Daily Regulation of Ionic Currents

 描述(申请人提供)：昼夜节律性是人类生理学的一个基本方面。昼夜节律紊乱是一种严重的健康负担，影响睡眠、心血管、代谢和精神障碍。要了解人体生理的昼夜节律如何对人类健康和疾病做出贡献，需要基本了解昼夜节律是如何产生和表达的。这项拟议研究的总体目标是确定在视交叉上核(大脑的时钟)中编码昼夜节律的基本机制。SCN回路在动作电位(AP)放电中经历同步的每日振荡，昼夜行为和生理特征由这种SCN回路节律建立。每日离子通道活动的调节是产生SCN神经元活动昼夜节律的关键基础。在这种离子通道上，BK钙和电压激活的钾通道(Kcnma1)是昼夜节律的中枢调节器。BK电流大小的日常调节导致SCN回路节律性，BK通道功能的丧失扰乱了昼夜的行为和生理节律。BK电流水平的昼夜差异是由β-2亚单位调节的，该亚单位导致白天BK通道失活。基于β-2功能的BK电流特性的昼夜变化是独一无二的，但尚不清楚β-2是如何调节AP活性来塑造SCN神经元活动的节律的。这些研究验证了这样一种假设，即β-2介导的失活是BK通道在SCN AP放电中动态作用所必需的关键特性，并且这一过程是昼夜行为的中心。这一假说将使用急性SCN脑片中BK电流和AP的电生理记录进行研究，提供数据以将AP波形的变化与β2亚单位的失活特性联系起来。此外，还将研究由BK的钙源昼夜节律变化引起的BK电流失活的后果。最后，将测试人类癫痫连锁突变和其他单核苷酸多态(SNP)对BK/β2电流特性的影响，并确定其与SCN和行为节律性的相关性。该项目的成果将是了解BK电流的日常调节如何调控SCN的兴奋性，为影响人类BK通道活动的机制提供新的生理学和翻译洞察力。

 DESCRIPTION (provided by applicant): Circadian rhythmicity is a fundamental aspect of human physiology. Disruption of circadian rhythm is a significant health burden, impacting sleep, cardiovascular, metabolic and psychiatric disorders. Understanding how circadian modulation of the body's physiology contributes to human health and disease requires a basic understanding of how circadian rhythms are generated and expressed. The overall goal of the proposed research is to identify the basic mechanisms of that encode circadian rhythmicity in the suprachiasmatic nucleus (SCN), the brain's clock. The SCN circuit undergoes synchronized daily oscillations in action potential (AP) firing, and circadian behavioral and physiological characteristics are established by this SCN circuit rhythm. Daily modulation of ion channel activity is a critical basis for generating the circadian rhythm in neuronal activity in the SCN. Oe such ion channel, the BK calcium- and voltage-activated potassium channel (Kcnma1) is a central regulator of circadian rhythm. Daily modulation of BK current magnitude drives SCN circuit rhythmicity, and loss of BK channel function disrupts circadian behavioral and physiological rhythms. The day-night difference in BK current level is mediated by the β2 subunit, which causes inactivation of BK channels during the day. The circadian variation in BK current properties based on β2 function is unique, but it is not clear how β2 regulates AP activiy to shape the rhythms in SCN neuronal activity. The proposed studies test the hypothesis that β2-mediated inactivation is the critical property required for the BK channel's dynamic role in SCN AP firing, and that this process is central to circadian behavior. This hypothesis will be investigated using electrophysiological recordings of BK currents and APs in acute SCN brain slices, providing data to correlate changes in AP waveforms with inactivating properties of the β2 subunit. Furthermore, the consequences for inactivation of BK currents that stem from circadian changes in BK's calcium source will be investigated. Lastly, the impact of a human epilepsy-linked mutation and other single nucleotide polymorphisms (SNPs) that vary BK/β2 current properties will be tested and the relevance to SCN and behavioral rhythmicity will be determined. The outcome of this project will be an understanding of how the daily regulation of BK currents governs SCN excitability, providing new physiological and translational insight into the mechanisms that influence human BK channel activity.