Biochemical characterization of a novel channel-activating site on nicotinic acetylcholine receptors.

A Schrattenholz, T Coban, B Schröder, K O Okonjo, J Kuhlmann, E F Pereira, E X Albuquerque, A Maelicke
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引用次数: 22

Abstract

We have studied the interaction of the reversible acetylcholine esterase inhibitor (-)physostigmine and several structurally related compounds with the nicotinic acetylcholine receptor (nAChR) from Torpedo marmorata electric tissue by means of ligand-induced ion flux into nAChR-rich membrane vesicles, direct binding studies and photoaffinity labeling. (-)Physostigmine acts as a channel-activating ligand at low concentrations and as a direct channel blocker at elevated concentrations. Channel activation is not inhibited by desensitizing concentrations of ACh or ACh-competitive ligands (including alpha-bungarotoxin and D-tubocurarine) but is inhibited by antibody FK1 and several other compounds. From photoaffinity labeling using tritiated physostigmine and mapping of the epitope for the Phy-competitive antibody FK1, the binding site for physostigmine is located within the alpha-subunit of the Torpedo nAChR and is distinct from the acetylcholine binding site. Our data suggest a second pathway of nAChR channel activation that may function physiologically as an allosteric control of receptor activity.

烟碱乙酰胆碱受体新通道激活位点的生化表征。
我们利用配体诱导的离子通量进入富含nAChR的膜泡、直接结合研究和光亲和标记等方法,研究了可逆乙酰胆碱酯酶抑制剂(-)蛇毒碱和几种结构相关化合物与鱼雷电组织中烟碱乙酰胆碱受体(nAChR)的相互作用。(-)毒豆碱在低浓度时作为通道激活配体,在高浓度时作为直接通道阻滞剂。乙酰胆碱或乙酰胆碱竞争配体(包括-bungarotoxin和D-tubocurarine)的脱敏浓度不会抑制通道激活,但会被抗体FK1和其他几种化合物抑制。利用氚化的毒豆蔻碱进行光亲和标记,并对物理竞争抗体FK1的表位进行定位,发现毒豆蔻碱的结合位点位于鱼雷nAChR的α亚基内,与乙酰胆碱的结合位点不同。我们的数据表明,nAChR通道激活的第二种途径可能在生理上作为受体活性的变构控制起作用。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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