• Proceedings of the Korean Society of Applied Pharmacology
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• 2003.11a
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• pp.70-70
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• 2003

Estrogen receptor is a ligand-activated transcription factor. Its action depends on the receptor, its ligand, and its coactivator proteins. As a consequence, the concentration of the receptor is a major component that governs the magnitude of the estrogen response. Despite the extensive knowledge on mechanism of estrogen receptor action, regulation of estrogen receptor itself is not very well understood. Estrogen receptor is known to be downregulated under hypoxia leading to inhibition of estrogen receptor mediated transcription activation. We have studied mechanism of loss of estrogen responsiveness under hypoxia. We found that Hif-l${\alpha}$, a major transcription factor regulating hypoxic response, inhibited transcription of estrogen response element driven luciferase gene by expression of HIF-l${\alpha}$/vp16 construct designed to contain transcription activity under normoxia. This loss of estrogen responsiveness appears to be the result of ER${\alpha}$ downregulation. ER${\alpha}$was downregulated at the levels of ligand-biding and protein within l2-24h, and the response was blocked by the proteasome inhibitor MG132, protein synthesis inhibitor cyclohexamide, and tyrosine kinase inhibitor Genistein. These results demonstrate that Hif-l${\alpha}$ downregulates ER${\alpha}$ by proteasome dependent pathway.

• Proceedings of the Korean Society of Applied Pharmacology
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• 2003.11a
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• pp.114-114
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• 2003

Ginseng is a medicinal herb widely used in Asian countries, and its pharmacological effects has been demonstrated in various systems such as cardiovascular, central nervous, and endocrine systems. Its effects are mainly attributed to the ginsenosides. We hypothesize that a component of Panax ginseng, ginsenoside-Rbl, acts by binding to estrogen receptor. We have investigated the estrogenic activity of ginsenoside-Rbl in a transient transfection system using estrogen receptors ${\alpha}$ or ${\beta}$ with estrogen -responsive luciferase plasmids in COS monkey kidney cells. Ginsenoside-Rbl activated both estrogen receptors ${\alpha}$ and ${\beta}$ in a dose-dependent manner (0.5 -100 M ). Activation was inhibited by the specific estrogen receptor antagonist ICI 182,780, indicating that the estrogenic effect of ginsenoside-Rbl is estrogen receptor dependent. Next, we evaluated the ability of ginsenoside-Rbl to induce estrogen-responsive progesterone receptor gene by semi-quantitative RT-PCR assays. MCF-7 cells treated with l7${\beta}$-estradiol or ginsenoside- Rb1 exhibited an increased expression of progesterone receptor mRNA. However, ginsenoside-Rbl failed to displace the specific binding of ［3H］17${\beta}$-estradiol to estrogen receptor in MCF-7 cells as examined by whole cell ligand binding assays, suggesting that there is no direct interaction of ginsenoside-Rbl with estrogen receptor. Our results indicate that estrogen-like activity of ginsenoside-Rbl is independent of direct estrogen receptor association.

• Proceedings of the PSK Conference
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• 2003.04a
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• pp.228.2-229
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• 2003

Estrogen Receptor is a ligand-activated transcription factor. The concentration of the receptor is a major component that regulates expression of estrogen-responsive genes. We have studied mechanism of estrogen receptor alpha (ER${\alpha}$) downregulation by HIF-1 using HIF-1${\alpha}$/VP16 constructs. ER${\alpha}$ is known to be downregulated under hypoxic condition. Transcriptional response under hypoxia is mediated through Hypoxia-inducible factor-1 (HIF-1), a transcription factor that is usullaly degraded but stabilized under hypoxia. (omitted)

• Development and Reproduction
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• v.13 no.4
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• pp.249-256
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• 2009

The estrogen receptor-related receptors (ERRs) are a group of nuclear receptor superfamily of transcription factors. ERRs and estrogen receptors (ERs) have overlapping affinities for coactivators and DNA binding sites, but differ markedly in ligand binding and activation. The three mammalian ERR genes have been implicated in diverse physiological processes ranging from placental development to maintenance of bone density, whereas the molecular diversity, function, and regulation of ERRs in non-mammalian species are not well understood. In the present study, to investigate the involvement of ERR in transcription and embryogenesis in marine invertebrates, a cDNA encoding ERR (SnERR) was cloned from the gonad in Strongylocentrotus nudus, by polymerase chain reaction (PCR). The amino acid sequence of SnERR showed high homology with that of S. purpuratus (91%). A phylogenetic tree clearly showed that SnERR is a member of the ERR family and clustered in echinodermata group as supported by a high bootstrap value. We examined gene expression of SnERR during embryonic development of S. nudus using real-time PCR. During the embryonic development, the mRNA of ERR was significantly high levels in early development stages (4~64 cell) and larval stages. The SnERR slightly activated transcription through the classical estrogen response elements (EREs) in the presence of genistein. In addition, peroxisome proliferator-activated receptor $\gamma$ coactivator (PGC)-$1\alpha$ knwon as a coactivator of ERR enhanced the snERR-mediated transactivation, suggesting that the PGC-$1\alpha$ is a coactivator of SnERR.

