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Vester SK, Davies AM, Beavil RL, Sandhar BS, Beavil AJ, Gould HJ, Sutton BJ, McDonnell JM. Expanding the Anti-Phl p 7 Antibody Toolkit: An Anti-Idiotype Nanobody Inhibitor. Antibodies (Basel) 2023; 12:75. [PMID: 37987253 PMCID: PMC10660547 DOI: 10.3390/antib12040075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Revised: 10/08/2023] [Accepted: 11/10/2023] [Indexed: 11/22/2023] Open
Abstract
We have previously produced a toolkit of antibodies, comprising recombinant human antibodies of all but one of the human isotypes, directed against the polcalcin family antigen Phl p 7. In this work, we complete the toolkit of human antibody isotypes with the IgD version of the anti-Phl p 7 monoclonal antibody. We also raised a set of nanobodies against the IgD anti-Phl p 7 antibody and identify and characterize one paratope-specific nanobody. This nanobody also binds to the IgE isotype of this antibody, which shares the same idiotype, and orthosterically inhibits the interaction with Phl p 7. The 2.1 Å resolution X-ray crystal structure of the nanobody in complex with the IgD Fab is described.
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Affiliation(s)
| | | | | | | | | | | | | | - James M. McDonnell
- Randall Centre for Cell and Molecular Biophysics, King’s College London, New Hunt’s House, London SE1 1UL, UK; (S.K.V.); (A.M.D.); (R.L.B.); (B.S.S.); (A.J.B.); (H.J.G.); (B.J.S.)
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2
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Affiliation(s)
- Brian J Sutton
- Randall Centre for Cell & Molecular Biophysics, King's College London, London, UK.
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3
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Davies AM, Beavil RL, Barbolov M, Sandhar BS, Gould HJ, Beavil AJ, Sutton BJ, McDonnell JM. Crystal structures of the human IgD Fab reveal insights into C H1 domain diversity. Mol Immunol 2023; 159:28-37. [PMID: 37267832 DOI: 10.1016/j.molimm.2023.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Revised: 05/17/2023] [Accepted: 05/20/2023] [Indexed: 06/04/2023]
Abstract
Antibodies of the IgD isotype remain the least well characterized of the mammalian immunoglobulin isotypes. Here we report three-dimensional structures for the Fab region of IgD, based on four different crystal structures, at resolutions of 1.45-2.75 Å. These IgD Fab crystals provide the first high-resolution views of the unique Cδ1 domain. Structural comparisons identify regions of conformational diversity within the Cδ1 domain, as well as among the homologous domains of Cα1, Cγ1 and Cμ1. The IgD Fab structure also possesses a unique conformation of the upper hinge region, which may contribute to the overall disposition of the very long linker sequence between the Fab and Fc regions found in human IgD. Structural similarities observed between IgD and IgG, and differences with IgA and IgM, are consistent with predicted evolutionary relationships for the mammalian antibody isotypes.
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Affiliation(s)
- Anna M Davies
- King's College London, Randall Centre for Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom
| | - Rebecca L Beavil
- King's College London, Randall Centre for Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom
| | - Momchil Barbolov
- King's College London, Randall Centre for Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom
| | - Balraj S Sandhar
- King's College London, Randall Centre for Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom
| | - Hannah J Gould
- King's College London, Randall Centre for Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom
| | - Andrew J Beavil
- King's College London, Randall Centre for Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom
| | - Brian J Sutton
- King's College London, Randall Centre for Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom
| | - James M McDonnell
- King's College London, Randall Centre for Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom.
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4
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Abstract
The evolution of IgE in mammals added an extra layer of immune protection at body surfaces to provide a rapid and local response against antigens from the environment. The IgE immune response employs potent expulsive and inflammatory forces against local antigen provocation, at the risk of damaging host tissues and causing allergic disease. Two well-known IgE receptors, the high-affinity FcεRI and low-affinity CD23, mediate the activities of IgE. Unlike other known antibody receptors, CD23 also regulates IgE expression, maintaining IgE homeostasis. This mechanism evolved by adapting the function of the complement receptor CD21. Recent insights into the dynamic character of IgE structure, its resultant capacity for allosteric modulation, and the potential for ligand-induced dissociation have revealed previously unappreciated mechanisms for regulation of IgE and IgE complexes. We describe recent research, highlighting structural studies of the IgE network of proteins to analyze the uniquely versatile activities of IgE and anti-IgE biologics.
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Affiliation(s)
- J M McDonnell
- Randall Centre for Cell and Molecular Biophysics and School of Basic and Medical Biosciences, King's College London, London, UK; , ,
| | | | - B J Sutton
- Randall Centre for Cell and Molecular Biophysics and School of Basic and Medical Biosciences, King's College London, London, UK; , ,
| | - H J Gould
- Randall Centre for Cell and Molecular Biophysics and School of Basic and Medical Biosciences, King's College London, London, UK; , ,
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5
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Ilkow VF, Davies AM, Dhaliwal B, Beavil AJ, Sutton BJ, McDonnell JM. Reviving lost binding sites: Exploring calcium-binding site transitions between human and murine CD23. FEBS Open Bio 2021; 11:1827-1840. [PMID: 34075727 PMCID: PMC8255853 DOI: 10.1002/2211-5463.13214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 05/21/2021] [Accepted: 05/31/2021] [Indexed: 11/27/2022] Open
Abstract
Immunoglobulin E (IgE) is a central regulatory and triggering molecule of allergic immune responses. IgE's interaction with CD23 modulates both IgE production and functional activities.CD23 is a noncanonical immunoglobulin receptor, unrelated to receptors of other antibody isotypes. Human CD23 is a calcium-dependent (C-type) lectin-like domain that has apparently lost its carbohydrate-binding capability. The calcium-binding site classically required for carbohydrate binding in C-type lectins is absent in human CD23 but is present in the murine molecule. To determine whether the absence of this calcium-binding site affects the structure and function of human CD23, CD23 mutant proteins with increasingly "murine-like" sequences were generated. Restoration of the calcium-binding site was confirmed by NMR spectroscopy, and structures of mutant human CD23 proteins were determined by X-ray crystallography, although no electron density for calcium was observed. This study offers insights into the evolutionary differences between murine and human CD23 and some of the functional differences between CD23 in different species.
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Affiliation(s)
- Veronica F. Ilkow
- Randall Centre for Cell & Molecular BiophysicsKing’s College LondonUK
- Asthma UK Centre in Allergic Mechanisms of AsthmaLondonUK
| | - Anna M. Davies
- Randall Centre for Cell & Molecular BiophysicsKing’s College LondonUK
- Asthma UK Centre in Allergic Mechanisms of AsthmaLondonUK
| | - Balvinder Dhaliwal
- Randall Centre for Cell & Molecular BiophysicsKing’s College LondonUK
- Asthma UK Centre in Allergic Mechanisms of AsthmaLondonUK
| | - Andrew J. Beavil
- Randall Centre for Cell & Molecular BiophysicsKing’s College LondonUK
- Asthma UK Centre in Allergic Mechanisms of AsthmaLondonUK
| | - Brian J. Sutton
- Randall Centre for Cell & Molecular BiophysicsKing’s College LondonUK
- Asthma UK Centre in Allergic Mechanisms of AsthmaLondonUK
| | - James M. McDonnell
- Randall Centre for Cell & Molecular BiophysicsKing’s College LondonUK
- Asthma UK Centre in Allergic Mechanisms of AsthmaLondonUK
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6
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Kubagawa H, Skopnik CM, Al-Qaisi K, Calvert RA, Honjo K, Kubagawa Y, Teuber R, Aliabadi PM, Enghard P, Radbruch A, Sutton BJ. Differences between Human and Mouse IgM Fc Receptor (FcµR). Int J Mol Sci 2021; 22:ijms22137024. [PMID: 34209905 PMCID: PMC8267714 DOI: 10.3390/ijms22137024] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 06/23/2021] [Accepted: 06/25/2021] [Indexed: 01/02/2023] Open
Abstract
Both non-immune "natural" and antigen-induced "immune" IgM are important for protection against pathogens and for regulation of immune responses to self-antigens. Since the bona fide IgM Fc receptor (FcµR) was identified in humans by a functional cloning strategy in 2009, the roles of FcµR in these IgM effector functions have begun to be explored. In this short essay, we describe the differences between human and mouse FcµRs in terms of their identification processes, cellular distributions and ligand binding activities with emphasis on our recent findings from the mutational analysis of human FcµR. We have identified at least three sites of human FcµR, i.e., Asn66 in the CDR2, Lys79 to Arg83 in the DE loop and Asn109 in the CDR3, responsible for its constitutive IgM-ligand binding. Results of computational structural modeling analysis are consistent with these mutational data and a model of the ligand binding, Ig-like domain of human FcµR is proposed. Serendipitously, substitution of Glu41 and Met42 in the CDR1 of human FcµR with mouse equivalents Gln and Leu, either single or more prominently in combination, enhances both the receptor expression and IgM binding. These findings would help in the future development of preventive and therapeutic interventions targeting FcµR.
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Affiliation(s)
- Hiromi Kubagawa
- Deutsches Rheuma-Forschungszentrum, 10117 Berlin, Germany; (C.M.S.); (K.A.-Q.); (R.T.); (P.M.A.); (A.R.)
- Correspondence: ; Tel.: +49-030-2846-0782
| | - Christopher M. Skopnik
- Deutsches Rheuma-Forschungszentrum, 10117 Berlin, Germany; (C.M.S.); (K.A.-Q.); (R.T.); (P.M.A.); (A.R.)
| | - Khlowd Al-Qaisi
- Deutsches Rheuma-Forschungszentrum, 10117 Berlin, Germany; (C.M.S.); (K.A.-Q.); (R.T.); (P.M.A.); (A.R.)
| | - Rosaleen A. Calvert
- Randall Centre for Cell and Molecular Biophysics, King’s College, London SE1 1UL, UK; (R.A.C.); (B.J.S.)
| | - Kazuhito Honjo
- Department of Pathology of University of Alabama at Birmingham, Birmingham, AL 35294, USA.; (K.H.); (Y.K.)
| | - Yoshiki Kubagawa
- Department of Pathology of University of Alabama at Birmingham, Birmingham, AL 35294, USA.; (K.H.); (Y.K.)
| | - Ruth Teuber
- Deutsches Rheuma-Forschungszentrum, 10117 Berlin, Germany; (C.M.S.); (K.A.-Q.); (R.T.); (P.M.A.); (A.R.)
| | - Pedram Mahmoudi Aliabadi
- Deutsches Rheuma-Forschungszentrum, 10117 Berlin, Germany; (C.M.S.); (K.A.-Q.); (R.T.); (P.M.A.); (A.R.)
| | - Philipp Enghard
- Department of Nephrology and Medical Intensive Care, Charité-Universitätmedizin, 10117 Berlin, Germany;
| | - Andreas Radbruch
- Deutsches Rheuma-Forschungszentrum, 10117 Berlin, Germany; (C.M.S.); (K.A.-Q.); (R.T.); (P.M.A.); (A.R.)
| | - Brian J. Sutton
- Randall Centre for Cell and Molecular Biophysics, King’s College, London SE1 1UL, UK; (R.A.C.); (B.J.S.)
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7
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Skopnik CM, Al-Qaisi K, Calvert RA, Enghard P, Radbruch A, Sutton BJ, Kubagawa H. Identification of Amino Acid Residues in Human IgM Fc Receptor (FcµR) Critical for IgM Binding. Front Immunol 2021; 11:618327. [PMID: 33584711 PMCID: PMC7873564 DOI: 10.3389/fimmu.2020.618327] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Accepted: 12/03/2020] [Indexed: 11/17/2022] Open
Abstract
Both non-immune “natural” and antigen-induced “immune” IgM are important for protection against infections and for regulation of immune responses to self-antigens. The roles of its Fc receptor (FcµR) in these IgM effector functions have begun to be explored. In the present study, by taking advantage of the difference in IgM-ligand binding of FcµRs of human (constitutive binding) and mouse (transient binding), we replaced non-conserved amino acid residues of human FcµR with mouse equivalents before establishment of cell lines stably expressing mutant or wild-type (WT) receptors. The resultant eight-different mutant FcµR-bearing cells were compared with WT receptor-bearing cells for cell-surface expression and IgM-binding by flow cytometric assessments using receptor-specific mAbs and IgM paraproteins as ligands. Three sites Asn66, Lys79-Arg83, and Asn109, which are likely in the CDR2, DE loop and CDR3 of the human FcµR Ig-like domain, respectively, were responsible for constitutive IgM binding. Intriguingly, substitution of Glu41 and Met42 in the presumed CDR1 with the corresponding mouse residues Gln and Leu, either single or more prominently in combination, enhanced both the receptor expression and IgM binding. A four-aa stretch of Lys24-Gly27 in the predicted A ß-strand of human FcµR appeared to be essential for maintenance of its proper receptor conformation on plasma membranes because of reduction of both receptor expression and IgM-binding potential when these were mutated. Results from a computational structural modeling analysis were consistent with these mutational data and identified a possible mode of binding of FcµR with IgM involving the loops including Asn66, Arg83 and Asn109 of FcµR interacting principally with the Cµ4 domain including Gln510 and to a lesser extent Cµ3 domain including Glu398, of human IgM. To our knowledge, this is the first experimental report describing the identification of amino acid residues of human FcµR critical for binding to IgM Fc.
