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Zorrilla Veloz RI, McKenzie T, Palacios BE, Hu J. Nuclear hormone receptors in demyelinating diseases. J Neuroendocrinol 2022; 34:e13171. [PMID: 35734821 PMCID: PMC9339486 DOI: 10.1111/jne.13171] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 04/20/2022] [Accepted: 05/27/2022] [Indexed: 11/28/2022]
Abstract
Demyelination results from the pathological loss of myelin and is a hallmark of many neurodegenerative diseases. Despite the prevalence of demyelinating diseases, there are no disease modifying therapies that prevent the loss of myelin or promote remyelination. This review aims to summarize studies in the field that highlight the importance of nuclear hormone receptors in the promotion and maintenance of myelination and the relevance of nuclear hormone receptors as potential therapeutic targets for demyelinating diseases. These nuclear hormone receptors include the estrogen receptor, progesterone receptor, androgen receptor, vitamin D receptor, thyroid hormone receptor, peroxisome proliferator-activated receptor, liver X receptor, and retinoid X receptor. Pre-clinical studies in well-established animal models of demyelination have shown a prominent role of these nuclear hormone receptors in myelination through their promotion of oligodendrocyte maturation and development. The activation of the nuclear hormone receptors by their ligands also promotes the synthesis of myelin proteins and lipids in mouse models of demyelination. There are limited clinical studies that focus on how the activation of these nuclear hormone receptors could alleviate demyelination in patients with diseases such as multiple sclerosis (MS). However, the completed clinical trials have reported improved clinical outcome in MS patients treated with the ligands of some of these nuclear hormone receptors. Together, the positive results from both clinical and pre-clinical studies point to nuclear hormone receptors as promising therapeutic targets to counter demyelination.
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Affiliation(s)
- Rocío I Zorrilla Veloz
- Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Cancer Biology Program, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, USA
| | - Takese McKenzie
- Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Neuroscience Program, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, USA
| | - Bridgitte E Palacios
- Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Cancer Biology Program, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, USA
- Neuroscience Program, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, USA
| | - Jian Hu
- Department of Cancer Biology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
- Cancer Biology Program, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, USA
- Neuroscience Program, The University of Texas MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, USA
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Huang F, Liu H, Lei Z, Li Z, Zhang T, Yang M, Zhou K, Sun C. Long noncoding RNA CCAT1 inhibits miR-613 to promote nonalcoholic fatty liver disease via increasing LXRα transcription. J Cell Physiol 2020; 235:9819-9833. [PMID: 32413192 DOI: 10.1002/jcp.29795] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 04/08/2020] [Accepted: 04/30/2020] [Indexed: 12/30/2022]
Abstract
Nonalcoholic fatty liver disease (NAFLD) is regarded as a threat to public health; however, the pathologic mechanism of NAFLD is not fully understood. We attempted to identify abnormally expressed long noncoding RNA (lncRNAs) and messenger RNA that may affect the occurrence and development of NAFLD in this study. The expression of differentially expressed lncRNAs in NAFLD was determined in oleic acid (OA)-treated L02 cells, and the functions of CCAT1 in lipid droplet formation were evaluated in vitro. Differentially expressed genes (DEGs) were analyzed by microarray analysis, and DEGs related to CCTA1 were selected and verified by weighted correlation network analysis. The dynamic effects of LXRα and CCTA1 on lipid droplet formation and predicted binding was examined. The binding between miR-631 and CCAT1 and LXRα was verified. The dynamic effects of miR-613 inhibition and CCTA1 silencing on lipid droplet formation were examined. The expression and correlations of miR-631, CCAT1, and LXRα were determined in tissue samples. As the results show, CCAT1 was induced by OA and upregulated in NAFLD clinical samples. CCAT1 silencing significantly suppressed lipid droplet accumulation in vitro. LXRα was positively correlated with CCAT1. By inhibiting miR-613, CCAT1 increased the transcription of LXRα and promoted LXRα expression. The expression of LXRα was significantly increased in NAFLD tissues and was positively correlated with CCAT1. In conclusion, CCAT1 increases LXRα transcription by serving as a competing endogenous RNA for miR-613 in an LXRE-dependent manner, thereby promoting lipid droplet formation and NAFLD. CCAT1 and LXRα might be potent targets for NAFLD treatment.
