Regulation of TFPI function by protein S

Hackeng, Tilman M.; Maurissen, Lisbeth F. A.; Castoldi, Elisabetta; Rosing, Jan

doi:10.1111/j.1538-7836.2009.03363.x

Cited by 59 publications

(53 citation statements)

References 34 publications

(47 reference statements)

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“…The first Kunitz domain of full length TFPIα inhibits FVIIa, the second inhibits FXa, whereas the third Kunitz domain interacts with protein S 13, 14, 15, 16. The interaction between TFPIα and protein S is associated with stimulation of the inhibition of FXa by TFPIα 17, 18. Full length FV has also been reported to potentiate the activity of TFPIα 19, 20.…”

Section: Introductionmentioning

confidence: 99%

Factor V‐short and protein S as synergistic tissue factor pathway inhibitor (TFPIα) cofactors

Dahlbäck

Guo

Livaja-Koshiar

et al. 2018

Research and Practice in Thrombosis and Haemostasis

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Essentials 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 (TFPIα). FV‐Short and TFPIα circulate in complex in plasma.ObjectivesThe aim was to elucidate whether FV‐Short affects TFPIα as inhibitor of coagulation FXa and to test whether the TFPIα‐cofactor activity of protein S is influenced by FV‐Short.MethodsRecombinant 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 FXa inhibitory activity of TFPIα was monitored both in a purified system and in a plasma‐based thrombin generation assay.Results FV‐Short had intrinsically weak TFPIα‐cofactor activity but with protein S present, FV‐Short yielded efficient inactivation of FXa. Protein S alone did not promote full TFPIα‐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 TFPIα‐cofactor activity. The synergistic TFPIα‐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 TFPIα in the regulation of FXa activity, whereas full length FV has lower activity. Our results suggest the formation of an efficient FXa‐inhibitory complex between FV‐Short, TFPIα and protein S on the surface of negatively charged phospholipids.

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Section: Introductionmentioning

confidence: 99%

Factor V‐short and protein S as synergistic tissue factor pathway inhibitor (TFPIα) cofactors

Dahlbäck

Guo

Livaja-Koshiar

et al. 2018

Research and Practice in Thrombosis and Haemostasis

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“…Recent studies have also identified PS as a cofactor to tissue factor pathway inhibitor (2,3). Tissue factor pathway inhibitor regulates the tissue factor-dependent initial step of coagulation by inactivating coagulation factors VIIa and Xa.…”

Section: Protein S (Ps)mentioning

confidence: 99%

Dependence on Vitamin K-dependent Protein S for Eukaryotic Cell Secretion of the β-Chain of C4b-binding Protein

Carlsson

Dahlbäck

2010

Journal of Biological Chemistry

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The anticoagulant vitamin K-dependent protein S (PS) circulates in plasma in two forms, 30% free and 70% being bound to the complement regulatory protein C4b-binding protein (C4BP). The major C4BP isoform consists of 7 ␣-chains and 1 ␤-chain (C4BP␤ ؉ ), the chains being linked by disulfide bridges.PS binds to the ␤-chain with high affinity. In plasma, PS is in molar excess over C4BP␤ ؉ and due to the high affinity, all C4BP␤ ؉ molecules contain a bound PS. Taken together with the observation that PS-deficient patients have decreased levels of C4BP␤ ؉ , this raises the question of whether PS is important for secretion of the ␤-chain from the cell. To test this hypothesis, HEK293 cells were stably and transiently transfected with ␤-chain cDNA in combinations with cDNAs for PS and/or the ␣-chain. The concentration of ␤-chains in the medium increased after co-transfection with PS cDNA, but not by ␣-chain cDNA, suggesting secretion of the ␤-chains from the cells to be dependent on concomitant synthesis of PS, but not of the ␣-chains. Thus, ␤-chains that were not disulfide-linked to the ␣-chains were secreted in complex with PS, either as monomers or dimers. Pulse-chase demonstrated that the complexes between PS and ␤-chain were formed intracellularly, in the endoplasmic reticulum. In conclusion, our results demonstrate that successful secretion of ␤-chains depends on intracellular complex formation with PS, but not on the ␣-chains. This provides an explanation for the decreased ␤-chain levels observed in PS-deficient patients. Protein S (PS)2 is an anticoagulant vitamin K-dependent protein functioning as a cofactor to activated protein C in the degradation of coagulation factors Va and VIIIa (1). Recent studies have also identified PS as a cofactor to tissue factor pathway inhibitor (2, 3). Tissue factor pathway inhibitor regulates the tissue factor-dependent initial step of coagulation by inactivating coagulation factors VIIa and Xa. In human plasma, 60 -70% of PS circulates bound to the complement regulator C4b-binding protein (C4BP) (4), and this fraction has impaired anticoagulant functions (5). PS is a 635-amino-acid-long single chain molecule with several distinct domains. The N-terminal Gla domain is followed by a thrombin-sensitive region, four epidermal growth factor (EGF)-like domains, and the large C-terminal sex hormone-binding globulin (SHBG)-like region, which comprises two laminin G-type domains. The binding site in PS for C4BP is located in the SHBG region of PS, and both laminin G domains are required (6). The binding site in PS has not been narrowed down further, even though there are several studies suggesting different regions of the SHBG domain to be of importance (7,8).C4BP acts as a cofactor for the down-regulation of the complement cascade and shares structural features with several other proteins participating in this system. It is composed of multiple disulfide-linked subunits (␣-and ␤-chains), each containing repeats of complement control protein (CCP) domains (9). There are several isoform...

