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Matherne MG, Phillips ES, Embrey SJ, Burke CM, Machado HL. Emerging functions of C/EBPβ in breast cancer. Front Oncol 2023; 13:1111522. [PMID: 36761942 PMCID: PMC9905667 DOI: 10.3389/fonc.2023.1111522] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 01/05/2023] [Indexed: 01/26/2023] Open
Abstract
Breast tumorigenesis relies on complex interactions between tumor cells and their surrounding microenvironment, orchestrated by tightly regulated transcriptional networks. C/EBPβ is a key transcription factor that regulates the proliferation and differentiation of multiple cell types and modulates a variety of biological processes such as tissue homeostasis and the immune response. In addition, C/EBPβ has well-established roles in mammary gland development, is overexpressed in breast cancer, and has tumor-promoting functions. In this review, we discuss context-specific roles of C/EBPβ during breast tumorigenesis, isoform-specific gene regulation, and regulation of the tumor immune response. We present challenges in C/EBPβ biology and discuss the importance of C/EBPβ isoform-specific gene regulation in devising new therapeutic strategies.
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Affiliation(s)
- Megan G. Matherne
- Department of Biochemistry and Molecular Biology, Tulane School of Medicine, New Orleans, LA, United States
| | - Emily S. Phillips
- Department of Biochemistry and Molecular Biology, Tulane School of Medicine, New Orleans, LA, United States
| | - Samuel J. Embrey
- Department of Biochemistry and Molecular Biology, Tulane School of Medicine, New Orleans, LA, United States
| | - Caitlin M. Burke
- Department of Biochemistry and Molecular Biology, Tulane School of Medicine, New Orleans, LA, United States
| | - Heather L. Machado
- Department of Biochemistry and Molecular Biology, Tulane School of Medicine, New Orleans, LA, United States,Tulane Cancer Center, Louisiana Cancer Research Consortium, New Orleans, LA, United States,*Correspondence: Heather L. Machado,
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2
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Spike AJ, Rosen JM. C/EBPß Isoform Specific Gene Regulation: It's a Lot more Complicated than you Think! J Mammary Gland Biol Neoplasia 2020; 25:1-12. [PMID: 32078094 PMCID: PMC7694698 DOI: 10.1007/s10911-020-09444-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Accepted: 02/06/2020] [Indexed: 11/29/2022] Open
Abstract
It has been almost 30 years since C/EBPß was discovered. Seminal studies have shown that C/EBPß is a master regulator of mammary gland development and has been shown to control and influence proliferation and differentiation through varying mechanisms. The single-exon C/EBPß mRNA yields at least three different protein isoforms which have diverse, specific, context-dependent, and often non-overlapping roles throughout development and breast cancer progression. These roles are dictated by a number of complex factors including: expression levels of other C/EBP family members and their stoichiometry relative to the isoform in question, binding site affinity, post-translational modifications, co-factor expression, and even hormone levels and lactogenic status. Here we summarize the historical work up to the latest findings in the field on C/EBPß in the mammary gland and in breast cancer. With the current emphasis on improving immunotherapy in breast cancer the role of specific C/EBPß isoforms in regulating specific chemokine and cytokine expression and the immune microenvironment will be of increasing interest.
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Affiliation(s)
- Aaron J Spike
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA
| | - Jeffrey M Rosen
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX, USA.
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3
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Wang W, Do HN, Aupperlee MD, Durairaj S, Flynn EE, Miksicek RJ, Haslam SZ, Schwartz RC. C/EBPβ LIP and c-Jun synergize to regulate expression of the murine progesterone receptor. Mol Cell Endocrinol 2018; 477:57-69. [PMID: 29870755 PMCID: PMC6153074 DOI: 10.1016/j.mce.2018.06.001] [Citation(s) in RCA: 4] [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] [Received: 12/05/2017] [Revised: 05/31/2018] [Accepted: 06/01/2018] [Indexed: 01/11/2023]
Abstract
CCAAT/enhancer binding protein β (C/EBPβ) is required for murine mammary ductal morphogenesis and alveologenesis. Progesterone is critical for proliferation and alveologenesis in adult mammary glands, and there is a similar requirement for progesterone receptor isoform B (PRB) in alveologenesis. We examined C/EBPβ regulation of PR expression. All three C/EBPβ isoforms, including typically inhibitory LIP, transactivated the PR promoter. LIP, particularly, strongly synergized with c-Jun to drive PR transcription. Endogenous C/EBPβ and c-Jun stimulated a PR promoter-reporter and these two factors showed promoter occupancy on the endogenous PR gene. Additionally, LIP overexpression elevated endogenous PR protein expression. In pregnancy, both PRB and the relative abundance of LIP among C/EBPβ isoforms increase. Consistent with a role in PRB expression, in vivo C/EBPβ and PR isoform A expression showed mutually exclusive localization in mammary epithelium, while C/EBPβ and PRB largely co-localized. We suggest a critical role for C/EBPβ, particularly LIP, in PRB expression.
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Affiliation(s)
- Weizhong Wang
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA
| | - Han Ngoc Do
- Cell and Molecular Biology Program, Michigan State University, East Lansing, MI, 48824, USA
| | - Mark D Aupperlee
- Department of Physiology, Michigan State University, East Lansing, MI, 48824, USA; Breast Cancer and the Environment Research Program, Michigan State University, East Lansing, MI, 48824, USA
| | - Srinivasan Durairaj
- Department of Physiology, Michigan State University, East Lansing, MI, 48824, USA
| | - Emily E Flynn
- Genetics Program, Michigan State University, East Lansing, MI, 48824, USA
| | - Richard J Miksicek
- Department of Physiology, Michigan State University, East Lansing, MI, 48824, USA
| | - Sandra Z Haslam
- Department of Physiology, Michigan State University, East Lansing, MI, 48824, USA; Breast Cancer and the Environment Research Program, Michigan State University, East Lansing, MI, 48824, USA
| | - Richard C Schwartz
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, 48824, USA; Breast Cancer and the Environment Research Program, Michigan State University, East Lansing, MI, 48824, USA.
