| 1. |
|
|
| 2. |
- Dahlbäck, Björn, et al.
(författare)
-
New functional test for the TFPIα cofactor activity of Protein S working in synergy with FV-Short
- 2019
-
Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 17:4, s. 585-595
-
Tidskriftsartikel (refereegranskat)abstract
- Essentials Protein S and FV-Short are synergistic cofactors to Tissue Factor Pathway Inhibitor α (TFPIα). An assay for the TFPIα synergistic cofactor activity of protein S with FV-Short was developed. The assay was specific for the synergistic TFPIα-cofactor activity of free protein S. Protein S deficient individuals with known mutations were correctly distinguished from controls. Summary: Background Protein S is an anticoagulant cofactor to both activated protein C and tissue factor pathway inhibitor (TFPIα). The TFPIα-cofactor activity of protein S is stimulated by a short isoform of factor V (FV-Short), the two proteins functioning in synergy. Objective Using the synergistic TFPIα-cofactor activity between protein S and FV-Short to develop a functional test for plasma protein S. Patients/Methods TFPIα-mediated inhibition of FXa in the presence of FV-Short, protein S and negatively charged phospholipid vesicles was monitored in time by synthetic substrate S2765. TFPIα, FXa and FV-Short were purified proteins, whereas diluted plasma from protein S deficient patients or controls were used as source for protein S. Results The assay was specific for free protein S demonstrating good correlation to free protein S plasma levels (r = 0.92) with a Y-axis intercept of −5%. Correlation to concentrations of total protein S (free and C4BPβ+-bound) was lower (r = 0.88) and the Y-axis intercept was +46%, which is consistent with the specificity for free protein S. The test distinguished protein S-deficient individuals from 6 families with known ProS1 mutations from family members having no mutation. Protein S levels of warfarin-treated protein S deficient cases were lower than protein S in cases treated with warfarin for other causes. Conclusions We describe a new assay measuring the TFPIα-cofactor activity of plasma protein S. The test identifies type I/III protein S deficiencies and will be a useful tool to detect type II protein S deficiency having defective TFPIα-cofactor activity.
|
|
| 3. |
- Dahlbäck, Björn, et al.
(författare)
-
Inherited resistance to activated protein C caused by presence of the FV:Q506 allele as a basis of venous thrombosis
- 1996
-
Ingår i: Haemostasis. - 0301-0147. ; 26:SUPPL. 4, s. 301-314
-
Tidskriftsartikel (refereegranskat)abstract
- Inherited resistance to activated protein C (APC) was recently discovered as a cause of familial thrombophilia and is now known to be the most common genetic risk factor for venous thrombosis. In a majority of cases, APC resistance is associated with a single point mutation in the factor V gene, which results in substitution of arginine (R) at position 506 by glutamine (Q) (FV:Q506). The mutation renders factor Va partially resistant to degradation by activated protein C (APC), which leads to a hypercoagulable state and a life-long 5-10-fold increased risk of venous thrombosis. The previously known inherited deficiencies of antithrombin, protein S or protein C, are in western societies together found in less than 10-15% of thrombosis patients, whereas APC resistance is present in 20 to 60% of the patients. A functional APC resistance test, which includes predilution of the patient plasma with factor V deficient plasma, is 100% sensitive and specific for the presence of FV:Q506. The FV:Q506 allele is common in populations of Caucasian origin (prevalence ranging between 1 and 15%), whereas it is not found in certain other ethnic groups such as in Japanese and Chinese. The thrombotic risk in individuals with APC resistant may be further increased by other genetic defects such as protein C or protein S deficiency and by exposure to circumstantial risk factors such as oral contraceptives, pregnancy, immobilisation and surgery.
|
|
| 4. |
- Dahlbäck, Björn, et al.
