Characterization of the G-protein linked orphan receptor GPRN1/RDC1.

Site specific antibodies were raised against the second intracellular loop of the G-protein coupled orphan receptor GPRN1 for analysis of receptor protein expression from a number of sources. Immunoblot analyses showed GPRN1 to be a 60 kDa membrane bound glycoprotein. It was found in AR4-2J, PC12 and SK-N-MC cell lines. High amounts of GPRN1 were found in rat stomach, liver, lung, brain, small intestine and pancreas, with lower amounts in spleen and kidney: none was detectable in rat heart. This distribution differs markedly from that of the closely related orphan receptor RDC1. The receptor shows high evolutionary conservation: immunoreactive 60 kDa GPRN1 was detected in membrane glycoprotein fractions from the livers of rat, toad, chick, stingray and shark. It is therefore predicted that GPRN1 and RDC1 represent two tissue specific subtypes of a 60 kDa receptor for a ligand which has likely been highly conserved throughout evolution and which is active upon many organs of the body.