Muscle-specific kinase myasthenia gravis IgG4 autoantibodies cause severe neuromuscular junction dysfunction in mice.
Publication year
2012Source
Brain, 135, Pt 4, (2012), pp. 1081-101ISSN
Annotation
01 april 2012
Publication type
Article / Letter to editor
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Organization
Cell Physiology
Paediatrics - OUD tm 2017
Laboratory of Genetic, Endocrine and Metabolic Diseases
Neurology
Human Genetics
Journal title
Brain
Volume
vol. 135
Issue
iss. Pt 4
Page start
p. 1081
Page end
p. 101
Subject
DCN MP - Plasticity and memory NCEBP 10: Human Movement & Fatigue; N4i 1: Pathogenesis and modulation of inflammation NCMLS 1: Infection and autoimmunityAbstract
Myasthenia gravis is a paralytic disorder with autoantibodies against acetylcholine receptors at the neuromuscular junction. A proportion of patients instead has antibodies against muscle-specific kinase, a protein essential for acetylcholine receptor clustering. These are generally of the immunoglobulin-G4 subclass and correlate with disease severity, suggesting specific myasthenogenic activity. However, immunoglobulin-G4 subclass antibodies are generally considered to be 'benign' and direct proof for their pathogenicity in muscle-specific kinase myasthenia gravis (or other immunoglobulin-G4-associated disorders) is lacking. Furthermore, the exact electrophysiological synaptic defects caused at neuromuscular junctions by human anti-muscle-specific kinase autoantibodies are hitherto unknown. We show that purified immunoglobulin-G4, but not immunoglobulin-G1-3, from patients with muscle-specific kinase myasthenia gravis binds to mouse neuromuscular junctions in vitro, and that injection into immunodeficient mice causes paralysis. Injected immunoglobulin-G4 caused reduced density and fragmented area of neuromuscular junction acetylcholine receptors. Detailed electrophysiological synaptic analyses revealed severe reduction of postsynaptic acetylcholine sensitivity, and exaggerated depression of presynaptic acetylcholine release during high-rate activity, together causing the (fatigable) muscle weakness. Intriguingly, compensatory transmitter release upregulation, which is the normal homeostatic response in acetylcholine receptor myasthenia gravis, was absent. This conveys extra vulnerability to neurotransmission at muscle-specific kinase myasthenia gravis neuromuscular junctions. Thus, we demonstrate that patient anti-muscle-specific kinase immunoglobulin-G4 is myasthenogenic, independent of additional immune system components, and have elucidated the underlying electrophysiological neuromuscular junction abnormalities.
This item appears in the following Collection(s)
- Academic publications [238441]
- Faculty of Medical Sciences [90373]
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