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Alshehri FS, Bashmeil AA, Alamar IA, Alouda SK. The natural anticoagulant protein S; hemostatic functions and deficiency. Platelets 2024; 35:2337907. [PMID: 38602463 DOI: 10.1080/09537104.2024.2337907] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Accepted: 03/27/2024] [Indexed: 04/12/2024]
Abstract
Protein S (PS) is a vital endogenous anticoagulant. It plays a crucial role in regulating coagulation by acting as a cofactor for the activated protein C (APC) and tissue factor pathway inhibitor (TFPI) pathways. Additionally, it possesses direct anticoagulant properties by impeding the intrinsic tenase and prothrombinase complexes. Protein S oversees the coagulation process in both the initiation and propagation stages through these roles. The significance of protein S in regulating blood clotting can be inferred from the significant correlation between deficits in protein S and an elevated susceptibility to venous thrombosis. This is likely because activated protein C and tissue factor pathway inhibitor exhibit low efficacy as anticoagulants when no cofactors exist. The precise biochemical mechanisms underlying the roles of protein S cofactors have yet to be fully elucidated. Nevertheless, recent scientific breakthroughs have significantly enhanced comprehension findings for these functions. The diagnosis of protein S deficiency, both from a technical and genetic standpoint, is still a subject of debate due to the complex structural characteristics of the condition. This paper will provide an in-depth review of the molecular structure of protein S and its hemostatic effects. Furthermore, we shall address the insufficiency of protein S and its methods of diagnosis and treatment.
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Affiliation(s)
- Fahad S Alshehri
- Pathology and Clinical Laboratory Medicine Department, Haematology Division, King Faisal Medical City for Southern Region, Abha, Saudi Arabia
- Pathology and Clinical Laboratory Medicine Department, Haematology Division, King Fahad Medical City, Riyadh, Saudi Arabia
| | - Abdullah A Bashmeil
- Pathology and Clinical Laboratory Medicine Department, Haematology Division, King Fahad Medical City, Riyadh, Saudi Arabia
| | - Ibrahim A Alamar
- Pathology and Clinical Laboratory Medicine Department, Haematology Division, King Fahad Medical City, Riyadh, Saudi Arabia
| | - Sarah K Alouda
- College of Applied Medical Science, Clinical Laboratory Department, King Saud University, Riyadh, Saudi Arabia
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2
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Qiao X, Yin J, Zheng Z, Li L, Feng X. Endothelial cell dynamics in sepsis-induced acute lung injury and acute respiratory distress syndrome: pathogenesis and therapeutic implications. Cell Commun Signal 2024; 22:241. [PMID: 38664775 PMCID: PMC11046830 DOI: 10.1186/s12964-024-01620-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Accepted: 04/17/2024] [Indexed: 04/28/2024] Open
Abstract
Sepsis, a prevalent critical condition in clinics, continues to be the leading cause of death from infections and a global healthcare issue. Among the organs susceptible to the harmful effects of sepsis, the lungs are notably the most frequently affected. Consequently, patients with sepsis are predisposed to developing acute lung injury (ALI), and in severe cases, acute respiratory distress syndrome (ARDS). Nevertheless, the precise mechanisms associated with the onset of ALI/ARDS remain elusive. In recent years, there has been a growing emphasis on the role of endothelial cells (ECs), a cell type integral to lung barrier function, and their interactions with various stromal cells in sepsis-induced ALI/ARDS. In this comprehensive review, we summarize the involvement of endothelial cells and their intricate interplay with immune cells and stromal cells, including pulmonary epithelial cells and fibroblasts, in the pathogenesis of sepsis-induced ALI/ARDS, with particular emphasis placed on discussing the several pivotal pathways implicated in this process. Furthermore, we discuss the potential therapeutic interventions for modulating the functions of endothelial cells, their interactions with immune cells and stromal cells, and relevant pathways associated with ALI/ARDS to present a potential therapeutic strategy for managing sepsis and sepsis-induced ALI/ARDS.
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Affiliation(s)
- Xinyu Qiao
- Shandong Provincial Key Laboratory for Rheumatic Disease and Translational Medicine, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan, China
- School of Clinical and Basic Medical Sciences, Shandong First Medical University& Shandong Academy of Medical Sciences, Jinan, 250117, Shandong, China
| | - Junhao Yin
- Shandong Provincial Key Laboratory for Rheumatic Disease and Translational Medicine, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan, China
- School of Clinical and Basic Medical Sciences, Shandong First Medical University& Shandong Academy of Medical Sciences, Jinan, 250117, Shandong, China
| | - Zhihuan Zheng
- Shandong Provincial Key Laboratory for Rheumatic Disease and Translational Medicine, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan, China
- School of Clinical and Basic Medical Sciences, Shandong First Medical University& Shandong Academy of Medical Sciences, Jinan, 250117, Shandong, China
| | - Liangge Li
- Shandong Provincial Key Laboratory for Rheumatic Disease and Translational Medicine, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan, China
- School of Clinical and Basic Medical Sciences, Shandong First Medical University& Shandong Academy of Medical Sciences, Jinan, 250117, Shandong, China
| | - Xiujing Feng
- Shandong Provincial Key Laboratory for Rheumatic Disease and Translational Medicine, The First Affiliated Hospital of Shandong First Medical University & Shandong Provincial Qianfoshan Hospital, Jinan, China.
- School of Clinical and Basic Medical Sciences, Shandong First Medical University& Shandong Academy of Medical Sciences, Jinan, 250117, Shandong, China.
- Key Laboratory of Endocrine Glucose & Lipids Metabolism and Brain Aging, Ministry of Education; Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, 250021, Shandong, China.
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3
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Sim MM, Mollica MY, Alfar HR, Hollifield M, Chung DW, Fu X, Gandhapudi S, Coenen DM, Prakhya KS, Mahmood DFD, Banerjee M, Peng C, Li X, Thornton AC, Porterfield JZ, Sturgill JL, Sievert GA, Barton-Baxter M, Zheng Z, Campbell KS, Woodward JG, López JA, Whiteheart SW, Garvy BA, Wood JP. Unfolded Von Willebrand Factor Binds Protein S and Reduces Anticoagulant Activity. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.08.579463. [PMID: 38370737 PMCID: PMC10871343 DOI: 10.1101/2024.02.08.579463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Protein S (PS), the critical plasma cofactor for the anticoagulants tissue factor (TF) pathway inhibitor (TFPI) and activated protein C (APC), circulates in two functionally distinct pools: free (anticoagulant) or bound to complement component 4b-binding protein (C4BP) (anti-inflammatory). Acquired free PS deficiency is detected in several viral infections, but its cause is unclear. Here, we identified a shear-dependent interaction between PS and von Willebrand Factor (VWF) by mass spectrometry. Consistently, plasma PS and VWF comigrated in both native and agarose gel electrophoresis. The PS/VWF interaction was blocked by TFPI but not APC, suggesting an interaction with the C-terminal sex hormone binding globulin (SHBG) region of PS. Microfluidic systems, mimicking arterial laminar flow or disrupted turbulent flow, demonstrated that PS stably binds VWF as VWF unfolds under turbulent flow. PS/VWF complexes also localized to platelet thrombi under laminar arterial flow. In thrombin generation-based assays, shearing plasma decreased PS activity, an effect not seen in the absence of VWF. Finally, free PS deficiency in COVID-19 patients, measured using an antibody that binds near the C4BP binding site in SHBG, correlated with changes in VWF, but not C4BP, and with thrombin generation. Our data suggest that PS binds to a shear-exposed site on VWF, thus sequestering free PS and decreasing its anticoagulant activity, which would account for the increased thrombin generation potential. As many viral infections present with free PS deficiency, elevated circulating VWF, and increased vascular shear, we propose that the PS/VWF interaction reported here is a likely contributor to virus-associated thrombotic risk.
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Affiliation(s)
- Martha M.S. Sim
- Department of Molecular and Cellular Biochemistry, University of Kentucky, KY, USA
| | - Molly Y. Mollica
- Bloodworks Northwest Research Institute, WA, USA
- Division of Hematology, School of Medicine, University of Washington, WA, USA
- Department of Mechanical Engineering, University of Maryland, Baltimore County, MD, USA
| | - Hammodah R. Alfar
- Department of Molecular and Cellular Biochemistry, University of Kentucky, KY, USA
| | - Melissa Hollifield
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky, KY, USA
| | - Dominic W. Chung
- Bloodworks Northwest Research Institute, WA, USA
- Department of Biochemistry, University of Washington, WA, USA
| | - Xiaoyun Fu
- Bloodworks Northwest Research Institute, WA, USA
- Division of Hematology, School of Medicine, University of Washington, WA, USA
| | - Siva Gandhapudi
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky, KY, USA
| | - Daniëlle M. Coenen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, KY, USA
| | | | | | - Meenakshi Banerjee
- Department of Molecular and Cellular Biochemistry, University of Kentucky, KY, USA
| | - Chi Peng
- Department of Pharmacology and Nutritional Sciences, University of Kentucky, KY, USA
| | - Xian Li
- Saha Cardiovascular Research Center, University of Kentucky, KY, USA
| | | | - James Z. Porterfield
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky, KY, USA
- Division of Infectious Disease, University of Kentucky, KY, USA
| | - Jamie L. Sturgill
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky, KY, USA
| | - Gail A. Sievert
- Center for Clinical and Translational Science, University of Kentucky, KY, USA
| | | | - Ze Zheng
- Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, USA
- Versiti Blood Research Institute, Milwaukee, WI, USA
| | - Kenneth S. Campbell
- Center for Clinical and Translational Science, University of Kentucky, KY, USA
| | - Jerold G. Woodward
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky, KY, USA
| | - José A. López
- Bloodworks Northwest Research Institute, WA, USA
- Division of Hematology, School of Medicine, University of Washington, WA, USA
| | - Sidney W. Whiteheart
- Department of Molecular and Cellular Biochemistry, University of Kentucky, KY, USA
- Saha Cardiovascular Research Center, University of Kentucky, KY, USA
| | - Beth A. Garvy
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky, KY, USA
| | - Jeremy P. Wood
- Department of Molecular and Cellular Biochemistry, University of Kentucky, KY, USA
- Saha Cardiovascular Research Center, University of Kentucky, KY, USA
- Division of Cardiovascular Medicine Gill Heart and Vascular Institute, University of Kentucky, KY, USA
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Petri A, Sasikumar P, Folgado PB, Jones D, Xu Y, Ahnström J, Salles-Crawley II, Crawley JTB. TFPIα anticoagulant function is highly dependent on protein S in vivo. SCIENCE ADVANCES 2024; 10:eadk5836. [PMID: 38306422 DOI: 10.1126/sciadv.adk5836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 01/04/2024] [Indexed: 02/04/2024]
Abstract
Tissue factor pathway inhibitor α (TFPIα) is the major physiological regulator of the initiation of blood coagulation. In vitro, TFPIα anticoagulant function is enhanced by its cofactor, protein S. To define the role of protein S enhancement in TFPIα anticoagulant function in vivo, we blocked endogenous TFPI in mice using a monoclonal antibody (14D1). This caused a profound increase in fibrin deposition using the laser injury thrombosis model. To explore the role of plasma TFPIα in regulating thrombus formation, increasing concentrations of human TFPIα were coinjected with 14D1, which dose-dependently reduced fibrin deposition. Inhibition of protein S cofactor function using recombinant C4b-binding protein β chain significantly reduced the anticoagulant function of human TFPIα in controlling fibrin deposition. We report an in vivo model that is sensitive to the anticoagulant properties of the TFPIα-protein S pathway and show the importance of protein S as a cofactor in the anticoagulant function of TFPIα in vivo.
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Affiliation(s)
- Anastasis Petri
- Centre for Haematology, Hammersmith Hospital Campus, Imperial College London, London, UK
| | - Parvathy Sasikumar
- Centre for Haematology, Hammersmith Hospital Campus, Imperial College London, London, UK
| | - Patricia Badia Folgado
- Centre for Haematology, Hammersmith Hospital Campus, Imperial College London, London, UK
| | - David Jones
- Centre for Haematology, Hammersmith Hospital Campus, Imperial College London, London, UK
| | - Yaoxian Xu
- Centre for Haematology, Hammersmith Hospital Campus, Imperial College London, London, UK
| | - Josefin Ahnström
- Centre for Haematology, Hammersmith Hospital Campus, Imperial College London, London, UK
| | - Isabelle I Salles-Crawley
- Centre for Haematology, Hammersmith Hospital Campus, Imperial College London, London, UK
- Vascular Biology Research Centre, Molecular and Clinical Sciences Research Institute, St. George's University of London, London, UK
| | - James T B Crawley
- Centre for Haematology, Hammersmith Hospital Campus, Imperial College London, London, UK
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Wilson HP, Pierre A, Paysse AL, Kumar N, Cooley BC, Rudra P, Dorsey AW, Polania-Villanueva D, Chatterjee S, Janbain M, Velez MC, Majumder R. Protein S antibody as an adjunct therapy for hemophilia B. Blood Adv 2024; 8:441-452. [PMID: 37773781 PMCID: PMC10827407 DOI: 10.1182/bloodadvances.2023010819] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 09/19/2023] [Accepted: 09/19/2023] [Indexed: 10/01/2023] Open
Abstract
ABSTRACT Hemophilia B (HB) is caused by an inherited deficiency of plasma coagulation factor IX (FIX). Approximately 60% of pediatric patients with HB possess a severe form of FIX deficiency (<1% FIX activity). Treatment typically requires replacement therapy through the administration of FIX. However, exogenous FIX has a limited functional half-life, and the natural anticoagulant protein S (PS) inhibits activated FIX (FIXa). PS ultimately limits thrombin formation, which limits plasma coagulation. This regulation of FIXa activity by PS led us to test whether inhibiting PS would extend the functional half-life of FIX and thereby prolong FIX-based HB therapy. We assayed clotting times and thrombin generation to measure the efficacy of a PS antibody for increasing FIX activity in commercially obtained plasma and plasma from pediatric patients with HB. We included 11 pediatric patients who lacked additional comorbidities and coagulopathies. In vivo, we assessed thrombus formation in HB mice in the presence of the FIXa ± PS antibody. We found an accelerated rate of clotting in the presence of PS antibody. Similarly, the peak thrombin formed was significantly greater in the presence of the PS antibody, even in plasma from patients with severe HB. Furthermore, HB mice injected with PS antibody and FIX had a 4.5-fold higher accumulation of fibrin at the thrombus induction site compared with mice injected with FIX alone. Our findings imply that a PS antibody would be a valuable adjunct to increase the effectiveness of FIX replacement therapy in pediatric patients who have mild, moderate, and severe HB.
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Affiliation(s)
- Hope P. Wilson
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, LA
- Department of Pediatric Hematology and Oncology, University of Alabama at Birmingham, Birmingham, AL
| | - Aliyah Pierre
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, LA
| | - Ashley L. Paysse
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, LA
| | - Narender Kumar
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, LA
| | - Brian C. Cooley
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, NC
| | | | - Adrianne W. Dorsey
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, LA
| | - Diana Polania-Villanueva
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, LA
| | - Sabyasachi Chatterjee
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, LA
| | - Maissaa Janbain
- Department of Hematology & Medical Oncology, Tulane University, New Orleans, LA
| | - Maria C. Velez
- Department of Pediatric Hematology and Oncology, Children's Hospital of New Orleans, New Orleans, LA
| | - Rinku Majumder
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, New Orleans, LA
- Department of Interdisciplinary Oncology, Louisiana State University Health Sciences Center, New Orleans, LA
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Gierula M, Noakes VM, Salles-Crawley II, Crawley JTB, Ahnström J. The TFPIα C-terminal tail is essential for TFPIα-FV-short-protein S complex formation and synergistic enhancement of TFPIα. J Thromb Haemost 2023; 21:3568-3580. [PMID: 37739040 DOI: 10.1016/j.jtha.2023.09.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2023] [Revised: 09/01/2023] [Accepted: 09/07/2023] [Indexed: 09/24/2023]
Abstract
BACKGROUND For maximal TFPIα functionality, 2 synergistic cofactors, protein S and FV-short, are required. Both interact with TFPIα, protein S through Kunitz 3 residues Arg199/Glu226 and FV-short with the C-terminus. How these interactions impact the synergistic enhancement remains unclear. OBJECTIVES To determine the importance of the TFPIα-protein S and TFPIα-FV-short interactions for TFPIα enhancement. METHODS TFPIα variants unable to bind protein S (K3m [R199Q/E226Q]) or FV-short (ΔCT [aa 1-249]) were generated. TFPIα-FV-short binding was studied by plate-binding and co-immunoprecipitation assays; functional TFPIα enhancement by FXa inhibition and prothrombin activation. RESULTS While WT TFPIα and TFPIα K3m bound FV-short with high affinity (Kd∼2nM), TFPIα ΔCT did not. K3m, in contrast to WT, did not incorporate protein S in a TFPIα-FV-short-protein S complex while TFPIα ΔCT bound neither FV-short nor protein S. Protein S enhanced WT TFPIα-mediated FXa inhibition, but not K3m, in the absence of FV-short. However, once FV-short was present, protein S efficiently enhanced TFPIα K3m (EC50: 4.7nM vs 2.0nM for WT). FXa inhibition by ΔCT was not enhanced by protein S alone or combined with FV-short. In FXa-catalyzed prothrombin activation assays, FV-short enhanced TFPIα K3m function in the presence of protein S (5.5 vs 10.4-fold enhancement of WT) whereas ΔCT showed reduced or lack of enhancement by FV-short and protein S, respectively. CONCLUSION Full TFPIα function requires the presence of both cofactors. While synergistic enhancement can be achieved in the absence of TFPIα-protein S interaction, only TFPIα with an intact C-terminus can be synergistically enhanced by protein S and FV-short.
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Li X, Song X, Mahmood DFD, Sim MMS, Bidarian SJ, Wood JP. Activated protein C, protein S, and tissue factor pathway inhibitor cooperate to inhibit thrombin activation. Thromb Res 2023; 230:84-93. [PMID: 37660436 PMCID: PMC10543463 DOI: 10.1016/j.thromres.2023.08.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2023] [Revised: 07/20/2023] [Accepted: 08/17/2023] [Indexed: 09/05/2023]
Abstract
INTRODUCTION Thrombin, the enzyme which converts fibrinogen into a fibrin clot, is produced by the prothrombinase complex, composed of factor Xa (FXa) and factor Va (FVa). Down-regulation of this process is critical, as excess thrombin can lead to life-threatening thrombotic events. FXa and FVa are inhibited by the anticoagulants tissue factor pathway inhibitor alpha (TFPIα) and activated protein C (APC), respectively, and their common cofactor protein S (PS). However, prothrombinase is resistant to either of these inhibitory systems in isolation. MATERIALS AND METHODS We hypothesized that these anticoagulants function best together, and tested this hypothesis using purified proteins and plasma-based systems. RESULTS In plasma, TFPIα had greater anticoagulant activity in the presence of APC and PS, maximum PS activity required both TFPIα and APC, and antibodies against TFPI and APC had an additive procoagulant effect, which was mimicked by an antibody against PS alone. In purified protein systems, TFPIα dose-dependently inhibited thrombin activation by prothrombinase, but only in the presence of APC, and this activity was enhanced by PS. Conversely, FXa protected FVa from cleavage by APC, even in the presence of PS, and TFPIα reversed this protection. However, prothrombinase assembled on platelets was still protected from inhibition, even in the presence of TFPIα, APC, and PS. CONCLUSIONS We propose a model of prothrombinase inhibition through combined targeting of both FXa and FVa, and that this mechanism enables down-regulation of thrombin activation outside of a platelet clot. Platelets protect prothrombinase from inhibition, however, supporting a procoagulant environment within the clot.
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Affiliation(s)
- Xian Li
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, United States of America
| | - Xiaohong Song
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, United States of America
| | - Dlovan F D Mahmood
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, United States of America
| | - Martha M S Sim
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, United States of America
| | - Sara J Bidarian
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, United States of America
| | - Jeremy P Wood
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, United States of America; Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, United States of America; Division of Cardiovascular Medicine, Gill Heart and Vascular Institute, University of Kentucky, Lexington, KY, United States of America.
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8
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Mohammed BM, Pelc LA, Rau MJ, Di Cera E. Cryo-EM structure of coagulation factor V short. Blood 2023; 141:3215-3225. [PMID: 36862974 PMCID: PMC10356581 DOI: 10.1182/blood.2022019486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Accepted: 02/22/2023] [Indexed: 03/04/2023] Open
Abstract
Coagulation factor V (fV) is the precursor of activated fV (fVa), an essential component of the prothrombinase complex required for the rapid activation of prothrombin in the penultimate step of the coagulation cascade. In addition, fV regulates the tissue factor pathway inhibitor α (TFPIα) and protein C pathways that inhibit the coagulation response. A recent cryogenic electron microscopy (cryo-EM) structure of fV has revealed the architecture of its A1-A2-B-A3-C1-C2 assembly but left the mechanism that keeps fV in its inactive state unresolved because of an intrinsic disorder in the B domain. A splice variant of fV, fV short, carries a large deletion of the B domain that produces constitutive fVa-like activity and unmasks epitopes for the binding of TFPIα. The cryo-EM structure of fV short was solved at 3.2 Å resolution and revealed the arrangement of the entire A1-A2-B-A3-C1-C2 assembly. The shorter B domain stretches across the entire width of the protein, making contacts with the A1, A2, and A3 domains but suspended over the C1 and C2 domains. In the portion distal to the splice site, several hydrophobic clusters and acidic residues provide a potential binding site for the basic C-terminal end of TFPIα. In fV, these epitopes may bind intramolecularly to the basic region of the B domain. The cryo-EM structure reported in this study advances our understanding of the mechanism that keeps fV in its inactive state, provides new targets for mutagenesis and facilitates future structural analysis of fV short in complex with TFPIα, protein S, and fXa.
