Originally identified as Kirsten ras associated gene (krag),[1]Sarcospan (SSPN) (is a 25-kDa transmembrane protein located in the dystrophin-associated protein complex of skeletal muscle cells, where it is most abundant.[1] It contains four transmembrane spanning helices with both N- and C-terminal domains located intracellularly.[2] Loss of SSPN expression occurs in patients with Duchenne muscular dystrophy. Dystrophin is required for proper localization of SSPN.[2] SSPN is also an essential regulator of Akt signaling pathways. Without SSPN, Akt signaling pathways will be hindered and muscle regeneration will not occur.[1]
Sarcospan in Muscular Dystrophy
The loss of dystrophin results in muscular dystrophy.[3] SSPN upregulates the levels of Utrophin-glycoprotein complex (UGC) to make up for the loss of dystrophin in the neuromuscular junction.[3] Sarcoglycans bind to SSPN and form the SG-SSPN complex, which interacts with dystroglycans (DG) and Utrophin leading to the formation of the UGC.[4] SSPN regulates the amount of Utrophin produced by the UGC to restore laminin binding due to the absence of dystrophin.[5] If laminin binding is not restored by SSPN, contraction of the membrane is present.[5] In dystrophic mdx mice, SSPN increases levels of Utrophin and restores the levels of laminin binding, reducing the symptoms of muscular dystrophy [5]
References
↑ 1.01.11.2Marshall JL, Crosbie-Watson RH (January 2013). "Sarcospan: a small protein with large potential for Duchenne muscular dystrophy". Skeletal Muscle. 3 (1): 1. doi:10.1186/2044-5040-3-1. PMID23282144.
↑ 2.02.1Crosbie RH, Heighway J, Venzke DP, Lee JC, Campbell KP (December 1997). "Sarcospan, the 25-kDa transmembrane component of the dystrophin-glycoprotein complex". The Journal of Biological Chemistry. 272 (50): 31221–4. doi:10.1074/jbc.272.50.31221. PMID9395445.