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Affiliation(s)
| | - Khlowd Al-Qaisi
- Humoral Immune Regulation, Deutsches Rheuma-Forschungszentrum, Berlin, Germany
| | - Rosaleen A Calvert
- Randall Centre for Cell and Molecular Biophysics, King's College London, London, United Kingdom
| | - Philipp Enghard
- Department of Nephrology and Medical Intensive Care, Charité-Universitätmedizin, Berlin, Germany
| | - Andreas Radbruch
- Humoral Immune Regulation, Deutsches Rheuma-Forschungszentrum, Berlin, Germany
| | - Brian J Sutton
- Randall Centre for Cell and Molecular Biophysics, King's College London, London, United Kingdom
| | - Hiromi Kubagawa
- Humoral Immune Regulation, Deutsches Rheuma-Forschungszentrum, Berlin, Germany
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8
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Santos AF, Barbosa‐Morais NL, Hurlburt BK, Ramaswamy S, Hemmings O, Kwok M, O’Rourke C, Bahnson HT, Cheng H, James L, Gould HJ, Sutton BJ, Maleki SJ, Lack G. IgE to epitopes of Ara h 2 enhance the diagnostic accuracy of Ara h 2-specific IgE. Allergy 2020; 75:2309-2318. [PMID: 32248566 DOI: 10.1111/all.14301] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2019] [Revised: 02/14/2020] [Accepted: 02/20/2020] [Indexed: 11/30/2022]
Abstract
BACKGROUND Understanding the discrepancy between IgE sensitization and allergic reactions to peanut could facilitate diagnosis and lead to novel means of treating peanut allergy. OBJECTIVE To identify differences in IgE and IgG4 binding to peanut peptides between peanut-allergic (PA) and peanut-sensitized but tolerant (PS) children. METHODS PA (n = 56), PS (n = 42) and nonsensitized nonallergic (NA, n = 10) patients were studied. Synthetic overlapping 15-mer peptides of peanut allergens (Ara h 1-11) were spotted onto microarray slides, and patients' samples were tested for IgE and IgG4 binding using immunofluorescence. IgE and IgG4 levels to selected peptides were quantified using ImmunoCAP. Diagnostic model comparisons were performed using likelihood-ratio tests between each specified nominal logistic regression models. RESULTS Seven peptides on Ara h 1, Ara h 2, and Ara h 3 were bound more by IgE of PA compared to PS patients on the microarray. IgE binding to one peptide on Ara h 5 and IgG4 binding to one Ara h 9 peptide were greater in PS than in PA patients. Using ImmunoCAP, IgE to the Ara h 2 peptides enhanced the diagnostic accuracy of Ara h 2-specific IgE. Ratios of IgG4/IgE to 4 out of the 7 peptides were higher in PS than in PA subjects. CONCLUSIONS Ara h 2 peptide-specific IgE added diagnostic value to Ara h 2-specific IgE. Ability of peptide-specific IgG4 to surmount their IgE counterpart seems to be important in established peanut tolerance.
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Affiliation(s)
- Alexandra F. Santos
- Department of Women and Children’s Health (Paediatric Allergy) School of Life Course Sciences Faculty of Life Sciences and Medicine King’s College London London UK
- Peter Gorer Department of Immunobiology School of Immunology and Microbial Sciences, Faculty of Life Sciences and Medicine King’s College London London UK
- Children’s Allergy ServiceEvelina London Children's Hospital, Guy’s and St Thomas’ Hospital London UK
- Asthma UK Centre in Allergic Mechanisms of Asthma London UK
| | - Nuno L. Barbosa‐Morais
- Faculdade de Medicina Instituto de Medicina Molecular João Lobo Antunes Universidade de Lisboa Lisbon Portugal
| | - Barry K. Hurlburt
- US Department of Agriculture Southern Regional Research Center New Orleans LA USA
| | - Sneha Ramaswamy
- Asthma UK Centre in Allergic Mechanisms of Asthma London UK
- Randall Centre for Cell & Molecular Biophysics King’s College London London UK
| | - Oliver Hemmings
- Department of Women and Children’s Health (Paediatric Allergy) School of Life Course Sciences Faculty of Life Sciences and Medicine King’s College London London UK
- Peter Gorer Department of Immunobiology School of Immunology and Microbial Sciences, Faculty of Life Sciences and Medicine King’s College London London UK
- Asthma UK Centre in Allergic Mechanisms of Asthma London UK
| | - Matthew Kwok
- Department of Women and Children’s Health (Paediatric Allergy) School of Life Course Sciences Faculty of Life Sciences and Medicine King’s College London London UK
- Peter Gorer Department of Immunobiology School of Immunology and Microbial Sciences, Faculty of Life Sciences and Medicine King’s College London London UK
- Asthma UK Centre in Allergic Mechanisms of Asthma London UK
| | | | | | - Hsiaopo Cheng
- US Department of Agriculture Southern Regional Research Center New Orleans LA USA
| | - Louisa James
- Blizard Institute Queen Mary University of London London UK
| | - Hannah J. Gould
- Asthma UK Centre in Allergic Mechanisms of Asthma London UK
- Randall Centre for Cell & Molecular Biophysics King’s College London London UK
| | - Brian J. Sutton
- Asthma UK Centre in Allergic Mechanisms of Asthma London UK
- Randall Centre for Cell & Molecular Biophysics King’s College London London UK
| | - Soheila J. Maleki
- US Department of Agriculture Southern Regional Research Center New Orleans LA USA
| | - Gideon Lack
- Department of Women and Children’s Health (Paediatric Allergy) School of Life Course Sciences Faculty of Life Sciences and Medicine King’s College London London UK
- Peter Gorer Department of Immunobiology School of Immunology and Microbial Sciences, Faculty of Life Sciences and Medicine King’s College London London UK
- Children’s Allergy ServiceEvelina London Children's Hospital, Guy’s and St Thomas’ Hospital London UK
- Asthma UK Centre in Allergic Mechanisms of Asthma London UK
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9
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Mitropoulou AN, Ceska T, Heads JT, Beavil AJ, Henry AJ, McDonnell JM, Sutton BJ, Davies AM. Engineering the Fab fragment of the anti-IgE omalizumab to prevent Fab crystallization and permit IgE-Fc complex crystallization. Acta Crystallogr F Struct Biol Commun 2020; 76:116-129. [PMID: 32133997 PMCID: PMC7057348 DOI: 10.1107/s2053230x20001466] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Accepted: 02/03/2020] [Indexed: 12/01/2022] Open
Abstract
Immunoglobulin E (IgE) plays a central role in the allergic response, in which cross-linking of allergen by FcεRI-bound IgE triggers mast cell and basophil degranulation and the release of inflammatory mediators. The high-affinity interaction between IgE and FcεRI is a long-standing target for therapeutic intervention in allergic disease. Omalizumab is a clinically approved anti-IgE monoclonal antibody that binds to free IgE, also with high affinity, preventing its interaction with FcεRI. All attempts to crystallize the pre-formed complex between the omalizumab Fab and the Fc region of IgE (IgE-Fc), to understand the structural basis for its mechanism of action, surprisingly failed. Instead, the Fab alone selectively crystallized in different crystal forms, but their structures revealed intermolecular Fab/Fab interactions that were clearly strong enough to disrupt the Fab/IgE-Fc complexes. Some of these interactions were common to other Fab crystal structures. Mutations were therefore designed to disrupt two recurring packing interactions observed in the omalizumab Fab crystal structures without interfering with the ability of the omalizumab Fab to recognize IgE-Fc; this led to the successful crystallization and subsequent structure determination of the Fab/IgE-Fc complex. The mutagenesis strategy adopted to achieve this result is applicable to other intractable Fab/antigen complexes or systems in which Fabs are used as crystallization chaperones.
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Affiliation(s)
- Alkistis N. Mitropoulou
- Randall Centre for Cell and Molecular Biophysics, King’s College London, New Hunt’s House, London SE1 1UL, UK
- Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | - Tom Ceska
- UCB Celltech, 208 Bath Road, Slough SL1 3WE, UK
| | | | - Andrew J. Beavil
- Randall Centre for Cell and Molecular Biophysics, King’s College London, New Hunt’s House, London SE1 1UL, UK
- Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | | | - James M. McDonnell
- Randall Centre for Cell and Molecular Biophysics, King’s College London, New Hunt’s House, London SE1 1UL, UK
- Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | - Brian J. Sutton
- Randall Centre for Cell and Molecular Biophysics, King’s College London, New Hunt’s House, London SE1 1UL, UK
- Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | - Anna M. Davies
- Randall Centre for Cell and Molecular Biophysics, King’s College London, New Hunt’s House, London SE1 1UL, UK
- Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
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10
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Bucaite G, Kang-Pettinger T, Moreira J, Gould HJ, James LK, Sutton BJ, McDonnell JM. Interplay between Affinity and Valency in Effector Cell Degranulation: A Model System with Polcalcin Allergens and Human Patient-Derived IgE Antibodies. J Immunol 2019; 203:1693-1700. [PMID: 31462504 DOI: 10.4049/jimmunol.1900509] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Accepted: 07/19/2019] [Indexed: 01/10/2023]
Abstract
An allergic reaction is rapidly generated when allergens bind and cross-link IgE bound to its receptor FcεRI on effector cells, resulting in cell degranulation and release of proinflammatory mediators. The extent of effector cell activation is linked to allergen affinity, oligomeric state, valency, and spacing of IgE-binding epitopes on the allergen. Whereas most of these observations come from studies using synthetic allergens, in this study we have used Timothy grass pollen allergen Phl p 7 and birch pollen allergen Bet v 4 to study these effects. Despite the high homology of these polcalcin family allergens, Phl p 7 and Bet v 4 display different binding characteristics toward two human patient-derived polcalcin-specific IgE Abs. We have used native polcalcin dimers and engineered multimeric allergens to test the effects of affinity and oligomeric state on IgE binding and effector cell activation. Our results indicate that polcalcin multimers are required to stimulate high levels of effector cell degranulation when using the humanized RBL-SX38 cell model and that multivalency can overcome the need for high-affinity interactions.
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Affiliation(s)
- Gintare Bucaite
- Randall Centre for Cell and Molecular Biophysics, King's College London, London SE1 1UL, United Kingdom.,Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, London SE1 1UL, United Kingdom
| | - Tara Kang-Pettinger
- Randall Centre for Cell and Molecular Biophysics, King's College London, London SE1 1UL, United Kingdom.,Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, London SE1 1UL, United Kingdom.,Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 7RH, United Kingdom; and
| | - Jorge Moreira
- Randall Centre for Cell and Molecular Biophysics, King's College London, London SE1 1UL, United Kingdom.,Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, London SE1 1UL, United Kingdom
| | - Hannah J Gould
- Randall Centre for Cell and Molecular Biophysics, King's College London, London SE1 1UL, United Kingdom.,Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, London SE1 1UL, United Kingdom
| | - Louisa K James
- Randall Centre for Cell and Molecular Biophysics, King's College London, London SE1 1UL, United Kingdom.,Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, London SE1 1UL, United Kingdom.,Blizard Institute, Barts and the London School of Medicine and Dentistry, Queen Mary University of London, London E1 2AT, United Kingdom
| | - Brian J Sutton
- Randall Centre for Cell and Molecular Biophysics, King's College London, London SE1 1UL, United Kingdom.,Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, London SE1 1UL, United Kingdom
| | - James M McDonnell
- Randall Centre for Cell and Molecular Biophysics, King's College London, London SE1 1UL, United Kingdom; .,Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, London SE1 1UL, United Kingdom
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11
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Nyamboya RA, Sutton BJ, Calvert RA. Mapping of the binding site for FcμR in human IgM-Fc. Biochim Biophys Acta Proteins Proteom 2019; 1868:140266. [PMID: 31449905 PMCID: PMC6905151 DOI: 10.1016/j.bbapap.2019.140266] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/17/2019] [Revised: 08/16/2019] [Accepted: 08/21/2019] [Indexed: 11/02/2022]
Abstract
FcμR is a high-affinity receptor for the Fc portion of human IgM. It participates in B cell activation, cell survival and proliferation, but the full range of its functions remains to be elucidated. The receptor has an extracellular immunoglobulin (Ig)-like domain homologous to those in Fcα/μR and pIgR, but unlike these two other IgM receptors which also bind IgA, FcμR exhibits a binding specificity for only IgM-Fc. Previous studies have suggested that the IgM/FcμR interaction mainly involves the Cμ4 domains with possible contributions from either Cμ3 or Cμ2. To define the binding site more precisely, we generated three recombinant IgM-Fc proteins with specific mutations in the Cμ3 and Cμ4 domains, as well as a construct lacking the Cμ2 domains, and analyzed their interaction with the extracellular Ig-like domain of FcμR using surface plasmon resonance analysis. There is a binding site for FcμR in each IgM heavy chain. Neither the absence of the Cμ2 domains nor the quadruple mutant D340S/Q341G/D342S/T343S (in Cμ3 adjacent to Cμ2) affected FcμR binding, whereas double mutant K361D/D416R (in Cμ3 at the Cμ4 interface) substantially decreased binding, and a single mutation Q510R (in Cμ4) completely abolished FcμR binding. We conclude that glutamine at position 510 in Cμ4 is critical for IgM binding to FcμR. This will facilitate discrimination between the distinct effects of FcμR interactions with soluble IgM and with the IgM BCR.
