P2Y 13 receptor is responsible for ADP-mediated degranulation in RBL-2H3 rat mast cells

Abstract

Extracellular ADP is known to play many important physiological roles. In this study, we identified the P2Y 13 receptor in a rat mast cell line (RBL-2H3) and explored the functional role of ADP, its endogenous agonist. ADP induced both intracellular calcium mobilization and release of hexosaminidase (Hex). In an assay of intracellular calcium, ADP was 100-fold less potent than and equally efficacious as the P2Y 1 receptor-selective agonist MRS2365. However, ADP was more potent and efficacious than MRS2365 in inducing Hex release and in enhancing antigen-induced Hex release. ADP-induced intracellular calcium mobilization was blocked by phospholipase C inhibitor U73122 and by P2Y 1 receptor-selective antagonist MRS2500, but not by pertussis toxin (PTX), suggesting a mechanism mediated by the G q-coupled P2Y 1 receptor, but not P2Y 13 (G i-coupled) or P2X receptors. ADP-induced Hex release was blocked by PTX and a selective P2Y 13 receptor antagonist MRS2211, but not by MRS2500 or P2Y 1 receptor-specific siRNA, suggesting a G i-coupled P2Y 13 receptor-related mechanism. Measurement of gene expression confirmed high expression of both P2Y 1 and P2Y 13 receptors (in comparison to a previously reported P2Y 14 receptor) in RBL-2H3 cells. Thus, we demonstrated that ADP-mediated intracellular calcium mobilization and Hex release in RBL-2H3 cells are via P2Y 1 and P2Y 13 receptors, respectively. Selective antagonists of the P2Y 13 receptor might be novel therapeutic agents for various allergic conditions.