Growth Hormone and Prolactin Stimulate Tyrosine Phosphorylation of Insulin Receptor Substrate-1, -2, and -3, Their Association with p85 Phosphatidylinositol 3-Kinase (PI3-kinase), and Concomitantly PI3-kinase Activation via JAK2 Kinase

• Published in: The Journal of biological chemistry Vol. 273; no. 25; pp. 15719 - 15726
• Main Authors: Yamauchi, T, Kaburagi, Y, Ueki, K, Tsuji, Y, Stark, G R, Kerr, I M, Tsushima, T, Akanuma, Y, Komuro, I, Tobe, K, Yazaki, Y, Kadowaki, T
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 19-06-1998
• Subjects: Androstadienes - pharmacology; Animals; Enzyme Activation; Growth Hormone - pharmacology; Insulin Antagonists - pharmacology; Insulin Receptor Substrate Proteins; Intracellular Signaling Peptides and Proteins; Janus Kinase 2; Liver - drug effects; Liver - enzymology; Mice; Phosphatidylinositol 3-Kinases - metabolism; Phosphoproteins - metabolism; Prolactin - pharmacology; Protein-Tyrosine Kinases - metabolism; Proto-Oncogene Proteins; Receptor, Insulin - metabolism; Tyrosine - metabolism; Wortmannin
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.273.25.15719

Growth hormone (GH) and prolactin (PRL) binding to their receptors, which belong to the cytokine receptor superfamily, activate
Janus kinase (JAK) 2 tyrosine kinase, thereby leading to their biological actions. We recently showed that GH mainly stimulated
tyrosine phosphorylation of epidermal growth factor receptor and its association with Grb2, and concomitantly stimulated mitogen-activated
protein kinase activity in liver, a major target tissue. Using specific antibodies, we now show that GH was also able to induce
tyrosine phosphorylation of insulin receptor substrate (IRS)-1/IRS-2 in liver. In addition, the major tyrosine-phosphorylated
protein in anti-p85 phosphatidylinositol 3-kinase (PI3-kinase) immunoprecipitate from liver of wild-type mice was IRS-1, and
IRS-2 in IRS-1 deficient mice, but not epidermal growth factor receptor. These data suggest that tyrosine phosphorylation
of IRS-1 may be a major mechanism for GH-induced PI3-kinase activation in physiological target organ of GH, liver. We also
show that PRL was able to induce tyrosine phosphorylation of both IRS-1 and IRS-2 in COS cells transiently transfected with
PRLR and in CHO-PRLR cells. Moreover, we show that tyrosine phosphorylation of IRS-3 was induced by both GH and PRL in COS
cells transiently transfected with IRS-3 and their cognate receptors. By using the JAK2-deficient cell lines or by expressing
a dominant negative JAK2 mutant, we show that JAK2 is required for the GH- and PRL-dependent tyrosine phosphorylation of IRS-1,
-2, and -3. Finally, a specific PI3-kinase inhibitor, wortmannin, completely blocked the anti-lipolytic effect of GH in 3T3
L1 adipocytes. Taken together, the role of IRS-1, -2, and -3 in GH and PRL signalings appears to be phosphorylated by JAK2,
thereby providing docking sites for p85 PI3-kinase and activating PI3-kinase and its downstream biological effects.