Changes in tyrosine phosphorylation of insulin receptor and insulin receptor substrate-1 (IRS-1) and association of p85 subunit of phosphatidylinositol 3-kinase with IRS-1 after feeding in rat liver in vivo

1997 ◽  
Vol 154 (2) ◽  
pp. 267-273 ◽  
Author(s):  
Y Ito ◽  
M Ariga ◽  
S-I Takahashi ◽  
A Takenaka ◽  
T Hidaka ◽  
...  
Keyword(s):  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Rat Liver ◽  
Insulin Receptor Substrate ◽  
Β Subunit ◽  
Phosphatidylinositol 3 Kinase ◽  
Insulin Receptor Substrate 1 ◽  
Insulin Receptor Tyrosine Kinase ◽  
Phosphatidylinositol 3

Abstract The binding of insulin to its receptor rapidly induces intrinsic insulin receptor tyrosine kinase activity, resulting in tyrosine phosphorylation of various cytosolic substrates, such as insulin receptor substrate-1 (IRS-1) which, in turn, associates with a p85 subunit of phosphatidylinositol 3-kinase (PI 3-kinase) followed by activation of this enzyme. In the present study, we have examined these early steps of insulin signalling in rat liver in vivo after food ingestion. After fasting for 22 h, a 12% casein diet was available ad libitum throughout the 8-h experimental period. Plasma insulin concentrations increased within 45 min after feeding, reached a maximum at 1·5 h and gradually decreased until 8 h. Autophosphorylation of the insulin receptor β-subunit in liver was detected even during fasting and increased about 1·5-fold at 1·5 h after feeding. Basal tyrosine phosphorylation of IRS-1 was detectable during starvation, increased about twofold at 3 h after feeding and levels were maintained until 8 h. The content of the p85 subunit of PI 3-kinase associated with IRS-1 also increased after feeding in parallel with the changes in tyrosine phosphorylation of IRS-1. Because tyrosine phosphorylation of the insulin receptor β-subunit and IRS-1 and the association of the p85 subunit of PI 3-kinase with IRS-1 in liver were closely correlated with the changes in the plasma concentration of insulin, we concluded that endogenous insulin secreted in response to eating caused these insulin-dependent intracellular changes in the liver. Journal of Endocrinology (1997) 154, 267–273

scholarly journals Angiotensin II induces tyrosine phosphorylation of insulin receptor substrate 1 and its association with phosphatidylinositol 3-kinase in rat heart

1995 ◽  
Vol 310 (3) ◽  
pp. 741-744 ◽  
Author(s):  
M J A Saad ◽  
L A Velloso ◽  
C R O Carvalho
Keyword(s):  
Angiotensin Ii ◽  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
Rat Heart ◽  
Fold Increase ◽  
At1 Receptor ◽  
Insulin Receptor Substrate ◽  
Phosphatidylinositol 3 Kinase ◽  
Insulin Receptor Substrate 1

We have investigated whether angiotensin II (AII) is able to induce insulin receptor substrate 1 (IRS-1) phosphorylation and its association with phosphatidylinositol 3-kinase (PI 3-kinase) in the rat heart in vivo. The phosphorylation state of IRS-1 following infusion of insulin or AII via the vena cava was assessed after immunoprecipitation with an anti-peptide antibody to IRS-1 followed by immunoblotting with an anti-phosphotyrosine antibody and an anti-PI 3-kinase antibody. Densitometry indicated a 5.6 +/- 1.3-fold increase in IRS-1 phosphorylation after stimulation with AII and a 12.8 +/- 3.1-fold increase after insulin. The effect was maximal at an AII concentration of 10(-8) M and occurred 1 min after infusion. There was also a 6.1 +/- 1.2-fold increase in IRS-1-associated PI 3-kinase in response to AII. In the isolated perfused heart the result was similar, showing a direct effect of AII on this pathway. When the animals were pretreated for 1 h with DuP 753, a non-peptide AII-receptor 1 (AT1 receptor) antagonist, there was a marked reduction in the AII-induced tyrosine phosphorylation of IRS-1, suggesting that phosphorylation is initially mediated by the AT1 receptor. We conclude that AII stimulates tyrosine phosphorylation of IRS-1 and its association with PI 3-kinase. This pathway thus represents an additional signalling mechanism stimulated by AII in the rat heart in vivo.

scholarly journals Insulin-Like Growth Factor I-Induced Degradation of Insulin Receptor Substrate 1 Is Mediated by the 26S Proteasome and Blocked by Phosphatidylinositol 3′-Kinase Inhibition

2000 ◽  
Vol 20 (5) ◽  
pp. 1489-1496 ◽  
Author(s):  
Adrian V. Lee ◽  
Jennifer L. Gooch ◽  
Steffi Oesterreich ◽  
Rebecca L. Guler ◽  
Douglas Yee
Keyword(s):  
Growth Factor ◽  
Insulin Receptor ◽  
Tyrosine Phosphorylation ◽  
26S Proteasome ◽  
Insulin Receptor Substrate ◽  
Phosphatidylinositol 3 Kinase ◽  
Insulin Receptor Substrate 1 ◽  
Erk Activation ◽  
Igf I ◽  
Phosphatidylinositol 3

ABSTRACT Insulin receptor substrate 1 (IRS-1) is a critical adapter protein involved in both insulin and insulin-like growth factor (IGF) signaling. Due to the fact that alteration of IRS-1 levels can affect the sensitivity and response to both insulin and IGF-I, we examined the ability of each of these ligands to affect IRS-1 expression. IGF-I (10 nM) stimulation of MCF-7 breast cancer cells caused a transient tyrosine phosphorylation of IRS-1 that was maximal at 15 min and decreased thereafter. The decrease in tyrosine phosphorylation of IRS-1 was paralleled by an apparent decrease in IRS-1 levels. The IGF-mediated decrease in IRS-1 expression was posttranscriptional and due to a decrease in the half-life of the IRS-1 protein. Insulin (10 nM) caused tyrosine phosphorylation of IRS-1 but not degradation, whereas high concentrations of insulin (10 μM) resulted in degradation of IRS-1. IGF-I (10 nM) stimulation resulted in transient IRS-1 phosphorylation and extracellular signal-related kinase (ERK) activation. In contrast, insulin (10 nM) caused sustained IRS-1 phosphorylation and ERK activation. Inhibition of 26S proteasome activity by the use of lactacystin or MG132 completely blocked IGF-mediated degradation of IRS-1. Furthermore, coimmunoprecipitation experiments showed an association between ubiquitin and IRS-1 that was increased by treatment of cells with IGF-I. Finally, IGF-mediated degradation of IRS-1 was blocked by inhibition of phosphatidylinositol 3′-kinase activity but was not affected by inhibition of ERK, suggesting that this may represent a direct negative-feedback mechanism resulting from downstream IRS-1 signaling. We conclude that IGF-I can cause ligand-mediated degradation of IRS-1 via the ubiquitin-mediated 26S proteasome and a phosphatidylinositol 3′-kinase-dependent mechanism and that control of degradation may have profound effects on downstream activation of signaling pathways.

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