1
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Marar TT, Boffa MB. Identification of heparin interaction sites on thrombin-activatable fibrinolysis inhibitor that modulate plasmin-mediated activation, thermal stability, and antifibrinolytic potential. Res Pract Thromb Haemost 2024; 8:102459. [PMID: 38983903 PMCID: PMC11231710 DOI: 10.1016/j.rpth.2024.102459] [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: 04/25/2024] [Accepted: 05/17/2024] [Indexed: 07/11/2024] Open
Abstract
Background Thrombin-activatable fibrinolysis inhibitor (TAFI) is a plasma zymogen that provides a molecular link between coagulation and fibrinolysis. Studies have shown that the presence of glycosaminoglycans accelerates TAFI activation by plasmin and stabilizes activated TAFI (TAFIa). Objectives We aimed to define the elements of TAFI structure that allow these effects. Methods Based on crystallographic studies and homology to heparin-binding proteins, we performed mutagenesis of surface-exposed charged residues on TAFI that putatively constitute heparin-binding sites. We determined heparin binding, kinetics of activation by plasmin in the presence or absence of heparin, thermal stability, and antifibrinolytic potential of each variant. Results Mutagenesis of Lys211 and Lys212 did not impair heparin binding but affected the ability of TAFI to be activated by plasmin. Mutagenesis of Lys306 and His308 did not impair heparin binding, but mutation of His308 had a severe negative effect on TAFI/TAFIa function. Mutation of Arg320 and Lys324 in combination markedly decreased heparin binding but had no effect on heparin-mediated acceleration of TAFI activation by plasmin while somewhat decreasing TAFIa stabilization by heparin. Mutagenesis of Lys327 and Arg330 decreased (but did not eliminate) heparin binding while decreasing the ability of heparin to accelerate plasmin-mediated TAFI activation, stabilize TAFIa, and increase the antifibrinolytic ability of TAFIa. A quadruple mutant of Arg320, Lys324, Lys327, and Arg330 completely lost heparin-binding ability and stabilization of the enzyme by heparin. Conclusion Basic residues in the dynamic flap of TAFIa define a functionally relevant heparin-binding site, but additional heparin-binding sites may be present on TAFI.
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Affiliation(s)
- Tanya T Marar
- Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada
| | - Michael B Boffa
- Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada
- Department of Biochemistry, The University of Western Ontario, London, Ontario, Canada
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2
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Mertens JC, Blanc-Guillemaud V, Claesen K, Cardona P, Hendriks D, Tyl B, Molina CA. Carboxypeptidase U (TAFIa) Is Rapidly Activated and Deactivated Following Thrombolysis and Thrombectomy in Stroke Patients. Transl Stroke Res 2021; 13:959-969. [PMID: 34796454 DOI: 10.1007/s12975-021-00962-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 10/19/2021] [Accepted: 10/27/2021] [Indexed: 11/29/2022]
Abstract
The antifibrinolytic enzyme carboxypeptidase U (CPU, TAFIa, CPB2) is an appealing target for the treatment of acute ischemic stroke (AIS). Increased insights in CPU activation and inactivation during thrombolysis (rtPA) with or without endovascular thrombectomy (EVT) are required to develop CPU inhibitors as profibrinolytic agents with optimal benefits/risks. Therefore, CPU kinetics during ischemic stroke treatment were evaluated. AIS patients with documented cerebral artery occlusion receiving rtPA (N = 20) or rtPA + EVT (N = 16) were included. CPU activation during thrombolysis was measured by an ultrasensitive HPLC-based CPU activity method and by an ELISA measuring both CPU and inactivated CPU (CPU + CPUi). Intravenous blood samples were collected at admission and throughout the first 24 h. Additional in situ blood samples were collected in the rtPA + EVT cohort proximal from the thrombus. The NIHSS score was determined at baseline and 24 h. CPU activity and CPU + CPUi levels increased upon rtPA administration and reached peak values at the end of thrombolysis (1 h). High inter-individual variability was observed in both groups. CPU activity decreased rapidly within 3 h, while CPU + CPUi levels were still elevated at 7 h. CPU activity or CPU + CPUi levels were similar in in situ and peripheral samples. No correlation between CPU or CPU + CPUi and NIHSS or thrombus localization was found. The CPU system was rapidly activated and deactivated following thrombolysis and thrombectomy in stroke patients, suggesting that a CPU inhibitor would have to be administered during rtPA infusion and over the next few hours. The high CPU generation variability suggests that some patients may not respond to the treatment. EudraCT number 2017-002760-41.
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Affiliation(s)
- Joachim C Mertens
- Laboratory of Medical Biochemistry, University of Antwerp, Antwerp, Belgium
| | - Vanessa Blanc-Guillemaud
- Cardiovascular and Metabolic Diseases Center for Therapeutic Innovation, Institut de Recherches Internationales Servier, Suresnes Cedex, France.
| | - Karen Claesen
- Laboratory of Medical Biochemistry, University of Antwerp, Antwerp, Belgium
| | - Pere Cardona
- Department of Neurology, Hospital de Bellvitge, Hospitalet de Llobregat-Barcelona, Spain
| | - Dirk Hendriks
- Laboratory of Medical Biochemistry, University of Antwerp, Antwerp, Belgium
| | - Benoit Tyl
- Cardiovascular and Metabolic Diseases Center for Therapeutic Innovation, Institut de Recherches Internationales Servier, Suresnes Cedex, France
| | - Carlos A Molina
- Stroke Unit, Neurology Department, Vall d'Hebron University Hospital, Barcelona, Spain.,Departament de Medicina, Universitat Autónoma de Barcelona, Barcelona, Spain
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3
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Livingstone SA, Wildi KS, Dalton HJ, Usman A, Ki KK, Passmore MR, Li Bassi G, Suen JY, Fraser JF. Coagulation Dysfunction in Acute Respiratory Distress Syndrome and Its Potential Impact in Inflammatory Subphenotypes. Front Med (Lausanne) 2021; 8:723217. [PMID: 34490308 PMCID: PMC8417599 DOI: 10.3389/fmed.2021.723217] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2021] [Accepted: 07/29/2021] [Indexed: 12/12/2022] Open
Abstract
The Acute Respiratory Distress Syndrome (ARDS) has caused innumerable deaths worldwide since its initial description over five decades ago. Population-based estimates of ARDS vary from 1 to 86 cases per 100,000, with the highest rates reported in Australia and the United States. This syndrome is characterised by a breakdown of the pulmonary alveolo-epithelial barrier with subsequent severe hypoxaemia and disturbances in pulmonary mechanics. The underlying pathophysiology of this syndrome is a severe inflammatory reaction and associated local and systemic coagulation dysfunction that leads to pulmonary and systemic damage, ultimately causing death in up to 40% of patients. Since inflammation and coagulation are inextricably linked throughout evolution, it is biological folly to assess the two systems in isolation when investigating the underlying molecular mechanisms of coagulation dysfunction in ARDS. Although the body possesses potent endogenous systems to regulate coagulation, these become dysregulated and no longer optimally functional during the acute phase of ARDS, further perpetuating coagulation, inflammation and cell damage. The inflammatory ARDS subphenotypes address inflammatory differences but neglect the equally important coagulation pathway. A holistic understanding of this syndrome and its subphenotypes will improve our understanding of underlying mechanisms that then drive translation into diagnostic testing, treatments, and improve patient outcomes.
