CDNA CLONING AND CHARACTERIZATION OF A3I, AN ALTERNATIVELY SPLICED RAT A3 ADENOSINE RECEPTOR VARIANT

A cDNA encoding a variant form of the A3 adenosine (Ado) receptor was isolated from rat by reverse transcription of brain mRNA followed by P CR. The full-length receptor (A3i) cDNA encodes 337 amino acids and sh ares complete sequence identity with the rat A3 Ado receptor, except f or the presence of a seventeen amino acid insert located in the second intracellular domain. In contrast to the rat A3 receptor, stable expr ession of A3i in CHO cells resulted in poor coupling to Gi proteins. A nalysis of receptor transcripts by RT-PCR suggests that the A3 Ado rec eptor mRNAs are products of alternative splicing. Sequence analysis of A3 genomic DNA identified a 1.7 kb intron that is likely alternativel y spliced to produce the A3 and A3i receptors.