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Bérubé C, Guay LD, Fraser T, Lapointe V, Cardinal S, Biron É. Convenient route to Fmoc-homotyrosine via metallaphotoredox catalysis and its use in the total synthesis of anabaenopeptin cyclic peptides. Org Biomol Chem 2023; 21:9011-9020. [PMID: 37921761 DOI: 10.1039/d3ob01608k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2023]
Abstract
Herein, we report the first solid-phase total synthesis of the natural cyclic peptide anabaenopeptin F and the use of metallaphotoredox catalysis to overcome the key challenges associated with the preparation of the non-proteinogenic amino acid homotyrosine contained in these peptides. Starting from L-homoserine, enantiopure Fmoc-protected homotyrosine was prepared in a straightforward manner by metallaphotoredox catalysis with N-Fmoc-(S)-2-amino-4-bromobutanoic acid and 4-tert-butoxybromobenzene partners. The prepared protected amino acid was used in solid-phase peptide synthesis to achieve the total synthesis of anabaenopeptin F and establish the stereochemistry of the isoleucine residue. Protease inhibition studies with the synthesized anabaenopeptin F showed inhibitory activities against carboxypeptidase B in the low nanomolar range. The high convergency of the synthetic methodologies paves the way for the rapid access to N-Fmoc-protected non-proteinogenic and unnatural amino acids and the total synthesis of complex bioactive peptides containing these amino acids.
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Affiliation(s)
- Christopher Bérubé
- Faculté de Pharmacie, Université Laval, Québec, Québec, Canada, G1 V 0A6.
- Laboratory of Medicinal Chemistry, Centre de Recherche du CHU de Québec-Université Laval, 2705 Boulevard Laurier, Québec, Québec, Canada, G1 V 0A6
| | - Louis-David Guay
- Faculté de Pharmacie, Université Laval, Québec, Québec, Canada, G1 V 0A6.
- Laboratory of Medicinal Chemistry, Centre de Recherche du CHU de Québec-Université Laval, 2705 Boulevard Laurier, Québec, Québec, Canada, G1 V 0A6
| | - Tommy Fraser
- Département de Biologie, Chimie et Géographie, Université du Québec à Rimouski, 300 allée des Ursulines, Rimouski, Québec, Canada, G5L 3A1
| | - Victor Lapointe
- Faculté de Pharmacie, Université Laval, Québec, Québec, Canada, G1 V 0A6.
- Laboratory of Medicinal Chemistry, Centre de Recherche du CHU de Québec-Université Laval, 2705 Boulevard Laurier, Québec, Québec, Canada, G1 V 0A6
| | - Sébastien Cardinal
- Département de Biologie, Chimie et Géographie, Université du Québec à Rimouski, 300 allée des Ursulines, Rimouski, Québec, Canada, G5L 3A1
| | - Éric Biron
- Faculté de Pharmacie, Université Laval, Québec, Québec, Canada, G1 V 0A6.
- Laboratory of Medicinal Chemistry, Centre de Recherche du CHU de Québec-Université Laval, 2705 Boulevard Laurier, Québec, Québec, Canada, G1 V 0A6
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Xu J, Li Y, Kaur L, Singh J, Zeng F. Functional Food Based on Potato. Foods 2023; 12:foods12112145. [PMID: 37297391 DOI: 10.3390/foods12112145] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2023] [Revised: 05/19/2023] [Accepted: 05/24/2023] [Indexed: 06/12/2023] Open
Abstract
Potato (Solanum tuberosum L.) has gradually become a stable food worldwide since it can be a practical nutritional supplement and antioxidant as well as an energy provider for human beings. Financially and nutritionally, the cultivation and utility of potatoes is worthy of attention from the world. Exploring the functionality and maximizing the utilization of its component parts as well as developing new products based on the potato is still an ongoing issue. To maximize the benefits of potato and induce new high-value products while avoiding unfavorable properties of the crop has been a growing trend in food and medical areas. This review intends to summarize the factors that influence changes in the key functional components of potatoes and to discuss the focus of referenced literature which may require further research efforts. Next, it summarizes the application of the latest commercial products and potential value of components existing in potato. In particular, there are several main tasks for future potato research: preparing starchy foods for special groups of people and developing fiber-rich products to supply dietary fiber intake, manufacturing bio-friendly and specific design films/coatings in the packaging industry, extracting bioactive proteins and potato protease inhibitors with high biological activity, and continuing to build and examine the health benefits of new commercial products based on potato protein. Notably, preservation methods play a key role in the phytochemical content left in foods, and potato performs superiorly to many common vegetables when meeting the demands of daily mineral intake and alleviating mineral deficiencies.
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Affiliation(s)
- Jian Xu
- Research & Development Center for Eco-Material and Eco-Chemistry, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Yang Li
- Research & Development Center for Eco-Material and Eco-Chemistry, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
| | - Lovedeep Kaur
- Riddet Institute, School of Food and Advanced Technology, Massey University, Palmerston North 4442, New Zealand
| | - Jaspreet Singh
- Riddet Institute, School of Food and Advanced Technology, Massey University, Palmerston North 4442, New Zealand
| | - Fankui Zeng
- Research & Development Center for Eco-Material and Eco-Chemistry, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
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van Moorsel MVA, Poolen GC, Koekman CA, Verhoef S, de Maat S, Barendrecht A, van Kleef ND, Meijers JCM, Schiffelers RM, Maas C, Urbanus RT. VhH anti-thrombomodulin clone 1 inhibits TAFI activation and enhances fibrinolysis in human whole blood under flow. J Thromb Haemost 2022; 20:1213-1222. [PMID: 35170225 PMCID: PMC9311061 DOI: 10.1111/jth.15674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Revised: 02/09/2022] [Accepted: 02/10/2022] [Indexed: 11/28/2022]
Abstract
BACKGROUND Thrombomodulin on endothelial cells can form a complex with thrombin. This complex has both anticoagulant properties, by activating protein C, and clot-protective properties, by activating thrombin-activatable fibrinolysis inhibitor (TAFI). Activated TAFI (TAFIa) inhibits plasmin-mediated fibrinolysis. OBJECTIVES TAFIa inhibition is considered a potential antithrombotic strategy. So far, this goal has been pursued by developing compounds that directly inhibit TAFIa. In contrast, we here describe variable domain of heavy-chain-only antibody (VhH) clone 1 that inhibits TAFI activation by targeting human thrombomodulin. METHODS Two llamas (Lama Glama) were immunized, and phage display was used to select VhH anti-thrombomodulin (TM) clone 1. Affinity was determined with surface plasmon resonance and binding to native TM was confirmed with flow cytometry. Clone 1 was functionally assessed by competition, clot lysis, and thrombin generation assays. Last, the effect of clone 1 on tPA-mediated fibrinolysis in human whole blood was investigated in a microfluidic fibrinolysis model. RESULTS VhH anti-TM clone 1 bound recombinant TM with a binding affinity of 1.7 ± 0.4 nM and showed binding to native TM. Clone 1 competed with thrombin for binding to TM and attenuated TAFI activation in clot lysis assays and protein C activation in thrombin generation experiments. In a microfluidic fibrinolysis model, inhibition of TM with clone 1 fully prevented TAFI activation. DISCUSSION We have developed VhH anti-TM clone 1, which inhibits TAFI activation and enhances tPA-mediated fibrinolysis under flow. Different from agents that directly target TAFIa, our strategy should preserve direct TAFI activation via thrombin.
