Variations in dystrophin complex in red and white caudal muscles from Torpedo marmorata

We present an up-to-date study on the nature, at the protein level, of vari ous members of the dystrophin complex at the muscle cell membrane by compar ing red and white caudal muscles from Torpedo marmorata. Our investigations involved immunodetection approaches and Western blotting analysis. We dete rmined the presence or absence of different molecules belonging to the dyst rophin family complex by analyzing their localization and molecular weight. Specific antibodies directed against dystrophin, i.e., DRP2 alpha -dystrob revin, beta -dystroglycan, alpha -syntrophin, alpha-, beta-, gamma-, acid d elta -sarcoglycan, and sarcospan, were used. The immunofluorescence study ( confocal microscopy) showed differences in positive immunoreactions at the sarcolemmal membrane in these slow-type and fast-type skeletal muscle fiber s. Protein extracts from T. marmorata red and white muscles were analyzed b y Western blotting and confirmed the presence of dystrophin and associated proteins at the expected molecular weights. Differences were confirmed by c omparative immunoprecipitation analysis of enriched membrane preparations w ith anti-beta -dystroglycan polyclonal antibody. These experiments revealed clear complex or non-complex formation between members of the dystrophin s ystem, depending on the muscle type analyzed. Differences in the potential function of these various dystrophin complexes in fast or slow muscle fiber s are discussed in relation to previous data obtained in corresponding mamm alian tissues.