Erythropoietin induces Raf-1 activation and Raf-1 is required for erythropoietin-mediated proliferation.
Erythropoietin mediates the rapid phosphorylation of Raf-1 in the murine cell lines HCD-57 and FDC-P1/ER, which proliferate in response to this cytokine. Phosphorylation occurs at both serine and tyrosine residues and as such is similar to the Raf-1 phosphorylation seen after interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor, and interleukin-2 stimulation in other murine cell lines. Such data suggest that these growth factors may share a common mechanism(s) of Raf-1 phosphorylation. Furthermore, in association with Raf-1 phosphorylation, erythropoietin induces a 2-3-fold increase in Raf-1 kinase activity as measured in immune complex kinase assays in vitro. Finally, a c-raf antisense oligodeoxyribonucleotide, which specifically decreases intracellular Raf-1 levels, also substantially inhibits both erythropoietin and IL-3-directed DNA synthesis. Together, these results provide evidence that activated Raf-1 is a necessary component of erythropoietin and IL-3 growth signaling pathways.
Carroll
M P
MP
Johns Hopkins Oncology Center, Johns Hopkins University School of Medicine, Baltimore, Maryland 21231.
Spivak
J L
JL
McMahon
M
M
Weich
N
N
Rapp
U R
UR
May
W S
WS
D000818:Animals; D002455:Cell Division / Q000502:physiology*; D004247:DNA / Q000096:biosynthesis / Q000187:drug effects; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D004921:Erythropoietin / Q000378:metabolism / Q000502:physiology*; D005786:Gene Expression Regulation; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D007376:Interleukin-2 / Q000494:pharmacology; D007377:Interleukin-3 / Q000494:pharmacology; D051379:Mice; D016376:Oligonucleotides, Antisense; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf; D014162:Transfection
D007376:Interleukin-2; D007377:Interleukin-3; D016376:Oligonucleotides, Antisense; D011518:Proto-Oncogene Proteins; D004921:Erythropoietin; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D004247:DNA; D011494:Protein Kinases; D019908:Proto-Oncogene Proteins c-raf