Targeting Scap to Lower ApoB-Containing Lipoproteins (ApoBCL) Production

靶向 Scap 降低含 ApoB 脂蛋白 (ApoBCL) 的产生

• 批准号: 10543872
• 负责人: Arun Radhakrishnan
• 金额: $ 54.12万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-01-01 至 2026-12-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10543872
• 关键词: Animal Experiments; Animal Feed; Animal Model; Apolipoproteins B; Applications Grants; Binding; Binding Proteins; Binding Sites; Blood; Carbohydrates; Cell Nucleus; Chemicals; Cholesterol; Complex; Coronary Arteriosclerosis; Coronary heart disease; Development; Diet; Dissociation; Drug Kinetics; Eligibility Determination; Endoplasmic Reticulum; Fatty Acids; Gene Activation; Genes; Goals; Golgi Apparatus; Hamsters; Heart Diseases; Hepatic; High Fat Diet; Laboratories; Lead; Lipids; Lipoproteins; Liver; Medicine; Membrane; Membrane Proteins; Metabolic; Modeling; Modification; Molecular; Mus; Nuclear; Patients; Peptide Hydrolases; Plasma; Process; Production; Property; Proteins; Rapid screening; Regulatory Element; Research Project Grants; Residual state; Risk; Risk Reduction; Science; Specificity; Stabilizing Agents; Sterols; Structure; Transcriptional Activation; Triglycerides; Wild Type Mouse; cardiovascular risk factor; cholesterol-binding protein; improved; in vivo; indexing; inhibitor; lipid biosynthesis; lipid disorder; mimetics; nanomolar; novel; novel drug class; novel strategies; novel therapeutic intervention; novel therapeutics; prevent; protein complex; small molecule; small molecule inhibitor; three dimensional structure; transcription factor

Elevated plasma levels of triglyceride-rich ApoBCLs (ApoB-Containing Lipoproteins) constitute a major component of the residual risk for coronary heart disease (CHD) in patients who have been treated with statins and/or PCSK9 inhibitors. To mitigate the ApoBCL risk component, we need a deeper understanding of the machinery that controls the production of ApoBCLs. This machinery is comprised of two membrane proteins, Scap and Sterol Regulatory Element-Binding Proteins (SREBPs). Scap is a protein embedded in the endoplasmic reticulum (ER) membrane through eight transmembrane helices. Scap forms complexes with SREBPs, which are also bound to the ER membrane through two transmembrane helices. SREBPs contain transcription factor domains that control the synthesis of fatty acids, triglycerides, and cholesterol, which form the lipid component of ApoBCLs. Activation of SREBPs requires their transport by Scap to the Golgi where two proteases release their transcription factor domain that can now enter the nucleus for target gene activation. When cholesterol in the ER rises and binds to Scap, it traps SREBPs in the ER, thus preventing proteolytic cleavage and nuclear entry. A major hurdle in understanding Scap’s switch-like molecular mechanism and how it controls SREBPs and ApoBCL production is the lack of a soluble cholesterol-mimetic compound that specifically binds and inhibits Scap. This proposal is based on a recent breakthrough in our laboratory involving the development of a novel high- throughput and rapid screening protocol, which has identified the first small molecule that binds specifically to Scap’s cholesterol-binding site and blocks activation of SREBPs. Scap contains two large loops (Loop1 and Loop7) that extend into the lumen of the ER bind each other when cholesterol in the ER is low. When ER cholesterol rises, it binds to Loop1, causing Loop1 to dissociate from Loop7, trapping the Scap/SREBP complex in the ER and blocking the transcriptional activation of all SREBP target genes. In Aim 1, we outline studies to improve the potency of our recently discovered cholesterol-mimetic Scap inhibitor and will use these inhibitors to understand how Loop1 dissociates from Loop7. The inhibitors will also be used as stabilizing agents to enable structural determination of Scap, which will elucidate the cholesterol binding mechanism at an atomic level. In Aim 2, we outline our approach to optimizing the in vivo pharmacokinetic properties of our various Scap inhibitors, after which we will explore their effects in inhibiting Scap and SREBP target genes in livers of mice under different metabolic conditions. Our previous studies involving genetically altered mice revealed that inhibition of Scap in the liver blocks SREBPs and markedly reduces synthesis of fatty acids, triglycerides, and cholesterol, dramatically lowering ApoBCL production in these models and also in wild-type mice fed a high fat diet and in hamsters fed a high carbohydrate diet. If these proof-of-concept studies are successful, our inhibitors might lead companies to develop new drugs to reduce plasma ApoBCLs and prevent coronary heart disease.

富含甘油三酯的 ApoBCL（含 ApoB 脂蛋白）的血浆水平升高是导致 接受他汀类药物治疗的患者冠心病 (CHD) 残余风险的组成部分 和/或PCSK9抑制剂。为了减轻 ApoBCL 风险成分，我们需要更深入地了解 控制 ApoBCL 生产的机器。该机器由两种膜蛋白组成， Scap 和甾醇调节元件结合蛋白 (SREBP)。 Scap是一种嵌入在 内质网（ER）膜通过八个跨膜螺旋。 Scap 形成复合物 SREBP，也通过两个跨膜螺旋与 ER 膜结合。 SREBP 包含 控制脂肪酸、甘油三酯和胆固醇合成的转录因子结构域， ApoBCL 的脂质成分。 SREBP 的激活需要通过 Scap 运输到高尔基体，其中两个 蛋白酶释放其转录因子结构域，现在可以进入细胞核激活靶基因。 当 ER 中的胆固醇升高并与 Scap 结合时，它会捕获 ER 中的 SREBP，从而阻止蛋白水解 裂解和核进入。理解 Scap 类开关分子机制及其作用的主要障碍 它控制 SREBP 和 ApoBCL 的产生，因为缺乏可溶性胆固醇模拟化合物， 特异性结合并抑制 Scap。 该提案基于我们实验室最近的一项突破，涉及开发一种新型的高 通量和快速筛选方案，已鉴定出第一个特异性结合的小分子 Scap 的胆固醇结合位点并阻止 SREBP 的激活。 Scap 包含两个大循环（Loop1 和 当 ER 中的胆固醇较低时，延伸到 ER 腔内的 Loop7）会相互结合。当急诊室 胆固醇升高，它与 Loop1 结合，导致 Loop1 与 Loop7 分离，捕获 Scap/SREBP 复合物 ER 中并阻断所有 SREBP 靶基因的转录激活。在目标 1 中，我们概述了以下研究： 提高我们最近发现的类胆固醇 Scap 抑制剂的效力，并将使用这些抑制剂 了解 Loop1 如何与 Loop7 分离。该抑制剂还将用作稳定剂，以实现 Scap 的结构测定，这将在原子水平上阐明胆固醇结合机制。在 目标 2，我们概述了优化各种 Scap 体内药代动力学特性的方法 抑制剂，之后我们将探讨它们对小鼠肝脏中Scap和SREBP靶基因的抑制作用 在不同的代谢条件下。我们之前对基因改造小鼠的研究表明 抑制肝脏中的 Scap 可阻断 SREBP，并显着减少脂肪酸、甘油三酯和 胆固醇，显着降低这些模型以及喂食高脂肪的野生型小鼠中 ApoBCL 的产生 饮食和仓鼠喂养高碳水化合物饮食。如果这些概念验证研究成功，我们的抑制剂 可能会促使公司开发新药来减少血浆 ApoBCL 并预防冠心病。