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Affiliation(s)
- Bassem M. Mohammed
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO
| | - Leslie A. Pelc
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO
| | - Michael J. Rau
- Washington University Center for Cellular Imaging, Washington University School of Medicine, St. Louis, MO
| | - Enrico Di Cera
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO
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Sim MM, Wood JP. Dysregulation of Protein S in COVID-19. Best Pract Res Clin Haematol 2022; 35:101376. [PMID: 36494145 PMCID: PMC9395234 DOI: 10.1016/j.beha.2022.101376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Revised: 08/10/2022] [Accepted: 08/15/2022] [Indexed: 12/15/2022]
Abstract
Coronavirus Disease 2019 (COVID-19) has been widely associated with increased thrombotic risk, with many different proposed mechanisms. One such mechanism is acquired deficiency of protein S (PS), a plasma protein that regulates coagulation and inflammatory processes, including complement activation and efferocytosis. Acquired PS deficiency is common in patients with severe viral infections and has been reported in multiple studies of COVID-19. This deficiency may be caused by consumption, degradation, or clearance of the protein, by decreased synthesis, or by binding of PS to other plasma proteins, which block its anticoagulant activity. Here, we review the functions of PS, the evidence of acquired PS deficiency in COVID-19 patients, the potential mechanisms of PS deficiency, and the evidence that those mechanisms may be occurring in COVID-19.
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Affiliation(s)
- Martha M.S. Sim
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA
| | - Jeremy P. Wood
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY, USA,Gill Heart and Vascular Institute, Division of Cardiovascular Medicine, Department of Internal Medicine, University of Kentucky, Lexington, KY, USA,Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY, USA,Corresponding author. University of Kentucky, 741 S Limestone, BBSRB B359, Lexington, KY, 40536, USA
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10
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Sim MM, Banerjee M, Myint T, Garvy BA, Whiteheart SW, Wood JP. Total Plasma Protein S Is a Prothrombotic Marker in People Living With HIV. J Acquir Immune Defic Syndr 2022; 90:463-471. [PMID: 35616596 PMCID: PMC9246910 DOI: 10.1097/qai.0000000000002994] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Accepted: 03/21/2022] [Indexed: 01/30/2023]
Abstract
BACKGROUND HIV-1 infection is associated with multiple procoagulant changes and increased thrombotic risk. Possible mechanisms for this risk include heigthened expression of procoagulant tissue factor (TF) on circulating monocytes, extracellular vesicles, and viral particles and/or acquired deficiency of protein S (PS), a critical cofactor for the anticoagulant protein C (PC). PS deficiency occurs in up to 76% of people living with HIV-1 (PLWH). As increased ex vivo plasma thrombin generation is a strong predictor of mortality, we investigated whether PS and plasma TF are associated with plasma thrombin generation. METHODS We analyzed plasma samples from 9 healthy controls, 17 PLWH on first diagnosis (naive), and 13 PLWH on antiretroviral therapy (ART). Plasma thrombin generation, total and free PS, PC, C4b-binding protein, and TF activity were measured. RESULTS We determined that the plasma thrombin generation assay is insensitive to PS, because of a lack of PC activation, and developed a modified PS-sensitive assay. Total plasma PS was reduced in 58% of the naive and 38% of the ART-treated PLWH samples and correlated with increased thrombin generation in the modified assay. Conversely, plasma TF was not increased in our patient population, suggesting that it does not significantly contribute to ex vivo plasma thrombin generation. CONCLUSION These data suggest that reduced total plasma PS contributes to the thrombotic risk associated with HIV-1 infection and can serve as a prothrombotic biomarker. In addition, our refined thrombin generation assay offers a more sensitive tool to assess the functional consequences of acquired PS deficiency in PLWH.
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Affiliation(s)
- Martha M.S. Sim
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY
| | - Meenakshi Banerjee
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY
| | - Thein Myint
- Division of Infectious Diseases, Department of Internal Medicine, University of Kentucky, Lexington, KY
- Bluegrass Care Clinic, Kentucky Clinic, University of Kentucky, Lexington, KY
| | - Beth A. Garvy
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky, Lexington, KY
| | - Sidney W. Whiteheart
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY
- Lexington Veterans’ Affairs Healthcare System, Lexington, KY
| | - Jeremy P. Wood
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY
- Gill Heart and Vascular Institute, Division of Cardiovascular Medicine, Department of Internal Medicine, University of Kentucky, Lexington, KY
- Saha Cardiovascular Research Center, University of Kentucky, Lexington, KY
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11
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Lansdell TA, Chambers LC, Dorrance AM. Endothelial Cells and the Cerebral Circulation. Compr Physiol 2022; 12:3449-3508. [PMID: 35766836 DOI: 10.1002/cphy.c210015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Endothelial cells form the innermost layer of all blood vessels and are the only vascular component that remains throughout all vascular segments. The cerebral vasculature has several unique properties not found in the peripheral circulation; this requires that the cerebral endothelium be considered as a unique entity. Cerebral endothelial cells perform several functions vital for brain health. The cerebral vasculature is responsible for protecting the brain from external threats carried in the blood. The endothelial cells are central to this requirement as they form the basis of the blood-brain barrier. The endothelium also regulates fibrinolysis, thrombosis, platelet activation, vascular permeability, metabolism, catabolism, inflammation, and white cell trafficking. Endothelial cells regulate the changes in vascular structure caused by angiogenesis and artery remodeling. Further, the endothelium contributes to vascular tone, allowing proper perfusion of the brain which has high energy demands and no energy stores. In this article, we discuss the basic anatomy and physiology of the cerebral endothelium. Where appropriate, we discuss the detrimental effects of high blood pressure on the cerebral endothelium and the contribution of cerebrovascular disease endothelial dysfunction and dementia. © 2022 American Physiological Society. Compr Physiol 12:3449-3508, 2022.
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Affiliation(s)
- Theresa A Lansdell
- Department of Pharmacology and Toxicology, College of Osteopathic Medicine, Michigan State University, East Lansing, MI, 48824, USA
| | - Laura C Chambers
- Department of Pharmacology and Toxicology, College of Osteopathic Medicine, Michigan State University, East Lansing, MI, 48824, USA
| | - Anne M Dorrance
- Department of Pharmacology and Toxicology, College of Osteopathic Medicine, Michigan State University, East Lansing, MI, 48824, USA
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12
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Mast AE, Ruf W. Regulation of coagulation by tissue factor pathway inhibitor: Implications for hemophilia therapy. J Thromb Haemost 2022; 20:1290-1300. [PMID: 35279938 PMCID: PMC9314982 DOI: 10.1111/jth.15697] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 02/08/2022] [Accepted: 03/07/2022] [Indexed: 11/27/2022]
Abstract
Tissue factor pathway inhibitor (TFPI) is an alternatively spliced anticoagulant protein that primarily dampens the initiation phase of coagulation before thrombin is generated. As such, TFPI's actions are localized to cells expressing TF and to sites of injury, where it is an important regulator of bleeding in hemophilia. The major splice isoforms TFPIα and TFPIβ localize to different sites within and surrounding the vasculature. Both forms directly inhibit factor Xa (FXa) via their Kunitz 2 domain and inhibit TF-FVIIa via their Kunitz 1 domain in a tight complex primarily localized to cells. By forming complexes localized to distinct cellular microenvironments and engaging additional cell surface receptors, TFPI alters cellular trafficking and signaling pathways driven by coagulation proteases of the TF pathway. TFPIα, which circulates in complex with FV and protein S, also serves an inhibitor of FXa independent of the TF initiation complex and prevents the formation of an active prothrombinase. This regulation of thrombin generation in the context of vessel injury is effectively blocked by antibodies to Kunitz 2 domain of TFPI and exploited as a therapy to restore efficient hemostasis in hemophilia.
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Affiliation(s)
- Alan E. Mast
- Versiti Blood Research InstituteMilwaukeeWisconsinUSA
| | - Wolfram Ruf
- Center for Thrombosis and HemostasisJohannes Gutenberg University Medical CenterMainzGermany
- Department of Immunology and MicrobiologyScripps ResearchLa JollaCaliforniaUSA
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13
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Teraz-Orosz A, Gierula M, Petri A, Jones D, Keniyopoullos R, Folgado PB, Santamaria S, Crawley JTB, Lane DA, Ahnström J. Laminin G1 residues of protein S mediate its TFPI cofactor function and are competitively regulated by C4BP. Blood Adv 2022; 6:704-715. [PMID: 34731882 PMCID: PMC8791571 DOI: 10.1182/bloodadvances.2021005382] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Accepted: 10/20/2021] [Indexed: 11/29/2022] Open
Abstract
Protein S is a cofactor in the tissue factor pathway inhibitor (TFPI) anticoagulant pathway. It enhances TFPIα-mediated inhibition of factor (F)Xa activity and generation. The enhancement is dependent on a TFPIα-protein S interaction involving TFPIα Kunitz 3 and protein S laminin G-type (LG)-1. C4b binding protein (C4BP), which binds to protein S LG1, almost completely abolishes its TFPI cofactor function. However, neither the amino acids involved in TFPIα enhancement nor the mechanisms underlying the reduced TFPI cofactor function of C4BP-bound protein S are known. To screen for functionally important regions within protein S LG1, we generated 7 variants with inserted N-linked glycosylation attachment sites. Protein S D253T and Q427N/K429T displayed severely reduced TFPI cofactor function while showing normal activated protein C (APC) cofactor function and C4BP binding. Based on these results, we designed 4 protein S variants in which 4 to 6 surface-exposed charged residues were substituted for alanine. One variant, protein S K255A/E257A/D287A/R410A/K423A/E424A, exhibited either abolished or severely reduced TFPI cofactor function in plasma and FXa inhibition assays, both in the presence or absence of FV-short, but retained normal APC cofactor function and high-affinity C4BP binding. The C4BP β-chain was expressed to determine the mechanisms behind the reduced TFPI cofactor function of C4BP-bound protein S. Like C4BP-bound protein S, C4BP β-chain-bound protein S had severely reduced TFPI cofactor function. These results show that protein S Lys255, Glu257, Asp287, Arg410, Lys423, and Glu424 are critical for protein S-mediated enhancement of TFPIα and that binding of the C4BP β-chain blocks this function.
