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Nur77 Family of Nuclear Hormone Receptors
Abstract
Among the numerous steroidal and orphan nuclear receptors encoded within mammalian genomes, several are involved in the regulation of apoptosis. The authors review here recent studies on members of the Nur77 family of orphan receptors including Nur77, Nurr1 and Nor-1. These transcription factors were initially identified in nerve cells, but also play key roles in the development and the effector functions of T lymphocytes and other cells and tissues. Nur77 can also act as a modulator of transcription for other orphan steroid receptors. Regulation of the Nur77 orphan receptor family members are tightly associated with transcriptional co-factors including co-repressors and co-activators. Also, one interesting aspect of the Nur77 orphan receptor family members is that depending on its location in the mitochondria or nucleus, these orphan receptors exhibit differential roles in determining cell death or cell growth. Numerous studies demonstrated the importance of Nur77 subfamily members in regulations of early embryogenesis, thymocyte negative selection, gene expression in hypothalamic-pituitary adrenal axis, chronic inflammatory response, and vascular smooth muscle cell proliferation. This review intends to integrate the importance of nuclear receptors in health and disease, and as potential targets for drug discovery by comparing the difference and similarity in the biochemical mechanisms of action used by the classic steroid/endocrine receptors and the orphan receptors to lead to identification of novel targets in manipulating the transcriptional functions and physiologic pathways for the orphan nuclear receptors.
... The NR4A family of orphan nuclear receptors is comprised of three members: Nur77 (NR4A1; also known as TR3 and NGFI-B), Nurr1 (NR4A2; also known as NOT), and NOR1 (NR4A3; also known as MINOR). Initially identified more than ten years ago as early response genes to growth factors [1][2][3], these proteins are expressed in many different tissues and cell types, including liver, kidney, heart, skeletal muscle, brain, and macrophages [4][5][6]. ...
... Members of the NR4A family can activate gene expression in a ligand-independent manner, but the identities of target genes in many cells remain largely unknown. NR4A proteins can bind to their cognate DNA binding sites as monomers, homodimers, as heterodimers with other NR4A family members or-in the case of Nur77 and Nurr1-as heterodimers with RXR [4,6]. ...
... NR4A receptors are expressed in wide variety of cell types and tissues, including brain, liver, muscle, pituitary cells, adipose tissue, kidney, and macrophages [4,6]. Because they function in a ligand-independent manner, changes in NR4A expression are a major determinant of their activity as transcriptional regulators. ...
... The nuclear receptor IV subfamily members play redundant roles in TCR-mediated apoptosis [21] and brown fat thermogenesis [22,23]. However, they play different roles in development (reviewed in [24]). TR3/Nur77 also plays important roles in cancer cell biology, inflammation, metabolism diseases, stress and addiction (reviewed in [25][26][27][28]). ...
... We then generated serial deletion mutants, TR3∆ (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), TR3∆ (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40), TR3∆(41-60), TR3∆(61-80) and TR3∆(101-120), in which amino acid residues 1-20, 21-40, 41-60, 61-80 and 101-120 of TR3 were deleted ( Figure 4A). These mutants were expressed to similar levels in HUVECs ( Figure 4B) and subjected to actin stress fiber analysis, cell proliferation, migration, and monolayer permeability assays. ...
... These mutants were expressed to similar levels in HUVECs ( Figure 4B) and subjected to actin stress fiber analysis, cell proliferation, migration, and monolayer permeability assays. The data show that TR3∆(41-60) is unable, but TR3∆(1-20), TR3∆ (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40), TR3∆(61-80) and TR3∆(101-120), in a manner similar to TR3, are able to induce the formation of actin stress fibers ( Figure 4C), cell proliferation, migration and permeability ( Figure 4D, 4E and 4F, 5 vs. 1, p > 0.05, all others vs. 1, p < 0.005, and Supplemental Figure 5S). These data indicate that the amino acid residues 41-60 is required for the angiogenic responses of TR3. ...
Pathological angiogenesis is a hallmark of many diseases. We demonstrated that TR3/Nur77 is an excellent target for pro-angiogenesis and anti-angiogenesis therapies. Here, we report that TR3 transcriptionally regulates endothelial cell migration, permeability and the formation of actin stress fibers that is independent of RhoA GTPase. 1) Amino acid residues 344-GRR-346 and de-phosphorylation of amino acid residue serine 351 in the DNA binding domain, and 2) phosphorylation of amino acid residues in the 41-61 amino acid fragment of the transactivation domain, of TR3 are required for its induction of the formation of actin stress fibers, cell proliferation, migration and permeability. The 41-61 amino acid fragment contains one of the three potential protein interaction motifs in the transactivation domain of TR3, predicted by computational modeling and analysis. These studies further our understanding of the molecular mechanism, by which TR3 regulates angiogenesis, identify novel therapeutic targeted sites of TR3, and set the foundation for the development of high-throughput screening assays to identify compounds targeting TR3/Nur77 for pro-angiogenesis and anti-angiogenesis therapies.
... TR3/Nur77 (human: TR3, mouse: Nur77, rat: NGFI-B) belongs to nuclear receptor IV subfamily of transcription factors including TR3/Nur77, NOT1/Nurr1, and NOR1, all of which contain 3 functional domains, the transactivation domain, the DNA-binding domain, and the ligand-binding domain [see review by Hsu et al. (7)]. They are highly homologous in the DNA binding domain (.97%) but have much less similarity in the transactivation domains [,30%; reviewed by Hsu et al. (7)]. ...
... TR3/Nur77 (human: TR3, mouse: Nur77, rat: NGFI-B) belongs to nuclear receptor IV subfamily of transcription factors including TR3/Nur77, NOT1/Nurr1, and NOR1, all of which contain 3 functional domains, the transactivation domain, the DNA-binding domain, and the ligand-binding domain [see review by Hsu et al. (7)]. They are highly homologous in the DNA binding domain (.97%) but have much less similarity in the transactivation domains [,30%; reviewed by Hsu et al. (7)]. ...
... Due to their high homology in the DNA binding domain, they presumably regulate expression of similar genes, which may explain why they play redundant roles in T-cell receptor-mediated apoptosis and brown fat thermogenesis. However, they also play different roles in development [reviewed by Hsu et al. (7)]. ...
Tissue repair/wound healing, in which angiogenesis plays an important role, is a critical step in many diseases including chronic wound, myocardial infarction, stroke, cancer, and inflammation. Recently, we were the first to report that orphan nuclear receptor TR3/Nur77 is a critical mediator of angiogenesis and its associated microvessel permeability. Tumor growth and angiogenesis induced by VEGF-A, histamine, and serotonin are almost completely inhibited in Nur77 knockout mice. However, it is not known whether TR3/Nur77 plays any roles in wound healing. In these studies, skin wound-healing assay was performed in 3 types of genetically modified mice having various Nur77 activities. We found that ectopic induction of Nur77 in endothelial cells of mice is sufficient to improve skin wound healing. Although skin wound healing in Nur77 knockout mice is comparable to the wild-type control mice, the process is significantly delayed in the EC-Nur77-DN mice, in which a dominant negative Nur77 mutant is inducibly and specifically expressed in mouse endothelial cells. By a loss-of-function assay, we elucidate a novel feed-forward signaling pathway, integrin β4 → PI3K → Akt → FAK, by which TR3 mediates HUVEC migration. Furthermore, TR3/Nur77 regulates the expression of integrin β4 by targeting its promoter activity. In conclusion, expression of TR3/Nur77 improves wound healing by targeting integrin β4. TR3/Nur77 is a potential candidate for proangiogenic therapy. The results further suggest that TR3/Nur77 is required for pathologic angiogenesis but not for developmental/physiologic angiogenesis and that Nur77 and its family members play a redundant role in normal skin wound healing.-Niu, G., Ye, T., Qin, L., Bourbon, P. M., Chang, C., Zhao, S., Li, Y., Zhou, L., Cui, P., Rabinovitz, I., Mercurio, A. M., Zhao, D., Zeng, H. Orphan nuclear receptor TR3/Nur77 improves wound healing by upregulating the expression of integrin β4.
... The endothelium functions as functional barrier between the blood and out layer of vascular wall and critical for the maintaining of vascular tone [1]. Cardiovascular risk factors, such as hypercholesterolemia, obesity, and diabetes, initiate vascular inflammation and endothelial dysfunction, thus enhancing the development of cardiovascular disease, such as atherosclerosis and hypertension [1,23]. ...
... Orphan nuclear receptor 4A members (NR4As) are first identified as immediate early-response genes and their expression is induced by various external stimuli, including growth factors, inflammatory cytokines, and hormones [23]. NR4As consist of three members, namely Nur77 (NR4A1), Nurr1 (NR4A2), and NOR-1 (NR4A3). ...
Background
Nur77 belongs to the member of orphan nuclear receptor 4A family that plays critical roles in maintaining vascular homeostasis. This study aims to determine whether Nur77 plays a role in attenuating vascular dysfunction, and if so, to determine the molecular mechanisms involved.
Methods
Both Nur77 knockout (Nur77 KO) and Nur77 endothelial specific transgenic mice (Nur77-Tg) were employed to examine the functional significance of Nur77 in vascular endothelium in vivo. Endothelium-dependent vasodilatation to acetylcholine (Ach) and reactive oxygen species (ROS) production was determined under inflammatory and high glucose conditions. Expression of genes was determined by real-time PCR and western blot analysis.
Results
In response to tumor necrosis factor alpha (TNF-α) treatment and diabetes, the endothelium-dependent vasodilatation to Ach was significantly impaired in aorta from Nur77 KO as compared with those from the wild-type (WT) mice. Endothelial specific overexpression of Nur77 markedly prevented both TNF-α- and high glucose-induced endothelial dysfunction. Compared with WT mice, after TNF-α and high glucose treatment, ROS production in aorta was significantly increased in Nur77 KO mice, but it was inhibited in Nur77-Tg mice, as determined by dihydroethidium (DHE) staining. Furthermore, we demonstrated that Nur77 overexpression substantially increased the expression of several key enzymes involved in nitric oxide (NO) production and ROS scavenging, including endothelial nitric oxide synthase (eNOS), guanosine triphosphate cyclohydrolase 1 (GCH-1), glutathione peroxidase-1 (GPx-1), and superoxide dismutases (SODs). Mechanistically, we found that Nur77 increased GCH1 mRNA stability by inhibiting the expression of microRNA-133a, while Nur77 upregulated SOD1 expression through directly binding to the human SOD1 promoter in vascular endothelial cells.
Conclusion
Our results suggest that Nur77 plays an essential role in attenuating endothelial dysfunction through activating NO production and anti-oxidant pathways in vascular endothelium. Targeted activation of Nur77 may provide a novel therapeutic approach for the treatment of cardiovascular diseases associated with endothelial dysfunction.
... The nuclear receptor IV subfamily members play redundant roles in TCR-mediated apoptosis [21] and brown fat thermogenesis [22,23]. However, they play different roles in development (reviewed in [24]). TR3/Nur77 also plays important roles in carcinogenesis, inflammation, metabolism diseases, stress, and addiction (reviewed in [25][26][27][28]). ...
... TR3/Nur77 is an orphan nuclear receptor, without physiological ligand, which activities are regulated at transcriptional [24,56,57] and post-transcriptional levels [58][59][60]. In the presence of actinomycin D1, up-regulation of TR3 variants by VEGF and histamine are completely inhibited, indicating that these three TR3 transcript variants are regulated by transcription, which are further confirmed by the promoter luciferase studies. ...
