Coordinating Calcium Release

Science's STKE  28 Mar 2000:
Vol. 2000, Issue 25, pp. tw3
DOI: 10.1126/stke.2000.25.tw3

Several mechanisms exist for releasing intracellular stores of calcium: activation of inositol trisphosphate (IP3) receptors, activation of ryanodine receptors, and stimulation of Ca2+ release by nicotinic acid adenine dinucleotide phosphate (NAADP+). Santella et al. studied calcium fluxes in starfish oocytes in response to injected caged NAADP+. Photolysis of the caged NAADP+ led to an increase in intracellular calcium [Ca2+]i that was partially blocked by the addition of both heparin (to block Ca2+ release from IP3 receptors) and 8-NH2-cyclic ADPribose (to block Ca2+ release from ryanodine receptors). The authors suggest that NAADP+ initiates an increase in [Ca2+]i that triggers further release from IP3 and ryanodine receptor-operated stores. Additionally, NAADP+ stimulated an increase in [Ca2+]i from intracellular stores in immature oocytes, but the NAADP+-stimulated increase in [Ca2+]i in mature oocytes was derived from extracellular sources of calcium, suggesting that the NAADP+-sensitive compartment fused with the plasma membrane as a consequence of oocyte maturation.

Santella, L., Kyozuka, K., Genazzani, A.A., De Riso, L., and Carafoli, E. (2000) Nicotinic acid adenine dinucleotide phosphate-induced Ca2+ release. J. Biol. Chem. 275: 8301-8306. [Abstract] [Full Text]