title: Guanine nucleotide exchange factor GEF115 specifically mediates activation of Rho and serum response factor by the G protein alpha subunit Galpha13.
abstract: Signal transduction pathways that mediate activation of serum response factor (SRF) by heterotrimeric G protein alpha subunits were characterized in transfection systems. Galphaq, Galpha12, and Galpha13, but not Galphai, activate SRF through RhoA. When Galphaq, alpha12, or alpha13 were coexpressed with a Rho-specific guanine nucleotide exchange factor GEF115, Galpha13, but not Galphaq or Galpha12, showed synergistic activation of SRF with GEF115. The synergy between Galpha13 and GEF115 depends on the N-terminal part of GEF115, and there was no synergistic effect between Galpha13 and another Rho-specific exchange factor Lbc. In addition, the Dbl-homology (DH)-domain-deletion mutant of GEF115 inhibited Galpha13- and Galpha12-induced, but not GEF115 itself- or Galphaq-induced, SRF activation. The DH-domain-deletion mutant also suppressed thrombin- and lysophosphatidic acid-induced SRF activation in NIH 3T3 cells, probably by inhibition of Galpha12/13. The N-terminal part of GEF115 contains a sequence motif that is homologous to the regulator of G protein signaling (RGS) domain of RGS12. RGS12 can inhibit both Galpha12 and Galpha13. Thus, the inhibition of Galpha12/13 by the DH-deletion mutant may be due to the RGS activity of the mutant. The synergism between Galpha13 and GEF115 indicates that GEF115 mediates Galpha13-induced activation of Rho and SRF.
authors.affiliation: Department of Pharmacology and Physiology, University of Rochester, NY 14642, USA.
authors.forename: J
authors.initials: J
authors.lastname: Mao
authors.forename: H
authors.initials: H
authors.lastname: Yuan
authors.forename: W
authors.initials: W
authors.lastname: Xie
authors.forename: D
authors.initials: D
authors.lastname: Wu
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D020690:GTPase-Activating Proteins; D005786:Gene Expression Regulation; D020662:Guanine Nucleotide Exchange Factors; D007700:Kinetics; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D026362:Serum Response Factor; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014162:Transfection; D020742:rhoA GTP-Binding Protein
chemical_list: D004268:DNA-Binding Proteins; D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D011506:Proteins; D011993:Recombinant Fusion Proteins; D026362:Serum Response Factor; D014157:Transcription Factors; D008156:Luciferases; D019204:GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein