Inhibition of the proteasomal function in chondrocytes down-regulates growth plate chondrogenesis and longitudinal bone growth

Endocrinology. 2006 Aug;147(8):3761-8. doi: 10.1210/en.2005-1672. Epub 2006 May 4.


The proteasome is a large multiprotein complex that processes intracellular proteins functioning as cell cycle regulators and transcription factors. It has been shown that the chymotryptic component of the proteasome is an important regulator of osteoblast differentiation and bone formation, with inhibitors of the proteasome increasing osteoblast differentiation and bone formation. Yet, little is known about the effects of the proteasomal activity in the growth plate. In the present study, we cultured rat metatarsal bones in the presence of proteasome inhibitor I (PSI), a known inhibitor of the chymotrypsin-like activity of the 20S proteasome. PSI suppressed growth plate chondrocyte proliferation and hypertrophy/differentiation, and induced chondrocyte apoptosis. All these cellular effects led to reduced metatarsal linear growth. In cultured chondrocytes, PSI increased the expression of beta-catenin (a negative regulator of chondrogenesis) and reduced the DNA binding of nuclear factor kappaB, a transcription factor that stimulates growth plate chondrogenesis. In conclusion, our findings suggest that the proteasomal activity facilitates growth plate chondrogenesis and, in turn, longitudinal bone growth.

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Apoptosis / physiology
  • Cell Differentiation / drug effects
  • Cell Differentiation / physiology
  • Cells, Cultured
  • Chondrocytes / cytology
  • Chondrocytes / enzymology*
  • Chondrogenesis / drug effects
  • Chondrogenesis / physiology*
  • Cysteine Proteinase Inhibitors / pharmacology
  • Down-Regulation / drug effects
  • Down-Regulation / physiology
  • Gene Expression
  • Growth Plate / cytology
  • Growth Plate / enzymology
  • Growth Plate / growth & development*
  • I-kappa B Proteins / metabolism
  • Metatarsal Bones / cytology
  • Metatarsal Bones / enzymology
  • Metatarsal Bones / growth & development*
  • NF-KappaB Inhibitor alpha
  • NF-kappa B / metabolism
  • Oligopeptides / pharmacology
  • Organ Culture Techniques
  • Proteasome Endopeptidase Complex / metabolism*
  • Proteasome Inhibitors
  • Rats
  • Rats, Sprague-Dawley
  • beta Catenin / genetics
  • beta Catenin / metabolism


  • Cysteine Proteinase Inhibitors
  • I kappa B beta protein
  • I-kappa B Proteins
  • NF-kappa B
  • Nfkbia protein, rat
  • Oligopeptides
  • Proteasome Inhibitors
  • benzyloxycarbonyl-isoleucyl-glutamyl(O-tert-butyl)-alanyl-leucinal
  • beta Catenin
  • NF-KappaB Inhibitor alpha
  • Proteasome Endopeptidase Complex