Neutrophil proteases in plasminogen activation

Area of Science:

• Biochemistry
• Proteolysis
• Hemostasis

Background:

• Neutrophil proteases, including leukocyte elastase and cathepsin G, play roles in inflammation and tissue remodeling.
• Plasminogen is a key precursor to plasmin, a critical enzyme in fibrinolysis.
• Understanding protease interactions with plasminogen is vital for comprehending coagulation and fibrinolytic pathways.

Purpose of the Study:

• To investigate the degradation of porcine plasminogen by leukocyte elastase and cathepsin G.
• To determine the impact of these proteases on plasminogen activation in the presence of inhibitors and activators.
• To elucidate the specific role of elastase versus cathepsin G in enhancing plasmin expression.

Main Methods:

• Enzymatic assays to measure the hydrolysis of plasminogen by leukocyte elastase and cathepsin G.
• Kinetic analysis to determine reaction rates (kobs) for plasminogen degradation.
• Assessment of plasminogen activation by urokinase and tissue-type plasminogen activator in the presence of proteases and alpha 2-antiplasmin.

Main Results:

• Both elastase and cathepsin G hydrolyze plasminogen at the A447-I448 bond, yielding des-kringle1-4-plasminogen.
• Elastase demonstrates a significantly higher rate of plasminogen degradation (kobs > 10(5) mol-1 s-1) compared to cathepsin G (kobs < 300 mol-1 s-1).
• Elastase, but not cathepsin G, inactivates alpha 2-antiplasmin, enabling urokinase-mediated plasminogen activation and overcoming fibrin(ogen) fragment effects.

Conclusions:

• Leukocyte elastase is the primary neutrophil protease responsible for enhancing plasmin expression.
• The differential activity of elastase and cathepsin G on plasminogen and inhibitors dictates their pro-fibrinolytic potential.
• Elastase's ability to degrade plasminogen and inactivate alpha 2-antiplasmin highlights its significant role in modulating fibrinolysis.