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Takamori M. Myasthenia Gravis: From the Viewpoint of Pathogenicity Focusing on Acetylcholine Receptor Clustering, Trans-Synaptic Homeostasis and Synaptic Stability. Front Mol Neurosci 2020; 13:86. [PMID: 32547365 PMCID: PMC7272578 DOI: 10.3389/fnmol.2020.00086] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 04/28/2020] [Indexed: 12/18/2022] Open
Abstract
Myasthenia gravis (MG) is a disease of the postsynaptic neuromuscular junction (NMJ) where nicotinic acetylcholine (ACh) receptors (AChRs) are targeted by autoantibodies. Search for other pathogenic antigens has detected the antibodies against muscle-specific tyrosine kinase (MuSK) and low-density lipoprotein-related protein 4 (Lrp4), both causing pre- and post-synaptic impairments. Agrin is also suspected as a fourth pathogen. In a complex NMJ organization centering on MuSK: (1) the Wnt non-canonical pathway through the Wnt-Lrp4-MuSK cysteine-rich domain (CRD)-Dishevelled (Dvl, scaffold protein) signaling acts to form AChR prepatterning with axonal guidance; (2) the neural agrin-Lrp4-MuSK (Ig1/2 domains) signaling acts to form rapsyn-anchored AChR clusters at the innervated stage of muscle; (3) adaptor protein Dok-7 acts on MuSK activation for AChR clustering from “inside” and also on cytoskeleton to stabilize AChR clusters by the downstream effector Sorbs1/2; (4) the trans-synaptic retrograde signaling contributes to the presynaptic organization via: (i) Wnt-MuSK CRD-Dvl-β catenin-Slit 2 pathway; (ii) Lrp4; and (iii) laminins. The presynaptic Ca2+ homeostasis conditioning ACh release is modified by autoreceptors such as M1-type muscarinic AChR and A2A adenosine receptors. The post-synaptic structure is stabilized by: (i) laminin-network including the muscle-derived agrin; (ii) the extracellular matrix proteins (including collagen Q/perlecan and biglycan which link to MuSK Ig1 domain and CRD); and (iii) the dystrophin-associated glycoprotein complex. The study on MuSK ectodomains (Ig1/2 domains and CRD) recognized by antibodies suggested that the MuSK antibodies were pathologically heterogeneous due to their binding to multiple functional domains. Focussing one of the matrix proteins, biglycan which functions in the manner similar to collagen Q, our antibody assay showed the negative result in MG patients. However, the synaptic stability may be impaired by antibodies against MuSK ectodomains because of the linkage of biglycan with MuSK Ig1 domain and CRD. The pathogenic diversity of MG is discussed based on NMJ signaling molecules.
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Schumacher MA, Hedl M, Abraham C, Bernard JK, Lozano PR, Hsieh JJ, Almohazey D, Bucar EB, Punit S, Dempsey PJ, Frey MR. ErbB4 signaling stimulates pro-inflammatory macrophage apoptosis and limits colonic inflammation. Cell Death Dis 2017; 8:e2622. [PMID: 28230865 PMCID: PMC5386486 DOI: 10.1038/cddis.2017.42] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 01/14/2017] [Accepted: 01/17/2017] [Indexed: 02/07/2023]
Abstract
Efficient clearance of pro-inflammatory macrophages from tissues after resolution of a challenge is critical to prevent prolonged inflammation. Defects in clearance can contribute to conditions such as inflammatory bowel disease, and thus may be therapeutically targetable. However, the signaling pathways that induce termination of pro-inflammatory macrophages are incompletely defined. We tested whether the ErbB4 receptor tyrosine kinase, previously not known to have role in macrophage biology, is involved in this process. In vitro, pro-inflammatory activation of cultured murine and human macrophages induced ErbB4 expression; in contrast, other ErbB family members were not induced in pro-inflammatory cells, and other innate immune lineages (dendritic cells, neutrophils) did not express detectable ErbB4 levels. Treatment of activated pro-inflammatory macrophages with the ErbB4 ligand neuregulin-4 (NRG4) induced apoptosis. ErbB4 localized to the mitochondria in these cells. Apoptosis was accompanied by loss of mitochondrial membrane potential, and was dependent upon the proteases that generate the cleaved ErbB4 intracellular domain fragment, suggesting a requirement for this fragment and mitochondrial pathway apoptosis. In vivo, ErbB4 was highly expressed on pro-inflammatory macrophages but not neutrophils during experimental DSS colitis in C57Bl/6 mice. Active inflammation in this model suppressed NRG4 expression, which may allow for macrophage persistence and ongoing inflammation. Consistent with this notion, NRG4 levels rebounded during the recovery phase, and administration of exogenous NRG4 during colitis reduced colonic macrophage numbers and ameliorated inflammation. These data define a novel role for ErbB4 in macrophage apoptosis, and outline a mechanism of feedback inhibition that may promote resolution of colitis.
