Suchergebnisse

Metabolic reprogramming, a crucial cancer hallmark, shifts metabolic pathways such as glycolysis, tricarboxylic acid cycle or lipogenesis, to enable the growth characteristics of cancer cells. Here, we provide evidence that transketolase-like 1 (TKTL1) orchestrates aerobic glycolysis, fatty acid and nucleic acid synthesis, glutamine metabolism, protection against oxidative stress and cell proliferation. Furthermore, silencing of TKTL1 reduced the levels of sphingolipids such as lactosylceramide (a sphingolipid regulating cell survival, proliferation and angiogenesis) and phosphatidylinositol (which activates PI3K/Akt/mTOR signaling). Thus, in addition to its well-known roles in glucose and amino acid metabolism, TKTL1 also regulates lipid metabolism. In conclusion, our study provides unprecedented evidence that TKTL1 plays central roles in major metabolic processes subject to reprogramming in cancer cells and thus identifies TKTL1 as a promising target for new anti-cancer therapies. ; This work was supported by grants to M.C. (Agència de Gestió d'Ajuts Universitaris i de Recerca (AGAUR) – Generalitat de Catalunya, 2014SGR1017; ICREA Academia from the ICREA foundation; and MINECO-European Commission FEDER – Una manera de hacer Europa, SAF2014-56059-R), T.M.T. (MINECO-European Commission FEDER – Una manera de hacer Europa, SAF2015-66984-C2-1-R; and Xarxa de Referència en Biotecnologia) and P.C. (Research Foundation-Flanders (FWO), Belgian Science Policy grant (IUAP P7/03); long-term structural Methusalem funding by the Flemish Government; European Research Council (ERC) Advanced Research Grant (EU-ERC269073); and AXA Research Fund). ; Peer Reviewed

Carbohydrate response element-binding protein (ChREBP) is a transcription factor that mediates glucose signaling in mammalian liver, leading to the expression of different glycolytic and lipogenic genes, such as pyruvate kinase (L-PK) and fatty acid synthase (FAS). The current model for ChREBP activation in response to sugar phosphates holds that glucose metabolization to xylulose 5-phosphate (X-5-P) triggers the activation of protein phosphatase 2A, which dephosphorylates ChREBP and leads to its nuclear translocation and activation. However, evidence indicates that glucose 6-phosphate (G-6-P) is the most likely signal metabolite for the glucose-induced transcription of these genes. The glucose derivative that is responsible for carbohydrate-dependent gene expression remains to be identified. The difficulties in measuring G-6-P and X-5-P concentrations simultaneously and in changing them independently have hindered such identification. To discriminate between these possibilities, we adapted a liquid chromatography mass spectrometry method to identify and quantify sugar phosphates in human hepatocarcinoma cells (Hep G2) and rat hepatocytes in response to different carbon sources and in the presence/absence of a glucose-6-phosphate dehydrogenase inhibitor. We also used this method to demonstrate that these cells could not metabolize 2-deoxyglucose beyond 2-deoxyglucose-6-phosphate. The simultaneous quantification of sugar phosphates and FAS and L-PK expression levels demonstrated that both X-5-P and G-6-P play a role in the modulation of gene expression. In conclusion, this report presents for the first time a single mechanism that incorporates the effects of X-5-P and G-6-P on the enhancement of the expression of carbohydrate-responsive genes. © 2012 the American Physiological Society. ; This study was supported by the projects SAF2009-12602 and SAF2011-25726 and by RD06/0020/0046 and RD06/0014/0025 from Red Temática de Investigación Cooperativa en Cáncer and Red de Centros FIS-RECAVA, respectively, from the Instituto de Salud Carlos III, both funded by the Ministerio de Ciencia e Innovación-Spanish government and European Regional Development Funds "Una manera de hacer Europa." It has also received financial support from the European Union-funded project ETHERPATHS (FP7-KBBE-222639) (http://www.etherpaths.org/) and from the Agència de Gestió d'Ajuts Universitaris i de Recerca-Generalitat de Catalunya (2009SGR01308, 2006ITT-10007, and 2009CTP-00026). ; Peer Reviewed