scholarly journals Dysregulation of the Peroxisome Proliferator-Activated Receptor Target Genes by XPD Mutations

2005 ◽  
Vol 25 (14) ◽  
pp. 6065-6076 ◽  
Author(s):  
Emmanuel Compe ◽  
Pascal Drané ◽  
Camille Laurent ◽  
Karin Diderich ◽  
Cathy Braun ◽  
...  
Keyword(s):  
Target Genes ◽  
Genetic Disorders ◽  
Peroxisome Proliferator ◽  
Wild Type ◽  
Independent Manner ◽  
Peroxisome Proliferator Activated Receptor ◽  
Pol Ii ◽  
Knowing That ◽  
Peroxisome Proliferator Activated Receptors ◽  
Ppar Ligands

ABSTRACT Mutations in the XPD subunit of TFIIH give rise to human genetic disorders initially defined as DNA repair syndromes. Nevertheless, xeroderma pigmentosum (XP) group D (XP-D) patients develop clinical features such as hypoplasia of the adipose tissue, implying a putative transcriptional defect. Knowing that peroxisome proliferator-activated receptors (PPARs) are implicated in lipid metabolism, we investigated the expression of PPAR target genes in the adipose tissues and the livers of XPD-deficient mice and found that (i) some genes are abnormally overexpressed in a ligand-independent manner which parallels an increase in the recruitment of RNA polymerase (pol) II but not PPARs on their promoter and (ii) upon treatment with PPAR ligands, other genes are much less induced compared to the wild type, which is due to a lower recruitment of both PPARs and RNA pol II. The defect in transactivation by PPARs is likely attributable to their weaker phosphorylation by the cdk7 kinase of TFIIH. Having identified the phosphorylated residues in PPAR isotypes, we demonstrate how their transactivation defect in XPD-deficient cells can be circumvented by overexpression of either a wild-type XPD or a constitutively phosphorylated PPAR S/E. This work emphasizes that underphosphorylation of PPARs affects their transactivation and consequently the expression of PPAR target genes, thus contributing in part to the XP-D phenotype.

scholarly journals Peroxisome Proliferator-Activated Receptor Subtype- and Cell-Type-Specific Activation of Genomic Target Genes upon Adenoviral Transgene Delivery

2006 ◽  
Vol 26 (15) ◽  
pp. 5698-5714 ◽  
Author(s):  
Ronni Nielsen ◽  
Lars Grøntved ◽  
Hendrik G. Stunnenberg ◽  
Susanne Mandrup
Keyword(s):  
Target Genes ◽  
Receptor Subtype ◽  
Peroxisome Proliferator ◽  
Cell Type ◽  
Peroxisome Proliferator Activated Receptor ◽  
Molecular Events ◽  
Adenoviral Delivery ◽  
Cell Type Specific ◽  
Peroxisome Proliferator Activated Receptors ◽  
The Individual

ABSTRACT Investigations of the molecular events involved in activation of genomic target genes by peroxisome proliferator-activated receptors (PPARs) have been hampered by the inability to establish a clean on/off state of the receptor in living cells. Here we show that the combination of adenoviral delivery and chromatin immunoprecipitation (ChIP) is ideal for dissecting these mechanisms. Adenoviral delivery of PPARs leads to a rapid and synchronous expression of the PPAR subtypes, establishment of transcriptional active complexes at genomic loci, and immediate activation of even silent target genes. We demonstrate that PPARγ2 possesses considerable ligand-dependent as well as independent transactivation potential and that agonists increase the occupancy of PPARγ2/retinoid X receptor at PPAR response elements. Intriguingly, by direct comparison of the PPARs (α, γ, and β/δ), we show that the subtypes have very different abilities to gain access to target sites and that in general the genomic occupancy correlates with the ability to activate the corresponding target gene. In addition, the specificity and potency of activation by PPAR subtypes are highly dependent on the cell type. Thus, PPAR subtype-specific activation of genomic target genes involves an intricate interplay between the properties of the subtype- and cell-type-specific settings at the individual target loci.

scholarly journals MED14 Tethers Mediator to the N-Terminal Domain of Peroxisome Proliferator-Activated Receptor γ and Is Required for Full Transcriptional Activity and Adipogenesis

2010 ◽  
Vol 30 (9) ◽  
pp. 2155-2169 ◽  
Author(s):  
Lars Grøntved ◽  
Maria S. Madsen ◽  
Michael Boergesen ◽  
Robert G. Roeder ◽  
Susanne Mandrup
Keyword(s):  
Rna Polymerase Ii ◽  
Transcriptional Activity ◽  
Target Gene ◽  
Target Genes ◽  
Gene Activation ◽  
Proximal Promoter ◽  
Peroxisome Proliferator ◽  
Independent Manner ◽  
Peroxisome Proliferator Activated Receptor ◽  
Terminal Domain

