Multiple calcium stores: separate but interacting

Multiple mechanisms exist for increasing the concentration of intracellular calcium. This Perspective by Lee is one in a series on intracellular calcium release mechanisms and focuses on the calcium store operated by nicotinic acid adenine dinucleotide phosphate (NAADP). The characterization of the NAADP-operated calcium store as separate from the inositol trisphosphate (IP(3))-operated and cyclic ADP-ribose (cADPR)-operated calcium stores is discussed. Lee also addresses the role of NAADP in regulating intracellular calcium fluctuations during fertilization and hormonal activation of pancreatic acinar cells.