title: The essential role of profilin in the assembly of actin for microspike formation.
abstract: Profilin was first identified as an actin monomer binding protein; however, recent reports indicate its involvement in actin polymerization. To date, there is no direct evidence of a functional role in vivo for profilin in actin cytoskeletal reorganization. Here, we prepared a profilin mutant (H119E) defective in actin binding, but retaining the ability to bind to other proteins. This mutant profilin I suppresses actin polymerization in microspike formation induced by N-WASP, the essential factor in microspike formation. Profilin associates both in vivo and in vitro with N-WASP at proline-rich sites different from those to which Ash/Grb2 binds. This association between profilin and N-WASP is required for N-WASP-induced efficient microspike elongation. Moreover, we succeeded in reconstituting microspike formation in permeabilized cells using profilin I combined with N-WASP and its regulator, Cdc42. These findings provide the first evidence that profilin is a key molecule linking a signaling network to rapid actin polymerization in microspike formation.
authors.affiliation: Department of Biochemistry, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Suetsugu
authors.forename: H
authors.initials: H
authors.lastname: Miki
authors.forename: T
authors.initials: T
authors.lastname: Takenawa
mesh_terms: D016475:3T3 Cells; D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D003285:Contractile Proteins; D005786:Gene Expression Regulation; D051379:Mice; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D016501:Neurites; D051304:Profilins; D011485:Protein Binding; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal
chemical_list: D000199:Actins; D003285:Contractile Proteins; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; C495739:Pfn1 protein, mouse; D051304:Profilins; C495772:Wasl protein, mouse; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal