The Change Of Oxidative Phosphorylation Activity And The Molecular Mechanism In U251Cell By Serum Starvation

Oxidative phosphorylation is the main energy supply for normal life activities. While most of tumor cells in tumor tissue produce energy to complete cell proliferation through glycolysis, this phenomenon is called "Warburg effect". Recent studies have found that different kind of tumor cells have different energy metabolism way, at the same time, tumor cells can alter their metabolic ways to accommodate the growth of the cells in the different culture conditions and microenvironment. Therefore, the research of tumor metabolic pathways and molecular mechanisms is important for us to understand the growth, the proliferation mechanism and the clinical treatment of tumors.Serum is a essential component for cell growth, the cells will be arrested at GO/G1phase, when the cell growth is cultured in the serum-free or low-serum medium after a period of time. Therefore Serum starvation is an in vitro cell culture model against the environment. Studying the energy metabolic pathways, the oxidative phosphorylation activity and the changes of gene expression related to metabolism in tumor cells will contribute to tumor regulatory mechanisms of metabolism in serum starvation condition. In this study,293T cells and U251cells were chose as the study materials, cells were treated by two different respiratory inhibitors, to determine the energy of the main metabolic pathway. Then we study the cell producing energy mainly through glycolytic in main aspect of energy metabolic pathways, oxidative phosphorylation activity and the expression changes of related genes after starvation condition.Through a lot of related research, we find out that293T cell is sensitive to Oligomycin as it produce energy mainly through OXPHOS, but U251cell is sensitive to Oxamic acid and it’s mainly respiration way is glycolysis. When U251cell is treated by serum starvation, we figure out that its cell growth is inhibited; its cell cycle is arrested in G0/G1phase; and it’s cellular ATP content significantly increased. Besides,the protein expression and activity of Lactate dehydrogenase (LDH) is decreased but the protein expression and activity of pyruvate dehydrogenase (PDH) is increased. What’s more, the number of mitochondria and mitochondrial DNA copy is added; the expression of protein relating to OXPHOS is increased; the activity of mitochondrial oxidative phosphorylation respiratory chain complex I is increased.In summary, U251cell produce energy mainly through glycolysis with efficient Warburg effect. Additionally, after treated by serum starvation, U251cell’s cell growth is inhibited; cell cycle is arrested in GO/Gl phase; cellular ATP content is increased; anaerobic respiration is decreased; aerobic respiration is increased; the activity of OXPHOS is increased. At the same time, we found that the molecular mechanism of increasing oxidative phosphorylation activity in U251cell by serum starvation may be the improvement of the mitochondrion number through reducing the protein content of HIF-1α.