Nicotinic acid adenine dinucleotide phosphate (NAADP) binding protein. Confers NAADP sensitivity to the two pore channel complex (TPCs) by acting as TPC accessory protein necessary for NAADP-evoked Ca(2+) release. Found in a complex with LSM12, TPCN1 and TPCN2. Interacts with TPCN2. Colocalizes with TPCN2. Belongs to the LSM12 family.