The role of beta-secretase 1 (BACE1) in modulating excitatory synaptic and circuit function and behavior

项目摘要 阿尔茨海默病（AD）是痴呆症的最常见原因，是一种使人衰弱的疾病，其导致 逐渐丧失记忆认知障碍最终死亡AD的病理特征包括 细胞外淀粉样蛋白β（Aβ）斑块。β-分泌酶-1（β-site APP cleaving enzyme 1，BACE 1）是一种 毒性Aβ生成的限制酶。AD的转基因BACE 1 KO小鼠模型导致AD的抑制 这表明抑制BACE 1可能是治疗AD的合理策略。但人类 临床试验表明，BACE 1抑制剂在AD患者中无效，甚至恶化认知功能， 患者这种从工作台到床边的翻译失败是由于我们对BACE 1的不完全理解造成的 生理功能特别是，BACE 1中神经元和突触损伤的潜在机制 缺乏或抑制是知之甚少。在本提案中，我们将通过测试 假设BACE 1调节细胞类型和回路中的内在和突触神经生理学特性， 海马体中的特定方式，记忆存储的主要基质被AD破坏。我的初步数据 海马锥体神经元全细胞膜片钳技术显示，选择性BACE 1缺失， 兴奋性神经元导致神经元过度兴奋，表明BACE 1缺失破坏了内在神经元 以细胞自主的方式起作用。根据我的初步发现，我假设BACE 1调节了 通过离子通道调节海马PN的兴奋性和突触传递： 其尚未被完全阐明。在目标1中，我将全面确定 在我的兴奋性-BACE 1-KO小鼠（其中BACE 1选择性缺失的小鼠， 兴奋性PN），并表征兴奋性-BACE 1-KO中的突触传递和可塑性缺陷， 通过膜片钳电生理学方法。在目标2中，我将描述行为缺陷兴奋性-BACE 1- KO神经元，并通过使PN过度兴奋正常化来挽救突变小鼠中假设的认知缺陷 通过化学遗传学的方法。这项研究的发现将为神经元和突触的研究提供新的视角。 生理学、学习/记忆和行为的机制以及未来的AD治疗策略。重要的是， 完成这个项目将帮助我掌握膜片钳的最新概念和最先进的技术 电生理学、行为研究和体内遗传干扰，并增加我的科学交流 通过广泛的机会展示和发表我的研究技能。作为康州大学健康中心的一名医学博士/博士生， 我将有机会获得导师和专家，不仅直接促进我掌握必要的技术， 技能，但我也将有机会继续磨练我的临床技能，并获得专业经验 在我的研究期间和之后。完成我的培训和发展计划将是我迈向成功的关键一步。 未来的职业生涯作为一个医生，科学家研究神经退行性疾病的机制， 患者

PROJECT SUMMARY Alzheimer’s Disease (AD), the most common cause of dementia, is a debilitating disease that leads to progressive memory loss, cognitive impairment, and ultimately death. Pathological hallmarks of AD include extracellular amyloid beta (Aβ) plaques. β-secretase-1 (β-site APP cleaving enzyme 1, BACE1) is the rate- limiting enzyme of toxic Aβ generation. Transgenic BACE1 KO mouse models of AD led to suppression of AD pathology, which suggests that inhibiting BACE1 may be a rational strategy for AD treatment. However, human clinical trials have shown that BACE1 inhibitors are inefficacious, even worsening cognitive function, among AD patients. This benchtop-to-bedside translational failure is due to our incomplete understanding of BACE1’s physiological function. In particular, the mechanisms underlying neuronal and synaptic impairments in BACE1 deficiency or inhibition is poorly understood. In this proposal, we will address this knowledge gap by testing the hypothesis that BACE1 modulates intrinsic and synaptic neurophysiological properties in a cell-type- and circuit- specific manner in the hippocampus, a major substrate of memory storage derailed by AD. My preliminary data of whole-cell patch clamp of hippocampal pyramidal neurons (PNs) show that selective BACE1 deletion in excitatory neurons leads to neuronal hyperexcitability, suggesting that BACE1 deletion disrupts intrinsic neuronal function in a cell-autonomous manner. Given my preliminary findings, I hypothesize that BACE1 modulates excitability and synaptic transmission in hippocampal PNs by the regulation of ion channels – the identities of which have yet to be fully elucidated. In Aim 1, I will comprehensively determine the ionic basis underlying the hyperexcitability phenotype in my Excitatory-BACE1-KO mice (mice in which BACE1 is selectively deleted in excitatory PNs), and characterize the synaptic transmission and plasticity deficits in Excitatory-BACE1-KO, through patch clamp electrophysiology methods. In Aim 2, I will delineate behavioral deficits Excitatory-BACE1- KO neurons, and rescue hypothesized cognitive deficits in mutant mice by normalizing PN hyperexcitability through a chemogenetic approach. The findings from this study will provide insight into neuronal and synaptic physiology, mechanisms of learning/memory and behavior, and future AD therapeutic strategies. Importantly, completion of this project will help me master current concepts and state-of-the-art techniques in patch clamp electrophysiology, behavior studies, and in vivo genetic perturbation and increase my scientific communication skills through extensive opportunities to present and publish my studies. As an MD/PhD student at UConn Health, I will have access to mentors and experts that will not only directly facilitate my mastery of the necessary technical skills, but I will also have opportunities to continue honing my clinical skills and gain specialized experience during and after my research phase. Fulfilling my training and development plan will be a crucial step toward my future career as a physician-scientist studying the mechanisms underlying neurodegenerative disease in patients.