Human Fibroblasts Accelerate the Inhibition of Thrombin by Protease Nexin

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 83; no. 18; pp. 6858 - 6862
• Main Authors: Farrell, David H., Cunningham, Dennis D.
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01.09.1986; National Acad Sciences
• Subjects: Amyloid beta-Protein Precursor; Antithrombin III - pharmacology; Biological and medical sciences; Blood coagulation. Blood cells; Carrier Proteins - metabolism; Carrier Proteins - pharmacology; Cell membranes; Cells; Cells, Cultured; Cultured cells; Electrophoresis; Endothelial cells; Extracellular matrix; Extracellular Matrix - physiology; Fibroblasts; Fibroblasts - metabolism; Fundamental and applied biological sciences. Psychology; General aspects, investigation methods, hemostasis, fibrinolysis; Heparin; Humans; Molecular and cellular biology; Polysaccharide-Lyases - pharmacology; Protamines; Protamines - pharmacology; Protease Inhibitors - metabolism; Protease Nexins; Receptors, Cell Surface; Sulfates; Thrombin - antagonists & inhibitors; Human; Blood coagulation; Regulation(control); Proteinase; Plasma membrane; Enzyme inhibitor; Extracellular matrix; Thrombin; Fibroblast
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.83.18.6858

Protease nexin (PN) is a protein protease inhibitor secreted by human fibroblasts in culture that complexes and inhibits certain regulatory serine proteases. The PN-protease complexes then bind to these cells and are rapidly internalized and degraded. This report shows that the fibroblast surface accelerates the formation of PN-thrombin complexes. In contrast, it did not accelerate the formation of complexes between thrombin and antithrombin III, a closely related protease inhibitor found in plasma. These results support a role for PN in the regulation of certain proteases in the extravascular compartment at and near the surface of tissue cells. The activity that accelerated PN-thrombin complex formation was membrane-associated, since fixed cells, purified membranes, and extracellular matrix preparations all contained this activity. The ability of cells to accelebrate the reaction between PN and thrombin was inhibited by protamine, suggesting that the activity was similar to that of heparin. Heparitinase digestion of plasma membranes prior to assay reduced the activity by about 80%, suggesting that heparan sulfate may account for most of the accelerative activity.