Early-Onset Epileptic Encephalopathy Caused by Gain-of-Function Mutations in the Voltage Sensor of Kv7.2 and Kv7.3 Potassium Channel Subunits
Early-Onset Epileptic Encephalopathy Caused by Gain-of-Function Mutations in the Voltage Sensor of Kv7.2 and Kv7.3 Potassium Channel Subunits
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DOI：
10.1523/jneurosci.4423-14.2015
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发表时间：
2015-03-04
影响因子：
5.3
通讯作者：
Taglialatela, Maurizio
中科院分区：
文献类型：
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作者：
Miceli, Francesco;Soldovieri, Maria Virginia;Taglialatela, Maurizio
K(V)7.2(KCNQ2)和K(V)7.3(KCNQ3)基因突变编码神经元M-电流的电压门控K+通道亚基，与从良性家族性新生儿癫痫发作到严重癫痫脑病的广泛早期癫痫疾病有关。本工作的目的是研究最近在癫痫脑病和/或智力障碍患者中发现的K(V)7.2(R144Q、R201C和R201H)或K(V)7.3(R230C)电压敏感结构域突变导致通道功能障碍的分子机制。在转染人K(V)7.2和/或K(V)7.3 cDNA的哺乳动物细胞中的电生理学研究表明，这四个突变中的每一个都稳定了通道的激活状态，从而产生了功能获得效应，这与先前发现的突变所产生的功能丧失效应相反。多态结构模拟表明，K(V)7.2中的R201残基，对应于K(V)7.3中的R230，通过与邻近负电荷残基形成复杂的静电相互作用网络，稳定了静止和附近的电压敏感域态，这一结果也得到了二硫化物捕获实验的证实。使用海马区前馈抑制微电路的现实模型，发现锥体神经元的兴奋性在加入实验定义的突变M电流参数后增加，这表明网络相互作用的变化而不是细胞固有属性的变化可能是这些功能获得突变导致神经元超兴奋性的原因。综上所述，目前的结果表明K(V)7.2/3电流的功能获得突变可能导致人类癫痫的严重临床病程，从而揭示了疾病发病机制中未知的复杂程度。
Mutations in K(v)7.2 (KCNQ2) and K(v)7.3 (KCNQ3) genes, encoding for voltage-gated K+ channel subunits underlying the neuronal M-current, have been associated with a wide spectrum of early-onset epileptic disorders ranging from benign familial neonatal seizures to severe epileptic encephalopathies. The aim of the present work has been to investigate the molecular mechanisms of channel dysfunction caused by voltage-sensing domain mutations in K(v)7.2 (R144Q, R201C, and R201H) or K(v)7.3 (R230C) recently found in patients with epileptic encephalopathies and/or intellectual disability. Electrophysiological studies in mammalian cells transfected with human K(v)7.2 and/or K(v)7.3 cDNAs revealed that each of these four mutations stabilized the activated state of the channel, thereby producing gain-of-function effects, which are opposite to the loss-of-function effects produced by previously found mutations. Multistate structural modeling revealed that the R201 residue in K(v)7.2, corresponding to R230 in K(v)7.3, stabilized the resting and nearby voltage-sensing domain states by forming an intricate network of electrostatic interactions with neighboring negatively charged residues, a result also confirmed by disulfide trapping experiments. Using a realistic model of a feedforward inhibitory microcircuit in the hippocampal CA1 region, an increased excitability of pyramidal neurons was found upon incorporation of the experimentally defined parameters for mutant M-current, suggesting that changes in network interactions rather than in intrinsic cell properties may be responsible for the neuronal hyperexcitability by these gain-of-function mutations. Together, the present results suggest that gain-of-function mutations in K(v)7.2/3 currents may cause human epilepsy with a severe clinical course, thus revealing a previously unexplored level of complexity in disease pathogenetic mechanisms.