ATP induces c-fos expression in C6 glioma cells by activation of P(2y) receptors

Background. Extracellular ATP functions in the enteric nervous system as a neurotransmitter, and recent evidence suggests ATP may regulate development through effects on cellular proliferation. Methods. The action of ATP at purinoceptors and the role of second messenger pathways in c-fos mRNA expression in C6 glioma cells were investigated using the techniques of Northern and Western blotting. Results. Treatment of C6 cells with ATP caused a time- and dose-dependent increase in c-fos expression. The rank order of agonist potency was ATP = ADP > γsATP > αβATP > βγATP > AMP = UTP. The ATP-induced c-fos increment was inhibited by three P(2Y) receptor antagonists - suramin, reactive blue, and DIDS - by 99 ± 3, 89 ± 7, and 61 ± 14%, respectively. The ATP-stimulated c-fos expression was attenuated by phospholipase C inhibitor (U73122), protein kinase C (PKC) down-regulation (4α-phorbol 12-myristate 13acetate and chelerythrine), mitogen-activated protein (MAP) kinase inhibition (apigenin), an inhibitor of MAP kinase kinase (PD98059), down-regulation of adenylate cyclase (SQ22536), and inhibition of type II protein kinase A (8-(4-chlorophenylthio)adenosine-3',5'-cyclic monophosphorothioate), hut was not affected by inhibition of type I protein kinase A (8bromoadenosine-3',5'-cyclic monophosphorothioate) and inhibitors of calmodulin kinase (KN93 and KN62). Phosphorylated MAP kinase was increased in cells exposed to ATP. This effect was suppressed by chelerythrine. Conclusions. These studies demonstrate that ATP-induced c-fos mRNA expression is under multifactorial regulation. (C) 2000 Academic Press.