(författare)
-
Resistance to activated protein C, the FV:Q506 allele, and venous thrombosis
- 1996
-
Ingår i: Annals of Hematology. - : Springer Science and Business Media LLC. - 0939-5555 .- 1432-0584. ; 72:4, s. 166-176
-
Forskningsöversikt (refereegranskat)abstract
- Vitamin K-dependent protein C is an important regulator of blood coagulation. After its activation on the endothelial cell surface by thrombin bound to thrombomodulin, it cleaves and inactivates procoagulant cofactors Va and VIIIa, protein S and intact factor V working as cofactors. Until recently, genetic defects of protein C or protein S were, together with antithrombin III deficiency, the established major causes of familial venous thromboembolism, but they were found in fewer than 5-10% of patients with thrombosis. In 1993, inherited resistance to activated protein C (APC) was described as a major risk factor for venous thrombosis. It is found in up to 60% of patients with venous thrombosis. In more than 90% of cases, the molecular background for the APC resistance is a single point mutation in the factor V gene, which predicts substitution of an arginine (R) at position 506 by a glutamine (Q). Mutated factor V (FV:Q506) is activated by thrombin or factor Xa in normal way, but impaired inactivation of mutated factor Va by APC results in life-long hypercoagulability. The prevalence of the FV:Q506 allele in the general population of Western countries varies between 2 and 15%, whereas it is not found in several other populations with different ethnic backgrounds. Owing to the high prevalence of FV:Q506 in Western populations, it occasionally occurs in patients with deficiency of protein S, protein C, or antithrombin III. Individuals with combined defects suffer more severely from thrombosis, and often at a younger age, than those with single defects, suggesting severe thrombophilia to be a multigenetic disease.
|
|
| 5. |
- Garcia de Frutos, Pablo, et al.
(författare)
-
Differential regulation of alpha and beta chains of C4b-binding protein during acute-phase response resulting in stable plasma levels of free anticoagulant protein S
- 1994
-
Ingår i: Blood. - 1528-0020. ; 84:3, s. 815-822
-
Tidskriftsartikel (refereegranskat)abstract
- Regulation of C4b-binding protein (C4BP) isoforms during acute phase and its relationship to the plasma concentration of free protein S was elucidated. An assay for beta chain containing C4BP (C4BP beta+) was developed and the concentrations of total C4BP, C4BP beta+, total, free, and bound protein S were measured in patients with acute-phase response. Even though total C4BP was increased to 162% (mean value) of controls, the corresponding value of C4BP beta+ was only 122%. In the acute-phase group, total protein S was increased to the same extent as C4BP beta+ (mean value of 124%), whereas free protein S was not decreased. In controls, total and bound protein S correlated with total C4BP and C4BP beta+. However, in the acute-phase group, the correlation between bound protein S and total C4BP was lost, although the correlation between C4BP beta+ and protein S remained. The present results suggest stable levels of free protein S during acute phase to be the result of differential regulation of C4BP alpha- and beta-chain expression, and the concentration of free protein S to be the resulting molar excess of protein S over C4BP beta+. This mechanism ensures functional levels of free anticoagulant protein S despite high levels of C4BP.
|
|
| 6. |
- Garcia de Frutos, Pablo, et al.
(författare)
-
Differential regulation of α and β chains of C4b-binding protein during acute-phase response resulting in stable plasma levels of free anticoagulant protein S
- 1994
-
Ingår i: Blood. - 1528-0020. ; 84:3, s. 815-822
-
Tidskriftsartikel (refereegranskat)abstract
- Regulation of C4b-binding protein (C4BP) isoforms during acute phase and its relationship to the plasma concentration of free protein S was elucidated. An assay for β chain containing C4BP (C4BPβ+) was developed and the concentrations of total C4BP, C4BPβ+, total, free, and bound protein S were measured in patients with acute-phase response. Even though total C4BP was increased to 162% (mean value) of controls, the corresponding value of C4BPβ+ was only 122%. In the acute-phase group, total protein S was increased to the same extent as C4BPβ+ (mean value of 124%), whereas free protein S was not decreased. In controls, total and bound protein S correlated with total C4BP and C4BPβ+. However, in the acute-phase group, the correlation between bound protein S and total C4BP was lost, although the correlation between C4BPβ+ and protein S remained. The present results suggest stable levels of free protein S during acute phase to be the result of differential regulation of C4BP α- and β-chain expression, and the concentration of free protein S to be the resulting molar excess of protein S over C4BPβ+. This mechanism ensures functional levels of free anticoagulant protein S despite high levels of C4BP.
|
|
| 7. |
- Giri, Tusar K, et al.