Pathological angiogenesis is a hallmark of many diseases. Previously, we reported that orphan nuclear receptor TR3/Nur77 (human homolog, Nur77, mouse homolog) is a critical mediator of angiogenesis to regulate tumor growth and skin wound healing via down-regulating the expression of the junctional proteins and integrin β4. However, the molecular mechanism, by which TR3/Nur77 regulated angiogenesis, was still not completely understood. In this report by analyzing the integrin expression profile in endothelial cells, we found that the TR3/Nur77 expression highly increased the expression of integrins α1 and β5, decreased the expression of integrins α2 and β3, but had some or no effect on the expression of integrins αv, α3, α4, α5, α6, β1 and β7. In the angiogenic responses mediated by TR3/Nur77, integrin α1 regulated endothelial cell proliferation and adhesion, but not migration. Integrin β5 shRNA inhibited cell migration, but increased proliferation and adhesion. Integrin α2 regulated all of the endothelial cell proliferation, migration and adhesion. However, integrin β3 did not play any role in endothelial cell proliferation, migration and adhesion. TR3/Nur77 regulated the transcription of integrins α1, α2, β3 and β5, via various amino acid fragments within its transactivation domain and DNA binding domain. Furthermore, TR3/Nur77 regulated the integrin α1 promoter activity by directly interacting with a novel DNA element within the integrin α1 promoter. These studies furthered our understanding of the molecular mechanism by which TR3/Nur77 regulated angiogenesis, and supported our previous finding that TR3/Nur77 was an excellent therapeutic target for pathological angiogenesis. Therefore, targeting TR3/Nur77 inhibits several signaling pathways that are activated by various angiogenic factors.
... A mutation in the TCA codon for amino acid residue 130 (tyrosine 130, Y130), which produces a stop codon (TAA) in the Nur77 coding sequence (Y130/Stop) (see Fig. 2A), has been identified and selected. This generates a truncated nonfunctional protein lacking multiple domains that are essential for its activity (Hsu et al., 2004). The rat strain is denominated FHH-Nr4a1 m1Mcwi and was generously provided by Transposagen Biopharmaceutical Inc. (Lexington, KY, USA), and the NIH Rat Knockout Consortium Program (http://www.transposagenbio.com/knock-out-rat-consortium/). ...
... interface (Hsu et al., 2004). Behavioral comparison of FHH-Nr4a1 m1Mcwi mutant and wild type rats indicates no gross behavioral deficit. ...
Parkinson's disease (PD) is an idiopathic progressive neurodegenerative disorder characterized by the loss of midbrain dopamine neurons. Levodopa (l-dopa) is the main pharmacological approach to relieve PD motor symptoms. However, chronic treatment with l-Dopa is inevitably associated with the generation of abnormal involuntary movements (l-Dopa-induced dyskinesia). We have previously shown that Nr4a1 (Nur77), a transcription factor of the nuclear receptor family, is closely associated with dopamine neurotransmission in the mature brain. However, the role of Nr4a1 in the etiology of PD and its treatment remain elusive. We report here that the neurotoxin 6-hydroxydopamine in rat lead to a rapid up-regulation of Nr4a1 in the substantia nigra. Genetic disruption of Nr4a1 in rat reduced neurotoxin-induced dopamine cell loss and l-Dopa-induced dyskinesia, whereas virally-driven striatal overexpression of Nr4a1 enhanced or partially restored involuntary movements induced by chronic l-Dopa in wild type and Nr4a1-deficient rats, respectively. Collectively, these results suggest that Nr4a1 is involved in dopamine cell loss and l-dopa-induced dyskinesia in experimental PD.
... The nuclear receptor IV subfamily members play redundant roles in TCR-mediated apoptosis [21] and brown fat thermogenesis [22,23]. However, they play different roles in development (reviewed in [24]). TR3/Nur77 also plays important roles in carcinogenesis, inflammation, metabolism diseases, stress, and addiction (reviewed in [25][26][27][28]). ...
... TR3/Nur77 is an orphan nuclear receptor, without physiological ligand, which activities are regulated at transcriptional [24,56,57] and post-transcriptional levels [58][59][60]. In the presence of actinomycin D1, up-regulation of TR3 variants by VEGF and histamine are completely inhibited, indicating that these three TR3 transcript variants are regulated by transcription, which are further confirmed by the promoter luciferase studies. ...
TR3 has been reported to be an excellent target for angiogenesis therapies. We reported three TR3 transcript variant messenger RNAs (mRNAs) are expressed in human umbilical vein endothelial cell (HUVEC) and are differentially regulated by vascular endothelial growth factor (VEGF). TR3 transcript variant 1 (TR3-TV1) and variant 2 (TR3-TV2) encoding the same TR3 isoform 1 protein (TR3-iso1) that was named TR3 has been extensively studied. However, the function of TR3 isoform 2 protein (TR3-iso2) encoded by TR3 transcript variant 3 (TR3-TV3) is still not known. Here, we clone and express the novel TR3-iso2 protein and find that expression of TR3-iso2, in contrast to TR3-iso1, inhibits endothelial cell proliferation induced by VEGF-A, histamine, and phorbol-12-myristate-13-acetate (PMA). The differential function of TR3-iso2 correlates with the down-regulation of cyclin D1. However, TR3-iso2 plays similar roles in endothelial cell migration and monolayer permeability as TR3-iso1. We further demonstrate that several intracellular signaling pathways are involved in histamine-induced TR3 transcript variants, including histamine receptor H1-mediated phospholipase C (PLC)/calcium /calcineurin/protein kinase C (PKC)/protein kinase D (PKD) pathway and ERK pathway, as well as histamine receptor H3-mediated PKC-ERK pathway. Further, expressions of TR3-TV1, TR3-TV2, and TR3-TV3 by VEGF and histamine are regulated by different promoters, but not by their mRNA stability.
... The effects of psychostimulants on the expression of the Nr4a IEG family [27] have been less well studied [30]. That family consists of Nr4a1 (Nur77), Nr4a2 (Nurr1), and Nr4a3 (Nor-1) [20,27]. Acute METH was shown to cause increases in their expression in the dorsal striatum whereas those stimulatory effects were blunted by chronic pre-exposure to METH [30]. ...
... The present study was conducted to test the regional generalizability of the chronic psychostimulant-induced mRNA blunting phenomena by investigating the effects of acute and chronic METH on the expression of AP-1 [46] and Nr4a [20] IEGs in the NAc and midbrain of rats. Herein, we report that acute METH administration increased the levels of several IEGs in both structures. ...
The present study investigated whether chronic methamphetamine (METH) would suppress METH- induced mRNA expression of immediate early genes (IEGs) in the rat brain. Rats were given METH or saline over two weeks. After an overnight withdrawal, saline- and METH-pretreated rats received an acute saline or METH challenge. The acute METH challenge increased expression of members of activator protein 1 (AP-1) and Nr4a IEG families in the nucleus accumbens (NAc) and midbrain of saline-pretreated rats. Chronic METH exposure attenuated the effects of acute METH challenge on AP-1 IEG expression in the NAc. However, chronic METH failed to attenuate acute METH-induced increases of Nr4a1 and Nr4a3 expression in the NAc. In contrast to observations in the NAc, chronic METH did not prevent acute METH- induced changes in IEG expression in the midbrain. These results suggest that these two brain regions that are implicated in neuroplastic effects of illicit substances might be differentially affected by psychostimulants.
... NR4A receptors are immediate-early genes that are regulated by many physiological stimuli including growth factors, hormones, and inflammatory signals and are involved in a wide array of important biological processes, including cell apoptosis, brain development, glucose metabolism, and vascular remodeling [1,2]. The NR4A subfamily consists of 3 wellconserved members, Nur77 (NR4A1), Nurr1 (NR4A2), and NOR-1 (NR4A3), respectively [1]. ...
... NR4A receptors are immediate-early genes that are regulated by many physiological stimuli including growth factors, hormones, and inflammatory signals and are involved in a wide array of important biological processes, including cell apoptosis, brain development, glucose metabolism, and vascular remodeling [1,2]. The NR4A subfamily consists of 3 wellconserved members, Nur77 (NR4A1), Nurr1 (NR4A2), and NOR-1 (NR4A3), respectively [1]. So far, no ligands have been identified for these receptors and therefore they are classified as orphan receptors. ...
... It is also of interest to discuss the effects of acute and chronic effects of METH on Nr4a3 expression in contrast to the observations with Crem and Egr2 discussed above. Nr4a3 is a member of Nr4a1/Nur77 family of transcription factors (Nr4a1/Nur77/NGFIB, Nr4a2/ Nurr1 and Nr4a3/Nor-1) that belong the superfamily of steroid nuclear hormone receptor superfamily [71,72]. They participate in a number of biological functions including cellular proliferation, differentiation, and apoptosis [71,72]. ...
... Nr4a3 is a member of Nr4a1/Nur77 family of transcription factors (Nr4a1/Nur77/NGFIB, Nr4a2/ Nurr1 and Nr4a3/Nor-1) that belong the superfamily of steroid nuclear hormone receptor superfamily [71,72]. They participate in a number of biological functions including cellular proliferation, differentiation, and apoptosis [71,72]. Nr4a3 also regulates axonal guidance and pyramidal cell survival in the hippocampus [73]. ...
METH is an illicit drug of abuse that influences gene expression in the rat striatum. Histone modifications regulate gene transcription.
We therefore used microarray analysis and genome-scale approaches to examine potential relationships between the effects of METH on gene expression and on DNA binding of histone H4 acetylated at lysine 4 (H4K5Ac) in the rat dorsal striatum of METH-naive and METH-pretreated rats.
Acute and chronic METH administration caused differential changes in striatal gene expression. METH also increased H4K5Ac binding around the transcriptional start sites (TSSs) of genes in the rat striatum. In order to relate gene expression to histone acetylation, we binned genes of similar expression into groups of 100 genes and proceeded to relate gene expression to H4K5Ac binding. We found a positive correlation between gene expression and H4K5Ac binding in the striatum of control rats. Similar correlations were observed in METH-treated rats. Genes that showed acute METH-induced increased expression in saline-pretreated rats also showed METH-induced increased H4K5Ac binding. The acute METH injection caused similar increases in H4K5Ac binding in METH-pretreated rats, without affecting gene expression to the same degree. Finally, genes that showed METH-induced decreased expression exhibited either decreases or no changes in H4K5Ac binding.
Acute METH injections caused increased gene expression of genes that showed increased H4K5Ac binding near their transcription start sites.
... Since P-bodies are cytoplasmic granules that mediate RNA decay, and because NR4A1 has 2 highly conserved Cys 4 zinc fingers in its DBD, which might have RNA-binding capacity, we hypothesized that NR4A1 might function as an RBP that regulates the stability of mRNA [19,20]. We performed RBP immunoprecipitation sequencing (RIP-seq) to determine NR4A1-RNA associations. ...
Microglia-mediated neuroinflammation is involved in various neurological diseases, including ischemic stroke, but the endogenous mechanisms preventing unstrained inflammation is still unclear. The anti-inflammatory role of transcription factor nuclear receptor subfamily 4 group A member 1 (NR4A1) in macrophages and microglia has previously been identified. However, the endogenous mechanisms that how NR4A1 restricts unstrained inflammation remain elusive. Here, we observed that NR4A1 is up-regulated in the cytoplasm of activated microglia and localizes to processing bodies (P-bodies). In addition, we found that cytoplasmic NR4A1 functions as an RNA-binding protein (RBP) that directly binds and destabilizes Tnf mRNA in an N6-methyladenosine (m6A)-dependent manner. Remarkably, conditional microglial deletion of Nr4a1 elevates Tnf expression and worsens outcomes in a mouse model of ischemic stroke, in which case NR4A1 expression is significantly induced in the cytoplasm of microglia. Thus, our study illustrates a novel mechanism that NR4A1 posttranscriptionally regulates Tnf expression in microglia and determines stroke outcomes.
... Further research on the molecular mechanism of melanoma and the development of novel therapeutics with high efficiency and low toxicity is highly desired. Nur77 is an orphan nuclear receptor that widely expressed in different types of tumors, including melanoma (Hsu et al., 2004;To et al., 2012). Nur77 plays diverse roles in the regulation of cell proliferation, survival, and apoptosis Wu and Chen, 2018;Safe and Karki, 2021). ...
Introduction: Venlafaxine is one of the most commonly used anti-depressant and antineoplastic drug. Previous studies have predicted venlafaxine as an anti-cancer compound, but the therapeutic effects of venlafaxine in melanoma have not yet been demonstrated. Nur77 is an orphan nuclear receptor that highly expressed in melanoma cells and can interact with Bcl-2 to convert Bcl-2 from an antiapoptotic to a pro-apoptotic protein.
Method: We examined the effects of venlafaxine in MV3 cells in vitro and MV3 xenograft tumor in nude mice. Western-blot, PCR, TUNEL assay and immunofluorescence were used to reveal the growth of melanoma cells.
