The Calpain family of proteins are calcium-regulated thiol proteases which have broad endopeptidase activity throughout the body. Calpain small subunit 2, also known as CSS2 or CAPNS2, is a calcium-dependent protease that is expressed ubiquitously in the cytoplasm. Part of a heterodimer composed of a small subunit and a large subunit, CSS2 catalyzes proteolysis of various proteins involved in cytoskeletal remodeling and signal transduction. CSS2 also acts as a chaperone to the larger subunit, mediating its correct folding and conformation. When bound as a heterodimer, CSS2 is thought to keep the catalytic activity of the large subunit dormant. After binding calcium, CSS2 is released from the complex, thereby activating the large subunit and allowing CSS2 to translocate from the cytoplasm to the cell membrane. Defects in the gene encoding CSS2 result in incorrect calpain activity and retarded fetal development, suggesting that CSS2 expression is essential for proper growth.
Calcium-dependent protease small subunit 2; Calpain small subunit 2; calpain, small subunit 2; CSS2