Erythropoietin activates Raf1 by an Shc-independent pathway in CTLL-EPO-R cells.
Stimulation of the erythropoietin receptor (EPO-R) or the interleukin-2 receptor (IL-2-R) by their respective ligands has been reported to activate tyrosine phosphorylation of the cytoplasmic protein, Shc. We have recently characterized a cell line, CTLL-EPO-R, that contains functional cell-surface receptors for both EPO and IL-2. Although stimulation with IL-2 or IL-15 resulted in the rapid, dose-dependent tyrosine phosphorylation of Shc, stimulation with EPO failed to activate Shc. EPO, IL-2, and IL-15 activated the tyrosine phosphorylation of the adaptor protein, Shp2, and the association of Shp2/Grb2/cytokine receptor complexes. In addition, EPO, IL-2, and IL-15 activated Raf1 and ERK2, demonstrating that the Raf1/MEK/MAP kinase pathway was activated. These results indicate that multiple biochemical pathways are capable of conferring a mitogenic signal in CTLL-EPO-R. EPO can activate the Raf1/MEK/MAP kinase pathway via Shc-dependent or Shc-independent pathways, and Shc activation is not required for EPO-dependent cell growth in CTLL-EPO-R.
Barber
D L
DL
Division of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA.
Corless
C N
CN
Xia
K
K
Roberts
T M
TM
D'Andrea
A D
AD
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002417:Cattle; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004789:Enzyme Activation; D004921:Erythropoietin / Q000494:pharmacology*; D051380:GRB2 Adaptor Protein; D006801:Humans; D019409:Interleukin-15 / Q000502:physiology; D007376:Interleukin-2 / Q000502:physiology; D051379:Mice; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf; D017467:Receptors, Erythropoietin / Q000187:drug effects* / Q000502:physiology; D015375:Receptors, Interleukin-2 / Q000187:drug effects / Q000502:physiology; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction / Q000187:drug effects*; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D013602:T-Lymphocytes, Cytotoxic / Q000187:drug effects* / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D051380:GRB2 Adaptor Protein; C495948:GRB2 protein, human; C495949:Grb2 protein, mouse; D019409:Interleukin-15; D007376:Interleukin-2; D011506:Proteins; D011518:Proto-Oncogene Proteins; D017467:Receptors, Erythropoietin; D015375:Receptors, Interleukin-2; C528024:SHC1 protein, human; D055765:Shc Signaling Adaptor Proteins; C528034:Shc1 protein, mouse; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D004921:Erythropoietin; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases