Role of TTYH1 in mobilizing lipids and ApoE in glia: Implications for brain aging and neurodegeneration

项目摘要 脂质占人脑干重的一半以上。脑细胞依靠脂质代谢来满足能量 需要，执行信号功能，并调节膜的完整性和动力学。脂质组学改变 在衰老的大脑和神经退行性疾病如阿尔茨海默氏病中观察到了这种情况 (AD)和相关痴呆症（ADRD），这表明重编程的脂质代谢途径可能参与 发病机理值得注意的是，载脂蛋白E和其他脂质代谢相关基因已与 晚发性AD尽管有这些观察结果，某些脂质类的异常代谢是如何机械地 导致脑细胞功能障碍的原因在很大程度上还不清楚。我们试图找出分子途径 通过利用结合联合收割机和组学的方法，我们 转录组学分析鉴定了Tweety Homolog 1（TTYH1），其在人脑中的高表达 与APOE相关。TTYH1和APOE之间的这种相关性在AD患者的星形胶质细胞中丢失。使用 在人原代星形胶质细胞和果蝇模型中，我们发现TTYH1及其果蝇直系同源物是 ApoE分泌。细胞生物学实验进一步表明，TTYH1及其直系同源物是必需的， 自噬和脂滴（LD）分解。果蝇脑和人脑的脂质组学分析 TTYH1直系同源物缺陷的星形胶质细胞显示改变的磷脂丰度，指示升高的 胞浆磷脂酶A2（cPLA2）活性。这些初步发现告诉我们的总体假设， TTYH1是连接胶质LD分解和脂蛋白分泌的新途径所必需的。在目标1中，我们 将测试cPLA2激活的神经酰胺代谢物是否调节神经胶质中的LD分解，并定义 在这个过程中的TTYH1。目的2阐明TTYH 1调节脂蛋白分泌的机制。 星形胶质细胞TTYH1介导的脂质动员在脑老化和ADRD中的意义将在 目标3.我们将评估在果蝇衰老模型中干扰TTYH 1直系同源物的功能结果， ADRD。我们还将使用脑细胞的共培养来研究神经胶质TTYH1对神经元稳态的作用 来源于Ttyh 1条件性敲除小鼠。总之，该项目将整合分子遗传学和 脂质组学阐明了一种新的脂质代谢途径，该途径与TTYH1在脑老化和ADRD中的作用有关。 该项目的发现将有助于确定TTYH1及其相关分子是否可以作为 用于治疗神经变性的治疗靶点。

PROJECT SUMMARY Lipids occupy over half of the dry weight of human brain. Brain cells rely on lipid metabolism to meet energy needs, perform signaling functions, and regulate membrane integrity and dynamics. Alterations in lipidomic profiles have been observed in aging brains and in neurodegenerative diseases such as Alzheimer’s disease (AD) and related dementia (ADRD), suggesting that reprogramed lipid metabolic pathways may be involved in disease pathogenesis. Notably, APOE and other lipid metabolism related genes have been associated with late-onset AD. Despite these observations, how aberrant metabolism of certain lipid classes mechanistically contribute to brain cell malfunction remains largely undefined. We sought to identify molecular pathways pertinent to brain lipid metabolism by utilizing approaches that combine molecular genetics and omics. Our transcriptomic analysis identified Tweety Homolog 1 (TTYH1) whose expression in human brain highly correlates with APOE. Such correlation between TTYH1 and APOE is lost in astrocytes of AD patients. Using human primary astrocyte and Drosophila model, we found that TTYH1 and its fly ortholog are required for ApoE secretion. Cell biology experiments further suggest that TTYH1 and its ortholog are required for autophagy and lipid droplet (LD) breakdown in glia. Lipidomic analyses of drosophila brains and human astrocytes deficient in TTYH1 orthologs revealed altered phospholipid abundances indicative of elevated cytosolic phospholipase A2 (cPLA2) activity. These preliminary findings inform our overarching hypothesis that TTYH1 is essential for a novel pathway connecting glial LD breakdown to lipoprotein secretion. In aim 1, we will test if cPLA2-activating ceramide metabolites regulates LD breakdown in glia, and define the function of TTYH1 in this process. Aim 2 will elucidate the mechanism of how TTYH1 regulates lipoprotein secretion in astrocytes. The significance of TTYH1-mediated lipid mobilization in brain aging and ADRD will be evaluated in Aim 3. We will assess the functional outcomes of perturbing TTYH1 ortholog in drosophila models of aging and ADRD. We will also examine the role of glial TTYH1 on neuronal homeostasis using coculture of brain cells derived from Ttyh1 conditional knockout mice. In summary, the project will integrate molecular genetics and lipidomics to illuminate a novel lipid metabolic pathway that hinges on TTYH1 in brain aging and ADRD. Findings from this project will aid in defining whether TTYH1 and its associated molecular players can serve as therapeutic targets for treating neurodegeneration.