title: Ric-8A potentiates Gq-mediated signal transduction by acting downstream of G protein-coupled receptor in intact cells.
abstract: RIC-8 was originally found by genetic studies on C. elegans mutants that were resistant to inhibitors of acetylcholinesterase and reported to act in vitro as a guanine nucleotide exchange factor for G protein alpha subunits. However, the physiological role of a mammalian homolog Ric-8A on G protein-coupled receptor signaling in intact cells is largely unknown. We isolated Ric-8A using a yeast two-hybrid system with Galphaq and examined the role of Ric-8A on Gq-mediated signaling. The small interfering RNA of Ric-8A diminished the Gq-coupled receptor-mediated ERK activation and intracellular calcium mobilization in 293T cells. Ric-8A was translocated to the cell membrane in response to the Gq-coupled receptor stimulation. The expression of the myristoylation sequence-conjugated Ric-8A mutant was located in the membranes and shown to enhance the Gq-coupled receptor-mediated ERK activation. Moreover, this enhancement on ERK activation and the guanine nucleotide exchange activity of Ric-8A for Galphaq were inhibited by Gq selective inhibitor YM-254890. These results suggested that Ric-8A potentiates Gq-mediated signal transduction by acting as a novel-type regulator in intact cells.
authors.affiliation: Department of Cell Biology, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
authors.forename: Akiyuki
authors.initials: A
authors.lastname: Nishimura
authors.forename: Miyuki
authors.initials: M
authors.lastname: Okamoto
authors.forename: Yo
authors.initials: Y
authors.lastname: Sugawara
authors.forename: Norikazu
authors.initials: N
authors.lastname: Mizuno
authors.forename: Junji
authors.initials: J
authors.lastname: Yamauchi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Itoh
mesh_terms: D000818:Animals; D016367:Baculoviridae / Q000235:genetics / Q000378:metabolism; D001921:Brain / Q000166:cytology / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D019332:Endothelin-1 / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism*; D020868:Gene Silencing; D006147:Guanine / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D051379:Mice; D008856:Microscopy, Fluorescence; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000378:metabolism / Q000494:pharmacology; D021381:Protein Transport; D034741:RNA, Small Interfering / Q000096:biosynthesis / Q000378:metabolism; D051381:Rats; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013997:Time Factors; D020798:Two-Hybrid System Techniques
chemical_list: D019332:Endothelin-1; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D010456:Peptides, Cyclic; D034741:RNA, Small Interfering; D043562:Receptors, G-Protein-Coupled; C485884:Ric8a protein, mouse; C475455:YM-254890; D006147:Guanine; D048049:Extracellular Signal-Regulated MAP Kinases; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D002118:Calcium