Desmin is oxidized and nitrated in affected muscles in myotilinopathies and desminopathies

Degenerative diseases with abnormal protein aggregates are characterized by the accumulation of proteins with variable post-translational modifications including phosphorylation, glycoxidation, oxidation, and nitration. Myofibrillar myopathies, including myotilinopathies and desminopathies, are characterized by the intracytoplasmic focal accumulation of proteins in insoluble aggregates in muscle cells. By using single immunohistochemistry, monodimensional gel electrophoresis and Western blotting, and bidimensional gel electrophoresis, in-gel digestion, and mass spectometry, desmin was demonstrated to be a major target of oxidation and nitration in both desminopathies and myotilinopathies. Because oxidized and nitrated proteins may have toxic effects and may impair ubiquitin-proteasomal function, modified desmin can be considered to be an additional element in the pathogenesis of myofibrillar myopathies. In addition to desmin, pyruvate kinase muscle splice form M1 is oxidized, thus supporting complemental mitochondrial damage, at least in some cases of myotilinopathy.