Effect of Glycoprotein-Processing Inhibitors on the Mouse IgE Binding Capacity of Rat Basophilic Leukemia Cells

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Abstract
The basophile surface high affinity receptors for IgE (FcεR) are heavily glycosylated glycoproteins like the IgE Fc itself. Their functional expression in their physiological environment can be studied with the help of a recently developed CELISA (ELISA on cell) methodology. The relevance of the IgE and FcεR glycans for their interaction in situ has been probed using inhibitors of discrete trimming steps of N-linked carbohydrate processing. The IgE produced by mouse hybridoma cells in the presence of deoxynojirimycin (dNM), a glucosidase I inhibitor, keeps intact both its antigen and FcεR-binding capacities. Rat basophilic leukemia (RBL) cells cultured in presence of dNM or of another glucosidase I inhibitor, castanospermine (Cs), show marked decreases in their capacity to bind mouse monoclonal IgE. In contrast, their culture in the presence of either deoxymannojirimycin (dMM) or swainsonine (Sw) either does not affect or even slightly increases the membranous expression of FcεR capable to bind mouse IgE.