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High Iron Exposure from the Fetal Stage to Adulthood in Mice Alters Lipid Metabolism. Nutrients 2022; 14:nu14122451. [PMID: 35745181 PMCID: PMC9227341 DOI: 10.3390/nu14122451] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 06/02/2022] [Accepted: 06/07/2022] [Indexed: 12/11/2022] Open
Abstract
Iron supplementation is recommended during pregnancy and fetal growth. However, excess iron exposure may increase the risk of abnormal fetal development. We investigated the potential side effects of high iron levels in fetuses and through their adult life. C57BL/6J pregnant mice from 2 weeks of gestation and their offspring until 30 weeks were fed a control (CTRL, FeSO4 0 g/1 kg) or high iron (HFe, FeSO4 9.9 g/1 kg) diets. HFe group showed higher iron accumulation in the liver with increased hepcidin, reduced TfR1/2 mRNAs, and lowered ferritin heavy chain (FTH) proteins in both liver and adipose tissues despite iron loading. HFe decreased body weight, fat weight, adipocyte size, and triglyceride levels in the blood and fat, along with downregulation of lipogenesis genes, including PPARγ, C/EBPα, SREBP1c, FASN, and SCD1, and fatty acid uptake and oxidation genes, such as CD36 and PPARα. UCP2, adiponectin, and mRNA levels of antioxidant genes such as GPX4, HO-1, and NQO1 were increased in the HFe group, while total glutathione was reduced. We conclude that prolonged exposure to high iron from the fetal stage to adulthood may decrease fat accumulation by altering ferritin expression, adipocyte differentiation, and triglyceride metabolism, resulting in an alteration in normal growth.
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2
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Identification of microRNA that represses IRS-1 expression in liver. PLoS One 2018; 13:e0191553. [PMID: 29364977 PMCID: PMC5783395 DOI: 10.1371/journal.pone.0191553] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 01/07/2018] [Indexed: 11/19/2022] Open
Abstract
MicroRNAs (miRNAs) are short, non-coding RNAs that post-transcriptionally regulate gene expression and have been shown to participate in almost every cellular process. Several miRNAs have recently been implicated in glucose metabolism, but the roles of miRNAs in insulin-resistant conditions, such as obesity or type 2 diabetes, are largely unknown. Herein, we focused on miR-222, the expression of which was increased in the livers of high fat/high sucrose diet-fed mice injected with gold thioglucose (G+HFHSD). Overexpression of miR-222 in primary mouse hepatocytes attenuated Akt phosphorylation induced by insulin, indicating that miR-222 negatively regulates insulin signaling. As per in silico analysis, miR-222 potentially binds to the 3′ untranslated region (3′ UTR) of the IRS-1 gene, a key insulin signaling molecule. In fact, IRS-1 protein expression was decreased in the livers of G+HFHSD-fed mice. We further confirmed a direct interaction between miR-222 and the 3′ UTR of IRS-1 via luciferase assays. Our findings suggest that up-regulation of miR-222 followed by reduction in IRS-1 expression may be a viable mechanism of insulin resistance in the liver.
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3
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Chai SP, Fong JC. Synergistic induction of insulin resistance by endothelin-1 and cAMP in 3T3-L1 adipocytes. Biochim Biophys Acta Mol Basis Dis 2015; 1852:2048-55. [PMID: 26143144 DOI: 10.1016/j.bbadis.2015.06.026] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Revised: 05/30/2015] [Accepted: 06/25/2015] [Indexed: 12/27/2022]
Abstract
Both endothelin-1 (ET-1) and cAMP are implicated for inducing insulin resistance. Since we have shown previously that there is a crosstalk between ET-1 and cAMP signaling pathways in regulating glucose uptake in 3T3-L1 adipocytes, we extended our investigation in this study on whether they may have a synergistic effect on inducing insulin resistance. Our results showed that it was indeed the case. Insulin-stimulated glucose uptake, phosphorylation of PKB, IRS-1-associated PI3K, and IRS-1 tyrosine phosphorylation were all inhibited by ET-1 and 8-bromo cAMP in a synergistic manner. IRS-1 protein levels were similarly decreased by ET-1 and 8-bromo cAMP, attributable to suppressed mRNA expression. In addition, after correction for the loss in IRS-1 protein, the inhibition of insulin-stimulated IRS-1 tyrosine phosphorylation or IRS-1-associated PI3K was mainly caused by cAMP. Moreover, whereas IRS-2 protein levels were increased by cAMP or ET-1 plus cAMP, insulin-stimulated IRS-2-associated PI3K activities were abolished by both treatments. Furthermore, ET-1 and β-adrenergic agonists had similar synergistic inhibition on insulin-stimulated glucose uptake. In conclusion, we have shown that ET-1 and cAMP may synergistically induce insulin resistance in adipocytes via inhibiting IRS-1 expression as well as insulin-stimulated IRS-1/IRS-2 activities.