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Affiliation(s)
- Rosemary A Nyamboya
- Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London SE1 1UL, United Kingdom
| | - Brian J Sutton
- Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London SE1 1UL, United Kingdom
| | - Rosaleen A Calvert
- Randall Centre for Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London SE1 1UL, United Kingdom.
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Sutton BJ, Davies AM, Bax HJ, Karagiannis SN. IgE Antibodies: From Structure to Function and Clinical Translation. Antibodies (Basel) 2019; 8:E19. [PMID: 31544825 PMCID: PMC6640697 DOI: 10.3390/antib8010019] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2019] [Revised: 02/11/2019] [Accepted: 02/15/2019] [Indexed: 12/15/2022] Open
Abstract
Immunoglobulin E (IgE) antibodies are well known for their role in mediating allergic reactions, and their powerful effector functions activated through binding to Fc receptors FcεRI and FcεRII/CD23. Structural studies of IgE-Fc alone, and when bound to these receptors, surprisingly revealed not only an acutely bent Fc conformation, but also subtle allosteric communication between the two distant receptor-binding sites. The ability of IgE-Fc to undergo more extreme conformational changes emerged from structures of complexes with anti-IgE antibodies, including omalizumab, in clinical use for allergic disease; flexibility is clearly critical for IgE function, but may also be exploited by allosteric interference to inhibit IgE activity for therapeutic benefit. In contrast, the power of IgE may be harnessed to target cancer. Efforts to improve the effector functions of therapeutic antibodies for cancer have almost exclusively focussed on IgG1 and IgG4 subclasses, but IgE offers an extremely high affinity for FcεRI receptors on immune effector cells known to infiltrate solid tumours. Furthermore, while tumour-resident inhibitory Fc receptors can modulate the effector functions of IgG antibodies, no inhibitory IgE Fc receptors are known to exist. The development of tumour antigen-specific IgE antibodies may therefore provide an improved immune functional profile and enhanced anti-cancer efficacy. We describe proof-of-concept studies of IgE immunotherapies against solid tumours, including a range of in vitro and in vivo evaluations of efficacy and mechanisms of action, as well as ex vivo and in vivo safety studies. The first anti-cancer IgE antibody, MOv18, the clinical translation of which we discuss herein, has now reached clinical testing, offering great potential to direct this novel therapeutic modality against many other tumour-specific antigens. This review highlights how our understanding of IgE structure and function underpins these exciting clinical developments.
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Affiliation(s)
- Brian J Sutton
- King's College London, Randall Centre for Cell and Molecular Biophysics, London SE1 1UL, UK.
- Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK.
| | - Anna M Davies
- King's College London, Randall Centre for Cell and Molecular Biophysics, London SE1 1UL, UK.
- Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK.
| | - Heather J Bax
- King's College London, St John's Institute of Dermatology, London SE1 9RT, UK.
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Hansen K, Lau AM, Giles K, McDonnell JM, Struwe WB, Sutton BJ, Politis A. A Mass-Spectrometry-Based Modelling Workflow for Accurate Prediction of IgG Antibody Conformations in the Gas Phase. Angew Chem Int Ed Engl 2018; 57:17194-17199. [PMID: 30408305 PMCID: PMC6392142 DOI: 10.1002/anie.201812018] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Indexed: 11/09/2022]
Abstract
Immunoglobulins are biomolecules involved in defence against foreign substances. Flexibility is key to their functional properties in relation to antigen binding and receptor interactions. We have developed an integrative strategy combining ion mobility mass spectrometry (IM-MS) with molecular modelling to study the conformational dynamics of human IgG antibodies. Predictive models of all four human IgG subclasses were assembled and their dynamics sampled in the transition from extended to collapsed state during IM-MS. Our data imply that this collapse of IgG antibodies is related to their intrinsic structural features, including Fab arm flexibility, collapse towards the Fc region, and the length of their hinge regions. The workflow presented here provides an accurate structural representation in good agreement with the observed collision cross section for these flexible IgG molecules. These results have implications for studying other nonglobular flexible proteins.
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Affiliation(s)
- Kjetil Hansen
- Department of ChemistryKing's College London7 Trinity StreetLondonSE1 1DBUK
| | - Andy M. Lau
- Department of ChemistryKing's College London7 Trinity StreetLondonSE1 1DBUK
| | | | | | | | - Brian J. Sutton
- Randall Centre for Cell and Molecular BiophysicsKing's College LondonUK
| | - Argyris Politis
- Department of ChemistryKing's College London7 Trinity StreetLondonSE1 1DBUK
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14
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Hansen K, Lau AM, Giles K, McDonnell JM, Struwe WB, Sutton BJ, Politis A. A Mass‐Spectrometry‐Based Modelling Workflow for Accurate Prediction of IgG Antibody Conformations in the Gas Phase. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201812018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Kjetil Hansen
- Department of Chemistry King's College London 7 Trinity Street London SE1 1DB UK
| | - Andy M. Lau
- Department of Chemistry King's College London 7 Trinity Street London SE1 1DB UK
| | - Kevin Giles
- Waters Corp. Stamford Road Wilmslow SK9 4AX UK
| | - James M. McDonnell
- Randall Centre for Cell and Molecular Biophysics King's College London UK
| | | | - Brian J. Sutton
- Randall Centre for Cell and Molecular Biophysics King's College London UK
| | - Argyris Politis
- Department of Chemistry King's College London 7 Trinity Street London SE1 1DB UK
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15
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Ramaswamy S, Rasheed M, Morelli CF, Calvio C, Sutton BJ, Pastore A. The structure of PghL hydrolase bound to its substrate poly-γ-glutamate. FEBS J 2018; 285:4575-4589. [PMID: 30387270 PMCID: PMC6506827 DOI: 10.1111/febs.14688] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 10/05/2018] [Accepted: 10/30/2018] [Indexed: 11/28/2022]
Abstract
The identification of new strategies to fight bacterial infections in view of the spread of multiple resistance to antibiotics has become mandatory. It has been demonstrated that several bacteria develop poly‐γ‐glutamic acid (γ‐PGA) capsules as a protection from external insults and/or host defence systems. Among the pathogens that shield themselves in these capsules are Bacillus anthracis, Francisella tularensis and several Staphylococcus strains. These are important pathogens with a profound influence on human health. The recently characterised γ‐PGA hydrolases, which can dismantle the γ‐PGA‐capsules, are an attractive new direction that can offer real hope for the development of alternatives to antibiotics, particularly in cases of multidrug resistant bacteria. We have characterised in detail the cleaving mechanism and stereospecificity of the enzyme PghL (previously named YndL) from Bacillus subtilis encoded by a gene of phagic origin and dramatically efficient in degrading the long polymeric chains of γ‐PGA. We used X‐ray crystallography to solve the three‐dimensional structures of the enzyme in its zinc‐free, zinc‐bound and complexed forms. The protein crystallised with a γ‐PGA hexapeptide substrate and thus reveals details of the interaction which could explain the stereospecificity observed and give hints on the catalytic mechanism of this class of hydrolytic enzymes.
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Affiliation(s)
- Sneha Ramaswamy
- The Randall Centre for Cell & Molecular Biophysics, King's College London, UK
| | - Masooma Rasheed
- The Wohl Institute, King's College London, UK.,UK Dementia Research Institute at King's College London, UK
| | | | - Cinzia Calvio
- Department of Biology and Biotechnology, University of Pavia, Italy
| | - Brian J Sutton
- The Randall Centre for Cell & Molecular Biophysics, King's College London, UK
| | - Annalisa Pastore
- The Wohl Institute, King's College London, UK.,UK Dementia Research Institute at King's College London, UK.,Department of Molecular Medicine, University of Pavia, Italy
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16
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Chen JB, Ramadani F, Pang MOY, Beavil RL, Holdom MD, Mitropoulou AN, Beavil AJ, Gould HJ, Chang TW, Sutton BJ, McDonnell JM, Davies AM. Structural basis for selective inhibition of immunoglobulin E-receptor interactions by an anti-IgE antibody. Sci Rep 2018; 8:11548. [PMID: 30069035 PMCID: PMC6070508 DOI: 10.1038/s41598-018-29664-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 07/16/2018] [Indexed: 11/09/2022] Open
Abstract
Immunoglobulin E (IgE) antibodies play a central role in the allergic response: interaction with FcεRI on mast cells and basophils leads to immediate hypersensitivity reactions upon allergen challenge, while interaction with CD23/FcεRII, expressed on a variety of cells, regulates IgE synthesis among other activities. The receptor-binding IgE-Fc region has recently been found to display remarkable flexibility, from acutely bent to extended conformations, with allosteric communication between the distant FcεRI and CD23 binding sites. We report the structure of an anti-IgE antibody Fab (8D6) bound to IgE-Fc through a mixed protein-carbohydrate epitope, revealing further flexibility and a novel extended conformation with potential relevance to that of membrane-bound IgE in the B cell receptor for antigen. Unlike the earlier, clinically approved anti-IgE antibody omalizumab, 8D6 inhibits binding to FcεRI but not CD23; the structure reveals how this discrimination is achieved through both orthosteric and allosteric mechanisms, supporting therapeutic strategies that retain the benefits of CD23 binding.
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Affiliation(s)
- Jiun-Bo Chen
- Genomics Research Center, Academia Sinica, Taipei, 115, Taiwan
- King's College London, Randall Centre for Cell and Molecular Biophysics, London, SE1 1UL, United Kingdom
| | - Faruk Ramadani
- King's College London, Randall Centre for Cell and Molecular Biophysics, London, SE1 1UL, United Kingdom
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
| | - Marie O Y Pang
- King's College London, Randall Centre for Cell and Molecular Biophysics, London, SE1 1UL, United Kingdom
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
| | - Rebecca L Beavil
- King's College London, Randall Centre for Cell and Molecular Biophysics, London, SE1 1UL, United Kingdom
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma Protein Production Facility, London, United Kingdom
| | - Mary D Holdom
- King's College London, Randall Centre for Cell and Molecular Biophysics, London, SE1 1UL, United Kingdom
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
| | - Alkistis N Mitropoulou
- King's College London, Randall Centre for Cell and Molecular Biophysics, London, SE1 1UL, United Kingdom
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
| | - Andrew J Beavil
- King's College London, Randall Centre for Cell and Molecular Biophysics, London, SE1 1UL, United Kingdom
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
| | - Hannah J Gould
- King's College London, Randall Centre for Cell and Molecular Biophysics, London, SE1 1UL, United Kingdom
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
| | - Tse Wen Chang
- Genomics Research Center, Academia Sinica, Taipei, 115, Taiwan
| | - Brian J Sutton
- King's College London, Randall Centre for Cell and Molecular Biophysics, London, SE1 1UL, United Kingdom.
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom.
| | - James M McDonnell
- King's College London, Randall Centre for Cell and Molecular Biophysics, London, SE1 1UL, United Kingdom.
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom.
| | - Anna M Davies
- King's College London, Randall Centre for Cell and Molecular Biophysics, London, SE1 1UL, United Kingdom.
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom.
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17
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Doré KA, Kashiwakura JI, McDonnell JM, Gould HJ, Kawakami T, Sutton BJ, Davies AM. Crystal structures of murine and human Histamine-Releasing Factor (HRF/TCTP) and a model for HRF dimerisation in mast cell activation. Mol Immunol 2017; 93:216-222. [PMID: 29216544 PMCID: PMC5966295 DOI: 10.1016/j.molimm.2017.11.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 11/22/2017] [Indexed: 01/21/2023]
Abstract
In allergic disease, mast cell activation is conventionally triggered by allergen-mediated cross-linking of receptor-bound IgE on the cell surface. In addition to its diverse range of intracellular roles in apoptosis, cell proliferation and cancer, Histamine-Releasing Factor (HRF) also activates mast cells and basophils. A subset of IgE antibodies bind HRF through their Fab regions, and two IgE binding sites on HRF have been mapped. HRF can form dimers, and a disulphide-linked dimer is critical for activity. The current model for the activity of HRF in mast cell activation involves cross-linking of receptor-bound IgE by dimeric HRF, mediated by HRF/Fab interactions. HRF crystal and solution structures have provided little insight into either the formation of disulphide-linked HRF dimers or the ability of HRF to activate mast cells. We report the first crystal structure of murine HRF (mHRF) to 4.0Å resolution, revealing a conserved fold. We also solved the structure of human HRF (hHRF) in two new crystal forms, one at the highest resolution (1.4Å) yet reported. The high resolution hHRF structure reveals a disulphide-linked dimer, in which the two molecules are closely associated, and provides a model for the role of both human and murine HRF in mast cell activation.
