NAADP Signaling: New Kids on the Block

Nicotinic acid adenine dinucleotide phosphate (NAADP) is a universal Ca(2+) mobilizing second messenger essential for initiation of Ca(2+) signaling. Recently, novel molecular mechanisms of both its rapid formation upon receptor stimulation and its mode of action were discovered. Dual NADPH oxidase 2 (DUOX2) and hematological and neurological expressed 1-like protein (HN1L)/Jupiter microtubule-associated homolog 2 (JPT2) were discovered as NAADP-forming enzyme and NAADP receptor/binding protein—the new kids on the block. These novel aspects are reviewed and integrated into the previous view of NAADP signaling.