Results: Here, our data revealed that venlafaxine could reduce the growth, and induce apoptosis of melanoma cells through a Nur77-dependent way. Our results also showed that treatment with venlafaxine (20 mg/kg, i.p.) potently inhibited the growth of melanoma cells in nude mice. Mechanistically, venlafaxine activated JNK1/2 signaling, induced Nur77 expressions and mitochondrial localization, thereby promoting apoptosis of melanoma cells. Knockdown of Nur77 and JNK1/2, or inhibition of JNK1/2 signaling with its inhibitor SP600125 attenuated the anti-cancer effects of venlafaxine.
Conclusion: In summary, our results suggested venlafaxine as a potential therapy for melanoma.
... First, IL-4Rα blockade upregulates several members of the NUR77 orphan nuclear receptor genes including NR4A1 and NR4A2. This pathway restrains B cell receptor signaling [59] in a fashion we previously showed that restrains TCR signaling [63][64][65]. Such limitation of BCR signaling has been well described to limit the expansion of B cells in the early GC to curb immunodominance when B cells compete with each other in a limited niche [66]. ...
Here, we report a case of atopic dermatitis (AD) in a patient who received biweekly doses of dupilumab, an antibody against the IL-4 receptor α chain (IL-4Rα). Single cell RNA-sequencing showed that naïve B cells expressed the highest levels of IL4R compared to other B cell subpopulations. Compared to controls, the dupilumab-treated patient exhibited diminished percentages of IL4R + IGHD+ naïve B cells and down-regulation of IL4R, FCER2 (CD23), and IGHD. Dupilumab treatment resulted in upregulation of genes associated with apoptosis and inhibition of B cell receptor signaling and down-regulation of class-switch and memory B cell development genes. The dupilumab-treated patient exhibited a rapid decline in COVID-19 anti-spike and anti-receptor binding domain antibodies between 4 and 8 and 11 months post COVID-19 vaccination. Our data suggest that intact and persistent IL-4 signaling is necessary for maintaining robust survival and development of naïve B cells, and maintaining a long term vaccine response.
... The NR subfamily 4 (NR4A) group contains three proteins with no known physiologic ligands: NR4A1 (Nur77/Tr3), NR4A2 (Nurr1), and NR4A3 (Nor1) [130][131][132][133]. Their crystallographic structure suggests that the ligand binding pocket is occupied by hydrophobic amino acid side chains that preclude the binding with endogenous ligands [134]. ...
Nuclear receptors (NRs), are a wide family of ligand-regulated transcription factors sharing a common modular structure composed by an N-terminal domain and a ligand-binding domain connected by a short hinge linker to a DNA-binding domain. NRs are involved in many physiological processes, including metabolism, reproduction and development. Most of them respond to small lipophilic ligands, such as steroids, retinoids, and phospholipids, which act as conformational switches. Some NRs are still “orphan” and the search for their ligands is still ongoing. Upon DNA binding, NRs can act both as transcriptional activators or repressors of their target genes. Theoretically, the possibility to modulate NRs activity with small molecules makes them ideal therapeutic targets, although the complexity of their signaling makes drug design challenging. In this review, we discuss the role of NRs in erythropoiesis, in both homeostatic and stress conditions. This knowledge is important in view of modulating red blood cells production in disease conditions, such as anemias, and for the expansion of erythroid cells in culture for research purposes and for reaching the long-term goal of cultured blood for transfusion.
... Nur77 and the other Nr4a members share the structural organization common to most nuclear receptors. This structure consists of the N-terminal domain containing the Activation Function-1 (AF-1), the DNA-binding domain (DBD) and the C-terminal domain containing the ligand binding domain (LBD) and the transcriptional activation function-2 (AF-2) [4]. Nur77 and the other Nr4a family members can bind DNA as monomers to the NGFI-B response element (NBRE; AAAGGTCA) and as homodimers or heterodimers with another Nr4a family member to the synthetic consensus Nur-response element (NurRE; TGACCTTTX 6 AAAGGTCA). ...
Nur77 (NGFI-B) is a nuclear receptor that belongs to the Nr4a family of orphan nuclear receptors (Nr4a1). This transcription factor has been implicated in the regulation of multiple functions, such as cell cycle regulation, apoptosis, inflammation, glucose and lipid metabolism, and brain function. However, the mechanisms involved in its different regulatory properties remain unclear. In search for regulatory mechanisms of Nur77 function, we identified that Protein Inhibitor of Activated STAT gamma (PIASγ), an E3 SUMO-protein ligase, potently repressed Nur77 transcriptional activity in HEK-293T cells. This PIASγ activity was sensitive to Sentrin SUMO-specific protease 1 (SENP1). Substitution of two putative phylogenetically well-conserved small ubiquitin-like modifier (SUMO) acceptor sites, lysine 102 (K102) and 577 (K577) by arginine residues (R) modulated Nur77 transcriptional activity. In particular, Nur77-K102R and Nur77-K102R/K577R mutants strongly decreased the transcriptional activity of Nur77, whereas single K577R substitution increased transcriptional activity of Nur77. Repression of Nur77 transcriptional activity by SUMO2 and PIASγ was reduced by the K577R mutation, whereas the K102R mutant remained insensitive to SUMO2. Interestingly, the roles of these SUMO acceptor sites in Nur77 are distinct from previously observed activities on its close homolog Nurr1. Thus, the present study identified SUMO2 and PIASγ as important transcriptional co-regulators of Nur77.
... Nur77 (NR4A1, TR3 or NGFIB) is a key member of the Nuclear receptor 4A (NR4A) receptor subfamily. This subfamily of nuclear receptors plays crucial roles in various biological processes, including early embryogenesis regulation, thymocytes negative selection, gene expression in hypothalamic-pituitary adrenal axis, chronic inflammatory response, and vascular smooth muscle cell proliferation [200][201][202][203]. They are orphan receptors (no known endogenous ligand) and lack a conventional DNA binding domain. ...
Cytokine storm generates during various systemic acute infections, including sepsis and current pandemic called COVID-19 (severe) causing devastating inflammatory conditions, which include multi-organ failure or multi-organ dysfunction syndrome (MODS) and death of the patient. Toll-like receptors (TLRs) are one of the major pattern recognition receptors (PRRs) expressed by immune cells as well as non-immune cells, including neurons, which play a crucial role in generating cytokine storm. They recognize microbial-associated molecular patterns (MAMPs, expressed by pathogens) and damage or death-associate molecular patterns (DAMPs; released and/expressed by damaged/killed host cells). Upon recognition of MAMPs and DAMPs, TLRs activate downstream signaling pathways releasing several pro-inflammatory mediators [cytokines, chemokines, interferons, and reactive oxygen and nitrogen species (ROS or RNS)], which cause acute inflammation meant to control the pathogen and repair the damage. Induction of an exaggerated response due to genetic makeup of the host and/or persistence of the pathogen due to its evasion mechanisms may lead to severe systemic inflammatory condition called sepsis in response to the generation of cytokine storm and organ dysfunction. The activation of TLR-induced inflammatory response is hardwired to the induction of several negative feedback mechanisms that come into play to conclude the response and maintain immune homeostasis. This state-of-the-art review describes the importance of TLR signaling in the onset of the sepsis-associated cytokine storm and discusses various host-derived endogenous negative regulators of TLR signaling pathways. The subject is very important as there is a vast array of genes and processes implicated in these negative feedback mechanisms. These molecules and mechanisms can be targeted for developing novel therapeutic drugs for cytokine storm-associated diseases, including sepsis, severe COVID-19, and other inflammatory diseases, where TLR-signaling plays a significant role.
... NR4A1 (NUR77) is a member of the steroid hormone nuclear receptor superfamily, but specific ligands for this receptor have not yet been identified. NUR77 activates target genes as a transcription factor or induces apoptosis depending upon the stimulus [11]. A number of studies have found that NUR77 family members share a highly conserved DNA binding domain consisting of two C4 zinc fingers that recognize its cognate sequence. ...
NR4A1 (NUR77) is an orphan nuclear receptor that has been implicated in both cell survival and apoptosis. However, the role of NUR77 in trophoblast function during early placenta development has not been fully elucidated. In this study, we showed that NUR77 expression was significantly lower in the villi of the recurrent miscarriage (RM) group compared to that in the healthy controls (HCs) group. We used immunohistochemistry and found that NUR77 was highly expressed in human placental villi during early pregnancy, especially in syncytiotrophoblast (STB), and was expressed at a much lower level in STB from the RM group than in those from HC group. Western blotting data further confirmed that NUR77 was highly expressed in primary human term placental STB and the FSK-induced BeWo cell line. Moreover, antibody array screening and ELISA revealed that NUR77 promoted significant placental growth factor (PGF) expression during trophoblast fusion. Ectopic overexpression and knockdown experiments demonstrated that PGF was a novel downstream target of NUR77, and serum PGF expression correlated positively with trophoblast NUR77 mRNA levels in HCs and RM patients. Importantly, bioinformatics analysis identified two NUR77 binding sites in the PGF promoter region, and chromatin immunoprecipitation (ChIP) coupled with Western blotting analysis further verified that NUR77 bound directly to the PGF promoter region and promoted PGF expression. Furthermore, in a BeWo/HTR-8 co-culture system, FSK-induced BeWo-secreted PGF promoted HTR-8 cell migration and invasion, and an anti-PGF antibody reversed this effect. Collectively, these results indicated that NUR77 may play a key role in regulating trophoblast invasion at early pregnancy.
Key messages
• NUR77 expression was significantly decreased in the syncytiotrophoblast of the recurrent miscarriage group compared to that in the healthy control group.
• NUR77 promoted PGF expression during trophoblast fusion.
• ChIP and western blotting experiments verified that NUR77 bound directly to the PGF promoter region and activated PGF expression in trophoblast.
• Trophoblast-derived PGF promoted HTR-8 cell migration and invasion in a cell co-culture system.
... Most studies on the mechanism through which NR4A1 is regulated have focused principally on post-translational modifications, such as acetylation, ubiquitylation [22], and phosphorylation [23]. Despite our work and other previous studies reporting that NR4A1 is regulated by histone acetylation [24,25], AP-1, NF-κB [26], and miRNA-124 [27], little is known about the transcriptional and post-transcriptional regulation of NR4A1, especially whether it is regulated by lncRNA. ...
Long non-coding RNAs (lncRNAs) play important roles in tumorigenesis and cancer progression. The orphan nuclear receptor subfamily 4 group A member 1 (NR4A1) acts as an oncogene, and is involved in colorectal cancer (CRC) development. However, the mechanism through which lncRNA regulates NR4A1 expression remains unknown. We aimed to identify lncRNAs that regulate NR4A1 and assess their underlying mechanisms in CRC. We first identified an antisense lncRNA of NR4A1 that was up-regulated in CRC tissues and cells with rapid amplification of cDNA ends (RACE), and designated it as NR4A1AS. Spearman correlation analysis showed that NR4A1AS was positively correlated with NR4A1 mRNA levels in 37 CRC tissues. Mechanistically, NR4A1AS stabilized NR4A1 mRNA by forming RNA–RNA complexes via partial base-pairing and up-regulated NR4A1 expression in CRC cells. RNA immunoprecipitation (RIP) assays revealed that knockdown of NR4A1AS expression by siRNA enhanced up-frameshift 1 (UPF1) recruitment to NR4A1 mRNA, thereby decreasing NR4A1 mRNA stability. Moreover, depletion of NR4A1AS was found to mimic the effect of NR4A1 knockdown, specifically by suppressing cell proliferation, migration and invasion, and inducing apoptosis and cell cycle arrest. Accordingly, restoring NR4A1 expression ameliorated the effects of NR4A1AS knockdown on tumor growth and metastasis of CRC cells in vitro and in vivo. Thus, we conclude that NR4A1AS up-regulates NR4A1 expression by forming RNA–RNA complexes and blocking UPF1-mediated mRNA destabilization, and it functions in tumor growth and metastasis of CRC cells at least partly through regulating NR4A1, suggesting that NR4A1AS might be as a potential target for RNA-based anti-CRC drug studies.
... The nuclear receptor IV subfamily members play redundant roles in TCR-mediated apoptosis (21) and brown fat thermogenesis (22,23). However, they play different roles in development (reviewed in (24)). TR3/Nur77 also plays important roles in cancer cell biology, inflammation, metabolic diseases, stress and addiction (reviewed in (25)(26)(27)(28)). ...
Pathological angiogenesis is a hallmark of many diseases. Previously, we reported that orphan nuclear receptor TR3/Nur77 was a critical mediator of angiogenesis to regulate tumor growth and skin wound healing via regulating the expression of the junctional proteins and integrins. However, the molecular mechanism, by which TR3/Nur77 regulates angiogenesis is not completely understood. Here, we were the first to find that TR3/Nur77, via its various amino acid fragments, regulated the expression of DLL4 and Jagged 1 in cultured endothelial cells. DLL4 and Jagged1 mediated TR3/Nur77-induced angiogenic responses and signaling molecules, but not the expression of integrins. Instead, integrins regulated the expressions of DLL4 and Jagged1 induced by TR3/Nur77. Further, DLL4, Jagged1 and integrins α1, α2, β3 and β5 were regulated by TR3/Nur77 in animal sepsis models of lipopolysaccharide (LPS)-induced endotoxemia, and cecal ligation and puncture (CLP), in which, TR3/Nur77 expression was significantly and tranciently increased. Mouse survival rates were greatly increased in Nur77 knockout mice bearing both CLP and LPS models. The results elucidated a novel axis of VEGF/histamine ➔ TR3/Nur77 ➔ integrins ➔ DLL4/Jagged1 in angiogenesis, and demonstrated that TR3/Nur77 was an excellent target for sepsis. These studies supported our previous findings that TR3/Nur77 was an excellent therapeutic target, and further our understanding of the molecular mechanism, by which TR3/Nur77 regulated angiogenesis.
... Brain and other organ development Giguere 20 PPARα NR1C1 45 Hsu et al, 46 Ranhotra 47 NURR1 NR4A2 3 Brain function (dopaminergic system) and immune activity ...
Nuclear hormone receptors (NRs) are evolutionarily conserved ligand-dependent transcription factors. They are essential for human life, mediating the actions of lipophilic molecules, such as steroid hormones and metabolites of fatty acid, cholesterol, and external toxic compounds. The C2H2-type zinc finger proteins (ZNFs) form the largest family of the transcription factors in humans and are characterized by multiple, tandemly arranged zinc fingers. Many of the C2H2-type ZNFs are conserved throughout evolution, suggesting their involvement in preserved biological activities, such as general transcriptional regulation and development/differentiation of organs/tissues observed in the early embryonic phase. However, some C2H2-type ZNFs, such as those with the Krüppel-associated box (KRAB) domain, appeared relatively late in evolution and have significantly increased family members in mammals including humans, possibly modulating their complicated transcriptional network and/or supporting the morphological development/functions specific to them. Such evolutional characteristics of the C2H2-type ZNFs indicate that these molecules influence the NR functions conserved through evolution, whereas some also adjust them to meet with specific needs of higher organisms. We review the interaction between NRs and C2H2-type ZNFs by focusing on some of the latter molecules.
... Nur77 is an orphan nuclear steroid receptor that belongs to the steroid/thyroid hormone receptor superfamily of transcription factors [24]. Furthermore, the Nur77 protein also has a function quite distinct from transcription regulation: it translocates from the nucleus to mitochondria in order to initiate apoptosis [25]. ...
... The nuclear orphan NR4A subfamily includes three members, namely Nur77 (also called NR4A1), Nurr1(NR4A2) and Nor1 (NR4A3) 13 . These receptors have no known ligands and therefore are sometimes referred to as orphan nuclear receptors. ...
Objective:
Thrombomodulin is highly expressed on the lumenal surface of vascular endothelial cells (ECs) and possesses potent anticoagulant, antifibrinolytic, and anti-inflammatory activities in the vessel wall. However, the regulation of thrombomodulin expression in ECs remains largely unknown.
Approaches and results:
In this study, we characterized nuclear receptor 4A family as a novel regulator of thrombomodulin expression in vascular ECs. We demonstrated that both nuclear receptors 4A, Nur77 and Nor1, robustly increase thrombomodulin mRNA and protein levels in human vascular ECs and in mouse liver tissues after adenovirus-mediated transduction of Nur77 and Nor1 cDNAs. Moreover, Nur77 deficiency and knockdown of Nur77 and Nor1 expression markedly attenuated the basal and vascular endothelial growth factor165-stimulated thrombomodulin expression. Mechanistically, we found that Nur77 and Nor1 increase thrombomodulin expression by acting through 2 different mechanisms. We showed that Nur77 barely affects thrombomodulin promoter activity, but significantly increases thrombomodulin mRNA stability, whereas Nor1 enhances thrombomodulin expression mainly through induction of Kruppel-like factors 2 and 4 in vascular ECs. Furthermore, we demonstrated that both Nur77 and Nor1 significantly increase protein C activity and inhibit tumor necrosis factor α-induced prothrombotic effects in human ECs. Deficiency of Nur77 increases susceptibility to arterial thrombosis, whereas enhanced expression of Nur77 and Nor1 protects mice from arterial thrombus formation.
Conclusions:
Our results identified nuclear receptors 4A as novel regulators of thrombomodulin expression and function in vascular ECs and provided a proof-of-concept demonstration that targeted increasing expression of Nur77 and Nor1 in the vascular endothelium might represent a novel therapeutic approach for the treatment of thrombotic disorders.
... NR4A1 is expressed at low to moderate levels in many major physiological systems, including the central nervous system, endocrine, reproductive, immune, gastrointestinal, cardiovascular, respiratory and structural. [22,23] It is known to play a vital role in tumor-cell apoptosis from multiple tissue types and in the well-studied apoptotic signaling of thymocytes [24] and within the hypothalmic-pituitary axis. [25] The structural biology of NR4A1 is inconclusive. ...
A 4.1μs molecular dynamics simulation of the NR4A1 (hNur77) apo-protein has been
undertaken and a previously undetected druggable pocket has become apparent that is located remotely from the ‘traditional’ nuclear receptor ligand-binding site. A NR4A1/bisindole ligand complex at this novel site has been found to be stable over 1 μs of simulation and to result in an interesting conformational transmission to a remote loop that has the capacity to communicate with a NBRE within a RXR-α/NR4A1 heterodimer. Several features of the simulations undertaken indicate how NR4A1 can be affected by alternate-site
modulators.
... Nuclear import of HDAC7 leads to repression of NR4A1 transcription in developing thymocytes [8]. NR4A1 (also known as NUR77, TR3 or nerve growth factor induced NGFI-B) belongs to the family of nuclear orphan receptors which act as immediate early response genes, and is important for neuronal differentiation, T cell tolerance induction and apoptosis [9] [10] [11]. In this study we demonstrate that ROCK signaling controls nucleocytoplasmic shuttling of HDAC7 and modulates the expression of its target gene NR4A1. ...
... In the cytosol, Nur77 unmasks the BH-3 domain of Bcl-2, converting Bcl-2 into a pro-apoptotic molecule (12). Thus, the general consensus is that the opposing effects of nuclear and cytosolic Nur77 are chemical-dependent (11,17). Because both Nur77 and BAs have a dual role in regulating apoptosis and proliferation, the current study tests the hypothesis that Nur77 mediates the effects of BAs. ...
Unlabelled:
Bile acids (BA) are endogenous agents capable of causing cancer throughout the gastrointestinal (GI) tract. To uncover the mechanism by which BAs exert carcinogenic effects, both human liver and colon cancer cells as well as mouse primary hepatocytes were treated with BAs and assayed for viability, genotoxic stress, and transcriptional response. BAs induced both Nur77 (NR4A1) and proinflammatory gene expression. The intracellular location of BA-induced Nur77 was time dependent; short-term (1-3 hours) exposure induced nuclear Nur77, whereas longer (1-2 days) exposure also increased cytosolic Nur77 expression and apoptosis. Inhibiting Nur77 nuclear export with leptomycin B decreased lithocholic acid (LCA)-induced apoptosis. Extended (7 days) treatment with BA generated resistance to BA with increased nuclear Nur77, viability, and mobility. While, knockdown of Nur77 in BA-resistant cells increased cellular susceptibility to LCA-induced apoptosis. Moreover, in vivo mouse xenograft experiments demonstrated that BA-resistant cells form larger tumors with elevated Nur77 expression compared with parental controls. DNA-binding and gene expression assays identified multiple survival genes (CDK4, CCND2, MAP4K5, STAT5A, and RBBP8) and a proapoptosis gene (BID) as Nur77 targets. Consistently, BA-induced upregulation of the aforementioned genes was abrogated by a lack of Nur77. Importantly, Nur77 was overexpressed in high percentage of human colon and liver cancer specimens, and the intracellular location of Nur77 correlated with elevated serum total BA levels in patients with colon cancer. These data show for the first time that BAs via Nur77 have a dual role in modulating cell survival and death.
Implications:
These findings establish a direct link between Nur77 and the carcinogenic effect of BAs.
... Furthermore, nuclear receptors consist of an N-terminal domain mediating transactivation and a C-terminal ligandbinding domain. Specific ligands for the NR4A family of transcription factors have not been identified, classifying them as orphan nuclear receptors (Hsu et al., 2004). At the C-terminal domain both Nur77 and Nurr1 can heterodimerize with RXRs and mediate retinoid responses (Wallen-Mackenzie et al., 2003). ...
... NR4A family members consist of an N-terminal domain mediating transactivation and a C-terminal ligandbinding domain (Hsu et al., 2004). These members are thought to act as constitutively active transcription factors that bind the promoter of target genes on consensus NBRE (AAAGGTCA) sites. ...
A number of studies have indicated that Nurr1, which belongs to a novel class of orphan nuclear receptors (the NR4A family), is important for carcinogenesis. Here we investigated expression of Nurr1 protein in benign and malignant human prostate tissues and association with clinicopathologic features using immunohistochemical techniques. Moreover, we also investigated the ability of Nurr1 to influence proliferation, migration, invasion and apoptosis of human prostate cancer cells using small interfering RNA silencing. Immunohistochemical analysis revealed that the expression of Nurr1 protein was higher in prostate cancer tissues than in benign prostate tissue (P < 0.001), levels being positively correlated with tumor T classification (P = 0.003), N classification (P = 0.017), M classification (P = 0.011) and the Gleason score (P = 0.020) of prostate cancer patients. In vitro, silencing of endogenous Nurr1 attenuated cell proliferation, migration and invasion, and induced apoptosis of prostate cancer cells. These results suggest that Nurr1 may be used as an indicator for prostate cancer progression and be useful for novel potential therapeutic strategies.
... One gene affected by the loss of Sin3a under both conditions, but misregulated in opposite directions, was Nr4a1. Highly homologous in genomic structure to its two family members, Nr4a2 (Nurr1) and Nr4a3 (Nor1), Nr4a1 functions as an immediate early response gene activated through numerous physiological signals (Hsu et al., 2004). It encodes a nuclear receptor that acts in a ligand-independent manner, with the activation-function 1 domain of the protein mediating transactivation and coactivator recruitment (Wansa et al., 2002). ...
Chromatin modifier Swi-independent 3a (SIN3A), together with associated histone deacetylases, influences gene expression during development and differentiation through a variety of transcription factors in a cell-specific manner. Sin3a is essential for the maintenance of inner cell mass cells of mouse blastocysts, embryonic fibroblasts, and myoblasts, but is not required for the survival of trophectoderm or Sertoli cells. To better understand how this transcriptional regulator modulates cells at different developmental stages within a single lineage, we used conditional gene targeting in mice to ablate Sin3a from perinatal quiescent male gonocytes and from postnatal differentiating spermatogonia. Mitotic germ cells expressing stimulated by retinoic acid gene 8 (Stra8) that lacked Sin3a exhibited increased DNA damage and apoptosis, yet collectively progressed through meiosis and spermiogenesis and generated epididymal sperm at approximately 50% of control levels, sufficient for normal fertility. In contrast, perinatal gonocytes lacking Sin3a underwent rapid depletion that coincided with cell cycle reentry, exhibiting 2.5-fold increased histone H3 phosphorylation upon cycling that suggested a prophase/metaphase block; germ cells were almost entirely absent two weeks after birth, resulting in sterility. Gene expression profiling of neonatal testes containing Sin3a-deleted gonocytes identified upregulated transcripts highly associated with developmental processes and pattern formation, and downregulated transcripts involved in nuclear receptor activity, including Nr4a1 (Nur77). Interestingly, Nr4a1 levels were elevated in testes containing Stra8-expressing, Sin3a-deleted spermatogonia. SIN3A directly binds to the Nr4a1 promoter, and Nr4a1 expression is diminished upon spermatogonial differentiation in vitro. We conclude that within the male germline, Sin3a is required for the mitotic reentry of gonocytes, but is dispensable for the maintenance of differentiating spermatogonia and subsequent spermatogenic processes.
