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Haufe Y, Loser D, Danker T, Nicke A. Symmetrical Bispyridinium Compounds Act as Open Channel Blockers of Cation-Selective Ion Channels. ACS Pharmacol Transl Sci 2024; 7:771-786. [PMID: 38495220 PMCID: PMC10941285 DOI: 10.1021/acsptsci.3c00308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 01/12/2024] [Accepted: 01/16/2024] [Indexed: 03/19/2024]
Abstract
Current treatments against organophosphate poisoning (OPP) do not directly address effects mediated by the overstimulation of nicotinic acetylcholine receptors (nAChR). Non-oxime bispyridinium compounds (BPC) promote acetylcholine esterase-independent recovery of organophosphate-induced paralysis. Here, we test the hypothesis that they act by positive modulatory action on nAChRs. Using two-electrode voltage clamp analysis in combination with mutagenesis and molecular docking analysis, the potency and molecular mode of action of a series of nine BPCs was investigated on human α7 and muscle-type nAChRs expressed in Xenopus laevis oocytes. The investigated BPCs inhibited α7 and/or muscle-type nAChRs with IC50 values in the high nanomolar to high micromolar range. Further analysis of the most potent analogues revealed a noncompetitive, voltage-dependent inhibition. Co-application with the α7-selective positive allosteric modulator PNU120596 and generation of α7/5HT3 receptor chimeras excluded direct interaction with the PNU120596 binding site and binding to the extracellular domain of the α7 nAChR, suggesting that they act as open channel blockers (OCBs). Molecular docking supported by mutagenesis localized the BPC binding area in the outer channel vestibule between the extracellular and transmembrane domains. Analysis of BPC action on other cation-selective channels suggests a rather nonspecific inhibition of pentameric cation channels. BPCs have been shown to ameliorate organophosphate-induced paralysis in vitro and in vivo. Our data support molecular action as OCBs at α7 and muscle-type nAChRs and suggest that their positive physiological effects are more complex than anticipated and require further investigation.
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Affiliation(s)
- Yves Haufe
- Walther
Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, LMU Munich, 80336 Munich, Germany
| | - Dominik Loser
- NMI
Natural and Medical Sciences Institute at the University of Tübingen, 72770 Reutlingen, Germany
| | - Timm Danker
- NMI
Natural and Medical Sciences Institute at the University of Tübingen, 72770 Reutlingen, Germany
| | - Annette Nicke
- Walther
Straub Institute of Pharmacology and Toxicology, Faculty of Medicine, LMU Munich, 80336 Munich, Germany
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2
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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 DOI: 10.1007/s00401-023-02603-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [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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Cai Y, Han L, Zhu D, Peng J, Li J, Ding J, Luo J, Hong R, Wang K, Wan W, Xie C, Zhou X, Zhang Y, Hao Y, Guan Y. A Stable Cell Line Expressing Clustered AChR: A Novel Cell-Based Assay for Anti-AChR Antibody Detection in Myasthenia Gravis. Front Immunol 2021; 12:666046. [PMID: 34305897 PMCID: PMC8297518 DOI: 10.3389/fimmu.2021.666046] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 05/28/2021] [Indexed: 12/13/2022] Open
Abstract
Cell-based assays (CBAs) and radioimmunoprecipitation assay (RIPA) are the most sensitive methods for identifying anti-acetylcholine receptor (AChR) antibody in myasthenia gravis (MG). But CBAs are limited in clinical practice by transient transfection. We established a stable cell line (KL525) expressing clustered AChR by infecting HEK 293T cells with dual lentiviral vectors expressing the genes encoding the human AChR α1, β1, δ, ϵ and the clustering protein rapsyn. We verified the stable expression of human clustered AChR by immunofluorescence, immunoblotting, and real-time PCR. Fluorescence-activated cell sorting (FACS) was used to detect anti-AChR antibodies in 103 MG patients and 58 healthy individuals. The positive results of MG patients reported by the KL525 was 80.6% (83/103), 29.1% higher than the 51.4% (53/103) of RIPA. 58 healthy individuals tested by both the KL525 CBA and RIPA were all negative. In summary, the stable expression of clustered AChR in our cell line makes it highly sensitive and advantageous for broad clinical application in CBAs.
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Affiliation(s)
- Yu Cai
- Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Lu Han
- Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Desheng Zhu
- Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Jing Peng
- Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Jianping Li
- Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Jie Ding
- Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Jiaying Luo
- Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Ronghua Hong
- Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Kan Wang
- Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Wenbin Wan
- Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Chong Xie
- Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Xiajun Zhou
- Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Ying Zhang
- Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Yong Hao
- Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Yangtai Guan
- Department of Neurology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
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Timperley CM, Bird M, Gore SJ, Lindsay CD, Rice H, Tattersall JEH, Whitmore CL, Green AC. 3-Quinuclidinyl-α-methoxydiphenylacetate: A multi-targeted ligand with antimuscarinic and antinicotinic effects designed for the treatment of anticholinesterase poisoning. Toxicol Lett 2020; 325:67-76. [PMID: 32017982 DOI: 10.1016/j.toxlet.2020.01.027] [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: 10/01/2019] [Revised: 01/29/2020] [Accepted: 01/31/2020] [Indexed: 10/25/2022]
Abstract
Racemic 3-quinuclidinyl-α-methoxydiphenylacetate (MB266) was synthesised. Its activity at muscarinic acetylcholine receptors (mAChRs), and muscle and neuronal nicotinic acetylcholine receptors (nAChRs), was compared to that of atropine and racemic 3-quinucidinyl benzilate (QNB) using a functional assay based on agonist-induced elevation of intracellular calcium ion concentration in CN21, Chinese Hamster Ovary (CHO) and SHSY5Y human cell lines. MB266 acted as an antagonist at acetylcholine receptors, displaying 18-fold selectivity for mAChR versus nAChR (compared to the 15,200-fold selectivity observed for QNB). Thus O-methylation of QNB reduced the affinity for mAChR antagonism and increased the relative potency at both muscle and neuronal nAChRs. Despite MB266 having a pharmacological profile potentially useful for the treatment of anticholinesterase poisoning, its administration did not improve the neuromuscular function in a soman-poisoned guinea-pig diaphragm preparation pretreated with the organophosphorus nerve agent soman. Consideration should be given to exploring the potential of MB266 for possible anticonvulsant action in vitro as part of a multi-targeted ligand approach.
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Affiliation(s)
- Christopher M Timperley
- Chemical, Biological and Radiological (CBR) Division, Defence Science and Technology Laboratory (Dstl), Porton Down, Salisbury, Wiltshire SP4 0JQ, UK.
