scholarly journals Insulin-like growth factor induces phosphorylation of immunoreactive insulin receptor substrate and its association with phosphatidylinositol-3 kinase in human thymocytes.

1995 ◽  
Vol 182 (2) ◽  
pp. 593-597 ◽  
Author(s):  
R Kooijman ◽  
J J Lauf ◽  
A C Kappers ◽  
G T Rijkers
Keyword(s):  
T Cells ◽  
Growth Factor ◽  
Insulin Receptor ◽  
Signaling Pathway ◽  
Insulin Receptor Substrate ◽  
Type I ◽  
Insulin Like Growth Factor ◽  
Phosphatidylinositol 3 Kinase ◽  
Igf I ◽  
Phosphatidylinositol 3

Insulin receptor substrate 1 (IRS-1) is the principle cellular substrate for insulin and insulin-like growth factor I (IGF-I) receptor signaling. After phosphorylation of tyrosine residues within the YMXM or YXXM motifs, IRS-1 associates with phosphatidylinositol-3 kinase (PI3K). This signaling pathway and the presence of an IRS-1-like molecule have been demonstrated in IRS-1-transfected and in nontransfected hematopoietic cell lines, respectively. IGF-I has been implicated in lymphocyte development and function, and recently, we showed that functional type-I IGF receptors are present on human thymocytes and peripheral T cells. In this study, we addressed IGF-I signal transduction in nontransformed, freshly isolated, human thymocytes, as well as in blood T cells. Using Western blot analysis, we found that IGF-I induced phosphorylation of a 160-180-kD protein (pp170) in human thymocytes and that phosphorylated pp170 becomes associated with PI3K and is recognized by anti-IRS-1. In blood T cells, this immunoreactive IRS-1 (irIRS-1) is less abundantly expressed than in thymocytes, as assessed with immunoblotting. As a consequence, phosphorylated pp170 was not or hardly detectable after stimulation with IGF-I, and irIRS-1 was not detected in PI3K immunoprecipitates from lysates of IGF-I-stimulated T cells. However, IGF-I induced the tyrosine phosphorylation of other cellular proteins, indicating that differential expression of irIRS-1 contributes to a distinct signaling pathway in T cells.

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.

scholarly journals Role of the Insulin-Like Growth Factor I/Insulin Receptor Substrate 1 Axis in Rad51 Trafficking and DNA Repair by Homologous Recombination

2003 ◽  
Vol 23 (21) ◽  
pp. 7510-7524 ◽  
Author(s):  
Joanna Trojanek ◽  
Thu Ho ◽  
Luis Del Valle ◽  
Michal Nowicki ◽  
Jin Ying Wang ◽  
...  
Keyword(s):  
Dna Repair ◽  
Growth Factor ◽  
Homologous Recombination ◽  
Insulin Receptor ◽  
Insulin Receptor Substrate ◽  
Insulin Like Growth Factor ◽  
Insulin Receptor Substrate 1 ◽  
Factor I ◽  
Igf I

ABSTRACT The receptor for insulin-like growth factor I (IGF-IR) controls normal and pathological growth of cells. DNA repair pathways represent an unexplored target through which the IGF-IR signaling system might support pathological growth leading to cellular transformation. However, this study demonstrates that IGF-I stimulation supports homologous recombination-directed DNA repair (HRR). This effect involves an interaction between Rad51 and the major IGF-IR signaling molecule, insulin receptor substrate 1 (IRS-1). The binding occurs within the cytoplasm, engages the N-terminal domain of IRS-1, and is attenuated by IGF-I-mediated IRS-1 tyrosine phosphorylation. In the absence of IGF-I stimulation, or if mutated IGF-IR fails to phosphorylate IRS-1, localization of Rad51 to the sites of damaged DNA is diminished. These results point to a direct role of IRS-1 in HRR and suggest a novel role for the IGF-IR/IRS-1 axis in supporting the stability of the genome.

scholarly journals Insulin-like growth factor binding to the atypical insulin receptors of a human lymphoid-derived cell line (IM-9)

1990 ◽  
Vol 266 (3) ◽  
pp. 737-742 ◽  
Author(s):  
H A Jonas ◽  
A J Cox
Keyword(s):  
Growth Factor ◽  
Affinity Chromatography ◽  
Insulin Receptor ◽  
Binding Sites ◽  
Insulin Binding ◽  
Type I ◽  
Insulin Like Growth Factor ◽  
Igf Receptors ◽  
Type I Igf Receptor ◽  
Igf I

The cells of the IM-9 human lymphocyte-derived line contain a sub-population of insulin-binding sites whose immunological and hormone-binding characteristics closely resemble those of the atypical insulin-binding sites of human placenta. These binding sites, which have moderately high affinity for multiplication-stimulating activity [MSA, the rat homologue of insulin-like growth factor (IGF) II] and IGF-I, are identified on IM-9 cells by 125I-MSA binding. They account for approximately 30% of the total insulin-receptor population, and do not react with a monoclonal antibody to the type I IGF receptor (alpha IR-3). The relative concentrations of unlabelled insulin, MSA and IGF-I required to displace 50% of 125I-MSA from these binding sites (1:4.7:29 respectively) are maintained for cells, particulate membranes, Triton-solubilized membranes precipitated either by poly(ethylene glycol) or a polyclonal antibody (B-10) to the insulin receptor, and receptors purified by insulin affinity chromatography. Because the atypical insulin/MSA-binding sites outnumber the type I IGF receptors in IM-9 cells by approximately 10-fold, they also compete with the latter receptors for 125I-IGF-I binding. Thus 125I-IGF-I binding to IM-9 cells is inhibited by moderately low concentrations of insulin (relative potency ratios for insulin compared with IGF-I are approx. 1/14 to 1/4) and is partially displaced (65-80%) by alpha IR-3. When type I IGF receptors are blocked by alpha IR-3 or removed by B-10 immunoprecipitation or insulin affinity chromatography, the hormone-displacement patterns for 125I-IGF-I binding resemble those of the atypical insulin/MSA-binding sites.

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