Autophagy in skeletal muscle.

Muscle mass represents 40-50% of the human body and, in mammals, is one of the most important sites for the control of metabolism. Moreover, during catabolic conditions, muscle proteins are mobilized to sustain gluconeogenesis in the liver and to provide alternative energy substrates for organs. However, excessive protein degradation in the skeletal muscle is detrimental for the economy of the body and it can lead to death. The ubiquitin-proteasome and autophagy-lysosome systems are the major proteolytic pathways of the cell and are coordinately activated in atrophying muscles. However, the role and regulation of the autophagic pathway in skeletal muscle is still largely unknown. This review will focus on autophagy and discuss its beneficial or detrimental role for the maintenance of muscle mass.