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Binding of latent matrix metalloproteinase 9 to fibrin: activation via a plasmin-dependent pathway
1Department of Laboratory Medicine, University of Connecticut Health Center, Farmington, USA.
Abstract:
The binding of two matrix metalloproteinases (MMP) to fibrin was evaluated. MMP-2 (72-kDa) and MMP-9 (92-, 130-, and 225-kDa) were selected since both contain a fibronectin-like region and fibronectin binds fibrin. Gelatin zymography indicated selective and dose dependent binding of MMP-9 to fibrin. No MMP-2 binding to fibrin occurred. Densitometry revealed that the 130- and 225-kDa forms demonstrated similar sigmoidal binding profiles whereas 92-kDa uptake was hyperbolic. Fibronectin and TIMP-1 competition studies indicated that the fibronectin and C-terminal MMP-9 domains, respectively, were not involved with fibrin binding. The MMP-9 collagen-like region may be of regulatory significance since type I and II fibrillar and type IV basement membrane collagens demonstrated fibrin binding. During fibrinolysis, latent fibrin-bound MMP-9 was processed to lower molecular weight forms consistent with proteolytic activation. This process was inhibited by epsilon-aminocaproic acid, indicating a plasmin-dependent pathway. The significance of these findings to procoagulant activity and MMP-mediated extracellular matrix destruction during inflammation and tumor invasion and metastasis is discussed.
Insights
Matrix metalloproteinase-9 (MMP-9) selectively binds to fibrin, unlike MMP-2. This fibrin binding and activation of MMP-9 during fibrinolysis are crucial for extracellular matrix degradation in inflammation and cancer.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Matrix metalloproteinases (MMPs) are enzymes involved in extracellular matrix (ECM) degradation.
- Fibrin is a key component of blood clots and the ECM.
- MMP-2 and MMP-9 possess fibronectin-like regions, suggesting potential interactions with fibrin.
Purpose of the Study:
- To investigate the binding interactions between MMP-2, MMP-9, and fibrin.
- To elucidate the molecular domains and activation pathways of MMP-9 involved in fibrin binding.
- To discuss the implications for ECM destruction in inflammation and cancer metastasis.
Main Methods:
- Gelatin zymography to assess MMP binding to fibrin.
- Densitometry to quantify MMP binding.
- Competition studies using fibronectin and TIMP-1.
- Analysis of MMP-9 processing during fibrinolysis.
Main Results:
- MMP-9 exhibited selective, dose-dependent binding to fibrin, while MMP-2 did not.
- Different molecular weight forms of MMP-9 showed distinct binding kinetics (sigmoidal and hyperbolic).
- The fibronectin-like and C-terminal domains of MMP-9 were not involved in fibrin binding; the collagen-like region may be significant.
- Fibrin-bound MMP-9 was activated during fibrinolysis via a plasmin-dependent pathway, inhibited by epsilon-aminocaproic acid.
Conclusions:
- MMP-9, but not MMP-2, binds to fibrin, suggesting a specific role in fibrin-associated processes.
- The collagen-like region of MMP-9 appears critical for fibrin interaction.
- Plasmin-dependent activation of fibrin-bound MMP-9 contributes to ECM degradation, potentially impacting inflammation, tumor invasion, and metastasis.