Differential involvement of cell surface sialic acid residues in wheat germ agglutinin binding to parental and wheat germ agglutinin-resistant chinese hamster ovary cells

Two Chinese hamster ovary (CHO) cell mutants selected for resistance to wheat germ agglutinin (WGA) have been shown to exhibit defective sialylation of membrane glycoproteins and a membrane glycolipid, GM₃. The mutants (termed Wga^R_II and Wga^R_III) have been previously shown to belong to different genetic complementation groups and to exhibit different WGA-binding abilities. These mutants and a WGA-resistant CHO cell mutant termed Wga^R_I (which also possesses a surface sialylation defect arising from a deficient iV-acetylglucosami-nyltransferase activity), have enabled us to investigate the role of sialic acid in WGA binding at the cell surface. Scatchard plots of the binding of ¹²⁵I-WGA (1 ng/ml to 1 mg/ml) to parental and Wga^R CHO cells before and after a brief treatment with neuraminidase provide evidence for several different groups of sialic acid residues at the CHO cell surface which may be distinguished by their differential involvement in WGA binding to CHO cells.