钠离子通道疾病及其抑制剂生物学功能研究进展

电压门控型钠离子通道(Voltage-gated sodium channel,VGSC)广泛分布于兴奋性细胞,是电信号扩大和传导的主要介质,在神经细胞以及心肌细胞兴奋传导等方面发挥重要作用。钠离子通道结构和功能的异常会改变细胞的兴奋性,从而导致多种疾病的发生,如神经性疼痛、癫痫,以及心律失常等。目前临床上多采用钠离子通道抑制剂治疗上述疾病。近些年,研究人员陆续从动物的毒液中分离纯化出具有调控钠离子通道功能的神经毒素。这些神经毒素多为化合物或小分子多肽。现已有医药研发公司将这些天然的神经毒素进行定向设计改造成钠离子通道靶向药物用于临床疾病的治疗。此外,来源于七鳃鳗Lampetra japonica口腔腺的富含半胱氨酸分泌蛋白(Cysteine-rich buccal gland protein,CRBGP)也首次被证明能够抑制海马神经元和背根神经元的钠离子电流。以下针对钠离子通道疾病及其抑制剂生物学功能的最新研究进展进行分析归纳。     

电压门控钠离子通道疾病的研究进展

细胞膜上的电压门控钠离子通道（Voltage-gated Sodium Channels,VGSCs）是细胞形成动作电位过程中重要的组成构件,由一个大的α亚基和一个或多个不同的β亚基组成,中央是具高度选择性只允许钠离子通过的亲水通道。电压门控钠离子通道在调节细胞膜电位、维持细胞离子稳态、细胞增殖和凋亡等生理过程中发挥着重要作用,因而钠离子通道自身的异变或是相关基因的变异都可能引起一系列身体病变。本文主要介绍了电压门控钠离子通道的结构与功能,阐述了其与癌细胞侵袭转移和神经病理性疼痛的关系,并介绍了几种典型的由钠离子通道基因变异引起的疾病。随着对电压门控钠离子通道及其异常分子机制研究的不断深入,新成果将为生理学、药理学和病理学等领域的研究提供理论基础和新的研究思路,为离子通道疾病的临床预防、诊断与治疗找到新途径。     

蝎β型昆虫毒素的结构及其与钠通道作用机制

蝎毒素是蝎为防卫的需要而产生的一系列活性短肽.其中蝎昆虫特异性毒素可特异性结合并调控昆虫可兴奋细胞膜上的钠离子通道,是研究离子通道结构与功能的首选探针,并在转基因抗虫植物及生物杀虫剂研究方面具有潜在的应用价值.本文对蝎β型昆虫毒素的结构与功能及其对钠离子通道的作用方式和β毒素的电压传感器捕获(voltage sensor-trapping)模型做一综述,为进一步揭示蝎β毒素的结构与功能的关系和在农作物抗虫领域的应用提供依据.     

离子通道对胰岛β细胞中胰岛素分泌的调控作用

胰岛β细胞是胰岛细胞的一种,属于内分泌细胞,主要的生理功能是分泌胰岛素以应对葡萄糖水平的升高,其在维持葡萄糖稳态中起着重要作用。研究表明,胰岛素分泌受到多种机制的调控,其中包括多种离子通道。近年来,国内外学者越来越关注离子通道调控胰岛素分泌的过程。本文主要就钠离子通道、钾离子通道、钙离子通道以及3种离子通道之间的相互作用对胰岛素分泌的调控进行简述,同时,简单介绍了离子通道抑制剂在糖尿病临床中的应用,并展望了离子通道研究在未来糖尿病治疗方面的潜在应用价值。     

电压门控钠离子通道与恶性肿瘤的转移

电压门控钠离子通道(VGSC)是可兴奋组织中动作电位的关键离子通道,具有重要的生理功能.近年来国内外研究发现,VGSC在转移的前列腺癌、乳腺癌、卵巢癌、宫颈癌等细胞中表达,其增加了癌细胞的运动和侵袭,促使了癌症的转移,其还将被作为治疗靶点而进行药物开发和临床应用.     