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Affiliation(s)
- Marc V. A. van Moorsel
- Central Diagnostic LaboratoryUniversity Medical Center UtrechtUtrecht UniversityUtrechtThe Netherlands
| | - Geke C. Poolen
- Central Diagnostic LaboratoryUniversity Medical Center UtrechtUtrecht UniversityUtrechtThe Netherlands
- Center for Benign HaematologyThrombosis and HaemostasisVan Creveldkliniek, University Medical Center UtrechtUtrecht UniversityUtrechtThe Netherlands
| | - Cornelis A. Koekman
- Central Diagnostic LaboratoryUniversity Medical Center UtrechtUtrecht UniversityUtrechtThe Netherlands
| | - Sandra Verhoef
- Central Diagnostic LaboratoryUniversity Medical Center UtrechtUtrecht UniversityUtrechtThe Netherlands
| | - Steven de Maat
- Central Diagnostic LaboratoryUniversity Medical Center UtrechtUtrecht UniversityUtrechtThe Netherlands
| | - Arjan Barendrecht
- Central Diagnostic LaboratoryUniversity Medical Center UtrechtUtrecht UniversityUtrechtThe Netherlands
| | - Nadine D. van Kleef
- Central Diagnostic LaboratoryUniversity Medical Center UtrechtUtrecht UniversityUtrechtThe Netherlands
| | - Joost C. M. Meijers
- Department of Experimental Vascular MedicineAmsterdam Cardiovascular Sciences, Amsterdam UMCUniversity of AmsterdamAmsterdamThe Netherlands
- Department of Molecular HematologySanquin ResearchAmsterdamThe Netherlands
| | - Raymond M. Schiffelers
- Central Diagnostic LaboratoryUniversity Medical Center UtrechtUtrecht UniversityUtrechtThe Netherlands
| | - Coen Maas
- Central Diagnostic LaboratoryUniversity Medical Center UtrechtUtrecht UniversityUtrechtThe Netherlands
| | - Rolf T. Urbanus
- Central Diagnostic LaboratoryUniversity Medical Center UtrechtUtrecht UniversityUtrechtThe Netherlands
- Center for Benign HaematologyThrombosis and HaemostasisVan Creveldkliniek, University Medical Center UtrechtUtrecht UniversityUtrechtThe Netherlands
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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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Claesen K, Mertens JC, Leenaerts D, Hendriks D. Carboxypeptidase U (CPU, TAFIa, CPB2) in Thromboembolic Disease: What Do We Know Three Decades after Its Discovery? Int J Mol Sci 2021; 22:ijms22020883. [PMID: 33477318 PMCID: PMC7830380 DOI: 10.3390/ijms22020883] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 01/12/2021] [Accepted: 01/13/2021] [Indexed: 02/01/2023] Open
Abstract
Procarboxypeptidase U (proCPU, TAFI, proCPB2) is a basic carboxypeptidase zymogen that is converted by thrombin(-thrombomodulin) or plasmin into the active carboxypeptidase U (CPU, TAFIa, CPB2), a potent attenuator of fibrinolysis. As CPU forms a molecular link between coagulation and fibrinolysis, the development of CPU inhibitors as profibrinolytic agents constitutes an attractive new concept to improve endogenous fibrinolysis or to increase the efficacy of thrombolytic therapy in thromboembolic diseases. Furthermore, extensive research has been conducted on the in vivo role of CPU in (the acute phase of) thromboembolic disease, as well as on the hypothesis that high proCPU levels and the Thr/Ile325 polymorphism may cause a thrombotic predisposition. In this paper, an overview is given of the methods available for measuring proCPU, CPU, and inactivated CPU (CPUi), together with a summary of the clinical data generated so far, ranging from the current knowledge on proCPU concentrations and polymorphisms as potential thromboembolic risk factors to the positioning of different CPU forms (proCPU, CPU, and CPUi) as diagnostic markers for thromboembolic disease, and the potential benefit of pharmacological inhibition of the CPU pathway.
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Parizi LF, Ali A, Tirloni L, Oldiges DP, Sabadin GA, Coutinho ML, Seixas A, Logullo C, Termignoni C, DA Silva Vaz I. Peptidase inhibitors in tick physiology. MEDICAL AND VETERINARY ENTOMOLOGY 2018; 32:129-144. [PMID: 29111611 DOI: 10.1111/mve.12276] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 06/23/2017] [Accepted: 10/07/2017] [Indexed: 06/07/2023]
Abstract
Peptidase inhibitors regulate a wide range of physiological processes involved in the interaction between hematophagous parasites and their hosts, including tissue remodeling, the immune response and blood coagulation. In tick physiology, peptidase inhibitors have a crucial role in adaptation to improve parasitism mechanisms, facilitating blood feeding by interfering with defense-related host peptidases. Recently, a larger number of studies on this topic led to the description of several new tick inhibitors displaying interesting novel features, for example a role in pathogen transmission to the host. A comprehensive review discussing these emerging concepts can therefore shed light on peptidase inhibitor functions, their relevance to tick physiology and their potential applications. Here, we summarize and examine the general characteristics, functional diversity and action of tick peptidase inhibitors with known physiological roles in the tick-host-pathogen interaction.
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Affiliation(s)
- L F Parizi
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
- Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - A Ali
- Department of Zoology, Abdul Wali Khan University, Mardan, Pakistan
- Escola de Enfermagem de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brazil
| | - L Tirloni
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - D P Oldiges
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - G A Sabadin
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - M L Coutinho
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
- Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
| | - A Seixas
- Departamento de Farmacociências, Universidade Federal de Ciências da Saúde de Porto Alegre, RS, Brazil
- Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, RJ, Brazil
| | - C Logullo
- Laboratório de Química e Função de Proteínas e Peptídeos-CBB and Unidade de Experimentação Animal, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, RJ, Brazil
- Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, RJ, Brazil
| | - C Termignoni
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
- Departamento de Bioquímica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Porto Alegre, Brazil
- Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, RJ, Brazil
| | - I DA Silva Vaz
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
- Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil
- Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, RJ, Brazil
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Comuth WJ, Henriksen LØ, van de Kerkhof D, Husted SE, Kristensen SD, de Maat MPM, Münster AMB. Comprehensive characteristics of the anticoagulant activity of dabigatran in relation to its plasma concentration. Thromb Res 2018; 164:32-39. [PMID: 29475179 DOI: 10.1016/j.thromres.2018.02.141] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2017] [Revised: 02/08/2018] [Accepted: 02/16/2018] [Indexed: 10/18/2022]
Abstract
BACKGROUND Issues with laboratory measurement of dabigatran include: 1. Do coagulation assays reflect dabigatran plasma concentrations? 2. Do samples from patients treated with dabigatran have the same coagulability as dabigatran-spiked samples from healthy volunteers? 3. What is the long-term stability of dabigatran after storage at -80 °C? This study aims to evaluate these questions. MATERIALS AND METHODS Ecarin chromogenic assay (ECA), a laboratory-developed diluted thrombin time (LD-dTT), prothrombin time (PT) and activated partial thromboplastin time (APTT) and ROTEM® were used to measure dabigatran anticoagulant activity and liquid chromatography-tandem mass spectrometry (LC-MS/MS) to measure dabigatran plasma concentrations. ROTEM® (EXTEM, INTEM, FIBTEM) was performed in whole blood and the other assays in platelet poor plasma (PPP), both in samples spiked with dabigatran (0, 25, 50, 100, 250, 500 and 1000 ng/mL) from healthy donors and in ex vivo samples from patients treated with dabigatran etexilate. Citrated PPP samples were frozen and stored at -80 °C, 1, 3, 6 and 12 months until analysis. RESULTS EXTEM and FIBTEM clotting time (CT), ECA and LD-dTT correlate well with dabigatran plasma concentrations. With the exception of few ROTEM® parameters, there were no differences between spiked and patient samples. Samples were stable for at least 12 months at -80 °C. CONCLUSIONS EXTEM and FIBTEM CT, ECA and LD-dTT are suitable for measuring the effect of dabigatran in treated patients. In general, results from spiked plasma samples are similar to those of patient samples. Storage of dabigatran plasma samples for up to 12 months does not influence measured levels.
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Affiliation(s)
- Willemijn J Comuth
- Department of Clinical Biochemistry, Hospital Unit West, Herning, Holstebro, Denmark; Department of Cardiology, Hospital Unit West, Herning, Denmark; Faculty of Health, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark.
| | - Linda Ø Henriksen
- Department of Clinical Biochemistry, Hospital Unit West, Herning, Holstebro, Denmark
| | - Daan van de Kerkhof
- Department of Clinical Biochemistry, Catharina Hospital, Eindhoven, The Netherlands
| | - Steen E Husted
- Department of Cardiology, Hospital Unit West, Herning, Denmark; Faculty of Health, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark
| | - Steen D Kristensen
- Faculty of Health, Institute of Clinical Medicine, Aarhus University, Aarhus, Denmark; Department of Cardiology, Aarhus University Hospital, Aarhus, Denmark
| | - Moniek P M de Maat
- Department of Haematology, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Anna-Marie B Münster
- Department of Clinical Biochemistry, Hospital of South West Denmark, Esbjerg, Denmark; Unit for Thrombosis Research, Esbjerg, Denmark
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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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9
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Timofeev АV. [Basic carboxypeptidases of blood: significance for coagulology]. BIOMEDIT︠S︡INSKAI︠A︡ KHIMII︠A︡ 2016; 62:141-9. [PMID: 27143370 DOI: 10.18097/pbmc20166202141] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
This review considers the basic metallocarboxypeptidases of human blood and their role in coagulologic disorders. In includes information on the history of the discovery and biological characteristics of potential enzymes-regulators of the fibrinolytic process: carboxypeptidase U and carboxypeptidase N. Certain attention is paid to the biochemical mechanisms and the main modern concepts of the antifibrinolytic effects of these enzymes.
