Decreased muscle atrophy F-box (MAFbx) expression in regenerating muscle after muscle-damaging exercise

Muscle Nerve. 2008 Oct;38(4):1246-53. doi: 10.1002/mus.21110.


A muscle-specific ubiquitin ligase, Muscle Atrophy F-box (MAFbx), is known to mediate the degradation of muscle-specific transcription factor MyoD in vitro. Its regulation in regenerating skeletal muscle, however, has not been clarified. We looked for evidence of MAFbx downregulation in the course of regeneration after muscle damaging exercise. The soleus and gastrocnemius muscles of mice were subjected to forced eccentric contraction by electrical stimulation to induce muscle damage. The expression of developmental myosin heavy chain (MHCd) suggested that muscle regeneration took place from Day 3 after exercise. mRNA and protein expression of MAFbx decreased on Days 3, 5, and 7, while MyoD protein increased on Days 3, 5, and 7. Although further study is required to establish the causal relationships, downregulation of MAFbx may have reduced MyoD degradation in favor of muscle regeneration.

MeSH terms

  • Animals
  • Disease Models, Animal
  • Down-Regulation / physiology*
  • Electric Stimulation
  • Gene Expression Regulation / physiology
  • Immunohistochemistry
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Muscle Contraction / physiology
  • Muscle Fibers, Skeletal / cytology
  • Muscle Fibers, Skeletal / metabolism
  • Muscle Proteins / genetics
  • Muscle Proteins / metabolism*
  • Muscle, Skeletal / injuries
  • Muscle, Skeletal / metabolism*
  • Muscle, Skeletal / physiopathology
  • Muscular Diseases / genetics
  • Muscular Diseases / metabolism*
  • Muscular Diseases / physiopathology
  • MyoD Protein / metabolism
  • Physical Conditioning, Animal / adverse effects*
  • RNA, Messenger / metabolism
  • Regeneration / physiology*
  • SKP Cullin F-Box Protein Ligases / genetics
  • SKP Cullin F-Box Protein Ligases / metabolism*


  • Muscle Proteins
  • MyoD Protein
  • MyoD1 myogenic differentiation protein
  • RNA, Messenger
  • Fbxo32 protein, mouse
  • SKP Cullin F-Box Protein Ligases