Ceramide traffic in C6 glioma cells: Evidence for CERT-dependent and independent transport from ER to the Golgi apparatus
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- 作者：Paola Giussani ; Thomas Colleoni ; Loredana Brioschi ; Rosaria Bassi ; Kentaro Hanada ; Guido Tettamanti ; Laura Riboni ; Paola Viani
- 关键词：Ceramide ; CERT ; Nitric oxide ; Glioma cells ; Sphingolipid traffic
- 刊名：Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids
- 出版年：2008
- 出版时间：January-February 2008
- 年：2008
- 卷：1781
- 期：1-2
- 页码：40-51
- 全文大小：1316 K
文摘
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.