Acetylome mapping of tibialis anterior muscle from mdx mice upon pharmacological Sirtuin1 activation

Duchenne muscular dystrophy (DMD) is an X-linked muscular disease, characterized by dystrophin deficiency due to a mutation in the gene encoding for this protein. Dystrophin deficiency leads to a cascade of several events, such as membrane instability, chronic inflammation, muscle degeneration and myofiber necrosis. As muscle regeneration processes decrease, muscle fibers are gradually replaced by connective and adipose tissue.

While remarkable progress has been made in genetic approaches to restore dystrophin, or its function, targeting secondary pathological mechanisms remains an important issue to improve the efficacy of therapeutic interventions depending on tackling either the lacking gene or the downstream consequences. Besides, genetic approaches seem to be effective only in a limited number of patients and for this reason, it is necessary to focus on pharmacological strategies applicable to all DMD patients.An emerging therapeutic target for DMD seems to be the activation of Sirtuin1 (SIRT1). SIRT1 belongs to a class of NAD+-dependent class III histone/deacetylase proteins, the sirtuins. These enzymes modulate the activity of different nuclear and cytoplasmatic proteins, which in turn regulate several cellular processes. Sirtuins, and especially the SIRT1 isoform, promote longevity by delaying cellular aging, inhibit apoptosis, regulate the cell cycle, the glucose homeostasis and the insulin secretion, and are involved in inflammation, oxidative stress and mitochondrial biogenesis.

SIRT1 is found both in the nucleus and in the cytosol and exerts its action by deacetylating histone and non-histone proteins. SIRT1 is expressed in different tissues including skeletal muscle, where it deacetylates and activates peroxisome proliferator-activated receptor-gamma coactivator (PGC-1α) thus improving muscle resistance, enhancing muscle fiber-type switching and decreasing the process of muscle wasting. Hence, the activation of the SIRT1 in skeletal muscle ameliorates the phenotype of the X-linked recessive, muscle-wasting disease DMD.

Therefore, we decided to map the differences in the acetylome of tibialis anterior muscle samples from mdx mice (a common DMD murine model): samples derived from five mdx mice were compared to samples derived from other five mdx mice treated with an activator of SIRT1. We used an unbiased label-free quantitative proteomic approach, upon enrichment for acetylated peptides with PTMScan Acetyl-Lysine motif. In this way, out of 141 unique acetylation sites we identified 28 sites that were differentially abundant in the two conditions of interest; moreover, we analysed the corresponding proteins to map them in GO biological processes using David software. In conclusion, our results indicate that the modulation of SIRT1 activity leads to beneficial effects in skeletal muscles from mdx mice, especially confirming SIRT1 activation impact on muscle contraction.