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Chuquisana O, Stascheit F, Keller CW, Pučić-Baković M, Patenaude AM, Lauc G, Tzartos S, Wiendl H, Willcox N, Meisel A, Lünemann JD. Functional Signature of LRP4 Antibodies in Myasthenia Gravis. NEUROLOGY(R) NEUROIMMUNOLOGY & NEUROINFLAMMATION 2024; 11:e200220. [PMID: 38507656 PMCID: PMC10959168 DOI: 10.1212/nxi.0000000000200220] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Accepted: 01/26/2024] [Indexed: 03/22/2024]
Abstract
BACKGROUND AND OBJECTIVES Antibodies (Abs) specific for the low-density lipoprotein receptor-related protein 4 (LRP4) occur in up to 5% of patients with myasthenia gravis (MG). The objective of this study was to profile LRP4-Ab effector actions. METHODS We evaluated the efficacy of LRP4-specific compared with AChR-specific IgG to induce Ab-dependent cellular phagocytosis (ADCP), Ab-dependent cellular cytotoxicity (ADCC), and Ab-dependent complement deposition (ADCD). Functional features were additionally assessed in an independent AChR-Ab+ MG cohort. Levels of circulating activated complement proteins and frequency of Fc glycovariants were quantified and compared with demographically matched 19 healthy controls. RESULTS Effector actions that required binding of Fc domains to cellular FcRs such as ADCC and ADCP were detectable for both LRP4-specific and AChR-specific Abs. In contrast to AChR-Abs, LRP4-binding Abs showed poor efficacy in inducing complement deposition. Levels of circulating activated complement proteins were not substantially increased in LRP4-Ab-positive MG. Frequency of IgG glycovariants carrying 2 sialic acid residues, indicative for anti-inflammatory IgG activity, was decreased in patients with LRP4-Ab-positive MG. DISCUSSION LRP4-Abs are more effective in inducing cellular FcR-mediated effector mechanisms than Ab-dependent complement activation. Their functional signature is different from AChR-specific Abs.
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Affiliation(s)
- Omar Chuquisana
- From the Department of Neurology with Institute of Translational Neurology (O.C., C.W.K., H.W., J.D.L.), University Hospital Münster; Department of Neurology with Experimental Neurology (F.S., A.M.); Neuroscience Clinical Research Center (F.S., A.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany; Genos Glycoscience Research Laboratory (M.P.-B., A.-M.P., G.L.), Zagreb; Faculty of Pharmacy and Biochemistry (G.L.), University of Zagreb, Croatia; Tzartos NeuroDiagnostics (S.T.); Department of Neurobiology (S.T.), Hellenic Pasteur Institute, Athens, Greece; Nuffield Department of Clinical Neurosciences (N.W.), Weatherall Institute of Molecular Medicine, University of Oxford, United Kingdom; and Center for Stroke Research Berlin (A.G.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany
| | - Frauke Stascheit
- From the Department of Neurology with Institute of Translational Neurology (O.C., C.W.K., H.W., J.D.L.), University Hospital Münster; Department of Neurology with Experimental Neurology (F.S., A.M.); Neuroscience Clinical Research Center (F.S., A.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany; Genos Glycoscience Research Laboratory (M.P.-B., A.-M.P., G.L.), Zagreb; Faculty of Pharmacy and Biochemistry (G.L.), University of Zagreb, Croatia; Tzartos NeuroDiagnostics (S.T.); Department of Neurobiology (S.T.), Hellenic Pasteur Institute, Athens, Greece; Nuffield Department of Clinical Neurosciences (N.W.), Weatherall Institute of Molecular Medicine, University of Oxford, United Kingdom; and Center for Stroke Research Berlin (A.G.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany
| | - Christian W Keller
- From the Department of Neurology with Institute of Translational Neurology (O.C., C.W.K., H.W., J.D.L.), University Hospital Münster; Department of Neurology with Experimental Neurology (F.S., A.M.); Neuroscience Clinical Research Center (F.S., A.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany; Genos Glycoscience Research Laboratory (M.P.-B., A.-M.P., G.L.), Zagreb; Faculty of Pharmacy and Biochemistry (G.L.), University of Zagreb, Croatia; Tzartos NeuroDiagnostics (S.T.); Department of Neurobiology (S.T.), Hellenic Pasteur Institute, Athens, Greece; Nuffield Department of Clinical Neurosciences (N.W.), Weatherall Institute of Molecular Medicine, University of Oxford, United Kingdom; and Center for Stroke Research Berlin (A.G.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany
| | - Maja Pučić-Baković
- From the Department of Neurology with Institute of Translational Neurology (O.C., C.W.K., H.W., J.D.L.), University Hospital Münster; Department of Neurology with Experimental Neurology (F.S., A.M.); Neuroscience Clinical Research Center (F.S., A.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany; Genos Glycoscience Research Laboratory (M.P.-B., A.-M.P., G.L.), Zagreb; Faculty of Pharmacy and Biochemistry (G.L.), University of Zagreb, Croatia; Tzartos NeuroDiagnostics (S.T.); Department of Neurobiology (S.T.), Hellenic Pasteur Institute, Athens, Greece; Nuffield Department of Clinical Neurosciences (N.W.), Weatherall Institute of Molecular Medicine, University of Oxford, United Kingdom; and Center for Stroke Research Berlin (A.G.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany
| | - Anne-Marie Patenaude
- From the Department of Neurology with Institute of Translational Neurology (O.C., C.W.K., H.W., J.D.L.), University Hospital Münster; Department of Neurology with Experimental Neurology (F.S., A.M.); Neuroscience Clinical Research Center (F.S., A.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany; Genos Glycoscience Research Laboratory (M.P.-B., A.-M.P., G.L.), Zagreb; Faculty of Pharmacy and Biochemistry (G.L.), University of Zagreb, Croatia; Tzartos NeuroDiagnostics (S.T.); Department of Neurobiology (S.T.), Hellenic Pasteur Institute, Athens, Greece; Nuffield Department of Clinical Neurosciences (N.W.), Weatherall Institute of Molecular Medicine, University of Oxford, United Kingdom; and Center for Stroke Research Berlin (A.G.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany
| | - Gordan Lauc
- From the Department of Neurology with Institute of Translational Neurology (O.C., C.W.K., H.W., J.D.L.), University Hospital Münster; Department of Neurology with Experimental Neurology (F.S., A.M.); Neuroscience Clinical Research Center (F.S., A.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany; Genos Glycoscience Research Laboratory (M.P.-B., A.-M.P., G.L.), Zagreb; Faculty of Pharmacy and Biochemistry (G.L.), University of Zagreb, Croatia; Tzartos NeuroDiagnostics (S.T.); Department of Neurobiology (S.T.), Hellenic Pasteur Institute, Athens, Greece; Nuffield Department of Clinical Neurosciences (N.W.), Weatherall Institute of Molecular Medicine, University of Oxford, United Kingdom; and Center for Stroke Research Berlin (A.G.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany
| | - Socrates Tzartos
- From the Department of Neurology with Institute of Translational Neurology (O.C., C.W.K., H.W., J.D.L.), University Hospital Münster; Department of Neurology with Experimental Neurology (F.S., A.M.); Neuroscience Clinical Research Center (F.S., A.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany; Genos Glycoscience Research Laboratory (M.P.-B., A.-M.P., G.L.), Zagreb; Faculty of Pharmacy and Biochemistry (G.L.), University of Zagreb, Croatia; Tzartos NeuroDiagnostics (S.T.); Department of Neurobiology (S.T.), Hellenic Pasteur Institute, Athens, Greece; Nuffield Department of Clinical Neurosciences (N.W.), Weatherall Institute of Molecular Medicine, University of Oxford, United Kingdom; and Center for Stroke Research Berlin (A.G.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany
| | - Heinz Wiendl
- From the Department of Neurology with Institute of Translational Neurology (O.C., C.W.K., H.W., J.D.L.), University Hospital Münster; Department of Neurology with Experimental Neurology (F.S., A.M.); Neuroscience Clinical Research Center (F.S., A.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany; Genos Glycoscience Research Laboratory (M.P.-B., A.-M.P., G.L.), Zagreb; Faculty of Pharmacy and Biochemistry (G.L.), University of Zagreb, Croatia; Tzartos NeuroDiagnostics (S.T.); Department of Neurobiology (S.T.), Hellenic Pasteur Institute, Athens, Greece; Nuffield Department of Clinical Neurosciences (N.W.), Weatherall Institute of Molecular Medicine, University of Oxford, United Kingdom; and Center for Stroke Research Berlin (A.G.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany
| | - Nick Willcox
- From the Department of Neurology with Institute of Translational Neurology (O.C., C.W.K., H.W., J.D.L.), University Hospital Münster; Department of Neurology with Experimental Neurology (F.S., A.M.); Neuroscience Clinical Research Center (F.S., A.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany; Genos Glycoscience Research Laboratory (M.P.-B., A.-M.P., G.L.), Zagreb; Faculty of Pharmacy and Biochemistry (G.L.), University of Zagreb, Croatia; Tzartos NeuroDiagnostics (S.T.); Department of Neurobiology (S.T.), Hellenic Pasteur Institute, Athens, Greece; Nuffield Department of Clinical Neurosciences (N.W.), Weatherall Institute of Molecular Medicine, University of Oxford, United Kingdom; and Center for Stroke Research Berlin (A.G.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany
| | - Andreas Meisel
- From the Department of Neurology with Institute of Translational Neurology (O.C., C.W.K., H.W., J.D.L.), University Hospital Münster; Department of Neurology with Experimental Neurology (F.S., A.M.); Neuroscience Clinical Research Center (F.S., A.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany; Genos Glycoscience Research Laboratory (M.P.-B., A.-M.P., G.L.), Zagreb; Faculty of Pharmacy and Biochemistry (G.L.), University of Zagreb, Croatia; Tzartos NeuroDiagnostics (S.T.); Department of Neurobiology (S.T.), Hellenic Pasteur Institute, Athens, Greece; Nuffield Department of Clinical Neurosciences (N.W.), Weatherall Institute of Molecular Medicine, University of Oxford, United Kingdom; and Center for Stroke Research Berlin (A.G.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany
| | - Jan D Lünemann
- From the Department of Neurology with Institute of Translational Neurology (O.C., C.W.K., H.W., J.D.L.), University Hospital Münster; Department of Neurology with Experimental Neurology (F.S., A.M.); Neuroscience Clinical Research Center (F.S., A.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany; Genos Glycoscience Research Laboratory (M.P.-B., A.-M.P., G.L.), Zagreb; Faculty of Pharmacy and Biochemistry (G.L.), University of Zagreb, Croatia; Tzartos NeuroDiagnostics (S.T.); Department of Neurobiology (S.T.), Hellenic Pasteur Institute, Athens, Greece; Nuffield Department of Clinical Neurosciences (N.W.), Weatherall Institute of Molecular Medicine, University of Oxford, United Kingdom; and Center for Stroke Research Berlin (A.G.M.), Charité-Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Germany
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Barrantes FJ. Modulation of a rapid neurotransmitter receptor-ion channel by membrane lipids. Front Cell Dev Biol 2024; 11:1328875. [PMID: 38274273 PMCID: PMC10808158 DOI: 10.3389/fcell.2023.1328875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Accepted: 12/26/2023] [Indexed: 01/27/2024] Open
Abstract
Membrane lipids modulate the proteins embedded in the bilayer matrix by two non-exclusive mechanisms: direct or indirect. The latter comprise those effects mediated by the physicochemical state of the membrane bilayer, whereas direct modulation entails the more specific regulatory effects transduced via recognition sites on the target membrane protein. The nicotinic acetylcholine receptor (nAChR), the paradigm member of the pentameric ligand-gated ion channel (pLGIC) superfamily of rapid neurotransmitter receptors, is modulated by both mechanisms. Reciprocally, the nAChR protein exerts influence on its surrounding interstitial lipids. Folding, conformational equilibria, ligand binding, ion permeation, topography, and diffusion of the nAChR are modulated by membrane lipids. The knowledge gained from biophysical studies of this prototypic membrane protein can be applied to other neurotransmitter receptors and most other integral membrane proteins.
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Affiliation(s)
- Francisco J. Barrantes
- Biomedical Research Institute (BIOMED), Catholic University of Argentina (UCA)–National Scientific and Technical Research Council (CONICET), Buenos Aires, Argentina
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3
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San PP, Jacob S. Role of complement in myasthenia gravis. Front Neurol 2023; 14:1277596. [PMID: 37869140 PMCID: PMC10585143 DOI: 10.3389/fneur.2023.1277596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 09/18/2023] [Indexed: 10/24/2023] Open
Abstract
Myasthenia gravis is a prototypic neuroimmune disorder with autoantibodies targeting the acetylcholine receptor complex at the neuromuscular junction. Patients present with mainly ocular muscle weakness and tend to have a generalized muscle weakness later in the clinical course. The weakness can be severe and fatal when bulbar muscles are heavily involved. Acetylcholine receptor antibodies are present in the majority of patients and are of IgG1 and IgG3 subtypes which can activate the complement system. The complement involvement plays a major role in the neuromuscular junction damage and the supporting evidence in the literature is described in this article. Complement therapies were initially studied and approved for paroxysmal nocturnal hemoglobinuria and in the past decade, those have also been studied in myasthenia gravis. The currently available randomized control trial and real-world data on the efficacy and safety of the approved and investigational complement therapies are summarized in this review.
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Affiliation(s)
- Pyae Phyo San
- Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, United Kingdom
| | - Saiju Jacob
- Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham, United Kingdom
- Department of Neurology, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom
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4
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Pham MC, Masi G, Patzina R, Obaid AH, Oxendine SR, Oh S, Payne AS, Nowak RJ, O'Connor KC. Individual myasthenia gravis autoantibody clones can efficiently mediate multiple mechanisms of pathology. Acta Neuropathol 2023; 146:319-336. [PMID: 37344701 PMCID: PMC11380498 DOI: 10.1007/s00401-023-02603-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 06/15/2023] [Accepted: 06/16/2023] [Indexed: 06/23/2023]
Abstract
Serum autoantibodies targeting the nicotinic acetylcholine receptor (AChR) in patients with autoimmune myasthenia gravis (MG) can mediate pathology via three distinct molecular mechanisms: complement activation, receptor blockade, and antigenic modulation. However, it is unclear whether multi-pathogenicity is mediated by individual or multiple autoantibody clones. Using an unbiased B cell culture screening approach, we generated a library of 11 human-derived AChR-specific recombinant monoclonal autoantibodies (mAb) and assessed their binding properties and pathogenic profiles using specialized cell-based assays. Five mAbs activated complement, three blocked α-bungarotoxin binding to the receptor, and seven induced antigenic modulation. Furthermore, two clonally related mAbs derived from one patient were each highly efficient at more than one of these mechanisms, demonstrating that pathogenic mechanisms are not mutually exclusive at the monoclonal level. Using novel Jurkat cell lines that individually express each monomeric AChR subunit (α2βδε), these two mAbs with multi-pathogenic capacity were determined to exclusively bind the α-subunit of AChR, demonstrating an association between mAb specificity and pathogenic capacity. These findings provide new insight into the immunopathology of MG, demonstrating that single autoreactive clones can efficiently mediate multiple modes of pathology. Current therapeutic approaches targeting only one autoantibody-mediated pathogenic mechanism may be evaded by autoantibodies with multifaceted capacity.
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Affiliation(s)
- Minh C Pham
- Department of Immunobiology, Yale University School of Medicine, 300 George Street-Room 353J, New Haven, CT, 06511, USA
| | - Gianvito Masi
- Department of Immunobiology, Yale University School of Medicine, 300 George Street-Room 353J, New Haven, CT, 06511, USA
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06511, USA
| | - Rosa Patzina
- Department of Immunobiology, Yale University School of Medicine, 300 George Street-Room 353J, New Haven, CT, 06511, USA
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06511, USA
| | - Abeer H Obaid
- Department of Immunobiology, Yale University School of Medicine, 300 George Street-Room 353J, New Haven, CT, 06511, USA
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06511, USA
- Institute of Biomedical Studies, Baylor University, Waco, TX, 76706, USA
| | - Seneca R Oxendine
- Department of Immunobiology, Yale University School of Medicine, 300 George Street-Room 353J, New Haven, CT, 06511, USA
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06511, USA
| | - Sangwook Oh
- Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Aimee S Payne
- Department of Dermatology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Richard J Nowak
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06511, USA
| | - Kevin C O'Connor
- Department of Immunobiology, Yale University School of Medicine, 300 George Street-Room 353J, New Haven, CT, 06511, USA.
- Department of Neurology, Yale University School of Medicine, New Haven, CT, 06511, USA.
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Barrantes FJ. Fluorescence microscopy imaging of a neurotransmitter receptor and its cell membrane lipid milieu. Front Mol Biosci 2022; 9:1014659. [PMID: 36518846 PMCID: PMC9743973 DOI: 10.3389/fmolb.2022.1014659] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 11/01/2022] [Indexed: 05/02/2024] Open
Abstract
Hampered by the diffraction phenomenon, as expressed in 1873 by Abbe, applications of optical microscopy to image biological structures were for a long time limited to resolutions above the ∼200 nm barrier and restricted to the observation of stained specimens. The introduction of fluorescence was a game changer, and since its inception it became the gold standard technique in biological microscopy. The plasma membrane is a tenuous envelope of 4 nm-10 nm in thickness surrounding the cell. Because of its highly versatile spectroscopic properties and availability of suitable instrumentation, fluorescence techniques epitomize the current approach to study this delicate structure and its molecular constituents. The wide spectral range covered by fluorescence, intimately linked to the availability of appropriate intrinsic and extrinsic probes, provides the ability to dissect membrane constituents at the molecular scale in the spatial domain. In addition, the time resolution capabilities of fluorescence methods provide complementary high precision for studying the behavior of membrane molecules in the time domain. This review illustrates the value of various fluorescence techniques to extract information on the topography and motion of plasma membrane receptors. To this end I resort to a paradigmatic membrane-bound neurotransmitter receptor, the nicotinic acetylcholine receptor (nAChR). The structural and dynamic picture emerging from studies of this prototypic pentameric ligand-gated ion channel can be extrapolated not only to other members of this superfamily of ion channels but to other membrane-bound proteins. I also briefly discuss the various emerging techniques in the field of biomembrane labeling with new organic chemistry strategies oriented to applications in fluorescence nanoscopy, the form of fluorescence microscopy that is expanding the depth and scope of interrogation of membrane-associated phenomena.
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Affiliation(s)
- Francisco J. Barrantes
- Biomedical Research Institute (BIOMED), Catholic University of Argentina (UCA)–National Scientific and Technical Research Council (CONICET), Buenos Aires, Argentina
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Zouvelou V, Michail M, Belimezi M, Haroniti A, Zisimopoulou P. Characterization of the nicotinic acetylcholine receptor antibodies after an unexpected increase of antibody titer in thymoma associated myasthenia gravis patients. Neuromuscul Disord 2022; 32:847-850. [PMID: 36028368 DOI: 10.1016/j.nmd.2022.08.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 07/25/2022] [Accepted: 08/08/2022] [Indexed: 11/16/2022]
Abstract
Two thymoma-associated myasthenia gravis patients with chronic well-controlled disease but an unexpected increase in anti-nAChR autoantibodies titer are reported. The specificity of anti-nAChR autoantibodies directed against extracellular parts of the receptor was studied in order to investigate the discrepancy between clinical and immunological status. Analysis of the anti-nAChR autoantibodies recognizing the extracellular parts of the nAChR revealed that when the concentration of anti-nAChR autoantibodies titer increased both patients had non-anti-α1 autoantibodies. Since the clinical profile of both patients remained unchanged, the increase of non-anti-α1 autoantibodies did not affect the 2 patients' disease progression. Thus, immunotherapy modification due to an increase of anti-nAChR autoantibodies titer could be erroneous and potentially harmful.
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Affiliation(s)
- Vasiliki Zouvelou
- 1st Department of Neurology, Eginition Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Maria Michail
- Laboratory of Molecular Neurobiology and Immunology, Hellenic Pasteur Institute, Athens, Greece; Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
| | - Maria Belimezi
- Diagnostic Department, Hellenic Pasteur Institute, Athens, Greece
| | - Anna Haroniti
- Laboratory of Molecular Neurobiology and Immunology, Hellenic Pasteur Institute, Athens, Greece
| | - Paraskevi Zisimopoulou
- Laboratory of Molecular Neurobiology and Immunology, Hellenic Pasteur Institute, Athens, Greece.
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Michail M, Zouvelou V, Belimezi M, Haroniti A, Zouridakis M, Zisimopoulou P. Analysis of nAChR Autoantibodies Against Extracellular Epitopes in MG Patients. Front Neurol 2022; 13:858998. [PMID: 35418927 PMCID: PMC8995881 DOI: 10.3389/fneur.2022.858998] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Accepted: 02/28/2022] [Indexed: 01/12/2023] Open
Abstract
Myasthenia gravis (MG) is an autoimmune disorder caused by autoantibodies targeting components of the postsynaptic membrane of the neuromuscular junction (NMJ), leading to neuromuscular transmission deficiency. In the vast majority of patients, these autoantibodies target the nicotinic acetylcholine receptor (nAChR), a heteropentameric ion channel anchored to the postsynaptic membrane of the NMJ. Autoantibodies in patients with MG may target all the subunits of the receptor at both their extracellular and intracellular regions. Here, we combine immunoadsorption with a cell-based assay to examine the specificity of the patients' autoantibodies against the extracellular part of the nAChR. Our results reveal that these autoantibodies can be divided into distinct groups, based on their target, with probably different impacts on disease severity. Although our findings are based on a small sample group of patients, they strongly support that additional analysis of the specificity of the autoantibodies of patients with MG could serve as a valuable tool for the clinicians' decision on the treatment strategy to be followed.
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Affiliation(s)
- Maria Michail
- Laboratory of Molecular Neurobiology and Immunology, Hellenic Pasteur Institute, Athens, Greece.,Department of Biology, National and Kapodistrian University of Athens, Athens, Greece
| | - Vasiliki Zouvelou
- Department of Neurology, Eginition Hospital, National and Kapodistrian University of Athens, Athens, Greece
| | - Maria Belimezi
- Diagnostic Department, Hellenic Pasteur Institute, Athens, Greece
| | - Anna Haroniti
- Laboratory of Molecular Neurobiology and Immunology, Hellenic Pasteur Institute, Athens, Greece
| | - Marios Zouridakis
- Laboratory of Molecular Neurobiology and Immunology, Hellenic Pasteur Institute, Athens, Greece
| | - Paraskevi Zisimopoulou
- Laboratory of Molecular Neurobiology and Immunology, Hellenic Pasteur Institute, Athens, Greece
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Barrantes FJ. Possible implications of dysregulated nicotinic acetylcholine receptor diffusion and nanocluster formation in myasthenia gravis. Neural Regen Res 2021; 16:242-246. [PMID: 32859770 PMCID: PMC7896218 DOI: 10.4103/1673-5374.290880] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Myasthenia gravis is a rare and invalidating disease affecting the neuromuscular junction of voluntary muscles. The classical form of this autoimmune disease is characterized by the presence of antibodies against the most abundant protein in the neuromuscular junction, the nicotinic acetylcholine receptor. Other variants of the disease involve autoimmune attack of non-receptor scaffolding proteins or enzymes essential for building or maintaining the integrity of this peripheral synapse. This review summarizes the participation of the above proteins in building the neuromuscular junction and the destruction of this cholinergic synapse by autoimmune aggression in myasthenia gravis. The review also covers the application of a powerful biophysical technique, superresolution optical microscopy, to image the nicotinic receptor in live cells and follow its motional dynamics. The hypothesis is entertained that anomalous nanocluster formation by antibody crosslinking may lead to accelerated endocytic internalization and elevated turnover of the receptor, as observed in myasthenia gravis.
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Frykman H, Kumar P, Oger J. Immunopathology of Autoimmune Myasthenia Gravis: Implications for Improved Testing Algorithms and Treatment Strategies. Front Neurol 2020; 11:596621. [PMID: 33362698 PMCID: PMC7755715 DOI: 10.3389/fneur.2020.596621] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 11/19/2020] [Indexed: 12/13/2022] Open
Abstract
Myasthenia gravis (MG) is a heterogeneous condition, characterized by autoantibodies (Abs) that target functionally important structures within neuromuscular junctions (NMJ), thus affecting nerve-to-muscle transmission. MG patients are more often now subgrouped based on the profile of serum autoantibodies, which segregate with clinical presentation, immunopathology, and their response to therapies. The serological testing plays an essential role in confirming MG diagnosis and guiding disease management, although a small percentage of MG patients remain negative for antibodies. With the advancements in new highly effective pathophysiologically-specific immunotherapeutic options, it has become increasingly important to identify the specific Abs responsible for the pathogenicity in individual MG patients. There are several new assays and protocols being developed for the improved detection of Abs in MG patients. This review focuses on the divergent immunopathological mechanisms in MG, and discusses their relevance to improved diagnostic and treatment. We propose a comprehensive "reflex testing," algorithm for the presence of MG autoantibodies, and foresee that in the near future, the convenience and specificity of novel assays will permit the clinicians to consider them into routine systematic testing, thus stimulating laboratories to make these tests available. Moreover, adopting treatment driven testing algorithms will be crucial to identify subgroups of patients potentially benefiting from novel immunotherapies for MG.
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Affiliation(s)
- Hans Frykman
- Department of Medicine, University of British Columbia, Vancouver, BC, Canada.,BC Neuroimmunology Lab, University of British Columbia, Vancouver, BC, Canada
| | - Pankaj Kumar
- BC Neuroimmunology Lab, University of British Columbia, Vancouver, BC, Canada
| | - Joel Oger
- Department of Medicine, University of British Columbia, Vancouver, BC, Canada.,BC Neuroimmunology Lab, University of British Columbia, Vancouver, BC, Canada
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Lazaridis K, Tzartos SJ. Myasthenia Gravis: Autoantibody Specificities and Their Role in MG Management. Front Neurol 2020; 11:596981. [PMID: 33329350 PMCID: PMC7734299 DOI: 10.3389/fneur.2020.596981] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 10/30/2020] [Indexed: 12/11/2022] Open
Abstract
Myasthenia gravis (MG) is the most common autoimmune disorder affecting the neuromuscular junction, characterized by skeletal muscle weakness and fatigability. It is caused by autoantibodies targeting proteins of the neuromuscular junction; ~85% of MG patients have autoantibodies against the muscle acetylcholine receptor (AChR-MG), whereas about 5% of MG patients have autoantibodies against the muscle specific kinase (MuSK-MG). In the remaining about 10% of patients no autoantibodies can be found with the classical diagnostics for AChR and MuSK antibodies (seronegative MG, SN-MG). Since serological tests are relatively easy and non-invasive for disease diagnosis, the improvement of methods for the detection of known autoantibodies or the discovery of novel autoantibody specificities to diminish SN-MG and to facilitate differential diagnosis of similar diseases, is crucial. Radioimmunoprecipitation assays (RIPA) are the staple for MG antibody detection, but over the past years, using cell-based assays (CBAs) or improved highly sensitive RIPAs, it has been possible to detect autoantibodies in previously SN-MG patients. This led to the identification of more patients with antibodies to the classical antigens AChR and MuSK and to the third MG autoantigen, the low-density lipoprotein receptor-related protein 4 (LRP4), while antibodies against other extracellular or intracellular targets, such as agrin, Kv1.4 potassium channels, collagen Q, titin, the ryanodine receptor and cortactin have been found in some MG patients. Since the autoantigen targeted determines in part the clinical manifestations, prognosis and response to treatment, serological tests are not only indispensable for initial diagnosis, but also for monitoring treatment efficacy. Importantly, knowing the autoantibody profile of MG patients could allow for more efficient personalized therapeutic approaches. Significant progress has been made over the past years toward the development of antigen-specific therapies, targeting only the specific immune cells or autoantibodies involved in the autoimmune response. In this review, we will present the progress made toward the development of novel sensitive autoantibody detection assays, the identification of new MG autoantigens, and the implications for improved antigen-specific therapeutics. These advancements increase our understanding of MG pathology and improve patient quality of life by providing faster, more accurate diagnosis and better disease management.
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Affiliation(s)
| | - Socrates J Tzartos
- Tzartos NeuroDiagnostics, Athens, Greece.,Department of Neurobiology, Hellenic Pasteur Institute, Athens, Greece
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11
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Abstract
Thirty to fifty percent of patients with acetylcholine receptor (AChR) antibody (Ab)-negative myasthenia gravis (MG) have Abs to muscle specific kinase (MuSK) and are referred to as having MuSK-MG. MuSK is a 100 kD single-pass post-synaptic transmembrane receptor tyrosine kinase crucial to the development and maintenance of the neuromuscular junction. The Abs in MuSK-MG are predominantly of the IgG4 immunoglobulin subclass. MuSK-MG differs from AChR-MG, in exhibiting more focal muscle involvement, including neck, shoulder, facial and bulbar-innervated muscles, as well as wasting of the involved muscles. MuSK-MG is highly associated with the HLA DR14-DQ5 haplotype and occurs predominantly in females with onset in the fourth decade of life. Some of the standard treatments of AChR-MG have been found to have limited effectiveness in MuSK-MG, including thymectomy and cholinesterase inhibitors. Therefore, current treatment involves immunosuppression, primarily by corticosteroids. In addition, patients respond especially well to B cell depletion agents, e.g., rituximab, with long-term remissions. Future treatments will likely derive from the ongoing analysis of the pathogenic mechanisms underlying this disease, including histologic and physiologic studies of the neuromuscular junction in patients as well as information derived from the development and study of animal models of the disease.