| | - Mike Bird
- Chemical, Biological and Radiological (CBR) Division, Defence Science and Technology Laboratory (Dstl), Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
| | - Samuel J Gore
- Chemical, Biological and Radiological (CBR) Division, Defence Science and Technology Laboratory (Dstl), Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
| | - Christopher D Lindsay
- Chemical, Biological and Radiological (CBR) Division, Defence Science and Technology Laboratory (Dstl), Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
| | - Helen Rice
- Chemical, Biological and Radiological (CBR) Division, Defence Science and Technology Laboratory (Dstl), Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
| | - John E H Tattersall
- Chemical, Biological and Radiological (CBR) Division, Defence Science and Technology Laboratory (Dstl), Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
| | - Charlotte L Whitmore
- Chemical, Biological and Radiological (CBR) Division, Defence Science and Technology Laboratory (Dstl), Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
| | - A Christopher Green
- Chemical, Biological and Radiological (CBR) Division, Defence Science and Technology Laboratory (Dstl), Porton Down, Salisbury, Wiltshire SP4 0JQ, UK
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5
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Cetin H, Webster R, Liu WW, Nagaishi A, Koneczny I, Zimprich F, Maxwell S, Cossins J, Beeson D, Vincent A. Myasthenia gravis AChR antibodies inhibit function of rapsyn-clustered AChRs. J Neurol Neurosurg Psychiatry 2020; 91:526-532. [PMID: 32165373 PMCID: PMC7231439 DOI: 10.1136/jnnp-2019-322640] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2019] [Revised: 02/24/2020] [Accepted: 02/25/2020] [Indexed: 11/27/2022]
Abstract
OBJECTIVE Direct inhibition of acetylcholine receptor (AChR) function by autoantibodies (Abs) is considered a rare pathogenic mechanism in myasthenia gravis (MG), but is usually studied on AChRs expressed in cell lines, rather than tightly clustered by the intracellular scaffolding protein, rapsyn, as at the intact neuromuscular junction. We hypothesised that clustered AChRs would provide a better target for investigating the functional effects of AChR-Abs. METHODS Acetylcholine-induced currents were measured using whole-cell patch clamping and a fast perfusion system to assess fast (<2 min) functional effects of the serum samples. The sensitivity, specificity and rapidity of the system were first demonstrated by applying maternal AChR-Ab positive plasmas known to inhibit fetal AChR function in TE671 cells. Eleven previously untested AChR-Ab positive MG sera, 10 AChR-Ab negative MG sera and 5 healthy control sera were then applied to unclustered and rapsyn-clustered human adult AChRs in CN21 cells. RESULTS The maternal AChR-Ab positive plasmas reduced fetal AChR currents, but not adult AChR currents, by >80% within 100 s. Only 2/11 AChR-Ab positive sera inhibited AChR currents in unclustered AChRs, but 6/11 AChR-Ab positive sera compared with none of the 10 AChR-Ab negative sera (p=0.0020) inhibited rapsyn-clustered AChR currents, and current inhibition by the AChR-Ab positive sera was greater when the AChRs were clustered (p=0.0385). None of the sera had detectable effects on desensitisation or recovery from desensitisation. CONCLUSION These results show that antibodies can inhibit AChR function rapidly and demonstrate the importance of clustering in exploring pathogenic disease mechanisms of MG Abs.
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Affiliation(s)
- Hakan Cetin
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK.,Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Richard Webster
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK
| | - Wei Wei Liu
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK
| | - Akiko Nagaishi
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK
| | - Inga Koneczny
- Institute of Neurology, Medical University of Vienna, Vienna, Austria
| | - Fritz Zimprich
- Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Susan Maxwell
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK
| | - Judith Cossins
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, UK
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6
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Assessment of false transmitters as treatments for nerve agent poisoning. Toxicol Lett 2020; 321:21-31. [DOI: 10.1016/j.toxlet.2019.12.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 12/04/2019] [Accepted: 12/08/2019] [Indexed: 11/20/2022]
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7
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Hepnarova V, Muckova L, Ring A, Pejchal J, Herman D, Misik J, Hrabinova M, Jun D, Soukup O. Pharmacological and toxicological in vitro and in vivo effect of higher doses of oxime reactivators. Toxicol Appl Pharmacol 2019; 383:114776. [DOI: 10.1016/j.taap.2019.114776] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2019] [Revised: 09/18/2019] [Accepted: 10/04/2019] [Indexed: 12/26/2022]
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8
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Cetin H, Liu W, Cheung J, Cossins J, Vanhaesebrouck A, Maxwell S, Vincent A, Beeson D, Webster R. Rapsyn facilitates recovery from desensitization in fetal and adult acetylcholine receptors expressed in a muscle cell line. J Physiol 2019; 597:3713-3725. [PMID: 31158924 PMCID: PMC6767687 DOI: 10.1113/jp277819] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Accepted: 06/03/2019] [Indexed: 01/29/2023] Open
Abstract
Key points The physiological significance of the developmental switch from fetal to adult acetylcholine receptors in muscle (AChRs) and the functional impact of AChR clustering by rapsyn are not well studied. Using patch clamp experiments, we show that recovery from desensitization is faster in the adult AChR isoform. Recovery from desensitization is determined by the AChR isoform‐specific cytoplasmic M3–M4 domain. The co‐expression of rapsyn in muscle cells induced AChR clustering and facilitated recovery from desensitization in both fetal and adult AChRs. In fetal AChRs, facilitation of recovery kinetics by rapsyn was independent of AChR clustering. These effects could be crucial adaptations to motor neuron firing rates, which, in rodents, have been shown to increase around the time of birth when AChRs cluster at the developing neuromuscular junctions.
Abstract The neuromuscular junction (NMJ) is the site of a number of autoimmune and genetic disorders, many involving the muscle‐type nicotinic acetylcholine receptor (AChR), although there are aspects of normal NMJ development and function that need to be better understood. In particular, there are still questions regarding the implications of the developmental switch from fetal to adult AChRs, as well as how their functions might be modified by rapsyn that clusters the AChRs. Desensitization of human muscle AChRs was investigated using the patch clamp technique to measure whole‐cell currents in muscle‐type (TE671/CN21) and non‐muscle (HEK293) cell lines expressing either fetal or adult AChRs. Desensitization time constants were similar with both AChR isoforms but recovery time constants were shorter in cells expressing adult compared to fetal AChRs (P < 0.0001). Chimeric experiments showed that recovery from desensitization was determined by the M3–M4 cytoplasmic loops of the γ‐ and ε‐subunits. Expression of rapsyn in TE671/CN21 cells induced AChR aggregation and also, surprisingly, shortened recovery time constants in both fetal and adult AChRs. However, this was not dependent on clustering because rapsyn also facilitated recovery from desensitization in HEK293 cells expressing a δ‐R375H AChR mutant that did not form clusters in C2C12 myotubes. Thus, rapsyn interactions with AChRs lead not only to clustering, but also to a clustering independent faster recovery from desensitization. Both effects of rapsyn could be a necessary adjustment to the motor neuron firing rates that increase around the time of birth. The physiological significance of the developmental switch from fetal to adult acetylcholine receptors in muscle (AChRs) and the functional impact of AChR clustering by rapsyn are not well studied. Using patch clamp experiments, we show that recovery from desensitization is faster in the adult AChR isoform. Recovery from desensitization is determined by the AChR isoform‐specific cytoplasmic M3–M4 domain. The co‐expression of rapsyn in muscle cells induced AChR clustering and facilitated recovery from desensitization in both fetal and adult AChRs. In fetal AChRs, facilitation of recovery kinetics by rapsyn was independent of AChR clustering. These effects could be crucial adaptations to motor neuron firing rates, which, in rodents, have been shown to increase around the time of birth when AChRs cluster at the developing neuromuscular junctions.
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Affiliation(s)
- Hakan Cetin
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, UK.,Department of Neurology, Medical University of Vienna, Vienna, Austria
| | - Wei Liu
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - Jonathan Cheung
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - Judith Cossins
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - An Vanhaesebrouck
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - Susan Maxwell
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - Angela Vincent
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - David Beeson
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, UK
| | - Richard Webster
- Nuffield Department of Clinical Neurosciences, University of Oxford, John Radcliffe Hospital, Oxford, UK
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9
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Knuhtsen A, Whitmore C, McWhinnie FS, McDougall L, Whiting R, Smith BO, Timperley CM, Green AC, Kinnear KI, Jamieson AG. α-Conotoxin GI triazole-peptidomimetics: potent and stable blockers of a human acetylcholine receptor. Chem Sci 2019. [DOI: 10.1039/c8sc04198a] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A conotoxin peptidomimetic was developed as a potential muscle relaxant that is highly potent and blood plasma stable.
