Differential expression of the estrogen receptor-related receptor gamma in the mouse brain

Evolution of the expression and regulation of the nuclear hormone receptor ERR gene family in the chordate lineage

The Estrogen Related Receptor (ERR) nuclear hormone receptor genes have a wide diversity of roles in vertebrate development. In embryos, ERR genes are expressed in several tissues, including the central and peripheral nervous systems. Here we seek to establish the evolutionary history of chordate ERR genes, their expression and their regulation. We examine ERR expression in mollusc, amphioxus and sea squirt embryos, finding the single ERR orthologue is expressed in the nervous system in all three, with muscle expression also found in the two chordates. We show that most jawed vertebrates and lampreys have four ERR paralogues, and that vertebrate ERR genes were ancestrally linked to Estrogen Receptor genes. One of the lamprey paralogues shares conserved expression domains with jawed vertebrate ERRγ in the embryonic vestibuloacoustic ganglion, eye, brain and spinal cord. Hypothesising that conserved expression derives from conserved regulation, we identify a suite of pan-vertebrate conserved non-coding sequences in ERR introns. We use transgenesis in lamprey and chicken embryos to show that these sequences are regulatory and drive reporter gene expression in the nervous system. Our data suggest an ancient association between ERR and the nervous system, including expression in cells associated with photosensation and mechanosensation. This includes the origin in the vertebrate common ancestor of a suite of regulatory elements in the 3' introns that drove nervous system expression and have been conserved from this point onwards.

Expression and function of estrogen receptors and estrogen-related receptors in the brain and their association with Alzheimer's disease

While estrogens are well known for their pivotal role in the female reproductive system, they also play a crucial function in regulating physiological processes associated with learning and memory in the brain. Moreover, they have neuroprotective effects in the pathogenesis of Alzheimer's disease (AD). Importantly, AD has a higher incidence in older and postmenopausal women than in men, and estrogen treatment might reduce the risk of AD in these women. In general, estrogens bind to and activate estrogen receptors (ERs)-mediated transcriptional machineries, and also stimulate signal transduction through membrane ERs (mERs). Estrogen-related receptors (ERRs), which share homologous sequences with ERs but lack estrogen-binding capabilities, are widely and highly expressed in the human brain and have also been implicated in AD pathogenesis. In this review, we primarily provide a summary of ER and ERR expression patterns in the human brain. In addition, we summarize recent studies on their role in learning and memory. We then review and discuss research that has elucidated the functions and importance of ERs and ERRs in AD pathogenesis, including their role in Aβ clearance and the reduction of phosphorylated tau levels. Elucidation of the mechanisms underlying ER- and ERR-mediated transcriptional machineries and their functions in healthy and diseased brains would provide new perspectives for the diagnosis and treatment of AD. Furthermore, exploring the potential role of estrogens and their receptors, ERs, in AD will facilitate a better understanding of the sex differences observed in AD, and lead to novel sex-specific therapeutic approaches.

Brain nuclear receptors and cardiovascular function

Brain-heart interaction has raised up increasing attentions. Nuclear receptors (NRs) are abundantly expressed in the brain, and emerging evidence indicates that a number of these brain NRs regulate multiple aspects of cardiovascular diseases (CVDs), including hypertension, heart failure, atherosclerosis, etc. In this review, we will elaborate recent findings that have established the physiological relevance of brain NRs in the context of cardiovascular function. In addition, we will discuss the currently available evidence regarding the distinct neuronal populations that respond to brain NRs in the cardiovascular control. These findings suggest connections between cardiac control and brain dynamics through NR signaling, which may lead to novel tools for the treatment of pathological changes in the CVDs.

Discovery of new ERRγ agonists regulating dopaminergic neuronal phenotype in SH-SY5Y cells

The discovery of small molecules that regulate specific neuronal phenotypes is important for the development of new therapeutic candidates for neurological diseases. Estrogen-related receptor γ (ERRγ), an orphan nuclear receptor widely expressed in the central nervous system (CNS), is closely related to the regulation of neuronal metabolism and differentiation. We previously reported that upregulation of ERRγ could enhance dopaminergic neuronal phenotypes in the neuroblastoma cell line, SH-SY5Y. In this study, we designed and synthesized a series of new ERRγ agonists using the X-ray crystal structure of the GSK4716-bound ERRγ complex and known synthetic ligands. Our new ERRγ agonists exhibited increased transcriptional activities of ERRγ. In addition, our molecular docking results supported the experimental findings for ERRγ agonistic activity of the potent analogue, 5d. Importantly, 5d not only enhanced the expression of dopaminergic neuronal-specific molecules, TH and DAT but also activated the relevant signaling events, such as the CREB-mediated signaling pathway. The results of the present study may provide useful clues for the development of novel ERRγ agonists for neurological diseases related to the dopaminergic nervous system.

