Key Laboratory of Protein Chemistry and Developmental Biology of Ministry of Education, College of Life Sciences, Hunan Normal University, Changsha 410081, China.
Toxins (Basel). 2019 Nov 20;11(12):680. doi: 10.3390/toxins11120680.
It has been reported that Heteropodatoxin3 (HpTx3), a peptidic neurotoxin purified from the venom of the spider species Heteropoda venatoria, could inhibit K4.2 channels. Our present study newly found that HpTx3 also has potent and selective inhibitory action on Na1.7, with an IC of 135.61 ± 12.98 nM. Without effect on the current-voltage (I-V) relationship of Na1.7, HpTx3 made minor alternation in the voltage-dependence of activation and steady-state inactivation of Na1.7 (4.15 mV and 7.29 mV, respectively) by interacting with the extracellular S3-S4 loop (S3b-S4 sequence) in domain II and the domain IV of the Na channel subtype, showing the characteristics of both pore blocker and gate modifier toxin. During the interaction of HpTx3 with the S3b-S4 sequence of Na1.7, the amino acid residue D in the sequence played a key role. When administered intraperitoneally or intramuscularly, HpTx3 displayed potent analgesic activity in a dose-dependent manner in different mouse pain models induced by formalin, acetic acid, complete Freund's adjuvant, hot plate, or spared nerve injury, demonstrating that acute, inflammatory, and neuropathic pains were all effectively inhibited by the toxin. In most cases HpTx3 at doses of ≥ 1mg/kg could produce the analgesic effect comparable to that of 1 mg/kg morphine. These results suggest that HpTx3 not only can be used as a molecular probe to investigate ion channel function and pain mechanism, but also has potential in the development of the drugs that treat the Na1.7 channel-related pain.
据报道，从蜘蛛物种 Heteropoda venatoria 的毒液中纯化得到的肽类神经毒素 Heteropodatoxin3（HpTx3）可以抑制 K4.2 通道。我们的研究新发现，HpTx3 对 Na1.7 也具有强大且选择性的抑制作用，IC50 为 135.61 ± 12.98 nM。HpTx3 对 Na1.7 的电流-电压（I-V）关系没有影响，但通过与 Na 通道亚型的 II 域和 IV 域中的细胞外 S3-S4 环（S3b-S4 序列）相互作用，对 Na1.7 的激活和稳态失活的电压依赖性产生轻微改变（分别为 4.15 mV 和 7.29 mV），表现出通道孔阻滞剂和门控修饰毒素的特征。在 HpTx3 与 Na1.7 的 S3b-S4 序列相互作用期间，序列中的氨基酸残基 D 发挥了关键作用。HpTx3 经腹腔或肌肉内给药，在不同的福尔马林、乙酸、完全弗氏佐剂、热板或 spared 神经损伤诱导的小鼠疼痛模型中，以剂量依赖性方式表现出强大的镇痛活性，表明急性、炎症和神经性疼痛均被毒素有效抑制。在大多数情况下，剂量≥1mg/kg 的 HpTx3 可产生与 1mg/kg 吗啡相当的镇痛效果。这些结果表明，HpTx3 不仅可用作研究离子通道功能和疼痛机制的分子探针，而且在开发治疗 Na1.7 通道相关疼痛的药物方面具有潜力。
