Intracellular binding of fukutin and alpha-dystroglycan: relation to glycosylation of alpha-dystroglycan.

The functions of fukutin, a gene product responsible for Fukuyama type congenital muscular dystrophy, still remain unclear, although a relation to the glycosylation of alpha-dystroglycan is presumed. To investigate the functions of fukutin, immunohistochemistry, examination using cultured astrocytes, enzyme-linked immunosorbent assay (ELISA)-based binding assay and immunoprecipitation were performed using control muscle and central nervous system tissues. Immunohistochemistry showed that alpha-dystroglycan and fukutin were co-expressed, especially in the glial cytoplasm and glia limitans of the central nervous system. An anti-fukutin antibody added to the culture medium did not bring about any changes in the astrocytes cultured on laminin-coated dishes. Together with the immunohistochemical results, the intracellular function of fukutin is considered. ELISA-based binding assay and immunoprecipitation may suggest the direct binding of fukutin and alpha-dystroglycan, at least in part. Fukutin seems to bind to both the hypoglycosylated and fully glycosylated form of alpha-dystroglycan, and seems bind to the core area rather than the sugar chain of alpha-dystroglycan. Fukutin may directly interact with alpha-dystroglycan during glycosylation, but further examinations are needed to confirm these details.