MECHANISMS OF ACETYLCHOLINE RECEPTOR AGGREGATION IN A SIMPLE MODEL SYSTEM

细胞表面成分在突触区域的定位是一个重要的机制。 发育神经生物学的重要问题。 已经显示 弥散表达受体的侧向迁移使得 对发育中的神经肌肉细胞上受体聚集的贡献 交界处。 由于电场提供了一种方便的手段， 膜组分的迁移，它们的使用构成了一种有用的 研究受体定位的实验系统。 在 特别是非洲蛙的球形肌细胞培养物 非洲爪蟾已经显示响应于这种反应而聚集受体。 领域的 在场已经终止之后继续聚类， 并且对乙酰胆碱受体具有特异性。 这些意见使 这是一个强大的模型系统，可以用来探索 潜在的受体聚集，因为i）培养的细胞形成 受体迅速聚集，对精确可测量的刺激作出反应， ii）实验可以在没有神经突、细胞- 基质接触或外源因子，和iii）培养的细胞是 几何简单，允许高分辨率定量受体 密度的 拟议研究的目标是进一步研究 负责提供的模型系统中受体的聚集 非洲爪蟾文化的影响 实验将利用全球和本地 应用外部电场培养非洲爪蟾肌肉细胞。 在这些操作之后，数字视频显微镜分析 将进行荧光标记细胞，以表征 乙酰胆碱受体等成分的分布。 三 将讨论广泛的问题： 1.什么样的分子事件触发了场诱导的聚集 乙酰胆碱受体？ 2.其他突触后分子如何对电刺激做出反应？ fields？ 3.与受体竞争相关的参数是什么？ 邻近的集群？ 对这些问题的研究将增加我们对世界的理解。 负责突触发育形成的体内机制 联系人. 这些问题在知识上是至关重要的， 发展神经生物学的重要性， 神经突触紊乱 受体的重要性 从疾病的破坏性影响， 重症肌无力，这减少了可用受体的数量， 交界处。 此外，实验结果和理论考虑 表明神经元竞争受体的机制与 到突触连接的发展完善，一个伟大的主题， 关注发展性残疾。

Localization of cell-surface components to synaptic regions is an important problem in developmental neurobiology. It has been shown that lateral migration of diffusely-expressed receptors makes a major contribution to receptor clustering at the developing neuromuscular junction. As electric fields offer a convenient means to induce lateral migration of membrane components, their use constitutes a useful experimental system with which to study receptor localization. In particular, cultures of spherical muscle cells from the African frog Xenopus laevis have been shown to cluster receptors in response to such fields. The clustering continues after the field has been terminated, and is specific for acetylcholine receptors. These observations render this a powerful model system with which to probe the mechanisms underlying receptor clustering, because i) the cultured cells form receptor clusters rapidly in response to precisely measurable stimuli, ii) experiments can be conducted in the absence of neurites, cell- substrate contacts, or exogenous factors, and iii) the cultured cells are geometrically simple, permitting high-resolution quantitation of receptor density. The goal of the proposed study is to examine further the mechanisms responsible for the clustering of receptors in the model system afforded by the Xenopus cultures. the experiments will utilize global and local application of external electric fields to cultured Xenopus muscle cells. Following these manipulations, digital video-microscopic analysis of fluorescently labeled cells will be performed in order to characterize the distributions of acetylcholine receptors and other components. Three broad questions will be addressed: 1. What molecular event(s) trigger the field-induced clustering of acetylcholine receptors? 2. How do other post-synaptic molecules behave in response to electric fields? 3. What are the parameters relevant to competition for receptors between neighboring clusters? Examination of these questions will increase our understanding of the in vivo mechanisms responsible for the developmental formation of synaptic contacts. The questions are intellectually crucial within the context of developmental neurobiology, and also have significance with respect to synapse-based disorders. The fundamental importance of receptor clustering is clear from the devastating effects of diseases such as myasthenia gravis, which reduce the number of available receptors at the junction. Moreover, experimental results and theoretical considerations suggest that the mechanisms by which neurons compete for receptors relate to the developmental refinement of synaptic connections, a topic of great interest with respect to developmental disabilities.