Galectin-1 upregulates glucose transporter-1 expression level via protein kinase C, phosphoinositol-3 kinase, and mammalian target of rapamycin pathways in mouse embryonic stem cells

Although galectin-1 is expressed in various stem cells, our understanding of the functional roles of galectin-1 in embryonic stem (ES) cells is still fragmentary and incomplete. Thus, this study investigated the effect of galectin-1 on the 2-deoxyglucose (2-DG) uptake and its related signal cascades. Galectin-1 significantly increased 2-deoxyglucose uptake time- and dose-dependently. In addition, galectin-1-induced 2-deoxyglucose uptake was inhibited by glucose transporter-1 siRNA. Moreover, galectin-1 increased glucose transporter-1 mRNA and protein expression levels, which were inhibited by a disruption in transcription by actinomycin D and translation by the cycloheximide. Subsequently, the galectin-1-induced 2-deoxyglucose uptake was attenuated by these inhibitors. In investigation of signal transduction involved in this process, galectin-1 increased intracellular Ca²⁺ concentration and the protein kinase C activation, which induced extracellular signal regulated kinase1/2 phosphorylation. On the other hand, phosphoinositol-3-kinase/Akt activated by galectin-1 was not involved in extracellular signal regulated kinase1/2 pathway. Moreover, mammalian target of rapamycin signal pathway was stimulated in response to galectin-1. Finally, galectin-1-induced increase of glucose transporter-1 expression and 2-deoxyglucose uptake were inhibited by blocking of Ca²⁺/protein kinase C/extracellular signal regulated kinase1/2, phosphoinositol-3-kinase/Akt, and mammalian target of rapamycin pathways. In conclusion, galectin-1 upregulates glucose uptake through Ca²⁺/protein kinase C/extracellular signal regulated kinase1/2, phosphoinositol-3-kinase/Akt, and mammalian target of rapamycin pathways in mouse ES cells.