... 10 Nur77 binds to the NGFI-B (NGF-induced B factor)-response element (NBRE) and the Nur-response element (NurRE) sequences in DNA and is able to stimulate transcription from NBRE-and NurRE-dependent reporter genes. 11 Nur77 regulates distinct cellular processes in a tissue-specific manner. For example, Nur77 is expressed in human adult liver and has been shown to regulate gluconeogenesis and hepatic lipid metabolism. ...
We aimed to investigate whether vascular endothelial growth factor (VEGF) influences apolipoprotein M (ApoM) expression and pre-β-high-density lipoprotin (HDL) formation, and whether forkhead box A2 (Foxa2) and Nur77 are involved in this process.
We analyzed the serum VEGF concentrations of 264 adults who underwent a medical checkup and found that VEGF concentration was positively correlated with serum triglyceride, total cholesterol, LDL cholesterol (LDL-C), very-low-density lipoprotein cholesterol (VLDL-C), and ApoB concentrations, but was negatively correlated with serum high-density lipoprotein cholesterol (HDL-C) and ApoM concentrations. We further investigated the effects of VEGF on ApoM expression and pre-β-HDL formation, and the mechanisms responsible, in HepG2 cells and mouse primary hepatocytes. VEGF markedly downregulated ApoM expression and pre-β-HDL formation. At the same time, expression of Foxa2 was also inhibited, whereas expression of Nur77 was increased by treatment with VEGF. Furthermore, small interfering (si) RNA knockdown of Foxa2 made the downregulation of VEGF on ApoM expression and pre-β-HDL formation even more obvious. In addition, siRNA knockdown of Nur77 significantly compensated for the inhibitory effect of VEGF on Foxa2 expression, whereas the Nur77 agonist cytosporone B led to the downregulation of Foxa2 expression more significantly than VEGF. Moreover, overexpression of a Nur77 transgene in C57BL/6 mice resulted in decreased serum ApoM and pre-β-HDL levels, whereas si-Nur77-treated mice displayed upregulated serum ApoM and pre-β-HDL levels.
These results provide evidence that VEGF may first downregulate expression of Foxa2 by enhancing Nur77 activity and then decrease expression of ApoM and pre-β-HDL formation. Therefore, our study may be useful in understanding the critical effect of VEGF in the pathogenesis of atherosclerosis.
... The regulation of the NR4A family of nuclear receptors has been proven to be one of the main targets of histone acetylation during memory formation. Hence, known components of their regulation (Hsu et al, 2004) have been incorporated into the model, adding elements of the corepressor complexes that may warrant exploration. For example, Cabin1, a calcineurin-dependent repressor that can recruit KDACs, can compete with p300 for binding of transcription factors such as MEF that can induce expression of Nr4a genes (Youn and Liu, 2000), establishing a direct link between calcium-dependent gene activation and histone acetylation. ...
Long-term memory formation requires transcription and protein synthesis. Over the past few decades, a great amount of knowledge has been gained regarding the molecular players that regulate the transcriptional program linked to memory consolidation. Epigenetic mechanisms have been shown to be essential for the regulation of neuronal gene expression, and histone acetylation has been one of the most studied and best characterized. In this review, we summarize the lines of evidence that have shown the relevance of histone acetylation in memory in both physiological and pathological conditions. Great advances have been made in identifying the writers and erasers of histone acetylation marks during learning. However, the identities of the upstream regulators and downstream targets that mediate the effect of changes in histone acetylation during memory consolidation remain restricted to a handful of molecules. We outline a general model by which corepressors and coactivators regulate histone acetylation during memory storage and discuss how the recent advances in high-throughput sequencing have the potential to radically change our understanding of how epigenetic control operates in the brain.Neuropsychopharmacology Reviews advance online publication, 6 June 2012; doi:10.1038/npp.2012.86.
... Nuclear receptors (NRs) are a class of ligand-dependent transcription factors that control variety of physiological processes. 1,2 Because NR transcriptional activity can be regulated by natural and synthetic small-molecule ligands, NRs have become an important target for the development of new drugs in the recent years. [3][4][5] Nearly half of the 48 human NRs still have no known natural ligands, and receptors lacking ligands are referred to as orphan nuclear receptors. ...
Neuron-derived clone 77 (Nur77) is an orphan nuclear receptor with currently no known natural ligands. Here we applied a metabolomics platform for detecting protein-metabolite interactions (PMIs) to identify lipids that bind to Nur77. Using this approach, we discovered that the Nur77 ligand-binding domain (Nur77LBD) enriches unsaturated fatty acids (UFAs) in tissue lipid mixtures. The interaction of Nur77 with arachidonic acid and docosahexaenoic acid was subsequently characterized using a number of biophysical and biochemical assays. Together these data indicate that UFAs bind to Nur77LBD to cause changes in the conformation and oligomerization of the receptor. UFAs are the only endogenous lipids reported to bind to Nur77, which highlights the use of metabolomics in the discovery of novel PMIs.
... Fenretinide-induced apoptosis of human liver cancer cells is Nur77 dependent, and the sensitivity of the cancer cells to fenretinide-induced apoptosis is positively associated with cytoplasmic enrichment of Nur77 [7]. Nur77 (also known as NR4A1, TR3 or NGFI-B), an immediate-early response gene, is rapidly induced by a diverse group of agents, including growth factors, mitogens, phorbol esters, and substances that influence cyclic AMPdependent synthesis pathways [8]. By interacting with other nuclear receptors such as retinoid x receptor (RXRα), Nur77 can exert pleiotropic biological activities ranging from survival and differentiation to cell death in response to different extracellular stimuli [9]. ...
Fenretinide, a synthetic retinoid, is a promising anticancer agent based on many in vitro, animal, and chemoprevention clinical trial studies. However, cells such as HepG2 human liver cancer cells are resistant to the apoptotic effect of fenretinide. Previously, we have shown that fenretinide-induced apoptosis is Nur77 dependent, and the sensitivity of the cancer cells to fenretinide-induced apoptosis is positively associated with cytoplasmic enrichment of Nur77. The goal of current study was to identify means to modulate nuclear export of Nur77 in order to improve the efficacy of fenretinide. Fenretinide treatment deactivated ERK1/2 in Huh7 cells, but activated ERK1/2 in HepG2 cells, which was positively associated with the sensitivity of cells to the apoptotic effect of fenretinide. Neither fenretinide nor ERK1/2 inhibitor PD98059 alone could affect the survival of HepG2 cells, but the combination of both induced cell death and increased caspase 3/7 activity. In fenretinide sensitive Huh7 cells, activation of ERK1/2 by epidermal growth factor (EGF) prevented fenretinide-induced cell death and caspase 3/7 induction. In addition, modulation of ERK1/2 changed the intracellular localization of Nur77. Fenretinide/PD98059-induced cell death of HepG2 cell was positively associated with induction and cytoplasmic location as well as mitochondria enrichment of Nur77. The effect was specific for ERK1/2 because other mitogen activated protein kinases such as P38, Akt, and JNK did not have correlated changes in their phosphorylation levels. Taken together, the current study demonstrates that ERK1/2-modulated Nur77 intracellular location dictates the efficacy of fenretinide-induced apoptosis.
... Animals chronically treated with METH and challenged with METH also showed marked decreases (−67%, p<0.0055) in NAB2 mRNA levels. Figure 4 shows the effects of METH on the members of the nuclear receptor subfamily 4, group A (Nr4a) family of transcription factors (Hsu et al. 2004). Acute METH caused significant increases in Nr4a1 (2.0-fold, p<0.0036; ...
Repeated injections of cocaine cause blunted responses to acute cocaine challenge-induced increases in the expression of immediate early genes (IEGs).
The aim of this study was to test if chronic methamphetamine (METH) exposure might cause similar blunting of acute METH-induced increases in IEG expression.
Repeated saline or METH injections were given to rats over 14 days. After 1 day of withdrawal, they received a single injection of saline or METH (5 mg/kg). Acute injection of METH increased c-fos, fosB, fra2, junB, Egr1-3, Nr4a1 (Nur77), and Nr4a3 (Nor-1) mRNA levels in the striatum of saline-pretreated rats. Chronic METH treatment alone reduced the expression of AP1, Erg1-3, and Nr4a1 transcription factors below control levels. Acute METH challenge normalized these values in METH-pretreated rats. Unexpectedly, acute METH challenge to METH-pretreated animals caused further decreases in Nr4a2 (Nurr1) mRNA levels. In contrast, the METH challenge caused significant but blunted increases in Nr4a3 and Arc expression in METH-pretreated rats. There were also chronic METH-associated decreases in the expression of cAMP responsive element binding protein (CREB) which modulates IEG expression via activation of the cAMP/PKA/CREB signal transduction pathway. Chronic METH exposure also caused significant decreases in preprotachykinin, but not in prodynorphin, mRNA levels.
These results support the accumulated evidence that chronic administration of psychostimulants is associated with blunting of their acute stimulatory effects on IEG expression. The METH-induced renormalization of the expression of several IEGs in rats chronically exposed to METH hints to a potential molecular explanation for the recurrent self-administration of the drug by human addicts.
... Nur77 (also known as TR3, NGFI-B, TIS1, and NAK-1) is an orphan nuclear steroid receptor that belongs to the steroid/thyroid hormone receptor superfamily, which acts as transcription factors (for a review, see [79]). The physiological ligand for the Nur77 monomer and homodimer has not been identified and might not be present, although cytosporone B was shown to be a naturally occurring agonist for Nur77 [80]. ...
An important mechanism in apoptotic regulation is changes in the subcellular distribution of pro- and anti-apoptotic proteins. Among the proteins that change in their localization and may promote apoptosis are nuclear proteins. Several of these nuclear proteins such as p53, Nur77, histone H1.2, and nucleophosmin were reported to accumulate in the cytosol and/or mitochondria and to promote the mitochondrial apoptotic pathway in response to apoptotic stressors. In this review, we will discuss the functions of these and other nuclear proteins in promoting the mitochondrial apoptotic pathway, the mechanisms that regulate their accumulation in the cytosol and/or mitochondria and the potential role of Bax and Bak in this process. This article is part of a Special Issue entitled Mitochondria: the deadly organelle.
... Nur77 (also called NR4A1, TR3, NAK-1, and NGFI-B) plays important roles in the regulation of cellular proliferation, apoptosis, and energy metabolism. It belongs to the NR4A (nuclear receptor group 4A) subfamily of nuclear hormone receptors and its DNA-binding domain (DBD) shows 90% homology with other subfamily members, Nurr1 and Nor-1 [1] [2]. All of NR4A subfamilies are encoded by immediate early genes whose expression is induced in response to a variety of signals including mitogens and cellular stress [3] [4] [5]. ...
Although the roles of Nur77, an orphan member of the nuclear hormone receptor superfamily, in the control of cellular proliferation, apoptosis, inflammation, and glucose metabolism, are well recognized, the molecular mechanism regulating the activity and expression of Nur77 is not fully understood. Acetylation of transcription factors has emerged recently as a major post-translational modification that regulates protein stability and transcriptional activity. Here, we examined whether Nur77 is acetylated, and we characterized potential associated factors. First, Nur77 was found to be an acetylated protein when examined by immunoprecipitation and western blotting using acetyl protein-specific antibodies. Second, expression of p300, which possesses histone acetyltransferase activity, enhanced the acetylation and protein stability of Nur77. Treatment with a histone deacetylase (HDAC) inhibitor, trichostatin A, also increased Nur77 acetylation. Among the several types of HDACs, HDAC1 was found as the major enzyme affecting protein level of Nur77. HDAC1 decreased the acetylation level, protein level, and transcriptional activity of Nur77. Interestingly, overexpression of Nur77 induced expression of both p300 and HDAC1. Finally, the expression of Nur77 increased along with that of p300, but decreased with induction of HDAC1 after treatment with epithelial growth factor, nerve growth factor, or 6-mercaptopurine, suggesting that the self-control of the acetylation status contributes to the transient induction of Nur77 protein. Taken together, these results demonstrate that acetylation of Nur77 is modulated by p300 and HDAC1, and suggest that acetylation is an important post-translational modification for the rapid turnover of Nur77 protein.
