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 death in vitro and in vivo. We characterized ATP-evoked Ca2+ transients and membrane currents in thymocytes to better understand the role of P2XR during thymocyte development. ATP4-, 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 the P2XR antagonists suramin and pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS). The more selective P2XR agonist alphabeta-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 role 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 propose more specifically a role associated with death by neglect.
Freedman
B D
BD
Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia 19104, USA. bruce@vet.upenn.edu
Liu
Q H
QH
Gaulton
G
G
Kotlikoff
M I
MI
Hescheler
J
J
Fleischmann
B K
BK
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D016923:Cell Death; D015870:Gene Expression; D051379:Mice; D008810:Mice, Inbred C57BL; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013950:Thymus Gland / Q000166:cytology*
D018048:Receptors, Purinergic P2; D000255:Adenosine Triphosphate; D002118:Calcium