EFFECT OF DEXAMETHASONE ON THE CARBOHYDRATE CHAINS OF THE INSULIN-RECEPTOR

Dexamethasone treatment of IM-9 lymphocytes and Fao hepatoma cells res ulted in an increase in synthesis of the insulin receptor. The recepto rs synthesized after stimulation with the glucocorticoid had altered c arbohydrate structure. The carbohydrate side chains of the insulin rec eptor were less branched on the dexamethasone-treated cells; i.e.,the ratio of saccharides with three and four branches to those bearing onl y two branches was decreased. The predominant polymannose oligosacchar ide after dexamethasone treatment was Man(9)GlcNAc (vs Man(6)GlcNAc in the control cell). Both of these changes are consistent with a less c omplete processing of the N-linked carbohydrate units and were not obs erved for the total cellular glycoproteins, whereas all glycoproteins manifested an increased sialylation in Fao cells after dexamethasone t reatment. These data indicate that glucocorticoid treatment results in alterations in branching of carbohydrate side chains, in the size of polymannose chains and in sialylation of the insulin receptor. (C) 199 4 Academic Press, Inc.