Protein and glycoprotein synthesis by Friend erythroleukaemic cells during erythroid differentiation

The proteins synthesized by Friend erythroleukemic cells (line 707 B) have been studied by high-resolution polyacrylamide gel electrophoresis at various stages after the induction of erythroid differentiation by addition of dimethyl sulphoxide to the medium. After 24 h of differentiation, the rate of synthesis of most of the more abundant proteins is reduced, correlating with the reduction in the proliferation rate of the cells. However, the qualitative composition of the major proteins synthesized by control and differentiating cells remains very similar until at least 96 h after the induction of differentiation. Proteins characteristic of the mature erythrocyte membrane are an exception to the reduction in synthesis in line with the proliferation rate, for they continue to be synthesized at similar rates to those found in control cells. Only two major proteins (an as yet unidentified cytoplasmic protein and globin) are reproducibly induced, while the synthesis of a few proteins is almost completely abolished. In contrast to the similarity of the synthesis of the major proteins in the control and differentiating cells, the synthesis of glycoproteins that bind to Concanavalin A is markedly changed. The synthesis of many Concanavalin A-binding glycoproteins is abolished and they disappear from differentiating cells. The synthesis of a major glycoprotein is, however, induced early in differentiation. This protein, which has an apparent molecular weight of 100,000, becomes the most abundant Concanavalin A-binding glycoprotein in the cell.