(författare)
-
A new direct, fast and quantitative enzyme-linked ligandsorbent assay for measurement of free protein S antigen
- 1998
-
Ingår i: Thrombosis and Haemostasis. - 0340-6245. ; 79:4, s. 767-772
-
Tidskriftsartikel (refereegranskat)abstract
- A new method to determine the concentration of the free protein S in plasma is described. It is an enzyme-linked ligandsorbent assay (ELSA) which utilises the protein S binding capacity of the natural ligand C4b-binding protein (C4BP) to capture the free protein S from plasma samples. The use of C4BP as ligand in the assay is possible due to the high affinity (Kd = 0.1 nM) of the interaction between protein S and C4BP and to a slow rate of complex dissociation. A monoclonal antibody (HPS 54) was conjugated with horseradish peroxidase and used as target antibody. This antibody recognises a Ca2+ dependent epitope in the first EGF-like domain of protein S and does not interfere with C4BP binding sites of protein S. Addition of calcium in the assay helped prevent dissociation of the C4BP-protein S-HPS 54 complex. Three different experiments demonstrated the assay to be specific for free protein S. First, near-identical dose response curves were obtained with protein S in plasma and with purified protein S. Second, addition of purified C4BP to normal plasma resulted in loss of free protein S. Third, protein S depleted plasma gave zero values and around 80% of purified protein S added to protein S depleted plasma, and approximately 70% of protein S added to protein S deficient plasma samples, was recovered with the assay. The assay is fast (involves only a single incubation step of 30 min), sensitive and the range of measurement is 3% to 200% of free protein S when plasma dilution 1:20 represents 100%. Intra- and inter-assay coefficients of variation at two levels were 2.3-4.3% and 5.1-7.4%, respectively. In a large protein S deficient family, the assay showed 100% sensitivity and specifity for the causative mutation. Moreover, free protein S levels in anticoagulated protein S deficient patients were completely separated from those obtained in non-anticoagulated controls. The new assay for free protein S is suitable for automation and it provides a useful means for routine clinical purposes to detect protein S deficiencies.
|
|
| 8. |
|
|
| 9. |
- Hillarp, Andreas, et al.
(författare)
-
Activated protein C resistance : from phenotype to genotype and clinical practice
- 1995
-
Ingår i: Blood Reviews. - 0268-960X. ; 9:4, s. 201-212
-
Tidskriftsartikel (refereegranskat)abstract
- The anticoagulant protein C system is an important regulator of the blood coagulation process. Its targets are the procoagulant cofactors factor Va and factor VIIIa, which are cleaved and inactivated by activated protein C, protein S and intact factor V working as cofactors. Genetic defects of protein C or protein S were, together with antithrombin III deficiency, the previously established major causes of familial venous thromboembolism. However, these abnormalities are found in less than 5-10% of patients with thrombosis. Inherited resistance to activated protein C was recently identified as a major risk factor for venous thromboembolism. The activated protein C-resistance phenotype is found in 20-60% of the patients with venous thrombosis, depending on selection criteria and on the prevalence of activated protein C-resistance in the population. The frequency of activated protein C-resistance is 2-10% in the normal populations studied so far. In more than 90% of cases, the molecular background for the activated protein C-resistance is a single point mutation in the factor V gene, which predicts substitution of an arginine at position 506 by a glutamine. Mutated factor V is activated by thrombin or factor Xa in the normal way, but impaired inactivation of mutated factor Va by activated protein C results in a life-long hypercoagulability. Owing to the high prevalence of activated protein C-resistance in the population, it occasionally occurs in patients with deficiency of protein S, protein C or antithrombin III. Individuals with combined defects suffer more severely from thrombosis, and often at a younger age, than those with single defects, suggesting thrombophilia to be a multigenetic disease.
|
|
| 10. |
- Hillarp, Andreas, et al.
(författare)
-
The 20210 A allele of the prothrombin gene is a common risk factor among Swedish outpatients with verified deep venous thrombosis
- 1997
-
Ingår i: Thrombosis and Haemostasis. - 0340-6245. ; 78:3, s. 2-990
-
Tidskriftsartikel (refereegranskat)abstract
- A dimorphism in the 3'-untranslated region of the prothrombin gene (G to A transition at position 20210) has recently been reported to be associated with increases in plasma prothrombin levels and in the risk of venous thrombosis. We have examined the prothrombin dimorphism among 99 unselected outpatients with phlebography verified deep venous thrombosis, and in 282 healthy controls. The prevalence of the 20210 A allele was 7.1% (7/99) in the patient group, and 1.8% (5/282) in the healthy control group (p = 0.0095). The relative risk of venous thrombosis was calculated to be 4.2 (95% CI, 1.3 to 13.6), and was still significant when adjustment was made for age, sex and the factor V:R506Q mutation causing APC resistance [odds ratio 3.8 (95% CI, 1.1 to 13.2)]. As previously reported, 28% of the patients were carriers of the factor V:R506Q mutation. Thus, 34% (one patient carried both traits) of unselected patients with deep venous thrombosis were carriers of an inherited prothrombotic disorder. To sum up, our results confirm the 20210 A allele of the prothrombin gene to be an important risk factor for venous thrombosis.
|
|