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Affiliation(s)
- А V Timofeev
- Russian Research Institute of Haematology and Transfusiology, Saint Petersburg, Russia
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10
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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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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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Hendrickx MLV, Zatloukalova M, Hassanzadeh-Ghassabeh G, Muyldermans S, Gils A, Declerck PJ. In vitro and in vivo characterisation of the profibrinolytic effect of an inhibitory anti-rat TAFI nanobody. Thromb Haemost 2014; 111:824-32. [PMID: 24402608 DOI: 10.1160/th13-08-0645] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Accepted: 12/03/2013] [Indexed: 11/05/2022]
Abstract
One of the main disadvantages of current t-PA thrombolytic treatment is the increased bleeding risk. Upon activation, thrombin activatable fibrinolysis inhibitor (TAFI) is a very powerful antifibrinolytic enzyme. Therefore, co-administration of a TAFI inhibitor during thrombolysis could reduce the required t-PA dose without compromising the thrombolytic efficacy. In this study we generated and characterised a nanobody that is inhibitory towards rat TAFI and evaluated its profibrinolytic property in vitro and in vivo. Nanobody VHH-rTAFI-i81 inhibits (at a 16-fold molar ratio nanobody over TAFI) the thrombin/thrombomodulin (T/TM)-mediated activation of rat TAFI (rTAFI) by 83 ± 1.8% with an IC50 of 0.46 (molar ratio nanobody over TAFI). The affinity (KA) of VHH-rTAFI-i81 for rTAFI, as determined by surface plasmon resonance (Biacore®), is 2.5 ± 0.2 x 10(10) M(-1) and illustrates a very strong binding. In an in vitro clot lysis assay, administration of VHH-rTAFI-i81 strongly enhances the degree of lysis and reduces time to reach full lysis of t-PA-mediated clot lysis. Epitope mapping discloses that Lys392 is of primary importance for the nanobody/rTAFI interaction besides minor contributions of Tyr175 and Glu183. In vivo application of VHH-rTAFI-i81 in a tissue factor-induced mouse thromboembolism model significantly decreases fibrin deposition in the lungs in the absence of exogenous administered t-PA. Nanobody VHH-rTAFI-i81 is a very potent inhibitor of T/TM-mediated TAFI activation. Co-administration of this nanobody and t-PA enhances the fibrinolytic efficacy. In an in vivo mouse thromboembolism model, VHH-rTAFI-i81 reduces fibrin deposition in the lungs.
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Affiliation(s)
| | | | | | | | | | - Paul J Declerck
- Paul Declerck, Laboratory for Therapeutic and Diagnostic Antibodies, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Campus Gasthuisberg, O&N2, PB 820, Herestraat 49, B-3000 Leuven, Belgium, Tel.: +32 16 32 34 31, Fax: +32 16 32 34 60, E-mail:
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13
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Recovery of native protein from potato root water by expanded bed adsorption with amberlite XAD7HP. BIOTECHNOL BIOPROC E 2013. [DOI: 10.1007/s12257-013-0234-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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14
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Foley JH, Kim PY, Mutch NJ, Gils A. Insights into thrombin activatable fibrinolysis inhibitor function and regulation. J Thromb Haemost 2013; 11 Suppl 1:306-15. [PMID: 23809134 DOI: 10.1111/jth.12216] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Fibrinolysis is initiated when the zymogen plasminogen is converted to plasmin via the action of plasminogen activators. Proteolytic cleavage of fibrin by plasmin generates C-terminal lysine residues capable of binding both plasminogen and the plasminogen activator, thereby stimulating plasminogen activator-mediated plasminogen activation and propagating fibrinolysis. This positive feedback mechanism is regulated by activated thrombin activatable fibrinolysis inhibitor (TAFIa), which cleaves C-terminal lysine residues from the fibrin surface, thereby decreasing its cofactor activity. TAFI can be activated by thrombin alone, but the rate of activation is accelerated when in complex with thrombomodulin. Plasmin is also known to activate TAFI. TAFIa has no known physiologic inhibitors and consequently, its primary regulatory mechanism involves its intrinsic thermal instability. The rate of TAFI activation and stability of the active form, TAFIa, function in maintaining its concentration above the threshold value required to down-regulate fibrinolysis. Although all methods to quantify TAFI or TAFIa have their limitations, epidemiologic studies have indicated that elevated TAFI levels are correlated with an increased risk of venous thrombosis. Major efforts have been made to develop TAFI inhibitors that can either directly interfere with TAFIa activity or impair its activation. However, the anti-inflammatory properties of TAFIa might complicate the development and application of a TAFIa inhibitor that aims to increase the efficiency of thrombolytic therapy.
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Affiliation(s)
- J H Foley
- Centre for Blood Research, University of British Columbia, Vancouver, BC, Canada
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15
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Weitz JI, Eikelboom JW, Samama MM. New antithrombotic drugs: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest 2012; 141:e120S-e151S. [PMID: 22315258 DOI: 10.1378/chest.11-2294] [Citation(s) in RCA: 161] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
This article focuses on new antithrombotic drugs that are in or are entering phase 3 clinical testing. Development of these new agents was prompted by the limitations of existing antiplatelet, anticoagulant, or fibrinolytic drugs. Addressing these unmet needs, this article (1) outlines the rationale for development of new antithrombotic agents; (2) describes the new antiplatelet, anticoagulant, and fibrinolytic drugs; and (3) provides clinical perspectives on the opportunities and challenges faced by these novel agents.
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Affiliation(s)
- Jeffrey I Weitz
- Thrombosis and Atherosclerosis Research Institute and Department of Medicine, McMaster University, Hamilton, ON, Canada; Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, Canada.
| | - John W Eikelboom
- Thrombosis and Atherosclerosis Research Institute and Department of Medicine, McMaster University, Hamilton, ON, Canada
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16
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Hendrickx MLV, DE Winter A, Buelens K, Compernolle G, Hassanzadeh-Ghassabeh G, Muyldermans S, Gils A, Declerck PJ. TAFIa inhibiting nanobodies as profibrinolytic tools and discovery of a new TAFIa conformation. J Thromb Haemost 2011; 9:2268-77. [PMID: 21883886 DOI: 10.1111/j.1538-7836.2011.04495.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Because activated thrombin activatable fibrinolysis inhibitor (TAFIa) has very powerful antifibrinolytic properties, co-administration of t-PA and a TAFIa inhibitor enhances t-PA treatment. OBJECTIVE We aimed to generate nanobodies specifically inhibiting the TAFIa activity and to test their effect on t-PA induced clot lysis. RESULTS Five nanobodies, raised towards an activated more stable TAFIa mutant (TAFIa A(147) -C(305) -I(325) -I(329) -Y(333) -Q(335) ), are described. These nanobodies inhibit specifically TAFIa activity, resulting in an inhibition of up to 99% at a 16-fold molar excess of nanobody over TAFIa, IC(50) 's range between 0.38- and > 16-fold molar excess. In vitro clot lysis experiments in the absence of thrombomodulin (TM) demonstrate that the nanobodies exhibit profibrinolytic effects. However, in the presence of TM, one nanobody exhibits an antifibrinolytic effect whereas the other nanobodies show a slight antifibrinolytic effect at low concentrations and a pronounced profibrinolytic effect at higher concentrations. This biphasic pattern was highly dependent on TM and t-PA concentration. The nanobodies were found to bind in the active-site region of TAFIa and their time-dependent differential binding behavior during TAFIa inactivation revealed the occurrence of a yet unknown intermediate conformational transition. CONCLUSION These nanobodies are very potent TAFIa inhibitors and constitute useful tools to accelerate fibrinolysis. Our data also demonstrate that the profibrinolytic effect of TAFIa inhibition may be reversed by the presence of TM. The identification of a new conformational transition provides new insights into the conformational inactivation of the unstable TAFIa.
