scholarly journals The Adipogenic Acetyltransferase Tip60 Targets Activation Function 1 of Peroxisome Proliferator-Activated Receptor γ

Endocrinology ◽  
2007 ◽  
Vol 149 (4) ◽  
pp. 1840-1849 ◽  
Author(s):  
Olivier van Beekum ◽  
Arjan B. Brenkman ◽  
Lars Grøntved ◽  
Nicole Hamers ◽  
Niels J. F. van den Broek ◽  
...  
Keyword(s):  
Transcriptional Activity ◽  
Target Genes ◽  
Activation Function ◽  
Specific Gene ◽  
Chimeric Proteins ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Interacting Protein ◽  
And Function ◽  
Interfering Rna

The transcription factor peroxisome proliferator-activated receptor γ (PPARγ) plays a key role in the regulation of lipid and glucose metabolism in adipocytes, by regulating their differentiation, maintenance, and function. The transcriptional activity of PPARγ is dictated by the set of proteins with which this nuclear receptor interacts under specific conditions. Here we identify the HIV-1 Tat-interacting protein 60 (Tip60) as a novel positive regulator of PPARγ transcriptional activity. Using tandem mass spectrometry, we found that PPARγ and the acetyltransferase Tip60 interact in cells, and through use of chimeric proteins, we established that coactivation by Tip60 critically depends on the N-terminal activation function 1 of PPARγ, a domain involved in isotype-specific gene expression and adipogenesis. Chromatin immunoprecipitation experiments showed that the endogenous Tip60 protein is recruited to PPARγ target genes in mature 3T3-L1 adipocytes but not in preadipocytes, indicating that Tip60 requires PPARγ for its recruitment to PPARγ target genes. Importantly, we show that in common with disruption of PPARγ function, small interfering RNA-mediated reduction of Tip60 protein impairs differentiation of 3T3-L1 preadipocytes. Taken together, these findings qualify the acetyltransferase Tip60 as a novel adipogenic factor.

The serine/threonine phosphatase PPM1B (PP2Cβ) selectively modulates PPARγ activity

2013 ◽  
Vol 451 (1) ◽  
pp. 45-53 ◽  
Author(s):  
Ismayil Tasdelen ◽  
Olivier van Beekum ◽  
Olena Gorbenko ◽  
Veerle Fleskens ◽  
Niels J. F. van den Broek ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Transcriptional Activity ◽  
Target Genes ◽  
Cellular Proteins ◽  
Peroxisome Proliferator ◽  
Serine Residue ◽  
Intact Cells ◽  
Peroxisome Proliferator Activated Receptor ◽  
Interacting Protein

Reversible phosphorylation is a widespread molecular mechanism to regulate the function of cellular proteins, including transcription factors. Phosphorylation of the nuclear receptor PPARγ (peroxisome-proliferator-activated receptor γ) at two conserved serine residue (Ser112 and Ser273) results in an altered transcriptional activity of this transcription factor. So far, only a very limited number of cellular enzymatic activities has been described which can dephosphorylate nuclear receptors. In the present study we used immunoprecipitation assays coupled to tandem MS analysis to identify novel PPARγ-regulating proteins. We identified the serine/threonine phosphatase PPM1B [PP (protein phosphatase), Mg2+/Mn2+ dependent, 1B; also known as PP2Cβ] as a novel PPARγ-interacting protein. Endogenous PPM1B protein is localized in the nucleus of mature 3T3-L1 adipocytes where it can bind to PPARγ. Furthermore we show that PPM1B can directly dephosphorylate PPARγ, both in intact cells and in vitro. In addition PPM1B increases PPARγ-mediated transcription via dephosphorylation of Ser112. Finally, we show that knockdown of PPM1B in 3T3-L1 adipocytes blunts the expression of some PPARγ target genes while leaving others unaltered. These findings qualify the phosphatase PPM1B as a novel selective modulator of PPARγ activity.

scholarly journals Thioredoxin Binding Protein-2/Thioredoxin-Interacting Protein Is a Critical Regulator of Insulin Secretion and Peroxisome Proliferator-Activated Receptor Function

