Altered glycosylation of α(s)β1 integrins from rat colon carcinoma cells decreases their interaction with fibronectin

Malignant cell transformation is generally accompanied by changes in their interactions with environing matrix proteins in a way to facilitate their migration and generate invasion. Our results show the binding of rat colon adenocarcinoma PROb cells to fibronectin strongly reduced when compared to normal rat intestine epithelial cells. This decrease was not due to the level of α(s)β1 integrins expressed at the surface of the cell line. However, β₁- and α_(s)-associated subunits appeared to be structurally altered as shown by immunoprecipitation followed by electrophoresis. Pulse chase experiments using ³⁵S methionine evidenced differences in the biosynthesis of β1- and α (s) associated integrins: normal epithelial IEC18 cells required 16 h for maximal biosynthesis of the completely mature β1 subunit, while PROb cells did it within 4-6 h. Studies using endoglycosidases O, H, D, and N glycanase confirmed that the molecular weight alterations were due to abnormal glycosylation and suggested that α(s)β1 integrins of PROb cells could bear both mature complex and immature high mannose types while IEC18 cells borne only mature complex type oligosaccharidic chains. Treatment of both cell types with castanospermine, an inhibitor of N-glycosylation, reduced the differences observed in their adhesion to the fibronectin without significantly affecting β1 receptors expression at the cell surface. These results strongly suggest a role of the glycosylation of β1 receptors in the adhesion of rat colon adenocarcinoma PROb cells to fibronectin substrata. © 1996 Wiley-Liss, Inc.