Proteomic analysis of dystrophin deficiency and associated changes in the aged mdx-4cv heart model of dystrophinopathy-related cardiomyopathy

Cardiomyopathy is a serious complication in Duchenne muscular dystrophy, an X-linked neuromuscular disease of childhood that is triggered by primary abnormalities in the dystrophin gene. In order to directly correlate the deficiency in the membrane cytoskeletal protein dystrophin to secondary abnormalities in the dystrophic heart, this study has used label-free mass spectrometry to compare protein expression patterns in the aged mdx-4cv heart model of dystrophinopathy versus wild type heart. This report is the first successful identification of members of the cardiac dystrophin-glycoprotein complex by comparative whole tissue proteomics. The mass spectrometric analysis confirmed the loss of dystrophin and concomitant reduction of syntrophin and sarcoglycans in the dystrophin-deficient heart. Proteomic profiling of secondary changes identified distinct alterations in the basal lamina component laminin, the Ca(2+)-binding protein sarcalumenin, the matricellular protein periostin, the proteoglycans asporin and lumican, the cardiac-specific myosin light chain kinase, heat shock proteins and a large number of mitochondrial and glycolytic enzymes. The proteomic findings indicate that the molecular pathogenesis of muscular dystrophy-associated cardiomyopathy is highly complex and involves impairments, modulations and/or adaptations of mitochondrial metabolism, glycolysis, protein chaperoning and ion homeostasis, as well as the maintenance of the contractile apparatus, the intracellular cytoskeleton and the extracellular matrisome.

Significance: The X-linked inherited disorder Duchenne muscular dystrophy is the most frequently inherited neuromuscular disease of childhood. Primary abnormalities in the dystrophin gene trigger progressive skeletal muscle wasting and impaired cardiorespiratory functions. In order to improve our general understanding of the molecular pathogenesis of muscular dystrophy-associated cardiomyopathy and to identify new marker candidates of cardiac changes in dystrophinopathy, we have carried out a comparative proteomic study of the mdx-4cv mouse model of Duchenne muscular dystrophy. The mass spectrometric profiling of whole heart preparations has identified the reduction in the dystrophin-glycoprotein complex and a large variety of secondary changes in the dystrophic heart. Cardiac proteins with a changed abundance were shown to be involved in fibre contraction, energy metabolism, cellular signalling, the cytoskeletal network, the extracellular matrix and the stress response. In the future, the newly identified cardiac proteins may be useful to improve predictive, diagnostic, prognostic or therapy-monitoring approaches in the field of muscular dystrophy and cardiomyopathy.