Nicotinic Acid Adenine Dinucleotide Phosphate (NAADP) and Endolysosomal Two-pore Channels Modulate Membrane Excitability and Stimulus-Secretion Coupling in Mouse Pancreatic Cells

作者：Arredouani Abdelilah^*; Ruas Margarida; Collins Stephan C; Parkesh Raman; Clough Frederick; Pillinger Toby; Coltart George; Rietdorf Katja; Royle Andrew; Johnson Paul; Braun Matthias; Zhang Quan; Sones William; Shimomura Kenju; Morgan Anthony J; Lewis Alexander M; Chuang Kai Ting; Tunn Ruth; Gadea Joaquin; Teboul Lydia; Heister Paula M; Tynan Patricia W; Bellomo Elisa A; Rutter Guy A; Rorsman Patrik; Churchill Grant C; Parrington John; Galione Antony

来源：JOURNAL OF BIOLOGICAL CHEMISTRY, 2015, 290(35): 21376-21392.

DOI：10.1074/jbc.M115.671248

• diabetes
• endosome
• insulin
• lysosome
• nicotinic acid adenine dinucleotide phosphate (NAADP)
• TPC1
• TPC2

Background: TPCs are regulated by NAADP and other factors. Results: NAADP-induced Ca2+ release from acidic stores evokes depolarizing currents in pancreatic cells. Inhibition of NAADP signaling or TPC knock out attenuates Ca2+ signaling and insulin secretion. Conclusion: NAADP-evoked Ca2+ release enhances cell excitability and insulin secretion in response to glucose or sulfonylureas. Significance: NAADP signaling pathways offer novel therapeutic targets for diabetes treatment.
Pancreatic cells are electrically excitable and respond to elevated glucose concentrations with bursts of Ca2+ action potentials due to the activation of voltage-dependent Ca2+ channels (VDCCs), which leads to the exocytosis of insulin granules. We have examined the possible role of nicotinic acid adenine dinucleotide phosphate (NAADP)-mediated Ca2+ release from intracellular stores during stimulus-secretion coupling in primary mouse pancreatic cells. NAADP-regulated Ca2+ release channels, likely two-pore channels (TPCs), have recently been shown to be a major mechanism for mobilizing Ca2+ from the endolysosomal system, resulting in localized Ca2+ signals. We show here that NAADP-mediated Ca2+ release from endolysosomal Ca2+ stores activates inward membrane currents and depolarizes the cell to the threshold for VDCC activation and thereby contributes to glucose-evoked depolarization of the membrane potential during stimulus-response coupling. Selective pharmacological inhibition of NAADP-evoked Ca2+ release or genetic ablation of endolysosomal TPC1 or TPC2 channels attenuates glucose- and sulfonylurea-induced membrane currents, depolarization, cytoplasmic Ca2+ signals, and insulin secretion. Our findings implicate NAADP-evoked Ca2+ release from acidic Ca2+ storage organelles in stimulus-secretion coupling in cells.

• 出版日期2015-8-28