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Bindesbøll C, Fan Q, Nørgaard RC, MacPherson L, Ruan HB, Wu J, Pedersen TÅ, Steffensen KR, Yang X, Matthews J, Mandrup S, Nebb HI, Grønning-Wang LM. Liver X receptor regulates hepatic nuclear O-GlcNAc signaling and carbohydrate responsive element-binding protein activity. J Lipid Res 2015; 56:771-85. [PMID: 25724563 DOI: 10.1194/jlr.m049130] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Liver X receptor (LXR)α and LXRβ play key roles in hepatic de novo lipogenesis through their regulation of lipogenic genes, including sterol regulatory element-binding protein (SREBP)-1c and carbohydrate responsive element-binding protein (ChREBP). LXRs activate lipogenic gene transcription in response to feeding, which is believed to be mediated by insulin. We have previously shown that LXRs are targets for glucose-hexosamine-derived O-linked β-N-acetylglucosamine (O-GlcNAc) modification enhancing their ability to regulate SREBP-1c promoter activity in vitro. To elucidate insulin-independent effects of feeding on LXR-mediated lipogenic gene expression in vivo, we subjected control and streptozotocin-treated LXRα/β(+/+) and LXRα/β(-/-) mice to a fasting-refeeding regime. We show that under hyperglycemic and hypoinsulinemic conditions, LXRs maintain their ability to upregulate the expression of glycolytic and lipogenic enzymes, including glucokinase (GK), SREBP-1c, ChREBPα, and the newly identified shorter isoform ChREBPβ. Furthermore, glucose-dependent increases in LXR/retinoid X receptor-regulated luciferase activity driven by the ChREBPα promoter was mediated, at least in part, by O-GlcNAc transferase (OGT) signaling in Huh7 cells. Moreover, we show that LXR and OGT interact and colocalize in the nucleus and that loss of LXRs profoundly reduced nuclear O-GlcNAc signaling and ChREBPα promoter binding activity in vivo. In summary, our study provides evidence that LXRs act as nutrient and glucose metabolic sensors upstream of ChREBP by modulating GK expression, nuclear O-GlcNAc signaling, and ChREBP expression and activity.
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Affiliation(s)
- Christian Bindesbøll
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway
| | - Qiong Fan
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway
| | - Rikke C Nørgaard
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway
| | - Laura MacPherson
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S1A8, Canada
| | - Hai-Bin Ruan
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06519 Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06519
| | - Jing Wu
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06519 Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06519
| | - Thomas Å Pedersen
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, 5230 Odense M, Denmark
| | - Knut R Steffensen
- Division of Clinical Chemistry Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, C174, SE-141 86 Stockholm, Sweden
| | - Xiaoyong Yang
- Program in Integrative Cell Signaling and Neurobiology of Metabolism, Yale University School of Medicine, New Haven, CT 06519 Section of Comparative Medicine, Yale University School of Medicine, New Haven, CT 06519 Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06519
| | - Jason Matthews
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5S1A8, Canada
| | - Susanne Mandrup
- Department of Biochemistry and Molecular Biology, University of Southern Denmark, 5230 Odense M, Denmark
| | - Hilde I Nebb
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway
| | - Line M Grønning-Wang
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, N-0316 Oslo, Norway
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Candelaria NR, Addanki S, Zheng J, Nguyen-Vu T, Karaboga H, Dey P, Gabbi C, Vedin LL, Liu K, Wu W, Jonsson PK, Lin JZ, Su F, Bollu LR, Hodges SE, McElhany AL, Issazadeh MA, Fisher WE, Ittmann MM, Steffensen KR, Gustafsson JÅ, Lin CY. Antiproliferative effects and mechanisms of liver X receptor ligands in pancreatic ductal adenocarcinoma cells. PLoS One 2014; 9:e106289. [PMID: 25184494 PMCID: PMC4153644 DOI: 10.1371/journal.pone.0106289] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2014] [Accepted: 07/30/2014] [Indexed: 11/18/2022] Open
Abstract
Pancreatic ductal adenocarcinoma (PDAC) is difficult to detect early and is often resistant to standard chemotherapeutic options, contributing to extremely poor disease outcomes. Members of the nuclear receptor superfamily carry out essential biological functions such as hormone signaling and are successfully targeted in the treatment of endocrine-related malignancies. Liver X receptors (LXRs) are nuclear receptors that regulate cholesterol homeostasis, lipid metabolism, and inflammation, and LXR agonists have been developed to regulate LXR function in these processes. Intriguingly, these compounds also exhibit antiproliferative activity in diverse types of cancer cells. In this study, LXR agonist treatments disrupted proliferation, cell-cycle progression, and colony-formation of PDAC cells. At the molecular level, treatments downregulated expression of proteins involved in cell cycle progression and growth factor signaling. Microarray experiments further revealed changes in expression profiles of multiple gene networks involved in biological processes and pathways essential for cell growth and proliferation following LXR activation. These results establish the antiproliferative effects of LXR agonists and potential mechanisms of action in PDAC cells and provide evidence for their potential application in the prevention and treatment of PDAC.
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Affiliation(s)
- Nicholes R. Candelaria
- Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Sridevi Addanki
- Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Jine Zheng
- Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Trang Nguyen-Vu
- Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Husna Karaboga
- Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Prasenjit Dey
- Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Chiara Gabbi
- Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Lise-Lotte Vedin
- Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden
| | - Ka Liu
- Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Wanfu Wu
- Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Philip K. Jonsson
- Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Jean Z. Lin
- Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
- Center for Diabetes Research, Houston Methodist Research Institute, Houston, Texas, United States of America
| | - Fei Su
- Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Lakshmi Reddy Bollu
- Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Sally E. Hodges
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas, United States of America
- The Elkins Pancreas Center at Baylor College of Medicine, Houston, Texas, United States of America
| | - Amy L. McElhany
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas, United States of America
- The Elkins Pancreas Center at Baylor College of Medicine, Houston, Texas, United States of America
| | - Mehdi A. Issazadeh
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas, United States of America
- The Elkins Pancreas Center at Baylor College of Medicine, Houston, Texas, United States of America
| | - William E. Fisher
- Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas, United States of America
- The Elkins Pancreas Center at Baylor College of Medicine, Houston, Texas, United States of America
| | - Michael M. Ittmann
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Knut R. Steffensen
- Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden
| | - Jan-Åke Gustafsson
- Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
- Department of Biosciences and Nutrition at NOVUM, Karolinska Institutet, Huddinge, Sweden
| | - Chin-Yo Lin
- Center for Nuclear Receptors and Cell Signaling, Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
- * E-mail:
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Pehkonen P, Welter-Stahl L, Diwo J, Ryynänen J, Wienecke-Baldacchino A, Heikkinen S, Treuter E, Steffensen KR, Carlberg C. Genome-wide landscape of liver X receptor chromatin binding and gene regulation in human macrophages. BMC Genomics 2012; 13:50. [PMID: 22292898 PMCID: PMC3295715 DOI: 10.1186/1471-2164-13-50] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Accepted: 01/31/2012] [Indexed: 12/15/2022] Open
Abstract
Background The liver X receptors (LXRs) are oxysterol sensing nuclear receptors with multiple effects on metabolism and immune cells. However, the complete genome-wide cistrome of LXR in cells of human origin has not yet been provided. Results We performed ChIP-seq in phorbol myristate acetate-differentiated THP-1 cells (macrophage-type) after stimulation with the potent synthetic LXR ligand T0901317 (T09). Microarray gene expression analysis was performed in the same cellular model. We identified 1357 genome-wide LXR locations (FDR < 1%), of which 526 were observed after T09 treatment. De novo analysis of LXR binding sequences identified a DR4-type element as the major motif. On mRNA level T09 up-regulated 1258 genes and repressed 455 genes. Our results show that LXR actions are focused on 112 genomic regions that contain up to 11 T09 target genes per region under the control of highly stringent LXR binding sites with individual constellations for each region. We could confirm that LXR controls lipid metabolism and transport and observed a strong association with apoptosis-related functions. Conclusions This first report on genome-wide binding of LXR in a human cell line provides new insights into the transcriptional network of LXR and its target genes with their link to physiological processes, such as apoptosis. The gene expression microarray and sequence data have been submitted collectively to the NCBI Gene Expression Omnibus http://www.ncbi.nlm.nih.gov/geo under accession number GSE28319.
