海葵Radianthus macrodactylus：皮群海葵毒素的一种新来源

海葵是季胺盐(四乙胺、黄海葵素)、生物胺(组胺、5—HT、多巴胺)、多肽(神经毒素、心脏毒素、蛋白酶抑制剂)以及蛋白质(细胞毒素、酶)等生物活性物质的丰富来源。在过去10年中,有关多肽神经毒素选择性地作用于兴奋膜的钠通道的课题一直为研究者所关注。 近几年,作者致力于研究海葵Radianthus macrodactylus产生的同源性神     

海葵Radianthus macrodactylus：皮群海葵毒素的一种新来源

海葵是季胺盐(四乙胺、黄海葵素)、生物胺(组胺、5—HT、多巴胺)、多肽(神经毒素、心脏毒素、蛋白酶抑制剂)以及蛋白质(细胞毒素、酶)等生物活性物质的丰富来源。     

舟山黄海葵兴奋性毒素AX-1的分离纯化及鉴定

目的从舟山黄海葵(AnthopLeura xanthogrammica)的刺细胞中分离纯化多肽类毒素分子并进行功能鉴定。方法通过反复冻融法以及多步高效液相色谱分离技术从舟山黄海葵毒素中分离到一种新型多肽类毒素,进行质谱鉴定和三维结构模拟,并运用膜片钳技术检测海葵毒素多肽对大鼠背根神经节(DRG)细胞的河豚毒素-敏感型(TTX-S)和河豚毒素-不敏感型(TTX-R)钠离子通道的影响。结果获得由48个氨基酸组成,相对分子质量为5018.2的多肽毒素分子,命名为AX-1,含3对二硫键;三维结构模拟表明该毒素多肽的结构以反平行β-折叠片以及loop结构为主,该毒素能抑制大鼠背根神经节细胞的钠离子通道的失活并显著增加钠离子通道的电流。结论AX-1是一种兴奋性多肽毒素,可作为潜在的强心肽药物。     

电压门控钠离子通道与肿瘤

目的综述电压门控钠离子通道(voltage-gated sodium channels,VGSCs)在不同肿瘤发生、发展过程中的作用。方法根据已有的关于电压门控钠离子通道在不同肿瘤细胞中的表达有所不同,阐述VGSC与不同类型肿瘤发生、发展的相关性。结果侵袭性较强的肿瘤细胞中一般有特异性的VGSCα亚基的表达,而相应的侵袭性较弱的细胞中则无VGSC的表达。结论VGSC在肿瘤细胞中的异常表达,可作为治疗靶点而进行相关药物的开发和临床应用。     

电压门控钠离子通道与疼痛

目的综述电压门控钠离子通道(voltage-gated sodium channels,VGSCs)与疼痛发生发展的相关性。方法根据已有的介绍电压门控钠离子通道与疼痛的文献共29篇,叙述不同α亚基与辅助亚基(β亚基)在疼痛发生与维持中的作用。结果特异性表达在外周神经系统中的钠离子通道NaV1.7、NaV1.8和NaV1.9,以及只在哺乳动物胚胎时期或神经元损伤后表达水平上调的NaV1.3与疼痛密切相关。结论 疼痛相关的电压门控钠离子通道亚型可作为疼痛性疾病治疗的药物筛选靶点。     

Ion Channel Modulators for Treatment of Neuropsychiatric Disorders

离子通道是神经细胞产生电信号的物质基础。神经电信号亦是调节递质释放、突触信号传递、动作电位传播等神经元功能活动的基础。本报告以电压门控钾离子通道为例,重点阐述Kv7（KCNQ／M-通道）钾通道作为靶点及其调节剂在神经精神疾病中治疗作用。     

酸敏感离子通道对大电导钙激活钾通道的抑制及其相互作用

酸敏感离子通道(acid-sensing ion channels,ASICs)是神经细胞的非电压门控阳离子通道,广泛分布于中枢及外周神经系统,参与痛觉、触觉、酸味觉的形成。在突触可塑性、学习记忆功能、炎症及脑缺血等生理病理过程中发挥重要作用。     

人参皂苷对电压门控离子通道的影响

离子通道是细胞膜和细胞器膜等生物膜上一类允许离子通透的蛋白质。许多离子通道,如大多数钠通道、钾通道、钙通道和部分氯通道受电压门控调节,这些电压门控离子通道具有广泛的生理功能。人参皂苷是中药人参、西洋参和三七等五加科人参属植物的主要活性成分,包括Ra1,Ra2,Rb1,Rb2,Rb3,Rc,Rd,Rg3和Rh2等原人参二醇,以及Re,Rf,Rg1,Rg2和Rh1等原人参三醇等。本文综述了人参皂苷多种成分对各种电压门控钠通道、钾通道、钙通道和氯通道的不同作用特点及可能的机制,提示人参皂苷多种成分不仅能直接作用于电压门控离子通道,还可以通过G蛋白和一氧化氮等信号通路途径,间接影响电压门控离子通道功能。     

