Orphan Nuclear Receptor Research Articles

Orphan nuclear receptor NUR77 relieves insulin resistance in HTR-8/SVneo trophoblast cells through activation of autophagy and insulin signaling.

Gestational diabetes mellitus (GDM) is a common pregnancy complication with a high incidence in women. Orphan nuclear receptor NUR77 is involved in regulating glucose metabolism. However, its role in GDM has not been fully elucidated yet. In this study, an animal model of GDM was established by feeding mice with a high-fat diet (HFD) before and during pregnancy. NUR77 expression was abnormally upregulated in placenta tissues of GDM mice. We performed gain- and loss-of-function studies of NUR77 in HTR-8/SVneo cells. Cells were incubated with 1 × 10-6M insulin for 48h to induce insulin resistance (IR). The expression of NUR77 was downregulated in HTR-8/SVneo cells following IR induction. Overexpression of NUR77 promoted cell proliferation, migration, and invasion. Notably, NUR77 promoted glucose uptake and enhanced insulin sensitivity in vitro. NUR77 increased the ratio of p-insulin receptor β (IRβ)Tyr1361/IRβ, p-insulin receptor substrate (IRS)-1Tyr612/IRS-1, p-Akt/Akt and decreased p-IRS-1Ser307/IRS-1, as well as lowered the expression of glucose transport protein type 1 (GLUT1) and elevated GLUT4. These results suggest the involvement of IRβ/IRS/Akt/GLUT4 signaling activation in the regulatory effects of NUR77 on IR in HTR-8/SVneo cells. Silencing of NUR77 displayed opposite effects. Besides, NUR77 enhanced the expression of autophagy-related protein Beclin 1 and the ratio of LC3II/LC3I. Further study demonstrated that the inhibitory effect of NUR77 on IR was partially attributed to the activation of autophagy. Therefore, we demonstrate that NUR77 enhances insulin sensitivity in HTR-8/SVneo cells likely through activating IRβ/IRS/Akt/GLUT4 pathway and regulating autophagy.

JMJD3 Promotes Porphyromonas gingivalis Lipopolysaccharide-Induced Th17-Cell Differentiation by Modulating the STAT3-RORc Signaling Pathway.

The immune response mediated by Th17 cells is essential in the pathogenesis of periodontitis. Emerging evidence has demonstrated that lipopolysaccharide from Porphyromonas gingivalis (Pg-LPS) could promote Th17-cell differentiation directly, while the downstream signaling remains elusive. This study was aimed to explore the role of JMJD3 (a JmjC family histone demethylase) and signal transducers and activators of transcription 3 (STAT3) in Th17-cell differentiation triggered by Pg-LPS and clarify the interaction between them. We found that the expression of JMJD3 and STAT3 was significantly increased under Th17-polarizing conditions. Pg-LPS could promote Th17-cell differentiation from CD4+ T cells, with an increased expression of JMJD3 and STAT3 compared to the culture without Pg-LPS. The coimmunoprecipitation results showed that the interactions of JMJD3 and STAT3, STAT3 and retinoid-related orphan nuclear receptor γt (RORγt) were enhanced following Pg-LPS stimulation during Th17-cell differentiation. Further blocking assays were performed and the results showed that inhibition of STAT3 or JMJD3 both suppressed the Th17-cell differentiation, JMJD3 inhibitor could reduce the expression of STAT3 and p-STAT3, while JMJD3 expression was not affected when STAT3 was inhibited. Taken together, this study found that JMJD3 could promote Pg-LPS induced Th17-cell differentiation by modulating the STAT3-RORc signaling pathway.

042 Epidermal loss of RORα accelerates skin inflammation in a mouse model of atopic dermatitis

One of the most common skin diseases is atopic dermatitis (AD), a chronic inflammation featuring skin barrier dysfunction and immune dysregulation. Previously, we reported that the nuclear orphan nuclear receptor RORα was highly expressed in the epidermis of human skin and positively regulated the expression of skin barrier-related genes, including filaggrin, in human keratinocytes. In contrast, RORα was downregulated in AD lesions. We then aimed to evaluate the in vivo function of RORα in regulating AD pathogenesis, using the newly generated mice with epidermis-specific Rora knockout (RoraΔepi) and an AD mouse model induced by MC903.

