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Acquasaliente L, Pierangelini A, Pagotto A, Pozzi N, De Filippis V. From haemadin to haemanorm: Synthesis and characterization of full-length haemadin from the leech Haemadipsa sylvestris and of a novel bivalent, highly potent thrombin inhibitor (haemanorm). Protein Sci 2023; 32:e4825. [PMID: 37924304 PMCID: PMC10683372 DOI: 10.1002/pro.4825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2023] [Revised: 10/25/2023] [Accepted: 10/27/2023] [Indexed: 11/06/2023]
Abstract
Hirudin from Hirudo medicinalis is a bivalent α-Thrombin (αT) inhibitor, targeting the enzyme active site and exosite-I, and is currently used in anticoagulant therapy along with its simplified analogue hirulog. Haemadin, a small protein (57 amino acids) isolated from the land-living leech Haemadipsa sylvestris, selectively inhibits αT with a potency identical to that of recombinant hirudin (KI = 0.2 pM), with which it shares a common disulfide topology and overall fold. At variance with hirudin, haemadin targets exosite-II and therefore (besides the free protease) it also blocks thrombomodulin-bound αT without inhibiting the active intermediate meizothrombin, thus offering potential advantages over hirudin. Here, we produced in reasonably high yields and pharmaceutical purity (>98%) wild-type haemadin and the oxidation resistant Met5 → nor-Leucine analogue, both inhibiting αT with a KI of 0.2 pM. Thereafter, we used site-directed mutagenesis, spectroscopic, ligand-displacement, and Hydrogen/Deuterium Exchange-Mass Spectrometry techniques to map the αT regions relevant for the interaction with full-length haemadin and with the synthetic N- and C-terminal peptides Haem(1-10) and Haem(45-57). Haem(1-10) competitively binds to/inhibits αT active site (KI = 1.9 μM) and its potency was enhanced by 10-fold after Phe3 → β-Naphthylalanine exchange. Conversely to full-length haemadin, haem(45-57) displays intrinsic affinity for exosite-I (KD = 1.6 μM). Hence, we synthesized a peptide in which the sequences 1-9 and 45-57 were joined together through a 3-Glycine spacer to yield haemanorm, a highly potent (KI = 0.8 nM) inhibitor targeting αT active site and exosite-I. Haemanorm can be regarded as a novel class of hirulog-like αT inhibitors with potential pharmacological applications.
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Affiliation(s)
- Laura Acquasaliente
- Laboratory of Protein Chemistry & Molecular Hematology, Department of Pharmaceutical and Pharmacological Sciences, School of MedicineUniversity of PadovaPaduaItaly
| | - Andrea Pierangelini
- Laboratory of Protein Chemistry & Molecular Hematology, Department of Pharmaceutical and Pharmacological Sciences, School of MedicineUniversity of PadovaPaduaItaly
| | - Anna Pagotto
- Laboratory of Protein Chemistry & Molecular Hematology, Department of Pharmaceutical and Pharmacological Sciences, School of MedicineUniversity of PadovaPaduaItaly
| | - Nicola Pozzi
- Laboratory of Protein Chemistry & Molecular Hematology, Department of Pharmaceutical and Pharmacological Sciences, School of MedicineUniversity of PadovaPaduaItaly
- Department of Biochemistry and Molecular Biology, Edward A. Doisy Research CenterSaint Louis UniversitySt. LouisMissouriUSA
| | - Vincenzo De Filippis
- Laboratory of Protein Chemistry & Molecular Hematology, Department of Pharmaceutical and Pharmacological Sciences, School of MedicineUniversity of PadovaPaduaItaly
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Kumar S, Wulf J, Basore K, Pozzi N. Structural analyses of β 2-glycoprotein I: is there a circular conformation? J Thromb Haemost 2023; 21:3511-3521. [PMID: 37536570 PMCID: PMC10834832 DOI: 10.1016/j.jtha.2023.07.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 07/10/2023] [Accepted: 07/17/2023] [Indexed: 08/05/2023]
Abstract
BACKGROUND Antiphospholipid antibodies targeting β2-glycoprotein I (β2GPI) cause thrombosis and pregnancy morbidity in antiphospholipid syndrome (APS) patients. How these antibodies recognize β2GPI remains controversial. OBJECTIVES This study aimed to elucidate the structure of β2GPI and evaluate how pathogenic anti-domain I (DI) antibodies recognize it in human plasma. METHODS β2GPI was made recombinant and purified from human plasma using different protocols. Structural and functional analyses were conducted using orthogonal techniques, namely, electron microscopy, size-exclusion chromatography, single-molecule Förster resonance energy transfer, and microfluidic diffusional sizing. RESULTS Electron microscopy and size-exclusion chromatography showed that the structure of β2GPI produced recombinantly and purified from plasma is elongated, even when subjected to conditions previously reported to favor circularization. Single-molecule Förster resonance energy transfer analyses of β2GPI labeled at positions 88 in DII and 278 in DV showed that these residues are located >90 Å apart, consistent with an elongated form. They also documented that the distance between these 2 residues did not change when the protein was reconstituted in human plasma. Microfluidic diffusional sizing documented that β2GPI binds with moderate affinity to a prototypical anti-DI antibody targeting the epitope G40-R43 despite being elongated. CONCLUSION Circulating β2GPI is elongated and, therefore, fully capable of binding to anti-DI antibodies. Binding of β2GPI to negatively charged phospholipids drives autoantibody recognition by increasing the local concentration of the antigen and not by dramatically changing its conformation. These findings clarify the structural properties of β2GPI, which have important implications for understanding APS pathogenesis and the development of APS diagnostics and therapeutics.
