Intramembrane aspartic acid in SCAP protein governs cholesterol-induced conformational change
Intramembrane aspartic acid in SCAP protein governs cholesterol-induced conformational change
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DOI：
10.1073/pnas.0500206102
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发表时间：
2005-03-01
影响因子：
11.1
通讯作者：
Goldstein, JL
中科院分区：
文献类型：
--
作者：
Feramisco, JD;Radhakrishnan, A;Goldstein, JL
多位膜蛋白 SCAP 将甾醇调节元件结合蛋白 (SREBP) 从内质网 (ER) 转运至高尔基体，从而激活胆固醇合成。内质网膜上的胆固醇积累会将 SCAP 改变为另一种构象，其中它与称为 Insigs 的内质网滞留蛋白结合，从而终止胆固醇合成。在这里，我们证明 SCAP 第六跨膜螺旋中保守的 Asp-428 对于 SCAP 从 Insigs 解离至关重要。在转染的仓鼠细胞中，当细胞中甾醇耗尽时，其中 Asp-428 被丙氨酸 (D428A) 取代的突变型 SCAP 仍保持 Insig 结合构象。结果，突变的 SCAP 未能与 Insigs 分离，也未能将 SREBP 携带到高尔基体。这些数据确定了 SCAP 中的重要功能残基，并提供了遗传证据，表明 SCAP 的构象决定了动物细胞中胆固醇合成的速率。
The polytopic membrane protein SCAP transports sterol regulatory element-binding proteins (SREBPs) from the endoplasmic reticulum (ER) to the Golgi, thereby activating cholesterol synthesis. Cholesterol accumulation in the ER membranes changes SCAP to an alternate conformation in which it binds ER retention proteins called Insigs, thereby terminating cholesterol synthesis. Here, we show that the conserved Asp-428 in the sixth transmembrane helix of SCAP is essential for SCAP's dissociation from Insigs. In transfected hamster cells, mutant SCAP in which Asp-428 is replaced by alanine (D428A) remained in an Insig-binding conformation when cells were depleted of sterols. As a result, mutant SCAP failed to dissociate from Insigs, and it failed to carry SREBPs to the Golgi. These data identify an important functional residue in SCAP, and they provide genetic evidence that the conformation of SCAP dictates the rate of cholesterol synthesis in animal cells.