title: Double suppression of the Gα protein activity by RGS proteins.
abstract: Regulator of G protein signaling (RGS) proteins accelerate GTP hydrolysis on G protein α subunits, restricting their activity downstream from G protein-coupled receptors. Here we identify Drosophila Double hit (Dhit) as a dual RGS regulator of Gαo. In addition to the conventional GTPase-activating action, Dhit possesses the guanine nucleotide dissociation inhibitor (GDI) activity, slowing the rate of GTP uptake by Gαo; both activities are mediated by the same RGS domain. These findings are recapitulated using homologous mammalian Gαo/i proteins and RGS19. Crystal structure and mutagenesis studies provide clues into the molecular mechanism for this unprecedented GDI activity. Physiologically, we confirm this activity in Drosophila asymmetric cell divisions and HEK293T cells. We show that the oncogenic Gαo mutant found in breast cancer escapes this GDI regulation. Our studies identify Dhit and its homologs as double-action regulators, inhibiting Gαo/i proteins both through suppression of their activation and acceleration of their inactivation through the single RGS domain.
authors.affiliation: Department of Pharmacology and Toxicology, University of Lausanne, Rue du Bugnon 27, 1005 Lausanne, Switzerland.
authors.forename: Chen
authors.initials: C
authors.lastname: Lin
authors.affiliation: Department of Pharmacology and Toxicology, University of Lausanne, Rue du Bugnon 27, 1005 Lausanne, Switzerland.
authors.forename: Alexey
authors.initials: A
authors.lastname: Koval
authors.affiliation: Institute of Protein Research, Russian Academy of Sciences, Institutskaya Street 4, 142290 Pushchino, Russian Federation.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Tishchenko
authors.affiliation: Institute of Protein Research, Russian Academy of Sciences, Institutskaya Street 4, 142290 Pushchino, Russian Federation.
authors.forename: Azat
authors.initials: A
authors.lastname: Gabdulkhakov
authors.affiliation: Institute of Protein Research, Russian Academy of Sciences, Institutskaya Street 4, 142290 Pushchino, Russian Federation.
authors.forename: Uliana
authors.initials: U
authors.lastname: Tin
authors.affiliation: Department of Pharmacology and Toxicology, University of Lausanne, Rue du Bugnon 27, 1005 Lausanne, Switzerland.
authors.forename: Gonzalo P
authors.initials: GP
authors.lastname: Solis
authors.affiliation: Department of Pharmacology and Toxicology, University of Lausanne, Rue du Bugnon 27, 1005 Lausanne, Switzerland; Institute of Protein Research, Russian Academy of Sciences, Institutskaya Street 4, 142290 Pushchino, Russian Federation. Electronic address: vladimir.katanaev@unil.ch.
authors.forename: Vladimir L
authors.initials: VL
authors.lastname: Katanaev
mesh_terms: D020121:5' Untranslated Regions; D000595:Amino Acid Sequence; D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism; D018360:Crystallography, X-Ray; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster; D005260:Female; D044385:GTP-Binding Protein alpha Subunits / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006160:Guanosine Triphosphate / Q000737:chemistry; D057809:HEK293 Cells; D006801:Humans; D006868:Hydrolysis; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames; D017434:Protein Structure, Tertiary; D020710:RGS Proteins / Q000378:metabolism*; D015398:Signal Transduction; D013997:Time Factors
chemical_list: D020121:5' Untranslated Regions; D029721:Drosophila Proteins; D044385:GTP-Binding Protein alpha Subunits; D020710:RGS Proteins; C582291:dhit protein, Drosophila; C097187:regulator of G-protein signalling 19; D006160:Guanosine Triphosphate