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Affiliation(s)
- Petri Pehkonen
- School of Medicine, Institute of Biomedicine, University of Eastern Finland, FIN-70210 Kuopio, Finland
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Kim GH, Park K, Yeom SY, Lee KJ, Kim G, Ko J, Rhee DK, Kim YH, Lee HK, Kim HW, Oh GT, Lee KU, Lee JW, Kim SW. Characterization of ASC-2 as an antiatherogenic transcriptional coactivator of liver X receptors in macrophages. Mol Endocrinol 2009; 23:966-74. [PMID: 19342446 DOI: 10.1210/me.2008-0308] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Activating signal cointegrator-2 (ASC-2) functions as a transcriptional coactivator of many nuclear receptors and also plays important roles in the physiology of the liver and pancreas by interacting with liver X receptors (LXRs), which antagonize the development of atherosclerosis. This study was undertaken to establish the specific function of ASC-2 in macrophages and atherogenesis. Intriguingly, ASC-2 was more highly expressed in macrophages than in the liver and pancreas. To inhibit LXR-specific activity of ASC-2, we used DN2, which contains the C-terminal LXXLL motif of ASC-2 and thereby acts as an LXR-specific, dominant-negative mutant of ASC-2. In DN2-overexpressing transgenic macrophages, cellular cholesterol content was higher and cholesterol efflux lower than in control macrophages. DN2 reduced LXR ligand-dependent increases in the levels of ABCA1, ABCG1, and apolipoprotein E (apoE) transcripts as well as the activity of luciferase reporters driven by the LXR response elements (LXREs) of ABCA1, ABCG1, and apoE genes. These inhibitory effects of DN2 were reversed by overexpression of ASC-2. Chromatin immunoprecipitation analysis demonstrated that ASC-2 was recruited to the LXREs of the ABCA1, ABCG1, and apoE genes in a ligand-dependent manner and that DN2 interfered with the recruitment of ASC-2 to these LXREs. Furthermore, low-density lipoprotein receptor (LDLR)-null mice receiving bone marrow transplantation from DN2-transgenic mice showed accelerated atherogenesis when administered a high-fat diet. Taken together, these results indicate that suppression of the LXR-specific activity of ASC-2 results in both defective cholesterol metabolism in macrophages and accelerated atherogenesis, suggesting that ASC-2 is an antiatherogenic coactivator of LXRs in macrophages.
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Affiliation(s)
- Geun Hyang Kim
- Department of Pharmacology, University of Ulsan College of Medicine, Seoul, Korea
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Stromal growth and epithelial cell proliferation in ventral prostates of liver X receptor knockout mice. Proc Natl Acad Sci U S A 2009; 106:558-63. [PMID: 19122149 DOI: 10.1073/pnas.0811295106] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
With specific liver X receptor alpha and beta (LXRalpha and LXRbeta) antibodies, we found that LXRalpha is strongly expressed in the luminal and basal cells of prostatic epithelium. The ventral prostates (VP) of LXRalpha(-/-) mice are characterized by the presence of smooth-muscle actin-positive stromal overgrowth around the prostatic ducts and by numerous fibrous nodules pushing into the ducts and causing obstruction, so that most of the ducts were extremely dilated. BrdU labeling and Ki67 staining revealed epithelial and stromal proliferation in the fibrous nodules. However, the dense stroma surrounding the ducts was not positive for proliferation markers. There was no detectable difference between WT and LXRalpha(-/-) mice VP in the expression of the androgen receptor, but there was an increase in nuclear expression of Snail and Smad 2/3, indicating enhanced TGF-beta signaling. Upon treatment of WT mice for 3 months with the LXR agonist T2320 or for 3 weeks with beta-sitosterol, LXRalpha was downregulated, and a VP phenotype similar to that of LXRalpha(-/-) mice resulted. We conclude that in rodents, LXRalpha seems to control VP stromal growth and that LXRalpha(-/-) mice may be a useful model to study prostatic stromal hyperplasia. Because LXRalpha is expressed in the epithelium, the excessive stromal growth in LXRalpha(-/-) mice indicates that LXRalpha is essential for epithelial stromal communication.