Perinatal Exposure of Bisphenol A Differently Affects Dendritic Spines of Male and Female Grown-Up Adult Hippocampal Neurons

Perinatal exposure to Bisphenol A (BPA) at a very low dose may modulate the development of synapses of the hippocampus during growth to adulthood. Here, we demonstrate that perinatal exposure to 30 μg BPA/kg per mother’s body weight/day significantly altered the dendritic spines of the grownup rat hippocampus. The density of the spine was analyzed by imaging of Lucifer Yellow-injected CA1 glutamatergic neurons in adult hippocampal slices. In offspring 3-month male hippocampus, the total spine density was significantly decreased by BPA exposure from 2.26 spines/μm (control, no BPA exposure) to 1.96 spines/μm (BPA exposure). BPA exposure considerably changed the normal 4-day estrous cycle of offspring 3-month females, resulting in a 4∼5 day estrous cycle with 2-day estrus stages in most of the subjects. In the offspring 3-month female hippocampus, the total spine density was significantly increased by BPA exposure at estrus stage from 2.04 spines/μm (control) to 2.25 spines/μm (BPA exposure). On the other hand, the total spine density at the proestrus stage was moderately decreased from 2.33 spines/μm (control) to 2.19 spines/μm (BPA exposure). Thus, after the perinatal exposure to BPA, the total spine density in males became lower than that in females. Concerning the BPA effect on the morphology of spines, the large-head spine was significantly changed with its significant decrease in males and moderate change in females.

The emerging role of estrogen related receptorα in complications of non-small cell lung cancers

Approximately 85% of lung cancer cases are recognized as non-small cell lung cancer (NSCLC) with a perilous (13–17%) 5-year survival in Europe and the USA. Although tobacco smoking has consistently emerged as the leading cause of NSCLC complications, its consequences are distinctly manifest with respect to sex bias, due to differential gene and sex hormone expression. Estrogen related receptor α (ERRα), a member of the nuclear orphan receptor superfamily is normally expressed in the lungs, and activates various nuclear genes without binding to the ligands, such as estrogens. In NSCLC ERRα expression is significantly higher compared with healthy individuals. It is well established ERα and ERβ‚ have 93% and 60% identity in the DNA and ligand binding domains, respectively. ERα and ERRα have 69% (70% with ERRα-1) and 34% (35% with ERRα-1) identity, respectively; ERRα and ERRβ‚ have 92 and 61% identity, respectively. However, whether there is distinctive ERRα interaction with mammalian estrogens or concurrent involvement in non-ER signalling pathway activation is not known. Relevant to NSCLC, ERRα promotes proliferation, invasion and migration by silencing the tumor suppressor proteins p53 and pRB, and accelerates G₂-M transition during cell division. Epithelial to mesenchymal transition (EMT) and activation of Slug (an EMT associated transcription factor) are the prominent mechanisms by which ERRα activates NSCLC metastasis. Based on these observations, the present article focuses on the feasibility of antiERRα therapy alone and in combination with antiER as a therapeutic strategy for NSCLC complications.

Mitochondrial Etiology of Neuropsychiatric Disorders

The brain has the highest mitochondrial energy demand of any organ. Therefore, subtle changes in mitochondrial energy production will preferentially affect the brain. Considerable biochemical evidence has accumulated revealing mitochondrial defects associated with neuropsychiatric diseases. Moreover, the mitochondrial genome encompasses over a thousand nuclear DNA genes plus hundreds to thousands of copies of the maternally inherited mitochondrial DNA (mtDNA). Therefore, partial defects in either the nuclear DNA or mtDNA genes or combinations of the two can be sufficient to cause neuropsychiatric disorders. Inherited and acquired mtDNA mutations have recently been associated with autism spectrum disorder, which parallels previous evidence of mtDNA variation in other neurological diseases. Therefore, mitochondrial dysfunction may be central to the etiology of a wide spectrum of neurological diseases. The mitochondria and the nucleus communicate to coordinate energy production and utilization, providing the potential for therapeutics by manipulating nuclear regulation of mitochondrial gene expression.

Emerging Roles of Estrogen-Related Receptors in the Brain: Potential Interactions with Estrogen Signaling

In addition to their well-known role in the female reproductive system, estrogens can act in the brain to regulate a wide range of behaviors and physiological functions in both sexes. Over the past few decades, genetically modified animal models have greatly increased our knowledge about the roles of estrogen receptor (ER) signaling in the brain in behavioral and physiological regulations. However, less attention has been paid to the estrogen-related receptors (ERRs), the members of orphan nuclear receptors whose sequences are homologous to ERs but lack estrogen-binding ability. While endogenous ligands of ERRs remain to be determined, they seemingly share transcriptional targets with ERs and their expression can be directly regulated by ERs through the estrogen-response element embedded within the regulatory region of the genes encoding ERRs. Despite the broad expression of ERRs in the brain, we have just begun to understand the fundamental roles they play at molecular, cellular, and circuit levels. Here, we review recent research advancement in understanding the roles of ERs and ERRs in the brain, with particular emphasis on ERRs, and discuss possible cross-talk between ERs and ERRs in behavioral and physiological regulations.

