CLONING AND EXPRESSION OF THE A(2A) ADENOSINE RECEPTOR FROM GUINEA-PIG BRAIN

A full-length complementary DNA (cDNA) clone encoding the guinea pig b rain A(2) adenosine receptor has been isolated by polymerase chain rea ction (PCR) and low-stringency-hybridization screening of a guinea pig brain cDNA library. This cDNA contains a long open reading frame enco ding a 409-amino acid-residue protein which is highly homologous to th e A(2) adenosine receptors previously cloned from other species. Hydro phobicity analysis of the deduced protein sequence reveals seven hydro phobic regions, characteristic of a member of the G-protein-coupled re ceptor superfamily. Radioligand binding assay and functional (GTPase a nd cAMP) assays of the receptor, transiently expressed in mammalian ce lls, demonstrate typical characteristics of the A(2) type adenosine re ceptor. The messenger RNA (mRNA) of this A(2) receptor is found in the brain, heart, kidney and spleen. Receptor autoradiography with [H-3]C GS21680, a specific A(2) agonist, and in situ hybridization with A(2) cRNA probe in guinea pig brain indicate that the receptor is expressed exclusively in the caudate nucleus. The pharmacological profile and a natomical distribution of this receptor indicate that it is of the A(2 a) subtype. This work represents the first cloning of an A(2a) recepto r in a rodent species, offers a complete pharmacological characterizat ion of the receptor and provides an anatomical comparison between bind ing profile and gene expression of the receptor.