EPSILON-SARCOGLYCAN, A BROADLY EXPRESSED HOMOLOG OF THE GENE MUTATED IN LIMB-GIRDLE MUSCULAR-DYSTROPHY 2D

The sarcoglycans are transmembrane components of the dystrophin-glycop rotein complex, which links the cytoskeleton to the extracellular matr ix in adult muscle fibers. Mutations in all four known sarcoglycan gen es (alpha, beta, gamma, and delta) have been found in humans with limb -girdle muscular dystrophy. We have identified a novel protein, epsilo n-sarcoglycan, that shares 44% amino acid identity with alpha-sarcogly can (adhalin). We show that epsilon-sarcoglycan is a membrane-associat ed glycoprotein and document its expression by Northern blotting, immu noblotting, and immunofluorescence. In contrast to alpha-delta sarcogl ycans, which are expressed predominantly or exclusively in striated mu scle, epsilon-sarcoglycan is broadly distributed in muscle and nonmusc le cells of both embryos and adults. These results raise the possibili ty that sarcoglycan-containing complexes mediate membrane-matrix inter actions in many cell types.