Enhanced fibrinolysis by proteolysed coagulation factor Xa

Area of Science:

• Biochemistry
• Hematology
• Molecular Biology

Background:

• Coagulation factor Xa (FXa) is known to enhance plasminogen activation by tissue plasminogen activator (tPA).
• Proteolytic cleavage of FXa yields FXa-beta and Xa33/13, which possess plasminogen binding sites crucial for this enhancement.
• The specific role of these cleaved forms in plasmin generation and clot lysis remained uncharacterized.

Purpose of the Study:

• To demonstrate the function of Xa33/13 in plasmin generation.
• To investigate the role of FXaalpha/beta and Xa33/13 in clot lysis experiments.
• To elucidate the mechanism by which FXa modulates fibrinolysis.

Main Methods:

• Purified Xa33/13 was used to measure tPA-dependent plasmin generation.
• Western blots were employed to confirm in situ conversion of FXa forms.
• Chemical modification of FXa active sites was performed to assess cofactor function in plasminogen activation and fibrinolysis.

Main Results:

• Purified Xa33/13 increased tPA-dependent plasmin generation over 10-fold.
• In situ conversion of FXaalpha/beta to Xa33/13 correlated with enhanced plasmin generation.
• FXaalpha/beta and Xa33/13 significantly reduced fibrin clot lysis times (up to 7-fold) and accelerated initial fibrin cleavage.

Conclusions:

• Proteolytic modulation of coagulation factor Xa enhances fibrinolysis.
• Modified FXa acts as a potent cofactor for tPA, promoting plasmin generation and accelerating clot dissolution.
• FXa may prime fibrin's cofactor activity, playing a critical role in regulating blood clot breakdown.