P.145 - Molecular pathogenesis of caveolin-3-related limb-girdle muscular dystrophy

Abstract

Caveolin-3 is a muscle-specific protein involved in caveolae-formation, signal transduction, lipid metabolism, cell growth, mechanoprotection and apoptotic cell death. The protein, localized to the sarcolemma, usually appears during the myoblastic differentiation and interacts with the dystroglycan complex. Diseases caused by mutations in the CAV3 gene are called Caveolinopathies. To date, more than 40 pathogenic nonsynonimous CAV3 mutations have been described leading different disease phenotypes, such as Limb-girdle muscular dystrophy (LGMD), rippling muscle disease (RMD), distal myopathy (DM) and hyperCKemia (HCK). A transgenic animal model harboring a p.Pro105Leu missense mutation (Cav3P105L) represents a suitable phenocopy of a human LGMD caused by the same mutation. To understand the molecular aspects of the skeletal muscle impaired by this mutation, we performed unbiased label-free quantitative LC-MS/MS investigations of quadriceps muscles. Our data revealed up-regulation of 130 and down-regulation of 43 proteins. Notably, further immunoblot and immunohistochemistry studies confirmed the proteomic findings and were also in accordance with electron microscopic findings. Interestingly, localization studies of sarcolemma proteins, identified as affected in the proteome profile, do suggest a contribution in the molecular genesis of Caveolinopathy. To further elucidate the pathogenic character of Cav3P105L and to identify new binging partners of the wild-type protein, unbiased interaction screening (TAP-assay) was performed. These studies revealed a new binding partner for missense mutant CAV3 proteins, supporting the idea of a pathogenic gain of function. As this binding partner mediates plasma membrane repair in muscle and has been linked to the pathophysiology of Dyferlinopathies, our data strengthens the concept of common pathomechanisms in LGMD caused by mutations of components of the dystroglycan complex.