ISOLATION AND CHARACTERIZATION OF AN AVIAN A(1) ADENOSINE RECEPTOR GENE AND A RELATED CDNA CLONE

We have isolated the gene for a chick A(1) adenosine receptor along with a cDNA that codes for the same adenosine receptor. The cDNA clone was isolated from both adipose tissue and heart cDNA libraries and encodes a 324-amino acid protein with 80% identity with mammalian A(1) adenosine receptors. Transient expression of the cDNA in human embryonic kidney (HEK) 293 cells shows that it encodes a protein that binds [H-3]CCPA (2-chloro-N-6-[cyclopentyl-2,3,4,5-H-3] cylopentyladeno sine, a specific agonist radioligand, with a K-D of 5.6+/-2.4 nM. Cyclic AMP measurements in HEK 293 cells co-transfected with the chick cDNA and a cDNA for a luteinizing hormone/choriogonadotropin receptor shows that A(1) adenosine receptor agonists antagonize the cyclic AMP-elevating effect of bovine luteinizing hormone. Two partial genomic clones were isolated. The first contains 5'-untranslated sequence including a putative promoter region which does not contain a TATA box, an intron and the first third of the coding sequence of the A(1) adenosine receptor cDNA. The coding sequence of this partial genomic clone terminates at a second intron. The second partial genomic clone contains the rest of the coding sequence and the 3'-untranslated elements in a single exon. Thus the chick A(1) adenosine receptor gene contains one intron in the 5'-untranslated region and a minimum of one intron in the coding sequence.