Homeostatic Regulation of Presynaptic Function by Dendritic mTORC1

树突状 mTORC1 对突触前功能的稳态调节

• 批准号: 8059437
• 负责人: Fredrick Earl Henry
• 金额: $ 3.17万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-03-01 至 2014-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8059437
• 关键词: AMPA Receptors; Address; Affect; Behavioral; Brain; Brain-Derived Neurotrophic Factor; Cells; Cognitive; Complex; Data; Defect; Dendrites; Disease; Electrophysiology (science); Excision; Feedback; Foundations; Fragile X Syndrome; Genetic; Goals; Hand; Hippocampus (Brain); Human; Immunofluorescence Immunologic; Impaired cognition; Laboratories; Learning; Link; Long-Term Potentiation; Maintenance; Memory; Mental Retardation; Molecular Biology Techniques; Nervous system structure; Neurons; PTEN gene; Phase; Phosphorylation; Play; Presynaptic Terminals; Probability; Process; Protein Biosynthesis; Pyramidal Cells; Regulation; Research; Role; Signal Pathway; Signal Transduction; Site; Slice; Stereotyping; Structure; Synapses; Synaptic plasticity; Syndrome; Tern; Testing; Therapeutic; Therapeutic Intervention; Translational Regulation; Translations; Tuberous sclerosis protein complex; Ursidae Family; Work; autism spectrum disorder; disability; human FRAP1 protein; immunocytochemistry; innovation; insight; interest; mTOR protein; molecular phenotype; nervous system disorder; neuronal cell body; neuropathology; neurotransmitter release; novel; postsynaptic; presynaptic; prevent; programs; protein complex; public health relevance; receptor; research study; response; synaptic function

DESCRIPTION (provided by applicant): Activity dependent changes in synaptic structure and function are often dependent on the spatially regulated translation of dendritically localized mRNAs. Despite growing interest in local protein synthesis in neurons, there is a fundamental gap in our understanding of how changes in activity differentially regulate the translation of specific mRNAs and how this process is altered in neuropathologies related to cognitive impairment and mental retardation. Recent work has established a pivotal role for the mammalian target of rapamycin complex 1 (mTORC1) in regulating the translation of subsets of mRNAs in the dendrite in response to stereotyped pat- terns of stimulation. mTORC1 is essential for certain forms of long-lasting synaptic plasticity, such as the induction of late phase-LTP in the hippocampus. However, a unique role for mTORC1 in homeostatic forms of synaptic plasticity, in which compensatory changes in synapse strength are implemented as a form of negative feedback, is less clear. The long-term goal of this research is to understand the contribution of dendritic pro- tein synthesis to the induction and maintenance of homeostatic changes in synaptic strength. The objective of this particular application is to elucidate the role played by mTORC1 signaling in a novel form of homeostatic plasticity involving fast acting, postsynaptic modulation of presynaptic function via dendritic secretion of brain-derived neurotrophic factor (BDNF) as a retrograde signal. The central hypothesis is that postsynaptic mTORC1 signaling regulates a local translational program in dendrites that functions to modulate neurotransmitter release from apposed presynaptic terminals. Guided by extensive preliminary data collected in the applicant's laboratory, this hypothesis will be address by pursuing the following two aims: 1) Determine if postsynaptic mTORC1 signaling is necessary and sufficient for homeostatic regulation of presynaptic function; and 2) determine the extent to which mTORC1 operates locally in dendrites to regulate BDNF translation and enhance presynaptic function after AMPAR blockade. Under Aim 1, changes in presynaptic efficacy will be assessed via electrophysiology and immunofluorescence under conditions of cell specific activation or inhibition of mTORC1. These manipulations depend on a previously established genetic approach which has been proven feasible in the applicant's hands. Under Aim 2, experiments will involve spatially restricted manipulation of mTORC1 activity in combination with immunofluorescence analyses to examine changes in BDNF expression and presynaptic function in small dendritic regions. The experiments outlined in this proposal are expected to reveal novel links between postsynaptic regulation of mTORC1 function, local dendritic BDNF synthesis, and retrograde modulation of presynaptic function. By characterizing a unique role for local protein synthesis under control of mTORC1, this project is genuinely innovative and has the potential to provide a foundation on which to establish novel targets of therapeutic intervention for neurological disorders such as tuberous sclerosis complex and ASD, as well as significantly advance the field of synaptic plasticity at large. PUBLIC HEALTH RELEVANCE: Several diseases that result in cognitive impairment and mental retardation have been associated with dysregulation of local protein synthesis in dendrites, specifically via overactive signaling of mTOR complex 1 (mTORC1). While several diseases related to Autism spectrum disorders, such as fragile X syndrome, tuberous sclerosis complex, and PTEN harmatoma syndrome, are all associated with overactive mTORC1 signaling in the nervous system, it is not clear how this signaling alters the function of synaptic connections between neurons to cause the behavioral and cognitive abnormalities seen in these disorders. This project will explore the role of mTORC1 in controlling synapse function in the hippocampus, a brain structure known to play a pivotal role in learning and memory, and will thus provide insights for targeting this signaling pathway as a therapeutic option for autism spectrum disorders.

