title: Identification and characterization of Ibe, a novel type III effector protein of A/E pathogens targeting human IQGAP1.
abstract: Enteropathogenic Escherichia coli (EPEC), atypical enteropathogenic Escherichia coli (ATEC) and enterohemorrhagic Escherichia coli (EHEC) belong to the family of attaching and effacing (A/E) pathogens. Pathogenicity is mediated by subversion of host cell functions involving type III secretion system (TTSS)-dependent effector proteins. In this study, we have identified and characterized a novel TTSS-dependent effector protein encoded at the 5'-end of the locus of enterocyte effacement (LEE) pathogenicity island (PAI) of ATEC strain 3431-4/86 (O8:H(-)). Using affinity purification we identified IQGAP1, a scaffolding protein involved in the regulation of the actin cytoskeleton, as a putative host cell target. Accordingly, we termed the novel effector protein 'Ibe' for IQGAP1-binding effector. The interaction of Ibe and IQGAP1 was confirmed by co-immunoprecipitation from ATEC-infected cells and immunofluorescence analysis, which revealed colocalization of Ibe and IQGAP1 in ATEC-induced pedestals and actin-rich membrane ruffles. This suggests that the putative effector function of Ibe is mediated via IQGAP1. The Ibe-independent recruitment of IQGAP1 to ATEC-induced pedestals implies a general role for IQGAP1 in the subversion of host cell functions during infection. Homologues of the novel effector Ibe are widely distributed among EPEC, ATEC and EHEC strains but are not necessarily genetically linked to the LEE as they have occasionally also been found to be encoded within lambdoid prophages.
authors.affiliation: Institut für Infektiologie, Zentrum für Molekularbiologie der Entzündung (ZMBE), Westfälische Wilhelms-Universität Münster, Münster, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Buss
authors.forename: Daniel
authors.initials: D
authors.lastname: Müller
authors.forename: Christian
authors.initials: C
authors.lastname: Rüter
authors.forename: Gerhard
authors.initials: G
authors.lastname: Heusipp
authors.forename: M Alexander
authors.initials: MA
authors.lastname: Schmidt
mesh_terms: D001422:Bacterial Adhesion; D020895:Enterocytes / Q000382:microbiology; D054324:Enterohemorrhagic Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity* / Q000502:physiology; D054308:Enteropathogenic Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity* / Q000502:physiology; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D054884:Host-Pathogen Interactions; D006801:Humans; D047468:Immunoprecipitation; D020703:ras GTPase-Activating Proteins / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; C101203:IQ motif containing GTPase activating protein 1; D020703:ras GTPase-Activating Proteins