1
|
Zaman K, Breitman A, Malik I, Fortenberry YM. Positive Allosteric Modulation of Antithrombin's Inhibitory Activity by RNA Aptamers. Nucleic Acid Ther 2023; 33:277-286. [PMID: 37093131 DOI: 10.1089/nat.2022.0047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2023] Open
Abstract
The leading cause of death in adults in the United States is cardiovascular disease, with mortality and morbidity mainly attributed to thromboembolism. Heparin is the most common therapy used for treating venous and arterial thrombosis. Heparin effectively accelerates the inhibition of coagulation proteases thrombin and factor Xa through the serine protease inhibitor (serpin) antithrombin (AT). Heparin is an essential therapeutic anticoagulant because of its effectiveness and the availability of protamine sulfate as an antidote. However, heparin therapy has several limitations. Thus, new anticoagulants, including direct thrombin inhibitors (ie, argatroban) and low-molecular-weight heparins (ie, fondaparinux), are used to treat some thromboembolic disorders. We developed and characterized a family of novel RNA-based aptamers that bind AT using two novel selection schemes. One of the aptamers, AT-16, accelerates factor Xa inhibition by AT in the absence of heparin. AT-16's effect on thrombin inhibition by AT is less effective compared to factor Xa. AT-16 induces a conformational change in AT that is different from that induced by heparin. This study demonstrates that an AT-specific RNA aptamer, AT-16, exhibits a positive allosteric modulator effect on AT's inhibition of factor Xa.
Collapse
Affiliation(s)
- Khalequz Zaman
- Biology Department, Case Western Reserve University, Cleveland, Ohio, USA
| | - Adi Breitman
- Biology Department, Case Western Reserve University, Cleveland, Ohio, USA
| | - Isa Malik
- Biology Department, Case Western Reserve University, Cleveland, Ohio, USA
| | | |
Collapse
|
2
|
Rezaie AR, Giri H. Anticoagulant and signaling functions of antithrombin. J Thromb Haemost 2020; 18:3142-3153. [PMID: 32780936 PMCID: PMC7855051 DOI: 10.1111/jth.15052] [Citation(s) in RCA: 55] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Revised: 07/25/2020] [Accepted: 08/04/2020] [Indexed: 12/19/2022]
Abstract
Antithrombin (AT) is a major plasma glycoprotein of the serpin superfamily that regulates the proteolytic activity of the procoagulant proteases of both intrinsic and extrinsic pathways. Two important structural features that participate in the regulatory function of AT include a mobile reactive center loop that binds to active site of coagulation proteases, trapping them in the form of inactive covalent complexes, and a basic D-helix that binds to therapeutic heparins and heparan sulfate proteoglycans (HSPGs) on vascular endothelial cells. The binding of D-helix of AT by therapeutic heparins promotes the reactivity of the serpin with coagulation proteases by several orders of magnitude by both a conformational activation of the serpin and a template (bridging) mechanism. In addition to its essential anticoagulant function, AT elicits a potent anti-inflammatory signaling response when it binds to distinct vascular endothelial cell HSPGs, thereby inducing prostacyclin synthesis. Syndecans-4 has been found as a specific membrane-bound HSPG receptor on endothelial cells that relays the signaling effect of AT to the relevant second messenger molecules in the signal transduction pathways inside the cell. However, following cleavage by coagulation proteases and/or by spontaneous conversion to a latent form, AT loses both its anti-inflammatory activity and high-affinity interaction with heparin and HSPGs. Interestingly, these low-affinity heparin conformers of AT elicit potent proapoptotic and antiangiogenic activities by also binding to specific HSPGs by unknown mechanisms. This review article will summarize current knowledge about mechanisms through which different conformers of AT exert their serine protease inhibitory and intracellular signaling functions in these biological pathways.
Collapse
Affiliation(s)
- Alireza R. Rezaie
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Hemant Giri
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma 73104
| |
Collapse
|
3
|
Lu Y, Villoutreix BO, Biswas I, Ding Q, Wang X, Rezaie AR. Thr90Ser Mutation in Antithrombin is Associated with Recurrent Thrombosis in a Heterozygous Carrier. Thromb Haemost 2020; 120:1045-1055. [PMID: 32422680 DOI: 10.1055/s-0040-1710590] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Antithrombin (AT) is a serine protease inhibitor that regulates the activity of coagulation proteases of both intrinsic and extrinsic pathways. We identified an AT-deficient patient with a heterozygous Thr90Ser (T90S) mutation who experiences recurrent venous thrombosis. To understand the molecular basis of the clotting defect, we expressed AT-T90S in mammalian cells, purified it to homogeneity, and characterized its properties in established kinetics, binding, and coagulation assays. The possible effect of mutation on the AT structure was also evaluated by molecular modeling. Results demonstrate the inhibitory activity of AT-T90S toward thrombin and factor Xa has been impaired three- to fivefold in both the absence and presence of heparin. The affinity of heparin for AT-T90S has been decreased by four- to fivefold. Kinetic analysis revealed the stoichiometry of AT-T90S inhibition of both thrombin and factor Xa has been elevated by three- to fourfold in both the absence and presence of heparin, suggesting that the reactivity of coagulation proteases with AT-T90S has been elevated in the substrate pathway. The anticoagulant activity of AT-T90S has been significantly impaired as analyzed in the AT-deficient plasma supplemented with AT-T90S. The anti-inflammatory effect of AT-T90S was also decreased. Structural analysis predicts the shorter side-chain of Ser in AT-T90S has a destabilizing effect on the structure of AT and/or the AT-protease complex, possibly increasing the size of an internal cavity and altering a hydrogen-bonding network that modulates conformations of the allosterically linked heparin-binding site and reactive center loop of the serpin. This mutational effect increases the reactivity of AT-T90S with coagulation proteases in the substrate pathway.
Collapse
Affiliation(s)
- Yeling Lu
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, United States
| | - Bruno O Villoutreix
- Drugs and Molecules for Living Systems, Inserm, Institut Pasteur de Lille, University of Lille, Lille, France
| | - Indranil Biswas
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, United States
| | - Qiulan Ding
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xuefeng Wang
- Department of Laboratory Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Alireza R Rezaie
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, United States.,Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| |
Collapse
|
4
|
Panicker SR, Biswas I, Giri H, Cai X, Rezaie AR. PKC (Protein Kinase C)-δ Modulates AT (Antithrombin) Signaling in Vascular Endothelial Cells. Arterioscler Thromb Vasc Biol 2020; 40:1748-1762. [PMID: 32404004 DOI: 10.1161/atvbaha.120.314479] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Native and latent conformers of AT (antithrombin) induce anti-inflammatory and proapoptotic signaling activities, respectively, in vascular endothelial cells by unknown mechanisms. Synd-4 (syndecan-4) has been identified as a receptor that is involved in transmitting signaling activities of AT in endothelial cells. Approach and Results: In this study, we used flow cytometry, signaling assays, immunoblotting and confocal immunofluorescence microscopy to investigate the mechanism of the paradoxical signaling activities of high-affinity heparin (native) and low-affinity heparin (latent) conformers of AT in endothelial cells. We discovered that native AT binds to glycosaminoglycans on vascular endothelial cells via its heparin-binding D-helix to induce anti-inflammatory signaling responses by recruiting PKC (protein kinase C)-δ to the plasma membrane and promoting phosphorylation of the Synd-4 cytoplasmic domain at Ser179. By contrast, the binding of latent AT to endothelial cells to a site(s), which is not competed by the native AT, induces a proapoptotic effect by localizing PKC-δ to the perinuclear/nuclear compartment in endothelial cells. Overexpression of a dominant-negative form of PKC-δ resulted in inhibition of anti-inflammatory and proapoptotic signaling activities of both native and latent AT. CONCLUSIONS These results indicate that the native and latent conformers of AT may exert their distinct intracellular signaling effects through differentially modulating the subcellular localization of PKC-δ in endothelial cells.
Collapse
Affiliation(s)
- Sumith R Panicker
- From the Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation (S.R.P., I.B., H.G., X.C., A.R.R.)
| | - Indranil Biswas
- From the Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation (S.R.P., I.B., H.G., X.C., A.R.R.)
| | - Hemant Giri
- From the Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation (S.R.P., I.B., H.G., X.C., A.R.R.)
| | - Xiaofeng Cai
- From the Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation (S.R.P., I.B., H.G., X.C., A.R.R.)
| | - Alireza R Rezaie
- From the Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation (S.R.P., I.B., H.G., X.C., A.R.R.).,Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City (A.R.R.)
| |
Collapse
|
5
|
Li M, Christen JM, Dittmer NT, Cao X, Zhang X, Jiang H, Kanost MR. The Manduca sexta serpinome: Analysis of serpin genes and proteins in the tobacco hornworm. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2018; 102:21-30. [PMID: 30237077 PMCID: PMC6249112 DOI: 10.1016/j.ibmb.2018.09.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 09/14/2018] [Accepted: 09/16/2018] [Indexed: 06/02/2023]
Abstract
Members of the serpin superfamily of proteins occur in animals, plants, bacteria, archaea and some viruses. They adopt a variety of physiological functions, including regulation of immune system, modulation of apoptosis, hormone transport and acting as storage proteins. Most members of the serpin family are inhibitors of serine proteinases. In this study, we searched the genome of Manduca sexta and identified 32 serpin genes. We analyzed the structure of these genes and the sequences of their encoded proteins. Three M. sexta genes (serpin-1, serpin-15, and serpin-28) have mutually exclusive alternatively spliced exons encoding the carboxyl-terminal reactive center loop of the protein, which is the site of interaction with target proteases. We discovered that MsSerpin-1 has 14 splicing isoforms, including two undiscovered in previous studies. Twenty-eight of the 32 M. sexta serpins include a putative secretion signal peptide and are predicted to be extracellular proteins. Phylogenetic analysis of serpins in M. sexta and Bombyx mori indicates that 17 are orthologous pairs, perhaps carrying out essential physiological functions. Analysis of the reactive center loop and hinge regions of the protein sequences indicates that 16 of the serpin genes encode proteins that may lack proteinase inhibitor activity. Our annotation and analysis of these serpin genes and their transcript profiles should lead to future advances in experimental study of their functions in insect biochemistry.
Collapse
Affiliation(s)
- Miao Li
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA
| | - Jayne M Christen
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA
| | - Neal T Dittmer
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA
| | - Xiaolong Cao
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA
| | - Xiufeng Zhang
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA
| | - Haobo Jiang
- Department of Entomology and Plant Pathology, Oklahoma State University, Stillwater, OK 74078, USA
| | - Michael R Kanost
- Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS 66506, USA.
| |
Collapse
|
6
|
Minsky BB, Abzalimov RR, Niu C, Zhao Y, Kirsch Z, Dubin PL, Savinov SN, Kaltashov IA. Mass Spectrometry Reveals a Multifaceted Role of Glycosaminoglycan Chains in Factor Xa Inactivation by Antithrombin. Biochemistry 2018; 57:4880-4890. [PMID: 29999301 DOI: 10.1021/acs.biochem.8b00199] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Factor Xa (fXa) inhibition by antithrombin (AT) enabled by heparin or heparan sulfate is critical for controlling blood coagulation. AT activation by heparin has been investigated extensively, while interaction of heparin with trapped AT/fXa intermediates has received relatively little attention. We use native electrospray ionization mass spectrometry to study the role of heparin chains of varying length [hexa-, octa-, deca-, and eicosasaccharides (dp6, dp8, dp10, and dp20, respectively)] in AT/fXa complex assembly. Despite being critical promoters of AT/Xa binding, shorter heparin chains are excluded from the final products (trapped intermediates). However, replacement of short heparin segments with dp20 gives rise to a prominent ionic signal of ternary complexes. These species are also observed when the trapped intermediate is initially prepared in the presence of a short oligoheparin (dp6), followed by addition of a longer heparin chain (dp20), indicating that binding of heparin to AT/fXa complexes takes place after the inhibition event. The importance of the heparin chain length for its ability to associate with the trapped intermediate suggests that the binding likely occurs in a bidentate fashion (where two distinct segments of oligoheparin make contacts with the protein components, while the part of the chain separating these two segments is extended into solution to minimize electrostatic repulsion). This model is corroborated by both molecular dynamics simulations with an explicit solvent and ion mobility measurements in the gas phase. The observed post-inhibition binding of heparin to the trapped AT/fXa intermediates hints at the likely role played by heparan sulfate in their catabolism.
Collapse
|
7
|
Dinarvand P, Yang L, Villoutreix BO, Rezaie AR. Expression and functional characterization of two natural heparin-binding site variants of antithrombin. J Thromb Haemost 2018; 16:330-341. [PMID: 29215785 PMCID: PMC5809256 DOI: 10.1111/jth.13920] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Indexed: 02/02/2023]
Abstract
Essentials Heparin-binding site (HBS) variants of antithrombin (AT) are associated with thrombosis risk. HSB variants have, in general, normal progressive inhibitory activity but reduced heparin affinity. Thrombosis in HSB carriers has been primarily attributed to the loss of heparin cofactor activity. Results here demonstrate that HSB variants of AT also lack anti-inflammatory signaling functions. SUMMARY Background Several heparin-binding site (HBS) variants of antithrombin (AT) have been identified that predispose carriers to a higher incidence of thrombosis. Thrombosis in carriers of HBS variants has been primarily attributed to a loss in their heparin-dependent anticoagulant function. Objective The objective of this study was to determine whether HSB mutations affect the anti-inflammatory functions of variants. Methods Two HBS variants of AT (AT-I7N and AT-L99F), which are known to be associated with a higher incidence of thrombosis, were expressed in mammalian cells and purified to homogeneity. These variants were characterized by kinetic assays followed by analysis of their activities in established cellular and/or in vivo inflammatory models. The possible effects of mutations on AT structure were also evaluated by molecular modeling. Results The results indicated that, whereas progressive inhibitory activities of variants were minimally affected, their heparin affinity and inhibitory activity in the presence of heparin were markedly decreased. Unlike wild-type AT, neither AT variant was capable of inhibiting activation of nuclear factor-κB or downregulation of expression of cell adhesion molecules in response to lipopolysaccharide (LPS). Similarly, neither variant elicited barrier protective activity in response to LPS. Structural analysis suggested that the L99F substitution locally destabilizes AT structure. Conclusions It is concluded that the L99F mutation of AT is associated with destabilization of the serpin structure, and that the loss of anti-inflammatory signaling function of the HBS variants may also contribute to enhanced thrombosis in carriers of HBS mutations.
Collapse
Affiliation(s)
- Peyman Dinarvand
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis
| | - Likui Yang
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation
| | - Bruno O. Villoutreix
- Inserm U973, Université Paris Diderot, Sorbonne Paris Cité, Molécules Thérapeutiques In Silico, Paris, France
| | - Alireza R. Rezaie
- Cardiovascular Biology Research Program, Oklahoma Medical Research Foundation
- Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| |
Collapse
|
8
|
Meekins DA, Zhang X, Battaile KP, Lovell S, Michel K. 1.45 Å resolution structure of SRPN18 from the malaria vector Anopheles gambiae. Acta Crystallogr F Struct Biol Commun 2016; 72:853-862. [PMID: 27917832 PMCID: PMC5137461 DOI: 10.1107/s2053230x16017854] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 11/08/2016] [Indexed: 12/28/2022] Open
Abstract
Serine protease inhibitors (serpins) in insects function within development, wound healing and immunity. The genome of the African malaria vector, Anopheles gambiae, encodes 23 distinct serpin proteins, several of which are implicated in disease-relevant physiological responses. A. gambiae serpin 18 (SRPN18) was previously categorized as non-inhibitory based on the sequence of its reactive-center loop (RCL), a region responsible for targeting and initiating protease inhibition. The crystal structure of A. gambiae SRPN18 was determined to a resolution of 1.45 Å, including nearly the entire RCL in one of the two molecules in the asymmetric unit. The structure reveals that the SRPN18 RCL is extremely short and constricted, a feature associated with noncanonical inhibitors or non-inhibitory serpin superfamily members. Furthermore, the SRPN18 RCL does not contain a suitable protease target site and contains a large number of prolines. The SRPN18 structure therefore reveals a unique RCL architecture among the highly conserved serpin fold.
Collapse
Affiliation(s)
| | - Xin Zhang
- Division of Biology, Kansas State University, USA
| | - Kevin P. Battaile
- IMCA–CAT, Hauptman–Woodward Medical Research Institute, Argonne National Laboratory, USA
| | - Scott Lovell
- Protein Structure Laboratory, Del Shankel Structural Biology Center, University of Kansas, USA
| | | |
Collapse
|
9
|
Roth R, Swanson R, Izaguirre G, Bock SC, Gettins PGW, Olson ST. Saturation Mutagenesis of the Antithrombin Reactive Center Loop P14 Residue Supports a Three-step Mechanism of Heparin Allosteric Activation Involving Intermediate and Fully Activated States. J Biol Chem 2015; 290:28020-28036. [PMID: 26359493 DOI: 10.1074/jbc.m115.678839] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Indexed: 11/06/2022] Open
Abstract
Past studies have suggested that a key feature of the mechanism of heparin allosteric activation of the anticoagulant serpin, antithrombin, is the release of the reactive center loop P14 residue from a native state stabilizing interaction with the hydrophobic core. However, more recent studies have indicated that this structural change plays a secondary role in the activation mechanism. To clarify this role, we expressed and characterized 15 antithrombin P14 variants. The variants exhibited basal reactivities with factors Xa and IXa, heparin affinities and thermal stabilities that were dramatically altered from wild type, consistent with the P14 mutations perturbing native state stability and shifting an allosteric equilibrium between native and activated states. Rapid kinetic studies confirmed that limiting rate constants for heparin allosteric activation of the mutants were altered in conjunction with the observed shifts of the allosteric equilibrium. However, correlations of the P14 mutations' effects on parameters reflecting the allosteric activation state of the serpin were inconsistent with a two-state model of allosteric activation and suggested multiple activated states. Together, these findings support a minimal three-state model of allosteric activation in which the P14 mutations perturb equilibria involving distinct native, intermediate, and fully activated states wherein the P14 residue retains an interaction with the hydrophobic core in the intermediate state but is released from the core in the fully activated state, and the bulk of allosteric activation has occurred in the intermediate.
Collapse
Affiliation(s)
- Ryan Roth
- Center for Molecular Biology of Oral Diseases and Departments of Periodontics
| | - Richard Swanson
- Center for Molecular Biology of Oral Diseases and Departments of Periodontics
| | - Gonzalo Izaguirre
- Center for Molecular Biology of Oral Diseases and Departments of Periodontics
| | - Susan C Bock
- Departments of Medicine and Bioengineering, University of Utah, Salt Lake City, Utah 84132
| | - Peter G W Gettins
- Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60612
| | - Steven T Olson
- Center for Molecular Biology of Oral Diseases and Departments of Periodontics.
| |
Collapse
|
10
|
Driguez PA, Potier P, Trouilleux P. Synthetic oligosaccharides as active pharmaceutical ingredients: lessons learned from the full synthesis of one heparin derivative on a large scale. Nat Prod Rep 2014; 31:980-9. [PMID: 24705477 DOI: 10.1039/c4np00012a] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Covering: up to November 2013. Heparin and heparan sulfate are natural polysaccharides with strong structural variations, which are responsible for their numerous specific biological properties. One key target of heparin, among others, is antithrombin, a serine protease inhibitor that, upon activation, mainly targets anticoagulation factors IIa and Xa. It is well documented that inhibition of the latter is due to a specific pentasaccharidic sequence, its synthetic analog being the registered drug fondaparinux. The replacement of hydroxyls by methoxy groups, N-sulfates by O-sulfonates and the modulation of the sulfation pattern gave rise to both idraparinux and its neutralizable form, idrabiotaparinux, two pentasaccharides with a significantly increased half-life compared to fondaparinux. Although numerous efforts have been devoted to improving the chemoenzymatic preparation of heparin fragments, enzymes are usually selective for their natural substrates, which limits the generation of some specific non-natural structures. Up to now, total synthesis has proved to be a valuable approach for the preparation of tailor-made and pure saccharides in the milligram to gram scale. This highlight will focus on the synthesis and the technical challenges associated with the development and the production of complex carbohydrates which will be exemplified with idrabiotaparinux. Particular attention will be paid to the process improvements needed in order to implement the production in a pilot plant, achieving batch generation on a multi-kilogram scale with a purity higher than 99.5%, and with no unknown impurity over 0.1%.
Collapse
Affiliation(s)
- Pierre-Alexandre Driguez
- Sanofi R&D, Early to Candidate Unit, 1 Avenue Pierre Brossolette, 91385 Chilly-Mazarin Cedex, France
| | | | | |
Collapse
|
11
|
Rashid Q, Abid M, Jairajpuri MA. Elucidating the specificity of non-heparin-based conformational activators of antithrombin for factor Xa inhibition. J Nat Sci Biol Med 2014; 5:36-42. [PMID: 24678194 PMCID: PMC3961949 DOI: 10.4103/0976-9668.127282] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Introduction: Antithrombin, the principal inhibitor of coagulation proteases, requires allosteric activation by its physiological cofactor, heparin or heparin sulfate to achieve physiologically permissible rates. This forms the basis of heparin's use as a clinical anticoagulant. However, heparin therapy is beset with severe complications, giving rise to the need to search new non-heparin activators of antithrombin, devoid of these complications and with favorable safety profiles. Materials and Methods: We chose some representative organic compounds that have been shown to be involved in coagulation modulation by affecting antithrombin and applied a blind docking protocol to find the binding energy and interactions of the modified (sulfated) versus unmodified organic scaffolds. Results and Conclusion: Increased sulfation plays a key role in shifting the specificity of organic compounds like quercetin, diosmin, rutin, mangiferin, isomangostin, Trapezifolixanthone and benzofuran towards the heparin binding site (HBS). However, in hesperetin and tetrahydroisoquinoline, sulfation shifts the specificity away from HBS. We have further tried to elucidate changes in the binding affinity of quercetin on account of gradual increase in the number of hydroxyl groups being substituted by sulfate groups. The results show gradual increase in binding energy with increase in sulfation. A theoretical screening approach is an ideal mechanism to predict lead molecules as activators of antithrombin and in determining the specificity for antithrombin.
Collapse
Affiliation(s)
- Qudsia Rashid
- Department of Bio-Sciences, Protein Conformation and Enzymology Lab, New Delhi, India
| | - Mohammad Abid
- Department of Organic Synthesis Lab, Jamia Millia Islamia, New Delhi, India
| | | |
Collapse
|
12
|
|
13
|
Wang J, Wang Y, Wang J, Gao J, Tong C, Manithody C, Li J, Rezaie AR. Antithrombin is protective against myocardial ischemia and reperfusion injury. J Thromb Haemost 2013; 11:1020-8. [PMID: 23582062 PMCID: PMC3702629 DOI: 10.1111/jth.12243] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Indexed: 11/30/2022]
Abstract
BACKGROUND Antithrombin (AT) is a plasma serpin inhibitor that regulates the proteolytic activity of procoagulant proteases of the clotting cascade. In addition to its anticoagulant activity, AT also possesses potent anti-inflammatory properties. OBJECTIVES The objective of this study was to investigate the anti-inflammatory activity of wild-type AT (AT-WT) and a reactive centre loop mutant of AT (AT-RCL) which is not capable of inhibiting thrombin. METHODS The cardioprotective activities of AT-WT and AT-RCL were monitored in a mouse model of ischemia/reperfusion (I/R) injury in which the left anterior descending coronary artery was occluded and then released. RESULTS We demonstrate that AT markedly reduces myocardial infarct size by a mechanism that is independent of its anticoagulant activity. Thus, AT-RCL attenuated myocardial infarct size to the same extent as AT-WT in this acute injury model. Further studies revealed that AT binds to vascular heparan sulfate proteoglycans via its heparin-binding domain to exert its protective activity as evidenced by the therapeutic AT-binding pentasaccharide (fondaparinux) abrogating the cardioprotective activity of AT and a heparin-site mutant of AT exhibiting no cardioprotective property. We further demonstrate that AT up-regulates the production of prostacyclin in myocardial tissues and inhibits expression of pro-inflammatory cytokines tumor necrosis factor (TNF)-α and interleukin (IL)-6 in vivo by attenuating ischemia/reperfusion-induced JNK and NF-κB signaling pathways. CONCLUSIONS The present results suggest that both AT and the non-anticoagulant AT-RCL, through their anti-inflammatory signaling effects, elicit potent cardioprotective responses. Thus, AT may have therapeutic potential for treating cardiac I/R injury.
Collapse
Affiliation(s)
- Jingying Wang
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo-SUNY, Buffalo, NY
| | - Yanqing Wang
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo-SUNY, Buffalo, NY
| | - Jinli Wang
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo-SUNY, Buffalo, NY
| | - Junjie Gao
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo-SUNY, Buffalo, NY
| | - Chao Tong
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo-SUNY, Buffalo, NY
| | - Chandrashekhara Manithody
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, MO
| | - Ji Li
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, University at Buffalo-SUNY, Buffalo, NY
| | - Alireza R. Rezaie
- Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, MO
| |
Collapse
|
14
|
Shi X, Huang Y, Mao Y, Naimy H, Zaia J. Tandem mass spectrometry of heparan sulfate negative ions: sulfate loss patterns and chemical modification methods for improvement of product ion profiles. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2012; 23:1498-511. [PMID: 22825743 PMCID: PMC4146577 DOI: 10.1007/s13361-012-0429-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 06/04/2012] [Accepted: 06/06/2012] [Indexed: 05/05/2023]
Abstract
Heparan sulfate (HS) is a polysaccharide modified with sulfation, acetylation, and epimerization that enable its binding with protein ligands and regulation of important biological processes. Tandem mass spectrometry has been employed to sequence linear biomolecules e.g., proteins and peptides. However, its application in structural characterization of HS is limited due to the neutral loss of sulfate (SO(3)) during collisional induced dissociation (CID). In this report, we studied the dissociation patterns of HS disaccharides and demonstrate that the N-sulfate (N-S) bond is especially facile during CID. We identified factors that influence the propensities of such losses from precursor ions and proposed a Free Proton Index (FPI) to help select ions that are able to produce meaningful backbone dissociations. We then investigated the thermodynamics and kinetics of SO(3) loss from sulfates that are protonated, deprotonated, and metal-adducted using density functional theory computations. The calculations showed that sulfate loss from a protonated site was much more facile than that from a deprotonated or metal-adducted site. Further, the loss of SO(3) from N-sulfate was energetically favored by 3-8 kcal/mol in transition states relative to O-sulfates, making it more prone to this process by a substantial factor. In order to reduce the FPI, representing the number of labile sulfates in HS native chains and oligosaccharides, we developed a series of chemical modifications to selectively replace the N-sulfates of the glucosamine with deuterated acetyl group. These modifications effectively reduced the sulfate density on the HS oligosaccharides and generated considerably more backbone dissociation using on-line LC/tandem MS.
Collapse
Affiliation(s)
- Xiaofeng Shi
- Department of Biochemistry and Center for Biomedical Mass Spectrometry, Boston University School of Medicine, Boston, MA 02118, USA
| | | | | | | | | |
Collapse
|
15
|
Abstract
Essentially the same steps are required to solve the crystal structure of a serpin as for any other protein: produce and purify protein, grow crystals, collect diffraction data, find estimates of the phase angles, and then refine and validate the structure. For the phasing step, experimental phasing methods involving heavy atom soaks were required for the first few structures, but with the large number of serpin structures now available, molecular replacement has become the method of choice. Two things are special about serpins. First, because of the central role of conformational change in serpin mechanism, it is advisable to consider a variety of molecular replacement models in different conformations and then to allow for rigid-body motions in the initial refinement steps. Second, probably owing to the flexibility of serpins, the average serpin crystal is significantly less well ordered than the average crystal of another protein, which increases the difficulty of solving and refining their structures.
Collapse
|
16
|
Wu MJ, McKay S, Howes N, Chin J, Hegedus E. Identification of novel serpin isoforms and serpin polymorphisms among Australian wheat cultivars. J Cereal Sci 2012. [DOI: 10.1016/j.jcs.2011.11.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
17
|
Pol-Fachin L, Franco Becker C, Almeida Guimarães J, Verli H. Effects of glycosylation on heparin binding and antithrombin activation by heparin. Proteins 2011; 79:2735-45. [PMID: 21769943 DOI: 10.1002/prot.23102] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2010] [Revised: 05/31/2011] [Accepted: 06/07/2011] [Indexed: 11/06/2022]
Abstract
Antithrombin (AT), a serine protease inhibitor, circulates in blood in two major isoforms, α and β, which differ in their amount of glycosylation and affinity for heparin. After binding to this glycosaminoglycan, the native AT conformation, relatively inactive as a protease inhibitor, is converted to an activated form. In this process, β-AT presents the higher affinity for heparin, being suggested as the major AT glycoform inhibitor in vivo. However, either the molecular basis demonstrating the differences in heparin binding to both AT isoforms or the mechanism of its conformational activation are not fully understood. Thus, the present work evaluated the effects of glycosylation and heparin binding on AT structure, function, and dynamics. Based on the obtained data, besides the native and activated forms of AT, an intermediate state, previously proposed to exist between such conformations, was also spontaneously observed in solution. Additionally, Asn135-linked oligosaccharide caused a bending in AT-bounded heparin, moving such polysaccharide away from helix D, which supports its reduced affinity for α-AT. The obtained data supported the proposal of an atomic-level, solvent and amino acid residues accounting, putative model for the transmission of the conformational signal from heparin binding exosite to β-sheet A and the reactive center loop, also supporting the identification of differences in such transmission between the serpin glycoforms involving helix D, where the Asn135-linked oligosaccharide stands. Such intramolecular rearrangements, together with heparin dynamics over AT surface, may support an atomic-level explanation for the Asn135-linked glycan influence over heparin binding and AT activation.
Collapse
Affiliation(s)
- Laercio Pol-Fachin
- Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Av Bento Gonçalves 9500, CP 15005, Porto Alegre 91500-970, RS, Brazil
| | | | | | | |
Collapse
|
18
|
|
19
|
Olson ST, Richard B, Izaguirre G, Schedin-Weiss S, Gettins PGW. Molecular mechanisms of antithrombin-heparin regulation of blood clotting proteinases. A paradigm for understanding proteinase regulation by serpin family protein proteinase inhibitors. Biochimie 2010; 92:1587-96. [PMID: 20685328 PMCID: PMC2974786 DOI: 10.1016/j.biochi.2010.05.011] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2010] [Accepted: 05/18/2010] [Indexed: 11/20/2022]
Abstract
Serpin family protein proteinase inhibitors regulate the activity of serine and cysteine proteinases by a novel conformational trapping mechanism that may itself be regulated by cofactors to provide a finely-tuned time and location-dependent control of proteinase activity. The serpin, antithrombin, together with its cofactors, heparin and heparan sulfate, perform a critical anticoagulant function by preventing the activation of blood clotting proteinases except when needed at the site of a vascular injury. Here, we review the detailed molecular understanding of this regulatory mechanism that has emerged from numerous X-ray crystal structures of antithrombin and its complexes with heparin and target proteinases together with mutagenesis and functional studies of heparin-antithrombin-proteinase interactions in solution. Like other serpins, antithrombin achieves specificity for its target blood clotting proteinases by presenting recognition determinants in an exposed reactive center loop as well as in exosites outside the loop. Antithrombin reactivity is repressed in the absence of its activator because of unfavorable interactions that diminish the favorable RCL and exosite interactions with proteinases. Binding of a specific heparin or heparan sulfate pentasaccharide to antithrombin induces allosteric activating changes that mitigate the unfavorable interactions and promote template bridging of the serpin and proteinase. Antithrombin has thus evolved a sophisticated means of regulating the activity of blood clotting proteinases in a time and location-dependent manner that exploits the multiple conformational states of the serpin and their differential stabilization by glycosaminoglycan cofactors.
Collapse
Affiliation(s)
- Steven T Olson
- Center for Molecular Biology of Oral Diseases, University of Illinois at Chicago, Chicago, IL 60612, USA.
| | | | | | | | | |
Collapse
|
20
|
Kandasamy S, Jain A, Kumar R, Agarwal SK, Joshi P, Mitra A. Molecular characterization and expression profile of uterine serpin (SERPINA14) during different reproductive phases in water buffalo (Bubalus bubalis). Anim Reprod Sci 2010; 122:133-41. [DOI: 10.1016/j.anireprosci.2010.08.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2009] [Revised: 07/22/2010] [Accepted: 08/06/2010] [Indexed: 11/29/2022]
|
21
|
Yang L, Manithody C, Qureshi SH, Rezaie AR. Inhibitory properties of the P1 Tyr variant of antithrombin. Biochemistry 2010; 49:2680-6. [PMID: 20184328 DOI: 10.1021/bi100120a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Antithrombin (AT) and protein Z-dependent protease inhibitor (ZPI) are among two physiological serpin inhibitors in plasma that are involved in the regulation of the clotting cascade. Unlike AT, which can inhibit the proteolytic activity of all coagulation proteases, ZPI has narrower protease specificity, inhibiting only factors Xa (fXa) and XIa. Unlike an Arg at the P1 site of the AT reactive center loop (RCL), this residue is a Tyr in ZPI. To investigate the contribution of P1 Tyr in restricting the specificity of ZPI, we engineered an AT mutant in which the P1 Arg of the RCL was replaced with the P1 Tyr of ZPI (AT-R393Y). The reactivity of AT-R393Y with fXa and thrombin was decreased 155- and 970-fold, respectively. However, the serpin mutant inhibited chymotrypsin with an efficiency higher by >4 orders of magnitude. By contrast, chymotrypsin did not exhibit any reactivity with ZPI. The substitution of Asp-189 of fXa with the corresponding residue of chymotrypsin (Ser) did not improve the reactivity of the protease mutant with AT-R393Y; however, the fXa mutant reacted normally with ZPI. These results suggest that the contribution of P1 Tyr to restricting the protease specificity of ZPI is RCL context-dependent and that in addition to P1 Tyr, other structural features within and/or outside the ZPI RCL are involved in determining the protease specificity of the serpin. The results further suggest that thrombin is less tolerant than fXa in accommodating the nonoptimal P1 Tyr of the AT mutant in its active-site pocket.
Collapse
Affiliation(s)
- Likui Yang
- Edward A. Doisy Department of Biochemistry and Molecular Biology, St. Louis University School of Medicine, St. Louis, Missouri 63104, USA
| | | | | | | |
Collapse
|
22
|
Yang L, Manithody C, Qureshi SH, Rezaie AR. Contribution of exosite occupancy by heparin to the regulation of coagulation proteases by antithrombin. Thromb Haemost 2009; 103:277-83. [PMID: 20024502 DOI: 10.1160/th09-08-0585] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Accepted: 10/25/2009] [Indexed: 11/05/2022]
Abstract
Heparin promotes the antithrombin (AT) inactivation of factors IXa (fIXa) and Xa (fXa) through a conformational activation of the serpin and also by a template mechanism in the presence of physiological levels of Ca2+. Recently, it was reported that heparin induces conformational changes in the active-sites of fIXa and fXa, raising the possibility that heparin also modulates the reactivity of these proteases with AT by this mechanism. To test this possibility, we prepared an AT mutant in which four critical heparin-binding residues of the serpin (Arg-45, Arg-46, Lys-114, and Arg-129) were replaced with non-basic residues. This mutant lost its affinity for heparin, but retained its normal reactivity with coagulation proteases. Thus, the high-affinity AT-binding pentasaccharide fragment of heparin had no cofactor effect on the reactivity of the AT mutant with coagulation proteases. Full-length heparin-concentration dependence of the AT inhibition of fIXa and fXa revealed that in contrast to a greater than 4-5 orders of magnitude accelerating effect for heparin on the AT inhibition of fIXa and fXa, heparin exhibits a negligible cofactor effect (<2-fold) on the mutant AT inhibition of these proteases. The same results were obtained for the mutant AT inhibition of thrombin and factor VIIa, however, heparin accelerated the mutant AT inhibition of factor XIa ~10-fold. We conclude that, with the exception of factor XIa, heparin-mediated conformational modulation of the active-sites of coagulation proteases makes a minor contribution to the regulation of these proteases by AT.
Collapse
Affiliation(s)
- L Yang
- Department of Biochemistry and Molecular Biology, St. Louis University School of Medicine, 1100 South Grand Blvd., St. Louis, MO 63104, USA
| | | | | | | |
Collapse
|
23
|
Gettins PGW, Olson ST. Activation of antithrombin as a factor IXa and Xa inhibitor involves mitigation of repression rather than positive enhancement. FEBS Lett 2009; 583:3397-400. [PMID: 19818773 DOI: 10.1016/j.febslet.2009.10.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Revised: 09/25/2009] [Accepted: 10/01/2009] [Indexed: 11/19/2022]
Abstract
Allosteric activation of antithrombin as a rapid inhibitor of factors IXa and Xa requires binding of a high-affinity heparin pentasaccharide. The currently-accepted mechanism involves removal of a constraint on the antithrombin reactive center loop (RCL) so that the proteinase can simultaneously engage both the P1 arginine and an exosite at Y253. Recent results suggest that this mechanism is incorrect in that activation can be achieved without loop expulsion, while the exosite can be engaged in both low and high activity states. We propose a quite different mechanism in which heparin activates antithrombin by mitigating an unfavorable surface interaction, by altering its nature, and by moving the attached proteinase away from the site of the unfavorable interaction through RCL expulsion.
Collapse
Affiliation(s)
- Peter G W Gettins
- Department of Biochemistry and Molecular Genetics, and Center for Structural Biology, University of Illinois at Chicago, IL 60612-4316, USA.
| | | |
Collapse
|
24
|
Yang L, Qureshi SH, Manithody C, Rezaie AR. Role of P2 glycine in determining the specificity of antithrombin reaction with coagulation proteases. Biochem Biophys Res Commun 2009; 389:162-7. [PMID: 19715676 DOI: 10.1016/j.bbrc.2009.08.118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2009] [Accepted: 08/21/2009] [Indexed: 11/30/2022]
Abstract
Structural data suggests that bulky hydrophobic residues at the S2-S4 sub-sites of factor Xa (fXa) restrict the preference of this pocket for small and non-polar residues like Gly at the P2 position of substrates and inhibitors. However, kinetic studies monitoring the cleavage specificity of 10-residue peptides by fXa have identified Phe as the most preferred P2 residue and Gln-Phe-Arg-Ser-Leu-Ser as the most preferred P3-P3' residues for recognition by fXa. To determine whether this mechanism of specificity is also true for fXa reaction with antithrombin (AT), we prepared two AT mutants having either a Phe at the P2 or Gln-Phe-Arg-Ser-Leu-Ser at the P3-P3' positions of the reactive center loop. Inhibition kinetic studies indicated that the reactivity of P2-Phe with fXa was significantly (approximately 5-fold) impaired, however, the P3-P3' mutant exhibited 1.5-fold improved reactivity with the protease, suggesting cooperative effects between P3-P3' residues influence the P2 specificity of AT. Substitution of Tyr-99 of fXa with a Gly dramatically impaired the reactivity of fXa with wild-type AT, but improved its reactivity with the serpin mutants in the absence, but not in the presence of pentasaccharide. AT with a P2-Phe inhibited thrombin with >150-fold impaired reactivity, however, the defect was restored by either pentasaccharide or by replacing Leu-99 of thrombin with a Gly. The P3-P3' mutant rapidly inhibited factors VIIa and XIa independent of pentasaccharide. These results indicate that P2-Gly plays a key role in determining the S2 sub-site specificity and target protease selectivity of AT in circulation.
Collapse
Affiliation(s)
- Likui Yang
- Department of Biochemistry and Molecular Biology, St. Louis University School of Medicine, St. Louis, MO 63104, USA
| | | | | | | |
Collapse
|
25
|
Abstract
Serpins form an enormous superfamily of 40-60-kDa proteins found in almost all types of organisms, including humans. Most are one-use suicide substrate serine and cysteine proteinase inhibitors that have evolved to finely regulate complex proteolytic pathways, such as blood coagulation, fibrinolysis, and inflammation. Despite distinct functions for each serpin, there is much redundancy in the primary specificity-determining residues. However, many serpins exploit additional exosites to generate the exquisite specificity that makes a given serpin effective only when certain other criteria, such as the presence of specific cofactors, are met. With a focus on human serpins, this minireview examines use of exosites by nine serpins in the initial complex-forming phase to modulate primary specificity in either binary serpin-proteinase complexes or ternary complexes that additionally employ a protein or other cofactor. A frequent theme is down-regulation of inhibitory activity unless the exosite(s) are engaged. In addition, the use of exosites by maspin and plasminogen activator inhibitor-1 to indirectly affect proteolytic processes is considered.
Collapse
Affiliation(s)
- Peter G W Gettins
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
| | | |
Collapse
|
26
|
Ko CW, Wei Z, Marsh RJ, Armoogum DA, Nicolaou N, Bain AJ, Zhou A, Ying L. Probing nanosecond motions of plasminogen activator inhibitor-1 by time-resolved fluorescence anisotropy. MOLECULAR BIOSYSTEMS 2009; 5:1025-31. [DOI: 10.1039/b901691k] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
|
27
|
Savi P, Herault JP, Duchaussoy P, Millet L, Schaeffer P, Petitou M, Bono F, Herbert JM. Reversible biotinylated oligosaccharides: a new approach for a better management of anticoagulant therapy. J Thromb Haemost 2008; 6:1697-706. [PMID: 18647228 DOI: 10.1111/j.1538-7836.2008.03089.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE In order to obtain a neutralizable antithrombotic, a chimeric molecule (SSR126517E) containing the sequence of a long-lasting antithrombin (AT)-dependent anti-factor Xa pentasaccharide, idraparinux, linked to a biotin molecule was synthesized and tested for anticoagulant and antithrombotic activity. METHODS SSR126517E was tested in several models in vitro and in vivo for its pharmacological properties as well as its ability to be neutralized by avidin. RESULTS SSR126517E displayed exactly the same properties as idraparinux. In vitro, SSR126517E had a very high affinity for AT (K(d) < 1 nm) and showed a potent anti-FXa effect and inhibition of thrombin generation with IC(50) values similar to those of idraparinux. Ex vivo, after intravenous administration to rats, SSR126517E produced a potent and long-lasting anti-FXa effect comparable to that obtained with idraparinux; as with idraparinux, the subcutaneous bioavailability was 100%. In vivo, SSR126517E was a potent antithrombotic in rat and mouse venous and arterial thrombosis models. Direct comparison in rats showed that SSR126517E was as active as idraparinux, when administered at the same molar dose. Furthermore, injection of avidin triggered the immediate elimination of SSR126517E from the bloodstream, resulting in complete neutralization of the antithrombotic activity of SSR126517E. CONCLUSIONS These results show for the first time that coupling an oligosaccharide with biotin has no effect on the former's pharmacokinetic and pharmacologic properties and renders neutralization easy by injection of avidin.
Collapse
Affiliation(s)
- P Savi
- Thrombosis and Angiogenesis Department, Sanofi-Aventis Recherche & Développement, Toulouse, France.
| | | | | | | | | | | | | | | |
Collapse
|
28
|
McRae SJ, Ginsberg JS. New anticoagulants for the prevention and treatment of venous thromboembolism. Vasc Health Risk Manag 2007; 1:41-53. [PMID: 17319097 PMCID: PMC1993925 DOI: 10.2147/vhrm.1.1.41.58936] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Anticoagulant therapy is effective at preventing the development of venous thromboembolism in high-risk patients, and reduces morbidity and mortality in individuals with established thromboembolic disease. Vitamin K antagonists and heparins are currently the most commonly used anticoagulant drugs, but they have practical limitations. Therefore, new antithrombotic agents with predictable dose-responses (thereby decreasing the need for monitoring without compromising efficacy or safety), ideally available in an oral formulation and with a rapidly reversible anticoagulant effect, are needed. New drugs fulfilling some of the above criteria have been developed and have proven to be effective agents for the treatment and prevention of venous thromboembolism.
Collapse
Affiliation(s)
- Simon J McRae
- Department of Medicine, McMaster University, Hamilton, ON, Canada.
| | | |
Collapse
|
29
|
Yang YH, Hwang KK, FitzGerald J, Grossman JM, Taylor M, Hahn BH, Chen PP. Antibodies against the activated coagulation factor X (FXa) in the antiphospholipid syndrome that interfere with the FXa inactivation by antithrombin. THE JOURNAL OF IMMUNOLOGY 2007; 177:8219-25. [PMID: 17114499 PMCID: PMC1950736 DOI: 10.4049/jimmunol.177.11.8219] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Antiphospholipid Ab have been shown to promote thrombosis and fetal loss in the antiphospholipid syndrome (APS). Previously, we found IgG anti-thrombin Ab in some APS patients that could interfere with inactivation of thrombin by antithrombin (AT). Considering that activated coagulation factor X (FXa) is homologous to thrombin in the catalytic domains and is also regulated primarily by AT, we hypothesized that some thrombin-reactive Ab may bind to FXa and interfere with AT inactivation of FXa. To test these hypotheses, we studied reactivity of eight patient-derived monoclonal IgG antiphospholipid Ab with FXa and the presence of IgG anti-FXa Ab in APS patients and investigated the effects of FXa-reactive mAb on AT inactivation of FXa. The results revealed that six of six thrombin-reactive IgG mAb bound to FXa and that the levels of plasma IgG anti-FXa Ab in 38 APS patients were significantly higher than those in 30 normal controls (p < 0.001). When the mean plus 3 SDs of the 30 normal controls was used as the cutoff, 5 of 38 APS patients (13.2%) had IgG anti-FXa Ab. Importantly, three of six FXa-reactive mAb significantly inhibited AT inactivation of FXa. Combined, these results indicate that anti-FXa Ab may contribute to thrombosis by interfering with the anticoagulant function of AT on FXa in some APS patients.
Collapse
Affiliation(s)
- Yao-Hsu Yang
- Division of Rheumatology, Department of Medicine, University of California, Los Angeles, CA, USA
- Department of Pediatrics, National Taiwan University Hospital, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Kwan-Ki Hwang
- Division of Rheumatology, Department of Medicine, University of California, Los Angeles, CA, USA
- Address correspondence and reprint requests to Kwan-Ki Hwang, PhD, Department of Medicine/Rheumatology, UCLA, 1000 Veteran Ave, Los Angeles, CA 90095-1670; E-Mail:
| | - John FitzGerald
- Division of Rheumatology, Department of Medicine, University of California, Los Angeles, CA, USA
| | - Jennifer M. Grossman
- Division of Rheumatology, Department of Medicine, University of California, Los Angeles, CA, USA
| | - Mihaela Taylor
- Division of Rheumatology, Department of Medicine, University of California, Los Angeles, CA, USA
| | - Bevra H. Hahn
- Division of Rheumatology, Department of Medicine, University of California, Los Angeles, CA, USA
| | - Pojen P. Chen
- Division of Rheumatology, Department of Medicine, University of California, Los Angeles, CA, USA
| |
Collapse
|
30
|
Rezaie AR. Pentasaccharide enhances the inactivation of factor Xa by antithrombin by promoting the assembly of a Michaelis-type intermediate complex. Demonstration by rapid kinetic, surface plasmon resonance, and competitive binding studies. Biochemistry 2006; 45:5324-9. [PMID: 16618121 PMCID: PMC2538365 DOI: 10.1021/bi060056r] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
It has been demonstrated that a unique pentasaccharide fragment of heparin (H5) activates AT by exposing an exosite on the serpin that is a recognition site for interaction with the basic autolysis loop (residues 143-154) of fXa. In support of this, the substitution of Arg-150 of fXa with Ala (R150A) impaired the reactivity of the mutant with AT by 1 order of magnitude specifically in the presence H5. To understand the mechanism by which heparin activation of AT improves the reactivity of the serpin with fXa, the H5-catalyzed reaction of AT with fXa, fXa R150A, and fXa S195A was studied using rapid kinetic, surface plasmon resonance, and competitive binding methods. The pseudo-first-order rate constants for the H5-catalyzed AT inhibition of both fXa and fXa R150A exhibited a linear dependence on the serpin concentration, thereby yielding second-order rate constants of 1.0 x 10(6) and 1.5 x 10(5) M(-)(1) s(-)(1), respectively. On the other hand, an approximately 70-saccharide, high-affinity heparin-catalyzed AT inhibition of both fXa derivatives showed a saturable dependence on the inhibitor concentration, yielding an identical rate constant of approximately 20 s(-)(1), but different ternary fXa-heparin-AT dissociation constants (K(E,ATH)) of approximately 130 and approximately 1780 nM for wild-type and R150A fXa, respectively. Competitive kinetic and surface plasmon resonance binding studies using the catalytically inactive S195A mutant of fXa yielded dissociation constants of 255 and 610 nM, respectively, for the mutant protease interaction with the AT-H5 complex. These results suggest that H5 enhances the reactivity of AT with fXa primarily by lowering the K(E,ATH) for the formation of a Michaelis-type serpin-protease encounter complex.
Collapse
Affiliation(s)
- Alireza R Rezaie
- Edward A. Doisy Department of Biochemistry and Molecular Biology, St. Louis University School of Medicine, St. Louis, Missouri 63104, USA.
| |
Collapse
|
31
|
Chu CL, Goerges AL, Nugent MA. Identification of common and specific growth factor binding sites in heparan sulfate proteoglycans. Biochemistry 2005; 44:12203-13. [PMID: 16142919 DOI: 10.1021/bi050241p] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The structural complexity within heparan sulfate has suggested that it contains multiple protein-specific binding sites. To evaluate the selectivity of growth factor binding to heparan sulfate, we conducted a detailed study of the intercompetition of fibroblast growth factor-2 (FGF-2) and heparin-binding epidermal growth factor-like growth factor (HB-EGF) binding to heparan sulfate (HS) on bovine aortic smooth muscle cells. Radioligand binding assays were conducted, and an analytical method was developed for determining the apparent binding constants and numbers of specific and shared binding sites within HS. These studies revealed the presence of two general classes of HS-binding sites for FGF-2 and HB-EGF. The major class (approximately 10(6) sites per cell) was able to bind to either growth factor with relatively low affinity (K(d) = 12 and 44 nM for FGF-2 and HB-EGF, respectively) and was termed "common" binding sites. However, both FGF-2 and HB-EGF also showed specific high affinity (0.6 and 6.1 nM for FGF-2 and HB-EGF, respectively) binding to a minor subset (118,000 and 28,000 sites per cell for FGF-2 and HB-EGF, respectively) of "unique" binding sites, which were unable to bind the other growth factor. These studies indicate that growth factor binding to HS involves multiple binding sites of variable affinity, density, and selectivity. The approach outlined in this study could be applied to aid in the evaluation of the relative biological roles of these selective and nonselective growth factor binding domains within HS.
