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Lugenbühl JF, Viho EMG, Binder EB, Daskalakis NP. Stress molecular signaling in interaction with cognition. Biol Psychiatry 2024:S0006-3223(24)01628-7. [PMID: 39368530 DOI: 10.1016/j.biopsych.2024.09.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2024] [Revised: 09/02/2024] [Accepted: 09/27/2024] [Indexed: 10/07/2024]
Abstract
Exposure to stressful life events is associated with a high risk of developing psychiatric disorders with a wide variety of symptoms. Cognitive symptoms in stress-related psychiatric disorders can be particularly challenging to understand, both for those experiencing them and for healthcare providers. To gain insights, it is important to capture stress-induced structural, epigenomic, transcriptomic, and proteomic changes in relevant brain regions such as the amygdala, hippocampus, locus coeruleus and prefrontal cortex, resulting in long-lasting alterations in brain function. In this review, we will emphasize a subset of stress molecular mechanisms altering neuroplasticity, neurogenesis, and balance between excitatory and inhibitory neurons. We then discuss how to identify genetic risk factors that may accelerate stress-driven or stress-induced cognitive impairment. Despite the development of new technologies such as single-cell resolution sequencing, our understanding of the molecular effects of stress in the brain remains to be deepened. A better understanding of the diversity of stress effects in different brain regions and cell types is a pre-requisite to open new avenues for mechanism-informed prevention and treatment of stress-related cognitive symptoms.
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Affiliation(s)
- Justina F Lugenbühl
- Department of Psychiatry, McLean Hospital, Harvard Medical School, Belmont, MA, USA; Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA; Department of Psychiatry and Neuropsychology, School for Mental Health, and Neuroscience (MHeNs), Maastricht University, Maastricht, Netherlands
| | - Eva M G Viho
- Department Genes and Environment, Max Planck Institute of Psychiatry, Munich, Germany
| | - Elisabeth B Binder
- Department Genes and Environment, Max Planck Institute of Psychiatry, Munich, Germany.
| | - Nikolaos P Daskalakis
- Department of Psychiatry, McLean Hospital, Harvard Medical School, Belmont, MA, USA; Stanley Center for Psychiatric Research, Broad Institute of MIT and Harvard, Cambridge, MA, USA
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2
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Martinez GJ, Appleton M, Kipp ZA, Loria AS, Min B, Hinds TD. Glucocorticoids, their uses, sexual dimorphisms, and diseases: new concepts, mechanisms, and discoveries. Physiol Rev 2024; 104:473-532. [PMID: 37732829 PMCID: PMC11281820 DOI: 10.1152/physrev.00021.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Revised: 08/07/2023] [Accepted: 09/10/2023] [Indexed: 09/22/2023] Open
Abstract
The normal stress response in humans is governed by the hypothalamic-pituitary-adrenal (HPA) axis through heightened mechanisms during stress, raising blood levels of the glucocorticoid hormone cortisol. Glucocorticoids are quintessential compounds that balance the proper functioning of numerous systems in the mammalian body. They are also generated synthetically and are the preeminent therapy for inflammatory diseases. They act by binding to the nuclear receptor transcription factor glucocorticoid receptor (GR), which has two main isoforms (GRα and GRβ). Our classical understanding of glucocorticoid signaling is from the GRα isoform, which binds the hormone, whereas GRβ has no known ligands. With glucocorticoids being involved in many physiological and cellular processes, even small disruptions in their release via the HPA axis, or changes in GR isoform expression, can have dire ramifications on health. Long-term chronic glucocorticoid therapy can lead to a glucocorticoid-resistant state, and we deliberate how this impacts disease treatment. Chronic glucocorticoid treatment can lead to noticeable side effects such as weight gain, adiposity, diabetes, and others that we discuss in detail. There are sexually dimorphic responses to glucocorticoids, and women tend to have a more hyperresponsive HPA axis than men. This review summarizes our understanding of glucocorticoids and critically analyzes the GR isoforms and their beneficial and deleterious mechanisms and the sexual differences that cause a dichotomy in responses. We also discuss the future of glucocorticoid therapy and propose a new concept of dual GR isoform agonist and postulate why activating both isoforms may prevent glucocorticoid resistance.
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Affiliation(s)
- Genesee J Martinez
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, Kentucky, United States
| | - Malik Appleton
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, Kentucky, United States
| | - Zachary A Kipp
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, Kentucky, United States
| | - Analia S Loria
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, Kentucky, United States
- Barnstable Brown Diabetes Center, University of Kentucky College of Medicine, Lexington, Kentucky, United States
| | - Booki Min
- Department of Microbiology and Immunology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States
| | - Terry D Hinds
- Department of Pharmacology and Nutritional Sciences, University of Kentucky College of Medicine, Lexington, Kentucky, United States
- Barnstable Brown Diabetes Center, University of Kentucky College of Medicine, Lexington, Kentucky, United States
- Markey Cancer Center, University of Kentucky, Lexington, Kentucky, United States
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3
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Ni Z, Zhou XY, Aslam S, Niu DK. Characterization of Human Dosage-Sensitive Transcription Factor Genes. Front Genet 2019; 10:1208. [PMID: 31867040 PMCID: PMC6904359 DOI: 10.3389/fgene.2019.01208] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Accepted: 11/01/2019] [Indexed: 11/13/2022] Open
Abstract
Copy number changes in protein-coding genes are detrimental if the consequent changes in protein concentrations disrupt essential cellular functions. The dosage sensitivity of transcription factor (TF) genes is particularly interesting because their products are essential in regulating the expression of genetic information. From four recently curated data sets of dosage-sensitive genes (genes with conserved copy numbers across mammals, ohnologs, and two data sets of haploinsufficient genes), we compiled a data set of the most reliable dosage-sensitive (MRDS) genes and a data set of the most reliable dosage-insensitive (MRDIS) genes. The MRDS genes were those present in all four data sets, while the MRDIS genes were those absent from any one of the four data sets and with the probability of being loss of function-intolerant (pLI) values < 0.5 in both of the haploinsufficient gene data sets. Enrichment analysis of TF genes among the MRDS and MRDIS gene data sets showed that TF genes are more likely to be dosage-sensitive than other genes in the human genome. The nuclear receptor family was the most enriched TF family among the dosage-sensitive genes. TF families with very few members were also deemed more likely to be dosage-sensitive than TF families with more members. In addition, we found a certain number of dosage-insensitive TFs. The most typical were the Krüppel-associated box domain-containing zinc-finger proteins (KZFPs). Gene ontology (GO) enrichment analysis showed that the MRDS TFs were enriched for many more terms than the MRDIS TFs; however, the proteins interacting with these two groups of TFs did not show such sharp differences. Furthermore, we found that the MRDIS KZFPs were not significantly enriched for any GO terms, whereas their interacting proteins were significantly enriched for thousands of GO terms. Further characterizations revealed significant differences between MRDS TFs and MRDIS TFs in the lengths and nucleotide compositions of DNA-binding sites as well as in expression level, protein size, and selective force.
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Affiliation(s)
- Zhihua Ni
- MOE Key Laboratory for Biodiversity Science and Ecological Engineering and Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
- College of Life Sciences, Hebei University, Baoding, China
| | - Xiao-Yu Zhou
- MOE Key Laboratory for Biodiversity Science and Ecological Engineering and Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Sidra Aslam
- MOE Key Laboratory for Biodiversity Science and Ecological Engineering and Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
| | - Deng-Ke Niu
- MOE Key Laboratory for Biodiversity Science and Ecological Engineering and Beijing Key Laboratory of Gene Resource and Molecular Development, College of Life Sciences, Beijing Normal University, Beijing, China
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4
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Chow CC, Simons SS. An Approach to Greater Specificity for Glucocorticoids. Front Endocrinol (Lausanne) 2018; 9:76. [PMID: 29593646 PMCID: PMC5859375 DOI: 10.3389/fendo.2018.00076] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 02/19/2018] [Indexed: 11/13/2022] Open
Abstract
Glucocorticoid steroids are among the most prescribed drugs each year. Nonetheless, the many undesirable side effects, and lack of selectivity, restrict their greater usage. Research to increase glucocorticoid specificity has spanned many years. These efforts have been hampered by the ability of glucocorticoids to both induce and repress gene transcription and also by the lack of success in defining any predictable properties that control glucocorticoid specificity. Correlations of transcriptional specificity have been observed with changes in steroid structure, receptor and chromatin conformation, DNA sequence for receptor binding, and associated cofactors. However, none of these studies have progressed to the point of being able to offer guidance for increased specificity. We summarize here a mathematical theory that allows a novel and quantifiable approach to increase selectivity. The theory applies to all three major actions of glucocorticoid receptors: induction by agonists, induction by antagonists, and repression by agonists. Simple graphical analysis of competition assays involving any two factors (steroid, chemical, peptide, protein, DNA, etc.) yields information (1) about the kinetically described mechanism of action for each factor at that step where the factor acts in the overall reaction sequence and (2) about the relative position of that step where each factor acts. These two pieces of information uniquely provide direction for increasing the specificity of glucocorticoid action. Consideration of all three modes of action indicate that the most promising approach for increased specificity is to vary the concentrations of those cofactors/pharmaceuticals that act closest to the observed end point. The potential for selectivity is even greater when varying cofactors/pharmaceuticals in conjunction with a select class of antagonists.
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Affiliation(s)
- Carson C. Chow
- Mathematical Biology Section, NIDDK/LBM, National Institutes of Health, Bethesda, MD, United States
- *Correspondence: Carson C. Chow, ; S. Stoney Simons, Jr.,
| | - S. Stoney Simons
- Steroid Hormones Section, NIDDK/LERB, National Institutes of Health, Bethesda, MD, United States
- *Correspondence: Carson C. Chow, ; S. Stoney Simons, Jr.,
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Lempiäinen JK, Niskanen EA, Vuoti KM, Lampinen RE, Göös H, Varjosalo M, Palvimo JJ. Agonist-specific Protein Interactomes of Glucocorticoid and Androgen Receptor as Revealed by Proximity Mapping. Mol Cell Proteomics 2017; 16:1462-1474. [PMID: 28611094 DOI: 10.1074/mcp.m117.067488] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Revised: 06/02/2017] [Indexed: 11/06/2022] Open
Abstract
Glucocorticoid receptor (GR) and androgen receptor (AR) are steroid-inducible transcription factors (TFs). The GR and the AR are central regulators of various metabolic, homeostatic and differentiation processes and hence important therapeutic targets, especially in inflammation and prostate cancer, respectively. Hormone binding to these steroid receptors (SRs) leads to DNA binding and activation or repression of their target genes with the aid of interacting proteins, coregulators. However, protein interactomes of these important drug targets have remained poorly defined. We used proximity-dependent biotin identification to map the protein interaction landscapes of GR and AR in the presence and absence of their cognate agonist (dexamethasone, 5α-dihydrotestosterone) and antagonist (RU486, enzalutamide) in intact human cells. We reproducibly identified more than 30 proteins that interacted with the GR in an agonist-specific manner and whose interactions were significantly influenced by the DNA-binding function of the receptor. Interestingly, the agonist-dependent interactome of the GR overlapped considerably with that of the AR. In addition to known coactivators, corepressors and components of BAF (SWI/SNF) chromatin-remodeling complex, we identified a number of proteins, including lysine methyltransferases and demethylases that have not been previously linked to glucocorticoid or androgen signaling. A substantial number of these novel agonist-dependent GR/AR-interacting proteins, e.g. BCOR, IRF2BP2, RCOR1, and TLE3, have previously been implicated in transcription repression. This together with our data on the effect of BCOR, IRF2BP2, and RCOR1 on GR target gene expression suggests multifaceted functions and roles for SR coregulators. These first high confidence SR interactomes will aid in therapeutic targeting of the GR and the AR.
