Protein tyrosine phosphatase 2 (SHP-2) moderates signaling by gp130 but is not required for the induction of acute-phase plasma protein genes in hepatic cells.
Signals propagated via the gp130 subunit of the interleukin-6 (IL-6)-type cytokine receptors mediate, among various cellular responses, proliferation of hematopoietic cells and induction of acute-phase plasma protein (APP) genes in hepatic cells. Hematopoietic growth control by gp130 is critically dependent on activation of both STAT3 and protein tyrosine phosphatase 2 (SHP-2). To investigate whether induction of APP genes has a similar requirement for SHP-2, we constructed two chimeric receptors, G-gp130 and G-gp130(Y2F), consisting of the transmembrane and cytoplasmic domains of gp130 harboring either a wild-type or a mutated SHP-2 binding site, respectively, fused to the extracellular domain of the granulocyte colony-stimulating factor (G-CSF) receptor. Rat hepatoma H-35 cells stably expressing the chimeric receptors were generated by retroviral transduction. Both chimeric receptors transmitted a G-CSF-induced signal characteristic of that triggered by IL-6 through the endogenous gp130 receptor; i.e., both activated the appropriate JAK, induced DNA binding activity by STAT1 and STAT3, and up-regulated expression of the target APP genes, those for alpha-fibrinogen and haptoglobin. Notwithstanding these similarities in the patterns of signaling responses elicited, mutation of the SHP-2 interaction site in G-gp130(Y2F) abrogated ligand-activated receptor recruitment of SHP-2 as expected. Moreover, the tyrosine phosphorylation state of the chimeric receptor, the associated JAK activity, and the induced DNA binding activity of STAT1 and STAT3 were maintained at elevated levels and for an extended period of time in G-gp130(Y2F)-expressing cells following G-CSF treatment compared to that in cells displaying the G-gp130 receptor. H-35 cells ectopically expressing G-gp130(Y2F) were also found to display an enhanced sensitivity to G-CSF and a higher level of induction of APP genes. Overexpression of the enzymatically inactive SHP-2 enhanced the signaling by the wild-type but not by the Y2F mutant G-gp130 receptor. These results indicate that gp130 signaling for APP gene induction in hepatic cells differs qualitatively from that controlling the proliferative response in hematopoietic cells in not being strictly dependent on SHP-2. The data further suggest that SHP-2 functions normally to attenuate gp130-mediated signaling in hepatic (and, perhaps, other) cells by moderating JAK action.
Kim
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Department of Molecular and Cellular Biology, Roswell Park Cancer Institute, Buffalo, New York 14263, USA.
Hawley
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TS
Hawley
R G
RG
Baumann
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D000209:Acute-Phase Proteins / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D050822:Cytokine Receptor gp130; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D053613:Janus Kinase 1; D053614:Janus Kinase 2; D008099:Liver / Q000166:cytology; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D054648:Protein Phosphatase 2; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D051381:Rats; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D053634:TYK2 Kinase; D015534:Trans-Activators / Q000378:metabolism; D014407:Tumor Cells, Cultured
D000209:Acute-Phase Proteins; D015703:Antigens, CD; D004268:DNA-Binding Proteins; C494199:IL6ST protein, human; C494201:Il6st protein, rat; D047908:Intracellular Signaling Peptides and Proteins; D008562:Membrane Glycoproteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C494081:Stat1 protein, rat; C494088:Stat3 protein, rat; D015534:Trans-Activators; D050822:Cytokine Receptor gp130; D011505:Protein-Tyrosine Kinases; C507904:JAK1 protein, human; C507924:JAK2 protein, human; C507906:Jak1 protein, rat; C507927:Jak2 protein, rat; D053613:Janus Kinase 1; D053614:Janus Kinase 2; D053634:TYK2 Kinase; C070139:TYK2 protein, human; C499357:Tyk2 protein, rat; D054648:Protein Phosphatase 2; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516727:Ptpn11 protein, rat; C509250:Ptpn6 protein, rat