摘要：N -Acetylglucosaminyltransferase III (GnT-III), which catalyzes the synthesis of a bisecting GlcNAc residue of N -glycans, is thought to be involved in the function of glycoproteins such as growth factor receptors. We investigated the effects of the overexpression of GnT-III on the hepatocyte growth factor (HGF) receptor c-Met, a glycoprotein, in human hepatocarcinoma HepG2 cells. GnT-III activity was elevated about 250-fold in HepG2 cells stably transfected with the GnT-III gene, whereas no significant change in GnT-III activity was observed in mock transfectants. Cell scattering assay revealed that HGF-induced cell scattering was enhanced depending on the GnT-III activities in the GnT-III transfectants. Western blot analysis and E-PHA lectin blot analysis showed that the level of c-Met protein was the same in both transfectants; however, the bisecting GlcNAc residue on c-Met was detected only in the GnT-III transfectants. Although the peak level of c-Met phosphorylation was not different in both transfectants, the level of tyrosine phosphorylation of c-Met decreased more rapidly in the GnT-III transfectants than in the mock transfectants. Furthermore, HGF-induced extracellular-regulated kinase (ERK) phosphorylation was slightly higher in the GnT-III transfectants than in the mock transfectants. These results show that overexpression of GnT-III in HepG2 cells enhances HGF-induced cell scattering, which may result from, at least in part, enhancement of HGF-induced ERK phosphorylation.
