Different studies demonstrate that in glial cells ceramide (Cer) exerts antiproliferative and proapoptotic effects, and strongly support that Cer-signalling is altered in glial tumors. The control of ceramide levels in glial cells involves specific enzymes which are known to be localized in different subcellular compartments as well as Cer movements along the sphingomyelin biosynthetic pathway. A key element in defining the role of Cer in sphingolipid metabolism and signalling is its hydrophobic nature, and its consequent inability to spontaneously move among different subcellular sites where the enzymes of its metabolism and its molecular targets are located. Based on this evidence, the biological effect exerted by Cer may depend on the presence of specific signalling pools of this bioactive sphingoid in the cell, as well as the regulation of its intracellular traffic. Recently, the identification in CHO cells of the Cer specific carrier protein CERT have revealed a novel pathway for the delivery of Cer to the Golgi apparatus for sphingomyelin biosynthesis. In this study we investigated the metabolic and functional role of CERT in glioma cells. All glioma cells analyzed constitutively express CERT, the protein being mainly associated to thecytosolic fraction. Metabolic experiments performed with different radioactive metabolic precursors of sphigolipids indicate that, in all analyzed glioma cells, downregulation of CERT by RNA interference technology promoted a significant but not complete reduction of the amount of Cer converted to SM. This suggests that in glioma cells CERT mediated Cer transport contributes in addressing ceramide toward sphingomyelin biosynthesis. Since the regulation of sphingomyelin biosynthesis represents a crucial step in the role of ceramide on glial cell proliferation we evaluated the possible role of CERT in the control of glioma cell proliferation. We found that in all glioma cells down regulation of CERT resulted in an increased cell proliferation associated to higher ERK1/2 phosphorylation. In vitro and in vivo experiments indicated that CERT is necessary for the inhibition exerted by Cer on ERK activation. In conclusion these results suggest that CERT, besides the involvement in sphingolipid metabolism, participates to Cer signalling and could play a role in the control of glioma cell proliferation.

Metabolic and functional role of the ceramide binding protein CERT in glioma cells / P. Giussani, T. Colleoni, R. Bassi, L. Brioschi, G. Tettamanti, K. Hanada, L. Riboni, P. Viani. - In: NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY. - ISSN 0028-1298. - 374:4(2007 Jan), pp. 328-329. ((Intervento presentato al 5. convegno International Meeting of the Sphingolipid Club tenutosi a Calella de la Costa nel 2006 [10.1007/s00210-006-0116-8].

Metabolic and functional role of the ceramide binding protein CERT in glioma cells

P. Giussani
Primo
;
T. Colleoni
Secondo
;
R. Bassi;L. Brioschi;G. Tettamanti;L. Riboni
Penultimo
;
P. Viani
Ultimo
2007-01

Abstract

Different studies demonstrate that in glial cells ceramide (Cer) exerts antiproliferative and proapoptotic effects, and strongly support that Cer-signalling is altered in glial tumors. The control of ceramide levels in glial cells involves specific enzymes which are known to be localized in different subcellular compartments as well as Cer movements along the sphingomyelin biosynthetic pathway. A key element in defining the role of Cer in sphingolipid metabolism and signalling is its hydrophobic nature, and its consequent inability to spontaneously move among different subcellular sites where the enzymes of its metabolism and its molecular targets are located. Based on this evidence, the biological effect exerted by Cer may depend on the presence of specific signalling pools of this bioactive sphingoid in the cell, as well as the regulation of its intracellular traffic. Recently, the identification in CHO cells of the Cer specific carrier protein CERT have revealed a novel pathway for the delivery of Cer to the Golgi apparatus for sphingomyelin biosynthesis. In this study we investigated the metabolic and functional role of CERT in glioma cells. All glioma cells analyzed constitutively express CERT, the protein being mainly associated to thecytosolic fraction. Metabolic experiments performed with different radioactive metabolic precursors of sphigolipids indicate that, in all analyzed glioma cells, downregulation of CERT by RNA interference technology promoted a significant but not complete reduction of the amount of Cer converted to SM. This suggests that in glioma cells CERT mediated Cer transport contributes in addressing ceramide toward sphingomyelin biosynthesis. Since the regulation of sphingomyelin biosynthesis represents a crucial step in the role of ceramide on glial cell proliferation we evaluated the possible role of CERT in the control of glioma cell proliferation. We found that in all glioma cells down regulation of CERT resulted in an increased cell proliferation associated to higher ERK1/2 phosphorylation. In vitro and in vivo experiments indicated that CERT is necessary for the inhibition exerted by Cer on ERK activation. In conclusion these results suggest that CERT, besides the involvement in sphingolipid metabolism, participates to Cer signalling and could play a role in the control of glioma cell proliferation.
Settore BIO/10 - Biochimica
Settore BIO/12 - Biochimica Clinica e Biologia Molecolare Clinica
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/30633
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