Effect of Hypoxia on 2-Deoxyglucose Uptake and Cell Cycle Regulatory Protein Expression of Mouse Embryonic Stem Cells: Involvement of Ca2+ /PKC, MAPKs and HIF-1α

Abstract

This study investigated the signal molecules linking the alteration in 2-dexoyglucose (2-DG) uptake and DNA synthesis in mouse embryonic stem (ES) cells under hypoxia. Hypoxia increased the 2-DG uptake and GLUT-1 protein expression level while the undifferentiated state of ES cells and cell viability were not affected by the hypoxia (1 - 48h). Subsequently, [³H] thymidine incorporation was significantly increased at 12 hours of hypoxic exposure. Hypoxia increased the Ca²⁺ uptake and PKC β _I, ε, and ζ translocation from the cytosol to the membrane fraction. Moreover, hypoxia increased the level of p44/42 mitogen-activated protein kinases (MAPKs) phosphorylation and hypoxia inducible factor-1α (HIF-1α) in a time-dependent manner. On the other hand, inhibition of these pathways blocked the hypoxia-induced increase in the 2-DG uptake and GLUT-1 protein expression level. Under hypoxia, cell cycle regulatory protein expression [cyclin D1, cyclin E, cyclin-dependent kinase (CDK) 2, and CDK 4] were increased in a time-dependent manner, which were blocked by PD 98059. pRB protein was also increased in a time-dependent manner. In conclusion, under hypoxia, there might be a parallel relationship between the expression of GLUT1 and DNA synthesis, which is mediated by the Ca²⁺ /PKC, MAPK, and the HIF-1α signal pathways in mouse ES cells.