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Molecular cloning, tissue distribution and chromosomal localization of a novel member of the opioid receptor gene family
Author(s) -
Chen Yan,
Fan Yi,
Liu Jian,
Mestek Anton,
Tian Mingting,
Kozak Christine A.,
Yu Lei
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)00560-5
Subject(s) - microbiology and biotechnology , biology , opioid receptor , complementary dna , receptor , δ opioid receptor , 5 ht5a receptor , gene , genetics , opioid
A cDNA was isolated from rat brain by low stringency hybridization with the rat μ opioid receptor cDNA. Sequence analysis of this clone indicated that it contains an open reading frame capable of encoding a 367 amino acid protein. The deduced amino acid sequence of this protein shows high degrees of homology to all three opioid receptors, μ, κ, and δ, suggesting that it is a member of the opioid receptor gene family. RNA blot analysis detected high level expression of the receptor mRNA in the brain. Southern blot analysis suggests that it is a single‐copy gene, and mapping studies localized the gene on mouse chromosome 2. Despite the high sequence homologies between this protein and the other opioid receptors, expression studies of this clone in COS‐7 cells did not show binding to [ 3 H]diprenorphine, a ligand that binds to the other three opioid receptors. Furthermore, co‐expression of this receptor with a G protein‐activated potassium channel in Xenopus oocytes did not show functional coupling upon stimulation with μ, κ and δ agonists. Given the similar degrees of high homology to the μ, κ and δ opioid receptors and the lack of apparent affinity for their ligands, this receptor does not appear to belong to any of the three known classes of opioid receptors. Rather, it represents a novel member of the opioid receptor gene family, not identified from previous pharmacological studies.