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Schröder M, Loos S, Naumann SK, Bachran C, Krötschel M, Umansky V, Helming L, Swee LK. Identification of inhibitors of myeloid-derived suppressor cells activity through phenotypic chemical screening. Oncoimmunology 2016; 6:e1258503. [PMID: 28197378 DOI: 10.1080/2162402x.2016.1258503] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 10/26/2016] [Accepted: 11/03/2016] [Indexed: 01/04/2023] Open
Abstract
Tumors are infiltrated by cells of the immune system that interact through complex regulatory networks. Although tumor-specific CD8+ T cells can be found in peripheral blood and tumor samples from cancer patients, their function is inhibited by immunosuppressive cells such as regulatory T cells, tumor-associated macrophages, and myeloid-derived suppressor cells (MDSC). Recent clinical successes have demonstrated that alleviating immunosuppression and T cell exhaustion translates into long-term clinical benefits. Although tremendous progress has been achieved, tools that afford unbiased approaches and screenings to uncover new potential inhibitors or gene targets are lacking. In this study, we describe a system based on immortalized progenitors that allows straightforward investigation of myeloid cells. We show that bone marrow progenitors immortalized through the transduction of NUP98-HOXB4 transgene can be differentiated into CD11b+Gr-1+ MDSC that express Arginase-1 and PD-L1, produce reactive oxygen and nitrogen species, and suppress T cell function in vitro. To uncover chemical probes that interfere with MDSC biology, we performed a chemical phenotypic screening and identified 3-deazaneplanocin A as a novel modulator of MDSC functions. We characterized and compared the effect of 3-deazaneplanocin-A and all-trans retinoic acid, a well-known modulator of MDSC activity, on the expression of effector molecules and immunosuppressive functions of MDSC. Altogether, this proof-of-principle opens new possibilities for the identification of drugs targeting myeloid cells with immunosuppressive activities.
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Affiliation(s)
| | - Simone Loos
- BioMed X Innovation Center , Heidelberg, Germany
| | | | | | | | - Viktor Umansky
- Skin Cancer Unit, German Cancer Research Center (DKFZ), Heidelberg, Germany; Department of Dermatology, Venereology and Allergology, University Medical Center Mannheim, Ruprecht-Karl University of Heidelberg, Heidelberg, Germany
| | | | - Lee Kim Swee
- BioMed X Innovation Center , Heidelberg, Germany
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5
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Sawada S, Chosa N, Takizawa N, Yokota J, Igarashi Y, Tomoda K, Kondo H, Yaegashi T, Ishisaki A. Establishment of mesenchymal stem cell lines derived from the bone marrow of green fluorescent protein-transgenic mice exhibiting a diversity in intracellular transforming growth factor-β and bone morphogenetic protein signaling. Mol Med Rep 2016; 13:2023-31. [PMID: 26781600 PMCID: PMC4768972 DOI: 10.3892/mmr.2016.4794] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Accepted: 08/04/2015] [Indexed: 12/28/2022] Open
Abstract
Cytokines and their intercellular signals regulate the multipotency of mesenchymal stem cells (MSCs). The present study established the MSC lines SG-2, -3, and -5 from the bone marrow of green fluorescent protein (GFP)-transgenic mice. These cell lines clearly expressed mouse MSC markers Sca-1 and CD44, and SG-2 and -5 cells retained the potential for osteogenic and adipogenic differentiation in the absence of members of the transforming growth factor (TGF)-β superfamily. By contrast, SG-3 cells only retained adipogenic differentiation potential. Analysis of cytokine and cytokine receptor expression in these SG cell lines showed that bone morphogenetic protein (BMP) receptor 1B was most highly expressed in the SG-3 cells, which underwent osteogenesis in response to BMP, while TGF-β receptor II was most highly expressed in SG-3 and -5 cells. However, it was unexpectedly noted that phosphorylation of Smad 2, a major transcription factor, was induced by TGF-β1 in SG-2 cells but not in SG-3 or -5 cells. Furthermore, TGF-β1 clearly induced the expression of Smad-interacting transcription factor CCAAT/enhancer binding protein-β in SG-2 but not in SG-3 or -5 cells. These results demonstrated the establishment of TGF-β-responsive SG-2 MSCs, BMP-responsive SG-3 MSCs and TGF-β/BMP-unresponsive SG-5 MSCs, each of which was able to be traced by GFP fluorescence after transplantation into in vivo experimental models. In conclusion, the present study suggested that these cell lines may be used to explore how the TGF-β superfamily affects the proliferation and differentiation status of MSCs in vivo.
