Biochem Biophys Res Commun 2002 Jul 26;2954:806-11. doi: 10.1016/s0006-291x(02)00761-1.

Effect of luminal and extravesicular Ca2+ on NAADP binding and release properties.

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Nicotinic acid adenine dinucleotide phosphate (NAADP) has been shown to be a powerful Ca2+ release agent in numerous systems, including echinoderms, plants, and mammalian cells. NAADP has been shown to release Ca2+ via a separate mechanism to IP3 and ryanodine receptors, and specific binding sites have recently been characterised. However, functional studies have shown that there is a functional interplay between the NAADP-sensitive mechanism and the other two. In particular, it appears that activation of the NAADP receptor might act as a trigger to facilitate responses from IP3 and ryanodine receptors. To further characterise this interplay, we have investigated the effects of luminal and cytosolic Ca2+ on the NAADP receptor in sea urchin egg homogenates. We report that neither cytosolic nor luminal Ca2+ appears to influence NAADP binding. Conversely, emptying of stores significantly amplifies NAADP-induced fractional Ca2+-release, providing a mechanism of self-adjustment independent of store loading.

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Genes referenced: LOC100887844 LOC115919080 LOC576539 LOC590297 LOC593358