NAADP + is an agonist of the human P2Y 11 purinergic receptor

Abstract

Nicotinic acid adenine dinucleotide phosphate (NAADP +) is an intracellular second messenger releasing Ca 2+ from intracellular stores in different cell types. In addition, it is also active in triggering [Ca 2+] i increase when applied extracellularly and various underlying mechanisms have been proposed. Here, we used hP2Y 11-transfected 1321N1 astrocytoma cells to unequivocally establish whether extracellular NAADP + is an agonist of the P2Y 11 receptor, as previously reported for β-NAD + [I. Moreschi, S. Bruzzone, R.A. Nicholas, et al., Extracellular NAD + is an agonist of the human P2Y11 purinergic receptor in human granulocytes, J. Biol. Chem. 281 (2006) 31419–31429]. Extracellular NAADP + triggered a concentration-dependent two-step elevation of [Ca 2+] i in 1321N1-hP2Y 11 cells, but not in wild-type 1321N1 cells, secondary to the intracellular production of IP 3, cAMP and cyclic ADP-ribose (cADPR). Specifically, the transient [Ca 2+] i rise proved to be related to IP 3 overproduction and to consequent Ca 2+ mobilization, while the sustained [Ca 2+] i elevation was caused by the cAMP/ADP-ribosyl cyclase (ADPRC)/cADPR signalling cascade and by influx of extracellular Ca 2+. In human granulocytes, endogenous P2Y 11 proved to be responsible for the NAADP +-induced cell activation (as demonstrated by the use of NF157, a selective and potent inhibitor of P2Y 11), unveiling a role of NAADP + as a pro-inflammatory cytokine. In conclusion, we provide unequivocal evidence for the activation of a member of the P2Y receptor subfamily by NAADP +.