Tarantula huwentoxin-IV inhibits neuronal sodium channels by binding to receptor site 4 and trapping the domain II voltage sensor in the closed configuration
Tarantula huwentoxin-IV inhibits neuronal sodium channels by binding to receptor site 4 and trapping the domain II voltage sensor in the closed configuration
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DOI：
10.1074/jbc.m708447200
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发表时间：
2008-10-03
影响因子：
4.8
通讯作者：
Cummins, Theodore R.
中科院分区：
文献类型：
--
作者：
Xiao, Yucheng;Bingham, Jon-Paul;Cummins, Theodore R.
肽类毒素具有高亲和力、不同的药理学功能和亚型特异性，是研究电压门控钠通道（VGSC）结构与功能关系的有力工具。虽然一些有趣的抑制剂已被报道从狼蛛毒液，很少有人知道他们与VGSC的相互作用的机制。我们发现，虎纹捕鸟蛛毒素-IV（HWTX-IV），一个35个残基的肽从狼蛛Ornithoctonus huwena毒液，优先抑制神经元VGSC亚型rNav1.2，rNav1.3和hNav1.7相比，肌肉亚型rNav1.4和hNav1.5。在检测的五种VGSC中，hNav1.7对HWTX-IV最敏感（IC 50类似于26 nM）。在应用1 μ M HWTX-IV后，只能在极端去极化（>+ 100 mV）下引发hNav1.7电流。持续数分钟的极端去极化或中度去极化可诱导hNav1.7通道从HWTX-IV抑制中恢复。定点突变分析表明，毒素停靠在位于结构域II的胞外S3-S4接头的神经毒素受体位点4。hNav1.7中的突变E818 Q和D816 N使hNav1.7的毒素亲和力降低了约300倍，而rNav1.4中的回复突变（N655 D/Q657 E）和hNav1.5中的相应突变（R812 D/S814 E）大大增加了肌肉VGSC对HWTX-IV的敏感性。我们的数据确定了一种新的机制，钠通道抑制狼蛛毒素涉及结合神经毒素受体网站4。相反，蝎β-毒素，陷阱的IIS 4电压传感器在一个向外的配置，我们建议，HWTX-IV陷阱的电压传感器域II在向内，封闭的配置。
Peptide toxins with high affinity, divergent pharmacological functions, and isoform-specific selectivity are powerful tools for investigating the structure-function relationships of voltage-gated sodium channels (VGSCs). Although a number of interesting inhibitors have been reported from tarantula venoms, little is known about the mechanism for their interaction with VGSCs. We show that huwentoxin-IV (HWTX-IV), a 35-residue peptide from tarantula Ornithoctonus huwena venom, preferentially inhibits neuronal VGSC subtypes rNav1.2, rNav1.3, and hNav1.7 compared with muscle subtypes rNav1.4 and hNav1.5. Of the five VGSCs examined, hNav1.7 was most sensitive to HWTX-IV (IC50 similar to 26 nM). Following application of 1 mu M HWTX-IV, hNav1.7 currents could only be elicited with extreme depolarizations (>+ 100 mV). Recovery of hNav1.7 channels from HWTX-IV inhibition could be induced by extreme depolarizations or moderate depolarizations lasting several minutes. Site-directed mutagenesis analysis indicated that the toxin docked at neurotoxin receptor site 4 located at the extracellular S3-S4 linker of domain II. Mutations E818Q and D816N in hNav1.7 decreased toxin affinity for hNav1.7 by similar to 300-fold, whereas the reverse mutations in rNav1.4 (N655D/Q657E) and the corresponding mutations in hNav1.5 (R812D/S814E) greatly increased the sensitivity of the muscle VGSCs to HWTX-IV. Our data identify a novel mechanism for sodium channel inhibition by tarantula toxins involving binding to neurotoxin receptor site 4. In contrast to scorpion beta-toxins that trap the IIS4 voltage sensor in an outward configuration, we propose that HWTX-IV traps the voltage sensor of domain II in the inward, closed configuration.