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Affiliation(s)
- Joanna K Lempiäinen
- From the ‡Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland
| | - Einari A Niskanen
- From the ‡Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland
| | - Kaisa-Mari Vuoti
- From the ‡Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland
| | - Riikka E Lampinen
- From the ‡Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland
| | - Helka Göös
- §Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Markku Varjosalo
- §Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Jorma J Palvimo
- From the ‡Institute of Biomedicine, University of Eastern Finland, Kuopio, Finland;
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6
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Weikum ER, Knuesel MT, Ortlund EA, Yamamoto KR. Glucocorticoid receptor control of transcription: precision and plasticity via allostery. Nat Rev Mol Cell Biol 2017; 18:159-174. [PMID: 28053348 PMCID: PMC6257982 DOI: 10.1038/nrm.2016.152] [Citation(s) in RCA: 342] [Impact Index Per Article: 48.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The glucocorticoid receptor (GR) is a constitutively expressed transcriptional regulatory factor (TRF) that controls many distinct gene networks, each uniquely determined by particular cellular and physiological contexts. The precision of GR-mediated responses seems to depend on combinatorial, context-specific assembly of GR-nucleated transcription regulatory complexes at genomic response elements. In turn, evidence suggests that context-driven plasticity is conferred by the integration of multiple signals, each serving as an allosteric effector of GR conformation, a key determinant of regulatory complex composition and activity. This structural and mechanistic perspective on GR regulatory specificity is likely to extend to other eukaryotic TRFs.
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Affiliation(s)
- Emily R Weikum
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road, Atlanta, Georgia 30322, USA
| | - Matthew T Knuesel
- Department of Cellular and Molecular Pharmacology, University of California San Francisco School of Medicine, 600 16th Street, San Francisco, California 94143, USA
| | - Eric A Ortlund
- Department of Biochemistry, Emory University School of Medicine, 1510 Clifton Road, Atlanta, Georgia 30322, USA
| | - Keith R Yamamoto
- Department of Cellular and Molecular Pharmacology, University of California San Francisco School of Medicine, 600 16th Street, San Francisco, California 94143, USA
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7
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Newton R, Giembycz MA. Understanding how long-acting β 2 -adrenoceptor agonists enhance the clinical efficacy of inhaled corticosteroids in asthma - an update. Br J Pharmacol 2016; 173:3405-3430. [PMID: 27646470 DOI: 10.1111/bph.13628] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Revised: 08/19/2016] [Accepted: 08/21/2016] [Indexed: 12/18/2022] Open
Abstract
In moderate-to-severe asthma, adding an inhaled long-acting β2 -adenoceptor agonist (LABA) to an inhaled corticosteroid (ICS) provides better disease control than simply increasing the dose of ICS. Acting on the glucocorticoid receptor (GR, gene NR3C1), ICSs promote anti-inflammatory/anti-asthma gene expression. In vitro, LABAs synergistically enhance the maximal expression of many glucocorticoid-induced genes. Other genes, including dual-specificity phosphatase 1(DUSP1) in human airways smooth muscle (ASM) and epithelial cells, are up-regulated additively by both drug classes. Synergy may also occur for LABA-induced genes, as illustrated by the bronchoprotective gene, regulator of G-protein signalling 2 (RGS2) in ASM. Such effects cannot be produced by either drug alone and may explain the therapeutic efficacy of ICS/LABA combination therapies. While the molecular basis of synergy remains unclear, mechanistic interpretations must accommodate gene-specific regulation. We explore the concept that each glucocorticoid-induced gene is an independent signal transducer optimally activated by a specific, ligand-directed, GR conformation. In addition to explaining partial agonism, this realization provides opportunities to identify novel GR ligands that exhibit gene expression bias. Translating this into improved therapeutic ratios requires consideration of GR density in target tissues and further understanding of gene function. Similarly, the ability of a LABA to interact with a glucocorticoid may be suboptimal due to low β2 -adrenoceptor density or biased β2 -adrenoceptor signalling. Strategies to overcome these limitations include adding-on a phosphodiesterase inhibitor and using agonists of other Gs-coupled receptors. In all cases, the rational design of ICS/LABA, and derivative, combination therapies requires functional knowledge of induced (and repressed) genes for therapeutic benefit to be maximized.
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Affiliation(s)
- Robert Newton
- Department of Cell Biology and Anatomy, Airways Inflammation Research Group, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Mark A Giembycz
- Department of Physiology and Pharmacology, Airways Inflammation Research Group, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
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8
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Pradhan MA, Blackford JA, Devaiah BN, Thompson PS, Chow CC, Singer DS, Simons SS. Kinetically Defined Mechanisms and Positions of Action of Two New Modulators of Glucocorticoid Receptor-regulated Gene Induction. J Biol Chem 2015; 291:342-54. [PMID: 26504077 DOI: 10.1074/jbc.m115.683722] [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: 08/04/2015] [Indexed: 11/06/2022] Open
Abstract
Most of the steps in, and many of the factors contributing to, glucocorticoid receptor (GR)-regulated gene induction are currently unknown. A competition assay, based on a validated chemical kinetic model of steroid hormone action, is now used to identify two new factors (BRD4 and negative elongation factor (NELF)-E) and to define their sites and mechanisms of action. BRD4 is a kinase involved in numerous initial steps of gene induction. Consistent with its complicated biochemistry, BRD4 is shown to alter both the maximal activity (Amax) and the steroid concentration required for half-maximal induction (EC50) of GR-mediated gene expression by acting at a minimum of three different kinetically defined steps. The action at two of these steps is dependent on BRD4 concentration, whereas the third step requires the association of BRD4 with P-TEFb. BRD4 is also found to bind to NELF-E, a component of the NELF complex. Unexpectedly, NELF-E modifies GR induction in a manner that is independent of the NELF complex. Several of the kinetically defined steps of BRD4 in this study are proposed to be related to its known biochemical actions. However, novel actions of BRD4 and of NELF-E in GR-controlled gene induction have been uncovered. The model-based competition assay is also unique in being able to order, for the first time, the sites of action of the various reaction components: GR < Cdk9 < BRD4 ≤ induced gene < NELF-E. This ability to order factor actions will assist efforts to reduce the side effects of steroid treatments.
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Affiliation(s)
- Madhumita A Pradhan
- From the Steroid Hormones Section, NIDDK/Laboratory of Endocrinology and Receptor Biology
| | - John A Blackford
- From the Steroid Hormones Section, NIDDK/Laboratory of Endocrinology and Receptor Biology
| | | | | | - Carson C Chow
- the Mathematical Biology Section, NIDDK/Laboratory of Biological Modeling, National Institutes of Health, Bethesda, Maryland 20892
| | | | - S Stoney Simons
- From the Steroid Hormones Section, NIDDK/Laboratory of Endocrinology and Receptor Biology,
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9
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Abstract
The different amounts of residual partial agonist activity (PAA) of antisteroids under assorted conditions have long been useful in clinical applications but remain largely unexplained. Not only does a given antagonist often afford unequal induction for multiple genes in the same cell but also the activity of the same antisteroid with the same gene changes with variations in concentration of numerous cofactors. Using glucocorticoid receptors as a model system, we have recently succeeded in constructing from first principles a theory that accurately describes how cofactors can modulate the ability of agonist steroids to regulate both gene induction and gene repression. We now extend this framework to the actions of antisteroids in gene induction. The theory shows why changes in PAA cannot be explained simply by differences in ligand affinity for receptor and requires action at a second step or site in the overall sequence of reactions. The theory also provides a method for locating the position of this second site, relative to a concentration limited step (CLS), which is a previously identified step in glucocorticoid-regulated transactivation that always occurs at the same position in the overall sequence of events of gene induction. Finally, the theory predicts that classes of antagonist ligands may be grouped on the basis of their maximal PAA with excess added cofactor and that the members of each class differ by how they act at the same step in the overall gene induction process. Thus, this theory now makes it possible to predict how different cofactors modulate antisteroid PAA, which should be invaluable in developing more selective antagonists.
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Affiliation(s)
- Carson C Chow
- Mathematical Biology Section, NIDDK/LBM, National Institutes of Health, Bethesda, MD 20892-5621, USA
| | - Karen M Ong
- Mathematical Biology Section, NIDDK/LBM, National Institutes of Health, Bethesda, MD 20892-5621, USA ; Computational Biology Program, New York University School of Medicine, New York, NY 10016, USA
| | - Benjamin Kagan
- Steroid Hormones Section, NIDDK/LERB, National Institutes of Health, Bethesda, MD 20892-1772, USA ; Science Department, Tuscarora High School, Loudoun County Public Schools, Leesburg, VA 20176, USA
| | - S Stoney Simons
- Steroid Hormones Section, NIDDK/LERB, National Institutes of Health, Bethesda, MD 20892-1772, USA
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10
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C. Chow C, M. Ong K, Kagan B, Stoney Simons Jr. S. Theory of partial agonist activity of steroid hormones. AIMS MOLECULAR SCIENCE 2015. [DOI: 10.3934/molsci.2015.2.101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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11
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Blackford JA, Brimacombe KR, Dougherty EJ, Pradhan M, Shen M, Li Z, Auld DS, Chow CC, Austin CP, Simons SS. Research resource: modulators of glucocorticoid receptor activity identified by a new high-throughput screening assay. Mol Endocrinol 2014; 28:1194-206. [PMID: 24850414 DOI: 10.1210/me.2014-1069] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Glucocorticoid steroids affect almost every type of tissue and thus are widely used to treat a variety of human pathological conditions. However, the severity of numerous side effects limits the frequency and duration of glucocorticoid treatments. Of the numerous approaches to control off-target responses to glucocorticoids, small molecules and pharmaceuticals offer several advantages. Here we describe a new, extended high-throughput screen in intact cells to identify small molecule modulators of dexamethasone-induced glucocorticoid receptor (GR) transcriptional activity. The novelty of this assay is that it monitors changes in both GR maximal activity (A(max)) and EC(50) (the position of the dexamethasone dose-response curve). Upon screening 1280 chemicals, 10 with the greatest changes in the absolute value of A(max) or EC(50) were selected for further examination. Qualitatively identical behaviors for 60% to 90% of the chemicals were observed in a completely different system, suggesting that other systems will be similarly affected by these chemicals. Additional analysis of the 10 chemicals in a recently described competition assay determined their kinetically defined mechanism and site of action. Some chemicals had similar mechanisms of action despite divergent effects on the level of the GR-induced product. These combined assays offer a straightforward method of identifying numerous new pharmaceuticals that can alter GR transactivation in ways that could be clinically useful.
