scholarly journals Insulin Induces Heterologous Desensitization of G Protein-Coupled Receptor and Insulin-Like Growth Factor I Signaling by Downregulating β-Arrestin-1

2002 ◽  
Vol 22 (17) ◽  
pp. 6272-6285 ◽  
Author(s):  
Stéphane Dalle ◽  
Takeshi Imamura ◽  
David W. Rose ◽  
Dorothy Sears Worrall ◽  
Satoshi Ugi ◽  
...  
Keyword(s):  
Growth Factor ◽  
Map Kinase ◽  
Insulin Treatment ◽  
Ectopic Expression ◽  
Wild Type ◽  
Factor I ◽  
Igf I ◽  
Heterologous Desensitization ◽  
Kinase Phosphorylation ◽  
G Protein Coupled

ABSTRACT β-Arrestin-1 mediates agonist-dependent desensitization and internalization of G protein-coupled receptors (GPCRs) and is also essential for GPCR mitogenic signaling. In addition, insulin-like growth factor I receptor (IGF-IR) endocytosis is facilitated by β-arrestin-1, and internalization is necessary for IGF-I-stimulated mitogen-activated protein (MAP) kinase activation. Here, we report that treatment of cells for 12 h with insulin (100 ng/ml) induces an ∼50% decrease in cellular β-arrestin-1 content due to ubiquitination of β-arrestin-1 and proteosome-mediated degradation. This insulin-induced decrease in β-arrestin-1 content was blocked by inhibition of phosphatidylinositol-3 kinase (PI-3 kinase) and MEK with wortmannin and PD98059, respectively. We also found a marked decrease in the association of β-arrestin-1 with the IGF-IR and a 55% inhibition of IGF-I-stimulated MAP kinase phosphorylation. In insulin-treated, β-arrestin-1-downregulated cells, there was complete inhibition of lysophosphatidic acid (LPA) or isoproterenol (ISO)-stimulated MAP kinase phosphorylation. This was associated with a decrease in β-arrestin-1 association with the β2-AR as well as a decrease in β-arrestin-1-Src and Src-β2-AR association. Ectopic expression of wild-type β-arrestin-1 in insulin-treated cells in which endogenous β-arrestin-1 had been downregulated rescued IGF-I- and LPA-stimulated MAP kinase phosphorylation. In conclusion, we found the following. (i) Chronic insulin treatment leads to enhanced β-arrestin-1 degradation. (ii) This downregulation of endogenous β-arrestin-1 is associated with decreased IGF-I-, LPA-, and ISO-mediated MAP kinase signaling, which can be rescued by ectopic expression of wild-type β-arrestin-1. (iii) Finally, these results describe a novel mechanism for heterologous desensitization, whereby insulin treatment can impair GPCR signaling, and highlight the importance of β-arrestin-1 as a target molecule for this desensitization mechanism.

scholarly journals Identification of domains of the insulin-like growth factor I receptor that are required for protection from apoptosis.

1997 ◽  
Vol 17 (1) ◽  
pp. 427-435 ◽  
Author(s):  
R O'Connor ◽  
A Kauffmann-Zeh ◽  
Y Liu ◽  
S Lehar ◽  
G I Evan ◽  
...  
Keyword(s):  
Growth Factor ◽  
Kinase Domain ◽  
Insulin Like Growth Factor ◽  
Wild Type ◽  
Atp Binding Site ◽  
Factor I ◽  
C Terminus ◽  
Igf I ◽  
Growth Factor I ◽  
Induced Apoptosis

Using a series of insulin-like growth factor I (IGF-I) receptor mutants, we have attempted to define domains required for transmitting the antiapoptotic signal from the receptor and to compare these domains with those required for mitogenesis or transformation. In FL5.12 cells transfected with wild-type IGF-I receptors, IGF-I affords protection from interleukin 3 withdrawal but is not mitogenic. An IGF-I receptor lacking a functional ATP binding site provided no protection from apoptosis. However, receptors mutated at tyrosine residue 950 or in the tyrosine cluster (1131, 1135, and 1136) within the kinase domain remained capable of suppressing apoptosis, although such mutations are known to inactivate transforming and mitogenic functions. In the C terminus of the IGF-I receptor, two mutations, one at tyrosine 1251 and one which replaced residues histidine 1293 and lysine 1294, abolished the antiapoptotic function, whereas mutation of the four serines at 1280 to 1283 did not. Interestingly, receptors truncated at the C terminus had enhanced antiapoptotic function. In Rat-1/ c-MycER fibroblasts, the Y950F mutant and the tyrosine cluster mutant could still provide protection from c-Myc-induced apoptosis, whereas mutant Y1250/1251F could not. These studies demonstrate that the domains of the IGF-I receptor required for its antiapoptotic function are distinct from those required for its proliferation or transformation functions and suggest that domains of the receptor required for inhibition of apoptosis are necessary but not sufficient for transformation.

A functional insulin-like growth factor I receptor is required for the mitogenic and transforming activities of the epidermal growth factor receptor

1994 ◽  
Vol 14 (7) ◽  
pp. 4588-4595
Author(s):  
D Coppola ◽  
A Ferber ◽  
M Miura ◽  
C Sell ◽  
C D'Ambrosio ◽  
...  
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Mouse Embryo ◽  
Wild Type Mouse ◽  
Insulin Like Growth Factor ◽  
Wild Type ◽  
Factor I ◽  
Igf I ◽  
Epidermal Growth ◽  
Growth Factor I

When wild-type mouse embryo cells are stably transfected with a plasmid constitutively overexpressing the epidermal growth factor (EGF) receptor (EGFR), the resulting cells can grow in serum-free medium supplemented solely with EGF. Supplementation with EGF also induces in these cells the transformed phenotype (growth in soft agar). However, when the same EGFR expression plasmid is introduced and overexpressed in cells derived from littermate embryos in which the insulin-like growth factor I (IGF-I) receptor genes have been disrupted by homologous recombination, the resulting cells are unable to grow or to be transformed by the addition of EGF. Reintroduction into these cells (null for the IGF-I receptor) of a wild-type (but not of a mutant) IGF-I receptor restores EGF-mediated growth and transformation. Our results indicate that at least in mouse embryo fibroblasts, the EGFR requires the presence of a functional IGF-I receptor for its mitogenic and transforming activities.

scholarly journals A functional insulin-like growth factor I receptor is required for the mitogenic and transforming activities of the epidermal growth factor receptor.

1994 ◽  
Vol 14 (7) ◽  
pp. 4588-4595 ◽  
Author(s):  
D Coppola ◽  
A Ferber ◽  
M Miura ◽  
C Sell ◽  
C D'Ambrosio ◽  
...  
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Mouse Embryo ◽  
Wild Type Mouse ◽  
Insulin Like Growth Factor ◽  
Wild Type ◽  
Factor I ◽  
Igf I ◽  
Epidermal Growth ◽  
Growth Factor I

When wild-type mouse embryo cells are stably transfected with a plasmid constitutively overexpressing the epidermal growth factor (EGF) receptor (EGFR), the resulting cells can grow in serum-free medium supplemented solely with EGF. Supplementation with EGF also induces in these cells the transformed phenotype (growth in soft agar). However, when the same EGFR expression plasmid is introduced and overexpressed in cells derived from littermate embryos in which the insulin-like growth factor I (IGF-I) receptor genes have been disrupted by homologous recombination, the resulting cells are unable to grow or to be transformed by the addition of EGF. Reintroduction into these cells (null for the IGF-I receptor) of a wild-type (but not of a mutant) IGF-I receptor restores EGF-mediated growth and transformation. Our results indicate that at least in mouse embryo fibroblasts, the EGFR requires the presence of a functional IGF-I receptor for its mitogenic and transforming activities.

scholarly journals Susceptibility to Apoptosis in Insulin-like Growth Factor-I Receptor-deficient Brown Adipocytes

2004 ◽  
Vol 15 (11) ◽  
pp. 5101-5117 ◽  
Author(s):  
Angela M. Valverde ◽  
Cecilia Mur ◽  
Michael Brownlee ◽  
Manuel Benito
Keyword(s):  
Growth Factor ◽  
Dna Fragmentation ◽  
Caspase 3 ◽  
Cell Types ◽  
Caspase 8 ◽  
Insulin Like Growth Factor ◽  
Wild Type ◽  
Brown Adipocytes ◽  
Factor I ◽  
Igf I

Fetal brown adipocytes are insulin-like growth factor-I (IGF-I) target cells. To assess the importance of the IGF-I receptor (IGF-IR) in brown adipocytes during fetal life, we have generated immortalized brown adipocyte cell lines from the IGF-IR-/- mice. Using this experimental model, we demonstrate that the lack of IGF-IR in fetal brown adipocytes increased the susceptibility to apoptosis induced by serum withdrawal. Culture of cells in the absence of serum and growth factors produced rapid DNA fragmentation (4 h) in IGF-IR-/- brown adipocytes, compared with the wild type (16 h). Consequently, cell viability was decreased more rapidly in fetal brown adipocytes in the absence of IGF-IR. Furthermore, caspase-3 activity was induced much earlier in cells lacking IGF-IR. At the molecular level, IGF-IR deficiency in fetal brown adipocytes altered the balance of the expression of several proapoptotic (Bcl-xS and Bim) and antiapoptotic (Bcl-2 and Bcl-xL) members of the Bcl-2 family. This imbalance was irreversible even though in IGF-IR-reconstituted cells. Likewise, cytosolic cytochrome c levels increased rapidly in IGF-IR-deficient cells compared with the wild type. A rapid entry of Foxo1 into the nucleus accompanied by a rapid exit from the cytosol and an earlier activation of caspase-8 were observed in brown adipocytes lacking IGF-IR upon serum deprivation. Activation of caspase-8 was inhibited by 50% in both cell types by neutralizing anti-Fas-ligand antibody. Adenoviral infection of wild-type brown adipocytes with constitutively active Foxol (ADA) increased the expression of antiapoptotic genes, decreased Bcl-xL and induced caspase-8 and -3 activities, with the final outcome of DNA fragmentation. Up-regulation of uncoupling protein-1 (UCP-1) expression in IGF-IR-deficient cells by transduction with PGC-1α or UCP-1 ameliorated caspase-3 activation, thereby retarding apoptosis. Finally, insulin treatment prevented apoptosis in both cell types. However, the survival effect of insulin on IGF-IR-/- brown adipocytes was elicited even in the absence of phosphatidylinositol 3-kinase/Akt signaling. Thus, our results demonstrate for the first time the unique role of IGF-IR in maintaining the balance of death and survival in fetal brown adipocytes.

scholarly journals Signalling pathways of insulin-like growth factor-I that are augmented by cAMP in FRTL-5 cells

2000 ◽  
Vol 348 (2) ◽  
pp. 409-416 ◽  
Author(s):  
Miyako ARIGA ◽  
Taku NEDACHI ◽  
Masakazu AKAHORI ◽  
Hideki SAKAMOTO ◽  
Yoshiaki ITO ◽  
...  
Keyword(s):  
Growth Factor ◽  
Dna Synthesis ◽  
Map Kinase ◽  
Tyrosine Phosphorylation ◽  
Signalling Pathways ◽  
Insulin Like Growth Factor ◽  
Dibutyryl Camp ◽  
Factor I ◽  
Igf I ◽  
Growth Factor I

We have reported that pretreatment of rat FRTL-5 thyroid cells with thyrotropin (TSH) markedly potentiates the mitogenic response to insulin-like growth factor-I (IGF-I). The present study was undertaken to determine whether the augmentation by cAMP of IGF-I-dependent tyrosine phosphorylation of known IGF-I receptor substrates plays an important role in the cAMP-dependent potentiation of DNA synthesis induced by IGF-I. Pretreatment with TSH or dibutyryl cAMP did not affect the IGF-I-dependent tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1). In contrast, cAMP pretreatment potentiated the tyrosine phosphorylation of IRS-2 induced by IGF-I, but did not affect the amount of IRS-2. We found that the IGF-I-dependent tyrosine phosphorylation of 66 kDa Shc (Src homology collagen) was markedly increased by cAMP pretreatment, and that this change was mainly due to an increase in the levels of 66 kDa Shc protein. Under these conditions, cAMP pretreatment significantly increased binding of Grb2 (growth-factor-receptor-bound protein 2) to Shc in response to IGF-I, and activation of MAP kinase (mitogen-activated protein kinase) induced by IGF-I was also enhanced by cAMP. The presence of PD98059, an inhibitor of MEK (MAP-kinase/Erk kinase), during treatment with IGF-I partially inhibited the cAMP-dependent augmentation of DNA synthesis in response to IGF-I. On the other hand, cAMP pretreatment increased binding of the phosphoinositide 3-kinase (PI 3-kinase) p85 subunit to IRS-2, which was reflected in PI 3-kinase activity. LY294002, a PI 3-kinase inhibitor, strongly depressed IGF-I-dependent DNA synthesis after pretreatment with and without TSH or dibutyryl cAMP. Our results suggest that the interaction between cAMP-dependent and IGF-I-dependent pathways leads to an augmentation of cell proliferation, which is mediated, at least in part, through the MAP kinase and PI 3-kinase signalling pathways. These effects are mediated by changes in tyrosine phosphorylation of IGF-I receptor substrates, including IRS-2 and Shc.

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