Regulation on the expression and N-glycosylation of integrins by N-acetylglucosaminyltransferase V.

The expressions of integrin alpha5, beta1, and alpha6 were studied in H7721 cells by means of flow cytometric and RT-PCR method after transfected with sense and antisense cDNA of N-acetylglucosaminyltransferase V (GnT-V). The transfected cells were characterized by Northern blot. It was found that the order of expression from high to low was beta1>alpha5>alpha6. Transfection of sense GnT-V up-regulated alpha5 and alpha6, but not beta1 subunit, while antisense GnT-V down-regulated alpha5 and beta1, but not alpha6. The alterations of surface integrin subunits were quite compatible with the changes of their mRNAs. Using enzyme-labeled lectin analysis, it was shown that alpha5 subunit contained only C(2)C(2) biantennary N-glycan, which was not regulated by sense and antisense GnT-V. In contrast, beta1 subunit contained both biantennary and tri-/tetra-antennary N-glycans with GlcNAcbeta1,6Manalpha1,6-branch, and the latter was up- and down-regulated by the sense and antisense GnT-V, respectively. Therefore, the amount of biantennary N-glycans on beta1 subunit, but not the integrin protein, was correlated to the cell adhesion to fibronectin and laminin, which was reduced and elevated in the sense and antisense GnT-V-transfected cells, respectively, as we previously reported.