| 1. |
- Ahnström, Josefin, et al.
(author)
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Activated protein C cofactor function of protein S: a novel role for a gamma-carboxyglutamic acid residue
- 2011
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 117:24, s. 6685-6693
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Journal article (peer-reviewed)abstract
- Protein S has an important anticoagulant function by acting as a cofactor for activated protein C (APC). We recently reported that the EGF1 domain residue Asp95 is critical for APC cofactor function. In the present study, we examined whether additional interaction sites within the Gla domain of protein S might contribute to its APC cofactor function. We examined 4 residues, composing the previously reported "Face1" (N33S/P35T/E36A/Y39V) variant, as single point substitutions. Of these protein S variants, protein S E36A was found to be almost completely inactive using calibrated automated thrombography. In factor Va inactivation assays, protein S E36A had 89% reduced cofactor activity compared with wild-type protein S and was almost completely inactive in factor VIIIa inactivation; phospholipid binding was, however, normal. Glu36 lies outside the omega-loop that mediates Ca2+-dependent phospholipid binding. Using mass spectrometry, it was nevertheless confirmed that Glu36 is gamma-carboxylated. Our finding that Gla36 is important for APC cofactor function, but not for phospholipid binding, defines a novel function (other than Ca2+ coordination/phospholipid binding) for a Gla residue in vitamin K-dependent proteins. It also suggests that residues within the Gla and EGF1 domains of protein S act cooperatively for its APC cofactor function. (Blood. 2011;117(24):6685-6693)
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| 2. |
- Andersson, Helena M., et al.
(author)
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Activated protein C cofactor function of protein S: a critical role for Asp95 in the EGF1-like domain
- 2010
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 115:23, s. 4878-4885
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Journal article (peer-reviewed)abstract
- Protein S has an established role in the protein C anticoagulant pathway, where it enhances the factor Va (FVa) and factor VIIIa (FVIIIa) inactivating property of activated protein C (APC). Despite its physiological role and clinical importance, the molecular basis of its action is not fully understood. To clarify the mechanism of the protein S interaction with APC, we have constructed and expressed a library of composite or point variants of human protein S, with residue substitutions introduced into the Gla, thrombin-sensitive region (TSR), epidermal growth factor 1 (EGF1), and EGF2 domains. Cofactor activity for APC was evaluated by calibrated automated thrombography (CAT) using protein S-deficient plasma. Of 27 variants tested initially, only one, protein S D95A (within the EGF1 domain), was largely devoid of functional APC cofactor activity. Protein S D95A was, however, gamma-carboxylated and bound phospholipids with an apparent dissociation constant (Kd(app)) similar to that of wildtype (WT) protein S. In a purified assay using FVa R506Q/R679Q, purified protein S D95A was shown to have greatly reduced ability to enhance APC-induced cleavage of FVa Arg306. It is concluded that residue Asp95 within EGF1 is critical forAPC cofactor function of protein S and could define a principal functional interaction site for APC. (Blood. 2010;115(23):4878-4885)
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| 3. |
- Dahlbäck, Björn
(author)
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Advances in understanding pathogenic mechanisms of thrombophilic disorders.
- 2008
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 112:1, s. 19-27
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Journal article (peer-reviewed)abstract
- Venous thromboembolism is a major medical problem, annually affecting 1 in 1000 individuals. It is a typical multifactorial disease, involving both genetic and circumstantial risk factors that affect a delicate balance between procoagulant and anticoagulant forces. In the last 50 years, the molecular basis of blood coagulation and the anticoagulant systems that control it have been elucidated. This has laid the foundation for discoveries of both common and rare genetic traits that tip the natural balance in favor of coagulation, with a resulting lifelong increased risk of venous thrombosis. Multiple mutations in the genes for anticoagulant proteins such as antithrombin, protein C, and protein S have been identified and constitute important risk factors. Two single mutations in the genes for coagulation factor V (FV Leiden) and prothrombin (20210G>A), resulting from approximately 20,000-year-old mutations with subsequent founder effects, are common in the general population and constitute major genetic risk factors for thrombosis. In celebration of the 50-year anniversary of the American Society of Hematology, this invited review highlights discoveries that have contributed to our present understanding of the systems that control blood coagulation and the genetic factors that are involved in the pathogenesis of venous thrombosis.
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| 4. |
- Dahlbäck, Björn
(author)
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Anticoagulant factor V and thrombosis risk
- 2004
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 103:11, s. 3995-3995
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Journal article (other academic/artistic)
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| 5. |
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| 6. |
- Dahlbäck, Björn
(author)
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Treating hemophilia by targeting protein S?
- 2018
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In: Blood. - : American Society of Hematology. - 0006-4971 .- 1528-0020. ; 131:12, s. 1271-1272
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Journal article (peer-reviewed)abstract
- In this issue of Blood, Prince et al report that by targeting anticoagulant protein S (PS), they could achieve hemostasis and prevent hemarthrosis in murine models of hemophilia.1
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| 7. |
- Happonen, Kaisa, et al.
