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

轴突损伤是神经损伤的早期事件，导致细胞退行性变化，包括躯体内质网 压力，突触丢失，过度兴奋，甚至细胞死亡。仍需基础工作才能理解 轴突-胞体损伤信号如何传播以影响长投射中的这些深刻的逆行变化 锥体细胞。了解这一信号对于未来神经保护的发展至关重要。 接近了。轴突损伤导致大量钙离子流入胞浆，启动轴突到胞体的信号转导， 导致依赖转录的逆行突触丢失和过度兴奋。证据表明，要么是 内质网依赖的钙波或钙激活的微管转运媒介 这种长距离轴突到胞体的信号。一个庞大的内质网从远端轴突延伸到整个神经元 终末至树突棘，影响钙的可用性，但轴突内质网参与的程度 轴突损伤导致的突触丢失和超兴奋性仍不清楚。此外，虽然大鼠损伤模型是 作为这项研究的支柱，目前尚不清楚人类谷氨酸能神经元是如何随着其数量的减少而减少的 再生能力不同，其伤害信号机制也不同。实验上容易驾驭的多车厢， 微流体室使轴突的操纵独立于胞体和树突，提供了 研究小鼠和人类干细胞来源的神经元中轴突到胞体通讯的重要工具。 我们发现，在我们的微流室中接受远端轴突切断的海马锥体神经元经历了 躯体内质网应激、逆行突触丢失和高兴奋性。减少局部钙内流 损伤和阻断转录可防止轴突切断所致的树突棘丢失；因此，钙信号和 快速转录介导轴突损伤后突触丢失。我们的长期目标是确定关键分子 导致轴突损伤后逆行突触丢失和过度兴奋的运动员和他们的动作时机。 目的1研究轴突内质网对大鼠和人轴突切断后躯体内质网应激的影响 谷氨酸能神经元。目的2研究轴突内质网信号对轴突切断诱导的突触的影响 失落和过度兴奋。综上所述，这项研究为确定ER在 锥体细胞中轴突到胞体的损伤信号。此外，该项目可能导致新的身份识别 治疗在神经元损伤的早期阶段，并可能对其他 内质网应激和轴突损伤都很普遍的神经紊乱。

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.