Evidence for a role of oestrogen receptor-related receptor in the regulation of male sexual behaviour in the moth Agrotis ipsilon

The oestrogen receptor-related receptors (ERRs) are orphan nuclear receptors that were originally identified on the basis of their close homology to the oestrogen receptors. The three mammalian ERR genes participate in the regulation of vital physiological processes including reproduction, development and metabolic homeostasis. Although unique ERRs have been found in insects, data on the function and regulation of these receptors remain sparse. In the present study, a 2095-bp full-length cDNA encoding an ERR, termed AiERR, was isolated from males of the moth Agrotis ipsilon and deposited in the GenBank database under the accession number KT944662. The predicted AiERR protein shared an overall identity of 47-82% with other known insect and mammalian ERR homologues. AiERR exhibited a broad tissue expression pattern with the detection of one transcript of approximately 2 kb in the primary olfactory centres, the antennal lobes (AL). In adult males, the amount of AiERR mRNA in the AL increased concomitantly with age and responses to the female-emitted sex pheromone. Moreover, AiERR knockdown induced an inhibition in the sex pheromone-orientated flight of male. Using A. ipsilon as a model, our study demonstrates that the insect ERR is critical for the performance of male sexual behaviour, probably by acting on central pheromone processing.

Immunohistochemical profiling of estrogen-related receptor gamma in rat brain and colocalization with estrogen receptor alpha in the preoptic area

Estrogen-related receptor (ERR) is a member of the nuclear receptor superfamily that has strong homology with estrogen receptor (ER) α. Despite the lack of endogenous ligands, ERR serves as transcription factors through their constitutively active structure with or without interaction with ERα. Among the three subtypes of ERR (α, β, and γ), ERRγ is highly expressed in brain, but the distribution of ERRγ is poorly characterized. Therefore, we investigated ERRγ immunoreactivity throughout the rostro-caudal axis in rat brain. Immunohistochemistry revealed localization of ERRγ protein in the cell nucleus, and a ubiquitous distribution of ERRγ in brain regions including the olfactory bulb, cerebrum, brain stem, and cerebellum. Selective intense immunoreactivity was observed in the reticular thalamic nucleus, zona incerta, circular nucleus, interpeduncular nucleus, pontine nucleus, and parasolitary nucleus. Most ERRγ-immunoreactive (ir) regions were also positive for ERα and/or ERβ, which suggests that ERRγ is involved in modulation of estrogen signaling in adult rat brain. Double immunofluorescence demonstrated colocalization of ERRγ with ERα within the anteroventral periventricular nucleus of the preoptic area (AVPV) and medial preoptic nucleus (MPO), which are major target sites for estrogen action. The results of this study suggest that ERRγ function in the brain is affected by estrogens through an interaction with ERα. The findings also provide basic information on brain region-specific ERRγ function.

Dependence of hippocampal function on ERRγ-regulated mitochondrial metabolism

Neurons utilize mitochondrial oxidative phosphorylation (OxPhos) to generate energy essential for survival, function, and behavioral output. Unlike most cells that burn both fat and sugar, neurons only burn sugar. Despite its importance, how neurons meet the increased energy demands of complex behaviors such as learning and memory is poorly understood. Here we show that the estrogen-related receptor gamma (ERRγ) orchestrates the expression of a distinct neural gene network promoting mitochondrial oxidative metabolism that reflects the extraordinary neuronal dependence on glucose. ERRγ(-/-) neurons exhibit decreased metabolic capacity. Impairment of long-term potentiation (LTP) in ERRγ(-/-) hippocampal slices can be fully rescued by the mitochondrial OxPhos substrate pyruvate, functionally linking the ERRγ knockout metabolic phenotype and memory formation. Consistent with this notion, mice lacking neuronal ERRγ in cerebral cortex and hippocampus exhibit defects in spatial learning and memory. These findings implicate neuronal ERRγ in the metabolic adaptations required for memory formation.

Estrogen-related receptor gamma regulates dopaminergic neuronal phenotype by activating GSK3β/NFAT signaling in SH-SY5Y cells

The orphan nuclear receptor estrogen-related receptor gamma (ERRγ) is highly expressed in the nervous system during embryogenesis and in adult brains, but its physiological role in neuronal development remains unknown. In this study, we evaluated the relevance of ERRγ in regulating dopaminergic (DAergic) phenotype and the corresponding signaling pathway. We used retinoic acid (RA) to differentiate human neuroblastoma SH-SY5Y cells. RA induced neurite outgrowth of SH-SY5Y cells with an increase in DAergic neuron-like properties, including up-regulation of tyrosine hydroxylase, dopamine transporter, and vesicular monoamine transporter 2. ERRγ, but not ERRα, was up-regulated by RA, and participated in RA effect on SH-SY5Y cells. ERRγ over-expression enhanced mature DAergic neuronal phenotype with neurite outgrowth as with RA treatment; and RA-induced increase in DAergic phenotype was attenuated by silencing ERRγ expression. ERRγ appears to have a crucial role in morphological and functional regulation of cells that is selective for DAergic neurons. Polo-like kinase 2 was up-regulated in ERRγ-over-expressing SH-SY5Y cells, which was involved in phosphorylation of glycogen synthase kinase 3β and resulting downstream activation of nuclear factor of activated T cells. The likely involvement of ERRγ in regulating the DAergic neuronal phenotype makes this orphan nuclear receptor a novel target for understanding DAergic neuronal differentiation. We propose the relevance of estrogen-related receptor gamma (ERRγ) in regulating dopaminergic neuronal phenotype: ERRγ is up-regulated by retinoic acid in SH-SY5Y cells, and enhances dopaminergic phenotypes and induces neurite outgrowth; Polo-like kinase 2 (PLK2) and glycogen synthase kinase 3 beta/nuclear factor of activated T cells (GSK3β/NFAT) signaling are responsible for the ERRγ effect. Our findings provide the first insights into the role of ERRγ in the brain, as a novel approach toward understanding dopaminergic differentiation.