ABSTRACT The Mediator subunit MED1/TRAP220/DRIP205/PBP interacts directly with many nuclear receptors and was long thought to be responsible for tethering Mediator to peroxisome proliferator-activated receptor (PPAR)-responsive promoters. However, it was demonstrated recently that PPARγ can recruit Mediator by MED1-independent mechanisms. Here, we show that target gene activation by ectopically expressed PPARγ and PPARα is independent of MED1. Consistent with this finding, recruitment of PPARγ, MED6, MED8, TATA box-binding protein (TBP), and RNA polymerase II (RNAPII) to the enhancer and proximal promoter of the PPARγ target gene Fabp4 is also independent of MED1. Using a small interfering RNA (siRNA)-based approach, we identify MED14 as a novel critical Mediator component for PPARγ-dependent transactivation, and we demonstrate that MED14 interacts directly with the N terminus of PPARγ in a ligand-independent manner. Interestingly, MED14 knockdown does not affect the recruitment of PPARγ, MED6, and MED8 to the Fabp4 enhancer but does reduce their occupancy of the Fabp4 proximal promoter. In agreement with the necessity of MED14 for PPARγ transcriptional activity, we show that knockdown of MED14 impairs adipogenesis of 3T3-L1 cells. Thus, MED14 constitutes a novel anchoring point between Mediator and the N-terminal domain of PPARγ that is necessary for functional PPARγ-mediated recruitment of Mediator and transactivation of PPARγ subtype-specific target genes.

scholarly journals PPARαLigands as Antitumorigenic and Antiangiogenic Agents

PPAR Research ◽  
2008 ◽  
Vol 2008 ◽  
pp. 1-8 ◽  
Author(s):  
Ambra Pozzi ◽  
Jorge H. Capdevila
Keyword(s):  
Target Genes ◽  
Suppressor Gene ◽  
Migration And Invasion ◽  
Antiangiogenic Agents ◽  
Peroxisome Proliferator ◽  
Cell Functions ◽  
Obesity And Diabetes ◽  
Brown Adipose ◽  
Peroxisome Proliferator Activated Receptors ◽  
Ppar Ligands

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear receptor family of ligand-activated transcription factors. This subfamily is composed of three members—PPARα, PPARδ, and PPARγ—that differ in their cell and tissue distribution as well as in their target genes. PPARαis abundantly expressed in liver, brown adipose tissue, kidney, intestine, heart, and skeletal muscle; and its ligands have been used to treat diseases such as obesity and diabetes. The recent finding that members of the PPAR family, including the PPARα, are expressed by tumor and endothelial cells together with the observation that PPAR ligands regulate cell growth, survival, migration, and invasion, suggested that PPARs also play a role in cancer. In this review, we focus on the contribution of PPARαto tumor and endothelial cell functions and provide compelling evidence that PPARαcan be viewed as a new class of ligand activated tumor “suppressor” gene with antiangiogenic and antitumorigenic activities. Given that PPAR ligands are currently used in medicine as hypolipidemic drugs with excellent tolerance and limited toxicity, PPARαactivation might offer a novel and potentially low-toxic approach for the treatment of tumor-associated angiogenesis and cancer.

scholarly journals Regulation of Peroxisome Proliferator-Activated Receptors by E6-Associated Protein

PPAR Research ◽  
2008 ◽  
Vol 2008 ◽  
pp. 1-8 ◽  
Author(s):  
Lakshmi Gopinathan ◽  
Daniel B. Hannon ◽  
Russell W. Smith ◽  
Jeffrey M. Peters ◽  
John P. Vanden Heuvel
Keyword(s):  
Ubiquitin Ligase ◽  
Target Genes ◽  
Peroxisome Proliferator ◽  
Mrna Levels ◽  
Independent Manner ◽  
Coordinate Regulation ◽  
Protein Levels ◽  
Ubiquitin Ligase Activity ◽  
Peroxisome Proliferator Activated Receptors

