Ceramide traffic in C6 glioma cells: Evidence for CERT-dependent and independent transport from ER to the Golgi apparatus
Ceramide traffic in C6 glioma cells: Evidence for CERT-dependent and independent transport from ER to the Golgi apparatus
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DOI：
10.1016/j.bbalip.2007.11.002
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发表时间：
2008-01-01
影响因子：
4.8
通讯作者：
Viani, Paola
中科院分区：
文献类型：
--
作者：
Giussani, Paola;Colleoni, Thomas;Viani, Paola
神经酰胺的细胞内运动受到其疏水性的强烈限制，神经酰胺运输的机制可以代表鞘脂代谢和信号传导的一个重要方面。最近神经酰胺特异性载体蛋白CERT的鉴定揭示了神经酰胺递送到高尔基体进行鞘磷脂生物合成的新途径。在本研究中，我们研究了CERT在C6胶质瘤细胞中的代谢和功能作用。发现这些细胞组成性地表达CERT，该蛋白主要与细胞质部分相关。对不同放射性鞘脂代谢前体的代谢实验表明，通过RNAi技术下调CERT导致神经酰胺对鞘磷脂的代谢显著但不完全减少，但不影响其对鞘脂糖生物合成的利用。由于一氧化氮是C6胶质瘤细胞中神经酰胺ER-to-Golgi运输和代谢的抑制剂，我们评估了cert介导的神经酰胺运输可能代表一氧化氮靶点的可能性。结果表明，CERT下调不影响一氧化氮对Cer代谢的抑制活性，一氧化氮与CERT沉默对神经酰胺利用的影响是叠加的。这些结果有力地表明，cert介导的和cert独立的一氧化氮敏感的Cer转运在C6胶质瘤细胞中共存，并分别有助于控制这些细胞的鞘脂代谢和Cer水平。(c) 2007 Elsevier b.v.版权所有
Intracellular movements of ceramide are strongly limited by its hydrophobic nature,and the mechanisms involved in ceramide transport can represent a crucial aspect of sphingolipid metabolism and signaling. The recent identification of the ceramide specific carrier protein CERT has revealed a novel pathway for the delivery of ceramide to the Golgi apparatus for sphingomyelin biosynthesis. In this study we investigated the metabolic and functional role of CERT in C6 glioma cells. These cells were found to constitutively express CERT, the protein being mainly associated with the cytosolic fraction. Metabolic experiments performed with different radioactive metabolic precursors of sphingolipids demonstrated that the down regulation of CERT by RNAi technology resulted in a significant but not complete reduction of ceramide metabolism to sphingomyelin, without affecting its utilization for glycosphingolipid biosynthesis. Since nitric oxide is an inhibitor of ceramide ER-to-Golgi traffic and metabolism in C6 glioma cells, we evaluated the possibility that the CERT-mediated transport of ceramide might represent a target for nitric oxide. The data obtained demonstrate that CERT down regulation does not affect the inhibitory activity of nitric oxide on Cer metabolism, and the effects of nitric oxide and CERT silencing on ceramide utilization were additive. These results strongly suggest that a CERT-mediated and a CERT-independent, nitric oxide-sensitive Cer transport coexist in C6 glioma cells and can separately contribute to the control of sphingolipid metabolism and Cer levels in these cells. (c) 2007 Elsevier B.V All rights reserved.