• ATP;
  • cyclic AMP;
  • inositol phosphates;
  • P2Y receptors;
  • P2Y11 receptor;
  • protein kinase C;
  • Ca2+ mobilization
  • The human P2Y11 (hP2Y11) receptor was stably expressed in two cell lines, 1321N1 human astrocytoma cells (1321N1-hP2Y11) and Chinese hamster ovary cells (CHO-hP2Y11), and its coupling to phospholipase C and adenylyl cyclase was assessed.

  • In 1321N1-hP2Y11 cells, ATP promoted inositol phosphate (IP) accumulation with low μM potency (EC50=8.5±0.1 μM), whereas it was 15 fold less potent (130±10 μM) in evoking cyclic AMP production.

  • In CHO-hP2Y11 cells, ATP promoted IP accumulation with slightly higher potency (EC50=3.6±1.3 μM) than in 1321N1-hP2Y11 cells, but it was still 15 fold less potent in promoting cyclic AMP accumulation (EC50=62.4±15.6 μM) than for IP accumulation. Comparable differences in potencies for promoting the two second messenger responses were observed with other adenosine nucleotide analogues.

  • In 1321N1-hP2Y11 and CHO-hP2Y11 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-hP2Y11 cells, whereas chelation had no effect on either the efficacy or potency of ATP in CHO-hP2Y11 cells.

  • We conclude that coupling of hP2Y11 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-hP2Y11 and CHO-hP2Y11 cells.

British Journal of Pharmacology (2001) 132, 318–326; doi:10.1038/sj.bjp.0703788