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Affiliation(s)
| | - Charlotte Whitmore
- Chemical, Biological and Radiological Division
- Defence Science and Technology Laboratory
- Salisbury
- SP4 0JQ UK
| | | | | | - Rachel Whiting
- Chemical, Biological and Radiological Division
- Defence Science and Technology Laboratory
- Salisbury
- SP4 0JQ UK
| | - Brian O. Smith
- Institute of Molecular, Cell & Systems Biology
- College of Medical, Veterinary & Life Sciences
- University of Glasgow
- Glasgow
- G12 8QQ UK
| | - Christopher M. Timperley
- Chemical, Biological and Radiological Division
- Defence Science and Technology Laboratory
- Salisbury
- SP4 0JQ UK
| | - A. Christopher Green
- Chemical, Biological and Radiological Division
- Defence Science and Technology Laboratory
- Salisbury
- SP4 0JQ UK
| | - Kenneth I. Kinnear
- Chemical, Biological and Radiological Division
- Defence Science and Technology Laboratory
- Salisbury
- SP4 0JQ UK
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Muneoka S, Nakamura R, Hoshino M, Utsugisawa K, Makino T. Development of a novel immunoassay to select antibodies against intact membrane antigens by using the homogeneous AlphaLISA system. J Biosci Bioeng 2018; 126:522-526. [DOI: 10.1016/j.jbiosc.2018.04.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Revised: 04/13/2018] [Accepted: 04/25/2018] [Indexed: 12/11/2022]
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11
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Heterogeneity of auto-antibodies against nAChR in myasthenic serum and their pathogenic roles in experimental autoimmune myasthenia gravis. J Neuroimmunol 2018; 320:64-75. [PMID: 29759142 DOI: 10.1016/j.jneuroim.2018.04.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Revised: 04/23/2018] [Accepted: 04/23/2018] [Indexed: 11/20/2022]
Abstract
Many myasthenia gravis (MG) patients have auto-antibodies against the nicotinic acetylcholine receptor (nAChR), and monoclonal antibodies against the main immunogenic region (MIR) of nAChR can induce experimental autoimmune MG (EAMG). We investigated whether Fab fragment of MIR antibody (Fab35) could block the pathogenicity of polyclonal antibodies. Fab35 partially inhibited nAChR downmodulation, blocked EAMG serum-induced binding of polyclonal antibodies and complement deposition in vitro. Moreover, Fab35 did not ameliorate the EAMG serum-induced EAMG phenotype in rats. These results suggested that the EAMG serum possessed several different pathogenic antibodies that might be sufficient to induce the EAMG phenotype.
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Analysis of peripheral B cells and autoantibodies against the anti-nicotinic acetylcholine receptor derived from patients with myasthenia gravis using single-cell manipulation tools. PLoS One 2017; 12:e0185976. [PMID: 29040265 PMCID: PMC5645109 DOI: 10.1371/journal.pone.0185976] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Accepted: 09/23/2017] [Indexed: 11/23/2022] Open
Abstract
The majority of patients with myasthenia gravis (MG), an organ-specific autoimmune disease, harbor autoantibodies that attack the nicotinic acetylcholine receptor (nAChR-Abs) at the neuromuscular junction of skeletal muscles, resulting in muscle weakness. Single cell manipulation technologies coupled with genetic engineering are very powerful tools to examine T cell and B cell repertoires and the dynamics of adaptive immunity. These tools have been utilized to develop mAbs in parallel with hybridomas, phage display technologies and B-cell immortalization. By applying a single cell technology and novel high-throughput cell-based binding assays, we identified peripheral B cells that produce pathogenic nAChR-Abs in patients with MG. Although anti-nAChR antibodies produced by individual peripheral B cells generally exhibited low binding affinity for the α-subunit of the nAChR and great sequence diversity, a small fraction of these antibodies bound with high affinity to native-structured nAChRs on cell surfaces. B12L, one such Ab isolated here, competed with a rat Ab (mAb35) for binding to the human nAChR and thus considered to recognize the main immunogenic region (MIR). By evaluating the Ab in in vitro cell-based assays and an in vivo rat passive transfer model, B12L was found to act as a pathogenic Ab in rodents and presumably in humans.These findings suggest that B cells in peripheral blood may impact MG pathogenicity. Our methodology can be applied not only to validate pathogenic Abs as molecular target of MG treatment, but also to discover and analyze Ab production systems in other human diseases.
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13
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Ring A, Strom BO, Turner SR, Timperley CM, Bird M, Green AC, Chad JE, Worek F, Tattersall JEH. Bispyridinium Compounds Inhibit Both Muscle and Neuronal Nicotinic Acetylcholine Receptors in Human Cell Lines. PLoS One 2015; 10:e0135811. [PMID: 26274808 PMCID: PMC4537131 DOI: 10.1371/journal.pone.0135811] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Accepted: 07/27/2015] [Indexed: 11/30/2022] Open
Abstract
Standard treatment of poisoning by organophosphorus anticholinesterases uses atropine to reduce the muscarinic effects of acetylcholine accumulation and oximes to reactivate acetylcholinesterase (the effectiveness of which depends on the specific anticholinesterase), but does not directly address the nicotinic effects of poisoning. Bispyridinium molecules which act as noncompetitive antagonists at nicotinic acetylcholine receptors have been identified as promising compounds and one has been shown to improve survival following organophosphorus poisoning in guinea-pigs. Here, we have investigated the structural requirements for antagonism and compared inhibitory potency of these compounds at muscle and neuronal nicotinic receptors and acetylcholinesterase. A series of compounds was synthesised, in which the length of the polymethylene linker between the two pyridinium moieties was increased sequentially from one to ten carbon atoms. Their effects on nicotinic receptor-mediated calcium responses were tested in muscle-derived (CN21) and neuronal (SH-SY5Y) cells. Their ability to inhibit acetylcholinesterase activity was tested using human erythrocyte ghosts. In both cell lines, the nicotinic response was inhibited in a dose-dependent manner and the inhibitory potency of the compounds increased with greater linker length between the two pyridinium moieties, as did their inhibitory potency for human acetylcholinesterase activity in vitro. These results demonstrate that bispyridinium compounds inhibit both neuronal and muscle nicotinic receptors and that their potency depends on the length of the hydrocarbon chain linking the two pyridinium moieties. Knowledge of structure-activity relationships will aid the optimisation of molecular structures for therapeutic use against the nicotinic effects of organophosphorus poisoning.
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Affiliation(s)
- Avi Ring
- Norwegian Defence Research Establishment, Kjeller, Norway
| | | | - Simon R. Turner
- Dstl Porton Down, Salisbury, Wiltshire, United Kingdom
- Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
| | | | - Michael Bird
- Dstl Porton Down, Salisbury, Wiltshire, United Kingdom
| | | | - John E. Chad
- Institute for Life Sciences, University of Southampton, Southampton, United Kingdom
| | - Franz Worek
- Bundeswehr Institute of Pharmacology and Toxicology, Munich, Germany
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Zoltowska K, Webster R, Finlayson S, Maxwell S, Cossins J, Müller J, Lochmüller H, Beeson D. Mutations in GFPT1 that underlie limb-girdle congenital myasthenic syndrome result in reduced cell-surface expression of muscle AChR. Hum Mol Genet 2013; 22:2905-13. [DOI: 10.1093/hmg/ddt145] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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15
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Zisimopoulou P, Brenner T, Trakas N, Tzartos SJ. Serological diagnostics in myasthenia gravis based on novel assays and recently identified antigens. Autoimmun Rev 2013; 12:924-30. [PMID: 23537507 DOI: 10.1016/j.autrev.2013.03.002] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/12/2013] [Indexed: 10/27/2022]
Abstract
Myasthenia gravis (MG) is the most common immune-mediated disorder of the neuromuscular junction with a prevalence of 200-300/million population and its study has established paradigms for exploring other antibody-mediated diseases. Most MG patients (~85%) have autoantibodies against the muscle acetylcholine receptor (AChR-MG), whereas about 6% of MG patients have autoantibodies against the muscle specific kinase (MuSK-MG). Until recently no autoantibodies could be detected in the remaining patients (seronegative MG). Probably, the most sensitive assays for the detection of the autoantibodies in MG sera have been the radioimmunoprecipitation assays (RIPA) for both types of MG. However, with recent novel methods, not yet used routinely, it has been shown that the "seronegative" MG group includes patients with low levels of autoantibodies or of low affinity, against the known autoantigens, or even with antibodies to recently identified autoantigens. Since MG is heterogeneous in terms of pathophysiology, depending on the autoantigen targeted and on other factors (e.g. presence of thymoma), the serological tests are crucial in verifying the initial clinical diagnosis, whereas frequent measurement of autoantibody levels is important in monitoring the course of the disease and the efficacy of treatment. In addition, in AChR-MG, autoantibodies against the muscle proteins titin and ryanodin receptor have been identified; these antibodies are useful for the classification of MG, indicating the concomitant presence of thymoma, and as prognostic markers.
