title: Galphaq directly activates p63RhoGEF and Trio via a conserved extension of the Dbl homology-associated pleckstrin homology domain.
abstract: The coordinated cross-talk from heterotrimeric G proteins to Rho GTPases is essential during a variety of physiological processes. Emerging data suggest that members of the Galpha(12/13) and Galpha(q/11) families of heterotrimeric G proteins signal downstream to RhoA via distinct pathways. Although studies have elucidated mechanisms governing Galpha(12/13)-mediated RhoA activation, proteins that functionally couple Galpha(q/11) to RhoA activation have remained elusive. Recently, the Dbl-family guanine nucleotide exchange factor (GEF) p63RhoGEF/GEFT has been described as a novel mediator of Galpha(q/11) signaling to RhoA based on its ability to synergize with Galpha(q/11) resulting in enhanced RhoA signaling in cells. We have used biochemical/biophysical approaches with purified protein components to better understand the mechanism by which activated Galpha(q) directly engages and stimulates p63RhoGEF. Basally, p63RhoGEF is autoinhibited by the Dbl homology (DH)-associated pleckstrin homology (PH) domain; activated Galpha(q) relieves this autoinhibition by interacting with a highly conserved C-terminal extension of the PH domain. This unique extension is conserved in the related Dbl-family members Trio and Kalirin and we show that the C-terminal Rho-specific DH-PH cassette of Trio is similarly activated by Galpha(q).
authors.affiliation: Department of Pharmacology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
authors.forename: Rafael J
authors.initials: RJ
authors.lastname: Rojas
authors.forename: Marielle E
authors.initials: ME
authors.lastname: Yohe
authors.forename: Svetlana
authors.initials: S
authors.lastname: Gershburg
authors.forename: Takeharu
authors.initials: T
authors.lastname: Kawano
authors.forename: Tohru
authors.initials: T
authors.lastname: Kozasa
authors.forename: John
authors.initials: J
authors.lastname: Sondek
mesh_terms: D000595:Amino Acid Sequence; D001671:Biochemistry / Q000379:methods; D001703:Biophysics / Q000379:methods; D019281:Dimerization; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000737:chemistry* / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D064067:Rho Guanine Nucleotide Exchange Factors; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
chemical_list: C475063:ARHGEF25 protein, human; D020662:Guanine Nucleotide Exchange Factors; C057811:MCF2 protein, human; D011518:Proto-Oncogene Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D017346:Protein Serine-Threonine Kinases; C099628:TRIO protein, human; D043802:GTP-Binding Protein alpha Subunits, Gq-G11