PDF(Sci-hub)
Abstract：
Mutations in the KCNT1 (Slack, KNa1.1) sodium-activated potassium channel produce severe epileptic encephalopathies. Expression in heterologous systems has shown that the disease-causing mutations give rise to channels that have increased current amplitude. It is not known, however, whether such gain of function occurs in human neurons, nor whether such increased KNa current is expected to suppress or increase the excitability of cortical neurons. Using genetically engineered human induced pluripotent stem cell (iPSC)-derived neurons, we have now found that sodium-dependent potassium currents are increased several-fold in neurons bearing a homozygous P924L mutation. In current-clamp recordings, the increased KNa current in neurons with the P924L mutation acts to shorten the duration of action potentials and to increase the amplitude of the afterhyperpolarization that follows each action potential. Strikingly, the number of action potentials that were evoked by depolarizing currents as well as maximal firing rates were increased in neurons expressing the mutant channel. In networks of spontaneously active neurons, the mean firing rate, the occurrence of rapid bursts of action potentials, and the intensity of firing during the burst were all increased in neurons with the P924L Slack mutation. The feasibility of an increased KNa current to increase firing rates independent of any compensatory changes was validated by numerical simulations. Our findings indicate that gain-of-function in Slack KNa channels causes hyperexcitability in both isolated neurons and in neural networks and occurs by a cell-autonomous mechanism that does not require network interactions.SIGNIFICANCE STATEMENT KCNT1 mutations lead to severe epileptic encephalopathies for which there are no effective treatments. This study is the first demonstration that a KCNT1 mutation increases the Slack current in neurons. It also provides the first explanation for how this increased potassium current induces hyperexcitability, which could be the underlining factor causing seizures.
摘要：
KCNT1中的突变（Slack，KNa1.1）钠激活钾通道可产生严重的癫痫性脑病。在异源系统中的表达已经表明,致病突变产生具有增加的电流幅度的通道。不知道,然而,这种功能的获得是否发生在人类神经元中，这种增加的KNa电流是否会抑制或增加皮质神经元的兴奋性。使用基因工程人类诱导多能干细胞（iPSC）衍生的神经元，我们现在发现,在带有纯合P924L突变的神经元中,钠依赖性钾电流增加了数倍.在电流钳记录中，具有P924L突变的神经元中增加的KNa电流可以缩短动作电位的持续时间，并增加每个动作电位之后的超极化后的幅度。引人注目的是，在表达突变通道的神经元中，由去极化电流引起的动作电位数量以及最大放电率增加。在自发活跃的神经元网络中，平均射击率，动作电位快速爆发的发生，在P924LSlack突变的神经元中，爆发期间的放电强度均增加。通过数值模拟验证了增加KNa电流以独立于任何补偿性变化来增加点火速率的可行性。我们的发现表明，SlackKNa通道的功能获得会导致孤立的神经元和神经网络的过度兴奋，并通过不需要网络相互作用的细胞自主机制发生。显著性声明KCNT1突变导致严重的癫痫性脑病，没有有效的治疗方法。这项研究首次证明了KCNT1突变会增加神经元中的Slack电流。它还提供了第一个解释这种增加的钾电流如何诱导过度兴奋，这可能是导致癫痫发作的重要因素。
