Pharmacological characterisation of the P2Y(11) receptor in stably transfected haematological cell lines

The recently cloned P2Y(11) receptor is unique amongst P2Y receptors with i ts coupling to the adenylyl cyclase pathway. P2Y(11) has previously been sh own to be expressed in human acute promyelocytic leukemia (APL) HL-60 and N B4 cell lines, and both cell types elevate cyclic AMP (cAMP) levels upon st imulation with extracellular ATP. Acute erythroleukemic K562 cells and acut e monocytic leukemia U937 cells did not elevate cAMP levels upon exposure t o 1 mM extracellular ATP. However, K562 and U937 cells stably transfected w ith P2Y(11) (K11 and U11 cells, respectively) were responsive to extracellu lar ATP, with an EC50 of 31 and 21 muM, respectively. The most potent agoni sts in both K11 and U11 cells were ATP gammaS (adenosine 5'-O-[3-thiotripho sphate]), ATP alphaS (adenosine 5'-O-[1-thiotriphosphate]), dATP and ADP be taS (adenosine 5'-O-[2-thiobisphosphate]), which were of similar or greater potency compared to ATP itself. ADP and alpha,beta -methylene ATP were les s potent compared to ATP. The order of potency for ATP breakdown products w as ATP > ADP > AMP greater than or equal to Ado. UTP, a known activator of P2Y(2) and P2Y(4), was largely ineffective. In the transfected cells, ATP-i nduced cAMP elevation was inhibited by suramin (0.5 mM), but not XAC (20 mu M) nor PPADS (100 muM). AMPS inhibited ATP-induced cAMP elevation in both K 11 and U11 cells (EC50 3 mM) and may be a P2Y(11)-selective inhibitor. Thes e results are similar to those observed for HL-60 cells and NB4 cells impli cating P2Y(11) as the receptor responsible for the ATP-induced cAMP elevati ons in these cells.