The influence of axonal ER on retrograde synapse loss following axon damage

轴突损伤是神经创伤的早期事件，导致逆行性细胞变化，包括体细胞ER 压力，突触丧失，过度兴奋，甚至细胞死亡。基础工作仍然需要了解 轴突-索马损伤信号如何传播以影响长投射中这些深刻的逆行变化 锥体细胞了解这种信号传导对于神经保护性药物的未来发展至关重要。 接近。轴突损伤导致大量钙流入胞质溶胶以启动轴突至索马信号传导， 导致转录依赖性逆行突触丧失和过度兴奋。有证据表明， 内质网（ER）依赖性钙波或钙启动的微管转运介导 这种从轴突到索马的长距离信号传递。一个巨大的内质网从远端轴突延伸到整个神经元 终末树突棘，影响钙的可用性，但轴突ER参与的程度， 轴突损伤诱导的突触丧失和过度兴奋性仍然未知。此外，虽然大鼠损伤模型是 作为这项研究的支柱，目前还不清楚人类的多巴胺能神经元， 再生能力，不同的损伤信号传导机制。实验上易于处理的多隔间， 微流体腔室能够独立于胞体和树突操纵轴突， 研究小鼠和人类干细胞衍生神经元中轴突与索马通讯的重要工具。 我们发现，在我们的微流体室中，海马锥体神经元受到远端轴突切断， 体细胞ER应激、逆行性突触丢失和过度兴奋。减少局部的钙内流， 损伤和阻断转录防止轴突切断诱导的树突棘丢失;因此，钙信号传导和 快速转录介导轴突损伤后的突触丢失。我们的长期目标是找出 运动员和他们的行动时间，导致逆行突触损失和过度兴奋后轴突损伤。 目的1研究轴突雌激素受体对大鼠和人类轴突切断诱导的体细胞雌激素受体应激的影响 神经元。目的2研究轴突ER信号对轴突切断诱导的突触的影响 失落和过度兴奋总之，这项研究提供了一个关键的第一步，在确定ER的作用， 锥体细胞中轴突至索马损伤信号传导。此外，该项目可能导致新的识别 在神经元损伤的早期阶段的治疗，并可能有更广泛的影响， 其中ER应激和轴突损伤均普遍存在的神经系统疾病。

Axon injury is an early event of neurotrauma that leads to retrograde cellular changes, including somatic ER stress, synapse loss, hyper-excitability, and even cell death. Foundational work remains needed to understand how axon-to-soma injury signals propagate to effect these profound retrograde changes in long projection pyramidal cells. Understanding this signaling is critical for the future development of neuroprotective approaches. Axon injury causes massive influx of calcium into the cytosol to initiate axon-to-soma signaling, leading to transcription-dependent retrograde synapse loss and hyperexcitability. Evidence suggests either an endoplasmic reticulum (ER)-dependent calcium wave or calcium-primed microtubule-based transport mediates this long-range axon-to-soma signaling. A vast ER network extends throughout the neuron from distal axon terminals to dendritic spines, influencing the availability of calcium, but the extent of axonal ER involvement in axon injury-induced synapse loss and hyper-excitability remains unknown. Further, while rat injury models are a mainstay of this research, it remains unclear how human glutamatergic neurons, with their diminished regenerative capacity, differ in their injury signaling mechanisms. Experimentally tractable multi-compartment, microfluidic chambers enable manipulation of axons independently from somata and dendrites, providing an important tool to investigate axon-to-soma communication in both murine and human stem cell-derived neurons. We found that hippocampal pyramidal neurons subjected to distal axotomy in our microfluidic chambers undergo somatic ER stress, retrograde synapse loss, and hyper-excitability. Reducing calcium influx locally at the site of injury and blocking transcription prevents axotomy-induced dendritic spine loss; thus, calcium signaling and rapid transcription mediate synapse loss following axon injury. Our long-term goal is to identify key molecular players and their timing of action that cause retrograde synapse loss and hyper-excitability following axon injury. Aim 1 will determine the influence of axonal ER on axotomy-induced somatic ER stress in both rat and human glutamatergic neurons. Aim 2 will examine the influence of axonal ER signaling on axotomy-induced synapse loss and hyper-excitability. Together, this study provides a critical first step in defining the role of ER during axon-to-soma injury signaling in pyramidal cells. Further, this project may lead to the novel identification of therapeutics during early stages of neuron damage and will likely have broader implications for other neurological disorders where both ER stress and axon damage are prevalent.