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Affiliation(s)
- Suresh Kumar
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St Louis, Missouri, USA
| | - John Wulf
- Washington University Center for Cellular Imaging, Washington University School of Medicine, St Louis, Missouri, USA
| | - Katherine Basore
- Washington University Center for Cellular Imaging, Washington University School of Medicine, St Louis, Missouri, USA
| | - Nicola Pozzi
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St Louis, Missouri, USA.
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Ponzar N, Pozzi N. Probing the conformational dynamics of thiol-isomerases using non-canonical amino acids and single-molecule FRET. Methods 2023; 214:8-17. [PMID: 37068599 DOI: 10.1016/j.ymeth.2023.04.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 04/11/2023] [Accepted: 04/12/2023] [Indexed: 04/19/2023] Open
Abstract
Disulfide bonds drive protein correct folding, prevent protein aggregation, and stabilize three-dimensional structures of proteins and their assemblies. Dysregulation of this activity leads to several disorders, including cancer, neurodegeneration, and thrombosis. A family of 20+ enzymes, called thiol-isomerases (TIs), oversee this process in the endoplasmic reticulum of human cells to ensure efficacy and accuracy. While the biophysical and biochemical properties of cysteine residues are well-defined, our structural knowledge of how TIs select, interact and process their substrates remains poorly understood. How TIs structurally and functionally respond to changes in redox environment and other post-translational modifications remain unclear, too. We recently developed a workflow for site-specific incorporation of non-canonical amino acids into protein disulfide isomerase (PDI), the prototypical member of TIs. Combined with click chemistry, this strategy enabled us to perform single-molecule biophysical studies of PDI under various solution conditions. This paper details protocols and discusses challenges in performing these experiments. We expect this approach, combined with other emerging technologies in single-molecule biophysics and structural biology, to facilitate the exploration of the mechanisms by which TIs carry out their fascinating but poorly understood roles in humans, especially in the context of thrombosis.
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Affiliation(s)
- Nathan Ponzar
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO, 63104, USA
| | - Nicola Pozzi
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO, 63104, USA.
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Chinnaraj M, Pengo V, Pozzi N. A Novel ELISA Assay for the Detection of Anti-Prothrombin Antibodies in Antiphospholipid Syndrome Patients at High Risk of Thrombosis. Front Immunol 2021; 12:741589. [PMID: 34567006 PMCID: PMC8455811 DOI: 10.3389/fimmu.2021.741589] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 08/25/2021] [Indexed: 12/03/2022] Open
Abstract
Autoantibodies targeting prothrombin (aPT) can be found in antiphospholipid syndrome (APS) patients. However, their detection has proven difficult to standardize. Here, we developed a new ELISA assay to improve the identification of aPT and compared its performance with currently available anti-phosphatidylserine/prothrombin antibodies (aPS/PT) and autoantibodies targeting prothrombin bound to the plastic plate (aPT-A) assays using a cohort of 27 APS patients at high risk of thrombosis. We generated a novel prothrombin variant, ProTS525A-Biot, carrying an artificial tag at the C-terminus suitable for site-specific biotinylation and added the mutation S525A to improve stability. ProTS525A-Biot was immobilized to neutravidin-coated plates at the desired density and with a defined orientation, i.e., pointing the N-terminal fragment-1 toward the solvent. Antibodies against ProTS525A-Biot (aPT-Bio) were found in 24 out of 27 triple-positive APS patients (88%). When compared to aPS/PT and aPT-A, aPT-Bio showed an excellent linear correlation with aPS/PT (R2 = 0.85) but not with aPT-A (R2 = 0.40). Since aPS/PT but not aPT-A are an emerging biomarker of thrombosis in APS, this method may find utility for detecting pathogenic aPT in APS but also other prothrombotic conditions such as COVID-19.
