Binding of plasminogen to extracellular matrix

Area of Science:

• Biochemistry
• Cell Biology
• Extracellular Matrix Research

Background:

• Plasminogen immobilization on surfaces enhances conversion to plasmin by tissue plasminogen activator (t-PA).
• Endothelial cells synthesize an extracellular matrix (ECM) in vitro.

Purpose of the Study:

• To investigate the binding of human plasminogen to ECM synthesized by endothelial cells.
• To characterize the functional consequences of plasminogen binding to the ECM.

Main Methods:

• In vitro synthesis of endothelial cell extracellular matrix.
• Binding assays for human plasminogen to the ECM.
• Enzymatic assays measuring plasminogen activation kinetics and plasmin activity.
• Inhibition studies using alpha 2-plasmin inhibitor.

Main Results:

• Specific, saturable, reversible, and lysine-binding site-dependent binding of plasminogen to the ECM was observed.
• Matrix-immobilized plasminogen showed a 100-fold decrease in Km for t-PA activation compared to fluid phase plasminogen.
• Plasmin generated on the ECM was protected from alpha 2-plasmin inhibitor and converted Glu-plasminogen to Lys-plasminogen, further enhancing activation.
• ECM facilitated equally efficient activation by both t-PA and urokinase.

Conclusions:

• The extracellular matrix binds and localizes plasminogen.
• ECM significantly improves plasminogen activation kinetics.
• ECM prolongs the activity of generated plasmin by protecting it from inhibition.