LOCALIZATION OF DYSTROPHIN AND DYSTROPHIN-RELATED PROTEIN AT THE ELECTROMOTOR SYNAPSE AND NEUROMUSCULAR-JUNCTION IN TORPEDO-MARMORATA

The immunological identification of dystrophin isoforms at the neuromuscular junction and Torpedo marmorata electromotor synapse was attempted using various antibodies. A polyclonal antibody raised against electrophoretically purified dystrophin from T. marmorata electrocyte has been thoroughly investigated. This antibody recognized dystrophin in the electric tissue as well as sarcolemmal and synaptic neuromuscular junction dystrophin in all studies species (T. marmorata, rat, mice and human) at serum dilutions as high as 1:10,000. At variance, no staining of either the sarcolemma or neuromuscular junction was observed in Duchenne muscular dystrophy or mdx mice skeletal muscles. In these muscles, other members of the dystrophin superfamily, in particular the dystrophin-related protein(s) encoded by autosomal genes are present. These data thus demonstrate the specificity of our antibodies for dystrophin. Anti-dystrophin-related protein antibodies [Khurana et al. (1991) Neuromusc. Disorders 1, 185-194] which gave a strong immunostaining of the neuromuscular junction in various species, including T. marmorata, cross-reacted weakly with the postsynaptic membrane of the electrocyte. Taken together, these observations are in favor of the existence of a protein very homologous to dystrophin at the electromotor synapse in T. marmorata, whereas both dystrophin and dystrophin-related protein co-localize at the neuromuscular junction as in all species studied. The electrocyte thus offers the unique opportunity to study the interaction of dystrophin with components of the postsynaptic membrane.