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Affiliation(s)
| | | | | | - David Jones
- Centre for Haematology, Imperial College London, London, UK
| | | | | | | | | | - David A. Lane
- Centre for Haematology, Imperial College London, London, UK
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14
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Dahlbäck B, Tran S. The preAR2 region (1458-1492) in factor V-Short is crucial for the synergistic TFPIα-cofactor activity with protein S and the assembly of a trimolecular factor Xa-inhibitory complex comprising FV-Short, protein S, and TFPIα. J Thromb Haemost 2022; 20:58-68. [PMID: 34623729 DOI: 10.1111/jth.15547] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Accepted: 10/05/2021] [Indexed: 01/22/2023]
Abstract
BACKGROUND Factor V-Short (FV756-1458) is a natural splice variant in which 702 residues are deleted from the B domain. It exposes an acid region (AR2; 1493-1537) that binds tissue factor pathway inhibitor alpha (TFPIα). Protein S also interacts with TFPIα and serves as TFPIα-cofactor in factor Xa (FXa) inhibition. FV-Short and protein S function as synergistic TFPIα-cofactors in inhibition of FXa. FV810-1492 is an artificial FV-Short variant that cannot synergize with protein S as TFPIα cofactor even though it contains AR2 and binds TFPIα. OBJECTIVE To elucidate the mechanisms for the synergism between FV756-1458 and protein S as TFPIα cofactors. METHODS Four FV-Short variants were created, FV756-1458 and FV712-1458 contained the preAR2 region (1458-1492), whereas FV810-1492 and FV713-1492 lacked this region. The synergistic TFPIα cofactor activity between FV-Short variants and protein S was analyzed by FXa-inhibition. A microtiter-based assay tested binding between FV-Short variants, protein S, and TFPIα. RESULTS The two preAR2-containing FV-Short variants were active as synergistic TFPIα cofactors, whereas the other two were inactive. All variants bound to TFPIα. None of the FV-Short variants bound directly to protein S. The combination of TFPIα and preAR2-containing FV-Short variants bound protein S, whereas TFPIα together with the preAR2-minus variants did not. Protein S potentiated TFPIα-binding to the preAR2-containing variants and binding between TFPIα and protein S was stimulated only by the preAR2-containing variants. CONCLUSION The preAR2 region is demonstrated to be crucial for the synergistic TFPIα-cofactor activity between FV-Short and protein S and for the assembly of a trimolecular FXa-inhibitory complex comprising FV-Short, protein S, and TFPIα.
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Affiliation(s)
- Björn Dahlbäck
- Department of Translational Medicine, Lund University, University Hospital, Malmö, Sweden
| | - Sinh Tran
- Department of Translational Medicine, Lund University, University Hospital, Malmö, Sweden
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15
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Ahnström J, Gilbert GE. Factor V mutation illuminates the dominant anticoagulant role and importance of an unidentified platelet modifier. J Thromb Haemost 2021; 19:1168-1170. [PMID: 33880872 DOI: 10.1111/jth.15273] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 02/16/2021] [Accepted: 02/16/2021] [Indexed: 11/27/2022]
Affiliation(s)
| | - Gary E Gilbert
- Department of Research, VA Boston Healthcare System, Boston, Massachusetts, USA
- Department of Medicine, VA Boston Healthcare System, Boston, Massachusetts, USA
- Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA
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16
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Gierula M, Ahnström J. Anticoagulant protein S-New insights on interactions and functions. J Thromb Haemost 2020; 18:2801-2811. [PMID: 32702208 DOI: 10.1111/jth.15025] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 06/25/2020] [Accepted: 07/10/2020] [Indexed: 01/21/2023]
Abstract
Protein S is a critical regulator of coagulation that functions as a cofactor for the activated protein C (APC) and tissue factor pathway inhibitor (TFPI) pathways. It also has direct anticoagulant functions, inhibiting the intrinsic tenase and prothrombinase complexes. Through these functions, protein S regulates coagulation during both its initiation and its propagation phases. The importance of protein S in hemostatic regulation is apparent from the strong association between protein S deficiencies and increased risk for venous thrombosis. This is most likely because both APC and TFPIα are inefficient anticoagulants in the absence of any cofactors. The detailed molecular mechanisms involved in protein S cofactor functions remain to be fully clarified. However, recent advances in the field have greatly improved our understanding of these functions. Evidence suggests that protein S anticoagulant properties often depend on the presence of synergistic cofactors and the formation of multicomponent complexes on negatively charged phospholipid surfaces. Their high affinity binding to negatively charged phospholipids helps bring the anticoagulant proteins to the membranes, resulting in efficient and targeted regulation of coagulation. In this review, we provide an update on protein S and how it functions as a critical hemostatic regulator.
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17
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Patel‐Hett S, Martin EJ, Mohammed BM, Rakhe S, Sun P, Barrett JC, Nolte ME, Kuhn J, Pittman DD, Murphy JE, Brophy DF. Marstacimab, a tissue factor pathway inhibitor neutralizing antibody, improves coagulation parameters of ex vivo dosed haemophilic blood and plasmas. Haemophilia 2019; 25:797-806. [DOI: 10.1111/hae.13820] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 06/18/2019] [Accepted: 06/21/2019] [Indexed: 02/06/2023]
Affiliation(s)
- Sunita Patel‐Hett
- Rare Disease Research Unit Early Clinical Development, Pfizer Inc Cambridge MA USA
| | - Erika J. Martin
- Coagulation Advancement Laboratory, Department of Pharmacotherapy & Outcomes Science Virginia Commonwealth University (VCU) Richmond VA USA
| | - Bassem M. Mohammed
- Coagulation Advancement Laboratory, Department of Pharmacotherapy & Outcomes Science Virginia Commonwealth University (VCU) Richmond VA USA
- Department of Clinical Pharmacy, Faculty of Pharmacy Cairo University Cairo Egypt
- Department of Pathology, Microbiology, and Immunology Vanderbilt University Medical Center Nashville TN USA
| | - Swapnil Rakhe
- Rare Disease Research Unit Early Clinical Development, Pfizer Inc Cambridge MA USA
| | - Pengling Sun
- Rare Disease Research Unit Early Clinical Development, Pfizer Inc Cambridge MA USA
| | - John C. Barrett
- Division of Hematology/Oncology, Department of Internal Medicine VCU Richmond VA USA
| | - Melinda E. Nolte
- Division of Hematology/Oncology, Department of Internal Medicine VCU Richmond VA USA
| | - Janice Kuhn
- Division of Hematology/Oncology, Department of Internal Medicine VCU Richmond VA USA
| | - Debra D. Pittman
- Rare Disease Research Unit Early Clinical Development, Pfizer Inc Cambridge MA USA
| | - John E. Murphy
- Rare Disease Research Unit Early Clinical Development, Pfizer Inc Cambridge MA USA
| | - Donald F. Brophy
- Coagulation Advancement Laboratory, Department of Pharmacotherapy & Outcomes Science Virginia Commonwealth University (VCU) Richmond VA USA
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18
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O'Donnell JS, O'Sullivan JM, Preston RJS. Advances in understanding the molecular mechanisms that maintain normal haemostasis. Br J Haematol 2019; 186:24-36. [DOI: 10.1111/bjh.15872] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- James S. O'Donnell
- Haemostasis Research Group Department of Molecular and Cellular Therapeutics Irish Centre for Vascular Biology Royal College of Surgeons in Ireland Dublin Ireland
| | - Jamie M. O'Sullivan
- Haemostasis Research Group Department of Molecular and Cellular Therapeutics Irish Centre for Vascular Biology Royal College of Surgeons in Ireland Dublin Ireland
| | - Roger J. S. Preston
- Haemostasis Research Group Department of Molecular and Cellular Therapeutics Irish Centre for Vascular Biology Royal College of Surgeons in Ireland Dublin Ireland
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19
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Post-transcriptional, post-translational and pharmacological regulation of tissue factor pathway inhibitor. Blood Coagul Fibrinolysis 2018; 29:668-682. [PMID: 30439766 DOI: 10.1097/mbc.0000000000000775] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
: Tissue factor (TF) pathway inhibitor (TFPI) is an endogenous natural anticoagulant that readily inhibits the extrinsic coagulation initiation complex (TF-FVIIa-Xa) and prothrombinase (FXa, FVa and calcium ions). Alternatively, spliced TFPI isoforms (α, β and δ) are expressed by vascular and extravascular cells and regulate thrombosis and haemostasis, as well as cell signalling functions of TF complexes via protease-activated receptors (PARs). Proteolysis of TFPI plays an important role in regulating physiological roles of the TF pathway in host defense and possibly haemostasis. Elimination of TFPI inhibition has therefore been proposed as an approach to improve haemostasis in haemophilia patients. In this review, we focus on posttranscription and translational modification of TFPI and its function in thrombosis and how pharmacological inhibitors and endogenous proteases interfere with TFPI and alter haemostasis.
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20
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Girard TJ, Grunz K, Lasky NM, Malone JP, Broze GJ. Re-evaluation of mouse tissue factor pathway inhibitor and comparison of mouse and human tissue factor pathway inhibitor physiology. J Thromb Haemost 2018; 16:2246-2257. [PMID: 30194803 PMCID: PMC6235150 DOI: 10.1111/jth.14288] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Indexed: 11/30/2022]
Abstract
Essentials Mouse models are often used to define roles of tissue factor pathway inhibitor (TFPI) in man. TFPI isoform-specific KOs reveal unexpected differences between mouse and human TFPI physiology. Mouse plasma contains 20 times more TFPI than man, derived from TFPIγ, a form not found in man. TFPIγ null mice, expressing only TFPI isoforms α and β, may better reflect the human situation. SUMMARY: Background Mouse models can provide insight into the pathophysiology of human thrombosis and hemostasis. Tissue factor pathway inhibitor (TFPI) regulates coagulation through protein S (PS)-enhanced factor (F) Xa inhibition and FXa-dependent inhibition of FVIIa/tissue factor (TF) activity. TFPI is expressed as isoforms α and β in man, and α, β and γ in the mouse. Objective Assess the reliability of extending TFPI-related studies in mice to humans. Method Compare mouse and human TFPI physiology using a variety of methods. Results Mouse TFPI and human TFPI are similar in regard to: (i) the mechanisms for FVIIa/TF and FXa inhibition; (ii) TFPIα is a soluble form and TFPIβ is glycosyl phosphatidyl inositol (GPI) membrane anchored; (iii) the predominant circulating form of TFPI in plasma is lipoprotein-associated; (iv) low levels of TFPIα circulate in plasma and increase following heparin treatment; and (v) TFPIα is the isoform in platelets. They differ in that: (i) mouse TFPI circulates at a ~20-fold higher concentration; (ii) mouse lines with isolated isoform deletions show this circulating mouse TFPI is derived from TFPIγ; (iii) sequences homologous to the mouse TFPIγ exon are present in many species, including man, but in primates are unfavorable for splicing; and (iv) tandem mass spectrometry (MS/MS) detects sequences for TFPI isoforms α and β in human plasma and α and γ in mouse plasma. Conclusion To dissect the pathophysiological roles of human TFPIα and TFPIβ, studies in TFPIγ null mice, expressing only α and β, only α or only β should better reflect the human situation.