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Affiliation(s)
- John A Blackford
- Steroid Hormones Section (J.A.B., E.J.D., M.P., S.S.S.), Laboratory of Endocrinology and Receptor Biology, and Laboratory of Biological Modeling (C.C.C.), National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; and National Center for Advancing Translational Sciences (K.R.B., M.S., Z.L., D.S.A., C.P.A.), National Institutes of Health, Rockville, Maryland 20892
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12
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Miranda TB, Voss TC, Hager GL. High-throughput fluorescence-based screen to identify factors involved in nuclear receptor recruitment to response elements. Methods Mol Biol 2014; 1042:3-12. [PMID: 23979996 DOI: 10.1007/978-1-62703-526-2_1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
The glucocorticoid receptor is an inducible transcription factor which plays important roles in many -physiological processes. Upon activation, GR interacts with regulatory elements and modulates the expression of genes. Although GR is widely expressed in multiple tissues, its binding sites within chromatin and the genes it regulates are tissue specific. Many accessory proteins and cofactors are thought to play a role in dictating GR's function; however, mechanisms involved in targeting GR to specific sites in the genome are not well understood. Here we describe a high-throughput fluorescence-based method to identify factors involved in GR loading at response elements. This screen utilizes a genetically engineered cell line that contains 200 repeats of a glucocorticoid response promoter and expresses GFP-tagged GR. Upon treatment with corticosteroids, GFP-GR forms a steady-state distribution at the promoter array, and its concentration at this focal point can be quantitatively determined. This system provides a novel approach to identify activities important for GR loading at its response element using siRNA libraries to target factors that enhance or inhibit receptor localization.
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Affiliation(s)
- Tina B Miranda
- Laboratory of Receptor Biology and Gene Expression, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
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13
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Simons SS, Edwards DP, Kumar R. Minireview: dynamic structures of nuclear hormone receptors: new promises and challenges. Mol Endocrinol 2013; 28:173-82. [PMID: 24284822 DOI: 10.1210/me.2013-1334] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Therapeutic targeting of nuclear receptors (NRs) is presently restricted due to 2 constraints: 1) a limited knowledge of the structural dynamics of intact receptor when complexed to DNA and coregulatory proteins; and 2) the inability to more selectively modulate NR actions at specific organ/gene targets. A major obstacle has been the current lack of understanding about the function and structure of the intrinsically disordered N-terminal domain that contains a major regulatory transcriptional activation function (AF1). Current studies of both mechanism of action and small molecule-selective receptor modulators for clinical uses target the structured pocket of the ligand-binding domain to modulate coregulatory protein interactions with the other activation function AF2. However, these approaches overlook AF1 activity. Recent studies have shown that highly flexible intrinsically disordered regions of transcription factors, including that of the N-terminal domain AF1 of NRs, not only are critical for several aspects of NR action but also can be exploited as drug targets, thereby opening unique opportunities for endocrine-based therapies. In this review article, we discuss the role of structural flexibilities in the allosteric modulation of NR activity and future perspectives for therapeutic interventions.
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Affiliation(s)
- S Stoney Simons
- Steroid Hormones Section (S.S.S.), Laboratory of Endocrinology and Receptor Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892; Departments of Molecular & Cellular Biology and Pathology & Immunology (D.P.E.), Baylor College of Medicine, Houston, Texas 77030; and Department of Basic Sciences (R.K.), The Commonwealth Medical College, Scranton, Pennsylvania 18510
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14
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Mark P, Lewis J, Jones M, Keelan J, Waddell B. The inflammatory state of the rat placenta increases in late gestation and is further enhanced by glucocorticoids in the labyrinth zone. Placenta 2013; 34:559-66. [DOI: 10.1016/j.placenta.2013.04.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2013] [Revised: 03/22/2013] [Accepted: 04/07/2013] [Indexed: 10/26/2022]
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15
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Robertson S, Rohwer JM, Hapgood JP, Louw A. Impact of glucocorticoid receptor density on ligand-independent dimerization, cooperative ligand-binding and basal priming of transactivation: a cell culture model. PLoS One 2013; 8:e64831. [PMID: 23717665 PMCID: PMC3661511 DOI: 10.1371/journal.pone.0064831] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Accepted: 04/18/2013] [Indexed: 11/26/2022] Open
Abstract
Glucocorticoid receptor (GR) levels vary between tissues and individuals and are altered by physiological and pharmacological effectors. However, the effects and implications of differences in GR concentration have not been fully elucidated. Using three statistically different GR concentrations in transiently transfected COS-1 cells, we demonstrate, using co-immunoprecipitation (CoIP) and fluorescent resonance energy transfer (FRET), that high levels of wild type GR (wtGR), but not of dimerization deficient GR (GRdim), display ligand-independent dimerization. Whole-cell saturation ligand-binding experiments furthermore establish that positive cooperative ligand-binding, with a concomitant increased ligand-binding affinity, is facilitated by ligand-independent dimerization at high concentrations of wtGR, but not GRdim. The down-stream consequences of ligand-independent dimerization at high concentrations of wtGR, but not GRdim, are shown to include basal priming of the system as witnessed by ligand-independent transactivation of both a GRE-containing promoter-reporter and the endogenous glucocorticoid (GC)-responsive gene, GILZ, as well as ligand-independent loading of GR onto the GILZ promoter. Pursuant to the basal priming of the system, addition of ligand results in a significantly greater modulation of transactivation potency than would be expected solely from the increase in ligand-binding affinity. Thus ligand-independent dimerization of the GR at high concentrations primes the system, through ligand-independent DNA loading and transactivation, which together with positive cooperative ligand-binding increases the potency of GR agonists and shifts the bio-character of partial GR agonists. Clearly GR-levels are a major factor in determining the sensitivity to GCs and a critical factor regulating transcriptional programs.
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Affiliation(s)
- Steven Robertson
- Department of Biochemistry, University of Stellenbosch, Matieland, Stellenbosch, Republic of South Africa
| | - Johann M. Rohwer
- Department of Biochemistry, University of Stellenbosch, Matieland, Stellenbosch, Republic of South Africa
| | - Janet P. Hapgood
- Department of Molecular and Cell Biology, University of Cape Town, Cape Town, Republic of South Africa
| | - Ann Louw
- Department of Biochemistry, University of Stellenbosch, Matieland, Stellenbosch, Republic of South Africa
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16
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Zhang Z, Sun Y, Cho YW, Chow CC, Simons SS. PA1 protein, a new competitive decelerator acting at more than one step to impede glucocorticoid receptor-mediated transactivation. J Biol Chem 2012; 288:42-58. [PMID: 23161582 DOI: 10.1074/jbc.m112.427740] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Numerous cofactors modulate the gene regulatory activity of glucocorticoid receptors (GRs) by affecting one or more of the following three major transcriptional properties: the maximal activity of agonists (A(max)), the potency of agonists (EC(50)), and the partial agonist activity of antisteroids (PAA). Here, we report that the recently described nuclear protein, Pax2 transactivation domain interaction protein (PTIP)-associated protein 1 (PA1), is a new inhibitor of GR transactivation. PA1 suppresses A(max), increases the EC(50), and reduces the PAA of an exogenous reporter gene in a manner that is independent of associated PTIP. PA1 is fully active with, and strongly binds to, the C-terminal half of GR. PA1 reverses the effects of the coactivator TIF2 on GR-mediated gene induction but is unable to augment the actions of the corepressor SMRT. Analysis of competition assays between PA1 and TIF2 with an exogenous reporter indicates that the kinetic definition of PA1 action is a competitive decelerator at two sites upstream from where TIF2 acts. With the endogenous genes IGFBP1 and IP6K3, PA1 also represses GR induction, increases the EC(50), and decreases the PAA. ChIP and re-ChIP experiments indicate that PA1 accomplishes this inhibition of the two genes via different mechanisms as follows: PA1 appears to increase GR dissociation from and reduce GR transactivation at the IGFBP1 promoter regions but blocks GR binding to the IP6K3 promoter. We conclude that PA1 is a new competitive decelerator of GR transactivation and can act at more than one molecularly defined step in a manner that depends upon the specific gene.
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Affiliation(s)
- Zhenhuan Zhang
- Steroid Hormones Section, National Institutes of Health, Bethesda, Maryland 20892, USA
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17
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Wong C, Chen S. The development, application and limitations of breast cancer cell lines to study tamoxifen and aromatase inhibitor resistance. J Steroid Biochem Mol Biol 2012; 131:83-92. [PMID: 22265958 PMCID: PMC3369003 DOI: 10.1016/j.jsbmb.2011.12.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Revised: 11/28/2011] [Accepted: 12/12/2011] [Indexed: 12/20/2022]
Abstract
Estrogen plays important roles in hormone receptor-positive breast cancer. Endocrine therapies, such as the antiestrogen tamoxifen, antagonize the binding of estrogen to estrogen receptor (ER), whereas aromatase inhibitors (AIs) directly inhibit the production of estrogen. Understanding the mechanisms of endocrine resistance and the ways in which we may better treat these types of resistance has been aided by the development of cellular models for resistant breast cancers. In this review, we will discuss what is known thus far regarding both de novo and acquired resistance to tamoxifen or AIs. Our laboratory has generated a collection of AI- and tamoxifen-resistant cell lines in order to comprehensively study the individual types of resistance mechanisms. Through the use of microarray analysis, we have determined that our cell lines resistant to a particular AI (anastrozole, letrozole, or exemestane) or tamoxifen are distinct from each other, indicating that these mechanisms can be quite complex. Furthermore, we will describe two novel de novo AI-resistant cell lines that were generated from our laboratory. Initial characterization of these cells reveals that they are distinct from our acquired AI-resistant cell models. In addition, we will review potential therapies which may be useful for overcoming resistant breast cancers through studies using endocrine resistant cell lines. Finally, we will discuss the benefits and shortcomings of cell models. Together, the information presented in this review will provide us a better understanding of acquired and de novo resistance to tamoxifen and AI therapies, the use of appropriate cell models to better study these types of breast cancer, which are valuable for identifying novel treatments and strategies for overcoming both tamoxifen and AI-resistant breast cancers.
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Affiliation(s)
- Cynthie Wong
- Division of Tumor Cell Biology, Beckman Research Institute of the City of Hope, Duarte, CA 91010, USA
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18
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The hypersensitive glucocorticoid response specifically regulates period 1 and expression of circadian genes. Mol Cell Biol 2012; 32:3756-67. [PMID: 22801371 DOI: 10.1128/mcb.00062-12] [Citation(s) in RCA: 101] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Glucocorticoids regulate gene expression by binding and activating the glucocorticoid receptor (GR). While ligand affinity determines the global sensitivity of the response, additional proteins act on the genome to tune sensitivity of some genes. However, the genomic extent and specificity of dose-specific glucocorticoid responses are unknown. We show that dose-specific glucocorticoid responses are extraordinarily specific at the genomic scale, able to distinctly express a single gene, the circadian rhythm gene for Period 1 (PER1), at concentrations consistent with the nighttime nadir of human cortisol. We mapped the PER1 response to a single GR binding site. The specific GR binding sequence did not impact sensitivity, and we instead attributed the response to a combination of additional transcription factors and chromatin accessibility acting in the same locus. The PER1 hypersensitive response element is conserved in the mouse, where we found similar upregulation of Per1 in pituitary cells. Targeted and transient overexpression of PER1 led to regulation of additional circadian rhythm genes hours later, suggesting that hypersensitive expression of PER1 impacts circadian gene expression. These findings show that hypersensitive GR binding occurs throughout the genome, drives targeted gene expression, and may be important to endocrine mediation of peripheral circadian rhythms.
