The Domain II S4-S5 Linker in Nav1.9: A Missense Mutation Enhances Activation, Impairs Fast Inactivation, and Produces Human Painful Neuropathy
The Domain II S4-S5 Linker in Nav1.9: A Missense Mutation Enhances Activation, Impairs Fast Inactivation, and Produces Human Painful Neuropathy
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DOI：
10.1007/s12017-015-8347-9
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发表时间：
2015-06-01
影响因子：
3.5
通讯作者：
Waxman, Stephen G.
中科院分区：
文献类型：
--
作者：
Han, Chongyang;Yang, Yang;Waxman, Stephen G.
疼痛的小纤维神经病是一种具有挑战性的疾病，没有有效的治疗方法。在一半的受试者中可以确定非遗传原因。钠通道Nav1.7和Nav1.8的功能获得变异最近与疼痛性小纤维神经病变有关。最近，钠通道Nav1.9的突变与人类疼痛障碍有关，在疼痛性小纤维神经病患者中发现了两种功能获得突变。在这里，我们报告了一种新的Nav1.9突变，在区域II S4-S5连接体中被精氨酸（G699R）取代的甘氨酸699，在一个患有疼痛性小纤维神经病变的患者中发现。在这项研究中，我们通过电压钳法检测了不产生内源性Nav1.8或Nav1.9电流的颈上神经节神经元的突变通道，并提供了一个Nav1.9在相对高水平表达的新平台。电压箝位分析表明，与野生型Nav1.9通道相比，突变使通道激活（-10.1 mV），去极化（+6.3 mV），稳态快速失活，减慢失活，增强斜坡响应。电流钳分析显示，G699R突变通道通过静息膜电位去极化、电流阈值降低和诱发放电增加，使背根神经节神经元过度兴奋。这些观察结果表明，结构域II S4-S5连接子在Nav1.9的门控中起着重要作用，并表明该连接子的突变与一种常见的疼痛疾病有关。
Painful small fiber neuropathy is a challenging medical condition with no effective treatment. Non-genetic causes can be identified in one half of the subjects. Gain-of-function variants of sodium channels Nav1.7 and Nav1.8 have recently been associated with painful small fiber neuropathy. More recently, mutations of sodium channel Nav1.9 have been linked to human pain disorders, with two gain-of-function mutations found in patients with painful small fiber neuropathy. Here we report a novel Nav1.9 mutation, a glycine 699 substitution by arginine (G699R) in the domain II S4-S5 linker, identified in a patient with painful small fiber neuropathy. In this study, we assayed the mutant channels by voltage-clamp in superior cervical ganglion neurons, which do not produce endogenous Nav1.8 or Nav1.9 currents, and provide a novel platform where Nav1.9 is expressed at relatively high levels. Voltage-clamp analysis showed that the mutation hyperpolarizes (-10.1 mV) channel activation, depolarizes (+6.3 mV) steady-state fast inactivation, slows deactivation, and enhances ramp responses compared with wild-type Nav1.9 channels. Current-clamp analysis showed that the G699R mutant channels render dorsal root ganglion neurons hyperexcitable, via depolarized resting membrane potential, reduced current threshold and increased evoked firing. These observations show that the domain II S4-S5 linker plays an important role in the gating of Nav1.9 and demonstrates that a mutation in this linker is linked to a common pain disorder.