Investigation of the effects of subchronic low dose oral exposure to bisphenol A (BPA) and ethinyl estradiol (EE) on estrogen receptor expression in the juvenile and adult female rat hypothalamus

Concerns have been raised regarding the long-term impacts of early life exposure to the ubiquitous environmental contaminant bisphenol A (BPA) on brain organization. Because BPA has been reported to affect estrogen signaling, and steroid hormones play a critical role in brain sexual differentiation, there is also concern that BPA exposure could alter neural sex differences. Here, we examine the impact of subchronic exposure from gestation to adulthood to oral doses of BPA below the current no-observed-adverse-effect level (NOAEL) of 5 mg/kg body weight (bw)/day on estrogen receptor (ESR) expression in sexually dimorphic brain regions of prepubertal and adult female rats. The dams were gavaged daily with vehicle (0.3% carboxymethylcellulose), 2.5, 25, 260, or 2700 μg BPA/kg bw/day, or 0.5 or 5.0 μg ethinyl estradiol (EE)/kg bw/day from gestational day 6 until labor began. Offspring were then gavaged directly from the day after birth until the day before scheduled sacrifice on postnatal days 21 or 90. Using in situ hybridization, one or more BPA doses produced significant decreases in Esr1 expression in the juvenile female rat anteroventral periventricular nucleus (AVPV) of the hypothalamus and significant decreases in Esr2 expression in the adult female rat AVPV and medial preoptic area (MPOA), relative to vehicle controls. BPA did not simply reproduce EE effects, indicating that BPA is not acting solely as an estrogen mimic. The possible consequences of long-term changes in hypothalamic ESR expression resulting from subchronic low dose BPA exposure on neuroendocrine effects are discussed and being addressed in ongoing, related work.

Sex-specific epigenetic disruption and behavioral changes following low-dose in utero bisphenol A exposure

Bisphenol A (BPA) is an estrogenic endocrine disruptor widely used in the production of plastics. Increasing evidence indicates that in utero BPA exposure affects sexual differentiation and behavior; however, the mechanisms underlying these effects are unknown. We hypothesized that BPA may disrupt epigenetic programming of gene expression in the brain. Here, we provide evidence that maternal exposure during pregnancy to environmentally relevant doses of BPA (2, 20, and 200 µg/kg/d) in mice induces sex-specific, dose-dependent (linear and curvilinear), and brain region-specific changes in expression of genes encoding estrogen receptors (ERs; ERα and ERβ) and estrogen-related receptor-γ in juvenile offspring. Concomitantly, BPA altered mRNA levels of epigenetic regulators DNA methyltransferase (DNMT) 1 and DNMT3A in the juvenile cortex and hypothalamus, paralleling changes in estrogen-related receptors. Importantly, changes in ERα and DNMT expression in the cortex (males) and hypothalamus (females) were associated with DNA methylation changes in the ERα gene. BPA exposure induced persistent, largely sex-specific effects on social and anxiety-like behavior, leading to disruption of sexually dimorphic behaviors. Although postnatal maternal care was altered in mothers treated with BPA during pregnancy, the effects of in utero BPA were not found to be mediated by maternal care. However, our data suggest that increased maternal care may partially attenuate the effects of in utero BPA on DNA methylation. Overall, we demonstrate that low-dose prenatal BPA exposure induces lasting epigenetic disruption in the brain that possibly underlie enduring effects of BPA on brain function and behavior, especially regarding sexually dimorphic phenotypes.

Murine lupus susceptibility locus Sle1c2 mediates CD4+ T cell activation and maps to estrogen-related receptor γ

Sle1c is a sublocus of the NZM2410-derived Sle1 major lupus susceptibility locus. We have shown previously that Sle1c contributes to lupus pathogenesis by conferring increased CD4(+) T cell activation and increased susceptibility to chronic graft-versus-host disease (cGVHD), which mapped to the centromeric portion of the locus. In this study, we have refined the centromeric sublocus to a 675-kb interval, termed Sle1c2. Mice from recombinant congenic strains expressing Sle1c2 exhibited increased CD4(+) T cell intrinsic activation and cGVHD susceptibility, similar to mice with the parental Sle1c. In addition, B6.Sle1c2 mice displayed a robust expansion of IFN-γ-expressing T cells. NZB complementation studies showed that Sle1c2 expression exacerbated B cell activation, autoantibody production, and renal pathology, verifying that Sle1c2 contributes to lupus pathogenesis. The Sle1c2 interval contains two genes, only one of which, Esrrg, is expressed in T cells. B6.Sle1c2 CD4(+) T cells expressed less Esrrg than B6 CD4(+) T cells, and Esrrg expression was correlated negatively with CD4(+) T cell activation. Esrrg encodes an orphan nuclear receptor that regulates oxidative metabolism and mitochondrial functions. In accordance with reduced Esrrg expression, B6.Sle1c2 CD4(+) T cells present reduced mitochondrial mass and altered mitochondrial functions as well as altered metabolic pathway utilization when compared with B6 CD4(+) T cells. Taken together, we propose Esrrg as a novel lupus susceptibility gene regulating CD4(+) T cell function through their mitochondrial metabolism.

