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Localization of mRNAs at Synaptic Sites on Dendrites

树突突触位点 mRNA 的定位

基本信息

批准号：
7991764
负责人：
OSWALD STEWARD
金额：
$ 32.16万
依托单位：
UNIVERSITY OF CALIFORNIA-IRVINE
依托单位国家：
美国
项目类别：
财政年份：
1978
资助国家：
美国
起止时间：
1978-06-01 至 2012-11-30
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): The experiments of this proposal will define the mechanisms and functional role of mRNA localization and local translation at synaptic sites on neuronal dendrites. Local synthesis of critical proteins at synapses is necessary for long-lasting forms of synaptic plasticity including long-term potentiation (LTP) and long-term depression (LTD), and for the consolidation of memory. Recent studies indicate that the core neurological defect in a common neurological disorder Fragile X Mental Retardation Syndrome (FXS), may involve a disruption of protein synthesis at synapses due to the loss of Fragile X Mental Retardation Protein, the product of the Fmr1 gene which is defective in FXS. Thus, studies of mRNA transport, localization and translation may reveal new targets for therapy for this important and prevalent neurological disorder. Our previous studies have revealed aspects of the mechanisms underlying the selective targeting of mRNA to active synapses through studies of the unique immediate early gene (IEG) Arc, activity-regulated cytoskeleton-associated protein. Arc is strongly induced by physiological activity and its mRNA is rapidly delivered throughout dendrites based on a targeting signal in the mRNA sequence. Arc mRNA localizes selectively at active synapses, and mediates a local synthesis of Arc protein. Both the transcription of Arc mRNA in the nucleus, and the targeting of the newly synthesized transcript to active synapses are triggered by NMDA receptor activation of ERK1/2 and the MAP kinase pathway. Our studies have also revealed that other mRNAs are localized in different ways. The experiments of the present proposal will continue to identify and characterize mRNAs that are localized in dendrites, and further characterize the mechanisms underlying the docking of mRNAs at active synapses using in vivo and in vitro preparations. We will test the hypothesis that the docking mechanism involves a molecular scaffold beneath synapses or within the postsynaptic specialization that is modified by signals generated by intense synaptic activity. We will test the hypothesis that Arc mRNA contains sequences that determine that the mRNA will be transported into dendrites (a dendritic transport sequence) and sequence(s) that cause the mRNA to dock selectively at active synapses (a synaptic targeting sequence) by assessing targeting of exogenously expressed transcripts containing portions of Arc mRNA. Our previous studies indicate that other dendritic mRNAs do not re-localize to active synapses, and so we will determine whether these mRNAs are immobile in dendrites or instead lack the necessary targeting sequences. Together, our studies will reveal key features of the mechanism through which protein synthesis at synapses is regulated, thus providing insights into the fundamental mechanisms that underlie protein synthesis-dependent synaptic modifications, including the mechanisms that are disrupted in FXS and other neurological disorders that affect mRNA transport and localization. This research program will define biological mechanisms that make it possible for nerve cells to modify their connections with one-another (synapses) by controlling the synthesis of the protein building blocks of synapses at the synaptic contact site. These studies will provide novel insights into the basic mechanisms underlying information storage in the brain and neurological disorders that disrupt this fundamental mechanism, including Fragile-X Mental Retardation Syndrome.

描述（由申请人提供）：本提案的实验将定义神经元树突上突触位点处mRNA定位和局部翻译的机制和功能作用。关键蛋白质在突触的局部合成对于突触可塑性的持久形式（包括长时程增强（LTP）和长时程抑制（LTD））以及对于记忆的巩固是必需的。最近的研究表明，在一种常见的神经系统疾病脆性X智力迟钝综合征（FXS）的核心神经系统缺陷，可能涉及在突触处的蛋白质合成的破坏，由于脆性X智力迟钝蛋白的损失，在FXS中有缺陷的Fmr 1基因的产物。因此，mRNA的转运，定位和翻译的研究可能会揭示新的目标，为这种重要的和普遍的神经系统疾病的治疗。我们以前的研究已经揭示了通过研究独特的立即早期基因（IEG）Arc（活性调节的细胞因子相关蛋白）选择性靶向mRNA至活性突触的机制。Arc由生理活性强烈诱导，并且其mRNA基于mRNA序列中的靶向信号快速递送通过树突。Arc mRNA选择性地定位于活跃的突触，并介导Arc蛋白的局部合成。Arc mRNA在细胞核中的转录和新合成的转录物靶向活性突触都是由ERK 1/2和MAP激酶通路的NMDA受体激活触发的。我们的研究还揭示了其他mRNA以不同的方式定位。本提案的实验将继续鉴定和表征位于树突中的mRNA，并进一步表征使用体内和体外制剂的mRNA在活性突触处对接的潜在机制。我们将测试的假设，对接机制涉及突触下的分子支架或突触后的专业化，是由强烈的突触活动产生的信号修改。我们将通过评估含有Arc mRNA部分的外源表达转录物的靶向，检验Arc mRNA含有决定mRNA将被转运到树突的序列（树突转运序列）和导致mRNA选择性停靠在活性突触处的序列（突触靶向序列）的假设。我们以前的研究表明，其他树突mRNA不会重新定位到活跃的突触，因此我们将确定这些mRNA是否在树突中是固定的，或者缺乏必要的靶向序列。总之，我们的研究将揭示突触蛋白质合成调节机制的关键特征，从而深入了解蛋白质合成依赖性突触修饰的基本机制，包括在FXS和其他影响mRNA转运和定位的神经系统疾病中被破坏的机制。这项研究计划将定义生物学机制，使神经细胞能够通过控制突触接触部位的突触蛋白质构建块的合成来修改它们与彼此（突触）的连接。这些研究将为大脑中信息存储的基本机制和破坏这种基本机制的神经系统疾病提供新的见解，包括脆性X智力迟钝综合征。