Glucose-dependent glycosylation of secretory glycoprotein in mouse myeloma cells

Abstract

The mouse myeloma tumor, MOPC-46, produces a kappa-type immunoglobulin light chain that may be isolated from the urine of tumor-bearing animals. This protein possesses a single carbohydrate side chain, attached by glycosylamine linkage to asparagine residue 28. When viable single cell suspensions of the tumor are incubated in vitro in minimum essential medium containing sodium pyruvate as a source of carbon and energy, the major protein synthesized and secreted corresponds to a nonglycosylated form of the kappa light chain. However, when glucose or mannose are substituted for sodium pyruvate as a source of carbon, the immunoglobulin light chain is synthesized and secreted in the fully glycosylated, native form. The dependence of normal glycosylation of the protein on the presence of either glucose or mannose in the medium is relatively specific for these compounds since substitution with either fructose, galactose, glycerol, ribose, or N-acetylglucosamine was ineffective. The nonglycosylated protein produced in the presence of sodium pyruvate was characterized as nonglycosylated MOPC-46 light chain by immunoprecipitation and gel electrophoresis. An identical nonglycosylated protein was produced by tumor cells in the presence of glucose when the incubation mixtures contained tunicamycin.