Protein kinase C-epsilon is necessary for erythropoietin's up-regulation of c-myc and for factor-dependent DNA synthesis. Evidence for discrete signals for growth and differentiation.
Erythropoietin regulates the transcription of the protooncogenes c-myc and c-myb by discrete protein kinase C (PKC)-dependent and protein serine/threonine phosphatase-dependent pathways, respectively (Spangler, R., Bailey, S. C., and Sytkowski, A. J. (1991) J. Biol. Chem. 266, 681-684; Patel H. R, Choi H.-S, and Sytkowski A. J. (1992) J. Biol. Chem. 267, 21300-21302). In the present study we demonstrate that up-regulation of c-myc requires the PKC-epsilon isoform and that this pathway is required for erythropoietin-induced DNA synthesis (growth) but apparently not for beta-globin expression (differentiation). Treatment of Rauscher murine erythroleukemia cells resulted in phosphorylation of phospholipase C-gamma1 and activation of PKC-epsilon as evidenced by its translocation from soluble to particulate subcellular fractions. Artificial down-regulation of PKC-epsilon with antisense oligodeoxynucleotides blocked erythropoietin's up-regulation of c-myc in a concentration-dependent manner. In contrast, antisense oligodeoxynucleotides to PKC-alpha, -beta, -gamma, -delta, and -zeta had no effect. Although down-regulation of PKC-epsilon blocked the increase in c-myc expression, it did not inhibit erythropoietin induction of beta-globin expression, a marker of erythroid differentiation. However, down-regulation of PKC-epsilon did block factor-dependent DNA synthesis quantified by measurement of [3H]thymidine incorporation into newly synthesized DNA of normal murine erythroid cells. The results are consistent with discrete intracellular signals regulating erythroid cell growth and differentiation.
Laboratory for Cellular and Molecular Biology, Division of Hematology and Oncology, New England Deaconess Hospital, Department of Medicine, Harvard Medical School, Boston, Massachusetts 02215, USA.
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Li
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Davis
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Sytkowski
D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D004261:DNA Replication / Q000187:drug effects*; D015536:Down-Regulation / Q000187:drug effects; D004789:Enzyme Activation; D004921:Erythropoietin / Q000494:pharmacology*; D016259:Genes, myc; D007527:Isoenzymes / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D051744:Protein Kinase C-epsilon; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects*
D007527:Isoenzymes; D016376:Oligonucleotides, Antisense; D004921:Erythropoietin; D014443:Tyrosine; C497256:Prkce protein, mouse; D011493:Protein Kinase C; D051744:Protein Kinase C-epsilon