Nanomolar dose of bisphenol A rapidly modulates spinogenesis in adult hippocampal neurons

We demonstrated the rapid effects of 10nM bisphenol A (BPA) on the spinogenesis of adult rat hippocampal slices. The density of spines was analyzed by imaging Lucifer Yellow-injected CA1 neurons in slices. Not only the total spine density but also the head diameter distribution of spine was quantitatively analyzed. Spinogenesis was significantly enhanced by BPA within 2h. In particular, the density of middle-head spine (with head diameter of 0.4-0.5μm) was significantly increased. Hydroxytamoxifen, an antagonist of both estrogen-related receptor gamma (ERRγ) and estrogen receptors (ERα/ERβ), blocked the BPA-induced enhancement of the spine density. However, ICI 182,780, an antagonist of ERα/ERβ, did not suppress the BPA effects. Therefore, ERRγ is deduced to be a high affinity receptor of BPA, responsible for modulation of spinogenesis. The BPA-induced enhancement of spinogenesis was also suppressed by MAP kinase inhibitor, PD98059, and the blocker of NMDA receptors, MK-801. Washout of BPA for additional 2h after 2h BPA treatment abolished the BPA-induced enhancement of spinogenesis, suggesting that the BPA effect was reversible. ERRγ was localized at synapses as well as cell bodies of principal neurons. ERRγ at synapses may contribute to the observed rapid effect. The level of BPA in the hippocampal slices was determined by mass-spectrometric analysis.

Clinical implication of estrogen-related receptor (ERR) expression in uterine endometrial cancers

Estrogen receptor (ER)alpha and ERbeta mRNAs levels decreased with clinical stage, myometrial invasion and dedifferentiation. On the other hand, ERRalpha mRNA levels and histoscores increased with clinical stage and myometrial invasion, regardless of dedifferentiation. ERRalpha can bind to the steroid receptor coactivator family without any ligands, and drive transcription activity of the target genes. The competitive interaction of ERRalpha/ER expression associated with the use of common cofactors during loosing estrogen dependency might cause their expression manner. The up-regulation of ERRalpha might be related to tumor growth and advancement in uterine endometrial cancers. It is speculated that ERRalpha is a candidate for prognostic factors in uterine endometrial cancer, although ERRs are not directly related to growth of uterine endometrial cancer.

Rapid pain modulation with nuclear receptor ligands

We discuss and present new data regarding the physiological and molecular mechanisms of nuclear receptor activation in pain control, with a particular emphasis on non-genomic effects of ligands at peroxisome proliferator-activated receptor (PPAR), GPR30, and classical estrogen receptors. PPARalpha agonists rapidly reduce both acute and chronic pain in a number of pain assays. These effects precede transcriptional anti-inflammatory actions, and are mediated in part by IK(ca) and BK(ca) channels on DRG neurons. In contrast to the peripheral site of action of PPARalpha ligands, the dorsal horn supports the expression of PPARgamma. Intrathecal administration of PPARgamma ligands rapidly (< or =5 min) attenuated mechanical and thermal hypersensitivity associated with nerve injury in a dose-dependent manner that could be blocked with PPARgamma antagonists. By contrast, a PPARgamma antagonist itself rapidly increased the mechanical allodynia associated with nerve injury. These data suggest that ligand-dependent, non-genomic activation of spinal PPARgamma decreases behavioral signs of inflammatory and neuropathic pain. We also report that the GPR30 is expressed on cultured sensory neurons, that activation of the receptor elicits signaling to increase calcium accumulation. This signaling may contribute to increased neuronal sensitivity as treatment with the GPR30 agonist induces hyperalgesia. Finally, application of the membrane-impermeable 17beta-E(2)-BSA rapidly (within 15 min) enhanced BK-stimulated inositol phosphate (IP) accumulation and PGE(2)-mediated cAMP accumulation in trigeminal ganglion cultures. We conclude that nuclear receptor ligands may operate through rapid, non-genomic mechanisms to modulate inflammatory and neuropathic pain.

Direct evidence revealing structural elements essential for the high binding ability of bisphenol A to human estrogen-related receptor-gamma

BACKGROUND

Various lines of evidence have shown that bisphenol A [BPA; HO-C6H4-C(CH3)2-C6H4-OH] acts as an endocrine disruptor when present in very low doses. We have recently demonstrated that BPA binds strongly to human estrogen-related receptor-gamma (ERR-gamma ) in a binding assay using [3H]4-hydroxytamoxifen ([3H]4-OHT). We also demonstrated that BPA inhibits the deactivation activity of 4-OHT.

OBJECTIVES

In the present study, we intended to obtain direct evidence that BPA interacts with ERR-gamma as a strong binder, and also to clarify the structural requirements of BPA for its binding to ERR-gamma.

METHODS

We examined [3H]BPA in the saturation binding assay using the ligand binding domain of ERR-gamma and analyzed the result using Scatchard plot analysis. A number of BPA derivatives were tested in the competitive binding assay using [3H]BPA as a tracer and in the luciferase reporter gene assay.

RESULTS

[3H]BPA showed a KD of 5.50 nM at a Bmax of 14.4 nmol/mg. When we examined BPA derivatives to evaluate the structural essentials required for the binding of BPA to ERR-gamma , we found that only one of the two phenol-hydroxyl groups was essential for the full binding. The maximal activity was attained when one of the methyl groups was removed. All of the potent BPA derivatives retained a high constitutive basal activity of ERR-gamma in the luciferase reporter gene assay and exhibited a distinct inhibitory activity against 4-OHT.

