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Expression of c-fos gene inhibits proteoglycan synthesis in transfected chondrocyte
M Tsuji1, S Funahashi, M Takigawa
1Tokyo Institute for Immunopharmacology, Japan.
Abstract:
The effect of expression of c-fos gene on proteoglycan synthesis, one of the important markers of cartilage metabolism, was examined by introducing the c-fos DNA into HCS 2/8 chondrocytes. The [35S]sulfate incorporation into proteoglycan was decreased in the c-fos transfectants expressing exogenous c-fos mRNA, when compared to a control transfectant. A significant increase in transcription of MMP-3 with the suppressed transcription of aggrecan and TIMP-1 were also observed in the c-fos transfectants. Moreover, analysis of the effect of AP-1 proteins on the collagenase and TIMP-1 promoters in gastric carcinoma KKLS cells revealed that c-Fos combined with any of the Jun-related proteins failed to stimulate the TIMP-1 promoter, though collagenase promoter was effectively activated by any Fos/Jun-related protein heterocomplex. These findings indicate that the c-fos expression may govern the cartilage metabolism and hence may play an important role in the pathogenesis of joint destruction in arthritis.
Insights
The c-fos gene
Area of Science:
- Molecular Biology
- Cartilage Metabolism
- Gene Expression
Background:
- Cartilage degradation is a hallmark of arthritis.
- Proteoglycans are key markers of cartilage metabolism.
- The role of c-fos in cartilage metabolism is not well understood.
Purpose of the Study:
- To investigate the effect of c-fos gene expression on proteoglycan synthesis in chondrocytes.
- To explore the impact of c-fos on matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) gene transcription.
- To analyze the role of AP-1 proteins in regulating collagenase and TIMP-1 gene expression.
Main Methods:
- Introducing c-fos DNA into HCS 2/8 chondrocytes.
- Measuring [35S]sulfate incorporation to assess proteoglycan synthesis.
- Analyzing gene transcription of MMP-3, aggrecan, and TIMP-1 using quantitative methods.
- Investigating AP-1 protein effects on collagenase and TIMP-1 promoters in KKLS cells.
Main Results:
- c-fos expression decreased proteoglycan synthesis in chondrocytes.
- c-fos transfectants showed increased MMP-3 transcription and suppressed aggrecan and TIMP-1 transcription.
- Fos/Jun heterocomplexes activated the collagenase promoter but failed to stimulate the TIMP-1 promoter in KKLS cells.
Conclusions:
- c-fos expression negatively regulates cartilage metabolism by affecting proteoglycan synthesis and matrix-degrading enzyme expression.
- These findings suggest c-fos plays a significant role in the joint destruction observed in arthritis.
- Targeting c-fos pathways may offer therapeutic strategies for managing arthritis.