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Affiliation(s)
- Samantha A Livingstone
- Critical Care Research Group, The Prince Charles Hospital, Brisbane, QLD, Australia.,Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia
| | - Karin S Wildi
- Critical Care Research Group, The Prince Charles Hospital, Brisbane, QLD, Australia.,Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia.,Cardiovascular Research Institute Basel (CRIB), Basel, Switzerland
| | | | - Asad Usman
- Department of Anesthesiology and Critical Care, The University of Pennsylvania, Philadelphia, PA, United States
| | - Katrina K Ki
- Critical Care Research Group, The Prince Charles Hospital, Brisbane, QLD, Australia.,Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia
| | - Margaret R Passmore
- Critical Care Research Group, The Prince Charles Hospital, Brisbane, QLD, Australia.,Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia
| | - Gianluigi Li Bassi
- Critical Care Research Group, The Prince Charles Hospital, Brisbane, QLD, Australia.,Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia.,Department of Pulmonology and Critical Care, Hospital Clínic de Barcelona, Universitad de Barcelona and IDIBAPS, CIBERES, Barcelona, Spain
| | - Jacky Y Suen
- Critical Care Research Group, The Prince Charles Hospital, Brisbane, QLD, Australia.,Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia
| | - John F Fraser
- Critical Care Research Group, The Prince Charles Hospital, Brisbane, QLD, Australia.,Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia
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4
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Sillen M, Declerck PJ. Thrombin Activatable Fibrinolysis Inhibitor (TAFI): An Updated Narrative Review. Int J Mol Sci 2021; 22:ijms22073670. [PMID: 33916027 PMCID: PMC8036986 DOI: 10.3390/ijms22073670] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Revised: 03/26/2021] [Accepted: 03/29/2021] [Indexed: 01/02/2023] Open
Abstract
Thrombin activatable fibrinolysis inhibitor (TAFI), a proenzyme, is converted to a potent attenuator of the fibrinolytic system upon activation by thrombin, plasmin, or the thrombin/thrombomodulin complex. Since TAFI forms a molecular link between coagulation and fibrinolysis and plays a potential role in venous and arterial thrombotic diseases, much interest has been tied to the development of molecules that antagonize its function. This review aims at providing a general overview on the biochemical properties of TAFI, its (patho)physiologic function, and various strategies to stimulate the fibrinolytic system by interfering with (activated) TAFI functionality.
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5
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Wang J, Qian Y, Xu L, Shao Y, Zhang H, Shi F, Chen J, Cui S, Chen X, Zhu D, Hu R, Chen Z. Hyaluronic acid-shelled, peptide drug conjugate-cored nanomedicine for the treatment of hepatocellular carcinoma. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2020; 117:111261. [PMID: 32919628 DOI: 10.1016/j.msec.2020.111261] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 05/14/2020] [Accepted: 07/01/2020] [Indexed: 12/13/2022]
Abstract
Peptide-drug conjugate (PDC) is a promising prodrug in drug delivery systems. To fabricate nanostructures with proper molecular design which can self-assemble to spherical morphologies is very important for PDC chemotherapy. In this study, a novel PDC (PDC-DOX2), in which two doxorubicin (DOX) molecules are conjugated onto a short peptide (KIGLFRWR) with self-assembly function, was designed and synthesized. PDC-DOX2 with self-assembly properties forms a spherical structure under hydrophobic interaction in water. Hyaluronic acid (HA) was then coated on PDC-DOX2 micelles to form a HA-shelled, peptide-doxorubicin conjugate-cored nanomedicine (HA@PDC-DOX2). The amount of HA can regulate the particle size and stabilization of HA@PDC-DOX2. In addition, HA can actively enhance the targeting effects of PDC-DOX2 micelles since it can interact with overexpressed receptors in cancer cells. The core-shell structured HA@PDC-DOX2 nanomedicine showed significantly enhanced potency against hepatocellular carcinoma compared to PDC-DOX2 micelles as well as free DOX. In this work, a novel PDC which can self-assemble to spherical morphologies and a core-shell structure HA@PDC-DOX2 nanomedicine are designed and prepared. It provides a convenient strategy for the size control of PDC assemblies and constructs effective PDC-based drug delivery systems for cancer treatment.
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Affiliation(s)
- Jingjing Wang
- College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210023, China
| | - Ying Qian
- College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210023, China
| | - Liu Xu
- College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210023, China
| | - Yurou Shao
- College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210023, China
| | - Hu Zhang
- College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210023, China
| | - Fanli Shi
- College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210023, China
| | - Jiaxin Chen
- College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210023, China
| | - Siqi Cui
- College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210023, China
| | - Xiaoyan Chen
- College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210023, China
| | - Dongwei Zhu
- College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210023, China
| | - Rongfeng Hu
- Key Laboratory of Xin'an Medicine, Ministry of Education, Anhui Province Key Laboratory of R&D of Chinese Medicine, Anhui University of Chinese Medicine, Hefei, Anhui 230038, China
| | - Zhipeng Chen
- College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, Jiangsu 210023, China.
