Not all injury-induced muscle proteolysis is due to increased activity of the ubiquitin/proteasome system: Evidence for up-regulation of macrophage-associated lysosomal proteolysis in a model of local trauma

Abstract

A characteristic response to injury is a dramatic loss of skeletal muscle protein owing to increased muscle protein breakdown. Over the past decade, numerous studies have indicated that up-regulaton of the ubiquitin-proteasome system is a common mechanism underlying such injury-induced muscle proteolysis. However, a recent study using a single-impact trauma to the gastrocnemius muscle found that, although the rate of muscle proteolysis was dramatically increased, the ubiquitin-proteasome system was not involved. Rather, an increase in lysosomal activity, through infiltration of the damaged tissue by mononuclear macrophages, is responsible for the high rates of protein breakdown. © 2003 International Life Sciences Institute.