Endosomal/lysosomal processing of gangliosides affects neuronal cholesterol sequestration in Niemann-Pick disease type C.
Endosomal/lysosomal processing of gangliosides affects neuronal cholesterol sequestration in Niemann-Pick disease type C.
复制标题
神经节苷脂的内体/溶酶体加工影响 C 型尼曼-皮克病的神经元胆固醇隔离。
DOI：
10.1016/j.ajpath.2011.04.017
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Walkley,StevenU
中科院分区：
文献类型：
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作者：
Zhou,Sharon;Davidson,Cristin;McGlynn,Robert;Stephney,Gloria;Dobrenis,Kostantin;Vanier,MarieT;Walkley,StevenU
C 型尼曼-匹克病 (NPC) 是一种由 NPC1 或 NPC2 蛋白缺陷引起的严重神经内脏溶酶体贮积症。尽管大量研究支持胆固醇储存的首要作用，但据报道，缺乏 NPC1 和合成所有复杂神经节苷脂所需的酶（β1,4GalNAc 转移酶）的双突变小鼠的神经元表现出胆固醇封存显着减少。在这里，我们发现缺乏这种酶的 NPC2 缺陷小鼠也表现出胆固醇降低，但基因限制仅合成 a 系列神经节苷脂可将神经元胆固醇储存完全恢复到典型的疾病水平。通过共聚焦显微镜检查缺乏 NPC1 或 NPC2 的神经元中隔离化合物的亚细胞位置，发现胆固醇和两种主要储存神经节苷脂（GM2 和 GM3）并不始终共定位于相同的细胞内囊泡内。为了确定 GM2 和 GM3 共定位的缺乏是否是由于合成途径与降解途径表达的差异所致，我们生成了同时缺乏 NPC1 和溶酶体 β-半乳糖苷酶的小鼠，因此无法在溶酶体中产生 GM2 和 GM3。双突变体缺乏两种神经节苷脂，表明每种神经节苷脂都是内体/溶酶体加工的产物。出乎意料的是，与单突变体相比，双突变体中的 GM1 积累增加，这与 NPC1 在神经节苷脂挽救中的直接作用一致。这些研究进一步证明 NPC1 和 NPC2 蛋白参与鞘脂和胆固醇的内体/溶酶体加工。
Niemann-Pick disease type C (NPC) is a severe neurovisceral lysosomal storage disorder caused by defects in NPC1 or NPC2 proteins. Although numerous studies support the primacy of cholesterol storage, neurons of double-mutant mice lacking both NPC1 and an enzyme required for synthesis of all complex gangliosides (β1,4GalNAc transferase) have been reported to exhibit dramatically reduced cholesterol sequestration. Here we show that NPC2-deficient mice lacking this enzyme also exhibit reduced cholesterol, but that genetically restricting synthesis to only a-series gangliosides fully restores neuronal cholesterol storage to typical disease levels. Examining the subcellular locations of sequestered compounds in neurons lacking NPC1 or NPC2 by confocal microscopy revealed that cholesterol and the two principal storage gangliosides (GM2 and GM3) were not consistently co-localized within the same intracellular vesicles. To determine whether the lack of GM2 and GM3 co-localization was due to differences in synthetic versus degradative pathway expression, we generated mice lacking both NPC1 and lysosomal β-galactosidase, and therefore unable to generate GM2 and GM3 in lysosomes. Double mutants lacked both gangliosides, indicating that each is the product of endosomal/lysosomal processing. Unexpectedly, GM1 accumulation in double mutants increased compared to single mutants consistent with a direct role for NPC1 in ganglioside salvage. These studies provide further evidence that NPC1 and NPC2 proteins participate in endosomal/lysosomal processing of both sphingolipids and cholesterol.