IMMUNOLOGICAL IDENTIFICATION OF A(1) ADENOSINE RECEPTORS IN BRAIN CORTEX

The A(1) adenosine receptor from pig brain cortex has been identified by means of two antipeptide antibodies against two domains of the rece ptor molecule: PC/10 antiserum was raised against a part of the third intracellular loop, and PC/20 antiserum was raised against a part of t he second extracellular loop, PC/10 antibody was able to recognize a 3 9-kDa band that corresponded to the A, receptor, as demonstrated by im munoblotting and by immunoprecipitation of the molecule cross-linked t o )-2-azido-N-2-p-hydroxy(phenylisopropyl)adenosine. Besides the 39-kD a band, PC/20 also recognized a 74-kDa form that does not seem to corr espond to a receptor-G protein complex, The occurrence of the two band s was detected and analyzed in samples from different species and tiss ues showing a heterogeneous distribution of both, The 74-kDa form can be converted into the 39-kDa form by treatment with agonists or antago nists of A, adenosine receptors, These results suggest that A, adenosi ne receptor can occur in dimers and that the dimer-monomer conversion might be regulated by adenosine as the physiological ligand. Since the 74-kDa aggregates were not recognized by PC/10, it is likely that par t of the third intracellular loop participates in the protein-protein interaction. (C) 1995 Wiley-Liss, Inc.