Diverse regulation of AKT and GSK-3β by O-GlcNAcylation in various types of cells.

Protein kinase B (AKT) and glycogen synthase kinase-3β (GSK-3β) are major components of insulin-AKT signaling that plays crucial roles in various types of tissue. Recent studies found that these two kinases are modified posttranslationally by O-GlcNAcylation. Here, we demonstrate that O-GlcNAcylation regulated phosphorylation/activation of AKT and GSK-3β in different manners in kidney HEK-293FT cells, but did not affect these two kinases in hepatic HepG2 cells. In neuronal cells, O-GlcNAcylation regulated phosphorylation of AKT negatively, but had no effect on GSK-3β. These results suggest protein-specific and cell type-specific regulation of AKT and GSK-3β by O-GlcNAcylation. Therefore, studies on the roles of AKT and GSK-3β O-GlcNAcylation should be done in a tissue- and cell type-specific manner.