Uncovering the mechanisms of Ephexin5 function in dendritic spine plasticity and Alzheimer's disease

摘要/项目摘要 阿尔茨海默病(AD)与树突棘进行性丧失有关，微观树突状细胞 作为突触交流场所的结构，对记忆的存储是必不可少的。级别 Ephexin5，一种树突棘密度的调节因子，似乎是促进AD诱导的关键 树突状脊椎缺失。Ephexin5的底物专一性及其活性调节 仍然不为人所知。这个项目的目标是确定Ephexin5信号转导的机制 发生在正常生理和疾病中。我的假设是E5经历了一种磷酸化- 底物特异性从RhoA到rac1/CDc42的依赖性转变，与其在调节脊柱可塑性中的作用有关 对阿尔茨海默病的生理学有贡献。利用双光子荧光寿命成像与基因耦合 编码的FRET生物传感器，我将光学探测活组织中GTP酶的活性。我将定义底物 神经元E5在正常生理环境和AD诱导的细胞损伤模型中的特异性。 使用质谱仪，我将确定Ephexin5的磷酸化是否在神经元信号传递或 在类似AD的细胞状态下，并使用磷酸化突变分析，我将检查磷酸化如何影响E5 底物专一性。我的结果将进一步加深对学习和记忆的分子机制的了解 并有可能确定AD的新治疗靶点。 这个项目的培训将在加州大学戴维斯分校进行，我的导师和赞助商Karen Zito和 突触实时成像专家，联合发起人詹姆斯·特里默，神经元蛋白质结构专家 和功能。我将获得先进的活细胞成像和质谱学方面的关键技术技能，这将 协助完成这项研究项目。此外，我还将磨练指导、管理、 交流和写作。

ABSTRACT / PROJECT SUMMARY Alzheimer’s Disease (AD) is associated with a progressive loss of dendritic spines, microscopic dendritic structures that serve as the sites of synaptic communication and are essential for the storage of memory. Levels of the RhoGEF Ephexin5, a regulator of dendritic spine density, appear to be key in facilitating AD-induced dendritic spine loss. Much about the substrate specificity of Ephexin5 and the regulation of Ephexin5 activity remain unknown. The goal of this project is to determine the mechanisms by which Ephexin5 signaling occurs in normal physiology and disease. It is my hypothesis that E5 undergoes a phosphorylation- dependent shift in substrate specificity from RhoA to Rac1/Cdc42, relevant to its role in regulating spine plasticity and contributing to the physiology of AD. Using 2-photon fluorescence lifetime imaging coupled with genetically encoded FRET biosensors, I will optically probe the activity of GTPases in live tissue. I will define the substrate specificity of neuronal E5 under normal physiological contexts, and in a model of AD-induced cellular damage. Using mass spectrometry, I will determine if phosphorylation of Ephexin5 changes during neuronal signaling or in an AD-like cellular state, and using phosphomutant analysis I will examine how phosphorylation influences E5 substrate specificity. My results will further the knowledge of the molecular mechanisms of learning and memory and have the potential to identify novel therapeutic targets for AD. Training for this project will take place at UC Davis, with the support of my mentor and Sponsor, Karen Zito, an expert in the live-imaging of synapses, and Co-sponsor James Trimmer, and expert in neuronal protein structure and function. I will acquire key technical skills in advanced live-cell imaging and mass spectrometry, which will aid in the completion of this research project. Additionally I will hone skills of mentorship, management, communication, and writing.