Melatonin ameliorates Parkinson’s disease via regulating microglia polarization in a RORα‐dependent pathway

An important pathophysiological component of Parkinson’s Disease (PD) is circadian rhythm disorder, closely related to a decrease in circulated melatonin (MLT) level. It has been reported recently that retinoic acid-associated orphan nuclear receptor (RORα), for the potentiallyendogenous ligand MLT, plays an important role in various diseases. However, the function of RORα in the pathogenesis of neurodegenerative diseases remains much unclear. Here, we showed in a cellular PD model that RORα expression was down-regulated in 1 methyl 4 phenyl pyridinium ion (MPP+)-treated BV2 cells but up-regulated by MLT. Of a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) - induced mouse model with RORα levels reduced in the midbrain tissue, MLT treatment (intraperitoneal 20 mg/kg/d for 7 days) significantly increased the RORα levels and protected dopamine neurons, with decreased inflammation and increased anti-inflammatory M2-like phenotype in the microglia. Furthermore, siRNA-mediated knockdown implied the involvement of signal transducer and activator of transcription (STAT) pathway. In conclusion, MLT ameliorates neuroinflammation by inhibiting STAT-related pro-inflammatory (M1-like) polarization of microglia, revealing alternative options for neuroprotective treatment of PD.

Acute liver injury induces expression of FGF23 in hepatocytes via orphan nuclear receptor ERRγ signaling

Acute liver injury induces expression of FGF23 in hepatocytes via orphan nuclear receptor ERRγ signaling

Dietary Curcuma, a Powerful Epigenome Modulator in Breast Cancer: an In Silico Study

The inhibition of DNA methyltransferase-1 enzyme can strongly decrease the capacity of cells to enhance the tumour-genesis process. Members of the Estrogen-Related Receptors family regulate several elements of cellular metabolism. These are orphan nuclear receptors that regulate a wide range of functional gene networks involved in breast carcinogenesis and the regulation of associated methionine and folate cycles, providing a proven direct relationship to DNA methylation as a result. Moreover, dietary phytochemicals, such as Curcumin, can involve epigenetic modification, which may decrease the development of many types of cancer, especially breast cancer in women. We conducted this study to investigate the effect of Curcuma (PubChem ID: 969516) on the epigenetic modification and inhibition of the DNA methyltransferase-1 (PDB ID: 3PTA) activity and Estrogen-Related Receptors (PDB ID: 1XB7) using Molecular docking approach and computational tools that may inform whether the Curcuma could provide this protective anticancer effect or not. Interestingly, the DNA methyltrasferase1-Curcumin and Estrogen-Related Receptors-Curcumin complexes display a docking score of -6.9 and -7.1 kcal/mol, respectively. Furthermore, Curcumin displays hydrogen, Pi-Cation, Pi-Anion and Van der Waals bonds with active site residues of the targeted molecules. By targeting DNA methylation via the combined inhibition of estrogen-related receptors and DNMT1, our research opens up a new therapeutic path for breast cancer treatment.Keywords: curcumin, breast cancer, epigenetic, molecular docking, treatment.

Estrogen-Related Receptor α: A Significant Regulator and Promising Target in Bone Homeostasis and Bone Metastasis.

Bone homeostasis is maintained with the balance between bone formation and bone resorption, which is involved in the functional performance of osteoblast and osteoclast. Disruption of this equilibrium usually causes bone disorders including osteoporosis, osteoarthritis, and osteosclerosis. In addition, aberrant activity of bone also contributes to the bone metastasis that frequently occurs in the late stage of aggressive cancers. Orphan nuclear receptor estrogen-related receptor (ERRα) has been demonstrated to control the bone cell fate and the progression of tumor cells in bone through crosstalk with various molecules and signaling pathways. However, the defined function of this receptor in bone is inconsistent and controversial. Therefore, we summarized the latest research and conducted an overview to reveal the regulatory effect of ERRα on bone homeostasis and bone metastasis, this review may broaden the present understanding of the cellular and molecular model of ERRα and highlight its potential implication in clinical therapy.

