Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON, K1H 8M5, Canada; Ottawa Institute of Systems Biology, University of Ottawa, ON, K1H 8M5, Canada; Dr. Eric Poulin Centre for Neuromuscular Disease (CNMD), University of Ottawa, ON, K1H 8M5, Canada
Chantal A. Pileggi
Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON, K1H 8M5, Canada; Ottawa Institute of Systems Biology, University of Ottawa, ON, K1H 8M5, Canada
Charbel Y. Karam
Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON, K1H 8M5, Canada; Ottawa Institute of Systems Biology, University of Ottawa, ON, K1H 8M5, Canada
Luke S. Kennedy
Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON, K1H 8M5, Canada; Ottawa Institute of Systems Biology, University of Ottawa, ON, K1H 8M5, Canada
Claire Fong-McMaster
Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON, K1H 8M5, Canada; Ottawa Institute of Systems Biology, University of Ottawa, ON, K1H 8M5, Canada
Miroslava Cuperlovic-Culf
Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON, K1H 8M5, Canada; Ottawa Institute of Systems Biology, University of Ottawa, ON, K1H 8M5, Canada; National Research Council of Canada, Digital Technologies Research Centre, 1200 Montreal Road, Ottawa, ON, K1A 0R6, Canada
Mary-Ellen Harper
Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON, K1H 8M5, Canada; Ottawa Institute of Systems Biology, University of Ottawa, ON, K1H 8M5, Canada; Corresponding author. Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON, K1H 8M5, Canada.
Cysteine, the rate-controlling amino acid in cellular glutathione synthesis is imported as cystine, by the cystine/glutamate antiporter, xCT, and subsequently reduced to cysteine. As glutathione redox is important in muscle regeneration in aging, we hypothesized that xCT exerts upstream control over skeletal muscle glutathione redox, metabolism and regeneration. Bioinformatic analyses of publicly available datasets revealed that expression levels of xCT and GSH-related genes are inversely correlated with myogenic differentiation genes. Muscle satellite cells (MuSCs) isolated from Slc7a11sut/sut mice, which harbour a mutation in the Slc7a11 gene encoding xCT, required media supplementation with 2-mercaptoethanol to support cell proliferation but not myotube differentiation, despite persistently lower GSH. Slc7a11sut/sut primary myotubes were larger compared to WT myotubes, and also exhibited higher glucose uptake and cellular oxidative capacities. Immunostaining of myogenic markers (Pax7, MyoD, and myogenin) in cardiotoxin-damaged tibialis anterior muscle fibres revealed greater MuSC activation and commitment to differentiation in Slc7a11sut/sut muscle compared to WT mice, culminating in larger myofiber cross-sectional areas at 21 days post-injury. Slc7a11sut/sut mice subjected to a 5-week exercise training protocol demonstrated enhanced insulin tolerance compared to WT mice, but blunted muscle mitochondrial biogenesis and respiration in response to exercise training. Our results demonstrate that the absence of xCT inhibits cell proliferation but promotes myotube differentiation by regulating cellular metabolism and glutathione redox. Altogether, these results support the notion that myogenesis is a redox-regulated process and may help inform novel therapeutic approaches for muscle wasting and dysfunction in aging and disease.