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Affiliation(s)
- Michael A Schumacher
- The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, CA 90027, USA.,Departments of Pediatrics and of Biochemistry and Molecular Biology, University of Southern California Keck School of Medicine, Los Angeles, CA 90089, USA
| | - Matija Hedl
- Department of Medicine, Yale School of Medicine, New Haven, CT 06510, USA
| | - Clara Abraham
- Department of Medicine, Yale School of Medicine, New Haven, CT 06510, USA
| | - Jessica K Bernard
- The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, CA 90027, USA.,Departments of Pediatrics and of Biochemistry and Molecular Biology, University of Southern California Keck School of Medicine, Los Angeles, CA 90089, USA.,University of Southern California Herman Ostrow School of Dentistry, Los Angeles, CA 90089, USA
| | - Patricia R Lozano
- The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, CA 90027, USA
| | - Jonathan J Hsieh
- The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, CA 90027, USA.,Departments of Pediatrics and of Biochemistry and Molecular Biology, University of Southern California Keck School of Medicine, Los Angeles, CA 90089, USA
| | - Dana Almohazey
- The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, CA 90027, USA.,Departments of Pediatrics and of Biochemistry and Molecular Biology, University of Southern California Keck School of Medicine, Los Angeles, CA 90089, USA.,University of Southern California Herman Ostrow School of Dentistry, Los Angeles, CA 90089, USA
| | - Edie B Bucar
- The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, CA 90027, USA.,Departments of Pediatrics and of Biochemistry and Molecular Biology, University of Southern California Keck School of Medicine, Los Angeles, CA 90089, USA
| | - Shivesh Punit
- The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, CA 90027, USA
| | - Peter J Dempsey
- Department of Pediatrics, University of Colorado Medical School, Aurora, CO 80045, USA
| | - Mark R Frey
- The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, CA 90027, USA.,Departments of Pediatrics and of Biochemistry and Molecular Biology, University of Southern California Keck School of Medicine, Los Angeles, CA 90089, USA
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Vrolix K, Fraussen J, Losen M, Stevens J, Lazaridis K, Molenaar PC, Somers V, Bracho MA, Le Panse R, Stinissen P, Berrih-Aknin S, Maessen JG, Van Garsse L, Buurman WA, Tzartos SJ, De Baets MH, Martinez-Martinez P. Clonal heterogeneity of thymic B cells from early-onset myasthenia gravis patients with antibodies against the acetylcholine receptor. J Autoimmun 2014; 52:101-12. [PMID: 24439114 DOI: 10.1016/j.jaut.2013.12.008] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Accepted: 12/12/2013] [Indexed: 10/25/2022]
Abstract
Myasthenia gravis (MG) with antibodies against the acetylcholine receptor (AChR-MG) is considered as a prototypic autoimmune disease. The thymus is important in the pathophysiology of the disease since thymus hyperplasia is a characteristic of early-onset AChR-MG and patients often improve after thymectomy. We hypothesized that thymic B cell and antibody repertoires of AChR-MG patients differ intrinsically from those of control individuals. Using immortalization with Epstein-Barr Virus and Toll-like receptor 9 activation, we isolated and characterized monoclonal B cell lines from 5 MG patients and 8 controls. Only 2 of 570 immortalized B cell clones from MG patients produced antibodies against the AChR (both clones were from the same patient), suggesting that AChR-specific B cells are not enriched in the thymus. Surprisingly, many B cell lines from both AChR-MG and control thymus samples displayed reactivity against striated muscle proteins. Striational antibodies were produced by 15% of B cell clones from AChR-MG versus 6% in control thymus. The IgVH gene sequence analysis showed remarkable similarities, concerning VH family gene distribution, mutation frequency and CDR3 composition, between B cells of AChR-MG patients and controls. MG patients showed clear evidence of clonal B cell expansion in contrast to controls. In this latter aspect, MG resembles multiple sclerosis and clinically isolated syndrome, but differs from systemic lupus erythematosus. Our results support an antigen driven immune response in the MG thymus, but the paucity of AChR-specific B cells, in combination with the observed polyclonal expansions suggest a more diverse immune response than expected.
