The sarcoglycan transmembrane proteins are members of the dystrophin
complex. Sarcoglycans cluster together to form a complex, which is localized
in the cell membrane of skeletal, cardiac and smooth muscle fibers. Four
sarcoglycan subunit proteins, designated α-, β-, γ- and δ-sarcoglycan, form
a complex on the skeletal muscle cell surface membrane. A genetic defect in
any one of these proteins causes the loss or marked decrease of the whole
sarcoglycan complex, which is observed in the autosomal recessive muscular
dystrophy, sarcoglycanopathy. In smooth muscle, β- and δ-sarcoglycans are
associated with ε-sarcoglycan, a glycoprotein homologous to α-sarcoglycan.
Additionally, a complete deficiency in δ-sarcoglycan is the cause of the Syrian
hamster BIO.14 cardiomyopathy.