Characterization of the dysferlin protein and its binding partners reveals rational design for therapeutic strategies for the treatment of dysferlinopathies

Abstract

Dysferlinopathies are incurable recessively inherited muscular dystrophies caused by loss of the dysferlin protein. Dysferlin is essential for the plasma membrane repair of skeletal muscle cells and is required for myotube formation. To design treatment strategies for dysferlinopathies, we studied dysferlinOs molecular biology and characterized the functionality of dysferlinOs seven C2 domains, its degradation pathway and its interaction with a novel protein, histone deacetylase 6. The results indicate that dysferlin and histone deacetylase 6 form a triad interaction with alpha-tubulin to modulate the acetylated alpha-tubulin levels of muscle cells, which may play a regulatory role during myotube formation. Furthermore, the characterization of dysferlinOs C2 domains revealed that there is functional redundancy in their ability to localize dysferlin to, and effect repair of, the plasma membrane. Taking these results into consideration, we designed shorter, functional dysferlin molecules for usage in gene therapy. To find a novel pharmacological therapy for patients with dysferlin deficiency, we investigated the inhibition of dysferlinOs degradation pathway. We demonstrated that when salvaged from proteasomal degradation, missense mutated dysferlin retained its biological activities for plasmalemmal localization, plasmalemmal repair and myotube formation. Further studies using recombinant missense mutated dysferlin constructs showed that certain missense mutants are intrinsically biologically active; whereas others lack functionality even when their levels are increased by transient transfection or by inhibiting their proteasomal degradation. Proteasomal inhibition represents a novel potential pharmacological treatment strategy for patients with dysferlin deficiency.