Antigens Associated with N- and L-Type Calcium Channels in Lambert-Eaton Myasthenic Syndrome |
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Authors: | Oussama El Far,Bé atrice Marquè ze,Christian Leveque,Nicole Martin-Moutô t,Bethan Lang,John Newsom-Davis,&dagger Akira Yoshida,&dagger Masami Takahashi, Michael J. Seagar |
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Affiliation: | INSERM U374, Institut Jean Roche, Facultéde Medécine Secteur Nord, Marseille, France;; Neuroscience Group, Institute of Molecular Medicine, John Radcliffe Hospital, Headington, Oxford, England;and; Mitsubishi Kasei Institute of Life Science, Tokyo, Japan |
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Abstract: | Abstract: In Lambert-Eaton myasthenic syndrome neurotransmitter release is reduced by an autoimmune response directed against the calcium channel complex of the nerve terminal. Autoantibodies were detected by immunoprecipitation assays using solubilized receptors labeled with ligands selective for N-type (125I-ω conotoxin GVIA) and L-type ([3H]PN200-110) calcium channels. Sera with a high antibody titer (>3 n M ) against rat brain N-type channels contained autoantibodies that immunoprecipitated neuronal and muscle L-type channels. These IgG fractions stained a 55-kDa protein in immunoblots of purified skeletal muscle dihydropyridine receptor, suggesting that they contain autoantibodies against the β subunit of the calcium channel. A distinct antibody population in the same fractions reacted with a nerve terminal 65-kDa protein that is unrelated to the β subunit and displays properties similar to those of synaptotagmin. |
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Keywords: | Lambert-Eaton myasthenic syndrome Autoantibodies ω-Conotoxin GVIA 1,4-Dihydropyridine Calcium channel β subunit Synaptotagmin |
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