Grb10 Identified as a Potential Regulator of Growth Hormone (GH) Signaling by Cloning of GH Receptor Target Proteins

The cloning of receptor targets procedure, used so far to identify proteins associated with tyrosine kinase receptors was modified to clone SH2 proteins able to bind to the growth hormone receptor (GHR). The cytoplasmic region of GHR, a member of the cytokine receptor superfamily does not contain ty...

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Bibliographic Details
Published in:The Journal of biological chemistry 1998-06, Vol.273 (26), p.15906-15912
Main Authors: Moutoussamy, S, Renaudie, F, Lago, F, Kelly, P A, Finidori, J
Format: Article
Language:English
Subjects:
Animals
Binding Sites
Cloning, Molecular
GRB10 Adaptor Protein
Growth Hormone - physiology
Janus Kinase 2
Mice
Phosphorylation
Protein-Tyrosine Kinases - physiology
Proteins - genetics
Proteins - physiology
Proto-Oncogene Proteins
Receptors, Somatotropin - genetics
Receptors, Somatotropin - physiology
Signal Transduction
Transfection
Tumor Cells, Cultured
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Description
Summary:The cloning of receptor targets procedure, used so far to identify proteins associated with tyrosine kinase receptors was modified to clone SH2 proteins able to bind to the growth hormone receptor (GHR). The cytoplasmic region of GHR, a member of the cytokine receptor superfamily does not contain tyrosine kinase activity. It was thus phosphorylated in bacteria by the Elk tyrosine kinase and radiolabeled to screen a mouse expression library. With this probe, we identified Shc and the p85 subunit of phosphatidylinositol 3-kinase as direct targets of the receptor. The other proteins identified, Csk, Shb, Grb4, and Grb10 are new potential transducers for cytokine receptors. We show in Huh-7 hepatoma cells that Grb10 and GHR associate under GH stimulation. Co-transfections in 293 cells further show that Grb10 interacts with both the GHR and Jak2. Functional tests demonstrate that Grb10 inhibits transcription of two reporter genes containing, respectively, the serum response element of c -fos and the GH response element 2 of the Spi2.1 gene, whereas it has no effect on a reporter gene containing only Stat5 binding elements. Our results suggest that Grb10 is a new target for a member of the cytokine receptor family that down-regulates some GH signaling pathways downstream of Jak2 and independently of Stat5.
ISSN:0021-9258
1083-351X
DOI:10.1074/jbc.273.26.15906