Discovery of three novel orphan G-protein-coupled receptors

We have discovered three novel human genes, GPR34, GPR44, and GPR45, encodi ng family A G-protein-coupled receptors (GPCRs). The receptor encoded by GP R34 is most similar to the P2Y receptor subfamily, while the receptor encod ed by GPR44 is most similar to chemoattractant receptors. The receptor enco ded by GPR45 is the mammalian orthologue of a putative lysophosphatidic aci d receptor from Xenopus laevis. Partial sequence of GPR34 was discovered du ring a search of the GenBank database of expressed sequence tags (ESTs). Th is sequence information was used both to isolate the full-length translatio nal open reading frame from a human genomic library and to assemble a conti g hom additional GPR34 EST cDNAs. Northern blot and in situ hybridization a nalyses revealed GPR34 mRNA transcripts in several human and rat brain regi ons. Also, we used polymerase chain reaction (PCR) to amplify human genomic DNA using degenerate oligonucleotides designed from sequences encoding tra nsmembrane domains 3 and 7 of opioid and somatostatin receptors. Two PCR pr oducts partially encoding novel GPCRs, named GPR44 and GPR45, were discover ed and used to isolate the full-length translational open reading frames fr om a human genomic library. Both GPR44 and GPR45 are expressed in the centr al nervous system and periphery. For chromosomal localization fluorescence in situ hybridization analysis was performed to assign GPR34 to chromosomes 4p12 and Xp11.3, GPR44 to chromosome 11q12-q13.3, and GPR45 to chromosome 2q11.1-q12. (C) 1999 Academic Press.