Collapse
Affiliation(s)
- Chia Lin Chu
- Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA
| | | | | |
Collapse
|
32
|
Abstract
Unfractionated heparin and vitamin K antagonists such as warfarin have been used as the anticoagulants of choice for over five decades. Subsequently, low molecular weight heparins (LMWHs) became widely available and have provided several advantages, especially in infants and children. The field of anticoagulation, however, has undergone a major revolution with better understanding of the structure of coagulation proteins and the development of a host of new drugs with highly specific actions. Many of these drugs have undergone extensive clinical testing in adults and have been approved for specific indications in adults. Unfortunately, clinical data and the reported use of these drugs in children are extremely limited. A lack of familiarity with the actions and pharmacokinetic properties of these drugs could be a major contributing factor. This review focuses on several of the new anticoagulants, with a special emphasis on those that could be potentially beneficial in pediatric patients with thromboembolic disorders. The need for well-designed trials with large-scale participation by pediatric hematologists in order to improve the antithrombotic care of young infants and children is also emphasized.
Collapse
Affiliation(s)
- Vinod V Balasa
- Hemophilia and Thrombosis Center, Division of Hematology/Oncology, Cincinnati Children's Hospital Medical Center, University of Cincinnati School of Medicine, Cincinnati, OH 45229, USA.
| |
Collapse
|
33
|
Kurihara M, Watanabe K, Inoue S, Wada Y, Ono M, Wakiyama M, Iida H, Kinoshita S, Hamasaki N. Characterization of two novel mutations of the antithrombin gene observed in Japanese thrombophilic patients. Thromb Res 2005; 115:351-8. [PMID: 15733967 DOI: 10.1016/j.thromres.2004.08.025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2004] [Revised: 07/20/2004] [Accepted: 08/02/2004] [Indexed: 11/23/2022]
Abstract
We investigated the molecular basis of reduced functional levels of antithrombin (AT) in two individuals suffering from thromboembolic events. In each case direct sequencing of amplified DNA revealed 13,260-13,262 del in one patient and 2511C>A in the other patient, predicting a heterozygous E381del and P16H, respectively. Both patients had no 20210A allele and factor V Leiden mutation. To understand the molecular mechanism responsible for antithrombin deficiency, stable expression experiments were performed using HEK293 cells transfected with the expression vector containing the wild-type or the mutated recombinant cDNA. In these experiments, the media levels of the two mutated antithrombins were the same as that of wild type, but the specific activity of the E381del mutant decreased significantly compared with that of wild type. These results showed that the E381del mutation was responsible for type II deficiency, whereas the other mutation, P16H, did not produce any definite abnormality which could contribute to antithrombin deficiency.
Collapse
Affiliation(s)
- Masako Kurihara
- Department of Clinical Chemistry and Laboratory Medicine, Kyushu University Hospital, 3-1-1, Maidashi, Hgashi-Ku, Fukuoka 812-8582, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Langdown J, Johnson DJD, Baglin TP, Huntington JA. Allosteric Activation of Antithrombin Critically Depends upon Hinge Region Extension. J Biol Chem 2004; 279:47288-97. [PMID: 15326167 DOI: 10.1074/jbc.m408961200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Antithrombin (AT) inhibits most of the serine proteases generated in the blood coagulation cascade, but its principal targets are factors IXa, Xa, and thrombin. Heparin binding to AT, via a specific pentasaccharide sequence, alters the conformation of AT in a way that promotes efficient inhibition of factors IXa and Xa, but not of thrombin. The conformational change most likely to be relevant to protease recognition is the expulsion of the N-terminal portion of the reactive center loop (hinge region) from the main beta-sheet A. Here we investigate the hypothesis that the exosites on the surface of AT are accessible for interaction with a protease only when the hinge region is fully extended, as seen in the related Michaelis complex between heparin cofactor II and thrombin. We engineered a disulfide bond between residues 222 on strand 3A and 381 in the reactive center loop to prevent the extension of the hinge region upon pentasaccharide binding. The disulfide bond did not significantly alter the ability of the variant to bind to heparin or to inhibit thrombin. Although the basal rate of factor Xa inhibition was not affected, that of factor IXa inhibition was reduced to the limit of detection. In addition, the disulfide bond completely abrogated the pentasaccharide accelerated inhibition of factors Xa and IXa. We conclude that AT hinge region extension is the activating conformational change for inhibition of factors IXa and Xa, and propose models for the progressive and activated AT Michaelis complexes with thrombin, factor Xa, and factor IXa.
Collapse
Affiliation(s)
- Jonathan Langdown
- Department of Haematology, Cambridge Institute for Medical Research, Division of Structural Medicine, Thrombosis Research Unit, University of Cambridge, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 2XY, United Kingdom
| | | | | | | |
Collapse
|
35
|
Dementiev A, Petitou M, Herbert JM, Gettins PGW. The ternary complex of antithrombin–anhydrothrombin–heparin reveals the basis of inhibitor specificity. Nat Struct Mol Biol 2004; 11:863-7. [PMID: 15311268 DOI: 10.1038/nsmb810] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2004] [Accepted: 06/11/2004] [Indexed: 11/09/2022]
Abstract
Antithrombin, the principal physiological inhibitor of the blood coagulation proteinase thrombin, requires heparin as a cofactor. We report the crystal structure of the rate-determining encounter complex formed between antithrombin, anhydrothrombin and an optimal synthetic 16-mer oligosaccharide. The antithrombin reactive center loop projects from the serpin body and adopts a canonical conformation that makes extensive backbone and side chain contacts from P5 to P6' with thrombin's restrictive specificity pockets, including residues in the 60-loop. These contacts rationalize many earlier mutagenesis studies on thrombin specificity. The 16-mer oligosaccharide is just long enough to form the predicted bridge between the high-affinity pentasaccharide-binding site on antithrombin and the highly basic exosite 2 on thrombin, validating the design strategy for this synthetic heparin. The protein-protein and protein-oligosaccharide interactions together explain the basis for heparin activation of antithrombin as a thrombin inhibitor.
Collapse
Affiliation(s)
- Alexey Dementiev
- Department of Biochemistry and Molecular Genetics, College of Medicine, University of Illinois at Chicago, 900 S. Ashland, Chicago, Illinois 60607, USA
| | | | | | | |
Collapse
|
36
|
Jeter ML, Ly LV, Fortenberry YM, Whinna HC, White RR, Rusconi CP, Sullenger BA, Church FC. RNA aptamer to thrombin binds anion-binding exosite-2 and alters protease inhibition by heparin-binding serpins. FEBS Lett 2004; 568:10-4. [PMID: 15196911 DOI: 10.1016/j.febslet.2004.04.087] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2004] [Revised: 04/19/2004] [Accepted: 04/20/2004] [Indexed: 11/15/2022]
Abstract
We studied the RNA aptamer Toggle-25/thrombin interaction during inhibition by antithrombin (AT), heparin cofactor II (HCII) and protein C inhibitor (PCI). Thrombin inhibition was reduced 3-fold by Toggle-25 for AT and HCII, but it was slightly enhanced for PCI. In the presence of glycosaminoglycans, AT and PCI had significantly reduced thrombin inhibition with Toggle-25, but it was only reduced 3-fold for HCII. This suggested that the primary effect of aptamer binding was through the heparin-binding site of thrombin, anion-binding exosite-2 (exosite-2). We localized the Toggle-25 binding site to Arg 98, Glu 169, Lys 174, Asp 175, Arg 245, and Lys 248 of exosite-2. We conclude that a RNA aptamer to thrombin exosite-2 might provide an effective clinical reagent to control heparin's anticoagulant action.
Collapse
Affiliation(s)
- Martha L Jeter
- Department of Pathology and Laboratory Medicine, Carolina Cardiovascular Biology Center, The University of North Carolina at Chapel Hill, School of Medicine, Chapel Hill, NC 27599-7035, USA
| | | | | | | | | | | | | | | |
Collapse
|
37
|
Abstract
Heparin is a major anticoagulant with activity mediated primarily through its interaction with antithrombin (AT). Heparan sulfate (HS), structurally related to heparin, binds a wide range of proteins of different functionality, taking part in various physiological and pathological processes. The heparin-AT complex, the most well understood facet of anticoagulation, serves as a prototypical example of the important role of heparin/HS in vascular biology. Extensive studies have identified common structural features in heparin/HS-binding sites of proteins. These include the elucidation of consensus sequences in proteins, patterns of clusters of basic and nonbasic residues, and common spatial arrangements of basic amino acids in the heparin-binding sites. Although these studies have provided valuable information, heparin/HS-binding proteins differ widely in structure. The prediction of heparin/HS-binding proteins from sequence information is not currently possible, and elucidation of protein-binding sites requires the individual study of each glycosaminoglycan-protein complex. Thus, x-ray crystallography and site-directed mutagenesis experiments are among the most powerful tools, providing accurate structural information, facilitating the characterization of heparin-protein complexes. Heparin and structurally related heparan sulfate bind a large number of proteins, taking part in a wide range of biological processes, particularly ones involved in vascular biology. Heparin-binding domains share certain common structural features, but there is no absolute dependency on specific sequences or protein folds.
