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Transforming growth factor beta modulates the expression of collagenase and metalloproteinase inhibitor
D R Edwards1, G Murphy, J J Reynolds
1Department of Biochemistry, University of Oxford, UK.
Abstract:
Exposure of quiescent MRC-5 human fibroblasts to growth factors such as epidermal growth factor, basic fibroblast growth factor or embryonal carcinoma-derived growth factor resulted in the induction of mRNA transcripts encoding the metalloproteinases collagenase and stromelysin and the specific metalloproteinase inhibitor TIMP, whilst expression of collagen and fibronectin was relatively unaffected. Exposure of quiescent cells to growth factors in the presence of transforming growth factor beta (TGF-beta) resulted in inhibition of collagenase induction and a synergistic increase in TIMP expression. TGF-beta alone did not significantly induce metalloproteinase or TIMP expression. These effects on mRNA transcripts were reflected in increased secretion of TIMP protein and collagenase activity. Nuclear run-off analysis of growth factor-induced transcription revealed that the TGF-beta modulation of TIMP and collagenase expression was due to transcriptional mechanisms. The observations suggest that TGF-beta exerts a selective effect on extracellular matrix deposition by modulating the action of other growth factors on metalloproteinase and TIMP expression.
Insights
Transforming growth factor beta (TGF-beta) selectively modulates growth factor-induced metalloproteinase and TIMP expression in human fibroblasts at the transcriptional level. This impacts extracellular matrix deposition.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Growth factors regulate extracellular matrix (ECM) deposition.
- Metalloproteinases and their inhibitors (TIMPs) are key regulators of ECM remodeling.
Purpose of the Study:
- To investigate the role of transforming growth factor beta (TGF-beta) in modulating growth factor-induced expression of metalloproteinases and TIMPs in human fibroblasts.
- To elucidate the transcriptional mechanisms underlying TGF-beta's effects.
Main Methods:
- Treatment of quiescent MRC-5 human fibroblasts with various growth factors, including epidermal growth factor, basic fibroblast growth factor, and TGF-beta.
- Analysis of mRNA transcripts for collagenase, stromelysin, TIMP, collagen, and fibronectin using Northern blotting.
- Measurement of secreted TIMP protein and collagenase activity.
- Nuclear run-off assays to assess transcriptional regulation.
Main Results:
- Growth factors induced collagenase, stromelysin, and TIMP mRNA, while collagen and fibronectin expression remained largely unchanged.
- TGF-beta inhibited growth factor-induced collagenase expression and synergistically increased TIMP expression.
- TGF-beta alone had minimal effect on metalloproteinase and TIMP expression.
- These transcript changes were mirrored by increased TIMP protein secretion and collagenase activity.
- Nuclear run-off assays confirmed that TGF-beta's modulation of TIMP and collagenase expression occurred at the transcriptional level.
Conclusions:
- TGF-beta selectively alters the response of fibroblasts to other growth factors regarding ECM-related gene expression.
- TGF-beta exerts its regulatory effects on metalloproteinase and TIMP expression via transcriptional mechanisms.
- These findings suggest TGF-beta plays a crucial role in controlling ECM deposition by fine-tuning the balance between matrix-degrading enzymes and their inhibitors.