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Affiliation(s)
- M L V Hendrickx
- Laboratory for Pharmaceutical Biology, Faculty of Pharmaceutical Sciences, Katholieke Universiteit Leuven, Leuven, Belgium
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17
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Declerck PJ. Thrombin activatable fibrinolysis inhibitor. Hamostaseologie 2011; 31:165-6, 168-73. [PMID: 21629966 DOI: 10.5482/ha-1155] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Accepted: 05/26/2011] [Indexed: 12/14/2022] Open
Abstract
Thrombin activatable fibrinolysis inhibitor (TAFI) was discovered two decades ago as a consequence of the identification of an unstable carboxypeptidase (CPU), which was formed upon thrombin activation of the respective pro-enzyme (proCPU). The antifibrinolytic function of the activated form (TAFIa, CPU) is directly linked to its capacity to remove C-terminal lysines from the surface of the fibrin clot. No endogenous inhibitors have been identified, but TAFIa activity is regulated by its intrinsic temperature-dependent instability with a half-life of 8 to 15 min at 37 °C. A variety of studies have demonstrated a role for TAFI/TAFIa in venous and arterial diseases. In addition, a role in inflammation and cell migration has been shown. Since an elevated level of TAFIa it is a potential risk factor for thrombotic disorders, many inhibitors, both at the level of activation or at the level of activity, have been developed and were proven to exhibit a profibrinolytic effect in animal models. Pharmacologically active inhibitors of the TAFI/TAFIa system may open new ways for the prevention of thrombotic diseases or for the establishment of adjunctive treatments during thrombolytic therapy.
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Affiliation(s)
- P J Declerck
- Katholieke Universiteit Leuven, Campus Gasthuisberg, Herestraat 49, Leuven, Belgium.
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18
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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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19
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Abstract
See also Sanglas L, Arolas JL, Valnickova Z, Aviles FX, Enghild JJ, Gomis-Rüth FX. Insights into the molecular inactivation mechanism of human activated thrombin-activatable fibrinolysis inhibitor. This issue, pp 1056-65.
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Affiliation(s)
- A Gils
- Laboratory for Pharmaceutical Biology, Faculty of Pharmaceutical Sciences, Katholieke Universiteit Leuven, Leuven, Belgium.
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20
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Sanglas L, Arolas JL, Valnickova Z, Aviles FX, Enghild JJ, Gomis-Rüth FX. Insights into the molecular inactivation mechanism of human activated thrombin-activatable fibrinolysis inhibitor. J Thromb Haemost 2010; 8:1056-65. [PMID: 20088943 DOI: 10.1111/j.1538-7836.2010.03740.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
SUMMARY BACKGROUND Thrombin-activatable fibrinolysis inhibitor (TAFI) is a validated target for thrombotic diseases. TAFI is converted in vivo to activated TAFI (TAFIa) by removal of its pro-domain. Whereas TAFI is stable and persists in the circulation, possibly in complex with plasminogen, TAFIa is unstable and poorly soluble, with a half-life of minutes. OBJECTIVES In order to study the molecular determinants of this instability, we studied the influence of protein inhibitors on human TAFIa. RESULTS We found that protein inhibitors significantly reduced the instability and insolubility of TAFIa. In addition, we solved the 2.5-A resolution crystal structure of human TAFIa in complex with a potent protein inhibitor, tick-derived carboxypeptidase inhibitor, which gives rise to a stable and soluble TAFIa species. The structure revealed a significant reduction in the flexibility of dynamic segments when compared with the structures of bovine and human TAFI. We also identified two latent hotspots, loop Lbeta2beta3 and segment alpha5-Lalpha5beta7-beta7, where conformational destabilization may begin. These hotspots are also present in TAFI, but the pro-domain may provide sufficient stabilization and solubility to guarantee protein persistence in vivo. When the pro-domain is removed, the free TAFIa moiety becomes unstable, its activity is suppressed, and the molecule becomes insoluble. CONCLUSIONS The present study corroborates the function of protein inhibitors in stabilizing human TAFIa and it provides a rigid and high-resolution mold for the design of small molecule inhibitors of this enzyme, thus paving the way for novel therapy for thrombotic disorders.
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Affiliation(s)
- L Sanglas
- Departament de Bioquímica i Biologia Molecular, Facultat de Ciències, Institut de Biotecnologia i de Biomedicina, Universitat Autònoma de Barcelona, Bellaterra, Spain
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21
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Willemse JL, Heylen E, Nesheim ME, Hendriks DF. Carboxypeptidase U (TAFIa): a new drug target for fibrinolytic therapy? J Thromb Haemost 2009; 7:1962-71. [PMID: 19719827 PMCID: PMC3170991 DOI: 10.1111/j.1538-7836.2009.03596.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Procarboxypeptidase U (TAFI) is a recently discovered plasma procarboxypeptidase that upon activation by thrombin or thrombin-thrombomodulin turns into a potent antifibrinolytic enzyme. Its prominent bridging function between coagulation and fibrinolysis raised the interest of many research groups and of the pharmaceutical industry. The development of carboxypeptidase U (CPU) inhibitors as profibrinolytic agents is an attractive concept and possibilities for rational drug design will become more readily available in the near future as a result of the recently published crystal structure. Numerous studies have been performed and many of them show beneficial effects of CPU inhibitors for the improvement of endogenous fibrinolysis in different animal sepsis and thrombosis models. CPU inhibitors combined with tissue-type plasminogen activator (t-PA) seem to increase the efficiency of pharmacological thrombolysis allowing lower dosing of t-PA and subsequently fewer bleeding complications. This review will focus on recently obtained in vivo data and the benefits/risks of targeting CPU for the treatment of thrombotic disorders.
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Affiliation(s)
- Johan L. Willemse
- Laboratory of Medical Biochemistry, University of Antwerp, Antwerp, Belgium
| | - Evelien Heylen
- Laboratory of Medical Biochemistry, University of Antwerp, Antwerp, Belgium
| | - Michael. E. Nesheim
- Departments of Biochemistry and Medicine, Queen’s University, Ontario, Canada
| | - Dirk F. Hendriks
- Laboratory of Medical Biochemistry, University of Antwerp, Antwerp, Belgium
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22
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Hillmayer K, Vancraenenbroeck R, De Maeyer M, Compernolle G, Declerck PJ, Gils A. Discovery of novel mechanisms and molecular targets for the inhibition of activated thrombin activatable fibrinolysis inhibitor. J Thromb Haemost 2008; 6:1892-9. [PMID: 18752573 DOI: 10.1111/j.1538-7836.2008.03130.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
BACKGROUND Thrombin activatable fibrinolysis inhibitor (TAFI) is an important regulator of fibrinolysis and an attractive target to develop profibrinolytic drugs. OBJECTIVE To analyze the (inhibitory) properties of five monoclonal antibodies (mAbs) directed towards rat TAFI (i.e. MA-RT13B2, MA-RT30D8, MA-RT36A3F5, MA-RT36B2 and MA-RT82F12). METHODS AND RESULTS Direct interference of the mAb with rat activated TAFI (TAFIa) activity was assayed using a chromogenic activity assay. This revealed reductions of 79% +/- 1%, 54% +/- 4%, and 19% +/- 2% in activity in the presence of a 16-fold molar excess of MA-RT13B2, MA-RT36A3F5, and MA-RT82F12, respectively whereas MA-RT30D8 and MA-RT36B2 had no direct inhibitory effect. Additionally, MA-RT13B2 and MA-RT36A3F5 reduced rat TAFIa half-life by 56% +/- 2% and 61% +/- 3%. Tissue-type plasminogen activator mediated in vitro clot lysis was determined using rat plasma. Compared to potato tuber carboxypeptidase inhibitor, MA-RT13B2, MA-RT30D8, MA-RT36A3F5, and MA-RT82F12 reduced clot lysis times by 86% +/- 14%, 100% +/- 5%, 100% +/- 10%, and 100% +/- 11%, respectively. During epitope mapping, Arg(227) and Ser(251) were identified as major residues interacting with MA-RT13B2. Arg(188) and His(192) contribute to the interaction with MA-RT36A3F5. Arg(227), Ser(249), Ser(251), and Tyr(260) are involved in the binding of MA-RT30D8 and MA-RT82F12 with rat TAFI(a). The following mechanisms of inhibition have been deduced: MA-RT13B2 and MA-RT36A3F5 have a destabilizing effect on rat TAFIa whereas MA-RT30D8 and MA-RT82F12 partially block the access to the active site of TAFIa or interact with the binding of TAFIa to the blood clot. CONCLUSIONS The described inhibitory mAb towards rat TAFIa will facilitate TAFI research in murine models. Additionally, we reveal novel molecular targets for the direct inhibition of TAFIa through different mechanisms.
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Affiliation(s)
- K Hillmayer
- Laboratory for Pharmaceutical Biology, Faculty of Pharmaceutical Sciences, Katholieke Universiteit Leuven, Leuven
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23
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Weitz JI, Hirsh J, Samama MM. New antithrombotic drugs: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Chest 2008; 133:234S-256S. [PMID: 18574267 DOI: 10.1378/chest.08-0673] [Citation(s) in RCA: 190] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
This chapter focuses on new antithrombotic drugs that are in phase II or III clinical testing. Development of these new agents was prompted by limitations of existing antiplatelet, anticoagulant, or fibrinolytic drugs. Addressing these unmet needs, this chapter (1) outlines the rationale for development of new antithrombotic agents, (2) describes the new antiplatelet, anticoagulant, and fibrinolytic drugs, and (3) provides clinical perspectives on the opportunities and challenges faced by these novel agents.
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Affiliation(s)
- Jeffrey I Weitz
- From the Henderson Research Center, McMaster University, Hamilton, ON, Canada.
| | - Jack Hirsh
- From the Henderson Research Center, McMaster University, Hamilton, ON, Canada
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24
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Crystal structures of TAFI elucidate the inactivation mechanism of activated TAFI: a novel mechanism for enzyme autoregulation. Blood 2008; 112:2803-9. [PMID: 18559974 DOI: 10.1182/blood-2008-03-146001] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Thrombin-activatable fibrinolysis inhibitor (TAFI) is a pro-metallocarboxypeptidase that can be proteolytically activated (TAFIa). TAFIa is unique among carboxypeptidases in that it spontaneously inactivates with a short half-life, a property that is crucial for its role in controlling blood clot lysis. We studied the intrinsic instability of TAFIa by solving crystal structures of TAFI, a TAFI inhibitor (GEMSA) complex and a quadruple TAFI mutant (70-fold more stable active enzyme). The crystal structures show that TAFIa stability is directly related to the dynamics of a 55-residue segment (residues 296-350) that includes residues of the active site wall. Dynamics of this flap are markedly reduced by the inhibitor GEMSA, a known stabilizer of TAFIa, and stabilizing mutations. Our data provide the structural basis for a model of TAFI auto-regulation: in zymogen TAFI the dynamic flap is stabilized by interactions with the activation peptide. Release of the activation peptide increases dynamic flap mobility and in time this leads to conformational changes that disrupt the catalytic site and expose a cryptic thrombin-cleavage site present at Arg302. This represents a novel mechanism of enzyme control that enables TAFI to regulate its activity in plasma in the absence of specific inhibitors.
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25
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Walker JB, Binette TM, Mackova M, Lambkin GR, Mitchell L, Bajzar L. Proteolytic cleavage of carboxypeptidase N markedly increases its antifibrinolytic activity. J Thromb Haemost 2008; 6:848-55. [PMID: 18221361 DOI: 10.1111/j.1538-7836.2008.02912.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Carboxypeptidase N (CPN) is a constitutively active basic carboxypeptidase sharing specificity with activated thrombin-activable fibrinolysis inhibitor (TAFIa). Generally, CPN is regarded as being non-antifibrinolytic. However, this assumption has not been thoroughly investigated, particularly with respect to long-term antifibrinolysis. In addition, a recent report has shown that plasmin cleavage increases the catalytic activity of CPN. Therefore, we investigated the antifibrinolytic properties of CPN and plasmin-cleaved CPN (CPNc). METHODS CPN was incubated with plasmin for various periods of time and the prolongation of clot lysis at various concentrations of CPN/CPNc mixture was investigated in TAFI-depleted plasma. CPN cleavage was analyzed by electrophoresis and catalytic activity was determined by monitoring cleavage of the small substrate, FA-Ala-Lys. RESULTS CPN exhibited antifibrinolytic properties in plasma clot lysis assays when present at supraphysiological concentrations. Depletion of CPN from plasma decreased the lysis time of clots formed from minimally diluted plasma at low tissue-type plasminogen activator (t-PA) concentrations. Plasmin cleavage of CPN markedly increased the antifibrinolytic properties. CPN and CPNc prolonged lysis in a non-saturable, dose-dependent, and t-PA-dependent manner. At sufficient concentration, CPN and CPNc prolonged lysis at least forty-fivefold. CPNc was 700% more antifibrinolytic than CPN but only 7% more active toward FA-Ala-Lys. The active site inhibitor GEMSA eliminated the antifibrinolytic effects of CPN and CPNc. Antifibrinolytic activity correlated with cleavage of active and/or regulatory subunits, presumably generating heterodimeric CPNc. CONCLUSIONS Limited proteolysis of CPN by plasmin generates an enzyme with greatly increased antifibrinolytic properties. We speculate that (patho)physiological proteolysis of CPN may generate a long-term antifibrinolytic enzyme.
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Affiliation(s)
- J B Walker
- Pediatric Thrombosis Program, Department of Pediatrics, University of Alberta, Edmonton, AB, Canada
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Gong H, Zhou J, Liao M, Hatta T, Harnnoi T, Umemiya R, Inoue N, Xuan X, Fujisaki K. Characterization of a carboxypeptidase inhibitor from the tick Haemaphysalis longicornis. JOURNAL OF INSECT PHYSIOLOGY 2007; 53:1079-87. [PMID: 17651749 DOI: 10.1016/j.jinsphys.2007.06.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2007] [Revised: 06/01/2007] [Accepted: 06/05/2007] [Indexed: 05/16/2023]
Abstract
A carboxypeptidase inhibitor called HlTCI was isolated from Haemaphysalis longicornis in this study. The full-length cDNA of HlTCI contains an open reading frame (ORF) of 291bp, encoding 96 amino acid residues consisting of a predicted 19-residue signal peptide and a putative mature 77-residue protein. The expected mature protein is cysteine-rich and has 12 cysteine residues assumed to construct six disulfide bridges. The deduced peptide sequence shows 63.9% homology to the carboxypeptidase inhibitor from another ixodid tick, Rhipicephalus bursa. Reverse-transcription PCR (RT-PCR) indicated that HlTCI was specifically expressed in the ovary from partially engorged adult ticks. The recombinant protein of HlTCI (rHlTCI) with glutathione S-transferase (GST) was expressed in Escherichia coli strain BL21 (DE3) and purified by glutathione-Sepharose 4B beads. rHlTCI showed inhibitory activity against digestive metallocarboxypeptidases A and B, but the activity was affected by the increase of the temperature treatment. High concentrations of rHlTCI were shown to significantly accelerate fibrinolysis in vitro. This effect of rHlTCI on clot lysis suggests its promising potential for use in some thrombotic disorders.
