A new feature of Mpl receptor: ligand-induced transforming activity in FRE rat fibroblasts.
Mpl is the receptor for thrombopoietin, the primary regulator of platelet production by megakaryocytes. Upon stimulation by its ligand, Mpl receptor induces proliferation and differentiation of hematopoietic cell lines of various origins. In this paper, we show that Mpl is also able to transform FRE rat fibroblasts in the presence of MGDF (pegylated Megakaryocyte Growth and Development Factor), a modified form of its ligand. We also demonstrate that upon MGDF stimulation Mpl receptor activates the classical transduction pathways described for hematopoietic cell lines in FRE cells. Introduction of Mpl deletion mutants in FRE cells allowed us to demonstrate that the C-terminal region of the Mpl intracytoplasmic domain, which is involved in hematopoietic differentiation, is necessary for the transformation process. Within that region, site-directed mutagenesis showed that the Y112 residue, which is required for Shc phosphorylation, is essential for rat fibroblast transformation by Mpl/MGDF, suggesting the involvement of Shc in Mpl-mediated transformation. Interestingly, we showed that transformation correlated with strong and sustained MAPK activation. Neither Jak2, Stat3 nor Stat5 phosphorylation was sufficient to induce the transformation process. Taken altogether, our results suggest the oncogenicity of Mpl in fibroblastic cells in the presence of its ligand.
Challier
C
C
Institut National de la Santé et de la Recherche Médicale, U506, Hôpital Paul Brousse, Villejuif, France.
Cocault
L
L
Flon
M
M
Pauchard
M
M
Porteu
F
F
Gisselbrecht
S
S
Souyri
M
M
D016475:3T3 Cells / Q000378:metabolism / Q000821:virology; D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D002471:Cell Transformation, Neoplastic; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000473:pathology; D005822:Genetic Vectors / Q000235:genetics; D053614:Janus Kinase 2; D009052:Leukemia Virus, Murine / Q000235:genetics; D008024:Ligands; D020935:MAP Kinase Signaling System; D051379:Mice; D008894:Milk Proteins; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009154:Mutation; D009363:Neoplasm Proteins; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D018121:Receptors, Cytokine; D053628:Receptors, Thrombopoietin; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D013926:Thrombopoietin / Q000378:metabolism / Q000494:pharmacology; D015534:Trans-Activators / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D004268:DNA-Binding Proteins; D008024:Ligands; D008894:Milk Proteins; D009363:Neoplasm Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D018121:Receptors, Cytokine; D053628:Receptors, Thrombopoietin; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D055765:Shc Signaling Adaptor Proteins; C528034:Shc1 protein, mouse; C528035:Shc1 protein, rat; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; C494087:Stat3 protein, mouse; C494088:Stat3 protein, rat; D015534:Trans-Activators; C082218:MPL protein, human; D013926:Thrombopoietin; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; C507926:Jak2 protein, mouse; C507927:Jak2 protein, rat; D053614:Janus Kinase 2; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases