Identification of a novel G-protein coupled receptor expressed in distinct brain regions and a defined olfactory zone.

PCR-approaches with degenerated oligonucleotide primers have been employed in trying to identify novel members of the G-protein coupled receptor (GPCR) superfamily from rat brain. Screening a rat brain library with an amplification product showing some features of a GPCR gene led to the isolation of a full-length clone (RA1c); the encoded polypeptide comprises seven distinct hydrophobic stretches as well as several other hallmarks of GPCRs. Sequence comparison revealed a rather low but significant homology to GPCRs; RA1c shares about 30% sequence identity with various olfactory receptors and about 27% with several peptide receptors. By Northern blot and especially by in situ hybridization analysis it could be demonstrated that the RA1c receptor is expressed only in very distinct areas of the brain and in addition in a defined zone of the olfactory epithelium.