ASICs——治疗神经系统相关疾病药物作用的新靶点

酸敏感离子通道（Acid sensing ion channels，ASICs）是一种可以被H+激活的质子门控阳离子通道。近年来研究发现，ASICs参与癫痫、炎症性疼痛、缺血性脑损伤等神经系统相关疾病的病理过程，它被认为是治疗神经系统相关疾病药物作用的一个新靶点。本文主要综述ASICs在神经系统相关疾病中的调节作用，以及ASICs相关药物的最新研究进展。     

MinK相关多肽的研究进展

MinK相关多肽是一个独特的离子通道辅助亚基家族,参与调解多种通道亚基,改变其电压门控特性、电导率及其药理学特性。该文简要介绍了MinK相关多肽的基因和分子结构、参与调控的通道亚基及其可能的生理和病理学意义等。     

Novel peptide toxins recently isolated from sea anemones

Sea anemones are a rich source of peptide toxins acting on ion channels. Two classes of peptide toxins, site-3 sodium channel toxins and Kv1 potassium channel toxins, have been well characterized and some of them used as valuable pharmacological reagents. Recently, the following six peptides toxins, which structurally constitute a new family but target different ion channels, have been isolated: BDS-I and -II (Kv3 potassium channel toxins) from Anemonia sulcata, APETx1 (human ether-a-go-go-related gene potassium channel toxin) and APETx2 (acid-sensing sodium channel toxin) from Anthopleura elegantissima, BcIV (sodium channel toxin) from Bunodosoma caissarum and Am II (whose target is unknown) from Antheopsis maculata. In addition, the following structurally novel peptide toxins have also emerged in sea anemones: gigantoxin I (epidermal growth factor-like toxin) from Stichodactyla gigantea and acrorhagins I and II from acrorhagi (specialized aggressive organs) of Actinia equina. This review deals with the structural and functional features of these recently isolated sea anemone peptide toxins that are promising tools in studying the physiology of diverse ion channels.     

Sea anemone venom as a source of insecticidal peptides acting on voltage-gated Na+ channels.

Sea anemones produce a myriad of toxic peptides and proteins of which a large group acts on voltage-gated Na+ channels. However, in comparison to other organisms, their venoms and toxins are poorly studied. Most of the known voltage-gated Na+ channel toxins isolated from sea anemone venoms act on neurotoxin receptor site 3 and inhibit the inactivation of these channels. Furthermore, it seems that most of these toxins have a distinct preference for crustaceans. Given the close evolutionary relationship between crustaceans and insects, it is not surprising that sea anemone toxins also profoundly affect insect voltage-gated Na+ channels, which constitutes the scope of this review. For this reason, these peptides can be considered as insecticidal lead compounds in the development of insecticides.     

Actions of sea anemone type 1 neurotoxins on voltage-gated sodium channel isoforms

As voltage-gated Na⁺ channels are responsible for the conduction of electrical impulses in most excitable tissues in the majority of animals (except nematodes), they have become important targets for the toxins of venomous animals, from sea anemones to molluscs, scorpions, spiders and even fishes. During their evolution, different animals have developed a set of cysteine-rich peptides capable of binding different extracellular sites of this channel protein. A fundamental question concerning the mechanism of action of these toxins is whether they act at a common receptor site in Na⁺ channels when exerting their different pharmacological effects, or at distinct receptor sites in different Na_v channels subtypes whose particular properties lead to these pharmacological differences. The α-subunits of voltage-gated Na⁺ channels (Na_v1.x) have been divided into at least nine subtypes on the basis of amino acid sequences. Sea anemones have been extensively studied from the toxinological point of view for more than 40 years. There are about 40 sea anemone type 1 peptides known to be active on Na_v1.x channels and all are 46-49 amino acid residues long, with three disulfide bonds and their molecular weights range between 3000 and 5000 Da. About 12 years ago a general model of Na_v1.2-toxin interaction, developed for the α-scorpion toxins, was shown to fit also to action of sea anemone toxin such as ATX-II. According to this model these peptides are specifically acting on the type 3 site known to be between segments 3 and 4 in domain IV of the Na⁺ channel protein. This region is indeed responsible for the normal Na⁺ currents fast inactivation that is potently slowed by these toxins. This fundamental “gain-of-function” mechanism is responsible for the strong increase in the action potential duration. They constitute a class of tools by means of which physiologists and pharmacologists can study the structure/function relationships of channel proteins. As most of the structural and electrophysiological studies were performed on type 1 sea anemone sodium channel toxins, we will present a comprehensive and updated review on the current understanding of the physiological actions of these Na channel modifiers.     