Endocrinology ◽  
2008 ◽  
Vol 150 (3) ◽  
pp. 1225-1234 ◽  
Author(s):  
Shin-ichi Oka ◽  
Eiji Yoshihara ◽  
Akiko Bizen-Abe ◽  
Wenrui Liu ◽  
Mutsumi Watanabe ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Target Genes ◽  
Binding Protein ◽  
Dynamic Change ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Interacting Protein ◽  
Thioredoxin Interacting Protein ◽  
Nutritional Transition ◽  
Coordinated Regulation

The feeding-fasting nutritional transition triggers a dynamic change in metabolic pathways and is a model for understanding how these pathways are mutually organized. The targeted disruption of the thioredoxin binding protein-2 (TBP-2)/thioredoxin-interacting protein (Txnip)/VDUP1 gene in mice results in lethality with hypertriglyceridemia and hypoglycemia during fasting. To investigate the molecular mechanism of the nutritional transition and the role of TBP-2, microarray analyses were performed using the liver of TBP-2−/− mice in the fed and fasted states. We found that the fasting-induced reduction in the expression of lipogenic genes targeted by insulin (SREBP-1), such as FASN and THRSP, was abolished in TBP-2−/− mice, and the expression of lipoprotein lipase is down-regulated, which was consistent with the lipoprotein profile. TBP-2−/− mice also exhibited enhanced glucose-induced insulin secretion and sensitivity. Another feature of the hepatic gene expression in fed TBP-2−/− mice was the augmented expression of peroxisome proliferator activated receptor (PPAR) target genes, such as CD36, FABP2, ACOT1, and FGF21, to regulate fatty acid consumption. In TBP-2−/− mice, PPARα expression was elevated in the fed state, whereas the fasting-induced up-regulation of PPARα was attenuated. We also detected an increased expression of PPARγ coactivator-1α protein in fed TBP-2−/− mice. TBP-2 overexpression significantly inhibited PPARα-mediated transcriptional activity induced by a specific PPARα ligand in vitro. These results suggest that TBP-2 is a key regulator of PPARα expression and signaling, and coordinated regulation of PPARα and insulin secretion by TBP-2 is crucial in the feeding-fasting nutritional transition. TBP-2/Txnip is a key regulator of PPARα expression and signaling, and coordinated regulation of PPARα and insulin secretion by TBP-2/Txnip is crucial in fasting response.

Peroxisomal bifunctional enzyme binds and activates the activationfunction-1 region of the peroxisome proliferator-activated receptor α

2001 ◽  
Vol 353 (2) ◽  
pp. 253-258 ◽  
Author(s):  
Cristiana E. JUGE-AUBRY ◽  
Stéphane KUENZLI ◽  
Jean-Charles SANCHEZ ◽  
Denis HOCHSTRASSER ◽  
Christoph A. MEIER
Keyword(s):  
Amino Acids ◽  
Transcriptional Activity ◽  
Hormone Receptors ◽  
Affinity Purification ◽  
Fold Increase ◽  
Activation Function ◽  
Bifunctional Enzyme ◽  
Peroxisome Proliferator ◽  
Dependent Manner ◽  
Peroxisome Proliferator Activated Receptor

The transcriptional activity of peroxisome proliferator-activated receptors (PPARs), and of nuclear hormone receptors in general, is subject to modulation by cofactors. However, most currently known co-activating proteins interact in a ligand-dependent manner with the C-terminal ligand-regulated activation function (AF)-2 domain of nuclear receptors. Since PPARα exhibits a strong constitutive transactivating function contained within an N-terminal AF-1 region, it can be speculated that a different set of cofactors might interact with this region of PPARs. An affinity purification approach was used to identify the peroxisomal enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase (bifunctional enzyme, BFE) as a protein which strongly and specifically interacted with the N-terminal 92 amino acids of PPARα. ProteinŐprotein interaction assays with the cloned BFE confirmed this interaction, which could be mapped to amino acids 307Ő514 of the BFE and the N-terminal 70 amino acids of PPARα. Moreover, transient transfection experiments in hepatoma cells revealed a 2.2-fold increase in the basal and ligand-stimulated transcriptional activity of PPARα in the presence of BFE. This stimulatory effect is preferentially observed for the PPARα isoform and it is significantly stronger (4.8-fold) in non-hepatic cells, which presumably express lower levels of endogenous BFE. Hence, the BFE represents the first known cofactor capable of activating the AF-1 domain of PPAR without requiring additional regions of this receptor. These data are compatible with a model whereby the PPAR-regulated BFE is able to modulate its own expression through an enhancement of the activity of PPARα, representing a novel peroxisomalŐnuclear feed-forward regulatory loop.

scholarly journals The effect of human GATA4 gene mutations on the activity of target gonadal promoters

2008 ◽  
Vol 42 (2) ◽  
pp. 149-160 ◽  
Author(s):  
Marie France Bouchard ◽  
Hiroaki Taniguchi ◽  
Robert S Viger
Keyword(s):  
Dna Binding ◽  
Gene Transcription ◽  
Transcriptional Activity ◽  
Target Genes ◽  
Heart Defects ◽  
Gene Mutations ◽  
Significant Loss ◽  
Specific Gene ◽  
Mutant Proteins ◽  
And Function

GATA transcription factors are crucial regulators of cell-specific gene expression in many tissues including the gonads. Although clinical cases of reproductive dysfunction have yet to be formally linked to GATA gene mutations, they have begun to be reported in other systems. Heterozygous GATA4 mutations have been associated with cases of congenital heart defects. Little is known, however, about the effect of these mutations on gonadal gene transcription. Since individuals carrying these mutations do not appear to suffer from gross reproductive defects, we hypothesized that this might be due to the differential transcriptional properties of the mutant proteins on heart versus gonadal target genes. Five mutations (S52F, E215D, G295S, V266M, and E359X) were recreated in the rat GATA4 protein. Several parameters were used to analyze the transcriptional properties of the mutants: activation of known gonadal target promoters (Star, Cyp19a1, and Inha), DNA binding, and interaction with GATA4 transcriptional partners. Three mutations (S52F, G295S, and E359X) reduced GATA4 transcriptional activity on the different gonadal promoters. With the exception of the G295S mutant, which showed a significant loss of DNA-binding affinity, the decrease in activity of the other GATA4 mutants was not associated with a change in DNA binding. All GATA4 mutants retained their ability to interact and cooperate with their major gonadal partners (NR5A1 and NR5A2) thereby compensating in part for the loss in intrinsic GATA4 transcriptional activity. Thus, unlike the heart, where the GATA4 mutations have deleterious effects, our data suggest that they would have a lesser impact on gonadal gene transcription and function.

SUMO modification selectively regulates transcriptional activity of peroxisome-proliferator-activated receptor γ in C2C12 myotubes

2010 ◽  
Vol 433 (1) ◽  
pp. 155-161 ◽  
Author(s):  
Sung Soo Chung ◽  
Byung Yong Ahn ◽  
Min Kim ◽  
Jun Ho Kho ◽  
Hye Seung Jung ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Transcriptional Activity ◽  
Target Genes ◽  
C2c12 Cells ◽  
C2c12 Myotubes ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Mouse Muscle ◽  
Fatty Acid Binding ◽  
Specific Protease

PPAR (peroxisome-proliferator-activated receptor) γ, a nuclear receptor, can be conjugated with SUMO (small ubiquitin-like modifier), which results in the negative regulation of its transcriptional activity. In the present study, we tested whether de-SUMOylation of PPARγ affects the expression of PPARγ target genes in mouse muscle cells and investigated the mechanism by which de-SUMOylation increases PPARγ transcriptional activity. We found that the SUMO-specific protease SENP2 [SUMO1/sentrin/SMT3 (suppressor of mif two 3 homologue 1)-specific peptidase 2] effectively de-SUMOylates PPARγ–SUMO conjugates. Overexpression of SENP2 in C2C12 cells increased the expression of some PPARγ target genes, such as FABP3 (fatty-acid-binding protein 3) and CD36 (fatty acid translocase), both in the absence and presence of rosiglitazone. In contrast, overexpression of SENP2 did not affect the expression of another PPARγ target gene ADRP (adipose differentiation-related protein). De-SUMOylation of PPARγ increased ChIP (chromatin immunoprecipitation) of both a recombinant PPRE (PPAR-response element) and endogenous PPREs of the target genes CD36 and FABP3, but ChIP of the PPRE in the ADRP promoter was not affected by SENP2 overexpression. In conclusion, these results indicate that SENP2 de-SUMOylates PPARγ in myotubes, and de-SUMOylation of PPARγ selectively increases the expression of some PPARγ target genes.

scholarly journals Structural basis of altered potency and efficacy displayed by a major in vivo metabolite of the anti-diabetic PPARγ drug pioglitazone

2018 ◽  
Author(s):  
Sarah A. Mosure ◽  
Jinsai Shang ◽  
Richard Brust ◽  
Jie Zheng ◽  
Patrick R. Griffin ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Activation Function ◽  
Structural Basis ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Exchange Mass Spectrometry ◽  
Pparγ Agonist ◽  
A Cell ◽  
And Function

ABSTRACTThe thiazolidinedione (TZD) pioglitazone (Pio) is an FDA-approved drug for type 2 diabetes mellitus that binds and activates the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ). Although TZDs have potent antidiabetic effects, they also display harmful side effects that have necessitated a better understanding of their mechanisms of action. In particular, little is known about the effect of in vivo TZD metabolites on the structure and function of PPARγ. Here, we present a structure-function comparison of Pio and a major in vivo metabolite, 1-hydroxypioglitazone (PioOH). PioOH displayed a lower binding affinity and reduced potency in coregulator recruitment assays compared to Pio. To determine the structural basis of these findings, we solved an X-ray crystal structure of PioOH bound to PPARγ ligand-binding domain (LBD) and compared it to a published Pio-bound crystal structure. PioOH exhibited an altered hydrogen bonding network that could underlie its reduced affinity and potency compared to Pio. Solution-state structural analysis using NMR spectroscopy and hydrogen/deuterium exchange mass spectrometry (HDX-MS) analysis revealed that PioOH stabilizes the PPARγ activation function-2 (AF-2) coactivator binding surface better than Pio. In support of AF-2 stabilization, PioOH displayed stabilized coactivator binding in biochemical assays and better transcriptional efficacy (maximal transactivation response) in a cell-based assay that reports on the activity of the PPARγ LBD. These results, which indicate that Pio hydroxylation affects both its potency and efficacy as a PPARγ agonist, contribute to our understanding of PPARγ-binding drug metabolite interactions and may assist in future PPARγ drug design efforts.

scholarly journals Coordinated Regulation of PPAR Expression and Activity through Control of Chromatin Structure in Adipogenesis and Obesity

PPAR Research ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Jérôme Eeckhoute ◽  
Frédérik Oger ◽  
Bart Staels ◽  
Philippe Lefebvre
Keyword(s):  
Chromatin Structure ◽  
Target Genes ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Chromatin Remodelers ◽  
Regulatory Pathways ◽  
Activation Of Transcription ◽  
And Function ◽  
White Fat ◽  
Expression And Activity

The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) is required for differentiation and function of mature adipocytes. Its expression is induced during adipogenesis where it plays a key role in establishing the transcriptome of terminally differentiated white fat cells. Here, we review findings indicating that PPARγexpression and activity are intricately regulated through control of chromatin structure. Hierarchical and combinatorial activation of transcription factors, noncoding RNAs, and chromatin remodelers allows for temporally controlled expression of PPARγand its target genes through sequential chromatin remodelling. In obesity, these regulatory pathways may be altered and lead to modified PPARγactivity.

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 Lipin1 regulates PPARγ transcriptional activity

2013 ◽  
Vol 453 (1) ◽  
pp. 49-60 ◽  
Author(s):  
Hee Eun Kim ◽  
Eunju Bae ◽  
Deok-yoon Jeong ◽  
Min-Ji Kim ◽  
Won-Ji Jin ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Transcriptional Activity ◽  
Thyroid Hormone Receptor ◽  
Specific Gene ◽  
Physical Interaction ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Transcriptional Activation Domain ◽  
Enhancer Binding Protein ◽  
Key Factor

PPARγ (peroxisome-proliferator-activated receptor γ) is a master transcription factor involved in adipogenesis through regulating adipocyte-specific gene expression. Recently, lipin1 was found to act as a key factor for adipocyte maturation and maintenance by modulating the C/EBPα (CCAAT/enhancer-binding protein α) and PPARγ network; however, the precise mechanism by which lipin1 affects the transcriptional activity of PPARγ is largely unknown. The results of the present study show that lipin1 activates PPARγ by releasing co-repressors, NCoR1 (nuclear receptor co-repressor 1) and SMRT (silencing mediator of retinoid and thyroid hormone receptor), from PPARγ in the absence of the ligand rosiglitazone. We also identified a novel lipin1 TAD (transcriptional activation domain), between residues 217 and 399, which is critical for the activation of PPARγ, but not PPARα. Furthermore, this TAD is unique to lipin1 since this region does not show any homology with the other lipin isoforms, lipin2 and lipin3. The activity of the lipin1 TAD is enhanced by p300 and SRC-1 (steroid receptor co-activator 1), but not by PCAF (p300/CBP-associated factor) and PGC-1α (PPAR co-activator 1α). The physical interaction between lipin1 and PPARγ occurs at the lipin1 C-terminal region from residues 825 to 926, and the VXXLL motif at residue 885 is critical for binding with and the activation of PPARγ. The action of lipin1 as a co-activator of PPARγ enhanced adipocyte differentiation; the TAD and VXXLL motif played critical roles, but the catalytic activity of lipin1 was not directly involved. Collectively, these data suggest that lipin1 functions as a key regulator of PPARγ activity through its ability to release co-repressors and recruit co-activators via a mechanism other than PPARα activation.

scholarly journals Definition of the Molecular Basis for Estrogen Receptor-Related Receptor-α-Cofactor Interactions

2007 ◽  
Vol 21 (1) ◽  
pp. 62-76 ◽  
Author(s):  
Stéphanie Gaillard ◽  
Mary A. Dwyer ◽  
Donald P. McDonnell
Keyword(s):  
Estrogen Receptor ◽  
Nuclear Receptor ◽  
Target Genes ◽  
Activation Function ◽  
Peroxisome Proliferator ◽  
Orphan Nuclear Receptor ◽  
Peroxisome Proliferator Activated Receptor ◽  
Hormone Response Elements ◽  
Phage Libraries ◽  
Definition Of

Abstract Estrogen receptor-related receptor-α (ERRα) is an orphan nuclear receptor that does not appear to require a classical small molecule ligand to facilitate its interaction with coactivators and/or hormone response elements within target genes. Instead, the apo-receptor is capable of interacting in a constitutive manner with coactivators that stimulate transcription by acting as protein ligands. We have screened combinatorial phage libraries for peptides that selectively interact with ERRα to probe the architecture of the ERRα-coactivator pocket. In this manner, we have uncovered a fundamental difference in the mechanism by which this receptor interacts with peroxisome proliferator-activated receptor-γ coactivator-1α, as compared with members of the steroid receptor coactivator subfamily of coactivators. Our findings suggest that it may be possible to develop ERRα ligands that exhibit different pharmacological activities as a consequence of their ability to differentially regulate coactivator recruitment. In addition, these findings have implications beyond ERRα because they suggest that subtle alterations in the structure of the activation function-2 pocket within any nuclear receptor may enable differential recruitment of coactivators, an observation of notable pharmaceutical importance.

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