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Affiliation(s)
- Katy A Doré
- King's College London, Randall Centre for Cell and Molecular Biophysics, New Hunt's House, London, SE1 1UL, United Kingdom; Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
| | - Jun-Ichi Kashiwakura
- Laboratory for Allergic Disease, RIKEN Center for Integrative Medical Sciences, Yokohama, 230-0045, Japan
| | - James M McDonnell
- King's College London, Randall Centre for Cell and Molecular Biophysics, New Hunt's House, London, SE1 1UL, United Kingdom; Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
| | - Hannah J Gould
- King's College London, Randall Centre for Cell and Molecular Biophysics, New Hunt's House, London, SE1 1UL, United Kingdom; Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
| | - Toshiaki Kawakami
- Laboratory for Allergic Disease, RIKEN Center for Integrative Medical Sciences, Yokohama, 230-0045, Japan; Division of Cell Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA, 92037, USA; Department of Dermatology, University of California San Diego, School of Medicine, La Jolla, CA, 92093, USA
| | - Brian J Sutton
- King's College London, Randall Centre for Cell and Molecular Biophysics, New Hunt's House, London, SE1 1UL, United Kingdom; Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom.
| | - Anna M Davies
- King's College London, Randall Centre for Cell and Molecular Biophysics, New Hunt's House, London, SE1 1UL, United Kingdom; Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom.
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18
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Doré KA, Davies AM, Drinkwater N, Beavil AJ, McDonnell JM, Sutton BJ. Thermal sensitivity and flexibility of the Cε3 domains in immunoglobulin E. Biochim Biophys Acta Proteins Proteom 2017; 1865:1336-1347. [PMID: 28844738 PMCID: PMC5652521 DOI: 10.1016/j.bbapap.2017.08.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Revised: 07/14/2017] [Accepted: 08/07/2017] [Indexed: 01/25/2023]
Abstract
Immunoglobulin E (IgE) is the antibody that plays a central role in the mechanisms of allergic diseases such as asthma. Interactions with its receptors, FcεRI on mast cells and CD23 on B cells, are mediated by the Fc region, a dimer of the Cε2, Cε3 and Cε4 domains. A sub-fragment lacking the Cε2 domains, Fcε3–4, also binds to both receptors, although receptor binding almost exclusively involves the Cε3 domains. This domain also contains the N-linked glycosylation site conserved in other isotypes. We report here the crystal structures of IgE-Fc and Fcε3–4 at the highest resolutions yet determined, 1.75 Å and 2.0 Å respectively, revealing unprecedented detail regarding the carbohydrate and its interactions with protein domains. Analysis of the crystallographic B-factors of these, together with all earlier IgE-Fc and Fcε3–4 structures, shows that the Cε3 domains exhibit the greatest intrinsic flexibility and quaternary structural variation within IgE-Fc. Intriguingly, both well-ordered carbohydrate and disordered polypeptide can be seen within the same Cε3 domain. A simplified method for comparing the quaternary structures of the Cε3 domains in free and receptor-bound IgE-Fc structures is presented, which clearly delineates the FcεRI and CD23 bound states. Importantly, differential scanning fluorimetric analysis of IgE-Fc and Fcε3–4 identifies Cε3 as the domain most susceptible to thermally-induced unfolding, and responsible for the characteristically low melting temperature of IgE. The Cε3 domains of IgE are most susceptible to thermally induced unfolding determined by differential scanning fluorimetry. The Cε3 domains are responsible for the characteristically low melting temperature of IgE. The Cε3 domains exhibit the greatest intrinsic flexibility. Quaternary structural diversity of Cε3 domains is compared across all known structures using a simplified single parameter. Human IgE-Fc and Fcε3–4 domain structures are determined at the highest resolutions yet reported (1.75 Å and 2.0 Å).
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Affiliation(s)
- Katy A Doré
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom; Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
| | - Anna M Davies
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom; Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
| | - Nyssa Drinkwater
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom; Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
| | - Andrew J Beavil
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom; Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
| | - James M McDonnell
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom; Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom
| | - Brian J Sutton
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom; Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom.
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Davies AM, Allan EG, Keeble AH, Delgado J, Cossins BP, Mitropoulou AN, Pang MOY, Ceska T, Beavil AJ, Craggs G, Westwood M, Henry AJ, McDonnell JM, Sutton BJ. Allosteric mechanism of action of the therapeutic anti-IgE antibody omalizumab. J Biol Chem 2017; 292:9975-9987. [PMID: 28438838 PMCID: PMC5473249 DOI: 10.1074/jbc.m117.776476] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Revised: 04/19/2017] [Indexed: 02/03/2023] Open
Abstract
Immunoglobulin E and its interactions with receptors FcϵRI and CD23 play a central role in allergic disease. Omalizumab, a clinically approved therapeutic antibody, inhibits the interaction between IgE and FcϵRI, preventing mast cell and basophil activation, and blocks IgE binding to CD23 on B cells and antigen-presenting cells. We solved the crystal structure of the complex between an omalizumab-derived Fab and IgE-Fc, with one Fab bound to each Cϵ3 domain. Free IgE-Fc adopts an acutely bent structure, but in the complex it is only partially bent, with large-scale conformational changes in the Cϵ3 domains that inhibit the interaction with FcϵRI. CD23 binding is inhibited sterically due to overlapping binding sites on each Cϵ3 domain. Studies of omalizumab Fab binding in solution demonstrate the allosteric basis for FcϵRI inhibition and, together with the structure, reveal how omalizumab may accelerate dissociation of receptor-bound IgE from FcϵRI, exploiting the intrinsic flexibility and allosteric potential of IgE.
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Affiliation(s)
- Anna M Davies
- From the Randall Division of Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London SE1 1UL
- the Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London SE1 1UL, and
| | - Elizabeth G Allan
- From the Randall Division of Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London SE1 1UL
- the Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London SE1 1UL, and
| | - Anthony H Keeble
- From the Randall Division of Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London SE1 1UL
- the Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London SE1 1UL, and
| | - Jean Delgado
- UCB-Celltech, 208 Bath Road, Slough SL1 3WE, United Kingdom
| | | | - Alkistis N Mitropoulou
- From the Randall Division of Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London SE1 1UL
- the Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London SE1 1UL, and
| | - Marie O Y Pang
- From the Randall Division of Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London SE1 1UL
- the Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London SE1 1UL, and
| | - Tom Ceska
- UCB-Celltech, 208 Bath Road, Slough SL1 3WE, United Kingdom
| | - Andrew J Beavil
- From the Randall Division of Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London SE1 1UL
- the Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London SE1 1UL, and
| | - Graham Craggs
- UCB-Celltech, 208 Bath Road, Slough SL1 3WE, United Kingdom
| | - Marta Westwood
- UCB-Celltech, 208 Bath Road, Slough SL1 3WE, United Kingdom
| | | | - James M McDonnell
- From the Randall Division of Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London SE1 1UL,
- the Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London SE1 1UL, and
| | - Brian J Sutton
- From the Randall Division of Cell and Molecular Biophysics, King's College London, New Hunt's House, Guy's Campus, London SE1 1UL,
- the Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London SE1 1UL, and
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20
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Zhang X, Calvert RA, Sutton BJ, Doré KA. IgY: a key isotype in antibody evolution. Biol Rev Camb Philos Soc 2017; 92:2144-2156. [DOI: 10.1111/brv.12325] [Citation(s) in RCA: 62] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Revised: 01/31/2017] [Accepted: 02/09/2017] [Indexed: 01/12/2023]
Affiliation(s)
- Xiaoying Zhang
- Department of Basic Veterinary, College of Veterinary Medicine; Northwest A&F University; Yangling 712100 China
| | - Rosaleen A. Calvert
- The Randall Division of Cell & Molecular Biophysics, King's College London; London SE1 1UL U.K
| | - Brian J. Sutton
- The Randall Division of Cell & Molecular Biophysics, King's College London; London SE1 1UL U.K
| | - Katy A. Doré
- The Randall Division of Cell & Molecular Biophysics, King's College London; London SE1 1UL U.K
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21
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Davies AM, Rispens T, Ooijevaar-de Heer P, Aalberse RC, Sutton BJ. Room temperature structure of human IgG4-Fc from crystals analysed in situ. Mol Immunol 2016; 81:85-91. [PMID: 27915153 PMCID: PMC5226057 DOI: 10.1016/j.molimm.2016.11.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 11/14/2016] [Accepted: 11/20/2016] [Indexed: 02/07/2023]
Abstract
Room temperature structure of human IgG4-Fc solved from crystals analysed in situ. Structure reveals changes in crystal packing at different temperatures. Structure reveals physiologically relevant conformation of a key Fcγ receptor binding loop.
The Fc region of IgG antibodies (Cγ2 and Cγ3 domains) is responsible for effector functions such as antibody-dependent cell-mediated cytotoxicity and phagocytosis, through engagement with Fcγ receptors, although the ability to elicit these functions differs between the four human IgG subclasses. A key determinant of Fcγ receptor interactions is the FG loop in the Cγ2 domain. High resolution cryogenic IgG4-Fc crystal structures have revealed a unique conformation for this loop, which could contribute to the particular biological properties of this subclass. To further explore the conformation of the IgG4 Cγ2 FG loop at near-physiological temperature, we solved a 2.7 Å resolution room temperature structure of recombinant human IgG4-Fc from crystals analysed in situ. The Cγ2 FG loop in one chain differs from the cryogenic structure, and adopts the conserved conformation found in IgG1-Fc; however, this conformation participates in extensive crystal packing interactions. On the other hand, at room temperature, and free from any crystal packing interactions, the Cγ2 FG loop in the other chain adopts the conformation previously observed in the cryogenic IgG4-Fc structures, despite both conformations being accessible. The room temperature human IgG4-Fc structure thus provides a more complete and physiologically relevant description of the conformation of this functionally critical Cγ2 FG loop.
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Affiliation(s)
- Anna M Davies
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom; Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom.
| | - Theo Rispens
- Sanquin Research, Amsterdam 1066 CX, The Netherlands; University of Amsterdam, Academic Medical Centre Landsteiner Laboratory, The Netherlands
| | - Pleuni Ooijevaar-de Heer
- Sanquin Research, Amsterdam 1066 CX, The Netherlands; University of Amsterdam, Academic Medical Centre Landsteiner Laboratory, The Netherlands
| | - Rob C Aalberse
- Sanquin Research, Amsterdam 1066 CX, The Netherlands; University of Amsterdam, Academic Medical Centre Landsteiner Laboratory, The Netherlands
| | - Brian J Sutton
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom; Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom.
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Chen JB, James LK, Davies AM, Wu YCB, Rimmer J, Lund VJ, Chen JH, McDonnell JM, Chan YC, Hutchins GH, Chang TW, Sutton BJ, Kariyawasam HH, Gould HJ. Antibodies and superantibodies in patients with chronic rhinosinusitis with nasal polyps. J Allergy Clin Immunol 2016; 139:1195-1204.e11. [PMID: 27658758 PMCID: PMC5380656 DOI: 10.1016/j.jaci.2016.06.066] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2015] [Revised: 05/07/2016] [Accepted: 06/13/2016] [Indexed: 01/19/2023]
Abstract
Background Chronic rhinosinusitis with nasal polyps is associated with local immunoglobulin hyperproduction and the presence of IgE antibodies against Staphylococcus aureus enterotoxins (SAEs). Aspirin-exacerbated respiratory disease is a severe form of chronic rhinosinusitis with nasal polyps in which nearly all patients express anti-SAEs. Objectives We aimed to understand antibodies reactive to SAEs and determine whether they recognize SAEs through their complementarity-determining regions (CDRs) or framework regions. Methods Labeled staphylococcal enterotoxin (SE) A, SED, and SEE were used to isolate single SAE-specific B cells from the nasal polyps of 3 patients with aspirin-exacerbated respiratory disease by using fluorescence-activated cell sorting. Recombinant antibodies with “matched” heavy and light chains were cloned as IgG1, and those of high affinity for specific SAEs, assayed by means of ELISA and surface plasmon resonance, were recloned as IgE and antigen-binding fragments. IgE activities were tested in basophil degranulation assays. Results Thirty-seven SAE-specific, IgG- or IgA-expressing B cells were isolated and yielded 6 anti-SAE clones, 2 each for SEA, SED, and SEE. Competition binding assays revealed that the anti-SEE antibodies recognize nonoverlapping epitopes in SEE. Unexpectedly, each anti-SEE mediated SEE-induced basophil degranulation, and IgG1 or antigen-binding fragments of each anti-SEE enhanced degranulation by the other anti-SEE. Conclusions SEEs can activate basophils by simultaneously binding as antigens in the conventional manner to CDRs and as superantigens to framework regions of anti-SEE IgE in anti-SEE IgE-FcεRI complexes. Anti-SEE IgG1s can enhance the activity of anti-SEE IgEs as conventional antibodies through CDRs or simultaneously as conventional antibodies and as “superantibodies” through CDRs and framework regions to SEEs in SEE–anti-SEE IgE-FcεRI complexes.