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Affiliation(s)
- Mathivanan Chinnaraj
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO, United States
| | - Vittorio Pengo
- Thrombosis Research Laboratory, Department of Cardiac-Thoracic-Vascular Sciences and Public Health, University of Padova, Padua, Italy.,Arianna Foundation on Anticoagulation, Bologna, Italy
| | - Nicola Pozzi
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, MO, United States
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Kumar S, Chinnaraj M, Planer W, Zuo X, Macor P, Tedesco F, Pozzi N. An allosteric redox switch in domain V of β 2-glycoprotein I controls membrane binding and anti-domain I autoantibody recognition. J Biol Chem 2021; 297:100890. [PMID: 34197876 PMCID: PMC8326733 DOI: 10.1016/j.jbc.2021.100890] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Revised: 06/09/2021] [Accepted: 06/16/2021] [Indexed: 01/27/2023] Open
Abstract
β2-glycoprotein I (β2GPI) is an abundant multidomain plasma protein that plays various roles in the clotting and complement cascades. It is also the main target of antiphospholipid antibodies (aPL) in the acquired coagulopathy known as antiphospholipid syndrome (APS). Previous studies have shown that β2GPI adopts two interconvertible biochemical conformations, oxidized and reduced, depending on the integrity of the disulfide bonds. However, the precise contribution of the disulfide bonds to β2GPI structure and function is unknown. Here, we substituted cysteine residues with serine to investigate how the disulfide bonds C32-C60 in domain I (DI) and C288-C326 in domain V (DV) regulate β2GPI's structure and function. Results of our biophysical and biochemical studies support the hypothesis that the C32-C60 disulfide bond plays a structural role, whereas the disulfide bond C288-C326 is allosteric. We demonstrate that absence of the C288-C326 bond, unlike absence of the C32-C60 bond, diminishes membrane binding without affecting the thermodynamic stability and overall structure of the protein, which remains elongated in solution. We also document that, while absence of the C32-C60 bond directly impairs recognition of β2GPI by pathogenic anti-DI antibodies, absence of the C288-C326 disulfide bond is sufficient to abolish complex formation in the presence of anionic phospholipids. We conclude that the disulfide bond C288-C326 operates as a molecular switch capable of regulating β2GPI's physiological functions in a redox-dependent manner. We propose that in APS patients with anti-DI antibodies, selective rupture of the C288-C326 disulfide bond may be a valid strategy to lower the pathogenic potential of aPL.
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Affiliation(s)
- Suresh Kumar
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St Louis, Missouri, USA
| | - Mathivanan Chinnaraj
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St Louis, Missouri, USA
| | - William Planer
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St Louis, Missouri, USA
| | - Xiaobing Zuo
- X-Ray Science Division, Argonne National Laboratory, Lemont, Illinois, USA
| | - Paolo Macor
- Department of Life Sciences, University of Trieste, Trieste, Italy
| | - Francesco Tedesco
- Istituto Auxologico Italiano, IRCCS, Laboratory of Immuno-Rheumatology, Milan, Italy
| | - Nicola Pozzi
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St Louis, Missouri, USA.