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6
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Ni R, Neves MAD, Wu C, Cerroni SE, Flick MJ, Ni H, Weitz JI, Gross PL, Kim PY. Activated thrombin-activatable fibrinolysis inhibitor (TAFIa) attenuates fibrin-dependent plasmin generation on thrombin-activated platelets. J Thromb Haemost 2020; 18:2364-2376. [PMID: 32506822 PMCID: PMC7719609 DOI: 10.1111/jth.14950] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 05/29/2020] [Accepted: 05/29/2020] [Indexed: 12/16/2022]
Abstract
BACKGROUND Thrombin-activated platelets can promote fibrinolysis by binding plasminogen in a fibrinogen-dependent manner and enhancing its activation by tissue-type plasminogen activator (t-PA). Whether t-PA also binds to activated platelets and the mechanism for regulation of platelet-dependent fibrinolysis remain unknown. OBJECTIVES Determine the mechanism of plasminogen and t-PA binding on thrombin-activated platelets and its regulation by activated thrombin-activatable fibrinolysis inhibitor (TAFIa). METHODS Plasminogen and t-PA binding with or without TAFIa treatment was quantified using flow cytometry. Plasmin generation on platelets was quantified using a plasmin-specific substrate. Mass spectrometry analyses identified fibrinogen as a potential target of TAFIa. Thrombus formation was studied in mice lacking fibrinogen (Fg-/- ) using intravital microscopy. RESULTS Plasminogen and t-PA bind to platelets activated by thrombin but not by other agonists, including protease-activated receptor agonists (PAR-AP). Plasminogen binds via its kringle domains because ε-aminocaproic acid eliminates binding, whereas t-PA binds via its finger and kringle domains. Plasminogen binding is fibrinogen-dependent because it is abolished on (a) Fg-/- platelets, and (b) thrombi in Fg-/- mice. Binding requires thrombin-mediated fibrinogen modification because addition of batroxobin to PAR-AP activated platelets has no effect on plasminogen binding but induces t-PA binding. TAFIa reduces plasminogen and t-PA binding to thrombin-activated platelets and attenuates plasmin generation in a concentration-dependent manner. Mass spectrometry identified K556 on the fibrinogen alpha-chain as a potential thrombin cleavage site that generates a TAFIa sensitive C-terminal lysine residue. CONCLUSION These findings provide novel mechanistic insights into how platelets activated by thrombin at sites of vascular injury can influence fibrinolysis.
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Affiliation(s)
- Ran Ni
- Thrombosis and Atherosclerosis Research Institute, Hamilton, ON, Canada
- Departments of Medicine and Medical Sciences, McMaster University, Hamilton, ON, Canada
| | - Miguel A. D. Neves
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto Platelet Immunobiology Group, Toronto, ON, Canada
| | - Chengliang Wu
- Thrombosis and Atherosclerosis Research Institute, Hamilton, ON, Canada
| | | | - Matthew J. Flick
- Division of Experimental Hematology and Cancer Biology, Cancer and Blood Diseases Institute, Cincinnati Children’s Research Foundation, Cincinnati, OH, USA
| | - Heyu Ni
- Department of Laboratory Medicine, Keenan Research Centre for Biomedical Science, Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto Platelet Immunobiology Group, Toronto, ON, Canada
- Canadian Blood Services Centre for Innovation, Toronto, ON, Canada
- Department of Medicine and Physiology, University of Toronto, Toronto, ON, Canada
| | - Jeffrey I. Weitz
- Thrombosis and Atherosclerosis Research Institute, Hamilton, ON, Canada
- Departments of Medicine and Medical Sciences, McMaster University, Hamilton, ON, Canada
| | - Peter L. Gross
- Thrombosis and Atherosclerosis Research Institute, Hamilton, ON, Canada
- Departments of Medicine and Medical Sciences, McMaster University, Hamilton, ON, Canada
| | - Paul Y. Kim
- Thrombosis and Atherosclerosis Research Institute, Hamilton, ON, Canada
- Departments of Medicine and Medical Sciences, McMaster University, Hamilton, ON, Canada
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7
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Identification and characterization of a factor Va-binding site on human prothrombin fragment 2. Sci Rep 2019; 9:2436. [PMID: 30792421 PMCID: PMC6385242 DOI: 10.1038/s41598-019-38857-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Accepted: 01/11/2019] [Indexed: 11/18/2022] Open
Abstract
The fragment 2 domain (F2) of prothrombin and its interaction with factor (F) Va is known to contribute significantly to prothrombinase-catalyzed activation of prothrombin. The extent to which the F2-FVa interaction affects the overall thrombin generation, however, is uncertain. To study this interaction, nuclear magnetic resonance spectroscopy of recombinant F2 was used to identify seven residues within F2 that are significantly responsive to FVa binding. The functional role of this region in interacting with FVa during prothrombin activation was verified by the FVa-dependent inhibition of thrombin generation using peptides that mimic the same region of F2. Because six of the seven residues were within a 9-residue span, these were mutated to generate a prothrombin derivative (PT6). These mutations led to a decreased affinity for FVa as determined by surface plasmon resonance. When thrombin generation by an array of FXa containing prothrombinase components was monitored, a 54% decrease in thrombin generation was observed with PT6 compared with the wild-type, only when FVa was present. The functional significance of the specific low-affinity binding between F2 and FVa is discussed within the context of a dynamic model of molecular interactions between prothrombin and FVa engaging multiple contact sites.
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8
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Wu C, Stafford AR, Fredenburgh JC, Weitz JI, Gils A, Declerck PJ, Kim PY. Lys 42/43/44 and Arg 12 of thrombin-activable fibrinolysis inhibitor comprise a thrombomodulin exosite essential for its antifibrinolytic potential. Thromb Haemost 2017. [PMID: 28640323 DOI: 10.1160/th17-01-0054] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The thrombin-thrombomodulin (TM) complex activates thrombin-activable fibrinolysis inhibitor (TAFI) more efficiently than thrombin alone. The exosite on TAFI required for its TM-dependent activation by thrombin has not been identified. Based on previous work by us and others, we generated TAFI variants with one or more of residues Lys 42, Lys 43, Lys 44 and Arg 12 within the activation peptide mutated to alanine. Mutation of one, two, or three Lys residues or the Arg residue alone decreased the catalytic efficiency of TAFI activation by thrombin-TM by 2.4-, 3.2-, 4.7-, and 15.0-fold, respectively, and increased the TAFI concentrations required for half-maximal prolongation of clot lysis times (K1/2) by 3-, 4,- 15-, and 24-fold, respectively. Mutation of all four residues decreased the catalytic efficiency of TAFI activation by 45.0-fold, increased the K1/2 by 130-fold, and abolished antifibrinolytic activity in a clot lysis assay at physiologic levels of TAFI. Similar trends in the antifibrinolytic activity of the TAFI variants were observed when plasma clots were formed using HUVECs as the source of TM. When thrombin was used as the activator, mutation of all four residues reduced the rate of activation by 1.1-fold compared with wild-type TAFI, suggesting that these mutations only impacted activation kinetics in the presence of TM. Surface plasmon resonance data suggest that mutation of the four residues abrogates TM binding with or without thrombin. Therefore, Lys 42, Lys 43, Lys 44 and Arg 12 are critical for the interaction of TAFI with the thrombin-TM complex, which modulates its antifibrinolytic potential.