CONCLUSION

These results indicate that the phenol derivatives are potent candidates for the endocrine disruptor that binds to ERR-gamma.

Clinical implication of estrogen-related receptor (ERR) expression in ovarian cancers

The expression of estrogen receptor (ER)alpha and ERbeta mRNAs did not show any specific manner according to clinical backgrounds in ovarian cancers. On the other hand, the levels of estrogen-related receptor (ERR)alpha mRNA increased with clinical stages regardless of histopathological types in ovarian cancers. However, ERRbeta and ERRgamma mRNA levels were extremely low to determine reliably. ERRalpha can bind to the steroid receptor coactivator family without any ligands, and drive transcription activity of the target genes. The manner of ERR and ER gene expressions might show an independent usage of common cofactors. It is speculated that the up regulation of ERRalpha might be related to advancement of ovarian cancers regardless of plausible interaction via cofactors regulated by ERs. Although ERRalpha is not directly related to growth of ovarian cancer, ERRalpha is a candidate for prognostic factors for ovarian cancer.

Molecular cloning and functional study of rat estrogen receptor-related receptor gamma in rat prostatic cells

BACKGROUND

Based on high homology of ERRs with ERs, we hypothesize that ERRs might functionally cross talk with ERs or independently in prostatic cells.

METHODS

We examined the ERRgamma expressions in rat prostates and Nb rat prostate cancer model, and its growth regulation in stable transfectants of prostatic cells.

RESULTS

We cloned the ERRgamma cDNA from rat prostate by RACE-PCR. Its expression was confirmed by Northern and immunoblottings. Real-time RT-PCR showed that its expression in castrated prostates was androgen-dependent. ERRgamma was expressed in prostatic epithelial cells, but showed reduced expressions in neoplastic prostates. Transfections confirmed that ERRgamma was expressed in prostatic cells as nuclear protein and transcriptionally active without estradiol. Its overexpression in ERRgamma-stable transfectants of NbE-1 and MAT-Lu cells inhibited their in vitro proliferation, anchorage-independent growth in soft-agar and tumorigenicity in nude mice.

CONCLUSIONS

Our studies show that ERRgamma is functionally expressed in rat prostate and may play anti-proliferative actions in prostatic cells. Its co-expression with ERs suggests that besides ERs, ligand-independent ERRgamma is also involved in prostatic growth and functions.

Localization of Oestrogen Receptors Within Various Bovine Ovarian Cell Types at Different Stages of the Oestrous Cycle

In the present study oestrogen receptor alpha(ERalpha) and oestrogen receptor beta (ERbeta) mRNA were localized in various ovarian cell types of 23 cows at different stages of the oestrous cycle. ERalpha was detected by immunohistochemistry and the localization of ERbeta mRNA was examined using in situ hybridization. The immunostaining of ERalpha was low in the ovarian follicles, tunica albuginea and surface epithelium, but high in cells of the deep stroma and superficial stroma, which indicates a functional role of ERalpha in the cells surrounding the follicles. In contrast, ERbeta mRNA scores were low to moderate in primordial and primary follicles, and increased with the development of the follicle. ERbeta mRNA scores were higher in cystic follicles than in obliterative follicles. In the corpora lutea and corpora albicantia the scores for ERbeta mRNA were moderate. Furthermore, in the corpora lutea, ERbeta mRNA levels showed cyclic variations and were low during early dioestrus. The correlation between plasma progesterone levels and the score for ER was low and negative in all ovarian cell types. This study demonstrates the predominant role of ERbeta over ERalpha in bovine ovarian structures. Furthermore, the colocalization of both ERbeta mRNA and ERalpha in most cell types suggests possible interactions between both ER subtypes.

Endocrine disruptor bisphenol A strongly binds to human estrogen-related receptor gamma (ERRgamma) with high constitutive activity

Bisphenol A (BPA) has been acknowledged as an estrogenic chemical able to interact with human estrogen receptors (ER). Many lines of evidence reveal that BPA has an impact as an endocrine disruptor even at low doses. However, its binding to ER and hormonal activity is extremely weak, making the intrinsic significance of low dose effects obscure. We thus supposed that BPA might interact with nuclear receptor(s) other than ER. Here we show that BPA strongly binds to human estrogen-related receptor gamma (ERRgamma), an orphan receptor and one of 48 human nuclear receptors. In a binding assay using [3H]4-hydroxytamoxifen (4-OHT) as a tracer, BPA exhibited a definite dose-dependent receptor binding curve with the IC50 value of 13.1 nM. 4-Nonylphenol and diethylstilbestrol were considerably weaker (5-50-fold less than BPA). When examined in the reporter gene assay for ERRgamma using HeLa cells, BPA completely preserved ERRgamma's high constitutive activity. Notably, BPA exhibited a distinct antagonist action to reverse the inverse agonist activity of 4-OHT, retaining high basal activity. ERRgamma is expressed in a tissue-restricted manner, for example very strongly in the mammalian brain during development, and in the adult in the brain, lung and other tissues. It will now be important to evaluate whether BPA's hitherto reported low dose effects may be mediated through ERRgamma.