电压门控性钠离子通道与伤害性感受

伤害性感受器激活引起疼痛的概念,现已广泛被人们接受,大量实验表明,伤害性感受器兴奋性的变化与一些离子通道有关,对河豚毒素不敏感的电压依赖性钠离子通道（TTXr)选择性地分布于与伤害性感受有关的初级感受神经元,炎症反应和神经损伤诱发的慢性疼痛可诱发这种TTXr功能及基因表达的变化,TTXr通道蛋白的反义寡核苷酸（antisense ODN)处理可对抗炎症或神经损伤引起的痛觉过敏或超敏,提示TTXr在伤害性感受中起重要作用,有望成为特异性镇痛药物的药理作用靶点。     

昆虫钠离子通道基因突变及其与杀虫剂抗性关系的研究进展

昆虫电压门控钠离子通道(voltage-gated sodium channel)存在于所有可兴奋细胞的细胞膜上,在动作电位的产生和传导上起重要作用,是有机氯和拟除虫菊酯杀虫剂的靶标位点。在农业和医学害虫控制过程中,由于有机氯和拟除虫菊酯杀虫剂的广泛使用,抗药性问题日益突出。其中,由于钠离子通道基因突变,降低了钠离子通道对有机氯和拟除虫菊酯类杀虫剂的亲和性,从而产生击倒抗性(knock-down resistance, kdr),已成为抗性产生的重要机制之一。本文综述了昆虫钠离子通道的跨膜拓扑结构、功能、进化及其基因的克隆;更重要的是总结了已报道的40多种昆虫40个钠离子通道基因非同义突变,以及钠离子通道基因选择性mRNA剪接和编辑,以及它们与杀虫剂抗性的关系;也评述了钠离子通道基因突变引起蛋白质结构的改变,从而对杀虫剂抗性的影响机制。这些研究对于进一步鉴定与杀虫剂抗性相关的突变及抗性机制,开发有机氯和拟除虫菊酯类杀虫剂抗性分子监测方法具有重要意义。     

家蚕para钠通道cDNA片段克隆与序列分析

昆虫神经系统para型钠离子通道是拟除虫菊酯类杀虫剂的主要靶标,已有的研究表明钠离子通道基因发生点突变与昆虫对菊酯类杀虫剂的抗性密切相关。本文通过RT-PCR方法克隆获得了编码家蚕Bombyx mori L.钠离子通道的cDNA片段(GenBank No.EF521818),该片段全长4882bp,部分ORF包含3986bp核苷酸,翻译成1328个氨基酸。蛋白序列分析表明,PCR扩增获得的家蚕钠离子通道cDNA片段所编码的氨基酸与其他昆虫的para型钠离子通道α亚基的氨基酸具有很高的同源相似性,与棉铃虫Heliothis virescens Fabricius、埃及伊蚊Aedes aegypti L.、德国小蠊Blattella germanica L.、果蝇Drosophila melanogaster Meigen和家蝇Musca domestica L.的相似性分别为95%、82%、80%、79%、77%。     

击倒抗性和钠离子通道

综述了击倒抗性与钠离子通道关系的研究进展。毒理学和电生理学的研究表明,在许多拟除虫菊酯类杀虫剂抗性昆虫中存在击倒抗性。分子遗传学研究进一步发现,击倒抗性与钠离子通道位点连锁。最近的研究表明,昆虫神经系统对拟除虫菊酯类杀虫剂敏感性下降的击倒抗性机制是钠离子通道结构基因突变。但仍有一些问题,如突变的保守性和分布,需要进一步研究、阐明。     

昆虫钠离子通道的研究进展

昆虫只有一个或两个电压门控钠离子通道α亚基基因,但两种转录后修饰(选择性剪切和RNA编辑)实现了昆虫钠离子通道的功能多样性.昆虫β辅助亚基TipE和TEH1-4在钠离子通道表达和调控中也起着重要作用.电压门控钠离子通道在动作电位的产生和传递中至关重要,是多种天然和人工合成神经毒素及杀虫剂的作用靶标,包括广泛使用的拟除虫...     

Peptide Toxins in Sea Anemones: Structural and Functional Aspects

Sea anemones are a rich source of two classes of peptide toxins, sodium channel toxins and potassium channel toxins, which have been or will be useful tools for studying the structure and function of specific ion channels. Most of the known sodium channel toxins delay channel inactivation by binding to the receptor site 3 and most of the known potassium channel toxins selectively inhibit Kv1 channels. The following peptide toxins are functionally unique among the known sodium or potassium channel toxins: APETx2, which inhibits acid-sensing ion channels in sensory neurons; BDS-I and II, which show selectivity for Kv3.4 channels and APETx1, which inhibits human ether-a-go-go-related gene potassium channels. In addition, structurally novel peptide toxins, such as an epidermal growth factor (EGF)-like toxin (gigantoxin I), have also been isolated from some sea anemones although their functions remain to be clarified.     

Distribution and function of voltage-gated sodium channels in the nervous system

Voltage-gated sodium channels (VGSCs) are the basic ion channels for neuronal excitability, which are crucial for the resting potential and the generation and propagation of action potentials in neurons. To date, at least nine distinct sodium channel isoforms have been detected in the nervous system. Recent studies have identified that voltage-gated sodium channels not only play an essential role in the normal electrophysiological activities of neurons but also have a close relationship with neurological diseases. In this study, the latest research findings regarding the structure, type, distribution, and function of VGSCs in the nervous system and their relationship to neurological diseases, such as epilepsy, neuropathic pain, brain tumors, neural trauma, and multiple sclerosis, are reviewed in detail.     

Bibliometric analysis of recent sodium channel research

Although sodium channels have been a hot multidisciplinary focus for decades and most of nerve system drugs worked on alerting sodium channel function, the trends and future directions of sodium channel studies have not been comprehensive analyzed bibliometrically. Herein, we collected the scientific publications of sodium channels research and constructed a model to evaluate the current trend systematically.

Publications were selected from the Web of Science Core Collection (WoSCC) database from 2013 to 2017. Microsoft Excel 2016, Prism 6, and CiteSpace V software were used to analyze publication outputs, journal sources, countries, territories, institutions, authors, and research areas. A total of 4,275 publications on sodium channel research were identified. PLoS ONE ranked top for publishing 170 papers. The United States of America had the largest number of publications (1,595), citation frequency (19,490), and H-index (53). S. G. Waxman (62 publications) and W. A. Catterall (585 citations) were the most productive authors and had the greatest co-citation counts. This is the first report that shows the trends and future development in sodium channel publications, and our study provides a clear profile for the contribution to this field by countries, authors, keywords, and institutions.     

海南捕鸟蛛毒素-Ⅵ，一种新型的抑制昆虫电压门控钠通道失活的狼蛛神经毒素

通过阳离子交换和反相HPLC柱层析从海南捕鸟蛛（Ornithoconus hainana）粗毒中分离到一种新型的神经毒素,海南捕鸟蛛毒素-Ⅵ(HNTX-Ⅵ), 由34个氨基酸残基组成,含有6个保守的半胱氨酸残基. 运用全细胞膜片钳技术,研究了HNTX-Ⅵ对电压门控钠通道的影响.先前从海南捕鸟蛛粗毒中分离到的几种毒素,具有抑制哺乳动物钠通道激活的特性.本文研究结果表明,HNTX-Ⅵ能以类似于δ-atractoxins作用方式延缓蜚蠊背侧不成对中间(dorsal unpaired median,DUM）神经细胞的钠通道的失活,且导致钠通道稳态失活变得不完全,在预钳制电压大于-55 mV时形成不完全失活结构. HNTX-Ⅵ的这种新的功能不仅为探索钠通道的门控机制提供了有用的工具,也为开发新的安全的杀虫剂提供理论基础.     

Voltage gated sodium channels as drug discovery targets

Voltage-gated sodium (Na_V) channels are a family of transmembrane ion channel proteins. They function by forming a gated, water-filled pore to help establish and control cell membrane potential via control of the flow of ions between the intracellular and the extracellular environments. Blockade of Na_Vs has been successfully accomplished in the clinic to enable control of pathological firing patterns that occur in a diverse range of conditions such as chronic pain, epilepsy, and cardiac arrhythmias. First generation sodium channel modulator drugs, despite low inherent subtype selectivity, preferentially act on over-excited cells which reduces undesirable side effects in the clinic. However, the limited therapeutic indices observed with the first generation demanded a new generation of sodium channel inhibitors. The structure, function and the state of the art in sodium channel modulator drug discovery are discussed in this chapter.     