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16
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Turner SR, Chad JE, Price M, Timperley CM, Bird M, Green AC, Tattersall JEH. Protection against nerve agent poisoning by a noncompetitive nicotinic antagonist. Toxicol Lett 2011; 206:105-11. [PMID: 21641979 DOI: 10.1016/j.toxlet.2011.05.1035] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 05/20/2011] [Accepted: 05/23/2011] [Indexed: 11/18/2022]
Abstract
The acute toxicity of organophosphorus (OP) nerve agents arises from accumulation of acetylcholine (ACh) and overstimulation of ACh receptors. The mainstay of current pharmacotherapy is the competitive muscarinic antagonist, atropine. Nicotinic antagonists have not been used due to the difficulties of administering a dose of a competitive neuromuscular blocker sufficient to antagonise the effects of excessive ACh, but not so much that it paralyses the muscles. An alternative approach would be to use a noncompetitive antagonist whose effects would not be overcome by increasing ACh concentrations. This study demonstrates that the compound 1,1'-(propane-1,3-diyl)bis(4-tert-butylpyridinium), which blocks open nicotinic ion channels noncompetitively, is able to reverse the neuromuscular paralysis after nerve agent poisoning in vitro and to protect guinea pigs against poisoning by nerve agents when used as part of a therapeutic drug combination including a muscarinic antagonist. In contrast to the oxime HI-6, this compound was equally effective in protecting against poisoning by sarin or tabun. Further studies should identify more effective compounds with this action and optimise doses for protection against nerve agent poisoning in vivo.
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Affiliation(s)
- S R Turner
- Biomedical Sciences Department, Dstl Porton Down, Salisbury SP40JQ, Wiltshire, UK
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17
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Abstract
The diagnostic use of antibodies is dependent on sensitivity and specificity of the methods of antibody detection, which have been developed and improved over the years. Here, we review the different methods for the detection of acetylcholine receptor and muscle-specific kinase antibodies, which are, so far, the only antibodies recognised as pathogenic in myasthenia gravis (MG). Seronegative MG patients will benefit from more sensitive methods of antibody detection. The most recent developments in antibody detection assays, particularly those based on cells expressing target antigens, allow rapid and reliable identification of autoantibodies, improving the diagnosis and treatment of MG patients. The same approaches to antibody detection are now being applied to a wide range of other autoantigens and other autoimmune diseases.
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Affiliation(s)
- M Isabel Leite
- Department of Clinical Neurology, John Radcliffe Hospital, University of Oxford, West Wing OX3 9DS, UK
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18
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Maclennan CA, Vincent A, Marx A, Willcox N, Gilhus NE, Newsom-Davis J, Beeson D. Preferential expression of AChR epsilon-subunit in thymomas from patients with myasthenia gravis. J Neuroimmunol 2008; 201-202:28-32. [PMID: 18657869 DOI: 10.1016/j.jneuroim.2008.06.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2008] [Revised: 06/16/2008] [Accepted: 06/17/2008] [Indexed: 11/19/2022]
Abstract
The role of antigen expression by thymomas in myasthenia gravis (MG) is not clear. Previous reports of acetylcholine receptor (AChR) mRNA expression by the highly sensitive reverse transcription-polymerase chain reactions (RT-PCR) produced varying results. To try to clarify this issue, we first used RT-PCR but then turned to the more accurate and quantitative RNase protection assays (RPA) to assess AChR subunit mRNA expression in thymomas from 25 patients (22 with MG). By RT-PCR, all five AChR subunits could be detected in many thymomas. However, by RPA, the mRNA for the adult-specific AChR epsilon-subunit was found in 13/25 (52%) thymomas, but not mRNA for the other subunits. AChR epsilon-subunit was more frequently detected in thymomas of A or AB histology (WHO classification) than those with B1-B3 histology. Overall, 6/6 with thymomas of A or AB histology were positive compared with only 8/19 with B histology (p=0.02). Autoantibodies in the two patients with the highest levels of epsilon-subunit mRNA bound better to adult (alpha(2)betadeltaepsilon) AChR than to fetal (alpha(2)betadeltagamma) AChR, whereas the other sera bound better to fetal AChR. The greater abundance of mRNA for AChR epsilon-subunit than for other subunits suggests that the AChR epsilon-subunit may play a distinctive role in autosensitization in MG-associated thymomas, particularly those of type A or AB.
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Affiliation(s)
- Calman A Maclennan
- Neurosciences Group, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford OX3 9DS, UK
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19
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Chan KH, Lachance DH, Harper CM, Lennon VA. Frequency of seronegativity in adult-acquired generalized myasthenia gravis. Muscle Nerve 2008; 36:651-8. [PMID: 17654558 DOI: 10.1002/mus.20854] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We determined the prevalence of muscle acetylcholine receptor (AChR) antibodies in patients with adult-acquired generalized myasthenia gravis (MG), the seroconversion rate at 12 months, and the prevalence of muscle-specific tyrosine kinase (MuSK) antibody among persistently seronegative patients. We identified 562 consecutive Mayo Clinic patients with MG based on clinical and electrophysiological criteria. At presentation, 508 patients (90.4%) tested positive for AChR binding or AChR modulating antibodies. After 12 months, 15.2% of initially seronegative patients had become seropositive, yielding a seronegativity rate of 8.2% (95% confidence interval: 6.2-9.6%). Among seronegative patients not receiving immunosuppressants, 38% were MuSK antibody-positive and 43% were seropositive for nonmuscle autoantibodies. Classification as seronegative MG should be reserved for nonimmunosuppressed patients with generalized MG who lack muscle AChR binding, AChR modulating, or MuSK antibodies at presentation and at follow-up of at least 12 months.
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Affiliation(s)
- Koon Ho Chan
- Department of Laboratory Medicine & Pathology, Mayo Clinic, College of Medicine, 200 First Street S.W., Rochester, Minnesota 55905, USA
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20
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Kostelidou K, Trakas N, Tzartos SJ. Extracellular domains of the β, γ and ε subunits of the human acetylcholine receptor as immunoadsorbents for myasthenic autoantibodies: A combination of immunoadsorbents results in increased efficiency. J Neuroimmunol 2007; 190:44-52. [PMID: 17764755 DOI: 10.1016/j.jneuroim.2007.07.018] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Revised: 07/24/2007] [Accepted: 07/25/2007] [Indexed: 11/19/2022]
Abstract
Myasthenia gravis (MG) is usually caused by autoantibodies against the human muscle acetylcholine receptor (AChR). Plasmapheresis offers a therapeutic option, but, as well as removing the pathogenic anti-AChR autoantibodies, it non-specifically removes indispensable immunoglobulins. An attractive alternative to plasmapheresis would be the extracorporeal specific removal of the autoantibodies using AChR-based immunoadsorbents. Previously, we used the N-terminal extracellular domain (ECD) of the AChR alpha subunit to immunoadsorb anti-alpha subunit autoantibodies from MG sera. In this study, we immobilised the beta -, gamma- and epsilon-AChR ECDs on Sepharose and tested them as immunoadsorbents on 50 MG sera. A given ECD removed a different percentage of autoantibodies from different sera and different ECDs removed different percentages from the same serum; on average, the beta-, gamma- and epsilon-ECDs removed 22%, 20% and 15.5% of the autoantibodies, respectively. Immunoadsorption was completed in 3 min, 1 mug of ECD removed approximately 2 pmol of autoantibodies, and the immunoadsorbent could be recycled approximately 4 times. The combined use of two (alpha+gamma) or four (alpha+beta+gamma+epsilon) ECDs in a single immunoadsorbent resulted in much higher (often additive) immunoadsorption. These results show that MG sera have autoantibodies against several AChR subunits, and suggest that the combined use of all AChR ECDs could provide the basis for a novel, antigen-specific therapy for MG.
