KY peptidase (Kyphoscoliosis peptidase) is a 561 amino acid cytoskeleton protease that interacts with several sarcomeric cytoskeletal proteins, including Filamin 2. KY peptidase probably plays a role in the maturation, function and stabilization of the neuromuscular junction. KY-null mouse mutants exhibit distinct irregular subceullular Filamin 2 localization, suggesting that KY peptidase deficiency may be the cause of several types of limb-girdle muscular dystrophies.