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Affiliation(s)
- Shunsuke Sawada
- Division of Cellular Biosignal Sciences, Department of Biochemistry, Iwate Medical University, Yahaba, Iwate 028‑3694, Japan
| | - Naoyuki Chosa
- Division of Cellular Biosignal Sciences, Department of Biochemistry, Iwate Medical University, Yahaba, Iwate 028‑3694, Japan
| | - Naoki Takizawa
- Division of Cellular Biosignal Sciences, Department of Biochemistry, Iwate Medical University, Yahaba, Iwate 028‑3694, Japan
| | - Jun Yokota
- Division of Cellular Biosignal Sciences, Department of Biochemistry, Iwate Medical University, Yahaba, Iwate 028‑3694, Japan
| | - Yasuyuki Igarashi
- Division of Cellular Biosignal Sciences, Department of Biochemistry, Iwate Medical University, Yahaba, Iwate 028‑3694, Japan
| | - Koichi Tomoda
- Department of Otolaryngology, Dentistry and Oral Surgery, Kansai Medical University, Hirakata, Osaka 573‑1010, Japan
| | - Hisatomo Kondo
- Department of Prosthodontics and Oral Implantology, Iwate Medical University School of Dentistry, Morioka, Iwate 020‑8505, Japan
| | - Takashi Yaegashi
- Division of Periodontology, Department of Conservative Dentistry, Iwate Medical University School of Dentistry, Morioka, Iwate 020‑8505, Japan
| | - Akira Ishisaki
- Division of Cellular Biosignal Sciences, Department of Biochemistry, Iwate Medical University, Yahaba, Iwate 028‑3694, Japan
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Perino A, Pols TWH, Nomura M, Stein S, Pellicciari R, Schoonjans K. TGR5 reduces macrophage migration through mTOR-induced C/EBPβ differential translation. J Clin Invest 2014; 124:5424-36. [PMID: 25365223 DOI: 10.1172/jci76289] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 09/30/2014] [Indexed: 02/06/2023] Open
Abstract
The bile acid-responsive G protein-coupled receptor TGR5 is involved in several metabolic processes, and recent studies suggest that TGR5 activation may promote pathways that are protective against diet-induced diabetes. Here, we investigated the role of macrophage-specific TGR5 signaling in protecting adipose tissue from inflammation and associated insulin resistance. Examination of adipose tissue from obese mice lacking macrophage Tgr5 revealed enhanced inflammation, increased chemokine expression, and higher macrophage numbers compared with control obese animals. Moreover, macrophage-specific deletion of Tgr5 exacerbated insulin resistance in obese animals. Conversely, pharmacological activation of TGR5 markedly decreased LPS-induced chemokine expression in primary macrophages. This reduction was mediated by AKT-dependent activation of mTOR complex 1, which in turn induced the differential translation of the dominant-negative C/EBPβ isoform, liver inhibitory protein (LIP). Overall, these studies reveal a signaling pathway downstream of TGR5 that modulates chemokine expression in response to high-fat diet and suggest that targeting this pathway has the potential to be therapeutically exploited for prevention of chronic inflammatory diseases and type 2 diabetes mellitus.
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7
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Rehm A, Gätjen M, Gerlach K, Scholz F, Mensen A, Gloger M, Heinig K, Lamprecht B, Mathas S, Bégay V, Leutz A, Lipp M, Dörken B, Höpken UE. Dendritic cell-mediated survival signals in Eμ-Myc B-cell lymphoma depend on the transcription factor C/EBPβ. Nat Commun 2014; 5:5057. [PMID: 25266931 DOI: 10.1038/ncomms6057] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 08/21/2014] [Indexed: 01/07/2023] Open
Abstract
The capacity of dendritic cells (DCs) to regulate tumour-specific adaptive immune responses depends on their proper differentiation and homing status. Whereas DC-associated tumour-promoting functions are linked to T-cell tolerance and formation of an inflammatory milieu, DC-mediated direct effects on tumour growth have remained unexplored. Here we show that deletion of DCs substantially delays progression of Myc-driven lymphomas. Lymphoma-exposed DCs upregulate immunomodulatory cytokines, growth factors and the CCAAT/enhancer-binding protein β (C/EBPβ). Moreover, Eμ-Myc lymphomas induce the preferential translation of the LAP/LAP* isoforms of C/EBPβ. C/EBPβ(-/-) DCs are unresponsive to lymphoma-associated cytokine changes and in contrast to wild-type DCs, they are unable to mediate enhanced Eμ-Myc lymphoma cell survival. Antigen-specific T-cell proliferation in lymphoma-bearing mice is impaired; however, this immune suppression is reverted by the DC-restricted deletion of C/EBPβ. Thus, we show that C/EBPβ-controlled DC functions are critical steps for the creation of a lymphoma growth-promoting and -immunosuppressive niche.
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Affiliation(s)
- Armin Rehm
- 1] Department of Hematology, Oncology and Tumorimmunology, Max-Delbrück-Center for Molecular Medicine, MDC, 13125 Berlin, Germany [2] Department of Hematology and Oncology, Charité-Universitätsmedizin Berlin, Campus Virchow-Klinikum, 13353 Berlin, Germany
| | - Marcel Gätjen
- Department of Hematology, Oncology and Tumorimmunology, Max-Delbrück-Center for Molecular Medicine, MDC, 13125 Berlin, Germany
| | - Kerstin Gerlach
- Department of Hematology, Oncology and Tumorimmunology, Max-Delbrück-Center for Molecular Medicine, MDC, 13125 Berlin, Germany
| | - Florian Scholz
- Department of Tumor Genetics and Immunogenetics, Max-Delbrück-Center for Molecular Medicine, MDC, 13125 Berlin, Germany
| | - Angela Mensen
- 1] Department of Hematology, Oncology and Tumorimmunology, Max-Delbrück-Center for Molecular Medicine, MDC, 13125 Berlin, Germany [2]
| | - Marleen Gloger
- Department of Hematology, Oncology and Tumorimmunology, Max-Delbrück-Center for Molecular Medicine, MDC, 13125 Berlin, Germany
| | - Kristina Heinig
- Department of Tumor Genetics and Immunogenetics, Max-Delbrück-Center for Molecular Medicine, MDC, 13125 Berlin, Germany
| | - Björn Lamprecht
- Department of Hematology, Oncology and Tumorimmunology, Max-Delbrück-Center for Molecular Medicine, MDC, 13125 Berlin, Germany
| | - Stephan Mathas
- 1] Department of Hematology, Oncology and Tumorimmunology, Max-Delbrück-Center for Molecular Medicine, MDC, 13125 Berlin, Germany [2] Department of Hematology and Oncology, Charité-Universitätsmedizin Berlin, Campus Virchow-Klinikum, 13353 Berlin, Germany
