Role of STARD4 in sterol transport between the endocytic recycling compartment and the plasma membrane.
Role of STARD4 in sterol transport between the endocytic recycling compartment and the plasma membrane.
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DOI：
10.1091/mbc.e16-07-0499
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发表时间：
2017-04-15
影响因子：
3.3
通讯作者：
Maxfield FR
中科院分区：
文献类型：
--
作者：
Iaea DB;Mao S;Lund FW;Maxfield FR
使用荧光显微镜测量质膜和内吞再循环隔室之间的固醇运输的动力学。STARD 4是一种小的可溶性固醇转运蛋白，负责总转运的25%和非囊泡转运的33%。胆固醇升高显著增加固醇转运速率常数。胆固醇是哺乳动物细胞膜的重要组成部分。细胞膜和内吞再循环室（ERC）都高度富集胆固醇。胆固醇在细胞器中的丰度和分布受到囊泡和非囊泡固醇转运过程机制的严格控制。使用荧光胆固醇类似物脱氢麦角甾醇，我们研究了甾醇之间的质膜和ERC使用荧光恢复后光漂白和一种新的甾醇流出测定。我们发现，在U2 OS细胞系中，这些细胞器之间的甾醇运输有一个t1/2 = 1/2 -15分钟。大约70%的甾醇运输是ATP独立的，因此是非囊泡。增加细胞胆固醇水平显著增加双向转运速率常数，但胆固醇水平的降低只有适度的影响。可溶性固醇转运蛋白STARD 4占质膜和ERC之间总固醇转运的约25%，占非囊泡固醇转运的约33%。这项研究表明，非囊泡固醇运输机制和STARD 4，特别是占很大一部分的固醇运输之间的质膜和ERC。
The kinetics of sterol transport between the plasma membrane and the endocytic recycling compartment is measured using fluorescence microscopy. STARD4, a small, soluble sterol transport protein, is responsible for 25% of the total transport and 33% of nonvesicular transport. Elevated cholesterol dramatically increases sterol transport rate constants. Cholesterol is an essential constituent of membranes in mammalian cells. The plasma membrane and the endocytic recycling compartment (ERC) are both highly enriched in cholesterol. The abundance and distribution of cholesterol among organelles are tightly controlled by a combination of mechanisms involving vesicular and nonvesicular sterol transport processes. Using the fluorescent cholesterol analogue dehydroergosterol, we examined sterol transport between the plasma membrane and the ERC using fluorescence recovery after photobleaching and a novel sterol efflux assay. We found that sterol transport between these organelles in a U2OS cell line has a t1/2 =12–15 min. Approximately 70% of sterol transport is ATP independent and therefore is nonvesicular. Increasing cellular cholesterol levels dramatically increases bidirectional transport rate constants, but decreases in cholesterol levels have only a modest effect. A soluble sterol transport protein, STARD4, accounts for ∼25% of total sterol transport and ∼33% of nonvesicular sterol transport between the plasma membrane and ERC. This study shows that nonvesicular sterol transport mechanisms and STARD4 in particular account for a large fraction of sterol transport between the plasma membrane and the ERC.