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

项目总结/摘要 载脂蛋白E（ApoE）基因型是阿尔茨海默病（AD）最强的遗传危险因素。现行 有证据表明ApoE同种型影响淀粉样蛋白β（Aβ）、tau、神经炎症和突触可塑性。在 除了同种型外，ApoE蛋白水平的改变已被证明会影响神经炎症和Aβ 间隙以前，我们报道了ApoE受体，低密度脂蛋白受体（LDLR）， 在调节ApoE清除率和脑中Aβ水平方面。脑中LDLR的过度表达 通过降低ApoE水平和增加Aβ清除率抑制淀粉样蛋白形成。这些有益效果 仅观察到LDLR的2倍过表达。然而，将这些观察转化为 由于对细胞和分子机制的理解不足， 调节脑内LDLR水平的有效方法。为了克服这一关键障碍，我们建议 研究LDLR诱导降解物（IDOL）调节LDLR、ApoE、Aβ和 τ的在与Tontonoz博士（HHMI，加州大学洛杉矶分校）的合作中，我们发现IDOL基因的全局缺失显着 增加脑中LDLR水平并降低apoE水平。IDOL是一种E3泛素连接酶， LDLR并将其作为降解目标。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，基于这些有力的初步数据， 我们现在建议使用以下方法来确定IDOL影响ApoE和Aβ的细胞和分子机制： 从整体和条件性敲除IDOL小鼠模型分离的原代细胞。我们假设 IDOL缺失的有益作用是通过LDLR介导的ApoE水平降低和ApoER 2- 介导的Reelin信号传导。为了验证小时假说，我们将应用创新的方法，如分子生物学， 动力学模拟，体内稳定同位素脉冲追踪质谱，以及体内Aβ和细胞因子 微透析在细胞细节中解读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.