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Affiliation(s)
- Jiun-Bo Chen
- Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom; Genomics Research Center, Academia Sinica, Taipei, Taiwan
| | - Louisa K James
- Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom; MRC & Asthma UK Centre for Allergic Mechanisms of Asthma, King's College London, Guy's Campus, London, United Kingdom
| | - Anna M Davies
- Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom; MRC & Asthma UK Centre for Allergic Mechanisms of Asthma, King's College London, Guy's Campus, London, United Kingdom
| | - Yu-Chang Bryan Wu
- Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom; MRC & Asthma UK Centre for Allergic Mechanisms of Asthma, King's College London, Guy's Campus, London, United Kingdom
| | - Joanne Rimmer
- Allergy and Rhinology, Royal National Throat Nose Ear Hospital, London, United Kingdom
| | - Valerie J Lund
- Allergy and Rhinology, Royal National Throat Nose Ear Hospital, London, United Kingdom
| | - Jou-Han Chen
- Genomics Research Center, Academia Sinica, Taipei, Taiwan
| | - James M McDonnell
- Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom; MRC & Asthma UK Centre for Allergic Mechanisms of Asthma, King's College London, Guy's Campus, London, United Kingdom
| | - Yih-Chih Chan
- Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom; MRC & Asthma UK Centre for Allergic Mechanisms of Asthma, King's College London, Guy's Campus, London, United Kingdom
| | - George H Hutchins
- Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom
| | - Tse Wen Chang
- Genomics Research Center, Academia Sinica, Taipei, Taiwan
| | - Brian J Sutton
- Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom; MRC & Asthma UK Centre for Allergic Mechanisms of Asthma, King's College London, Guy's Campus, London, United Kingdom
| | - Harsha H Kariyawasam
- Allergy and Rhinology, Royal National Throat Nose Ear Hospital, London, United Kingdom
| | - Hannah J Gould
- Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom; MRC & Asthma UK Centre for Allergic Mechanisms of Asthma, King's College London, Guy's Campus, London, United Kingdom.
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23
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Abstract
IgG4, the least represented human IgG subclass in serum, is an intriguing antibody with unique biological properties, such as the ability to undergo Fab-arm exchange and limit immune complex formation. The lack of effector functions, such as antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity, is desirable for therapeutic purposes. IgG4 plays a protective role in allergy by acting as a blocking antibody, and inhibiting mast cell degranulation, but a deleterious role in malignant melanoma, by impeding IgG1-mediated anti-tumor immunity. These findings highlight the importance of understanding the interaction between IgG4 and Fcγ receptors. Despite a wealth of structural information for the IgG1 subclass, including complexes with Fcγ receptors, and structures for intact antibodies, high-resolution crystal structures were not reported for IgG4-Fc until recently. Here, we highlight some of the biological properties of human IgG4, and review the recent crystal structures of IgG4-Fc. We discuss the unexpected conformations adopted by functionally important Cγ2 domain loops, and speculate about potential implications for the interaction between IgG4 and FcγRs.
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Affiliation(s)
- Anna M Davies
- Randall Division of Cell and Molecular Biophysics, King's College London, London, UK.,Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | - Brian J Sutton
- Randall Division of Cell and Molecular Biophysics, King's College London, London, UK.,Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
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24
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Abstract
IgG4 is the least abundant subclass of IgG in normal human serum, but elevated IgG4 levels are triggered in response to a chronic antigenic stimulus and inflammation. Since the immune system is exposed to tumor-associated antigens over a relatively long period of time, and tumors notoriously promote inflammation, it is unsurprising that IgG4 has been implicated in certain tumor types. Despite differing from other IgG subclasses by only a few amino acids, IgG4 possesses unique structural characteristics that may be responsible for its poor effector function potency and immunomodulatory properties. We describe the unique attributes of IgG4 that may be responsible for these regulatory functions, particularly in the cancer context. We discuss the inflammatory conditions in tumors that support IgG4, the emerging and proposed mechanisms by which IgG4 may contribute to tumor-associated escape from immune surveillance and implications for cancer immunotherapy.
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Affiliation(s)
- Silvia Crescioli
- St. John's Institute of Dermatology, Division of Genetics and Molecular Medicine; Faculty of Life Sciences and Medicine, King's College London, London, UK. .,NIHR Biomedical Research Centre at Guy's and St. Thomas's Hospitals and King's College London, King's College London, London, UK.
| | - Isabel Correa
- St. John's Institute of Dermatology, Division of Genetics and Molecular Medicine; Faculty of Life Sciences and Medicine, King's College London, London, UK. .,NIHR Biomedical Research Centre at Guy's and St. Thomas's Hospitals and King's College London, King's College London, London, UK.
| | - Panagiotis Karagiannis
- St. John's Institute of Dermatology, Division of Genetics and Molecular Medicine; Faculty of Life Sciences and Medicine, King's College London, London, UK. .,NIHR Biomedical Research Centre at Guy's and St. Thomas's Hospitals and King's College London, King's College London, London, UK.
| | - Anna M Davies
- Randall Division of Cell and Molecular Biophysics, Faculty of Life Sciences and Medicine, King's College London, London, UK. .,Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK.
| | - Brian J Sutton
- Randall Division of Cell and Molecular Biophysics, Faculty of Life Sciences and Medicine, King's College London, London, UK. .,Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK.
| | - Frank O Nestle
- St. John's Institute of Dermatology, Division of Genetics and Molecular Medicine; Faculty of Life Sciences and Medicine, King's College London, London, UK. .,NIHR Biomedical Research Centre at Guy's and St. Thomas's Hospitals and King's College London, King's College London, London, UK.
| | - Sophia N Karagiannis
- St. John's Institute of Dermatology, Division of Genetics and Molecular Medicine; Faculty of Life Sciences and Medicine, King's College London, London, UK. .,NIHR Biomedical Research Centre at Guy's and St. Thomas's Hospitals and King's College London, King's College London, London, UK. .,St. John's Institute of Dermatology, Division of Genetics and Molecular Medicine, Kings' College London and NIHR Biomedical Research Centre at Guy's and St. Thomas's Hospitals and King's College London, Guy's Hospital, Tower Wing, 9th Floor, London, SE1 9RT, UK.
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25
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Chen HX, He F, Sun Y, Luo Y, Qiu HJ, Zhang XY, Sutton BJ. Generation and characterization of chicken-sourced single-chain variable fragments (scFvs) against porcine interferon-gamma (pIFN-γ). J Immunoassay Immunochem 2015; 36:27-44. [PMID: 24568649 DOI: 10.1080/15321819.2014.892511] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Development of chicken-sourced antibodies offers an alternative strategy for the development of highly specific antibodies against mammalian proteins with conserved epitopes due to the phylogenetic distance between avian and mammalian species. In this study, the single-chain variable fragments (scFvs) against porcine interferon-gamma was screened and characterized from a hyperimmunized chicken phage display library. The expressed soluble scFvs exhibited highly specific recognition of porcine interferon-gamma in ELISA, Western blot, and immunofluorescence staining assays. Results of the current study indicate that it is possible to develop scFv IgY antibodies to a mammalian interferon by using Biopanning technology. Furthermore, it also confirms that monoclonal avian IgY antibody technique could be applied as a promising tool to produce immunoglobulin molecules with high specificity and affinity towards conserved mammalian epitopes or antigens.
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Affiliation(s)
- Hong-Xiu Chen
- a Division of Swine Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agriculture Science , Harbin , Heilongjiang , China
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26
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Affiliation(s)
- Brian J. Sutton
- Randall Division of Cell and Molecular Biophysics; King's College London; London UK
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma; London UK
| | - Anna M. Davies
- Randall Division of Cell and Molecular Biophysics; King's College London; London UK
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma; London UK
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27
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Davies AM, Tata R, Trentham DR, Sutton BJ, Brown PR. Characterisation of a phosphinothricin N-acetyltransferase from Pseudomonas syringae. Acta Crystallogr A Found Adv 2015. [DOI: 10.1107/s2053273315096576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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28
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Mitropoulou AN, Davies AM, Dodev TS, James LK, Beavil RL, Gould HJ, McDonnell JM, Beavil AJ, Sutton BJ. The crystal structure of a common allergen in complex with its specific patient-derived antibody. Acta Crystallogr A Found Adv 2015. [DOI: 10.1107/s2053273315096059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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29
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Hussein D, Starr A, Heikal L, McNeill E, Channon KM, Brown PR, Sutton BJ, McDonnell JM, Nandi M. Validating the GTP-cyclohydrolase 1-feedback regulatory complex as a therapeutic target using biophysical and in vivo approaches. Br J Pharmacol 2015; 172:4146-57. [PMID: 26014146 PMCID: PMC4543619 DOI: 10.1111/bph.13202] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Revised: 05/12/2015] [Accepted: 05/13/2015] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND AND PURPOSE 6R-L-erythro-5,6,7,8-tetrahydrobiopterin (BH4 ) is an essential cofactor for nitric oxide biosynthesis. Substantial clinical evidence indicates that intravenous BH4 restores vascular function in patients. Unfortunately, oral BH4 has limited efficacy. Therefore, orally bioavailable pharmacological activators of endogenous BH4 biosynthesis hold significant therapeutic potential. GTP-cyclohydrolase 1 (GCH1), the rate limiting enzyme in BH4 synthesis, forms a protein complex with GCH1 feedback regulatory protein (GFRP). This complex is subject to allosteric feed-forward activation by L-phenylalanine (L-phe). We investigated the effects of L-phe on the biophysical interactions of GCH1 and GFRP and its potential to alter BH4 levels in vivo. EXPERIMENTAL APPROACH Detailed characterization of GCH1-GFRP protein-protein interactions were performed using surface plasmon resonance (SPR) with or without L-phe. Effects on systemic and vascular BH4 biosynthesis in vivo were investigated following L-phe treatment (100 mg·kg(-1) , p.o.). KEY RESULTS GCH1 and GFRP proteins interacted in the absence of known ligands or substrate but the presence of L-phe doubled maximal binding and enhanced binding affinity eightfold. Furthermore, the complex displayed very slow association and dissociation rates. In vivo, L-phe challenge induced a sustained elevation of aortic BH4 , an effect absent in GCH1(fl/fl)-Tie2Cre mice. CONCLUSIONS AND IMPLICATIONS Biophysical data indicate that GCH1 and GFRP are constitutively bound. In vivo, data demonstrated that L-phe elevated vascular BH4 in an endothelial GCH1 dependent manner. Pharmacological agents which mimic the allosteric effects of L-phe on the GCH1-GFRP complex have the potential to elevate endothelial BH4 biosynthesis for numerous cardiovascular disorders.
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Affiliation(s)
- D Hussein
- Institute of Pharmaceutical Science, Faculty of Life Sciences & Medicine, King's College LondonLondon, UK
| | - A Starr
- Institute of Pharmaceutical Science, Faculty of Life Sciences & Medicine, King's College LondonLondon, UK
| | - L Heikal
- Institute of Pharmaceutical Science, Faculty of Life Sciences & Medicine, King's College LondonLondon, UK
| | - E McNeill
- British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe HospitalOxford, UK
| | - K M Channon
- British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe HospitalOxford, UK
| | - P R Brown
- The Randall Division of Cell and Molecular Biophysics, Faculty of Life Sciences & Medicine, King's College LondonLondon, UK
| | - B J Sutton
- The Randall Division of Cell and Molecular Biophysics, Faculty of Life Sciences & Medicine, King's College LondonLondon, UK
| | - J M McDonnell
- The Randall Division of Cell and Molecular Biophysics, Faculty of Life Sciences & Medicine, King's College LondonLondon, UK
| | - M Nandi
- Institute of Pharmaceutical Science, Faculty of Life Sciences & Medicine, King's College LondonLondon, UK
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30
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Abstract
Despite their wide use as therapeutic, diagnostic and detection agents, the limitations of polyclonal and monoclonal antibodies have inspired scientists to design the next generation biomedical agents, so-called antibody mimetics that offer many advantages over conventional antibodies. Antibody mimetics can be constructed by protein-directed evolution or fusion of complementarity-determining regions through intervening framework regions. Substantial progress in exploiting human, butterfly (Pieris brassicae) and bacterial systems to design and select mimetics using display technologies has been made in the past 10 years, and one of these mimetics [Kalbitor® (Dyax)] has made its way to market. Many challenges lie ahead to develop mimetics for various biomedical applications, especially those for which conventional antibodies are ineffective, and this review describes the current characteristics, construction and applications of antibody mimetics compared to animal-sourced antibodies. The possible limitations of mimetics and future perspectives are also discussed.
