抄録
High glucose accelerates O-N-acetylglucosaminylation (O-GlcNAcylation) of proteins and causes diabetic complications. In the present study, we found that treatment of HuH-7 human hepatoma cells with high glucose or the protein O-N-acetylglucosaminidase (O-GlcNAcase) inhibitor O-(2-acetoamide-2-deoxy-D-glucopyranosylidene)amino-N-phenylcarbamate (PUGNAc) increased the cell surface expression of E-selectin. A dual luciferase reporter assay indicated that high glucose and PUGNAc suppressed promoter activities of the cyclic AMP response element (CRE) and enhanced those of activator protein 1 (AP-1). Enhanced CRE promoter activities in HuH-7 cells treated with dibutyryl cAMP or co-transfected with a protein kinase A expression vector pFC-PKA that enhances the phosphorylation of CRE binding protein (CREB) were suppressed by PUGNAc. In contrast, PUGNAc further increased the enhanced AP-1 promoter activity in cells transfected with a mitogen-activated protein kinase kinase kinase expression vector pFC-MEKK that enhances c-Jun phosphorylation. Immuno-blotting using an anti-O-GlcNAc antibody revealed that high glucose and PUGNAc accelerated protein O-GlcNAcylation and that there were substantial differences in the O-GlcNAcylated proteins in the cytoplasmic and nuclear fractions. In addition, PUGNAc increased the nuclear import of O-GlcNAcylated CREB. These results suggest that protein O-GlcNAcylation modulates the promoter activities of E-selectin gene, suppression of CRE and enhancement of AP-1, and enhances E-selectin protein expression on hepatocytes.