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Affiliation(s)
| | - David P. Richman
- Department of Neurology, University of California, Davis, Davis, CA, United States
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12
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Lazaridis K, Tzartos SJ. Autoantibody Specificities in Myasthenia Gravis; Implications for Improved Diagnostics and Therapeutics. Front Immunol 2020; 11:212. [PMID: 32117321 PMCID: PMC7033452 DOI: 10.3389/fimmu.2020.00212] [Citation(s) in RCA: 112] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Accepted: 01/27/2020] [Indexed: 12/13/2022] Open
Abstract
Myasthenia gravis (MG) is an autoimmune disease characterized by muscle weakness and fatiguability of skeletal muscles. It is an antibody-mediated disease, caused by autoantibodies targeting neuromuscular junction proteins. In the majority of patients (~85%) antibodies against the muscle acetylcholine receptor (AChR) are detected, while in 6% antibodies against the muscle-specific kinase (MuSK) are detected. In ~10% of MG patients no autoantibodies can be found with the classical diagnostics for AChR and MuSK antibodies (seronegative MG, SN-MG), making the improvement of methods for the detection of known autoantibodies or the discovery of novel antigenic targets imperative. Over the past years, using cell-based assays or improved highly sensitive immunoprecipitation assays, it has been possible to detect autoantibodies in previously SN-MG patients, including the identification of the low-density lipoprotein receptor-related protein 4 (LRP4) as a third MG autoantigen, as well as AChR and MuSK antibodies undetectable by conventional methods. Furthermore, antibodies against other extracellular or intracellular targets, such as titin, the ryanodine receptor, agrin, collagen Q, Kv1.4 potassium channels and cortactin have been found in some MG patients, which can be useful biomarkers. In addition to the improvement of diagnosis, the identification of the patients' autoantibody specificity is important for their stratification into respective subgroups, which can differ in terms of clinical manifestations, prognosis and most importantly their response to therapies. The knowledge of the autoantibody profile of MG patients would allow for a therapeutic strategy tailored to their MG subgroup. This is becoming especially relevant as there is increasing progress toward the development of antigen-specific therapies, targeting only the specific autoantibodies or immune cells involved in the autoimmune response, such as antigen-specific immunoadsorption, which have shown promising results. We will herein review the advances made by us and others toward development of more sensitive detection methods and the identification of new antibody targets in MG, and discuss their significance in MG diagnosis and therapy. Overall, the development of novel autoantibody assays is aiding in the more accurate diagnosis and classification of MG patients, supporting the development of advanced therapeutics and ultimately the improvement of disease management and patient quality of life.
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Affiliation(s)
| | - Socrates J Tzartos
- Department of Neurobiology, Hellenic Pasteur Institute, Athens, Greece.,Tzartos NeuroDiagnostics, Athens, Greece
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13
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Mosqueira A, Camino PA, Barrantes FJ. Antibody‐induced crosslinking and cholesterol‐sensitive, anomalous diffusion of nicotinic acetylcholine receptors. J Neurochem 2019; 152:663-674. [DOI: 10.1111/jnc.14905] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 09/27/2019] [Accepted: 10/25/2019] [Indexed: 02/04/2023]
Affiliation(s)
- Alejo Mosqueira
- Laboratory of Molecular Neurobiology Biomedical Research institute (BIOMED) UCA–CONICET Buenos Aires Argentina
| | - Pablo A. Camino
- Laboratory of Molecular Neurobiology Biomedical Research institute (BIOMED) UCA–CONICET Buenos Aires Argentina
| | - Francisco J. Barrantes
- Laboratory of Molecular Neurobiology Biomedical Research institute (BIOMED) UCA–CONICET Buenos Aires Argentina
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14
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Myasthenia Gravis: Pathogenic Effects of Autoantibodies on Neuromuscular Architecture. Cells 2019; 8:cells8070671. [PMID: 31269763 PMCID: PMC6678492 DOI: 10.3390/cells8070671] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 06/26/2019] [Accepted: 06/28/2019] [Indexed: 12/13/2022] Open
Abstract
Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction (NMJ). Autoantibodies target key molecules at the NMJ, such as the nicotinic acetylcholine receptor (AChR), muscle-specific kinase (MuSK), and low-density lipoprotein receptor-related protein 4 (Lrp4), that lead by a range of different pathogenic mechanisms to altered tissue architecture and reduced densities or functionality of AChRs, reduced neuromuscular transmission, and therefore a severe fatigable skeletal muscle weakness. In this review, we give an overview of the history and clinical aspects of MG, with a focus on the structure and function of myasthenic autoantigens at the NMJ and how they are affected by the autoantibodies' pathogenic mechanisms. Furthermore, we give a short overview of the cells that are implicated in the production of the autoantibodies and briefly discuss diagnostic challenges and treatment strategies.
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15
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Lazaridis K, Dalianoudis I, Baltatzidi V, Tzartos SJ. Specific removal of autoantibodies by extracorporeal immunoadsorption ameliorates experimental autoimmune myasthenia gravis. J Neuroimmunol 2017; 312:24-30. [DOI: 10.1016/j.jneuroim.2017.09.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2017] [Revised: 09/03/2017] [Accepted: 09/05/2017] [Indexed: 11/29/2022]
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16
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Noridomi K, Watanabe G, Hansen MN, Han GW, Chen L. Structural insights into the molecular mechanisms of myasthenia gravis and their therapeutic implications. eLife 2017; 6. [PMID: 28440223 PMCID: PMC5404922 DOI: 10.7554/elife.23043] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2016] [Accepted: 03/29/2017] [Indexed: 12/05/2022] Open
Abstract
The nicotinic acetylcholine receptor (nAChR) is a major target of autoantibodies in myasthenia gravis (MG), an autoimmune disease that causes neuromuscular transmission dysfunction. Despite decades of research, the molecular mechanisms underlying MG have not been fully elucidated. Here, we present the crystal structure of the nAChR α1 subunit bound by the Fab fragment of mAb35, a reference monoclonal antibody that causes experimental MG and competes with ~65% of antibodies from MG patients. Our structures reveal for the first time the detailed molecular interactions between MG antibodies and a core region on nAChR α1. These structures suggest a major nAChR-binding mechanism shared by a large number of MG antibodies and the possibility to treat MG by blocking this binding mechanism. Structure-based modeling also provides insights into antibody-mediated nAChR cross-linking known to cause receptor degradation. Our studies establish a structural basis for further mechanistic studies and therapeutic development of MG. DOI:http://dx.doi.org/10.7554/eLife.23043.001 Myasthenia gravis is a disease that causes chronic weakness in muscles. It affects more than 20 in every 100,000 people and diagnosis is becoming more common due to increased awareness of the disease. However, most current treatments only temporarily relieve symptoms so there is a need to develop more effective therapies. The disease occurs when the immune system produces molecules called antibodies that bind to and destroy a receptor protein called nAChR. This receptor is normally found at the junctions between nerve cells and muscle cells, and its destruction disrupts communication between the nervous system and the muscle. However, it is not known exactly how these antibodies bind to nAChR, partly due to the lack of a detailed three-dimensional structure of the antibodies and nAChR together. The human nAChR protein is made up of several subunits, including one called alpha1 that is the primary target of Myasthenia gravis antibodies. Noridomi et al. used a technique known as X-ray crystallography to generate a highly detailed three-dimensional model of the structure of the alpha1 subunit with an antibody from rats that acts as in a similar way to human Myasthenia gravis antibodies. The structure reveals the points of contact between the antibodies and a core region of the nAChR alpha1 subunit and suggests that many different Myasthenia gravis antibodies may bind to nAChR in the same way. These findings may aid the development of drugs that bind to and disable Myasthenia gravis antibodies to relieve the symptoms of the disease. DOI:http://dx.doi.org/10.7554/eLife.23043.002
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Affiliation(s)
- Kaori Noridomi
- Department of Chemistry, University of Southern California, Los Angeles, United States
| | - Go Watanabe
- USC Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, United States
| | - Melissa N Hansen
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, United States
| | - Gye Won Han
- Department of Chemistry, Bridge Institute, University of Southern California, Los Angeles, United States
| | - Lin Chen
- Department of Chemistry, University of Southern California, Los Angeles, United States.,USC Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, United States.,Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, United States
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Lazaridis K, Baltatzidi V, Trakas N, Koutroumpi E, Karandreas N, Tzartos SJ. Characterization of a reproducible rat EAMG model induced with various human acetylcholine receptor domains. J Neuroimmunol 2017; 303:13-21. [DOI: 10.1016/j.jneuroim.2016.12.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2016] [Revised: 12/04/2016] [Accepted: 12/05/2016] [Indexed: 01/08/2023]
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18
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Melzer N, Ruck T, Fuhr P, Gold R, Hohlfeld R, Marx A, Melms A, Tackenberg B, Schalke B, Schneider-Gold C, Zimprich F, Meuth SG, Wiendl H. Clinical features, pathogenesis, and treatment of myasthenia gravis: a supplement to the Guidelines of the German Neurological Society. J Neurol 2016; 263:1473-94. [PMID: 26886206 PMCID: PMC4971048 DOI: 10.1007/s00415-016-8045-z] [Citation(s) in RCA: 148] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2015] [Revised: 01/20/2016] [Accepted: 01/21/2016] [Indexed: 01/20/2023]
Abstract
