Role of ORPs in Sterol Transport from Plasma Membrane to ER and Lipid Droplets in Mammalian Cells
Role of ORPs in Sterol Transport from Plasma Membrane to ER and Lipid Droplets in Mammalian Cells
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DOI：
10.1111/j.1600-0854.2010.01142.x
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发表时间：
2011-02-01
期刊：
影响因子：
4.5
通讯作者：
Ikonen, Elina
中科院分区：
文献类型：
--
作者：
Jansen, Maurice;Ohsaki, Yuki;Ikonen, Elina
在这项研究中，我们研究了HeLa细胞中固醇从质膜(PM)到内质网(ER)和脂滴(LDS)的转运机制。通过过量表达所有哺乳动物氧固醇结合蛋白相关蛋白(ORPs)，我们发现特别是ORP1S和ORP2促进了PM到LD的类固醇运输。这反映了从PM到ER的运输刺激，而不是从ER到LDS的运输。ORP1S和ORP2的双重敲除抑制了类固醇从PM到内质网和低密度脂蛋白的运输，表明这些ORP在这一过程中发挥了生理作用。ORPs中介导与内质网中VAMP相关蛋白(VAP)相互作用的两个酸性途径中的两个苯丙氨酸(FFAT)基序对于促进ORPs的固醇转运并不是必需的。然而，VAP-A和VAP-B的沉默减缓了PM到LD的类固醇运输。这伴随着ORP2的加速降解和几个含有FFAT基序的ORPs水平的下降，表明VAP通过稳定ORPs在固醇运输中发挥作用。
In this study, we investigated the mechanisms of sterol transport from the plasma membrane (PM) to the endoplasmic reticulum (ER) and lipid droplets (LDs) in HeLa cells. By overexpressing all mammalian oxysterol-binding protein-related proteins (ORPs), we found that especially ORP1S and ORP2 enhanced PM-to-LD sterol transport. This reflected the stimulation of transport from the PM to the ER, rather than from the ER to LDs. Double knockdown of ORP1S and ORP2 inhibited sterol transport from the PM to the ER and LDs, suggesting a physiological role for these ORPs in the process. A two phenylalanines in an acidic tract (FFAT) motif in ORPs that mediates interaction with VAMP-associated proteins (VAPs) in the ER was not necessary for the enhancement of sterol transport by ORPs. However, VAP-A and VAP-B silencing slowed down PM-to-LD sterol transport. This was accompanied by enhanced degradation of ORP2 and decreased levels of several FFAT motif-containing ORPs, suggesting a role for VAPs in sterol transport by stabilization of ORPs.