描述（由申请人提供）：突触结构和功能的活动依赖性变化通常取决于树突定位的mRNA的空间调节翻译。尽管对神经元中局部蛋白质合成的兴趣日益增加，但我们对活动的变化如何差异化调节特定mRNA的翻译以及与认知障碍和智力障碍有关的神经病理学的改变仍然存在根本差距。最近的工作已经确立了雷帕霉素复合物1（MTORC1）哺乳动物靶标在调节树突中mRNA亚群的翻译方面的关键作用。 MTORC1对于某些形式的持久突触可塑性至关重要，例如海马后期LTP的诱导。但是，MTORC1在突触可塑性的稳态形式中的独特作用，其中突触强度的补偿性变化被作为负反馈的一种形式实现。这项研究的长期目标是了解树突状素合成对突触强度稳态变化的诱导和维持的贡献。该特定应用的目的是阐明MTORC1信号传导的作用，以一种新型的稳态可塑性形式，涉及快速作用，突触后调节突触前功能通过脑源性神经营养因子（BDNF）作为逆行信号的树突性分泌。中心假设是突触后MTORC1信号传导调节树突中的局部翻译程序，该程序功能可调节从拟议的突触前终端中释放神经递质的释放。在申请人实验室收集的广泛初步数据的指导下，该假设将通过追求以下两个目的来解决：1）确定突触后MTORC1信号是否有必要且足以对稳态调节突触前功能； 2）确定MTORC1在树突中局部运行的程度，以调节BDNF翻译并在AMPAR阻断后增强突触前功能。在AIM 1下，在细胞特异性激活或MTORC1抑制条件下，将通过电生理学和免疫荧光评估突触前的变化。这些操作取决于先前确定的遗传方法，该方法已被证明在申请人的手中可行。在AIM 2下，实验将涉及对MTORC1活性的空间限制操纵与免疫荧光分析的结合，以检查小树突状区域中BDNF表达和突触前功能的变化。预计该提案中概述的实验将揭示MTORC1功能的突触后调节，局部树突状BDNF合成与突触前功能的逆行调制之间的新联系。通过表征MTORC1控制下局部蛋白质合成的独特作用，该项目具有创新性，并有可能为建立针对结核性硬化症复杂和ASD等神经疾病的治疗干预措施的新颖靶标提供基础，并显着提高了整个突触可塑性的领域。 公共卫生相关性：几种导致认知障碍和智力低下的疾病与树突中局部蛋白质合成的失调有关，特别是通过MTOR复合物1（MTORC1）的过度活跃信号传导（MTORC1）。虽然几种与自闭症谱系障碍有关的疾病，例如脆弱的X综合征，结节性硬化症复合物和PTEN Harmatoma综合征，都与神经系统中过度活跃的MTORC1信号有关，但尚不清楚这种信号如何改变神经元之间的突触连接的功能，从而导致行为和认知能力依靠这些不景气，这些信号在这些方面都在这些散发性和认知性依赖性。该项目将探讨MTORC1在控制海马中的突触功能中的作用，这是一种已知在学习和记忆中发挥关键作用的大脑结构，因此将提供洞察力，以将这种信号通路作为自闭症谱系障碍的治疗选择。