scholarly journals Heterodimerization between Members of the Nur Subfamily of Orphan Nuclear Receptors as a Novel Mechanism for Gene Activation

1999 ◽  
Vol 19 (11) ◽  
pp. 7549-7557 ◽  
Author(s):  
Mario Maira ◽  
Christine Martens ◽  
Alexandre Philips ◽  
Jacques Drouin
Keyword(s):  
Mammalian Cells ◽  
Target Genes ◽  
Lymphoid Cells ◽  
Orphan Receptor ◽  
Target Sequence ◽  
Related Factor ◽  
Orphan Nuclear Receptor ◽  
Orphan Nuclear Receptors

ABSTRACT We have recently shown that the orphan nuclear receptor Nur77 (NGFI-B) is most active in transcription when it is interacting with a cognate DNA sequence as a homodimer. Further, we have shown that the target for Nur77 dimers, the Nur response element (NurRE), is responsive to physiological stimuli in both endocrine and lymphoid cells, whereas other DNA targets of Nur77 action are not. The Nur77 subfamily also includes two related receptors, Nur-related factor 1 (Nurr1) and neuron-derived orphan receptor 1 (NOR-1). Often, more than one member of this subfamily is induced in response to extracellular signals. We now show that Nur77 and Nurr1 form heterodimers in vitro in the presence or absence of NurRE, and we have documented interactions between these proteins in vivo by using a two-hybrid system in mammalian cells. These heterodimers synergistically enhance transcription from NurRE reporters in comparison to that seen with homodimers. The naturally occurring NurRE from the pro-opiomelanocortin gene preferentially binds and activates transcription in the presence of Nur77 homo- or heterodimers, while a consensus NurRE sequence does not show this preference. Taken together, the data indicate that members of the Nur77 subfamily are most potent as heterodimers and that different dimers exhibit target sequence preference. Thus, we propose that a combinatorial code relying on specific NurRE sequences might be responsible for the activation of subsets of target genes by one of the members of the Nur77 subfamily of transcription factors.

scholarly journals Transcriptional Regulation of HumanRev-erbαGene Expression by the Orphan Nuclear Receptor Retinoic Acid-related Orphan Receptor α

2002 ◽  
Vol 277 (51) ◽  
pp. 49275-49281 ◽  
Author(s):  
Eric Raspè ◽  
Gisèle Mautino ◽  
Caroline Duval ◽  
Coralie Fontaine ◽  
Hélène Duez ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Hepg2 Cells ◽  
Gene Promoter ◽  
Orphan Receptor ◽  
Similar Response ◽  
Orphan Nuclear Receptor ◽  
Orphan Nuclear Receptors ◽  
Mrna Accumulation

The Rev-erb and retinoic acid-related orphan receptors (ROR) are two related families of orphan nuclear receptors that recognize similar response elements but have opposite effects on transcription. Recently, theRev-erbαgene promoter has been characterized and shown to harbor a functional Rev-erbα-binding site known as Rev-DR2, responsible for negative feedback down-regulation of promoter activity by Rev-erbα itself. The present study aimed to investigate whetherRev-erbαgene expression is regulated by RORα. Gel shift analysis demonstrated thatin vitrotranslated hRORα1 protein binds to the Rev-DR2 site, both as monomer and dimer. Chromatin immunoprecipitation assays demonstrated that binding of RORα to this site also occurredin vivoin human hepatoma HepG2 cells. The Rev-DR2 site was further shown to be functional as it conferred hRORα1 responsiveness to a heterologous promoter and to the natural humanRev-erbαgene promoter in these cells. Mutation of this site in the context of the naturalRev-erbαgene promoter abolished its activation by RORα, indicating that this site plays a key role in hRORα1 action. Finally, adenoviral overexpression of hRORα1 in HepG2 cells led to enhanced hRev-erbα mRNA accumulation, further confirming the physiological importance of RORα1 in the regulation of Rev-erbα expression.

scholarly journals Maximal killing of lymphoma cells by DNA damage–inducing therapy requires not only the p53 targets Puma and Noxa, but also Bim

Blood ◽  
2010 ◽  
Vol 116 (24) ◽  
pp. 5256-5267 ◽  
Author(s):  
Lina Happo ◽  
Mark S. Cragg ◽  
Belinda Phipson ◽  
Jon M. Haga ◽  
Elisa S. Jansen ◽  
...  
Keyword(s):  
Dna Damage ◽  
Drug Resistance ◽  
Target Genes ◽  
B Cell Lymphoma ◽  
Chemotherapeutic Agents ◽  
Lymphoid Cells ◽  
Lymphoma Cells ◽  
P53 Target Genes

Abstract DNA-damaging chemotherapy is the backbone of cancer treatment, although it is not clear how such treatments kill tumor cells. In nontransformed lymphoid cells, the combined loss of 2 proapoptotic p53 target genes, Puma and Noxa, induces as much resistance to DNA damage as loss of p53 itself. In Eμ-Myc lymphomas, however, lack of both Puma and Noxa resulted in no greater drug resistance than lack of Puma alone. A third B-cell lymphoma-2 homology domain (BH)3-only gene, Bim, although not a direct p53 target, was up-regulated in Eμ-Myc lymphomas incurring DNA damage, and knockdown of Bim levels markedly increased the drug resistance of Eμ-Myc/Puma−/−Noxa−/− lymphomas both in vitro and in vivo. Remarkably, c-MYC–driven lymphoma cell lines from Noxa−/−Puma−/−Bim−/− mice were as resistant as those lacking p53. Thus, the combinatorial action of Puma, Noxa, and Bim is critical for optimal apoptotic responses of lymphoma cells to 2 commonly used DNA-damaging chemotherapeutic agents, identifying Bim as an additional biomarker for treatment outcome in the clinic.

scholarly journals Astaxanthin Treatment Induces Maturation and Functional Change of Myeloid-Derived Suppressor Cells in Tumor-Bearing Mice

Antioxidants ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 350
Author(s):  
Seong Mun Jeong ◽  
Yeon-Jeong Kim
Keyword(s):  
Mhc Class Ii ◽  
Target Genes ◽  
Suppressor Cells ◽  
Functional Change ◽  
Related Factor ◽  
Mrna Levels ◽  
Myeloid Derived Suppressor Cells ◽  
Antitumor Effects

Myeloid-derived suppressor cells (MDSCs) are immature myeloid cells which accumulate in stress conditions such as infection and tumor. Astaxanthin (ATX) is a well-known antioxidant agent and has a little toxicity. It has been reported that ATX treatment induces antitumor effects via regulation of cell signaling pathways, including nuclear factor erythroid-derived 2-related factor 2 (Nrf2) signaling. In the present study, we hypothesized that treatment with ATX might induce maturation of MDSCs and modulate their immunosuppressive activity. Both in vivo and in vitro treatment with ATX resulted in up-regulation of surface markers such as CD80, MHC class II, and CD11c on both polymorphonuclear (PMN)-MDSCs and mononuclear (Mo)-MDSCs. Expression levels of functional mediators involved in immune suppression were significantly reduced, whereas mRNA levels of Nrf2 target genes were increased in ATX-treated MDSCs. In addition, ATX was found to have antioxidant activity reducing reactive oxygen species level in MDSCs. Finally, ATX-treated MDSCs were immunogenic enough to induce cytotoxic T lymphocyte response and contributed to the inhibition of tumor growth. This demonstrates the role of ATX as a regulator of the immunosuppressive tumor environment through induction of differentiation and functional conversion of MDSCs.

scholarly journals Modulating PKCα Activity to Target Wnt/β-Catenin Signaling in Colon Cancer

Cancers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 693 ◽  
Author(s):  
Sébastien Dupasquier ◽  
Philippe Blache ◽  
Laurence Picque Lasorsa ◽  
Han Zhao ◽  
Jean-Daniel Abraham ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Transcriptional Activity ◽  
Target Genes ◽  
Tumor Development ◽  
Orphan Receptor ◽  
Nuclear Accumulation ◽  
Kinase C ◽  
Extracellular Signal

Inactivating mutations of the tumor suppressor Adenomatosis Polyposis Coli (APC), which are found in familial adenomatosis polyposis and in 80% of sporadic colorectal cancers (CRC), result in constitutive activation of the Wnt/β-catenin pathway and tumor development in the intestine. These mutations disconnect the Wnt/β-catenin pathway from its Wnt extracellular signal by inactivating the APC/GSK3-β/axin destruction complex of β-catenin. This results in sustained nuclear accumulation of β-catenin, followed by β-catenin-dependent co-transcriptional activation of Wnt/β-catenin target genes. Thus, mechanisms acting downstream of APC, such as those controlling β-catenin stability and/or co-transcriptional activity, are attractive targets for CRC treatment. Protein Kinase C-α (PKCα) phosphorylates the orphan receptor RORα that then inhibits β-catenin co-transcriptional activity. PKCα also phosphorylates β-catenin, leading to its degradation by the proteasome. Here, using both in vitro (DLD-1 cells) and in vivo (C57BL/6J mice) PKCα knock-in models, we investigated whether enhancing PKCα function could be beneficial in CRC treatment. We found that PKCα is infrequently mutated in CRC samples, and that inducing PKCα function is not deleterious for the normal intestinal epithelium. Conversely, di-terpene ester-induced PKCα activity triggers CRC cell death. Together, these data indicate that PKCα is a relevant drug target for CRC treatment.

scholarly journals Spermatogenesis and Testis Development Are Normal in Mice Lacking Testicular Orphan Nuclear Receptor 2

2002 ◽  
Vol 22 (13) ◽  
pp. 4661-4666 ◽  
Author(s):  
Chih-Rong Shyr ◽  
Loretta L. Collins ◽  
Xiao-Min Mu ◽  
Kenneth A. Platt ◽  
Chawnshang Chang
Keyword(s):  
Protein Expression ◽  
Nuclear Receptor ◽  
Expression Patterns ◽  
Orphan Receptor ◽  
Orphan Nuclear Receptor ◽  
Male Mice ◽  
Orphan Nuclear Receptors ◽  
Nuclear Receptor Superfamily ◽  
Testis Development

ABSTRACT Early in vitro cell culture studies suggested that testicular orphan nuclear receptor 2 (TR2), a member of the nuclear receptor superfamily, may play important roles in the control of several pathways including retinoic acids, vitamin D, thyroid hormones, and ciliary neurotrophic factor. Here we report the surprising results showing that mice lacking TR2 are viable and have no serious developmental defects. Male mice lacking TR2 have functional testes, including normal sperm number and motility, and both male and female mice lacking TR2 are fertile. In heterozygous TR2+/− male mice we found that β-galactosidase, the indicator of TR2 protein expression, was first detected at the age of 3 weeks and its expression pattern was restricted mainly in the spermatocytes and round spermatids. These protein expression patterns were further confirmed with Northern blot analysis of TR2 mRNA expression. Together, results from TR2-knockout mice suggest that TR2 may not play essential roles in spermatogenesis and normal testis development, function, and maintenance. Alternatively, the roles of TR2 may be redundant and could be played by other close members of the nuclear receptor superfamily such as testicular orphan receptor 4 (TR4) or unidentified orphan receptors that share many similar functions with TR2. Further studies with double knockouts of both orphan nuclear receptors, TR2 and TR4, may reveal their real physiological roles.

Discovery and Optimization of a Series of Sulfonamide Inverse Agonists for the Retinoic Acid Receptor-Related Orphan Receptor-α

2019 ◽  
Vol 15 (6) ◽  
pp. 676-684
Author(s):  
Christelle Doebelin ◽  
Yuanjun He ◽  
Sean Campbell ◽  
Philippe Nuhant ◽  
Naresh Kumar ◽  
...  
Keyword(s):  
Retinoic Acid Receptor ◽  
Research Effort ◽  
Pharmacokinetic Profile ◽  
Orphan Receptor ◽  
Orphan Nuclear Receptor ◽  
Inverse Agonists ◽  
Close Family Member ◽  
Per Oral

Background: Despite a massive industry endeavor to develop RORγ-modulators for autoimmune disorders, there has been no indication of efforts to target the close family member RORα for similar indications. This may be due to the misconception that RORα is redundant to RORγ, or the inherent difficulty in cultivating tractable starting points for RORα. RORα-selective modulators would be useful tools to interrogate the biology of this understudied orphan nuclear receptor. Objectives: he goal of this research effort was to identify and optimize synthetic ligands for RORα starting from the known LXR agonist T0901317. Methods: Fourty-five analogs of the sulfonamide lead (1) were synthesized and evaluated for their ability to suppress the transcriptional activity of RORα, RORγ, and LXRα in cell-based assays. Analogs were characterized by 1H-NMR, 13C-NMR, and LC-MS analysis. The pharmacokinetic profile of the most selective RORα inverse agonist was evaluated in rats with intraperitoneal (i.p.) and per oral (p.o.)dosing. Results: Structure-activity relationship studies led to potent dual RORα/RORγ inverse agonists as well as RORα-selective inverse agonists (20, 28). LXR activity could be reduced by removing the sulfonamide nitrogen substituent. Attempts to improve the potency of these selective leads by varying substitution patterns throughout the molecule proved challenging. Conclusion: The synthetic RORα-selective inverse agonists identified (20, 28) can be utilized as chemical tools to probe the function of RORα in vitro and in vivo.

The effect of manganese exposure on GnRH secretion via Nrf2/mGluR5/COX-2/PGE2/signaling pathway

2019 ◽  
Vol 35 (3) ◽  
pp. 211-227 ◽  
Author(s):  
Zhipeng Qi ◽  
Chao Mi ◽  
Fengdi Wu ◽  
Xinxin Yang ◽  
Yanqi Sang ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Target Genes ◽  
Metabotropic Glutamate Receptor ◽  
Morphological Changes ◽  
Control Group ◽  
Related Factor ◽  
Gnrh Secretion ◽  
Cox 2

There are limited studies focused on the precise mechanism of gonadotropin-releasing hormone (GnRH) secretion dysfunction after overexposure to manganese (Mn). The objective of the present study was to explore the mechanism of Mn disruption of GnRH synthesis via nuclear factor erythroid-2-related factor-2 (Nrf2)/metabotropic glutamate receptor-5 (mGluR5)/cyclooxygenase-2 (COX-2)/prostaglandin E2 (PGE2) signaling pathway in vitro and in vivo. Primary astrocytes were cultured and treated with different doses of Mn, tert-butylhydroquinonet (tBHQ; Nrf2 agonists), 3-[(2-methyl-4-thaizolyl) ethynyl] pyridine (MTEP; mGluR5 inhibitor), and celecoxib (COX-2 inhibitor) to measure the levels of COX-2, mGluR5, Nrf2, and Nrf2 target genes. Mice were randomly divided into 11 groups, of which included the control group, 12.5-, 25-, and 50-mg/kg MnCl2 group, dimethyl sulfoxide (DMSO) group, tBHQ control group, tBHQ pretreatment group, MTEP control group, MTEP pretreatment group, celecoxib control group, and celecoxib pretreatment group. The injection was administered every day for 2 weeks. Then, levels of GnRH, PGE2, COX-2, mGluR5, Nrf2, Nrf2 target genes, and morphological changes in the hypothalamus of mice were measured. Mn reduced protein levels of Nrf2 and mRNA expression of Nrf2 target genes and increased mGluR5, COX-2, PGE2, and GnRH levels. Meanwhile, injury-related histomorphology changes in the hypothalamus of mice were significantly present. In conclusion, excessive exposure to Mn disrupts GnRH secretion through Nrf2/mGluR5/COX-2/PGE2 signaling pathway.

scholarly journals BH3-only proteins Puma and Bim are rate-limiting for γ-radiation– and glucocorticoid-induced apoptosis of lymphoid cells in vivo

Blood ◽  
2005 ◽  
Vol 106 (13) ◽  
pp. 4131-4138 ◽  
Author(s):  
Miriam Erlacher ◽  
Ewa M. Michalak ◽  
Priscilla N. Kelly ◽  
Verena Labi ◽  
Harald Niederegger ◽  
...  
Keyword(s):  
Dna Damage ◽  
Target Genes ◽  
Cultured Cells ◽  
Lymphoid Cells ◽  
Whole Body ◽  
Γ Radiation ◽  
B Cell Leukemia ◽  
Induced Apoptosis

Numerous p53 target genes have been implicated in DNA damage–induced apoptosis signaling, but proapoptotic Bcl-2 (B-cell leukemia 2) family members of the BH3 (Bcl-2 homolog region [BH] 3)–only subgroup appear to play the critical initiating role. In various types of cultured cells, 3 BH3-only proteins, namely Puma (p53 up-regulated modulator of apoptosis), Noxa, and Bim (Bcl-2 interacting mediator of cell death), have been shown to initiate p53-dependent as well as p53-independent apoptosis in response to DNA damage and treatment with anticancer drugs or glucocorticoids. In particular, the absence of Puma or Bim renders thymocytes and mature lymphocytes refractory to varying degrees to death induced in vitro by growth factor withdrawal, DNA damage, or glucocorticoids. To assess the in vivo relevance of these findings, we subjected mice lacking Puma, Noxa, or Bim to whole-body γ-radiation or the glucocorticoid dexamethasone and compared lymphocyte survival with that in wild-type and BCL2–transgenic mice. Absence of Puma or Bcl-2 overexpression efficiently protected diverse types of lymphocytes from the effects of γ-radiation in vivo, and loss of Bim provided lower but significant protection in most lymphocytes, whereas Noxa deficiency had no impact. Furthermore, both Puma and Bim were found to contribute significantly to glucocorticoid-induced killing. Our results thus establish that Puma and Bim are key initiators of γ-radiation– and glucocorticoid-induced apoptosis in lymphoid cells in vivo.

scholarly journals Bile acids inhibit duodenal secretin expression via orphan nuclear receptor small heterodimer partner (SHP)

2009 ◽  
Vol 297 (1) ◽  
pp. G90-G97 ◽  
Author(s):  
Ian P. Y. Lam ◽  
Leo T. O. Lee ◽  
Hueng-Sik Choi ◽  
Gianfranco Alpini ◽  
Billy K. C. Chow
Keyword(s):  
Gene Expression ◽  
Bile Acids ◽  
Nuclear Receptor ◽  
Target Genes ◽  
In Vivo Studies ◽  
Control Group ◽  
Orphan Nuclear Receptor ◽  
Small Heterodimer Partner

Small heterodimer partner (SHP) is an orphan nuclear receptor in which gene expression can be upregulated by bile acids. It regulates its target genes by repressing the transcriptional activities of other nuclear receptors including NeuroD, which has been shown to regulate secretin gene expression. Here, we evaluated the regulation on duodenal secretin gene expression by SHP and selected bile acids, cholic acid (CA) and chenodeoxycholic acid (CDCA). In vitro treatment of CDCA or fexaramine elevated the SHP transcript level and occupancy on secretin promoter. The increase in the SHP level, induced by bile acid treatment or overexpression, reduced secretin gene expression, whereas this gene inhibitory effect was reversed by silencing of endogenous SHP. In in vivo studies, double-immunofluorescence staining demonstrated the coexpression of secretin and SHP in mouse duodenum. Feeding mice with 1% CA-enriched rodent chow resulted in upregulation of SHP and a concomitant decrease in secretin transcript and protein levels in duodenum compared with the control group fed with normal chow. A diet enriched with 5% cholestyramine led to a decrease in SHP level and a corresponding increase in secretin expression. Overall, this study showed that bile acids via SHP inhibit duodenal secretin gene expression. Because secretin is a key hormone that stimulates bile flow in cholangiocytes, this pathway thus provides a novel means to modulate secretin-stimulated choleresis in response to intraduodenal bile acids.

scholarly journals Structure-based analyses of Salmonella RcsB variants unravel new features of the Rcs regulon

2021 ◽  
Author(s):  
Juanjo Huesa ◽  
Joaquín Giner-Lamia ◽  
M Graciela Pucciarelli ◽  
Francisco Paredes-Martínez ◽  
Francisco García-del Portillo ◽  
...  
Keyword(s):  
Dna Binding ◽  
Target Genes ◽  
Structural Data ◽  
Enteric Bacteria ◽  
Target Sequence ◽  
Active Conformation ◽  
Functional Studies ◽  
Binding Domains

Abstract RcsB is a transcriptional regulator that controls expression of numerous genes in enteric bacteria. RcsB accomplishes this role alone or in combination with auxiliary transcriptional factors independently or dependently of phosphorylation. To understand the mechanisms by which RcsB regulates such large number of genes, we performed structural studies as well as in vitro and in vivo functional studies with different RcsB variants. Our structural data reveal that RcsB binds promoters of target genes such as rprA and flhDC in a dimeric active conformation. In this state, the RcsB homodimer docks the DNA-binding domains into the major groove of the DNA, facilitating an initial weak read-out of the target sequence. Interestingly, comparative structural analyses also show that DNA binding may stabilize an active conformation in unphosphorylated RcsB. Furthermore, RNAseq performed in strains expressing wild-type or several RcsB variants provided new insights into the contribution of phosphorylation to gene regulation and assign a potential role of RcsB in controlling iron metabolism. Finally, we delimited the RcsB box for homodimeric active binding to DNA as the sequence TN(G/A)GAN4TC(T/C)NA. This RcsB box was found in promoter, intergenic and intragenic regions, facilitating both increased or decreased gene transcription.

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