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21
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Kostelidou K, Trakas N, Zouridakis M, Bitzopoulou K, Sotiriadis A, Gavra I, Tzartos SJ. Expression and characterization of soluble forms of the extracellular domains of the beta, gamma and epsilon subunits of the human muscle acetylcholine receptor. FEBS J 2006; 273:3557-68. [PMID: 16884496 DOI: 10.1111/j.1742-4658.2006.05363.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The nicotinic acetylcholine receptor (AChR) is a ligand-gated ion channel found in muscles and neurons. Muscle AChR, formed by five homologous subunits (alpha2 beta gamma delta or alpha2 beta gamma epsilon), is the major antigen in the autoimmune disease, myasthenia gravis (MG), in which pathogenic autoantibodies bind to, and inactivate, the AChR. The extracellular domain (ECD) of the human muscle alpha subunit has been heterologously expressed and extensively studied. Our aim was to obtain satisfactory amounts of the ECDs of the non-alpha subunits of human muscle AChR for use as starting material for the determination of the 3D structure of the receptor ECDs and for the characterization of the specificities of antibodies in sera from patients with MG. We expressed the N-terminal ECDs of the beta (amino acids 1-221; beta1-221), gamma (amino acids 1-218; gamma1-218), and epsilon (amino acids 1-219; epsilon1-219) subunits of human muscle AChR in the yeast, Pichia pastoris. beta1-221 was expressed at approximately 2 mg.L(-1) culture, whereas gamma1-218 and epsilon1-219 were expressed at 0.3-0.8 mg.L(-1) culture. All three recombinant polypeptides were glycosylated and soluble; beta1-221 was mainly in an apparently dimeric form, whereas gamma1-218 and epsilon1-219 formed soluble oligomers. CD studies of beta1-221 suggested that it has considerable beta-sheet secondary structure with a proportion of alpha-helix. Conformation-dependent mAbs against the ECDs of the beta or gamma subunits specifically recognized beta1-221 or gamma1-218, respectively, and polyclonal rabbit antiserum raised against purified beta1-221 bound to (125)I-labeled alpha-bungarotoxin-labeled human AChR. Moreover, immobilization of each ECD on Sepharose beads and incubation of the ECD-Sepharose matrices with MG sera caused a significant reduction in the concentrations of autoantibodies in the sera, showing specific binding to the recombinant ECDs. These results suggest that the expressed proteins present some near-native conformational features and are thus suitable for our purposes.
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22
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Hewer R, Matthews I, Chen S, McGrath V, Evans M, Roberts E, Nute S, Sanders J, Furmaniak J, Smith BR. A sensitive non-isotopic assay for acetylcholine receptor autoantibodies. Clin Chim Acta 2006; 364:159-66. [PMID: 16051208 DOI: 10.1016/j.cccn.2005.05.035] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2005] [Revised: 05/13/2005] [Accepted: 05/18/2005] [Indexed: 11/19/2022]
Abstract
BACKGROUND Detection and measurement of serum acetylcholine receptor autoantibodies (AChRAb) are useful in the diagnosis and management of myasthenia gravis (MG). An immunoprecipitation assay (IPA) based on AChR labelled with 125I-alpha bungarotoxin is widely used for measurement of AChRAb, but a non-isotopic assay of sensitivity and specificity comparable to IPA is not available as yet. METHODS A new AChRAb ELISA, which is based on the ability of AChRAb to compete with 3 different AChR monoclonal antibodies (MAbs 1-3) for binding sites on affinity purified fetal and adult-type AChR preparations, is described. The sensitivity and specificity of the ELISA were assessed by comparing assay results with a conventional IPA. RESULTS There was good agreement between the IPA and the ELISA for measurement of AChRAb (r = 0.85; n = 83; p <0.001). 76/83 MG sera were positive in the ELISA, whilst 72/83 were positive by IPA. Eight sera were positive in the ELISA (inhibition range 18%-46%) but negative by IPA (0.33-0.47 nmol/L toxin bound) and 4 sera were negative in the ELISA (inhibition range -1% to15%) whilst positive by IPA (0.56-2.9 nmol/L toxin bound). Overall 80/83 (96%) of the MG sera were AChRAb positive in one or both assays. In addition, all 191 control serum samples which were negative for AChRAb by IPA were below or equal to 16% of inhibition in our ELISA. The AChRAb ELISA also showed good inter-assay and intra-assay precision. CONCLUSION The AChRAb ELISA we have described has sensitivity and specificity at least as high as our current radioactive IPA. It has good precision and good handling characteristics making it suitable for routine use.
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Affiliation(s)
- Rachel Hewer
- FIRS Laboratories, RSR Ltd., Parc Ty Glas, Llanishen, Cardiff, CF14 5DU, UK
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23
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Protopapadakis E, Kokla A, Tzartos SJ, Mamalaki A. Isolation and characterization of human anti-acetylcholine receptor monoclonal antibodies from transgenic mice expressing human immunoglobulin loci. Eur J Immunol 2005; 35:1960-8. [PMID: 15915538 DOI: 10.1002/eji.200526173] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The isolation of human antibodies against muscle acetylcholine receptor (AChR), the autoantigen involved in myasthenia gravis (MG), is important for the development of therapeutically useful reagents. Monovalent antibody fragments from monoclonal antibodies against the main immunogenic region (MIR) of AChR protect the receptor from the destructive activity of MG autoantibodies. Human anti-AChR alpha-subunit antibody fragments with therapeutic potential have been isolated using phage display antibody libraries. An alternative approach for obtaining human mAb has been provided by the development of humanized mice. In this report, we show that immunization of transgenic mouse strains with the extracellular domain of the human AChR alpha-subunit results in antibody responses and isolation of hybridomas producing human mAb. Four specific IgM mAb were isolated and analyzed. mAb170 recognized the native receptor the best and was capable of inducing AChR antigenic modulation, suggesting its specificity for a pathogenic epitope. Moreover, the recombinant antigen-binding (Fab) fragment of this mAb competed with an anti-MIR mAb, revealing that its antigenic determinant lies in or near the MIR. Finally, Fab170 was able to compete with MG autoantibodies and protect the AChR against antigenic modulation induced by MG sera. This approach will be useful for isolating additional mAb with therapeutic potential against the other AChR subunits.
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24
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Fostieri E, Tzartos SJ, Berrih-Aknin S, Beeson D, Mamalaki A. Isolation of potent human Fab fragments against a novel highly immunogenic region on human muscle acetylcholine receptor which protect the receptor from myasthenic autoantibodies. Eur J Immunol 2005; 35:632-43. [PMID: 15627975 DOI: 10.1002/eji.200425671] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In the autoimmune disease myasthenia gravis (MG), antibodies against the muscle nicotinic acetylcholine receptor (AChR) cause loss of functional AChR in the neuromuscular junction. To isolate AChR-specific human antibody fragments (Fab), a phage-display library was constructed from an MG patient's thymic B lymphocytes. The first Fab isolated had a low affinity for human AChR, but two sequential antibody chain shufflings using the MG donor heavy and light chain gene repertoires resulted in isolating two new Fab with an approximately 30-fold higher binding ability. The selected Fab contained extensively mutated heavy and light chains and probably represent intraclonal variants of a common progenitor having diverged in vivo by somatic hypermutation. Interestingly, the isolated Fab bound to an extracellular highly immunogenic region located either on an alpha-subunit site affected by the gamma/epsilon-subunits or on the interface between alpha- and gamma/epsilon-subunits. This region is not the previously described "main immunogenic region" (MIR), although it seems to be close to it, as one improved Fab and an anti-MIR mAb competed for AChR binding with distinctly different subpopulations of MG sera. Furthermore, this Fab protected surface AChR in cell cultures against MG autoantibody-induced antigenic modulation, suggesting a potential therapeutic use in MG, especially in combination with a human anti-MIR Fab.
