Myasthenia gravis pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Pathophysiology
Myasthenia gravis is a neuromuscular disease caused by an autoimmune reactions. The main problem in this disease is the abnormal transmission of nerve impulses to muscle fibers in NMJ.[1] In the nerve terminals of alpha motor neurons, there are lots of vesicles containing Ach. When the action potential reaches the synaptic end, voltage gated Ca channels will open and trigger the release of these vesicles. Ach will diffuse into synaptic cleft and binds to AchR. The action of Ach will end with the work of AchE. Ach receptors consist of 5 subunits and are transmembrane proteins. There are other proteins which help AchR clustering and signal transduction including MuSK. It is the receptor of a protein named agrin. When these two bind to each other, the result is maintaining the clustering of AchRs.[2][1][3]
Not all of the MG patients share the same auto antibodies. One of these autoantibodies is antibody against AchR. They will destruct AchR by 3 mechanisms. First they will activate the complement system, second they will increase the degradation af AchR by AB binding and third by blocking AchR’s function.[4] The other type of autoantibody in MG patients are antibody against MsUK protein (muscle-specific receptor tyrosine kinase).(8-9)
References
- ↑ 1.0 1.1 Hoch W, McConville J, Helms S, Newsom-Davis J, Melms A, Vincent A (March 2001). "Auto-antibodies to the receptor tyrosine kinase MuSK in patients with myasthenia gravis without acetylcholine receptor antibodies". Nat. Med. 7 (3): 365–8. doi:10.1038/85520. PMID 11231638.
- ↑ Horton RM, Manfredi AA, Conti-Tronconi BM (May 1993). "The 'embryonic' gamma subunit of the nicotinic acetylcholine receptor is expressed in adult extraocular muscle". Neurology. 43 (5): 983–6. PMID 7684117.
- ↑ Ruegg MA, Bixby JL (January 1998). "Agrin orchestrates synaptic differentiation at the vertebrate neuromuscular junction". Trends Neurosci. 21 (1): 22–7. PMID 9464682.
- ↑ Sahashi K, Engel AG, Lambert EH, Howard FM (March 1980). "Ultrastructural localization of the terminal and lytic ninth complement component (C9) at the motor end-plate in myasthenia gravis". J. Neuropathol. Exp. Neurol. 39 (2): 160–72. PMID 7373347.