Coordination of agonist-induced Ca2+-signalling patterns by NAADP in pancreatic acinar cells

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Abstract
Many hormones and neurotransmitters evoke Ca2+ release fromintracellular stores, often triggering agonist-specific signatures of intracellular Ca2+ concentration1,2,3,4,5. Inositol trisphosphate (InsP3)1 and cyclic adenosine 5′-diphosphate-ribose (cADPR)6,7 are established Ca2+-mobilizing messengers that activate Ca2+ release through intracellular InsP3 and ryanodine receptors, respectively8,9,10. However, in pancreatic acinar cells, neither messenger can explain the complex pattern of Ca2+ signals triggered by the secretory hormone cholecystokinin (CCK). We show here that the Ca2+-mobilizing molecule nicotinic acid adenine dinucleotide phosphate (NAADP)7,11,12,13,14,15, an endogenous metabolite of β-NADP, triggers a Ca2+ response that varies from short-lasting Ca2+ spikes to a complex mixture of short-lasting (1–2 s) and long-lasting (0.2–1 min) Ca2+ spikes. Cells were significantly more sensitive to NAADP than to either cADPR or InsP3, whereas higher concentrations of NAADP selectively inactivated CCK-evoked Ca2+ signals in pancreatic acinar cells, indicating that NAADP may function as an intracellular messenger in mammalian cells.