The structure of the oligosaccharides of alpha3beta1 integrin from human ureter epithelium (HCV29) cell line.

There is a growing line of evidence that glycosylation of alpha and beta subunits is important for the function of integrins. Integrin alpha3beta1, from human ureter epithelium cell-line HCV29, was isolated by affinity chromatography on laminin GD6 peptide. Characterization of its carbohydrate moieties was carried out using sodium dodecyl sulfate/polyacrylamide gel electrophoresis followed by Western blotting on Immobilon P and on-blot deglycosylation with peptide N-glycosidase-F. Profiles of N-glycans for each subunit were obtained by matrix-assisted laser desorption/ionization mass spectrometry. Our findings demonstrated, in both subunits of integrin alpha3beta1, the presence of complex type oligosaccharides with a wide heterogeneity. Bi- tri- and tetraantennary structures were the most common, while high-mannose type structures were minor. Also the presence of short poly-N-acetyllactosamine entities was shown. These results show that while the predominant oligosaccharides of both subunits are identical, some slight differences between them do exist.

Differences of alpha3beta1 integrin glycans from different human bladder cell lines.

Expression as well as properties of integrins are altered upon transformation. Cell adhesion regulated by integrins is modulated by glycosylation, one of the most frequent biochemical alteration associated with tumorogenesis. Characterisation of carbohydrate moieties of alpha3beta1 integrin on the cultured human bladder carcinoma (T-24, Hu456, HCV 29T) and human normal ureter and bladder epithelium (HCV 29, Hu609) cell lines was carried out after an electrophoresis and blotting, followed by immunochemical identification of alpha3 and beta1 integrin chains and analysis of their carbohydrates moieties using highly specific digoxigenin-labelled lectins. In all the studied cell lines alpha3beta1 integrin was glycosylated although in general each subunit differently. Basic structures recognized in beta1 subunit were tri- or tetraantennary complex type glycans in some cases sialylated (T-24, HCV 29, HCV 29T) and fucosylated (Hu609, HCV 29T). Positive reaction with Phaseolus vulgaris agglutinin and Datura stramonium agglutinin suggesting the presence of beta1-6 branched N-linked oligosaccharides was found in cancerous cell lines (T-24, Hu456) as well as in normal bladder epithelium cells (Hu609). High mannose type glycan was found only in beta1 subunit from Hu456 transitional cell cancer line. On the other hand alpha3 subunit was much less glycosylated except the invasive cancer cell line T-24 where high mannose as well as sialylated tri- or tetraantennary complex type glycans were detected. This observation suggests that changes in glycosylation profile attributed to invasive phenotype are rather associated with alpha3 not beta1 subunit.