The binding of peroxisome proliferator‐activated receptor γ (PPARγ) to the orphan nuclear receptor Nur77 facilitates the ubiquitination and degradation of Nur77, and leads to aberrant fatty acid uptake for breast cancer progression. Because of its crucial role in clinical prognosis, the interaction between Nur77 and PPARγ is an attractive target for anti‐breast‐cancer therapy. However, developing an inhibitor of the Nur77‐PPARγ interaction poses a technical challenge due to the absence of the crystal structure of PPARγ and its corresponding interactive model with Nur77. Here, ST‐CY14, a stapled peptide, is identified as a potent modulator of Nur77 with a KD value of 3.247 × 10⁻⁸ M by in silico analysis, rational design, and structural modification. ST‐CY14 effectively increases Nur77 protein levels by blocking the Nur77‐PPARγ interaction, thereby inhibiting lipid metabolism in breast tumor cells. Notably, ST‐CY14 significantly suppresses breast cancer growth and bone metastasis in mice. The findings demonstrate the feasibility of exploiting directly Nur77‐PPARγ interaction in breast cancer, and generate what to the best knowledge is the first direct inhibitor of the Nur77‐PPARγ interaction available for impeding fatty acid uptake and therapeutic development.
How to efficiently regenerate jawbone defects caused by trauma, jaw osteomyelitis, tumors, or intrinsic genetic diseases is still challenging. Ectoderm-derived jawbone defect has been reported to be regenerated by selectively recruiting cells from its embryonic origin. Therefore, it is important to explore the strategy for promoting ectoderm-derived jaw bone marrow mesenchymal stem cells (JBMMSCs) on the repair of homoblastic jaw bone. Glial cell-derived neurotrophic factor (GDNF) is an important growth factor and is essential in the process of proliferation, migration and differentiation of nerve cells. However, whether GDNF promoting the function of JBMMSCs and the relative mechanism are not clear. Our results showed that activated astrocytes and GDNF were induced in the hippocampus after mandibular jaw defect. In addition, the expression of GDNF in the bone tissue around the injured area was also significantly increased after injury. Data from in vitro experiments demonstrated that GDNF could effectively promote the proliferation and osteogenic differentiation of JBMMSCs. Furthermore, when implanted in the defected jaw bone, JBMMSCs pretreated with GDNF exhibited enhanced repair effect compared with JBMMSCs without treatment. Mechanical studies found that GDNF induced the expression of Nr4a1 in JBMMSCs, activated PI3K/Akt signaling pathway and then enhanced the proliferation and osteogenic differentiation capacities of JBMMSCs. Our studies reveal that JBMMSCs are good candidates for repairing jawbone injury and pretreated with GDNF is an efficient strategy for enhancing bone regeneration.
Non-communicable diseases (NCDs) are a global epidemic with diverse pathogenesis. Among them, oxidative stress and inflammation are the most fundamental co-morbid features. Therefore, multi-targets and multi-pathways therapies with significant anti-oxidant and anti-inflammatory activities are potential effective measures for preventing and treating NCDs. The flavonol glycoside compound hyperoside (Hyp) is widely found in a variety of fruits, vegetables, beverages, and medicinal plants and has various health benefits, especially excellent anti-oxidant and anti-inflammatory properties targeting nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor-κB (NF-κB) signaling pathways. In this review, we summarize the pathogenesis associated with oxidative stress and inflammation in NCDs and the biological activity and therapeutic potential of Hyp. Our findings reveal that the anti-oxidant and anti-inflammatory activities regulated by Hyp are associated with numerous biological mechanisms, including positive regulation of mitochondrial function, apoptosis, autophagy, and higher-level biological damage activities. Hyp is thought to be beneficial against organ injuries, cancer, depression, diabetes, and osteoporosis, and is a potent anti-NCDs agent. Additionally, the sources, bioavailability, pharmacy, and safety of Hyp have been established, highlighting the potential to develop Hyp into dietary supplements and nutraceuticals.
Homocysteine (Hcy) is associated with non‐alcoholic fatty liver disease (NAFLD). NR4A1 is involved in hepatic lipid metabolism. However, the potential role of NR4A1 in Hcy‐associated NAFLD remains elusive. We aimed to elucidate the regulation of NR4A1 and its significance in Hcy‐induced NAFLD. Hcy induced steatosis and elevated the expression of CD36 and FATP2 in HepG2 cells. Furthermore, Hcy enhanced p300 and decreased HDAC7 recruitment to the NR4A1 promoter, resulting in histone H3K27 hyperacetylation and NR4A1 up‐regulation. Moreover, NR4A1 depletion not only mimicked, but also exaggerated the effects of Hcy on steatosis, whereas NR4A1 agonist Cytosporone B (CsnB) blocked Hcy‐induced steatosis. In hyperhomocysteinemia mice, CsnB attenuated hyperhomocysteinemia‐induced hepatic steatosis. Thus, Hcy transiently and rapidly induces NR4A1 expression to reduce Hcy‐induced steatosis. This article is protected by copyright. All rights reserved.
Insulin-like growth factor-binding protein 3 (IGFBP-3) is the most abundant IGFBP in circulation, interacts with high affinity to IGFs altering their function. Emerging evidence has indicated that IGFBP3 mostly involved in human disease such as diabetes, Alzheimer’s disease, and cancer. It has been determined that IGFBP3 expression is decreased in various cancer cell lines by promoter methylation and proteases digestion. Therefore, bioavailable form of IGF-I increases in circulation promoting the tumorigenesis and progression of cancer. IGFBP3 function in cancer suppressing can be divided in two ways: IGF-dependent, and IGF-independent action. Recently it has been shown that IGFBP3 has vital roles independent of IGFs. Despite decades of unremitting research, this function of IGFBP-3 has not been clarified. However, it has been suggested that IGFBP3 independently can bind to its receptors in the nucleus including retinoid receptors (RXRs) peroxisome proliferator activated receptors (PPARγ), Nur77 vitamin D response (VDR), and/or cell surface receptors such as transmembrane protein 219 (TMEM219), low-density lipoprotein receptor-related protein 1 (LRP-1), and epidermal growth factor receptor (EGFR) inducing apoptosis. In this review, we described further mechanisms of IGF-independent action of IGFBP3. © 2017, Isfahan University of Medical Sciences(IUMS). All rights reserved.
Innate immunity constitutes the first line of defense against pathogenic and dangerous insults. However, it is a double-edged sword, as it functions in both clearance of infection and inflammatory damage. It is therefore important that innate immune responses are tightly controlled to prevent harmful excessive inflammation. Nuclear receptors (NRs) are a family of transcription factors that play critical roles in various physiological responses. Orphan NRs are a subset of NRs for which the ligands and functions are unclear. Accumulating evidence has revealed that orphan NRs play essential roles in innate immune responses to prevent pathogenic inflammatory responses and to enhance antimicrobial host defenses. In this review, we describe current knowledge on the roles and mechanisms of orphan NRs in the regulation of innate immune responses. Discovery of new functions of orphan NRs would facilitate development of novel preventive and therapeutic strategies against human inflammatory diseases.
IntroductionFunctions of NR4A Receptor SubfamilyStructures of NR4A1 and NR4A2Modulators of the NR4A SubfamilyConclusions and OutlookReferences
The interaction between macrophages and oxLDL plays a crucial role in the initiation and progression of atherosclerosis. As a key initiator in a number of plaque promoting processes, oxLDL induces variable effects such as cell apoptosis or proliferation. Orphan nuclear receptor Nur77 is potently induced in macrophages by diverse stimuli, suggesting that it is of importance in vascular inflammation resulting in atherosclerosis, but whether Nur77 induction is detrimental or protective is unclear. In our study, we explore the role of Nur77 in the regulation of oxLDL-induced macrophage apoptosis and the signaling pathways that are involved. We found that oxLDL induced Nur77 expression in a dose and time dependent fashion, and cell viability was decreased in parallel. To determine whether Nur77 induction contributes to the loss of cell viability or is a protective mechanism, the effect of Nur77 overexpression was examined. Importantly, Nur77 overexpression inhibited the oxLDL-induced decrease of cell viability, inhibited the production of apoptotic bodies and restored DNA synthesis following oxLDL exposure. Furthermore, we found that Nur77 induction is mediated through the p38 MAPK signaling pathway. After pretreatment with SB203580, cell viability was decreased, the expression of CyclinA2 and PCNA was attenuated and the percentage of cell apoptosis was enhanced. Likewise, Nur77 overexpression increased the expression of the cell cycle genes PCNA and p21, and attenuated the increase in caspase-3. On the other hand, knockdown of Nur77 expression by specific siRNA resulted in the increased expression of caspase 3. The results demonstrate that Nur77 is induced by oxLDL via the p38 MAPK signaling pathway, which is involved in the regulation of cell survival. Nur77 enhanced cell survival via suppressing apoptosis, without affecting cell proliferation of activated macrophages, which may be beneficial in patients with atherosclerosis.
Aldosterone is one of the mineralocorticoids synthesized and secreted by the adrenal glands, and it plays pivotal roles in regulating extracellular fluid volume and blood pressure. Autonomous excessive aldosterone secretion resulting from adrenocortical diseases is known as primary aldosteronism, and it constitutes one of the most frequent causes of secondary hypertension. Therefore, it is important to understand the molecular mechanisms of aldosterone synthesis in both normal and pathological adrenal tissues. Various factors have been suggested to be involved in regulation of aldosterone biosynthesis, and several adrenocortical cell lines have been developed for use as in vitro models of adrenal aldosterone-producing cells, for analysis of the underlying molecular mechanisms. In this review, we summarize the available reports on the regulation of aldosterone biosynthesis in the normal adrenal cortex, in associated disorders, and in in vitro models.
Copyright © 2015 Elsevier Ltd. All rights reserved.
Objective: Apoptosis is characterized by distinct morphological and biochemical changes that occur upon activation of a family of serine proteases known as caspases. Reactive oxygen species (ROS) induce apoptosis in many cell systems. Nuclear receptor subfamily 4, group A, member 1 (NR4A1) has been shown to induce apoptosis in a number of cell lineages, but can also paradoxically act as a death inhibitory factor. In the current study, we focused on the potential role of NR4A1 in hydrogen peroxide (H2O2)-induced apoptosis of normal human umbilical cord fibroblast (HUC-F2) cells.
Methods: Growth of HUC-F2 cells treated with H2O2 was measured by MTT assay. Analysis of gene expression was performed with a STEP ONE PLUS Real Time PCR system. Inactivation of NR4A1 was treated with siRNA. Apoptosis was measured by Beckman Coulter flow cytometer after inhibition of NR4A1 with siRNA and H2O2 treatment. Caspase -3, -8 and -9 was measured by caspase assay kit.
Results: H2O2 treatment led to enhanced NR4A1 expression. Moreover inhibition of NR4A1 with specific siRNA in HUC-F2 cells triggered an increase in apoptosis and caspase-8 and -3 activities following the addition of H2O2.
Discussion: Our results collectively suggest that NR4A1 is a regulator that inhibits extrinsic apoptosis in HUC-F2 cells during oxidative stress through reduction of caspase-8 and -3 activities.
Nuclear receptors (Nurs) represent a large family of gene expression regulating proteins. Gathering evidence indicates an important role for Nurs as transcription factors in dopamine neurotransmission. Nur77, a member of the Nur superfamily, plays a role in mediating the effects of antiparkinsonian and neuroleptic drugs. Besides, Nur77 survival and apoptotic roles depend largely on its subcellular localization. Estrogens are known for their neuroprotective properties, as demonstrated in animal and clinical studies. However, their action on Nur77 translocation pertaining to neuroprotection has not been investigated yet. The aim of our study was to perform a kinetic study on the effect of neurotoxic 6-hydroxydopamine (6-OHDA) and 17β-estradiol (E2) on the subcellular localization of Nur77 with reference to the modulation of apoptosis in PC12 cells. Our results demonstrate that E2 administration alone does not affect Nur77 cytoplasmic/nuclear ratio, mRNA levels, or apoptosis in PC12 cells. The neurotoxin 6-OHDA significantly enhances cytoplasmic localization of Nur77 after merely 3 h, while precipitating apoptosis. 6-OHDA also increases Nur77 transcription, which could partly explain the rise in cytoplasmic localization of the protein. Finally, treatment with both E2 and 6-OHDA delays Nur77 accumulation in the cytoplasm and delays cell death for a few hours in our cellular paradigm. Pre-treatment with E2 does not alter the increase in levels of Nur77 mRNA produced by 6-OHDA, suggesting that a raise in nuclear translocation is likely responsible for the stabilization of the cytoplasmic/nuclear ratio until 6 h. These results suggest an intriguing cooperation between E2 and Nur77 toward cellular fate guidance.