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Awasthi S, Simons SS. Separate regions of glucocorticoid receptor, coactivator TIF2, and comodulator STAMP modify different parameters of glucocorticoid-mediated gene induction. Mol Cell Endocrinol 2012; 355:121-34. [PMID: 22342989 PMCID: PMC3312974 DOI: 10.1016/j.mce.2012.02.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Accepted: 02/02/2012] [Indexed: 11/16/2022]
Abstract
Increased specificity in steroid-regulated gene expression is a long-sought goal of endocrinologists. Considerable progress has resulted from the discovery of coactivators, corepressors, and comodulators that adjust the total activity (A(max)) of gene induction. Two less frequently quantitated, but equally potent, means of improving specificity are the concentration of agonist steroid required for half-maximal activity (EC(50)) and the residual or partial agonist activity displayed by most antisteroids (PAA). It is usually assumed that the modulatory activity of transcriptional cofactors coordinately regulates A(max), EC(50), and PAA. Here we examine the hypothesis that these three parameters can be independently modified by separate protein domains. The test system involves three differently sized fragments of each of three factors (glucocorticoid receptor [GR], coactivator TIF2, and comodulator STAMP), which are shown to form a ternary complex and similarly affect the induction properties of transfected and endogenous genes. Twenty-five different fragment combinations of the ternary complex are examined for their ability to modulate the A(max), EC(50), and PAA of a transiently transfected synthetic reporter gene. Different combinations selectively alter one, two, or all three parameters. These results clearly demonstrate that A(max), EC(50), and PAA can be independently regulated under some conditions by different pathways or molecular interactions. This new mechanistic insight suggests that selected activities of individual transcription factors are attractive targets for small molecules, which would have obvious clinical applications for increasing the specificity of steroids during endocrine therapies.
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Affiliation(s)
- Smita Awasthi
- Steroid Hormones Section, NIDDK/LERB, National Institutes of Health, Bethesda, MD, United States
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20
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Simons SS, Chow CC. The road less traveled: new views of steroid receptor action from the path of dose-response curves. Mol Cell Endocrinol 2012; 348:373-82. [PMID: 21664235 PMCID: PMC3184374 DOI: 10.1016/j.mce.2011.05.030] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Revised: 04/28/2011] [Accepted: 05/13/2011] [Indexed: 10/25/2022]
Abstract
Conventional studies of steroid hormone action proceed via quantitation of the maximal activity for gene induction at saturating concentrations of agonist steroid (i.e., A(max)). Less frequently analyzed parameters of receptor-mediated gene expression are EC(50) and PAA. The EC(50) is the concentration of steroid required for half-maximal agonist activity and is readily determined from the dose-response curve. The PAA is the partial agonist activity of an antagonist steroid, expressed as percent of A(max) under the same conditions. Recent results demonstrate that new and otherwise inaccessible mechanistic information is obtained when the EC(50) and/or PAA are examined in addition to the A(max). Specifically, A(max), EC(50), and PAA can be independently regulated, which suggests that novel pathways and factors may preferentially modify the EC(50) and/or PAA with little effect on A(max). Other approaches indicate that the activity of receptor-bound factors can be altered without changing the binding of factors to receptor. Finally, a new theoretical model of steroid hormone action not only permits a mechanistically based definition of factor activity but also allows the positioning of when a factor acts, as opposed to binds, relative to a kinetically defined step. These advances illustrate some of the benefits of expanding the mechanistic studies of steroid hormone action to routinely include EC(50) and PAA.
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Affiliation(s)
- S Stoney Simons
- Steroid Hormones Section, NIDDK/CEB, NIDDK, National Institutes of Health, Bethesda, MD 20892-1772, United States.
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21
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Kim ST, Lee SK, Gye MC. Cyclic Changes in the Expression ofp57kip2in Human Endometrium and its Regulation by Steroid Hormones in Endometrial Stromal Cells In Vitro. Reprod Sci 2011; 19:92-101. [DOI: 10.1177/1933719111414209] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Sung Tae Kim
- Renal Division, Department of Internal Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Sung Ki Lee
- Department of Obstetrics and Gynecology, Konyang University Hospital, Daejeon, Korea
| | - Myung Chan Gye
- Department of Life Science, College of Natural Sciences, Hanyang University, Seoul, Korea
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22
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Fernandes-Rosa FL, Hubert EL, Fagart J, Tchitchek N, Gomes D, Jouanno E, Benecke A, Rafestin-Oblin ME, Jeunemaitre X, Antonini SR, Zennaro MC. Mineralocorticoid receptor mutations differentially affect individual gene expression profiles in pseudohypoaldosteronism type 1. J Clin Endocrinol Metab 2011; 96:E519-27. [PMID: 21159846 DOI: 10.1210/jc.2010-1486] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Type 1 pseudohypoaldosteronism (PHA1), a primary form of mineralocorticoid resistance, is due to inactivating mutations of the NR3C2 gene, coding for the mineralocorticoid receptor (MR). OBJECTIVE The objective of the study was to assess whether different NR3C2 mutations have distinct effects on the pattern of MR-dependent transcriptional regulation of aldosterone-regulated genes. DESIGN AND METHODS Four MR mutations affecting residues in the ligand binding domain, identified in families with PHA1, were tested. MR proteins generated by site-directed mutagenesis were analyzed for their binding to aldosterone and were transiently transfected into renal cells to explore the functional effects on the transcriptional activity of the receptors by cis-trans-cotransactivation assays and by measuring the induction of endogenous gene transcription. RESULTS Binding assays showed very low or absent aldosterone binding for mutants MR(877Pro), MR(848Pro), and MR(947stop) and decreased affinity for aldosterone of MR(843Pro). Compared with wild-type MR, the mutations p.Leu843Pro and p.Leu877Pro displayed half-maximal aldosterone-dependent transactivation of reporter genes driven by mouse mammary tumor virus or glucocorticoid response element-2 dependent promoters, whereas MR(848Pro) and MR(947stop) nearly or completely lost transcriptional activity. Although MR(848Pro) and MR(947stop) were also incapable of inducing aldosterone-dependent gene expression of endogenous sgk1, GILZ, NDRG2, and SCNN1A, MR(843Pro) retained complete transcriptional activity on sgk1 and GILZ gene expression, and MR(877Pro) negatively affected the expression of sgk1, NDRG2, and SCNN1A. CONCLUSIONS Our data demonstrate that MR mutations differentially affect individual gene expression in a promoter-dependent manner. Investigation of differential gene expression profiles in PHA1 may allow a better understanding of the molecular substrate of phenotypic variability and to elucidate pathogenic mechanisms underlying the disease.
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Affiliation(s)
- Fábio L Fernandes-Rosa
- Department of Puericulture and Pediatrics, School of Medicine of Ribeirao Preto, University of Sao Paulo, Ribeirao Preto 14040-900, Brazil
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23
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Abstract
The last decade has seen an incredible breakthrough in technologies that allow histones, transcription factors (TFs), and RNA polymerases to be precisely mapped throughout the genome. From this research, it is clear that there is a complex interaction between the chromatin landscape and the general transcriptional machinery and that the dynamic control of this interface is central to gene regulation. However, the chromatin remodeling enzymes and general TFs cannot, on their own, recognize and stably bind to promoter or enhancer regions. Rather, they are recruited to cis regulatory regions through interaction with site-specific DNA binding TFs and/or proteins that recognize epigenetic marks such as methylated cytosines or specifically modified amino acids in histones. These "recruitment" factors are modular in structure, reflecting their ability to interact with the genome via one region of the protein and to simultaneously bind to other regulatory proteins via "effector" domains. In this chapter, we provide examples of common effector domains that can function in transcriptional regulation via their ability to (a) interact with the basal transcriptional machinery and general co-activators, (b) interact with other TFs to allow cooperative binding, and (c) directly or indirectly recruit histone and chromatin modifying enzymes.
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Affiliation(s)
- Seth Frietze
- Department of Biochemistry and Molecular Biology, University of Southern California, Los Angeles, CA, 90033, USA,
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24
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Simons SS. Glucocorticoid receptor cofactors as therapeutic targets. Curr Opin Pharmacol 2010; 10:613-9. [PMID: 20801081 DOI: 10.1016/j.coph.2010.08.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Revised: 08/02/2010] [Accepted: 08/02/2010] [Indexed: 10/19/2022]
Abstract
Numerous transcriptional cofactors (e.g. coactivators, corepressors, and comodulators) are known to alter the maximal transcriptional activity (A(max)) in gene induction and repression by steroid receptors in general and glucocorticoid receptors (GRs) in particular. However, recent data advance the earlier reports that these same factors also modify other parameters of glucocorticoid receptor transcriptional activity: the potency of agonists (or EC₅₀ and the partial agonist activity of antisteroids (or PAA). In several instances, factors modulate the EC₅₀ and/or PAA without changing A(max). Thus, studies of all three parameters reveal new factors acting at various stages of receptor action, thereby increasing the potential therapeutic targets for adjusting GR actions in pathological situations.
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Affiliation(s)
- S Stoney Simons
- Steroid Hormones Section, Bldg. 10, Room 8N-307B, NIDDK/CEB, National Institutes of Health (NIH), Bethesda, MD 20892-1772, USA.
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25
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Karmakar S, Gao T, Pace MC, Oesterreich S, Smith CL. Cooperative activation of cyclin D1 and progesterone receptor gene expression by the SRC-3 coactivator and SMRT corepressor. Mol Endocrinol 2010; 24:1187-202. [PMID: 20392877 DOI: 10.1210/me.2009-0480] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Although the ability of coactivators to enhance the expression of estrogen receptor-alpha (ERalpha) target genes is well established, the role of corepressors in regulating 17beta-estradiol (E2)-induced gene expression is poorly understood. Previous studies revealed that the silencing mediator of retinoic acid and thyroid hormone receptor (SMRT) corepressor is required for full ERalpha transcriptional activity in MCF-7 breast cancer cells, and we report herein the E2-dependent recruitment of SMRT to the regulatory regions of the progesterone receptor (PR) and cyclin D1 genes. Individual depletion of SMRT or steroid receptor coactivator (SRC)-3 modestly decreased E2-induced PR and cyclin D1 expression; however, simultaneous depletion revealed a cooperative effect of this coactivator and corepressor on the expression of these genes. SMRT and SRC-3 bind directly in an ERalpha-independent manner, and this interaction promotes E2-dependent SRC-3 binding to ERalpha measured by co-IP and SRC-3 recruitment to the cyclin D1 gene as measured by chromatin IP assays. Moreover, SMRT stimulates the intrinsic transcriptional activity of all of the SRC family (p160) coactivators. Our data link the SMRT corepressor directly with SRC family coactivators in positive regulation of ERalpha-dependent gene expression and, taken with the positive correlation found for SMRT and SRC-3 in human breast tumors, suggest that SMRT can promote ERalpha- and SRC-3-dependent gene expression in breast cancer.