Peroxisome proliferator-activated receptors (PPARs) are nuclear receptors (NRs) that regulate genes involved in lipid and glucose metabolism. PPAR activity is regulated by interactions with cofactors and of interest are cofactors with ubiquitin ligase activity. The E6-associated protein (E6-AP) is an E3 ubiquitin ligase that affects the activity of other NRs, although its effects on PPARs have not been examined. E6-AP inhibited the ligand-independent transcriptional activity of PPARαand PPARβ, with marginal effects on PPARγ, and decreased basal mRNA levels of PPARαtarget genes. Inhibition of PPARαactivity required the ubiquitin ligase function of E6-AP, but occurred in a proteasome-independent manner. PPARαinteracted with E6-AP, and in mice treated with PPARαagonist clofibrate, mRNA and protein levels of E6-AP were increased in wildtype, but not in PPARαnull mice, indicating a PPARα-dependent regulation. These studies suggest coordinate regulation of E6-AP and PPARα, and contribute to our understanding of the role of PPARs in cellular metabolism.

scholarly journals Hepatic sirtuin 1 is dispensable for fibrate-induced peroxisome proliferator-activated receptor-α function in vivo

2014 ◽  
Vol 306 (7) ◽  
pp. E824-E837 ◽  
Author(s):  
Jessica A. Bonzo ◽  
Chad Brocker ◽  
Changtao Jiang ◽  
Rui-Hong Wang ◽  
Chu-Xia Deng ◽  
...  
Keyword(s):  
Gene Expression ◽  
Knockout Mice ◽  
High Fat Diet ◽  
Target Genes ◽  
Sirtuin 1 ◽  
Peroxisome Proliferator ◽  
Wild Type ◽  
High Fat ◽  
Peroxisome Proliferator Activated Receptor

Peroxisome proliferator-activated receptor-α (PPARα) mediates metabolic remodeling, resulting in enhanced mitochondrial and peroxisomal β-oxidation of fatty acids. In addition to the physiological stimuli of fasting and high-fat diet, PPARα is activated by the fibrate class of drugs for the treatment of dyslipidemia. Sirtuin 1 (SIRT1), an important regulator of energy homeostasis, was downregulated in fibrate-treated wild-type mice, suggesting PPARα regulation of Sirt1 gene expression. The impact of SIRT1 loss on PPARα functionality in vivo was assessed in hepatocyte-specific knockout mice that lack the deacetylase domain of SIRT1 ( Sirt1 ΔLiv). Knockout mice were treated with fibrates or fasted for 24 h to activate PPARα. Basal expression of the PPARα target genes Cyp4a10 and Cyp4a14 was reduced in Sirt1 ΔLiv mice compared with wild-type mice. However, no difference was observed between wild-type and Sirt1 ΔLiv mice in either fasting- or fibrate-mediated induction of PPARα target genes. Similar to the initial results, there was no difference in fibrate-activated PPARα gene induction. To assess the relationship between SIRT1 and PPARα in a pathophysiological setting, Sirt1 ΔLiv mice were maintained on a high-fat diet for 14 wk, followed by fibrate treatment. Sirt1 ΔLiv mice exhibited increased body mass compared with control mice. In the context of a high-fat diet, Sirt1 ΔLiv mice did not respond to the cholesterol-lowering effects of the fibrate treatment. However, there were no significant differences in PPARα target gene expression. These results suggest that, in vivo, SIRT1 deacetylase activity does not significantly impact induced PPARα activity.

scholarly journals Plasticizers May Activate Human Hepatic Peroxisome Proliferator-Activated ReceptorαLess Than That of a Mouse but May Activate Constitutive Androstane Receptor in Liver

PPAR Research ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Yuki Ito ◽  
Toshiki Nakamura ◽  
Yukie Yanagiba ◽  
Doni Hikmat Ramdhan ◽  
Nozomi Yamagishi ◽  
...  
Keyword(s):  
Animal Studies ◽  
Target Genes ◽  
Species Differences ◽  
Corn Oil ◽  
Constitutive Androstane Receptor ◽  
Vehicle Control ◽  
Peroxisome Proliferator ◽  
Wild Type ◽  
Peroxisome Proliferator Activated Receptor ◽  
Ethylhexyl Phthalate

