P2Y12receptor stimulation inhibits β‐adrenergic receptor‐induced differentiation by reversing the cyclic AMP‐dependent inhibition of protein kinase B
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Open Access
- 22 March 2004
- journal article
- Published by Wiley in Journal of Neurochemistry
- Vol. 89 (2) , 442-453
Abstract
Cyclic AMP‐dependent induction of differentiation by activation of the β‐adrenergic receptor is correlated with inhibition of protein kinase B activity concomitant with growth arrest and increase in glial fibrillary acidic protein (GFAP) synthesis in rat C6 glioma cells. Costimulation of the β‐adrenergic receptor with purinergic receptors activated by 2‐methylthio‐adenosine‐5′‐diphosphate (2MeSADP) increased protein kinase B (PKB) phosphorylation above the level measured in non‐stimulated cells and abolished cAMP‐dependent differentiation. Transfection of cells with constitutively active PKB confirmed that reactivation of PKB is involved in the 2MeSADP‐dependent inhibition of GFAP synthesis. The P2Y12and P2Y13receptor antagonist AR‐C69931MX [N6‐(2‐methylthioethyl)‐2‐(3,3,3‐trifluoropropylthio)‐β,γ‐dichloro‐methylene ATP] decreased PKB phosphorylation to the level in non‐stimulated cells, whereas the P2Y13antagonists pyridoxalphosphate‐6‐azophenyl‐2′,4′‐disulfonic acid (PPADS) andP1,P3‐di(adenosine‐5′) tetraphosphate (Ap4A) did not alter the 2MeSADP‐induced phosphorylation of PKB, showing that enhanced PKB activity and subsequent phosphorylation of glycogen synthase kinase‐3 is due to stimulation of the P2Y12receptor. In addition, experiments in the presence of pertussis toxin and phosphatidylinositol 3‐kinase (PI 3‐K) activity assays demonstrated that the P2Y12receptor‐mediated increase in PKB phosphorylation is Giprotein‐ and PI 3‐K‐dependent. The presented data demonstrated that a cAMP‐dependent inhibition of PKB induces differentiation of C6 glioma cells and that inhibition of adenylate cyclase and reactivation of the PI 3‐K/PKB pathway by the P2Y12receptor reverses differentiation into enhanced proliferation.Keywords
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