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Affiliation(s)
- Sudipan Karmakar
- Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
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26
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He Y, Blackford JA, Kohn EC, Simons SS. STAMP alters the growth of transformed and ovarian cancer cells. BMC Cancer 2010; 10:128. [PMID: 20374646 PMCID: PMC2858746 DOI: 10.1186/1471-2407-10-128] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Accepted: 04/07/2010] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Steroid receptors play major roles in the development, differentiation, and homeostasis of normal and malignant tissue. STAMP is a novel coregulator that not only enhances the ability of p160 coactivator family members TIF2 and SRC-1 to increase gene induction by many of the classical steroid receptors but also modulates the potency (or EC50) of agonists and the partial agonist activity of antisteroids. These modulatory activities of STAMP are not limited to gene induction but are also observed for receptor-mediated gene repression. However, a physiological role for STAMP remains unclear. METHODS The growth rate of HEK293 cells stably transfected with STAMP plasmid and overexpressing STAMP protein is found to be decreased. We therefore asked whether different STAMP levels might also contribute to the abnormal growth rates of cancer cells. Panels of different stage human cancers were screened for altered levels of STAMP mRNA. Those cancers with the greatest apparent changes in STAMP mRNA were pursued in cultured cancer cell lines. RESULTS Higher levels of STAMP are shown to have the physiologically relevant function of reducing the growth of HEK293 cells but, unexpectedly, in a steroid-independent manner. STAMP expression was examined in eight human cancer panels. More extensive studies of ovarian cancers suggested the presence of higher levels of STAMP mRNA. Lowering STAMP mRNA levels with siRNAs alters the proliferation of several ovarian cancer tissue culture lines in a cell line-specific manner. This cell line-specific effect of STAMP is not unique and is also seen for the conventional effects of STAMP on glucocorticoid receptor-regulated gene transactivation. CONCLUSIONS This study indicates that a physiological function of STAMP in several settings is to modify cell growth rates in a manner that can be independent of steroid hormones. Studies with eleven tissue culture cell lines of ovarian cancer revealed a cell line-dependent effect of reduced STAMP mRNA on cell growth rates. This cell-line dependency is also seen for STAMP effects on glucocorticoid receptor-mediated transactivation. These preliminary findings suggest that further studies of STAMP in ovarian cancer may yield insight into ovarian cancer proliferation and may be useful in the development of biomarker panels.
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Affiliation(s)
- Yuanzheng He
- Steroid Hormones Section, Clinical Endocrinology Branch, NIDDK, National Institutes of Health, Bethesda, MD 20892-1772, USA
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27
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A theoretical framework for gene induction and experimental comparisons. Proc Natl Acad Sci U S A 2010; 107:7107-12. [PMID: 20351279 DOI: 10.1073/pnas.0911095107] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ligand-mediated gene induction by steroid receptors is a multistep process characterized by a dose-response curve for gene product that follows a first-order Hill equation. This behavior has classically been explained by steroid binding to receptor being the rate-limiting step. However, this predicts a constant potency of gene induction (EC(50)) for a given receptor-steroid complex, which is challenged by the findings that various cofactors/reagents can alter this parameter in a gene-specific manner. These properties put strong constraints on the mechanisms of gene induction and raise two questions: How can a first-order Hill dose-response curve (FHDC) arise from a multistep reaction sequence, and how do cofactors modify potency? Here we introduce a theoretical framework in which a sequence of steps yields an FHDC for the final product as a function of the initial agonist concentration. An exact determination of all constants is not required to describe the final FHDC. The theory predicts mechanisms for cofactor/reagent effects on gene-induction potency and maximal activity and it assigns a relative order to cofactors in the sequence of steps. The theory is supported by several observations from glucocorticoid receptor-mediated gene induction. It identifies the mechanism and matches the measured dose-response curves for different concentrations of the combination of cofactor Ubc9 and receptor. It also predicts that an FHDC cannot involve the DNA binding of preformed receptor dimers, which is validated experimentally. The theory is general and can be applied to any biochemical reaction that shows an FHDC.
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28
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Berry A, Matthews L, Jangani M, Plumb J, Farrow S, Buchan N, Wilson PA, Singh D, Ray DW, Donn RP. Interferon-inducible factor 16 is a novel modulator of glucocorticoid action. FASEB J 2010; 24:1700-13. [PMID: 20086048 PMCID: PMC3000051 DOI: 10.1096/fj.09-139998] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Previously, we used cDNA expression profiling to identify genes associated with glucocorticoid (Gc) sensitivity. We now identify which of these directly influence Gc action. Interferon-inducible protein 16 (IFI16), bone morphogenetic protein receptor type II (BMPRII), and regulator of G-protein signaling 14 (RGS14) increased Gc transactivation, whereas sialyltransferase 4B (SIAT4B) had a negative effect. Amyloid β (A4) precursor-protein binding, family B, member 1 (APBB1/Fe65) and neural cell expressed developmentally down-regulated 9 (NEDD9) were without effect. Only IFI16 potentiated Gc repression of NF-κB. In addition, IFI16 affected basal expression, and Gc induction of endogenous target genes. IFI16 did not affect glucocorticoid receptor (GR) expression, ligand-dependent repression of GR expression, or the ligand-dependent induction of GR phosphorylation on Ser-211 or Ser-203. Coimmunoprecipitation revealed an interaction, suggesting that IFI16 modulation of GR function is mediated by protein crosstalk. Transfection analysis with GR mutants showed that the ligand-binding domain of GR binds IFI16 and is the target domain for IFI16 regulation. Analysis of human lung sections identified colocalization of GR and IFI16, suggesting a physiologically relevant interaction. We demonstrate that IFI16 is a novel modulator of GR function and show the importance of analyzing variation in Gc sensitivity in humans, using appropriate technology, to drive discovery.—Berry, A., Matthews, L. Jangani, M., Plumb, J., Farrow, S., Buchan, N., Wilson, P. A., Singh, D., Ray, D., W., Donn, R. P. Interferon-inducible factor 16 is a novel modulator of glucocorticoid action.
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Affiliation(s)
- A Berry
- Arthritis Research Campaign Epidemiology Unit, University of Manchester, Manchester, UK
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29
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Nath-Sain S, Marignani PA. LKB1 catalytic activity contributes to estrogen receptor alpha signaling. Mol Biol Cell 2009; 20:2785-95. [PMID: 19369417 DOI: 10.1091/mbc.e08-11-1138] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The tumor suppressor serine-threonine kinase LKB1 is mutated in Peutz-Jeghers syndrome (PJS) and in epithelial cancers, including hormone-sensitive organs such as breast, ovaries, testes, and prostate. Clinical studies in breast cancer patients show low LKB1 expression is related to poor prognosis, whereas in PJS, the risk of breast cancer is similar to the risk from germline mutations in breast cancer (BRCA) 1/BRCA2. In this study, we investigate the role of LKB1 in estrogen receptor alpha (ERalpha) signaling. We demonstrate for the first time that LKB1 binds to ERalpha in the cell nucleus in which it is recruited to the promoter of ERalpha-responsive genes. Furthermore, LKB1 catalytic activity enhances ERalpha transactivation compared with LKB1 catalytically deficient mutants. The significance of our discovery is that we demonstrate for the first time a novel functional link between LKB1 and ERalpha. Our discovery places LKB1 in a coactivator role for ERalpha signaling, broadening the scientific scope of this tumor suppressor kinase and laying the groundwork for the use of LKB1 as a target for the development of new therapies against breast cancer.
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Affiliation(s)
- Suchita Nath-Sain
- Faculty of Medicine, Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
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30
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Sun Y, Tao YG, Kagan BL, He Y, Simons SS. Modulation of transcription parameters in glucocorticoid receptor-mediated repression. Mol Cell Endocrinol 2008; 295:59-69. [PMID: 18583028 PMCID: PMC2662735 DOI: 10.1016/j.mce.2008.05.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2008] [Revised: 05/09/2008] [Accepted: 05/13/2008] [Indexed: 12/25/2022]
Abstract
Glucocorticoid receptors (GRs) affect both gene induction and gene repression. The disparities of receptor binding to DNA and increased vs. decreased gene expression have suggested significant mechanistic differences between GR-mediated induction and repression. Numerous transcription factors are known to modulate three parameters of gene induction: the total activity (Vmax) and position of the dose-response curve with glucocorticoids (EC50) and the percent partial agonist activity with antiglucocorticoids. We have examined the effects on GR-mediated repression of five modulators (coactivators TIF2 [GRIP1, SRC-2] and SRC-1, corepressor SMRT, and comodulators STAMP and Ubc9), a glucocorticoid steroid (deacylcortivazol [DAC]) of very different structure, and an inhibitor of histone deacetylation (trichostatin A [TSA]). These factors interact with different domains of GR and thus are sensitive topological probes of GR action. These agents altered the Vmax, EC50, and percent partial agonist activity of endogenous and exogenous repressed genes similarly to that previously observed for GR-regulated gene induction. Collectively, these results suggest that GR-mediated induction and repression share many of the same molecular interactions and that the causes for different levels of gene transcription arise from more distal downstream steps.
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Affiliation(s)
| | | | | | | | - S. Stoney Simons
- Address correspondence to Dr. S. Stoney Simons, Jr., Bldg. 10, Room 8N-307B, NIDDK/CEB, NIH, Bethesda, MD 20892-1772 (Phone: 301-496-6796; FAX: 301-402-3572; e-mail: )
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Cho IJ, Kim SG. A novel mitogen-activated protein kinase phosphatase-1 and glucocorticoid receptor (GR) interacting protein-1-dependent combinatorial mechanism of gene transrepression by GR. Mol Endocrinol 2008; 23:86-99. [PMID: 18945810 DOI: 10.1210/me.2008-0257] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Glucocorticoids have major antiinflammatory effects. Because COX-2 is the rate-limiting enzyme for proinflammatory prostaglandins, this study investigated the combinatorial inhibitory role of glucocorticoid receptor (GR) in COX-2 gene induction in macrophages and sought to identify the molecular mechanisms for that inhibition. Glucocorticoid-activated GR repressed COX-2 gene induction by lipopolysaccharide (LPS). Activated GR inhibited LPS-induced activator protein 1 activity, which in turn decreased activating transcription factor 2/c-Jun phosphorylation. The inhibition of MAPK-dependent activating transcription factor 2/c-Jun phosphorylation by GR in COX-2 repression was a result of MAPK phosphatase-1 (MKP-1) induction. Although GR did not inhibit LPS-induced p65 phosphorylation or nuclear factor-kappaB DNA binding activity, deletion of the nuclear factor-kappaB binding site in the COX-2 gene suppressed the ability of glucocorticoid to attenuate COX-2 induction. Chromatin immunoprecipitation and transfection assays revealed that a p65 DNA complex involving GR-bound GR-interacting protein 1 (GRIP1) also contributed to COX-2 repression. Additional knockdown and transfection assays identified other inflammatory genes coordinately regulated by MKP-1 and GRIP1. In summary, activated GR was found to antagonize the LPS-dependent induction of the COX-2 gene via a novel combinatorial mechanism involving MKP-1-mediated activator protein 1 inhibition and GR/GRIP1 recruitment to the p65 DNA complex; moreover, this work facilitated the identification of other GR-responding MKP-1/GRIP1-regulated genes.