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Affiliation(s)
- Abdul Rasheed Baloch
- a College of Veterinary Medicine, Northwest A&F University , Yangling , Shaanxi , China
| | - Abdul Wahid Baloch
- b Department of Plant Breeding and Genetics , Sindh Agriculture University , Tandojam , Pakistan , and
| | - Brian J Sutton
- c Randall Division of Cell and Molecular Biophysics, King's College London , London , UK
| | - Xiaoying Zhang
- a College of Veterinary Medicine, Northwest A&F University , Yangling , Shaanxi , China
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31
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Levin M, Davies AM, Liljekvist M, Carlsson F, Gould HJ, Sutton BJ, Ohlin M. Human IgE against the major allergen Bet v 1--defining an epitope with limited cross-reactivity between different PR-10 family proteins. Clin Exp Allergy 2014; 44:288-99. [PMID: 24447087 PMCID: PMC4215112 DOI: 10.1111/cea.12230] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Revised: 09/24/2013] [Accepted: 10/25/2013] [Indexed: 02/05/2023]
Abstract
Background The interaction between IgE and allergen is a key event at the initiation of an allergic response, and its characteristics have substantial effects on the clinical manifestation. Despite this, the molecular details of the interaction between human IgE and the major birch allergen Bet v 1, one of the most potent tree allergens, still remain poorly investigated. Objective To isolate Bet v 1-specific human monoclonal IgE and characterize their interaction with the allergen. Methods Recombinant human IgE were isolated from a combinatorial antibody fragment library and their interaction with Bet v 1 assessed using various immunological assays. The structure of one such IgE in the single-chain fragment variable format was determined using X-ray crystallography. Results We present four novel Bet v 1-specific IgE, for one of which we solve the structure, all with their genetic origin in the IGHV5 germline gene, and demonstrate that they target two non-overlapping epitopes on the surface of Bet v 1, thereby fulfilling the basic criteria for FcεRI cross-linkage. We further define these epitopes and for one epitope pinpoint single amino acid residues important for the interaction with human IgE. This provides a potential explanation, at the molecular level, for the differences in recognition of isoforms of Bet v 1 and other allergens in the PR-10 protein family displayed by IgE targeting this epitope. Finally, we present the first high-resolution structure of a human allergen-specific IgE fragment in the single-chain fragment variable (scFv) format. Conclusions and Clinical Relevance We here display the usefulness of allergen-specific human monoclonal IgE as a tool in studies of the crucial molecular interaction taking place at the initiation of an allergic response. Such studies may aid us in development of better diagnostic tools and guide us in the development of new therapeutic compounds.
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Affiliation(s)
- M Levin
- Department of Immunotechnology, Lund University, Lund, Sweden
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32
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Abstract
The first crystal structure of deglycosylated human IgG4-Fc is reported at 2.7 Å resolution. The asymmetric unit comprises a novel interlocked arrangement of two IgG4-Fc molecules. The CH2 domains are oriented in an “open” arrangement. The structure of the CH2 domain DE loop is altered in the absence of carbohydrate. Crystal packing reveals a hexameric Fc arrangement.
The Fc region of IgG antibodies, important for effector functions such as antibody-dependent cell-mediated cytotoxicity, antibody-dependent cellular phagocytosis and complement activation, contains an oligosaccharide moiety covalently attached to each CH2 domain. The oligosaccharide not only orients the CH2 domains but plays an important role in influencing IgG effector function, and engineering the IgG-Fc oligosaccharide moiety is an important aspect in the design of therapeutic monoclonal IgG antibodies. Recently we reported the crystal structure of glycosylated IgG4-Fc, revealing structural features that could explain the anti-inflammatory biological properties of IgG4 compared with IgG1. We now report the crystal structure of enzymatically deglycosylated IgG4-Fc, derived from human serum, at 2.7 Å resolution. Intermolecular CH2-CH2 domain interactions partially bury the CH2 domain surface that would otherwise be exposed by the absence of oligosaccharide, and two Fc molecules are interlocked in a symmetric, open conformation. The conformation of the CH2 domain DE loop, to which oligosaccharide is attached, is altered in the absence of carbohydrate. Furthermore, the CH2 domain FG loop, important for Fcγ receptor and C1q binding, adopts two different conformations. One loop conformation is unique to IgG4 and would disrupt binding, consistent with IgG4's anti-inflammatory properties. The second is similar to the conserved conformation found in IgG1, suggesting that in contrast to IgG1, the IgG4 CH2 FG loop is dynamic. Finally, crystal packing reveals a hexameric arrangement of IgG4-Fc molecules, providing further clues about the interaction between C1q and IgG.
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Affiliation(s)
- Anna M Davies
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom; Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom.
| | - Roy Jefferis
- University of Birmingham, College of Medical & Dental Sciences, School of Immunity & Infection, Edgbaston, Birmingham B15 2TT, United Kingdom
| | - Brian J Sutton
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, London SE1 1UL, United Kingdom; Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom.
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33
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Drinkwater N, Cossins B, Keeble AH, Wright M, Cain K, Hailu H, Oxbrow A, Delgado J, Shuttleworth LK, Kao MWP, McDonnell JM, Beavil AJ, Henry AJ, Sutton BJ. Human immunoglobulin E flexes between acutely bent and extended conformations. Nat Struct Mol Biol 2014; 21:397-404. [PMID: 24632569 PMCID: PMC3977038 DOI: 10.1038/nsmb.2795] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Accepted: 02/13/2014] [Indexed: 11/17/2022]
Abstract
Crystallographic and solution studies have shown that IgE molecules are acutely bent in their Fc region. Crystal structures reveal the Cɛ2 domain pair folded back onto the Cɛ3-Cɛ4 domains, but is the molecule exclusively bent or can the Cɛ2 domains adopt extended conformations and even 'flip' from one side of the molecule to the other? We report the crystal structure of IgE-Fc captured in a fully extended, symmetrical conformation and show by molecular dynamics, calorimetry, stopped-flow kinetic, surface plasmon resonance (SPR) and Förster resonance energy transfer (FRET) analyses that the antibody can indeed adopt such extended conformations in solution. This diversity of conformational states available to IgE-Fc offers a new perspective on IgE function in allergen recognition, as part of the B-cell receptor and as a therapeutic target in allergic disease.
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Affiliation(s)
- Nyssa Drinkwater
- King’s College London, Randall Division of Cell and Molecular Biophysics, New Hunt’s House, Guy’s Campus, London, SE1 1UL, UK
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, New Hunt’s House, Guy’s Campus, London, SE1 1UL, UK
| | | | - Anthony H Keeble
- King’s College London, Randall Division of Cell and Molecular Biophysics, New Hunt’s House, Guy’s Campus, London, SE1 1UL, UK
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, New Hunt’s House, Guy’s Campus, London, SE1 1UL, UK
| | | | | | | | | | | | | | - Michael W-P Kao
- King’s College London, Randall Division of Cell and Molecular Biophysics, New Hunt’s House, Guy’s Campus, London, SE1 1UL, UK
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, New Hunt’s House, Guy’s Campus, London, SE1 1UL, UK
| | - James M McDonnell
- King’s College London, Randall Division of Cell and Molecular Biophysics, New Hunt’s House, Guy’s Campus, London, SE1 1UL, UK
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, New Hunt’s House, Guy’s Campus, London, SE1 1UL, UK
| | - Andrew J Beavil
- King’s College London, Randall Division of Cell and Molecular Biophysics, New Hunt’s House, Guy’s Campus, London, SE1 1UL, UK
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, New Hunt’s House, Guy’s Campus, London, SE1 1UL, UK
| | | | - Brian J Sutton
- King’s College London, Randall Division of Cell and Molecular Biophysics, New Hunt’s House, Guy’s Campus, London, SE1 1UL, UK
- Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, New Hunt’s House, Guy’s Campus, London, SE1 1UL, UK
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34
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Dhaliwal B, Pang MOY, Yuan D, Beavil AJ, Sutton BJ. A range of Cℇ3-Cℇ4 interdomain angles in IgE Fc accommodate binding to its receptor CD23. Acta Crystallogr F Struct Biol Commun 2014; 70:305-9. [PMID: 24598915 PMCID: PMC3944690 DOI: 10.1107/s2053230x14003355] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2014] [Accepted: 02/14/2014] [Indexed: 05/20/2024] Open
Abstract
The antibody IgE plays a central role in allergic disease, functioning principally through two cell-surface receptors: FcℇRI and CD23. FcℇRI on mast cells and basophils mediates the immediate hypersensitivity response, whilst the interaction of IgE with CD23 on B cells regulates IgE production. Crystal structures of the lectin-like `head' domain of CD23 alone and bound to a subfragment of IgE consisting of the dimer of Cℇ3 and Cℇ4 domains (Fcℇ3-4) have recently been determined, revealing flexibility in the IgE-binding site of CD23. Here, a new crystal form of the CD23-Fcℇ3-4 complex with different molecular-packing constraints is reported, which together with the earlier results demonstrates that conformational variability at the interface extends additionally to the IgE Fc and the quaternary structure of its domains.
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Affiliation(s)
- Balvinder Dhaliwal
- Randall Division of Cell and Molecular Biophysics, King’s College London, New Hunt’s House, Guy’s Campus, London SE1 1UL, England
| | - Marie O. Y. Pang
- Randall Division of Cell and Molecular Biophysics, King’s College London, New Hunt’s House, Guy’s Campus, London SE1 1UL, England
| | - Daopeng Yuan
- Randall Division of Cell and Molecular Biophysics, King’s College London, New Hunt’s House, Guy’s Campus, London SE1 1UL, England
| | - Andrew J. Beavil
- Randall Division of Cell and Molecular Biophysics, King’s College London, New Hunt’s House, Guy’s Campus, London SE1 1UL, England
| | - Brian J. Sutton
- Randall Division of Cell and Molecular Biophysics, King’s College London, New Hunt’s House, Guy’s Campus, London SE1 1UL, England
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35
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Godlewska M, Góra M, Buckle AM, Porebski BT, Kemp EH, Sutton BJ, Czarnocka B, Banga JP. A redundant role of human thyroid peroxidase propeptide for cellular, enzymatic, and immunological activity. Thyroid 2014; 24:371-82. [PMID: 23668778 PMCID: PMC3926150 DOI: 10.1089/thy.2013.0127] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND Thyroid peroxidase (TPO) is a dimeric membrane-bound enzyme of thyroid follicular cells, responsible for thyroid hormone biosynthesis. TPO is also a common target antigen in autoimmune thyroid disease (AITD). With two active sites, TPO is an unusual enzyme, and thus there is much interest in understanding its structure and role in AITD. Homology modeling has shown TPO to be composed of different structural modules, as well as a propeptide sequence. During the course of studies to obtain homogeneous preparations of recombinant TPO for structural studies, we investigated the role of the large propeptide sequence in TPO. METHODS An engineered recombinant human TPO preparation expressed in Chinese hamster ovary (CHO) cells lacking the propeptide (TPOΔpro; amino acid residues 21-108) was characterized and its properties compared to wild-type TPO. Plasma membrane localization was determined by cell surface protein biotinylation, and biochemical studies were performed to evaluate enzymatic activity and the effect of deglycosylation. Immunological investigations using autoantibodies from AITD patients and other epitope-specific antibodies that recognize conformational determinants on TPO were evaluated for binding to TPOΔpro by flow cytometry, immunocytochemistry, and capture enzyme-linked immunosorbent assay. Molecular modeling and dynamics simulation of TPOΔpro comprising a dimer of myeloperoxidase-like domains was performed in order to investigate the impact of propeptide removal and the role of glycosylation. RESULTS The TPOΔpro was expressed on the cell surface at comparable levels to wild-type TPO. The TPOΔpro was enzymatically active and recognized by patients' autoantibodies and a panel of epitope-specific antibodies, confirming structural integrity of the two major conformational determinants recognized by autoantibodies. Faithful intracellular trafficking and N-glycosylation of TPOΔpro was also maintained. Molecular modeling and dynamics simulations were consistent with these observations. CONCLUSIONS Our results point to a redundant role for the propeptide sequence in TPO. The successful expression of TPOΔpro in a membrane-anchored, enzymatically active form that is insensitive to intramolecular proteolysis, and importantly is recognized by patients' autoantibodies, is a key advance for purification of substantial quantities of homogeneous preparation of TPO for crystallization, structural, and immunological studies.
