Enhanced glycosylation of a melanoma cell surface glycoprotein by retinoic acid: carbohydrate chain analysis by lectin binding.

Retinoic acid (RA) inhibits the growth of mouse S91-C2 melanoma cells and enhances the glycosylation of a cell surface sialoglycoprotein (gp160). The present study analyzed the binding of 125I-labeled lectins to gp160 within polyacrylamide slab gels after electrophoretic separation of cellular macromolecules. Wheat germ agglutinin (WGA) and concanavalin A (Con A) bound to gp160 of RA-treated cells (RA-gp160) more extensively than to gp160 of control cells (C-gp160). Lens culinaris hemagglutinin (LCH), pokeweed mitogen (PWM), Ricinus communis agglutinin I (RCAI), and peanut agglutinin (PNA) failed to bind to either C-gp160 or to RA-gp160. The binding of WGA was greatly diminished after sialic acid removal. In contrast, desialylation made possible the binding of RCAI to RA-gp160. LCH, PWM and PNA did not bind to gp160 even after desialylation. Smith degradation exposed WGA-binding sites on RA-gp 160. These results suggest that gp 160 contains one or more highly branched, sialylated, N-linked complex-type side chains and lacks O-linked oligosaccharides and poly N-acetyllactosamine side chains.