O-GlcNAcylation of SERCA protects skeletal muscle in hibernating Spermophilus dauricus from disuse atrophy

Long-term inactivity of skeletal muscle results in muscular disuse atrophy; however, hibernating animals do not experience muscular disuse atrophy during the hibernation period. The molecular mechanism underlining the anti-atrophy effect in these animals is unclear. O-linked N acetyl-β-D-glucosaminylation (O-GlcNAcylation) and its effect on cell signaling pathways are important mechanisms underlying muscular disuse atrophy; thus, in this study, we investigated O-GlcNAcylation changes during hibernation in Spermophilus dauricus to explore the role of O-GlcNAcylation in the muscle disuse atrophy resistance of hibernating animals. The results showed that during hibernation, the muscle fiber cross-sectional area and ratio of muscle fiber did not change, and the morphological structure of the muscle remained intact, with normal contractile function. The level of O-GlcNAcylation decreased during hibernation, but quickly returned to normal in the periodic arousal stage. The O-GlcNAcylation level of sarcoplasmic/endoplasmic reticulum calcium ATPase 1 (SERCA1) decreased, whereas its activity increased. The decrease in O-GlcNAcylation of SERCA could result in the decreased binding of phospholamban to SERCA1, thus decreasing its inhibition to SERCA1 activity. This in turn can inhibit muscle cell calcium overload, maintain muscle cell calcium homeostasis, and stabilize the calpain proteolytic pathway, ultimately inhibiting skeletal muscle atrophy. Our results demonstrate that periodic arousal along with returning O-GlcNAcylation level to normal are important mechanisms in preventing disuse atrophy of skeletal muscle during hibernation.