The structural and molecular determinants of resurgent sodium current

描述（申请人提供）：许多神经元中的电压门控钠通道，包括小脑和脑干中的几种类型，是专门用于快速放电动作电位的。这种快速的放电部分是由于钠电流的复苏，这是一种不寻常的电流，在复极时从正电位流向负电位。恢复电流流过电压门控的Na通道1亚基，这些亚基被内源性蛋白质阻断后通过开放状态恢复。恢复Na电流的中断与放电减少和运动缺陷相关，包括共济失调和震颤，而与疼痛和运动障碍相关的Na通道突变增加了恢复电流和放电率。总之，这些发现表明，恢复的钠电流是神经元输出和正常运动功能的关键决定因素。先前的结果表明Na通道2亚基Nav24作为阻滞剂的作用；然而，Nav24并不足以在所有类型的细胞中产生再生Na电流。在这里提出的实验中，我们将进一步研究阻滞的生物物理和分子决定因素。我们将通过测试一系列24衍生肽阻断通道的能力来评估阻断的结构要求。我们还将测试表达系统中允许回火电流所必需的1个亚单元的特性。确认潜在阻断蛋白的身份和确定阻断的生物物理机制将有助于我们进一步了解恢复Na电流和快速放电之间的联系，这对运动行为的控制很重要。

DESCRIPTION (provided by applicant): Voltage-gated Na channels in many neurons, including several types in the cerebellum and brainstem, are specialized to allow rapid firing of action potentials. This rapid firing is due in part to resurgent Na current, an unusual current that flows upon repolarization from positive to negative potentials. Resurgent current flows through voltage-gated Na channel 1 subunits that are recovering through open states from block by an endogenous protein. Disruption of resurgent Na current correlates with reduced firing and motor deficiencies, including ataxia and tremor, whereas Na channel mutations implicated in pain and movement disorders increase both resurgent current and firing rates. Together, these findings suggest resurgent Na current is a key determinant of neuronal output and thus, normal motor function. Previous results indicate a role for the Na channel 2 subunit Nav24 as a blocker; however, Nav24 is not sufficient to produce resurgent Na current in all cell types. In the experiments proposed here, we will further investigate the biophysical and molecular determinants of block. We will evaluate structural requirements for block by testing the ability of a series of 24- derived peptides to block channels. We will also test the properties of 1 subunits that are necessary to permit resurgent current in an expression system. Confirming the identity of potential blocking proteins and identifying the biophysical mechanisms of block will help us to further understand the connection between resurgent Na current and rapid firing that is important for control of motor behaviors. PUBLIC HEALTH RELEVANCE: Neurons in the brain transmit information by firing action potentials, which depend on an influx of Na ions into the cell. A subset of neurons that are important for normal motor behavior are specialized to fire action potentials particularly rapidly, in part due to the presence of resurgent Na current that results from endogenous block of Na channels. The goal of the experiments proposed here is to define the structural and molecular determinants of block, in hopes of further understanding the relationship between resurgent current and normal neuronal activity.