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Affiliation(s)
| | | | | | | | | | | | - Paul Y Kim
- Paul Y. Kim, Thrombosis and Atherosclerosis Research Institute, 237 Barton St. East, Hamilton, Ontario, L8L 2X2, Canada, Tel.: +1 905 521 2100, Fax: +1 905 575 2646, E-mail:
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9
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The impact of the endothelial protein C receptor on thrombin generation and clot lysis. Thromb Res 2017; 152:30-37. [DOI: 10.1016/j.thromres.2017.02.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 02/01/2017] [Accepted: 02/02/2017] [Indexed: 11/22/2022]
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10
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Satoh T, Satoh K, Yaoita N, Kikuchi N, Omura J, Kurosawa R, Numano K, Al-Mamun E, Siddique MAH, Sunamura S, Nogi M, Suzuki K, Miyata S, Morser J, Shimokawa H. Activated TAFI Promotes the Development of Chronic Thromboembolic Pulmonary Hypertension: A Possible Novel Therapeutic Target. Circ Res 2017; 120:1246-1262. [PMID: 28289017 DOI: 10.1161/circresaha.117.310640] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2017] [Revised: 03/07/2017] [Accepted: 03/10/2017] [Indexed: 11/16/2022]
Abstract
RATIONALE Pulmonary hypertension is a fatal disease; however, its pathogenesis still remains to be elucidated. Thrombin-activatable fibrinolysis inhibitor (TAFI) is synthesized by the liver and inhibits fibrinolysis. Plasma TAFI levels are significantly increased in chronic thromboembolic pulmonary hypertension (CTEPH) patients. OBJECTIVE To determine the role of activated TAFI (TAFIa) in the development of CTEPH. METHODS AND RESULTS Immunostaining showed that TAFI and its binding partner thrombomodulin (TM) were highly expressed in the pulmonary arteries (PAs) and thrombus in patients with CTEPH. Moreover, plasma levels of TAFIa were increased 10-fold in CTEPH patients compared with controls. In mice, chronic hypoxia caused a 25-fold increase in plasma levels of TAFIa with increased plasma levels of thrombin and TM, which led to thrombus formation in PA, vascular remodeling, and pulmonary hypertension. Consistently, plasma clot lysis time was positively correlated with plasma TAFIa levels in mice. Additionally, overexpression of TAFIa caused organized thrombus with multiple obstruction of PA flow and reduced survival rate under hypoxia in mice. Bone marrow transplantation showed that circulating plasma TAFI from the liver, not in the bone marrow, was activated locally in PA endothelial cells through interactions with thrombin and TM. Mechanistic experiments demonstrated that TAFIa increased PA endothelial permeability, smooth muscle cell proliferation, and monocyte/macrophage activation. Importantly, TAFIa inhibitor and peroxisome proliferator-activated receptor-α agonists significantly reduced TAFIa and ameliorated animal models of pulmonary hypertension in mice and rats. CONCLUSIONS These results indicate that TAFIa could be a novel biomarker and realistic therapeutic target of CTEPH.
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Affiliation(s)
- Taijyu Satoh
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (T.S., K. Satoh, N.Y., N.K., J.O., R.K., K.N., E.A.-M., M.A.H.S., S.S., M.N., K. Suzuki, S.M., H.S.); and Department of Hematology, Stanford School of Medicine, CA (J.M.)
| | - Kimio Satoh
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (T.S., K. Satoh, N.Y., N.K., J.O., R.K., K.N., E.A.-M., M.A.H.S., S.S., M.N., K. Suzuki, S.M., H.S.); and Department of Hematology, Stanford School of Medicine, CA (J.M.)
| | - Nobuhiro Yaoita
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (T.S., K. Satoh, N.Y., N.K., J.O., R.K., K.N., E.A.-M., M.A.H.S., S.S., M.N., K. Suzuki, S.M., H.S.); and Department of Hematology, Stanford School of Medicine, CA (J.M.)
| | - Nobuhiro Kikuchi
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (T.S., K. Satoh, N.Y., N.K., J.O., R.K., K.N., E.A.-M., M.A.H.S., S.S., M.N., K. Suzuki, S.M., H.S.); and Department of Hematology, Stanford School of Medicine, CA (J.M.)
| | - Junichi Omura
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (T.S., K. Satoh, N.Y., N.K., J.O., R.K., K.N., E.A.-M., M.A.H.S., S.S., M.N., K. Suzuki, S.M., H.S.); and Department of Hematology, Stanford School of Medicine, CA (J.M.)
| | - Ryo Kurosawa
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (T.S., K. Satoh, N.Y., N.K., J.O., R.K., K.N., E.A.-M., M.A.H.S., S.S., M.N., K. Suzuki, S.M., H.S.); and Department of Hematology, Stanford School of Medicine, CA (J.M.)
| | - Kazuhiko Numano
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (T.S., K. Satoh, N.Y., N.K., J.O., R.K., K.N., E.A.-M., M.A.H.S., S.S., M.N., K. Suzuki, S.M., H.S.); and Department of Hematology, Stanford School of Medicine, CA (J.M.)
| | - Elias Al-Mamun
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (T.S., K. Satoh, N.Y., N.K., J.O., R.K., K.N., E.A.-M., M.A.H.S., S.S., M.N., K. Suzuki, S.M., H.S.); and Department of Hematology, Stanford School of Medicine, CA (J.M.)
| | - Mohammad Abdul Hai Siddique
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (T.S., K. Satoh, N.Y., N.K., J.O., R.K., K.N., E.A.-M., M.A.H.S., S.S., M.N., K. Suzuki, S.M., H.S.); and Department of Hematology, Stanford School of Medicine, CA (J.M.)
| | - Shinichiro Sunamura
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (T.S., K. Satoh, N.Y., N.K., J.O., R.K., K.N., E.A.-M., M.A.H.S., S.S., M.N., K. Suzuki, S.M., H.S.); and Department of Hematology, Stanford School of Medicine, CA (J.M.)
| | - Masamichi Nogi
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (T.S., K. Satoh, N.Y., N.K., J.O., R.K., K.N., E.A.-M., M.A.H.S., S.S., M.N., K. Suzuki, S.M., H.S.); and Department of Hematology, Stanford School of Medicine, CA (J.M.)
| | - Kota Suzuki
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (T.S., K. Satoh, N.Y., N.K., J.O., R.K., K.N., E.A.-M., M.A.H.S., S.S., M.N., K. Suzuki, S.M., H.S.); and Department of Hematology, Stanford School of Medicine, CA (J.M.)
| | - Satoshi Miyata
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (T.S., K. Satoh, N.Y., N.K., J.O., R.K., K.N., E.A.-M., M.A.H.S., S.S., M.N., K. Suzuki, S.M., H.S.); and Department of Hematology, Stanford School of Medicine, CA (J.M.)
| | - John Morser
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (T.S., K. Satoh, N.Y., N.K., J.O., R.K., K.N., E.A.-M., M.A.H.S., S.S., M.N., K. Suzuki, S.M., H.S.); and Department of Hematology, Stanford School of Medicine, CA (J.M.)
| | - Hiroaki Shimokawa
- From the Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan (T.S., K. Satoh, N.Y., N.K., J.O., R.K., K.N., E.A.-M., M.A.H.S., S.S., M.N., K. Suzuki, S.M., H.S.); and Department of Hematology, Stanford School of Medicine, CA (J.M.).
