Microsomal Transfer Protein Modulates Lipoprotein Metabolism and Retinal lipid Homeostasis

微粒体转移蛋白调节脂蛋白代谢和视网膜脂质稳态

• 批准号: 10372593
• 负责人: Kathleen Boesze-Battaglia
• 金额: $ 25.49万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-03-01 至 2024-02-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10372593
• 关键词: ATP binding cassette transporter 1; Ablation; Acids; Address; Aging; Apical; Apolipoproteins; Apolipoproteins B; Blindness; Bruch' s basal membrane structure; Cardiac Myocytes; Cell Culture System; Cell Culture Techniques; Cell physiology; Cells; Characteristics; Cholesterol; Cholesterol Homeostasis; Choroid; Complex; Consequentialism; Deposition; Development; Disease; Endoplasmic Reticulum; Energy-Generating Resources; Enterocytes; Equilibrium; Fatty Acids; Foundations; Functional disorder; Gatekeeping; Genes; Genetic; Health; Hepatocyte; Homeostasis; Human; Inflammation; Inflammatory; Inflammatory Response; Ingestion; Intracellular Accumulation of Lipids; Lead; Lesion; Lipids; Lipoproteins; Liver; Low-Density Lipoproteins; Mediating; Metabolic; Metabolism; Missense Mutation; Mitotic; Morphology; Mouse Protein; Neural Retina; Pathologic; Pathway interactions; Patients; Phagocytosis; Pharmacology; Plasma; Play; Process; Production; Protein Deficiency; Proteins; Recycling; Regulation; Retina; Retinal Degeneration; Retinal Diseases; Retinal Pigments; Role; Secondary to; Structure of retinal pigment epithelium; System; Testing; Toxic effect; Vision; age related; cholesterol transporters; density; environmental stressor; human fetal retinal pigment epithelial cell; in vivo; induced pluripotent stem cell; lipid metabolism; lipid transfer protein; mouse model; negative affect; normal aging; novel; oxidation; prevent; protein function; western diet

Lipid handling is one of the most critical functions of the retinal pigment epithelium (RPE) a single mitotically inactive cell layer that is situated between the neural retina and the Bruch's membrane-Choroid. Visual function depends on the intimate structural, functional and metabolic interactions between the RPE and the neural retina. Within this complex, lipid metabolism is tightly regulated, and its' dysregulation triggers accumulation of excess lipids within the RPE and the adjacent Bruch's membrane and choroidal vasculature. In the human retina the accumulation of neutral lipid deposits is a characteristic of aging and precedes disease associated-lesions. A significant proportion of this neutral lipid is enclosed within apolipoprotein B100 containing lipoproteins (Blps) that resemble cardiomyocyte associated Blps. The prodigious amount of lipid that must be processed by the RPE, through the recycling and metabolism of lipid rich outer segments and ingestion of circulating lipoproteins, predicts that to prevent lipid overload the RPE synthesize and secrete Blp. In this regard, RPE shares metabolic similarity with cardiomyocytes; both utilize fatty acids as an energy source and both secrete unique EC rich Blps. While it has been shown that MTP-mediated secretion of Blps protects cardiomyocytes from lipid accumulation, there is a paucity of studies regarding Blp assembly/secretion by RPE in vivo. In these studies we will use mouse models and cell culture to decipher the pathological consequences associated with dysregulation of Blp assembly and secretion pathway by inhibiting or genetic ablation of the Mttp gene in RPE. Microsomal transfer protein (MTP), the product of the MTTP gene, is an endoplasmic reticulum-resident lipid transfer protein necessary for Blp assembly and secretion. In the first specific aim we will test the hypothesis that MTP-mediated secretion of Blp is a mechanism for protecting against RPE lipid overload. To test the contribution of localized synthesis and secretion of Blp by the RPE to retinal lipid homeostasis and cell function in a metabolically intact system, we generated the RPE-specific MTP deficient (RPEMttp) mouse. In the second specific aim we will test the hypothesis that Blp assembly is modulated by the daily load of ingested OS lipids. We will use RPE differentiated from human induced pluripotent stem cells (iPSCs) to investigate the mechanism by which lipids taken up through outer segment phagocytosis regulate MTP activity and Blp production. Using these cells, we will determine if loss of MTP, either through gene ablation (KD of MTP in iRPE) or pharmacological inhibition, contributes to RPE steatosis. Collectively, these exploratory studies will address the specific role of local Blp assembly in retinal lipid homeostasis. Dysregulation of Blp function can cause non- autonomous changes that negatively affect the entire system and lead to vision loss. These studies maybe foundational to study subsequent steps in the development of age-related changes such as inflammation and degeneration associated with dysregulation of lipoprotein metabolism.

脂质处理是视网膜色素上皮 (RPE) 最关键的功能之一 位于神经视网膜和布鲁赫膜脉络膜之间的不活跃细胞层。视觉功能 取决于 RPE 和神经视网膜之间密切的结构、功能和代谢相互作用。 在这个复合体中，脂质代谢受到严格调节，其失调会引发过量的积累 RPE 以及邻近的布鲁赫膜和脉络膜脉管系统内的脂质。在人类视网膜中 中性脂质沉积物的积累是衰老的特征并且先于疾病相关病变。一个 这种中性脂质的很大一部分被包含在含有脂蛋白 (Blps) 的载脂蛋白 B100 内 类似于心肌细胞相关的 Blp。必须经过处理的大量脂质 RPE，通过富含脂质的外节的回收和代谢以及循环脂蛋白的摄入， 预测为了防止脂质超载，RPE 合成并分泌 Blp。在这方面，RPE 与代谢 与心肌细胞相似；两者都利用脂肪酸作为能量来源，并且都分泌独特的富含 EC 的 Blp。 虽然已经表明 MTP 介导的 Blp 分泌可以保护心肌细胞免受脂质积累， 关于体内 RPE 组装/分泌 Blp 的研究很少。在这些研究中我们将使用鼠标 模型和细胞培养破译与 Blp 失调相关的病理后果 通过抑制或基因消除 RPE 中 Mttp 基因的组装和分泌途径。微粒体转移 蛋白（MTP）是MTTP基因的产物，是一种内质网驻留脂质转运蛋白 Blp 组装和分泌所必需的。在第一个具体目标中，我们将检验 MTP 介导的假设 Blp 的分泌是防止 RPE 脂质超载的机制。测试本地化的贡献 RPE 合成和分泌 Blp，以维持代谢完整的视网膜脂质稳态和细胞功能 系统中，我们生成了 RPE 特异性 MTP 缺陷（RPEMttp）小鼠。在第二个具体目标中，我们将 检验 Blp 组装受每日摄入 OS 脂质负荷调节的假设。我们将使用 RPE 从人类诱导多能干细胞 (iPSC) 中分化出来，以研究脂质的作用机制 通过外节吞噬作用摄取调节 MTP 活性和 Blp 产生。使用这些细胞，我们 将确定 MTP 是否通过基因消融（iRPE 中 MTP 的 KD）或药物抑制而丧失， 导致 RPE 脂肪变性。总的来说，这些探索性研究将解决当地 BLP 的具体作用 视网膜脂质稳态中的组装。 Blp 功能失调会导致非自主变化， 对整个系统产生负面影响并导致视力丧失。这些研究可能是学习的基础 与年龄相关的变化（例如炎症和退化）发展的后续步骤 脂蛋白代谢失调。