Open AccessFactor V‐short and protein S as synergistic tissue factor pathway inhibitor ( TFPI α) cofactors
Author(s) -
Dahlbäck Björn,
Guo Li Jun,
LivajaKoshiar Ruzica,
Tran Sinh
Publication year - 2018
Publication title -
research and practice in thrombosis and haemostasis
Language(s) - English
Resource type - Journals
ISSN - 2475-0379
DOI - 10.1002/rth2.12057
Subject(s) - tissue factor pathway inhibitor , cofactor , thrombin , tissue factor , protein s , protein c , recombinant dna , microbiology and biotechnology , biochemistry , factor v , coagulation , chemistry , biology , enzyme , platelet , medicine , immunology , gene , thrombosis
AbstractEssentials FV‐Short, a normal splice isoform of Factor V, binds tissue factor pathway inhibitor (TFPIα) with high affinity. FV‐Short functions as a synergistic TFPIα cofactor with protein S in inhibition of Factor Xa. FV‐Short is much more efficient as TFPIα cofactor than full length FV. TFPIα‐cofactor activity of FV‐Short is lost upon activation of coagulation by thrombin‐mediated cleavage.Background FV ‐Short is a normal splice variant of Factor V ( FV ) having a short B domain, which exposes a high affinity‐binding site for tissue factor pathway inhibitor α ( TFPI α). FV ‐Short and TFPI α circulate in complex in plasma. Objectives The aim was to elucidate whether FV ‐Short affects TFPI α as inhibitor of coagulation FX a and to test whether the TFPI α‐cofactor activity of protein S is influenced by FV ‐Short. Methods Recombinant FV , wild‐type FV ‐Short and a FV ‐Short thrombin‐cleavage resistant variant were expressed and purified. The influence of FV and FV ‐Short variants and/or protein S on the FX a inhibitory activity of TFPI α was monitored both in a purified system and in a plasma‐based thrombin generation assay. Results FV ‐Short had intrinsically weak TFPI α‐cofactor activity but with protein S present, FV ‐Short yielded efficient inactivation of FX a. Protein S alone did not promote full TFPI α‐activity. Intact FV was inefficient at low protein S concentrations and had 10‐fold lower activity compared to FV ‐Short at physiological protein S levels. Activation of FV ‐Short by thrombin resulted in the loss of the TFPI α‐cofactor activity. The synergistic TFPI α‐cofactor activity of FV ‐Short and protein S was also demonstrated in plasma using a thrombin generation assay. Conclusions FV ‐Short and protein S are highly efficient, synergistic cofactors to TFPI α in the regulation of FX a activity, whereas full length FV has lower activity. Our results suggest the formation of an efficient FX a‐inhibitory complex between FV ‐Short, TFPI α and protein S on the surface of negatively charged phospholipids.