The ubiquitin–proteasome system in regulation of the skeletal muscle homeostasis and atrophy: from basic science to disorders

Skeletal muscle is one of the most abundant and highly plastic tissues. The ubiquitin-proteasome system (UPS) is recognised as a major intracellular protein degradation system, and its function is important for muscle homeostasis and health. Although UPS plays an essential role in protein degradation during muscle atrophy, leading to the loss of muscle mass and strength, its deficit negatively impacts muscle homeostasis and leads to the occurrence of several pathological phenotypes. A growing number of studies have linked UPS impairment not only to matured muscle fibre degeneration and weakness, but also to muscle stem cells and deficiency in regeneration. Emerging evidence suggests possible links between abnormal UPS regulation and several types of muscle diseases. Therefore, understanding of the role of UPS in skeletal muscle may provide novel therapeutic insights to counteract muscle wasting, and various muscle diseases. In this review, we focussed on the role of proteasomes in skeletal muscle and its regeneration, including a brief explanation of the structure of proteasomes. In addition, we summarised the recent findings on several diseases and elaborated on how the UPS is related to their pathological states.