Microglial lysosomes and selective neuronal vulnerability

项目总结/摘要 这项提案的总体目标是揭示小胶质细胞属性的中央调节器，这些属性可以影响 突触突触功能障碍与衰老过程中认知能力下降和神经元健康密切相关。很长的- 神经科学中一个长期存在的谜团是，为什么一些中枢神经系统神经元更容易受到与年龄相关的突触的影响， 丧失和神经退行性疾病。小胶质细胞处于有利位置，可以影响整个大脑中的突触。 寿命，被装备以诱导突触形成、突触消除和改变突触组成 通过多种机制。此外，小胶质细胞的突触相关属性在衰老过程中发生变化， 包括它们的细胞过程运动性、吞噬行为和炎性因子的产生。我们和 其他人最近发现，小胶质细胞表现出区域特异性表型， 小胶质细胞对突触健康的调节各不相同。此外，我们的初步数据表明，腹侧被盖 黑质区（VTA）和黑质部（SNc）小胶质细胞开始增殖并产生炎症 小鼠中年期间的因素，以及其他基底神经节核中小胶质细胞出现之前的几个月。这些“口袋” 早期炎症可能对附近的多巴胺神经元的突触功能有害，这些神经元高度依赖于突触功能。 在衰老过程中容易出现功能衰退和退行性疾病。在这里，我们将调查这种可能性 小胶质细胞溶酶体可以同时调节这些细胞的多种突触相关属性， 溶酶体功能的区域差异引起小胶质细胞老化和突触的区域差异 易损性.溶酶体通常被认为是纯粹的降解细胞器，但新的数据表明， 与细胞膜再循环和细胞内信号传导密切相关，这些信号传导可以塑造细胞特性。的确， 溶酶体在调节巨噬细胞表型，包括它们的炎症特征， 吞噬作用和对衰老的反应。我们的研究结果表明，溶酶体发挥类似的调节作用， 我们在VTA/SNc小胶质细胞中观察到的区域特异性表型和对衰老的反应 伴随着溶酶体丰度、溶酶体成分表达的显着差异 基因，以及蛋白质-脂质聚集体的溶酶体过载率，与其他基底细胞中的小胶质细胞相比， 神经节核尽管如此，令人惊讶的是，很少有人知道小胶质细胞溶酶体在体内。专注于基础 神经节和小鼠的工作，我们将使用多学科的方法来定义的组成和功能 跨脑区域和寿命的小胶质细胞溶酶体的状态（目标1）。我们开发了新的方法， 操纵小胶质细胞溶酶体过载，并将确定这如何塑造突触相关的小胶质细胞 老化过程中的属性（目标2）。最后，我们将直接测量小胶质细胞溶酶体过载如何影响 寿命突触的完整性和功能在不同的大脑区域（目标3）。这些研究将揭示这些 细胞器是小胶质细胞表型的中央管弦乐队，并将识别促进细胞增殖的分子靶点。 神经保护性小胶质细胞表型，以保护脆弱的神经元群体中的突触功能。

Project Summary / Abstract The overall goal of this proposal is to reveal central regulators of microglial attributes that can impact synapses. Synaptic dysfunction is tightly linked to declining cognition and neuronal health during aging. A long- standing mystery in neuroscience is why some CNS neurons are more vulnerable to age-associated synapse loss and neurodegenerative disease. Microglia are well-positioned to influence synapses throughout the lifespan, being equipped to induce synapse formation, synapse elimination and alter synapse composition through multiple mechanisms. Moreover, synapse-relevant attributes of microglia change during aging, including their cell process motility, phagocytic behaviors, and production of inflammatory factors. We and others recently discovered that microglia exhibit region-specific phenotypes, raising the possibility that microglial regulation of synaptic health varies. In addition, our preliminary data indicate that ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) microglia begin to proliferate and produce inflammatory factors during midlife in mice, and months before microglia in other basal ganglia nuclei. These “pockets” of early inflammation are likely detrimental to synaptic function of nearby dopamine neurons, which are highly vulnerable to functional decline and degenerative disease during aging. Here, we will investigate the possibility that microglial lysosomes can simultaneously regulate multiple synapse-relevant attributes of these cells, and that regional differences in lysosome function give rise to regional variation in microglial aging and synapse vulnerability. Lysosomes are typically viewed as purely degradative organelles, but new data show that they are intimately involved in membrane recycling and intracellular signaling that can shape cell properties. Indeed, lysosomes play a central role in regulating macrophage phenotype, including their inflammatory profiles, phagocytosis, and responses to aging. Our findings suggest that lysosomes play similar regulatory roles within microglia; the region-specific phenotypes and responses to aging that we observe within VTA/SNc microglia were accompanied by prominent differences in lysosome abundance, expression of lysosome component genes, and rates of lysosome overload with protein-lipid aggregates, compared to microglia in other basal ganglia nuclei. Nonetheless, surprising little is known about microglial lysosomes in vivo. Focusing on the basal ganglia and working in mice, we will use multidisciplinary approaches to define the composition and functional status of microglial lysosomes across brain regions and lifespan (Aim 1). We developed novel methods to manipulate microglial lysosome overload and will determine how this shapes synapse-relevant microglial attributes during aging (Aim 2). Finally, we will directly measure how microglial lysosome overload affects lifespan synaptic integrity and function in distinct brain regions (Aim 3). These studies will reveal whether these organelles are central orchestrators of microglial phenotype and will identify molecular targets for promoting neuroprotective microglial phenotypes to preserve synaptic function in vulnerable populations of neurons.