Enzymatic modification of the surface carbohydrates of Friend erythroleukemic cells.

Surface carbohydrates of Friend erythroleukemic-cells were modified by treatment with the exoglycosidases, alpha-galactosidase, beta-galactosidase, and neuraminidase without affecting cell growth and viability either in the presence of absence of 1.8% DMSO as inducer. When cells were incubated with a combination of alpha-galactosidase and neuraminidase and then induced, they showed an increased rate of differentiation as measured by the formation of benzidine-positive cells. These enzymes used singly, or beta-galactosidase treatment alone, or in combination with neuraminidase, did not change the rate of differentiation. Cell-surface labeling and electrophoretic separation of the glycoconjugates revealed that two regions of approximate molecular weights of 195,000 and 185,000 were neuraminidase-sensitive and one other of molecular weight of about 75,000 was sensitive to alpha-galactosidase. Both untreated and the combined alpha-galactosidase, neuraminidase-modified cells exhibited the same rate of uptake of carbon-14 DMSO, ruling out the possibility that the observed increased rate of differentiation was due to faster penetration of DMSO into enzyme-treated cells. On the other hand, the decrease in the rate of uptake of rubidium-86, an analogue of K+, by treated-induced cells was significantly enhanced over that observed with untreated-induced cells, suggesting that alpha-galactosidase plus neuraminidase modification of the cell surface was affecting at least one of the early events occurring in the Friend erythroleukemic cell differentiation program.