Control of cell proliferation via redox-regulated expression of glycolytic genes

KA Brand MD, U Aulwurm Phd, D Fabian PhD, B Hamm-Kuenzelmann PhD, R Netzker Phd, D Schaefer PhD, C Weigert PhD

University Erlangen-Nuremberg Medical Faculty, Erlangen, Bavaria Germany

AIMS: We reported previously a transition of ATP production by mitogen stimulated lymphocytes during cell cycle progession from mainly glucose oxidation in the G1 phase to predominantly glycolytic degradation to lactate in the S phase. Concomitantly the rate of oxygen utilization and, as a consequence the production of reactive oxygen species (ROS) was markedly decreased. This prompted us to study the regulatory mechanisms involved in these metabolic changes. METHODS: Transcriptional regulation of the glycolytic enzymes aldolase and pyruvate kinase was studied by site-directed mutagenesis of promoter/luciferase constructs, transient transfections and reporter gene assays as well as by mobility shift assays, Western and Northern blots. RESULTS: In the aldolase AH1 promoter 5 binding sites (GC boxes) for the stimulating transcription factor Sp1 and a response element for the activating protein AP1 were identified. In the pyruvate kinase M promoter 4 out of 5 binding sites for Sp1 turned out to be functional in the transfection assays. Moreover, Sp1 in nuclear extracts of resting lymphocytes (G0cells) revealed less binding efficiency to its DNA consensus sequence, due to the presence of more ROS than in nuclear extracts, obtained from S phase cells. The concentration of Sp1 was equal in both nuclear extracts as shown by Western blots. CONCLUSION: Reduction of ROS formation during the S phase enables proliferating cells to increase the expression of glycolytic genes and consequently to produce sufficient ATP via glycolysis. Despite the low yield of ATP, proliferating cells preferentially use the glycolytic pathway (Warburg effect), in order to minimize oxidative stress during the phases of the cell cycle, when maximally enhanced biosynthesis and cell division do occur.

KEY WORDS: Proliferation, glycolysis, reactive oxygen species.

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Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Paris, France; February 9 - 12, 2002; in the section on Novel Therapies, Part 1.