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11
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Zhou X, Weeks SD, Ameloot P, Callewaert N, Strelkov SV, Declerck PJ. Elucidation of the molecular mechanisms of two nanobodies that inhibit thrombin-activatable fibrinolysis inhibitor activation and activated thrombin-activatable fibrinolysis inhibitor activity. J Thromb Haemost 2016; 14:1629-38. [PMID: 27279497 DOI: 10.1111/jth.13381] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Indexed: 11/30/2022]
Abstract
UNLABELLED Essentials Thrombin-activatable fibrinolysis inhibitor (TAFI) is a risk factor for cardiovascular disorders. TAFI inhibitory nanobodies represent a promising step in developing profibrinolytic therapeutics. We have solved three crystal structures of TAFI in complex with inhibitory nanobodies. Nanobodies inhibit TAFI through distinct mechanisms and represent novel profibrinolytic leads. SUMMARY Background Thrombin-activatable fibrinolysis inhibitor (TAFI) is converted to activated TAFI (TAFIa) by thrombin, plasmin, or the thrombin-thrombomodulin complex (T/TM). TAFIa is antifibrinolytic, and high levels of TAFIa are associated with an increased risk for cardiovascular disorders. TAFI-inhibitory nanobodies represent a promising approach for developing profibrinolytic therapeutics. Objective To elucidate the molecular mechanisms of inhibition of TAFI activation and TAFIa activity by nanobodies with the use of X-ray crystallography and biochemical characterization. Methods and results We selected two nanobodies for cocrystallization with TAFI. VHH-a204 interferes with all TAFI activation modes, whereas VHH-i83 interferes with T/TM-mediated activation and also inhibits TAFIa activity. The 3.05-Å-resolution crystal structure of TAFI-VHH-a204 reveals that the VHH-a204 epitope is localized to the catalytic moiety (CM) in close proximity to the TAFI activation site at Arg92, indicating that VHH-a204 inhibits TAFI activation by steric hindrance. The 2.85-Å-resolution crystal structure of TAFI-VHH-i83 reveals that the VHH-i83 epitope is located close to the presumptive thrombomodulin-binding site in the activation peptide (AP). The structure and supporting biochemical assays suggest that VHH-i83 inhibits TAFIa by bridging the AP to the CM following TAFI activation. In addition, the 3.00-Å-resolution crystal structure of the triple TAFI-VHH-a204-VHH-i83 complex demonstrates that the two nanobodies can simultaneously bind to TAFI. Conclusions This study provides detailed insights into the molecular mechanisms of TAFI inhibition, and reveals a novel mode of TAFIa inhibition. VHH-a204 and VHH-i83 merit further evaluation as potential profibrinolytic therapeutics.
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Affiliation(s)
- X Zhou
- Department of Pharmaceutical and Pharmacologic Sciences, Laboratory for Therapeutic and Diagnostic Antibodies, KU Leuven, Belgium
| | - S D Weeks
- Department of Pharmaceutical and Pharmacologic Sciences, Laboratory for Biocrystallography, KU Leuven, Belgium
| | - P Ameloot
- Flanders Institute for Biotechnology, Medical Biotechnology Center, Ghent, Belgium
- Department of Biochemistry and Microbiology, Laboratory for Protein Biochemistry and Biomolecular Engineering, Ghent University, Ghent, Belgium
| | - N Callewaert
- Flanders Institute for Biotechnology, Medical Biotechnology Center, Ghent, Belgium
- Department of Biochemistry and Microbiology, Laboratory for Protein Biochemistry and Biomolecular Engineering, Ghent University, Ghent, Belgium
| | - S V Strelkov
- Department of Pharmaceutical and Pharmacologic Sciences, Laboratory for Biocrystallography, KU Leuven, Belgium
| | - P J Declerck
- Department of Pharmaceutical and Pharmacologic Sciences, Laboratory for Therapeutic and Diagnostic Antibodies, KU Leuven, Belgium
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12
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Marar TT, Boffa MB. Identification of a thrombomodulin interaction site on thrombin-activatable fibrinolysis inhibitor that mediates accelerated activation by thrombin. J Thromb Haemost 2016; 14:772-83. [PMID: 26816270 DOI: 10.1111/jth.13275] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2015] [Indexed: 11/26/2022]
Abstract
BACKGROUND Thrombin-activatable fibrinolysis inhibitor (TAFI) is a human plasma zymogen that provides a molecular connection between coagulation and fibrinolysis. TAFI is activated through proteolytic cleavage by thrombin, thrombin in complex with the endothelial cell cofactor thrombomodulin (TM) or plasmin. Evidence from several studies suggests that TM and TAFI make direct contact at sites remote from the activating cleavage site to facilitate acceleration of thrombin-mediated TAFI activation. The elements of TAFI structure that allow accelerated activation of thrombin by TM are incompletely defined. OBJECTIVES To identify TM interaction regions on TAFI that mediate acceleration of activation by thrombin and therefore indicate TM binding sites on TAFI. METHODS We mutated selected surface-exposed charged residues on TAFI to alanine in order to identify sites that mediate acceleration of activation by TM. The kinetics of activation of the mutants by thrombin in the presence or absence of TM, as well as their thermal stabilities and antifibrinolytic potentials, were determined. RESULTS TAFI variants R15A, E28A, K59A, D75A/E77A/D78A, E99A and E106A all exhibited moderately reduced catalytic efficiencies of activation by thrombin-TM. TAFI variants R377A and, particularly, R12A and R12A/R15A exhibited severely reduced activation by thrombin-TM that was not explained by differences in activation by thrombin alone. CONCLUSIONS We have identified R12 as a critical residue for the activation of TAFI by thrombin-TM, extending a previous report that identified a role for this residue. R12 is likely to directly bind to TM while another key residue, R377, may affect the thrombin-TAFI interaction specifically in the presence of TM.
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Affiliation(s)
- T T Marar
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada
| | - M B Boffa
- Department of Chemistry and Biochemistry, University of Windsor, Windsor, ON, Canada
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13
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Plug T, Meijers JCM. Structure-function relationships in thrombin-activatable fibrinolysis inhibitor. J Thromb Haemost 2016; 14:633-44. [PMID: 26786060 DOI: 10.1111/jth.13261] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Indexed: 11/30/2022]
Abstract
Thrombin-activatable fibrinolysis inhibitor (TAFI) is an important regulator in the balance of coagulation and fibrinolysis. TAFI is a metallocarboxypeptidase that circulates in plasma as zymogen. Activated TAFI (TAFIa) cleaves C-terminal lysine or arginine residues from peptide substrates. The removal of C-terminal lysine residues from partially degraded fibrin leads to reduced plasmin formation and thus attenuation of fibrinolysis. TAFI also plays a role in inflammatory processes via the removal of C-terminal arginine or lysine residues from bradykinin, thrombin-cleaved osteopontin, C3a, C5a and chemerin. TAFI has been studied extensively over the past three decades and recent publications provide a wealth of information, including crystal structures, mutants and structural data obtained with antibodies and peptides. In this review, we combined and compared available data on structure/function relationships of TAFI.