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Affiliation(s)
- Efrosini Fostieri
- Department of Biochemistry, Hellenic Pasteur Institute, Athens, Greece
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25
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Cossins J, Webster R, Maxwell S, Burke G, Vincent A, Beeson D. A mouse model of AChR deficiency syndrome with a phenotype reflecting the human condition. Hum Mol Genet 2004; 13:2947-57. [PMID: 15471888 DOI: 10.1093/hmg/ddh320] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The two subtypes of mammalian muscle nicotinic acetylcholine receptors (AChR) are generated by the substitution of the epsilon (adult) subunit for the gamma (fetal) subunit within the AChR pentamer. Null mutations of the adult AChR epsilon-subunit gene are the most common cause of the AChR deficiency syndrome. This is a disorder of neuromuscular transmission characterized by non-progressive fatigable muscle weakness present throughout life. In contrast with the human disorder, mice with AChR epsilon-subunit null mutations die between 10 and 14 weeks of age. We generated transgenic mice that constitutively express the human AChR gamma-subunit in an AChR epsilon-subunit 'knock-out' background. These mice, in which neuromuscular transmission is mediated by fetal AChR, live well into adult life but show striking similarities to human AChR deficiency syndrome. They display fatigable muscle weakness, reduced miniature endplate potentials and endplate potentials, reduced motor endplate AChR number and altered endplate morphology. Our results illustrate how species differences in the control of ion-channel gene expression may affect disease phenotype, demonstrate that expression of adult AChR subtype is not essential for long-term survival, and suggest that in patients with AChR deficiency syndrome, up-regulation of the gamma-subunit could be a beneficial therapeutic strategy.
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Affiliation(s)
- Judy Cossins
- Neuroscience Group, Weatherall Institute of Molecular Medicine, The John Radcliffe, Oxford, UK
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26
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Ohta K, Fujinami A, Saida T, Nishimura M, Kuno S, Ohta M. Frequency of anti-AChR epsilon subunit-specific antibodies in MG. Autoimmunity 2003; 36:151-4. [PMID: 12911281 DOI: 10.1080/0891693031000094935] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
A definite diagnosis of myasthenia gravis (MG) relies heavily on acetylcholine receptor (AChR) antibody testing. The relatively high number of antibody-negative patients therefore, causes frequent uncertainty in confirming the diagnosis. We evaluated the sensitivity and specificity of a new, commercially available AChR antibody test that uses an approximately equal mixture of AChR from TE671-epsilon (adult type) and TE671-gamma (fetal type) cells. This assay was used to re-examine 365 seronegative MG sera in which AChR antibody had not been detected by the standard assay that uses fetal type AChR. The new assay detected anti-AChR antibodies in 17 (15.5%) of 110 patients with ocular type and in 33 (12.9%) of 255 patients with generalized type MG. Anti-AChR epsilon subunit-specific antibodies were present in 13.7% of the patients in whom no AChR antibody had been detected by the standard assay, showing an increase from 79 to 82% in overall diagnostic sensitivity.
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Affiliation(s)
- Kiyoe Ohta
- Clinical Research Center, Utano National Hospital, Kyoto 616-8255, Japan
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27
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28
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Sims GP, Shiono H, Willcox N, Stott DI. Somatic hypermutation and selection of B cells in thymic germinal centers responding to acetylcholine receptor in myasthenia gravis. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2001; 167:1935-44. [PMID: 11489973 DOI: 10.4049/jimmunol.167.4.1935] [Citation(s) in RCA: 133] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The muscle weakness in myasthenia gravis (MG) is mediated by autoantibodies against the nicotinic acetylcholine receptor (AChR) at the neuromuscular junction. Production of these pathogenic autoantibodies is believed to be associated with germinal centers (GC) and anti-AChR-secreting plasma cells in the hyperplastic thymus of patients with early onset MG (EOMG). Here, we describe the repertoire of rearranged heavy chain V genes and their clonal origins in GC from a typical EOMG patient. Three hundred fifteen rearranged Ig V(H) genes were amplified, cloned, and sequenced from sections of four thymic GC containing AChR-specific B cells. We found that thymic GC contain a remarkably heterogeneous population of B cells. Both naive and circulating memory B cells undergo Ag-driven clonal proliferation, somatic hypermutation, and selection. Numerous B cell clones were present, with no individual clone dominating the response. Comparisons of B cell clonal sequences from different GC and known anti-AChR Abs from other patients showed convergent mutations in the complementarity determining regions. These results are consistent with AChR driving an ongoing GC response in the thymus of EOMG patients. This is the first detailed analysis of B cell clones in human GC responding to a defined protein Ag, and the response we observed may reflect the effects of chronic stimulation by autoantigen.
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Affiliation(s)
- G P Sims
- Department of Immunology and Bacteriology, University of Glasgow, Western Infirmary, Glasgow, Scotland.
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29
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Brownlow S, Webster R, Croxen R, Brydson M, Neville B, Lin JP, Vincent A, Newsom-Davis J, Beeson D. Acetylcholine receptor δ subunit mutations underlie a fast-channel myasthenic syndrome and arthrogryposis multiplex congenita. J Clin Invest 2001. [DOI: 10.1172/jci200112935] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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30
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Brownlow S, Webster R, Croxen R, Brydson M, Neville B, Lin JP, Vincent A, Newsom-Davis J, Beeson D. Acetylcholine receptor delta subunit mutations underlie a fast-channel myasthenic syndrome and arthrogryposis multiplex congenita. J Clin Invest 2001; 108:125-30. [PMID: 11435464 PMCID: PMC209343 DOI: 10.1172/jci12935] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Limitation of movement during fetal development may lead to multiple joint contractures in the neonate, termed arthrogryposis multiplex congenita. Neuromuscular disorders are among the many different causes of reduced fetal movement. Many congenital myasthenic syndromes (CMSs) are due to mutations of the adult-specific epsilon subunit of the acetylcholine receptor (AChR), and, thus, functional deficits do not arise until late in gestation. However, an earlier effect on the fetus might be predicted with some defects of other AChR subunits. We studied a child who presented at birth with joint contractures and was subsequently found to have a CMS. Mutational screening revealed heteroallelic mutation within the AChR delta subunit gene, delta 756ins2 and delta E59K. Expression studies demonstrate that delta 756ins2 is a null mutation. By contrast, both fetal and adult AChR containing delta E59K have shorter than normal channel activations that predict fast decay of endplate currents. Thus, delta E59K causes dysfunction of fetal as well as the adult AChR and would explain the presence of joint contractures on the basis of reduced fetal movement. This is the first report of the association of AChR gene mutations with arthrogryposis multiplex congenita. It is probable that mutations that severely disrupt function of fetal AChR will underlie additional cases.
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Affiliation(s)
- S Brownlow
- Neurosciences Group, Weatherall Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford, United Kingdom
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31
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Blaes F, Beeson D, Plested P, Lang B, Vincent A. IgG from ?seronegative? myasthenia gravis patients binds to a muscle cell line, TE671, but not to human acetylcholine receptor. Ann Neurol 2001. [DOI: 10.1002/1531-8249(200004)47:4<504::aid-ana14>3.0.co;2-q] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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32
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Fostieri E, Beeson D, Tzartos SJ. The conformation of the main immunogenic region on the alpha-subunit of muscle acetylcholine receptor is affected by neighboring receptor subunits. FEBS Lett 2000; 481:127-30. [PMID: 10996310 DOI: 10.1016/s0014-5793(00)01980-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Myasthenia gravis (MG) is caused by autoantibodies to the acetylcholine receptor (AChR). Experiments with fetal (alpha(2)betagammadelta) and adult (alpha(2)betaepsilondelta) AChR and with recombinant subunit dimers showed that some monoclonal antibodies (mAbs) against the main immunogenic region (MIR), located on the alpha-subunit of the AChR, bind better to fetal AChR and to alphagamma subunit dimer than to adult AChR and alphaepsilon dimer and equally to both alphabeta and alphadelta. However, other anti-MIR mAbs prefer adult AChR and alphaepsilon dimer, bind well to alphabeta but weakly to alphadelta. These results suggest that the MIR conformation is affected by the neighboring gamma/epsilon- and delta-subunits and may contribute to understanding the antibody specificities in MG.
