title: WAVE regulatory complex activation by cooperating GTPases Arf and Rac1.
abstract: The WAVE regulatory complex (WRC) is a critical element in the control of actin polymerization at the eukaryotic cell membrane, but how WRC is activated remains uncertain. While Rho GTPase Rac1 can bind and activate WRC in vitro, this interaction is of low affinity, suggesting other factors may be important. By reconstituting WAVE-dependent actin assembly on membrane-coated beads in mammalian cell extracts, we found that Rac1 was not sufficient to engender bead motility, and we uncovered a key requirement for Arf GTPases. In vitro, Rac1 and Arf1 were individually able to bind weakly to recombinant WRC and activate it, but when both GTPases were bound at the membrane, recruitment and concomitant activation of WRC were dramatically enhanced. This cooperativity between the two GTPases was sufficient to induce WAVE-dependent bead motility in cell extracts. Our findings suggest that Arf GTPases may be central components in WAVE signalling, acting directly, alongside Rac1.
authors.affiliation: Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, CB21QP, United Kingdom. vk103@cam.ac.uk
authors.forename: Vassilis
authors.initials: V
authors.lastname: Koronakis
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Hume
authors.forename: Daniel
authors.initials: D
authors.lastname: Humphreys
authors.forename: Tao
authors.initials: T
authors.lastname: Liu
authors.forename: Ole
authors.initials: O
authors.lastname: Hørning
authors.forename: Ole N
authors.initials: ON
authors.lastname: Jensen
authors.forename: Emma J
authors.initials: EJ
authors.lastname: McGhie
mesh_terms: D020823:ADP-Ribosylation Factor 1 / Q000502:physiology*; D000199:Actins / Q000737:chemistry*; D000818:Animals; D006801:Humans; D008081:Liposomes / Q000737:chemistry; D015398:Signal Transduction; D051300:Wiskott-Aldrich Syndrome Protein Family / Q000502:physiology*; D020830:rac1 GTP-Binding Protein / Q000502:physiology*
chemical_list: D000199:Actins; D008081:Liposomes; C114864:WASF1 protein, human; D051300:Wiskott-Aldrich Syndrome Protein Family; D020823:ADP-Ribosylation Factor 1; D020830:rac1 GTP-Binding Protein