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Affiliation(s)
- Haiyan Gong
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido, Japan
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27
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Walker JB, Bajzar L. Complete inhibition of fibrinolysis by sustained carboxypeptidase B activity: the role and requirement of plasmin inhibitors. J Thromb Haemost 2007; 5:1257-64. [PMID: 17389009 DOI: 10.1111/j.1538-7836.2007.02541.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND The antifibrinolytic effect of activated thrombin-activatable fibrinolysis inhibitor (TAFIa) and carboxypeptidase B (CPB) displays threshold behavior. When CPB was used to simulate conditions mimicking continuous TAFIa activity, it affected the lysis of plasma clots differently to clots formed from a minimal fibrinolytic system comprising fibrinogen, plasminogen and alpha(2)-antiplasmin. Whereas CPB saturably prolonged clot lysis in the purified system, the effect of CPB did not appear saturable in plasma clots. METHODS To rationalize this difference, we investigated the effects of alpha(2)-antiplasmin, alpha(2)-macroglobulin, antithrombin and aprotinin on CPB-mediated antifibrinolysis. RESULTS CPB alone prolonged fibrinolysis in a saturable manner and the efficacy of CPB increased with decreasing tissue-type plasminogen activator (t-PA) concentration. The inhibitors by themselves did not halt fibrinolysis and the potency of each inhibitor in the absence of CPB mirrored their solution-phase plasmin inhibitory potentials: alpha(2)-antiplasmin approximately equal to aprotinin >> alpha(2)-macroglobulin >> antithrombin. With both CPB and inhibitor present, a synergistic effect was observed. The antifibrinolytic sensitivity to CPB was related to the plasmin inhibitory potential of the inhibitor. CONCLUSIONS Fibrinolysis could be completely inhibited by alpha(2)-antiplasmin, alpha(2)-macroglobulin and antithrombin, but not aprotinin, in the presence of CPB, and occurred only when the irreversible inhibitor or pool of inhibitors were in excess of plasminogen. Western blot analysis indicated that the CPB-mediated shutdown of fibrinolysis was a result of plasminogen consumption prior to clot lysis. The CPB concentration required for fibrinolytic shutdown was dependent on t-PA concentration and the inhibitory potential of the irreversible inhibitor pool.
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Affiliation(s)
- J B Walker
- Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
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Valnickova Z, Thøgersen IB, Potempa J, Enghild JJ. Thrombin-activable Fibrinolysis Inhibitor (TAFI) Zymogen Is an Active Carboxypeptidase. J Biol Chem 2007; 282:3066-76. [PMID: 17138567 DOI: 10.1074/jbc.m606559200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thrombin-activable fibrinolysis inhibitor (TAFI) is a carboxypeptidase found in human plasma, presumably as an inactive zymogen. The current dogma is that proteolytic activation by thrombin/thrombomodulin generates the active enzyme (TAFIa), which down-regulates fibrinolysis by removing C-terminal lysine residues from partially degraded fibrin. In this study, we have shown that the zymogen exhibits continuous and stable carboxypeptidase activity against large peptide substrates, and we suggest that the activity down-regulates fibrinolysis in vivo.
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Affiliation(s)
- Zuzana Valnickova
- Center for Insoluble Protein Structure at the Department of Molecular Biology, Science Park, University of Aarhus, Gustav Wieds Vej 10c, 8000 Aarhus C, Denmark
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Bird E, Tamura J, Bostwick JS, Steinbacher TE, Stewart A, Liu Y, Baumann J, Feyen J, Tamasi J, Schumacher WA. Is exogenous tissue plasminogen activator necessary for antithrombotic efficacy of an inhibitor of thrombin activatable fibrinolysis inhibitor (TAFI) in rats? Thromb Res 2007; 120:549-58. [PMID: 17229457 DOI: 10.1016/j.thromres.2006.11.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2006] [Revised: 11/16/2006] [Accepted: 11/20/2006] [Indexed: 10/23/2022]
Abstract
INTRODUCTION TAFI indirectly reduces the action of tPA on plasminogen. Whether exogenous tPA is necessary for TAFI inhibitor efficacy is unclear. Potato carboxypeptidase inhibitor (PCI), a TAFI inhibitor, has shown variable tPA dependence in rat models of arteriovenous shunt thrombosis (required) and microthrombosis (not required). This study was designed to further explore the importance of exogenous tPA in revealing PCI activity in rat models of venous and arterial thrombosis and provoked bleeding. METHODS PCI was given as a bolus (5, 10 mg/kg) +/- infusion (5, 10 mg/kg/h) and with or without low dose tPA (5, 10, 25 microg/kg/min). In each instance tPA was adjusted to produce subthreshold thrombus reduction. Arterial thrombosis was induced by FeCl2; venous thrombosis by tissue factor or FeCl2. Bleeding was induced by kidney incision with PCI given (5 mg + 5 mg/kg/h) in the presence or absence of tPA (10, 150, 200 microg/kg/min). RESULTS PCI was ineffective without exogenous tPA in all tested thrombosis models. With exogenous tPA, PCI decreased thrombus weight 85% in tissue factor thrombosis, 59% in FeCl2 thrombosis, and 46% in arterial thrombosis. PCI prolonged bleeding only when combined with a relatively high tPA dose (200 microg/kg/min) that increased bleeding alone. CONCLUSIONS If the current results predict clinical efficacy, the need for exogenous tPA in combination with TAFI inhibition is a potential problem. However, in acute settings where intravenous fibrinolytics are administered, or indications in which tPA production increases, TAFI inhibitors may prove to be safe and moderately effective profibrinolytic agents.
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Affiliation(s)
- Eileen Bird
- Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, New Jersey, 08543, United States.
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Arolas JL, Bronsoms S, Ventura S, Aviles FX, Calvete JJ. Characterizing the tick carboxypeptidase inhibitor: molecular basis for its two-domain nature. J Biol Chem 2006; 281:22906-16. [PMID: 16760476 DOI: 10.1074/jbc.m602301200] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tick carboxypeptidase inhibitor (TCI) is a small, disulfide-rich protein that selectively inhibits metallocarboxypeptidases and strongly accelerates the fibrinolysis of blood clots. TCI consists of two domains that are structurally very similar, each containing three disulfide bonds arranged in an almost identical fashion. The oxidative folding and reductive unfolding pathways of TCI and its separated domains have been characterized by kinetic and structural analysis of the acid-trapped folding intermediates. TCI folding proceeds through a sequential formation of 1-, 2-, 3-, 4-, 5-, and 6-disulfide species to reach the native form. Folding intermediates of TCI comprise two predominant 3-disulfide species (named IIIa and IIIb) and a major 6-disulfide scrambled isomer (Xa) that consecutively accumulate along the reaction and are strongly prevented by the presence of protein disulfide isomerase. This study demonstrates that IIIa and IIIb are 3-disulfide species containing the native disulfide pairings of the N- and C-terminal domains of TCI, respectively, and explains why the two domains of TCI fold sequentially and independently. Also, we show that the reductive unfolding of TCI undergoes two main independent unfolding events through the formation of IIIa and IIIb intermediates. Together, the comparison of the folding, stability, and inhibitory activity of TCI with those of the isolated domains reveals the reasons behind the two-domain nature of this protein: both domains contribute to the specificity and high affinity of its double-headed binding to carboxypeptidases. The results obtained herein provide valuable information for the design of more potent and selective TCI molecules.
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Affiliation(s)
- Joan L Arolas
- Institut de Biotecnologia i Biomedicina and Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona
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Ceresa E, Van de Borne K, Peeters M, Lijnen HR, Declerck PJ, Gils A. Generation of a stable activated thrombin activable fibrinolysis inhibitor variant. J Biol Chem 2006; 281:15878-83. [PMID: 16595693 DOI: 10.1074/jbc.m509839200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activated thrombin activable fibrinolysis inhibitor (TAFIa), generated upon activation of TAFI, exerts an antifibrinolytic effect. TAFIa is a thermolabile enzyme, inactivated through a conformational change. The objective of the current study was to generate a stable variant of human TAFIa. Using a site-directed as well as a random mutagenesis approach to generate a library of TAFI mutants, we identified two mutations that increase TAFIa stability, i.e. a Ser305 to Cys and a Thr329 to Ile mutation, respectively. Combining these mutations in TAFI-Ala147-Ile325, the most stable isoform of TAFIa (half-life of 9.4 +/- 0.4 min), revealed a TAFIa half-life of 70 +/- 3.1 min (i.e. an 11-fold increase versus 6.3 +/- 0.3 min for TAFIa-Ala147-Thr325, the most frequently occurring isoform of TAFI in humans) at 37 degrees C. Moreover, clot lysis (induced by tissue plasminogen activator) experiments in which TAFI-Ala147-Cys305-Ile325-Ile329 was added to TAFI-depleted plasma revealed a 50% clot lysis time of 313 +/- 77 min (i.e. a 3.0-fold increase versus 117 +/- 10 min for TAFI-Ala147-Thr325). The availability of a more stable TAFIa variant will facilitate the search for inhibitors and allow further structural analysis to elucidate the mechanisms of the instability of TAFIa.