Collapse
Affiliation(s)
- Eva M Muñoz
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
| | | |
Collapse
|
38
|
Johnson DJD, Huntington JA. The Influence of Hinge Region Residue Glu-381 on Antithrombin Allostery and Metastability. J Biol Chem 2004; 279:4913-21. [PMID: 14623882 DOI: 10.1074/jbc.m311644200] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Antithrombin becomes an efficient inhibitor of factor Xa and thrombin by binding a specific pentasaccharide sequence found on a small fraction of the heparan sulfate proteoglycans lining the microvaculature. In the structure of native antithrombin, the reactive center loop is restrained due to the insertion of its hinge region into the main beta-sheet A, whereas in the heparin-activated state the reactive center loop is freed from beta-sheet A. In both structures, hinge region residue Glu-381 makes several stabilizing contacts. To determine the role of these contacts in the allosteric mechanism of antithrombin activation, we replaced Glu-381 with an alanine. This variant is less active toward its target proteases than control antithrombin, due to a perturbation of the equilibrium between the two forms, and to an increase in stoichiometry of inhibition. Pentasaccharide binding affinity is reduced 4-fold due to an increase in the off-rate. These data suggest that the main role of Glu-381 is to stabilize the activated conformation. Stability studies also showed that the E381A variant is resistant to continued insertion of its reactive center loop upon incubation at 50 degrees C, suggesting new stabilizing interactions in the native structure. To test this hypothesis, and to aid in the interpretation of the kinetic data we solved to 2.6 A the structure of the variant. We conclude that wild-type Glu-381 interactions stabilize the activated state and decreases the energy barrier to full loop insertion.
Collapse
Affiliation(s)
- Daniel J D Johnson
- University of Cambridge, Department of Haematology, Cambridge Institute for Medical Research, Division of Structural Medicine, Thrombosis Research Unit, Wellcome Trust MRC Building, Hills Road, Cambridge CB2 2XY, United Kingdom
| | | |
Collapse
|
39
|
Schedin-Weiss S, Desai UR, Bock SC, Olson ST, Björk I. Roles of N-Terminal Region Residues Lys11, Arg13, and Arg24 of Antithrombin in Heparin Recognition and in Promotion and Stabilization of the Heparin-Induced Conformational Change. Biochemistry 2003; 43:675-83. [PMID: 14730971 DOI: 10.1021/bi030173b] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The N-terminal region residues, Lys11, Arg13, and Arg24, of the plasma coagulation inhibitor, antithrombin, have been implicated in binding of the anticoagulant polysaccharide, heparin, from the identification of natural mutants with impaired heparin binding or by the X-ray structure of a complex of the inhibitor with a high-affinity heparin pentasaccharide. Mutations of Lys11 or Arg24 to Ala in this work each reduced the affinity for the pentasaccharide approximately 40-fold, whereas mutation of Arg13 to Ala led to a decrease of only approximately 7-fold. All three substitutions resulted in the loss of one ionic interaction with the pentasaccharide and those of Lys11 or Arg24 also in 3-5-fold losses in affinity of nonionic interactions. Only the mutation of Lys11 affected the initial, weak interaction step of pentasaccharide binding, decreasing the affinity of this step approximately 2-fold. The mutations of Lys11 and Arg13 moderately, 2-7-fold, altered both rate constants of the second, conformational change step, whereas the substitution of Arg24 appreciably, approximately 25-fold, reduced the reverse rate constant of this step. The N-terminal region of antithrombin is thus critical for high-affinity heparin binding, Lys11 and Arg24 being responsible for maintaining appreciable and comparable binding energy, whereas Arg13 is less important. Lys11 is the only one of the three residues that is involved in the initial recognition step, whereas all three residues participate in the conformational change step. Lys11 and Arg13 presumably bind directly to the heparin pentasaccharide by ionic, and in the case of Lys11, also nonionic interactions. However, the role of Arg24 most likely is indirect, to stabilize the heparin-induced P-helix by interacting intramolecularly with Glu113 and Asp117, thereby positioning the crucial Lys114 residue for optimal ionic and nonionic interactions with the pentasaccharide. Together, these findings show that N-terminal residues of antithrombin make markedly different contributions to the energetics and dynamics of binding of the pentasaccharide ligand to the native and activated conformational states of the inhibitor that could not have been predicted from the X-ray structure.
Collapse
Affiliation(s)
- Sophia Schedin-Weiss
- Department of Molecular Biosciences, Swedish University of Agricultural Sciences, Uppsala Biomedical Center, SE-751 23 Uppsala, Sweden
| | | | | | | | | |
Collapse
|
40
|
Dewerchin M, Hérault JP, Wallays G, Petitou M, Schaeffer P, Millet L, Weitz JI, Moons L, Collen D, Carmeliet P, Herbert JM. Life-threatening thrombosis in mice with targeted Arg48-to-Cys mutation of the heparin-binding domain of antithrombin. Circ Res 2003; 93:1120-6. [PMID: 14592998 DOI: 10.1161/01.res.0000103634.69868.4f] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Antithrombin (AT) inhibits thrombin and some other coagulation factors in a reaction that is dramatically accelerated by binding of a pentasaccharide sequence present in heparin/heparan-sulfate to a heparin-binding site on AT. Based on the involvement of R47 in the heparin/AT interaction and the frequent occurrence of R47 mutations in AT deficiency patients, targeted knock-in of the corresponding R48C substitution in AT in mice was performed to generate a murine model of spontaneous thrombosis. The mutation efficiently abolished the effect of heparin-like molecules on coagulation inhibition in vitro and in vivo. Mice homozygous for the mutation (AT(m/m) mice) developed spontaneous, life-threatening thrombosis, occurring as early as the day of birth. Only 60% of the AT(m/m) offspring reached weaning age, with further loss at different ages. Thrombotic events in adult homozygotes were most prominent in the heart, liver, and in ocular, placental, and penile vessels. In the neonate, spontaneous death invariably was associated with major thrombosis in the heart. This severe thrombotic phenotype underlines a critical function of the heparin-binding site of antithrombin and its interaction with heparin/heparan-sulfate moieties in health, reproduction, and survival, and represents an in vivo model for comparative analysis of heparin-derived and other antithrombotic molecules.
Collapse
Affiliation(s)
- Mieke Dewerchin
- Center for Transgene Technology and Gene Therapy, VIB, KULeuven Campus Gasthuisberg O&N, Herestraat 49, B-3000 Leuven, Belgium.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Yang L, Manithody C, Walston TD, Cooper ST, Rezaie AR. Thrombomodulin enhances the reactivity of thrombin with protein C inhibitor by providing both a binding site for the serpin and allosterically modulating the activity of thrombin. J Biol Chem 2003; 278:37465-70. [PMID: 12878585 DOI: 10.1074/jbc.m307243200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Thrombomodulin (TM), or its epidermal growth factor-like domains 456 (TM456), enhances the catalytic efficiency of thrombin toward both protein C and protein C inhibitor (PCI) by 2-3 orders of magnitude. Structural and mutagenesis data have indicated that the interaction of basic residues of the heparin-binding exosite of protein C with the acidic residues of TM4 is partially responsible for the efficient activation of the substrate by the thrombin-TM456 complex. Similar to protein C, PCI has a basic exosite (H-helix) that constitutes the heparin-binding site of the serpin. To determine whether TM accelerates the reactivity of thrombin with PCI by providing a binding site for the H-helix of the serpin, an antithrombin (AT) mutant was constructed in which the H-helix of the serpin was replaced with the same region of PCI (AT-PCIH-helix). Unlike PCI, the H-helix of AT is negatively charged. It was discovered that TM456 slightly (<2-fold) impaired the reactivity of AT with thrombin; however, it enhanced the reactivity of AT-PCIH-helix with the protease by an order of magnitude. Further studies revealed that the substitution of Arg35 of thrombin with an Ala also resulted in an order of magnitude enhancement in reactivity of the protease with both PCI and AT-PCIH-helix independent of TM. We conclude that TM enhances the reactivity of PCI with thrombin by providing both a binding site for the serpin and a conformational modulation of the extended binding pocket of thrombin.
Collapse
Affiliation(s)
- Likui Yang
- Edward A. Doisy Department of Biochemistry and Molecular Biology, St. Louis University School of Medicine, St. Louis, Missouri 63104, USA
| | | | | | | | | |
Collapse
|
42
|
Wiebe EM, Stafford AR, Fredenburgh JC, Weitz JI. Mechanism of catalysis of inhibition of factor IXa by antithrombin in the presence of heparin or pentasaccharide. J Biol Chem 2003; 278:35767-74. [PMID: 12832413 DOI: 10.1074/jbc.m304803200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Because of the homology between factor IXa and factor Xa (f.IXa and f.Xa, respectively), and the critical upstream position of f.IXa in the coagulation cascade, the contribution of the heparin-derived pentasaccharide to antithrombin-mediated inhibition of f.IXa was investigated. Pentasaccharide promotes inhibition of both f.IXa and f.Xa generated in recalcified plasma. This result demonstrates that antithrombin is the predominant inhibitor of f.IXa in plasma, and that the activity of antithrombin is promoted by pentasaccharide. Kinetic experiments reveal that pentasaccharide increases the rates of antithrombin-mediated inhibition of both f.IXa and f.Xa by 2 orders of magnitude. These findings indicate that pentasaccharide-induced conformational changes in antithrombin enhance its capacity to inhibit both f.IXa and f.Xa. In the presence of Ca2+, full-length heparin produces an additional approximately 10-fold increase in the rates of inhibition of both enzymes, consistent with a template role of heparin. Heparin binding to f.Xa was previously shown to be promoted in the presence of Ca2+. Binding studies with f.IXa reveal a 10-fold higher affinity for heparin in the presence of Ca2+ compared with its absence. Thus, Ca2+ promotes heparin-catalyzed inhibition of f.IXa and f.Xa by antithrombin by augmenting the template mechanism. These results indicate that heparin-mediated catalysis of f.IXa inhibition by antithrombin reflects both pentasaccharide-induced conformational changes and heparin-mediated bridging of antithrombin to f.IXa. Furthermore, our data suggest that the efficacy of pentasaccharide for prevention and treatment of thrombotic disorders may reflect its action at two sites in the coagulation system.
