Pharmacological profile of a novel cyclic AMP-linked P2 receptor on undifferentiated HL-60 leukemia cells

1 Extracellular ATP (EC50 = 146 +/- 57 mu M) and various ATP analogues activated cyclic AMP production in undifferentiated HL-60 cells. 2 The order of agonist potency was: ATP gamma S (adenosine 5'-O-[3-thiotriphosphate]) greater than or equal to BzATP (2'&3'O-(4-benzoylbenzoyl)-adenosine-5'-triphosphate) greater than or equal to dATP > ATP. The following agonists tin order of effectiveness at 1 mM) were all less effective than ATP at concentrations up to 1 mM: beta,gamma methylene ATP greater than or equal to 2-methylthioATP > ADP greater than or equal to Ap4A (P-1, P(4-)di(adenosine5') tetraphosphate) greater than or equal to Adenosine > UTP. The poor response to UTP indicates that P2Y(2) receptors are not responsible for ATP-dependent activation of adenylyl cyclase. 3 Several thiophosphorylated analogs of ATP were more potent activators of cyclic AMP production than ATP. Of these, ATP gamma S (EC50=30.4+/-6.9 mu M) was a full agonist. However, adenosine 5'-O-[2-thiodiphosphate] (ATP alpha S; EC50 = 45 +/- 15 mu M) and adenosine 5'-O-[2-thiodiphosphate] (ADP beta S; EC50 = 33.3 +/- 5.0 mu M) were partial agonists. 4 ADP beta S (IC50 = 146 +/- 32 mu M) and adenosine 5'-O-thiomonophosphate (AMPS; IC50 = 343 +/- 142 mu M) inhibited cyclic AMP production by a submaximal concentration of ATP (100 mu M). Consistent with its partial agonist activity, ADP beta S was estimated to maximally suppress ATP-induced cyclic AMP production by about 65%. AMPS has not been previously reported to inhibit P2 receptors. 5 The broad spectrum P2 receptor antagonist, suramin (500 mu M), abolished ATP-stimulated cyclic AMP production by HL-60 cells but the adenosine receptor antagonists xanthine amine congener (XAC; 20 mu M) and 8-sulpho-phenyltheophylline (8-SPT; 100 mu M) were without effect. 6 Extracellular ATP also activated protein kinase A (PK-A) consistent with previous findings that PK-A activation is involved in ATP-induced differentiation of HL-60 cells (Jiang et al., 1997). 7 Taken together, the data indicate the presence of a novel cyclic AMP-linked P2 receptor on undifferentiated HL-60 cells.