A uniquely adaptable pore is consistent with NALCN being an ion sensor

NALCN is an intriguing, orphan ion channel among the 4x6TM family of related voltage-gated cation channels, sharing a common architecture of four homologous domains consisting of six transmembrane helices, separated by three cytoplasmic linkers and delimited by N and C-terminal ends. NALCN is one of the shortest 4x6TM family members, lacking much of the variation that provides the diverse palate of gating features, and tissue specific adaptations of sodium and calcium channels. NALCN’s most distinctive feature is that that it possesses a highly adaptable pore with a calcium-like EEEE selectivity filter in radially symmetrical animals and a more sodium-like EEKE or EKEE selectivity filter in bilaterally symmetrical animals including vertebrates. Two lineages of animals evolved alternative calcium-like EEEE and sodium-like EEKE / EKEE pores, spliced to regulate NALCN functions in differing cellular environments, such as muscle (heart and skeletal) and secretory tissue (brain and glands), respectively. A highly adaptable pore in an otherwise conserved ion channel in the 4x6TM channel family is not consistent with a role for NALCN in directly gating a significant ion conductance that can be either sodium ions or calcium ions. NALCN was proposed to be an expressible Gd³⁺-sensitive, NMDG⁺-impermeant, non-selective and ohmic leak conductance in HEK-293T cells, but we were unable to distinguish these reported currents from leaky patch currents (I_LP) in control HEK-293T cells. We suggest that NALCN functions as a sensor for the much larger UNC80/UNC79 complex, in a manner consistent with the coupling mechanism known for other weakly or non-conducting 4x6TM channel sensor proteins such as Na_x or Ca_v1.1. We propose that NALCN serves as a variable sensor that responds to calcium or sodium ion flux, depending on whether the total cellular current density is generated more from calcium-selective or sodium-selective channels.     

Predicting ion channels and their types by the dipeptide mode of pseudo amino acid composition

Ion channels are integral membrane proteins that control movement of ions into or out of cells. They are key components in a wide range of biological processes. Different types of ion channels have different biological functions. With the appearance of vast proteomic data, it is highly desirable for both basic research and drug-target discovery to develop a computational method for the reliable prediction of ion channels and their types. In this study, we developed a support vector machine-based method to predict ion channels and their types using primary sequence information. A feature selection technique, analysis of variance (ANOVA), was introduced to remove feature redundancy and find out an optimized feature set for improving predictive performance. Jackknife cross-validated results show that the proposed method can discriminate ion channels from non-ion channels with an overall accuracy of 86.6%, classify voltage-gated ion channels and ligand-gated ion channels with an overall accuracy of 92.6% and predict four types (potassium, sodium, calcium and anion) of voltage-gated ion channels with an overall accuracy of 87.8%, respectively. These results indicate that the proposed method can correctly identify ion channels and provide important instructions for drug-target discovery. The predictor can be freely downloaded from http://cobi.uestc.edu.cn/people/hlin/tools/IonchanPred/.     

Patch-clamp profile of ion channels in resting murine B lymphocytes

Summary Patch-clamp studies of single ion channel currents in freshly isolated murine B lymphocytes are characterized here according to their respective unitary conductances, ion selectivities, regulatory factors, distributions and kinetic behavior. The most prevalent ion channel in murine B lymphocytes is a large conductance (348 pS) nonselective anion channel. This report characterizes additional conductances including: two chloride channels (40 and 128 pS), a calcium-activated potassium channel (93 pS), and an outwardly rectifying potassium channel which displays two distinct conductances (18 and 30 pS). Like the anion channel, both chloride channels exhibit little activity in the cellattached patch configuration. The kinetic behavior of all of these channels is complex, with variable periods of bursting and flickering activity interspersed between prolonged closed/open intervals (dwell times). It is likely that some of these channels play an important role in the signal transduction of B cell activation.     

Molecular basis of ion permeability in a voltage‐gated sodium channel

Voltage‐gated sodium channels are essential for electrical signalling across cell membranes. They exhibit strong selectivities for sodium ions over other cations, enabling the finely tuned cascade of events associated with action potentials. This paper describes the ion permeability characteristics and the crystal structure of a prokaryotic sodium channel, showing for the first time the detailed locations of sodium ions in the selectivity filter of a sodium channel. Electrostatic calculations based on the structure are consistent with the relative cation permeability ratios (Na⁺ ≈ Li⁺ ≫ K⁺, Ca²⁺, Mg²⁺) measured for these channels. In an E178D selectivity filter mutant constructed to have altered ion selectivities, the sodium ion binding site nearest the extracellular side is missing. Unlike potassium ions in potassium channels, the sodium ions in these channels appear to be hydrated and are associated with side chains of the selectivity filter residues, rather than polypeptide backbones.