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首页> 外文期刊>Cell metabolism >Switch-like control of SREBP-2 transport triggered by small changes in ER cholesterol: a delicate balance.
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Switch-like control of SREBP-2 transport triggered by small changes in ER cholesterol: a delicate balance.

机译：ER胆固醇的微小变化触发了SREBP-2转运的开关状控制：微妙的平衡。

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摘要

Animal cells control their membrane lipid composition within narrow limits, but the sensing mechanisms underlying this control are largely unknown. Recent studies disclosed a protein network that controls the level of one lipid-cholesterol. This network resides in the endoplasmic reticulum (ER). A key component is Scap, a tetrameric ER membrane protein that binds cholesterol. Cholesterol binding prevents Scap from transporting SREBPs to the Golgi for activation. Using a new method to purify ER membranes from cultured cells, we show that Scap responds cooperatively to ER cholesterol levels. When ER cholesterol exceeds 5% of total ER lipids (molar basis), SREBP-2 transport is abruptly blocked. Transport resumes when ER cholesterol falls below the 5% threshold. The 5% threshold is lowered to 3% when cells overexpress Insig-1, a Scap-binding protein. Cooperative interactions between cholesterol, Scap, and Insig create a sensitive switch that controls the cholesterol composition of cell membranes with remarkable precision.
机译：动物细胞将其膜脂质组成控制在狭窄的范围内，但这种控制的感应机制在很大程度上尚不清楚。最近的研究揭示了控制一种脂质胆固醇水平的蛋白质网络。该网络位于内质网（ER）中。关键成分是Scap，一种结合胆固醇的四聚体ER膜蛋白。胆固醇结合阻止Scap将SREBPs转运至高尔基体进行活化。使用一种新的方法从培养的细胞中纯化ER膜，我们显示Scap协同响应ER胆固醇水平。当ER胆固醇超过总ER脂质（以摩尔计）的5％时，SREBP-2转运会突然被阻断。当ER胆固醇降至5％阈值以下时，运输恢复。当细胞过表达Scap结合蛋白Insig-1时，阈值从5％降低到3％。胆固醇，Scap和Insig之间的协作相互作用产生了一个灵敏的开关，该开关可以以极高的精度控制细胞膜的胆固醇成分。

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