Identification of IQGAP as a putative target for the small GTPases, Cdc42 and Rac1

J Biol Chem. 1996 Sep 20;271(38):23363-7. doi: 10.1074/jbc.271.38.23363.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actin Cytoskeleton / ultrastructure
  • Amino Acid Sequence
  • Cell Compartmentation
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Cell Membrane / chemistry
  • Cell Membrane / ultrastructure
  • Cells, Cultured
  • GTP Phosphohydrolases / genetics
  • GTP Phosphohydrolases / metabolism*
  • GTP-Binding Proteins / genetics
  • GTP-Binding Proteins / metabolism*
  • GTPase-Activating Proteins
  • Glutathione Transferase / metabolism
  • Guanosine 5'-O-(3-Thiotriphosphate) / metabolism
  • Insulin / pharmacology
  • Molecular Sequence Data
  • Peptide Fragments / metabolism
  • Phosphatidylinositol 3-Kinases
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism
  • Precipitin Tests
  • Protein Binding
  • Protein-Serine-Threonine Kinases / metabolism
  • Proteins / genetics
  • Proteins / metabolism*
  • Recombinant Fusion Proteins / metabolism
  • Wiskott-Aldrich Syndrome Protein
  • cdc42 GTP-Binding Protein
  • ras GTPase-Activating Proteins


  • Cell Cycle Proteins
  • GTPase-Activating Proteins
  • Insulin
  • Peptide Fragments
  • Proteins
  • Recombinant Fusion Proteins
  • Wiskott-Aldrich Syndrome Protein
  • ras GTPase-Activating Proteins
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • Glutathione Transferase
  • Phosphatidylinositol 3-Kinases
  • Phosphotransferases (Alcohol Group Acceptor)
  • Protein-Serine-Threonine Kinases
  • GTP Phosphohydrolases
  • GTP-Binding Proteins
  • cdc42 GTP-Binding Protein