Pharmacological characterisation of the P2Y11 receptor in stably transfected haematological cell lines

The recently cloned P2Y11 receptor is unique amongst P2Y receptors with its coupling to the adenylyl cyclase pathway. P2Y11 has previously been shown to be expressed in human acute promyelocytic leukemia (APL) HL-60 and NB4 cell lines, and both cell types elevate cyclic AMP (cAMP) levels upon stimulation with extracellular ATP. Acute erythroleukemic K562 cells and acute monocytic leukemia U937 cells did not elevate cAMP levels upon exposure to 1 mM extracellular ATP. However, K562 and U937 cells stably transfected with P2Y11 (K11 and U11 cells, respectively) were responsive to extracellular ATP, with an EC50 of 31 and 21 microM, respectively. The most potent agonists in both K11 and U11 cells were ATPgammaS (adenosine 5'-O-[3-thiotriphosphate]), ATPalphaS (adenosine 5'-O-[1-thiotriphosphate]), dATP and ADPbetaS (adenosine 5'-O-[2-thiobisphosphate]), which were of similar or greater potency compared to ATP itself. ADP and alpha,beta-methylene ATP were less potent compared to ATP. The order of potency for ATP breakdown products was ATP > ADP > AMP > or = Ado. UTP, a known activator of P2Y2 and P2Y4, was largely ineffective. In the transfected cells, ATP-induced cAMP elevation was inhibited by suramin (0.5 mM), but not XAC (20 microM) nor PPADS (100 microM). AMPS inhibited ATP-induced cAMP elevation in both K11 and U11 cells (EC50 approximately 3 mM) and may be a P2Y11-selective inhibitor. These results are similar to those observed for HL-60 cells and NB4 cells implicating P2Y11 as the receptor responsible for the ATP-induced cAMP elevations in these cells.