Mechanism of expression of voltage-gated sodium and calcium channels

电压门控钠通道和钙通道的表达机制

基本信息

批准号：
16390056
负责人：
OKAMURA Yasushi
金额：
$ 7.3万
依托单位：
National Institute of Natural Sciences Okazaki Research Facilities
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16390056/
关键词：
ion channel voltage sensor inactivation persistent sodium current sodium channel ankyrin PTEN phosphatase

项目摘要

Ankyrin-G, a modular protein, plays a critical role in clustering voltage-gated sodium channels (Nav channels) in nodes of Ranvier and initial segments of mammalian neurons. However, direct effects of ankyrin-G on electrophysiological properties of Nav channels remai elusive. In this study, we explored whether ankyrin-G has a role in modifying gating properties of the neuronal Nav1.6 channel that is predominantly localized at nodes of Ranvier and initial segments. TsA201 cells transfected with the human Nav1.6 cDNA alone exhibited significant persistent sodium current (Ina-p). On the other hand, Ina-p was barely detected upon co-expression with ankyrin-G. Ankyrin-B, another ankyrin, did not show such an effect. Expression of chimeras between the two isofrms of ankyrin suggests that the membrane-binding domain of ankyurin-G is critical for reducing the Ina-p of Nav1.6. These results suggest that ankyrin-G regulates neuronal excitability not only through clustering Nav channels but also … More by directly modifying their channel gating. Changes is membraine potential affect ion channels, and transporters, which then alter intracellular chemical conditions. Ohter signaling pathways coupled to membrane potential have been suggested but their underlying mechanism are unknown. We have identified a novel protein from the ascidian Ciona intestinalis which has a transmembrane voltage sensing domain homologous to the S1-S4 segments of voltage-gated channels and a cytoplasmic domain similar to phosphatase and tension homologue (PTEN). This protein, named Ci-VSP (voltage-sensor containing phosphatase), displays channel-like "gating" currents and directly translates changes in membrane potential into the turnover of phosphoinositides. The activity of the phosphoinositide phosphatase in Ci-VSP is tuned within a physiological range of membrane potential. Immunocytochemical studies show that Ci-VSP is expressed in Ciona sperm tail membranes, suggesting a role in sperm function or morphology. Our data demonstrate that voltage sensing can function beyond channel proteins and thus more ubiquitously than previously appreciated. Less

锚蛋白-G 是一种模块化蛋白，在 Ranvier 节点和哺乳动物神经元初始片段中的电压门控钠通道（Nav 通道）聚集中发挥着关键作用。然而，锚蛋白-G 对 Nav 通道电生理特性的直接影响仍然难以捉摸。在这项研究中，我们探讨了锚蛋白-G 是否在改变神经元 Nav1.6 通道的门控特性方面发挥作用，该通道主要位于 Ranvier 节点和初始节段。转染人 Nav1.6 cDNA 的 TsA201 细胞单独表现出显着的持续钠电流 (Ina-p)，而 Ina-p 在与另一种锚蛋白 -B 共表达时几乎检测不到。锚蛋白的两个异构体之间嵌合体的表达表明锚蛋白-G 的膜结合结构域对于减少 Ina-p 至关重要。 Nav1.6.这些结果表明锚蛋白-G 不仅通过聚集 Nav 通道来调节神经兴奋性，还通过直接改变其通道门控来影响离子通道和转运蛋白，从而改变细胞内的化学条件。已经提出了与膜电位耦合的信号通路，但其潜在机制尚不清楚，我们已经从海鞘中鉴定出一种新的蛋白质，其具有与膜电位同源的跨膜电压传感结构域。电压门控通道的 S1-S4 片段和类似于磷酸酶和张力同源物 (PTEN) 的细胞质结构域这种蛋白质被称为 Ci-VSP（含有磷酸酶的电压传感器），显示出类似通道的“门控”电流并直接翻译变化。 Ci-VSP 中磷酸肌醇磷酸酶的活性在膜的生理范围内进行调节。免疫细胞化学研究表明，Ci-VSP 在海鞘精子尾膜中表达，这表明其在精子功能或形态中发挥作用。我们的数据表明，电压传感的功能可以超越通道蛋白，因此比以前认为的更普遍。