Differential binding of tetrodotoxin and its derivatives to voltage-sensitive sodium channel subtypes (Nav1.1 to Nav1.7)
Differential binding of tetrodotoxin and its derivatives to voltage-sensitive sodium channel subtypes (Nav1.1 to Nav1.7)
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DOI：
10.1111/bph.13985
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发表时间：
2017-11-01
影响因子：
7.3
通讯作者：
Konoki, Keiichi
中科院分区：
文献类型：
--
作者：
Tsukamoto, Tadaaki;Chiba, Yukie;Konoki, Keiichi
背景与目的为了开发治疗化合物，已尝试开发亚型选择性配体来抑制电压敏感钠通道(VSSCs)。河豚毒素(TTX)是一种来自河豚的毒素，对血管干细胞有强烈的抑制作用。许多TTX类似物已被鉴定来自海洋和陆地来源，尽管它们对特定的VSSC亚型的特异性尚未被研究。在这里，我们描述了11个TTX类似物与人VSSC亚型Na(V)1.1-Na(V)1.7的结合。结果TTX对Na(V)1.1-Na(V)1.7的抑制作用与文献报道一致，而5-脱氧-10，7-内酯类似物和4，9-脱水类似物对Na(V)1.1-Na(V)1.7无抑制作用。与其他对河豚毒素敏感的亚型相比，奇立奎毒素与Na(V)1.7的结合较少。Na(V)1.7、Thr(1425)和Ile(1426)TTX结合位点上的两个氨基酸残基分别突变为Met和Asp，因为这两个残基在其他亚型中发现在相同的位置。两个突变体，Na(V)1.7 T1425M和Na(V)1.7 I1426D，分别与奇立曲霉毒素的结合亲和力增加了16倍和5倍。结论和应用根据已报道的TTX-VSSC络合物的模型，奇立曲霉毒素与Na(V)1.7结合的降低归因于其C11-OH和/或C12-NH2。在哺乳动物VSSC的晶体结构被解决之前，Chiriquoxin是一个有用的工具来探测TTX结合位点的配置。
BACKGROUND AND PURPOSEThe development of subtype-selective ligands to inhibit voltage-sensitive sodium channels (VSSCs) has been attempted with the aim of developing therapeutic compounds. Tetrodotoxin (TTX) is a toxin from pufferfish that strongly inhibits VSSCs. Many TTX analogues have been identified from marine and terrestrial sources, although their specificity for particular VSSC subtypes has not been investigated. Herein, we describe the binding of 11 TTX analogues to human VSSC subtypes Na(v)1.1-Na(v)1.7.EXPERIMENTAL APPROACHEach VSSC subtype was transiently expressed in HEK293T cells. The inhibitory effects of TTX analogues on each subtype were assessed using whole-cell patch-clamp recordings.KEY RESULTSThe inhibitory effects of TTX on Na(v)1.1-Na(v)1.7 were observed in accordance with those reported in the literature; however, the 5-deoxy-10,7-lactone-type analogues and 4,9-anhydro-type analogues did not cause inhibition. Chiriquitoxin showed less binding to Na(v)1.7 compared to the other TTX-sensitive subtypes. Two amino acid residues in the TTX binding site of Na(v)1.7, Thr(1425) and Ile(1426) were mutated to Met and Asp, respectively, because these residues were found at the same positions in other subtypes. The two mutants, Na(v)1.7 T1425M and Na(v)1.7 I1426D, had a 16-fold and 5-fold increase in binding affinity for chiriquitoxin, respectively.CONCLUSIONS AND IMPLICATIONSThe reduced binding of chiriquitoxin to Na(v)1.7 was attributed to its C11-OH and/or C12-NH2, based on reported models for the TTX-VSSC complex. Chiriquitoxin is a useful tool for probing the configuration of the TTX binding site until a crystal structure for the mammalian VSSC is solved.