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Affiliation(s)
- Feizhou Huang
- Emergency Department, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Huaizheng Liu
- Emergency Department, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Zhao Lei
- Emergency Department, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Zhenzhou Li
- Emergency Department, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Tianyi Zhang
- Emergency Department, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Mingshi Yang
- Emergency Department, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Kefu Zhou
- Emergency Department, The Third Xiangya Hospital, Central South University, Changsha, China
| | - Chuanzheng Sun
- Emergency Department, The Third Xiangya Hospital, Central South University, Changsha, China
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Mosialou I, Zannis VI, Kardassis D. Regulation of human apolipoprotein m gene expression by orphan and ligand-dependent nuclear receptors. J Biol Chem 2010; 285:30719-30. [PMID: 20660599 DOI: 10.1074/jbc.m110.131771] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Apolipoprotein M (apoM) plays an important role in the biogenesis and the metabolism of anti-atherogenic HDL particles in plasma and is expressed primarily in the liver and the kidney. We investigated the role of hormone nuclear receptors in apoM gene regulation in hepatic cells. Overexpression via adenovirus-mediated gene transfer and siRNA-mediated gene silencing established that hepatocyte nuclear factor 4 (HNF-4) is an important regulator of apoM gene transcription in hepatic cells. apoM promoter deletion analysis combined with DNA affinity precipitation and chromatin immunoprecipitation assays revealed that HNF-4 binds to a hormone-response element (HRE) in the proximal apoM promoter (nucleotides -33 to -21). Mutagenesis of this HRE decreased basal hepatic apoM promoter activity to 10% of control and abolished the HNF4-mediated transactivation of the apoM promoter. In addition to HNF-4, homodimers of retinoid X receptor and heterodimers of retinoid X receptor with receptors for retinoic acid, thyroid hormone, fibrates (peroxisome proliferator-activated receptor), and oxysterols (liver X receptor) were shown to bind with different affinities to the proximal HRE in vitro and in vivo. Ligands of these receptors strongly induced human apoM gene transcription and apoM promoter activity in HepG2 cells, whereas mutations in the proximal HRE abolished this induction. These findings provide novel insights into the role of apoM in the regulation of HDL by steroid hormones and into the development of novel HDL-based therapies for diseases such as diabetes, obesity, metabolic syndrome, and coronary artery disease that affect a large proportion of the population in Western countries.
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Affiliation(s)
- Ioanna Mosialou
- Department of Biochemistry, University of Crete Medical School and Institute of Molecular Biology and Biotechnology, Foundation of Research and Technology-Hellas, Heraklion 71003, Greece
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Christoffolete MA, Doleschall M, Egri P, Liposits Z, Zavacki AM, Bianco AC, Gereben B. Regulation of thyroid hormone activation via the liver X-receptor/retinoid X-receptor pathway. J Endocrinol 2010; 205:179-86. [PMID: 20176747 PMCID: PMC3133926 DOI: 10.1677/joe-09-0448] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Thyroid hormone receptor (TR) and liver X-receptor (LXR) are the master regulators of lipid metabolism. Remarkably, a mouse with a targeted deletion of both LXR alpha and LXR beta is resistant to western diet-induced obesity, and exhibits ectopic liver expression of the thyroid hormone activating type 2 deiodinase (D2). We hypothesized that LXR/retinoid X-receptor (RXR) signaling inhibits hepatic D2 expression, and studied this using a luciferase reporter containing the human DIO2 (hDIO2) promoter in HepG2 cells. Given that, in contrast to mammals, the chicken liver normally expresses D2, the chicken DIO2 (cDIO2) promoter was also studied. 22(R)-OH-cholesterol negatively regulated hDIO2 in a dose-dependent manner (100 microM, approximately twofold), while it failed to affect the cDIO2 promoter. Truncations in the hDIO2 promoter identified the region -901 to -584 bp as critical for negative regulation. We also investigated if 9-cis retinoic acid (9-cis RA), the ligand for the heterodimeric partner of TR and LXR, RXR, could regulate the hDIO2 promoter. Notably, 9-cis RA repressed the hDIO2 luciferase reporter (1 microM, approximately fourfold) in a dose-dependent manner, while coexpression of an inactive mutant RXR abolished this effect. However, it is unlikely that RXR homodimers mediate the repression of hDIO2 since mutagenesis of a DR-1 at -506 bp did not interfere with 9-cis RA-mediated repression. Our data indicate that hDIO2 transcription is negatively regulated by both 22(R)-OH-cholesterol and 9-cis RA, which is consistent with LXR/RXR involvement. In vivo, the inhibition of D2-mediated tri-iodothyronine (T(3)) production by cholesterol/9-cis RA could function as a feedback loop, given that T(3) decreases hepatic cholesterol levels.