Ginger is a commonly used spice with anti-inflammatory potential. Colitis is the common pathological lesion of inflammatory bowel diseases. In this study, we investigated the therapeutic effects of ginger and its component zingerone in mice with 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced colitis. Ginger and zingerone ameliorated TNBS-induced colonic injury in a dose-dependent manner. Pathway analysis of ginger- and zingerone-regulated gene expression profiles showed that ginger and zingerone significantly regulated cytokine-related pathways. Network analysis showed that nuclear factor-κB (NF-κB) and interleukin-1β (IL-1β) were key molecules involved in the expression of ginger- and zingerone-affected genes. Ex vivo imaging and immunohistochemical staining further verified that ginger and zingerone suppressed TNBS-induced NF-κB activation and IL-1β protein level in the colon. In conclusion, ginger improved TNBS-induced colitis via modulation of NF-κB activity and IL-1β signalling pathway. Moreover, zingerone might be the active component of ginger responsible for the amelioration of colitis induced by TNBS.
NR4A1 (Nur77), NR4A2 (Nurr1) and NR4A3 (Nor-1) are three members of the orphan nuclear receptor (NR) family referred to as NR4A family. This subgroup activates gene expression in a constitutive ligand-independent manner. These nuclear receptors are classified as early response genes that are induced by a diverse range of signals. These orphan NRs have been implicated in cell cycle regulation, apoptosis, inflammation, metabolism and more recently in carcinogenesis. The ultimate growth of a tumor depends not only on the rate of tumor cell proliferation, but also the rate of apoptosis and NR4A1 controls both, survival and death of cancer cells. It has been demonstrated that NR4A1 activities are regulated through its subcellular localisation. In the nucleus, NR4A1 can function in a context dependent manner either as an oncogenic survival factor, promoting cancer cell growth or as the opposite through the activation of apoptosis. Additionally, in an atypical fashion, it is a potent killer when migrating to the mitochondria, where it binds to Bcl-2 and converts its survival phenotype, triggering cytochrome c release and apoptosis. The most convincing evidence that nuclear orphan receptors function as critical tumor suppressors is the observation that the NR4A1 and NR4A3 double knock out mouse develops rapidly acute myeloid leukemia. Down regulation of NR4A1 and NR4A3 was a common feature in leukemic blasts from human AML patients. In particular, the recent identification of pro-apoptotic agents inducing NR4A expression or acting as agonists suggests that these members could serve as potential targets for cancer therapy.
Introduction:
The orphan nuclear receptor Nur77 (also known as NR4A1, NGFIB, TR3, TIS1, NAK-1, or N10) is a unique transcription factor encoded by an immediate early gene. Nur77 signaling is deregulated in many cancers and constitutes an important molecule for drug targeting.
Areas covered:
Nur77 as a versatile transcription factor that displays distinct dual roles in cell proliferation and apoptosis. In addition, several recent insights into Nur77's non-genomic signaling through its physical interactions with various signaling proteins and its phosphorylation-dependent regulation will be highlighted. The possible mechanisms by which Nur77 supports carcinogenesis and specific examples in different human cancers will be summarized. Different approaches to target Nur77 using mimetics, natural products, and synthetic compounds are also described.
Expert opinion:
These latest findings shed light on the novel roles of Nur77 as an exploitable target for new cancer therapeutics. Further work which focuses on a more complete understanding of the Nur77 interactome as well as how the different networks of Nur77 functional interactions are orchestrated in a stimulus or context-specific way will aid the development of more selective, non-toxic approaches for targeting Nur77 in future.
Trichostatin A (TSA) and trapoxin (TPX), inhibitors of the eukaryotic cell cycle and inducers of morphological reversion of transformed cells, inhibit histone deacetylase (HDAC) at nanomolar concentrations. Recently, FK228 (also known as FR901228 and depsipeptide) and MS-275, antitumor agents structurally unrelated to TSA, have been shown to be potent HDAC inhibitors. These inhibitors activate the expression of p21Waf1 in a p53-independent manner. Changes in the expression of regulators of the cell cycle, differentiation, and apoptosis with increased histone acetylation may be responsible for the cell cycle arrest and antitumor activity of HDAC inhibitors. TSA has been suggested to block the catalytic reaction by chelating a zinc ion in the active site pocket through its hydroxamic acid group. On the other hand, an epoxyketone has been suggested to be the functional group of TPX capable of alkylating the enzyme. We synthesized a novel TPX analogue containing a hydroxamic acid instead of the epoxyketone. The hybrid compound, called cyclic hydroxamic-acid-containing peptide 1 (CHAP1) inhibited HDAC at low nanomolar concentrations. The HDAC1 inhibition by CHAP1 was reversible, as is that by TSA, in contrast to irreversible inhibition by TPX. Interestingly, HDAC6, but not HDAC1 or HDAC4, was resistant to TPX and CHAP1, while TSA inhibited these HDACs to a similar degree. CHAP31, the strongest HDAC inhibitor obtained from a variety of CHAP derivatives, exhibited antitumor activity in BDF1 mice bearing B16/BL6 tumor cells. These results suggest that CHAP31 is promising as a novel therapeutic agent for cancer treatment, and that CHAP may serve as a basis for new HDAC inhibitors and be useful for combinatorial synthesis and high-throughput screening.
Fas and Fas ligand are critical regulators of lymphocyte homeostasis. Disruption of this pathway in the spontaneous mouse mutant gld leads to autoimmunity characterized by the appearance of a population of CD4- 8- B220+ T cells and the production of autoantibodies. Nur77 is a transcription factor that is induced upon TCR signaling. Constitutive thymic expression of Nur77 leads to apoptosis. We have previously shown that introduction of this Nur77 transgene can eliminate the accumulation of abnormal T cells in the periphery of gld/gld mice. In this report, we further characterized the effects of the Nur77 transgene on the gld phenotype. Nur77-mediated apoptosis is evident in the thymuses of mice with either a gld/gld homozygous or gld/+ heterozygous background. Consequently, few mature T cells are generated in these mice. In addition, mature T cells exhibit a diminished response to proliferative signals through CD3. Interestingly, the Nur77 transgene failed to reduce serum levels of Igs and anti-DNA Abs to wild-type levels. These data suggest that the rescue of the T cell lymphoproliferative syndrome in gld/gld mice by the Nur77 transgene is mediated by events in the thymus and that B cell autoimmune disease associated with the gld mutation can develop independently of the T cell abnormality.
A major question in end-stage T cell development is how T cell receptor(TCR) ligation on immature CD4(+)CD8(+) double positive thymocytes is translated into either survival (positive selection) or apoptotic (negative selection) signals. Because different types of antigen-presenting cells (APCs) induce positive or negative selection in the thymus and express different costimulatory molecules, involvement of such costimulatory molecules in determining cell fate of DP thymocytes is considered here. If TCR-generated signals are modulated by APCs, this should be reflected in the activation of distinct biochemical pathways. We here demonstrate that costimulatory signals involved in negative selection also are required for induction of protein expression of Nur77 and its family members. These transcription factors are critically involved in negative but not positive selection. In contrast, the signals that costimulate negative selection are not required for induction of several molecular events associated with positive selection. These include activation of the immediate early gene Egr-1, the mitogen-activated protein kinase ERK2, and surface expression of the CD69 marker. Thus, costimulation for negative selection selectively provides signals for activation of apoptotic mediators. These data provide molecular insights into how TCR-engagement by ligands on different thymic APCs can determine cell fate.
Modulation of many signaling pathways in antigen-stimulated T and B cells results in global changes in gene expression. Here we investigate the contribution of calcium signaling to gene expression in T cells using cell lines from two severe-combined immunodeficiency patients with several cytokine deficiencies and diminished activation of the transcription factor NFAT nuclear factor of activated T cells. These T cells show a strong defect in transmembrane calcium influx that is also apparent in their B cells and fibroblasts. DNA microarray analysis of calcium entry-deficient and control T cells shows that Ca2+ signals both activate and repress gene expression and are largely transduced through the phosphatase calcineurin. We demonstrate an elaborate network of signaling pathways downstream of the T cell receptor, explaining the complexity of changes in gene expression during T cell activation.
The novel retinoid 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid (AHPN/CD437) inhibits cell proliferation and is a very effective inducer of apoptosis in a variety of carcinoma cell lines. In order to obtain greater insight into the mechanism of AHPN-induced growth arrest and apoptosis, we began to examine AHPN-induced changes in gene expression by cDNA array screening using human lung carcinoma H460 cells. This analysis identified several AHPN-inducible genes, including the immediate-early genes Egr-1 and Nur77. AHPN was able to increase Egr-1 and Nur77 mRNA expression and protein in a variety of carcinoma cell lines. This induction appeared to be regulated at the transcriptional level and was specific for AHPN since an RAR- and an RXR-selective retinoid were inactive. These results suggest that the induction of Egr-1 and Nur77 by AHPN is independent of nuclear retinoid receptors and involves a novel mechanism. Overexpression of Bcl-2, which inhibits AHPN-induced apoptosis but not growth arrest in human T cell lymphoma Molt-4 cells, did not block the induction of immediate-early gene expression. Treatment of H460 cells with AHPN induced activation of the p38 MAP-kinase but not the ERK1/2 signaling pathway. However, inhibition of the ERK1/2 signaling pathway by PD98059 blocked the induction of Egr-1 and Nur77 mRNA while the p38 MAPK inhibitor PD169316 had little effect. Expression of a dominant-negative ERK1 completely abolished the increase in Egr-1 mRNA. Treatment with MAPK inhibitors or expression of dnERK1 reduced but did not block AHPN-induced apoptosis. Our results suggest that the induction of Egr-1 in H460 by AHPN requires active ERK1/2 and is independent of p38 activation. Egr-1, in cooperation with several other growth-suppressor proteins, is likely involved in AHPN-induced inhibition of cell growth and cell death.
Autoreactive thymocytes can be eliminated by clonal deletion during their development in the thymus. The precise developmental stage(s) at which clonal deletion occurs in a normal thymus has been difficult to assess, in large part because of the absence of a specific marker for TCR-mediated apoptosis. In this report, we reveal that Nur77 expression can be used as a specific marker of clonal deletion in an unmanipulated thymus and directly identify TCRintCD4+CD8+ and semimature CD4+CD8- thymocytes as the principal targets of deletion. These data indicate that clonal deletion normally occurs at a relatively late stage of development, as cells mature from CD4+CD8+ thymocytes to single-positive T cells.
The orphan nuclear receptor TR3/Nur77 has emerged as a viable candidate in the coordinate regulation of cell proliferation and apoptosis, essential for maintaining normal architecture in rapidly renewing tissues such as the colonic mucosa. TR3 induces apoptosis in a number of cell lineages exposed to proapoptotic stimuli by directly targeting the mitochondria, inducing cytochrome c release. Here we report a distinctly different mechanism of TR3-mediated apoptosis in colon cancer cells. Nucleus-to-cytoplasm translocation of a green fluorescent protein-TR3 construct, but not its direct mitochondrial targeting, was associated with apoptosis induced by the short-chain fatty acid, butyrate. Similar results were observed for the nonsteroidal anti-inflammatory drug, sulindac, and the chemotherapeutic drug, 5-fluorouracil. A mutant TR3 construct lacking DNA-binding ability exerted a potent proapoptotic effect in colon cancer cells that was associated with cytochrome c release, an action dependent upon cytoplasmic localization of the construct, but, again, not its direct mitochondrial targeting. We identified a potential role for BAX recruitment to the mitochondria, secondary to cytoplasmic translocation of TR3, in inducing cytochrome c release and in mediating apoptosis. Therefore, TR3 translocation from the nucleus may initiate the apoptotic cascade in colon cancer cells by stimulating other cytosolic proapoptotic molecules to associate with mitochondria.
