Role of APP-related Proteins During Neuronal Migration

描述（由申请人提供）：本提案的长期目标是确定与淀粉样蛋白前体蛋白（APP）相关的蛋白质在正常发育过程中的体内功能，并深入了解这些功能的扰动如何有助于阿尔茨海默病（AD）的病理。AD涉及APP中β -淀粉样蛋白片段（Abeta）的分裂及其随后在神经系统中聚集成致密斑块。虽然Abeta本身具有神经毒性作用，APP必须发挥在AD中也被破坏的生理作用。各种研究表明，APP可能通过与多种细胞内信号通路的相互作用，作为跨膜受体调节神经元的迁移和生长。特别令人信服的是，实验证明APP695（被认为是APP的神经元异构体）直接与异源三聚体G蛋白go - α结合，并能调节其活性。然而，由于哺乳动物神经系统的复杂性，对这些相互作用的功能分析一直被排除在外。为了解决这个问题，我们建立了一个模型系统（Manduca sexta的肠神经系统），在这个模型系统中，一组已识别的迁移神经元（EP细胞）可以在胚胎培养的完整神经系统中被可视化和操作。这些神经元表达一种与go - α共定位的app样蛋白（msAPPL），初步研究表明，EP细胞抑制msAPPL表达会扰乱其迁移，其方式与内源性go - α介导的信号事件的破坏一致。本研究的目的是研究msAPPL加工在神经元迁移行为中的作用，阐明msAPPL与go - α相互作用的性质，并确定msAPPL是否作为go - α偶联受体在体内调节神经元迁移。这些研究将为app相关蛋白在发育中的神经系统功能的分子机制提供新的见解，并应作为未来研究这些机制的破坏如何导致AD病理的基础。

DESCRIPTION (provided by applicant): The long-term goals of this proposal are to determine the in vivo functions of a protein related to the amyloid precursor protein (APP) during normal development, and to gain insight into how perturbations of these functions may contribute to the pathology of Alzheimer's disease (AD). AD involves the cleavage of beta-amyloid fragments (Abeta) from APP and its subsequent aggregation into dense plaques in the nervous system. Although Abeta itself has neurotoxic effects, APP must play physiological roles that are also disrupted in AD. A variety of studies have suggested that APP may regulate neuronal migration and outgrowth by acting as a transmembrane receptor, possibly via interactions with several intracellular signaling pathways. Particularly compelling are experiments demonstrating that APP695 (considered a neuronal isoform of APP) binds directly to the heterotrimeric G protein Go-alpha and can regulate its activity. However, a functional analysis of these interactions has been precluded by complexities associated with the mammalian nervous system. To address this issue, a model system (the enteric nervous system of Manduca sexta) has been established in which an identified set of migratory neurons (the EP cells) can be visualized and manipulated within the intact nervous system in embryonic culture. These neurons express an APP-like protein (msAPPL) that co-localizes with Go-alpha in their leading processes, and preliminary studies have shown that inhibition of msAPPL expression by the EP cells perturbs their migration in a manner consistent with the disruption of endogenous Go-alpha-mediated signaling events. The goals of this proposal are to investigate the role of msAPPL processing with respect to neuronal migratory behavior, to clarify the nature of msAPPL interactions with Go-alpha, and to determine whether msAPPL acts as a Go-alpha-coupled receptor that regulates neuronal migration in vivo. These studies will lend new insight into the molecular mechanisms by which APP-related proteins function in the developing nervous system, and they should serve as the foundation for future research into how disruption of these mechanisms contributes to the pathology of AD.