Abstract 236: Nuclear receptor 4A1 ligands target T-cell exhaustion in colorectal cancer

Abstract Colorectal cancer (CRC) is a highly complex disease with multiple risk factors. The orphan nuclear receptor 4A1 (NR4A1) is overexpressed in several cancers and is a negative prognostic factor for cancer patient survival. Previous reports indicate a potential role for overexpression of NR4A1 in T-cell exhaustion and in this study, we aim to investigate the antitumorigenic activity of two bis-indole derived ligands (DIMs) that act as receptor antagonists. Immune competent C57BL/6 mice and mouse MC-38 colon cancer cells were used and tumor Infiltrating Lymphocytes (TILs) were isolated from mice either untreated or treated with CDIM/NR4A1 antagonists. FACS analysis and Real -Time PCR were performed to determine expression of exhaustion markers in these tumor T-cell population. 1,1-Bis(3΄-indolyl)-1-(3-bromo-5-trifluoromethoxyphenyl)methane (DIM-3-Br-5-OCF3) and the 3,5-dichlorophenyl analog (DIM-3,5-Cl2) at doses of 2.5 and 7.5 mg/kg/d inhibited tumor growth and downregulated expression of PD-L1, an NR4A1-regulated gene in MC-38 - derived tumors and cells. The mouse MC-38 colon cancer cell line was used in a syngeneic mouse model of colon cancer and tumor infiltrating lymphocytes (TILs) from MC-38 cell-derived colon tumors exhibited multiple markers of T-cell exhaustion in both CD8+ and CD4+ T-cells. Lymphocytes from an enlarged spleen in these tumor-bearing animals also exhibited markers of CD8+ and CD4+ T-cell exhaustion. Analysis of CD8+ cells from TILs showed that treatment with the NR4A1 antagonists modulated expression of several genes associated with T-cell exhaustion namely a decrease in TOX, TOX2 and NFAT mRNAs, activation of T-Bet. The percentage of CD8+ and CD4+ T-cells from tumors and spleen expressing PD-1, 2B4 and TIGIT was decreased in the treated vs control mice and TIM3 expression was also decreased in CD8+ (tumors and spleen) and CD4+ (tumors) T-cells. These findings suggest that NR4A1 antagonists are highly effective as anticancer agents in this mouse syngeneic colon tumor model by inactivating the pro-oncogenic activities of NR4A1 in tumors and by remediating NR4A1-regulated T-cell exhaustion in tumor and splenic lymphocytes. Citation Format: Kumaravel Mohankumar, Gus Wright, Subhashree Kumaravel, Rupesh Shrestha, Lei Zhang, Maen Abdelrahim, Robert S. Chapkin, Stephen Safe. Nuclear receptor 4A1 ligands target T-cell exhaustion in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 236.

Abstract 1778: NR2F2 mediates cell growth and endocrine resistance in NF1 loss, ER+ breast cancer

Abstract Genomic loss of in Neurofibromin 1 (NF1) is a recurrent mechanism driving metastatic progression and resistance to endocrine therapy in ER-positive breast cancer, via activation of the MAPK pathway, induction of cyclin D1 expression and modulation of estrogen receptor signaling. To identify specific mediators of tumor growth in NF1 mutant cancers, we performed a genetic knockout (KO) screen in isogenic WT and NF1 KO breast cancer cells. After employing stringent cutoff criteria, we found 28 genes that are specifically essential for NF1 KO cells but not WT cells. Among these genes, NR2F2, encoding an orphan nuclear receptor, was one of the top candidates. We validated that its loss significantly impaired the growth of multiple models of NF1 null, ER+ breast cancer. Loss of NF1 leads to the hyperactivation of Ras which sequentially activates multiple effector pathways, including the MAPK pathway and the PI3K-AKT pathway. We found that MAPK activation upon NF1 loss led to elevated NR2F2 expression levels. A negative correlation between NF1 and NR2F2 expression was further confirmed in public gene expression databases. These data suggested that induction of NR2F2 expression might be one mechanism that mediates endocrine resistance caused by NF1 loss. Consistently, we found that exogenous expression of NR2F2 could confer endocrine resistance while its knockout hypersensitized ER+ breast cancer cells to endocrine therapies and significantly attenuated NF1 loss induced resistance. RNA-seq analysis revealed that estrogen response gene sets were among the most enriched signatures upon NF1 KO, NR2F2 over-expression (OE) or NR2F2 KO. NF1 KO or NR2F2 OE decreased the expression of early estrogen response genes and impaired their E2-induced expression, most of which could be rescued by NR2F2 KO, suggesting a regulatory effect of NR2F2 on ER transcriptional activity. To further define these mechanisms, ongoing integrative analyses of NR2F2 qPlex-RIME, ER and NR2F2 ChIP-Sequencing and ATAC-Sequencing will be presented. Taken together, our studies identify NR2F2 as a MAPK driven transcript whose induction mediates endocrine resistance, and may serve as a novel therapeutic target to overcome anti-estrogen resistant breast cancer growth. Citation Format: Yanyan Cai, Peihua Zhao, Fan Wu, Hong Shao, Pedram Razavi, Guotai Xu, Maurizio Scaltriti, Sarat Chandarlapaty. NR2F2 mediates cell growth and endocrine resistance in NF1 loss, ER+ breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1778.

Feeding activates FGF15‐SHP‐TFEB‐mediated lipophagy in the gut

Lysosome‐mediated macroautophagy, including lipophagy, is activated under nutrient deprivation but is repressed after feeding. We show that, unexpectedly, feeding activates intestinal autophagy/lipophagy in a manner dependent on both the orphan nuclear receptor, small heterodimer partner (SHP/NR0B2), and the gut hormone, fibroblast growth factor‐15/19 (FGF15/19). Furthermore, postprandial intestinal triglycerides (TGs) and apolipoprotein‐B48 (ApoB48), the TG‐rich chylomicron marker, were elevated in SHP‐knockout and FGF15‐knockout mice. Genomic analyses of the mouse intestine indicated that SHP partners with the key lysosomal activator, transcription factor‐EB (TFEB) to upregulate the transcription of autophagy/lipolysis network genes after feeding. FGF19 treatment activated lipophagy, reducing TG and ApoB48 levels in HT29 intestinal cells, which was dependent on TFEB. Mechanistically, feeding‐induced FGF15/19 signaling increased the nuclear localization of TFEB and SHP via PKC beta/zeta‐mediated phosphorylation, leading to increased transcription of the TFEB/SHP target lipophagy genes, Ulk1 and Atgl. Collectively, these results demonstrate that paradoxically after feeding, FGF15/19‐activated SHP and TFEB activate gut lipophagy, limiting postprandial TGs. As excess postprandial lipids cause dyslipidemia and obesity, the FGF15/19‐SHP‐TFEB axis that reduces intestinal TGs via lipophagic activation provides promising therapeutic targets for obesity‐associated metabolic disease.

C-Abl tyrosine kinase inhibition attenuate oxidative stress-induced pancreatic β-Cell dysfunction via glutathione antioxidant system

Chronic oxidative stress, which is caused by aberrant non-receptor tyrosine kinase (c-Abl) signaling, plays a key role in the progression of β-cell loss in diabetes mellitus. Recent studies, however, have linked ferroptotic-like death to the β-cell loss in diabetes mellitus. Here, we report that oxidative stress-driven reduced/oxidized glutathione (GSH/GSSG) loss and proteasomal degradation of glutathione peroxidase 4 (GPX4) promote ferroptotic-like cell damage through increased lipid peroxidation. Mechanistically, treatment with GNF2, a non-ATP competitive c-Abl kinase inhibitor, selectively preserves β-cell function by inducing the orphan nuclear receptor estrogen-related receptor gamma (ERRγ). ERRγ-driven glutaminase 1 (GLS1) expression promotes the elevation of the GSH/GSSG ratio, and this increase leads to the inhibition of lipid peroxidation by GPX4. Strikingly, pharmacological inhibition of ERRγ represses the expression of GLS1 and reverses the GSH/GSSG ratio linked to mitochondrial dysfunction and increased lipid peroxidation mediated by GPX4 degradation. Inhibition of GLS1 suppresses the ERRγ agonist DY131-induced GSH/GSSG ratio linked to ferroptotic-like death owing to the loss of GPX4. Furthermore, immunohistochemical analysis showed enhanced ERRγ and GPX4 expression in the pancreatic islets of GNF2-treated mice compared to that in streptozotocin-treated mice. Altogether, our results provide the first evidence that the orphan nuclear receptor ERRγ-induced GLS1 expression augments the glutathione antioxidant system, and its downstream signaling leads to improved β-cell function and survival under oxidative stress conditions.

High throughput screening for compounds to the orphan nuclear receptor NR2F6.

NR2F6 is considered an orphan nuclear receptor since its endogenous ligand has yet to be identified. Recently, NR2F6 has emerged as a novel cancer therapeutic target. NR2F6 has been demonstrated to be upregulated or overexpressed in several cancers. Importantly, Nr2f6-/- mice spontaneously reject tumors and develop host-protective immunological memory, a consequence of NR2F6 acting as an immune checkpoint in effector T cells. Collectively, these data suggest that modulation of NR2F6 activity may have important clinical applications in the fight against cancer. The nuclear receptor superfamily of ligand-regulated transcription factors has proven to be an excellent source of targets for therapeutic intervention of a broad range of diseases. Approximately 15% of FDA approved drugs target NRs, demonstrating their clinical efficacy. To identify small molecule regulators of NR2F6 activity, with the overall goal of immuno-oncology, we developed and initiated a high-throughput cell-based assay that specifically measures the transcriptional activity of NR2F6. We completed automated screening of approximately 666,000 compounds and identified 5,008 initial hits. Further screening efforts, including counterscreening assays, confirmed 128 of these hits, most of which had IC50s of equal to or less than 5μM potencies. Here, we report, for the first time, the identification of several small molecule compounds to the orphan nuclear receptor, NR2F6.

1446-P: Sex-Specific Effects of Nr4a1 in the Pancreatic Beta Cell

A central aspect of type 2 diabetes disease progression is impaired functional β-cell mass. The hyperglycemic and hyperlipidemic environment present in type 2 diabetes corresponds with impaired beta cell function. The orphan nuclear receptor Nr4a1 is critical for fuel utilization in various tissues, however little is known regarding its function in the β-cell. Nr4a1 expression is decreased in the β-cell of rodent models of type 2 diabetes, as well as in primary human islets from type 2 diabetics. Here we demonstrate sex specific effects of β-cell specific Nr4a1 deletion under high fat chow feeding. While female and male βNr4a1-/- mice were no different than wild type controls when fed a standard chow diet, a clear sex dependent difference is observed when fed a high fat diet. High fat fed male βNr4a1-/- have improved fasting and non-fasting blood glucose levels, high fat fed female βNr4a1-/- mice have impaired glucose tolerance as early as two months after beginning high fat feeding. Furthermore, female βNr4a1-/- mice have decreased β-cell mass and improved insulin tolerance. Given the sex specific differences in glucose tolerance, we demonstrated that female mice fed a high fat diet have increased circulating estrogen, and that treatment of INS-1 832/13 cells and primary mouse islets with estradiol resulted in increased expression of Nr4a1 and not the other two Nr4a family members. Our data suggest that Nr4a1 is critical for estrogen mediated maintenance of beta cell function and mass under obesogenic conditions, and that loss of Nr4a1 under conditions of obesity and overnutrition in females results in impaired beta cell compensation and function. Disclosure J.S.Tessem: None. J.Herring: None. Funding National Institutes of Health (1R15DK124835-01A1)

The nuclear receptors SF1 and COUP-TFII cooperate on the Insl3 promoter in Leydig cells.

The insulin-like 3 (INSL3) hormone produced by Leydig cells is essential for proper male sex differentiation, but the regulation of Insl3 expression remains poorly understood. This study describes a new physical and functional cooperation between the nuclear receptors SF1 and COUP-TFII in Insl3 expression. INSL3, a hormone abundantly produced by Leydig cells, is essential for testis descent during fetal life and bone metabolism in adults. The mechanisms regulating Insl3 expression in Leydig cells have been studied in several species but remain poorly understood. To date, only a handful of transcription factors are known to activate the Insl3 promoter and include the nuclear receptors AR, NUR77, COUP-TFII, and SF1, as well as the Krüppel-like factor KLF6. Some of these transcription factors are known to transcriptionally cooperate on the Insl3 promoter, but the mechanisms at play remain unknown. Here, we report that COUP-TFII and SF1 functionally cooperate on the Insl3 promoter from various species but not on the Inha, Akr1c14, Cyp17a1, Hsd3b1, Star, Gsta3, and Amhr2 promoters that are known to be regulated by COUP-TFII and/or SF1. The Insl3 promoter contains species-conserved binding sites for COUP-TFII (-91 bp) and SF1 (-134 bp). Mutation of either the COUP-TFII or the SF1 sequence had no impact on the COUP-TFII/SF1 cooperation, but the mutation of both binding sites abolished the cooperation. In agreement with this, we found that COUP-TFII and SF1 physically interact in Leydig cells. Finally, we report that the transcriptional cooperation is not limited to COUP-TFII and SF1 as it also occurred between all NR2F and NR5A family members. Our data provide new mechanistic insights into the cooperation between the orphan nuclear receptors COUP-TFII and SF1 in the regulation of Insl3 gene expression in Leydig cells.

ERRγ Ligand Regulates Adult Neurogenesis and Depression-like Behavior in a LRRK2-G2019S-associated Young Female Mouse Model of Parkinson's Disease.

Adult neurogenesis, a process controlling the proliferation to maturation of newly generated neurons in the post-developmental brain, is associated with various brain functions and pathogenesis of neuropsychological diseases, such as Parkinson's disease (PD) and depression. Because orphan nuclear receptor estrogen-related receptor γ (ERRγ) plays a role in the differentiation of neuronal cells, we investigated whether an ERRγ ligand enhances adult neurogenesis and regulates depressive behavior in a LRRK2-G2019S-associated mouse model of PD. Young female LRRK2-G2019S mice (7-9weeks old) showed depression-like behavior without dopaminergic neuronal loss in the nigrostriatal pathway nor motor dysfunction. A significant decrease in adult hippocampal neurogenesis was detected in young female LRRK2-G2019S mice, but not in comparable male mice. A synthetic ERRγ ligand, (E)-4-hydroxy-N'-(4-(phenylethynyl)benzylidene)benzohydrazide (HPB2), ameliorated depression-like behavior in young female LRRK2-G2019S mice and enhanced neurogenesis in the hippocampus, as evidenced by increases in the number of bromodeoxyuridine/neuronal nuclei-positive cells and in the intensity and number of doublecortin-positive cells in the hippocampal dentate gyrus (DG). Moreover, HPB2 significantly increased the number of spines and the number and length of dendrites in the DG of young female LRRK2-G2019S mice. Furthermore, HPB2 upregulated brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB) signaling, one of the important factors regulating neurogenesis, as well as phosphorylated cAMP-response element binding protein-positive cells in the DG of young female LRRK2-G2019S mice. Together, these results suggest ERRγ as a novel therapeutic target for PD-associated depression by modulating adult neurogenesis and BDNF/TrkB signaling.

Effects of Estrogens on Osteoimmunology: A Role in Bone Metastasis

Bone loss associated with estrogen deficiency indicates a fundamental role of these hormones in skeletal growth and bone remodeling. In the last decades, growing recent evidence demonstrated that estrogens can also affect the immune compartment of the bone. In this review, we summarize the impacts of estrogens on bone immune cells and their consequences on bone homeostasis, metastasis settlement into the bone and tumor progression. We also addressed the role of an orphan nuclear receptor ERRalpha (“Estrogen-receptor Related Receptor alpha”) on macrophages and T lymphocytes, and as an immunomodulator in bone metastases. Hence, this review links estrogens to bone immune cells in osteo-oncology.

Nuclear receptor Nr1d1 alleviates asthma by abating GATA3 gene expression and Th2 cell differentiation.

Nuclear receptors are a unique family of transcription factors that play cardinal roles in physiology and plethora of human diseases. The adopted orphan nuclear receptor Nr1d1 is a constitutive transcriptional repressor known to modulate several biological processes. In this study, we found that Nr1d1 plays a decisive role in T helper (Th)-cell polarization and transcriptionally impedes the formation of Th2 cells by directly binding to the promoter region of GATA binding protein 3 (GATA3) gene. Nr1d1 interacts with its cellular companion, the nuclear receptor corepressor and histone deacetylase 3 to form a stable repression complex on the GATA3 promoter. The presence of Nr1d1 also imparts protection against associated inflammatory responses in murine model of asthma and its ligand SR9011 eased disease severity by suppressing Th2 responses. Moreover, Chip-seq profiling uncovered Nr1d1 interactions with other gene subsets that impedes Th2-linked pathways and regulates metabolism, immunity and brain functions, therefore, providing empirical evidence regarding the genetic link between asthma and other comorbid conditions. Thus, Nr1d1 emerges as a molecular switch that could be targeted to subdue asthma.

Retinoid orphan nuclear receptor alpha (RORα) suppresses the epithelial–mesenchymal transition (EMT) by directly repressing Snail transcription

Retinoid orphan nuclear receptor alpha (RORα) is a member of the orphan nuclear factor family and regulates gene expression by binding to ROR response elements (ROREs). RORα has been identified as a potential tumor suppressor; however, how downregulation of RORα promotes cancer progression is not fully understood. Here, we showed that protein levels of RORα were downregulated during the Snail-, Twist-, or transforming growth factor-β–induced epithelial–mesenchymal transition (EMT). We found that silencing of RORα induced expression of mesenchymal markers in MCF10A cells, accompanied by enhanced cell invasion, migration, and mammosphere formation. Furthermore, ectopic expression of RORα suppressed transforming growth factor-β–induced EMT processes in MCF10A and HMLE cells. These results indicate that downregulation of RORα is crucial for the induction of EMT in mammary epithelial cells. By analyzing gene expression profiles in control and RORα-expressing cells, we also identified Snail, a key regulator of EMT, as a potential target of RORα. We show that RORα expression significantly inhibits Snail transcription in breast cancer cells. Chromatin immunoprecipitation analysis demonstrated that RORα bound to the ROREs in promoter region of SNAI1 gene, and using the luciferase reporter assay, we showed that binding to the ROREs was critical for RORα to repress Snail transcription. Finally, rescue experiments substantiated that Snail mediates RORα function in suppressing EMT and mammosphere formation. These results reveal a novel function of RORα in suppressing EMT and identify Snail as a direct target of RORα in mammary epithelial cells.

COUP-TFII in Kidneys, from Embryos to Sick Adults.

Chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) is an orphan nuclear hormone receptor of unknown ligands. This molecule has two interesting features: (1) it is a developmental gene, and (2) it is a potential hormone receptor. Here, we describe the possible roles of COUP-TFII in the organogenesis of the kidneys and protection from adult renal diseases, primarily in mouse models. COUP-TFII is highly expressed in embryos, including primordial kidneys, and is essential for the formation of metanephric mesenchyme and the survival of renal precursor cells. Although the expression levels of COUP-TFII are low and its functions are unknown in healthy adults, it serves as a reno-protectant molecule against acute kidney injury. These are good examples of how developmental genes exhibit novel functions in the etiology of adult diseases. We also discuss the ongoing research on the roles of COUP-TFII in podocyte development and diabetic kidney disease. In addition, the identification of potential ligands suggests that COUP-TFII might be a novel therapeutic target for renal diseases in the future.

Plant Alkaloid Tetrandrine Is a Nuclear Receptor 4A1 Antagonist and Inhibits Panc-1 Cell Growth In Vitro and In Vivo.

The orphan nuclear receptor 4A1 (NR4A1) is highly expressed in human pancreatic cancer cells and exerts pro-oncogenic activity. In a previous study, we demonstrated that fangchinoline (FCN), a natural inhibitor of nuclear NR4A1, induces NR4A1-dependent apoptosis in human pancreatic cancer cells. In this study, we evaluated FCN and its structural analogs (berbamine, isotetrandrine, tetrandrine, and tubocurarine) for their inhibitory effects on NR4A1 transactivity, and confirmed that tetrandrine (TTD) showed the highest inhibitory effect in pancreatic cancer cells. Moreover, in a tryptophan fluorescence quenching assay, TTD directly bound to the ligand binding domain (LBD) of NR4A1 with a KD value of 10.60 μM. Treatment with TTD decreased proliferation and induced apoptosis in Panc-1 human pancreatic cancer cells in part through the reduced expression of the Sp1-dependent anti-apoptotic gene survivin and induction of ROS-mediated endoplasmic reticulum stress, which are the well-known NR4A1-dependent proapoptotic pathways. Furthermore, at a dose of 25 mg/kg/day, TTD reduced tumor growth in an athymic nude mouse xenograft model bearing Panc-1 cells. These data show that TTD is an NR4A1 antagonist and that modulation of the NR4A1-mediated pro-survival pathways is involved in the antitumor effects of TTD.