Sarcoglycans are a family of membrane glycoproteins that associate to form the sarcoglycan protein complex, which is responsible for connecting the muscle fiber cytoskeleton to the extracellular matrix, thereby affording support and stability to the muscles. Alpha sarcoglycan is one of the proteins in this complex. In fact, alpha sarcoglycan is the protein that is most loosely associated with the other glycoproteins in the complex. This sarcoglycan complex itself, interacts with other proteins like dystrophins, dystrophin associated glycoproteins, and dystroglycans to form the dystrophin-glycoprotein complex, which in turn functions to bind actin to the extracellular matrix of myocytes. Expression studies indicate that the gene expresses itself mostly in the skeletal muscles, diaphragm, and cardiac muscles, while small amounts are also expressed in the bladder and small intestine.
Mutations in the SGCA gene are responsible for LGMDR3 (autosomal recessive limb-girdle muscular dystrophy-3). In patients with LGMDR3, alpha sarcoglycan is absent from the myocyte membranes, thereby explaining the physiology of the disease. In fact, the name adhalin for the protein product of the gene comes from the Arabic word for muscle (Adhal), which is severely affected in the disease condition.