Growth hormone, interferon-gamma, and leukemia inhibitory factor promoted tyrosyl phosphorylation of insulin receptor substrate-1.
The identification of JAK2 as a growth hormone (GH) receptor-associated, GH-activated tyrosine kinase has established tyrosyl phosphorylation as a signaling mechanism for GH. In the present study, GH is shown to stimulate tyrosyl phosphorylation of insulin receptor substrate 1 (IRS-1), the principle substrate of the insulin receptor. Tyrosyl phosphorylation of IRS-1 is a critical step in insulin signaling and provides binding sites for proteins with the appropriate Src homology 2 domains, including the 85-kDa regulatory subunit of phosphatidylinositol (PI) 3'-kinase. In 3T3-F442A fibroblasts, GH-dependent tyrosyl phosphorylation of IRS-1 was detected by 1 min and at GH concentrations as low as 5 ng/ml (0.23 nM). Tyrosyl phosphorylation of IRS-1 was transient, with maximal stimulation detected at 30 min and diminished signal detected at 60 min. The ability of GH receptor (GHR) to transduce the signal for IRS-1 tyrosyl phosphorylation is mediated by the intracellular region of GHR between amino acids 295 and 380 by a mechanism not involving the two tyrosines in this region. This region of GHR is required for GH-dependent JAK2 association and activation (VanderKuur, J. A., Wang, X., Zhang, L., Campbell, G. S., Allevato, G., Billestrup, N., Norstedt, G., and Carter-Su, C. (1994) J. Biol. Chem. 269, 21709-21717). When other cytokines that activate JAK2 were tested for the ability to stimulate the tyrosyl phosphorylation of IRS-1, stimulation was detected with interferon-gamma and leukemia inhibitory factor. The correlation between JAK2 tyrosyl phosphorylation and IRS-1 tyrosyl phosphorylation in response to GH, interferon-gamma, and leukemia inhibitory factor and in cells expressing different GHR mutants, provides evidence that IRS-1 may interact with JAK2 or an auxiliary molecule that binds to JAK2. GH is also shown to stimulate binding of IRS-1 to the 85-kDa regulatory subunit of PI 3'-kinase. The ability of GH to stimulate tyrosyl phosphorylation of IRS-1 and its association with PI 3'-kinase provides a biochemical basis for responses shared by insulin and GH including the well characterized insulin-like metabolic effects of GH observed in a variety of cell types.
Argetsinger
L S
LS
Department of Physiology, University of Michigan Medical School, Ann Arbor 48109-0622, USA.
Hsu
G W
GW
Myers
M G
MG
Billestrup
N
N
White
M F
MF
Carter-Su
C
C
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004789:Enzyme Activation; D013006:Growth Hormone / Q000494:pharmacology*; D006131:Growth Inhibitors / Q000494:pharmacology*; D006801:Humans; D055504:Insulin Receptor Substrate Proteins; D007371:Interferon-gamma / Q000494:pharmacology*; D015850:Interleukin-6; D053614:Janus Kinase 2; D053605:Leukemia Inhibitory Factor; D008222:Lymphokines / Q000494:pharmacology*; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D051381:Rats; D011986:Receptors, Somatotropin / Q000235:genetics; D013552:Swine; D014443:Tyrosine / Q000378:metabolism*
D006131:Growth Inhibitors; C526292:IRS1 protein, human; D055504:Insulin Receptor Substrate Proteins; D015850:Interleukin-6; C526296:Irs1 protein, rat; C507837:LIF protein, human; D053605:Leukemia Inhibitory Factor; D008222:Lymphokines; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D011986:Receptors, Somatotropin; D014443:Tyrosine; D007371:Interferon-gamma; D013006:Growth Hormone; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; C507927:Jak2 protein, rat; D053614:Janus Kinase 2