Expression of estrogen receptor-related receptor isoforms and clinical significance in endometrial adenocarcinoma

Estrogen receptor-related receptors (ERRs) are members of orphan nuclear receptors closely related to the estrogen receptors (ERs). Researches showed that the ERRs bound to estrogen response elements and interfered in the ER signal pathway. Therefore, it might be associated with estrogen-dependent diseases. The purpose of this study was to explore whether ERRs were involved in the tumorigenesis of endometrial adenocarcinoma. We examined the expression of ERRs in endometrial adenocarcinoma and normal endometrium using semiquantitative reverse transcription-polymerase chain reaction and immunohistochemistry. Clinicopathologic features including FIGO stage, histologic grade, myometrial invasion, and nodal metastasis were reviewed. Results showed that messenger RNA (mRNA) levels of ERRalpha, ERRbeta, and ERRgamma were positively associated with the immunoreactivities (P= 0.009, P= 0.014, and P= 0.001, respectively). The expression rate and relative level of ERRalpha mRNA in ERalpha-positive endometrial adenocarcinomas were lower than in normal endometriums (P= 0.049 and P= 0.023), whereas the relative level of ERRgamma mRNA in ERalpha-positive endometrial adenocarcinomas was higher than in normal endometriums (P= 0.014). Expression of ERRalpha mRNA was positively correlated with FIGO stage (P= 0.019) and myometrial invasion (P= 0.043). A negative correlation was observed between expression of ERRgamma mRNA and nodal metastasis (P= 0.021). Results suggested that ERRalpha and ERRgamma might participate in the tumorigenesis of endometrial adenocarcinoma. ERRalpha and ERRgamma are promising to be new prognostic factors in endometrial adenocarcinoma.

Estrogen-related receptor in reproductive organs

Estrogen-related receptor (ERR) was studied in the placenta and uterine endometrium, especially endometrial cancers, among reproductive organs. In the placenta, the estrogen receptor (ER) alpha and beta mRNA levels increased from the first to the second trimester, and then decreased until normal term delivery. Estrogen-related receptor alpha, beta and gamma mRNA levels gradually increased up to the second trimester, and then comparatively rapidly increased until normal term delivery. In endometrial cancers, ER alpha and beta mRNA levels decreased with clinical stage, myometrial invasion and dedifferentiation. Estrogen-related receptor alpha levels increased with clinical stage and myometrial invasion, and the ERR gamma levels increased with myometrial invasion.  Estrogen-related receptors can bind to the steroid receptor coactivator family without any ligands, and drive transcription activity of the target genes. The manner of ERR and ER gene expressions might show a competitive interaction associated with the use of common cofactors. It is speculated that the upregulation of ERR is related to the placental growth after the downregulation of ER from the second trimester until delivery, and that ERR alpha and gamma are candidates for prognostic factors in endometrial cancer, although ERR are not directly related to tumor growth and advancement of endometrial cancer. (Reprod Med Biol 2005; 4: 129-131).

Estrogen-related receptor expression in placenta throughout gestation

Estrogen receptor (ER) alpha and beta mRNA levels increased from the first to the second trimester and then decreased until normal term delivery. Estrogen-related receptor (ERR) alpha, beta and gamma mRNA levels gradually increased up to the second trimester and then comparatively rapidly increased until normal term delivery. ERRs can bind to the steroid receptor coactivator family without any ligands and drive transcription activity of the target genes. The manner of ERR and ER gene expressions might show a competitive interaction associated with the use of common cofactors. It is speculated that the up-regulation of ERRs is related to placental growth after the down-regulation of ERs because of the remarkably high concentration of estrogens for ERs from the second trimester until delivery.

Identification of PNRC2 and TLE1 as activation function-1 cofactors of the orphan nuclear receptor ERRgamma

Estrogen-related receptor gamma (ERRgamma) is an orphan nuclear receptor highly expressed in heart, skeletal muscle, kidney, and brain. To identify activation function-1 (AF-1)-dependent cofactors involved in the transcriptional function of ERRgamma, we screened for human cDNAs coding for proteins that bind to the bacterial expressed AF-1 by biopanning of a phage display library. Phages displaying fusion proteins with full-length PNRC2 (proline-rich nuclear receptor co-regulatory protein 2), already shown to be a cofactor for other nuclear receptors, and with a polypeptide of the bHLH corepressor TLE1 bound to the AF-1 containing bait. Pull-down analyses demonstrated a direct interaction of the receptor with the newly identified full-length proteins. Surprisingly, not only PNRC2 but also the corepressor TLE1 functioned as ERRgamma coactivator in a reporter gene analysis.