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Affiliation(s)
- Thomas J. Girard
- Division of Hematology, Department of Medicine, Washington University School of Medicine, St. Louis, MO
| | - Kristin Grunz
- Division of Hematology, Department of Medicine, Washington University School of Medicine, St. Louis, MO
| | - Nina M. Lasky
- Division of Hematology, Department of Medicine, Washington University School of Medicine, St. Louis, MO
| | - James P. Malone
- Proteomics Core Laboratory, Institute of Clinical and Translational Sciences, Washington University School of Medicine, St. Louis, MO
| | - George J. Broze
- Division of Hematology, Department of Medicine, Washington University School of Medicine, St. Louis, MO
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21
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Anti-tissue factor pathway inhibitor (TFPI) therapy: a novel approach to the treatment of haemophilia. Int J Hematol 2018; 111:42-50. [PMID: 30302740 DOI: 10.1007/s12185-018-2548-6] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 10/04/2018] [Indexed: 02/07/2023]
Abstract
Novel approaches to the treatment of haemophilia are needed due to the limitations of the current standard of care, factor replacement therapy. Aspirations include lessening the treatment burden and effectively preventing joint damage. Treating haemophilia by restoring thrombin generation may be an effective approach. A promising target for restoring thrombin generation is tissue factor pathway inhibitor (TFPI), a multivalent Kunitz-type serine protease inhibitor that regulates tissue factor-induced coagulation via factor Xa-dependent feedback inhibition of the tissue factor-factor VIIa complex. Inhibition of TFPI reverts the coagulation process to a more primitive state evolutionarily, whilst regulation by other natural inhibitors is preserved. An aptamer and three monoclonal antibodies directed against TFPI have been investigated in clinical trials. As well as improving thrombin generation in the range associated with mild haemophilia, anti-TFPI therapies have the advantage of subcutaneous administration. However, the therapeutic window needs to be defined along with the potential for complications due to the novel mechanism of action. This review provides an overview of TFPI, its role in normal coagulation, the rationale for TFPI inhibition, and a summary of anti-TFPI therapies, previously or currently in development.
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22
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Chowdary P. Inhibition of Tissue Factor Pathway Inhibitor (TFPI) as a Treatment for Haemophilia: Rationale with Focus on Concizumab. Drugs 2018; 78:881-890. [PMID: 29845491 PMCID: PMC6013504 DOI: 10.1007/s40265-018-0922-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Replacement therapy with missing factor (F) VIII or IX in haemophilia patients for bleed management and preventative treatment or prophylaxis is standard of care. Restoration of thrombin generation through novel mechanisms has become the focus of innovation to overcome limitations imposed by protein replacement therapy. Tissue factor pathway inhibitor (TFPI) is a multivalent Kunitz-type serine protease inhibitor that regulates tissue factor (TF)-induced coagulation through a FXa-dependent feedback inhibition of the TF.FVIIa complex in plasma and on endothelial surfaces. Concizumab is a monoclonal, humanised antibody, specific for the second Kunitz domain of TFPI that binds and inhibits FXa, abolishing the inhibitory effect of TFPI. Concizumab restored thrombin generation in FVIII and FIX deficient plasmas and decreased blood loss in a rabbit haemophilia model. Phase 1 single and multiple dose escalation studies in haemophilia patients demonstrated a dose dependent decrease in TFPI levels and a pro-coagulant effect with increasing d-dimers and prothrombin fragment 1 + 2. A dose dependent increase in peak thrombin and endogenous thrombin potential was observed with values in the normal range when plasma TFPI levels were nearly undetectable. A few haemophilia patients in the highest dose cohorts with complete inhibition of plasma TFPI showed a decreased fibrinogen concentration with normal levels of anti-thrombin and platelets and no evidence of thrombosis. Pharmacokinetic parameters were influenced by binding to the target (TFPI), demonstrating target mediated drug disposition. A trend towards decreasing bleeding tendency was observed and this preventative effect is being studied in Phase 2 studies with additional data gathered to improve our understanding of the therapeutic window and potential for thrombosis.
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Affiliation(s)
- Pratima Chowdary
- Katharine Dormandy Haemophilia and Thrombosis Centre, Royal Free Hospital, Pond Street, London, NW3 2 QG, UK.
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23
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Bergmeier W, Antoniak S, Conway EM, Denis CV, George LA, Isermann B, Key NS, Krishnaswamy S, Lam WA, Lillicrap D, Liu J, Looney MR, López JA, Maas C, Peyvandi F, Ruf W, Sood AK, Versteeg HH, Wolberg AS, Wong PC, Wood JP, Weiler H. Advances in Clinical and Basic Science of Coagulation: Illustrated abstracts of the 9th Chapel Hill Symposium on Hemostasis. Res Pract Thromb Haemost 2018; 2:407-428. [PMID: 30046746 PMCID: PMC6046595 DOI: 10.1002/rth2.12095] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
This 9th Symposium on Hemostasis is an international scientific meeting held biannually in Chapel Hill, North Carolina. The meeting is in large measure the result of the close friendship between the late Dr. Harold R. Roberts of UNC Chapel Hill and Dr. Ulla Hedner of Novo Nordisk. When Novo Nordisk was developing the hemophilia therapy that would become NovoSeven, they sponsored a series of meetings to understand the basic biology and clinical applications of factor VIIa. The first meeting in Chapel Hill was held April 4-6, 2002 with Dr. Roberts as the organizer. Over the years, the conference emphasis has expanded from discussions of factor VIIa and tissue factor to additional topics in hemostasis and thrombosis. This year's meeting includes presentations by internationally renowned speakers that discuss the state-of-the-art on an array of important topics, including von Willebrand factor, engineering advances, coagulation and disease, tissue factor biology, therapeutic advances, and basic clotting factor biology. Included in this review article are illustrated abstracts provided by our speakers, which highlight the main conclusions of each invited talk. This will be the first meeting without Dr. Roberts in attendance, yet his commitment to excellent science and his focus on turning science to patient care are pervasively reflected in the presentations by our speakers.
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Affiliation(s)
- Wolfgang Bergmeier
- Department of Biochemistry and Biophysics University of North Carolina Chapel Hill NC USA
| | - Silvio Antoniak
- Department of Pathology and Laboratory Medicine University of North Carolina Chapel Hill NC USA
| | | | | | - Lindsey A George
- University of Pennsylvania Children's Hospital of Philadelphia Philadelphia PA USA
| | | | - Nigel S Key
- Department of Medicine University of North Carolina Chapel Hill NC USA
| | - Sriram Krishnaswamy
- University of Pennsylvania Children's Hospital of Philadelphia Philadelphia PA USA
| | - Wilbur A Lam
- Department of Pediatrics and the Wallace H. Coulter Department of Biomedical Engineering Emory University and Georgia Institute of Technology Atlanta GA USA
| | | | - Jian Liu
- Eshelman School of Pharmacy University of North Carolina Chapel Hill NC USA
| | - Mark R Looney
- University of California San Francisco San Francisco CA USA
| | - José A López
- School of Medicine Puget Sound Blood Center Research Institute University of Washington Seattle WA USA
| | - Coen Maas
- Department of Clinical Chemistry and Haematology University Medical Center Utrecht Utrecht the Netherlands
| | | | - Wolfram Ruf
- The Scripps Research Institute La Jolla CA USA
| | - Anil K Sood
- University of Texas MD Anderson Cancer Center Houston TX USA
| | | | - Alisa S Wolberg
- Department of Pathology and Laboratory Medicine University of North Carolina Chapel Hill NC USA
| | - Pancras C Wong
- Transfusion Medicine Hematology Bristol-Meyers Squibb Pennington NJ USA
| | - Jeremy P Wood
- Gill Heart and Vascular Institute University of Kentucky Lexington KY USA
| | - Hartmut Weiler
- Blood Research Institute Blood Center of Wisconsin Milwaukee WI USA
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24
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Thomassen S, Mastenbroek TG, Swieringa F, Winckers K, Feijge MAH, Schrijver R, Cosemans JMEM, Maroney SA, Mast AE, Hackeng TM, Heemskerk JWM. Suppressive Role of Tissue Factor Pathway Inhibitor-α in Platelet-Dependent Fibrin Formation under Flow Is Restricted to Low Procoagulant Strength. Thromb Haemost 2018; 118:502-513. [PMID: 29452445 DOI: 10.1055/s-0038-1627453] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Tissue factor pathway inhibitor-alpha (TFPI-α) is a Kunitz-type serine protease inhibitor, which suppresses coagulation by inhibiting the tissue factor (TF)/factor VIIa complex as well as factor Xa. In static plasma-phospholipid systems, TFPI-α thus suppresses both factor Xa and thrombin generation. In this article, we used a microfluidics approach to investigate how TFPI-α regulates fibrin clot formation in platelet thrombi at low wall shear rate. We therefore hypothesized that the anticoagulant effect of TFPI-α in plasma is a function of the local procoagulant strength-defined as the magnitude of thrombin generation under flow, due to local activities of TF/factor VIIa and factor Xa. To test this hypothesis, we modulated local coagulation by microspot coating of flow channels with 0 to 100 pM TF/collagen, or by using blood from patients with haemophilia A or B. For blood or plasma from healthy subjects, blocking of TFPI-α enhanced fibrin formation, extending from a platelet thrombus, under flow only at <2 pM coated TF. This enhancement was paralleled by an increased thrombin generation. For mouse plasma, genetic deficiency in TFPI enhanced fibrin formation under flow also at 0 pM TF microspots. On the other hand, using blood from haemophilia A or B patients, TFPI-α antagonism markedly enhanced fibrin formation at microspots with up to 100 pM coated TF. We conclude that, under flow, TFPI-α is capable to antagonize fibrin formation in a manner dependent on and restricted by local TF/factor VIIa and factor Xa activities.