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Affiliation(s)
- Erik Ceresa
- Laboratory for Pharmaceutical Biology and Phytopharmacology, Faculty of Pharmaceutical Sciences, Katholieke Universiteit Leuven, B-3000 Leuven, Belgium
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Wang X, Smith PL, Hsu MY, Ogletree ML, Schumacher WA. Murine model of ferric chloride-induced vena cava thrombosis: evidence for effect of potato carboxypeptidase inhibitor. J Thromb Haemost 2006; 4:403-10. [PMID: 16420573 DOI: 10.1111/j.1538-7836.2006.01703.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND/OBJECTIVE Thrombin-activatable fibrinolysis inhibitor (TAFI) is a plasma carboxypeptidase that renders a fibrin-containing thrombus less sensitive to lysis. In the present study, we describe the development of a murine model of vena cava thrombosis and its use to characterize the antithrombotic activity of potato carboxypeptidase inhibitor (PCI) of TAFIa (activated TAFI) in mice. METHODS/RESULTS Vena cava thrombosis was induced by various concentrations of FeCl(3) in C57BL/6 mice. A relatively mild stimulus (3.5% FeCl(3)) induced thrombosis that was consistent and sensitive to reference antithrombotic agents such as clopidogrel and heparin. Dose-response studies identified a PCI dose (5 mg kg(-1) bolus plus 5 mg kg(-1) h(-1), i.v.) that produced a maximum 45% decrease in vena cava thrombus mass as assessed by protein content (n = 8, P < 0.01 compared to vehicle) in the 3.5% FeCl(3)-induced model without exogenous tissue plasminogen activator administration. In contrast, PCI had no effect on 3.5% FeCl(3)-induced carotid artery thrombosis in mice. In a tail transection bleeding model, the 5 mg kg(-1) bolus plus 5 mg kg(-1) h(-1) dose of PCI increased tail-bleeding time up to 3.5 times control (n = 8, P < 0.05). The ex vivo activity of antithrombotic doses of PCI was also demonstrated by the enhanced lysis of whole blood clots formed in a thrombelastograph with the addition of a sub-threshold concentration of tPA. CONCLUSION These studies provide evidence for a role of TAFIa in venous thrombosis in mice, and describe an optimized vena cava injury model appropriate for the evaluation of antithrombotic drugs and the characterization of novel therapeutic targets.
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Affiliation(s)
- X Wang
- Department of Thrombosis Biology, Bristol Myers Squibb Company, Pennington, NJ 08534, USA.
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Bertina RM, van Tilburg NH, Haverkate F, Bouma BN, von dem Borne PAK, Meijers JCM, Campbell W, Eaton D, Hendriks DF, Willemse JL. Discovery of thrombin activatable fibrinolysis inhibitor (TAFI). J Thromb Haemost 2006; 4:256-7. [PMID: 16409476 DOI: 10.1111/j.1538-7836.2005.01666.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- R M Bertina
- Hemostasis and Thrombosis Research Centre, Department of Hematology, Leiden University Medical Centre, Leiden, The Netherlands.
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Willemse J, Leurs J, Verkerk R, Hendriks D. Development of a fast kinetic method for the determination of carboxypeptidase U (TAFIa) using C-terminal arginine containing peptides as substrate. Anal Biochem 2005; 340:106-12. [PMID: 15802136 DOI: 10.1016/j.ab.2005.01.039] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2004] [Indexed: 11/30/2022]
Abstract
Carboxypeptidase U (CPU, TAFIa) is a novel determinant of the fibrinolytic rate. It circulates in blood as an inactive zymogen, procarboxypeptidase U, which is activated during the process of coagulation and fibrinolysis. CPU has a very short half-life at 37 degrees C. Its intrinsic instability complicates the determination of kinetic parameters of different substrates using an endpoint method. We developed a fast kinetic assay for measuring continuously the release of the C-terminal arginine by CPU independent of the nature of the substrate peptide used, allowing us to perform substrate specificity studies of CPU. This method uses arginine kinase, pyruvate kinase, and lactate dehydrogenase as auxiliary enzymes. The CPU activities measured using this kinetic assay were in the range of 97-103% of those determined with our HPLC-assisted reference assay, and the obtained K(m) and k(cat) values for hippuryl-l-arginine and bradykinin were in good accordance with those described in the literature. As expected, no arginine cleaving was seen using dipeptides and peptide substrates with a proline in the penultimate position. The presented kinetic assay enables the fast screening of substrates with a C-terminal arginine and is a valuable new tool for the kinetic evaluation of both synthetic and physiological substrates of CPU.
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Affiliation(s)
- Johan Willemse
- Laboratory of Medical Biochemistry, University of Antwerp, B-2610 Antwerp, Belgium
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35
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Affiliation(s)
- M Nesheim
- Department of Biochemistry and Medicine, Queen's University, Kingston, Ontario, Canada.
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36
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Arolas JL, Popowicz GM, Bronsoms S, Aviles FX, Huber R, Holak TA, Ventura S. Study of a Major Intermediate in the Oxidative Folding of Leech Carboxypeptidase Inhibitor: Contribution of the Fourth Disulfide Bond. J Mol Biol 2005; 352:961-75. [PMID: 16126224 DOI: 10.1016/j.jmb.2005.07.065] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2005] [Revised: 07/18/2005] [Accepted: 07/26/2005] [Indexed: 10/25/2022]
Abstract
The oxidative folding pathway of leech carboxypeptidase inhibitor (LCI; four disulfide bonds) proceeds through the formation of two major intermediates (III-A and III-B) that contain three native disulfide bonds and act as strong kinetic traps in the folding process. The III-B intermediate lacks the Cys19-Cys43 disulfide bond that links the beta-sheet core with the alpha-helix in wild-type LCI. Here, an analog of this intermediate was constructed by replacing Cys19 and Cys43 with alanine residues. Its oxidative folding follows a rapid sequential flow through one, two, and three disulfide species to reach the native form; the low accumulation of two disulfide intermediates and three disulfide (scrambled) isomers accounts for a highly efficient reaction. The three-dimensional structure of this analog, alone and in complex with carboxypeptidase A (CPA), was determined by X-ray crystallography at 2.2A resolution. Its overall structure is very similar to that of wild-type LCI, although the residues in the region adjacent to the mutation sites show an increased flexibility, which is strongly reduced upon binding to CPA. The structure of the complex also demonstrates that the analog and the wild-type LCI bind to the enzyme in the same manner, as expected by their inhibitory capabilities, which were similar for all enzymes tested. Equilibrium unfolding experiments showed that this mutant is destabilized by approximately 1.5 kcal mol(-1) (40%) relative to the wild-type protein. Together, the data indicate that the fourth disulfide bond provides LCI with both high stability and structural specificity.
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Affiliation(s)
- Joan L Arolas
- Institut de Biotecnologia i de Biomedicina and Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
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37
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Arolas JL, Popowicz GM, Lorenzo J, Sommerhoff CP, Huber R, Aviles FX, Holak TA. The Three-Dimensional Structures of Tick Carboxypeptidase Inhibitor in Complex with A/B Carboxypeptidases Reveal a Novel Double-headed Binding Mode. J Mol Biol 2005; 350:489-98. [PMID: 15961103 DOI: 10.1016/j.jmb.2005.05.015] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2005] [Revised: 05/06/2005] [Accepted: 05/08/2005] [Indexed: 11/28/2022]
Abstract
The tick carboxypeptidase inhibitor (TCI) is a proteinaceous inhibitor of metallo-carboxypeptidases present in the blood-sucking tick Rhipicephalus bursa. The three-dimensional crystal structures of recombinant TCI bound to bovine carboxypeptidase A and to human carboxypeptidase B have been determined and refined at 1.7 A and at 2.0 A resolution, respectively. TCI consists of two domains that are structurally similar despite the low degree of sequence homology. The domains, each consisting of a short alpha-helix followed by a small twisted antiparallel beta-sheet, show a high level of structural homology to proteins of the beta-defensin-fold family. TCI anchors to the surface of mammalian carboxypeptidases in a double-headed manner not previously seen for carboxypeptidase inhibitors: the last three carboxy-terminal amino acid residues interact with the active site of the enzyme in a way that mimics substrate binding, and the N-terminal domain binds to an exosite distinct from the active-site groove. The structures of these complexes should prove valuable in the applications of TCI as a thrombolytic drug and as a basis for the design of novel bivalent carboxypeptidase inhibitors.
