Proteoglycan core protein is accumulated in cultured chondrocytes in the presence of the ionophore monensin.

The nature of the proteoglycan antigen which accumulates in chick embryo chondrocytes that had been incubated in monensin was examined. Both the culture media and cell lysates were immunoprecipitated using antibody which primarily is directed against core protein. Gel filtration and electrophoresis of the immunoprecipitates showed that molecules corresponding to completed proteoglycan, core protein, and link protein were present in the immunoprecipitates. Monensin caused the cellular accumulation of core protein which was both underglycosylated and undersulfated. These results suggest that monensin affects early events of proteoglycan biosynthesis and that it may be useful for elucidating those events.