title: Identification of IQGAP as a putative target for the small GTPases, Cdc42 and Rac1.
abstract: Cdc42 and Rac1 have been implicated in the regulation of various cell functions such as cell morphology, polarity, and cell proliferation. We have partially purified a Cdc42- and Rac1-associated protein with molecular mass of about 170 kDa (p170) from bovine brain cytosol. This protein interacted with guanosine 5'-(3-O-thio)triphosphate (GTPgammaS).glutathione S-transferase (GST)-Cdc42 and GTPgammaS++.GST-Rac1 but not with the GDP.GST-Cdc42, GDP.GST-Rac1, or GTPgammaS.GST-RhoA). We identified p170 as an IQGAP, which is originally identified as a putative Ras GTPase-activating protein. Recombinant IQGAP specifically interacted with GTPgammaS.Cdc42 and GTPgammaS.Rac1. The C-terminal fragment of IQGAP was responsible for their interactions. IQGAP was specifically immunoprecipitated with dominant-active Cdc42(Val12) or Rac1(Val12) from the COS7 cells expressing Cdc42(Val12) or Rac1(Val12), respectively. Immunofluorescence analysis revealed that IQGAP was accumulated at insulin- or Rac1-induced membrane ruffling areas. This accumulation of IQGAP was blocked by the microinjection of the dominant-negative Rac1(Asn17) or Cdc42(Asn17). Moreover, IQGAP was accumulated at the cell-cell junction in MDCK cells, where alpha-catenin and ZO-1 were localized. These results suggest that IQGAP is a novel target molecule for Cdc42 and Rac1.
authors.affiliation: Division of Signal Transduction, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma 630-01, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kuroda
authors.forename: M
authors.initials: M
authors.lastname: Fukata
authors.forename: K
authors.initials: K
authors.lastname: Kobayashi
authors.forename: M
authors.initials: M
authors.lastname: Nakafuku
authors.forename: N
authors.initials: N
authors.lastname: Nomura
authors.forename: A
authors.initials: A
authors.lastname: Iwamatsu
authors.forename: K
authors.initials: K
authors.lastname: Kaibuchi
mesh_terms: D008841:Actin Cytoskeleton / Q000648:ultrastructure; D000595:Amino Acid Sequence; D002451:Cell Compartmentation; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000737:chemistry / Q000648:ultrastructure; D002478:Cells, Cultured; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D005982:Glutathione Transferase / Q000378:metabolism; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D007328:Insulin / Q000494:pharmacology; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D051316:Wiskott-Aldrich Syndrome Protein; D020764:cdc42 GTP-Binding Protein; D020703:ras GTPase-Activating Proteins
chemical_list: D018797:Cell Cycle Proteins; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020690:GTPase-Activating Proteins; D005982:Glutathione Transferase; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D007328:Insulin; D010446:Peptide Fragments; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D017346:Protein Serine-Threonine Kinases; D011506:Proteins; D011993:Recombinant Fusion Proteins; D051316:Wiskott-Aldrich Syndrome Protein; D020764:cdc42 GTP-Binding Protein; D020703:ras GTPase-Activating Proteins