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Affiliation(s)
- Joan L Arolas
- Institut de Biotecnologia i Biomedicina and Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
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Neill EKT, Stewart RJ, Schneider MM, Nesheim ME. A functional assay for measuring activated thrombin-activatable fibrinolysis inhibitor in plasma. Anal Biochem 2005; 330:332-41. [PMID: 15203340 DOI: 10.1016/j.ab.2004.04.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2004] [Indexed: 10/26/2022]
Abstract
Thrombin-activatable fibrinolysis inhibitor (TAFI) is a procarboxypeptidase found in plasma that is activated by thrombin, the thrombin-thrombomodulin complex, or plasmin. The active carboxypeptidase, TAFIa, attenuates fibrinolysis by removing newly exposed carboxy-terminal lysine residues on fibrin. The half-maximal effect of TAFIa on clot lysis occurs at 1 nM and the maximal effect occurs at 20 nM. Since the circulating concentration of the procarboxypeptidase is approximately 75 nM, only a small portion needs to be activated to have a significant effect on clot lysis. Several assays to measure total plasma TAFI levels and plasma TAFIa levels after it is fully activated exist. However, no currently available assay is sufficiently sensitive and specific to measure endogenous TAFIa in plasma. We have devised a new sensitive and specific assay for TAFIa in plasma that is based on physiologic function. This assay is based on the fact that TAFIa decreases the cofactor activity of high-molecular-weight fibrin degradation products in the stimulation of plasminogen cleavage in a concentration-dependent fashion. With this assay, we can measure TAFIa concentrations as low as 10 pM in plasma and it is not affected by variability in other hemostatic factors. This assay is reliable and repeatable with intra- and interassay variabilities of 6.5 and 6.1%, respectively.
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Affiliation(s)
- Erin K T Neill
- Department of Biochemistry, Queen's University, Kingston, Ontario, Canada K7L 3N6
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Arolas JL, Lorenzo J, Rovira A, Castellà J, Aviles FX, Sommerhoff CP. A carboxypeptidase inhibitor from the tick Rhipicephalus bursa: isolation, cDNA cloning, recombinant expression, and characterization. J Biol Chem 2004; 280:3441-8. [PMID: 15561703 DOI: 10.1074/jbc.m411086200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A novel proteinaceous metallo-carboxypeptidase inhibitor, named tick carboxypeptidase inhibitor (TCI), was isolated from the ixodid tick Rhipicephalus bursa and N-terminally sequenced. The complete cDNA encoding this protein was cloned from tick mRNA by reverse transcription-PCR and rapid amplification of cDNA ends techniques. The full-length TCI cDNA contains an open reading frame coding for a precursor protein of 97 amino acid residues that consists of a predicted signal peptide of 22 residues and of mature TCI, a 75-residue cysteine-rich protein (12 Cys). The deduced amino acid sequence shows no homology to other known proteins; the C terminus, however, resembles those of other protein metallo-carboxypeptidase inhibitors, suggesting a common mechanism of inhibition. Recombinant TCI expressed in Escherichia coli is fully functional and inhibits carboxypeptidases of the A/B subfamily with equilibrium dissociation constants in the nanomolar range. Structural analyses by circular dichroism and nuclear magnetic resonance indicate that TCI is a protein strongly constrained by disulfide bonds, unusually stable over a wide pH range and highly resistant to denaturing conditions. As a tight binding inhibitor of plasma carboxypeptidase B, also known as thrombin-activatable fibrinolysis inhibitor, recombinant TCI stimulates fibrinolysis in vitro and thus may have potential for applications to prevent or treat thrombotic disorders.
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Affiliation(s)
- Joan L Arolas
- Institut de Biotecnologia i de Biomedicina and Departament de Sanitat i d'Anatomia Animals, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain
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Weitz JI, Hirsh J, Samama MM. New anticoagulant drugs: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy. Chest 2004; 126:265S-286S. [PMID: 15383475 DOI: 10.1378/chest.126.3_suppl.265s] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
This article about new anticoagulant drugs is part of the seventh American College of Chest Physicians Conference on Antithrombotic and Thrombolytic Therapy: Evidence-Based Guidelines. The limitations of existing oral and parenteral anticoagulant agents have prompted a search for novel agents. Focusing on new anticoagulant drugs for the prevention and treatment of arterial and venous thrombosis, this article (1) reviews arterial and venous thrombogenesis, (2) discusses the regulation of coagulation, (3) describes the pathways for testing new anticoagulant agents, (4) describes new anticoagulant strategies focusing primarily on agents in phase II or III clinical testing, and (5) provides clinical perspective as to which of these new strategies is most likely to succeed.
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Affiliation(s)
- Jeffrey I Weitz
- Henderson Research Centre, McMaster University, Hamilton, Ontario, Canada.
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Walker JB, Bajzar L. The intrinsic threshold of the fibrinolytic system is modulated by basic carboxypeptidases, but the magnitude of the antifibrinolytic effect of activated thrombin-activable fibrinolysis inhibitor is masked by its instability. J Biol Chem 2004; 279:27896-904. [PMID: 15128744 DOI: 10.1074/jbc.m401027200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Activated thrombin-activable fibrinolysis inhibitor (TAFIa) is intrinsically unstable, a property that complicates the study of its role in regulating fibrinolysis. To investigate the effect of basic carboxypeptidases on fibrinolysis under conditions of constant carboxypeptidase activity, we employed pancreatic carboxypeptidase B (CPB), a homologous, stable basic carboxypeptidase, as a surrogate for TAFIa. Clots formed from TAFI-depleted plasma or from purified components were supplemented with tissue-type plasminogen activator and either CPB or TAFIa. The clot lysis data indicate that the down-regulation of fibrinolysis mediated by basic carboxypeptidases involves a threshold mechanism. At carboxypeptidase concentrations above the threshold, plasminogen activation is maintained in a fully down-regulated state; experiments in plasma showed that fibrinolysis is essentially halted by saturating concentrations of TAFIa and that fibrinolysis can be prolonged more than 45-fold by a stable carboxypeptidase. The threshold carboxypeptidase concentration was dependent on tissue-type plasminogen activator and antiplasmin concentrations, indicating that the threshold is determined by the steady-state plasmin concentration. Although obvious with CPB, the threshold was masked by the intrinsic instability of TAFIa and became apparent only when the effect of TAFIa was investigated over the picomolar concentration range. Because of the threshold effect and the instability of TAFIa, exponential increases in TAFIa concentration generate linear increases in lysis time. A model relating lysis time to TAFIa concentration, TAFIa half-life, and the threshold concentration of TAFIa is provided. The threshold effect has potentially important implications regarding the role of TAFIa and the regulation of clot lysis in vivo.
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Affiliation(s)
- John B Walker
- Henderson Research Centre and McMaster University, 711 Concession Street, Hamilton, Ontario L8V 1C3, Canada
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Bajzar L, Jain N, Wang P, Walker JB. Thrombin activatable fibrinolysis inhibitor: Not just an inhibitor of fibrinolysis. Crit Care Med 2004; 32:S320-4. [PMID: 15118538 DOI: 10.1097/01.ccm.0000126361.00450.b1] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To review the activation of thrombin activatable fibrinolysis inhibitor (TAFI) and activity of activated TAFI (TAFIa) as it relates to the regulation of both fibrinolytic and proinflammatory substances. DATA SOURCE Published articles and reviews (from PubMed, published between 1962 and 2003) on experimental studies of coagulation, fibrinolysis, and inflammation. DATA SYNTHESIS AND CONCLUSIONS The principal physiologic role of TAFI is still a matter of debate. Although TAFI activation can result from proteolysis by a number of proteases, the most likely physiologic activators are thrombin (in complex with the cofactor thrombomodulin) and plasmin (in complex with polysaccharide cofactors). The activated enzyme, TAFIa, displays carboxypeptidase B-like activity and probably regulates both fibrinolysis and inflammation in response to injury and infection. At present, there is limited understanding of the role that TAFI plays in the interrelationships between coagulation, fibrinolysis, and inflammation. Although the potential therapeutic value of TAFIa inhibition/TAFI activation awaits further investigation, the data gathered to date suggest that, like activated protein C, TAFIa may play a pivotal role in regulating the crosstalk between coagulation, fibrinolysis, and inflammation.
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Affiliation(s)
- P F Marx
- Department Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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