CAPN3: A muscle­specific calpain with an important role in the pathogenesis of diseases (Review).

Calpains are a family of Ca2+­dependent cysteine proteases that participate in various cellular processes. Calpain 3 (CAPN3) is a classical calpain with unique N­terminus and insertion sequence 1 and 2 domains that confer characteristics such as rapid autolysis, Ca2+­independent activation and Na+ activation of the protease. CAPN3 is the only muscle­specific calpain that has important roles in the promotion of calcium release from skeletal muscle fibers, calcium uptake of sarcoplasmic reticulum, muscle formation and muscle remodeling. Studies have indicated that recessive mutations in CAPN3 cause limb­girdle muscular dystrophy (MD) type 2A and other types of MD; eosinophilic myositis, melanoma and epilepsy are also closely related to CAPN3. In the present review, the characteristics of CAPN3, its biological functions and roles in the pathogenesis of a number of disorders are discussed.