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性依赖性变化通常依赖于树突定位mrna的空间调节翻译。尽管人们对神经元中局部蛋白质合成的兴趣日益浓厚，但我们对活动变化如何差异调节特定mrna的翻译以及这一过程如何在与认知障碍和智力迟钝相关的神经病理中发生改变的理解存在根本差距。最近的研究已经确定了哺乳动物雷帕霉素靶点1 （mTORC1）在调节树突中mrna亚群的翻译中对刻板刺激模式的反应中的关键作用。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。然而，mTORC1在突触可塑性的稳态形式中的独特作用尚不清楚，其中突触强度的代偿性变化以负反馈的形式实现。本研究的长期目标是了解树突蛋白合成在诱导和维持突触强度的稳态变化中的作用。这一特殊应用的目的是阐明mTORC1信号在一种新形式的稳态可塑性中所起的作用，这种可塑性涉及通过树突分泌脑源性神经营养因子（BDNF）作为逆行信号对突触前功能的快速突触后调节。核心假设是突触后mTORC1信号调节树突中的局部翻译程序，该程序的功能是调节相对突触前末端的神经递质释放。在申请人实验室收集的大量初步数据的指导下，这一假设将通过追求以下两个目标来解决：1)确定突触后mTORC1信号传导对于突触前功能的稳态调节是否必要和充分；2)确定AMPAR阻断后mTORC1在树突中局部调控BDNF翻译和增强突触前功能的程度。在Aim 1中，在细胞特异性激活或抑制mTORC1的条件下，将通过电生理学和免疫荧光来评估突触前疗效的变化。这些操作依赖于先前建立的遗传方法，该方法在申请人手中已被证明是可行的。在Aim 2下，实验将涉及mTORC1活性的空间受限操作，并结合免疫荧光分析来检查小树突区域BDNF表达和突触前功能的变化。本提案中概述的实验有望揭示突触后mTORC1功能调节、局部树突BDNF合成和突触前功能逆行调节之间的新联系。通过表征mTORC1控制下局部蛋白合成的独特作用，该项目具有真正的创新性，有可能为建立结节性硬化症和ASD等神经系统疾病治疗干预的新靶点提供基础，并显著推进突触可塑性领域的发展。