To be or not to be… Nicotinic acid adenine dinucleotide phosphate (NAADP): A new intracellular second messenger?

Nicotinic acid adenine dinucleotide phosphate (NAADP) is a potent activator of intracellular Ca2+ release in several vertebrate and invertebrate systems. The role of the NAADP system in physiologicalprocesses is being extensively investigated at the present time. The NAADP receptor and its associated Ca2+ pool have been hypothesized to be important in several physiologicalprocesses including fertilization, T cell activation, and pancreaticsecretion. However, whether NAADP is a new second messenger ora tool for the discovery of a new Ca2+ channel is still an unansweredquestion. Research developed over the last two years has provided some important clues to whether NAADP is or not a physiological cellular messenger. In this short review, I will discuss some of these new findings that are helping us to find an answer to the important question: Is NAADP a second messenger or not?