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首页> 外文期刊>The Royal Society Proceedings B: Biological Sciences >Inward rectification of neuronal nicotinic acetylcholine receptors investigated by using the homomeric alpha 7 receptor.
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Inward rectification of neuronal nicotinic acetylcholine receptors investigated by using the homomeric alpha 7 receptor.

机译：神经元烟碱乙酰胆碱受体的向内整流通过使用同型α7受体进行了研究。

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摘要

The strong inward rectification observed in neuronal nicotinic ACh receptors was examined by using alpha-bungarotoxin sensitive, homomeric alpha 7 neuronal nicotinic ACh receptors derived from chick brain. Receptors were expressed in Xenopus laevis oocytes and functionally assessed by the two electrode voltage clamp technique. Site directed mutagenesis of residues thought to line the putative ion pore revealed that negatively charged glutamate residues located at the inner mouth of the channel are essential for rectification. This finding was confirmed both for the active open state and for receptors mutated to conduct in one of the desensitized states. No outward tail relaxations were observed with voltage jumps to depolarizing potentials, suggesting that rectification was not due to intrinsic gating. For the wild type receptor, intracellular injection of CDTA, a chelating agent having a high affinity for Mg2+, reduced rectification in a dose dependent manner, suggesting that rectification originates,in part, from open channel block by internal free Mg2+. These findings support the hypothesis that charged residues at the inner mouth of the pore influence the Mg2+ affinity of the blocking site.
机译：在神经元烟碱型ACh受体中观察到的强内向整流作用是通过使用源自鸡脑的α-真菌毒素敏感的同型α7神经元烟碱型ACh受体来检查的。受体在非洲爪蟾卵母细胞中表达，并通过两电极电压钳技术对其功能进行评估。定点诱变被认为位于推定的离子孔内，表明位于通道内口的带负电荷的谷氨酸残基对于整流至关重要。对于活跃的开放状态和突变为在脱敏状态之一中传导的受体都证实了这一发现。电压跃迁到去极化电位时，未观察到向外的尾部松弛，这表明整流不是由于固有的门控。对于野生型受体，细胞内注射CDTA（一种对Mg2 +具有高亲和力的螯合剂）以剂量依赖的方式减少了精馏，这表明精馏部分源自内部游离Mg2 +的开放通道阻滞。这些发现支持了假说，即在孔内口的带电残基影响封闭位点的Mg2 +亲和力。

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