Apolipoprotein A-I (apoA-I) has a key function in the reverse cholesterol transport. However, aggregation of apoA-I single point mutants can lead to hereditary amyloid pathology. Although several studies have tackled the biophysical and structural consequences introduced by these mutations, there is little information addressing the relationship between the evolutionary and structural features that contribute to the amyloid behavior of apoA-I. We combined evolutionary studies, in silico mutagenesis and molecular dynamics (MD) simulations to provide a comprehensive analysis of the conservation and pathogenic role of the aggregation-prone regions (APRs) present in apoA-I. Sequence analysis demonstrated that among the four amyloidogenic regions described for human apoA-I, only two (APR1 and APR4) are evolutionary conserved across different species of Sarcopterygii. Moreover, stability analysis carried out with the FoldX engine showed that APR1 contributes to the marginal stability of apoA-I. Structural properties of full-length apoA-I models suggest that aggregation is avoided by placing APRs into highly packed and rigid portions of its native fold. Compared to silent variants extracted from the gnomAD database, the thermodynamic and pathogenic impact of amyloid mutations showed evidence of a higher destabilizing effect. MD simulations of the amyloid variant G26R evidenced the partial unfolding of the alpha-helix bundle with the concomitant exposure of APR1 to the solvent, suggesting an insight into the early steps involved in its aggregation. Our findings highlight APR1 as a relevant component for apoA-I structural integrity and emphasize a destabilizing effect of amyloid variants that leads to the exposure of this region.

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影响载脂蛋白 AI 淀粉样蛋白行为的进化和结构限制

载脂蛋白 AI (apoA-I) 在胆固醇逆向转运中具有关键作用。然而，apoA-I 单点突变体的聚集可导致遗传性淀粉样蛋白病理。尽管有几项研究已经解决了这些突变带来的生物物理和结构后果，但很少有信息能够说明导致 apoA-I 淀粉样蛋白行为的进化和结构特征之间的关系。我们结合进化研究、计算机诱变和分子动力学 (MD) 模拟，对 apoA-I 中存在的易聚集区域 (APR) 的保护和致病作用进行了全面分析。序列分析表明，在为人 apoA-I 描述的四个淀粉样蛋白生成区域中，只有两个（APR1 和 APR4）在不同肉翅目物种中是进化保守的。此外，使用 FoldX 引擎进行的稳定性分析表明，APR1 有助于 apoA-I 的边际稳定性。全长 apoA-I 模型的结构特性表明，通过将 APR 放入其天然折叠的高度堆积和刚性部分，可以避免聚集。与从 gnomAD 数据库中提取的沉默变体相比，淀粉样蛋白突变的热力学和致病影响显示出更高的不稳定效应。淀粉样蛋白变体 G26R 的 MD 模拟证明了 α-螺旋束的部分展开，同时 APR1 暴露于溶剂中，这表明对其聚集的早期步骤有所了解。