(author)
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Gas6 fueling tumor-mediated thrombosis.
- 2016
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 127:6, s. 672-673
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Journal article (peer-reviewed)
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| 8. |
- Maurissen, Lisbeth F A, et al.
(author)
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Re-evaluation of the role of the protein S-C4b binding protein complex in activated protein C-catalyzed factor Va-inactivation
- 2008
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 111:6, s. 3034-3041
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Journal article (peer-reviewed)abstract
- Protein S expresses cofactor activity for activated protein C (APC) by enhancing the APC-catalyzed proteolysis at R-306 in factor Va. It is generally accepted that only free protein S is active and that complex formation with C4b-binding protein (C4BP) inhibits the APC-cofactor activity of protein S. However, the present study shows that protein S-C4BP expresses APC-cofactor activity and stimulates APC-catalyzed proteolysis at R-306 more than 10-fold, but instead inhibits proteolysis at R-506 by APC 3- to 4-fold. Free protein S stimulates APC-catalyzed cleavage at R-306 approximately 20-fold and has no effect on cleavage at R-506. The resulting net effect of protein S-C4BP complex formation on APC-catalyzed factor Va inactivation is a 6- to 8-fold reduction in factor Va inactivation when compared with free protein S, which is not explained by inhibition of APC-cofactor activity of protein S at R306, but by generation of a specific inhibitor for APC-catalyzed proteolysis at R-506 of factor Va. These results are of interest for carriers of the factor V-Leiden mutation (R(506)Q), as protein S-C4BP effectively enhances APC-catalyzed factor Va (R-306) inactivation in plasma containing factor V-Leiden.
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| 9. |
- Norström, Eva, et al.
(author)
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Functional characterization of recombinant FV Hong Kong and FV Cambridge.
- 2002
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 100:2, s. 524-530
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Journal article (peer-reviewed)abstract
- In factor V (FV) Cambridge (Arg306Thr) and Hong Kong (Arg306Gly), a cleavage site for anticoagulant activated protein C (APC), which is crucial for the inactivation of FVa, is lost. Although patients carrying FV Hong Kong have a normal APC response, those with FV Cambridge were reported to be APC resistant. To elucidate the molecular characteristics of the 2 FV mutants, we recreated them in a recombinant system and evaluated their functional properties. The 2 FV variants yielded identical APC resistance patterns, with APC responses being intermediate to those of wild-type FV and FV Leiden (Arg506Gln), which is known to be associated with the APC resistance phenotype. In the absence of protein S, APC mediated FVa inactivation curves obtained with the 2 variants were identical, resulting in partial FVa inactivation. In the presence of protein S, both FVa variants were almost completely inactivated because of protein S stimulation of the cleavage at Arg679. In a FVIIIa degradation system, both FV variants demonstrated slightly impaired APC cofactor activity. The ability of APC to cleave at Arg506 and at Arg679 in FVa Cambridge and Hong Kong and the slight decrease in APC cofactor activity of the 2 FV variants may explain the low thrombotic risk associated with these Arg306 mutations. In conclusion, we demonstrate that recombinant FV Cambridge and Hong Kong behave identically in in vitro assays and provide a mechanism for the low thrombotic risk associated with these FV mutations. (Blood. 2002;100:524-530)
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| 10. |
- Reglinska-Matveyev, Natalia, et al.
(author)
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TFPI cofactor function of protein S: essential role of the protein S SHBG-like domain
- 2014
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In: Blood. - : American Society of Hematology. - 1528-0020 .- 0006-4971. ; 123:25, s. 3979-3987
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Journal article (peer-reviewed)abstract
- Protein S is a cofactor for tissue factor pathway inhibitor (TFPI), accelerating the inhibition of activated factor X (FXa). TFPI Kunitz domain 3 residue Glu226 is essential for enhancement of TFPI by protein S. To investigate the complementary functional interaction site on protein S, we screened 44 protein S point, composite or domain swap variants spanning the whole protein S molecule for their TFPI cofactor function using a thrombin generation assay. Of these variants, two protein S/growth arrest-specific 6 chimeras, with either the whole sex hormone-binding globulin (SHBG)-like domain (Val243-Ser635; chimera III) or the SHBG laminin G-type 1 subunit (Ser283-Val459; chimera I), respectively, substituted by the corresponding domain in growth arrest-specific 6, were unable to enhance TFPI. The importance of the protein S SHBG-like domain (and its laminin G-type 1 subunit) for binding and enhancement of TFPI was confirmed in FXa inhibition assays and using surface plasmon resonance. In addition, protein S bound to C4b binding protein showed greatly reduced enhancement of TFPI-mediated inhibition of FXa compared with free protein S. We show that binding of TFPI to the protein S SHBG-like domain enables TFPI to interact optimally with FXa on a phospholipid membrane.
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