Enzymatic modification of the surface carbohydrates of friend erythroleukemic cells

Surface carbohydrates of Friend erythroleukemic‐cells were modified by treatment with the exoglycosidases, α‐galactosidase, β‐galactosidase, and neuraminidase without affecting cell growth and viability either in the presence or absence of 1.8% DMSO as inducer. When cells were incubated with a combination of α‐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 β‐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 α‐ galactosidase. Both untreated and the combined α‐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 α‐galactosidase plus neuraminidase modification of the cell surface was affecting at least one of the early events occuring in the Friend erythroleukemic cell differentiation program.