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Ruben E, Planer W, Chinnaraj M, Chen Z, Zuo X, Pengo V, De Filippis V, Alluri RK, McCrae KR, Macor P, Tedesco F, Pozzi N. The J-elongated conformation of β 2-glycoprotein I predominates in solution: implications for our understanding of antiphospholipid syndrome. J Biol Chem 2020; 295:10794-10806. [PMID: 32518155 PMCID: PMC7397106 DOI: 10.1074/jbc.ra120.013939] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Revised: 06/06/2020] [Indexed: 01/07/2023] Open
Abstract
β2-Glycoprotein I (β2GPI) is an abundant plasma protein displaying phospholipid-binding properties. Because it binds phospholipids, it is a target of antiphospholipid antibodies (aPLs) in antiphospholipid syndrome (APS), a life-threatening autoimmune thrombotic disease. Indeed, aPLs prefer membrane-bound β2GPI to that in solution. β2GPI exists in two almost equally populated redox states: oxidized, in which all the disulfide bonds are formed, and reduced, in which one or more disulfide bonds are broken. Furthermore, β2GPI can adopt multiple conformations (i.e. J-elongated, S-twisted, and O-circular). While strong evidence indicates that the J-form is the structure bound to aPLs, which conformation exists and predominates in solution remains controversial, and so is the conformational pathway leading to the bound state. Here, we report that human recombinant β2GPI purified under native conditions is oxidized. Moreover, under physiological pH and salt concentrations, this oxidized form adopts a J-elongated, flexible conformation, not circular or twisted, in which the N-terminal domain I (DI) and the C-terminal domain V (DV) are exposed to the solvent. Consistent with this model, binding kinetics and mutagenesis experiments revealed that in solution the J-form interacts with negatively charged liposomes and with MBB2, a monoclonal anti-DI antibody that recapitulates most of the features of pathogenic aPLs. We conclude that the preferential binding of aPLs to phospholipid-bound β2GPI arises from the ability of its preexisting J-form to accumulate on the membranes, thereby offering an ideal environment for aPL binding. We propose that targeting the J-form of β2GPI provides a strategy to block pathogenic aPLs in APS.
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Affiliation(s)
- Eliza Ruben
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri, USA
| | - William Planer
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri, USA
| | - Mathivanan Chinnaraj
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri, USA
| | - Zhiwei Chen
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri, USA
| | - Xiaobing Zuo
- X-Ray Science Division, Argonne National Laboratory, Argonne, Illinois, USA
| | - Vittorio Pengo
- Thrombosis Research Laboratory, Department of Cardiac Thoracic and Vascular Sciences, and Public Health, University of Padova, Padova, Italy,Arianna Foundation on Anticoagulation, Bologna, Italy
| | - Vincenzo De Filippis
- Department of Pharmaceutical & Pharmacological Sciences, University of Padua, Padua, Italy
| | - Ravi K. Alluri
- Department of Cellular and Molecular Medicine, Cleveland Clinic, Cleveland, Ohio, USA
| | - Keith R. McCrae
- Department of Cellular and Molecular Medicine, Cleveland Clinic, Cleveland, Ohio, USA
| | - Paolo Macor
- Department of Life Sciences, University of Trieste, Trieste, Italy
| | - Francesco Tedesco
- Istituto Auxologico Italiano, IRCCS, Laboratory of Immuno-Rheumatology, Milan, Italy
| | - Nicola Pozzi
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri, USA,For correspondence: Nicola Pozzi,
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Yin D, de Laat B, Devreese KMJ, Kelchtermans H. The clinical value of assays detecting antibodies against domain I of β2-glycoprotein I in the antiphospholipid syndrome. Autoimmun Rev 2018; 17:1210-1218. [PMID: 30316989 DOI: 10.1016/j.autrev.2018.06.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 06/18/2018] [Indexed: 02/07/2023]
Abstract
As the clinical symptoms of the antiphospholipid syndrome (APS) frequently occur irrespective of the syndrome, diagnosis predominantly depends on the laboratory assays measuring the level or function of antiphospholipid antibodies (aPLs). β2-glycoprotein I (β2GPI) is increasingly accepted as the most important target of aPLs. Anti-β2GPI antibodies constitute a heterogeneous population, but current in vivo and in vitro evidence show that especially the first domain (DI) of β2GPI contains an important pathogenic epitope. This epitope containing Glycine40-Arginine43 (G40-R43) has proven to be cryptic and only exposed when β2GPI is in its open conformation. A previous study demonstrated a highly variable exposure of the cryptic epitope in commercial anti-β2GPI assays, with implications on correct patient classification. Unexpectedly, recent unpublished data revealed impaired exposure of the pathogenic epitope in the commercially available anti-DI chemiluminescence immunoassay (CIA) assay detecting specific antibodies directed to DI. In this review we summarize the laboratory and clinical performance characteristics of the different anti-DI assays in published data and conclude with inconsistent results for both the correlation of anti-DI antibodies with clinical symptoms and the added value of anti-DI antibodies in the classification criteria of APS. Additionally, we hypothesize on possible explanations for the observed discrepancies. Finally, we highly advise manufacturers to use normal pooled plasma spiked with the monoclonal anti-DI antibodies to verify correct exposure of the cryptic epitope.
