title: Directional control of WAVE2 membrane targeting by EB1 and phosphatidylinositol 3,4,5-triphosphate.
abstract: Membrane targeting of WAVE2 along microtubules is mediated by a motor protein kinesin and requires Pak1, a downstream effector of Rac1. However, the mechanism by which WAVE2 targeting to the leading edge is directionally controlled remains largely unknown. Here we demonstrate that EB1, a microtubule plus-end-binding protein, constitutively associates with stathmin, a microtubule-destabilizing protein, in human breast cancer cells. Stimulation of the cells with insulin-like growth factor I (IGF-I) induced Pak1-dependent binding of the EB1-stathmin complex to microtubules that bear WAVE2 and colocalization of the complex with WAVE2 at the leading edge. Depletion of EB1 by small interfering RNA (siRNA) abrogated the IGF-I-induced WAVE2 targeting and stathmin binding to microtubules. On the other hand, chemotaxis chamber assays indicated that the IGF-I receptor (IGF-IR) was locally activated in the region facing toward IGF-I. In addition, IGF-I caused phosphatidylinositol 3-kinase (PI 3-kinase)-dependent production of phosphatidylinositol 3,4,5-triphosphate (PIP3) near activated IGF-IR and WAVE2 colocalization with it. Collectively, WAVE2-membrane targeting is directionally controlled by binding of the EB1-stathmin complex to WAVE2-bearing microtubules and by the interaction between WAVE2 and PIP3 produced near IGF-IR that is locally activated by IGF-I.
authors.affiliation: Molecular Cell Biology Division, Kanagawa Cancer Center Research Institute, Yokohama 241-0815, Japan. ktaka@gancen.asahi.yokohama.jp
authors.forename: Kazuhide
authors.initials: K
authors.lastname: Takahashi
authors.forename: Tacu
authors.initials: T
authors.lastname: Tanaka
authors.forename: Katsuo
authors.initials: K
authors.lastname: Suzuki
mesh_terms: D045744:Cell Line, Tumor; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D050777:Stathmin / Q000378:metabolism; D051300:Wiskott-Aldrich Syndrome Protein Family / Q000032:analysis / Q000378:metabolism*; D054462:p21-Activated Kinases / Q000378:metabolism; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: C500985:MAPRE1 protein, human; D008869:Microtubule-Associated Proteins; D018129:Phosphatidylinositol Phosphates; D034741:RNA, Small Interfering; D050777:Stathmin; D051300:Wiskott-Aldrich Syndrome Protein Family; C060974:phosphatidylinositol 3,4,5-triphosphate; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D017526:Receptor, IGF Type 1; C515903:PAK1 protein, human; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein