SIGNALING BY MUSK, A COMPONENT OF THE AGRIN RECEPTOR

麝香（AGRIN 受体的一个组成部分）发出的信号

• 批准号: 6351841
• 负责人: Steven Burden
• 金额: $ 41.04万
• 依托单位: NEW YORK UNIVERSITY SCHOOL OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-02-01 至 2003-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6351841
• 关键词: Sf9 cell line; Torpedo; agrin; biological signal transduction; cholinergic receptors; complementary DNA; dystrophin; enzyme activity; immunoaffinity chromatography; immunoprecipitation; laboratory mouse; muscle proteins; myofibrils; phosphorylation; protein purification; protein tyrosine kinase; synapses; western blottings

DESCRIPTION (Investigator's Abstract) Neuromuscular synapses form as a result of inductive interactions between motor neurons and muscle fibers. Following contact with the growth cone of a developing motor neuron, developing muscle fibers undergo a complex differentiation program in the synaptic region, and signals from the muscle in turn are thought to regulate the differentiation of the presynaptic terminals. Two different signaling pathways lead to the localization of acetylcholine receptors (AChRs) at synaptic sites. The signal for one pathway is agrin, a protein which is synthesized by motor neurons and which is secreted into the basal lamina at synaptic sites. Neither the receptor for agrin nor the mechanisms of agrin-mediated signaling, however, are known. The discovery of the muscle specific kinase , MuSK, and its role in agrin-mediated signaling provide an important advance in our understanding of how agrin signals to muscle. Current data support the idea that MuSK is a critical component of the agrin receptor complex but that another myotube-specific activity is required to bind agrin and to activate MuSK. The investigators will use minimal, functionally active forms of agrin, which stimulate MuSK but do not bind to alpha-dystroglycan, as affinity reagents to identify and isolate the functional agrin receptor from Torpedo electric organ postsynaptic membranes. In addition,they will determine whether the functional agrin receptor co-immunoprecipitates with MuSK, since co-immunoprecipitation may serve as an independent means to identify and purify the functional agrin receptor. These experiments will lead to the isolation of cDNAs encoding the agrin receptor. The molecules that are required for MuSK to respond to agrin and to initiate clustering of synaptic proteins are not known. They will adopt strategies that have been successfully applied to study other receptor tyrosine kinases to identify proteins that are tyrosine phosphorylated by agrin. Because proteins that are activated by MuSK may associate with MuSK, they will also identify proteins that co-immunoprecipitate with MuSK. They will identify and inhibit signaling pathways which are activated by agrin/MuSK to determine which, if any, signaling pathways are required for clustering synaptic proteins. They will determine whether AChRs are required to cluster other synaptic proteins and whether agrin-stimulated AChR tyrosine phosphorylation is required to cluster AChRs and other synaptic proteins. These studies will provide a better understanding of the mechanisms by which agrin signals through MuSK, regulates clustering of AChRs and other synaptic proteins, and organizes postsynaptic differentiation.

描述（研究者摘要）神经肌肉突触形成为 运动神经元和肌纤维之间感应相互作用的结果。 与发育中的运动神经元的生长锥接触后， 发育中的肌纤维经历复杂的分化程序 突触区和来自肌肉的信号被认为依次调节 突触前末梢的分化。 两种不同的信号 途径导致乙酰胆碱受体（AChR）定位于 突触位点。 一个途径的信号是集聚蛋白，一种蛋白质， 由运动神经元合成并分泌到基底层 突触位点。 无论是集聚蛋白受体还是其机制 然而，集聚蛋白介导的信号传导是已知的。 肌肉的发现 特定激酶 MuSK 及其在集聚蛋白介导的信号传导中的作用提供了 我们对 agrin 如何向肌肉发出信号的理解取得了重要进展。 目前的数据支持这样的观点：MuSK 是集聚蛋白的重要组成部分 受体复合体，但需要另一种肌管特异性活性 结合 agrin 并激活 MuSK。 研究人员将使用最少的、 集聚蛋白的功能活性形式，可刺激 MuSK 但不结合 α-肌营养不良聚糖，作为亲和试剂来识别和分离 鱼雷电器官突触后功能性聚集蛋白受体 膜。 此外，他们将确定功能性集聚蛋白是否 受体与 MuSK 进行免疫共沉淀，因为免疫共沉淀可能 作为识别和纯化功能性集聚蛋白的独立手段 受体。 这些实验将导致编码 cDNA 的分离 集聚蛋白受体。 MuSK 响应所需的分子 集聚蛋白和启动突触蛋白聚集的机制尚不清楚。 他们 将采用已成功应用于其他研究的策略 受体酪氨酸激酶识别酪氨酸蛋白质 被集聚蛋白磷酸化。 因为被 MuSK 激活的蛋白质可能 与 MuSK 相关联，他们还将识别出以下蛋白质： 与 MuSK 进行免疫共沉淀。 他们将识别并抑制信号传导 由 agrin/MuSK 激活的途径，以确定哪些（如果有） 信号通路是突触蛋白聚类所必需的。 他们会 确定 AChR 是否需要聚集其他突触蛋白并 是否需要集聚蛋白刺激的 AChR 酪氨酸磷酸化 簇 AChR 和其他突触蛋白。 这些研究将提供 更好地了解集聚蛋白通过 MuSK 发出信号的机制， 调节 AChR 和其他突触蛋白的聚集，并组织 突触后分化。