Three Ca2+ ATPases have been described in mammalian cells. They are located in the plasma membrane, endoplasmic reticulum or the Golgi apparatus. SERCA pumps are located in both the endoplasmic reticulum and in the Golgi membranes. They are known to transport two Ca2+ molecules per hydrolysis of one ATP1. Their structure includes ten transmembrane domains and their main role is to remove cytoplasmic Ca2+ ions in order to promote muscle relaxation1.
In mammals three genes encode three SERCA pumps. Each transcript undergoes tissue-dependent alternative splicing. SERCA1a and 1b are expressed in adult and neonatal skeletal muscle respectively. SERCA2a is also expressed in skeletal muscle, while SERCA2b is ubiquitously expressed. SERCA3 is expressed in a limited number of non-muscle cells2. Although all SERCAs are regulated, SERCA2b undergoes extensive regulation at the protein level, such as protein-protein interaction, phosphorylation and glycosylation1.
SERCA2 catalyzes the hydrolysis of ATP coupled with the translocation of calcium from the cytosol into the sarcoplasmic reticulum lumen, and is involved in regulation of the contraction/relaxation cycle. Mutations in this gene cause Darier-White disease, also known as keratosis follicularis, an autosomal dominant skin disorder characterized by loss of adhesion between epidermal cells and abnormal keratinization3,4.