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Affiliation(s)
- Shin-Pei Chai
- Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei 112, Taiwan, ROC
| | - Jim C Fong
- Institute of Biochemistry and Molecular Biology, National Yang-Ming University, Taipei 112, Taiwan, ROC.
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4
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Li J, Shan F, Xiong G, Chen X, Guan X, Wang JM, Wang WL, Xu X, Bai Y. EGF-induced C/EBPβ participates in EMT by decreasing the expression of miR-203 in esophageal squamous cell carcinoma cells. J Cell Sci 2014; 127:3735-44. [PMID: 24994936 DOI: 10.1242/jcs.148759] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Epithelial-mesenchymal transition (EMT) is a developmental program that is associated with esophageal squamous cell carcinoma (ESCC) progression and metastasis. Recently, C/EBPβ has been reported to be an EMT inducer in cancer. However, the detailed molecular mechanisms remain unclear. Here, we report for the first time, that the truncated CCAAT-enhancer-binding protein β (C/EBPβ) LIP isoform is abnormally overexpressed and correlated with cancer metastasis in clinical specimens of human ESCC. Furthermore, we demonstrate that C/EBPβ LIP mediates epithelial growth factor (EGF)-induced EMT and increases migration and invasion of esophageal cancer cells in a manner that is dependent on miR-203 inactivation. Finally, we identified miR-203 as a direct target of C/EBPβ LIP. Disruption of C/EBPβ LIP attenuated the EGF-mediated decrease in miR-203, whereas overexpression of C/EBPβ LIP alone markedly suppressed miR-203. In addition, we demonstrated that C/EBPβ LIP inhibited miR-203 transcription by directly interacting with a conserved distal regulatory element upstream of the miR-203 locus, and in doing so, orchestrated chromatin remodeling. In conclusion, our results have revealed a new regulatory mechanism that involves C/EBPβ-LIP-mediated downregulation of miR-203, which plays a key role in EMT and metastasis.
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Affiliation(s)
- Junxia Li
- Department of Medical Genetics, Third Military Medical University, Chongqing 400038, People's Republic of China
| | - Fabo Shan
- Department of Pathophysiology and High Altitude Physiology, Third Military Medical University, Chongqing 400038, People's Republic of China
| | - Gang Xiong
- Department of Thoracic and Cardiac Surgery, Southwest Hospital, Third Military Medical University, Chongqing 400038, People's Republic of China
| | - Xuedan Chen
- Department of Medical Genetics, Third Military Medical University, Chongqing 400038, People's Republic of China
| | - Xingying Guan
- Department of Medical Genetics, Third Military Medical University, Chongqing 400038, People's Republic of China
| | - Ju-Ming Wang
- Institute of Bioinformatics and Biosignal Transduction, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan 701, Taiwan
| | - Wen-Lin Wang
- Institute of Bioinformatics and Biosignal Transduction, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan 701, Taiwan
| | - Xueqing Xu
- Molecular Biology Center, State Key Laboratory of Trauma, Burn, and Combined Injury, Research Institute of Surgery and Daping Hospital, Third Military Medical University, Chongqing 400038, People's Republic of China
| | - Yun Bai
- Department of Medical Genetics, Third Military Medical University, Chongqing 400038, People's Republic of China
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5
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Knudsen KJ, Nelander Holm GM, Krabbe JS, Listov-Saabye N, Kiehr B, Dufva M, Svendsen JE, Oleksiewicz MB. Driving gradual endogenous c-myc overexpression by flow-sorting: intracellular signaling and tumor cell phenotype correlate with oncogene expression. Arch Toxicol 2011; 83:1061-74. [PMID: 19730820 DOI: 10.1007/s00204-009-0463-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2009] [Accepted: 08/20/2009] [Indexed: 11/28/2022]
Abstract