Myasthenia gravis (MG) is an autoimmune antibody-mediated disorder of neuromuscular synaptic transmission. The clinical hallmark of MG consists of fluctuating fatigability and weakness affecting ocular, bulbar and (proximal) limb skeletal muscle groups. MG may either occur as an autoimmune disease with distinct immunogenetic characteristics or as a paraneoplastic syndrome associated with tumors of the thymus. Impairment of central thymic and peripheral self-tolerance mechanisms in both cases is thought to favor an autoimmune CD4(+) T cell-mediated B cell activation and synthesis of pathogenic high-affinity autoantibodies of either the IgG1 and 3 or IgG4 subclass. These autoantibodies bind to the nicotinic acetylcholine receptor (AchR) itself, or muscle-specific tyrosine-kinase (MuSK), lipoprotein receptor-related protein 4 (LRP4) and agrin involved in clustering of AchRs within the postsynaptic membrane and structural maintenance of the neuromuscular synapse. This results in disturbance of neuromuscular transmission and thus clinical manifestation of the disease. Emphasizing evidence from clinical trials, we provide an updated overview on immunopathogenesis, and derived current and future treatment strategies for MG divided into: (a) symptomatic treatments facilitating neuromuscular transmission, (b) antibody-depleting treatments, and
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Affiliation(s)
- Nico Melzer
- Department of Neurology, University of Münster, Albert-Schweitzer-Campus 1, 48149 Münster, Germany
| | - Tobias Ruck
- Department of Neurology, University of Münster, Albert-Schweitzer-Campus 1, 48149 Münster, Germany
| | - Peter Fuhr
- Department of Neurology, University of Basel, Basel, Switzerland
| | - Ralf Gold
- Department of Neurology, University of Bochum, Bochum, Germany
| | - Reinhard Hohlfeld
- Institute of Clinical Neuroimmunology, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Alexander Marx
- Institute of Pathology, University Medical Centre Mannheim, University of Heidelberg, Mannheim, Germany
| | - Arthur Melms
- Department of Neurology, University of Erlangen, Erlangen, Germany
| | - Björn Tackenberg
- Department of Neurology, University of Marburg, Marburg, Germany
| | - Berthold Schalke
- Department of Neurology, University of Regensburg, Regensburg, Germany
| | | | - Fritz Zimprich
- Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Sven G. Meuth
- Department of Neurology, University of Münster, Albert-Schweitzer-Campus 1, 48149 Münster, Germany
| | - Heinz Wiendl
- Department of Neurology, University of Münster, Albert-Schweitzer-Campus 1, 48149 Münster, Germany
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20
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George S, Noack M, Vanek M, Rentzsch J, Röber N, Conrad K, Roggenbuck D, Küpper JH. Expression of nicotinic acetylcholine receptor subunits in HEp-2 cells for immunodetection of autoantibody specificities in sera from Myasthenia gravis patients. Clin Hemorheol Microcirc 2015; 61:385-96. [DOI: 10.3233/ch-151999] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- S. George
- Faculty of Science, Brandenburg University of Technology Cottbus-Senftenberg, Germany
- Institute of Immunology, Medical Faculty of the Technical University of Dresden, Germany
| | - M. Noack
- Faculty of Science, Brandenburg University of Technology Cottbus-Senftenberg, Germany
| | - M. Vanek
- Faculty of Science, Brandenburg University of Technology Cottbus-Senftenberg, Germany
| | - J. Rentzsch
- Faculty of Science, Brandenburg University of Technology Cottbus-Senftenberg, Germany
| | - N. Röber
- Institute of Immunology, Medical Faculty of the Technical University of Dresden, Germany
| | - K. Conrad
- Institute of Immunology, Medical Faculty of the Technical University of Dresden, Germany
| | - D. Roggenbuck
- Faculty of Science, Brandenburg University of Technology Cottbus-Senftenberg, Germany
- Generic Assays GmbH, Dahlewitz, Germany
| | - J.-H. Küpper
- Faculty of Science, Brandenburg University of Technology Cottbus-Senftenberg, Germany
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21
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Ha JC, Richman DP. Myasthenia gravis and related disorders: Pathology and molecular pathogenesis. Biochim Biophys Acta Mol Basis Dis 2015; 1852:651-7. [DOI: 10.1016/j.bbadis.2014.11.022] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 11/20/2014] [Accepted: 11/29/2014] [Indexed: 12/21/2022]
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22
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Guidelines for pre-clinical assessment of the acetylcholine receptor--specific passive transfer myasthenia gravis model-Recommendations for methods and experimental designs. Exp Neurol 2015; 270:3-10. [PMID: 25743217 DOI: 10.1016/j.expneurol.2015.02.025] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2014] [Revised: 02/13/2015] [Accepted: 02/17/2015] [Indexed: 11/21/2022]
Abstract
Antibodies against the muscle acetylcholine receptor (AChR) are the most common cause of myasthenia gravis (MG). Passive transfer of AChR antibodies from MG patients into animals reproduces key features of human disease, including antigenic modulation of the AChR, complement-mediated damage of the neuromuscular junction, and muscle weakness. Similarly, AChR antibodies generated by active immunization in experimental autoimmune MG models can subsequently be passively transferred to other animals and induce weakness. The passive transfer model is useful to test therapeutic strategies aimed at the effector mechanism of the autoantibodies. Here we summarize published and unpublished experience using the AChR passive transfer MG model in mice, rats and rhesus monkeys, and give recommendations for the design of preclinical studies in order to facilitate translation of positive and negative results to improve MG therapies.
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23
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Specific adsorbents for myasthenia gravis autoantibodies using mutants of the muscle nicotinic acetylcholine receptor extracellular domains. J Neuroimmunol 2015; 278:19-25. [DOI: 10.1016/j.jneuroim.2014.12.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 11/27/2014] [Accepted: 12/01/2014] [Indexed: 11/20/2022]
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Fuchs S, Aricha R, Reuveni D, Souroujon MC. Experimental Autoimmune Myasthenia Gravis (EAMG): from immunochemical characterization to therapeutic approaches. J Autoimmun 2014; 54:51-9. [PMID: 24970384 DOI: 10.1016/j.jaut.2014.06.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2014] [Accepted: 06/04/2014] [Indexed: 12/22/2022]
Abstract
Myasthenia Gravis (MG) is an organ-specific autoimmune disease. In high percentage of patients there are autoantibodies to the nicotinic acetylcholine receptor (AChR) that attack AChR on muscle cells at the neuromuscular junction, resulting in muscle weakness. Experimental Autoimmune Myasthenia Gravis (EAMG) is an experimental model disease for MG. EAMG is induced in several animal species by immunization with acetylcholine receptor (AChR), usually isolated from the electric organ of electric fish, which is a rich source for this antigen. Our lab has been involved for several decades in research of AChR and of EAMG. The availability of an experimental autoimmune disease that mimics in many aspects the human disease, provides an excellent model system for elucidating the immunological nature and origin of MG, for studying various existing treatment modalities and for attempting the development of novel treatment approaches. In this review in honor of Michael Sela and Ruth Arnon, we report first on our early pioneering contributions to research on EAMG. These include the induction of EAMG in several animal species, early attempts for antigen-specific treatment for EAMG, elicitation and characterization of monoclonal antibodies and anti-idiotypic antibodies, measuring humoral and cellular AChR-specific immune responses in MG patient and more. In the second part of the review we discuss more recent studies from our lab towards developing and testing novel treatment approaches for myasthenia. These include antigen-dependent treatments aimed at specifically abrogating the humoral and cellular anti-AChR responses, as well as immunomodulatory approaches that could be used either alone, or in conjunction with antigen-specific treatments, or alternatively, serve as steroid-sparing agents.
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Affiliation(s)
- Sara Fuchs
- Department of Immunology, The Weizmann Institute of Science, Rehovot 76100, Israel.
| | - Revital Aricha
- Department of Immunology, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Debby Reuveni
- Department of Immunology, The Weizmann Institute of Science, Rehovot 76100, Israel; Department of Natural Sciences, The Open University of Israel, Raanana, Israel
| | - Miriam C Souroujon
- Department of Immunology, The Weizmann Institute of Science, Rehovot 76100, Israel; Department of Natural Sciences, The Open University of Israel, Raanana, Israel
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25
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Lazaridis K, Zisimopoulou P, Giastas P, Bitzopoulou K, Evangelakou P, Sideri A, Tzartos SJ. Expression of human AChR extracellular domain mutants with improved characteristics. Int J Biol Macromol 2014; 63:210-7. [DOI: 10.1016/j.ijbiomac.2013.11.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2013] [Revised: 11/07/2013] [Accepted: 11/10/2013] [Indexed: 10/26/2022]
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26
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Trinh VB, Foster AJ, Fairclough RH. Design, synthesis, and characterization of a 39 amino acid peptide mimic of the main immunogenic region of the Torpedo acetylcholine receptor. Mol Immunol 2014; 59:79-90. [PMID: 24491490 DOI: 10.1016/j.molimm.2014.01.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2013] [Accepted: 01/04/2014] [Indexed: 11/16/2022]
Abstract
We have designed a 39 amino acid peptide mimic of the conformation-dependent main immunogenic region (MIR) of the Torpedo acetylcholine receptor (TAChR) that joins three discontinuous segments of the Torpedo α-subunit, α(1-12), α(65-79), and α(110 - 115) with two GS linkers: This 39MIR-mimic was expressed in E. coli as a fusion protein with an intein-chitin-binding domain (IChBD) to permit affinity collection on chitin beads. Six MIR-directed monoclonal antibodies (mAbs) bind to this complex and five agonist/antagonist site directed mAbs do not. The complex of MIR-directed mAb-132A with 39MIR has a Kd of (2.11±0.11)×10(-10)M, which is smaller than (7.13±1.20)×10(-10)M for the complex of mAb-132A with α(1-161) and about the same as 3.4×10(-10)M for that of mAb-132A with TAChR. Additionally, the 39MIR-IChBD adsorbs all MIR-directed antibodies (Abs) from an experimental autoimmune myasthenia gravis (EAMG) rat serum. Hence, the 39MIR-mimic has the potential to inactivate or remove pathogenic Torpedo MIR-directed Abs from EAMG sera and to direct a magic bullet to the memory B-cells that produce those pathogenic Abs. The hope is to use this as a guide to produce a mimic of the human MIR on the way to an antigen specific therapeutic agent to treat MG.
