibitors were measured by their ability to disrupt formation of attaching and effacing lesions by EPEC and STEC. HEp-2 cells were preincubated with inhibitors before infection with EPEC strain E2348/69 (serotype O127:H6), STEC strain CL56 (O157:H7), or a signaling-deficient EPEC mutant UMD864 (O127:H6). Attaching and effacing lesions were detected by immunofluorescence microscopy using a monoclonal antibody against Ã-actinin. While initial bacterial adherence to epithelial cells was not reduced, Ã-actinin accumulation in infected HEp-2 cells was blocked by enzyme inhibitors ET-18-OCH 3, wortmannin, LY294002, and NDGA, but not by NS-398. This study suggests that the cytoskeletal reorganizations induced during EPEC and STEC infections are dependent on phospholipase C, phosphoinositide 3-kinase, and 5-lipoxygenase, but cyclooxygenase-independent. Understanding the signal transduction responses to EPEC and STEC infections could provide the basis for the development of novel therapies for use in the prevention and treatment of these infections in humans.M.Sc