The orphan receptor cDNA RDC7 encodes an A1 adenosine receptor.

Abstract

The extensive amino acid sequence conservation among G protein‐coupled receptors has been exploited to clone new members of this large family by homology screening or by PCR. Out of four such receptor cDNAs we cloned recently, RDC7 corresponds to a relatively abundant transcript in the brain cortex, the thyroid follicular cell and the testis. We have now identified RDC7 as an A1 adenosine receptor. The A1 agonist CPA [N6‐cyclopentyladenosine] decreased by 80% cAMP accumulation in forskolin‐stimulated CHO cells stably transfected with RDC7. Specific binding of another A1 adenosine agonist, [3H]CHA [N6‐cyclohexyladenosine], was demonstrated on membranes from Cos cells transfected with a pSVL construct harbouring the RDC7 cDNA insert. The binding characteristics were similar to those of the natural brain A1 receptor. The recombinant and the natural receptors behaved also in the same way in displacement experiments involving a series of A1 adenosine agonists. The binding characteristics of RDC7 were compared to those of RDC8, another orphan receptor recently identified as an A2 adenosine receptor. The two molecular species RDC7 and RDC8 correspond clearly to the A1 and A2 receptor entities defined hitherto on a purely pharmacological basis.

Cloning and expression of a bovine adenosine A1 receptor cDNA

“…Binding data from recombinant rat receptors expressed in COS cells correlated well with published data on binding to rat brain receptors [10-141. Dog recombinant receptors expressed in COS cells bind ligands differently from rat receptors (little discrimination between A-PIA and NECA [9]) but similar to native receptors found on canine brain membranes. The bovine receptor pharmacology, which is very distinct from rat, canine and human [12] receptors, is maintained when purified bovine receptors are reconstituted into human platelet membranes [IS].…”

“…BW-Al433 and DPCPX were gifts of Dr. were designed. These encode a portion of the putative third tmnsmembrane tcgion of the dog adcnosinc A, recepior (RDC7) scqucnce [9]. The 3' terminal nonamers of the oligonucleotides arc complementary; a radiolabeled probe was made by the action of the Klenow fragment of DNA polymerase I on the annealed oligonuclcotide templates in the presence of ["'P]dCTP and three unlabeled deoxynucleosidc triphosphates.…”

Adenosine levels in the postimplantation mouse uterus: Quantitation by HPLC‐fluorometric detection and spatiotemporal regulation by 5′‐nucleotidase and adenosine deaminase

“…Physiologic responses to adenosine are commonly mediated by its binding to A, and A, receptors which are coupled to signal transduction pathways by guanine nucleotide regulatory proteins (Londos et al, 1978(Londos et al, , 1980Maenhaut et al, 1990;Libert et al, 1991). Elucidating the potential roles of adenosine in development will require the characterization and localization of these receptors in the embryo-decidual unit.…”

“…It is liberated from nucleotide pools under conditions of net ATP catabolism and, as a paracrine signal, invokes an array of physiological responses that collectively serve to protect cells during metabolic stress and tissue injury (Arch and Newsholme, 1978; for recent overviews, see Bruns, 1991;Engler and Gruber, 1991). Most of these actions are mediated by specific membrane adenosine receptors (A, and A,) which are coupled to signal transduction pathways by guanine nucleotide regulatory proteins (Londos et al, 1978(Londos et al, , 1980Maenhaut et al, 1990;Libert et al, 1991).…”

Thyroid expression of an A2 adenosine receptor transgene induces thyroid hyperplasia and hyperthyroidism.

“…They have been classified into A1 or A2 subtypes according to their inhibitory or stimulatory effects on adenylyl cyclase, respectively (Van Calker et al, 1979). Both receptors have recently been identified amongst cloned cDNAs of orphan G protein-coupled receptors and characterized at the molecular level (Maenhaut et al, 1990;Libert et al, 1989Libert et al, , 1991. In the course of the study of the A2 receptor, it appeared that its expression in a variety of cell types (by transfection of cDNA or microinjection of mRNA) resulted in the constitutive activation of adenylyl cyclase (Maenhaut et al, 1990).…”