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Mechanisms that regulate the anticoagulant function of coagulation factor V
1Department of Clinical Chemistry, Lund University, University Hospital Malmö, Sweden. elisabeth.thorelli@klkemi.mas.lu.se
Summary
Coagulation factor V has dual roles in blood clotting. Cleavage at Arg 1545 by thrombin abolishes its anticoagulant function, while activated protein C (APC) cleavage at Arg 506 generates an anticoagulant cofactor.
Area of Science:
- Biochemistry
- Hematology
- Molecular Biology
Background:
- Coagulation factor V (FV) is a key procoagulant protein, essential for thrombin generation.
- FV also possesses anticoagulant properties, acting as a cofactor for activated protein C (APC).
- APC downregulates coagulation by inactivating factors VIII/VIIIa and V/Va.
Purpose of the Study:
- To elucidate the molecular mechanisms regulating the anticoagulant activity of factor V.
- To investigate how thrombin and APC cleavage sites influence FV's dual functions.
- To understand the structural requirements for FV's cofactor activity with APC.
Main Methods:
- Thrombin activation assays of factor V.
- Factor VIIIa degradation assays in the presence of FV, protein S, and APC.
- Analysis of different FV activation intermediates and their cofactor activities.
Main Results:
- Thrombin cleavage at Arg 709 and Arg 1018 preserves FV's APC cofactor activity.
- Cleavage at Arg 1545 by thrombin abolishes FV's anticoagulant function, indicating the B-domain's importance.
- APC cleavage at Arg 506 converts FV into an anticoagulant cofactor, simultaneously inactivating its procoagulant potential.
Conclusions:
- The APC cofactor function of FV is dependent on the B-domain remaining attached to the A3 domain.
- Differential proteolytic cleavage by thrombin and APC dictates FV's role in hemostasis.
- FV's conversion into either a procoagulant or anticoagulant highlights intricate regulatory mechanisms balancing coagulation.