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C1 inhibitor cross-linking by tissue transglutaminase
J Hauert1, P A Patston, M Schapira
1Division of Hematology and Department of Medicine, Centre Hospitalier Universitaire Vaudois, CH-1011 Lausanne, Switzerland.
The Journal of Biological Chemistry
|May 9, 2000
Summary
Tissue transglutaminase modifies C1 inhibitor, a key regulator of complement and coagulation. This cross-linking to extracellular matrix components like fibrin may control local proteolytic activity.
Area of Science:
- Biochemistry
- Molecular Biology
- Proteomics
Background:
- C1 inhibitor (C1-INH) is a serpin superfamily proteinase inhibitor regulating complement and coagulation.
- C1-INH binds extracellular matrix (ECM) components, potentially localizing it to the perivascular space.
Purpose of the Study:
- To investigate if C1-INH serves as a substrate for plasma factor XIIIa or tissue transglutaminase (TG).
- To elucidate the mechanism and functional consequences of C1-INH modification by transglutaminases.
Main Methods:
- SDS-PAGE and autoradiography to detect [(3)H]putrescine incorporation.
- Proteolytic cleavage and peptide sequencing to identify the amine acceptor residue.
- Cross-linking assays using (125)I-labeled C1-INH and immobilized fibrin.
- Enzyme activity assays of cross-linked C1-INH.
Main Results:
- C1-INH incorporated [(3)H]putrescine in a calcium-dependent manner with tissue TG, but not factor XIIIa.
- Gln(453) was identified as the sole amine acceptor residue in C1-INH.
- Tissue TG cross-linked C1-INH to immobilized fibrin, preserving its inhibitory activity.
Conclusions:
- Tissue TG mediates the covalent cross-linking of C1-INH to ECM components, including fibrin.
- This TG-mediated cross-linking may represent a mechanism for C1-INH localization and local regulation of proteolytic pathways.