Endogenous arachidonic acid metabolism and protein phosphorylation have been examined in Friend erythroleukemia cells in response to the induction of differentiation by dimethyl sulfoxide and hexamethylene bisacetamide. 15-Hydroxyeicosatetraenoic acid levels were elevated in cells differentiated with hexamethylene bisacetamide or dimethyl sulfoxide compared with undifferentiated cells. Protein phosphorylation decreased markedly in differentiated cells compared with undifferentiated cells and the addition of 15-hydroperoxyeicosatetraenoic acid specifically decreased the phosphorylation of a 28-kilodalton protein. These findings indicate that products of 15-lipoxygenase may act as intracellular messengers in Friend erythroleukemia cells by affecting protein phosphorylation.

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PubMedDate not supplied

Changes in protein kinase activity within 30 min of induced differentiation in Friend erythroleukemia cells.

Induction of maturation in Friend erythroleukemia cells is accompanied by a programmed cessation in cell proliferation and a concomitant increase in hemoglobin production. To investigate the role of protein kinase activity in the initiation of Friend erythroleukemia cell differentiation, autoradiographs of one-dimensional, nondenaturing gels were prepared from Friend erythroleukemia cells either untreated or preincubated with dimethyl sulfoxide (DMSO) or aphidicolin for a 30-min period. Extracts were treated with cAMP or cGMP prior to electrophoresis and assayed for protein kinase activity in the presence of endogenous or exogenously added histone substrates. The data demonstrated differences in protein kinase activity following exposure of Friend erythroleukemia cells to either DMSO or aphidicolin for 30 min. These changes in enzyme activity varied with the treatment of the cells and the substrate used. Two sets of protein kinases, one responsive to cAMP and the other responsive to cGMP, were activated in control cultures. A different cAMP-responsive enzyme was active only in differentiating cells. Another protein kinase, activated by cGMP, was associated with both DMSO and aphidicolin treatment. All of these protein kinases had a histone substrate preference. One noncyclic nucleotide activated protein kinase phosphorylating endogenous substrates was associated only with DMSO-induced cells. These findings suggest a multifaceted role for protein kinases early in the maturation of Friend erythroleukemia cells.

Aphidicolin↗