From the Departments of Pediatrics and Biochemistry, Group on the Molecular and Cell Biology of Lipids, University of Alberta, Alberta, Canada (H.-M.G., F.W., A.A., S.D., D.-W.Z.); and Institute of Atherosclerosis in Taishan Medical University, Taian, China (S.Q., D.-W.Z.).
Arterioscler Thromb Vasc Biol. 2016 Feb;36(2):253-5. doi: 10.1161/ATVBAHA.115.306592. Epub 2015 Dec 22.
ATP-binding cassette transporter G1 (ABCG1) mediates cholesterol efflux to lipidated lipoproteins. Conflicting data about cellular localization of ABCG1 and its effect on cholesterol efflux have been reported. Here, we investigated the underlying mechanisms for these different observations.
Confocal microscopy and biotinylation were used to assess cell surface localization of ABCG1. We found that mouse ABCG1 (mABCG1) used in one previous study has a substitution of Leu to Pro at position 550 (mG1-L550P). When the corresponding Leu at position 562 in human ABCG1 (hABCG1) was mutated to Pro (hG1-L562P), the mutant hABCG1, like mG1-L550P, mainly resided intracellularly, whereas wild-type mABCG1 and hABCG1 were localized on the plasma membrane. However, replacement of this Leu with Pro had no significant effect on mABCG1- and hABCG1-mediated cholesterol efflux.
Leu at position 550/562 in mABCG1/hABCG1 is critical for their plasma membrane localization but not for ABCG1-mediated cholesterol efflux. Our findings indicate that the substitution of Leu to Pro at position 550 in mABCG1 may contribute to the non-cell surface localization of mABCG1 observed in the previous study.
三磷酸腺苷结合盒转运体 G1（ABCG1）介导胆固醇向酯化脂蛋白的外流。关于 ABCG1 的细胞定位及其对胆固醇外流的影响，已有相互矛盾的数据报道。在此，我们研究了这些不同观察结果的潜在机制。
使用共聚焦显微镜和生物素化来评估 ABCG1 的细胞表面定位。我们发现，之前一项研究中使用的小鼠 ABCG1（mABCG1）在位置 550 处发生亮氨酸到脯氨酸的取代（mG1-L550P）。当人 ABCG1（hABCG1）中位置 562 的相应亮氨酸突变为脯氨酸（hG1-L562P）时，突变的 hABCG1 与 mG1-L550P 一样，主要位于细胞内，而野生型 mABCG1 和 hABCG1 则位于质膜上。然而，这种亮氨酸到脯氨酸的替换对 mABCG1 和 hABCG1 介导的胆固醇外流没有显著影响。
mABCG1/hABCG1 中位置 550/562 的亮氨酸对于它们的质膜定位至关重要，但对于 ABCG1 介导的胆固醇外流并非如此。我们的发现表明，mABCG1 中位置 550 的亮氨酸到脯氨酸的取代可能导致之前研究中观察到的 mABCG1 的非质膜定位。