Collapse
Affiliation(s)
- Ericka M Wiebe
- Henderson Research Centre and McMaster University, Hamilton, Ontario L8V 1C3, Canada
| | | | | | | |
Collapse
|
43
|
Johnson DJD, Huntington JA. Crystal structure of antithrombin in a heparin-bound intermediate state. Biochemistry 2003; 42:8712-9. [PMID: 12873131 DOI: 10.1021/bi034524y] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Antithrombin is activated as an inhibitor of the coagulation proteases through its specific interaction with a heparin pentasaccharide. The binding of heparin induces a global conformational change in antithrombin which results in the freeing of its reactive center loop for interaction with target proteases and a 1000-fold increase in heparin affinity. The allosteric mechanism by which the properties of antithrombin are altered by its interactions with the specific pentasaccharide sequence of heparin is of great interest to the medical and protein biochemistry communities. Heparin binding has previously been characterized as a two-step, three-state mechanism where, after an initial weak interaction, antithrombin undergoes a conformational change to its high-affinity state. Although the native and heparin-activated states have been determined through protein crystallography, the number and magnitude of conformational changes render problematic the task of determining which account for the improved heparin affinity and how the heparin binding region is linked to the expulsion of the reactive center loop. Here we present the structure of an intermediate pentasaccharide-bound conformation of antithrombin which has undergone all of the conformational changes associated with activation except loop expulsion and helix D elongation. We conclude that the basis of the high-affinity state is not improved interaction with the pentasaccharide but a lowering of the global free energy due to conformational changes elsewhere in antithrombin. We suggest a mechanism in which the role of helix D elongation is to lock antithrombin in the five-stranded fully activated conformation.
Collapse
Affiliation(s)
- Daniel J D Johnson
- Department of Haematology, Cambridge Institute for Medical Research, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 2XY, United Kingdom
| | | |
Collapse
|
44
|
Paredes N, Wang A, Berry LR, Smith LJ, Stafford AR, Weitz JI, Chan AKC. Mechanisms responsible for catalysis of the inhibition of factor Xa or thrombin by antithrombin using a covalent antithrombin-heparin complex. J Biol Chem 2003; 278:23398-409. [PMID: 12695507 DOI: 10.1074/jbc.m302895200] [Citation(s) in RCA: 18] [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
Covalent antithrombin-heparin (ATH) complexes, formed spontaneously between antithrombin (AT) and unfractionated standard heparin (H), have a potent ability to catalyze the inhibition of factor Xa (or thrombin) by added AT. Although approximately 30% of ATH molecules contain two AT-binding sites on their heparin chains, the secondary site does not solely account for the increased activity of ATH. We studied the possibility that all pentasaccharide AT-binding sequences in ATH may catalyze factor Xa inhibition. Chromatography of ATH on Sepharose-AT resulted in >80% binding of the load. Similar chromatographies of non-covalent AT + H mixtures lead to a lack of binding for AT and fractionation of H into unbound (separate from AT) or bound material. Gradient elution of ATH from Sepharose-AT gave 2 peaks, a peak containing higher affinity material that had greater anti-factor Xa catalytic activity (708 units/mg heparin) compared with the peak containing lower affinity material (112 units/mg). Sepharose-AT chromatography of the ATH component with short heparin chains (<or=12 monosaccharides) resulted in active unbound (40%) and bound fractions (190 and 560 units/mg, respectively). Factor Xa-ATH or thrombin-ATH inhibitor complexes gave chromatograms on Sepharose-AT with more unbound material compared with that of free ATH. Also, ATH did not bind to Sepharose-heparin, and the intrinsic fluorescence due to activation of AT in ATH by its heparin chain was reversed at higher [NaCl] than that required to dissociate non-covalent AT.H complexes. Thus, exogenous AT can compete with the AT moiety of ATH for binding to the covalently linked heparin chain, leading to catalytic inhibition of factor Xa or thrombin. These data may suggest that access to pentasaccharide units in non-covalent AT.H complexes by free AT may be facile.
Collapse
|
45
|
Affiliation(s)
- George H Caughey
- Cardiovascular Research Institute and Department of Medicine, University of California at San Francisco, San Francisco, California 94143, USA.
| |
Collapse
|
46
|
Abstract
Clinically used anticoagulants are inhibitors of enzymes involved in the coagulation pathway, primarily thrombin and factor Xa. These agents can be either direct or indirect inhibitors of clotting enzymes. Heparin-based anticoagulants are indirect inhibitors that enhance the proteinase inhibitory activity of a natural anticoagulant, antithrombin. Despite its phenomenal success, current anticoagulation therapy suffers from the risk of serious bleeding. The need for safer and more effective antithrombotic agents clearly exists. The past decade has seen enormous effort directed toward discovering and/or designing new molecules with anticoagulant activity. These new molecules can be classified into (a). antithrombin and its mutants, (b). natural polysaccharides, (c). synthetic modified heparins and heparin-mimics, (d). synthetic oligosaccharides, and (e). synthetic non-sugar antithrombin activators. This review focuses on these efforts in designing or discovering new molecules that act through the antithrombin pathway of anticoagulation.
Collapse
Affiliation(s)
- Umesh R Desai
- Department of Medicinal Chemistry, Virginia Commonwealth University, Richmond, Virginia 23298-0540, USA.
| |
Collapse
|
47
|
Samama MM, Gerotziafas GT. Evaluation of the pharmacological properties and clinical results of the synthetic pentasaccharide (fondaparinux). Thromb Res 2003; 109:1-11. [PMID: 12679126 DOI: 10.1016/s0049-3848(03)00030-6] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fondaparinux (Arixtra) is the first of a new class of selective indirect antithrombin-dependent factor Xa inhibitors, which inhibits thrombin generation. Fondaparinux is a completely synthetic pentasaccharide. It is a single molecular entity with a well-defined pharmacological target. Fondaparinux has nearly complete bioavailability after subcutaneous injection. The pharmacokinetics of fondaparinux appears predictable and consistent. The peak plasma level is obtained about 2 h after the subcutaneous injection, indicating that a rapid onset of antithrombotic activity is obtained on initiation of treatment. The elimination half-life is about 17 h and it is dose-independent, which allows a convenient once-daily dosing regimen. Fondaparinux is eliminated exclusively by the kidneys. Thus, the estimation of the renal function especially in elderly patients is important for the treatment with fondaparinux, whereas it is contraindicated in patients with severe renal insufficiency. Phase II clinical studies have identified a subcutaneous dose of 2.5 mg once daily for prophylaxis of venous thromboembolism in patients undergoing major orthopaedic surgery. Four phase-III clinical trials using bilateral phlebography for the diagnosis of DVT, demonstrated a combined 50% relative risk reduction of asymptomatic venous thromboembolic events in orthopaedic surgery patients in comparison to the low-molecular-weight heparin (LMWH) enoxaparin. Hemorrhagic complications for fondaparinux were either comparable or higher than those for LMWH but the authors did not judge that the increased bleeding was clinically relevant. A dose ranging study led to the selection of the dose of 7.5 mg at a single daily subcutaneous injection as optimal for the treatment of VTE. In two phase III clinical trials, the dose of 7.5 mg/day is expected to be as efficacious and safe as heparin for the treatment of DVT or PE, respectively. Phase II studies show that the efficacy-to-safety ratio of fondaparinux in the treatment of unstable angina or as an adjunct to thrombolysis in acute myocardial infarction is promising. These results demonstrated that a single anti-Xa agent devoid of antithrombin activity is a potent antithrombotic drug. Fondaparinux has obtained FDA and European health authorities approval. Its use on a large scale will allow the evaluation of its efficacy and tolerance in the daily clinical practice. Chemical modifications of the original synthetic pentasaccharide increase the affinity to AT resulting in a more potent inhibition of FXa and longer half-life. Idraparinux is the first of these new oligosaccharides that we named "meta-pentasaccharides." After subcutaneous injection the half-life of idraparinux is about 80 h allowing a single injection per week. A dose-finding study has established the optimal dose given once a week to be compared with warfarin for the treatment of DVT.
Collapse
Affiliation(s)
- Meyer-Michel Samama
- Service d'Hématologie Biologique, Hôpital Hôtel-Dieu, 1, place du Parvis Notre Dame, F-75181 Paris Cedex 04, France.
| | | |
Collapse
|
48
|
Affiliation(s)
- Peter G W Gettins
- Department of Biochemistry & Molecular Genetics, University of Illinois at Chicago, M/C 536, 1819-53 West Polk Street, Chicago, Illinois 60612, USA.
| |
Collapse
|
49
|
Abstract
Fondaparinux sodium is the first in a new class of antithrombotic agents possessing selective inhibitory activity against factor Xa. The agent was designed and developed with the objective of overcoming the limitations of currently available therapies for the prevention and treatment of venous and arterial thromboembolic disease. Extensive data from preclinical and clinical trials demonstrate fondaparinux's favorable pharmacokinetic profile combined with promising efficacy and safety results in the prevention of venous thromboembolism following major orthopedic surgery, in the treatment of deep venous thrombosis, and in acute coronary syndromes.
Collapse
Affiliation(s)
- Alexander G G Turpie
- Hamilton Health Sciences-Hamilton General Hospital, 237 Barton Street East, Hamilton, Ontario, L8L 2X2 Canada
| |
Collapse
|
50
|
Manithody C, Yang L, Rezaie AR. Role of basic residues of the autolysis loop in the catalytic function of factor Xa. Biochemistry 2002; 41:6780-8. [PMID: 12022882 DOI: 10.1021/bi0255367] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The autolysis loop of factor Xa (fXa) has four basic residues (Arg(143), Lys(147), Arg(150), and Arg(154)) whose contribution to protease specificity of fXa has not been examined. Here, we substituted these basic residues individually with Ala in the fX cDNA and expressed them in mammalian cells using a novel expression/purification vector system. Following purification to homogeneity and activation by the factor X activator from Russell viper venom, the mutants were characterized with respect to their ability to assemble into the prothrombinase complex to activate prothrombin and interact with target plasma fXa inhibitors, tissue factor pathway inhibitor (TFPI) and antithrombin. We show that all mutants interacted with factor Va with normal affinities and exhibited wild-type-like prothrombinase activities toward prothrombin. Lys(147) and Arg(154) mutants were inhibited by TFPI approximately 2-fold slower than wild type; however, both Arg(143) and Arg(150) mutants were inhibited normally by the inhibitor. The reactivities of Arg(143) and Lys(147) mutants were improved approximately 2-fold with antithrombin in the absence but not in the presence of heparin cofactors. On the other hand, the pentasaccharide-catalyzed reactivity of antithrombin with the Arg(150) mutant was impaired by an order of magnitude. These results suggest that Arg(150) of the autolysis loop may specifically interact with the activated conformation of antithrombin.
Collapse
Affiliation(s)
- Chandrashekhara Manithody
- Edward A. Doisy Department of Biochemistry and Molecular Biology, St Louis University School of Medicine, 1402 S. Grand Boulevard, St Louis, MO 63104, USA
| | | | | |
Collapse
|