Exploring the role dense core vesicle release in glial immunity

摘要 神经胶质细胞在维护大脑健康和管理神经元应激和损伤方面发挥着重要作用。 神经变性触发强大的神经胶质免疫反应，包括细胞骨架动力学、神经胶质细胞 细胞迁移，吞噬活性增强。及时清除和降解退行性轴突和 神经胶质细胞产生的神经元碎片在大脑中提供神经保护。尽管神经胶质细胞对轴突的反应很重要 对于损伤神经元如何在神经胶质细胞中引发免疫反应，我们仍然知之甚少，令人惊讶。什么 信号从退化的神经元中释放出来？是什么促使这些伤害信号的释放？最后，如何 这些信号是由胶质细胞翻译的，从而对损伤做出有效的免疫反应吗？ 我们正在使用果蝇作为一个易于处理的模型来研究免疫 存在于活体神经元和神经胶质细胞之间的通讯中继器。苍蝇的神经系统包含 在分子和功能上与脊椎动物的神经胶质细胞相似的独特的神经胶质亚型。此外，历史悠久的 对成虫嗅觉系统和成虫翅膀的轴突切开分析表明，果蝇的轴突经历了 经典的沃勒变性(WD)计划，包括轴突内钙波增加，轴突 碎裂，随后被吞噬的胶质细胞清除。值得注意的是，我们的实验室最近发现了轴突 变性触发反应性包膜胶质细胞中胰岛素样信号(ILS)通路的激活， 反过来，它又能引起必要的神经胶质免疫反应，包括免疫基因的转录上调(如： 吞噬受体Draper)和吞噬活性。我们假设含有神经肽的致密物质 核心囊泡(DCV)广泛地从切断的轴突中释放出来，以触发局部神经胶质细胞的免疫反应。 在这里，我们建议使用静态和实时共聚焦成像、转录图谱和新开发的活体 记者调查神经细胞和胶质细胞之间的神经肽信号如何影响神经胶质免疫反应 神经损伤。具体地说，我们将1)监测成人切断神经的DCV动态和释放，2)利用 一种新的单次转录标记方法显示免疫mRNA在胶质细胞中的局部翻译 损伤部位的延伸，以及3)决定神经肽如何在不同的胶质细胞亚型之间传递信号 确保神经胶质细胞对退化轴突的反应正确进行。总而言之，这些发现将提供 令人兴奋的分子和细胞洞察力，了解神经元和胶质细胞之间的神经肽信号转导是如何调控的 急性和慢性退行性疾病的免疫反应。

SUMMARY Glial cells play an essential role in defending brain health and managing neuronal stress and damage. Neurodegeneration triggers robust glial immune responses, including changes in cytoskeletal dynamics, glial cell migration, and increased phagocytic activity. Timely removal and degradation of degenerating axons and neuronal debris by glia confers neuroprotection in the brain. Despite the importance of glial responses to axon injury, we still know surprisingly little about how damaged neurons invoke immune reactions in glial cells. What signals are released from degenerating neurons? What prompts the release of these injury cues? Finally, how are these signals translated by glia to carry out efficient immune responses to damage? We are using the fruit fly Drosophila melanogaster as a tractable model to investigate the immune communication relays that exist between neurons and glial cells in vivo. The fly nervous system contains distinct glial subtypes that are molecularly and functionally similar to vertebrate glia. Moreover, well-established axotomy assays in the adult olfactory system and the adult wing reveal that Drosophila axons undergo a classic Wallerian degeneration (WD) program, which includes increased intra-axonal calcium waves, axon fragmentation, and subsequent clearance by phagocytic glia. Notably, our lab has recently shown that axon degeneration triggers activation of the insulin-like signaling (ILS) pathway in reactive ensheathing glia, which, in turn, elicits essential glial immune responses, including transcriptional upregulation of immune genes (e.g. the engulfment receptor Draper) and phagocytic activity. We hypothesize that neuropeptide-containing dense core vesicles (DCVs) are broadly released from severed axons to trigger immune responses in local glial cells. Here, we propose to use static and live confocal imaging, transcriptional profiling, and newly developed in vivo reporters to investigate how neuropeptide signaling between neurons and glia informs glial immune responses to nerve injury. Specifically, we will 1) monitor DCV dynamics and release in adult severed nerves, 2) utilize novel single transcript labeling methods to visualize local translation of immune mRNA transcripts in glial extensions at sites of injury, and 3) determine how neuropeptide signaling between discrete glial subtypes ensures that glial responses to degenerating axons are properly carried out. Together, these findings will offer exciting molecular and cellular insight into how neuropeptide signaling between neurons and glia govern immune responses in both acute and chronic degenerative conditions.