VPB1047 - The FV-A2086D mutation results in impaired anticoagulant function.

Tuesday, July 12, 2022

6:30 PM – 7:30 PM

Location: Exhibition

Presentation Format: Virtual

Presenting Author(s)

Naruto Shimonishi, PhD

assistant professor
Nara Medical University
Kashihara, Nara, Japan

Co-Author(s)

KO

Kenichi Ogiwara

Assistant professor
Department of Pediatrics, Nara Medical University
Kashihara, Nara, Japan
KN

Keiji Nogami

Professor
Nara Medical University, Nara, Japan
Nara, Nara, Japan

Background: Coagulation factor V (FV) has procoagulant and anticoagulant functions. We reported the FV-W1920R mutation in a patient with deep vein thrombosis and which had resistance to activated protein C (APC) (Nogami et al. Blood 2014). FV-W1920R was located on the C1 domain in light chain. Recently FV-A2086D mutation (FV Besançon), which located on the C2 domain in light chain, with deep vein thrombosis was reported (Castoldi et al. JTH 2021). However the mechanism of thrombosis associated with FV-A2086D mutation was not fully evaluated.

Aims: To elucidate the mechanism(s) of anticoagulant functions in FV-A2086D.

Methods: We expressed the full-length FV using HEK293T cell. APC-catalyzed inactivation of FVa-A2086D was examined using the PT-based clotting assay and western blotting. A property of FVa-A2086D as the APC cofactor was examined in the FVIIIa degradation assay. Since the LCh region of FV is guessed to inhibit tissue factor TF-induced procoagulant function, thrombin generation and diluted PT were measured using normal plasma added exogenous FVa.

Results: FVa-WT:C was decreased by APC to ~10% of the initial level at 10 min. However, inactivation of FV-A2086D a:C was delayed and remained at ~60% of the initial level, irrespective of the presence of protein S. FVIIIa was inactivated by APC with FV-WT to ~25% of initial at 20 min. However, FVIIIa:C remained to ~50% in the presence of FV-A2086D. Compared to normal plasma, the decreased peak thrombin and prolonged PT was shown in normal plasma added FVa-WT. However, in normal plasma added FVa-A2086D, all the results were comparable to normal plasma, suggestive of no inhibitory effect of FVa-A2086D.

Conclusion(s): APC resistance of FV-A2086D resulted from significant loss of FVa susceptibility to APC and APC cofactor activity. Moreover, FV-A2086D lost anticoagulant function that inhibits TF-induced procoagulant function. These impaired anticoagulant functions might have led to the thrombosis.