Calumin, a Ca2+-binding protein on the endoplasmic reticulum, alters the ion permeability of Ca2+ release-activated Ca2+ (CRAC) channels

► We examine whether ER Ca2+-binding protein calumin modulates CRAC channel activity. ► Co-expression of calumin with Orai1 does not form CRAC channel. ► Calumin is directly associated with Orai1 and STIM1. ► Ca2+ permeability of CRAC channels is decreased when co-expressed with calumin. ► Ca2+ influx via CRAC channels is attenuated by co-transfection of calumin.