Ecto-nucleotide pyrophosphatase modulates the purinoceptor-mediated signal transduction and is inhibited by purinoceptor antagonists.
1. The effect of ecto-nucleotide pyrophosphatase (ecto-NPPase; EC 3.6.1. 9) on the ATP- and ADP-mediated receptor activation was studied in rat C6 glioma cells. The P2-purinoceptor antagonists pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) and reactive blue (RB2) are potent inhibitors (IC(50)=12+/-3 microM) of the latter enzyme. 4,4'-diisothiocyanatostilbene-2,2' disulfonic acid (DIDS), 5'-phosphoadenosine 3'-phosphate (PAP) and suramin were less potent inhibitors with an IC(50) of 22+/-4, 36+/-7 and 72+/-11 microM respectively. 2. P1-purinoceptor antagonists CGS 15943, cyclo-pentyl theophylline (CTP) and theophylline did not affect the activity of the ecto-NPPase. 3. ATP- and ADP-mediated P2Y(1)-like receptor activation inhibited the (-)-isoproterenol-induced increase of intracellular cyclic AMP concentration. PPADS, an ineffective P2Y-antagonist in C6, potentiated the ATP and ADP effect approximately 3 fold due to inhibition of nucleotide hydrolysis by the ecto-NPPase. 4. We conclude that ecto-NPPase has a modulator effect on purinoceptor-mediated signalling in C6 glioma cell cultures.
Grobben
B
B
Department of Biochemistry, Cellular Biochemistry, University of Antwerp, Universitaire Instelling Antwerpen, Universiteitplein 1, B-2610 Antwerpen-Wilrijk, Belgium.
Claes
P
P
Roymans
D
D
Esmans
E L
EL
Van Onckelen
H
H
Slegers
H
H
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D058919:Purinergic P2 Receptor Antagonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D011755:Pyrophosphatases / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058472:Receptors, Purinergic P2Y1; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
C546384:P2ry1 protein, rat; D010975:Platelet Aggregation Inhibitors; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D011755:Pyrophosphatases; C021899:nucleotide pyrophosphatase