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Affiliation(s)
- Il Je Cho
- Innovative Drug Research Center for Metabolic and Inflammatory Disease, College of Pharmacy, Seoul National University, Sillim-dong, Kwanak-gu, Seoul 151-742, Korea
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Simons SS. What goes on behind closed doors: physiological versus pharmacological steroid hormone actions. Bioessays 2008; 30:744-56. [PMID: 18623071 DOI: 10.1002/bies.20792] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Steroid-hormone-activated receptor proteins are among the best-understood class of factors for altering gene transcription in cells. Steroid receptors are of major importance in maintaining normal human physiology by responding to circulating concentrations of steroid in the nM range. Nonetheless, most studies of steroid receptor action have been conducted using the supra-physiological conditions of saturating concentrations (> or =100 nM) of potent synthetic steroid agonists. Here we summarize the recent developments arising from experiments using two clinically relevant conditions: subsaturating concentrations of agonist (to mimic the circulating concentrations in mammals) and saturating concentrations of antagonists (which are employed in endocrine therapies to block the actions of endogenous steroids). These studies have revealed new facets of steroid hormone action that could not be uncovered by conventional experiments with saturating concentrations of agonist steroids, such as a plethora of factors/conditions for the differential control of gene expression by physiological levels of steroid, a rational approach for examining the gene-specific variations in partial agonist activity of antisteroids, and a dissociation of steroid potency and efficacy that implies the existence of separate, and possibly novel, mechanistic steps and cofactors.
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Affiliation(s)
- S Stoney Simons
- Steroid Hormones Section, Bldg 10, Room 8N-307B, NIDDK/CEB, NIH, Bethesda, MD 20892-1772, USA
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Tao YG, Xu Y, Xu HE, Simons SS. Mutations of glucocorticoid receptor differentially affect AF2 domain activity in a steroid-selective manner to alter the potency and efficacy of gene induction and repression. Biochemistry 2008; 47:7648-62. [PMID: 18578507 DOI: 10.1021/bi800472w] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The transcriptional activity of steroid hormones is intimately associated with their structure. Deacylcortivazol (DAC) contains several features that were predicted to make it an inactive glucocorticoid. Nevertheless, gene induction and repression by complexes of glucocorticoid receptor (GR) with DAC occur with potency (lower EC 50) greater than and efficacy (maximal activity, or A max) equal to those of the very active and smaller synthetic glucocorticoid dexamethasone (Dex). Guided by a recent X-ray structure of DAC bound to the GR ligand binding domain (LBD), we now report that several point mutants in the LBD have little effect on the binding of either agonist steroid. However, these same mutations dramatically alter the A max and/or EC 50 of exogenous and endogenous genes in a manner that depends on steroid structure. In some cases, Dex is no longer a full agonist. These properties appear to result from a preferential inactivation of the AF2 activation domain in the GR LBD of Dex-bound, but not DAC-bound, receptors. The Dex-bound receptors display normal binding to, but a greatly reduced response to, the coactivator TIF2, thus indicating a defect in the transmission efficiency of GR-steroid complex information to the coactivator TIF2. In addition, all GR mutants that are active in gene induction with either Dex or DAC have greatly reduced activity in gene repression. This contrasts with the reports of GR mutations preferentially suppressing GR-mediated induction. The properties of these GR mutants in gene induction support the hypothesis that the A max and EC 50 of GR-controlled gene expression can be independently modified, indicate that the receptor can be modified to favor activity with a specific agonist steroid, and suggest that new ligands with suitable substituents may be able to affect the same LBD conformational changes and thereby broaden the therapeutic applications of glucocorticoid steroids.
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Affiliation(s)
- Yong-guang Tao
- Steroid Hormones Section, National Institute of Diabetes and Digestive and Kidney Diseases/Clinical Endocrinology Branch, National Institutes of Health, Bethesda, Maryland 20892, USA
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van der Laan S, Meijer OC. Pharmacology of glucocorticoids: Beyond receptors. Eur J Pharmacol 2008; 585:483-91. [DOI: 10.1016/j.ejphar.2008.01.060] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2007] [Revised: 01/11/2008] [Accepted: 01/24/2008] [Indexed: 11/28/2022]
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Szapary D, Song LN, He Y, Simons SS. Differential modulation of glucocorticoid and progesterone receptor transactivation. Mol Cell Endocrinol 2008; 283:114-26. [PMID: 18215457 PMCID: PMC2275900 DOI: 10.1016/j.mce.2007.11.031] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Accepted: 11/29/2007] [Indexed: 01/13/2023]
Abstract
The determinants of the different biological activities of progesterone receptors (PRs) vs. glucocorticoid receptors (GRs), which bind to the same DNA sequences, remain poorly understood. The mechanisms by which differential expression of a common target gene can be achieved by PR and GR include unequal agonist steroid concentrations for half maximal induction (EC50) and dissimilar amounts of residual partial agonist activity for antisteroids in addition to the more common changes in total gene induction, or Vmax. Several factors are known to alter some or all of these three parameters for GR-regulated gene induction and some (i.e., the corepressors NCoR and SMRT) modulate the EC50 and partial agonist activity for GR and PR induction of the same gene in opposite directions. The current study demonstrates that other factors known to modulate GR properties (GME, GMEB-2, Ubc9, and STAMP) can also differentially interact with PRs or alter several of the above induction parameters under otherwise identical conditions. These results support the hypothesis that the modulation of EC50, partial agonist activity, and Vmax by a given factor is not limited to one receptor in a specific cell line. Furthermore, the number of factors that unequally modulate PR and GR induction parameters is now greatly expanded, thereby increasing the possible mechanisms for differential gene regulation by PRs vs. GRs.
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Affiliation(s)
- Daniele Szapary
- Steroid Hormones Section, NIDDK/CEB, National Institutes of Health, Bethesda, MD 20892-1772, United States
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36
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van der Laan S, Lachize SB, Vreugdenhil E, de Kloet ER, Meijer OC. Nuclear receptor coregulators differentially modulate induction and glucocorticoid receptor-mediated repression of the corticotropin-releasing hormone gene. Endocrinology 2008; 149:725-32. [PMID: 18006628 DOI: 10.1210/en.2007-1234] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Nuclear receptor coregulators are proteins that modulate the transcriptional activity of steroid receptors and may explain cell-specific effects of glucocorticoid receptor action. Based on the uneven distribution of a number of coregulators in CRH-expressing cells in the hypothalamus of the rat brain, we tested the hypothesis that these proteins are involved as mediators in the glucocorticoid-induced repression of the CRH promoter. Therefore, we assessed the role of coregulator proteins on both induction and repression of CRH in the AtT-20 cell line, a model system for CRH repression by glucocorticoids. The steroid receptor coactivator 1a (SRC1a), SRC-1e, nuclear corepressor (N-CoR), and silencing mediator of the retinoid and thyroid hormone receptor (SMRT) were studied in this system. We show that the concentration of glucocorticoid receptor and the type of ligand, i.e. corticosterone or dexamethasone, determines the repression. Furthermore, overexpression of SRC1a, but not SRC1e, increased both efficacy and potency of the glucocorticoid receptor-mediated repression of the forskolin-induced CRH promoter. Unexpectedly, cotransfection of the corepressors N-CoR and SMRT did not affect the corticosterone-dependent repression but resulted in a marked decrease of the forskolin stimulation of the CRH gene. Altogether, our data demonstrate that 1) the concentration of the receptor, 2) the type of ligand, and 3) the coregulator recruited all determine the expression and the repression of the CRH gene. We conclude that modulation of coregulator activity may play a role in the control of the hypothalamus-pituitary-adrenal axis.
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Affiliation(s)
- S van der Laan
- Division of Medical Pharmacology, Leiden/Amsterdam Centre for Drug Research and Leiden University Medical Centre, 2300 RA, Leiden, The Netherlands.
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37
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Abstract
Glucocorticoid action in cells is mediated by a specific receptor protein, the glucocorticoid receptor (GR). GR is a member of a superfamily of ligand-inducible transcription factors that control a variety of physiological functions; such as, metabolism, development, and reproduction. Unliganded GR is predominantly localized within the cytoplasm but rapidly and efficiently translocates to the nucleus following hormone binding. This review will focus on the intracellular signaling pathway utilized by the GR including the mechanisms that control its intracellular trafficking, hormone binding and transcriptional regulation. Many receptor-interacting proteins are involved in distinct steps in GR signal transduction, each with a unique mechanism to regulate receptor action and providing potential drug targets for the manipulation of cellular responses to glucocorticoids.
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Affiliation(s)
- Marjet D Heitzer
- Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15260, USA
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38
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Caprio M, Fève B, Claës A, Viengchareun S, Lombès M, Zennaro MC. Pivotal role of the mineralocorticoid receptor in corticosteroid‐induced adipogenesis. FASEB J 2007; 21:2185-94. [PMID: 17384139 DOI: 10.1096/fj.06-7970com] [Citation(s) in RCA: 226] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In addition to their role in controlling water and salt homeostasis, recent work suggests that aldosterone and mineralocorticoid receptors (MR) may be involved in adipocyte biology. This is of particular relevance given the role of MR as a high-affinity receptor for both mineralocorticoids and glucocorticoids. We have thus examined the effect of aldosterone and MR on white adipose cell differentiation. When cells are cultured in a steroid-free medium, aldosterone promotes acquisition of the adipose phenotype of 3T3-L1 and 3T3-F442A cells in a time-, dose-, and MR-dependent manner. In contrast, late and long-term exposure to dexamethasone inhibits adipocyte terminal maturation. The aldosterone effect on adipose maturation was accompanied by induction of PPARgamma mRNA expression, which was blocked by the MR antagonist spironolactone. Under permissive culture conditions, specific MR down-regulation by siRNAs markedly inhibited 3T3-L1 differentiation by interfering with the transcriptional control of adipogenesis, an effect not mimicked by specific inactivation of the glucocorticoid receptor. These results demonstrate that MR represents an important proadipogenic transcription factor that may mediate both aldosterone and glucocorticoid effects on adipose tissue development. MR thus may be of pathophysiological relevance to the development of obesity and the metabolic syndrome.