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Affiliation(s)
- Dongmei Yin
- Cardiovascular Research Institute Maastricht, Maastricht University Medical Center, Maastricht, the Netherlands,; Synapse Research Institute, Maastricht, the Netherlands.
| | - Bas de Laat
- Cardiovascular Research Institute Maastricht, Maastricht University Medical Center, Maastricht, the Netherlands,; Synapse Research Institute, Maastricht, the Netherlands.
| | - Katrien M J Devreese
- Coagulation Laboratory, Department of Laboratory Medicine, Ghent University Hospital, Department of Diagnostic Sciences, Ghent University, Ghent, Belgium.
| | - Hilde Kelchtermans
- Cardiovascular Research Institute Maastricht, Maastricht University Medical Center, Maastricht, the Netherlands,; Synapse Research Institute, Maastricht, the Netherlands.
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Cavazzana I, Andreoli L, Limper M, Franceschini F, Tincani A. Update on Antiphospholipid Syndrome: Ten Topics in 2017. Curr Rheumatol Rep 2018. [DOI: 10.1007/s11926-018-0718-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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De Filippis V, Acquasaliente L, Pontarollo G, Peterle D. Noncoded amino acids in protein engineering: Structure-activity relationship studies of hirudin-thrombin interaction. Biotechnol Appl Biochem 2018; 65:69-80. [DOI: 10.1002/bab.1632] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2017] [Accepted: 12/06/2017] [Indexed: 11/12/2022]
Affiliation(s)
- Vincenzo De Filippis
- Laboratory of Protein Chemistry; Department of Pharmaceutical & Pharmacological Sciences; University of Padua; Padua Italy
| | - Laura Acquasaliente
- Laboratory of Protein Chemistry; Department of Pharmaceutical & Pharmacological Sciences; University of Padua; Padua Italy
| | - Giulia Pontarollo
- Laboratory of Protein Chemistry; Department of Pharmaceutical & Pharmacological Sciences; University of Padua; Padua Italy
| | - Daniele Peterle
- Laboratory of Protein Chemistry; Department of Pharmaceutical & Pharmacological Sciences; University of Padua; Padua Italy
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Molecular mapping of α-thrombin (αT)/β2-glycoprotein I (β2GpI) interaction reveals how β2GpI affects αT functions. Biochem J 2016; 473:4629-4650. [PMID: 27760842 DOI: 10.1042/bcj20160603] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 09/07/2016] [Accepted: 10/14/2016] [Indexed: 01/15/2023]
Abstract
β2-Glycoprotein I (β2GpI) is the major autoantigen in the antiphospholipid syndrome, a thrombotic autoimmune disease. Nonetheless, the physiological role of β2GpI is still unclear. In a recent work, we have shown that β2GpI selectively inhibits the procoagulant functions of human α-thrombin (αT; i.e. prolongs fibrin clotting time, tc, and inhibits αT-induced platelet aggregation) without affecting the unique anticoagulant activity of the protease, i.e. the proteolytic generation of the anticoagulant protein C (PC) from the PC zymogen, which interacts with αT exclusively at the protease catalytic site. Here, we used several different biochemical/biophysical techniques and molecular probes for mapping the binding sites in the αT-β2GpI complex. Our results indicate that αT exploits the highly electropositive exosite-II, which is also responsible for anchoring αT on the platelet GpIbα (platelet receptor glycoprotein Ibα) receptor, for binding to a continuous negative region on β2GpI structure, spanning domain IV and (part of) domain V, whereas the protease active site and exosite-I (i.e. the fibrinogen-binding site) remain accessible for substrate/ligand binding. Furthermore, we provided evidence that the apparent increase in tc, previously observed with β2GpI, is more likely caused by alteration in the ensuing fibrin structure rather than by the inhibition of fibrinogen hydrolysis. Finally, we produced a theoretical docking model of αT-β2GpI interaction, which was in agreement with the experimental results. Altogether, these findings help to understand how β2GpI affects αT interactions and suggest that β2GpI may function as a scavenger of αT for binding to the GpIbα receptor, thus impairing platelet aggregation while enabling normal cleavage of fibrinogen and PC.
