蜈蚣毒素来源的专一性Nav1.7抑制剂的结构功能及镇痛机制研究

Pain is a difficult issue for human health, but the high efficient and low toxicity drug for pain management is still limited. Nav1.7 is an important target for pain management and high selective inhibitor of Nav1.7 is a hot spot of analgesics. However no selective antagonists targeted on Nav1.7 have been found. The venoms of Scolopendra subspinipes mutilans L is a good source for pain management drug screen. Recently our group identified a new peptide toxin (μ-SLPTX-Ssm6a) selectively acting on sodium channel Nav1.7 isolated from the venoms of Scolopendra subspinipes mutilans L and this peptide showed a good analgesia effect on animal model （PNAS 110:17534-9, 2013). This work was recommended by Nature and Nature medicine as a highlight work and μ-SLPTX-Ssm6a was recommended as a good candidate of analgesics. In this proposal we will study the secondary structure, the structure and function of μ-SLPTX-Ssm6a by the mutations of toxin, the effect of μ-SLPTX-Ssm6a on kinetic of sodium channel and understand the molecular basis of μ-SLPTX-Ssm6a interacting with the sodium channel subtype Nav1.7. The analgesic effect of μ-SLPTX-Ssm6a on chronic pain will also be studied by animal model of pain.

疼痛一直困扰人们健康，目前缺乏高效低毒的疼痛治疗药物。钠离子通道亚型Nav1.7是治疗疼痛的重要靶点，该通道的高度选择性抑制剂是镇痛药物研发热点，但目前基本上还没有Na1.7的专一性抑制剂。蜈蚣是传统的疼痛治疗药物，最近我们从蜈蚣毒液中发现了一种选择性作用于Nav1.7离子通道的神经毒素μ-SLPTX-Ssm6a该毒素表现出良好的镇痛效果（PNAS 110:17534-9, 2013），被Nature和Nature medicine作为亮点工作专门评论，并认为μ-SLPTX-Ssm6a是优秀的镇痛候选药物。本项目将解析μ-SLPTX-Ssm6a化学特性和高级结构；通过μ-SLPTX-Ssm6a及Nav1.7定点突变研究其结构与功能关系；分析毒素对Nav1.7的通道动力学影响，识别其与Nav1.7相互作用的分子基础；构建疼痛模型研究μ-SLPTX-Ssm6a及其突变体的对慢性疼痛的治疗效果。

疼痛一直困扰人们健康，目前缺乏高效低毒的疼痛治疗药物。钠离子通道亚型Nav1.7是治疗疼痛的重要靶点，该通道的高度选择性抑制剂是镇痛药物研发热点，但目前基本上还没有Na1.7的专一性抑制剂。蜈蚣是传统的疼痛治疗药物，最近我们从蜈蚣毒液中发现了一种选择性作用于Nav1.7离子通道的神经毒素μ-SLPTX-Ssm6a，本项目深入研究了Ssm6a的与Nav1.7的相互作用机制。本研究首先构建了18个毒素的突变体，通过大肠杆菌表达的方法获得了足够的量，检测了每种突变体对Nav1.7的抑制效果，发现Ssm6a作用于Nav1.7的关键氨基酸残基主要位于N端，同时也解析了Ssm6a的空间结构。构建了Nav1.7和Nav1.5的嵌合体，发现Ssm6a作用于Nav1.7 DIIS3-S4片段，并构建了Nav1.7DIIS3-S4片段上的突变体，确定了Ssm6a结合Nav1.7的关键位点。Ssm6a在三种类疼痛模型上表现出了良好的镇痛效果，其镇痛效果和吗啡相当。本研究发现了Nav1.7的专一性抑制剂，并研究得到了其和Nav1.7的作用方式，为理解多肽毒素和钠通道相互作用的机制提供了新的工具，也为钠通道的镇痛药物的开发提供了新的模板或候选药物。