Structure and Function of Serum Amyloid A in Health and Disease

血清淀粉样蛋白 A 在健康和疾病中的结构和功能

基本信息

批准号：
10321653
负责人：
Olga Gursky
金额：
$ 31.35万
依托单位：
BOSTON UNIVERSITY MEDICAL CAMPUS
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-01-01 至 2023-12-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/10321653
关键词：
Acute Acute-Phase Proteins Address Affect Amyloid Amyloid beta-Protein Precursor Amyloidosis Anabolism Autoimmune Diseases Binding Biochemical Biological Markers Biophysics Blood CD36 gene Calorimetry Cell membrane Cells Cellular Membrane Cholesterol Chronic Circular Dichroism Clear Cell Complement Complex Complication Coupled Data Deposition Deuterium Disease Docking Drops Electron Microscopy Evolution Excision Face Fluorescence Future Health Heparin Heparitin Sulfate High Density Lipoprotein Cholesterol High Density Lipoproteins Homeostasis Hour Hydrogen Hydrophobic Surfaces Immune response Infection Inflammation Injury Kinetics Life Ligand Binding Ligands Lipid Binding Lipids Lipoprotein Binding Lipoproteins Liver Malignant Neoplasms Mass Spectrum Analysis Membrane Lipids Methods Molecular Molecular Conformation Molecular Sieve Chromatography Natural Immunity Nonesterified Fatty Acids Organ Pathogenicity Pathologic Patients Phase Phospholipase A2 Phospholipids Pilot Projects Plasma Plasma Proteins Play Process Proteins Proteolysis Public Health Publishing Reaction Receptor Cell Research Resolution Role Serum Serum amyloid A protein Shapes Site Structural Models Structure Study of serum Sulfate Surface Testing Tissues Titrations Trauma Triglycerides Work acute infection amyloid formation base chronic infection healing human disease injured insight lipid metabolism lipophilicity lipoprotein triglyceride molecular dynamics new therapeutic target novel novel therapeutics preference receptor receptor binding repaired stem synergism therapeutic target

项目摘要

Abstract This research is focused on normal and pathologic actions of serum amyloid A (SAA), an enigmatic biomarker of inflammation and a protein precursor of AA amyloidosis, a life-threatening complication of chronic inflammation. SAA is a small soluble intrinsically disordered protein that increases rapidly and dramatically up to 1,000-fold in plasma following inflammation, infection or injury. The advantage for survival of this steep but transient increase is unclear, and the beneficial role of SAA in immune response is obscure. However, evolutionarily conserved aspects of the SAA structure, its lipophilic character, and the rapid and major commitment of liver and local tissues to SAA biosynthesis strongly support the importance of SAA-lipid interactions. Our new structural model suggests how SAA binds lipids and cell receptors, thereby rerouting lipid metabolism. Pilot biochemical studies compel us to propose a vital new role for SAA in clearing cellular membrane debris from the injured sites. Our powerful biophysical and biochemical approach will determine the mechanism via which SAA sequesters phospholipids and other lipids from cell membranes to facilitate their breakdown and safe removal from the injured sites in a process that is prerequisite for tissue healing. We will also determine how various lipids and other factors modulate amyloid formation by SAA, and thereby help decelerate or block this pathogenic process. Three complementary specific aims develop new concepts fundamental to SAA action in immune response and amyloid formation. Aim 1 will use an array of biophysical, structural and cell-based methods to establish molecular underpinnings for SAA interactions with its functional ligands, lipids and CD36 cell receptor. We will test our new structural model suggesting that SAA binds lipids via a unique apolar face whose shape defines protein's preference for binding to highly curved lipoproteins or forming them de novo to sequester lipids. We will determine the SAA conformation on the lipid and quantify its binding to CD36. Aim 2 will probe a novel synergy between SAA and secretory phospholipase A2 (sPLA2), an acute-phase plasma protein upregulated simultaneously with SAA in inflammation. Pilot studies compel us to propose a novel beneficial function of SAA in solubilizing phospholipids and their hydrolytic products to generate substrates for sPLA2 and to remove its products. The results will establish the hitherto unknown vital primordial role of SAA. Aim 3 will determine effects of various lipids, their degradation products, pH and heparin sulfate on SAA amyloid formation. We will also test our new idea that plasma lipids such as triacylglycerol modulate the SAA release from its major plasma carrier, high-density lipoprotein, and ultimately form amyloid. The results will help determine whether lipid-lowering therapies hold promise for treating AA amyloidosis. Completion of this research will establish raison d'etre for this enigmatic protein, provide a molecular basis for its action in immune response and lipid homeostasis, and help find much-needed new therapies or repurpose existing ones to treat a life-threatening human disease.

抽象的这项研究的重点是血清淀粉样蛋白 A (SAA) 的正常和病理作用，SAA 是一种神秘的生物标志物炎症和 AA 淀粉样变性的蛋白质前体，AA 淀粉样变性是一种危及生命的慢性炎症并发症。 SAA 是一种小的可溶性本质无序蛋白质，其在体内的数量迅速增加至 1,000 倍。炎症、感染或受伤后的血浆。这种急剧但短暂的增长对生存的好处目前尚不清楚，SAA 在免疫反应中的有益作用也不清楚。然而，进化上保守 SAA 结构的各个方面、其亲脂性特征以及肝脏和局部组织的快速和主要承诺 SAA 生物合成有力地支持了 SAA-脂质相互作用的重要性。我们的新结构模型表明 SAA 如何结合脂质和细胞受体，从而改变脂质代谢。试点生化研究迫使我们提出 SAA 在清除受损部位细胞膜碎片方面的重要新作用。我们强大的生物物理和生化方法将确定 SAA 隔离磷脂的机制和细胞膜中的其他脂质，以促进其分解并从受伤部位安全清除是组织愈合的先决条件的过程。我们还将确定各种脂质和其他因素如何通过 SAA 调节淀粉样蛋白的形成，从而有助于减缓或阻止这一致病过程。三个互补的特定目标开发了 SAA 在免疫反应中的作用的基本新概念，以及淀粉样蛋白的形成。目标 1 将使用一系列生物物理、结构和基于细胞的方法来建立 SAA 与其功能配体、脂质和 CD36 细胞受体相互作用的分子基础。我们将测试我们的新结构模型，表明 SAA 通过独特的非极性面结合脂质，其形状定义蛋白质偏好与高度弯曲的脂蛋白结合或从头形成它们以隔离脂质。我们将确定脂质上的 SAA 构象并量化其与 CD36 的结合。目标 2 将探索新颖的协同作用 SAA 和分泌性磷脂酶 A2 (sPLA2) 之间的关系，分泌性磷脂酶 A2 是一种上调的急性期血浆蛋白与SAA同时发生炎症。试点研究迫使我们提出 SAA 的一种新的有益功能溶解磷脂及其水解产物以产生 sPLA2 底物并去除其产品。结果将确立 SAA 迄今为止未知的重要原始作用。目标3将决定效果各种脂质、其降解产物、pH 和硫酸肝素对 SAA 淀粉样蛋白形成的影响。我们也会测试我们的新想法是血浆脂质（例如三酰甘油）调节 SAA 从其主要血浆载体的释放，高密度脂蛋白，最终形成淀粉样蛋白。结果将有助于确定是否可以降脂疗法有望治疗 AA 型淀粉样变性。完成这项研究将为以下目的奠定存在的理由：这种神秘的蛋白质，为其在免疫反应和脂质稳态中的作用提供了分子基础，并且帮助寻找急需的新疗法或重新利用现有疗法来治疗危及生命的人类疾病。