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MESH Headings
- Adipocytes, White
- Adipogenesis/drug effects
- Adipogenesis/physiology
- Adipose Tissue, White
- Aldosterone/pharmacology
- Animals
- Cell Differentiation/drug effects
- Cells, Cultured/drug effects
- Dexamethasone/pharmacology
- Dose-Response Relationship, Drug
- Insulin/pharmacology
- Male
- Metabolic Syndrome/etiology
- Metabolic Syndrome/physiopathology
- Mice
- Obesity/etiology
- Obesity/physiopathology
- PPAR gamma/biosynthesis
- PPAR gamma/genetics
- Phenotype
- RNA, Messenger/biosynthesis
- RNA, Small Interfering/pharmacology
- Receptors, Glucocorticoid/biosynthesis
- Receptors, Glucocorticoid/drug effects
- Receptors, Mineralocorticoid/biosynthesis
- Receptors, Mineralocorticoid/genetics
- Receptors, Mineralocorticoid/physiology
- Spironolactone/pharmacology
- Swiss 3T3 Cells/cytology
- Swiss 3T3 Cells/drug effects
- Transcription, Genetic/drug effects
- Transcription, Genetic/physiology
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He Y, Simons SS. STAMP, a novel predicted factor assisting TIF2 actions in glucocorticoid receptor-mediated induction and repression. Mol Cell Biol 2006; 27:1467-85. [PMID: 17116691 PMCID: PMC1800712 DOI: 10.1128/mcb.01360-06] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The coactivator TIF2 was predicted to interact with an unknown factor to modify both the relative inhibition in glucocorticoid receptor (GR)-mediated gene repression and several parameters of agonists and antisteroids in GR-regulated induction. Here, we describe the isolation and characterization of the predicted factor as a new 1,277-amino-acid endogenous protein (STAMP). STAMP associates with coactivators (TIF2 and SRC-1) and is selective for a subset of the steroid/nuclear receptors including GRs. Transfected STAMP increases the effects of TIF2 in GR-mediated repression and induction. Conversely, the levels of both induction and repression of endogenous genes are reduced when STAMP small interfering RNAs are used to lower the level of endogenous STAMP. Endogenous STAMP colocalizes with GR in intact cells and is recruited to the promoters of endogenous GR-induced and -repressed genes. We suggest that STAMP is an important new, downstream component of GR action in both gene activation and gene repression.
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Affiliation(s)
- Yuanzheng He
- Clinical Endocrinology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bldg. 10, Room 8N307B, Bethesda, MD 20892-1772, USA
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Wu Y, Kawate H, Ohnaka K, Nawata H, Takayanagi R. Nuclear compartmentalization of N-CoR and its interactions with steroid receptors. Mol Cell Biol 2006; 26:6633-55. [PMID: 16914745 PMCID: PMC1592818 DOI: 10.1128/mcb.01534-05] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The repression mechanisms by the nuclear receptor corepressor (N-CoR) of steroid hormone receptor (SHR)-mediated transactivation were examined. Yellow fluorescent protein (YFP)-N-CoR was distributed as intranuclear discrete dots, while coexpression of androgen receptor (AR), glucocorticoid receptor alpha, and estrogen receptor alpha ligand-dependently triggered redistribution of YFP-N-CoR. In fluorescence recovery after photobleaching analysis, mobility of the N-CoR was reduced by 5alpha-dihydrotestosterone (DHT)-bound AR. The middle region of N-CoR mostly contributed to the interaction with agonist-bound SHRs and the suppression of their transactivation function. N-CoR impaired the DHT-induced N-C interaction of AR, and the impaired interaction was dose-dependently recovered by coexpression of SRC-1 and CBP. N-CoR also impaired the intranuclear complete (distinct) focus formation of SHRs. Coexpression of SRC-1 or CBP released YFP-N-CoR or endogenous N-CoR from incomplete foci and simultaneously recovered complete foci of AR-green fluorescent protein. These results indicate that the relative ratio of coactivators and corepressors determines the conformational equilibrium between transcriptionally active and inactive SHRs in the presence of agonists. The intranuclear foci formed by agonist-bound SHRs were completely destroyed by actinomycin D and alpha-amanitin, indicating that the focus formation does not precede the transcriptional activation. The focus formation may reflect the accumulation of SHR/coactivator complexes released from the transcriptionally active sites and thus be a mirror of transcriptionally active complex formation.
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Affiliation(s)
- Yin Wu
- Department of Geriatric Medicine, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
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Voss TC, John S, Hager GL. Single-cell analysis of glucocorticoid receptor action reveals that stochastic post-chromatin association mechanisms regulate ligand-specific transcription. Mol Endocrinol 2006; 20:2641-55. [PMID: 16873444 DOI: 10.1210/me.2006-0091] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The glucocorticoid receptor (GR) dynamically interacts with response elements in the mouse mammary tumor virus (MMTV) promoter to regulate steroid-dependent transcription. In a clonal mammary carcinoma cell line containing a tandem array of MMTV promoter-reporter gene cassettes integrated at a single genomic locus, direct binding of a green fluorescent protein (GFP)-GR fusion protein to the MMTV regulatory elements can be observed in living cells. After ligand treatment, MMTV-dependent transcription in individual cells was detected by RNA fluorescence in situ hybridization (FISH). High-resolution fluorescence images were acquired from large numbers of randomly selected cells. Images were analyzed with a novel automated computer algorithm, measuring the RNA FISH signal and the relative GFP-GR fluorescence intensity at the MMTV array for each cell. Although dexamethasone increased the mean RNA FISH signal approximately 10-fold, RU486 produced only about a 2-fold induction, as expected for this mixed antagonist. For all treatment conditions, the relative GFP-GR fluorescence at the array for the averaged cells paralleled the RNA FISH measurements, suggesting that image analysis accurately detected an increase in steady-state GR association with the MMTV array that was responsible for the increase in transcriptional activity. The antagonist-dependent decreases in GR association with the MMTV promoter were confirmed by chromatin immunoprecipitation experiments, supporting the image analysis results. A pronounced cell-to-cell variability was observed in RNA FISH signal and GR-MMTV association within treatment groups. We observed a nonlinear relationship between GR-MMTV association and RNA FISH in individual cells, indicating that differences in GR-MMTV interaction account for some, but not all, of the transcriptional heterogeneity between individual cells. In selected cell subpopulations with equal levels of GR-MMTV association, there was a decrease in RNA FISH signal with RU486 treatment compared with dexamethasone treatment. These results indicate that stochastic events occurring after GR-promoter association, such as the actions of chromatin remodeling complexes or other cofactors, change in a ligand-dependent manner and regulate heterogeneous transcription in individual cells.
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Affiliation(s)
- Ty C Voss
- Laboratory of Receptor Biology and Gene Expression, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-5055, USA
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42
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Hassan AQ, Koh JT. A functionally orthogonal ligand-receptor pair created by targeting the allosteric mechanism of the thyroid hormone receptor. J Am Chem Soc 2006; 128:8868-74. [PMID: 16819881 PMCID: PMC2515387 DOI: 10.1021/ja060760v] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Nuclear receptors are ligand-dependent transcription factors that are of interest as potential tools to artificially regulate gene expression. Ligand binding induces a conformational change involving helix-12 which forms part of the dimerization interface used to bind transcriptional coactivators. When triiodothyronine (T3) binds the thyroid hormone receptor (TR) it indirectly contacts helix-12 through intermediary residues His(435) and Phe(451) termed a His-Phe switch. The mutant TRbeta(H435A) is nonresponsive to physiological concentrations of T3 but can be activated by the synthetic hormone analogue QH2 which potently activates His435-->Ala mutant at concentrations that do not activate the wild-type receptors TRalpha and TRbeta. QH2 does not show antagonist behavior with the wild-type TRs. QH2's functionally orthogonal behavior with TRbeta(H435A) is preserved on the three consensus thyroid hormone response elements.
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Affiliation(s)
- A. Quamrul Hassan
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
| | - John T. Koh
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716
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van der Laan S, Lachize SB, Schouten TG, Vreugdenhil E, de Kloet ER, Meijer OC. Neuroanatomical distribution and colocalisation of nuclear receptor corepressor (N-CoR) and silencing mediator of retinoid and thyroid receptors (SMRT) in rat brain. Brain Res 2005; 1059:113-21. [PMID: 16212947 DOI: 10.1016/j.brainres.2005.08.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2005] [Revised: 08/03/2005] [Accepted: 08/05/2005] [Indexed: 01/17/2023]
Abstract
The two structurally related nuclear receptor corepressor (N-CoR) and silencing mediator of retinoid and thyroid receptors (SMRT) proteins have been found to differentially affect the transcriptional activity of numerous nuclear receptors, such as thyroid hormone, retinoic acid and steroid receptors. Because of the numerous effects mediated by nuclear receptors in brain, it is of interest to extend these in vitro data and to explore the cellular distribution of both corepressors in brain tissue. We therefore examined, using in situ hybridisation, whether the relative abundance of these two functionally distinct corepressors differed in rat brain and pituitary. We find that although both N-CoR and SMRT transcripts are ubiquitously expressed in brain, striking differences in their respective levels of expression could be observed in discrete areas of brain stem, thalamus, hypothalamus and hippocampus. Using dual-label immunofluorescence, we examined in selected glucocorticoid sensitive areas involved in the regulation of the hypothalamus-pituitary-adrenal axis activity, the respective protein abundance of N-CoR and SMRT. Protein abundance was largely concurrent with the mRNA expression levels, with SMRT relatively more abundant in hypothalamus and brain stem areas. Colocalisation of N-CoR and SMRT was demonstrated by confocal microscopy in most areas studied. Taken together, these findings are consistent with the idea that the uneven neuroanatomical distribution of N-CoR and SMRT protein may contribute to the site-specific effects exerted by hormones, such as glucocorticoids, in the brain.
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Affiliation(s)
- S van der Laan
- Division of Medical Pharmacology, Leiden/Amsterdam Centre for Drug Research and Leiden University Medical Center, The Netherlands.
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44
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Ki SH, Cho IJ, Choi DW, Kim SG. Glucocorticoid receptor (GR)-associated SMRT binding to C/EBPbeta TAD and Nrf2 Neh4/5: role of SMRT recruited to GR in GSTA2 gene repression. Mol Cell Biol 2005; 25:4150-65. [PMID: 15870285 PMCID: PMC1087722 DOI: 10.1128/mcb.25.10.4150-4165.2005] [Citation(s) in RCA: 110] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The expression of the glutathione S-transferase gene (GST), whose induction accounts for cancer chemoprevention, is regulated by activation of CCAAT/enhancer binding protein beta (C/EBPbeta) and NF-E2-related factor 2 (Nrf2). The present study investigated the repressing effects of activating glucocorticoid receptor (GR) on C/EBPbeta- and Nrf2-mediated GSTA2 gene induction and the mechanism. Dexamethasone that activates GR inhibited constitutive and oltipraz- or tert-butylhydroquinone (t-BHQ)-inducible GSTA2 expression in H4IIE cells. Also, dexamethasone repressed GSTA2 promoter-luciferase gene activity. Dexamethasone-GR activation did not inhibit nuclear translocation of C/EBPbeta or Nrf2 nor their DNA binding activities induced by oltipraz or t-BHQ. Deletion of the glucocorticoid response element (GRE) in the GSTA2 promoter abolished dexamethasone inhibition of the gene induction. Immunoprecipitation-immunoblotting, chromatin immunoprecipitation, and GST pull-down assays revealed that silencing mediator for retinoid and thyroid hormone receptors (SMRT), a corepressor recruited to steroid-GR complex for histone deacetylation, bound to TAD domain of C/EBPbeta and Neh4/5 domain of Nrf2. The GSTA2 promoter-luciferase activities were decreased by SMRT but not by truncated SMRTs. The small interference RNA (siRNA) against SMRT abolished SMRT repression of the gene induction by C/EBPbeta or Nrf2. The plasmid transfection and siRNA experiments directly evidenced the functional role of SMRT in GSTA2 repression. In conclusion, dexamethasone antagonizes C/EBPbeta- and Nrf2-mediated GSTA2 gene induction via ligand-GR binding to the GRE, and steroid-mediated GSTA2 repression involves inactivation of C/EBPbeta and Nrf2 by SMRT recruited to steroid-GR complex.