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Affiliation(s)
- Stella Thomassen
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
| | - Tom G Mastenbroek
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
| | - Frauke Swieringa
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands.,Department of Protein Dynamics, ISAS Leibnitz Institute Dortmund, Dortmund, Germany
| | - Kristien Winckers
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
| | - Marion A H Feijge
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
| | - Roy Schrijver
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
| | - Judith M E M Cosemans
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
| | - Susan A Maroney
- Blood Research Institute, Blood Center of Wisconsin, Milwaukee, Wisconsin, United States
| | - Alan E Mast
- Blood Research Institute, Blood Center of Wisconsin, Milwaukee, Wisconsin, United States.,Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, Michigan, United States
| | - Tilman M Hackeng
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
| | - Johan W M Heemskerk
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, The Netherlands
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Tanratana P, Ellery P, Westmark P, Mast AE, Sheehan JP. Elevated Plasma Factor IXa Activity in Premenopausal Women on Hormonal Contraception. Arterioscler Thromb Vasc Biol 2017; 38:266-274. [PMID: 29097362 DOI: 10.1161/atvbaha.117.309919] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2017] [Accepted: 10/12/2017] [Indexed: 01/30/2023]
Abstract
OBJECTIVE Combined oral contraceptives induce a reversible hypercoagulable state with an enhanced risk of venous thromboembolism, but the underlying mechanism(s) remain unclear. Subjects on combined oral contraceptives also demonstrate a characteristic resistance to APC (activated protein C) in the thrombin generation assay. Here, we report the potential role of plasma factor IXa (FIXa) as a mechanism for hormone-induced systemic hypercoagulability. APPROACH AND RESULTS A novel assay was used to determine FIXa activity in plasma samples from volunteer blood donors. Plasma from 36 premenopausal females on hormonal contraception and 35 not on hormonal contraception, 35 postmenopausal females, and 10 males were analyzed for FIXa activity, total PS (protein S), total tissue factor pathway inhibitor (TFPI), and TFPI-α antigen. Premenopausal females on hormonal contraception demonstrated significantly increased FIXa activity and decreased TFPI-α compared with the other groups. Remarkably, FIXa values were not normally distributed in the hormonal contraception group, but skewed toward the high end. Plasma FIXa activity inversely correlated with both TFPI-α and total PS antigen. Ex vivo determination of TF-dependent FIX activation in FV-deficient plasma demonstrated that inhibitory anti-TFPI antibodies enhanced FIXa generation by 2- to 3-fold, whereas addition of 75 nmol/L PS reduced FIXa generation by ≈2-fold. Further, increasing FIXa concentration enhanced APC resistance during TF-triggered plasma thrombin generation. CONCLUSIONS Elevation of plasma FIXa activity in association with reductions in TFPI-α and PS is a potential mechanism for systemic hypercoagulability and resistance to APC in premenopausal females on hormonal contraception.
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Affiliation(s)
- Pansakorn Tanratana
- From the Department of Pathology and Laboratory Medicine (P.T.), Department of Medicine/Hematology-Oncology (P.W., J.P.S.), University of Wisconsin School of Medicine and Public Health, Madison; Department of Pharmacology, Faculty of Science, Mahidol University, Bangkok, Thailand (P.T.); Blood Research Institute, Blood Center of Wisconsin, Milwaukee (P.E., A.E.M.); and School of Biomedical Sciences, Curtin University, Perth, Western Australia, Australia (P.E.)
| | - Paul Ellery
- From the Department of Pathology and Laboratory Medicine (P.T.), Department of Medicine/Hematology-Oncology (P.W., J.P.S.), University of Wisconsin School of Medicine and Public Health, Madison; Department of Pharmacology, Faculty of Science, Mahidol University, Bangkok, Thailand (P.T.); Blood Research Institute, Blood Center of Wisconsin, Milwaukee (P.E., A.E.M.); and School of Biomedical Sciences, Curtin University, Perth, Western Australia, Australia (P.E.)
| | - Pamela Westmark
- From the Department of Pathology and Laboratory Medicine (P.T.), Department of Medicine/Hematology-Oncology (P.W., J.P.S.), University of Wisconsin School of Medicine and Public Health, Madison; Department of Pharmacology, Faculty of Science, Mahidol University, Bangkok, Thailand (P.T.); Blood Research Institute, Blood Center of Wisconsin, Milwaukee (P.E., A.E.M.); and School of Biomedical Sciences, Curtin University, Perth, Western Australia, Australia (P.E.)
| | - Alan E Mast
- From the Department of Pathology and Laboratory Medicine (P.T.), Department of Medicine/Hematology-Oncology (P.W., J.P.S.), University of Wisconsin School of Medicine and Public Health, Madison; Department of Pharmacology, Faculty of Science, Mahidol University, Bangkok, Thailand (P.T.); Blood Research Institute, Blood Center of Wisconsin, Milwaukee (P.E., A.E.M.); and School of Biomedical Sciences, Curtin University, Perth, Western Australia, Australia (P.E.)
| | - John P Sheehan
- From the Department of Pathology and Laboratory Medicine (P.T.), Department of Medicine/Hematology-Oncology (P.W., J.P.S.), University of Wisconsin School of Medicine and Public Health, Madison; Department of Pharmacology, Faculty of Science, Mahidol University, Bangkok, Thailand (P.T.); Blood Research Institute, Blood Center of Wisconsin, Milwaukee (P.E., A.E.M.); and School of Biomedical Sciences, Curtin University, Perth, Western Australia, Australia (P.E.).
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Saadah NH, van der Meer PF, Brinkman HJM, de Korte D, Bontekoe IJ, Korsten HH, Middelburg RA, van der Bom JG, Schipperus MR. Effect of solvent/detergent‐treated pooled plasma on fibrinolysis in reconstituted whole blood. Transfusion 2017; 57:2381-2389. [DOI: 10.1111/trf.14260] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Revised: 06/02/2017] [Accepted: 06/04/2017] [Indexed: 12/21/2022]
Affiliation(s)
- Nicholas H. Saadah
- Center for Clinical Transfusion ResearchSanquin ResearchLeiden the Netherlands
- Department of Clinical EpidemiologyLeiden University Medical CenterLeiden the Netherlands
| | - Pieter F. van der Meer
- Center for Clinical Transfusion ResearchSanquin ResearchLeiden the Netherlands
- Product and Process DevelopmentSanquin Blood BankAmsterdam the Netherlands
| | | | - Dirk de Korte
- Product and Process DevelopmentSanquin Blood BankAmsterdam the Netherlands
- Department of Blood Cell ResearchSanquin ResearchAmsterdam the Netherlands
| | - Ido J. Bontekoe
- Product and Process DevelopmentSanquin Blood BankAmsterdam the Netherlands
| | - Herbert H. Korsten
- Product and Process DevelopmentSanquin Blood BankAmsterdam the Netherlands
| | - Rutger A. Middelburg
- Center for Clinical Transfusion ResearchSanquin ResearchLeiden the Netherlands
- Department of Clinical EpidemiologyLeiden University Medical CenterLeiden the Netherlands
| | - Johanna G. van der Bom
- Center for Clinical Transfusion ResearchSanquin ResearchLeiden the Netherlands
- Department of Clinical EpidemiologyLeiden University Medical CenterLeiden the Netherlands
| | - Martin R. Schipperus
- Department of HematologyHaga Teaching HospitalThe Hague the Netherlands
- Hemovigilance and Biovigilance OfficeTRIP National Hemovigilance FoundationLeiden the Netherlands
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Dahlbäck B. Novel insights into the regulation of coagulation by factor V isoforms, tissue factor pathway inhibitorα, and protein S. J Thromb Haemost 2017; 15:1241-1250. [PMID: 28671348 DOI: 10.1111/jth.13665] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Factor V (FV) is a regulator of both pro- and anticoagulant pathways. It circulates as a single-chain procofactor, which is activated by thrombin or FXa to FVa that serves as cofactor for FXa in prothrombin activation. The cofactor function of FVa is regulated by activated protein C (APC) and protein S. FV can also function as an anticoagulant APC cofactor in the inhibition of FVIIIa in the membrane-bound tenase complex (FIXa/FVIIIa). In recent years, it has become clear that FV also functions in multiple ways in the tissue factor pathway inhibitor (TFPI) anticoagulant pathway. Of particular importance is a FV splice variant (FV-Short) that serves as a carrier and cofactor to TFPIα in the inhibition of FXa. FV-Short is generated through alternative splicing of exon 13 that encodes the large activation B domain. A highly negatively charged binding site for TFPIα is exposed in the C-terminus of the FV-Short B domain, which binds the positively charged C-terminus of TFPIα, thus keeping TFPIα in circulation. The binding of TFPIα to FV-Short is also instrumental in localizing the inhibitor to the surface of negatively charged phospholipids, where TFPIα inhibits FXa in process that is stimulated by protein S. Plasma FV activation intermediates and partially proteolyzed platelet FV similarly bind TFPIα with high affinity and regulate formation of prothrombinase. The novel insights gained into the interaction between FV isoforms, TFPIα, and protein S have opened a new avenue for research about the mechanisms of coagulation regulation and also for future development of therapeutics aimed at modulating coagulation.
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Affiliation(s)
- B Dahlbäck
- Department of Translational Medicine, Lund University, University Hospital SUS, Malmö, Sweden
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Alshaikh NA, Rosing J, Thomassen MCLGD, Castoldi E, Simioni P, Hackeng TM. New functional assays to selectively quantify the activated protein C- and tissue factor pathway inhibitor-cofactor activities of protein S in plasma. J Thromb Haemost 2017; 15:950-960. [PMID: 28211163 DOI: 10.1111/jth.13657] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Indexed: 11/28/2022]
Abstract
Essentials Protein S is a cofactor of activated protein C (APC) and tissue factor pathway inhibitor (TFPI). There are no assays to quantify separate APC and TFPI cofactor activities of protein S in plasma. We developed assays to measure the APC- and TFPI-cofactor activities of protein S in plasma. The assays were sensitive to protein S deficiency, and not affected by the Factor V Leiden mutation. SUMMARY Background Protein S plays an important role in the down-regulation of coagulation as cofactor for activated protein C (APC) and tissue factor pathway inhibitor (TFPI). Aim To develop functional assays to quantify the APC- and TFPI-cofactor activities of protein S in plasma. Methods APC- and TFPI-cofactor activities of protein S in plasma were measured using calibrated automated thrombography in protein S-depleted plasma supplemented with a small amount of sample plasma either in the presence of anti-TFPI antibodies and APC (APC-cofactor activity) or at excess full-length TFPI without APC (TFPI-cofactor activity). Total and free protein S levels in plasma were measured by ELISAs. Results Average APC-cofactor activities of protein S were 113%, 108% and 89% in plasma from normal individuals (n = 15), FV Leiden heterozygotes (n = 14) and FV Leiden homozygotes (n = 7), respectively, whereas the average APC-cofactor activity of protein S in plasma from heterozygous protein S-deficient individuals (n = 21) was significantly lower (55%). Similar trends were observed for the TFPI-cofactor activity of protein S, with averages of 109%, 115% and 124% in plasma from individuals with normal protein S levels and different FV Leiden genotypes, and 64% in plasma from protein S-deficient patients. APC-cofactor activities of protein S correlated significantly with free and total protein S antigen levels, whereas TFPI-cofactor activities correlated less with protein S antigen levels. Conclusion We have developed functional protein S assays that measure both the APC- and TFPI-cofactor activities of protein S in plasma, which are hardly if at all affected by the FV Leiden mutation.
