第50回日本神経学会総会
<教育講演6>
重症筋無力症の進歩―シナプスの構造・機能と多様な抗体を中心として―
高守 正治
金沢西病院脳神経センター〔〒920-0025 金沢市駅西本町6丁目15-41〕
Autoantibodies impair acetylcholine receptor (AChR) in myasthenia gravis (MG) and P/Q-type voltage-gated calcium channel (VGCC) in Lambert-Eaton myasthenic syndrome (LEMS). (1) Some of MG and LEMS patients are "seronegative" for respective antibodies or modified by antibodies that recognize other proteins than AChR and VGCC such as MuSK, AChR allosteric site, membrane Na+ channel and ryanodine receptor-1 (RyR1) in MG, and synaptotagmin-1 in LEMS. (2) Autoimmune responses affect the proteins participating in the mechanisms to compensate for synaptic disorders on the basis of presynaptic Ca2+ homeostasis provided by VGCC and non-VGCC (receptor-operated TRPCs); they act as enhancers of Ca2+-mediated ACh release via phospholipase C signaling pathways including M1-type presynaptic muscarinic AChR, neurotrophin receptor (TrkB), and fast-mode of synaptic vesicle recycling. (3) The pathophysiology contributive to contractile fatigue in MG includes RyR1 and also TRPC3. The TRPC3 also forms a complex with STIM1 and Orai1 to make up for Ca2+ after sarcoplasmic Ca2+ release. The prevalent detection of anti-TRPC3 antibodies in MG with thymoma could affect muscle contractile machineries in addition to anti-RyR1-induced affection. (4) When one faces "seronegative" MG, one should be cautious to conformation-specific antibodies and also congenital myasthenic syndromes.
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(臨床神経, 49:789−793, 2009)
key words:ニコチン性およびムスカリン性アセチルコリン受容体, 電位依存性および非依存性カルシウムチャネル, シナプトタグミン, リアノジン受容体, 立体構造依存性抗体
(受付日:2009年5月22日)