IRSp53 is an essential intermediate between Rac and WAVE in the regulation of membrane ruffling.
Neural Wiskott-Aldrich syndrome protein (N-WASP) functions in several intracellular events including filopodium formation, vesicle transport and movement of Shigella frexneri and vaccinia virus, by stimulating rapid actin polymerization through the Arp2/3 complex. N-WASP is regulated by the direct binding of Cdc42 (refs 7, 8), which exposes the domain in N-WASP that activates the Arp2/3 complex. A WASP-related protein, WAVE/Scar, functions in Rac-induced membrane ruffling; however, Rac does not bind directly to WAVE, raising the question of how WAVE is regulated by Rac. Here we demonstrate that IRSp53, a substrate for insulin receptor with unknown function, is the 'missing link' between Rac and WAVE. Activated Rac binds to the amino terminus of IRSp53, and carboxy-terminal Src-homology-3 domain of IRSp53 binds to WAVE to form a trimolecular complex. From studies of ectopic expression, we found that IRSp53 is essential for Rac to induce membrane ruffling, probably because it recruits WAVE, which stimulates actin polymerization mediated by the Arp2/3 complex.
Miki
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Department of Biochemistry, Institute of Medical Science, University of Tokyo, and CREST, Japan Science and Technology Corporation.
Yamaguchi
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Suetsugu
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Takenawa
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T
D016475:3T3 Cells; D051377:Actin-Related Protein 2; D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism*; D003598:Cytoskeletal Proteins; D004926:Escherichia coli; D006801:Humans; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D051300:Wiskott-Aldrich Syndrome Protein Family; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D018909:src Homology Domains
C495926:ACTR2 protein, human; D051377:Actin-Related Protein 2; D000199:Actins; C495927:Actr2 protein, mouse; C119539:BAIAP2 protein, human; D003598:Cytoskeletal Proteins; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D011993:Recombinant Fusion Proteins; C120152:WASF2 protein, human; C495774:Wasf1 protein, mouse; C492303:Wasf2 protein, mouse; D051300:Wiskott-Aldrich Syndrome Protein Family; D020744:rac GTP-Binding Proteins