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Affiliation(s)
- N A Alshaikh
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
| | - J Rosing
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
| | - M C L G D Thomassen
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
| | - E Castoldi
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
| | - P Simioni
- Thrombotic and Haemorrhagic Unit, Department of Medicine (DIMED), 5th Chair of Internal Medicine, University of Padua Medical School, Padua, Italy
| | - T M Hackeng
- Department of Biochemistry, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, the Netherlands
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Abstract
Hemophilia is a severe bleeding disorder treated by infusion of the missing blood coagulation protein, factor VIII or factor IX. The discovery and characterization of the anticoagulant protein tissue factor pathway inhibitor (TFPI) led to the realization that inhibition of TFPI activity could restore functional hemostasis through the extrinsic blood coagulation pathway in a manner that does not require the activity of factors VIII or IX. There are currently several therapeutic agents that inhibit TFPI in development for treatment of hemophilia. A comprehensive understanding of TFPI structure, biochemistry, and cellular expression is necessary to understand how it modulates bleeding in hemophilia and the physiological impact of therapeutic agents targeting TFPI.
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Winckers K, Thomassen S, ten Cate H, Hackeng TM. Platelet full length TFPI-α in healthy volunteers is not affected by sex or hormonal use. PLoS One 2017; 12:e0168273. [PMID: 28158181 PMCID: PMC5291377 DOI: 10.1371/journal.pone.0168273] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 11/07/2016] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Only 10% of plasma TFPIα (TFPI) exists in the full length form, the rest circulates as a C-terminally truncated form. However, blood platelets exclusively contain full length TFPI, which is released at the site of injury upon platelet activation, and which could play an important local regulatory role in thrombin generation and prevention of thrombosis. METHODS The anticoagulant activities of full length and truncated TFPI were investigated using thrombin generation assays. Blood samples were obtained from 30 healthy volunteers (10 male subjects, 10 female subjects, and 10 females using oral contraceptives). Platelet TFPI was released in platelet rich plasma and in platelet isolates using convulxin or thrombin, and measured by free TFPI ELISA and thrombin generation assays. RESULTS Full length TFPI and platelet TFPI were much more potent inhibitors of thrombin generation than truncated TFPI, which was virtually inactive. Although mean plasma TFPI antigen levels decreased from men (0.30 nM) to women (0.20 nM) to women using oral contraceptives (0.11 nM), no relevant differences were found in platelet TFPI among those subgroups. CONCLUSIONS Platelets release similar amounts of TFPI regardless of plasma TFPI concentrations and is unaffected by sex or oral contraceptive use. We speculate that platelet TFPI is important to prevent systemic coagulation and thrombosis and restrict thrombus formation to the site of the growing platelet plug. The stable contribution of platelet TFPI to the anticoagulant potential in plasma is likely to become particularly relevant under conditions of low plasma TFPI levels in combination of oral contraceptives use.
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Affiliation(s)
- Kristien Winckers
- Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, the Netherlands
- Department of Internal Medicine, CARIM, Maastricht University Medical Centre, Maastricht, the Netherlands
| | - Stella Thomassen
- Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, the Netherlands
| | - Hugo ten Cate
- Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, the Netherlands
- Department of Internal Medicine, CARIM, Maastricht University Medical Centre, Maastricht, the Netherlands
| | - Tilman M. Hackeng
- Department of Biochemistry, Cardiovascular Research Institute Maastricht (CARIM), Maastricht University, Maastricht, the Netherlands
- * E-mail:
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Yau JW, Teoh H, Verma S. Endothelial cell control of thrombosis. BMC Cardiovasc Disord 2015; 15:130. [PMID: 26481314 PMCID: PMC4617895 DOI: 10.1186/s12872-015-0124-z] [Citation(s) in RCA: 415] [Impact Index Per Article: 46.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 10/09/2015] [Indexed: 02/07/2023] Open
Abstract
Hemostasis encompasses a set of tightly regulated processes that govern blood clotting, platelet activation, and vascular repair. Upon vascular injury, the hemostatic system initiates a series of vascular events and activates extravascular receptors that act in concert to seal off the damage. Blood clotting is subsequently attenuated by a plethora of inhibitors that prevent excessive clot formation and eventual thrombosis. The endothelium which resides at the interface between the blood and surrounding tissues, serves an integral role in the hemostatic system. Depending on specific tissue needs and local stresses, endothelial cells are capable of evoking either antithrombotic or prothrombotic events. Healthy endothelial cells express antiplatelet and anticoagulant agents that prevent platelet aggregation and fibrin formation, respectively. In the face of endothelial dysfunction, endothelial cells trigger fibrin formation, as well as platelet adhesion and aggregation. Finally, endothelial cells release pro-fibrinolytic agents that initiate fibrinolysis to degrade the clot. Taken together, a functional endothelium is essential to maintain hemostasis and prevent thrombosis. Thus, a greater understanding into the role of the endothelium can provide new avenues for exploration and novel therapies for the management of thromboembolisms.
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Affiliation(s)
- Jonathan W Yau
- Division of Cardiac Surgery, St. Michael's Hospital, Suite 8-003, Bond Wing, 30 Bond St., Toronto, ON, M5B 1W8, Canada.
| | - Hwee Teoh
- Division of Cardiac Surgery, St. Michael's Hospital, Suite 8-003, Bond Wing, 30 Bond St., Toronto, ON, M5B 1W8, Canada. .,Divisions of Endocrinology & Metabolism, Keenan Research Centre for Biomedical Science at St. Michael's Hospital, Toronto, ON, Canada.
| | - Subodh Verma
- Division of Cardiac Surgery, St. Michael's Hospital, Suite 8-003, Bond Wing, 30 Bond St., Toronto, ON, M5B 1W8, Canada. .,Department of Surgery, University of Toronto, Toronto, ON, Canada.
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32
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Westrick R, Fredman G. Platelets: Context-Dependent Vascular Protectors or Mediators of Disease. Arterioscler Thromb Vasc Biol 2015; 35:e25-9. [PMID: 26109740 DOI: 10.1161/atvbaha.115.305898] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Randal Westrick
- From the Department of Biological Sciences, Oakland University, Rochester, MI (R.W.); and Department of Medicine, Columbia University, New York, NY (G.F.)
| | - Gabrielle Fredman
- From the Department of Biological Sciences, Oakland University, Rochester, MI (R.W.); and Department of Medicine, Columbia University, New York, NY (G.F.).
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Shi M, Yin F, Gu H, Zhu J, Yin X. Tissue Factor Pathway Inhibitor-Coated Stents Inhibit Restenosis in a Rabbit Carotid Artery Model. Cardiovasc Ther 2015; 33:353-9. [PMID: 26280363 DOI: 10.1111/1755-5922.12152] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
INTRODUCTION Our aim was to study the efficacy and safety of tissue factor pathway inhibitor (TFPI)-coated stents in inhibiting restenosis in a rabbit carotid artery model. METHODS Subculture was conducted in aorta smooth muscle cell, which was taken from male Wistar rat, and the 3-5-generation cells were taken for plasmid transfection and cytotoxicity experiment. TFPI microspheres were made of a TFPI plasmid which was enwrapped by poly-l-glutamic acid (PLGA). TFPI-coated stents (n = 7) and bare metal stents (n = 6) were implanted into prepared carotid artery stenosis model of New Zealand white rabbits. The transfection efficiency of TFPI gene and its influence on animal tissue, restenosis inhibition, and biochemical indicator were observed. RESULT Tissue factor pathway inhibitor microspheres can transfect successfully into cells, and present no cytotoxicity. Autopsy results showed no pathological changes in liver and spleen of rabbits after implanting TFPI-coated stents. TFPI gene could transfect and express successfully in vessel wall cells, and thrombus was found in some lumens of bare metal stents group after 7 day, while no such thrombus was observed in coated stents group. Degree of hyperplasia of coronary endarterectomy in bare metal stents group was evidently higher than those in coated stents group. Obvious stent restenosis was discovered only in one case in bare metal stents group (diameter stenosis ≥50%). However, no case in coated stents group showed with stent restenosis. CONCLUSION Tissue factor pathway inhibitor-coated stents could successfully transfect TFPI gene into vessel wall cells, thereby inhibiting restenosis without obvious side effect in the rabbit carotid artery model.
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Affiliation(s)
- Mingyu Shi
- Department of Cardiovasology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Feng Yin
- Department of Cardiovasology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Hongyue Gu
- Department of Cardiovasology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Jing Zhu
- Department of Cardiovasology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Xinhua Yin
- Department of Cardiovasology, The First Affiliated Hospital of Harbin Medical University, Harbin, China
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Abstract
Tissue factor pathway inhibitor (TFPI) dampens the initiation of blood coagulation by inhibiting two potent procoagulant complexes, tissue factor-factor VIIa (TF-FVIIa) and early forms of prothrombinase. TFPI isoforms, TFPIα and TFPIβ, result from alternative splicing of mRNA, producing distinct C-terminal ends of the two proteins. Both isoforms inhibit TF-FVIIa, but only TFPIα can inhibit early forms of prothrombinase by binding of its positively charged C-terminus with high affinity to the acidic B-domain exosite of FVa, which is generated upon activation by FXa. TFPIα and TFPIβ are produced in cultured human endothelial cells, while platelets contain only TFPIα. Knowledge of the anticoagulant mechanisms and tissue expression patterns of TFPIα and TFPIβ have improved our understanding of the phenotypes observed in different mouse models of TFPI deficiency, the east Texas bleeding disorder, and the development of pharmaceutical agents that block TFPI function to treat hemophilia.