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Pancreatic exocrine insufficiency in LXRbeta-/- mice is associated with a reduction in aquaporin-1 expression. Proc Natl Acad Sci U S A 2008; 105:15052-7. [PMID: 18806227 DOI: 10.1073/pnas.0808097105] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Liver X receptors (LXRs) alpha and beta are nuclear oxysterol receptors with a key role in cholesterol, triglyceride, and glucose metabolism. In LXRbeta(-/-) mice on a normal diet, there is a reduction in size of perigonadal fat pad and, on high-fat diet there is resistance to obesity. In the present study, we investigated the reason for the resistance of LXRbeta(-/-) mice to weight gain. In LXRbeta(-/-) mice we found pancreatic exocrine insufficiency with reduced serum levels of amylase and lipase, reduced proteolytic activity in feces, chronic inflammatory infiltration, and, in the ductal epithelium, an increased apoptosis without compensatory proliferation. Electron microscopy revealed ductal dilatation with intraductal laminar structures characteristic of cystic fibrosis. To investigate the relationship between LXRbeta and pancreatic secretion, we studied the expression of LXRbeta and the water channel, aquaporin-1 (AQP1), in the ductal epithelium of the pancreas. In WT mice, ductal epithelial cells expressed LXRbeta in the nuclei and AQP1 on the plasma membrane. In LXRbeta(-/-) mice neither LXRbeta nor AQP1 was detectable. Moreover, in WT mice the LXR agonist (T2320) increased AQP1 gene expression. These data demonstrate that in LXRbeta(-/-) mice dietary resistance to weight gain is caused by pancreatic insufficiency and that LXRbeta regulates pancreatic exocrine secretion through the control of AQP1 expression. Pancreatic exocrine insufficiency is the main cause of malabsorption syndrome responsible for weight loss in adults and growth failure in children. Several genes are known to be involved in the pathogenesis and susceptibility to pancreatic insufficiency. LXRbeta should be included in that list.
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Mahajan MA, Samuels HH. Nuclear receptor coactivator/coregulator NCoA6(NRC) is a pleiotropic coregulator involved in transcription, cell survival, growth and development. NUCLEAR RECEPTOR SIGNALING 2008; 6:e002. [PMID: 18301782 PMCID: PMC2254332 DOI: 10.1621/nrs.06002] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/08/2007] [Accepted: 12/11/2007] [Indexed: 11/20/2022]
Abstract
NCoA6 (also referred to as NRC, ASC-2, TRBP, PRIP and RAP250) was originally isolated as a ligand-dependent nuclear receptor interacting protein. However, NCoA6 is a multifunctional coregulator or coactivator necessary for transcriptional activation of a wide spectrum of target genes. The NCoA6 gene is amplified and overexpressed in breast, colon and lung cancers. NCoA6 is a 250 kDa protein which harbors a potent N-terminal activation domain, AD1; and a second, centrally-located activation domain, AD2, which is necessary for nuclear receptor signaling. The intrinsic activation potential of NCoA6 is regulated by its C-terminal STL regulatory domain. Near AD2 is an LxxLL-1 motif which interacts with a wide spectrum of ligand-bound NRs with high-affinity. A second LxxLL motif (LxxLL-2) located towards the C-terminal region is more restricted in its NR specificity. The potential role of NCoA6 as a co-integrator is suggested by its ability to enhance transcriptional activation of a wide variety of transcription factors and from its in vivo association with a number of known cofactors including CBP/p300. NCoA6 has been shown to associate with at least three distinct coactivator complexes containing Set methyltransferases as core polypeptides. The composition of these complexes suggests that NCoA6 may play a fundamental role in transcriptional activation by modulating chromatin structure through histone methylation. Knockout studies in mice suggest that NCoA6 is an essential coactivator. NCoA6-/- embryos die between 8.5-12.5 dpc from general growth retardation coupled with developmental defects in the heart, liver, brain and placenta. NCoA6-/- MEFs grow at a reduced rate compared to WT MEFs and spontaneously undergo apoptosis, indicating the importance of NCoA6 as a prosurvival and anti-apoptotic gene. Studies with NCoA6+/- and conditional knockout mice suggest that NCoA6 is a pleiotropic coregulator involved in growth, development, wound healing and maintenance of energy homeostasis.
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Affiliation(s)
- Muktar A Mahajan
- Department of Pharmacology, NYU School of Medicine, New York, New York, USA.
