title: Cloning and expression of a human CDC42 GTPase-activating protein reveals a functional SH3-binding domain.
abstract: CDC42, a member of the Rho family of small GTP-binding proteins, regulates cytoskeletal rearrangements required for cell division. Activating mutations in CDC42 that are refractory to GTPase activation confer a phenotype of large, multinucleated cells. Like other small GTP-binding proteins, CDC42 is activated by a guanosine exchange factor and inactivated by a GTPase-activating protein (GAP). An unidentified 25-kDa platelet protein has been shown to function as a specific CDC42GAP. Here we report the cloning of a cDNA encoding this GAP from a human platelet-precursor cell line. Sequence analysis reveals the presence of three consensus box regions characteristic of rhoGAPs. A glutathione S-transferase fusion protein containing the three boxes derived from the new clone strongly stimulated the GTPase activity of CDC42 but was much less effective on other Rho proteins. This indicates that the cDNA clone encodes a specific GAP for CDC42. Sequence analysis also reveals a potential proline-rich Src homology 3 (SH3)-binding domain preceding the first consensus box. Binding experiments show that this motif can interact with the SH3 domains of p85 alpha and of c-Src. Thus, CDC42GAP may function as a link between CDC42 and other signaling pathways.
authors.affiliation: Department of Molecular Biology, Genentech, Inc., South San Francisco, California 94080.
authors.forename: E T
authors.initials: ET
authors.lastname: Barfod
authors.forename: Y
authors.initials: Y
authors.lastname: Zheng
authors.forename: W J
authors.initials: WJ
authors.lastname: Kuang
authors.forename: M J
authors.initials: MJ
authors.lastname: Hart
authors.forename: T
authors.initials: T
authors.lastname: Evans
authors.forename: R A
authors.initials: RA
authors.lastname: Cerione
authors.forename: A
authors.initials: A
authors.lastname: Ashkenazi
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D006801:Humans; D008969:Molecular Sequence Data; D011506:Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D020764:cdc42 GTP-Binding Protein
chemical_list: D018076:DNA, Complementary; D020690:GTPase-Activating Proteins; D011506:Proteins; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020764:cdc42 GTP-Binding Protein