Endoplasmic Reticulum Mitochondrial membranes in Alzheimer's disease

描述（由申请人提供）：阿尔茨海默病（AD）的特征是神经元损失，特别是在皮质和海马中，并伴有大脑中含有β-淀粉样蛋白（Aβ）的细胞外神经炎斑块和由过度磷酸化tau蛋白组成的细胞内神经原纤维缠结的积累。 AD 患者还表现出其他较少受到关注的特征，包括异常的胆固醇、磷脂和钙稳态，以及线粒体功能和动力学的改变。 Presenilin-1 (PS1)、presenilin-2 (PS2) 和 γ 分泌酶活性（处理淀粉样前体蛋白 (APP) 生成 Aß）均主要位于内质网 (ER) 的一个专门的亚区室中，该亚区室在物理和生化上与线粒体相连，称为线粒体相关 ER 膜 (MAM)。 MAM 参与胆固醇和磷脂代谢、钙稳态以及线粒体功能和动力学的调节。最近，我们发现MAM是脂筏样结构域，来自AD患者的细胞MAM活性大幅上调，内质网线粒体连接性增加，导致胆固醇、磷脂和钙稳态改变，以及线粒体动力学异常，这可能有助于解释该疾病的许多生化和形态学特征。基于这些发现，我们认为 MAM 功能障碍和 ER 线粒体连接改变是 AD 发病机制的早期致病事件。我们现在提出旨在从基础科学角度理解 MAM 功能的研究，最终目标是转化应用这些知识。具体来说，我们将 (1) 分析与 AD 更相关的细胞和组织中的 MAM 功能，包括 PS 缺陷的人神经母细胞瘤细胞、分化为神经元的人诱导多能干细胞以及从 PS1 敲入小鼠中移植的组织和神经元； (2) 分析 MAM 与其他区室（例如“本体”ER 或质膜）中的早老素和 γ-分泌酶调节，同时评估 γ-分泌酶复合物的其他成分（例如 APH-1、尼卡斯特林、PEN2）和调节剂（例如 CD147、GSAP 和 TMP21）的作用； (3)了解ER-线粒体通讯在AD发病机制中的作用，通过使用新型ER-线粒体“交联”质粒将ER与线粒体以不同的固定距离连接，以便以不依赖早老素的方式模拟ER-线粒体连接。

DESCRIPTION (provided by applicant): Alzheimer disease (AD) is characterized by neuronal loss, especially in the cortex and hippocampus, accompanied by accumulation in the brain of extracellular neuritic plaques containing ß-amyloid (Aß) and of intracellular neurofibrillary tangles consisting of hyperphosphorylated tau protein. AD patients also present with other features that have received less attention, including aberrant cholesterol, phospholipid, and calcium homeostasis, and altered mitochondrial function and dynamics. Presenilin-1 (PS1), presenilin-2 (PS2), and γ-secretase activity, which processes the amyloid precursor protein (APP) to generate Aß, are all located predominantly in a specialized subcompartment of the endoplasmic reticulum (ER) that is physically and biochemically connected to mitochondria, called mitochondria-associated ER membranes (MAM). MAM is involved in the regulation of cholesterol and phospholipid metabolism, calcium homeostasis, and in mitochondrial function and dynamics. Recently, we showed that MAM is lipid raft-like domain and that cells from AD patients have massively upregulated MAM activity and increased ER mitochondrial connectivity, resulting in altered cholesterol, phospholipid and calcium homeostasis, and aberrant mitochondrial dynamics, which may help explain many of the biochemical and morphological features of the disease. Based on these findings, we believe that MAM dysfunction and altered ER-mitochondrial connectivity are early causative events in the pathogenesis of AD. We now propose studies aimed at understanding MAM function from a basic science standpoint, with the ultimate goal of applying this knowledge translationally. Specifically, we will (1) analyze MAM function in cells and tissues that are more "AD-relevant," including PS-deficient human neuroblastoma cells, human induced pluripotent stem cells differentiated into neurons, and tissues and neurons explanted from PS1 knock-in mice; (2) analyze presenilins and γ-secretase regulation in MAM versus other compartments, such as "bulk" ER or the plasma membrane, while also assessing the role of other components (e.g. APH-1, nicastrin, PEN2) and regulators (e.g. CD147, GSAP, and TMP21) of the γ-secretase complex; and (3) understand the role of ER-mitochondrial communication in the pathogenesis of AD, by tethering ER to mitochondria at various fixed distances, using novel ER-mitochondria "crosslinking" plasmids, in order to mimic ER-mitochondrial connectivity in a presenilin-independent manner.