Enables calcium channel regulator activity. Involved in activation of store-operated calcium channel activity; calcium-mediated signaling using intracellular calcium source; and positive regulation of calcineurin-NFAT signaling cascade. Located in cortical endoplasmic reticulum; endoplasmic reticulum membrane; and endoplasmic reticulum-plasma membrane contact site. [provided by Alliance of Genome Resources, Apr 2022]