IGF-1R modulation of acute GH-induced STAT5 signaling: Role of protein tyrosine phosphatase activity

Yujun Gan, Yue Zhang, Ashiya Buckels, Andrew J. Paterson, Jing Jiang, Thomas L. Clemens, Zhong Yin Zhang, Keyong Du, Yingzi Chang, Stuart J. Frank

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16 Scopus citations


GH is a potent anabolic and metabolic factor that binds its cell surface receptor (GHR), activating the GHR-associated tyrosine kinase, Janus kinase 2, which phosphorylates and activates the latent transcription factor, signal transducer and activator of transcription 5 (STAT5). Some GH actions are mediated by the elaboration of IGF-1, which exerts effects by binding and activating the heterotetrameric tyrosine kinase growth factor receptor, IGF-1R. In addition to this GH-GHR-IGF-1-IGF-1R scheme, we have demonstrated in primary osteoblasts and in islet β-cells that then deletion or silencing of IGF-1R results in diminished GH-induced STAT5 phosphorylation, suggesting that the presence of IGF-1R may facilitate GH signaling. In this study, we explore potential roles for protein tyrosine phosphatase activity in modulating GH-induced signaling, comparing conditions in which IGF-1R is present or diminished. We confirm that in mouse primary osteoblasts harboring loxP sites flanking the IGF-1R gene, infection with an adenovirus that expresses the Cre recombinase results in IGF-1R deletion and diminished acute GH-induced STAT5 phosphorylation. Furthermore, we present a new model of IGF-1R silencing, in which expression of short hairpin RNA directed at IGF-1R greatly reduces IGF-1R abundance in LNCaP human prostate cancer cells. In both models, treatment with a chemical inhibitor of protein tyrosine phosphatase-1B (PTP-1B), but not one of src homology region 2 domain-containing phosphotase-1 (SHP-1) and SHP-2, reverses the loss of GH-induced STAT5 phosphorylation in cells lacking IGF-1R but has no effect in cells with intact IGF-1R. Furthermore, expression of either a dominant-negative PTP-1B or the PTP-1B-interacting inhibitory protein, constitutive photomorphogenesis 1, also rescues acute GH-induced STAT5 signaling in IGF-1R-deficient cells but has no effect in IGF-1R replete cells. By expressing a substrate-trapping mutant PTP-1B, we demonstrate that tyrosine phosphorylated Janus kinase-2 is a PTP-1B substrate only in cells lacking IGF-1R. Collectively, our data suggest that IGF-1R positively regulates acute GH signaling by preventing access of PTP-1B activity to Janus kinase 2 and thereby preventing PTP-1B-mediated suppression of GH-induced STAT5 activation.

Original languageEnglish (US)
Pages (from-to)1969-1979
Number of pages11
JournalMolecular Endocrinology
Issue number11
StatePublished - 2013

ASJC Scopus subject areas

  • Molecular Biology
  • Endocrinology

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    Gan, Y., Zhang, Y., Buckels, A., Paterson, A. J., Jiang, J., Clemens, T. L., Zhang, Z. Y., Du, K., Chang, Y., & Frank, S. J. (2013). IGF-1R modulation of acute GH-induced STAT5 signaling: Role of protein tyrosine phosphatase activity. Molecular Endocrinology, 27(11), 1969-1979. https://doi.org/10.1210/me.2013-1178