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Affiliation(s)
- Kathleen Vrolix
- Department of Neuroscience, School of Mental Health and Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Universiteitssingel 50, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Judith Fraussen
- Neuroimmunology group, Biomedical Research Institute and Transnationale Universiteit Limburg, School of Life Sciences, Hasselt University, Diepenbeek, Belgium
| | - Mario Losen
- Department of Neuroscience, School of Mental Health and Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Universiteitssingel 50, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Jo Stevens
- Department of Neuroscience, School of Mental Health and Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Universiteitssingel 50, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | | | - Peter C Molenaar
- Department of Neuroscience, School of Mental Health and Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Universiteitssingel 50, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Veerle Somers
- Neuroimmunology group, Biomedical Research Institute and Transnationale Universiteit Limburg, School of Life Sciences, Hasselt University, Diepenbeek, Belgium
| | - Maria Alma Bracho
- Centre Superior d'Investigació en Salut Pública (CSISP), Àrea de Genòmica i Salut, Conselleria de Sanitat, Generalitat Valenciana, València, Spain; Institut "Cavanilles" de Biodiversitat i Biologia Evolutiva (ICBiBE), Universitat de València, València, Spain; Centro de Investigación Biomédica en Red de Epidemiología y Salud Pública (CIBERESP), Ministerio de Ciencia e Innovación, Spain
| | - Rozen Le Panse
- UPMC UM 76/INSERM U974/CNRS UMR7215/Institute of Myology, 105 Bd de l'hôpital, Paris, France
| | - Piet Stinissen
- Neuroimmunology group, Biomedical Research Institute and Transnationale Universiteit Limburg, School of Life Sciences, Hasselt University, Diepenbeek, Belgium
| | - Sonia Berrih-Aknin
- UPMC UM 76/INSERM U974/CNRS UMR7215/Institute of Myology, 105 Bd de l'hôpital, Paris, France
| | - Jos G Maessen
- Department of Cardiothoracic Surgery, University Hospital, Maastricht, The Netherlands
| | - Leen Van Garsse
- Department of Cardiothoracic Surgery, University Hospital, Maastricht, The Netherlands
| | - Wim A Buurman
- Department of Neuroscience, School of Mental Health and Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Universiteitssingel 50, P.O. Box 616, 6200 MD Maastricht, The Netherlands
| | - Socrates J Tzartos
- Department of Biochemistry, Hellenic Pasteur Institute, GR 11521 Athens, Greece
| | - Marc H De Baets
- Department of Neuroscience, School of Mental Health and Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Universiteitssingel 50, P.O. Box 616, 6200 MD Maastricht, The Netherlands; Neuroimmunology group, Biomedical Research Institute and Transnationale Universiteit Limburg, School of Life Sciences, Hasselt University, Diepenbeek, Belgium
| | - Pilar Martinez-Martinez
- Department of Neuroscience, School of Mental Health and Neuroscience, Faculty of Health, Medicine and Life Sciences, Maastricht University, Universiteitssingel 50, P.O. Box 616, 6200 MD Maastricht, The Netherlands.
