Alteration of phosphotyrosine-containing proteins at the early stage of erythroid differentiation of mouse erythroleukemia (MEL) cells.

Following treatment of mouse erythroleukemia (MEL) cells with dimethyl sulfoxide and other typical erythroid inducing agents, the profile of cellular phosphotyrosine-containing proteins was drastically altered. We found that the level of almost all of the phosphotyrosine-containing proteins was either decreased or disappeared at a very early stage of differentiation. Addition of sodium orthovanadate (Na3VO4), a specific inhibitor of phosphotyrosine phosphatases, prevented the alteration as well as erythroid differentiation. Mutant MEL cells, which are resistant to differentiation by dimethyl sulfoxide, were apparently insensitive to the alteration. These results indicate that dephosphorylation of phosphotyrosine residues in cellular proteins is coupled with a reaction(s) which is responsible for triggering differentiation of MEL cells.