title: Integration of multiple signals through cooperative regulation of the N-WASP-Arp2/3 complex.
abstract: The protein N-WASP [a homolog to the Wiskott-Aldrich syndrome protein (WASP)] regulates actin polymerization by stimulating the actin-nucleating activity of the actin-related protein 2/3 (Arp2/3) complex. N-WASP is tightly regulated by multiple signals: Only costimulation by Cdc42 and phosphatidylinositol (4,5)-bisphosphate (PIP2) yields potent polymerization. We found that regulation requires N-WASP's constitutively active output domain (VCA) and two regulatory domains: a Cdc42-binding domain and a previously undescribed PIP(2)-binding domain. In the absence of stimuli, the regulatory modules together hold the VCA-Arp2/3 complex in an inactive "closed" conformation. In this state, both the Cdc42- and PIP2-binding sites are masked. Binding of either input destabilizes the closed state and enhances binding of the other input. This cooperative activation mechanism shows how combinations of simple binding domains can be used to integrate and amplify coincident signals.
authors.affiliation: Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94143-0450, USA.
authors.forename: K E
authors.initials: KE
authors.lastname: Prehoda
authors.forename: J A
authors.initials: JA
authors.lastname: Scott
authors.forename: R D
authors.initials: RD
authors.lastname: Mullins
authors.forename: W A
authors.initials: WA
authors.lastname: Lim
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins / Q000378:metabolism*; D020816:Amino Acid Motifs; D001665:Binding Sites; D001704:Biopolymers; D003598:Cytoskeletal Proteins; D020558:GTP Phosphohydrolases / Q000378:metabolism; D006801:Humans; D008954:Models, Biological; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D013816:Thermodynamics; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism
chemical_list: C495926:ACTR2 protein, human; C495928:ACTR3 protein, human; D051377:Actin-Related Protein 2; D051378:Actin-Related Protein 3; D000199:Actins; D001704:Biopolymers; D003598:Cytoskeletal Proteins; D009419:Nerve Tissue Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D011993:Recombinant Fusion Proteins; C495771:WASL protein, human; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; D020558:GTP Phosphohydrolases; D020764:cdc42 GTP-Binding Protein