Structure and Function of Hainantoxin-III, a Selective Antagonist of Neuronal Tetrodotoxin-sensitive Voltage-gated Sodium Channels Isolated from the Chinese Bird Spider Ornithoctonus hainana
Structure and Function of Hainantoxin-III, a Selective Antagonist of Neuronal Tetrodotoxin-sensitive Voltage-gated Sodium Channels Isolated from the Chinese Bird Spider Ornithoctonus hainana
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海南鸟蜘蛛神经元河豚毒素敏感电压门控钠通道选择性拮抗剂海南毒素-III的结构和功能
DOI：
10.1074/jbc.m112.426627
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发表时间：
2013-07-12
影响因子：
4.8
通讯作者：
Liang, Songping
中科院分区：
文献类型：
--
作者：
Liu, Zhonghua;Cai, Tianfu;Liang, Songping
本文研究了海南鸟爪蛛毒液中含有的一种33残基多肽——海南毒素iii （hainantoxin-III, HNTX-III）的结构和功能。它是神经元河豚毒素敏感电压门控钠通道的选择性拮抗剂。HNTX-III抑制Nav1.7电流振幅，但未显著改变激活、失活和复燃动力学。短极去极化部分激活毒素结合通道，表明HNTX-III的电压依赖性抑制。HNTX-III增加了极端去极化后Nav1.7电流的失活。HNTX-III.Nav1.7复合物以电压依赖的方式在长时间的强去极化中逐渐解离，未结合的毒素在长时间的复极化后反弹到Nav1.7。此外，嵌合通道分析表明，DIIS3-S4连接体对于HNTX-III与Nav1.7的结合至关重要。这些数据与HNTX-III与Nav1.7 site 4相互作用并捕获域II电压传感器处于关闭状态相一致。HNTX-III的溶液结构由二维核磁共振确定，并显示具有抑制剂胱氨酸结基序。结构分析表明，主要位于C端的某些碱性、疏水性和芳香残基可能构成一个两亲性表面，可能参与了HNTX-III与Nav1.7的结合。综上所述，我们的研究结果表明，HNTX-III在作用机制和结合特异性和亲和力方面不同于β -蝎子毒素和其他β -蜘蛛毒素。本研究结果有助于我们理解毒素-钠通道相互作用的机制，并为研究钠通道异构体的结构和功能以及开发镇痛药提供了有用的工具。
In the present study, we investigated the structure and function of hainantoxin-III (HNTX-III), a 33-residue polypeptide from the venom of the spider Ornithoctonus hainana. It is a selective antagonist of neuronal tetrodotoxin-sensitive voltage-gated sodium channels. HNTX-III suppressed Nav1.7 current amplitude without significantly altering the activation, inactivation, and repriming kinetics. Short extreme depolarizations partially activated the toxin-bound channel, indicating voltage-dependent inhibition of HNTX-III. HNTX-III increased the deactivation of the Nav1.7 current after extreme depolarizations. The HNTX-III.Nav1.7 complex was gradually dissociated upon prolonged strong depolarizations in a voltage-dependent manner, and the unbound toxin rebound to Nav1.7 after a long repolarization. Moreover, analysis of chimeric channels showed that the DIIS3-S4 linker was critical for HNTX-III binding to Nav1.7. These data are consistent with HNTX-III interacting with Nav1.7 site 4 and trapping the domain II voltage sensor in the closed state. The solution structure of HNTX-III was determined by two-dimensional NMR and shown to possess an inhibitor cystine knot motif. Structural analysis indicated that certain basic, hydrophobic, and aromatic residues mainly localized in the C terminus may constitute an amphiphilic surface potentially involved in HNTX-III binding to Nav1.7. Taken together, our results show that HNTX-III is distinct from beta-scorpion toxins and other beta-spider toxins in its mechanism of action and binding specificity and affinity. The present findings contribute to our understanding of the mechanism of toxin-sodium channel interaction and provide a useful tool for the investigation of the structure and function of sodium channel isoforms and for the development of analgesics.