Determinants of Sodium Channel Function: Ion Pair Interactions Across Domains

项目摘要/摘要 这个项目将研究钠的作用产生生物电信息的基本机制。 可兴奋细胞膜的通道蛋白。我们将把我们的注意力集中在 人体骨骼肌纤维中发现的钠通道。这一区域的突变导致了许多 遗传性疾病称为钠通道病，包括肌肉强直症和周期性瘫痪。在……里面 在这项工作中，我们将研究这个结构域的片段S1到S4相互作用的分子手段 控制钠离子通道基本功能的激活，或开放，以及快速失活，在此期间通道 不能对膜电位的变化作出反应。我们的假设针对假定的相互作用 S1至S3节段中带负电荷的氨基酸，即所谓的带正电荷的反电荷 S4片段中的氨基酸。我们将使用电压钳电生理学来测试突变的影响 这会逆转带负电荷或带正电荷的氨基酸的电荷。这些电荷反转突变将 比较对激活和两种形式的快速失活的影响。我们的目标是找出 与给定钠通道结构域的S4片段的反电荷相互作用，确定特定的 这一非对称通道的功能。为了做到这一点，我们将量化所有重大突变对 激活参数使用IFM/QQQ失活缺陷背景，并使用门控电流 直接测试电压传感器的运动。电荷固定化和电荷再动员的比较将允许 在两种形式的快速失活期间，S1-S3与S4片段相互作用的类似可量化测量，以及 在康复期间。最后，我们将建立电压传感器域的模型，在这些域中插入我们的突变 模型，然后运行模型的计算机模拟以响应膜电位的变化 这引发了它们在肌肉纤维中的典型功能。我们的研究将加深我们对分子的理解 钠通道电压敏感性的基础，并为研究产生的功能障碍提供了基础 通过肌肉纤维的经络病变突变。

Project Summary / Abstract This project will investigate basic mechanisms of bioelectric information as produced by the actions of sodium channel proteins of excitable cell membranes. We will focus our attention on the voltage-sensing domain of the sodium channel found in human skeletal muscle fibers. Mutations in this domain are responsible for a number of inherited diseases, called sodium channelopathies, and include muscle myotonia and periodic paralysis. In this work we will investigate the molecular means by which the segments of this domain, S1 to S4, interact to control basic sodium channel functions of activation, or opening, and fast inactivation, during which the channel is unable to respond to changes in membrane potential. Our hypotheses target putative interactions of negatively charged amino acids in segments S1 to S3, so-called countercharges, with positively charged amino acids in the segment S4. We will use voltage clamp electrophysiology to test the effects of mutations that reverse the charge of negatively, or positively charged amino acids. These charge-reversing mutations will be compared for effects on activation and for two forms of fast inactivation. Our goal is to identify countercharge interaction with the S4 segment of a given sodium channel domain, that determines a specific function of this asymmetric channel. To do this we will quantify the effects of all significant mutations on activation parameters using the IFM / QQQ inactivation deficient background, and using gating currents to directly test voltage sensor movement. Comparison of charge immobilization and its remobilization will allow a similar quantifiable measure of S1-S3 interaction with S4 segments during two forms of fast inactivation, and during recovery. Finally, we will build models of the voltage sensor domains, insert our mutations in these models, and then run computer simulations of the models in response to the change in membrane potential that elicits their typical function in muscle fibers. Our studies will further our understanding of the molecular basis of voltage-sensitivity in sodium channels and provide a foundation for studies on dysfunction produced by channelopathy mutations of muscle fibers.