title: Inhibition of WAVE Regulatory Complex Activation by a Bacterial Virulence Effector Counteracts Pathogen Phagocytosis.
abstract: To establish pathogenicity, bacteria must evade phagocytosis directed by remodeling of the actin cytoskeleton. We show that macrophages facilitate pathogen phagocytosis through actin polymerization mediated by the WAVE regulatory complex (WRC), small GTPases Arf and Rac1, and the Arf1 activator ARNO. To establish extracellular infections, enteropathogenic (EPEC) and enterohaemorrhagic (EHEC) Escherichia coli hijack the actin cytoskeleton by injecting virulence effectors into the host cell. Here, we find that the virulence effector EspG counteracts WRC-dependent phagocytosis, enabling EPEC and EHEC to remain extracellular. By reconstituting membrane-associated actin polymerization, we find that EspG disabled WRC activation through two mechanisms: EspG interaction with Arf6 blocked signaling to ARNO while EspG binding of Arf1 impeded collaboration with Rac1, thereby inhibiting WRC recruitment and activation. Investigating the mode of EspG interference revealed sites in Arf1 required for WRC activation and a mechanism facilitating pathogen evasion of innate host defenses.
authors.affiliation: Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK. Electronic address: d.humphreys@sheffield.ac.uk.
authors.forename: Daniel
authors.initials: D
authors.lastname: Humphreys
authors.affiliation: Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
authors.forename: Vikash
authors.initials: V
authors.lastname: Singh
authors.affiliation: Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK. Electronic address: vk103@cam.ac.uk.
authors.forename: Vassilis
authors.initials: V
authors.lastname: Koronakis
mesh_terms: D020823:ADP-Ribosylation Factor 1 / Q000378:metabolism; D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism; D054308:Enteropathogenic Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000378:metabolism*; D010587:Phagocytosis; D012475:Salmonella; D015398:Signal Transduction; D037521:Virulence Factors / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: D000089982:ADP-Ribosylation Factor 6; D029968:Escherichia coli Proteins; C429282:EspG protein, E coli; D046912:Multiprotein Complexes; D037521:Virulence Factors; D020823:ADP-Ribosylation Factor 1; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; D020830:rac1 GTP-Binding Protein
keywords: ADP-ribosylation factor; Rho GTPase; SCAR complex; type 3 secretion system; virulence effector