Role of αvβ5 and αvβ6 integrin glycosylation in the adhesion of a colonic adenocarcinoma cell line (HT29-D4)

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Abstract
We have previously characterized the expression of the αvβ5 and αvβ6 integrins as major receptors for the human colonic adenocarcinoma cell line (HT29-D4), on vitronectin and fibronectin, respectively [Lehmann et al. (1994): Cancer Res 54:2102–2107]. In the present work we investigated the glycosylation role of these integrins in their adhesive functions. To this end, we used glycohydrolases to show that cell surface integrins were N-glycosylated and sialylated, and that only the αv subunit carried some immature oligosaccharide side chains. To alter the glycosylation state of the cell surface αvβ5 and αvβ6 integrins, we used two oligosaccharide-processing inhibitors: 1-deoxymannojirimycin (dMNJ) and tunicamycin (TM). Following treatment of HT29-D4 cells with dMNJ, cell surface αvβ5 and αvβ6 carried only high-mannose-type sugar chains, while TM-treated cells expressed de-N-glycosylated integrins. Neither α/β heterodimers assembly nor cell surface expression were impaired in the presence of the drugs. Finally, we established that adhesion of dMNJ- or TM-treated cells was altered on both vitronectin and fibronectin substrata, whereas the adhesion of these cells on laminin or collagen type I was virtually unchanged.