Identification of ASPDH as a novel NAADP-binding protein

Nicotinic acid adenine dinucleotide phosphate (NAADP) is a signaling molecule that can induce calcium release from intracellular acidic stores. However, proteins that bind to NAADP are understudied. Here, we identify aspartate dehydrogenase domain-containing protein (ASPDH) as an NAADP-binding protein through biochemical purification from pig livers. Isothermal titration calorimetry (ITC) experiment using the recombinantly expressed protein shows a 1:1 binding stoichiometry and a Kd of 455 nM between NAADP and mouse ASPDH. In contrast, recombinantly expressed Jupiter microtubule-associated homolog 2 (JPT2) and SM-like protein LSM12, two proteins previously identified as NAADP-receptors, show no binding in ITC experiments.