Identification of bazedoxifene for the treatment of LGMD R2 by high throughput screening

Abstract

LGMD R2 is a rare genetic disorder characterized by progressive proximal muscle weakness and wasting caused by a recessive loss of function of dysferlin, a transmembrane protein controlling plasma membrane repair in skeletal muscles. We report here the development of anin vitrohigh-throughput assay using immortalized myoblasts and monitored reallocation of an aggregated mutant form of dysferlin (DYSFL1341P). Using this assay, we screened a library of 2239 drugs and identified two autophagy inducers, namely saracatinib and bazedoxifene, as potential drugs to repurpose for LGMD R2 patients carrying theDYSFL1341Pmutation. Functional characterization of these drugs revealed that saracatinib and bazedoxifene had a protective effect on the plasma membrane in osmotic shock assay. While saracatinib restores functionality in membrane resealing through a specific rescue of L1341P dysferlin from degradation, bazedoxifene demonstrates an additional protective effect on dysferlin KO mice muscle fibers. Finally, further investigations into the molecular mechanism of action of bazedoxifene revealed an induction of autophagy flux, which may underlie the molecule’s effect on the survival of LGMD R2 myofibers.