A primitive ATP receptor from the little skate Raja erinacea

P2Y ATP receptors are widely expressed in mammalian tissues and regulate a broad range of activities. Multiple subtypes of P2Y receptors have been ide ntified and are distinguished both on a molecular basis and by pharmacologi c substrate preference. Functional evidence suggests that hepatocytes from the little skate Raja erinacea express a primitive P2Y ATP receptor lacking pharmacologic selectivity, so we cloned and characterized this receptor. S kate hepatocyte cDNA was amplified with degenerate oligonucleotide probes d esigned to identify known P2Y subtypes. A single polymerase chain reaction product was found and used to screen a skate liver cDNA library. A 2314-bas e pair cDNA clone was generated that contained a 1074-base pair open readin g frame encoding a 357-amino acid gene product with 61-64% similarity to P2 Y(1) receptors and 21-37% similarity to other P2Y receptor subtypes. Pharma cology of the putative P2Y receptor was examined using the Xenopus oocyte e xpression system and revealed activation by a range of nucleotides. The rec eptor was expressed widely in skate tissue and was expressed to a similar e xtent in other primitive organisms. Phylogenetic analysis suggested that th is receptor is closely related to a common ancestor of the P2Y subtypes fou nd in mammals, avians, and amphibians. Thus, the skate liver P2Y receptor f unctions as a primitive P2Y ATP receptor with broad pharmacologic selectivi ty and is related to the evolutionary forerunner of P2Y(1) receptors of hig her organisms. This novel receptor should provide an effective comparative model for P2Y receptor pharmacology and may improve our understanding of nu cleotide specificity among the family of P2Y ATP receptors.