B3GNT2, a Polylactosamine Synthase, Regulates Glycosylation of EGFR in H7721 Human Hepatocellular Carcinoma Cells

The epidermal growth factor receptor (EGFR) is an important surface receptor with N-glycans in itsextracellular domain, whose glycosylation is essential for its function, especially in tumor cells. Here, wedemonstrated that polylactosamine is markedly increased in H7721 hepatocellular carcinoma cells after treatmentwith EGF, while it apparently declined after exposure to all-trans retinoic acid (ATRA). In the study of theenzymatic mechanism of this phenomenon, we explored changes in the expression of poly-N-acetyllactosamine(PLN) branching glycosyltransferases using RT-PCR. Among the four glycosyltransferases with alteredexpression, GnT-V was most elevated by EGF, while GnT-V and B3GNT2 were most declined by ATRA. Next,we conducted co-immunoprecipitation experiments to test whether B3GNT2 and EGFR associate with eachother. We observed that EGFR is a B3GNT2-targeting protein in H7721 cells. Taken together, these findingsindicated that the altered expression of B3GNT2 will remodel the PLN stucture of EGFR in H7721 cells, whichmay modify downstream signal transduction.