| | - Valérie Bégay
- Department of Cell Differentiation and Tumorigenesis, Max-Delbrück-Center for Molecular Medicine, MDC, 13125 Berlin, Germany
| | - Achim Leutz
- Department of Cell Differentiation and Tumorigenesis, Max-Delbrück-Center for Molecular Medicine, MDC, 13125 Berlin, Germany
| | - Martin Lipp
- Department of Tumor Genetics and Immunogenetics, Max-Delbrück-Center for Molecular Medicine, MDC, 13125 Berlin, Germany
| | - Bernd Dörken
- 1] Department of Hematology, Oncology and Tumorimmunology, Max-Delbrück-Center for Molecular Medicine, MDC, 13125 Berlin, Germany [2] Department of Hematology and Oncology, Charité-Universitätsmedizin Berlin, Campus Virchow-Klinikum, 13353 Berlin, Germany
| | - Uta E Höpken
- Department of Tumor Genetics and Immunogenetics, Max-Delbrück-Center for Molecular Medicine, MDC, 13125 Berlin, Germany
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Atlas E, Pope L, Wade MG, Kawata A, Boudreau A, Boucher JG. Bisphenol A increases aP2 expression in 3T3L1 by enhancing the transcriptional activity of nuclear receptors at the promoter. Adipocyte 2014; 3:170-9. [PMID: 25068083 PMCID: PMC4110093 DOI: 10.4161/adip.28436] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 03/03/2014] [Accepted: 03/04/2014] [Indexed: 01/22/2023] Open
Abstract
Environmental pollutants, such as bisphenol A (BPA), have the potential to affect the differentiation processes and the biology of the adipose tissue. The 3T3-L1 model is one of the murine cell models used extensively for the investigation of the molecular events that govern the differentiation of adipocytes from a committed preadipocyte to a mature, lipid laden adipocyte. Most of the studies investigating the effects of BPA on preadipocyte differentiation have investigated the effects of this chemical in the presence of an optimal differentiation cocktail containing high concentrations of the synthetic glucocorticoid dexamethasone, conditions that result in 90% to 100% of differentiated adipocytes. Our studies employed the 3T3-L1 cell model in the absence of exogenous glucocorticoids. We show that BPA is able to increase the differentiation of the 3T3-L1 cells under these conditions. Furthermore, the effect of BPA was observed in the absence of the synthetic glucocorticoid (dexamethasone), a hormone known to be required for the differentiation of the 3T3-L1 cells. In addition, BPA upregulated the mRNA expression and protein levels of the terminal marker of adipogenesis the fatty acid binding protein (aP2) in these cells. Interestingly, the known modulators of adipogenesis such as the peroxisome proliferator-activated receptor (PPAR) γ or CCAAT enhancer binding protein (C/EBP) α were not elevated at the mRNA or protein level in response to BPA. Furthermore, BPA upregulated the expression levels of the marker of adipogenesis aP2, through an effect on the transcriptional activity of C/EBPδ and the glucocorticoid receptor (GR) at its promoter.
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Zhang J, Li Y, Shan K, Wang L, Qiu W, Lu Y, Zhao D, Zhu G, He F, Wang Y. Sublytic C5b-9 induces IL-6 and TGF-β1 production by glomerular mesangial cells in rat Thy-1 nephritis through p300-mediated C/EBPβ acetylation. FASEB J 2013; 28:1511-25. [PMID: 24344329 DOI: 10.1096/fj.13-242693] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
CCAAT/enhancer-binding protein (C/EBPβ)-enhanced IL-6 and TGF-β1 promoter activity and p300-mediated C/EBPβ acetylation were involved in up-regulation of IL-6 and TGF-β1 expression in GMCs attacked by sublytic C5b-9. In detail, the elements of C/EBPβ binding to rat IL-6 and TGF-β1 promoter and 3 acetylated sites of rat C/EBPβ protein were first revealed. Furthermore, silencing the p300 or C/EBPβ gene in rat kidney significantly reduced the production of IL-6 and TGF-β1 and renal lesions in Thy-1N rats. Together, these data indicate that the mechanism of IL-6 and TGF-β1 production in renal tissue of Thy-1N rats is associated with sublytic C5b-9 up-regulated p300 and p300-mediated C/EBPβ acetylation as well as C/EBPβ-activated IL-6 and TGF-β1 genes.
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Affiliation(s)
- Jing Zhang
- 1Department of Microbiology and Immunology, Nanjing Medical University, Hanzhong Rd. 140, Nanjing, Jiangsu 210029, China.
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Hanzu FA, Musri MM, Sánchez-Herrero A, Claret M, Esteban Y, Kaliman P, Gomis R, Párrizas M. Histone demethylase KDM1A represses inflammatory gene expression in preadipocytes. Obesity (Silver Spring) 2013; 21:E616-25. [PMID: 23595969 DOI: 10.1002/oby.20479] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 03/19/2013] [Accepted: 03/20/2013] [Indexed: 11/07/2022]
Abstract
OBJECTIVE Persistent inflammation and impaired adipogenesis are frequent features of obesity and underlie the development of its complications. However, the factors behind adipose tissue dysfunction are not completely understood. Previously it was shown that histone demethylase KDM1A is required for adipogenesis. DESIGN AND METHODS Kdm1a expression was knocked down in 3T3-L1 preadipocytes by siRNA transfection and whole-genome expression profiling was performed by microarray hybridization. The role of NF-κβ and C/EBPβ was analyzed by incubation with the inhibitor parthenolide and by cebpb knockdown, respectively. RESULTS Knockdown of kdm1a or rcor2 in 3T3-L1 preadipocytes results in impaired differentiation and induction of inflammatory gene expression. Enhanced expression of il6 in kdm1a knocked down preadipocytes is associated with increased recruitment of C/EBPβ and the NF-κβ subunit RelA to the il6 promoter. Cebpb knockdown attenuates the induction of il6 expression in kdm1a knocked down cells, whereas simultaneous cebpb knockdown and NF-κβ inhibition abrogates it. Dietary-induced and genetic mouse models of obesity display decreased KDM1A in adipose tissue, and this correlates with increased expression of proinflammatory genes and C/EBPβ. CONCLUSION KDM1A represses the expression of inflammatory genes in preadipocytes. Dysregulated kdm1a expression in preadipocytes may thus participate in the development of obesity-associated inflammation.
