Differential coupling of the human P2Y(11) receptor to phospholipase C and adenylyl cyclase

1 The human P2Y(11) (hP2Y(11)) receptor was stably expressed in two cell lines, 1321N1 human astrocytoma cells (1321N1-hP2Y(11)) and Chinese hamster ovary cells (CHO-hP2Y(11)), and its coupling to phospholipase C and adenylyl cyclase was assessed. 2 In 1321N1-hP2Y(11) cells, ATP promoted inositol phosphate OF) accumulation with low muM potency (EC50 = 8.5 +/- 0.1 muM), whereas it was 15 fold less potent (130 +/- 10 muM) in evoking cyclic AMP production. 3 In CHO-hP2Y(11) cells, ATP promoted IP accumulation with slightly higher potency (EC50 = 3.6 +/- 1.3 muM) than in 1321N1-hP2Y(11) cells, but it was still 15 fold less potent in promoting cyclic AMP accumulation (EC50 = 62.4 +/- 15.6 muM) than for IP accumulation. Comparable differences in potencies for promoting the two second messenger responses were observed with other adenosine nucleotide analogues. 4 In 1321N1-hP2Y(11) and CHO-hP2Y(11) cells, down regulation of PKC by chronic treatment with phorbol ester decreased ATP-promoted cyclic AMP accumulation by 60-80% (P < 0.001) with no change in its potency. Likewise, chelation of intracellular Ca2+ decreased ATP-promoted cyclic AMP accumulation by 45% in 1321N1-hP2Y(11) cells, whereas chelation had no effect on either the efficacy or potency of ATP in CHO-hP2Y11 cells. 5 We conclude that coupling of hP2Y(11) receptors to adenylyl cyclase in these cell lines is much weaker than coupling to phospholipase C, and that activation of PKC and intracellular Ca2+ mobilization as consequences of inositol lipid hydrolysis potentiates the capacity of ATP to increase cyclic AMP accumulation in both 1321N1-hP2Y(11) and CHO-hP2Y1(1) cells.