Thrombopoietin-induced conformational change in p53 lies downstream of the p44/p42 mitogen activated protein kinase cascade in the human growth factor-dependent cell line M07e.
Thrombopoietin is a cytokine with potent megakaryocytopoietic and thrombopoietic activities in vivo. Wild-type p53 is a conformationally flexible, anti-oncogenic transcription factor that plays a principal role in mediating growth factor withdrawal-induced apoptosis in factor-dependent hematopoietic cells. We recently reported that Tpo induces a conformational change in and functional inactivation of p53, coincident with its anti-apoptotic effects, in the human factor-dependent cell line M07e. In an effort to identify potential signaling cascades through which Tpo illicits these effects on p53, we report here that treating M07e cells with MAPK kinase inhibitor PD98059 dramatically suppressed Tpo-induced conformational change in p53 as well as Tpo-enhanced viability in M07e cells in a p53-dependent manner. Furthermore, the expression of constitutively active Raf1 in M07e cells induced conformational change in p53 independent of Tpo stimulation. Inhibition of the JAK/STAT pathway revealed that JAK/STAT signaling plays an insignificant role in conformational modulation of p53 and apoptosis suppression. Inhibition of phosphatidylinositol-3 kinase did not have a significant effect on p53 conformation but did have a weak but significant effect on Tpo-enhanced viability. Cytokine-induced activation of the MAPK pathway and the subsequent functional neutralization of p53, may be an event by which apoptosis is commonly suppressed in hematopoiesis.
Department of Microbiology/Immunology, and Walther Oncology Center, Indiana University School of Medicine, Indianapolis 46202, USA.
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Ritchie
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Braun
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He
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Broxmeyer
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005838:Genotype; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D053614:Janus Kinase 2; D051379:Mice; D008894:Milk Proteins; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D050799:STAT5 Transcription Factor; D013926:Thrombopoietin / Q000494:pharmacology*; D013997:Time Factors; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry* / Q000235:genetics; D015854:Up-Regulation
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D008894:Milk Proteins; D011518:Proto-Oncogene Proteins; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D016159:Tumor Suppressor Protein p53; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D013926:Thrombopoietin; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one