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.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Actin Cytoskeleton / ultrastructure
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Amino Acid Sequence
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Cell Compartmentation
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism*
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Cell Membrane / chemistry
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Cell Membrane / ultrastructure
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Cells, Cultured
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GTP Phosphohydrolases / genetics
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GTP Phosphohydrolases / metabolism*
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GTP-Binding Proteins / genetics
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GTP-Binding Proteins / metabolism*
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GTPase-Activating Proteins
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Glutathione Transferase / metabolism
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Guanosine 5'-O-(3-Thiotriphosphate) / metabolism
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Insulin / pharmacology
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Molecular Sequence Data
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Peptide Fragments / metabolism
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Phosphatidylinositol 3-Kinases
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Phosphotransferases (Alcohol Group Acceptor) / metabolism
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Precipitin Tests
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Protein Binding
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Protein Serine-Threonine Kinases / metabolism
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Proteins / genetics
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Proteins / metabolism*
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Recombinant Fusion Proteins / metabolism
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Wiskott-Aldrich Syndrome Protein
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cdc42 GTP-Binding Protein
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ras GTPase-Activating Proteins
Substances
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Cell Cycle Proteins
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GTPase-Activating Proteins
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Insulin
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Peptide Fragments
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Proteins
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Recombinant Fusion Proteins
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Wiskott-Aldrich Syndrome Protein
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ras GTPase-Activating Proteins
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Guanosine 5'-O-(3-Thiotriphosphate)
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Glutathione Transferase
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Phosphotransferases (Alcohol Group Acceptor)
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Protein Serine-Threonine Kinases
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GTP Phosphohydrolases
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GTP-Binding Proteins
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cdc42 GTP-Binding Protein