title: Expression cloning of cDNA encoding a seven-helix receptor from human placenta with affinity for opioid ligands.
abstract: Here we report the expression cloning of cDNA encoding a putative opioid receptor from a human placenta cDNA library. Placental opioid receptors are of the kappa type. As the dynorphin opioid peptides are kappa-selective, a dynorphin ligand was used in an affinity-enrichment (panning) procedure to select transiently transfected COS-7 cells expressing kappa receptor binding sites. The cloned cDNA encodes a 440-residue protein of the seven-helix guanine nucleotide-binding protein (G-protein)-coupled receptor family. Ligand binding reveals a stereospecific site with typical opioid properties, which binds peptide and nonpeptide opioids with moderate affinity (Kd approximately 100 nM) and which lacks the expected kappa selectivity. The deduced transmembrane domain is 93% identical to the homologous region of the human neuromedin K (neurokinin B) receptor, but the N-terminal and C-terminal sequences have many dissimilarities. The expressed receptor binds opioid ligands but not tachykinins; and under the same conditions, a cloned rat neuromedin K receptor binds tachykinins but not opioids.
authors.affiliation: DNAX Research Institute of Molecular and Cellular Biology, Palo Alto, CA 94304.
authors.forename: G X
authors.initials: GX
authors.lastname: Xie
authors.forename: A
authors.initials: A
authors.lastname: Miyajima
authors.forename: A
authors.initials: A
authors.lastname: Goldstein
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D015870:Gene Expression; D066298:In Vitro Techniques; D008024:Ligands; D008969:Molecular Sequence Data; D009294:Narcotics / Q000378:metabolism; D010920:Placenta / Q000502:physiology; D012333:RNA, Messenger / Q000235:genetics; D011957:Receptors, Opioid / Q000235:genetics* / Q000378:metabolism; D017473:Receptors, Opioid, kappa; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D008024:Ligands; D009294:Narcotics; D012333:RNA, Messenger; D011957:Receptors, Opioid; D017473:Receptors, Opioid, kappa; D011994:Recombinant Proteins; D004247:DNA