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Affiliation(s)
- S A Maroney
- Blood Research Institute, Blood Center of Wisconsin, Milwaukee, WI, USA
| | - A E Mast
- Blood Research Institute, Blood Center of Wisconsin, Milwaukee, WI, USA
- Department of Cell Biology, Neurobiology and Anatomy, Medical College of Wisconsin, Milwaukee, WI, USA
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Wang J, Xiao J, Wen D, Wu X, Mao Z, Zhang J, Ma D. Endothelial cell-anchored tissue factor pathway inhibitor regulates tumor metastasis to the lung in mice. Mol Carcinog 2015; 55:882-96. [DOI: 10.1002/mc.22329] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 02/27/2015] [Accepted: 03/26/2015] [Indexed: 11/10/2022]
Affiliation(s)
- Jiping Wang
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology; Institute of Biomedical Sciences, School of Basic Medical Sciences, Collaborative Innovation Center of Genetics and Development, Fudan University; Shanghai China
| | - Jiajun Xiao
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology; Institute of Biomedical Sciences, School of Basic Medical Sciences, Collaborative Innovation Center of Genetics and Development, Fudan University; Shanghai China
| | - Danping Wen
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology; Institute of Biomedical Sciences, School of Basic Medical Sciences, Collaborative Innovation Center of Genetics and Development, Fudan University; Shanghai China
| | - Xie Wu
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology; Institute of Biomedical Sciences, School of Basic Medical Sciences, Collaborative Innovation Center of Genetics and Development, Fudan University; Shanghai China
| | - Zuohua Mao
- Department of Parasitology and Microbiology; Shanghai Medical College, Fudan University; Shanghai China
| | - Jin Zhang
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology; Institute of Biomedical Sciences, School of Basic Medical Sciences, Collaborative Innovation Center of Genetics and Development, Fudan University; Shanghai China
| | - Duan Ma
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology; Institute of Biomedical Sciences, School of Basic Medical Sciences, Collaborative Innovation Center of Genetics and Development, Fudan University; Shanghai China
- Children's Hospital; Fudan University; Shanghai China
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Somajo S, Ahnström J, Fernandez-Recio J, Gierula M, Villoutreix BO, Dahlbäck B. Amino acid residues in the laminin G domains of protein S involved in tissue factor pathway inhibitor interaction. Thromb Haemost 2015; 113:976-87. [PMID: 25716664 DOI: 10.1160/th14-09-0803] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 01/05/2015] [Indexed: 11/05/2022]
Abstract
Protein S functions as a cofactor for tissue factor pathway inhibitor (TFPI) and activated protein C (APC). The sex hormone binding globulin (SHBG)-like region of protein S, consisting of two laminin G-like domains (LG1 and LG2), contains the binding site for C4b-binding protein (C4BP) and TFPI. Furthermore, the LG-domains are essential for the TFPI-cofactor function and for expression of full APC-cofactor function. The aim of the current study was to localise functionally important interaction sites in the protein S LG-domains using amino acid substitutions. Four protein S variants were created in which clusters of surface-exposed amino acid residues within the LG-domains were substituted. All variants bound normally to C4BP and were fully functional as cofactors for APC in plasma and in pure component assays. Two variants, SHBG2 (E612A, I614A, F265A, V393A, H453A), involving residues from both LG-domains, and SHBG3 (K317A, I330A, V336A, D365A) where residues in LG1 were substituted, showed 50-60 % reduction in enhancement of TFPI in FXa inhibition assays. For SHBG3 the decreased TFPI cofactor function was confirmed in plasma based thrombin generation assays. Both SHBG variants bound to TFPI with decreased affinity in surface plasmon resonance experiments. The TFPI Kunitz 3 domain is known to contain the interaction site for protein S. Using in silico analysis and protein docking exercises, preliminary models of the protein S SHBG/TFPI Kunitz domain 3 complex were created. Based on a combination of experimental and in silico data we propose a binding site for TFPI on protein S, involving both LG-domains.
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Affiliation(s)
| | | | | | | | | | - Björn Dahlbäck
- Björn Dahlbäck MD, PhD, Professor of Blood Coagulation Research, Lund University, Department of Translational Medicine, Division of Clinical Chemistry, Wallenberg laboratory, floor 6, University Hospital, Malmö, S-20502 Malmö, Sweden, E-mail:
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Thomassen MCLGD, Heinzmann ACA, Herfs L, Hartmann R, Dockal M, Scheiflinger F, Hackeng TM, Rosing J. Tissue factor-independent inhibition of thrombin generation by tissue factor pathway inhibitor-α. J Thromb Haemost 2015; 13:92-100. [PMID: 25348176 DOI: 10.1111/jth.12766] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Indexed: 11/26/2022]
Abstract
BACKGROUND Tissue factor pathway inhibitor-α (TFPIα) inhibits factor Xa by forming a binary TFPI-FXa complex in a reaction that is stimulated by protein S. TF-FVIIa forms a quaternary complex with TFPIα and FXa, which shuts off the initiation of coagulation via the extrinsic pathway. AIM To investigate whether direct inhibition of FXa by TFPIα independently of TF plays a role in downregulating coagulation. METHODS Inhibition of FXa by TFPIα in plasma was determined by measuring thrombin generation triggered with FXa, the FX activator from Russell's viper venom (RVV-X), FXIa, or FIXa. TF-independent anticoagulant activities of TFPIα and its cofactor, protein S, were quantified: (i) after neutralization of TFPIα and protein S with anti-TFPI or anti-protein S antibodies; and (ii) in TFPI-depleted or protein S-depleted plasmas supplemented with varying amounts of TFPIα or protein S. RESULTS Both anti-TFPI and anti-protein S antibodies enhanced thrombin generation in plasma triggered with RVV-X, FXa, FIXa, or FXIa. Anti-TFPI and anti-protein S antibodies decreased the lag time and increased the peak height of thrombin generation to the same extent, indicating that inhibition of FXa by TFPIα requires the presence of protein S. TFPIα and protein S titrations in TFPI-depleted or protein S-depleted plasma in which thrombin formation was initiated with triggers other than TF also revealed TF-independent anticoagulant activity of TFPIα, which was completely dependent on the presence of protein S. CONCLUSION Direct inhibition of FXa by TFPIα contributes to the downregulation of coagulation.
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Affiliation(s)
- M C L G D Thomassen
- Department of Biochemistry, Maastricht University, Maastricht, The Netherlands
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Livaja Koshiar R, Somajo S, Norström E, Dahlbäck B. Erythrocyte-derived microparticles supporting activated protein C-mediated regulation of blood coagulation. PLoS One 2014; 9:e104200. [PMID: 25136857 PMCID: PMC4138094 DOI: 10.1371/journal.pone.0104200] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Accepted: 07/07/2014] [Indexed: 12/30/2022] Open
Abstract
Elevated levels of erythrocyte-derived microparticles are present in the circulation in medical conditions affecting the red blood cells. Erythrocyte-derived microparticles expose phosphatidylserine thus providing a suitable surface for procoagulant reactions leading to thrombin formation via the tenase and prothrombinase complexes. Patients with elevated levels of circulating erythrocyte-derived microparticles have increased thrombin generation in vivo. The aim of the present study was to investigate whether erythrocyte-derived microparticles are able to support the anticoagulant reactions of the protein C system. Erythrocyte-derived microparticles were isolated using ultracentrifugation after incubation of freshly prepared erythrocytes with the ionophore A23187 or from outdated erythrocyte concentrates, the different microparticles preparations yielding similar results. According to flow cytometry analysis, the microparticles exposed phoshatidylserine and bound lactadherin, annexin V, and protein S, which is a cofactor to activated protein C. The microparticles were able to assemble the tenase and prothrombinase complexes and to stimulate the formation of thrombin in plasma-based thrombin generation assay both in presence and absence of added tissue factor. The addition of activated protein C in the thrombin generation assay inhibited thrombin generation in a dose-dependent fashion. The anticoagulant effect of activated protein C in the thrombin generation assay was inhibited by a monoclonal antibody that prevents binding of protein S to microparticles and also attenuated by anti-TFPI antibodies. In the presence of erythrocyte-derived microparticles, activated protein C inhibited tenase and prothrombinase by degrading the cofactors FVIIIa and FVa, respectively. Protein S stimulated the Arg306-cleavage in FVa, whereas efficient inhibition of FVIIIa depended on the synergistic cofactor activity of protein S and FV. In summary, the erythrocyte-derived microparticle surface is suitable for the anticoagulant reactions of the protein C system, which may be important to balance the initiation and propagation of coagulation in vivo.
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Affiliation(s)
- Ruzica Livaja Koshiar
- Department of Laboratory Medicine, Division of Clinical Chemistry, Lund University, Skåne University Hospital, Malmö, Sweden
| | - Sofia Somajo
- Department of Laboratory Medicine, Division of Clinical Chemistry, Lund University, Skåne University Hospital, Malmö, Sweden
| | - Eva Norström
- Department of Laboratory Medicine, Division of Clinical Chemistry, Lund University, Skåne University Hospital, Malmö, Sweden
| | - Björn Dahlbäck
- Department of Laboratory Medicine, Division of Clinical Chemistry, Lund University, Skåne University Hospital, Malmö, Sweden
- * E-mail:
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Reglińska-Matveyev N, Andersson HM, Rezende SM, Dahlbäck B, Crawley JTB, Lane DA, Ahnström J. TFPI cofactor function of protein S: essential role of the protein S SHBG-like domain. Blood 2014; 123:3979-87. [PMID: 24740810 PMCID: PMC4064334 DOI: 10.1182/blood-2014-01-551812] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Accepted: 04/09/2014] [Indexed: 01/17/2023] Open
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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Affiliation(s)
| | - Helena M Andersson
- Centre for Haematology, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Suely M Rezende
- Department of Internal Medicine, Faculty of Medicine, Universidade Federal de Minas Gerais, Minas Gerais, Brazil; and
| | - Björn Dahlbäck
- Department of Laboratory Medicine, Faculty of Medicine, Lund University, Malmö, Sweden
| | - James T B Crawley
- Centre for Haematology, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - David A Lane
- Centre for Haematology, Faculty of Medicine, Imperial College London, London, United Kingdom
| | - Josefin Ahnström
- Centre for Haematology, Faculty of Medicine, Imperial College London, London, United Kingdom
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Abstract
Recent studies of the anticoagulant activities of the tissue factor (TF) pathway inhibitor (TFPI) isoforms, TFPIα and TFPIβ, have provided new insight into the biochemical and physiological mechanisms that underlie bleeding and clotting disorders. TFPIα and TFPIβ have tissue-specific expression patterns and anticoagulant activities. An alternative splicing event in the 5' untranslated region allows for translational regulation of TFPIβ expression. TFPIα has 3 Kunitz-type inhibitor domains (K1, K2, K3) and a basic C terminus, whereas TFPIβ has the K1 and K2 domains attached to a glycosylphosphatidyl inositol-anchored C terminus. TFPIα is the only isoform present in platelets, whereas endothelial cells produce both isoforms, secreting TFPIα and expressing TFPIβ on the cell surface. TFPIα and TFPIβ inhibit both TF-factor VIIa-dependent factor Xa (FXa) generation and free FXa. Protein S enhances FXa inhibition by TFPIα. TFPIα produces isoform-specific inhibition of prothrombinase during the initiation of coagulation, an anticoagulant activity that requires an exosite interaction between its basic C terminus and an acidic region in the factor Va B domain. Platelet TFPIα may be optimally localized to dampen initial thrombin generation. Similarly, endothelial TFPIβ may be optimally localized to inhibit processes that occur when endothelial TF is present, such as during the inflammatory response.
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