Involved in B-cell receptor (BCR)-induced Ca(2+) mobilization from intracellular stores. Promotes Lyn-mediated phosphorylation of IP3 receptors 1 and 2. Interacts with LYN, ITPR1 and ITPR2. Expressed in B-cell but not T-cell or myeloid cell lines. Highest expression in CD19(+) B-cells, with very low expression in other cell populations. Phosphorylated on tyrosines upon BCR activation. Disease susceptibility may be associated with variants affecting the gene represented in this entry.