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Affiliation(s)
- T Plug
- Department of Experimental Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
| | - J C M Meijers
- Department of Experimental Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
- Department of Plasma Proteins, Sanquin Research, Amsterdam, the Netherlands
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14
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Wu C, Kim PY, Swystun LL, Liaw PC, Weitz JI. Activation of protein C and thrombin activable fibrinolysis inhibitor on cultured human endothelial cells. J Thromb Haemost 2016; 14:366-74. [PMID: 26663133 DOI: 10.1111/jth.13222] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 11/23/2015] [Indexed: 12/01/2022]
Abstract
UNLABELLED ESSENTIALS: It is unknown if thrombin activatable fibrinolysis inhibitor (TAFI) and protein C compete on cells. TAFI and protein C activation on endothelial cells was simultaneously quantified. TAFI and protein C do not compete for activation on endothelial cells. TAFI and protein C are independently recognized by the thrombin-thrombomodulin complex. BACKGROUND When bound to thrombomodulin (TM), thrombin is a potent activator of protein C (PC) and thrombin activable fibrinolysis inhibitor (TAFI). By binding PC and presenting it to the thrombin-TM complex, endothelial cell PC receptor (EPCR) enhances PC activation. It is unknown whether PC and TAFI compete for the thrombin-TM complex on endothelial cells. OBJECTIVE To compare PC and TAFI activation on the surface of cultured human endothelial cells in the absence or presence of JRK1535 and/or CTM1009, inhibitory antibodies directed against EPCR and TM, respectively, and to determine whether PC and TAFI compete with each other for activation. METHODS PC and TAFI activation on endothelial cells were compared, and the effect of PC on TAFI activation and TAFI on PC activation was determined in the absence or presence of JRK1535 and/or CTM1009. RESULTS In the absence of antibodies, activation of PC was four-fold faster than that of TAFI. Blocking EPCR with JRK1535 resulted in a 53-fold decrease in PC activation and no effect on TAFI activation. Blocking TM with CTM1009 inhibited both TAFI and PC activation. Neither TAFI nor PC competed with each other in the absence or presence of JRK1535. CONCLUSIONS PC and TAFI are concurrently activated in a TM-dependent manner and do not compete for the thrombin-TM complex, raising the possibility that they interact with distinct activation complexes. EPCR selectively enhances PC activation so that PC and TAFI activation kinetics become comparable on endothelial cells.
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Affiliation(s)
- C Wu
- Thrombosis and Atherosclerosis Research Institute, Hamilton, ON, Canada
- Department of Medicine, McMaster University, Hamilton, ON, Canada
| | - P Y Kim
- Thrombosis and Atherosclerosis Research Institute, Hamilton, ON, Canada
- Department of Medicine, McMaster University, Hamilton, ON, Canada
| | - L L Swystun
- Department of Pathology and Molecular Medicine, Queen's University, Kingston, ON, Canada
| | - P C Liaw
- Thrombosis and Atherosclerosis Research Institute, Hamilton, ON, Canada
- Department of Medicine, McMaster University, Hamilton, ON, Canada
| | - J I Weitz
- Thrombosis and Atherosclerosis Research Institute, Hamilton, ON, Canada
- Department of Medicine, McMaster University, Hamilton, ON, Canada
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada
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15
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Plug T, Marquart JA, Marx PF, Meijers JCM. Selective modulation of thrombin-activatable fibrinolysis inhibitor (TAFI) activation by thrombin or the thrombin-thrombomodulin complex using TAFI-derived peptides. J Thromb Haemost 2015; 13:2093-101. [PMID: 26341360 DOI: 10.1111/jth.13133] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Indexed: 11/27/2022]
Abstract
BACKGROUND Thrombin-activatable fibrinolysis inhibitor (TAFI) is a risk factor for coronary heart disease. TAFI is proteolytically activated by thrombin, the thrombin-thrombomodulin complex and plasmin. Once active, it dampens fibrinolysis and inflammation. The aim of this study was to generate TAFI-derived peptides that specifically modulate TAFI activation and activity. METHODS Thirty-four overlapping TAFI peptides, and modifications thereof, were synthesized. The effects of these peptides on TAFI activation and TAFIa activity were determined. In addition, the binding of the peptides to thrombin were determined. RESULTS Four peptides (peptides 2, 18, 19 and 34) inhibited TAFI activation and two peptides (peptides 14 and 24) inhibited TAFIa activity directly. Peptide 2 (Arg12-Glu28) and peptide 34 (Cys383-Val401) inhibited TAFI activation by the thrombin-thrombomodulin complex with IC50 values of 7.3 ± 1.8 and 6.1 ± 0.9 μm, respectively. However, no inhibition was observed in the absence of thrombomodulin. This suggests that the regions Arg12-Glu28 and Cys383-Val401 in TAFI are involved in thrombomodulin-mediated TAFI activation. Peptide 18 (Gly205-Ser221) and peptide 19 (Arg214-Asp232) inhibited TAFI activation by thrombin and the thrombin-thrombomodulin complex. Furthermore, these peptides bound to thrombin (KD : 1.5 ± 0.4 and 0.52 ± 0.07 μm for peptides 18 and 19, respectively), suggesting that Gly205-Asp232 of TAFI is involved in binding to thrombin. Peptide 14 (His159-His175) inhibited TAFIa activity. The inhibition was TAFIa specific, because no effect on the homologous enzyme carboxypeptidase B was observed. CONCLUSIONS Thrombin-activatable fibrinolysis inhibitor-derived peptides show promise as new tools to modulate TAFI activation and TAFIa activity. Furthermore, these peptides revealed potential binding sites on TAFI for thrombin and the thrombin-thrombomodulin complex.
