The Degradative Pathway of Gangliosides GM1 and GM2 in Neuro2a Cells by Sialidase
The Degradative Pathway of Gangliosides GM1 and GM2 in Neuro2a Cells by Sialidase
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Neuro2a细胞中神经节苷脂GM1和GM2唾液酸酶的降解途径
DOI：
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发表时间：
1995
影响因子：
4.7
通讯作者：
G. Tettamanti
中科院分区：
文献类型：
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作者：
L. Riboni;Antonella Caminiti;R. Bassi;G. Tettamanti
摘要：将神经节苷类GM1 [3H标记在鞘氨酸（Sph）片段]和GM2 [3H标记在Sph或N -乙酰半乳糖胺（GalNAc）片段]分别给予培养的Neuro2a细胞不同的脉冲（1-4小时）和追逐（长达4小时）周期，并观察它们的代谢过程。[Sph‐3H]GM1的主要和最早形成的3H代谢物是GM2、asialo‐GM1、asialo‐GM2和乳糖‐神经酰胺，[Sph‐3H]GM2的主要和最早形成的3H代谢物是asialo‐GM2和乳糖‐神经酰胺。分离得到了asialo‐GM1和asialo‐GM2，并对其进行了化学表征。[3H]Asialo‐GM2在等摩尔[Sph‐3H]GM2和[GalNAc‐3H]GM2处理后产量相同。在低温或氯喹存在下，所有3H代谢产物（包括asialo‐GM2和asialo‐GM1）的形成都无法检测到，这表明神经节苷脂代谢过程是一个依赖于内吞作用和溶酶体的过程。这些结果表明，在Neuro2a细胞中，外源性GM1（和GM2）主要通过GM1→GM2→asialo‐GM2→→Sph途径降解，少部分GM1的降解顺序为GM1→asialo‐GM1→asialo‐GM2→→Sph。这些发现与Neuro2a细胞含有影响神经节苷脂GM1和GM2的唾液酸酶（可能是溶酶体性质）的假设是一致的。神经2a细胞中唾液酸酶介导的GM1和GM2的降解途径可能与这些细胞的肿瘤性质有关。
Abstract: Gangliosides GM1 [3H‐labeled at the sphingosine (Sph) moiety] and GM2 [3H‐labeled at the Sph or N‐acetylgalactosamine (GalNAc) moiety] were administered to cultured Neuro2a cells for varying pulse (1–4 h) and chase (up to 4 h) periods, and their metabolic processing was followed. The main and earliest formed 3H‐metabolites of [Sph‐3H]GM1 were GM2, asialo‐GM1, asialo‐GM2, and lactose‐ceramide, and those of [Sph‐3H]GM2 were asialo‐GM2 and lactose‐ceramide. The asialo‐GM1 and asialo‐GM2 formed were isolated and chemically characterized. [3H]Asialo‐GM2 was produced in identical amounts after treatment with equimolar [Sph‐3H]GM2 and [GalNAc‐3H]GM2. At low temperature or in the presence of chloroquine, the formation of all 3H‐metabolites, including asialo‐GM2 and asialo‐GM1, was undetectable, indicating that ganglioside metabolic processing was an endocytosis‐ and lysosome‐dependent process. These results demonstrate that in Neuro2a cells exogenous GM1 (and GM2) is mainly degraded through the pathway GM1 → GM2 → asialo‐GM2 →→ Sph, with a minor fraction of GM1 undergoing degradation with the sequence GM1 → asialo‐GM1 → asialo‐GM2 →→ Sph. These findings are consistent with the hypothesis that Neuro2a cells contain a sialidase (likely of lysosomal nature) affecting ganglioside GM1 and GM2. The sialidase‐mediated degradative pathway of GM1 and GM2 in Neuro2a cells might be related to the tumoral nature of these cells.