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Ogihara T, Chuang JC, Vestermark GL, Garmey JC, Ketchum RJ, Huang X, Brayman KL, Thorner MO, Repa JJ, Mirmira RG, Evans-Molina C. Liver X receptor agonists augment human islet function through activation of anaplerotic pathways and glycerolipid/free fatty acid cycling. J Biol Chem 2010; 285:5392-404. [PMID: 20007976 PMCID: PMC2820768 DOI: 10.1074/jbc.m109.064659] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Recent studies in rodent models suggest that liver X receptors (LXRs) may play an important role in the maintenance of glucose homeostasis and islet function. To date, however, no studies have comprehensively examined the role of LXRs in human islet biology. Human islets were isolated from non-diabetic donors and incubated in the presence or absence of two synthetic LXR agonists, TO-901317 and GW3965, under conditions of low and high glucose. LXR agonist treatment enhanced both basal and stimulated insulin secretion, which corresponded to an increase in the expression of genes involved in anaplerosis and reverse cholesterol transport. Furthermore, enzyme activity of pyruvate carboxylase, a key regulator of pyruvate cycling and anaplerotic flux, was also increased. Whereas LXR agonist treatment up-regulated known downstream targets involved in lipogenesis, we observed no increase in the accumulation of intra-islet triglyceride at the dose of agonist used in our study. Moreover, LXR activation increased expression of the genes encoding hormone-sensitive lipase and adipose triglyceride lipase, two enzymes involved in lipolysis and glycerolipid/free fatty acid cycling. Chronically, insulin gene expression was increased after treatment with TO-901317, and this was accompanied by increased Pdx-1 nuclear protein levels and enhanced Pdx-1 binding to the insulin promoter. In conclusion, our data suggest that LXR agonists have a direct effect on the islet to augment insulin secretion and expression, actions that should be considered either as therapeutic or unintended side effects, as these agents are developed for clinical use.
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Affiliation(s)
- Takeshi Ogihara
- From the Herman B Wells Center for Pediatric Research and
- the Departments of Pediatrics and
| | | | | | | | - Robert J. Ketchum
- the Department of Structural Medicine, Rocky Vista University, Parker, Colorado 80134
| | - Xiaolun Huang
- Surgery, University of Virginia, Charlottesville, Virginia 22904, and
| | | | | | - Joyce J. Repa
- the Departments of Physiology and
- Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Raghavendra G. Mirmira
- From the Herman B Wells Center for Pediatric Research and
- the Departments of Pediatrics and
- Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Carmella Evans-Molina
- From the Herman B Wells Center for Pediatric Research and
- Medicine, Indiana University School of Medicine, Indianapolis, Indiana 46202
- To whom correspondence should be addressed: Indiana University School of Medicine, 635 Barnhill Dr., MS 2031A, Indianapolis, IN 46202. Tel.: 317-274-4145; Fax: 317-274-4107; E-mail:
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Montemayor C, Montemayor OA, Ridgeway A, Lin F, Wheeler DA, Pletcher SD, Pereira FA. Genome-wide analysis of binding sites and direct target genes of the orphan nuclear receptor NR2F1/COUP-TFI. PLoS One 2010; 5:e8910. [PMID: 20111703 PMCID: PMC2811727 DOI: 10.1371/journal.pone.0008910] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2009] [Accepted: 01/04/2010] [Indexed: 11/18/2022] Open
Abstract
Background Identification of bona fide direct nuclear receptor gene targets has been challenging but essential for understanding regulation of organismal physiological processes. Results We describe a methodology to identify transcription factor binding sites and target genes in vivo by intersecting microarray data, computational binding site queries, and evolutionary conservation. We provide detailed experimental validation of each step and, as a proof of principle, utilize the methodology to identify novel direct targets of the orphan nuclear receptor NR2F1 (COUP-TFI). The first step involved validation of microarray gene expression profiles obtained from wild-type and COUP-TFI−/− inner ear tissues. Secondly, we developed a bioinformatic tool to search for COUP-TFI DNA binding sites in genomes, using a classification-type Hidden Markov Model trained with 49 published COUP-TF response elements. We next obtained a ranked list of candidate in vivo direct COUP-TFI targets by integrating the microarray and bioinformatics analyses according to the degree of binding site evolutionary conservation and microarray statistical significance. Lastly, as proof-of-concept, 5 specific genes were validated for direct regulation. For example, the fatty acid binding protein 7 (Fabp7) gene is a direct COUP-TFI target in vivo because: i) we identified 2 conserved COUP-TFI binding sites in the Fabp7 promoter; ii) Fapb7 transcript and protein levels are significantly reduced in COUP-TFI−/− tissues and in MEFs; iii) chromatin immunoprecipitation demonstrates that COUP-TFI is recruited to the Fabp7 promoter in vitro and in vivo and iv) it is associated with active chromatin having increased H3K9 acetylation and enrichment for CBP and SRC-1 binding in the newborn brain. Conclusion We have developed and validated a methodology to identify in vivo direct nuclear receptor target genes. This bioinformatics tool can be modified to scan for response elements of transcription factors, cis-regulatory modules, or any flexible DNA pattern.