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Ho YC, Ahuja KDK, Körner H, Adams MJ. β 2GP1, Anti-β 2GP1 Antibodies and Platelets: Key Players in the Antiphospholipid Syndrome. Antibodies (Basel) 2016; 5:E12. [PMID: 31557993 PMCID: PMC6698853 DOI: 10.3390/antib5020012] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 04/26/2016] [Accepted: 04/26/2016] [Indexed: 12/21/2022] Open
Abstract
Anti-beta 2 glycoprotein 1 (anti-β2GP1) antibodies are commonly found in patients with autoimmune diseases such as the antiphospholipid syndrome (APS) and systemic lupus erythematosus (SLE). Their presence is highly associated with increased risk of vascular thrombosis and/or recurrent pregnancy-related complications. Although they are a subtype of anti-phospholipid (APL) antibody, anti-β2GP1 antibodies form complexes with β2GP1 before binding to different receptors associated with anionic phospholipids on structures such as platelets and endothelial cells. β2GP1 consists of five short consensus repeat termed "sushi" domains. It has three interchangeable conformations with a cryptic epitope at domain 1 within the molecule. Anti-β2GP1 antibodies against this cryptic epitope are referred to as 'type A' antibodies, and have been suggested to be more strongly associated with both vascular and obstetric complications. In contrast, 'type B' antibodies, directed against other domains of β2GP1, are more likely to be benign antibodies found in asymptomatic patients and healthy individuals. Although the interactions between anti-β2GP1 antibodies, β2GP1, and platelets have been investigated, the actual targeted metabolic pathway(s) and/or receptor(s) involved remain to be clearly elucidated. This review will discuss the current understanding of the interaction between anti-β2GP1 antibodies and β2GP1, with platelet receptors and associated signalling pathways.
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Affiliation(s)
- Yik C Ho
- School of Health Sciences, University of Tasmania, Locked Bag 1322, Launceston, Tasmania 7250, Australia.
| | - Kiran D K Ahuja
- School of Health Sciences, University of Tasmania, Locked Bag 1322, Launceston, Tasmania 7250, Australia.
| | - Heinrich Körner
- Menzies Institute for Medical Research, University of Tasmania, Private Bag 23, Hobart, Tasmania 7001, Australia.
| | - Murray J Adams
- School of Health Sciences, University of Tasmania, Locked Bag 1322, Launceston, Tasmania 7250, Australia.
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New Tests to Detect Antiphospholipid Antibodies: Anti-Domain I Beta-2-Glycoprotein-I Antibodies. Curr Rheumatol Rep 2014; 16:402. [DOI: 10.1007/s11926-013-0402-7] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Ng DYW, Fahrer J, Wu Y, Eisele K, Kuan SL, Barth H, Weil T. Efficient delivery of p53 and cytochrome c by supramolecular assembly of a dendritic multi-domain delivery system. Adv Healthc Mater 2013; 2:1620-9. [PMID: 23657926 DOI: 10.1002/adhm.201200419] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2012] [Indexed: 11/10/2022]
Abstract
Versatile nanocarrier systems facilitating uptake of exogenous proteins are highly alluring in evaluating these proteins for therapeutic applications. The self-assembly of an efficient nano-sized protein transporter consisting of three different entities is presented: A streptavidin protein core functioning as an adapter, second generation polyamidoamine dendrons for facilitating cell uptake as well as two different therapeutic proteins (tumor suppressor p53 or pro-apoptotic cytochrome c as cargo). Well-defined dendrons containing a biotin core are prepared and display no cytotoxic behavior upon conjugation to streptavidin. The integration of biotinylated human recombinant p53 (B-p53) into the three component system allows excellent internalization into HeLa, A549 and SaOS osteosarcoma cells monitored via confocal microscopy, immunoblot analysis and co-localization studies. In addition, the conjugation of B-p53 to dendronized streptavidin preserves its specific DNA-binding in vitro, and its delivery into SaOS cells impairs cell viability with concomitant activation of caspases 3 and 7. The versatility of this system is further exhibited by the significant enhancement of the pro-apoptotic effects of internalized cytochrome c which is analyzed by flow cytometry and cell viability assays. These results demonstrate that the "bio-click" self-assembly of biotinylated dendrons and proteins on a streptavidin adapter yields a stable supramolecular complex. This efficient bionanotransporter provides an attractive platform for mediating the delivery of functional proteins of interest into living mammalian cells in a facile and rapid way.
