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

1 The human P2Y(11) (hP2Y(11)) receptor was stably expressed in two cell li nes, 1321N1 human astrocytoma cells (1321N1-hP2Y(11)) and Chinese hamster o vary 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) accumulatio n with low muM potency (EC50 = 8.5 +/- 0.1 muM), whereas it was 15 fold les s 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 potencie s 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 chro nic treatment with phorbol ester decreased ATP-promoted cyclic AMP accumula tion by 60-80% (P < 0.001) with no change in its potency. Likewise, chelati on of intracellular Ca2+ decreased ATP-promoted cyclic AMP accumulation by <similar to>45% in 1321N1-hP2Y(11) cells, whereas chelation had no effect o n either the efficacy or potency of ATP in CHO-hP2Y11 cells. 5 We conclude that coupling of hP2Y(11) receptors to adenylyl cyclase in th ese cell lines is much weaker than coupling to phospholipase C, and that ac tivation of PKC and intracellular Ca2+ mobilization as consequences of inos itol lipid hydrolysis potentiates the capacity of ATP to increase cyclic AM P accumulation in both 1321N1-hP2Y(11) and CHO-hP2Y1(1) cells.