title: Co-ordinate regulation of distinct host cell signalling pathways by multifunctional enteropathogenic Escherichia coli effector molecules.
abstract: Enteropathogenic Escherichia coli (EPEC) is a major cause of paediatric diarrhoea and a model for the family of attaching and effacing (A/E) pathogens. A/E pathogens encode a type III secretion system to transfer effector proteins into host cells. The EPEC Tir effector protein acts as a receptor for the bacterial surface protein intimin and is involved in the formation of Cdc42-independent, actin-rich pedestal structures beneath the adhered bacteria. In this paper, we demonstrate that EPEC binding to HeLa cells also induces Tir-independent, cytoskeletal rearrangement evidenced by the early, transient formation of filopodia-like structures at sites of infection. Filopodia formation is dependent on expression of the EPEC Map effector molecule - a protein that targets mitochondria and induces their dysfunction. We show that Map-induced filopodia formation is independent of mitochondrial targeting and is abolished by cellular expression of the Cdc42 inhibitory WASP-CRIB domain, demonstrating that Map has at least two distinct functions in host cells. The transient nature of the filopodia is related to an ability of EPEC to downregulate Map-induced cell signalling that, like pedestal formation, was dependent on both Tir and intimin proteins. The ability of Tir to downregulate filopodia was impaired by disrupting a putative GTPase-activating protein (GAP) motif, suggesting that Tir may possess such a function, with its interaction with intimin triggering this activity. Furthermore, we also found that Map-induced cell signalling inhibits pedestal formation, revealing that the cellular effects of Tir and Map must be co-ordinately regulated during infection. Possible implications of the multifunctional nature of EPEC effector molecules in pathogenesis are discussed.
authors.affiliation: Departmentof Pathology and Microbiology, School of Medical Sciences, University Walk, Bristol, UK. B.Kenny@bristol.ac.uk
authors.forename: Brendan
authors.initials: B
authors.lastname: Kenny
authors.forename: Sarah
authors.initials: S
authors.lastname: Ellis
authors.forename: Alan D
authors.initials: AD
authors.lastname: Leard
authors.forename: Jonathan
authors.initials: J
authors.lastname: Warawa
authors.forename: Harry
authors.initials: H
authors.lastname: Mellor
authors.forename: Mark A
authors.initials: MA
authors.lastname: Jepson
mesh_terms: D000199:Actins / Q000378:metabolism; D018829:Adhesins, Bacterial / Q000378:metabolism; D001422:Bacterial Adhesion; D002352:Carrier Proteins / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism / Q000382:microbiology; D003967:Diarrhea / Q000378:metabolism / Q000382:microbiology; D015536:Down-Regulation; D004847:Epithelial Cells / Q000378:metabolism / Q000382:microbiology; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism* / Q000472:pathogenicity* / Q000648:ultrastructure; D004927:Escherichia coli Infections / Q000378:metabolism / Q000382:microbiology; D029968:Escherichia coli Proteins; D006367:HeLa Cells; D006801:Humans; D008954:Models, Biological; D011485:Protein Binding; D011554:Pseudopodia / Q000502:physiology; D011956:Receptors, Cell Surface / Q000378:metabolism; D015398:Signal Transduction; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism
chemical_list: D000199:Actins; D018829:Adhesins, Bacterial; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D011956:Receptors, Cell Surface; C109287:Tir protein, E coli; C073819:eaeA protein, E coli; D020764:cdc42 GTP-Binding Protein