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Berrih-Aknin S, Le Panse R. [Myasthenia gravis and autoantibodies: Pathophysiology of the different subtypes]. Rev Med Interne 2013; 35:413-20. [PMID: 24156976 DOI: 10.1016/j.revmed.2013.09.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2013] [Accepted: 09/23/2013] [Indexed: 10/26/2022]
Abstract
Myasthenia gravis is characterized by muscle weakness and abnormal fatigability. It is an autoimmune disease caused by the presence of antibodies against components of the muscle membrane localized at the neuromuscular junction. In most cases, the autoantibodies are directed against the acetylcholine receptor (AChR). Recently, other targets have been described, such as muscle-specific kinase protein (MuSK) or lipoprotein related protein 4 (LRP4). The origin of the autoimmune response is not known, but thymic abnormalities and defects in immune regulation certainly play a major role in patients with anti-AChR antibodies. Genetic predisposition probably influences the occurrence of the disease. Sex hormones seem to play a role in the early form of the disease. Muscle weakness is fluctuating and worsens with exercise. Myasthenia gravis could be classified according to the location of the affected muscles (ocular versus generalized), the age of onset of symptoms, thymic abnormalities and profile of autoantibodies. These criteria are used to optimize the management and treatment of patients. In this review, we analyze the latest concepts of the pathophysiology of myasthenia gravis according to the different subgroups of the disease, including a description of the role of immunological, genetic and environmental factors. The potential viral hypothesis of this disease is discussed. Finally, we also discuss the biological assays available to validate the diagnosis.
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Affiliation(s)
- S Berrih-Aknin
- Unité mixte de recherche (UMR), CNRS UMR7215/Inserm U974/UPMC UM76/AIM, thérapie des maladies du muscle strié, groupe hospitalier Pitié-Salpêtrière, 105, boulevard de l'Hôpital, 75651 Paris cedex 13, France.
| | - R Le Panse
- Unité mixte de recherche (UMR), CNRS UMR7215/Inserm U974/UPMC UM76/AIM, thérapie des maladies du muscle strié, groupe hospitalier Pitié-Salpêtrière, 105, boulevard de l'Hôpital, 75651 Paris cedex 13, France
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Gomez AM, Vrolix K, Martínez-Martínez P, Molenaar PC, Phernambucq M, van der Esch E, Duimel H, Verheyen F, Voll RE, Manz RA, De Baets MH, Losen M. Proteasome inhibition with bortezomib depletes plasma cells and autoantibodies in experimental autoimmune myasthenia gravis. THE JOURNAL OF IMMUNOLOGY 2011; 186:2503-13. [PMID: 21239719 DOI: 10.4049/jimmunol.1002539] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Bortezomib, an inhibitor of proteasomes, has been reported to reduce autoantibody titers and to improve clinical condition in mice suffering from lupus-like disease. Bortezomib depletes both short- and long-lived plasma cells; the latter normally survive the standard immunosuppressant treatments targeting T and B cells. These findings encouraged us to test whether bortezomib is effective for alleviating the symptoms in the experimental autoimmune myasthenia gravis (EAMG) model for myasthenia gravis, a disease that is characterized by autoantibodies against the acetylcholine receptor (AChR) of skeletal muscle. Lewis rats were immunized with saline (control, n = 36) or Torpedo AChR (EAMG, n = 54) in CFA in the first week of an experimental period of 8 wk. After immunization, rats received twice a week s.c. injections of bortezomib (0.2 mg/kg in saline) or saline injections. Bortezomib induced apoptosis in bone marrow cells and reduced the amount of plasma cells in the bone marrow by up to 81%. In the EAMG animals, bortezomib efficiently reduced the rise of anti-AChR autoantibody titers, prevented ultrastructural damage of the postsynaptic membrane, improved neuromuscular transmission, and decreased myasthenic symptoms. This study thus underscores the potential of the therapeutic use of proteasome inhibitors to target plasma cells in Ab-mediated autoimmune diseases.
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Affiliation(s)
- Alejandro M Gomez
- Neuroimmunology Group, Department of Neuroscience, School of Mental Health and Neuroscience, Maastricht University, Maastricht, The Netherlands
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