Autophagy in Niemann-Pick C disease is dependent upon Beclin-1 and responsive to lipid trafficking defects
Autophagy in Niemann-Pick C disease is dependent upon Beclin-1 and responsive to lipid trafficking defects
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DOI：
10.1093/hmg/ddm100
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发表时间：
2007-06-15
影响因子：
3.5
通讯作者：
Lieberman, Andrew P.
中科院分区：
文献类型：
--
作者：
Pacheco, Chris D.;Kunkel, Robin;Lieberman, Andrew P.
尼曼-皮克C(NPC)病是一种常染色体隐性脂质储存障碍，其特征是鞘脂和胆固醇运输中断，导致认知障碍、共济失调和死亡，通常在儿童时期。大多数病例是由NPC1基因功能突变引起的，NPC1基因编码一种定位于晚期内小体的蛋白质，并在脂质分类和囊泡运输中发挥功能。在这里，我们证明了NPC1缺陷的原代人成纤维细胞，如NPC1(-/-)小鼠成纤维细胞，表现出自噬增加，表现为Lc3-II水平升高，大量自噬空泡和长寿命蛋白的加速降解。由于NPC1缺乏导致的自噬与Beclin-1的表达增加有关，而不是与Akt-mTor-p70 S6K信号通路的激活有关，Beclin-1的siRNA敲除减少了长寿命蛋白的降解。U18666A诱导野生型成纤维细胞胆固醇转运缺陷可增加Beclin-1和Lc3-II的表达，而NPC1缺陷的成纤维细胞经降脂化合物NB-DGJ处理后，Beclin-1和Lc3-II的表达均未发生改变。NPC2缺乏症和Sandhoff病患者的原代成纤维细胞也显示Beclin-1和Lc3-II水平升高。相比之下，正常运输鞘脂的高谢病成纤维细胞显示出野生型Beclin-1和LC3-II水平。我们的数据定义了Beclin-1在由于NPC1缺乏而激活自噬过程中的关键作用，并揭示了脂运输在几种鞘磷脂储存性疾病患者这一途径的调节中出人意料的作用。
Niemann-Pick C (NPC) disease is an autosomal recessive lipid storage disorder characterized by a disruption of sphingolipid and cholesterol trafficking that produces cognitive impairment, ataxia and death, often in childhood. Most cases are caused by loss of function mutations in the Npc1 gene, which encodes a protein that localizes to late endosomes and functions in lipid sorting and vesicle trafficking. Here, we demonstrate that NPC1-deficient primary human fibroblasts, like npc1(-/-) mice fibroblasts, showed increased autophagy as evidenced by elevated LC3-II levels, numerous autophagic vacuoles and enhanced degradation of long-lived proteins. Autophagy because of NPC1 deficiency was associated with increased expression of Beclin-1 rather than activation of the Akt-mTOR-p70 S6K signaling pathway, and siRNA knockdown of Beclin-1 decreased long-lived protein degradation. Induction of cholesterol trafficking defects in wild-type fibroblasts by treatment with U18666A increased Beclin-1 and LC3-II expression, whereas treatment of NPC1-deficient fibroblasts with sphingolipid-lowering compound NB-DGJ failed to alter the expression of either Beclin-1 or LC3-II. Primary fibroblasts from patients with two other sphingolipid storage diseases, NPC2 deficiency and Sandhoff disease, characterized by sphingolipid trafficking defects also showed elevation in Beclin-1 and LC3-II levels. In contrast, Gaucher disease fibroblasts, which traffic sphingolipids normally, showed wild-type levels of Beclin-1 and LC3-II. Our data define a critical role for Beclin-1 in the activation of autophagy because of NPC1 deficiency, and reveal an unexpected role for lipid trafficking in the regulation of this pathway in patients with several sphingolipid storage diseases.