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Affiliation(s)
- Felicia A Hanzu
- Diabetes and Obesity Laboratory, IDIBAPS, CIBERDEM, Barcelona, Spain; Endocrinology and Nutrition Unit, Hospital Clínic, Barcelona, Spain
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Abdou HS, Atlas E, Haché RJG. A positive regulatory domain in CCAAT/enhancer binding protein β (C/EBPΒ) is required for the glucocorticoid-mediated displacement of histone deacetylase 1 (HDAC1) from the C/ebpα promoter and maximum adipogenesis. Endocrinology 2013; 154:1454-64. [PMID: 23456364 DOI: 10.1210/en.2012-2061] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Glucocorticoids promote adipogenesis and contribute to the metabolic syndrome through a number of mechanisms. One of the effectors of glucocorticoid action is the CCAAT/enhancer binding protein β (C/EBPβ). C/EBPβ is a basic leucine-zipper transcription factor involved in diverse processes including differentiation, cellular proliferation, and inflammation. C/EBPβ transcriptional activity is regulated, in part, by its acetylation profile resulting from its dynamic interaction with either acetylases general control nonrepressed protein 5/p300/CBP associated factor (GCN5/PCAF) or deacetylase complexes (mSin3A/histone deacetylase 1 [HDAC1]). Glucocorticoid treatment of preadipocytes promotes C/EBPβ acetylation, leading to mSin3A/HDAC1 dissociation from C/EBPβ and resulting in C/ebpα promoter activation at the onset of adipogenesis, thus increasing the differentiation rate. We recently showed that the regulatory domain 1 (RD1) of C/EBPβ contains four residues (153-156) required for its interaction with HDAC1, therefore supporting RD1 proposed inhibitory role. In an attempt to further elucidate the intrinsic regulatory property of RD1, we sought to characterize the regulatory potential of the N terminus region of RD1 (residues 141-149). In this study, we show that C/EBPβΔ141-149 transcriptional activity was compromised on the C/ebpα, but not on the Pparγ, promoter. Additionally, the ability of C/EBPβΔ141-149 to induce adipogenesis in NIH 3T3 cells was compromised when compared with C/EBPβwt owing to a delayed expression of C/ebpα at the onset of differentiation. Furthermore, the data suggest that the reduced expression of C/ebpα in cells expressing C/EBPβΔ141-149 was due to a persistent recruitment of HDAC1 to the C/ebpα promoter after glucocorticoid treatment. Together, these results suggest that amino acids 141-149 of C/EBPβ act as a positive regulatory domain required for maximum transcriptional activity.
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Affiliation(s)
- Houssein-Salem Abdou
- Reproduction, Mother and Youth Health, CHUQ Research Centre, Quebec City, Quebec, Canada
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12
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Ravimohan S, Gama L, Engle EL, Zink MC, Clements JE. Early emergence and selection of a SIV-LTR C/EBP site variant in SIV-infected macaques that increases virus infectivity. PLoS One 2012; 7:e42801. [PMID: 22952612 PMCID: PMC3428313 DOI: 10.1371/journal.pone.0042801] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Accepted: 07/11/2012] [Indexed: 11/19/2022] Open
Abstract
CCAAT/enhancer binding protein (C/EBP)β, and C/EBP binding sites in the HIV/SIV-long terminal repeat (LTR) are crucial for regulating transcription and for IFNβ-mediated suppression of virus replication in macrophages, the predominant source of productive virus replication in the brain. We investigated sequence variation within the SIV-LTR C/EBP sites that may be under selective pressure in vivo and therefore associated with disease progression. Using the SIV-macaque model, we examined viral LTR sequences derived from the spleen, a site of macrophage and lymphocyte infection, and the brain from macaques euthanized at 10, 21, 42, 48 and 84 days postinoculation (p.i.). A dominant variant, DS1C/A, containing an adenine-to-guanine substitution and a linked cytosine-to-adenine substitution in the downstream (DS1) C/EBP site, was detected in the spleen at 10 days p.i. The DS1C/A genotype was not detected in the brain until 42 days p.i., after which it was the predominant replicating genotype in both brain and spleen. Functional characterization of the DS1C/A containing SIV showed increased infectivity with or without IFNβ treatment over the wild-type virus, SIV/17E-Fr. The DS1C/A C/EBP site had higher affinity for both protein isoforms of C/EBPβ compared to the wild-type DS1 C/EBP site. Cytokine expression in spleen compared to brain implicated IFNβ and IL-6 responses as part of the selective pressures contributing to emergence of the DS1C/A genotype in vivo. These studies demonstrate selective replication of virus containing the DS1C/A genotype that either emerges very early in spleen and spreads to the brain, or evolves independently in the brain when IFNβ and IL-6 levels are similar to that found in spleen earlier in infection.
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Affiliation(s)
- Shruthi Ravimohan
- Division of Infectious Diseases, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, United States of America.
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13
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Regulatory evolution through divergence of a phosphoswitch in the transcription factor CEBPB. Nature 2011; 480:383-6. [PMID: 22080951 DOI: 10.1038/nature10595] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Accepted: 09/28/2011] [Indexed: 12/22/2022]
Abstract
There is an emerging consensus that gene regulation evolves through changes in cis-regulatory elements and transcription factors. Although it is clear how nucleotide substitutions in cis-regulatory elements affect gene expression, it is not clear how amino-acid substitutions in transcription factors influence gene regulation. Here we show that amino-acid changes in the transcription factor CCAAT/enhancer binding protein-β (CEBPB, also known as C/EBP-β) in the stem-lineage of placental mammals changed the way it responds to cyclic AMP/protein kinase A (cAMP/PKA) signalling. By functionally analysing resurrected ancestral proteins, we identify three amino-acid substitutions in an internal regulatory domain of CEBPB that are responsible for the novel function. These amino-acid substitutions reorganize the location of key phosphorylation sites, introducing a new site and removing two ancestral sites, reversing the response of CEBPB to GSK-3β-mediated phosphorylation from repression to activation. We conclude that changing the response of transcription factors to signalling pathways can be an important mechanism of gene regulatory evolution.
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14
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Lechner MG, Liebertz DJ, Epstein AL. Characterization of cytokine-induced myeloid-derived suppressor cells from normal human peripheral blood mononuclear cells. THE JOURNAL OF IMMUNOLOGY 2010; 185:2273-84. [PMID: 20644162 DOI: 10.4049/jimmunol.1000901] [Citation(s) in RCA: 464] [Impact Index Per Article: 33.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Tumor immune tolerance can derive from the recruitment of suppressor cell populations, including myeloid-derived suppressor cells (MDSCs). In cancer patients, increased MDSCs correlate with more aggressive disease and a poor prognosis. Expression of 15 immune factors (TGFbeta, IL-1beta, IL-4, IL-6, IL-10, GM-CSF, M-CSF, IDO, fms-related tyrosine kinase 3 ligand, c-kit ligand, inducible NO synthase, arginase-1, TNF-alpha, cyclo-oxygenase 2, vascular endothelial growth factor [VEGF]) by MDSC-inducing human solid tumor cell lines was evaluated by RT-PCR. Based upon these data, cytokine mixtures were then tested for their ability to generate suppressive CD33(+) cells from healthy donor PBMCs in vitro by measuring their ability to inhibit the proliferation of, and IFN-gamma production by, fresh autologous human T cells after CD3/CD28 stimulation. Induced MDSCs were characterized with respect to their morphology, surface phenotype, and gene expression profile. MDSC-inducing cancer cell lines demonstrated multiple pathways for MDSC generation, including overexpression of IL-6, IL-1beta, cyclo-oxygenase 2, M-CSF, and IDO. CD33(+) cells with potent suppressive capacity were best generated in vitro by GM-CSF and IL-6, and secondarily by GM-CSF + IL-1beta, PGE(2), TNF-alpha, or VEGF. Characterization studies of cytokine-induced suppressive cells revealed CD33(+)CD11b(+)CD66b(+)HLA-DR(low)IL-13R alpha2(int) large mononuclear cells with abundant basophilic cytoplasm. Expression of inducible NO synthase, TGFbeta, NADPH oxidase, VEGF, and/or arginase-1 was also upregulated, and Transwell studies showed suppression of autologous T cells to be contact dependent. Suppressive CD33(+) cells generated from PBMCs by GM-CSF and IL-6 were consistent with human MDSCs. This study suggests that these cytokines are potential therapeutic targets for the inhibition of MDSC induction in cancer patients.
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Affiliation(s)
- Melissa G Lechner
- Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
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15
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Lee S, Miller M, Shuman JD, Johnson PF. CCAAT/Enhancer-binding protein beta DNA binding is auto-inhibited by multiple elements that also mediate association with p300/CREB-binding protein (CBP). J Biol Chem 2010; 285:21399-410. [PMID: 20452968 DOI: 10.1074/jbc.m110.128413] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Signaling through Ras GTPases controls the activity of many transcription factors including CCAAT/enhancer-binding protein (C/EBPbeta), which regulates oncogenic H-Ras(V12)-induced senescence and growth arrest. Here we report that C/EBPbeta (LAP) DNA binding is inhibited by N-terminal sequences and derepressed by oncogenic Ras signaling. Sequence and mutational analyses showed that auto-repression involves two LXXLF (phiXXphiphi)-like motifs (LX1 and LX2) and a third element, auto-inhibitory domain (AID), located within conserved region CR5. LX1 is a critical component of the transactivation domain and has been shown to mediate C/EBPbeta binding to the TAZ2 region of p300/CREB-binding protein coactivators. C/EBPbeta auto-repression also involves a C-terminal regulatory domain (CRD) adjacent to the leucine zipper. CRD contains a third phiXXphiphi motif (LX3) and a short sequence, KQL, which has similarity to a region in the protein-binding site of TAZ2. The C/EBPbeta N- and C-terminal domains physically associate in a manner that requires the basic region and CRD. We propose a model in which the regulatory sequences form a hydrophobic core that reciprocally inhibits DNA binding and transactivation. We also suggest a mechanism for C/EBPbeta derepression involving several recently identified modifications within AID and CRD. Finally, we show that association of activated C/EBPbeta with p300/CREB-binding protein requires the LX2 and AID auto-inhibitory elements. Thus, the N-terminal regulatory elements have dual roles in auto-inhibition and coactivator binding.
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Affiliation(s)
- Sook Lee
- Laboratory of Cancer Prevention, NCI-Frederick, National Institutes of Health, Frederick, Maryland 21702-1201, USA
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16
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Coordinated regulation of SIV replication and immune responses in the CNS. PLoS One 2009; 4:e8129. [PMID: 20019816 PMCID: PMC2790080 DOI: 10.1371/journal.pone.0008129] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Accepted: 09/11/2009] [Indexed: 11/19/2022] Open
Abstract
Central nervous system (CNS) invasion during acute-stage HIV-infection has been demonstrated in a small number of individuals, but there is no evidence of neurological impairment at this stage and virus infection in brain appears to be controlled until late-stage disease. Using our reproducible SIV macaque model to examine the earliest stages of infection in the CNS, we identified immune responses that differentially regulate inflammation and virus replication in the brain compared to the peripheral blood and lymphoid tissues. SIV replication in brain macrophages and in brain of SIV-infected macaques was detected at 4 days post-inoculation (p.i.). This was accompanied by upregulation of innate immune responses, including IFNβ, IFNβ-induced gene MxA mRNA, and TNFα. Additionally, IL-10, the chemokine CCL2, and activation markers in macrophages, endothelial cells, and astrocytes were all increased in the brain at four days p.i. We observed synchronous control of virus replication, cytokine mRNA levels and inflammatory markers (MHC Class II, CD68 and GFAP) by 14 days p.i.; however, control failure was followed by development of CNS lesions in the brain. SIV infection was accompanied by induction of the dominant-negative isoform of C/EBPβ, which regulates SIV, CCL2, and IL6 transcription, as well as inflammatory responses in macrophages and astrocytes. This synchronous response in the CNS is in part due to the effect of the C/EBPβ on virus replication and cytokine expression in macrophage-lineage cells in contrast to CD4+ lymphocytes in peripheral blood and lymphoid tissues. Thus, we have identified a crucial period in the brain when virus replication and inflammation are controlled. As in HIV-infected individuals, though, this control is not sustained in the brain. Our results suggest that intervention with antiretroviral drugs or anti-inflammatory therapeutics with CNS penetration would sustain early control. These studies further suggest that interventions should target HIV-infected individuals with increased CCL2 levels or HIV RNA in the CNS.
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Masuda T, Deng X, Tamai R. Mouse macrophages primed with alendronate down-regulate monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1alpha (MIP-1alpha) production in response to Toll-like receptor (TLR) 2 and TLR4 agonist via Smad3 activation. Int Immunopharmacol 2009; 9:1115-21. [PMID: 19501197 DOI: 10.1016/j.intimp.2009.05.010] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2009] [Revised: 05/28/2009] [Accepted: 05/28/2009] [Indexed: 11/29/2022]
Abstract
Alendronate is one of the nitrogen-containing bisphosphonates (NBPs) used as anti-bone resorptive drugs. However, NBPs have inflammatory side effects including osteomyelitis and osteonecrosis of the jaw. In the present study, we examined the effects of alendronate on chemokine production by the macrophage-like cell line, J774.1, when incubated with Pam(3)CSK(4) (a Toll-like receptor (TLR) 2 agonist) and Lipid A (a TLR4 agonist). Pretreatment of J774.1 cells with alendronate decreased the production of TLR ligand-induced monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1alpha (MIP-1alpha) but did not influence nuclear factor-kappaB (NF-kappaB) activation. While this agent induced caspase-8 activation, a caspase-8 inhibitor did not affect the decrease in MCP-1 production by alendronate and TLR ligands. Thus, the alendronate-mediated decrease in chemokine production was independent of NF-kappaB and caspase-8 activation. Although transforming growth factor-beta1 (TGF-beta1) is known to inhibit chemokine production by various cell types via Smad3 activation, pretreatment with alendronate did not increase TGF-beta1 production by J774.1 cells incubated in the presence or absence of TLR ligands. However, alendronate directly activated Smad3. These results suggest that by down-regulating MCP-1 and MIP-1alpha production via Smad3, long-term use of alendronate might inhibit normal activation and migration of osteoclasts and cause osteonecrosis.
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Affiliation(s)
- Takahiro Masuda
- Department of Endodontics and Periodontics, Ohu University Graduate School of Dentistry, Misumido, Tomitamachi, Koriyama, Fukushima, Japan
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18
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Liu Y, Nonnemacher MR, Wigdahl B. CCAAT/enhancer-binding proteins and the pathogenesis of retrovirus infection. Future Microbiol 2009; 4:299-321. [PMID: 19327116 DOI: 10.2217/fmb.09.4] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Previous studies indicate that two upstream CCAAT/enhancer-binding protein (C/EBP) sites and C/EBPbeta are required for subtype B HIV-1 gene expression in cells of the monocyte-macrophage lineage. The mechanisms of C/EBP regulation of HIV-1 transcription and replication remain unclear. This review focuses on studies concerning the role of C/EBP factors in HIV-1, human T-cell leukemia virus type 1, and SIV transcription in various cell types and tissues cultured in vitro, animal models and during human infection. The structure and function of the C/EBPbeta gene and the related protein isoforms are discussed along with the transcription factors, coactivators, viral proteins, cytokines and chemokines that affect C/EBP function.
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Affiliation(s)
- Yujie Liu
- Department of Microbiology & Immunology, Center for Molecular Virology & Neuroimmunology, Center for Cancer Biology, Philadelphia, PA 19129, USA
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19
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Kim YH, Kim DH, Lim H, Baek DY, Shin HK, Kim JK. The anti-inflammatory effects of methylsulfonylmethane on lipopolysaccharide-induced inflammatory responses in murine macrophages. Biol Pharm Bull 2009; 32:651-6. [PMID: 19336900 DOI: 10.1248/bpb.32.651] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Methylsulfonylmethane (MSM), also known as dimethyl sulfone and methyl sulfone, is an organic sulfur-containing compound that occurs naturally in a variety of fruits, vegetables, grains, and animals, including humans. In the present study, we demonstrated the anti-inflammatory effects of MSM in lipopolysaccharide (LPS)-stimulated murine macrophages, RAW264.7 cells. MSM significantly inhibited the release of nitric oxide and prostaglandin E(2) by alleviating the expression of inducible nitric oxide synthase and cyclooxygenase-2 in LPS-stimulated RAW264.7 cells. Furthermore, the levels of interleukin-6 and tumor necrosis factor-alpha were decreased by MSM treatment in cell culture supernatants. Further study indicated that the translocation of the p65 subunit of nuclear factor (NF)-kappaB to the nucleus was inhibited by MSM treatment in LPS-stimulated RAW264.7 cells, in which it helped block degradation of inhibitor of NF-kappaB. In addition, in vivo studies demonstrated that topical administration of MSM at 500-1250 microg/ear resulted in similar inhibitory activities in 12-O-tetradecanoylphorbol 13-acetate-induced mouse ear edema. Collectively, theses results indicate that MSM inhibits LPS-induced release of pro-inflammatory mediators in murine macrophages through downregulation of NF-kappaB signaling.