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Affiliation(s)
- Celina Montemayor
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America
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Abstract
In spite of numerous advances in recent years, the complete list of direct target genes for nuclear receptors remains elusive. The integrated application of new computational and experimental methods reviewed in this chapter provides insight into the complex network of regulatory pathways mediated by nuclear receptors which is expected to improve the understanding of the physiology and the pathology of metabolism, development, homeostasis, and other fundamental processes.
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Affiliation(s)
- Gabor Varga
- Discovery Informatics, Lilly Research Labs, Eli Lilly and Company, Indianapolis, IN, USA.
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Kotokorpi P, Venteclef N, Ellis E, Gustafsson JÅ, Mode A. The Human ADFP Gene Is a Direct Liver-X-Receptor (LXR) Target Gene and Differentially Regulated by Synthetic LXR Ligands. Mol Pharmacol 2009; 77:79-86. [DOI: 10.1124/mol.109.059063] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Drawid A, Gupta N, Nagaraj VH, Gélinas C, Sengupta AM. OHMM: a Hidden Markov Model accurately predicting the occupancy of a transcription factor with a self-overlapping binding motif. BMC Bioinformatics 2009; 10:208. [PMID: 19583839 PMCID: PMC2718928 DOI: 10.1186/1471-2105-10-208] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2008] [Accepted: 07/07/2009] [Indexed: 12/29/2022] Open
Abstract
Background DNA sequence binding motifs for several important transcription factors happen to be self-overlapping. Many of the current regulatory site identification methods do not explicitly take into account the overlapping sites. Moreover, most methods use arbitrary thresholds and fail to provide a biophysical interpretation of statistical quantities. In addition, commonly used approaches do not include the location of a site with respect to the transcription start site (TSS) in an integrated probabilistic framework while identifying sites. Ignoring these features can lead to inaccurate predictions as well as incorrect design and interpretation of experimental results. Results We have developed a tool based on a Hidden Markov Model (HMM) that identifies binding location of transcription factors with preference for self-overlapping DNA motifs by combining the effects of their alternative binding modes. Interpreting HMM parameters as biophysical quantities, this method uses the occupancy probability of a transcription factor on a DNA sequence as the discriminant function, earning the algorithm the name OHMM: Occupancy via Hidden Markov Model. OHMM learns the classification threshold by training emission probabilities using unaligned sequences containing known sites and estimating transition probabilities to reflect site density in all promoters in a genome. While identifying sites, it adjusts parameters to model site density changing with the distance from the transcription start site. Moreover, it provides guidance for designing padding sequences in gel shift experiments. In the context of binding sites to transcription factor NF-κB, we find that the occupancy probability predicted by OHMM correlates well with the binding affinity in gel shift experiments. High evolutionary conservation scores and enrichment in experimentally verified regulated genes suggest that NF-κB binding sites predicted by our method are likely to be functional. Conclusion Our method deals specifically with identifying locations with multiple overlapping binding sites by computing the local occupancy of the transcription factor. Moreover, considering OHMM as a biophysical model allows us to learn the classification threshold in a principled manner. Another feature of OHMM is that we allow transition probabilities to change with location relative to the TSS. OHMM could be used to predict physical occupancy, and provides guidance for proper design of gel-shift experiments. Based upon our predictions, new insights into NF-κB function and regulation and possible new biological roles of NF-κB were uncovered.
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Affiliation(s)
- Amar Drawid
- BioMAPS Institute for Quantitative Biology, Rutgers University, Piscataway, NJ, USA.
