BRAIN LIPID METABOLISM, DENDRITES AND SYNAPSES IN AGING AND ALZHEIMER'S DISEASE

衰老和阿尔茨海默病中的脑脂质代谢、树突和突触

• 批准号: 8721290
• 负责人: GUOJUN BU
• 金额: $ 30.54万
• 依托单位: MAYO CLINIC JACKSONVILLE
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-12-15 至 2015-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8721290
• 关键词: Age; Age-Months; Aging; Alzheimer' s Disease; Amyloid; Amyloid beta-Protein; Apolipoprotein E; Astrocytes; Biogenesis; Brain; Breeding; Cerebrosides; Cholesterol; Cholesterol Homeostasis; Coculture Techniques; Complement; Defect; Dendrites; Dendritic Spines; Dependovirus; Down-Regulation; Exhibits; Family; Glial Fibrillary Acidic Protein; Goals; Health; Homeostasis; Human; Impairment; Inferior; Knockout Mice; Knowledge; LDL-Receptor Related Protein 1; Late Onset Alzheimer Disease; Lipids; Lipoproteins; Low Density Lipoprotein Receptor; Measures; Mediating; Membrane; Memory impairment; Metabolic Pathway; Metabolism; Methods; Molecular; Movement Disorders; Mus; Neurites; Neuroglia; Neurons; Pathogenesis; Pathology; Pathway interactions; Peptides; Play; Process; Production; Prosencephalon; Protein Isoforms; Proteins; Public Health; Reagent; Risk Factors; Role; Signal Transduction; Staging; Synapses; System; Testing; Transgenic Mice; Vertebral column; abstracting; age related; aging brain; apolipoprotein E-3; apolipoprotein E-4; base; cholesterol sulfatide; density; lipid metabolism; lipid transport; nervous system disorder; novel; novel strategies; overexpression; particle; receptor; receptor expression; receptor function; risk variant; small hairpin RNA; synaptic function; synaptogenesis

PROJECT SUMMARY/ABSTRACT Brain lipids such as cholesterol play critical roles in neuronal membrane homeostasis and synapse functions. However, the mechanisms that govern their biogenesis and transport to neurons are poorly understood. Apolipoprotein E (apoE) is a major lipid transporter in the brain. Of the three human apoE isoforms (E2, E3 and E4), apoE4 is the predominant risk allele for late-onset AD. Brain apoE/lipoprotein particles, produced primarily by astrocytes, deliver cholesterol and other lipids to neurons via apoE receptors, which belong to the low-density lipoprotein receptor (LDLR) family. To ultimately understand why apoE4 is a risk factor for AD, it is essential to study the differential functions of apoE isoforms in brain lipid transport and synapse functions, and what specific roles apoE receptors play in these processes. We have demonstrated that brain apoE metabolism is mediated by both LDLR and LDLR-related protein 1 (LRP1). However, neuronal deletion of Lrp1, but not Ldlr, impairs cholesterol metabolism in mice. This suggests that LRP1 is the predominant cholesterol transport receptor in neurons. Conditional Lrp1 forebrain knockout (LRP1-KO) mice have decreased brain cholesterol, sulfatide and cerebroside; reduced dendritic spine density and branching; fewer synapses; and diminished synaptic functions. LRP1-KO mice have memory deficits and movement disorders consistent with compromised dendritic spine/synaptic integrity and synaptic functions. Interestingly, LRP1 levels are significantly reduced in human AD brains and in the apoE4-targeted replacement (TR) mice. ApoE4-TR, but not apoE3-TR mice, also exhibit impaired lipid metabolism and synaptic functions, and apoE4 is less stable compared to apoE3. Based on these observations, we hypothesize that apoE4 is inferior to apoE3 in transporting brain lipid and in supporting dendritic spine/synaptic integrity, particularly in aging brains, and that these apoE4 defects can be partially rescued by restoring the expression and function of apoE receptor LRP1. We propose three aims to test our hypothesis. In Aim 1, we will dissect the molecular and cellular mechanisms by which apoE isoforms transport lipids and regulate neuronal functions via LRP1- and LDLR-dependent pathways using astrocytes-secreted apoE/lipoprotein particles and glia-neuron co-culture system. In Aim 2, we will define age-dependent effects of apoE4 on brain lipid metabolism and synaptic functions and examine whether aging brains are more sensitive to the inferior functions of apoE4. In Aim 3, we will determine if overexpressed LRP1 in mouse brains is sufficient to rescue lipid and synaptic impairments in apoE4-TR mice by breeding apoE3-TR and apoE4-TR mice with LRP1 transgenic mice. Together, our proposed studies should generate critical knowledge on how apoE isoforms differentially regulate brain lipid metabolism and synaptic functions via apoE receptors, and why apoE4 is a strong risk factor for AD. Our studies may also define apoE and apoE receptors as critical targets for AD therapy.

项目摘要/摘要 胆固醇等脑脂质在神经元膜稳态和突触中起关键作用 功能。但是，控制其生物发生和转运到神经元的机制很差 理解。载脂蛋白E（APOE）是大脑中的主要脂质转运蛋白。在三个人类APOE同工型中 （E2，E3和E4），APOE4是迟到的AD的主要风险等位基因。脑APOE/脂蛋白颗粒， 主要由星形胶质细胞产生，通过APOE受体将胆固醇和其他脂质输送到神经元，这些脂肪受体 属于低密度脂蛋白受体（LDLR）家族。最终了解为什么APOE4是一种风险 AD的因素，必须研究脑脂质转运和 突触功能，以及APOE受体在这些过程中起何种特定角色。我们已经证明了 LDLR和LDLR相关蛋白1（LRP1）介导该脑APOE代谢。但是，神经元 LRP1的缺失，但不是LDLR会损害小鼠的胆固醇代谢。这表明LRP1是 神经元中的主要胆固醇转运受体。有条件的LRP1前脑敲除（LRP1-KO）小鼠 脑胆固醇，亚硫酸盐和大脑降低了；树突状脊柱密度和分支降低； 突触较少；并减少突触功能。 LRP1-KO小鼠有记忆缺陷和运动 与破坏的树突状脊柱/突触完整性和突触功能一致的疾病。有趣的是， 人类AD大脑和APOE4靶向替代（TR）小鼠的LRP1水平显着降低。 APOE4-TR，但不是APOE3-TR小鼠，也表现出脂质代谢和突触功能受损，APOE4 与APOE3相比，稳定性较低。基于这些观察结果，我们假设APOE4不如 APOE3在运输脑脂质和支持树突状脊柱/突触完整性方面，尤其是在 衰老的大脑，这些APOE4缺陷可以通过恢复表达和 APOE受体LRP1的功能。我们提出了三个旨在检验假设的目标。在AIM 1中，我们将剖析 APOE同工型通过脂质传输脂质并通过分子和细胞机制调节神经元功能 使用星形胶质细胞分泌的APOE/脂蛋白颗粒和神经胶质神经元的LRP1和LDLR依赖性途径 共培养系统。在AIM 2中，我们将定义APOE4对脑脂质代谢和 突触功能并检查衰老的大脑是否对APOE4的下部功能更敏感。在 AIM 3，我们将确定小鼠大脑中过表达的LRP1是否足以营救脂质和突触 通过用LRP1转基因小鼠繁殖APOE3-TR和APOE4-TR小鼠，APOE4-TR小鼠的损伤。 一起，我们提出的研究应产生有关APOE同工型如何差异化的关键知识 通过APOE受体调节脑脂质代谢和突触功能，为什么APOE4是强大的风险 AD的因素。我们的研究还可以将APOE和APOE受体定义为AD疗法的关键靶标。