Excess cholesterol originating from non-hepatic tissues is transported within high-density lipoprotein (HDL) particles to the liver for metabolism and excretion. Cholesterol efflux is initiated by lipid-free or lipid-poor apolipoprotein A1 (ApoA1) interacting with the transmembrane protein adenosine triphosphate-binding cassette transporter A1 (ABCA1), a key player in cholesterol homeostasis. Defective ABCA1 results in reduced serum levels of HDL cholesterol, deposition of cholesterol in arteries and an increased risk of early-onset cardiovascular disease. Over 300 genetic variants in ABCA1 have been reported, many of which are associated with reduced HDL cholesterol levels. Only a few of these have been functionally characterized. In this study, we have analyzed 51 previously unclassified missense variants affecting the extracellular domains of ABCA1 using a sensitive, easy and low-cost fluorescence-based assay. Among these, only 12 variants showed a distinct loss-of-function phenotype, asserting their direct association with severe HDL disorders. These findings emphasize the crucial role of functional characterization of genetic variants in pathogenicity assessment and precision medicine. The functional rescue of ABCA1 loss-of-function variants through proteasomal inhibition or by the use of the chemical chaperone 4-phenylbutyric acid was genotype-specific. Genotype-specific responses were also observed for the ability of ApoA1 to stabilize the different ABCA1 variants. In view of personalized medicine, this could potentially form the basis for novel therapeutic strategies.

中文翻译：

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使用基于荧光的测定法对影响 ABCA1 胞外域的错义变体进行功能表征。

来自非肝组织的过量胆固醇通过高密度脂蛋白（HDL）颗粒转运至肝脏进行代谢和排泄。胆固醇流出是由无脂或贫脂载脂蛋白 A1 (ApoA1) 与跨膜蛋白三磷酸腺苷结合盒转运蛋白 A1 (ABCA1) 相互作用引发的，而跨膜蛋白三磷酸腺苷结合盒转运蛋白 A1 (ABCA1) 是胆固醇稳态的关键参与者。ABCA1缺陷会导致血清HDL胆固醇水平降低、胆固醇在动脉中沉积以及早发性心血管疾病的风险增加。据报道，ABCA1 存在 300 多种遗传变异，其中许多与高密度脂蛋白胆固醇水平降低有关。其中只有少数已得到功能表征。在这项研究中，我们使用灵敏、简单且低成本的基于荧光的测定法分析了 51 个先前未分类的影响 ABCA1 细胞外结构域的错义变异。其中，只有 12 个变异表现出明显的功能丧失表型，表明它们与严重的 HDL 疾病有直接关系。这些发现强调了遗传变异的功能表征在致病性评估和精准医学中的关键作用。通过蛋白酶体抑制或使用化学伴侣 4-苯基丁酸对 ABCA1 功能丧失变异体的功能性挽救是基因型特异性的。还观察到 ApoA1 稳定不同 ABCA1 变体的能力的基因型特异性反应。鉴于个性化医疗，这可能成为新型治疗策略的基础。