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Wang Y, Rogers PM, Stayrook KR, Su C, Varga G, Shen Q, Nagpal S, Burris TP. The selective Alzheimer's disease indicator-1 gene (Seladin-1/DHCR24) is a liver X receptor target gene. Mol Pharmacol 2008; 74:1716-21. [PMID: 18815215 DOI: 10.1124/mol.108.048538] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The nuclear hormone receptors liver X receptor alpha (LXRalpha) and LXRbeta function as physiological receptors for oxidized cholesterol metabolites (oxysterols) and regulate several aspects of cholesterol and lipid metabolism. Seladin-1 was originally identified as a gene whose expression was down-regulated in regions of the brain associated with Alzheimer's disease. Seladin-1 has been demonstrated to be neuroprotective and was later characterized as 3beta-hydroxysterol-Delta24 reductase (DHCR24), a key enzyme in the cholesterologenic pathway. Seladin-1 has also been shown to regulate lipid raft formation. In a whole genome screen for direct LXRalpha target genes, we identified an LXRalpha occupancy site within the second intron of the Seladin-1/DHCR24 gene. We characterized a novel LXR response element within the second intron of this gene that is able to confer LXR-specific ligand responsiveness to reporter gene in both HepG2 and human embryonic kidney 293 cells. Furthermore, we found that Seladin-1/DHCR24 gene expression is significantly decreased in skin isolated from LXRbeta-null mice. Our data suggest that Seladin-1/DHCR24 is an LXR target gene and that LXR may regulate lipid raft formation.
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Affiliation(s)
- Yongjun Wang
- Nuclear Receptor Biology Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana, USA
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Wang Y, Rogers PM, Su C, Varga G, Stayrook KR, Burris TP. Regulation of cholesterologenesis by the oxysterol receptor, LXRalpha. J Biol Chem 2008; 283:26332-9. [PMID: 18676367 DOI: 10.1074/jbc.m804808200] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Cholesterol is required for normal cellular and physiological function, yet dysregulation of cholesterol metabolism is associated with diseases such as atherosclerosis. Cholesterol biosynthesis is regulated by end product negative feedback inhibition where the levels of sterols and oxysterols regulate the expression of cholesterologenic enzymes. Sterol regulatory element-binding protein-2 is responsive to both sterols and oxysterols and has been shown to mediate the transcriptional response of the cholesterologenic enzymes to these lipids. Here, we show that the nuclear hormone receptor for oxysterols, the liver X receptor alpha (LXRalpha), regulates cholesterol biosynthesis by directly silencing the expression of two key cholesterologenic enzymes (lanosterol 14alpha-demethylase (CYP51A1), and squalene synthase (farnesyl diphosphate farnesyl transferase 1)) via novel negative LXR DNA response elements (nLXREs) located in each of these genes. Examination of the CYP51A1 gene revealed that both the SRE and nLXRE are required for normal oxysterol-dependent repression of this gene. Thus, these data suggest that LXRalpha plays an important role in the regulation of cholesterol biosynthesis.
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Affiliation(s)
- Yongjun Wang
- Nuclear Receptor Biology Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana 70808, USA
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Stayrook KR, Rogers PM, Savkur RS, Wang Y, Su C, Varga G, Bu X, Wei T, Nagpal S, Liu XS, Burris TP. Regulation of human 3 alpha-hydroxysteroid dehydrogenase (AKR1C4) expression by the liver X receptor alpha. Mol Pharmacol 2007; 73:607-12. [PMID: 18024509 DOI: 10.1124/mol.107.039099] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Type I human hepatic 3alpha-hydroxysteroid dehydrogenase (AKR1C4) plays a significant role in bile acid biosynthesis, steroid hormone metabolism, and xenobiotic metabolism. Utilization of a hidden Markov model for predictive modeling of nuclear hormone receptor response elements coupled with chromatin immunoprecipitation/microarray technology revealed a putative binding site in the AKR1C4 promoter for the nuclear hormone receptor known as liver X receptor alpha, (LXRalpha [NR1H3]), which is the physiological receptor for oxidized cholesterol metabolites. The putative LXRalpha response element (LXRE), identified by chromatin immunoprecipitation, was approximately 1.5 kilobase pairs upstream of the transcription start site. LXRalpha was shown to bind specifically to this LXRE and mediate transcriptional activation of the AKR1C4 gene, leading to increased AKR1C4 protein expression. These data suggest that LXRalpha may modulate the bile acid biosynthetic pathway at a unique site downstream of CYP7A1 and may also modulate the metabolism of steroid hormones and certain xenobiotics.
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