Analysis of the interaction of tarantula toxin Jingzhaotoxin-III (β-TRTX-Cj1α) with the voltage sensor of Kv2.1 uncovers the molecular basis for cross-activities on Kv2.1 and Nav1.5 channels.
Analysis of the interaction of tarantula toxin Jingzhaotoxin-III (β-TRTX-Cj1α) with the voltage sensor of Kv2.1 uncovers the molecular basis for cross-activities on Kv2.1 and Nav1.5 channels.
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DOI：
10.1021/bi4006418
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发表时间：
2013-10
期刊：
影响因子：
2.9
通讯作者：
Huai Tao;Jin J Chen;Yueyue Xiao;Yuanyuan Wu;Haibo Su;Dan Li;Heng-Yen Wang;M. Deng;Meixia Wang;Zhong-hua Liu;S. Liang
中科院分区：
文献类型：
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作者：
Huai Tao;Jin J Chen;Yueyue Xiao;Yuanyuan Wu;Haibo Su;Dan Li;Heng-Yen Wang;M. Deng;Meixia Wang;Zhong-hua Liu;S. Liang
动物毒液含有一系列令人着迷的不同多肽毒素，这些毒素对不同类型的电压门控离子通道具有交叉作用。然而，其潜在的机制仍然知之甚少。JZTX-III(JZTX-III)是狼蛛的一种36个氨基酸残基的多肽，对大多数其他离子通道亚型的Nav1.5和Kv2.1通道具有特异性。JZTX-III通过与DIIS3-S4接头结合，在关闭状态下捕获NaV1.5 DII电压传感器。在本研究中，电生理实验显示JZTX-III对5种电压门控性钾通道亚型(Kv1.4、Kv3.1和Kv4.1-4.3)没有影响，而对Kv2.1有明显的抑制作用，IC50值为0.71±0.01μM。诱变和模拟数据表明，JZTX-III停靠在Kv2.1电压敏感桨上。Phe274、Lys280、Ser281、Leu283、Gln284和Val288的丙氨酸替换可使JZTX-III的亲和力分别降低7、9、34、12、9和7倍。其中，S281是最关键的决定因素，苏氨酸的替代只是略微降低了毒素的敏感性。相比之下，Ser281一次转换为ALA、Phe、Ile、Val或Glu，IC50值就增加了34倍。丙氨酸扫描突变实验表明，JZTX-III与Kv2.1通道结合的功能表面由四个疏水残基(Trp8、Trp28、Trp30和Val33)和三个带电残基(Arg13、Lys15和Glu34)组成。JZTX-III与Kv2.1和NaV1.5相互作用的生物活性表面只有部分重叠。这些结果有力地支持了这样的假设，即动物毒素可能使用部分重叠的生物活性表面来靶向两种不同类型的离子通道的电压传感器叶片。加深我们对毒素与电压门控钠、钾通道相互作用的分子机制的了解，可能为设计更有效的离子通道抑制剂提供新的分子见解。
Animal venoms contain a fascinating array of divergent peptide toxins that have cross-activities on different types of voltage-gated ion channels. However, the underlying mechanism remains poorly understood. Jingzhaotoxin-III (JZTX-III), a 36-residue peptide from the tarantula Chilobrachys jingzhao, is specific for Nav1.5 and Kv2.1 channels over the majority of other ion channel subtypes. JZTX-III traps the Nav1.5 DII voltage sensor at closed state by binding to the DIIS3-S4 linker. In this study, electrophysiological experiments showed that JZTX-III had no effect on five voltage-gated potassium channel subtypes (Kv1.4, Kv3.1, and Kv4.1-4.3), whereas it significantly inhibited Kv2.1 with an IC50 of 0.71 ± 0.01 μM. Mutagenesis and modeling data suggested that JZTX-III docks at the Kv2.1 voltage-sensor paddle. Alanine replacement of Phe274, Lys280, Ser281, Leu283, Gln284, and Val288 could decrease JZTX-III affinity by 7-, 9-, 34-, 12-, 9-, and 7-fold, respectively. Among them, S281 is the most crucial determinant, and the substitution with Thr only slightly reduced toxin sensitivity. In contrast, a single conversion of Ser281 to Ala, Phe, Ile, Val, or Glu increased the IC50 value by >34-fold. Alanine-scanning mutagenesis experiments indicated that the functional surface of JZTX-III bound to the Kv2.1 channel is composed of four hydrophobic residues (Trp8, Trp28, Trp30, and Val33) and three charged residues (Arg13, Lys15, and Glu34). The bioactive surfaces of JZTX-III interacting with Kv2.1 and Nav1.5 are only partially overlapping. These results strongly supported the hypothesis that animal toxins might use partially overlapping bioactive surfaces to target the voltage-sensor paddles of two different types of ion channels. Increasing our understanding of the molecular mechanisms of toxins interacting with voltage-gated sodium and potassium channels may provide new molecular insights into the design of more potent ion channel inhibitors.