Glycosylation of the basic fibroblast growth factor receptor. The contribution of carbohydrate to receptor function

We have examined the glycosylation of the basic fibroblast growth factor (bFGF) receptor to determine whether carbohydrates contribute to receptor structure and function. Using a combination of cross-linking and radioreceptor assays, we demonstrated that the two bFGF receptors in baby hamster kidney cells have protein cores of 100 and 125 kDa. They are glycosylated to high mannose forms of 115 and 140 kDa and further processed to their mature forms of 130 and 150 kDa. Because peptide:N-glycosidase F, but not endo-alpha-N-acetylgalactosamidase can reduce the size of the bFGF receptors, the carbohydrate residues of the receptor appear all N-linked. The inability of deglycosylated receptors to bind 125I-bFGF supports the notion that the carbohydrate residues are required for receptor function. Furthermore, the capacity of the wheat germ agglutinin lectin to inhibit 125I-bFGF binding and the biological activity of bFGF suggests that N-acetylglucosamine residues are functionally significant components of the receptor.