Impact of self-association on structure and function of apolipoprotein A-I

描述（由申请人提供）：本拨款申请的主要目标是证明载脂蛋白a - i （apoA-I）的自我结合是蛋白质的一种功能特征，其自我结合状态的改变与导致疾病的机制有关。自结合是几种可交换载脂蛋白的无脂形式的固有特性，包括apoa - 1，它是HDL的主要蛋白质成分，也是一种公认的抗动脉粥样硬化因子。单体无脂apoA-I被认为是具有生物活性的物种。但异常情况，如特异性突变或氧化，会产生一种改变的自我结合状态，可能导致apoa - 1功能障碍。虽然自结合在一些载脂蛋白中的功能作用已经确立，但由于技术限制，自结合对apoA-I功能的影响尚未被研究，这些限制在本项目中得到解决和克服。用Phes（¿W-apoA-I）取代apoA-I的Trps导致异常大且稳定的自结合物种。至少有四种自关联的W-apoA-I可以被分离出来，并将在这里作为自关联的模型来分析其在决定apoA-I的结构、功能和对导致功能障碍的机制的易感性方面的作用。本项目要调查的三个重叠区域是：1。定义自结合在apoa - 1结构的各个层次上的作用，从二级到四级。将建立apoA-I自结合分子间相互作用的性质，并确定增加自结合程度的脂质结合效率损失的结构细节。这种结构知识将有助于理解蛋白质自结合状态改变影响其生物学功能的机制。2. 描述无脂apoA-I的自我结合状态如何影响其作为高密度脂蛋白生物发生过程中细胞释放的脂质受体的功能。不同的apoA-I自相关物种在不同细胞膜转运体介导的脂质释放激活中的效率将被确定。包括ABCA1，这是apoA-I抗动脉粥样硬化功能的主要机制。a.证明无脂apoA-I的自我结合状态可调节导致功能障碍的蛋白易感性机制。不同的自我相关物种对与动脉粥样硬化和糖尿病发病机制有关的反应的脆弱性将被测试。还将评估自我结合在保护apoa - 1免受促进淀粉样蛋白纤维形成的条件中的可能作用，这是动脉粥样硬化进展的一种促进机制。这些研究对公共卫生具有重要意义，因为确定apoA- 1的新功能方面，这是已知最重要的抗动脉粥样硬化因子之一，具有制定新疗法和开发用于评估心血管疾病风险的新生物标志物的潜力。

DESCRIPTION (provided by applicant): The primary goal of this grant proposal is to demonstrate that self-association of apolipoprotein A-I (apoA-I) is a functional feature of the protein and that alteration of its native state of self-association is involved in mechanisms leading to disease. Self-association is an inherent property of the lipid-free forms of several exchangeable apolipoproteins, including apoA-I, the main protein component of HDL and an established antiatherogenic factor. Monomeric lipid-free apoA-I is believed to be the biologically active species. But abnormal conditions, such as specific mutations or oxidation, produce an altered state of self-association that may contribute to apoA-I dysfunction. Although the functional role of self-association in some apolipoproteins has been established, the influence of self-association on apoA-I function has not been studied before because of technical limitations that are addressed and overcome in this project. Replacement of apoA-I's Trps with Phes (¿W-apoA-I) leads to unusually large and stable self-associated species. At least four self-associated species of ¿W-apoA-I can be isolated and will be used here as a model of self-association to analyze its role in determining apoA-I's structure, function, and susceptibility to mechanisms leading to dysfunction. The three overlapping areas to be investigated in this project are: 1. Define the effects of self-association at all levels of apoA-I structure, from secondary to quaternary. The nature of the inter-molecular interactions that are involved in apoA-I self-association will be established and the structural details underlying the loss of lipid-binding efficiency for increasing degrees of self- association will be determined. This structural knowledge will help to understand the mechanisms whereby alteration of the protein self-association state affects its biological function. 2. Characterize how the self-association state o lipid-free apoA-I affects its function as recipient of lipids released from cells in the biogenesisof HDL. The efficiency of different apoA-I self-associated species in activating lipid release mediated by different cell membrane transporters will be determined. Including ABCA1, which is the primary mechanism underlying the anti-atherogenic function of apoA-I. a. Demonstrate that the self-association state of lipid-free apoA-I modulate the protein susceptibility to mechanisms leading to dysfunction. The vulnerability of different self-associated species to reactions that are implicated in the pathogenesis of atherosclerosis and diabetes will be tested. The possible role of self-association in protecting apoA-I from conditions which promote amyloid fibril formation, a contributing mechanism to atherosclerosis progression, will be also evaluated. These studies are highly significant for public health because determining a new functional aspect of apoA- I, which is one of the most important known anti-atherogenic factors, bears potential for the formulation of new therapies and the development of new biomarkers for the evaluation of cardiovascular disease risk.