Down-regulation of N-acetylglucosaminyltransferase-V induces ER stress by changing glycosylation and function of GLUT1

N-Acetylglucosaminyltransferase-V (GnT-V) is a key enzyme in the processing of N-glycans during synthesis of glycoproteins. We have reported that down-regulating GnT-V could induce endoplasmic reticulum stress (ER stress) in 7721 cells, a human hepatocarcinoma cell line. In a search for mechanisms of ER stress, we found that there was a prominent decline of glucose uptake in antisense GnT-V transfectant, furthermore, a decrease of tri- or tetra-antannary sugar chain of glucose transporter 1 (GLUT1). However, distribution of GLUT1 in antisense GnT-V transfectant was not affected. Glucose deprivation has been known to activate ER stress in tumor cells. Therefore, the data presented in this study indicate that the glycosylation change and decrease of transport activity of GLUT1 may be one possible mechanism of ER stress induced by down-regulating GnT-V, and GnT-V may contribute to the regulation of glucose uptake by modifying glycosylation of GLUT1 in some tumor cells.