Role of Multi-enzyme Complex in ApoBCL Secretion

多酶复合物在 ApoBCL 分泌中的作用

• 批准号: 10543873
• 负责人: JAY D. HORTON
• 金额: $ 57.4万
• 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/10543873
• 关键词: ADD-1 protein; ATP Citrate (pro-S)-Lyase; Acetyl-CoA Carboxylase; Acyltransferase; Apolipoproteins B; Binding; Cardiovascular system; Cholesterol; Co-Immunoprecipitations; Complement; Complex; Coronary heart disease; Cytoplasm; Cytosol; Data; Development; Dyslipidemias; Endoplasmic Reticulum; Enzymes; Event; Fatty-acid synthase; Genes; Genetic study; Goals; Hepatic; Hepatocyte; Hypertriglyceridemia; In Vitro; Individual; LDL Cholesterol Lipoproteins; Lipids; Lipoproteins; Liver; Location; Low-Density Lipoproteins; Metabolic; Metabolism; Mitochondria; Molecular; Multienzyme Complexes; Mus; New Agents; Organelles; Outcome; Palmitates; Physiological; Plasma; Polymers; Production; Program Research Project Grants; Proteins; Regulation; Research Project Grants; Residual state; Risk; Role; Series; Signal Transduction; Structural Protein; Triglycerides; Very low density lipoprotein; alpha-glycerophosphoric acid; cardiovascular risk factor; density; enzyme activity; gene synthesis; heart disease risk; hormonal signals; in vivo; inhibitor; insight; lipid metabolism; mitochondrial membrane; novel strategies; polymerization; posttranscriptional; protein protein interaction; stem; transcription factor

Project 2. Role of Multi-Enzyme Complexes in ApoBCL Secretion SUMMARY/ABSTRACT Although statins and PCSK9 inhibitors decrease LDL-Cholesterol (LDL-C) levels and reduce cardiovascular events, significant residual risk of CHD remains even in maximally treated individuals with low plasma levels of LDL-C. Multiple lines of evidence support the contention that elevated plasma levels of triglyceride (TG)-rich ApoB-Containing Lipoproteins (ApoBCLs) contribute significantly to this residual risk. Previously, we have shown that the transcription factor, SREBP-1c, leads to activation of all genes encoding the enzymes involved in FA synthesis. Excessive activation of SREBP-1c in liver results in high levels of FA and TG synthesis, VLDL secretion, and ultimately hypertriglyceridemia. The studies in this project will characterize a new post- translational regulatory mechanism that modulates FA and TG synthesis as well as VLDL production. The three enzymes that synthesize palmitate (C16:0) — ATP-citrate lyase (ACL), acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) — reside in the cytoplasm. The two enzymes that elongate and/or desaturate palmitate, ELOVL6 and SCD1, are located in the ER, and the first enzyme in the synthesis of glycerolipids, glycerol-3-phosphate acyltransferase 1 (GPAM), is located in the mitochondrial membrane. The distinct subcellular locations of these enzymes produce a unique spatial challenge for the efficient synthesis of FAs and TGs since the product of one enzyme is the substrate for the next. Our preliminary data suggest that the cytosolic FA synthesis enzymes form a complex. This discovery stemmed from the characterization of a SREBP-1c-regulated gene designated MIG12. We found that MIG12 bound directly to ACCs, facilitated ACC polymerization, and increased overall rates of FA synthesis in liver. MIG12 is structurally similar to another small protein designated S14. Our subsequent studies have shown that S14 co-immunoprecipitated MIG12, ACC, and FAS suggesting that these proteins form a complex in the cytosol. Here, we will identify and characterize all proteins in the FA synthesis complex and determine how these proteins associate with each other and with the ER and/or mitochondria. Next, we will determine whether the formation and disassociation of the FA synthesis complex is regulated by hormonal signals in vitro and in vivo. Finally, we will characterize the physiological function of lipogenic complex in vivo through a series of studies in mice that lack the key proteins required for the formation of the FA synthesis complex. Combined, these studies will provide important new insights into how the cytosolic lipogenic complex ultimately provides FAs to the ER for further elongation and/or desaturation as well as to GPAM for TG synthesis and VLDL secretion.

项目2.多酶复合体在载脂蛋白BCL分泌中的作用 摘要/摘要 尽管他汀类药物和PCSK9抑制剂可降低低密度脂蛋白(LDL-C)水平并减少心血管疾病 事件中，即使在接受最大限度治疗的低血浆血糖素水平的个体中，仍存在显著的冠心病残留风险 低密度脂蛋白-C多条证据支持这样一种观点，即升高富含甘油三酯的血浆水平 含ApoB的脂蛋白(ApoBCL)对这一残留风险有很大贡献。此前，我们有 研究表明，转录因子SREBP-1c导致编码相关酶的所有基因的激活 在脂肪酸合成中。肝脏中SREBP-1c的过度激活导致高水平的FA和TG合成，极低密度脂蛋白 分泌物，最终导致高甘油三酯血症。这个项目中的研究将描述一个新的职位- 调节脂肪酸和甘油三酯合成以及极低密度脂蛋白产生的翻译调控机制。 合成棕榈酸(C16：0)的三种酶--三磷酸腺苷-柠檬酸裂解酶(ACL)、乙酰辅酶A羧化酶 (ACC)和脂肪酸合成酶(Fas)-位于细胞质中。延长和/或伸长的两种酶 去饱和棕榈酸酯ELOVL6和SCD1位于内质网，是合成棕榈酸的第一个酶 甘油脂是位于线粒体膜上的甘油-3-磷酸酰基转移酶1(GPAM)。这个 这些酶的不同的亚细胞位置为有效地合成 Fas和TGS，因为一个酶的产物是下一个酶的底物。 我们的初步数据表明，胞质中的FA合成酶形成了一个复合体。这一发现 源于SREBP-1c调控的基因MIG12的特征。我们发现MIG12 直接与ACCs结合，促进ACC聚合，并增加肝脏中FA的总合成速率。 MIG12在结构上与另一种命名为S14的小蛋白相似。我们随后的研究表明， S14免疫共沉淀法检测到MIG12、ACC和Fas，提示这些蛋白在胞浆中形成一个复合体。 在这里，我们将鉴定和表征FA合成复合体中的所有蛋白质，并确定这些蛋白质是如何 蛋白质相互关联，并与内质网和/或线粒体相关联。接下来，我们将确定是否 在体外和体内，FA合成复合体的形成和解离都受到激素信号的调节。 最后，我们将通过一系列的研究来描述生脂复合体在体内的生理功能。 缺乏形成FA合成复合体所需的关键蛋白质的小鼠。总而言之，这些研究 将为胞质生脂复合体最终如何向内质网提供脂肪酸提供重要的新见解 用于进一步延长和/或降低饱和度，以及用于甘油三酯合成和极低密度脂蛋白的分泌。