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“…Because of the downregulation of thrombin generation by APC/protein S, an appreciable part of the reduction of thrombin generation by APC (shown by the gray area) is actually caused by the TFPI/protein S pathway. 27 Hence, in the presence of APC the TFPI/protein S system regains a grip on FXa-regulation even at high TF. A second example of TFPI activity at high TF is the observation that the APC-independent activity of protein S in clotting plasma, which we now know represents the ability of protein S to enhance the anticoagulant activity of TFPI, became particularly apparent in the presence of heparin.…”

Section: Hackeng and Rosing Protein S As Cofactor For Tfpi 2017mentioning

confidence: 99%

“…However, in various truncated forms of TFPI, Kunitz-3 is involved in cross-disulfide bonding between TFPI and low-density lipoprotein. 26 Of total TFPI, 80% is attached to the vessel wall, whereas 20% circulates in plasma (review 27 ). From the 20% plasma TFPI, 80% is bound to various lipoproteins and only 10% (Ϸ0.25 nmol/L) circulates as free full-length TFPI.…”

Section: Tfpimentioning

confidence: 99%

Protein S as Cofactor for TFPI

Hackeng

Rosing

2009

ATVB

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Abstract-In the last decades evidence was obtained that protein S not only acts as cofactor of activated protein C (APC) in the downregulation of coagulation, but also expresses anticoagulant activity in the absence of APC. The search for the mechanism(s) underlying the APC-independent anticoagulant activity of protein S was hampered by the fact that protein S exhibited 2 seemingly identical anticoagulant activities in model systems and in plasma. Later it was shown that the anticoagulant activity of purified protein S in model systems was dependent on the concentration of phospholipid vesicles and was explained by low amounts of protein S multimers generated during purification that effectively inhibited phospholipid-dependent coagulation reactions via competition for phospholipid binding sites. Plasma does not contain multimers, and the anticoagulant activity of protein S in plasma was not affected by the phospholipid concentration but was dependent on the amount of tissue factor (TF) used for initiation of thrombin generation. This led to the discovery that protein S acts as cofactor of tissue factor pathway inhibitor (TFPI) which stimulates the inhibition of factor Xa by TFPI Ϸ10-fold. The current review describes the background of the TFPI-cofactor activity of protein S as well as the rationale for the observation that the TFPI/protein S system particularly inhibits the TF pathway at low procoagulant stimuli. . It is well known that protein S acts as a cofactor of activated protein C (APC) in the proteolytic inactivation of blood coagulation factors Va and VIIIa, thus providing a negative feedback on coagulation and making the APC/protein S pathway essential for normal hemostasis. [2][3][4][5] Homozygous deficiencies in either protein C or protein S result in severe neonatal procoagulant phenotypes, whereas heterozygous deficiencies are associated with a 10-fold increased risk of venous thrombosis. 6 -8 More recently it has been shown that protein S also effectively inhibits thrombin generation in plasma in the absence of APC. 9 This anticoagulant property of protein S was especially observed at low TF concentrations (Ϸ1 pmol/L) leading to the concept that protein S took part in regulating the initiation phase of coagulation and effectively counteracts ongoing procoagulant processes in the circulation. 10 Interestingly, protein S had no effect on thrombin generation when coagulation was initiated through the intrinsic route, regardless of the amount of trigger used. 5 Because of the dependence of the anticoagulant activity of protein S on the TF concentration, a new role of protein S was identified as a cofactor for TFPI in the inhibition of FXa. 11 In contrast to investigations in plasma, many studies were performed in model systems using purified protein S preparations that also led to reports about APC-independent anticoagulant properties of protein S. [12][13][14][15][16] Although the anticoagulant activities in plasma and in model systems containing purified proteins initially looked mechanistic...

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Regulation of TFPI function by protein S

Cited by 59 publications

References 34 publications

Factor V‐short and protein S as synergistic tissue factor pathway inhibitor (TFPIα) cofactors

Factor V‐short and protein S as synergistic tissue factor pathway inhibitor (TFPIα) cofactors

Dependence on Vitamin K-dependent Protein S for Eukaryotic Cell Secretion of the β-Chain of C4b-binding Protein

Protein S as Cofactor for TFPI

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