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Affiliation(s)
- E Fostieri
- Department of Biochemistry, Hellenic Pasteur Institute, 127 Vas, Sofias Avenue 115 21 Athen, Greece
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33
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Croxen R, Newland C, Betty M, Vincent A, Newsom-Davis J, Beeson D. Novel functional epsilon-subunit polypeptide generated by a single nucleotide deletion in acetylcholine receptor deficiency congenital myasthenic syndrome. Ann Neurol 1999; 46:639-47. [PMID: 10514102 DOI: 10.1002/1531-8249(199910)46:4<639::aid-ana13>3.0.co;2-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Acetylcholine receptor (AChR) deficiency is a recessively inherited congenital myasthenic syndrome in which fatigable muscle weakness results from impaired neuromuscular transmission caused by reduced AChR numbers. In mature muscle, AChRs consist of alpha2 betadelta together with the adult-specific epsilon subunit. We have identified a deletion of the first nucleotide in exon 12 of the AChR epsilon-subunit gene (epsilon1267delG) and demonstrate its recessive inheritance segregates with disease in 6 unrelated cases of AChR deficiency. In addition, we found that both healthy and AChR-deficient muscle contain a population of AChR epsilon-subunit mRNA transcripts that retain intron 11. We investigated the possible consequences of combining this mutation with the alternative mRNA species through AChR expression studies in human embryonic kidney cells and Xenopus oocytes. Epsilon1267delG generates a polypeptide that lacks M4 and is not detected in surface AChR, whereas retention of intron 11 in the RNA transcript restores the reading frame, conserves M4, and generates a polypeptide that is incorporated into functional surface AChR, although at a reduced level, consistent with the disease phenotype. Our results indicate that for some AChR deficiency mutations located between M3 and M4, the retention of intron 11 in the epsilon-subunit mRNA transcripts may rescue adult AChR function.
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Affiliation(s)
- R Croxen
- Neurosciences Group, Institute of Molecular Medicine, The John Radcliffe, Oxford, UK
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34
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Jacobson L, Beeson D, Tzartos S, Vincent A. Monoclonal antibodies raised against human acetylcholine receptor bind to all five subunits of the fetal isoform. J Neuroimmunol 1999; 98:112-20. [PMID: 10430044 DOI: 10.1016/s0165-5728(99)00086-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The human muscle acetylcholine receptor (AChR) is an oligomeric membrane protein consisting of (alpha1)2,beta,delta,epsilon subunits in the adult form and (alpha 1)2,beta,gamma,delta in the fetal form. The adult AChR is the target for autoantibodies in myasthenia gravis (MG), and antibodies that block the function of fetal AChR can cross the placenta and paralyse the developing baby causing joint contractures. Monoclonal antibodies (mAbs) raised against purified AChR were characterised previously in terms of binding to five regions, three of which appeared to partially overlap, but the subunit localisation of the regions was not clearly established and they were assumed to be mainly on the immunodominant alpha subunits. We have studied binding of the mAbs to AChR subunit extracellular fragments expressed in E. coli, and to AChRs derived from TE671 cells and from fibroblast cell lines expressing human/Torpedo and Torpedo/mouse hybrid receptors. Using a combination of Western blotting and immunoprecipitation experiments, we demonstrate the subunit specificity of each mAb. The results confirm our previous observations but importantly show that only two of the regions are on the alpha subunit, the three others being on the beta, gamma and delta subunits of human AChR. Thus these mAbs should be useful in studies of AChR subunit expression in normal and diseased tissue, and to define further the binding sites of antibodies in MG patients.
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Affiliation(s)
- L Jacobson
- Neurosciences Group, Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, UK
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35
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Hill M, Beeson D, Moss P, Jacobson L, Bond A, Corlett L, Newsom-Davis J, Vincent A, Willcox N. Early-onset myasthenia gravis: a recurring T-cell epitope in the adult-specific acetylcholine receptor epsilon subunit presented by the susceptibility allele HLA-DR52a. Ann Neurol 1999; 45:224-31. [PMID: 9989625 DOI: 10.1002/1531-8249(199902)45:2<224::aid-ana13>3.0.co;2-b] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
No immunodominant T-cell epitopes have yet been reported in the human acetylcholine receptor (AChR), the target of the pathogenic autoantibodies in myasthenia gravis (MG). We have selected and characterized T cells from MG patients by restimulation in culture with recombinant human AChR to alpha, gamma and epsilon subunits; the gamma and epsilon distinguish the fetal and adult AChR isoforms, respectively. We obtained clones specific for the epsilon, rather than the alpha or gamma, subunit in 3 of the first 4 early-onset MG cases tested. They all responded to peptide epsilon201-219 and to low concentrations of adult but not fetal AChR. Moreover, although using different T-cell receptor genes, they were all restricted to HLA-DR52a (DRB3*0101), a member of the strongly predisposing HLA-A1-B8-DR3 haplotype. This apparently immunodominant epsilon201-219 epitope (plus DR52a) was also recognized by clones from an elderly patient whose MG had recently been provoked by the drug D-penicillamine. In all 4 cases, however, the serum antibodies reacted better with fetal than adult AChR and may thus be end products of determinant spreading initiated by adult AChR-specific T cell responses. Furthermore, as these T cells had a pathogenic Th1 phenotype, with the potential to induce complement-activating antibodies, they should be important targets for selective immunotherapy.
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Affiliation(s)
- M Hill
- Neurosciences Group, Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, England, UK
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36
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Vincent A, Willcox N, Hill M, Curnow J, MacLennan C, Beeson D. Determinant spreading and immune responses to acetylcholine receptors in myasthenia gravis. Immunol Rev 1998; 164:157-68. [PMID: 9795773 DOI: 10.1111/j.1600-065x.1998.tb01217.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In myasthenia gravis (MG), antibodies to the muscle acetylcholine receptor (AChR) cause muscle weakness. Experimental autoimmune myasthenia gravis (EAMG) can be induced by immunisation against purified AChR; the main immunogenic region (MIR) is a conformation-dependent site that includes alpha 67-76. EAMG can also occur after immunisation against extracellular AChR sequences, but this probably involves intramolecular determinant spreading. In MG patients, thymic hyperplasia and germinal centres are found in about 50%, and thymoma in 10-15%. The heterogeneous, high affinity, IgG anti-AChR antibodies appear to be end-products of germinal centre responses, and react mainly with the MIR or a site on fetal AChR; the latter contains a gamma subunit and is mainly expressed on myoid cells in the thymic medulla. T cells cloned against recombinant AChR subunits recognise principally two naturally processed epitopes: epsilon 201-219 derived from adult AChR which is expressed in muscle, and sometimes in thymic epithelium, and alpha 146-160, common to fetal and adult AChR. Since AChR is not normally co-expressed with class II, it is unclear how CD4+ responses to AChR alpha and epsilon subunits are initiated, and how and where these spread to induce antibodies against fetal AChR. Various possibilities, including upregulation of class II on muscle/myoid cells and involvement of CD8+ responses to AChR and other muscle antigens, are discussed.
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Affiliation(s)
- A Vincent
- Department of Clinical Neurology, John Radcliffe Hospital, Oxford, UK.