Insulin-exposed rat mammary cancer cells were flow sorted based on a c-myc reporter plasmid encoding a destabilized green fluorescent protein. Sorted cells exhibited gradual increases in c-myc levels. Cells overexpressing c-myc by only 10% exhibited phenotypic changes attributable to c-myc overexpression, such as cell cycle disturbances, increased cell size, and overexpression of the S6 ribosomal protein. Cells overexpressing c-myc by 70% exhibited additional phenotypic changes typical of c-myc overexpression, such as increased histone H3 phosphorylation, and reduced adherence. Sorted cells also exhibited overexpression of the IGF-1R, and slightly elevated expression of the IR. Increased susceptibility to the mitogenic effect of insulin was seen in a small proportion of the sorted cells, and insulin was more effective in activating the p44/42 MAPK pathway, but not the PI3K pathway, in the sorted cells than in the nonsorted cell population. To our knowledge, this is the first in vitro system allowing functional coupling between mitogenic signaling by a well-defined growth factor and gradual overexpression of the normal, endogenous c-myc gene. Thus, our flow-sorting approach provides an alternative modeling of the receptor-mediated carcinogenic process, compared to the currently used approaches of recombinant constitutive or conditional overexpression of oncogenic transmembrane receptor tyrosine kinases or oncogenic transcription factors.
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Affiliation(s)
- Kasper Jermiin Knudsen
- Institute for Micro and Nanotechnology, Technical University of Denmark, Lyngby, Denmark
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6
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Yan C, Cao J, Wu M, Zhang W, Jiang T, Yoshimura A, Gao H. Suppressor of cytokine signaling 3 inhibits LPS-induced IL-6 expression in osteoblasts by suppressing CCAAT/enhancer-binding protein {beta} activity. J Biol Chem 2010; 285:37227-39. [PMID: 20876575 DOI: 10.1074/jbc.m110.132084] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Suppressor of cytokine signaling 3 (SOCS3) is an important intracellular protein that inhibits cytokine signaling in numerous cell types and has been implicated in several inflammatory diseases. However, the expression and function of SOCS3 in osteoblasts are not known. In this study, we demonstrated that SOCS3 expression was transiently induced by LPS in osteoblasts, and apparently contributed to the inhibition of IL-6 induction by LPS treatment. We found that tyrosine 204 of the SOCS box, the SH2 domain, and the N-terminal kinase inhibitory region (KIR) of SOCS3 were all involved in its IL-6 inhibition. Furthermore, we demonstrated that CCAAT/enhancer-binding protein (C/EBP) β was activated by LPS (increased DNA binding activity), and played a key role in LPS-induced IL-6 expression in osteoblasts. We further provided the evidence that SOCS3 functioned as a negative regulator for LPS response in osteoblasts by suppressing C/EBPβ DNA binding activity. In addition, tyrosine 204 of the SOCS box, the SH2 domain, and the N-terminal kinase inhibitory region (KIR) of SOCS3 were all required for its C/EBPβ inhibition. These findings suggest that SOCS3 by interfering with C/EBPβ activation may have an important regulatory role during bone-associated inflammatory responses.
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Affiliation(s)
- Chunguang Yan
- Center for Experimental Therapeutics and Reperfusion Injury, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA
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7
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Mardilovich K, Pankratz SL, Shaw LM. Expression and function of the insulin receptor substrate proteins in cancer. Cell Commun Signal 2009; 7:14. [PMID: 19534786 PMCID: PMC2709114 DOI: 10.1186/1478-811x-7-14] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2009] [Accepted: 06/17/2009] [Indexed: 12/13/2022] Open
Abstract
The Insulin Receptor Substrate (IRS) proteins are cytoplasmic adaptor proteins that function as essential signaling intermediates downstream of activated cell surface receptors, many of which have been implicated in cancer. The IRS proteins do not contain any intrinsic kinase activity, but rather serve as scaffolds to organize signaling complexes and initiate intracellular signaling pathways. As common intermediates of multiple receptors that can influence tumor progression, the IRS proteins are positioned to play a pivotal role in regulating the response of tumor cells to many different microenvironmental stimuli. Limited studies on IRS expression in human tumors and studies on IRS function in human tumor cell lines and in mouse models have provided clues to the potential function of these adaptor proteins in human cancer. A general theme arises from these studies; IRS-1 and IRS-4 are most often associated with tumor growth and proliferation and IRS-2 is most often associated with tumor motility and invasion. In this review, we discuss the mechanisms by which IRS expression and function are regulated and how the IRS proteins contribute to tumor initiation and progression.
