Studies on the plasma membrane of normal and psoriatic keratinocytes. 6. Cell surface and shed glycoproteins

Quantification and characterization of [3H]-fucose-labeled cell surface glycoproteins are reported. Two approaches have been compared; first the analysis of glycoprotein shed spontaneously into the medium during incubation of keratinocytes in vitro, and second the study of material released by exposure of the cell to proteolytic enzymes. It is shown that psoriatic keratinocytes "shed" glycoprotein more rapidly than normal, although the material is of similar molecular weight (mainly "biantennary" transferrin type glycopeptides). By contrast, the percentage of glycoprotein released by proteolysis of psoriatic keratinocytes is normal, but the molecular weight distribution of the labeled glycopeptides is markedly altered. The abnormal turnover and composition of fucose-labeled glycoproteins from the cell surface may be related to the loss of growth control in psoriatic epidermis.