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Affiliation(s)
- Marlena Godlewska
- Department of Biochemistry and Molecular Biology, Medical Center of Postgraduate Education, Warsaw, Poland
| | - Monika Góra
- Department of Genetics, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - Ashley M. Buckle
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Monash University, Clayton, Australia
| | - Benjamin T. Porebski
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Monash University, Clayton, Australia
| | - E. Helen Kemp
- Department of Human Metabolism, School of Medicine, University of Sheffield, Sheffield, United Kingdom
| | - Brian J. Sutton
- Randall Division of Cell & Molecular Biophysics, King's College London, London, United Kingdom
| | - Barbara Czarnocka
- Department of Biochemistry and Molecular Biology, Medical Center of Postgraduate Education, Warsaw, Poland
| | - J. Paul Banga
- Division of Diabetes and Nutritional Sciences, School of Medicine, King's College London, London, United Kingdom
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36
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Affiliation(s)
- Brian J Sutton
- Randall Division of Cell & Molecular Biophysics and the Medical Research Council & Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, London, UK
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Rispens T, Davies AM, Ooijevaar-de Heer P, Absalah S, Bende O, Sutton BJ, Vidarsson G, Aalberse RC. Dynamics of inter-heavy chain interactions in human immunoglobulin G (IgG) subclasses studied by kinetic Fab arm exchange. J Biol Chem 2014; 289:6098-109. [PMID: 24425871 PMCID: PMC3937676 DOI: 10.1074/jbc.m113.541813] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interdomain interactions between the CH3 domains of antibody heavy chains are the first step in antibody assembly and are of prime importance for maintaining the native structure of IgG. For human IgG4 it was shown that CH3-CH3 interactions are weak, resulting in the potential for half-molecule exchange (“Fab arm exchange”). Here we systematically investigated non-covalent interchain interactions for CH3 domains in the other human subclasses, including polymorphisms (allotypes), using real-time monitoring of Fab arm exchange with a FRET-based kinetic assay. We identified structural variation between human IgG subclasses and allotypes at three amino acid positions (Lys/Asn-392, Val/Met-397, Lys/Arg-409) to alter the strength of inter-domain interactions by >6 orders of magnitude. Each substitution affected the interactions independent from the other substitutions in terms of affinity, but the enthalpic and entropic contributions were non-additive, suggesting a complex interplay. Allotypic variation in IgG3 resulted in widely different CH3 interaction strengths that were even weaker for IgG3 than for IgG4 in the case of allotype G3m(c3c5*/6,24*), whereas G3m(s*/15*) was equally stable to IgG1. These interactions are sufficiently strong to maintain the structural integrity of IgG1 during its normal life span; for IgG2 and IgG3 the inter-heavy chain disulfide bonds are essential to prevent half-molecule dissociation, whereas the labile hinge disulfide bonds favor half-molecule exchange in vivo for IgG4.
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Affiliation(s)
- Theo Rispens
- From Sanquin Research, 1066 CX Amsterdam, The Netherlands, and Landsteiner Laboratory, Academic Medical Centre, University of Amsterdam, 1105 AZ, The Netherlands
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Abstract
The neonatal Fc receptor (FcRn) mediates the transfer of IgG and albumin, also protects them from catabolism. This study characterized the expression of FcRn in different organs of neonatal and pubertal rats by reverse transcription-PCR (RT-PCR) and immunohistochemistry, demonstrates that FcRn is expressed in liver, kidney, intestine, heart, lung, spleen, skin and skeletal muscles at varying levels post-gestation from d 1 to d 63. This finding is contrary to previous studies claiming that FcRn is undetectable in most tissues after weaning. Lungs were the predominant organs for FcRn expression, whereas skin, liver and intestine are considerably less expressed organs. The expression of FcRn fluctuated in all the organs tested, and with a higher frequency before weaning compared to puberty. These findings may provide clues for the better understanding of FcRn function, and are important for determining the dosage levels for IgG and the constant region fragment (Fc)-containing therapeutic proteins whose half-life is regulated by FcRn.
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Affiliation(s)
- Zehua Tian
- College of Veterinary Medicine, Northwest A&F University , Yangling, Shaanxi , PR China
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39
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Davies AM, Rispens T, Ooijevaar-de Heer P, Gould HJ, Jefferis R, Aalberse RC, Sutton BJ. Structural determinants of unique properties of human IgG4-Fc. J Mol Biol 2013; 426:630-44. [PMID: 24211234 PMCID: PMC3905167 DOI: 10.1016/j.jmb.2013.10.039] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Revised: 10/19/2013] [Accepted: 10/29/2013] [Indexed: 12/24/2022]
Abstract
Human IgG4, normally the least abundant of the four subclasses of IgG in serum, displays a number of unique biological properties. It can undergo heavy-chain exchange, also known as Fab-arm exchange, leading to the formation of monovalent but bispecific antibodies, and it interacts poorly with FcγRII and FcγRIII, and complement. These properties render IgG4 relatively “non-inflammatory” and have made it a suitable format for therapeutic monoclonal antibody production. However, IgG4 is also known to undergo Fc-mediated aggregation and has been implicated in auto-immune disease pathology. We report here the high-resolution crystal structures, at 1.9 and 2.35 Å, respectively, of human recombinant and serum-derived IgG4-Fc. These structures reveal conformational variability at the CH3–CH3 interface that may promote Fab-arm exchange, and a unique conformation for the FG loop in the CH2 domain that would explain the poor FcγRII, FcγRIII and C1q binding properties of IgG4 compared with IgG1 and -3. In contrast to other IgG subclasses, this unique conformation folds the FG loop away from the CH2 domain, precluding any interaction with the lower hinge region, which may further facilitate Fab-arm exchange by destabilisation of the hinge. The crystals of IgG4-Fc also display Fc–Fc packing contacts with very extensive interaction surfaces, involving both a consensus binding site in IgG-Fc at the CH2–CH3 interface and known hydrophobic aggregation motifs. These Fc–Fc interactions are compatible with intact IgG4 molecules and may provide a model for the formation of aggregates of IgG4 that can cause disease pathology in the absence of antigen. The first high-resolution crystal structures of IgG4-Fc have been solved. Arg409 adopts two conformations, each with a different effect on the CH3–CH3 interface. Crystal packing analysis reveals a novel Fc–Fc interface. The CH2 domain FG loop adopts a unique conformation, affecting FcγR and C1q binding. The IgG4-Fc crystal structures explain unique biological properties of IgG4.
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Affiliation(s)
- Anna M Davies
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, United Kingdom; Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London SE1 9RT, United Kingdom.
| | - Theo Rispens
- Sanquin Research, Amsterdam 1066 CX, The Netherlands; Academic Medical Centre Landsteiner Laboratory, University of Amsterdam, Amsterdam 1066 CX, The Netherlands
| | - Pleuni Ooijevaar-de Heer
- Sanquin Research, Amsterdam 1066 CX, The Netherlands; Academic Medical Centre Landsteiner Laboratory, University of Amsterdam, Amsterdam 1066 CX, The Netherlands
| | - Hannah J Gould
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, United Kingdom; Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London SE1 9RT, United Kingdom
| | - Roy Jefferis
- College of Medical and Dental Sciences, School of Immunity and Infection, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
| | - Rob C Aalberse
- Sanquin Research, Amsterdam 1066 CX, The Netherlands; Academic Medical Centre Landsteiner Laboratory, University of Amsterdam, Amsterdam 1066 CX, The Netherlands
| | - Brian J Sutton
- Randall Division of Cell and Molecular Biophysics, King's College London, London SE1 1UL, United Kingdom; Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, London SE1 9RT, United Kingdom.
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Davies AM, Rispens T, Heer POD, Gould HJ, Jefferis R, Aalberse RC, Sutton BJ. Unique structural features of human IgG4 Fc. Acta Crystallogr A 2013. [DOI: 10.1107/s0108767313097006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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41
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Drinkwater N, Cossins B, Keeble AH, Wright M, McDonnell JM, Beavil AJ, Henry AJ, Sutton BJ. Human IgE flips between two acutely bent structures viaan ensemble of extended conformations. Acta Crystallogr A 2013. [DOI: 10.1107/s010876731309702x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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42
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Dhaliwal B, Pang MO, Yuan D, Yahya N, Fabiane SM, McDonnell JM, Gould HJ, Beavil AJ, Sutton BJ. Conformational plasticity at the IgE-binding site of the B-cell receptor CD23. Mol Immunol 2013; 56:693-7. [PMID: 23933509 PMCID: PMC3807792 DOI: 10.1016/j.molimm.2013.07.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 07/08/2013] [Indexed: 11/17/2022]
Abstract
The IgE antibody plays a central role in allergic disease. Binding of IgE to the B-cell receptor CD23 regulates IgE synthesis. Seven crystal forms of the IgE-binding head domain of CD23 have been analyzed and compared. The thirty-five independent structures reveal conformational plasticity in two IgE-binding loops.
IgE antibodies play a central role in allergic disease. They recognize allergens via their Fab regions, whilst their effector functions are controlled through interactions of the Fc region with two principal cell surface receptors, FcɛRI and CD23. Crosslinking of FcɛRI-bound IgE on mast cells and basophils by allergen initiates an immediate inflammatory response, while the interaction of IgE with CD23 on B-cells regulates IgE production. We have determined the structures of the C-type lectin “head” domain of CD23 from seven crystal forms. The thirty-five independent structures reveal extensive conformational plasticity in two loops that are critical for IgE binding.
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MESH Headings
- B-Lymphocytes/immunology
- B-Lymphocytes/metabolism
- Binding Sites/immunology
- Crystallography, X-Ray
- Humans
- Immunoglobulin E/chemistry
- Immunoglobulin E/immunology
- Immunoglobulin E/metabolism
- Models, Molecular
- Protein Binding/immunology
- Protein Conformation
- Protein Structure, Secondary
- Protein Structure, Tertiary
- Receptors, Antigen, B-Cell/chemistry
- Receptors, Antigen, B-Cell/immunology
- Receptors, Antigen, B-Cell/metabolism
- Receptors, IgE/chemistry
- Receptors, IgE/immunology
- Receptors, IgE/metabolism
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Affiliation(s)
- Balvinder Dhaliwal
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, Guy's Campus, London SE1 1UL, UK
- MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
- Corresponding author at: King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, Guy's Campus, London SE1 1UL, UK. Tel.: +44 020 7848 6422; fax: +44 020 7848 6435.
| | - Marie O.Y. Pang
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, Guy's Campus, London SE1 1UL, UK
- MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | - Daopeng Yuan
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, Guy's Campus, London SE1 1UL, UK
- MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | - Norhakim Yahya
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, Guy's Campus, London SE1 1UL, UK
- MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | - Stella M. Fabiane
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, Guy's Campus, London SE1 1UL, UK
- MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | - James M. McDonnell
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, Guy's Campus, London SE1 1UL, UK
- MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | - Hannah J. Gould
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, Guy's Campus, London SE1 1UL, UK
- MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | - Andrew J. Beavil
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, Guy's Campus, London SE1 1UL, UK
- MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
| | - Brian J. Sutton
- King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, Guy's Campus, London SE1 1UL, UK
- MRC & Asthma UK Centre in Allergic Mechanisms of Asthma, London, UK
- Corresponding author at: King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, Guy's Campus, London SE1 1UL, UK. Tel.: +44 020 7848 6423; fax: +44 020 7848 6410.
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Yuan D, Keeble AH, Hibbert RG, Fabiane S, Gould HJ, McDonnell JM, Beavil AJ, Sutton BJ, Dhaliwal B. Ca2+-dependent structural changes in the B-cell receptor CD23 increase its affinity for human immunoglobulin E. J Biol Chem 2013; 288:21667-77. [PMID: 23775083 PMCID: PMC3724626 DOI: 10.1074/jbc.m113.480657] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Immunoglobulin E (IgE) antibodies play a fundamental role in allergic disease and are a target for therapeutic intervention. IgE functions principally through two receptors, FcϵRI and CD23 (FcϵRII). Minute amounts of allergen trigger mast cell or basophil degranulation by cross-linking IgE-bound FcϵRI, leading to an inflammatory response. The interaction between IgE and CD23 on B-cells regulates IgE synthesis. CD23 is unique among Ig receptors in that it belongs to the C-type (calcium-dependent) lectin-like superfamily. Although the interaction of CD23 with IgE is carbohydrate-independent, calcium has been reported to increase the affinity for IgE, but the structural basis for this activity has previously been unknown. We have determined the crystal structures of the human lectin-like head domain of CD23 in its Ca2+-free and Ca2+-bound forms, as well as the crystal structure of the Ca2+-bound head domain of CD23 in complex with a subfragment of IgE-Fc consisting of the dimer of Cϵ3 and Cϵ4 domains (Fcϵ3-4). Together with site-directed mutagenesis, the crystal structures of four Ca2+ ligand mutants, isothermal titration calorimetry, surface plasmon resonance, and stopped-flow analysis, we demonstrate that Ca2+ binds at the principal and evolutionarily conserved binding site in CD23. Ca2+ binding drives Pro-250, at the base of an IgE-binding loop (loop 4), from the trans to the cis configuration with a concomitant conformational change and ordering of residues in the loop. These Ca2+-induced structural changes in CD23 lead to additional interactions with IgE, a more entropically favorable interaction, and a 30-fold increase in affinity of a single head domain of CD23 for IgE. Taken together, these results suggest that binding of Ca2+ brings an extra degree of modulation to CD23 function.
