Journal of Biological Chemistry
Volume 286, Issue 49, 9 December 2011, Pages 41949-41962
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Enzymology
Effects of Extracellular DNA on Plasminogen Activation and Fibrinolysis*

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The increased levels of extracellular DNA found in a number of disorders involving dysregulation of the fibrinolytic system may affect interactions between fibrinolytic enzymes and inhibitors. Double-stranded (ds) DNA and oligonucleotides bind tissue-(tPA) and urokinase (uPA)-type plasminogen activators, plasmin, and plasminogen with submicromolar affinity. The binding of enzymes to DNA was detected by EMSA, steady-state, and stopped-flow fluorimetry. The interaction of dsDNA/oligonucleotides with tPA and uPA includes a fast bimolecular step, followed by two monomolecular steps, likely indicating slow conformational changes in the enzyme. DNA (0.1–5.0 μg/ml), but not RNA, potentiates the activation of Glu- and Lys-plasminogen by tPA and uPA by 480- and 70-fold and 10.7- and 17-fold, respectively, via a template mechanism similar to that known for fibrin. However, unlike fibrin, dsDNA/oligonucleotides moderately affect the reaction between plasmin and α2-antiplasmin and accelerate the inactivation of tPA and two chain uPA by plasminogen activator inhibitor-1 (PAI-1), which is potentiated by vitronectin. dsDNA (0.1–1.0 μg/ml) does not affect the rate of fibrinolysis by plasmin but increases by 4–5-fold the rate of fibrinolysis by Glu-plasminogen/plasminogen activator. The presence of α2-antiplasmin abolishes the potentiation of fibrinolysis by dsDNA. At higher concentrations (1.0–20 μg/ml), dsDNA competes for plasmin with fibrin and decreases the rate of fibrinolysis. dsDNA/oligonucleotides incorporated into a fibrin film also inhibit fibrinolysis. Thus, extracellular DNA at physiological concentrations may potentiate fibrinolysis by stimulating fibrin-independent plasminogen activation. Conversely, DNA could inhibit fibrinolysis by increasing the susceptibility of fibrinolytic enzymes to serpins.

DNA
Fibrinolysis
Plasmin
Plasminogen
Serpin
Fibrinolytic Enzymes
Plasminogen Activation
Template

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*

This work was supported, in whole or in part, by National Institutes of Health Grants PO-1 076406 and P50 HL107186-02 from NHLBI. This work was also supported by the Texas Lung Injury Institute.

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All authors contributed equally to this work.