Activated Ki-Ras complements erythropoietin signaling in CTLL-2 cells, inducing tyrosine phosphorylation of a 160-kDa protein.
We have previously shown that expression of erythropoietin (EPO) receptor (EPOR) alone failed to confer EPO responsiveness on the interleukin 2-dependent T-cell line CTLL-2, whereas the introduction of the EPOR into interleukin 3-dependent pro-B-cell lines, such as BAF-B03, allowed the cells to proliferate in response to EPO. Here, we report that additional expression of v-Ki-Ras conferred EPO-dependent growth on CTLL-2 cells expressing the EPOR, with additional formation of a high-affinity EPOR. To investigate possible mechanisms of EPOR downstream signaling induced by v-Ki-Ras expression in these CTLL-2-derived cells, we carried out anti-phosphotyrosine immunoblot analysis of the EPOR complex immunoprecipitated with anti-EPOR antibody from lysates of cells with and without cytokine stimulation, revealing two 160-kDa and 130-kDa phosphotyrosyl proteins. An anti-JAK2 antibody did not react with these proteins, suggesting that they may represent cellular components involved in an EPO-EPOR signaling pathway induced by v-Ki-Ras. Similar phosphotyrosyl proteins were present among Friend erythroleukemia cell lines, in which the Friend virus gp55/EPOR complex on the cell surface constitutively sends signals for cell growth.
Yamamura
Y
Y
Department of Biochemistry, Tokyo Medical and Dental University School of Medicine, Japan.
Noda
M
M
Ikawa
Y
Y
D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D004921:Erythropoietin / Q000494:pharmacology*; D011905:Genes, ras; D016391:Genes, src; D006801:Humans; D053614:Janus Kinase 2; D008970:Molecular Weight; D009857:Oncogenes; D010750:Phosphoproteins / Q000737:chemistry; D019000:Phosphotyrosine; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D017467:Receptors, Erythropoietin / Q000502:physiology*; D015398:Signal Transduction; D013602:T-Lymphocytes, Cytotoxic; D014162:Transfection; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D017467:Receptors, Erythropoietin; D004921:Erythropoietin; D019000:Phosphotyrosine; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; D053614:Janus Kinase 2; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)