Wang et al. Oncogenesis (2018) 7:26 DOI 10.1038/s41389-018-0036-8 Oncogenesis ARTICLE Open Access Molecular link between glucose and glutamine consumption in cancer cells mediated by CtBP and SIRT4 Li Wang1, Jing-jing Li1,Li-yuGuo2, Peipei Li1, Zhiqiang Zhao1, Haisheng Zhou2 and Li-jun Di1 Abstract Glucose and Glutamine are two essential ingredients for cell growth. However, it remains open for investigation whether there is a general mechanism that coordinates the consumption of glucose and glutamine in cancer cells. Glutamine is mainly metabolized through the glutaminolysis pathway and our previous report indicated that CtBP increases GDH activity and promotes glutaminolysis through repressing the expression of SIRT4, a well-known mitochondrion-located factor that inhibits glutaminolysis pathway. CtBP is known to be a sensor of intracellular metabolic status; we thus hypothesized that a consensus CtBP-SIRT4-GDH axis may mediate the crosstalk between glycolysis and glutaminolysis. Herein, supporting this hypothesis, we observed the coordinated consumption of glucose and glutamine across different cell lines. This coordination was found to be related to CtBP repression activity on SIRT4 expression under high level of glucose but not low glucose level. Low level of glucose supply was found to decrease GDH activity via blocking CtBP dimerization. Mechanically, low glucose also abolished CtBP binding to SIRT4 promoter and the repression of SIRT4 expression. Consistently, the CtBP dimerization inhibitor MTOB mimicked low glucose effects on SIRT4 expression, and GDH activity suggest that CtBP requires high glucose supply to act as a suppressor of SIRT4 gene. In conclusion, we propose that a general molecular pathway composed by CtBP-SIRT4-GDH 1234567890():,; 1234567890():,; coordinating the metabolism of glucose and glutamine in cancer cells. Introduction other branching pathways such as one carbon metabolism Glucose and glutamine are critical nutrients indis- and pentose phosphate pathway (PPP) were also found to pensable for cancer cell growth1. Current knowledge be important channels to convert glucose to other about the metabolism of these two nutrients suggests that essential downstream molecules for cancer cell growth5,6. they are consumed by the cells through distinct path- Glutamine is mainly utilized through the glutaminolysis ways2,3. Glucose is transported into cells and further pathway and the research about this pathway has attrac- metabolized to pyruvate through the glycolysis pathway. ted great attention in recent years, because cancer cells The pyruvate either enters the mitochondria for tri- were found to rely on this pathway for durable supply of carboxylic acid (TCA) cycle, or it will be converted to carbon and nitrogen7. lactate. The latter pathway also represents a major The crosstalk between glycolysis and glutaminolysis has advantage for cancer cell growth4, even though some been noticed a long time ago; however, how these two processes influence each other is controversial. Previous studies indicated that the interactive activity of these two Correspondence: Haisheng Zhou ([email protected]) or L-j. Di pathways is mediated by some intermediate metabolites ([email protected]) such as pyruvate. Pyruvate is the end product of glycolysis 1 ’ Faculty of Health Sciences, University of Macau, Macau, People s Republic of and glutamine can also be used to produce pyruvate; China 2Department of Biochemistry and Molecular Biology, Anhui Medical University, however, the latter process is more complicated and needs Hefei 230032, China © The Author(s) 2018 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a linktotheCreativeCommons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Oncogenesis Wang et al. Oncogenesis (2018) 7:26 Page 2 of 10 to go through several enzymatic reactions belonging to Recent studies indicate that fast proliferating cells, in the TCA cycle8. The other way of interaction is through particular, the cancer cells, require the durable supply of serine synthesis pathway6. Glutamate provides an amine both energy and metabolites used as “building blocks.” group to 3-phosphopyruvate, a product converted from Both glucose and glutamine are consumed to fulfill this glycolysis intermediate 3-phosphoglycerate, to form 3- requirement11,12. Glucose, for instance, goes through the phosphoserine, the precursor of serine. The third inter- “aerobic glycolysis” process to accelerate the output of active mechanism between glycolysis and glutaminolysis ATP. However, glutamine is directly transported into the correlates with synthesis of nucleotide hexosamine, a TCA cycle to exaggerate the output of intermediate substrate for protein glycosylation, which requires the metabolites, especially the citrate, which can be further input from both glucose and glutamine. Wellen et al.9 converted to acetyl-CoA as a building block for the found that glycolysis is required for glutamine uptake in synthesis of fatty acid etc. Glutaminolysis mainly occurs in multiple types of mammalian cells and the mediating mitochondria where glutamine is converted to α-keto- factor, IL3Ra, was found to be glycosylated by hexosamine glutarate and enters the TCA cycle. Upon DNA damage, that is synthesized dependent on glucose. Consistently, glutaminolysis is halted temporarily to contribute to cell the conclusion of glycolysis promoting glutamine uptake cycle inhibition13. One of the known mediators of DNA has also been demonstrated in another independent study damage response in controlling glutaminolysis is SIRT4. using B cell as a model. In this study, withdrawal of glu- SIRT4 is a mitochondrion-localized Sirtuin family protein cose led to almost 10 times decrease in glutamine meta- with both deacetylation and ADP-ribosylation enzymatic bolism, but the mechanism has not been elaborated10. activities14. SIRT4 catalyzes the ADP-ribosylation of Fig. 1 a The schematic illustration of glycolysis and glutaminolysis pathways interconnected by TCA cycle in proliferation cells. b Growth curve of MCF-7 cells in both high glucose (HG) and low glucose (LG) conditions. c Glutamine consumption measurement of MCF-7 cells under HG and LG culture conditions. d Glucose and glutamine consumption rate measurement in MCF-7 cells treated with glycolysis inhibitors 2-DG, 3-BP, and 6-AN with increased dosage. To ensure the comparability, the cell number for each condition are the same. e Glutamine consumption rate in different cell lines culturing in HG (solid line) or LG (dashed line) conditions. Initial glutamine is 2 mM. The error bars represent the SD of three independent replicates. *p < 0.05, **p < 0.01 Oncogenesis Wang et al. Oncogenesis (2018) 7:26 Page 3 of 10 gutamate dehydrogenase (GDH), an enzyme converting whether glycolysis impacts glutaminolysis, we cultured glutamate to α-ketoglutarate, leading to repressed MCF-7 cells in high glucose (HG, 4.5 g/L glucose) med- glutaminolysis14. ium and low glucose (LG, 1 g/L glucose) medium but Our previous data indicated that SIRT4 expression is supplied with the same initial amount of glutamine repressed by a transcriptional co-repressor CtBP to con- (2 mM). We did not observe obvious increased apoptosis tribute to the maintenance of pH homeostasis of breast associated with 1 g/L glucose culture condition for MCF-7 cancer cells, which benefits cancer cells for their growth15. cells and MDA-MB-231 cells (data not shown). As Here we further report that CtBP repression of SIRT4 expected, the cells cultured in HG medium showed a expression is regulated by glycolysis activity in cancer cells much faster proliferation than the cells in LG medium and highlight a novel pathway that mediates the crosstalk (Fig. 1b). To monitor the ability of glutamine consump- between glycolysis and glutaminolysis. tion by each individual cell in HG and LG culture con- ditions, the glutamine consumption was normalized to Results cell number. Surprisingly, the cells cultured in LG med- Correlated glucose and glutamine consumption in cancer ium exhibited retarded glutamine consumption as shown cells in Fig. 1c. Glucose and glutamine are two major carbon sources To simulate the LG condition, we also applied for cancer cells and both of them can enter the TCA cycle glycolysis inhibitors including 2-deoxyglucose (2-DG), 3- to produce energy (Fig. 1a). In order to investigate Bromopyruvate (3-BP), and 6-aminonicotinamide (6-AN) Fig. 2 a, b SIRT4 gene expression measured by mRNA or protein in MCF-7 cells culturing in LG condition. The densitometry analysis of western blot bands was shown. c, d SIRT4 gene expression measured by mRNA or protein in MDA-MB-231 cells culturing in LG condition. The densitometry analysis of western blot bands was shown. e, f SIRT4 gene expression and p21 gene expression measured by mRNA or protein in MCF-7 cells treated by glycolysis inhibitors including 3-BP (40 uM), 2-DG (2 mM), and 6-AN(50 uM). g, h GDH activity assay in MCF-7 cells and MDA-MB-231 cells upon the cells were treated with LG condition. The error bars represent the SD of three independent replicates. *p < 0.05, **p < 0.01 Oncogenesis Wang et al. Oncogenesis (2018) 7:26 Page 4 of 10 Fig. 3 a SIRT4 gene expression measured by mRNA when the MCF-7 cells were transfected with CtBP1 or CtBP2 overexpression vector, or the CtBP knockdown oligo. b Glutamine consumption measurement in MCF-7 cells with or without stable expression of CtBP1 (left) or CtBP2 (right).