The ubiquitin-dependent proteolytic pathway in skeletal muscle: its role in pathological states.

It is generally accepted that muscle wasting is caused by an increase in protein breakdown which seems to be associated with an ATP-dependent, non-lysosomal proteolytic system based on conjugation of proteins to the small polypeptide ubiquitin. Increases in ubiquitin conjugates and in ubiquitin mRNAs are found in the skeletal muscle of experimental animals with various pathological conditions such as infection, acidosis or cancer cachexia. In this review, Josep Argilés and Francisco López-Soriano discuss the role of the ubiquitin-dependent proteolytic pathway in muscle weight loss in pathological situations.