Regulation by Gi2 proteins of v-fms-induced proliferation and transformation via Src-kinase and STAT3.
We previously showed that Gi2 proteins interfere with the transduction of CSF-1 receptor (CSF-1R) proliferation signals (Corre and Hermouet, 1995). To identify CSF-1R pathways controlled by Gi2, we transfected v-fms, the oncogenic equivalent of CSF-1R, in NIH3T3 cells in which Gi2 proteins were inactivated by stably expressing a dominant negative mutant form of the alpha subunit of Gi2 (alpha i2-G204A). Expression of alpha i2-G204A resulted in decreased Src-kinase activity, delayed activation of p42 ERK-MAPK, decreased cyclin D1 expression and reduced proliferation in response to serum. In alpha i2-G204A cells transfected with v-fms, Src-kinase activity remained deficient but p42 MAPK activity and cyclin D1 expression were similar to those of vector/v-fms cells, suggesting that v-fms bypasses Src to activate the ERK-MAPK cascade. However, DNA synthesis and focus formation were inhibited by up to 80% in alpha i2-G204A/v-fms cells compared to vector/v-fms cells. We found that tyrosine phosphorylation of STAT3, also activated by CSF-1R/v-fms, was inhibited in alpha i2-G204A/v-fms cells; in addition, expression of an 85 kDa, C-terminal truncated form of STAT3 (STAT3 delta) was constitutively increased. Both the inhibition of v-fms-induced STAT3 tyrosine phosphorylation and the increased expression of STAT3 delta were reproduced by transfecting a dominant negative mutant of Src. Last, we show that expression of STAT3 delta 55C, a mutant form of STAT3 lacking the last 55 C-terminal amino acids, is sufficient to inhibit DNA synthesis and v-fms-induced transformation in NIH3T3 cells. In summary, adequate regulation by Gi2 proteins of the activity of both Src-kinase and STAT3 is required for optimal cell proliferation in response to CSF-1R/v-fms.
Corre
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Groupe Cytokines, Récepteurs et Transduction de Signal, INSERM U463, Institut de Biologie, Nantes, France.
Baumann
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Hermouet
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D016475:3T3 Cells; D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000595:Amino Acid Sequence; D000818:Animals; D002455:Cell Division; D002472:Cell Transformation, Viral / Q000235:genetics / Q000502:physiology*; D019938:Cyclin D1 / Q000378:metabolism; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000502:physiology*; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000235:genetics / Q000502:physiology*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D051379:Mice; D008969:Molecular Sequence Data; D016281:Oncogene Protein gp140(v-fms) / Q000502:physiology*; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051076:Proto-Oncogene Proteins c-fyn; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000502:physiology; D050796:STAT3 Transcription Factor; D017384:Sequence Deletion; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D015534:Trans-Activators / Q000502:physiology*; D014162:Transfection
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D004268:DNA-Binding Proteins; D016281:Oncogene Protein gp140(v-fms); D011506:Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D050796:STAT3 Transcription Factor; D055765:Shc Signaling Adaptor Proteins; C528034:Shc1 protein, mouse; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D019938:Cyclin D1; C494960:Fyn protein, mouse; D051076:Proto-Oncogene Proteins c-fyn; D016392:Proto-Oncogene Proteins pp60(c-src); D019206:GTP-Binding Protein alpha Subunits, Gi-Go