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Affiliation(s)
- Yoon Hee Kim
- Center for Efficacy Assessment and Development of Functional Foods and Drugs, Hallym University, Korea
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20
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MicroRNA-155 modulates the interleukin-1 signaling pathway in activated human monocyte-derived dendritic cells. Proc Natl Acad Sci U S A 2009; 106:2735-40. [PMID: 19193853 DOI: 10.1073/pnas.0811073106] [Citation(s) in RCA: 569] [Impact Index Per Article: 37.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In response to inflammatory stimulation, dendritic cells (DCs) have a remarkable pattern of differentiation (maturation) that exhibits specific mechanisms to control immunity. Here, we show that in response to Lipopolysaccharides (LPS), several microRNAs (miRNAs) are regulated in human monocyte-derived dendritic cells. Among these miRNAs, miR-155 is highly up-regulated during maturation. Using LNA silencing combined to microarray technology, we have identified the Toll-like receptor/interleukin-1 (TLR/IL-1) inflammatory pathway as a general target of miR-155. We further demonstrate that miR-155 directly controls the level of TAB2, an important signal transduction molecule. Our observations suggest, therefore, that in mature human DCs, miR-155 is part of a negative feedback loop, which down-modulates inflammatory cytokine production in response to microbial stimuli.
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21
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Spooner CJ, Sebastian T, Shuman JD, Durairaj S, Guo X, Johnson PF, Schwartz RC. C/EBPbeta serine 64, a phosphoacceptor site, has a critical role in LPS-induced IL-6 and MCP-1 transcription. Cytokine 2007; 37:119-27. [PMID: 17433708 DOI: 10.1016/j.cyto.2007.03.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2006] [Revised: 01/14/2007] [Accepted: 03/05/2007] [Indexed: 11/20/2022]
Abstract
C/EBPbeta is a member of the CCAAT/enhancer binding protein family of transcription factors and has been shown to be a critical transcriptional regulator of various proinflammatory genes, including IL-6 and MCP-1. Serine 64 in the transactivation domain of C/EBPbeta has recently been identified as a Ras-induced phosphoacceptor site. The integrity of serine 64 along with threonine 189 is important for the Ha-ras(V12)-induced transformation of NIH3T3 cells, however no target genes dependent upon serine 64 for their expression have been reported. In order to evaluate a potential role of serine 64 in C/EBPbeta-regulated cytokine expression, we expressed a form of C/EBPbeta with an alanine substitution at serine 64 (C/EBPbeta(S64A)) in P388 murine B lymphoblasts, which lack endogenous C/EBPbeta expression and are normally unresponsive to LPS for expression of IL-6 and MCP-1. In comparison to wild type C/EBPbeta, which robustly supports the LPS-induced expression of IL-6 and MCP-1, C/EBPbeta(S64A) was severely impaired in its ability to support the LPS-induced transcription of IL-6 and MCP-1. Furthermore, LPS stimulation increased the level of phosphorylation detected at serine 64. Thus, serine 64, probably through its phosphorylation, is a critical determinant of C/EBPbeta activity in the transcription of IL-6 and MCP-1.
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Affiliation(s)
- Chauncey J Spooner
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
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22
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Mameli G, Deshmane SL, Ghafouri M, Cui J, Simbiri K, Khalili K, Mukerjee R, Dolei A, Amini S, Sawaya BE. C/EBPbeta regulates human immunodeficiency virus 1 gene expression through its association with cdk9. J Gen Virol 2007; 88:631-640. [PMID: 17251582 DOI: 10.1099/vir.0.82487-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Transcriptional regulation of the human immunodeficiency virus type 1 (HIV-1) is a complex event that requires the cooperative action of both viral (e.g. Tat) and cellular (e.g. C/EBPbeta, NF-kappaB) factors. The HIV-1 Tat protein recruits the human positive transcription elongation factor P-TEFb, consisting of cdk9 and cyclin T1, to the HIV-1 transactivation response (TAR) region. In the absence of TAR, Tat activates the HIV-1 long terminal repeat (LTR) through its association with several cellular factors including C/EBPbeta. C/EBPbeta is a member of the CCAAT/enhancer-binding protein family of transcription factors and has been shown to be a critical transcriptional regulator of HIV-1 LTR. We examined whether Tat-C/EBPbeta association requires the presence of the P-TEFb complex. Using immunoprecipitation followed by Western blot, we demonstrated that C/EBPbeta-cyclin T1 association requires the presence of cdk9. Further, due to its instability, cdk9 was unable to physically interact with C/EBPbeta in the absence of cyclin T1 or Tat. Using kinase assays, we demonstrated that cdk9, but not a cdk9 dominant-negative mutant (cdk9-dn), phosphorylates C/EBPbeta. Our functional data show that co-transfection of C/EBPbeta and cdk9 leads to an increase in HIV-1 gene expression when compared to C/EBPbeta alone. Addition of C/EBP homologous protein (CHOP) inhibits C/EBPbeta transcriptional activity in the presence and absence of cdk9 and causes a delay in HIV-1 replication in T-cells. Together, our data suggest that Tat-C/EBPbeta association is mediated through cdk9, and that phosphorylated C/EBPbeta may influence AIDS progression by increasing expression of HIV-1 genes.
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Affiliation(s)
- Giuseppe Mameli
- Section of Microbiology, Department of Biomedical Sciences, Center of Excellence for Biotechnology Development and Biodiversity Research, Sassari, Italy
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA
| | - Satish L Deshmane
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA
| | - Mohammad Ghafouri
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA
| | - Jianqi Cui
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA
| | - Kenneth Simbiri
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA
| | - Kamel Khalili
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA
| | - Ruma Mukerjee
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA
| | - Antonina Dolei
- Section of Microbiology, Department of Biomedical Sciences, Center of Excellence for Biotechnology Development and Biodiversity Research, Sassari, Italy
| | - Shohreh Amini
- Department of Biology, College of Science and Technology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA
| | - Bassel E Sawaya
- Department of Neuroscience, Center for Neurovirology, Temple University School of Medicine, 1900 N 12th Street 015-96, Philadelphia, PA 19122, USA
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