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Affiliation(s)
- Daopeng Yuan
- King's College London and the Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, Randall Division of Cell and Molecular Biophysics, Guy's Campus, London, SE1 1UL, United Kingdom
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44
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Davies AM, Rispens T, den Bleker TH, McDonnell JM, Gould HJ, Aalberse RC, Sutton BJ. Crystal structure of the human IgG4 C(H)3 dimer reveals the role of Arg409 in the mechanism of Fab-arm exchange. Mol Immunol 2012; 54:1-7. [PMID: 23164605 DOI: 10.1016/j.molimm.2012.10.029] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2012] [Revised: 10/16/2012] [Accepted: 10/18/2012] [Indexed: 12/20/2022]
Abstract
Antibodies of the human IgG4 subclass uniquely undergo a process of Fab-arm exchange in which the heavy-chains of antibodies of different specificities can dissociate and then recombine. The mechanism by which the resulting functionally monovalent but bi-specific antibodies are formed is not only key to understanding their biological role, but is also important for the design of therapeutic monoclonal antibodies. Both the hinge region and the C(H)3 domain interface are known to be involved, and of the residues that differ between human IgG1 and IgG4 in C(H)3, residue 409, the only difference at the interface itself, has been implicated. We report the high resolution (1.8Å) structure of the C(H)3 domain dimer of IgG4, and find that Arg409 in IgG4, when compared with Lys409 observed in high resolution IgG1 structures, disrupts a network of water-mediated hydrogen bonding that is conserved in IgG1. Other conformational differences were detected that are a consequence of the presence of Arg409, such as a widening of the separation between residues Asn390 in one domain and Ser 400 in the other, which opens up a groove at the edge of the interface in IgG4 compared with IgG1. The effect of all these differences on the C(H)3 interface, doubled as a result of the interface's two-fold symmetry, is weakening of the inter-domain interaction in IgG4 compared with IgG1. This suggests a mechanism by which Arg409 weakens the C(H)3 interface in IgG4, predisposing this human antibody subclass to Fab-arm exchange.
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Affiliation(s)
- Anna M Davies
- King's College London, Randall Division of Cell and Molecular Biophysics, London, SE1 1UL, United Kingdom
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Abstract
Aggressive angiomyxoma is a rare mesenchymal tumor that most commonly arises in the vulvovaginal region, perineum, and pelvis of women. The term aggressive emphasizes the often infiltrative nature of the tumor and its frequent association with local recurrence. Patients often present with nonspecific symptoms which are frequently misdiagnosed with more common entities, such as a Bartholin cyst, lipoma, or hernia. Histologic examination reveals a hypocellular and highly vascular tumor with a myxoid stroma containing cytologically bland stellate or spindled cells. The tumor cells are characteristically positive for estrogen and progesterone receptors, suggesting a hormonal role in the development of the tumor. Chromosomal translocation of the 12q13-15 band involving the HMGA2 gene has been described. Surgical excision is the treatment of choice, although treatment with gonadotropin-releasing hormone agonists is an emerging therapy. Metastases are exceedingly rare, and overall, the prognosis is good.
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Affiliation(s)
- Brian J Sutton
- Department of Pathology, Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157, USA
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46
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Borthakur S, Hibbert RG, Pang MOY, Yahya N, Bax HJ, Kao MW, Cooper AM, Beavil AJ, Sutton BJ, Gould HJ, McDonnell JM. Mapping of the CD23 binding site on immunoglobulin E (IgE) and allosteric control of the IgE-Fc epsilonRI interaction. J Biol Chem 2012; 287:31457-61. [PMID: 22815482 PMCID: PMC3438978 DOI: 10.1074/jbc.c112.397059] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
IgE, the antibody that mediates allergic responses, acts as part of a self-regulating protein network. Its unique effector functions are controlled through interactions of its Fc region with two cellular receptors, FcεRI on mast cells and basophils and CD23 on B cells. IgE cross-linked by allergen triggers mast cell activation via FcεRI, whereas IgE-CD23 interactions control IgE expression levels. We have determined the CD23 binding site on IgE, using a combination of NMR chemical shift mapping and site-directed mutagenesis. We show that the CD23 and FcεRI interaction sites are at opposite ends of the Cε3 domain of IgE, but that receptor binding is mutually inhibitory, mediated by an allosteric mechanism. This prevents CD23-mediated cross-linking of IgE bound to FcεRI on mast cells and resulting antigen-independent anaphylaxis. The mutually inhibitory nature of receptor binding provides a degree of autonomy for the individual activities mediated by IgE-FcεRI and IgE-CD23 interactions.
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Affiliation(s)
- Susmita Borthakur
- Randall Division of Cell and Molecular Biophysics, King's College London, Guy's Campus, London SE1 1UL, United Kingdom
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Hunt J, Keeble AH, Dale RE, Corbett MK, Beavil RL, Levitt J, Swann MJ, Suhling K, Ameer-Beg S, Sutton BJ, Beavil AJ. A fluorescent biosensor reveals conformational changes in human immunoglobulin E Fc: implications for mechanisms of receptor binding, inhibition, and allergen recognition. J Biol Chem 2012; 287:17459-17470. [PMID: 22442150 PMCID: PMC3366799 DOI: 10.1074/jbc.m111.331967] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Revised: 03/08/2012] [Indexed: 11/06/2022] Open
Abstract
IgE binding to its high affinity receptor FcεRI on mast cells and basophils is a key step in the mechanism of allergic disease and a target for therapeutic intervention. Early indications that IgE adopts a bent structure in solution have been confirmed by recent x-ray crystallographic studies of IgEFc, which further showed that the bend, contrary to expectation, is enhanced in the crystal structure of the complex with receptor. To investigate the structure of IgEFc and its conformational changes that accompany receptor binding in solution, we created a Förster resonance energy transfer (FRET) biosensor using biologically encoded fluorescent proteins fused to the N- and C-terminal IgEFc domains (Cε2 and Cε4, respectively) together with the theoretical basis for quantitating its behavior. This revealed not only that the IgEFc exists in a bent conformation in solution but also that the bend is indeed enhanced upon FcεRI binding. No change in the degree of bending was seen upon binding to the B cell receptor for IgE, CD23 (FcεRII), but in contrast, binding of the anti-IgE therapeutic antibody omalizumab decreases the extent of the bend, implying a conformational change that opposes FcεRI engagement. HomoFRET measurements further revealed that the (Cε2)(2) and (Cε4)(2) domain pairs behave as rigid units flanking the conformational change in the Cε3 domains. Finally, modeling of the accessible conformations of the two Fab arms in FcεRI-bound IgE revealed a mutual exclusion not seen in IgG and Fab orientations relative to the membrane that may predispose receptor-bound IgE to cross-linking by allergens.
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Affiliation(s)
- James Hunt
- MRC and Asthma UK Centre in Allergic Mechanisms of Asthma, Guy's Hospital Campus, London SE1 1UL; The Randall Division of Cell and Molecular Biophysics, Guy's Hospital Campus, London SE1 1UL; The Division of Asthma Allergy and Lung Biology, King's College London, Guy's Hospital Campus, London SE1 1UL
| | - Anthony H Keeble
- MRC and Asthma UK Centre in Allergic Mechanisms of Asthma, Guy's Hospital Campus, London SE1 1UL; The Randall Division of Cell and Molecular Biophysics, Guy's Hospital Campus, London SE1 1UL; The Division of Asthma Allergy and Lung Biology, King's College London, Guy's Hospital Campus, London SE1 1UL
| | - Robert E Dale
- The Randall Division of Cell and Molecular Biophysics, Guy's Hospital Campus, London SE1 1UL
| | - Melissa K Corbett
- The Randall Division of Cell and Molecular Biophysics, Guy's Hospital Campus, London SE1 1UL
| | - Rebecca L Beavil
- MRC and Asthma UK Centre in Allergic Mechanisms of Asthma, Guy's Hospital Campus, London SE1 1UL; The Randall Division of Cell and Molecular Biophysics, Guy's Hospital Campus, London SE1 1UL; The Division of Asthma Allergy and Lung Biology, King's College London, Guy's Hospital Campus, London SE1 1UL
| | - James Levitt
- The Department of Physics, King's College London, Strand, London WC2R 2LS
| | - Marcus J Swann
- Farfield Group Limited, Voyager, Chicago Avenue, Manchester Airport, Manchester, M90 3DQ, United Kingdom
| | - Klaus Suhling
- The Department of Physics, King's College London, Strand, London WC2R 2LS
| | - Simon Ameer-Beg
- The Randall Division of Cell and Molecular Biophysics, Guy's Hospital Campus, London SE1 1UL
| | - Brian J Sutton
- MRC and Asthma UK Centre in Allergic Mechanisms of Asthma, Guy's Hospital Campus, London SE1 1UL; The Randall Division of Cell and Molecular Biophysics, Guy's Hospital Campus, London SE1 1UL
| | - Andrew J Beavil
- MRC and Asthma UK Centre in Allergic Mechanisms of Asthma, Guy's Hospital Campus, London SE1 1UL; The Randall Division of Cell and Molecular Biophysics, Guy's Hospital Campus, London SE1 1UL; The Division of Asthma Allergy and Lung Biology, King's College London, Guy's Hospital Campus, London SE1 1UL.
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48
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Offermann DA, McKendrick JE, Sejberg JJP, Mo B, Holdom MD, Helm BA, Leatherbarrow RJ, Beavil AJ, Sutton BJ, Spivey AC. Synthesis and incorporation into cyclic peptides of tolan amino acids and their hydrogenated congeners: construction of an array of A-B-loop mimetics of the Cε3 domain of human IgE. J Org Chem 2012; 77:3197-214. [PMID: 22397517 DOI: 10.1021/jo202604q] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The disruption of the human immunolobulin E-high affinity receptor I (IgE-FcεRI) protein-protein interaction (PPI) is a validated strategy for the development of anti asthma therapeutics. Here, we describe the synthesis of an array of conformationally constrained cyclic peptides based on an epitope of the A-B loop within the Cε3 domain of IgE. The peptides contain various tolan (i.e., 1,2-biarylethyne) amino acids and their fully and partially hydrogenated congeners as conformational constraints. Modest antagonist activity (IC(50) ∼660 μM) is displayed by the peptide containing a 2,2'-tolan, which is the one predicted by molecular modeling to best mimic the conformation of the native A-B loop epitope in IgE.
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Affiliation(s)
- Daniel A Offermann
- Department of Chemistry, South Kensington Campus, Imperial College, London SW7 2AZ, UK
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Cooper AM, Hobson PS, Jutton MR, Kao MW, Drung B, Schmidt B, Fear DJ, Beavil AJ, McDonnell JM, Sutton BJ, Gould HJ. Soluble CD23 controls IgE synthesis and homeostasis in human B cells. J Immunol 2012; 188:3199-207. [PMID: 22393152 DOI: 10.4049/jimmunol.1102689] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
CD23, the low-affinity receptor for IgE, exists in membrane and soluble forms. Soluble CD23 (sCD23) fragments are released from membrane (m)CD23 by the endogenous metalloprotease a disintegrin and metalloprotease 10. When purified tonsil B cells are incubated with IL-4 and anti-CD40 to induce class switching to IgE in vitro, mCD23 is upregulated, and sCD23 accumulates in the medium prior to IgE synthesis. We have uncoupled the effects of mCD23 cleavage and accumulation of sCD23 on IgE synthesis in this system. We show that small interfering RNA inhibition of CD23 synthesis or inhibition of mCD23 cleavage by an a disintegrin and metalloprotease 10 inhibitor, GI254023X, suppresses IL-4 and anti-CD40-stimulated IgE synthesis. Addition of a recombinant trimeric sCD23 enhances IgE synthesis in this system. This occurs even when endogenous mCD23 is protected from cleavage by GI254023X, indicating that IgE synthesis is positively controlled by sCD23. We show that recombinant trimeric sCD23 binds to cells coexpressing mIgE and mCD21 and caps these proteins on the B cell membrane. Upregulation of IgE by sCD23 occurs after class-switch recombination, and its effects are isotype-specific. These results suggest that mIgE and mCD21 cooperate in the sCD23-mediated positive regulation of IgE synthesis on cells committed to IgE synthesis. Feedback regulation may occur when the concentration of secreted IgE becomes great enough to allow binding to mCD23, thus preventing further release of sCD23. We interpret these results with the aid of a model for the upregulation of IgE by sCD23.
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Affiliation(s)
- Alison M Cooper
- Medical Research Council and Asthma UK Centre in Allergic Mechanisms of Asthma, King's College London, Guy's Hospital, London SE1 9RT, UK
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Carr JL, Sejberg JJP, Saab F, Holdom MD, Davies AM, White AJP, Leatherbarrow RJ, Beavil AJ, Sutton BJ, Lindell SD, Spivey AC. Synthesis of the C19 methyl ether of aspercyclide A via germyl-Stille macrocyclisation and ELISA evaluation of both enantiomers following optical resolution. Org Biomol Chem 2011; 9:6814-24. [PMID: 21845261 DOI: 10.1039/c1ob05862b] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Aspercyclide A (1) is a biaryl ether containing 11-membered macrocyclic natural product antagonist of the human IgE-FcεRI protein-protein interaction (PPI); a key interaction in the signal transduction pathway for allergic disorders such as asthma. Herein we report a novel approach to the synthesis of the C19 methyl ether of aspercyclide A, employing a Pd(0)-catalysed, fluorous-tagged alkenylgermane/arylbromide macrocyclisation (germyl-Stille reaction) as the key step, and evaluation of both enantiomers of this compound via ELISA following optical resolution by CSP-HPLC. A crystal structure for germyl hydride 27 is also reported.
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Affiliation(s)
- James L Carr
- Department of Chemistry, South Kensington campus, Imperial College, London, UK SW7 2AZ
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