The role of NaV2.4 in mediation of resurgent sodium current

描述(申请人提供)：复极电流是电压门控钠(Na)电流中的一种不寻常的成分，在复极化时流动。这种电流可能在放电模式、内在兴奋性和钠电流的调制中发挥重要作用，并且已经在大脑的许多区域记录到。这些大脑区域与共济失调、帕金森氏症、亨廷顿氏症、自闭症和其他运动障碍有着广泛的联系。研究这一电流与这些疾病状态相关，因为任何完整的病理生理学模型都需要考虑这一电流。先前的工作表明，电流的复苏是由于一种蛋白质开放通道阻断颗粒的作用，该颗粒是独立的，但与钠通道阿尔法亚单位有关。然而，负责的蛋白质机制仍然是一个谜，它的发现将有助于详细研究机制，并促进其在原位的操作。有证据支持和反对β4钠通道亚单位(NaV2.4)是内源性阻断粒子的假设。在这里，我们打算首先通过使用RNAi方法抑制培养中的表达并记录复苏电流来直接测试亚基的必要性。其次，我们将研究这种击倒对射击模式的影响。最后，在前人工作的基础上，我们提出了实验来测试阻断机制是否是钠通道孔内局部麻醉剂受体位置的竞争性内源性配体。这些数据将对新的治疗操作和充分了解当前局麻药、抗心律失常和抗惊厥药物的效果很重要。总之，这些数据将有助于描述在许多大脑区域发现的钠电流关键成分的分子机制。

DESCRIPTION (provided by applicant): Resurgent current is an unusual component of voltage gated sodium (Na) current that flows upon repolarization. This current may play an important role in the firing patterns, intrinsic excitability, and modulation of sodium currents and it has been recorded in many brain regions. These brain regions have well-established links to ataxias, Parkinson's Disease, Huntington's Disease, autism, and other movement disorders. Studying this current has relevance for these disease states in that any complete models of pathophysiology would need to take this current into account. Prior work has suggested that resurgent current is due to the actions a proteinaceous open-channel blocking particle that is separate but associated with the Na channel alpha subunit. However, the protein machinery responsible still remains a mystery and its identification would aid detailed study of the mechanism and facilitate its manipulation in situ. There is evidence for and against the hypothesis that the beta4 Na channel subunit (NaV2.4) is the endogenous blocking particle. Here we intend to first test the necessity of the subunit directly by knocking down the expression in culture using an RNAi approach and recording resurgent current. Secondly we will examine the effect of this knockdown on firing patterns. Lastly, based on prior work we propose experiments to test if the blocking machinery is a competitive endogenous ligand for the local anesthetic receptor site within the sodium channel pore. This data will be important to new therapeutic manipulations and fully understanding the effects of current local anesthetic, anti-arrhythmic, and anticonvulsant drugs. Together these data will help characterize a molecular mechanism for a critical component of sodium currents found in a number of brain regions.