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Affiliation(s)
- David Yuen Wah Ng
- Institute of Organic Chemistry III, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany; Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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Pozzi N, Acquasaliente L, Frasson R, Cristiani A, Moro S, Banzato A, Pengo V, Scaglione GL, Arcovito A, De Cristofaro R, De Filippis V. β2 -Glycoprotein I binds to thrombin and selectively inhibits the enzyme procoagulant functions. J Thromb Haemost 2013; 11:1093-102. [PMID: 23578283 DOI: 10.1111/jth.12238] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Indexed: 08/31/2023]
Abstract
BACKGROUND This work was aimed at characterizing the interaction of β(2)-glycoprotein I (β(2)GPI), an abundant plasma protein of unknown function, with human thrombin, the final effector protease in the coagulation cascade. METHODS The β(2)GPI-thrombin interaction was studied by surface plasmon resonance (SPR), fluorescence, and molecular modeling. The effect of β(2)GPI on the procoagulant (fibrin generation and platelet aggregation) and anticoagulant (protein C activation) functions of thrombin were investigated with turbidimetric, immunocytofluorimetric and enzymatic assays. RESULTS SPR and fluorescence data indicated that β(2)GPI tightly bound thrombin (K(d) = 34 nM) by interacting with both protease exosites, while leaving the active site accessible. This picture is fully consistent with the theoretical model of the β(2)GPI-thrombin complex. In particular, blockage of thrombin exosites with binders specific for exosite-1 (hirugen and HD1 aptamer) or exosite-2 (fibrinogen γ'-peptide and HD22 aptamer) impaired the β2 GPI-thrombin interaction. Identical results were obtained with thrombin mutants having one of the two exosites selectively compromised by mutation (Arg73Ala and Arg101Ala). Fluorescence measurements indicated that β(2)GPI did not affect the affinity of the enzyme for active site inhibitors, such as p-aminobenzamidine and the hirudin(1-47) domain, in agreement with the structural model. β(2)GPI dose-dependently prolonged the thrombin clotting time and ecarin clotting time in β(2)GPI-deficient plasma. β(2)GPI inhibited thrombin-induced platelet aggregation (IC50 = 0.36 μM) by impairing thrombin cleavage of protease-activated receptor 1 (PAR1) (IC50 = 0.32 μM), both on gel-filtered platelets and in whole blood. Strikingly, β(2) GPI did not affect thrombin-mediated generation of the anticoagulant protein C. CONCLUSIONS β(2) GPI functions as a physiologic anticoagulant by inhibiting the key procoagulant activities of thrombin without affecting its unique anticoagulant function.
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Affiliation(s)
- N Pozzi
- Laboratory of Protein Chemistry, School of Medicine, University of Padua, Padova, Italy
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Mahler M, Norman GL, Meroni PL, Khamashta M. Autoantibodies to domain 1 of beta 2 glycoprotein 1: A promising candidate biomarker for risk management in antiphospholipid syndrome. Autoimmun Rev 2012; 12:313-7. [DOI: 10.1016/j.autrev.2012.05.006] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Accepted: 05/21/2012] [Indexed: 11/29/2022]
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Abstract
The antiphospholipid syndrome (APS) is diagnosed by the occurrence of thrombosis and/or specific pregnancy morbidity. However, the diagnosis of APS is not easy and is hampered by several problems including high prevalence of clinical symptoms and high variability between different assays resulting in a high false-positive rate. Currently APS can be diagnosed for example by detecting anti-β2-glycoprotein I antibodies by ELISA. It has been reported that β2-glycoprotein I (β2GPI) changes its conformation from a native to an active form and thereby it opens up enabling antibodies to bind a specific epitope. We amongst others have shown that epitope glycine40-arginine43 of domain I of β2GPI is predominantly responsible for binding thrombosis related antibodies. Antibodies with affinity towards other epitopes have not been associated with thrombosis. Despite these results the question remains whether these domain I antibodies are the only antibodies of importance for the detection of APS.
