ISOLATION OF A NOVEL CDNA-ENCODING A PUTATIVE MEMBRANE-RECEPTOR WITH HIGH HOMOLOGY TO THE CLONED MU-OPIOID, DELTA-OPIOID, AND KAPPA-OPIOID RECEPTORS

A rat brain cDNA library was screened for clones homologous to the rec ently cloned mouse delta-opioid receptor (DOR-1). Among the clones iso lated was Hyp 8-1, a clone with a unique nucleotide sequence capable o f encoding a putative protein which is 57-58% identical to the amino a cid sequences of the cloned delta, mu and kappa opioid receptors, indi cating a close relationship of Hyp 8-1 with the opioid receptor family . Several cDNAs representing possible splice variants of Hyp 8-1 were also isolated. Binding studies of COS-7 cells transfected with clone H yp 8-1 failed to demonstrate specific binding with several H-3-opioid ligands. In situ hybridization studies indicate that the mRNA for Hyp 8-1 is distributed discretely throughout the rat brain, in an overall pattern which is different from that of several other G-protein-couple d seven transmembrane receptors. Thus, it is likely that the Hyp 8-1 c DNA encodes a novel peptide receptor.