Role of microglial lysosomes in amyloid-A-beta degradation

我们已经描述了吞噬细胞消化太大而无法消化的物体的过程。 被吞噬我们称这个过程为消化性外食，我们已经证明了它在消化中的作用。 在动脉粥样硬化和死亡脂肪细胞消化中脂蛋白的大聚集体。我们 假设小胶质细胞利用消化性外食来修整和部分降解β-淀粉样蛋白。这可能是 小胶质细胞限制β-淀粉样斑块扩张的机制。消化性外食包括 在待降解的物体上形成紧密密封（溶酶体突触），分泌晚期内体 和溶酶体（LE/Ly）进入溶酶体突触，并通过V-ATP酶质子泵酸化。我们有 这表明培养的原代小胶质细胞在与β-淀粉样蛋白接触后形成溶酶体突触。在 目标1我们将继续描述这一点。首先，我们将确认我们的初步数据， 当它们与β-淀粉样蛋白相互作用时，它们分泌溶酶体， 这些地区的内容。然后，我们将量化这些细胞中淀粉样蛋白的时间依赖性降解， 隔间我们将确定抗Aβ IgG是否增加小胶质细胞对斑块的消化。我们将 还使用光学和电子显微镜检查AD模型小鼠消化道外食的证据。 我们通过以下方式部分表征了消化道外食所需的信号机制： 巨噬细胞，我们将用它作为研究小胶质细胞的模型。我们注意到， 我们描述了消化性外食重叠信号通路的遗传研究， 老年痴呆症在目标2中，我们将探讨其中一些突变对消化外食的影响。 这些将包括Trem 2 R47 H、Dap 12-/-和Trem 2-/-小鼠小胶质细胞。我们已经证明，药理学 PI 3-激酶和Akt以及其他信号分子的操纵改变了消化性外食， 巨噬细胞，我们将扩大我们的初步研究，这些药物对消化系统的影响， 小胶质细胞对淀粉样蛋白的外食。 已经提出小胶质细胞在神经病原纤维的传播中起作用，包括tau蛋白和神经胶质细胞。 未消化的Aβ纤维LE/Ly分泌是消化道外食的重要组成部分， 有助于tau细丝或Aβ原纤维的部分消化片段从小胶质细胞中扩散出来， 我们将在第三个目标中考察这一点。具体来说，我们将确定增强的LE/Ly是否 当小胶质细胞接触β-淀粉样蛋白时的分泌导致先前内吞的原纤维的分泌增强。 然后，我们将测试目标1&2中描述的处理对原纤维的内吞作用和消化的影响， 它们在与淀粉样蛋白接触时的分泌。在我们的组织培养研究中，我们将使用原代小鼠小胶质细胞 和人iPSC衍生的小胶质细胞。

We have characterized a process used by phagocytic cells to digest objects that are too large to be phagocytosed. We call this process digestive exophagy, and we have demonstrated its role in digestion of large aggregates of lipoproteins in atherosclerosis and also in the digestion of dead adipocytes. We hypothesize that microglia use digestive exophagy to trim and partially degrade β-amyloid. This may be the mechanism by which microglia limit the expansion of β-amyloid plaques. Digestive exophagy involves the formation of a tight seal on the object to be degraded (a lysosomal synapse), secretion of late endosomes and lysosomes (LE/Ly) into the lysosomal synapse, and acidification by V-ATPase proton pumps. We have evidence that primary microglia in culture form lysosomal synapses upon contact with β-amyloid. In Aim 1 we will continue to characterize this. First, we will confirm our preliminary data that microglia create acidified, F-actin-rich contact regions when they interact with β-amyloid and that they secrete lysosomal contents into these areas. We will then quantify time-dependent degradation of amyloid in these compartments. We will determine if anti- Aβ IgG increases digestion of the plaques by microglia. We will also use optical and electron microscopy to examine evidence for digestive exophagy in AD model mice. We have partially characterized the signaling mechanisms required for digestive exophagy by macrophages, and we will use this as a model for studies in microglia. We note that the signaling pathways we described for digestive exophagy overlap signaling pathways implicated in genetic studies of Alzheimer’s disease. In Aim 2 we will explore the effects of some of these mutations on digestive exophagy. These will include Trem2R47H, Dap12-/-, and Trem2-/- mouse microglia. We have shown that pharmacological manipulation of PI3-kinase and Akt as well as other signaling molecules alter digestive exophagy in macrophages, and we will extend our preliminary studies on the effects of these drugs on digestive exophagy of amyloid by microglia. Microglia have been proposed to play a role in the spread of neuropathic fibrils, including tau and undigested Aβ fibrils. LE/Ly secretion, which is an essential component of digestive exophagy, may contribute to the spread of partially digested fragments of tau filaments or Aβ fibrils out of microglial cells, and we will examine this in the third Aim. Specifically, we will determine whether the enhanced LE/Ly secretion when microglia contact β-amyloid leads to enhanced secretion of previously endocytosed fibrils. We will then test the effects of treatments described in Aims 1&2 on endocytosis and digestion of fibrils and their secretion upon contact with amyloid. In our tissue culture studies, we will use primary mouse microglia and human iPSC-derived microglial cells.