Deletion of IGF-I receptor (IGF-IR) in primary osteoblasts reduces GH-induced STAT5 signaling

Yujun Gan, Yue Zhang, Douglas DiGirolamo, Jing Jiang, Xiangdong Wang, Xuemei Cao, Kurt R. Zinn, David P. Carbone, Thomas Clemens, Stuart J. Frank

Research output: Contribution to journalArticle

Abstract

GH promotes longitudinal growth and regulates multiple cellular functions in humans and animals. GH signals by binding to GH receptor (GHR) to activate the tyrosine kinase, Janus kinase 2 (JAK2), and downstream pathways including signal transducer and activator of transcription 5 (STAT5), thereby regulating expression of genes including IGF-I. GH exerts effects both directly and via IGF-I, which signals by activating the IGF-I receptor (IGF-IR). IGF-IR is a cell surface receptor that contains intrinsic tyrosine kinase activity within its intracellular domain. In this study, we examined the potential role of IGF-IR in facilitating GH-induced signal transduction, using mouse primary calvarial osteoblasts with Lox-P sites flanking both IGF-IR alleles. These cells respond to both GH and IGF-I and in vitro infection with an adenovirus that drives expression of Cre recombinase (Ad-Cre) dramatically reduces IGF-IR abundance without affecting the abundance of GHR, JAK2, STAT5, or ERK. Notably, infection with Ad-Cre, but not a control adenovirus, markedly inhibited acute GH-induced STAT5 activity (more than doubling the ED50 and reducing the maximum activity by nearly 50%), while sparing GH-induced ERK activity, and markedly inhibited GH-induced transactivation of a STAT5-dependent luciferase reporter. The effect of Ad-Cre on GH signaling was specific, as platelet-derived growth factor-induced signaling was unaffected by Ad-Cre-mediated reduction of IGF-IR. Ad-Cre-mediated inhibition of GH signaling was reversed by adenoviral reexpression of IGF-IR, but not by infection with an adenovirus that drives expression of a hemagglutination-tagged somatostatin receptor, which drives expression of the unrelated somatostatin receptor, and Ad-Cre infection of nonfloxed osteoblasts did not affect GH signaling. Notably, infection with an adenovirus encoding a C-terminally truncated IGF-IR that lacks the tyrosine kinase domain partially rescued both acute GH-induced STAT5 activity and GH-induced IGF-I gene expression in cells in which endogenous IGF-IR was reduced. These data, in concert with our earlier findings that GH induces a GHR-JAK2-IGF-IR complex, suggest a novel function for IGF-IR. In addition to its role as a key IGF-I signal transducer, this receptor may directly facilitate acute GH signaling. The implications of these findings are discussed.

Original languageEnglish (US)
Pages (from-to)644-656
Number of pages13
JournalMolecular Endocrinology
Volume24
Issue number3
DOIs
StatePublished - Mar 2010
Externally publishedYes

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STAT5 Transcription Factor
IGF Type 1 Receptor
Osteoblasts
Adenoviridae Infections
Insulin-Like Growth Factor I
Adenoviridae
Janus Kinase 2
Protein-Tyrosine Kinases
Somatostatin Receptors
Gene Expression
Platelet-Derived Growth Factor
Hemagglutination
Cell Surface Receptors
Luciferases
Transducers
Transcriptional Activation
Cre recombinase
Signal Transduction

ASJC Scopus subject areas

  • Molecular Biology
  • Endocrinology

Cite this

Gan, Y., Zhang, Y., DiGirolamo, D., Jiang, J., Wang, X., Cao, X., ... Frank, S. J. (2010). Deletion of IGF-I receptor (IGF-IR) in primary osteoblasts reduces GH-induced STAT5 signaling. Molecular Endocrinology, 24(3), 644-656. https://doi.org/10.1210/me.2009-0357

Deletion of IGF-I receptor (IGF-IR) in primary osteoblasts reduces GH-induced STAT5 signaling. / Gan, Yujun; Zhang, Yue; DiGirolamo, Douglas; Jiang, Jing; Wang, Xiangdong; Cao, Xuemei; Zinn, Kurt R.; Carbone, David P.; Clemens, Thomas; Frank, Stuart J.

In: Molecular Endocrinology, Vol. 24, No. 3, 03.2010, p. 644-656.

Research output: Contribution to journalArticle

Gan, Y, Zhang, Y, DiGirolamo, D, Jiang, J, Wang, X, Cao, X, Zinn, KR, Carbone, DP, Clemens, T & Frank, SJ 2010, 'Deletion of IGF-I receptor (IGF-IR) in primary osteoblasts reduces GH-induced STAT5 signaling', Molecular Endocrinology, vol. 24, no. 3, pp. 644-656. https://doi.org/10.1210/me.2009-0357
Gan, Yujun ; Zhang, Yue ; DiGirolamo, Douglas ; Jiang, Jing ; Wang, Xiangdong ; Cao, Xuemei ; Zinn, Kurt R. ; Carbone, David P. ; Clemens, Thomas ; Frank, Stuart J. / Deletion of IGF-I receptor (IGF-IR) in primary osteoblasts reduces GH-induced STAT5 signaling. In: Molecular Endocrinology. 2010 ; Vol. 24, No. 3. pp. 644-656.
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