ION CHANNEL DISTRIBUTION AND MOBILITY

离子通道分布和迁移率

基本信息

批准号：
3477714
负责人：
WILLIAM M ROBERTS
金额：
$ 7.3万
依托单位：
UNIVERSITY OF OREGON
依托单位国家：
美国
项目类别：
财政年份：
1990
资助国家：
美国
起止时间：
1990-01-01 至 1994-12-31
项目状态：
已结题

项目摘要

The proposed experiments are directed at the long-term goal of understanding how neurons and other excitable cells regulate the complex patterns of electrical excitability and chemical sensitivity on their surfaces. Because ion channels are responsible for a cell's electrical properties and to a large extent determine how it will receive, integrate, and transmit information, a neuron must be able to synthesize the classes of ion channels appropriate for its functions, deliver them to specific positions on the surface, and remove them when their useful lifetimes expire. The proposed experiments address several aspects of these important cellular processes. Skeletal muscle fibers will be used because their surfaces are accessible for mapping ion channel distributions over large areas, and because they perform several functions common to excitable cells: they receive synaptic input, and initiate and propagate action potentials. Information gained from this study will be relevant to neurological disorders that involve altered excitability of neurons and specifically to disorders of neuromuscular transmission. The experiments will use twitch muscle fibers from frogs and garter snakes, and cultured embryonic chick muscle cells. Focal electrical recordings, using a patch voltage clamp technique will be used to map the spatial distribution of sodium channels on the cellular surface, with particular emphasis on the region of synaptic contact, where inputs are received and action potentials are initiated. The spatial resolution of the measurements will be about 1 muM, small enough to explore the distribution of channels within and between terminal boutons on snake fibers and close to synaptic gutters on frog fibers. Many of the experiments are designed to compare the organization of sodium channels and acetylcholine receptors that populate the postjunctional region of the muscle. They will determine whether the membrane is divided into microscopic domains that contain separate populations of ion channels, or whether the two types of channels intermingle. These results will be important to understand how channels are confined within the postjunctional membrane. Other experiments will explore the development of the neuromuscular junction, to determine whether the aggregation of these two types of channels around the neuromuscular junction occurs by similar of different mechanisms. Some experiments will measure the ability of sodium channels to migrate within the fluid membrane, an important factor in determining the channel distribution. These experiments attempt to resolve the discrepancies between two techniques that have given very different pictures of the mobility of sodium channels within the membrane. Finally, in vivo experiments will make the first measurements of the turnover rate and lifetime of sodium channels in adult muscles in living animals.

拟议的实验旨在实现以下长期目标：了解神经元和其他可兴奋细胞如何调节复合体其电兴奋性和化学敏感性的模式表面。因为离子通道负责细胞的电属性并在很大程度上决定了它将如何接收、集成、并传输信息，神经元必须能够合成类别适合其功能的离子通道，将它们输送到特定的表面上的位置，并在其使用寿命时将其移除到期。所提出的实验解决了这些问题的几个方面重要的细胞过程。将使用骨骼肌纤维，因为它们的表面可用于绘制离子通道分布图大面积，并且因为它们执行多种常见功能可兴奋细胞：它们接收突触输入，并启动和传播动作电位。从这项研究中获得的信息将与涉及神经元兴奋性改变的神经系统疾病特别针对神经肌肉传递障碍。实验将使用青蛙和吊袜带的抽搐肌纤维蛇和培养的胚胎鸡肌肉细胞。焦电气记录，使用贴片电压钳技术将用于映射细胞表面钠通道的空间分布特别强调突触接触区域，其中输入收到并启动动作电位。空间分辨率为测量值约为 1 μM，小到足以探索 Snake 上终端按钮内部和之间的通道分布纤维并靠近青蛙纤维上的突触沟。许多实验旨在比较钠通道的组织和乙酰胆碱受体，填充在连接后区域肌肉。他们将确定膜是否分为包含独立离子通道群的微观域，或两种类型的渠道是否混合。这些结果将是重要的是要了解渠道是如何限制在结后膜。其他实验将探索发展神经肌肉接头，以确定是否聚集神经肌肉接头周围的这两种类型的通道是通过不同机制的相似之处。一些实验将测量钠通道迁移的能力流体膜内，决定通道的重要因素分配。这些实验试图解决差异两种技术给出了截然不同的图像膜内钠通道的流动性。最后，体内实验将首次测量成人肌肉钠通道的周转率和寿命动物。