title: Optimization of WAVE2 complex-induced actin polymerization by membrane-bound IRSp53, PIP(3), and Rac.
abstract: WAVE2 activates the actin-related protein (Arp) 2/3 complex for Rac-induced actin polymerization during lamellipodium formation and exists as a large WAVE2 protein complex with Sra1/PIR121, Nap1, Abi1, and HSPC300. IRSp53 binds to both Rac and Cdc42 and is proposed to link Rac to WAVE2. We found that the knockdown of IRSp53 by RNA interference decreased lamellipodium formation without a decrease in the amount of WAVE2 complex. Localization of WAVE2 at the cell periphery was retained in IRSp53 knockdown cells. Moreover, activated Cdc42 but not Rac weakened the association between WAVE2 and IRSp53. When we measured Arp2/3 activation in vitro, the WAVE2 complex isolated from the membrane fraction of cells was fully active in an IRSp53-dependent manner but WAVE2 isolated from the cytosol was not. Purified WAVE2 and purified WAVE2 complex were activated by IRSp53 in a Rac-dependent manner with PIP(3)-containing liposomes. Therefore, IRSp53 optimizes the activity of the WAVE2 complex in the presence of activated Rac and PIP(3).
authors.affiliation: Department of Biochemistry, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo 108-8639, Japan.
authors.forename: Shiro
authors.initials: S
authors.lastname: Suetsugu
authors.forename: Shusaku
authors.initials: S
authors.lastname: Kurisu
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Oikawa
authors.forename: Daisuke
authors.initials: D
authors.lastname: Yamazaki
authors.forename: Atsushi
authors.initials: A
authors.lastname: Oda
authors.forename: Tadaomi
authors.initials: T
authors.lastname: Takenawa
mesh_terms: D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation / Q000502:physiology; D006801:Humans; D008081:Liposomes / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D011108:Polymers; D011485:Protein Binding / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D011554:Pseudopodia / Q000378:metabolism* / Q000648:ultrastructure; D034622:RNA Interference; D013347:Subcellular Fractions / Q000378:metabolism; D051300:Wiskott-Aldrich Syndrome Protein Family / Q000378:metabolism*; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; C119539:BAIAP2 protein, human; D008081:Liposomes; D009419:Nerve Tissue Proteins; D018129:Phosphatidylinositol Phosphates; D011108:Polymers; C120152:WASF2 protein, human; D051300:Wiskott-Aldrich Syndrome Protein Family; C060974:phosphatidylinositol 3,4,5-triphosphate; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins