Cholesterol addition to ER membranes alters conformation of SCAP, the SREBP escort protein that regulates cholesterol metabolism
Cholesterol addition to ER membranes alters conformation of SCAP, the SREBP escort protein that regulates cholesterol metabolism
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DOI：
10.1016/s1097-2765(02)00591-9
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发表时间：
2002-08-01
期刊：
影响因子：
16
通讯作者：
Goldstein, JL
中科院分区：
文献类型：
--
作者：
Brown, AJ;Sun, LP;Goldstein, JL
膜上的固醇积聚阻断了SCAP从内质网的出口，阻止了SREBP的切割并减少了胆固醇的合成。甾醇通过SCAP的甾醇感应结构域发挥作用，机制尚不明确。在这里，我们表明，在体外将胆固醇添加到内质网膜上导致SCAP的构象变化，通过揭示紧密间隔的胰蛋白酶切割位点来检测。两种SCAP突变体（Y298C和D443N）在体内不受甾醇调节，在体外也不受甾醇诱导的构象改变。25-羟基胆固醇是体内SCAP的有效调节剂，但在体外不能改变SCAP的构象，这表明在完整细胞中，氧甾醇通过将胆固醇从质膜转运到内质膜而起作用。这些研究证明了胆固醇对固醇调节机制的体外作用。
Sterol accumulation in membranes blocks the exit of SCAP from the ER, preventing SREBP cleavage and reducing cholesterol synthesis. Sterols act through SCAP's sterol-sensing domain by an obscure mechanism. Here, we show that addition of cholesterol to ER membranes in vitro causes a conformational change in SCAP, detected by the unmasking of closely spaced trypsin cleavage sites. Two mutant forms of SCAP (Y298C and D443N) that are refractory to sterol regulation in vivo are also refractory to sterol-induced conformational change in vitro. 25-hydroxycholesterol, a potent regulator of SCAP in vivo, fails to change SCAP's conformation in vitro, suggesting that oxysterols act in intact cells by translocating cholesterol from plasma membrane to ER. These studies demonstrate an in vitro effect of cholesterol on the sterol regulatory machinery.