Molecular Cloning of a Novel P2 Purinoceptor from Human Erythroleukemia Cells

Screening of a human erythroleukemia cell cDNA library with radiolabeled chicken P2Y(3) cDNA at low stringency revealed a cDNA clone encoding a novel G protein-coupled receptor with homology to P2 purinoceptors, This receptor, designated P2Y(7), has 352 amino acids and shares 23-30% amino acid identity with the P2Y(1)-P2Y(6) purinoceptors. The P2Y(7) cDNA was transiently expressed in COS-7 cells: binding studies thereon showed a very high affinity for ATP (37 +/- 6 nM), much less for UTP and ADP (similar to 1300 nM), and a novel rank order of affinities in the binding series studied of 8 nucleotides and suramin, The P2Y(7) receptor sequence appears to denote a different subfamily from that of all the other known P2Y purinoceptors, with only a few of their characteristic sequence motifs shared, The P2Y(7) receptor mRNA is abundantly present in the human heart and the skeletal muscle, moderately in the brain and liver, but not in the other tissues tested, The P2Y(7) receptor mRNA was also abundantly present in the rat heart and cultured neonatal rat cardiomyocytes, The P2Y(7) receptor is functionally coupled to phospholipase C in COS-7 cells transiently expressing this receptor, The P2Y(7) gene was shown to be localized to human chromosome 14. We have thus cloned a unique member of the P2Y purinoceptor family which probably plays a role in the regulation of cardiac muscle contraction.