title: Genghis Khan (Gek) as a putative effector for Drosophila Cdc42 and regulator of actin polymerization.
abstract: The small GTPases Cdc42 and Rac regulate a variety of biological processes, including actin polymerization, cell proliferation, and JNK/mitogen-activated protein kinase activation, conceivably via distinct effectors. Whereas the effector for mitogen-activated protein kinase activation appears to be p65PAK, the identity of effector(s) for actin polymerization remains unclear. We have found a putative effector for Drosophila Cdc42, Genghis Khan (Gek), which binds to Dcdc42 in a GTP-dependent and effector domain-dependent manner. Gek contains a predicted serine/threonine kinase catalytic domain that is 63% identical to human myotonic dystrophy protein kinase and has protein kinase activities. It also possesses a large coiled-coil domain, a putative phorbol ester binding domain, a pleckstrin homology domain, and a Cdc42 binding consensus sequence that is required for its binding to Dcdc42. To study the in vivo function of gek, we generated mutations in the Drosophila gek locus. Egg chambers homozygous for gek mutations exhibit abnormal accumulation of F-actin and are defective in producing fertilized eggs. These phenotypes can be rescued by a wild-type gek transgene. Our results suggest that this multidomain protein kinase is an effector for the regulation of actin polymerization by Cdc42.
authors.affiliation: Howard Hughes Medical Institute, Department of Physiology, University of California, San Francisco 94143, USA. lluo@stanford.edu
authors.forename: L
authors.initials: L
authors.lastname: Luo
authors.forename: T
authors.initials: T
authors.lastname: Lee
authors.forename: L
authors.initials: L
authors.lastname: Tsai
authors.forename: G
authors.initials: G
authors.lastname: Tang
authors.forename: L Y
authors.initials: LY
authors.lastname: Jan
authors.forename: Y N
authors.initials: YN
authors.lastname: Jan
mesh_terms: D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001704:Biopolymers; D004330:Drosophila / Q000201:enzymology*; D029721:Drosophila Proteins; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D000199:Actins; D001704:Biopolymers; C090145:Cdc42 protein, Drosophila; D029721:Drosophila Proteins; C109463:Gek protein, Drosophila; D017346:Protein Serine-Threonine Kinases; D019204:GTP-Binding Proteins