摘要
The Ca2+ signals that control almost every cellular activity are generated by regulating Ca2+ transport, usually via Ca2+-permeable channels, across the plasma membrane or the membranes of intracellular organelles. The most widespread and best understood of the intracellular Ca2+ channels are inositol trisphosphate receptors (IP3R) and ryanodine receptors, most of which are expressed in the endoplasmic or sarcoplasmic reticulum. However, accumulating evidence suggests physiological roles for many additional Ca2+ channels in both ER and other intracellular organelles. Interactions between these channels, whether mediated by Ca2+ itself or interactions between proteins, is a recurrent feature of the Ca2+ signals evoked by physiological stimuli. We focus on two specific examples, clustering of IP3Rs and NAADP (nicotinic acid dinucleotide phosphate)-evoked Ca2+ release from endo-lysosomes, to illustrate the diversity of Ca2+ channels and the interplay between them.