ATP-evoked Ca2+ transients and currents in murine thymocytes: possible role for P2X receptors in death by neglect

The P2X family of ATP receptors (P2XR) have been implicated in thymocyte de ath in vitro and in vivo. We characterized ATP-evoked Ca2+ transients and m embrane currents in thymocytes to better understand the role of P2XR during thymocyte development. ATP(4-), but not UTP or GTP, activated a sustained non-selective cation current in voltage-clamped CD4(-) CD8(-) and CD4(+)CD8 (+) thymocytes that was reversed by apyrase, which hydrolyzes ATP, and by t he P2XR antagonists suramin and pyridoxalphosphate-6-amophsnyl-2',4'-disulf onic acid (PPADS). The more selective P2XR agonist alpha beta-methylene ATP activated a smaller rapidly decaying current in both thymocyte populations . Reverse transcription-PCR results indicate that P2X1, P2X2, P2X6, and/or P2X7 are expressed in thymocytes. Finally, we used PPADS to examine the rol e of P2XR during thymocyte development in situ. PPADS-treated thymi yielded significantly more thymocytes (38 %), due to a selective increase in CD4()CD8(+) cells. Together these data suggest that one or more PPADS-sensitive P2XR (P2X1, P2X2, P2X7) are involved in thymocyte apoptosis, and we propos e more specifically a role associated with death by neglect.