Crucial step in cholesterol homeostasis: Sterols promote binding of SCAP to INSIG-1, a membrane protein that facilitates retention of SREBPs in ER
Crucial step in cholesterol homeostasis: Sterols promote binding of SCAP to INSIG-1, a membrane protein that facilitates retention of SREBPs in ER
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DOI：
10.1016/s0092-8674(02)00872-3
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发表时间：
2002-08-23
期刊：
影响因子：
64.5
通讯作者：
Brown, MS
中科院分区：
文献类型：
--
作者：
Yang, T;Espenshade, PJ;Brown, MS
使用免疫共沉淀和串联质谱，我们确定INSIG-1作为一种ER蛋白，结合SREBP裂解激活蛋白（SCAP）的甾醇敏感结构域，并促进SCAP/SREBP复合物在ER中的保留。在甾醇耗尽的细胞中，SCAP护送SREBP从ER到高尔基体进行蛋白水解加工，从而允许SREBP刺激胆固醇合成。如通过蓝色非变性PAGE所确定的，甜菊糖诱导SCAP与INSIG-11的结合，并且这与抑制SCAP从ER退出相关。INSIG-1的过表达增加了细胞对固醇介导的SREBP加工抑制的敏感性。突变体SCAP（Y298 C）不能结合INSIG-11，并且对固醇介导的ER退出抑制具有抗性。通过促进SCAP的固醇依赖性ER保留，INSIG-11在胆固醇稳态中起核心作用。
Using coimmunoprecipitation and tandem mass spectrometry, we identify INSIG-1 as an ER protein that binds the sterol-sensing domain of SREBP cleavage-activating protein (SCAP) and facilitates retention of the SCAP/SREBP complex in the ER. In steroldepleted cells, SCAP escorts SREBPs from ER to Golgi for proteolytic processing, thereby allowing SREBPs to stimulate cholesterol synthesis. Sterols induce binding of SCAP to INSIG-11, as determined by blue native-PAGE, and this is correlated with the inhibition of SCAP exit from the ER. Overexpression of INSIG-1 increases the sensitivity of cells to sterol-mediated inhibition of SREBP processing. Mutant SCAP(Y298C) fails to bind INSIG-11 and is resistant to sterol-mediated inhibition of ER exit. By facilitating sterol -dependent ER retention of SCAP, INSIG-11 plays a central role in cholesterol homeostasis.