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Affiliation(s)
- Vu B Trinh
- University of California, Davis-School of Medicine, Department of Neurology, One Shields Ave., 1515 Newton Ct. Room 510C, Davis, CA 95616, USA; Biochemistry and Molecular Biology Graduate Group and Biochemistry Molecular Cellular and Developmental Biology Graduate Group of UC Davis, Davis, CA 95616, USA
| | - Alex J Foster
- University of California, Davis-School of Medicine, Department of Neurology, One Shields Ave., 1515 Newton Ct. Room 510C, Davis, CA 95616, USA; Biochemistry and Molecular Biology Graduate Group and Biochemistry Molecular Cellular and Developmental Biology Graduate Group of UC Davis, Davis, CA 95616, USA
| | - Robert H Fairclough
- University of California, Davis-School of Medicine, Department of Neurology, One Shields Ave., 1515 Newton Ct. Room 510C, Davis, CA 95616, USA; Biochemistry and Molecular Biology Graduate Group and Biochemistry Molecular Cellular and Developmental Biology Graduate Group of UC Davis, Davis, CA 95616, USA.
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27
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Berrih-Aknin S, Le Panse R. Myasthenia gravis: a comprehensive review of immune dysregulation and etiological mechanisms. J Autoimmun 2014; 52:90-100. [PMID: 24389034 DOI: 10.1016/j.jaut.2013.12.011] [Citation(s) in RCA: 232] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 12/12/2013] [Indexed: 12/31/2022]
Abstract
Autoimmune myasthenia gravis (MG) is characterized by muscle weakness caused by antibodies directed against proteins of the neuromuscular junction. The main antigenic target is the acetylcholine receptor (AChR), but the muscle Specific Kinase (MuSK) and the low-density lipoprotein receptor-related protein (LRP4) are also targets. This review summarizes the clinical and biological data available for different subgroups of patients, who are classified according to antigenic target, age of onset, and observed thymic abnormalities, such as follicular hyperplasia or thymoma. Here, we analyze in detail the role of the thymus in the physiopathology of MG and propose an explanation for the development of the thymic follicular hyperplasia that is commonly observed in young female patients with anti-AChR antibodies. The influence of the pro-inflammatory environment is discussed, particularly the role of TNF-α and Th17-related cytokines, which could explain the escape of thymic T cells from regulation and the chronic inflammation in the MG thymus. Together with this immune dysregulation, active angiogenic processes and the upregulation of chemokines could promote thymic follicular hyperplasia. MG is a multifactorial disease, and we review the etiological mechanisms that could lead to its onset. Recent global genetic analyses have highlighted potential susceptibility genes. In addition, miRNAs, which play a crucial role in immune function, have been implicated in MG by recent studies. We also discuss the role of sex hormones and the influence of environmental factors, such as the viral hypothesis. This hypothesis is supported by reports that type I interferon and molecules mimicking viral infection can induce thymic changes similar to those observed in MG patients with anti-AChR antibodies.
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Affiliation(s)
- Sonia Berrih-Aknin
- INSERM U974, Paris, France; CNRS UMR 7215, Paris, France; UPMC Univ Paris 6, Paris, France; AIM, Institute of myology, Paris, France.
| | - Rozen Le Panse
- INSERM U974, Paris, France; CNRS UMR 7215, Paris, France; UPMC Univ Paris 6, Paris, France; AIM, Institute of myology, Paris, France.
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Huijbers MG, Lipka AF, Plomp JJ, Niks EH, van der Maarel SM, Verschuuren JJ. Pathogenic immune mechanisms at the neuromuscular synapse: the role of specific antibody-binding epitopes in myasthenia gravis. J Intern Med 2014; 275:12-26. [PMID: 24215230 DOI: 10.1111/joim.12163] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Autoantibodies against three different postsynaptic antigens and one presynaptic antigen at the neuromuscular junction are known to cause myasthenic syndromes. The mechanisms by which these antibodies cause muscle weakness vary from antigenic modulation and complement-mediated membrane damage to inhibition of endogenous ligand binding and blocking of essential protein-protein interactions. These mechanisms are related to the autoantibody titre, specific epitopes on the target proteins and IgG autoantibody subclass. We here review the role of specific autoantibody-binding epitopes in myasthenia gravis, their possible relevance to the pathophysiology of the disease and potential implications of epitope mapping knowledge for new therapeutic strategies.
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Affiliation(s)
- M G Huijbers
- Department of Neurology, Leiden University Medical Center, Leiden, the Netherlands; Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands
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Morell SW, Trinh VB, Gudipati E, Friend A, Page NA, Agius MA, Richman DP, Fairclough RH. Structural characterization of the main immunogenic region of the Torpedo acetylcholine receptor. Mol Immunol 2013; 58:116-31. [PMID: 24333757 DOI: 10.1016/j.molimm.2013.11.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2013] [Revised: 11/06/2013] [Accepted: 11/07/2013] [Indexed: 11/27/2022]
Abstract
To develop antigen-specific immunotherapies for autoimmune diseases, knowledge of the molecular structure of targeted immunological hotspots will guide the production of reagents to inhibit and halt production of antigen specific attack agents. To this end we have identified three noncontiguous segments of the Torpedo nicotinic acetylcholine receptor (AChR) α-subunit that contribute to the conformationally sensitive immunological hotspot on the AChR termed the main immunogenic region (MIR): α(1-12), α(65-79), and α(110-115). This region is the target of greater than 50% of the anti-AChR Abs in serum from patients with myasthenia gravis (MG) and animals with experimental autoimmune myasthenia gravis (EAMG). Many monoclonal antibodies (mAbs) raised in one species against an electric organ AChR cross react with the neuromuscular AChR MIR in several species. Probing the Torpedo AChR α-subunit with mAb 132A, a disease inducing anti-MIR mAb raised against the Torpedo AChR, we have determined that two of the three MIR segments, α(1-12) and α(65-79), form a complex providing the signature components recognized by mAb 132A. These two segments straddle a third, α(110-115), that seems not to contribute specific side chains for 132A recognition, but is necessary for optimum antibody binding. This third segment appears to form a foundation upon which the three-dimensional 132A epitope is anchored.
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Affiliation(s)
- Stuart W Morell
- University of California, Davis School of Medicine, Department of Neurology, One Shields Avenue, 1515 Newton Court, Room 510C, Davis, CA 95616, United States; Biochemistry, Molecular, Cellular, and Developmental Biology Graduate Group of UC Davis, United States
| | - Vu B Trinh
- University of California, Davis School of Medicine, Department of Neurology, One Shields Avenue, 1515 Newton Court, Room 510C, Davis, CA 95616, United States; Biochemistry, Molecular, Cellular, and Developmental Biology Graduate Group of UC Davis, United States
| | - Eswari Gudipati
- Biochemistry, Siemens Healthcare Diagnostics, 5210 Pacific Concourse Drive, Los Angeles, CA 90045, United States
| | - Alexander Friend
- University of California, Davis School of Medicine, Department of Neurology, One Shields Avenue, 1515 Newton Court, Room 510C, Davis, CA 95616, United States
| | - Nelson A Page
- University of California, Davis School of Medicine, Department of Neurology, One Shields Avenue, 1515 Newton Court, Room 510C, Davis, CA 95616, United States; Department of Physics Graduate Program, University of California, Davis, One Shields Avenue, Davis, CA 95616, United States
| | - Mark A Agius
- University of California, Davis School of Medicine, Department of Neurology, One Shields Avenue, 1515 Newton Court, Room 510C, Davis, CA 95616, United States; VANCHCS, 10535 Hospital Way, Mather, CA 95655, United States
| | - David P Richman
- University of California, Davis School of Medicine, Department of Neurology, One Shields Avenue, 1515 Newton Court, Room 510C, Davis, CA 95616, United States; Neurosciences Graduate Group of UC Davis, United States
| | - Robert H Fairclough
- University of California, Davis School of Medicine, Department of Neurology, One Shields Avenue, 1515 Newton Court, Room 510C, Davis, CA 95616, United States; Biochemistry, Molecular, Cellular, and Developmental Biology Graduate Group of UC Davis, United States; Biophysics Graduate Group of UC Davis, United States.
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Nicotinic acetylcholine receptor and the structural basis of neuromuscular transmission: insights from Torpedo postsynaptic membranes. Q Rev Biophys 2013; 46:283-322. [PMID: 24050525 PMCID: PMC3820380 DOI: 10.1017/s0033583513000061] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The nicotinic acetylcholine (ACh) receptor, at the neuromuscular junction, is a neurotransmitter-gated ion channel that has been fine-tuned through evolution to transduce a chemical signal into an electrical signal with maximum efficiency and speed. It is composed from three similar and two identical polypeptide chains, arranged in a ring around a narrow membrane pore. Central to the design of this assembly is a hydrophobic gate in the pore, more than 50 Å away from sites in the extracellular domain where ACh binds. Although the molecular properties of the receptor have been explored intensively over the last few decades, only recently have structures emerged revealing its complex architecture and illuminating how ACh entering the binding sites opens the distant gate. Postsynaptic membranes isolated from the (muscle-derived) electric organ of the Torpedo ray have underpinned most of the structural studies: the membranes form tubular vesicles having receptors arranged on a regular surface lattice, which can be imaged directly in frozen physiological solutions. Advances in electron crystallographic techniques have also been important, enabling analysis of the closed- and open-channel forms of the receptor in unreacted tubes or tubes reacted briefly with ACh. The structural differences between these two forms show that all five subunits participate in a concerted conformational change communicating the effect of ACh binding to the gate, but that three of them (αγ, β and δ) play a dominant role. Flexing of oppositely facing pore-lining α-helices is the principal motion determining the closed/open state of the gate. These results together with the findings of biochemical, biophysical and other structural studies allow an integrated description of the receptor and of its mode of action at the synapse.
