Role of LDLR in regulating metabolism of Apolipoprotein E and Amyloid-beta

项目摘要/摘要 载脂蛋白E(ApoE)基因是阿尔茨海默病(AD)最强的遗传危险因素。盛行 有证据表明，载脂蛋白E亚型影响淀粉样蛋白β(Aβ)、tau、神经炎症和突触可塑性。在……里面 除了异构体，载脂蛋白E蛋白水平的改变已经被证明影响神经炎症和Aβ 通行证。此前，我们报道了载脂蛋白E受体、低密度脂蛋白受体(LDLR)、 在调节脑内载脂蛋白E清除和Aβ水平方面。低密度脂蛋白受体在脑内的过度表达 通过降低载脂蛋白E水平和增加Aβ清除来抑制淀粉样蛋白的形成。这些有益的影响 LDLR的过度表达只有2倍。然而，将这些观察转化为 由于缺乏对细胞和分子机制的了解，以及缺乏 调节大脑低密度脂蛋白受体水平的有效方法。为了克服这一关键障碍，我们建议 研究低密度脂蛋白受体的可诱导降解物(IDOL)调节低密度脂蛋白受体、载脂蛋白E、Aβ和 陶先生。在与Tontonoz博士(HHMI，UCLA)的合作中，我们发现偶像基因的全球缺失显著 增加低密度脂蛋白受体水平，降低脑内载脂蛋白E水平。Idol是泛素化的E3泛素连接酶 LDLR，并将其作为降级目标。重要的是，Idol表达的缺失显著减少了淀粉样斑块 在AD小鼠模型中增加负担并改善神经炎症。基于这些强劲的初步数据， 我们现在建议用以下方法来确定偶像影响载脂蛋白E和Aβ的细胞和分子机制 从整体和条件性基因敲除偶像小鼠模型中分离出原代细胞。我们假设 Idol缺失的有利作用是通过LDLR介导的ApoE水平降低和ApoER2- 介导的Reelin信号。为了检验小时假说，我们将应用创新的方法，如分子 动力学模拟，体内稳定同位素脉冲追踪质谱，体内Aβ和细胞因子 微透析。破译细胞细节中的Idol通路可能有助于更好地理解ApoE信号转导 基础生物学和AD。

PROJECT SUMMARY/ABSTRACT Apolipoprotein E (ApoE) genotype is the strongest genetic risk factor for Alzheimer’s disease (AD). Prevailing evidence suggests that ApoE isoforms affect amyloid β (Aβ), tau, neuroinflammation, and synaptic plasticity. In addition to isoforms, alteration in ApoE protein levels has been shown to influence neuroinflammation and Aβ clearance. Previously, we reported the critical roles of ApoE receptor, low density lipoprotein receptor (LDLR), in regulating ApoE clearance and Aβ levels in the brain. Overexpression of LDLR in the brain dramatically inhibits amyloid formation by decreasing ApoE level and increasing Aβ clearance. These beneficial effects were seen with as little as just 2-fold over-expression of LDLR. However, translating these observations into therapy has been hampered by a poor understanding of cellular and molecular mechanism and a paucity of effective approach to regulate the levels of LDLR in the brain. To overcome this critical barrier, we propose to investigate cellular mechanism by which Inducible Degrader Of LDLR (IDOL) regulates LDLR, ApoE, Aβ, and tau. In collaboration with Dr. Tontonoz (HHMI, UCLA), we found that global deletion of IDOL gene dramatically increases LDLR levels and decreases apoE levels in the brain. IDOL is an E3 ubiquitin ligase that ubiquitinates LDLR and targets it for degradation. Importantly, loss of IDOL expression significantly reduced amyloid plaque burden and ameliorated neuroinflammation in an AD mouse model. Based on these strong preliminary data, we now propose to determine the cellular and molecular mechanism by which IDOL affects ApoE and Aβ using primary cells isolated from global and conditional knockout IDOL mouse model. We hypothesize that the beneficial effect of IDOL deletion is mediated through LDLR-mediated ApoE level reduction and ApoER2- mediated Reelin signaling. To test hour hypothesis, we will apply innovative methods, such as molecular dynamics simulation, in vivo stable isotope pulse chase mass spectrometry, and in vivo Aβ and cytokines microdialysis. Deciphering IDOL pathway in cellular details may help better understanding ApoE signaling in basic biology and AD.