Syncoilin, a novel member of the intermediate filament superfamily that interacts with alpha-dystrobrevin in skeletal muscle

Dystrophin coordinates the assembly of a complex of structural and signalin g proteins that are required for normal muscle function. A key component of the dystrophin protein complex is alpha -dystrobrevin, a dystrophin-associ ated protein whose absence results in neuromuscular junction defects and mu scular dystrophy. To gain further insights into the role of alpha -dystrobr evin in skeletal muscle, we used the yeast two-hybrid system to identify a novel alpha -dystrobrevin-binding partner called syncoilin. Syncoilin is a new member of the intermediate filament superfamily and is highly expressed in skeletal and cardiac muscle. In normal skeletal muscle, syn coilin is c oncentrated at the neuromuscular junction, where it colocalizes and coimmun oprecipitates with alpha -dystrobrevin-1. Expression studies in mammalian c ells demonstrate that, while alpha -dystrobrevin and syncoilin associate di rectly, overexpression of syncoilin does not result in the self-assembly of intermediate filaments. Finally, unlike many components of the dystrophin protein complex, we show that syncoiIin expression is upregulated in dystro phin-deficient muscle. These data suggest that alpha -dystrobrevin provides a link between the dystrophin protein complex and the intermediate filamen t network at the neuromuscular junction, which may be important for the mai ntenance and maturation of the synapse.