Defective endocytic trafficking of NPC1 and NPC2 underlying infantile Niemann-Pick type C disease
Defective endocytic trafficking of NPC1 and NPC2 underlying infantile Niemann-Pick type C disease
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DOI：
10.1093/hmg/ddg025
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发表时间：
2003-02-01
影响因子：
3.5
通讯作者：
Ikonen, E
中科院分区：
文献类型：
--
作者：
Blom, TS;Linder, MD;Ikonen, E
C 型尼曼-匹克 (NPC) 病是一种致命的隐性遗传性溶酶体胆固醇鞘脂沉积症。 95%的病例是由NPC1基因突变引起的，其余是由NPC2突变引起的。这里剖析了该疾病的严重婴儿形式的分子基础。患者成纤维细胞中的 NPC1 蛋白水平与对照细胞中相似。然而，该蛋白质部分地从晚期内吞细胞器错误定位到细胞周围。相反，NPC2 在储存胆固醇的晚期内吞细胞器中上调并积累。在 NPC1 基因中发现了两个点突变和一个四核苷酸缺失，导致氨基酸取代 C113R、P237S 和 37 个 C 端氨基酸缺失 (delC)。单个 NPC1 突变的过度表达表明 delC 产生不稳定的蛋白质，野生型和 NPC1-P237S 与 Rab7 阳性晚期内体共定位，而 NPC1-C113R 定位于 ER、Rab7 阴性内体和细胞表面。野生型或 NPC1-P237S 的表达清除了 NPC1 缺陷细胞中溶酶体胆固醇的积累，而 C113R 或 delC 则没有。在芬兰和瑞典人群样本中，未发现携带 C113R 或 delC 的等位基因，而大约 5% 的等位基因携带 P237S。我们的研究确定 P237S 是一种普遍的 NPC1 多态性，delC 和 C113R 是有害的 NPC1 突变。此外，他们表明 delC 导致 NPC1 和 C113R 快速降解，导致蛋白质内吞错配。这些变化伴随着 NPC2 的溶酶体积累，表明 NPC1 控制 NPC2 的内吞转运。
Niemann-Pick type C (NPC) disease is a fatal recessively inherited lysosomal cholesterol-sphingolipidosis. Mutations in the NPC1 gene cause similar to95% of the cases, the rest being caused by NPC2 mutations. Here the molecular basis of a severe infantile form of the disease was dissected. The level of NPC1 protein in the patient fibroblasts was similar to that in control cells. However, the protein was partially mislocalized from late endocytic organelles diffusely to the cell periphery. In contrast, NPC2 was upregulated and accumulated in cholesterol storing late endocytic organelles. Two point mutations and a four-nucleotide deletion were identified in the NPC1 gene, leading to the amino acid substitutions C113R, P237S and deletion of 37 C-terminal amino acids (delC). Overexpression of individual NPC1 mutations revealed that delC produced an unstable protein, wild-type and NPC1-P237S colocalized with Rab7-positive late endosomes whereas NPC1-C113R localized to the ER, Rab7-negative endosomes and the cell surface. Expression of wild-type or NPC1-P237S cleared the lysosomal cholesterol accumulation in NPC1-deficient cells whereas C113R or delC did not. in the Finnish and Swedish population samples, alleles carrying C113R or delC were not identified, whereas similar to5% of the alleles carried P237S. Our studies identify P237S as a prevalent NPC1 polymorphism and delC and C113R as deleterious NPC1 mutations. Moreover, they show that delC leads to rapid degradation of NPC1 and C113R to endocytic missorting of the protein. These changes are accompanied by lysosomal accumulation of NPC2, suggesting that NPC1 governs the endocytic transport of NPC2.