title: Cloning and characterization of GEF-H1, a microtubule-associated guanine nucleotide exchange factor for Rac and Rho GTPases.
abstract: The Rho-related small GTPases are critical elements involved in regulation of signal transduction cascades from extracellular stimuli to cell nucleus and cytoskeleton. The Dbl-like guanine nucleotide exchange factors (GEF) have been implicated in direct activation of these GTPases. Here we have identified a new member of the Dbl family, GEF-H1, by screening a human HeLa cell cDNA library. GEF-H1 encodes a 100-kDa protein containing the conserved structural array of a Dbl homology domain in tandem with a pleckstrin homology domain and is most closely related to the lfc oncogene, but additionally it contains a unique coiled-coil domain at the carboxyl terminus. Biochemical analysis reveals that GEF-H1 is capable of stimulating guanine nucleotide exchange of Rac and Rho but is inactive toward Cdc42, TC10, or Ras. Moreover, GEF-H1 binds to Rac and Rho proteins in both the GDP- and guanosine 5'-3-O-(thio)triphosphate-bound states without detectable affinity for Cdc42 or Ras. Immunofluorescence reveals that GEF-H1 colocalizes with microtubules through the carboxyl-terminal coiled-coil domain. Overexpression of GEF-H1 in COS-7 cells results in induction of membrane ruffles. These results suggest that GEF-H1 may have a direct role in activation of Rac and/or Rho and in bringing the activated GTPase to specific target sites such as microtubules.
authors.affiliation: Department of Pharmacology, Baylor College of Medicine, Houston, Texas 77030, USA. yren@bcm.tmc.edu
authors.forename: Y
authors.initials: Y
authors.lastname: Ren
authors.forename: R
authors.initials: R
authors.lastname: Li
authors.forename: Y
authors.initials: Y
authors.lastname: Zheng
authors.forename: H
authors.initials: H
authors.lastname: Busch
mesh_terms: D016475:3T3 Cells / Q000166:cytology; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells / Q000166:cytology; D004789:Enzyme Activation; D005455:Fluorescent Antibody Technique; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D020690:GTPase-Activating Proteins; D015723:Gene Library; D020662:Guanine Nucleotide Exchange Factors; D006150:Guanine Nucleotides / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D011506:Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics; D011994:Recombinant Proteins / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors; D017386:Sequence Homology, Amino Acid; D020744:rac GTP-Binding Proteins; D020703:ras GTPase-Activating Proteins; D020663:ras Guanine Nucleotide Exchange Factors; D020741:rho GTP-Binding Proteins
chemical_list: C577402:Arhgef2 protein, mouse; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D006150:Guanine Nucleotides; D008869:Microtubule-Associated Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D020703:ras GTPase-Activating Proteins; D020663:ras Guanine Nucleotide Exchange Factors; C085379:rho GTPase-activating protein; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins