Insulin exocytosis and glucose-mediated increase in cytoplasmic free Ca2+ concentration in the pancreatic beta-cell are independent of cyclic ADP-ribose

• Published in: The Journal of biological chemistry 1996-08, Vol.271 (32), p.19074-19079
• Main Authors: Webb, D L, Islam, M S, Efanov, A M, Brown, G, Köhler, M, Larsson, O, Berggren, P O
• Format: Article
• Language: English
• Subjects: Adenosine Diphosphate Ribose - analogs & derivatives; Adenosine Diphosphate Ribose - antagonists & inhibitors; Adenosine Diphosphate Ribose - metabolism; Animals; Calcium - metabolism; Cyclic ADP-Ribose; Cytoplasm - drug effects; Cytoplasm - metabolism; Exocytosis; Glucose - pharmacology; In Vitro Techniques; Insulin - metabolism; Islets of Langerhans - drug effects; Islets of Langerhans - metabolism; MEDICIN; Medicin och hälsovetenskap; MEDICINE; Mice; Mice, Obese; NAD - pharmacology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.271.32.19074

Stimulation of pancreatic beta-cells by glucose gives rise to an increase in the cytoplasmic free calcium concentration ([Ca2+]i) and exocytosis of insulin. Cyclic adenosine 5'-diphosphate ribose (cADPR), a metabolite of beta-NAD+, has been reported to increase [Ca2+]i in pancreatic beta-cells by releasing Ca2+ from inositol 1,4,5-trisphosphate-insensitive intracellular stores. In the present study, we have examined the role of cADPR in glucose-mediated increases in [Ca2+]i and insulin exocytosis. Dispersed ob/ob mouse beta-cell aggregates were either pressure microinjected with fura-2 salt or loaded with fura-2 acetoxymethyl ester, and [Ca2+]i was monitored by microfluorimetry. Microinjection of beta-NAD+ into fura-2-loaded beta-cells did not increase [Ca2+]i nor did it alter the cells' subsequent [Ca2+]i response to glucose. Cells microinjected with the cADPR antagonist 8NH2-cADPR increased [Ca2+]i in response to glucose equally well as those injected with cADPR. Finally, the ability of cADPR to promote exocytosis of insulin in electropermeabilized beta-cells was investigated. cADPR on its own did not increase insulin secretion nor did it potentiate Ca2+-induced insulin secretion. We conclude that cADPR neither plays a significant role in glucose-mediated increases in [Ca2+]i nor interacts directly with the molecular mechanisms regulating exocytosis of insulin in normal pancreatic beta-cells.