It has been previously shown that CD4+ T cells enter the apoptotic suicide program via the Fas ligand (FasL)/Fas-mediated pathway upon T cell receptor (TCR) stimulation. In Jurkat cells TCR stimulation regulates the de novo synthesis of FasL, while in the influenza hemagglutinin-specific CD4+ murine T cell hybridoma (IP-12-7) the cell surface appearance of a preformed FasL is initiated. Both processes are dependent on new mRNA and protein synthesis, involve up-regulation of nur77, and can be inhibited by retinoic acids (RA). Two groups of nuclearreceptors for RA have been identified: retinoic acid receptors (RAR) and retinoid X receptors (RXR). In this study various synthetic retinoids were used to define which receptors regulate TCR-mediated apoptosis. It is demonstrated that the inhibition is mediated via RARα, while RARγ enhances TCR-mediated apoptosis, and when both receptors are stimulated, the costimulation by RXR will promote the effect of RARα. Evidence is presented that these receptors affect the transcriptional activity of nur77 and consequently the expression of FasL. Our data suggest a complex interaction between the various isoforms of retinoid receptors in regulating T cell death and demonstrate that the target through which retinoids regulate TCR-mediated apoptosis is nur77.
Apoptotic death can be induced in T cell hybridomas by glucocorticoids or the stimulation via the TCR/CD3 complex. The two apoptotic processes are mutually antagonistic. We have previously proposed that positive selection of thymocytes for the formation of the T cell repertoire might be based on a similar mechanism. We analyzed the TCR/CD3-mediated signals essential for the regulation of apoptosis in T cell hybridomas. We suggest that both an increase in the intracellular Ca2+ level and an activation of protein kinase C are essential for the TCR/CD3-mediated apoptosis, because we obtained the following results: 1) either reduction of extracellular Ca2+ concentration or addition of a protein kinase inhibitor, 1-(5-isoquinolkinelsulfonyl)-2-methylpiperazine or N-(2-(methylamino)ethyl)-5-isoquinolinesulfonamide, inhibited anti-CD3-induced but not dexamethasone-induced DNA fragmentation. 2) The combination of ionomycin and PMA, but neither one alone nor the combination of ionomycin and cyclic nucleotide analogs, induced DNA fragmentation. On the contrary, we suggest that only an increase in the intracellular Ca2+ level is essential for the inhibition of glucocorticoid-induced apoptosis, because ionomycin alone as well as the combination of ionomycin and PMA inhibited dexamethasone- but not anti-CD3-induced DNA fragmentation.
When a human fetal muscle cDNA library was screened with the human thyroid hormone receptor alpha 2 cDNA at low stringency, we found a weakly hybridizing cDNA. The sequence of the insert was 2498 basepairs, with an open reading frame of 1794 basepairs encoding a protein of 598 amino acids and a predicted molecular mass of 64 kDa. The DNA-binding domain and the ligand-binding domain are similar to those of steroid and thyroid hormone receptors. Moreover, this cDNA is highly homologous to mouse nur77 and rat NGFI-B, which are early response genes induced by nerve growth factor and other serum growth factors. We designated this gene NAK1. The modulation of expression of NAK1 during stimulation of cell growth was studied. The mRNA of NAK1 was induced rapidly and transiently by growth-stimulating agents, such as adenosine diphosphate, in monkey kidney cells (BSC-1), by phytohemagglutinin in human lymphocytes, and by serum stimulation of arrested fibroblasts. It is expressed in human fetal muscle and adult liver, brain, and thyroid. NAK1 could be a nuclear receptor. It will be of great interest to determine the ligand for NAK1 and the genes that are regulated by it.
Recognition of self-antigens by immature thymocytes results in either activation-induced apoptosis (negative selection) or survival (positive selection). While it is believed that T cell receptor avidity plays a role in determining the outcome, the mechanisms responsible for this life or death decision are not known. Recent data concerning the mutual antagonism between activation- and glucocorticoid-induced apoptosis have prompted an examination of the potential interaction of these two signaling pathways in the regulation of antigen-specific selection.
NURR1 is an orphan member of the nuclear receptor superfamily of transcription factors that shares close sequence homology to the orphan nuclear receptor and immediate early gene product NUR77(NGF1 beta). The physiological role of NURR1 has not been established in mammalian cells. However, the observation that NURR1 and NUR77 interact with at least one common enhancer element (AAAAGGTCA), together with their partly overlapping but differential expression patterns in mammalian tissues, suggests that these proteins may have both shared and independent transcription regulatory functions. To identify potential target genes that may be regulated by NURR1, we analyzed its DNA binding properties to potential cis-acting enhancer elements. Using point mutagenesis of the AAAAGGTCA motif, we have identified three additional sequences that bind specifically to both NURR1 and NUR77, one of which serves as a functional enhancer element. Comparative analysis of the transcription regulatory properties of NURR1 and NUR77 indicates that the proteins can display opposing transregulatory activities that are influenced by the specific cis-acting sequences to which they bind. Our results indicate that the transcriptional responses of specific target genes to the NURR1/NUR77 subfamily may be differentially regulated by the relative cellular levels of NURR1 and NUR77 and influenced by the specific enhancer sequences that mediate their activity. Finally, we have identified several potential target genes of neuronal and neuroendocrine origin whose promoters contain this element.
NURR1 is an immediate early gene product and a member of the nuclear receptor superfamily of transcription factors. Using the NURR1 cDNA as a probe, we isolated the genomic DNA encoding NURR1 from a mouse 129SvEv genomic library. The NURR1 gene is approximately 6.2 kb long and is organized into 7 exons separated by 6 introns. Structural analysis of the NURR1 reveals that this gene shares a similar structure with that of the nuclear receptor NUR77/NGF1-B. As in NUR77, the promoter region of NURR1 lacks an identifiable TATA box, but is GC-rich. The proximal promoter region also contains an ATF/CREB consensus binding site that may participate in cAMP-mediated induction of this immediate early gene product. Isolation and structural characterization of the NURR1 gene provides information for further developmental and transcriptional regulation studies of this gene.
TCR signaling leading to thymocyte apoptosis is mediated through the expression of the Nur77 family of orphan nuclear receptors. MEF2 has been shown to be the major transcription factor responsible for calcium-dependent Nur77 transcription. Cabin1 was recently identified as a transcriptional repressor of MEF2, which can be released from MEF2 in a calcium-dependent fashion. The molecular basis of repression of MEF2 by Cabin1, however, has remained unknown. We report that Cabin1 represses MEF2 by two distinct mechanisms. Cabin1 recruits mSin3 and its associated histone deacetylases 1 and 2; Cabin1 also competes with p300 for binding to MEF2. Thus, activation of MEF2 and the consequent transcription of Nur77 are controlled by the association of MEF2 with the histone deacetylases via the calcium-dependent repressor Cabin1.
There is now a very large number of patients with coronary artery disease who have also undergone percutaneous interventions such as coronary angioplasty. Atherosclerosis and restenosis are two distinct pathologic processes with different underlying pathophysiologic mechanisms, different natural histories, different clinical presentations, and treatment strategies. Management strategies to target both processes are currently poorly applied in clinical practice. The development of integrated management strategies to target atherosclerosis, as well as restenosis in the postprocedural period remains a priority.
PTEN, a tumor suppressor gene, is essential for embryogenesis. We used the Cre-loxP system to generate a T cell-specific deletion of the Pten gene (Pten(flox/-) mice). All Pten(flox/-) mice develop CD4+ T cell lymphomas by 17 weeks. Pten(flox/-) mice show increased thymic cellularity due in part to a defect in thymic negative selection. Pten(flox/-) mice exhibit elevated levels of B cells and CD4+ T cells in the periphery, spontaneous activation of CD4+ T cells, autoantibody production, and hypergammaglobulinemia. Pten(flox/-) T cells hyperproliferate, are autoreactive, secrete increased levels of Th1/Th2 cytokines, resist apoptosis, and show increased phosphorylation of PKB/Akt and ERK. Peripheral tolerance to SEB is also impaired in Pten(flox/-) mice. PTEN is thus an important regulator of T cell homeostasis and self-tolerance.
Myocyte enhancer binding factor 2 (MEF2) proteins belong to the MADS box family of transcription factors and four MEF2 proteins, MEF2A, MEF2B, MEF2C and MEF2D, have been found. MEF2 proteins have been shown to play critical roles in differentiation of muscles and neuronal tissues. How transactivational activity of MEF2 proteins is regulated is not fully understood. MEF2 proteins are activated by several kinases, including Erk5 and calcium/calmodulin-dependent kinase, and interact with repressors, including histone deacetylases 4 and 5 (HDAC4 and HDAC5) and Cabin1. During the effort to understand regulation of MEF2 activity, we identified 14-3-3tau as a MEF2D-interacting molecule by yeast two-hybrid screening. We found that 14-3-3tau forms a complex with MEF2D in vivo and specifically enhances MEF2 transactivational activity. The results from transient transfection and co-precipitation experiments suggest that 14-3-3tau activates MEF2D by competitively inhibiting HDAC4 from binding to MEF2D and thereby affects muscle cell differentiation.
Nur-related factor 1 (Nurr1) has been implicated in liver generation after hepatectomy. We hypothesized that the genes in the nerve growth factor-induced gene B (NGFI-B) family was induced in liver ischemia-reperfusion injury.
Expression of the NGFI-B family genes was examined by the reverse transcription-polymerase chain reaction in rat and human livers. In situ hybridization was performed to check the localization of the NGFI-B gene in rat liver. Expression of phospho-Ser-133-specific cyclic adenosine-3' :5'-monophosphate response element binding (pCREB) protein was examined by Western blot analysis and gel shift assay, since the promoter region of the NGFI-B family genes contains CRE.
The expression of the NGFI-B family genes were recognized within 30 min after ischemia-reperfusion in rat liver, which was augmented by cycloheximide injection. In human specimens, the NGFI-B family genes expression was stronger than that before ischemic insult. pCREB protein was detected in the rat liver sampled 15 min after reperfusion. Gel shift assay suggested that CREB bound to neuron-derived orphan receptor gene in rat liver cells.
We recognized the early induction of the NGFI-B family genes after ischemia-reperfusion injury in rat and human livers. A pathway via CREB may be responsible for the induction.
Apoptosis represents an effective way to eliminate cancer cells. Unfortunately, advanced prostate tumors eventually progress to androgen-independent tumors, which are resistant to current therapeutic approaches that act by triggering apoptosis. Vitamin A and its natural and synthetic analogs (retinoids) induce apoptosis in prostate cancer cells in vitro and in animal models, mainly through induction of retinoic acid receptor-beta (RARbeta). Expression levels of RARbeta, however, are significantly reduced in hormone-independent prostate cancer cells. Recently, a new class of synthetic retinoids related to 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid (AHPN) (also called CD437) that effectively induces apoptosis of both hormone-dependent and -independent prostate cancer cells in a retinoid receptor-independent manner was identified and has drawn a lot of attention in the field. The apoptotic effect of AHPN requires expression of orphan receptor TR3 (also called nur77 or NGFI-B). Paradoxically, TR3 expression is also induced by androgen and other mitogenic agents in prostate cancer cells to confer their proliferation. The recent finding that TR3 migrates from the nucleus to mitochondria to trigger apoptosis in response to AHPN suggests that the opposing biological activities of TR3 are regulated by its subcellular localization. Thus, agents that induce translocalization of TR3 from the nucleus to mitochondria will have improved efficacy against prostate cancer. TR3, therefore, represents an unexplored molecule that may be an ideal target for developing new agents for prostate cancer therapy.
In vertebrates, both nuclear all-trans and 9-cis retinoic acid receptors (RAR and RXR) belonging to the steroid/thyroid/retinoid nuclear receptor superfamily play a crucial role in the vitamin A action. Qualitative analysis of all known RAR or RXR subtypes in both pooled and non-pooled peripheral blood mononuclear cells (PBMC) from healthy human subjects has been performed by reverse transcription and polymerase chain reaction (RT-PCR). Our data, based on qualitative RT-PCR analysis has shown that human PBMC are capable to express RAR alpha, RAR gamma, RXR alpha, and RXR beta.