Loss of PGC-specific expression of the orphan nuclear receptor ERR-β results in reduction of germ cell number in mouse embryos

Estrogen related receptor beta (ERR-beta) is an orphan nuclear receptor specifically expressed in a subset of extra-embryonic ectoderm of post-implantation embryos. ERR-beta is essential for placental development since the ERR-beta null mutants die at 10.5dpc due to the placenta abnormality. Here, we show that the ERR-beta is specifically expressed in primordial germ cells (PGC), obviously another important cell type for reproduction. Expression of the ERR-beta mRNA in embryonic germ cells started at E11.5 as soon as PGC reached genital ridges, and persisted until E15-E16 in both sexes. Immunostaining with anti-ERR-beta antibody revealed that the ERR-beta protein is exclusively expressed in germ cells in both male and female gonads from E11.5 to E16. 5. To study function of the ERR-beta in PGC, we complemented placental defects of the ERR-beta null mutants with wild-type tetraploid embryos, and analyzed germ cell development in the rescued embryos. It was found that development of gonad and PGC was not apparently affected, but number of germ cells was significantly reduced in male and female gonads, suggesting that the ERR-beta appears to be involved in proliferation of gonadal germ cells. The rescued embryos could develop to term and grow up to adulthood. The rescued ERR-beta null male were found to be fertile, but both male and female null mutants exhibited behavioural abnormalities, implying that the ERR-beta plays important roles in wider biological processes than previously thought.

Characterization of calmodulin binding to the orphan nuclear receptor Errgamma

The estrogen receptor-related receptor gamma (ERRgamma/ ERR3/NR3B3), a member of the nuclear receptor superfamily, activates transcription in the absence of ligands. In order to identify ligand-independent mechanisms of activation, we tested whether calmodulin (CaM), a key regulator of numerous cellular processes and a predominant intracellular receptor for Ca2+-signals, interacts with ERRgamma. In vitro pull-down experiments with calmodulin-Sepharose demonstrated a Ca2+-dependent interaction with cellularly expressed ERRgamma. As shown by truncation analysis, the CaM binding site is highly unusual in that it is composed of two discontinuous elements. Moreover, by surface plasmon resonance (SPR) biosensor technology, we detected a direct interaction of immobilized bacterially expressed ERR-gamma fusion protein with Ca2+-calmodulin. This is best described by a model which assumes a conformational change of the initially formed complex to a more stable form. Whereas in vitro DNA binding was calmodulin-independent, transient transfection analysis revealed a Ca2+-influx-dependent ERRgamma-mediated transcriptional activation of a luciferase reporter gene. Thus, we propose that CaM acts as a mediator in the Ca2+-dependent modulation of ERRgamma.

PGC-1 and PERC, coactivators of the estrogen receptor-related receptor gamma

The mouse nuclear receptor ERRgamma (estrogen receptor-related receptor gamma) is highly expressed in heart, skeletal muscle, kidney, and brain, as well as in the developing nervous system. We found that the expression of the coactivators PGC-1 (PGC-1alpha) and PERC (PGC-1beta) in mammalian cells augmented potently the transcriptional activation by ERRgamma. The constitutive activation function 2 (AF-2) of the orphan receptor was important for the synergistic enhancement. Functional receptor truncation analysis revealed an additional amino-terminal activation function, specific for the ERRgamma2 isoform and PGC-1. In vitro experiments showed a direct interaction of ERRgamma with both coactivators. Our findings suggest distinct regulatory functions for PGC-1 and PERC as tissue-specific coactivators for ERRgamma.

Domains of ERRgamma that mediate homodimerization and interaction with factors stimulating DNA binding

The estrogen receptor-related receptor gamma (ERRgamma/ERR3/NR3B3) is an orphan member of the nuclear receptor superfamily closely related to the estrogen receptors. To explore the DNA binding characteristics, the protein-DNA interaction was studied in electrophoretic mobility shift assays (EMSAs). In vitro translated ERRgamma binds as a homodimer to direct repeats (DR) without spacing of the nuclear receptor half-site 5'-AGGTCA-3' (DR-0), to extended half-sites, and to the inverted estrogen response element. Using ERRgamma deletion constructs, binding was found to be dependent on the presence of sequences in the ligand binding domain (LBD). A far-Western analysis revealed that ERRgamma forms dimers even in the absence of DNA. Two elements, located in the hinge region and in the LBD, respectively, are necessary for DNA-independent dimerization. DNA binding of bacterial expressed ERRgamma requires additional factors present in the serum and in cellular extracts. Fusion proteins of the germ cell nuclear factor (GCNF/NR6A1) with ERRgamma showed that the characteristic feature to be stimulated by additional factors can be transferred to a heterologous protein. The stimulating activity was further characterized and its target sequence narrowed down to a small element in the hinge region.

To ERR in the estrogen pathway

Estrogens control a variety of physiological and disease-linked processes, most notably reproduction, bone remodeling and breast cancer, and their effects are transduced through classic unclear receptors referred to as estrogen receptor-alpha (ER alpha) and ER beta. Recent results obtained using the estrogen-related receptors (ERR alpha, -beta and -gamma), a subfamily of orphan nuclear receptors closely related to the ERs, have shown that the ERRs share target genes, coregulatory proteins, ligands and sites of action with the ERs. In addition, the ERRs can actively influence the estrogenic response, suggesting that pharmacological modulation of ERR activity will be clinically useful to prevent and/or treat a variety of conditions related to women's health.

Developmental expression of the estrogen receptor-related receptor gamma in the nervous system during mouse embryogenesis

The ERR's (estrogen receptor-related receptors) are constitutive activators of the classical estrogen response element. In this report, we demonstrate that ERRgamma is highly expressed in the nervous system of the developing mouse embryo and that the adult pattern of expression of ERRgamma is, with few exceptions, established during embryogenesis. Transcripts are preferentially detected in already differentiating areas of the nervous system.