Dibutylphthalate (DBP), di(2-ethylhexyl)phthalate (DEHP), and di(2-ethylhexyl)adipate (DEHA) are used as plasticizers. Their metabolites activate peroxisome proliferator-activated receptor (PPAR) α, which may be related to their toxicities. However, species differences in the receptor functions between rodents and human make it difficult to precisely extrapolate their toxicity from animal studies to human. In this paper, we compared the species differences in the activation of mouse and human hepatic PPARα by these plasticizers using wild-type (mPPARα) and humanizedPPARα (hPPARα) mice. At 12 weeks old, each genotyped male mouse was classified into three groups, and fed daily for 2 weeks per os with corn oil (vehicle control), 2.5 or 5.0 mmol/kg DBP (696, 1392 mg/kg), DEHP (977, 1953 mg/kg), and DEHA (926, 1853 mg/kg), respectively. Generally, hepatic PPARα ofmPPARα mice was more strongly activated than that ofhPPARα mice when several target genes involving β-oxidation of fatty acids were evaluated. Interestingly, all plasticizers also activated hepatic constitutive androstane receptor (CAR) more inhPPARα mice than inmPPARα mice. Taken together, these plasticizers activated mouse and human hepatic PPARα as well as CAR. The activation of PPARα was stronger inmPPARα mice than inhPPARα mice, while the opposite was true of CAR.

scholarly journals Downregulation of peroxisome proliferator-activated receptor α and its coactivators in liver and skeletal muscle mediates the metabolic adaptations during lactation in mice

2009 ◽  
Vol 43 (6) ◽  
pp. 241-250 ◽  
Author(s):  
Anke Gutgesell ◽  
Robert Ringseis ◽  
Eileen Schmidt ◽  
Corinna Brandsch ◽  
Gabriele I Stangl ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Fatty Acid ◽  
Target Genes ◽  
Fatty Acid Uptake ◽  
Acid Oxidation ◽  
Peroxisome Proliferator ◽  
Acid Uptake ◽  
Wild Type ◽  
Peroxisome Proliferator Activated Receptor ◽  
Metabolic Adaptations

Previous studies have shown that genes involved in fatty acid uptake, fatty acid oxidation, and thermogenesis are downregulated in liver and skeletal muscle of rats during lactation. However, biochemical mechanisms underlying these important metabolic adaptations during lactation have not yet been elucidated. As all these genes are transcriptionally regulated by peroxisome proliferator-activated receptor α (Pparα), we hypothesized that their downregulation is mediated by a suppression of Pparα during lactation. In order to investigate this hypothesis, we performed an experiment with lactating and nonlactating Pparα knockout and corresponding wild-type mice. In wild-type mice, lactation led to a considerable downregulation of Pparα, Ppar coactivators Pgc1α and Pgc1β, and Pparα target genes involved in fatty acid uptake, fatty acid oxidation, and thermogenesis in liver and skeletal muscle (P<0.05). Pparα knockout mice had generally a lower expression of all these Pparα target genes in liver and skeletal muscle. However, in those mice, lactation did not lower the expression of genes involved in fatty acid utilization and thermogenesis in liver and skeletal muscle. Expression levels of Pparα target genes in lactating wild-type mice were similar than in lactating or nonlactating Pparα knockout mice. In conclusion, the present findings suggest that downregulation of Pparα and its coactivators in tissues with high rates of fatty acid catabolism is responsible for the reduced utilization of fatty acids in liver and skeletal muscle and the reduced thermogenesis occurring in the lactating animal, which aim to conserve energy and metabolic substrates for milk production in the mammary gland.

scholarly journals Peroxisome Proliferator-Activated Receptors and Acute Lung Injury

PPAR Research ◽  
2007 ◽  
Vol 2007 ◽  
pp. 1-8 ◽  
Author(s):  
Rosanna Di Paola ◽  
Salvatore Cuzzocrea
Keyword(s):  
Immune Responses ◽  
Metabolic Pathways ◽  
Target Genes ◽  
Inflammatory Diseases ◽  
Nuclear Hormone Receptor ◽  
Therapeutic Effects ◽  
Peroxisome Proliferator ◽  
Anti Inflammatory ◽  
Peroxisome Proliferator Activated Receptors ◽  
Ppar Ligands

Peroxisome proliferator-activated receptors are ligand-activated transcription factors belonging to the nuclear hormone receptor superfamily. PPARs regulate several metabolic pathways by binding to sequence-specific PPAR response elements in the promoter region of target genes, including lipid biosynthesis and glucose metabolism. Recently, PPARs and their respective ligands have been implicated as regulators of cellular inflammatory and immune responses. These molecules are thought to exert anti-inflammatory effects by negatively regulating the expression of proinflammatory genes. Several studies have demonstrated that PPAR ligands possess anti-inflammatory properties and that these properties may prove helpful in the treatment of inflammatory diseases of the lung. This review will outline the anti-inflammatory effects of PPARs and PPAR ligands and discuss their potential therapeutic effects in animal models of inflammatory lung disease.

scholarly journals New Target Genes for the Peroxisome Proliferator-Activated Receptor-γ(PPARγ) Antitumour Activity: Perspectives from the Insulin Receptor

