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Proteinase-activated receptor-1 regulation of macrophage elastase (MMP-12) secretion by serine proteinases
S L Raza1, L C Nehring, S D Shapiro
1Divisions of Dermatology and Respiratory and Critical Care, Department of Medicine, Children's Place,Washington University School of Medicine at Barnes-Jewish Hospital, St.Louis, MO 63110, USA.
Abstract:
The serine proteinases plasmin and thrombin convert proenzyme matrix metalloproteinases (MMPs) into catalytically active forms. In addition, we demonstrate that plasmin(ogen) and thrombin induce a significant increase in secretion of activated murine macrophage elastase (MMP-12) protein. Active serine protease is responsible for induction, as demonstrated by the absence of MMP-12 induction in plasminogen(Plg)-treated urokinase-type plasminogen activator-deficient macrophages. Since increased MMP-12 protein secretion was not accompanied by an increase in MMP-12 mRNA, we examined post-translational mechanisms. Protein synthesis was not required for early release of MMP-12 but was required for later secretion of activated enzyme. Immunofluorescent microscopy demonstrated basal expression in macrophages that increased following serine proteinase exposure. Inhibition of MMP-12 secretion by hirudin and pertussis toxin demonstrated a role for the thrombin G protein-coupled receptor (protease-activated receptor 1 (PAR-1)). PAR-1-activating peptides were able to induce MMP-12 release. Investigation of signal transduction pathways involved in this response demonstrate the requirement for protein kinase C, but not tyrosine kinase, activity. These data demonstrate that plasmin and thrombin regulate MMP-12 activity through distinct mechanisms: post-translational secretion of preformed MMP-12 protein, induction of protein secretion that is protein kinase C-mediated, and extracellular enzyme activation. Most importantly, we show that serine proteinase MMP-12 regulation in macrophages occurs via the protein kinase C-activating G protein-coupled receptor PAR-1.
Insights
Serine proteases like plasmin and thrombin activate matrix metalloproteinases (MMPs). These proteases also increase macrophage elastase (MMP-12) secretion via post-translational mechanisms and protein kinase C signaling through PAR-1.
Area of Science:
- Biochemistry
- Cell Biology
- Immunology
Background:
- Serine proteinases, including plasmin and thrombin, are known activators of proenzyme matrix metalloproteinases (MMPs).
- Macrophage elastase (MMP-12) plays a role in various physiological and pathological processes.
- Understanding the regulation of MMP-12 secretion and activation is crucial for developing targeted therapies.
Purpose of the Study:
- To investigate the mechanisms by which plasmin and thrombin regulate macrophage elastase (MMP-12) secretion and activation.
- To identify the specific signaling pathways involved in MMP-12 regulation by serine proteinases.
- To elucidate the role of protease-activated receptor 1 (PAR-1) in MMP-12 induction.
Main Methods:
- Treatment of murine macrophages with plasmin(ogen) and thrombin.
- Analysis of MMP-12 protein secretion and mRNA levels.
- Immunofluorescent microscopy to assess MMP-12 expression.
- Inhibition studies using hirudin and pertussis toxin.
- Activation of PAR-1 using specific peptides.
- Investigation of protein kinase C and tyrosine kinase activity.
Main Results:
- Plasmin and thrombin significantly increase the secretion of activated MMP-12 protein in macrophages.
- MMP-12 induction occurred post-translationally, without an increase in MMP-12 mRNA.
- Serine protease-induced MMP-12 secretion is mediated by the G protein-coupled receptor PAR-1.
- Protein kinase C activity is required for MMP-12 induction, while tyrosine kinase is not.
- Distinct mechanisms including post-translational secretion, protein kinase C-mediated induction, and extracellular activation regulate MMP-12.
Conclusions:
- Plasmin and thrombin regulate MMP-12 activity in macrophages through multiple mechanisms.
- PAR-1 activation by serine proteinases triggers MMP-12 secretion via protein kinase C signaling.
- These findings highlight a novel regulatory pathway for MMP-12 in macrophages with implications for inflammatory diseases.