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.
Li
Y
Y
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.
Davis
K L
KL
Sytkowski
A J
AJ
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