title: Molecular cloning and characterization of two novel retinoic acid-inducible orphan G-protein-coupled receptors (GPRC5B and GPRC5C).
abstract: Using homology searching of public databases with a metabotropic glutamate receptor sequence from Caenorhabditis elegans, two novel protein sequences (named RAIG-2 (HGMW-approved symbol GPRC5B) and RAIG-3 (HGMW-approved symbol GPRC5C) were identified containing seven putative transmembrane domains characteristic of G-protein-coupled receptors (GPCRs). RAIG-2 and RAIG-3 encode open reading frames of 403 and 442 amino acid polypeptides, respectively, and show 58% similarity to the recently identified retinoic acid-inducible gene-1 (RAIG-1, HGMW-approved symbol RAI3). Analysis of the three protein sequences places them within the type 3 GPCR family, which includes metabotropic glutamate receptors, GABA(B) receptors, calcium-sensing receptors, and pheromone receptors. However, in contrast to other type 3 GPCRs, RAIG-1, RAIG-2, and RAIG-3 have only short N-terminal domains. RAIG-2 and RAIG-3 cDNA sequences were cloned into the mammalian expression vector pcDNA3 with c-myc or HA epitope tags inserted at their N-termini, respectively. Transient transfection experiments in HEK239T cells using these constructs demonstrated RAIG-2 and RAIG-3 expression at the cell surface. Distribution profiles of mRNA expression obtained by semiquantitative Taq-Man PCR analysis showed RAIG-2 to be predominantly expressed in human brain areas and RAIG-3 to be predominantly expressed in peripheral tissues. In addition, expression of RAIG-2 and RAIG-3 mRNA was increased following treatment with all-trans-retinoic acid in a manner similar to that previously described for RAIG-1. Finally, RAIG-2 was mapped to chromosome 16p12 (D16S405-D16S3045) and RAIG-3 to chromosome 17q25 (D17S1352-D17S785). These results suggest that RAIG-1, RAIG-2, and RAIG-3 represent a novel family of retinoic acid-inducible receptors, most closely related to the type 3 GPCR subfamily, and provide further evidence for a linkage between retinoic acid and G-protein-coupled receptor signal transduction pathways.
authors.affiliation: Neuroscience Research, SmithKline Beecham, Harlow, Essex, United Kingdom.
authors.forename: M J
authors.initials: MJ
authors.lastname: Robbins
authors.forename: D
authors.initials: D
authors.lastname: Michalovich
authors.forename: J
authors.initials: J
authors.lastname: Hill
authors.forename: A R
authors.initials: AR
authors.lastname: Calver
authors.forename: A D
authors.initials: AD
authors.lastname: Medhurst
authors.forename: I
authors.initials: I
authors.lastname: Gloger
authors.forename: M
authors.initials: M
authors.lastname: Sims
authors.forename: D N
authors.initials: DN
authors.lastname: Middlemiss
authors.forename: M N
authors.initials: MN
authors.lastname: Pangalos
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001921:Brain / Q000502:physiology; D002885:Chromosomes, Human, Pair 16; D002886:Chromosomes, Human, Pair 17; D003001:Cloning, Molecular; D017931:DNA Primers / Q000737:chemistry; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D012333:RNA, Messenger / Q000032:analysis; D011956:Receptors, Cell Surface / Q000235:genetics* / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014018:Tissue Distribution; D014162:Transfection; D014212:Tretinoin / Q000494:pharmacology; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects
chemical_list: D017931:DNA Primers; C410799:GPRC5B protein, human; C417919:GPRC5C protein, human; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D014212:Tretinoin; D019204:GTP-Binding Proteins