ATP2C1, also known as secretory pathway Ca2+/Mn2+-ATPase (SPCA) 1, belongs to the family of P-type cation transport ATPases. This magnesium-dependent enzyme catalyzes the hydrolysis of ATP coupled with the transport of the calcium from the cytosol to the Golgi lumen. Defects in this gene cause Hailey-Hailey disease, an autosomal dominant disorder characterized by persistent blisters and erosions of the skin. Unlike the related protein ATP2C2, ATP2C1 is ubiquitously expressed and displays a lower maximal turnover rate for overall Ca2+-ATPase reaction and a higher apparent affinity for cytosolic Ca2+ activation of phosphorylation. Recent evidence suggests that ATP2C1 is a key regulator of insulin-like growth factor receptor (IGF1R) processing in tumor progression in basal breast cancers.