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Affiliation(s)
- T Plug
- Department of Experimental Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
| | - J A Marquart
- Department of Experimental Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
- Department of Plasma Proteins, Sanquin Research, Amsterdam, the Netherlands
| | - P F Marx
- Department of Experimental Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
| | - J C M Meijers
- Department of Experimental Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
- Department of Plasma Proteins, Sanquin Research, Amsterdam, the Netherlands
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16
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Plug T, Meijers JCM. New clues regarding the mysterious mechanism of activated thrombin-activatable fibrinolysis inhibitor self-destruction. J Thromb Haemost 2015; 13:1081-3. [PMID: 25777152 DOI: 10.1111/jth.12900] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 03/02/2015] [Indexed: 12/01/2022]
Affiliation(s)
- T Plug
- Department of Experimental Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
| | - J C M Meijers
- Department of Experimental Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, the Netherlands
- Department of Plasma Proteins, Sanquin Research, Amsterdam, the Netherlands
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17
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Zhou X, Declerck PJ. Generation of a stable thrombin-activatable fibrinolysis inhibitor deletion mutant exerting full carboxypeptidase activity without activation. J Thromb Haemost 2015; 13:1084-9. [PMID: 25773535 DOI: 10.1111/jth.12894] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2014] [Indexed: 11/27/2022]
Abstract
BACKGROUND Thrombin-activatable fibrinolysis inhibitor (TAFI) is a zymogen that can be activated to form activated TAFI (TAFIa) (Ala93-Val401) through removal of the N-terminal activation peptide (Phe1-Arg92). TAFIa is thermally unstable, and the role of the activation peptide in the activity and stability of TAFI zymogen remains unclear. OBJECTIVES To better understand the role of the activation peptide in the activity and stability of TAFI. METHODS We constructed a deletion mutant, TAFI-CIIYQ-∆1-73 , in which the first 73 amino acids of the activation peptide are absent. The intrinsic activity and functional stability were determined with a chromogenic assay. The activation of TAFI-CIIYQ-∆1-73 by TAFI activators was evaluated with western blot analysis. RESULTS In comparison with TAFI-CIIYQ, the deletion mutant exerted high intrinsic activity ('full' apparent TAFIa activity) without cleavage by TAFI activators. TAFI-CIIYQ-∆1-73 was cleavable by thrombin. However, in the presence of thrombomodulin, the thrombin-mediated cleavage of TAFI-CIIYQ-∆1-73 was not accelerated. TAFI-CIIYQ-∆1-73 showed a similar functional stability profile to that of TAFI-CIIYQ. Full cleavage by thrombin did not affect the apparent carboxypeptidase activity of TAFI-CIIYQ-∆1-73 , but resulted in a significant loss of functional stability. CONCLUSIONS A stable deletion mutant of TAFI with full carboxypeptidase activity without activation is described. The segment Ala74-Arg92 in the activation peptide contributes significantly to the role of the activation peptide in stabilization of the catalytic moiety in TAFI zymogen.
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Affiliation(s)
- X Zhou
- Department of Pharmaceutical and Pharmacological Sciences, Laboratory for Therapeutic and Diagnostic Antibodies, Katholieke Universiteit Leuven, Leuven, Belgium
| | - P J Declerck
- Department of Pharmaceutical and Pharmacological Sciences, Laboratory for Therapeutic and Diagnostic Antibodies, Katholieke Universiteit Leuven, Leuven, Belgium
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18
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Plug T, Kramer G, Meijers JCM. A role for arginine-12 in thrombin-thrombomodulin-mediated activation of thrombin-activatable fibrinolysis inhibitor. J Thromb Haemost 2014; 12:1717-25. [PMID: 25066897 DOI: 10.1111/jth.12674] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 07/14/2014] [Indexed: 11/28/2022]
Abstract
BACKGROUND Thrombin-activatable fibrinolysis inhibitor (TAFI) is a proenzyme that links coagulation and fibrinolysis. TAFI can be activated by thrombin, the thrombin-thrombomodulin complex and plasmin through cleavage of the first 92 amino acids from the enzyme. In silico analysis of the TAFI sequence revealed a potential thrombin cleavage site at Arg12. The aim of this study was to determine whether TAFI can be cleaved at Arg12 and whether this cleavage plays a role in TAFI activation. METHODS A peptide based on the first 18 amino acids of TAFI was used to determine whether thrombin was able to cleave at Arg12. Mass spectrometry was performed to determine whether the Arg12-cleaved peptide was released from full-length TAFI. Furthermore, a TAFI mutant in which Arg12 was replaced by a glutamine (TAFI-R12Q) was constructed and characterized with respect to its activation kinetics. RESULTS The peptide and mass spectrometry data showed that thrombin was able to cleave TAFI at Arg12, but with low efficiency in full-length TAFI. Characterization of TAFI-R12Q showed no difference in thrombin-mediated activation from wild-type TAFI. However, there was an approximately 60-fold impairment in activation of TAFI-R12Q by the thrombin-thrombomodulin complex. CONCLUSIONS Arg12 of TAFI plays an important role in thrombomodulin-mediated TAFI activation by thrombin. Thrombin is able to cleave TAFI at Arg12, but it remains to be determined whether Arg12 is part of an exosite for thrombomodulin or whether cleavage at Arg12 accelerates thrombomodulin-mediated TAFI activation.
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Affiliation(s)
- T Plug
- Department of Experimental Vascular Medicine, Academic Medical Center, Amsterdam, The Netherlands
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19
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Wang L, Jiang R, Sun XL. Recombinant thrombomodulin of different domains for pharmaceutical, biomedical, and cell transplantation applications. Med Res Rev 2013; 34:479-502. [PMID: 23804235 DOI: 10.1002/med.21294] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Thrombomodulin (TM) is a membrane glycoprotein mainly expressed by vascular endothelial cells and is involved in many physiological and pathological processes, such as coagulation, inflammation, cancer development, and embryogenesis. Human TM consists of 557 amino acids divided into five distinct domains: N-terminal lectin-like domain (designated as TMD1); six epidermal growth factor (EGF)-like domain (TMD2); Ser/Thr-rich domain (TMD3); transmembrane domain (TMD4); and cytoplasmic tail domain (TMD5). The different domains are responsible for different biological functions of TM. In the past decades, various domains of TM have been cloned and expressed for TM structural and functional study. Further, recombinant TMs of different domains show promising antithrombotic and anti-inflammatory activity in both rodents and primates and a recombinant soluble TM has been approved for therapeutic application. This review highlights recombinant TMs of diverse structures and their biological functions, as well as the complex interactions of TM with factors involved in the related biological processes. Particularly, recent advances in exploring recombinant TM of different domains for pharmaceutical, biomedical, and cell transplantation applications are summarized.
