The structural and molecular determinants of resurgent sodium current

描述(由申请人提供)：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，都是专门允许动作电位快速放电的。这种快速燃烧的部分原因是钠电流的复苏，这是一种不同寻常的电流，在从正电位到负电位的复极化过程中流动。复活的电流流经电压门控的Na通道1亚基，这些亚基正在从内源性蛋白质的阻断中恢复到开放状态。复苏的钠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有关的钠通道突变增加了复苏的电流和放电频率。综上所述，这些发现表明，复苏的钠电流是神经元输出的关键决定因素，因此，正常的运动功能。先前的结果表明，Na通道2亚单位Nav24具有阻滞剂的作用；然而，Nav24并不足以在所有类型的细胞中产生复苏性钠电流。在这里提出的实验中，我们将进一步研究BLOCK的生物物理和分子决定因素。我们将通过测试一系列24个衍生多肽对通道的阻断能力来评估对阻断通道的结构要求。我们还将测试1亚基的性质，这些亚基是允许表达系统中恢复电流所必需的。确认潜在的阻断蛋白的同一性和阻断的生物物理机制将有助于我们进一步了解复活的钠电流与快速放电之间的联系，这对控制运动行为具有重要意义。 与公共健康相关：大脑中的神经元通过激发动作电位来传递信息，动作电位依赖于钠离子进入细胞。对正常运动行为很重要的一部分神经元专门产生动作电位，这在一定程度上是由于钠通道内源性阻断所导致的钠电流的复苏。本实验的目的是确定阻滞剂的结构和分子决定因素，以期进一步了解复发性电流与正常神经元活动之间的关系。

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.