Increase in β1-6 GlcNAc branching caused by N- acetylglucosaminyltransferase V directs integrin β1 stability in human hepatocellular carcinoma cell line SMMC-7721

Abstract

In this study, an enzymatic inactive mutant of GnT-V (ΔcGnT-V) was constructed and transfected in SMMC 7721 cell line. Integrin β1 in ΔcGnT-V transfectants (Δc-7721) showed attenuation of the number of β1-6 GlcNAc branching, whereas those in wtGnT-V transfectants (wt-7721) presented a β1-6 GlcNAc-rich pattern. High integrin β1 expression was observed in wt-7721 compared with mock cells (7721 cell transfected with the vector pcDNA3), while transfection of ΔcGnT-V decreased the integrin β1 expression, despite of no significant changes on integrin β1 mRNA level in these cell lines. Pulse-chase experiment showed that Integrin β1 in Δc-7721 was prone to quick degradation and its half-life was less than 3 h, on the contrary, the alleviating degradation of β1 subunit was observed in wt-7721 where the β1 subunit half-life was about 16 h, meanwhile, the degradation rate of β1 subunit in mock cells was in between, about 10 h. More effective in promoting cell migration toward fibronectin and invasion through Matrigel was observed in wt-7721 while this was almost suppressed in Δc-7721. Our results suggest that the addition of β1-6 GlcNAc branching caused more fully glycosylated mature form on integrin β1 and inhibited β1 protein degradation. Glycosylation caused by GnT-V directs integrin β1 stability and more delivery to plasma membrane, subsequently promotes Fn-based cell migration and invasion. © 2006 Wiley-Liss, Inc.