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37
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Nagvekar N, Moody AM, Moss P, Roxanis I, Curnow J, Beeson D, Pantic N, Newsom-Davis J, Vincent A, Willcox N. A pathogenetic role for the thymoma in myasthenia gravis. Autosensitization of IL-4- producing T cell clones recognizing extracellular acetylcholine receptor epitopes presented by minority class II isotypes. J Clin Invest 1998; 101:2268-77. [PMID: 9593783 PMCID: PMC508815 DOI: 10.1172/jci2068] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Myasthenia gravis (MG) is caused by helper T cell-dependent autoantibodies against the muscle acetylcholine receptor (AChR). Thymic epithelial tumors (thymomas) occur in 10% of MG patients, but their autoimmunizing potential is unclear. They express mRNAs encoding AChR alpha and epsilon subunits, and might aberrantly select or sensitize developing thymocytes or recirculating peripheral T cells against AChR epitopes. Alternatively, there could be defective self-tolerance induction in the abundant maturing thymocytes that they usually generate. For the first time, we have isolated and characterized AChR-specific T cell clones from two MG thymomas. They recognize extracellular epitopes (alpha75-90 and alpha149-158) which are processed very efficiently from muscle AChR. Both clones express CD4 and CD8alpha, and have a Th-0 cytokine profile, producing IL-4 as well as IFN-gamma. They are restricted to HLA-DP14 and DR52a; expression of these minority isotypes was strong on professional antigen-presenting cells in the donors' tumors, although it is generally weak in the periphery. The two clones' T cell receptor beta chains are different, but their alpha chain sequences are very similar. These resemblances, and the striking contrasts with T cells previously cloned from non-thymoma patients, show that thymomas generate and actively induce specific T cells rather than merely failing to tolerize them against self antigens.
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Affiliation(s)
- N Nagvekar
- Neuroscience Group, Institute for Molecular Medicine, University of Oxford, OX3 9DS, United Kingdom
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38
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Vincent A, Jacobson L, Plested P, Polizzi A, Tang T, Riemersma S, Newland C, Ghorazian S, Farrar J, MacLennan C, Willcox N, Beeson D, Newsom-Davis J. Antibodies affecting ion channel function in acquired neuromyotonia, in seropositive and seronegative myasthenia gravis, and in antibody-mediated arthrogryposis multiplex congenita. Ann N Y Acad Sci 1998; 841:482-96. [PMID: 9668280 DOI: 10.1111/j.1749-6632.1998.tb10968.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
A new autoimmune disease affecting the neuromuscular junction has been defined. Acquired neuromyotonia is associated with antibodies to voltage-gated potassium channels that act, at least in part, by reducing potassium channel function with resulting neuronal hyperactivity. This condition is quite frequently associated with thymoma and, in many cases, antibodies to acetylcholine receptors are present as well as antibodies to VGKC. Improvements in techniques and the availability of cloned DNA and recombinant forms of the AChR subunits have led to new observations concerning the specificity and roles of antibodies in myasthenia gravis. The transfection of a cell line with the epsilon subunit means that we can now accurately compare antibodies reactive with adult and fetal human AChR. This may help to determine the relationship between AChR subunit expression in different tissues and the induction of antibodies that bind specifically to the two forms, as well as to clarify the role of antibodies to fetal or adult AChR in causing ocular muscle symptoms. Serum antibodies from a few mothers with obstetric histories of recurrent arthrogryposis multiplex congenita in their babies specifically inhibit the function of fetal AChR. These observations not only explain the cause of some cases of arthrogryposis multiplex congenita, but also suggest that other fetal-specific antibodies might be responsible for other fetal or neonatal conditions. An animal model has been established to enable us to investigate the role of maternal serum factors in causing such disorders. Seronegative MG has been the subject of many studies from our laboratory over the last ten years. The transience of the effects of SNMG plasmas on AChR function strongly suggests that the plasma antibodies do not bind directly to the AChR, but inhibit function by some indirect mechanism. They do not appear to act via the cAMP-dependent protein kinase pathway, and studies are in progress to investigate the involvement of other second messenger systems.
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Affiliation(s)
- A Vincent
- Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Headington, United Kingdom
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39
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Plested CP, Newsom-Davis J, Vincent A. Seronegative myasthenia plasmas and non-IgG fractions transiently inhibit nAChR function. Ann N Y Acad Sci 1998; 841:501-4. [PMID: 9668282 DOI: 10.1111/j.1749-6632.1998.tb10970.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- C P Plested
- Institute of Molecular Medicine, John Radcliffe Hospital, University of Oxford, Headington, United Kingdom
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40
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MacLennan C, Beeson D, Buijs AM, Vincent A, Newsom-Davis J. Acetylcholine receptor expression in human extraocular muscles and their susceptibility to myasthenia gravis. Ann Neurol 1997; 41:423-31. [PMID: 9124798 DOI: 10.1002/ana.410410404] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
In myasthenia gravis (MG), extraocular muscle (EOM) weakness is often an initial and persisting symptom. It has been proposed that acetylcholine receptor (AChR) from EOM is antigenically different from AChR of other innervated muscles and that the presence of antibodies to fetal AChR expressed in EOM causes their weakness. We have (1) studied mRNA expression for each of the AChR subunits (alpha, beta, gamma, delta, and epsilon) in human muscle, including EOM, and (2) compared the binding of sera from ocular myasthenia gravis (OMG) patients with fetal (alpha2 beta gamma delta) and adult (alpha2 beta epsilon delta) human AChRs. RNase protection assays showed that expression of the AChR gamma-subunit (fetal-type) mRNA in EOM was comparable with that in other innervated muscle types. By contrast, epsilon-subunit (adult-type) mRNA was expressed at much higher levels in EOM than in other muscles studied. Moreover, some OMG sera bound specifically to adult AChR. These results do not support the contention that susceptibility of EOM in MG results from expression of fetal AChR and indicate that the inclusion of antigen from a source rich in adult AChR in the MG diagnostic assay will increase the yield of positive results in OMG patients.
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MESH Headings
- Adolescent
- Adult
- Aged
- Base Sequence
- Cells, Cultured
- Child
- Child, Preschool
- DNA, Complementary/analysis
- Gene Amplification
- Humans
- Infant
- Middle Aged
- Muscle, Skeletal/chemistry
- Muscle, Skeletal/embryology
- Myasthenia Gravis/complications
- Ocular Motility Disorders/diagnosis
- Ocular Motility Disorders/immunology
- Oculomotor Muscles/chemistry
- RNA, Messenger/analysis
- Receptors, Cholinergic/analysis
- Receptors, Cholinergic/genetics
- Receptors, Cholinergic/immunology
- Transcription, Genetic
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Affiliation(s)
- C MacLennan
- Neurosciences Group, Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, UK
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41
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Riemersma S, Vincent A, Beeson D, Newland C, Hawke S, Vernet-der Garabedian B, Eymard B, Newsom-Davis J. Association of arthrogryposis multiplex congenita with maternal antibodies inhibiting fetal acetylcholine receptor function. J Clin Invest 1996; 98:2358-63. [PMID: 8941654 PMCID: PMC507687 DOI: 10.1172/jci119048] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Arthrogryposis multiplex congenita (AMC), characterized by multiple joint contractures developing in utero, results from lack of fetal movement. Some cases are genetically determined, but AMC occasionally complicates pregnancy in patients with myasthenia gravis (MG) suggesting involvement of circulating maternal antibodies. We previously demonstrated antibodies that inhibited the function of fetal acetylcholine receptor (AChR) in one healthy woman with an obstetric history of recurrent AMC. Here we study sera from this woman, from one other with a similar history, and from three (one asymptomatic) whose babies had neonatal MG and AMC. All five maternal sera had high titers of antibodies that inhibited alpha-Bungarotoxin (alpha-BuTx) binding to fetal AChR, and their sera markedly inhibited fetal AChR function with little effect on adult AChR function. Moreover, in a further survey, 3 of 20 sera from anti-AChR negative AMC mothers inhibited fetal AChR function significantly at 1:100 dilution. These results demonstrate the role of antibodies to fetal AChR and perhaps other muscle antigens in some cases of AMC. More generally, they suggest that placental transfer of antibodies directed at fetal antigens should be considered as a cause of other recurrent fetal or perinatal disorders.
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Affiliation(s)
- S Riemersma
- Neurosciences Group, Institute of Molecular Medicine, John Radcliffe Hospital, Oxford, United Kingdom
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