What do we really know about the ubiquitin-proteasome pathway in muscle atrophy?

Curr Opin Clin Nutr Metab Care. 2001 May;4(3):183-90. doi: 10.1097/00075197-200105000-00003.


Studies of many different rodent models of muscle wasting have indicated that accelerated proteolysis via the ubiquitin-proteasome pathway is the principal cause of muscle atrophy induced by fasting, cancer cachexia, metabolic acidosis, denervation, disuse, diabetes, sepsis, burns, hyperthyroidism and excess glucocorticoids. However, our understanding about how muscle proteins are degraded, and how the ubiquitin-proteasome pathway is activated in muscle under these conditions, is still very limited. The identities of the important ubiquitin-protein ligases in skeletal muscle, and the ways in which they recognize substrates are still largely unknown. Recent in-vitro studies have suggested that one set of ubquitination enzymes, E2(14K) and E3(alpha), which are responsible for the 'N-end rule' system of ubiquitination, plays an important role in muscle, especially in catabolic states. However, their functional significance in degrading different muscle proteins is still unclear. This review focuses on the many gaps in our understanding of the functioning of the ubiquitin-proteasome pathway in muscle atrophy, and highlights the strengths and limitations of the different experimental approaches used in such studies.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Culture Techniques
  • Cysteine Endopeptidases / genetics
  • Cysteine Endopeptidases / metabolism*
  • Cysteine Proteinase Inhibitors / pharmacology
  • Humans
  • Multienzyme Complexes / genetics
  • Multienzyme Complexes / metabolism*
  • Muscle Proteins / metabolism
  • Muscle, Skeletal / metabolism
  • Muscular Atrophy / enzymology
  • Muscular Atrophy / etiology*
  • Muscular Atrophy / metabolism
  • Proteasome Endopeptidase Complex
  • RNA, Messenger / metabolism
  • Ubiquitins / genetics
  • Ubiquitins / metabolism*
  • Wasting Syndrome / etiology
  • Wasting Syndrome / metabolism


  • Cysteine Proteinase Inhibitors
  • Multienzyme Complexes
  • Muscle Proteins
  • RNA, Messenger
  • Ubiquitins
  • Cysteine Endopeptidases
  • Proteasome Endopeptidase Complex