Comparison of sea anemone and scorpion toxins binding to Kv1 channels: an example of convergent evolution

Comparison of data from functional mapping carried out on scorpion and sea anemones toxins blocking currents through voltage-gated potassium channels revealed that, despite their different 3D structures, the binding cores of these toxins displayed some similarities. Further molecular modeling studies suggested that these similarities reflect the use by these toxins of a common binding mode to exert their blocking function. Therefore, scorpion and sea anemone toxins offer an example of mechanistic convergent evolution.     

Revisiting cangitoxin, a sea anemone peptide: purification and characterization of cangitoxins II and III from the venom of Bunodosoma cangicum.

Sodium channel toxins from sea anemones are employed as tools for dissecting the biophysical properties of inactivation in voltage-gated sodium channels. Cangitoxin (CGTX) is a peptide containing 48 amino acid residues and was formerly purified from Bunodosoma cangicum. Nevertheless, previous works reporting the isolation procedures for such peptide from B. cangicum secretions are controversial and may lead to incorrect information. In this paper, we report a simple and rapid procedure, consisting of two chromatographic steps, in order to obtain a CGTX analog directly from sea anemone venom. We also report a substitution of N16D in this peptide sample and the co-elution of an inseparable minor isoform presenting the R14H substitution. Peptides are named as CGTX-II and CGTX-III, and their effects over Nav1.1 channels in patch clamp experiments are demonstrated.     

Isolation and cDNA cloning of a potassium channel peptide toxin from the sea anemone Anemonia erythraea.

A potassium channel peptide toxin (AETX K) was isolated from the sea anemone Anemonia erythraea by gel filtration on Sephadex G-50, reverse-phase HPLC on TSKgel ODS-120T and anion-exchange HPLC on Mono Q. AETX K inhibited the binding of (125)I-alpha-dendrotoxin to rat synaptosomal membranes, although much less potently than alpha-dendrotoxin. Based on the determined N-terminal amino acid sequence, the nucleotide sequence of the full-length cDNA (609bp) encoding AETX K was elucidated by a combination of degenerate RT-PCR, 3'RACE and 5'RACE. The precursor protein of AETX K is composed of a signal peptide (22 residues), a propart (27 residues) ended with a pair of basic residues (Lys-Arg) and a mature peptide (34 residues). AETX K is the sixth member of the type 1 potassium channel toxins from sea anemones, showing especially high sequence identities with HmK from Heteractis magnifica and ShK from Stichodactyla helianthus. It has six Cys residues at the same position as the known type 1 toxins. In addition, the dyad comprising Lys and Tyr, which is considered to be essential for the binding of the known type 1 toxins to potassium channels, is also conserved in AETX K.     

Structure and function of delta-atracotoxins: lethal neurotoxins targeting the voltage-gated sodium channel.

Delta-atracotoxins (delta-ACTX), isolated from the venom of Australian funnel-web spiders, are responsible for the potentially lethal envenomation syndrome seen following funnel-web spider envenomation. They are 42-residue polypeptides with four disulfides and an "inhibitor cystine-knot" motif with structural but not sequence homology to a variety of other spider and marine snail toxins. Delta-atracotoxins induce spontaneous repetitive firing and prolongation of action potentials resulting in neurotransmitter release from somatic and autonomic nerve endings. This results from a slowing of voltage-gated sodium channel inactivation and a hyperpolarizing shift of the voltage-dependence of activation. This action is due to voltage-dependent binding to neurotoxin receptor site-3 in a similar, but not identical, fashion to scorpion alpha-toxins and sea anemone toxins. Unlike other site-3 neurotoxins, however, delta-ACTX bind with high affinity to both cockroach and mammalian sodium channels but low affinity to locust sodium channels. At present the pharmacophore of delta-ACTX is unknown but is believed to involve a number of basic residues distributed in a topologically similar manner to scorpion alpha-toxins and sea anemone toxins despite distinctly different protein scaffolds. As such, delta-ACTX provide us with specific tools with which to study sodium channel structure and function and determinants for phyla- and tissue-specific actions of neurotoxins interacting with site-3.     

Toxin determinants required for interaction with voltage-gated K channels

Ion channel-acting toxins are mainly short peptides generally present in minute amounts in the venoms of diverse animal species such as scorpions, snakes, spiders, marine cone snails and sea anemones. Interestingly, these peptides have evolved over time on the basis of clearly distinct architectural motifs present throughout the animal kingdom, but display convergent molecular determinants and functional homologies. As a consequence of this conservation of some key determinants, it has also been evidenced that toxin targets display some common evolutionary origins. Indeed, these peptides often target ion channels and ligand-gated receptors, though other interacting molecules such as enzymes have been further evidenced. In this review, we provide an overview of some selected peptides from various animal species that act on specific K⁺ conducting voltage-gated ion channels. In particular, we emphasize our global analysis on the structural determinants of these molecules that are required for the recognition of a particular ion channel pore structure, a property that should be correlated to the blocking efficacy of the K⁺ efflux out of the cell during channel opening. A better understanding of these molecular determinants is valuable to better specify and derive useful peptide pharmacological properties.