Effect of inhibitors of N‐linked oligosaccharide processing on the cell surface expression of a melanoma integrin

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Abstract
The role of trimming and processing of N‐linked oligosaccharides on the cell surface expression of the melanoma vitronectin receptor, a member of the integrin family of cell adhesion receptors, was examined by using specific glucosidase and mannosidase inhibitors. Inhibition of glucosidases I and II by castanospermine or N‐methylde‐oxynojirimycin delayed the vitronectin receptor α/β chain heterodimer assembly and α chain cleavage and resulted in a decrease in the level of expression cell surface receptor. Conversely, the vitronectin receptor synthesized in the presence of the mannosidase I and II inhibitors, 1‐deoxymannojirimycin and swainsonine, was transported normally to the cell surface with its α chain N‐linked oligosaccharides in an endoglycosidase H–sensitive from. In the presence of swainsonine, time course studies of the cell surface replacement of control, endoglycosidase H–resitant receptor with an endoglycosidase H–sensitive form demonstrated a vitronectin receptor half‐life of approximately 15–16 h. These studies provide evidence that the rates of assembly, proteolytic cleavage, and cell surface expression of the melanoma vitronectin receptor are dependent on the initial trimming of glucosyl residues from the α chain N‐linked oligosaccharides.