Processing inhibition of N-linked sugar chains associated with induction of Fc receptor-mediated phagocytosis in the mouse monocytoid cells

The concanavalin A staining of cellular glycoproteins and thedirect analysis of their sugar chains released by hydrazinolysisrevealed that the processing of N-linked sugar chains of someglycoproteins is suppressed by exposure of mouse monocytoidcells P388D1 to dimethyl sulphoxide, which can induce Fc receptor-mediatedphagocytosis. To elucidate the significance of altered glycosylationin inducing phagocytosis, the effects of exposure of the cellsto processing inhibitors (swainsonine and castanospermine) wereexamined and it was found that the cells are induced to acquirean ability to ingest IgG-coated sheep red blood cells, dependingon the dose of the inhibitors and incubation time. Analysisof the N-linked sugar chains liberated from cellular glycoproteinsby hydrazinolysis confirmed that the processing of the sugarchains is suppressed by the two inhibitors as expected. Sinceno significant alteration was induced in protein synthesis andDNA synthesis after exposure to the inhibitors, it is suggestedthat the altered glycosylation of cellular glycoproteins mayhave some direct role in the induction of Fc receptor-mediatedphagocytosis. The inhibitors did not affect the binding of theIgG-coated red blood cells to Fc receptors on the cells, non-specificphagocytosis of latex beads, and the contents of lysosomal enzymes,ß-glucuronidase and acid phosphatase. These resultssuggest that the glycosylation status of cellular glycoproteinsinfluences some specific processes involved in the ingestionof the ligands bound to Fc receptors. castanospermine macrophages phagocytosis swainsonine