MOLECULAR-CLONING OF A NOVEL P2 PURINOCEPTOR FROM HUMAN ERYTHROLEUKEMIA-CELLS

Screening of a human erythroleukemia cell cDNA library with radiolabel ed chicken P2Y(3) cDNA at low stringency revealed a cDNA clone encodin g 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 ther eon showed a very high affinity for ATP (37 +/- 6 nM), much less for U TP 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 o f all the other known P2Y purinoceptors, with only a few of their char acteristic sequence motifs shared, The P2Y(7) receptor mRNA is abundan tly 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) r eceptor mRNA was also abundantly present in the rat heart and cultured neonatal rat cardiomyocytes, The P2Y(7) receptor is functionally coup led to phospholipase C in COS-7 cells transiently expressing this rece ptor, 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 w hich probably plays a role in the regulation of cardiac muscle contrac tion.