The sterol-sensing domain of the Niemann-Pick C1 (NPC1) protein regulates trafficking of low density lipoprotein cholesterol
The sterol-sensing domain of the Niemann-Pick C1 (NPC1) protein regulates trafficking of low density lipoprotein cholesterol
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DOI：
10.1074/jbc.m414024200
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发表时间：
2005-08-05
影响因子：
4.8
通讯作者：
Ory, DS
中科院分区：
文献类型：
--
作者：
Millard, EE;Gale, SE;Ory, DS
尼曼-匹克C1（NPC 1）蛋白是细胞内固醇运输和胆固醇稳态调节的关键参与者。NPC 1含有一个五螺旋区域，该区域在进化上与参与甾醇相互作用或甾醇代谢的其他多位蛋白中发现的甾醇敏感结构域相关，包括甾醇调节元件结合蛋白裂解激活蛋白和羟甲基戊二酰辅酶A还原酶。为了深入了解NPC 1的固醇敏感结构域的作用，我们检查了NPC 1固醇敏感结构域中的点突变对低密度脂蛋白衍生的胆固醇和鞘脂的运输的影响。我们发现，NPC 1 P692 S功能缺失突变导致胆固醇向质膜和内质网的传递减少。相比之下，携带L 657 F或D 787 N点突变的NPC 1蛋白，其分别对应于激活SCAP L315 F和D443 N突变，表现出功能表型的获得。具体地，表达NPC 1 L 657 F或D 787 N突变的细胞系显示低密度脂蛋白胆固醇运输至质膜和内质网的速率增加近2倍，并且更快速地抑制固醇调节元件结合蛋白依赖性基因表达。鞘脂的运输在D 787 N和L 657 F细胞系中是完整的。我们发现D 787 N和L 657 F是激活NPC 1突变，这为胆固醇稳态蛋白中固醇敏感结构域的保守机制提供了证据。
The Niemann-Pick C1 ( NPC1) protein is a key participant in intracellular sterol trafficking and regulation of cholesterol homeostasis. NPC1 contains a pentahelical region that is evolutionarily related to sterol-sensing domains found in other polytopic proteins involved in sterol interactions or sterol metabolism, including sterol regulatory element-binding protein cleavage-activating protein and hydroxymethylglutaryl-CoA reductase. To gain insight into the role of the sterol-sensing domain of NPC1, we examined the effect of point mutations in the NPC1 sterol- sensing domain on the trafficking of low density lipoprotein-derived cholesterol and sphingolipids. We show that an NPC1 P692S loss of function mutation results in decreased cholesterol delivery to the plasma membrane and endoplasmic reticulum. By contrast, NPC1 proteins carrying a L657F or D787N point mutation, which correspond to the activating SCAP L315F and D443N mutations, respectively, exhibit a gain of function phenotype. Specifically, cell lines expressing the NPC1 L657F or D787N mutations show a nearly 2-fold increase in the rates of low density lipoprotein cholesterol trafficking to the plasma membrane and to the endoplasmic reticulum, and more rapid suppression of sterol regulatory element-binding protein-dependent gene expression. Trafficking of sphingolipids is intact in the D787N and L657F cell lines. Our finding that D787N and L657F are activating NPC1 mutations provide evidence for a conserved mechanism for the sterol- sensing domain among cholesterol homeostatic proteins.