Nicotinic acid adenine dinucleotide phosphate (NAADP) binding protein required for NAADP-evoked intracellular calcium release (PubMed:33758061, PubMed:33758062). Confers NAADP-sensitivity to the two pore channels (TPCs) complex (PubMed:33758061). Enables NAADP to activate Ca(2+) release from the endoplasmic reticulum through ryanodine receptors (PubMed:33758062). ; (Microbial infection) Involved in the endolysosomal trafficking of human coronavirus SARS-CoV-2.