PPAR Research ◽  
2009 ◽  
Vol 2009 ◽  
pp. 1-8 ◽  
Author(s):  
Daniela P. Foti ◽  
Francesco Paonessa ◽  
Eusebio Chiefari ◽  
Antonio Brunetti
Keyword(s):  
Insulin Receptor ◽  
Target Genes ◽  
Tumour Progression ◽  
Antitumour Activity ◽  
Peptide Hormone ◽  
Nuclear Hormone Receptor ◽  
Peroxisome Proliferator ◽  
Preclinical Research ◽  
Peroxisome Proliferator Activated Receptor ◽  
Wide Range

The insulin receptor (IR) plays a crucial role in mediating the metabolic and proliferative functions triggered by the peptide hormone insulin. There is considerable evidence that abnormalities in both IR expression and function may account for malignant transformation and tumour progression in some human neoplasias, including breast cancer. PPARγis a ligand-activated, nuclear hormone receptor implicated in many pleiotropic biological functions related to cell survival and proliferation. In the last decade, PPARγagonists—besides their known action and clinical use as insulin sensitizers—have proved to display a wide range of antineoplastic effects in cells and tissues expressing PPARγ, leading to intensive preclinical research in oncology. PPARγand activators affect tumours by different mechanisms, involving cell proliferation and differentiation, apoptosis, antiinflammatory, and antiangiogenic effects. We recently provided evidence that PPARγand agonists inhibit IR by non canonical, DNA-independent mechanisms affecting IR gene transcription. We conclude that IR may be considered a new PPARγ“target” gene, supporting a potential use of PPARγagonists as antiproliferative agents in selected neoplastic tissues that overexpress the IR.

scholarly journals Adverse Adipose Phenotype and Hyperinsulinemia in Gravid Mice Deficient in Placental Growth Factor

Endocrinology ◽  
2008 ◽  
Vol 149 (5) ◽  
pp. 2176-2183 ◽  
Author(s):  
Bianca Hemmeryckx ◽  
Rita van Bree ◽  
Berthe Van Hoef ◽  
Lisbeth Vercruysse ◽  
H. Roger Lijnen ◽  
...  
Keyword(s):  
Growth Factor ◽  
Adrenergic Receptors ◽  
Growth Factor Receptor ◽  
Placental Growth Factor ◽  
Peroxisome Proliferator ◽  
Vascular Endothelial ◽  
Wild Type ◽  
Peroxisome Proliferator Activated Receptor ◽  
Adipocyte Hypertrophy ◽  
Endothelial Growth Factor

Pregnancy-induced metabolic changes are regulated by signals from an expanded adipose organ. Placental growth factor (PlGF), acting through vascular endothelial growth factor receptor-1, may be among those signals. There is a steep rise in circulating PlGF during normal pregnancy, which is repressed in gravidas who develop preeclampsia. PlGF-deficiency in mice impairs adipose vascularization and development. Here we studied young-adult PlGF-deficient (PlGF−/−) and wild-type mice on a high-fat diet in the nongravid state and at embryonic day (E) 13.5 or E18.5 of gestation. Litter size and weight were normal, but E18.5 placentas were smaller in PlGF−/− pregnancies. PlGF−/− mice showed altered intraadipose dynamics, with the following: 1) less blood vessels and fewer brown, uncoupling protein (UCP)-1-positive, adipocytes in white sc and perigonadal fat compartments and 2) white adipocyte hypertrophy. The mRNA expression of β3-adrenergic receptors, peroxisome proliferator-activated receptor-γ coactivator-1α, and UCP-1 was decreased accordingly. Moreover, PlGF−/− mice showed hyperinsulinemia. Pregnancy-associated changes were largely comparable in PlGF−/− and wild-type dams. They included expanded sc fat compartments and adipocyte hypertrophy, whereas adipose expression of key angiogenesis/adipogenesis (vascular endothelial growth factor receptor-1, peroxisome proliferator-activated receptor-γ2) and thermogenesis (β3-adrenergic receptors, peroxisome proliferator-activated receptor-γ coactivator-1α, and UCP-1) genes was down-regulated; circulating insulin levels gradually increased during pregnancy. In conclusion, reduced adipose vascularization in PlGF−/− mice impairs adaptive thermogenesis in favor of energy storage, thereby promoting insulin resistance and hyperinsulinemia. Pregnancy adds to these changes by PlGF-independent mechanisms. Disturbed intraadipose dynamics is a novel mechanism to explain metabolic changes in late pregnancy in general and preeclamptic pregnancy in particular.

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