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Erythropoietin induces cytosolic protein phosphorylation and dephosphorylation in erythroid cells.

1991; Elsevier BV; Volume: 266; Issue: 35 Linguagem: Inglês

10.1016/s0021-9258(18)54402-1

1083-351X

Steven C. Bailey, Rudolph Spangler, Arthur J. Sytkowski,

Erythropoietin and Anemia Treatment

In the present study we have demonstrated that erythropoietin's signal is transduced rapidly to the cytosol resulting in specific phosphoryl-ationJdephosphorylation events.Erythropoietin treatment of Rauscher murine erythroleukemia cells previously labeled with [32P]orthophosphate results in a rapid increase in phosphorylation of two cytosolic proteins, designated pp96 and pp80, and a decrease in phosphorylation of another protein, designated pp90.The relative molecular mass and PI of pp80 are virtually identical to those reported for the protein kinase C substrate p80, or "MARCKS protein."Treatment of the cells with 12-0-tetradecanoylphorbol-13-acetate also increases pp80 but not pp96 phosphorylation, suggesting that erythropoietin triggers a protein kinase C-dependent pathway to pp80 and a protein kinase Cindependent pathway to pp96.The effect of erythropoietin on pp96 phosphorylation was also shown in nontransformed erythroid cells isolated from the spleens of phenylhydrazine-treated mice.In contrast, almost no "P labeling of pp80 or pp90 was detected, and pp80 and pp90 protein were nearly absent from these normal cells.These differences in expression and phosphorylation of erythropoietin-sensitive phosphoproteins may be related to the growth factor independence or dependence of the erythroid cells.