Factor V anticoagulant cofactor activity that targets the early phase of coagulation
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
Tissue factor pathway inhibitor (TFPI), the main inhibitor of initiation of coagulation, exerts an important anticoagulant role through the factor Xa (FXa)-dependent inhibition of tissue factor/factor VIIa (FVIIa). Protein S is a TFPI cofactor, enhancing the efficiency of FXa inhibition. TFPI can also inhibit prothrombinase assembly by directly interacting with coagulation factor V (FV) which has been activated by FXa. Since full-length TFPI associates with FV in plasma, we hypothesized that FV may influence TFPI inhibitory function. Using pure component FXa inhibition assays, we found that while FV alone did not influence TFPI-mediated FXa inhibition, it further enhanced TFPI in the presence of protein S, resulting in an ~8-fold reduction in Ki compared with TFPI alone. A FV variant (R709Q/R1018Q/R1545Q, FVΔIIa) that cannot be cleaved/activated by thrombin or FXa, also enhanced TFPI-mediated inhibition of FXa ~12-fold in the presence of protein S. In contrast, neither activated FV (FVa) nor recombinant B-domain-deleted FV could enhance TFPI-mediated inhibition of FXa in the presence of protein S, suggesting a functional contribution of the B domain. Using TFPI and protein S variants we show further that the enhancement of TFPI-mediated FXa inhibition by protein S and FV depends on a direct protein S/TFPI interaction and that the TFPI C-terminal tail is not essential for this enhancement. In FXa-catalyzed prothrombin activation assays, both FV and FVΔIIa (but not FVa) enhanced TFPI function in the presence of protein S. These results demonstrate a new anticoagulant (cofactor) function of FV that targets the early phase of coagulation before prothrombinase assembly.
Date Issued
2017-04-18
Date Acceptance
2017-04-18
Citation
Journal of Biological Chemistry, 2017, 292, pp.9335-9344
ISSN
0021-9258
Publisher
American Society for Biochemistry and Molecular Biology
Start Page
9335
End Page
9344
Journal / Book Title
Journal of Biological Chemistry
Volume
292
Copyright Statement
© 2017 by The American Society for Biochemistry and Molecular Biology, Inc. Author's Choice—Final version free via Creative Commons CC-BY license (https://creativecommons.org/licenses/by/4.0/)
Sponsor
British Heart Foundation
British Heart Foundation
Identifier
http://www.ncbi.nlm.nih.gov/pubmed/28420729
PII: M116.769570
Grant Number
PG/14/63/31036
FS/12/60/29874
Subjects
FV
TFPI
anticoagulant
coagulation factor
enzyme inhibitor
inhibition mechanism
phospholipid
protein S
protein-protein interaction
tissue factor pathway inhibitor
Publication Status
Published
Coverage Spatial
United States