Molecular characterization of a rat alpha 2B-adrenergic receptor.

Abstract

.alpha.2-Adrenergic receptors comprise a heterogeneous population based on pharmacologic and molecular evidence. We have isolated a cDNA clone (pRNG.alpha.2) encoding a rat .alpha.2-adrenergic receptor. A rat kidney cDNA library was screened with an oligonucleotide complementary to a highly conversed region found in all biogenic amine receptors described to date. The deduced amino acid sequence displays many features of guanyl nucleotide-binding protein-coupled receptors except it does not have a consensus N-linked glycosylation site near the amino terminus. Membranes prepared from COS cells transfected with pRNG.alpha.2 DNA display high affinity and saturable binding to [3H]rauwolscine (Kd = 2 nM). Competition curve data analysis shows that RNG.alpha.2 protein binds to a variety of adrenergic drugs with the following rank order of potency; yohimbine .gtoreq. chlorpromazine > prazosin .gtoreq. clonidine > norepinephrine .gtoreq. oxymetazoline. RNG.alpha.2 RNA accumulates in both rat kidney and neonatal rat lung (predominant species is 4000 nucleotides). When a cysteine residue (Cys-169) that is conserved among all members of the seven-transmembrane-region superfamily is changed to phenylalanine, the RNG.alpha.2 protein fails to bind [3H]rauwolscine after expression in COS cells. We conclude that pRNG.alpha.2 likely represents a cDNA for a rat .alpha.2B-adrenergic receptor.