Apolipoprotein conformation in amyloid and cardiovascular diseases

摘要 脂蛋白代谢异常是肥胖的一个标志，影响着40%的美国人。肥胖及其并发症-- 包括2型糖尿病(T2D)、心血管疾病、淀粉样蛋白和严重的病毒性疾病在内的疾病是主要的 过早死亡的原因。这项研究的最终目标是帮助诊断和治疗这些疾病。这 该项目解决了肥胖中脂蛋白功能方面的关键未解决问题。高的，低的，非常低的- 密度脂蛋白(高密度脂蛋白、低密度脂蛋白和极低密度脂蛋白)是由脂类和载脂蛋白组成的各种纳米颗粒， 血浆中的直接脂代谢。这一过程极其复杂，许多细节尚不清楚。我们目前的情况 重点是脂蛋白和蛋白质与硫酸肝素(HS)的相互作用，这种相互作用可以触发心脏和心脏功能。 血管和淀粉样变性疾病。我们将确定载脂蛋白-HS相互作用的分子机制 并改变了肥胖患者的脂蛋白功能。我们强大的方法，集成了广泛的生物化学- 生物学、生物物理学和计算工具，使我们能够假设令人信服的新假说，这些假说将得到检验 三个相辅相成的具体目标。目标1将确定肥胖时脂蛋白功能的变化。 治疗前后比较。健康和病态肥胖受试者的脂蛋白将根据 肝素结合亲和力，以及它们的生化和功能性质将被测定。我们的新假设 在强有力的先导性研究的支持下，将测试：脂蛋白脂肪酶作用于循环形成的小颗粒- 晚期极低密度脂蛋白为肥胖和治疗提供了新的生物标志物。目标2将定义生化 以及肥胖时血清淀粉样蛋白A(SAA)从高密度脂蛋白向低密度脂蛋白转移的功能细节。我们的初步研究表明 这种小蛋白的转移诱导低密度脂蛋白发生促动脉粥样硬化的变化，并提出了两个假设 接受测试：i)肥胖、SAA升高和动脉粥样硬化之间的新机制联系，以及ii)新的有益 SAA在肥胖中作为脂质清除剂的作用。目标3将确定HS和肝素如何影响SAA错误折叠 淀粉样蛋白A(AA)淀粉样变性，一种威胁生命的肥胖和慢性炎症并发症。SAA绑定到 HS是AA淀粉样变性的治疗靶点，但缺乏分子细节。我们的初步研究表明：i) SAA与HS结合启动淀粉样蛋白沉积的细胞外途径；ii)HS结合中的周期性阴离子阵列 淀粉样核中碱性残基的堆积和稳定淀粉样核。为了测试这些耐人寻味的新想法，我们将 结合生化、生物物理、氢-重离子交换质谱学和计算方法。 晶体和纤维中具有SAA原子结构的消耗臭氧层物质。结果：这项研究将确定新的机制 肥胖和动脉粥样硬化之间的联系；验证假设的SAA作为脂质清除剂的重要作用；澄清 它在淀粉样蛋白中的错误折叠途径；并有助于开发新的肥胖和相关诊断工具和治疗方法 精神错乱。这项研究的更广泛的影响是：它将：i)帮助理解和调节 肥胖、T2D和严重的新冠肺炎病，以及ii)揭示HS-淀粉样蛋白间质的分子基础 这些行为不仅会严重影响再生障碍性贫血，还会影响阿尔茨海默氏症和其他主要的淀粉样蛋白疾病。

Abstract Aberrant lipoprotein metabolism is a hallmark of obesity that affects >40% of Americans. Obesity and its com- plications, including type-2 diabetes (T2D), cardiovascular, amyloid and severe viral diseases, are the leading causes of premature death. The ultimate goal of this research is to help diagnose and treat these disorders. This project addresses critical unresolved questions in the lipoprotein functionality in obesity. High-, low- and very low- density lipoproteins (HDL, LDL and VLDL) are diverse nanoparticles comprised of lipids and apolipoproteins that direct lipid metabolism in plasma. This process is extremely complex and many details are unknown. Our current focus is on the interactions of lipoproteins and proteins with heparan sulfate (HS), which can trigger both cardio- vascular and amyloid diseases. We will determine the molecular mechanisms of apolipoprotein-HS interactions and altered lipoprotein functionality in obesity. Our powerful approach, which integrates a wide array of biochem- ical, biophysical and computational tools, enabled us to postulate compelling new hypotheses that will be tested in three complementary specific aims. Aim 1 will determine how lipoprotein functionality changes in obesity be- fore and after treatment. Lipoproteins from healthy and morbidly obese subjects will be isolated based on the heparin binding affinity, and their biochemical and functional properties will be determined. Our new hypothesis supported by strong pilot studies will be tested: small particles formed upon action of lipoprotein lipase on circu- lating VLDL provide novel biomarkers of obesity and readouts for treatment. Aim 2 will define the biochemical and functional details of serum amyloid A (SAA) transfer from HDL to LDL in obesity. Our pilot studies indicate that transfer of this small protein induces pro-atherogenic changes in LDL, and suggest two hypotheses that will be tested: i) new mechanistic links between obesity, elevated SAA and atherosclerosis, and ii) novel beneficial role of SAA as a lipid scavenger in obesity. Aim 3 will determine how HS and heparin affect SAA misfolding in amyloid A (AA) amyloidosis, a life-threatening complication of obesity and chronic inflammation. SAA binding to HS is a therapeutic target in AA amyloidosis but molecular details are lacking. Our pilot studies suggest that: i) SAA binding to HS initiates an extracellular pathway of amyloid deposition; ii) periodic anionic arrays in HS bind to stacks of basic residues in amyloid and stabilize amyloid nuclei. To test these intriguing new ideas, we will combine biochemical, biophysical, hydrogen-deuterium exchange mass spectrometry, and computational meth- ods with atomic structures of SAA in crystals and fibrils. Outcome: this research will identify new mechanistic links between obesity and atherosclerosis; verify the hypothetical vital role of SAA as a lipid scavenger; clarify its misfolding pathway in amyloid; and help develop new diagnostic tools and treatments for obesity and related disorders. Broader impact of this research is that it will: i) help understand and modulate the causal link between obesity, T2D and severe COVID-19 disease, and ii) uncover the molecular underpinnings of HS-amyloid inter- actions that can critically impact not only in AA but also Alzheimer's and other major amyloid diseases.