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Affiliation(s)
- Lin Wang
- Department of Chemistry, Chemical and Biomedical Engineering, Cleveland State University, Cleveland, Ohio 44115
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20
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Thrombomodulin: a bifunctional modulator of inflammation and coagulation in sepsis. Crit Care Res Pract 2012; 2012:614545. [PMID: 22482044 PMCID: PMC3299293 DOI: 10.1155/2012/614545] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Revised: 12/01/2011] [Accepted: 12/01/2011] [Indexed: 01/08/2023] Open
Abstract
Deregulated interplay between inflammation and coagulation plays a pivotal role in the pathogenesis of sepsis. Therapeutic approaches that simultaneously target both inflammation and coagulation hold great promise for the treatment of sepsis. Thrombomodulin is an endogenous anticoagulant protein that, in cooperation with protein C and thrombin-activatable fibrinolysis inhibitor, serves to maintain the endothelial microenvironment in an anti-inflammatory and anticoagulant state. A recombinant soluble form of thrombomodulin has been approved to treat patients suffering from disseminated intravascular coagulation (DIC) and has thus far shown greater therapeutic potential than heparin. A phase II clinical trial is currently underway in the USA to study the efficacy of thrombomodulin for the treatment of sepsis with DIC complications. This paper focuses on the critical roles that thrombomodulin plays at the intersection of inflammation and coagulation and proposes the possible existence of interactions with integrins via protein C. Finally, we provide a rationale for the clinical application of thrombomodulin for alleviating sepsis.
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Solulin increases clot stability in whole blood from humans and dogs with hemophilia. Blood 2012; 119:3622-8. [PMID: 22234684 DOI: 10.1182/blood-2011-11-392308] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Solulin is a soluble form of thrombomodulin that is resistant to proteolysis and oxidation. It has been shown to increase the clot lysis time in factor VIII (fVIII)-deficient plasma by an activated thrombin-activatable fibrinolysis inhibitor (TAFIa)-dependent mechanism. In the present study, blood was drawn from humans and dogs with hemophilia, and thromboelastography was used to measure tissue factor-initiated fibrin formation and tissue-plasminogen activator-induced fibrinolysis. The kinetics of TAFI and protein C activation by the thrombin-Solulin complex were determined to describe the relative extent of anticoagulation and antifibrinolysis. In severe hemophilia A, clot stability increased by > 4-fold in the presence of Solulin while minimally affecting clot lysis time. Patients receiving fVIII/fIX prophylaxis showed a similar trend of increased clot stability in the presence of Solulin. The catalytic efficiencies of TAFI and protein C activation by the thrombin-Solulin complex were determined to be 1.53 and 0.02/μM/s, respectively, explaining its preference for antifibrinolysis over anticoagulation at low concentrations. Finally, hemophilic dogs given Solulin had improved clot strength in thromboelastography assays. In conclusion, the antifibrinolytic properties of Solulin are exhibited in hemophilic human (in vitro) and dog (in vivo/ex vivo) blood at low concentrations. Our findings suggest the therapeutic utility of Solulin at a range of very low doses.
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22
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Conway EM. Thrombomodulin and its role in inflammation. Semin Immunopathol 2012; 34:107-25. [PMID: 21805323 DOI: 10.1007/s00281-011-0282-8] [Citation(s) in RCA: 216] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Accepted: 07/20/2011] [Indexed: 12/30/2022]
Abstract
The goal is to provide an extensive review of the physiologic role of thrombomodulin (TM) in maintaining vascular homeostasis, with a focus on its anti-inflammatory properties. Data were collected from published research. TM is a transmembrane glycoprotein expressed on the surface of all vascular endothelial cells. Expression of TM is tightly regulated to maintain homeostasis and to ensure a rapid and localized hemostatic and inflammatory response to injury. By virtue of its strategic location, its multidomain structure and complex interactions with thrombin, protein C (PC), thrombin activatable fibrinolysis inhibitor (TAFI), complement components, the Lewis Y antigen, and the cytokine HMGB1, TM exhibits a range of physiologically important anti-inflammatory, anti-coagulant, and anti-fibrinolytic properties. TM is an essential cofactor that impacts on multiple biologic processes. Alterations in expression of TM and its partner proteins may be manifest by inflammatory and thrombotic disorders. Administration of soluble forms of TM holds promise as effective therapies for inflammatory diseases, and infections and malignancies that are complicated by disseminated intravascular coagulation.
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Affiliation(s)
- Edward M Conway
- Division of Hematology-Oncology, Department of Medicine, Centre for Blood Research (CBR), University of British Columbia, Vancouver, BC, Canada.
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23
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Mishra N, Vercauteren E, Develter J, Bammens R, Declerck PJ, Gils A. Identification and characterisation of monoclonal antibodies that impair the activation of human thrombin activatable fibrinolysis inhibitor through different mechanisms. Thromb Haemost 2011; 106:90-101. [PMID: 21544309 DOI: 10.1160/th10-08-0546] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Accepted: 03/18/2011] [Indexed: 11/05/2022]
Abstract
Thrombin activatable fibrinolysis inhibitor (TAFI) forms a molecular link between coagulation and fibrinolysis and is a putative target to develop profibrinolytic drugs. Out of a panel of monoclonal antibodies (MA) raised against TAFI-ACIIYQ, we selected MA-TCK11A9, MA-TCK22G2 and MA-TCK27A4, which revealed high affinity towards human TAFI-TI-wt. MA-TCK11A9 was able to inhibit mainly plasmin-mediated TAFI activation, MA-TCK22G2 inhibited plasmin- and thrombin-mediated TAFI activation and MA-TCK27A4 inhibited TAFI activation by plasmin, thrombin and thrombin/thrombomodulin (T/TM) in a dose-dependent manner. These MA did not interfere with TAFIa activity. Using an eight-fold molar excess of MA over TAFI, all three MA were able to reduce clot lysis time significantly, i.e. in the presence of exogenous TM, MA-TCK11A9, MA-TCK22G2 and MA-TCK27A4 reduced clot lysis time by 47 ± 9.1%, 80 ± 8.6% and 92 ± 14%, respectively, compared to PTCI. This effect was even more pronounced in the absence of TM i.e. MA-TCK11A9, MA-TCK22G2 and MA-TCK27A4 reduced clot lysis time by 90 ± 14%, 140 ± 12% and 147 ± 29%, respectively, compared to PTCI. Mutagenesis analysis revealed that residues at position 268, 272 and 276 are involved in the binding of MA-TCK11A9, residues 147 and 148 in the binding of MA-TCK22G2 and residue 113 in the binding of MA-TCK27A4. The present study identified three MA, with distinct epitopes, that impair the activation of human TAFI and demonstrated that MA-TCK11A9 which mainly impairs plasmin-mediated TAFI activation can also reduce significantly clot lysis time in vitro.
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Affiliation(s)
- Niraj Mishra
- Laboratory for Pharmaceutical Biology, Faculty of Pharmaceutical Sciences, Katholieke Universiteit Leuven, O&N II, Leuven, Belgium
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Cagliani R, Fumagalli M, Riva S, Pozzoli U, Fracassetti M, Bresolin N, Comi GP, Sironi M. Polymorphisms in the CPB2 Gene Are Maintained by Balancing Selection and Result in Haplotype-Preferential Splicing of Exon 7. Mol Biol Evol 2010; 27:1945-54. [DOI: 10.1093/molbev/msq082] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
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