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Affiliation(s)
- L Pelkmans
- Laboratory of the Pathophysiology of Thrombin Generation, Department of Biochemistry, CARIM, Maastricht University Medical Centre, The Netherlands
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Banzato A, Frasson R, Acquasaliente L, Bison E, Bracco A, Denas G, Cuffaro S, Hoxha A, Ruffatti A, Iliceto S, De Filippis V, Pengo V. Circulating β2 glycoprotein I-IgG anti-β2 glycoprotein I immunocomplexes in patients with definite antiphospholipid syndrome. Lupus 2012; 21:784-6. [PMID: 22635233 DOI: 10.1177/0961203312440347] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Beta2-glycoprotein I (β(2)GPI), a relevant antigen in Antiphospholipid Syndrome (APS), binds anionic macromolecules including heparin (Hep). A possible formation of ternary complexes between β(2)GPI, antibodies and Hep in APS is thus possible. The aim of this study was to evaluate Hep-β(2)GPI interaction in patients with APS. The affinity of Heps of different length, including unfractionated Hep (UFH), low-molecular weight Hep (enoxaparin) and pentasaccharide (fondaparinux), to human β(2)GPI was estimated by fluorescence spectroscopy, yielding dissociation constant (K(d)) values of 1.1, 24.0 and 89.4 µM, demonstrating that the longer UFH binds to β(2)GPI far more tightly than the shorter ones. Plasma and protein G-purified IgGs from eight patients with APS (i.e. five with thromboembolic disease and three with catastrophic APS), were fractionated by affinity chromatography using a Hep (UFH)-bound column, eluted with a linear NaCl gradient. For each chromatographic analysis, fractions were collected in the whole NaCl gradient and tested by ELISA for the presence of β(2)GPI and anti-β(2)GPI IgG. The results of Hep-affinity chromatography and ELISAs concurrently indicate that either β(2)GPI and anti-β(2)GPI IgG elute from the Hep column in the same chromatographic peak, at a retention time identical to that of the purified, isolated β(2)GPI, thus suggesting that circulating immunocomplexes containing β(2)GPI are present in patients with APS.
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Affiliation(s)
- A Banzato
- Department of Cardiac Thoracic and Vascular Sciences, University of Padova, Italy.
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18
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Banzato A, Pozzi N, Frasson R, De Filippis V, Ruffatti A, Bison E, Padayattil S, Denas G, Pengo V. Antibodies to Domain I of β2Glycoprotein I are in close relation to patients risk categories in Antiphospholipid Syndrome (APS). Thromb Res 2011; 128:583-6. [DOI: 10.1016/j.thromres.2011.04.021] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2011] [Revised: 03/24/2011] [Accepted: 04/26/2011] [Indexed: 10/18/2022]
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van Os GMA, Meijers JCM, Agar Ç, Seron MV, Marquart JA, Åkesson P, Urbanus RT, Derksen RHWM, Herwald H, Mörgelin M, D E Groot PG. Induction of anti-β2 -glycoprotein I autoantibodies in mice by protein H of Streptococcus pyogenes. J Thromb Haemost 2011; 9:2447-56. [PMID: 21985124 DOI: 10.1111/j.1538-7836.2011.04532.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND The antiphospholipid syndrome (APS) is characterized by the persistent presence of anti-β(2) -glycoprotein I (β(2) -GPI) autoantibodies. β(2) -GPI can exist in two conformations. In plasma it is a circular protein, whereas it adopts a fish-hook conformation after binding to phospholipids. Only the latter conformation is recognized by patient antibodies. β(2) -GPI has been shown to interact with Streptococcus pyogenes. OBJECTIVE To evaluate the potential of S. pyogenes-derived proteins to induce anti-β(2) -GPI autoantibodies. METHODS AND RESULTS Four S. pyogenes surface proteins (M1 protein, protein H, streptococcal collagen-like protein A [SclA], and streptococcal collagen-like protein B [SclB]) were found to interact with β(2) -GPI. Only binding to protein H induces a conformational change in β(2) -GPI, thereby exposing a cryptic epitope for APS-related autoantibodies. Mice were injected with the four proteins. Only mice injected with protein H developed antibodies against the patient antibody-related epitope in domain I of β(2) -GPI. Patients with pharyngotonsillitis caused by S. pyogenes who developed anti-protein H antibodies also generated anti-β(2) -GPI antibodies. CONCLUSIONS Our study has demonstrated that a bacterial protein can induce a conformational change in β(2) -GPI, resulting in the formation of antiβ(2) -GPI autoantibodies. This constitutes a novel mechanism for the formation of anti-β(2) -GPI autoantibodies.
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Affiliation(s)
- G M A van Os
- Department of Clinical Chemistry and Hematology, University Medical Center, CX, Utrecht, the Netherlands
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