Sarcospan (SSPN)

Sarcospan, discovered by the research group of Kevin Campbell, is a 25-kDa transmembrane protein located in the dystrophin-associated protein complex of skeletal muscle cells. It contains four transmembrane spanning helices with both N- and C-terminal domains located intracellularly. Loss of sarcospan expression occurs in patients with Duchenne muscular dystrophy, indicating that dystrophin is required for proper localization of sarcospan. Interestingly, sarcospan knockout mice exhibit normal muscle structure and function, indicating that sarcospan is not necessary for muscle to develop.Isoform 1 is expressed exclusively in heart and skeletal muscle. Isoform 2 is expressed in heart, skeletal muscle, thymus, prostate, testis, ovary, small intestine, colon and spleen.