Two subtypes of G protein-coupled nucleotide receptors P2Y1 and P2Y2 are involved in calcium signalling in glioma C6 cells

摘要

class="enumerated" style="list-style-type:decimal">In glioma C6 cells, the stimulation of P2Y receptors by ADP, ATP and UTP initiated an increase in the intracellular Ca²⁺ concentration, in a process that involved the release of Ca²⁺ from InsP3-sensitive store and the capacitative, extracellular Ca²⁺ entry. The presence of external Ca²⁺ was not necessary to elevate Ca²⁺.The rank order of potencies of nucleotide analogues in stimulating [Ca²⁺]i was: 2MeSADP > ADP > 2MeSATP = 2ClATP > ATP > UTP. α,β-Methylene ATP, adenosine and AMP were ineffective.ADP and UTP effects were additive, while actions of ATP and UTP were not additive on [Ca²⁺]i increase. Similarly, cross-desensitization between ATP and UTP but not between ADP and UTP occurred.Suramin, a non-specific nucleotide receptors inhibitor, antagonized ATP-, UTP- and ADP-evoked Ca²⁺ responses. PPADS, a selective antagonist of the P2Y1 receptor-generated InsP3 accumulation, decreased ADP-initiated Ca²⁺ response with no effect on ATP and UTP.Pertussis toxin (PTX) reduced ADP- and ATP-induced Ca²⁺ increases. Short-term treatment with TPA, inhibited both ATP and ADP stimulatory effects on [Ca²⁺]i.ADP inhibited isoproterenol-induced cyclic AMP accumulation. PTX blocked this effect, but PPADS did not.RT – PCR analysis revealed the molecular identity of P2Y receptors expressed by glioma C6 cells to be both P2Y1 and P2Y2.It is concluded that both P2Y1 and P2Y2 receptors co-exist in glioma C6 cells. ADP acts as agonist of the first, and ATP and UTP of the second one. Both receptors are linked to phospholipase C (PLC).