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Yeom SY, Kim GH, Kim CH, Jung HD, Kim SY, Park JY, Pak YK, Rhee DK, Kuang SQ, Xu J, Han DJ, Song DK, Lee JW, Lee KU, Kim SW. Regulation of insulin secretion and beta-cell mass by activating signal cointegrator 2. Mol Cell Biol 2006; 26:4553-63. [PMID: 16738321 PMCID: PMC1489122 DOI: 10.1128/mcb.01412-05] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Activating signal cointegrator 2 (ASC-2) is a transcriptional coactivator of many nuclear receptors (NRs) and other transcription factors and contains two NR-interacting LXXLL motifs (NR boxes). In the pancreas, ASC-2 is expressed only in the endocrine cells of the islets of Langerhans, but not in the exocrine cells. Thus, we examined the potential role of ASC-2 in insulin secretion from pancreatic beta-cells. Overexpressed ASC-2 increased glucose-elicited insulin secretion, whereas insulin secretion was decreased in islets from ASC-2+/- mice. DN1 and DN2 are two dominant-negative fragments of ASC-2 that contain NR boxes 1 and 2, respectively, and block the interactions of cognate NRs with the endogenous ASC-2. Primary rat islets ectopically expressing DN1 or DN2 exhibited decreased insulin secretion. Furthermore, relative to the wild type, ASC-2+/- mice showed reduced islet mass and number, which correlated with increased apoptosis and decreased proliferation of ASC-2+/- islets. These results suggest that ASC-2 regulates insulin secretion and beta-cell survival and that the regulatory role of ASC-2 in insulin secretion appears to involve, at least in part, its interaction with NRs via its two NR boxes.
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Affiliation(s)
- Seon-Yong Yeom
- Asan Institute for Life Sciences, University of Ulsan College of Medicine, Songpa-gu, Seoul 138-736, South Korea
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Surugiu-Wärnmark I, Toresson G, Bülow L. The insufficiency of using SYBR green dyes in electrophoretic mobility shift assays of liver X receptor proteins. Anal Biochem 2006; 352:308-10. [PMID: 16574053 DOI: 10.1016/j.ab.2006.02.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2006] [Revised: 02/14/2006] [Accepted: 02/16/2006] [Indexed: 11/28/2022]
Affiliation(s)
- Ioana Surugiu-Wärnmark
- Department of Pure and Applied Biochemistry, Center for Chemistry and Chemical Engineering, Lund University, SE-221 00 Lund, Sweden.
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Kanaya E, Jingami H. The region of CQQQKPQRRP of PGC-1α interacts with the DNA-binding complex of FXR/RXRα. Biochem Biophys Res Commun 2006; 342:734-43. [PMID: 16494845 DOI: 10.1016/j.bbrc.2006.02.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2006] [Accepted: 02/04/2006] [Indexed: 12/12/2022]
Abstract
PGC-1alpha co-activates transcription by several nuclear receptors. To study the interaction among PGC-1alpha, RXRalpha/FXR, and DNA, we performed electrophoresis mobility shift assays. The RXRalpha/FXR proteins specifically bound to DNA containing the IR-1 sequence in the absence of ligand. When the fusion protein of GST-PGC-1alpha was added to the mixture of RXRalpha/FXR/DNA, the ligand-influenced retardation of the mobility was observed. The ligand for RXRalpha (9-cis-retinoic acid) was necessary for this retardation, whereas, the ligand for FXR, chenodeoxycholic acid, barely had an effect. The results obtained using truncated PGC-1alpha proteins suggested that two regions are necessary for PGC-1alpha to interact with the DNA-binding complex of RXRalpha/FXR. One is the region of the second leucine-rich motif, and the other is that of the amino acid sequence CQQQKPQRRP, present between the second and third leucine-rich motifs. The results obtained with the SPQSS mutation for KPQRR suggested that the basic amino acids are important for the interaction.
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Affiliation(s)
- Eiko Kanaya
- Department of Molecular Biology, Biomolecular Engineering Research Institute (BERI), Osaka, Japan
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Surugiu-Wärnmark I, Wärnmark A, Toresson G, Gustafsson JA, Bülow L. Selection of DNA aptamers against rat liver X receptors. Biochem Biophys Res Commun 2005; 332:512-7. [PMID: 15910755 DOI: 10.1016/j.bbrc.2005.04.147] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2005] [Accepted: 04/29/2005] [Indexed: 10/25/2022]
Abstract
Liver X receptors alpha and beta (LXRalpha; LXRbeta) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors. LXRs play an important role in the reverse cholesterol transport and govern the expression of many of the proteins that are indispensable for the regulation of normal cholesterol levels in the body. SELEX, an in vitro selection technology, was used on a single stranded DNA library harboring a 12 randomized nucleotide sequence in order to isolate aptamers showing affinity for LXRalpha. Enzyme-linked assays and surface plasmon resonance measurements showed that the selected aptamers had strong affinities for LXRalpha with apparent dissociation constants, K(d)s, in nanomolar range. All clones carried CG-repeats, indicating a probability for a similar manner of binding to LXRalpha. Very high cross-reactivities were observed when testing the aptamers with LXRbeta (up to 700%) and RXRalpha (up to 50%). If instead we regard the aptamer sequences as selected against LXRbeta, the cross-reactivities decrease considerably, to 17% for LXRalpha and 7% for RXRalpha. Therefore, in the future we are planning to use the obtained aptamers as binders for LXRbeta.
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Affiliation(s)
- Ioana Surugiu-Wärnmark
- Department of Pure and Applied Biochemistry, Center for Chemistry and Chemical Engineering, Lund University, SE-221 00 Lund, Sweden.
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Mahajan MA, Samuels HH. Nuclear hormone receptor coregulator: role in hormone action, metabolism, growth, and development. Endocr Rev 2005; 26:583-97. [PMID: 15561801 DOI: 10.1210/er.2004-0012] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Nuclear hormone receptor coregulator (NRC) (also referred to as activating signal cointegrator-2, thyroid hormone receptor-binding protein, peroxisome proliferator activating receptor-interacting protein, and 250-kDa receptor associated protein) belongs to a growing class of nuclear cofactors widely known as coregulators or coactivators that are necessary for transcriptional activation of target genes. The NRC gene is also amplified and overexpressed in breast, colon, and lung cancers. NRC is a 2063-amino acid protein that harbors a potent N-terminal activation domain (AD1) and a second more centrally located activation domain (AD2) that is rich in Glu and Pro. Near AD2 is a receptor-interacting domain containing an LxxLL motif (LxxLL-1), which interacts with a wide variety of ligand-bound nuclear hormone receptors with high affinity. A second LxxLL motif (LxxLL-2) located in the C-terminal region of NRC is more restricted in its nuclear hormone receptor specificity. The intrinsic activation potential of NRC is regulated by a C-terminal serine, threonine, leucine-regulatory domain. The potential role of NRC as a cointegrator is suggested by its ability to enhance transcriptional activation of a wide variety of transcription factors and from its in vivo association with a number of known transcriptional regulators including CBP/p300. Recent studies in mice indicate that deletion of both NRC alleles leads to embryonic lethality resulting from general growth retardation coupled with developmental defects in the heart, liver, brain, and placenta. NRC(-/-) mouse embryo fibroblasts spontaneously undergo apoptosis, indicating the importance of NRC as a prosurvival and antiapoptotic gene. Studies with 129S6 NRC(+/-) mice indicate that NRC is a pleiotropic regulator that is involved in growth, development, reproduction, metabolism, and wound healing.
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Affiliation(s)
- Muktar A Mahajan
- Departments of Pharmacology and Medicine, New York University School of Medicine, 550 First Avenue, New York, New York 10016, USA.
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Abstract
The year 2004 represents a milestone for the biosensor research community: in this year, over 1000 articles were published describing experiments performed using commercially available systems. The 1038 papers we found represent an approximately 10% increase over the past year and demonstrate that the implementation of biosensors continues to expand at a healthy pace. We evaluated the data presented in each paper and compiled a 'top 10' list. These 10 articles, which we recommend every biosensor user reads, describe well-performed kinetic, equilibrium and qualitative/screening studies, provide comparisons between binding parameters obtained from different biosensor users, as well as from biosensor- and solution-based interaction analyses, and summarize the cutting-edge applications of the technology. We also re-iterate some of the experimental pitfalls that lead to sub-optimal data and over-interpreted results. We are hopeful that the biosensor community, by applying the hints we outline, will obtain data on a par with that presented in the 10 spotlighted articles. This will ensure that the scientific community at large can be confident in the data we report from optical biosensors.
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Affiliation(s)
- Rebecca L Rich
- Center for Biomolecular Interaction Analysis, University of Utah, Salt Lake City, UT 84132, USA
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