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Marx A, Pfister F, Schalke B, Saruhan-Direskeneli G, Melms A, Ströbel P. The different roles of the thymus in the pathogenesis of the various myasthenia gravis subtypes. Autoimmun Rev 2013; 12:875-84. [DOI: 10.1016/j.autrev.2013.03.007] [Citation(s) in RCA: 218] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/12/2013] [Indexed: 01/13/2023]
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Abstract
In myasthenia gravis (MG) and experimental autoimmune MG (EAMG), many pathologically significant autoantibodies are directed to the main immunogenic region (MIR) of muscle nicotinic acetylcholine receptors (AChRs), a conformation-dependent region at the extracellular tip of α1 subunits of AChRs. Human muscle AChR α1 MIR sequences were integrated into Aplesia ACh-binding protein (AChBP). The chimera potently induced EAMG, while AChBP induced EAMG much less potently. AChBP is a water-soluble protein resembling the extracellular domain of AChRs; yet, rats immunized with chimeras developed autoantibodies to both extracellular and cytoplasmic domains of muscle AChRs. We propose that an initial autoimmune response directed at the MIR leads to an autoimmune response sustained by muscle AChRs. Autoimmune stimulation sustained by endogenous muscle AChR may be a target for specific immunosuppression. These studies show that the α1 MIR is highly myasthenogenic, and that AChR-like proteins distantly related to muscle AChR can induce EAMG and, potentially, MG.
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Affiliation(s)
- Jon Lindstrom
- Department of Neuroscience, Medical School of the University of Pennsylvania, Philadelphia, 19104-6074, USA.
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Lazaridis K, Zisimopoulou P, Lagoumintzis G, Skriapa L, Trakas N, Evangelakou P, Kanelopoulos I, Grapsa E, Poulas K, Tzartos S. Antigen-specific apheresis of autoantibodies in myasthenia gravis. Ann N Y Acad Sci 2013; 1275:7-12. [PMID: 23278571 DOI: 10.1111/j.1749-6632.2012.06788.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Myasthenia gravis (MG) is an autoimmune disorder affecting the neuromuscular junction, usually caused by autoantibodies against the acetylcholine receptor (AChR) or the muscle-specific kinase (MuSK). Our aim is the development of a therapy based on the selective extracorporeal elimination of anti-AChR or anti-MuSK antibodies. To this end, the extracellular domains of the AChR subunits and MuSK have been expressed in yeast to be used as adsorbents, after optimization, and to obtain large quantities of proteins with near-native structure. We have characterized these proteins with respect to their use as specific immunoadsorbents for MG autoantibodies, and have begun large-scale experiments in order to verify the feasibility of application of the method for therapy. Furthermore, we have initiated animal studies to test possible toxicity and safety issues of the adsorbents or the procedure itself. The successful completion of the scale-up and safety tests will allow the initiation of clinical trials.
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Meriggioli MN, Sanders DB. Muscle autoantibodies in myasthenia gravis: beyond diagnosis? Expert Rev Clin Immunol 2012; 8:427-38. [PMID: 22882218 DOI: 10.1586/eci.12.34] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Myasthenia gravis is an autoimmune disorder of the neuromuscular junction. A number of molecules, including ion channels and other proteins at the neuromuscular junction, may be targeted by autoantibodies leading to abnormal neuromuscular transmission. In approximately 85% of patients, autoantibodies, directed against the postsynaptic nicotinic acetylcholine receptor can be detected in the serum and confirm the diagnosis, but in general, do not precisely predict the degree of weakness or response to therapy. Antibodies to the muscle-specific tyrosine kinase are detected in approximately 50% of generalized myasthenia gravis patients who are seronegative for anti-acetylcholine receptor antibodies, and levels of anti-muscle-specific tyrosine kinase antibodies do appear to correlate with disease severity and treatment response. Antibodies to other muscle antigens may be found in the subsets of myasthenia gravis patients, potentially providing clinically useful diagnostic information, but their utility as relevant biomarkers (measures of disease state or response to treatment) is currently unclear.
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Affiliation(s)
- Matthew N Meriggioli
- Department of Neurology and Rehabilitation, College of Medicine, University of Illinois Hospital and Health Sciences System, Chicago, IL 60612, USA.
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Abstract
The synapse is a localized neurohumoral contact between a neuron and an effector cell and may be considered the quantum of fast intercellular communication. Analogously, the postsynaptic neurotransmitter receptor may be considered the quantum of fast chemical to electrical transduction. Our understanding of postsynaptic receptors began to develop about a hundred years ago with the demonstration that electrical stimulation of the vagus nerve released acetylcholine and slowed the heart beat. During the past 50 years, advances in understanding postsynaptic receptors increased at a rapid pace, owing largely to studies of the acetylcholine receptor (AChR) at the motor endplate. The endplate AChR belongs to a large superfamily of neurotransmitter receptors, called Cys-loop receptors, and has served as an exemplar receptor for probing fundamental structures and mechanisms that underlie fast synaptic transmission in the central and peripheral nervous systems. Recent studies provide an increasingly detailed picture of the structure of the AChR and the symphony of molecular motions that underpin its remarkably fast and efficient chemoelectrical transduction.
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Affiliation(s)
- Steven M Sine
- Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA.
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Ragheb S, Lisak RP. B-cell-activating factor and autoimmune myasthenia gravis. Autoimmune Dis 2011; 2011:939520. [PMID: 22235365 PMCID: PMC3251912 DOI: 10.4061/2011/939520] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Accepted: 10/08/2011] [Indexed: 11/26/2022] Open
Abstract
BAFF is a potent B-cell survival factor, and it plays an essential role in B-cell homeostasis and B-cell function in the periphery. Both normal and autoreactive B cells are BAFF dependent; however, excess BAFF promotes the survival, growth, and maturation of autoreactive B cells. When overexpressed, BAFF protects B cells from apoptosis, thereby contributing to autoimmunity. Three independent studies have shown higher BAFF levels in the circulation of MG patients. BAFF may play an important role in the pathogenesis of MG. BAFF antagonists may well provide new treatment options for MG patients, particularly those patients with thymic lymphoid follicular hyperplasia.
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Affiliation(s)
- Samia Ragheb
- Department of Neurology, Wayne State University School of Medicine, Detroit, MI 48201, USA
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37
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Abstract
Myasthenia gravis is an autoimmune neuromuscular disorder. There are several treatment options, including symptomatic treatment (acetylcholinesterase inhibitors), short-term immunosuppression (corticosteroids), long-term immunosuppression (azathioprine, cyclosporine, cyclophosphamide, methotrexate, mycophenolate mofetil, rituximab, tacrolimus), rapid acting short-term immunomodulation (intravenous immunoglobulin, plasma exchange), and long-term immunomodulation (thymectomy). This review explores in detail these different treatment options. Potential future treatments are also discussed.
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38
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Ching KH, Burbelo PD, Kimball RM, Clawson LL, Corse AM, Iadarola MJ. Recombinant expression of the AChR-alpha1 subunit for the detection of conformation-dependent epitopes in Myasthenia Gravis. Neuromuscul Disord 2010; 21:204-13. [PMID: 21195619 DOI: 10.1016/j.nmd.2010.12.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 10/15/2010] [Accepted: 12/03/2010] [Indexed: 12/21/2022]
Abstract
Detection of autoantibodies associated with neurological disease typically involves immunoprecipitation of radioactively labeled native proteins. We explored whether single receptor subunits, fused to Renilla luciferase (Ruc), could detect patient autoantibodies in Luciferase Immunoprecipitation Systems. Myasthenia Gravis patient sera were tested for conformational autoantibodies to only the α1-subunit of the nicotinic acetylcholine receptor (AChR). Using a panel of 10 AChR-α1 fragments, AChR-α1-Δ5-Ruc demonstrated the highest immunoreactivity with a conformational-specific antibody and the highest sensitivity in a pilot cohort. Testing a larger cohort with AChR-α1-Δ5-Ruc demonstrated 21% sensitivity and 97% specificity. A point mutation within Ruc increased the diagnostic performance of AChR-α1-Δ5 (32% sensitivity, 97% specificity). The (125)I-α-bungarotoxin multi-subunit AChR assay demonstrated 63% sensitivity and 97% specificity. These findings highlight the difficulty in detecting Myasthenia Gravis conformational epitopes across assay formats and lay the foundation for detecting autoantibodies to defined recombinant chains of the AChR and potentially other neurotransmitter receptors.
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Affiliation(s)
- Kathryn H Ching
- Neurobiology and Pain Therapeutics Section, Laboratory of Sensory Biology, National Institute of Dental and Craniofacial Research, 49 Convent Drive, Bethesda, MD 20892-4410, United States
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Vrolix K, Fraussen J, Molenaar PC, Losen M, Somers V, Stinissen P, De Baets MH, Martínez-Martínez P. The auto-antigen repertoire in myasthenia gravis. Autoimmunity 2010; 43:380-400. [PMID: 20380581 DOI: 10.3109/08916930903518073] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Myasthenia Gravis (MG) is an antibody-mediated autoimmune disorder affecting the postsynaptic membrane of the neuromuscular junction (NMJ). MG is characterized by an impaired signal transmission between the motor neuron and the skeletal muscle cell, caused by auto-antibodies directed against NMJ proteins. The auto-antibodies target the nicotinic acetylcholine receptor (nAChR) in about 90% of MG patients. In approximately 5% of MG patients, the muscle specific kinase (MuSK) is the auto-antigen. In the remaining 5% of MG patients, however, antibodies against the nAChR or MuSK are not detectable (idiopathic MG, iMG). Although only the anti-nAChR and anti-MuSK auto-antibodies have been demonstrated to be pathogenic, several other antibodies recognizing self-antigens can also be found in MG patients. Various auto-antibodies associated with thymic abnormalities have been reported, as well as many non-MG-specific auto-antibodies. However, their contribution to the cause, pathology and severity of the disease is still poorly understood. Here, we comprehensively review the reported auto-antibodies in MG patients and discuss their role in the pathology of this autoimmune disease.
