title: Inhibition of ecto-ATPase by the P2 purinoceptor agonists, ATPgammaS, alpha,beta-methylene-ATP, and AMP-PNP, in endothelial cells.
abstract: Ecto-ATPase is a plasma membrane-bound enzyme that sequentially dephosphorylates extracellular nucleotides such as ATP. This breakdown of ATP and other nucleotides makes it difficult to characterize and classify P2 purinoceptors. We have previously shown that the P2 purinergic antagonists, PPADS, suramin and reactive blue, act as ecto-ATPase inhibitors in various cell lines. Here, we show that the P2 purinergic agonists, ATPgammaS, alpha,beta-methylene ATP (alpha,beta-MeATP) and AMP-PNP, inhibit the ecto-ATPase of bovine pulmonary artery endothelial cells (CPAE), with pIC50 values of 5.2, 4.5 and 4.0, respectively. In CPAE, FPL67156, a selective ecto-ATPase inhibitor, also inhibits ecto-ATPase activity, with a pIC50 value of 4.0. In addition, alpha,beta-MeATP (3-100 microM), which itself does not induce phosphoinositide (PI) turnover, left-shifted the agonist-concentration effect (E/[A]) curves for ATP, 2MeS-ATP and UTP by approximate 100-300 fold, while those for ATPgammaS and AMP-PNP were only shifted approximately 2-3 fold. Moreover, in the presence of alpha,beta-MeATP, not only was the potentiation effect of PPADS on the UTP response lost, but a slight inhibition of the UTP response by PPADS was also seen. Thus, we conclude that the action of ATPgammaS, alpha,beta-MeATP and AMP-PNP as ecto-ATPase inhibitors account for their high agonist potency, and also provide information for the development of ecto-ATPase inhibitors of high selectivity and potency.
authors.affiliation: Department of Pharmacology, College of Medicine, National Taiwan University, Taipei.
authors.forename: B C
authors.initials: BC
authors.lastname: Chen
authors.forename: W W
authors.initials: WW
authors.lastname: Lin
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors*; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology*; D000345:Affinity Labels; D000818:Animals; D002417:Cattle; D004727:Endothelium / Q000201:enzymology / Q000378:metabolism; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D058910:Purinergic P2 Receptor Agonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D000345:Affinity Labels; D010975:Platelet Aggregation Inhibitors; D058910:Purinergic P2 Receptor Agonists; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D000266:Adenylyl Imidodiphosphate; C022571:adenosine 5'-O-(3-thiotriphosphate); D011732:Pyridoxal Phosphate; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; C027201:ectoATPase; C002630:alpha,beta-methyleneadenosine 5'-triphosphate