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Affiliation(s)
- Katerina Mardilovich
- Department of Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
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8
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The cell growth suppressor, mir-126, targets IRS-1. Biochem Biophys Res Commun 2008; 377:136-40. [PMID: 18834857 DOI: 10.1016/j.bbrc.2008.09.089] [Citation(s) in RCA: 193] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Accepted: 09/18/2008] [Indexed: 01/08/2023]
Abstract
miRNAs are a family of approximately 22-nuleotide-long noncoding RNAs involved in the formation and progress of tumors. Since traditional methods for the detection of miRNAs expression have many disadvantages, we developed a simple method called polyA RT PCR. With this method, we detected a series of miRNAs and found that mir-126 is one of the miRNAs underexpressed in breast cancer cells. Flow cytometry analysis showed that mir-126 inhibited cell cycle progression from G1/G0 to S. Further studies revealed that mir-126 targeted IRS-1 at the translation level. Knocking down of IRS-1 suppresses cell growth in HEK293 and breast cancer cell MCF-7, which recapitulates the effects of mir-126. In conclusion, we developed a simple method for high-throughput screening of miRNAs and found that mir-126, a cell growth suppressor, targets IRS-1.
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9
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Murata Y, Tsuruzoe K, Kawashima J, Furukawa N, Kondo T, Motoshima H, Igata M, Taketa K, Sasaki K, Kishikawa H, Kahn CR, Toyonaga T, Araki E. IRS-1 transgenic mice show increased epididymal fat mass and insulin resistance. Biochem Biophys Res Commun 2007; 364:301-7. [DOI: 10.1016/j.bbrc.2007.10.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2007] [Accepted: 10/01/2007] [Indexed: 10/22/2022]
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10
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Busek SU, Fantappie M, Malaquias LC, Wilson RA, Corrêa-Oliveira R, Oliveira GC. Cis-acting elements, CArG-, E-, CCAAT- and TATA-boxes may be involved in sexually regulated gene transcription in Schistosoma mansoni. Mem Inst Oswaldo Cruz 2003; 97 Suppl 1:85-90. [PMID: 12426599 DOI: 10.1590/s0074-02762002000900017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Schistosomes undergo various morphological and metabolic changes during their development, reflected in a finely tuned regulation of protein and/or gene expression. The mechanisms involved in the control of gene expression during the development of the parasite are not understood. Two actin genes had been previously cloned and observed to be differentially expressed during the maturation of the parasite. The SmAct gene contains four putative cis-regulatory elements (TATA-, CCAAT-, E- and CArG-boxes). Our objective was to investigate in greater detail the expression pattern of two actin genes and verify if the binding of nuclear proteins to the promoter elements of SmAct correlated with the expression profile observed. We detected little variation in the expression of actin genes during the first seven days of schistosomula culture in vitro. However, we observed significantly higher levels of expression in males compared to female adults. CArG and CCAAT elements bound to a greater extent and formed distinct complexes with male in comparison to female nuclear extracts. In contrast, female extracts bound weakly to the E-box probe while no binding was observed with male extracts. Taken together these results describe cis-acting elements that appear to be involved in sexually regulated gene expression in Schistosoma mansoni.
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Affiliation(s)
- S U Busek
- Centro de Pesquisas René Rachou, Fiocruz, Belo Horizonte, MG, 30190-002, Brasil
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11
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Van Obberghen E, Baron V, Delahaye L, Emanuelli B, Filippa N, Giorgetti-Peraldi S, Lebrun P, Mothe-Satney I, Peraldi P, Rocchi S, Sawka-Verhelle D, Tartare-Deckert S, Giudicelli J. Surfing the insulin signaling web. Eur J Clin Invest 2001; 31:966-77. [PMID: 11737239 DOI: 10.1046/j.1365-2362.2001.00896.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The diverse biological actions of insulin and insulin-like growth factor I (IGF-I) are initiated by binding of the polypeptides to their respective cell surface tyrosine kinase receptors. These activated receptors phosphorylate a series of endogenous substrates on tyrosine, amongst which the insulin receptor substrate (IRS) proteins are the best characterized. Their phosphotyrosine-containing motifs become binding sites for Src homology 2 (SH2) domains on proteins such as SH2 domain-containing protein-tyrosine-phosphatase (SHP)-2/Syp, growth factor receptor bound-2 protein, (Grb-2), and phosphatidyl inositol 3 kinase (PI3 kinase), which participate in activation of specific signaling cascades. However, the IRS molecules are not only platforms for signaling molecules, they also orchestrate the generation of signal specificity, integration of signals induced by several extracellular stimuli, and signal termination and modulation. An extensive review is beyond the scope of the present article, which will be centered on our own contribution and reflect our biases.
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Affiliation(s)
- E Van Obberghen
- Inserm U 145, IFR 50, Faculté de Médecine, Avenue de Valombrose, Nice Cedex, France.
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12
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Yoshizato K, Shirotani T, Furukawa N, Taguchi T, Motoshima H, Toyonaga T, Hirashima Y, Kawashima J, Ebina Y, Shichiri M, Araki E. Identification of a cis-acting element and a novel trans-acting factor of the human insulin receptor gene in HepG2 and rat liver cells. Biochem Biophys Res Commun 2001; 280:428-34. [PMID: 11162534 DOI: 10.1006/bbrc.2000.4140] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The liver is a major target organ of insulin and is important for glucose homeostasis. We analyzed the tissue specific regulation of the insulin receptor gene in the liver by studying the cis-acting element and trans-acting factor of the human insulin receptor gene in human hepatoma cell line, HepG2 cells. In the chloramphenicol acetyl transferase (CAT) assay with chimeric plasmids containing various deletions and insertions of the human insulin receptor promoter/CAT gene, a HepG2 cell specific cis-acting element was identified between nt -592 to -577 of the promoter. In electrophoretic mobility shift assay and UV cross-link analysis, a 35-kDa nuclear protein that bound to 5'-TCCCTCCC-3' (nt -588 to -581) sequence was identified in HepG2 cells as well as in rat hepatocytes. This nuclear protein, designated as hepatocyte-specific transcription factor of the insulin receptor gene (HTFIR), might play an important role in tissue-specific expression of the insulin receptor gene in the liver.
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Affiliation(s)
- K Yoshizato
- Department of Metabolic Medicine, Kumamoto University School of Medicine, Kumamoto, Japan
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13
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Lebrun P, Baron V, Hauck CR, Schlaepfer DD, Van Obberghen E. Cell adhesion and focal adhesion kinase regulate insulin receptor substrate-1 expression. J Biol Chem 2000; 275:38371-7. [PMID: 10967115 DOI: 10.1074/jbc.m006162200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Integrins are transmembrane receptors involved in interactions between cells and extracellular matrix proteins. Here we show that cell adhesion regulates insulin receptor substrate-1 (IRS-1) mRNA synthesis. When fibroblasts are held in suspension, lower levels of IRS-1 mRNA, but not of IRS-2 mRNA, are detected, and this effect is due to the negative regulation of IRS-1 transcription rather than to decreased mRNA stability. Upon fibronectin- or vitronectin-mediated integrin stimulation, the level of IRS-1 mRNA was restored within 4 h. The focal adhesion kinase (FAK) is known to be activated upon integrin stimulation, and we found that IRS-1 was not expressed in FAK(-)(/-) cells. Stable re-expression of epitope-tagged FAK in FAK(-)(/-) fibroblasts (DA2 cells) restored normal levels of IRS-1 expression, confirming that IRS-1 mRNA expression is regulated by FAK. It is known that integrins activate the JNK pathway. However, in adherent FAK(-)(/-) cells, we failed to detect activation of JNK, whereas JNK was stimulated in DA2 cells. This confirms the role of FAK in integrin-induced JNK stimulation. FAK-independent stimulation of JNK with anisomycin treatment both in FAK(-)(/-) cells and in suspended FAK(+/+) cells confirmed that IRS-1 mRNA transcription can be partially regulated by JNK. We suggest that integrins can modulate insulin and insulin-like growth factor-1 signaling pathways by regulating the levels of IRS-1 in cells and that FAK-mediated signaling to JNK is one pathway involved in this process.
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Affiliation(s)
- P Lebrun
- INSERM U145, Institut Federatif de Recherche 50, Avenue de Valombrose, 06107 Nice Cédex 2, France
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14
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Wang L, Shao J, Muhlenkamp P, Liu S, Klepcyk P, Ren J, Friedman JE. Increased insulin receptor substrate-1 and enhanced skeletal muscle insulin sensitivity in mice lacking CCAAT/enhancer-binding protein beta. J Biol Chem 2000; 275:14173-81. [PMID: 10747954 DOI: 10.1074/jbc.m000764200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CCAAT/enhancer-binding protein beta (C/EBPbeta) controls gene transcription and metabolic processes in a variety of insulin-sensitive tissues; however, its role in regulating insulin responsiveness in vivo has not been investigated. We performed hyperinsulinemic-euglycemic clamps in awake, non-stressed, chronically catheterized adult mice homozygous for a deletion in the gene for C/EBPbeta (C/EBPbeta(-/-)). Fasting plasma insulin, glucose, and free fatty acid (FFA) levels were significantly lower in C/EBPbeta(-/-) mice compared with wild-type (WT) controls. Acute hyperinsulinemia (4 h) suppressed hepatic glucose production, phosphoenolpyruvate carboxykinase mRNA, and plasma FFA to a similar extent in WT and C/EBPbeta(-/-) mice, suggesting that C/EBPbeta deletion does not alter the metabolic and gene regulatory response to insulin in liver and adipose tissue. In contrast, using submaximal (5 milliunits/kg/min) and maximal (20 milliunits/kg/min) insulin infusions, whole-body glucose disposal was 77% (p < 0.01) and 33% (p < 0.05) higher in C/EBPbeta(-/-) mice, respectively, compared with WT mice. Maximal insulin-stimulated 3-O-methylglucose uptake in isolated soleus muscle was 54% greater in C/EBPbeta(-/-) mice (p < 0.05). Furthermore, insulin-stimulated insulin receptor and Akt Ser(473) phosphorylation and phosphatidylinositol 3-kinase activity were 1.6-2.5-fold greater in skeletal muscle from C/EBPbeta(-/-) mice compared with WT mice. The level of insulin receptor substrate-1 protein was increased 2-fold in skeletal muscle from C/EBPbeta(-/-) mice. These results demonstrate that C/EBPbeta deletion decreases plasma FFA levels and increases insulin signal transduction specifically in skeletal muscle, and both contribute to increased whole-body insulin sensitivity.
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Affiliation(s)
- L Wang
- Department of Nutrition, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106-4935, USA
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15
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Matsumura T, Sakai M, Matsuda K, Furukawa N, Kaneko K, Shichiri M. Cis-acting DNA elements of mouse granulocyte/macrophage colony-stimulating factor gene responsive to oxidized low density lipoprotein. J Biol Chem 1999; 274:37665-72. [PMID: 10608823 DOI: 10.1074/jbc.274.53.37665] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We previously demonstrated that the induction of granulocyte/macrophage colony-stimulating factor (GM-CSF) played an important role in oxidized low density lipoprotein (Ox-LDL)-induced macrophage growth as a growth priming factor. The present study was undertaken to elucidate the transcriptional regulation of the GM-CSF gene using Raw 264.7 cells, a mouse macrophage cell line. Transient transfection into Raw 264.7 cells of several 5'-flanking regions of GM-CSF gene-luciferase fusion plasmids revealed the presence of two positive regulatory sites in regions spanning from -97 to -59 and from -59 to -37 and one negative regulatory site from -120 to -97 in unstimulated cells. When cells were stimulated by Ox-LDL, there was one positive responsive site from -225 to -120 and one negative responsive site from -97 to -59, which contained the NF-kappaB binding site. Computer analysis revealed the presence of a putative AP-2 binding site from -169 to -160. Mutagenesis of a putative AP-2 binding site and tandem repeat of this site in plasmid resulted in a complete loss and increased responsiveness to Ox-LDL, respectively. Electrophoretic mobility shift assay showed that Ox-LDL increased the binding of certain nuclear protein(s) to a putative AP-2 binding site but decreased their binding to NF-kappaB binding site. Supershift assay showed that nuclear proteins bound to NF-kappaB binding site contained, at least, p50 and p65 but could not demonstrate nuclear protein(s) bound to a putative AP-2 binding site. Our results suggested that a putative AP-2 binding site from -169 to -160 was a positive responsive element to Ox-LDL and that the NF-kappaB binding site from -91 to -82 was a negative responsive element in Ox-LDL-induced GM-CSF transcription.
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Affiliation(s)
- T Matsumura
- Department of Metabolic Medicine, Kumamoto University School of Medicine, Kumamoto 860-8556, Japan
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16
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Ji C, Chen Y, Centrella M, McCarthy TL. Activation of the insulin-like growth factor-binding protein-5 promoter in osteoblasts by cooperative E box, CCAAT enhancer-binding protein, and nuclear factor-1 deoxyribonucleic acid-binding sequences. Endocrinology 1999; 140:4564-72. [PMID: 10499512 DOI: 10.1210/endo.140.10.7061] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Insulin-like growth factor (IGF)-binding protein-5 (IGFBP-5) has IGF-dependent and -independent actions. PGE2 rapidly increases IGFBP-5 expression by osteoblasts through cAMP-dependent processes. A minimal DNA sequence required for basal and PGE2-stimulated IGFBP-5 promoter activity spans -69 to -35 bp. This region adjoins a functional TATA box and contains E box, CCAAT enhancer-binding protein (C/EBP), nuclear factor-1 (NF-1), and activator protein-2 (AP-2) transcription factor related binding motifs. In this study we compared minimal promoter sequences of -74 to +120 bp, without or with mutations in each potential regulatory element, by reporter gene expression and electrophoretic mobility shift assays. Mutation of the E box-related element reduced basal promoter activity by 50% and eliminated the 2-fold stimulatory effect of PGE2. In contrast, mutations in the C/EBP- or NF-1-related elements also reduced basal promoter activity without fully eliminating the PGE2 effect. Overexpression of C/EBPdelta stimulated basal IGFBP-5 promoter activity, and this effect was eliminated by mutating the C/EBP-binding site. However, mutation of the AP-2-binding site or overexpression of AP-2 did not correlate with basal or PGE2-induced promoter activation. By electrophoretic mobility shift assay, prominent gel shift complexes occurred with osteoblast nuclear extracts and 32P-labeled probes spanning the E box-, C/EBP-, and NF-1-related motifs. These gel shift complexes were depleted by specific binding site mutations and were enhanced by PGE2. Increased binding by extracts from PGE2-treated cultures was blocked by cycloheximide treatment. These results identify several elements as integral binding sequences for both basal and PGE2-stimulated IGFBP-5 promoter activity. They further reveal that multiple sequences within this cluster form a basic transcription unit where nuclear factors can accumulate in a protein synthesis-dependent way and enhance IGFBP-5 expression by osteoblasts in response to PGE2.
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Affiliation(s)
- C Ji
- Yale University School of Medicine, Section of Plastic Surgery, New Haven, Connecticut 06520-8041, USA
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17
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Salerno M, Sisci D, Mauro L, Guvakova MA, Ando S, Surmacz E. Insulin receptor substrate 1 is a target for the pure antiestrogen ICI 182,780 in breast cancer cells. Int J Cancer 1999; 81:299-304. [PMID: 10188734 DOI: 10.1002/(sici)1097-0215(19990412)81:2<299::aid-ijc21>3.0.co;2-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The pure antiestrogen ICI 182,780 inhibits insulin-like growth factor (IGF)-dependent proliferation in hormone-responsive breast cancer cells. However, the interactions of ICI 182,780 with IGF-I receptor (IGF-IR) intracellular signaling have not been characterized. Here, we studied the effects of ICI 182,780 on IGF-IR signal transduction in MCF-7 breast cancer cells and in MCF-7-derived clones overexpressing either the IGF-IR or its 2 major substrates, insulin receptor substrate 1 (IRS-1) or src/collagen homology proteins (SHC). ICI 182,780 blocked the basal and IGF-I-induced growth in all studied cells in a dose-dependent manner; however, the clones with the greatest IRS-1 overexpression were clearly least sensitive to the drug. Pursuing ICI 182,780 interaction with IRS-1, we found that the antiestrogen reduced IRS-1 expression and tyrosine phosphorylation in several cell lines in the presence or absence of IGF-I. Moreover, in IRS-1-overexpressing cells, ICI 182,780 decreased IRS-1/p85 and IRS-1/GRB2 binding. The effects of ICI 182,780 on IGF-IR protein expression were not significant; however, the drug suppressed IGF-I-induced (but not basal) IGF-IR tyrosine phosphorylation. The expression and tyrosine phosphorylation of SHC as well as SHC/GRB binding were not influenced by ICI 182,780. In summary, downregulation of IRS-1 may represent one of the mechanisms by which ICI 182,780 inhibits the growth of breast cancer cells. Thus, overexpression of IRS-1 in breast tumors could contribute to the development of antiestrogen resistance.
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Affiliation(s)
- M Salerno
- Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA
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18
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Wu Z, Rosen ED, Brun R, Hauser S, Adelmant G, Troy AE, McKeon C, Darlington GJ, Spiegelman BM. Cross-regulation of C/EBP alpha and PPAR gamma controls the transcriptional pathway of adipogenesis and insulin sensitivity. Mol Cell 1999; 3:151-8. [PMID: 10078198 DOI: 10.1016/s1097-2765(00)80306-8] [Citation(s) in RCA: 795] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mice deficient in C/EBP alpha have defective development of adipose tissue, but the precise role of C/EBP alpha has not been defined. Fibroblasts from C/EBP alpha(-/-) mice undergo adipose differentiation through expression and activation of PPAR gamma, though several clear defects are apparent. C/EBP alpha-deficient adipocytes accumulates less lipid, and they do not induce endogenous PPAR gamma, indicating that cross-regulation between C/EBP alpha and PPAR gamma is important in maintaining the differentiated state. The cells also show a complete absence of insulin-stimulated glucose transport, secondary to reduced gene expression and tyrosine phosphorylation for the insulin receptor and IRS-1. These results define multiple roles for C/EBP alpha in adipogenesis and show that cross-regulation between PPAR gamma and C/EBP alpha is a key component of the transcriptional control of this cell lineage.
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Affiliation(s)
- Z Wu
- Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA
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19
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Choi BH, Park CJ, Rho HM. Insulin activates the hepatitis B virus X gene through the activating protein-1 binding site in HepG2 cells. DNA Cell Biol 1998; 17:951-6. [PMID: 9839804 DOI: 10.1089/dna.1998.17.951] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Insulin stimulates cellular oncogenic activators such as c-jun, c-fos, and c-myc; and hepatitis B virus (HBV) X, a viral transactivator, is known to induce liver cancer in transgenic mice. In this respect, the effect of insulin on the expression of HBx protein was investigated in HepG2 cells. Insulin-stimulated transcription from the HBV X promoter in a dose-dependent manner was assessed by chloramphenicol acetyltransferase (CAT) assay. A mutation preventing AP-1 binding to the E element abolished the activation of the HBV X promoter by insulin. In addition, insulin stimulated the minimal thymidine kinase (tk) gene promoter activity through both the HBV E element and the consensus AP-1 binding site in HepG2 cells. An electrophoretic mobility shift assay (EMSA) using insulin-treated HepG2 nuclear extracts showed that insulin actually enhanced the binding of nuclear proteins to the HBV E element as well as to the consensus AP-1 binding site. Both HBV E and AP-1 oligonucleotides were effective competitors for this binding. These results showed that insulin elevated the expression of HBx protein through the AP-1 binding site of HBV EnI. We suggest that insulin can augment the role of HBx in the development of hepatocellular carcinoma (HCC) in HBV-infected liver, probably through interaction with other cellular oncogenes.
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Affiliation(s)
- B H Choi
- Department of Molecular Biology and Research Center for Cell Differentiation, Seoul National University, Korea
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