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Affiliation(s)
- Kathleen Vrolix
- Division of Neuroscience, School of Mental Health and Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Maastricht, The Netherlands
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40
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Souroujon MC, Brenner T, Fuchs S. Development of novel therapies for MG: Studies in animal models. Autoimmunity 2010; 43:446-60. [DOI: 10.3109/08916930903518081] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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41
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Lagoumintzis G, Zisimopoulou P, Kordas G, Lazaridis K, Poulas K, Tzartos SJ. Recent approaches to the development of antigen-specific immunotherapies for myasthenia gravis. Autoimmunity 2010; 43:436-45. [DOI: 10.3109/08916930903518099] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Main immunogenic region structure promotes binding of conformation-dependent myasthenia gravis autoantibodies, nicotinic acetylcholine receptor conformation maturation, and agonist sensitivity. J Neurosci 2009; 29:13898-908. [PMID: 19890000 DOI: 10.1523/jneurosci.2833-09.2009] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The main immunogenic region (MIR) is a conformation-dependent region at the extracellular apex of alpha1 subunits of muscle nicotinic acetylcholine receptor (AChR) that is the target of half or more of the autoantibodies to muscle AChRs in human myasthenia gravis and rat experimental autoimmune myasthenia gravis. By making chimeras of human alpha1 subunits with alpha7 subunits, both MIR epitopes recognized by rat mAbs and by the patient-derived human mAb 637 to the MIR were determined to consist of two discontiguous sequences, which are adjacent only in the native conformation. The MIR, including loop alpha1 67-76 in combination with the N-terminal alpha helix alpha1 1-14, conferred high-affinity binding for most rat mAbs to the MIR. However, an additional sequence corresponding to alpha1 15-32 was required for high-affinity binding of human mAb 637. A water soluble chimera of Aplysia acetylcholine binding protein with the same alpha1 MIR sequences substituted was recognized by a majority of human, feline, and canine myasthenia gravis sera. The presence of the alpha1 MIR sequences in alpha1/alpha7 chimeras greatly promoted AChR expression and significantly altered the sensitivity to activation. This reveals a structural and functional, as well as antigenic, significance of the MIR.
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43
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Luo J, Lindstrom J. Antigenic structure of the human muscle nicotinic acetylcholine receptor main immunogenic region. J Mol Neurosci 2009; 40:217-20. [PMID: 19705087 DOI: 10.1007/s12031-009-9271-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2009] [Accepted: 07/22/2009] [Indexed: 10/20/2022]
Abstract
The main immunogenic region on the alpha1 subunits of muscle nicotinic acetylcholine receptors provokes half or more of the autoantibodies in myasthenia gravis and its animal model. Many of these autoantibodies depend on the native conformation of the receptor for their ability to bind with high affinity. We mapped this region and explained the conformation dependence of its epitopes by making chimeras in which sequences of human muscle alpha1 subunits were replaced in human neuronal alpha7 subunits or Aplysia acetylcholine binding protein. These chimeras also revealed that the main immunogenic region can play a major role in promoting conformational maturation and, consequently, assembly of receptor subunits.
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Affiliation(s)
- Jie Luo
- Department of Neuroscience, Medical School of the University of Pennsylvania, Philadelphia, PA 19104-6074, USA.
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44
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Hoebeke J, Kaveri S, Strosberg AD. Immunology of muscarinic acetylcholine and beta-adrenergic catecholamine receptors. ACTA MEDICA SCANDINAVICA. SUPPLEMENTUM 2009; 715:107-10. [PMID: 2438905 DOI: 10.1111/j.0954-6820.1987.tb09910.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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45
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Fee DB, Kasarskis EJ. Myasthenia gravis associated with etanercept therapy. Muscle Nerve 2009; 39:866-70. [DOI: 10.1002/mus.21280] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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46
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Yi HJ, Chae CS, So JS, Tzartos SJ, Souroujon MC, Fuchs S, Im SH. Suppression of experimental myasthenia gravis by a B-cell epitope-free recombinant acetylcholine receptor. Mol Immunol 2008; 46:192-201. [DOI: 10.1016/j.molimm.2008.08.264] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 07/31/2008] [Accepted: 08/05/2008] [Indexed: 11/16/2022]
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47
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Lindstrom J, Luo J, Kuryatov A. Myasthenia gravis and the tops and bottoms of AChRs: antigenic structure of the MIR and specific immunosuppression of EAMG using AChR cytoplasmic domains. Ann N Y Acad Sci 2008; 1132:29-41. [PMID: 18567851 DOI: 10.1196/annals.1405.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The main immunogenic region (MIR), against which half or more of the autoantibodies to acetylcholine receptors (AChRs) in myasthenia gravis (MG) or experimental autoimmune MG (EAMG) are directed, is located at the extracellular end of alpha1 subunits. Rat monoclonal antibodies (mAbs) to the MIR efficiently compete with MG patient autoantibodies for binding to human muscle AChRs. Antibodies bound to the MIR do not interfere with cholinergic ligand binding or AChR function, but target complement and trigger antigenic modulation. Rat mAbs to the MIR also bind to human ganglionic AChR alpha3 subunits, but MG patient antibodies do not. By making chimeras of alpha1 subunits with alpha7 subunits or ACh binding protein, the structure of the MIR and its functional effects are being investigated. Many mAbs to the MIR bind only to the native conformation of alpha1 subunits because they bind to sequences that are adjacent only in the native structure. The MIR epitopes recognized by these mAbs are not recognized by most patient antibodies whose epitopes must be nearby. The presence of the MIR epitopes in alpha1/alpha7 chimeras greatly promotes AChR expression and sensitivity to activation. EAMG can be suppressed by treatment with denatured, bacterially expressed mixtures of extracellular and cytoplasmic domains of human alpha1, beta1, gamma, delta, and epsilon subunits. A mixture of only the cytoplasmic domains not only avoids the potential liability of provoking formation antibodies to pathologically significant epitopes on the extracellular surface, but also potently suppresses the development of EAMG.
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Affiliation(s)
- Jon Lindstrom
- Department of Neuroscience, Medical School of the University of Pennsylvania, 217 Stemmler Hall, Philadelphia, PA 19104, USA.
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48
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Losen M, Martínez-Martínez P, Phernambucq M, Schuurman J, Parren PW, De Baets MH. Treatment of Myasthenia Gravis by Preventing Acetylcholine Receptor Modulation. Ann N Y Acad Sci 2008; 1132:174-9. [DOI: 10.1196/annals.1405.034] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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49
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Lindstrom JM. Structure of the acetylcholine receptor and specificities of antibodies to it in myasthenia gravis. CIBA FOUNDATION SYMPOSIUM 2008:178-96. [PMID: 6923807 DOI: 10.1002/9780470720721.ch11] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Acetylcholine receptors in skeletal muscle and fish electric organs are intrinsic membrane proteins whose function is to bind acetylcholine released from the nerve ending and trigger the opening of a cation-specific channel in the postsynaptic membrane, thereby facilitating transmission of the nerve signal to the muscle. Investigations from several laboratories indicate that acetylcholine receptors from fish electric organs are composed of four homologous glycoprotein subunits of apparent relative molecular masses (Mr) approximating 40, 50, 57 and 64 x 10(3) designated, respectively, alpha, beta, gamma and delta. These subunits are present in receptor monomers in the mole ratio alpha 2 beta gamma delta. Receptor purified from skeletal muscle appears to have a similar structure. The alpha subunits are unknown. It is known that the cation channel regulated by acetylcholine binding is located within the receptor monomer. Experimental autoimmune myasthenia gravis (EAMG) is induced by immunizing animals with purified receptor. The mechanisms by which neuromuscular transmission is impaired in this model are very similar to those in myasthenia gravis (MG). Although there are many immunogenic determinants on receptors, and EAMG can be induced in rats by any of the denatured subunits, there is a main immunogenic region at which most of the antibodies to native receptors are directed. The main immunogenic region is a conformationally dependent part of the external surface of alpha subunits other than the acetylcholine-binding site or the attached carbohydrate. Antisera from MG patients are also directed primarily at this region. No correlation was detected between the specificities of antibodies to receptor in patients' sera and the severity of their weakness.
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50
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Vernino S, Lindstrom J, Hopkins S, Wang Z, Low PA. Characterization of ganglionic acetylcholine receptor autoantibodies. J Neuroimmunol 2008; 197:63-9. [PMID: 18485491 DOI: 10.1016/j.jneuroim.2008.03.017] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2008] [Revised: 03/28/2008] [Accepted: 03/28/2008] [Indexed: 10/22/2022]
Abstract
In myasthenia gravis (MG), autoantibodies bind to the alpha1 subunit and other subunits of the muscle nicotinic acetylcholine receptor (AChR). Autoimmune autonomic ganglionopathy (AAG) is an antibody-mediated neurological disorder caused by antibodies against neuronal AChRs in autonomic ganglia. Subunits of muscle and neuronal AChR are homologous. We examined the specificity of AChR antibodies in patients with MG and AAG. Ganglionic AChR autoantibodies found in AAG patients are specific for AChRs containing the alpha3 subunit. Muscle and ganglionic AChR antibody specificities are distinct. Antibody crossreactivity between AChRs with different alpha subunits is uncommon but can occur.
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Affiliation(s)
- Steven Vernino
- Department of Neurology, UT Southwestern Medical Center, Dallas Texas 75390-9036, United States.
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