Immediate-early intra-axonal signaling in neurodegeneration

神经退行性变中的即早期轴突内信号传导

• 批准号: 8953878
• 负责人: Chandler Anne Walker
• 金额: $ 6.87万
• 依托单位: COLUMBIA UNIVERSITY HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2017-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8953878
• 关键词: Acute; Adult; Age; Alzheimer' s Disease; Amyloid; Amyloid beta-Protein; Amyloidosis; Apoptotic; Axon; Axotomy; Back; Brain; Cell Death; Cell Nucleus; Cells; Cessation of life; Characteristics; Communication; Complex; Data; Dendrites; Deposition; Disease; Disease Progression; Distal; Early Intervention; Event; Exhibits; Exposure to; Fluorescent in Situ Hybridization; Frequencies; Functional disorder; Gene Expression; Goals; Hippocampus (Brain); Human; Immunofluorescence Immunologic; Impaired cognition; In Vitro; Injection of therapeutic agent; Injury; Investigation; Life; Mediating; Mediator of activation protein; Messenger RNA; Microfluidics; Modeling; Mus; Nerve Degeneration; Neurodegenerative Disorders; Neurofibrillary Tangles; Neurons; Pathogenesis; Pathology; Pathway interactions; Patients; Peptides; Peripheral; Peripheral Nervous System; Play; Prevalence; Protein Biosynthesis; Protein Synthesis Inhibition; Proteins; Publications; Publishing; RNA Sequences; Reporter; Research; Research Proposals; Role; Signal Transduction; Small Interfering RNA; Spinal cord injury; Synapses; Techniques; Testing; Translating; Translations; activating transcription factor 4; base; brain tissue; design; field study; functional decline; human FRAP1 protein; hyperphosphorylated tau; improved; in vivo; inhibitor/antagonist; injured; insight; mouse model; neuronal cell body; neurotransmission; novel; prevent; public health relevance; research study; response; retrograde transport; sciatic nerve; transcriptome sequencing

 DESCRIPTION (provided by applicant): Though the prevalence Alzheimer's disease (AD) continues to increase, the mechanisms underlying disease pathogenesis remain to be elusive. In order to delay or prevent disease progression, it is important to understand the earliest pathogenic alterations that occur in AD brain. Characteristics of AD pathology include the deposition of ß-amyloid (Aß) plaques and hyperphosphorylated tau tangles, though the pathophysiological relevance of these hallmarks in disease pathogenesis is unclear. The amyloid hypothesis suggests that oligomeric Aß peptides, toxic precursors of Aß plaques, play a causative role in neurodegenerative alterations observed in AD brains. Studies from brains of AD mouse models suggest that axonal exposure to Aß is sufficient to trigger neurodegeneration of the entire neuron, ultimately resulting in cell death. The role of intra- axonal signaling event in AD pathogenesis is further supported by studies in human AD brains showing that synaptic dysfunction precedes cell death. In our recently published study we demonstrate in vitro and in vivo that axonal Aß application does indeed induce neurodegeneration via local synthesis and retrograde transport of activating transcription factor 4 (ATF4), which is followed by ATF4-dependent pro-apoptotic changes in gene expression. Consistent with these findings, post-mortem brain tissues from AD patients exhibited higher frequencies of ATF4 mRNA and protein in axons and cell bodies compared to age-matched controls. My dissertation project is an organic extension of this study, which is primarily focused on the earliest intra-axonal signaling events that occur in response to Aß. My preliminary data shows that axonally applied Aß induces rapid Ca2+-dependent ribosomal activation, and inhibition of axonal protein synthesis and retrograde transport are both sufficient to block Aß-induced recruitment of Atf4 to axons. These findings are reminiscent of studies from the field of spinal cord injury, which show that axotomized peripheral neurons induce an immediate Ca2+ influx followed by rapid translation of resident mRNAs whose protein products play critical roles in retrograde injury signaling to the nucleus. Interestingly, RNA sequencing experiments of healthy hippocampal axons from our previous study reveal the presence of mRNAs encoding many of the proteins known to be involved in sciatic nerve retrograde injury signaling. Therefore, I hypothesize that, similar to injured axons of the peripheral nervous system, hippocampal axons challenged with Aß induce rapid Ca2+-dependent local translation of a retrograde signaling complex that informs cell bodies of a peripheral degenerative insult. The specific aims of this application to assess the role of immediate-early intra-axonal signaling induced by Aß will be: (i) to determine the mechanisms controlling Aß-induced immediate-early local protein synthesis and (ii) to demonstrate the rapid local synthesis of retrograde signaling complex components in response to Aß. These studies will provide insight into the earliest intra-axonal pathogenic signals induce by Aß, which can improve our understanding of how neurodegeneration spreads retrogradely throughout the brain.

 描述（由申请人提供）：尽管阿尔茨海默病（AD）的患病率持续增加，但疾病发病机制仍然难以理解。为了延缓或预防疾病进展，重要的是要了解AD脑中发生的最早致病性改变。AD病理学的特征包括β-淀粉样蛋白（A β）斑块的沉积和过度磷酸化的tau缠结，尽管这些标志在疾病发病机制中的病理生理学相关性尚不清楚。淀粉样蛋白假说表明，寡聚腺苷酸肽，毒性前体的腺苷酸斑块，发挥了致病作用，在AD脑神经退行性改变中观察到的。对AD小鼠模型的大脑的研究表明，轴突暴露于AAF足以引发整个神经元的神经变性，最终导致细胞死亡。轴突内信号传导事件在AD发病机制中的作用进一步得到人AD脑中的研究的支持，该研究显示突触功能障碍先于细胞死亡。在我们最近发表的研究中，我们证明了在体外和体内，轴突April的应用确实通过激活转录因子4（ATF 4）的局部合成和逆行转运诱导神经变性，随后是基因表达中的ATF 4依赖性促凋亡变化。与这些发现一致，与年龄匹配的对照组相比，AD患者的死后脑组织在轴突和细胞体中表现出更高的ATF 4 mRNA和蛋白频率。我的论文项目是这项研究的有机延伸，主要集中在最早的轴突内信号事件发生在响应Ablation。我的初步数据表明，轴突应用的AAF诱导快速的Ca 2+依赖性核糖体激活，轴突蛋白合成和逆行转运的抑制都足以阻断AAF诱导的Atf 4向轴突的募集。这些发现让人想起了脊髓损伤领域的研究，这些研究表明，轴突切断的外周神经元诱导立即的Ca 2+内流，随后是驻留mRNA的快速翻译，其蛋白质产物在向细胞核的逆行损伤信号传导中起关键作用。有趣的是，我们以前研究中健康海马轴突的RNA测序实验揭示了编码许多已知参与坐骨神经逆行损伤信号传导的蛋白质的mRNA的存在。因此，我假设，类似于周围神经系统的损伤轴突，海马轴突的挑战与Ablation诱导快速钙依赖性的本地翻译的逆行信号复合体，通知细胞体的外周退行性损伤。本申请的具体目的是评估由AAF诱导的立即早期轴突内信号传导的作用：（i）确定控制AAF诱导的立即早期局部蛋白质合成的机制和（ii）证明响应于AAF的逆行信号传导复合物组分的快速局部合成。这些研究将提供对Ablation诱导的最早轴突内致病信号的深入了解，这可以提高我们对神经变性如何在整个大脑中逆行传播的理解。