Microglial lysosomes and selective neuronal vulnerability

项目摘要/摘要 这项提案的总体目标是揭示可能影响小胶质细胞属性的中央调控因素 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状况密切相关。一个很长的- 神经科学中一个悬而未决的谜团是为什么一些中枢神经系统神经元更容易受到年龄相关突触的影响 丢失和神经退行性疾病。小胶质细胞处于良好的位置，可以影响整个脑区的突触。 寿命，具有诱导突触形成、消除突触和改变突触组成的能力 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会发生变化， 包括它们的细胞突起运动、吞噬行为和炎症因子的产生。我们和 其他人最近发现小胶质细胞表现出区域特有的表型，这增加了一种可能性 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 黑质致密部和vta区小胶质细胞开始增殖并产生炎性反应。 在小鼠的中年，以及其他基底节核团中小胶质细胞出现之前的几个月。这些“口袋”里的 早期炎症可能损害附近多巴胺神经元的突触功能，而多巴胺神经元的高度 在衰老过程中易患功能衰退和退行性疾病。在这里，我们将调查是否有可能 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，并且 溶酶体功能的区域差异导致小胶质细胞衰老和突触的区域差异 脆弱性。溶酶体通常被认为是纯粹的降解细胞器，但新的数据表明，它们 与膜循环和细胞内信号密切相关，这些信号可以塑造细胞的特性。的确， 溶酶体在调节巨噬细胞表型，包括其炎症特征方面起着核心作用。 吞噬作用和对衰老的反应。我们的发现表明，溶酶体在体内起着类似的调节作用 小胶质细胞：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、溶酶体组分表达的显著差异 与其他基础的小胶质细胞相比，溶酶体内蛋白质-脂肪聚合体超载的基因和比率 神经节核团。然而，令人惊讶的是，人们对体内的小胶质细胞溶酶体知之甚少。专注于基础 神经节和在小鼠身上工作，我们将使用多学科方法来定义组成和功能 跨脑区的小胶质细胞溶酶体的状况和寿命(目标1)。我们开发了新的方法来 操纵小胶质细胞溶酶体超载，并将决定这将如何形成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超载的影响。 不同脑区的寿命、突触完整性和功能(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心协调器，将识别促进 神经保护性小胶质细胞表型以保护脆弱神经元群体的突触功能。

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.