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Affiliation(s)
- Sung Hwan Ki
- College of Pharmacy, Seoul National University, Sillim-dong, Kwanak-gu, Seoul 151-742, South Korea
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45
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Wang D, Simons SS. Corepressor binding to progesterone and glucocorticoid receptors involves the activation function-1 domain and is inhibited by molybdate. Mol Endocrinol 2005; 19:1483-500. [PMID: 15774497 DOI: 10.1210/me.2005-0012] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Corepressors are known to interact via their receptor interaction domains (RIDs) with the ligand binding domain in the carboxyl terminal half of steroid/nuclear receptors. We now report that a portion of the activation function-1 domain of glucocorticoid receptors (GRs) and progesterone receptors (PRs), which is the major transactivation sequence, is necessary but not sufficient for corepressor [nuclear receptor corepressor (NCoR) and silencing mediator of retinoid and thyroid hormone receptor (SMRT)] RID binding to GRs and PRs in both mammalian two-hybrid and coimmunoprecipitation assays. Importantly, these two receptor sequences are functionally interchangeable in the context of GR for transactivation, corepressor binding, and corepressor modulatory activity assays. This suggests that corepressors may act in part by physically blocking portions of receptor activation function-1 domains. However, differences exist in corepressor binding to GRs and PRs. The C-terminal domain of PRs has a higher affinity for corepressor than that of GRs. The ability of some segments of the coactivator TIF2 to competitively inhibit corepressor binding to receptors is different for GRs and PRs. With each receptor, the cell-free binding of corepressors to ligand-free receptor is prevented by sodium molybdate, which is a well-known inhibitor of receptor activation to the DNA-binding state. This suggests that receptor activation precedes binding to corepressors. Collectively, these results indicate that corepressor binding to GRs and PRs involve both N- and C-terminal sequences of activated receptors but differ in ways that may contribute to the unique biological responses of each receptor in intact cells.
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Affiliation(s)
- Dongqing Wang
- Steroid Hormones Section, National Institute of Diabetes and Digestive and Kidney Diseases/Laboratory of Molecular and Cellular Biology, National Institutes of Health, Bethesda, Maryland 20892, USA
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Cho S, Kagan BL, Blackford JA, Szapary D, Simons SS. Glucocorticoid Receptor Ligand Binding Domain Is Sufficient for the Modulation of Glucocorticoid Induction Properties by Homologous Receptors, Coactivator Transcription Intermediary Factor 2, and Ubc9. Mol Endocrinol 2005; 19:290-311. [PMID: 15539428 DOI: 10.1210/me.2004-0134] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Several factors modulate the position of the dose-response curve of steroid receptor-agonist complexes and the partial agonist activity of antagonist complexes, thereby causing differential gene activation by circulating hormones and unequal gene repression during endocrine therapies with antisteroids. We now ask whether the modulatory activity of three factors (homologous receptor, coactivator transcription intermediary factor 2, and Ubc9) requires the same or different domains of glucocorticoid receptors (GRs). In all cases, we find that neither the amino terminal half of the receptor, which contains the activation function-1 activation domain, nor the DNA binding domain is required. This contrasts with the major role of activation function-1 in determining the amount of gene expression and partial agonist activity of antisteroids with most steroid receptors. However, the situation is more complicated with Ubc9, where GR N-terminal sequences prevent the actions of Ubc9, but not added GR or transcription intermediary factor 2, at low GR concentrations. Inhibition is relieved by deletion of these sequences or by replacement with the comparable region of progesterone receptors but not by overexpression of the repressive sequences. These results plus the binding of C-terminal GR sequences to the suppressive N-terminal domain implicate an intramolecular mechanism for the inhibition of Ubc9 actions at low GR concentrations. A shift from noncooperative to cooperative steroid binding at high GR concentrations suggests that conformational changes reposition the inhibitory N-terminal sequence to allow Ubc9 interaction with elements of the ligand binding domain. Collectively, these results indicate a dominant role of GR C-terminal sequences in the modulation of the dose-response curve and partial agonist activity of GR complexes. They also reveal mechanistic differences both among individual modulators and between the ability of the same factors to regulate the total amount of gene expression.
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Affiliation(s)
- Sehyung Cho
- Steriod Hormones Section, National Institute of Diabetes and Digestive and Kidney Diseases/LMCB, National Institutes of Health, Bethesda, Maryland 20892, USA
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Corrigan CJ, Lee TH. Glucocorticoid Action and Resistance in Asthma. Allergol Int 2005. [DOI: 10.2332/allergolint.54.235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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Smith CL, O'Malley BW. Coregulator function: a key to understanding tissue specificity of selective receptor modulators. Endocr Rev 2004; 25:45-71. [PMID: 14769827 DOI: 10.1210/er.2003-0023] [Citation(s) in RCA: 640] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Ligands for the nuclear receptor superfamily control many aspects of biology, including development, reproduction, and homeostasis, through regulation of the transcriptional activity of their cognate receptors. Selective receptor modulators (SRMs) are receptor ligands that exhibit agonistic or antagonistic biocharacter in a cell- and tissue context-dependent manner. The prototypical SRM is tamoxifen, which as a selective estrogen receptor modulator, can activate or inhibit estrogen receptor action. SRM-induced alterations in the conformation of the ligand-binding domains of nuclear receptors influence their abilities to interact with other proteins, such as coactivators and corepressors. It has been postulated, therefore, that the relative balance of coactivator and corepressor expression within a given target cell determines the relative agonist vs. antagonist activity of SRMs. However, recent evidence reveals that the cellular environment also plays a critical role in determining SRM biocharacter. Cellular signaling influences the activity and subcellular localization of coactivators and corepressors as well as nuclear receptors, and this contributes to gene-, cell-, and tissue-specific responses to SRM ligands. Increased understanding of the effect of cellular environment on nuclear receptors and their coregulators has the potential to open the field of SRM discovery and research to many members of the nuclear receptor superfamily.
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Affiliation(s)
- Carolyn L Smith
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
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Reiter R, Oh AS, Wellstein A, Riegel AT. Impact of the nuclear receptor coactivator AIB1 isoform AIB1-Δ3 on estrogenic ligands with different intrinsic activity. Oncogene 2004; 23:403-9. [PMID: 14691461 DOI: 10.1038/sj.onc.1207202] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The nuclear receptor coactivator amplified in breast cancer 1 (AIB1) and its more active isoform AIB1-Delta3 are overexpressed in breast cancer and preneoplastic breast tissue. However, the impact of these proteins on the transcriptional activity of natural estrogens or selective estrogen receptor modulators (SERMs) has not been determined. Here we show that AIB1-Delta3 causes a significant increase in the efficacy of 17beta-estradiol at both estrogen receptor-alpha (ER-alpha) and ER-beta in ovarian, breast and endometrial cancer cell lines. AIB1-Delta3 also significantly increased the efficacy of the natural estrogen genistein at both ER-alpha and ER-beta, whereas AIB1 had no effect on either the potency or efficacy of genistein at either receptor. The estrogenic efficacy of the partial agonist tamoxifen was significantly increased in all cell lines at ER-alpha by overexpression of AIB1-Delta3 both on transfected and endogenous estrogen responsive genes. In contrast, overexpression of AIB1 or AIB1-Delta3 had no effect on the potency or efficacy of the SERM raloxifene. We conclude that overexpression of the AIB1-Delta3 isoform will increase the estrogenicity of a variety of natural and pharmacologic compounds in tissues that develop hormone-dependent neoplasias and overexpression of these cofactors may be a contributing factor to the hormone-driven development of neoplasia and to antiestrogen resistance of breast cancers.
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Affiliation(s)
- Ronald Reiter
- Department of Oncology, Lombardi Cancer Center, Georgetown University, Washington, DC 20057, USA
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Betrabet SS, Choudhuri J, Gill-Sharma M. Use of viral promoters in mammalian cell-based bioassays: How reliable? J Transl Med 2004; 2:1. [PMID: 14720299 PMCID: PMC331422 DOI: 10.1186/1479-5876-2-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2003] [Accepted: 01/14/2004] [Indexed: 11/20/2022] Open
Abstract
Cell-based bioassays have been suggested for screening of hormones and drug bioactivities. They are a plausible alternative to animal based methods. The technique used is called receptor/reporter system. Receptor/reporter system was initially developed as a research technique to understand gene function. Often reporter constructs containing viral promoters were used because they could be expressed with very 'high' magnitude in a variety of cell types in the laboratory. On the other hand mammalian genes are expressed in a cell/tissue specific manner, which makes them (i.e. cells/tissues) specialized for specific function in vivo. Therefore, if the receptor/reporter system is to be used as a cell-based screen for testing of hormones and drugs for human therapy then the choice of cell line as well as the promoter in the reporter module is of prime importance so as to get a realistic measure of the bioactivities of 'test' compounds. We evaluated two conventionally used viral promoters and a natural mammalian promoter, regulated by steroid hormone progesterone, in a cell-based receptor/reporter system. The promoters were spliced into vectors expressing enzyme CAT (chloramphenicol acetyl transferase), which served as a reporter of their magnitudes and consistencies in controlling gene expressions. They were introduced into breast cell lines T47D and MCF-7, which served as a cell-based source of progesterone receptors. The yardstick of their reliability was highest magnitude as well as consistency in CAT expression on induction by sequential doses of progesterone. All the promoters responded to induction by progesterone doses ranging from 10-12 to 10-6 molar by expressing CAT enzyme, albeit with varying magnitudes and consistencies. The natural mammalian promoter showed the most coherence in magnitude as well as dose dependent expression profile in both the cell lines. Our study casts doubts on use of viral promoters in a cell-based bioassay for measuring bioactivities of drugs and hormones for human therapy and suggests caution regardingtranslation in toto, of a research technique as a cell-based bioassay for drug screening.
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Affiliation(s)
- Shrikant S Betrabet
- National Institute for Research in Reproductive Health. (ICMR), Jahangir Merwanji Street. Parel, Mumbai.400 012, India
| | - Jyoti Choudhuri
- National Institute for Research in Reproductive Health. (ICMR), Jahangir Merwanji Street. Parel, Mumbai.400 012, India
| | - Manjit Gill-Sharma
- National Institute for Research in Reproductive Health. (ICMR), Jahangir Merwanji Street. Parel, Mumbai.400 012, India
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