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Nature Cell Biology 3, 484–491 (1 May 2001) | doi:10.1038/35074551

WIP regulates N-WASP-mediated actin polymerization and filopodium formation

Narcisa Martinez-Quiles , Rajat Rohatgi , In|[eacute]|s M. Ant|[oacute]|n , Miguel Medina , Stephen P. Saville , Hiroaki Miki , Hideki Yamaguchi , Tadaomi Takenawa , John H. Hartwig , Raif S. Geha & Narayanaswamy Ramesh

Induction of filopodia is dependent on activation of the small GTPase Cdc42 and on neural Wiskott–Aldrich-syndrome protein (N-WASP). Here we show that WASP-interacting protein (WIP) interacts directly with N-WASP and actin. WIP retards N-WASP/Cdc42-activated actin polymerization mediated by the Arp2/3 complex, and stabilizes actin filaments. Microinjection of WIP into NIH 3T3 fibroblasts induces filopodia; this is inhibited by microinjection of anti-N-WASP antibody. Microinjection of anti-WIP antibody inhibits induction of filopodia by bradykinin, by an active Cdc42 mutant (Cdc42(V12)) and by N-WASP. Our results indicate that WIP and N-WASP may act as a functional unit in filopodium formation, which is consistent with their role in actin-tail formation in cells infected with vaccinia virus or Shigella.