Examining Mechanism and Physiological Significance of HMG CoA Reductase ER-Associated Degradation

检查 HMG CoA 还原酶 ER 相关降解的机制和生理意义

• 批准号: 9978121
• 负责人: Russell Alfred DeBose-Boyd
• 金额: $ 42.93万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-15 至 2023-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9978121
• 关键词: 25-hydroxycholesterol; 26S proteasome; Acceleration; Atherosclerosis; Binding; Cardiovascular Diseases; Cell physiology; Cells; Cholesterol; Clinical; Complex; Cornea; Cultured Cells; Cytosol; Detergents; Development; Dimethylallyltranstransferase; Dislocations; Dolichol; Drug Prescriptions; Effectiveness; Electron Microscopy; Endoplasmic Reticulum; Enzymes; Estrogen receptor positive; Eye diseases; Feedback; Glean; Goals; Golgi Apparatus; Grant; Heme; Human; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Hydroxymethylglutaryl-CoA reductase; Incidence; Knock-in; Knock-in Mouse; LDL Cholesterol Lipoproteins; Liver; Mediating; Membrane; Membrane Proteins; Molecular; Molecular Conformation; Molecular Structure; Mus; Mutation; Myocardial Infarction; Outcome; Pharmaceutical Preparations; Pharmacology; Physiological; Plasma; Process; Production; Proteins; Reaction; Regulation; Resistance; Schnyder corneal dystrophy; Sterols; Structure; System; Time; Ubiquinone; Ubiquinone Q2; Ubiquitination; Vitamin K 2; Wild Type Mouse; X-Ray Crystallography; cholesterol control; clinical effect; cryogenics; farnesyl pyrophosphate; geranylgeranyl pyrophosphate; high throughput screening; hypercholesterolemia; insight; isoprenoid; multicatalytic endopeptidase complex; novel strategies; novel therapeutics; prevent; protein degradation; response; synthetic enzyme; ubiquitin ligase

Project Summary Multiple feedback mechanisms converge on the polytopic, ER (endoplasmic reticulum)-localized enzyme HMG CoA reductase (HMGCR), which catalyzes a key step in synthesis of cholesterol and essential nonsterol isoprenoids including Fpp (farnesyl pyrophosphate) and GGpp (geranylgeranyl pyrophosphate). Fpp and GGpp can become attached to many cellular proteins and are utilized in synthesis of dolichol, ubiquinone, heme, and vitamin K2. One mechanism for feedback control of HMGCR involves sterol-induced ubiquitination, which marks the enzyme for extraction across ER membranes and subsequent release into the cytosol for proteasome- mediated ERAD (ER-associated degradation). GGpp augments ERAD of HMGCR by enhancing its membrane extraction. We recently discovered that GGpp inhibits sterol-induced binding of HMGCR to UBIAD1 (UbiA prenyltransferase domain-containing protein-1), which utilizes GGpp to synthesize vitamin K2. This inhibition allows for membrane extraction of HMGCR and ER-to-Golgi transport of UBIAD1. Mutations in UBIAD1 cause SCD (Schnyder corneal dystrophy), an autosomal dominant eye disease characterized by corneal accumulation of cholesterol. SCD-associated UBIAD1 resists GGpp-induced release from HMGCR and becomes trapped in the ER where it blocks HMGCR ERAD. Building on discoveries summarized above, we are now poised to 1) elucidate mechanisms through which sterols promote ubiquitination of HMGCR; 2) determine the molecular structure of HMGCR; 3) establish how ubiquitinated HMGCR is removed from ER membranes for ERAD; and 4) ascertain the physiological significance of HMGCR ERAD. Collectively, these studies will provide key information regarding mechanisms by which polytopic HMGCR is removed from ER membranes and delivered cytosolic proteasomes for ERAD. In addition, these studies have significant clinical implications. HMGCR is the target of statins, widely prescribed drugs that lower plasma LDL-cholesterol and reduce cardiovascular disease. However, statins trigger responses that cause accumulation of HMGCR, which blunts their clinical effects. This increase results in part, from slowed ERAD of HMGCR. Thus, elucidating mechanisms for HMGCR ERAD holds promise for development of new therapies that increase the efficacy of statins and further reduce heart attacks.

项目概要 多种反馈机制集中在多位、ER（内质网）定位酶 HMG 上 CoA 还原酶 (HMGCR)，催化胆固醇和必需非甾醇合成的关键步骤 类异戊二烯包括 Fpp（法尼基焦磷酸）和 GGpp（香叶基香叶基焦磷酸）。 Fpp 和 GGpp 可以附着在许多细胞蛋白质上，并用于合成多醇、泛醌、血红素和 维生素K2。 HMGCR 反馈控制的一种机制涉及甾醇诱导的泛素化，这标志着 跨内质网膜提取的酶，随后释放到胞质溶胶中用于蛋白酶体- 介导的 ERAD（ER 相关降解）。 GGpp 通过增强 HMGCR 的膜来增强 HMGCR 的 ERAD 萃取。我们最近发现 GGpp 抑制甾醇诱导的 HMGCR 与 UBIAD1 (UbiA 含有异戊烯基转移酶结构域的蛋白-1)，利用 GGpp 合成维生素 K2。这种抑制 允许膜提取 HMGCR 和 UBIAD1 的 ER 至高尔基体转运。 UBIAD1突变导致 SCD（施奈德角膜营养不良），一种以角膜积聚为特征的常染色体显性眼病 胆固醇。 SCD 相关的 UBIAD1 抵抗 GGpp 诱导的 HMGCR 释放并被困在 ER 阻断 HMGCR ERAD。 基于上述总结的发现，我们现在准备：1）阐明机制 甾醇促进 HMGCR 泛素化； 2)确定HMGCR的分子结构； 3）建立 如何从 ER 膜上去除泛素化 HMGCR 以进行 ERAD； 4) 确定生理 HMGCR ERAD 的意义。总的来说，这些研究将提供有关机制的关键信息 通过该方法，多位 HMGCR 从 ER 膜上去除，并为 ERAD 提供胞质蛋白酶体。在 此外，这些研究具有重要的临床意义。 HMGCR 是他汀类药物的靶点，被广泛使用 降低血浆低密度脂蛋白胆固醇并减少心血管疾病的药物。然而，他汀类药物会引发反应 会导致 HMGCR 积累，从而削弱其临床效果。这种增长的部分原因是速度放缓 HMGCR 的 ERAD。因此，阐明 HMGCR ERAD 的机制有望开发新的 提高他汀类药物疗效并进一步减少心脏病发作的疗法。