title: Cloning and characterization of a novel regulator of G protein signalling in human platelets.
abstract: In an effort to understand the modulation of G protein-coupled receptor (GPCR)-mediated signalling in platelets, we sought to identify which regulators of G protein signalling proteins (RGSs) are present in human platelets. Using degenerate oligonucleotides, we performed RT-PCR with human platelet and megakaryocytic cell line RNA. In addition to confirming the presence of several known RGS transcripts, we found a novel RGS domain-containing transcript in platelet RNA. Northern blot analysis of multiple human tissues indicates that this transcript is most abundantly expressed in platelets compared to other tissues examined. Full-length cloning of this novel RGS, which we now term RGS18, demonstrates that this transcript is predicted to encode a 235-amino acid protein that is most closely related to RGS5 (46% identity) and that has approximately 30-40% identity to other RGS proteins. RGS18 is expressed in platelet, leukocyte, and megakaryocyte cell lines and binds to endogenous Galphai1, Galphai2, Galphai3, and Galphaq but not Galphaz, Galphas or Galpha12 in vitro.
authors.affiliation: Cardiovascular Drug Discovery, Aventis Pharmaceuticals, 500 Arcola Road, Collegeville, PA 19426, USA.
authors.forename: Alison W
authors.initials: AW
authors.lastname: Gagnon
authors.forename: David L
authors.initials: DL
authors.lastname: Murray
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Leadley
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001792:Blood Platelets / Q000378:metabolism*; D015153:Blotting, Western; D002352:Carrier Proteins / Q000235:genetics; D002460:Cell Line; D003001:Cloning, Molecular; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008533:Megakaryocytes / Q000378:metabolism; D008969:Molecular Sequence Data; D020710:RGS Proteins / Q000235:genetics* / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014018:Tissue Distribution
chemical_list: D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D020710:RGS Proteins; C466958:RGS18 protein, human; C422991:Rgs18 protein, mouse; D020962:Heterotrimeric GTP-Binding Proteins