The National and Local Joint Engineering Laboratory of Animal Peptide Drug Development, College of Life Sciences, Hunan Normal University, Changsha 410081, China.
Toxins (Basel). 2018 Oct 10;10(10):408. doi: 10.3390/toxins10100408.
Exploring the interaction of ligands with voltage-gated sodium channels (Nas) has advanced our understanding of their pharmacology. Herein, we report the purification and characterization of a novel non-selective mammalian and bacterial Nas toxin, JZTx-14, from the venom of the spider . This toxin potently inhibited the peak currents of mammalian Na1.2⁻1.8 channels and the bacterial NaChBac channel with low IC values (<1 µM), and it mainly inhibited the fast inactivation of the Na1.9 channel. Analysis of Na1.5/Na1.9 chimeric channel showed that the Na1.5 domain II S3⁻4 loop is involved in toxin association. Kinetics data obtained from studying toxin⁻Na1.2 channel interaction showed that JZTx-14 was a gating modifier that possibly trapped the channel in resting state; however, it differed from site 4 toxin HNTx-III by irreversibly blocking Na currents and showing state-independent binding with the channel. JZTx-14 might stably bind to a conserved toxin pocket deep within the Na1.2⁻1.8 domain II voltage sensor regardless of channel conformation change, and its effect on Nas requires the toxin to trap the S3⁻4 loop in its resting state. For the NaChBac channel, JZTx-14 positively shifted its conductance-voltage (G⁻V) and steady-state inactivation relationships. An alanine scan analysis of the NaChBac S3⁻4 loop revealed that the 108th phenylalanine (F108) was the key residue determining the JZTx-14⁻NaChBac interaction. In summary, this study provided JZTx-14 with potent but promiscuous inhibitory activity on both the ancestor bacterial Nas and the highly evolved descendant mammalian Nas, and it is a useful probe to understand the pharmacology of Nas.
探索配体与电压门控钠离子通道（Nas）的相互作用，提高了我们对其药理学的认识。在此，我们报告了一种新型非选择性哺乳动物和细菌 Nas 毒素 JZTx-14 的纯化和表征，该毒素来自蜘蛛的毒液。该毒素强烈抑制哺乳动物 Na1.2⁻1.8 通道和细菌 NaChBac 通道的峰值电流，IC 值较低（<1 µM），主要抑制 Na1.9 通道的快速失活。Na1.5/Na1.9 嵌合通道分析表明，Na1.5 结构域 II S3⁻4 环参与毒素结合。从研究毒素- Na1.2 通道相互作用获得的动力学数据表明，JZTx-14 是一种门控修饰剂，可能将通道固定在静止状态；然而，它与位点 4 毒素 HNTx-III 不同，因为它不可逆地阻断 Na 电流并与通道呈状态独立结合。JZTx-14 可能稳定地结合到 Na1.2⁻1.8 结构域 II 电压传感器内的保守毒素口袋中，而与通道构象变化无关，其对 Nas 的作用需要毒素将 S3⁻4 环固定在静止状态。对于 NaChBac 通道，JZTx-14 正向移动其电导-电压（G⁻V）和稳态失活关系。NaChBac S3⁻4 环的丙氨酸扫描分析表明，第 108 位苯丙氨酸（F108）是决定 JZTx-14-NaChBac 相互作用的关键残基。总之，这项研究提供了 JZTx-14 对祖先细菌 Nas 和高度进化的后代哺乳动物 Nas 均具有强大但混杂的抑制活性，是了解 Nas 药理学的有用探针。
