Early changes in phosphoprotein patterns of Friend erythroleukaemia cells induced by dimethylsulphoxide or phorbol esters.

Immediate changes in protein phosphorylation in Friend erythroleukaemia cells (FELC) were examined in response to stimulation with dimethylsulphoxide (DMSO), which triggers cell differentiation, 12-O-tetra-decanoyl-phorbol 13-acetate (TPA), a tumour promoter, and the Ca++ ionophore A23187. The effects of the cyclic nucleotides, cAMP and cGMP, on the patterns of phosphoproteins were also analysed. Autoradiographs of two-dimensional gels reveal that within 30 min of treatment by the various agents differences in the patterns of protein phosphorylation can be seen. Treatment with DMSO and TPA altered the phosphoprotein patterns in different ways. These patterns were distinct from those observed in untreated and cyclic nucleotide treated cells. Treatment with the calcium ionophore caused a unique phosphorylation pattern unlike any of the others. These data suggest that the very early changes seen in the patterns of protein phosphorylation in FELC may be related to the induction of differentiation.