Myofibrillar myopathy-6 (MFM6) is rare, autosomal dominant neuromuscular disease that is characterised by devastating childhood muscular dystrophy, restrictive cardiomyopathy, and respiratory insufficiency. MFM-6 is caused by single base mutation in the gene encoding the co-chaperone BAG3 (Bcl-2 associated athanogene 3), resulting in a single amino acid exchange (P209L) in the human protein. BAG3 is strongly expressed in cross-striated muscles and plays a key role in the turnover of muscle-proteins by chaperone-assisted selected autophagy (CASA). To gain deeper insights into the pathophysiological mechanisms of the disease, we have recently generated a transgenic mouse model of the human mutation BAG3P209L, in which a fusion protein consisting of the human BAG3P209L and the green fluorescent protein eGFP are conditionally overexpressed. Ubiquitous overexpression of BAG3P209L-eGFP leads to a severe phenotype between the second and fourth week of life, including decreased body weight, skeletal muscle weakness, and heart failure. Here we investigate changes in the total proteome of skeletal muscle. Using biochemical fractionation, we further distinguish between changes in soluble protein content and proteins accumulation in triton x100-insoluble pellet fraction containing cytoskeletal and aggregating proteins