NA+ CHANNELS IN NORMAL & ABNORMAL NERVE MEMBRANE

拟议研究的中心主题是描述细胞的特征 和离子通道表达进化的分子基础 神经系统。这是在一个独特的NB2a模型系统中追求的 神经母细胞瘤细胞，它保留了两条不同的途径 正常发育的差异化方案。这些细胞在被诱导后 为了与db cAMP或维甲酸鉴别，延长轴突或 树枝状突起。这项研究计划的重点是一个 神经元分化的表型特征，表达 Na+通道的异构体，我们之前已经证明了不同的 在“轴突”和“树突状”NB2a细胞之间。应用范围很广 长期目标是：1)确定细胞和分子 神经细胞中Na+通道异构体表达的调控机制； 20以确定具有特殊功能的Na+通道亚型在哪里 特性作为不同基因的产物而产生；并确定 它们在分子结构上的差异解释了这些 专用属性以及它们所扮演的角色；3)应用这些 研究以加深我们对神经兴奋性机制的理解 正常状态和疾病状态。 具体目标和实验设计是：1)表征 解释不同时间进程的蛋白质合成事件 分化过程中两种Na+通道亚型的表达 轴突和树突状NB2a细胞。这将包括对 Na+通道亚型的寿命和周转率；2)至 鉴定参与基因表达的信使核糖核酸转录本 分化的NB2a细胞中的两种Na+通道亚型 两种Na+通道亚型是否是不同基因的产物 物种，并确定mRNA转录在Na+通道中的作用 表达；3)建立相互作用研究的模型体系 两种钠离子通道亚型表达的变化 神经支配和去神经支配。使用的主要实验方法 包括：1)表征Na+通道亚型在不同发育阶段的表达 测定高亲和力和低亲和力的NB2a细胞分化 STX受体；2)鉴定Na+通道基因 与大鼠脑Na+通道II cRNA探针杂交。 该项目与健康相关的是，分发和 各种钠离子通道亚型在正常和异常中的作用 兴奋性膜决定正常生理和病理生理学 这些组织中的脉冲传导。NB2a电池提供了一个模型 系统将开始研究Na+通道的功能和分布 可兴奋膜中的异构体。这些属性与以下内容相关：1) 神经系统功能正常；2)神经系统疾病，如 多发性硬化症、阿尔茨海默病和肌营养不良症； 心血管冲动传导、心律失常的发生和作用 抗心律失常药。

The central theme of the proposed studies is to characterize the cellular and molecular bases underlying the evolution of ion channel expression in the nervous system. This is pursued in a unique model system of NB2a neuroblastoma cell, which have retained two distinct pathways of the differentiation program of normal development. These cells, when induced to differentiate with db cAMP or retinoic acid, extend either axonal or dendritic processes respectively. This Research Plan focuses upon one phenotypic characteristic of neuronal differentiation, the expression of isoforms of the Na+ channel, which we have previously shown to differ between "axonal" and "dendritic" NB2a cells. The application's broad long-term objectives are: 1) To determine the cellular and molecular mechanisms controlling expression of Na+ channel isoforms in nerve cells; 20 To determine whither Na+ channel isoforms with specialized functional properties arise as products of distinct genes; and to determine the differences in their molecular structure which account for these specialized properties, and the roles they serve; 3) To apply these studies to further our understanding of nerve excitability mechanisms in normal and disease states. The specific aims and experimental design are: 1) To characterize the events of protein synthesis which account for the different time courses of expression of the two Na+ channel subtypes during differentiation of axonal and dendritic NB2a cells. This will include a comparison of the lifetime and turnover rates of the Na+ channel subtypes; 2) To characterize transcripts of mRNA species involved in expression of the two Na+ channel subtypes in differentiated NB2a cells, to determine whether the two Na+ channel subtypes are products of distinct gene species, and to determine the role of mRNA transcription in Na+ channel expression; 3) To establish a model system for studying the reciprocal changes in expression of the two Na+ channel subtypes which occur with innervation and denervation. The major experimental methods used include: 1) characterizing expression of Na+ channel subtypes during NB2a cell differentiation by measurement of high- and low-affinity [3H]- STX receptors; 2) characterizing Na+ channel mRNA species by hybridization with a rat brain Na+ channel II cRNA probe. The health relatedness of the project is that the distribution and function of the various Na+ channel isoforms in normal and abnormal excitable membranes determines the normal physiology and pathophysiology of impulse conduction in these tissues. The NB2a cells provide a model system to begin studying function and distribution of Na+ channel isoforms in excitable membranes. These properties are relevant in : 1) normal function of the nervous system; 2) nervous system diseases such as multiple sclerosis, Alzheimer's disease, and muscular dystrophy; and 3) cardiovascular impulse conduction, arrhythmia generation, and action of anti-arrhythmic agents.