• Bulletin of the Korean Chemical Society
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• v.34 no.4
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• pp.1051-1054
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• 2013

Closo-carborane has been considered as an efficient boron-carrier for boron neutron capture therapy (BNCT) and an attractive surrogate of lipophilic phenyl or cyclohexyl ring in drug design. Despite a great number of carborane-containing ligands have been synthesized and evaluated, molecular modeling studies of carborane ligands with macromolecules have been rarely reported. We herein describe a facile docking and scoring-function strategy of 16 carborane ligands with an estrogen receptor by using the commercial Gaussian, Chem3D Pro and Discovery Studio (DS) computational programs. Docked poses of the carborane ligands in silico exhibited similar binding modes to that of the crystal ligand in the active site of estrogen receptor. Score analysis of the best docked pose for each ligand indicated that the Ligscore1 and the Dockscore have a moderate correlation with in vitro biological activity. This is the first report on the scoring-correlation studies of carborane ligands with macromolecules. The integrated Gaussian-DS approach has a potential application for virtual screening, De novo design, and optimization of carborane ligands in medicinal chemistry.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.6
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• pp.2161-2166
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• 2015

Estrogen receptors (ERs) are steroid receptors located in the cytoplasm and on the nuclear membrane. The sequence similarities of human $ER{\alpha}$, mouse $ER{\alpha}$, rat $ER{\alpha}$, dog $ER{\alpha}$, and cat $ER{\alpha}$ are above 90%, but structures of $ER{\alpha}$ may different among species. Estrogen can be agonist and antagonist depending on its target organs. This hormone play roles in several diseases including breast cancer. There are variety of the relative binding affinity (RBA) of ER and estrogen species in comparison to $17{\beta}-estradiol$ (E2), which is a natural ligand of both $ER{\alpha}$ and $ER{\beta}$. The RBA of the estrogen species are as following: diethyl stilbestrol (DES) > hexestrol > dienestrol > $17{\beta}-estradiol$ (E2) > 17- estradiol > moxestrol > estriol (E3) >4-OH estradiol > estrone-3-sulfate. Estrogen mimetic drugs, selective estrogen receptor modulators (SERMs), have been used as hormonal therapy for ER positive breast cancer and postmenopausal osteoporosis. In the postgenomic era, in silico models have become effective tools for modern drug discovery. These provide three dimensional structures of many transmembrane receptors and enzymes, which are important targets of de novo drug development. The estimated inhibition constants (Ki) from computational model have been used as a screening procedure before in vitro and in vivo studies.

• Journal of the East Asian Society of Dietary Life
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• v.15 no.3
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• pp.315-322
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• 2005

In this study we report on the estrogen activity of silkworm pupa and herb extracts in vitro. The estrogenic activity of these resources was investigated by competition binding assays with estrogen receptor $\alpha(ER{\alpha})\;or\;ER{\beta}$, and viability of MCF-7 cells, a human breast cancer cell line. Saturation ligand-binding analysis of $ER{\alpha}\;and\;ER{\beta}$ revealed that all plant extracts competed with estrogen ligand for binding to both ER subtypes with a similar preference and degree and competed stronger with ligand for binding to $ER{\beta}\;than\;to\;ER{\alpha}$. The highest $ER{\alpha}-binding$ sample was silkworm pupa aqueous extract The highest $ER{\beta}-binding$ sample was silkworm pupa oil. These samples were further tested for bioactivity based on their ability to regulate cell growth rate in ER(+) breast cancer cell line, MCF-7 cells. Our studies showed that silkworm pupa, soritae, sesame, yam, pueraria, malt, ginseng, Polygonum multiflorum, and Curcuma longa significantly stimulated the growth of MCF-7 cells (P<0.05). In summary, these results suggested that silkworm pupa and herbs might be useful as potential phytoestrogens.

• Journal of Ginseng Research
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• v.27 no.3
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• pp.93-97
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• 2003

Alternative or complementary medicine plays an important role in health care system. Ginseng, being one of the most popular oriental herbs, is believed to contain various steroid hormone activity. Ginseng has been demonstrated pharmacological effect in the cardiovascular, endocrine, central nervous, and immune system. Our objective was to study that total saponin might mediate some of their actions by binding to the steroid hormone receptor, as they share many of the actions of steroid hormone in various physiological system. Using total saponin from Panax Ginseng, we have studied the possibility of total saponin being a potential estrogen receptor, androgen receptor, and retinoic acid receptor ligand. Total saponin activated the transcription of both the estrogen and androgen responsive luciferase reporter plasmids at a concentration of 100$\mu\textrm{g}$/ml in COS cells transiently transfected with the corresponding receptor and hormone responsive receptor plasmids. And total saponin caused a concentration-dependent stimulation of estrogen receptor. Total saponin increased the expression of estrogen responsive c-fos proto-oncogene at the protein level in MCF7 cells at 24 h treatment as examined by Western analysis. The c-fos induction was used as a specific marker of estrogen responsiveness. This activation was inhibited by the specific estrogen receptor antagonist, ICI 182,780. However, total saponin failed to activate the retinoic acid receptor in COS cells transiently transfected with the corresponding receptor and retinoic acid responsive reporter plasmids. These results show that total saponin is capable of activating estrogen and androgen receptors.

• Environmental Mutagens and Carcinogens
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• v.22 no.3
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• pp.175-182
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• 2002

Endocrine disruptors (EDs) are the chemicals that affect endocrine systems through activation or inhibition of steroid hormone response. It is necessary to have a good system to evaluate rapidly and accurately endocrine-disrupting activities of suspected chemicals and their degradation products. The key targets of EDs are nuclear hormone receptors, which bind to steroid hormones and regulate their gene transcription. We constructed a co-expression system of Gal4p DNA binding domain (DBD)- ligand binding domain of human estrogen receptor $\alpha$ or $\beta$, and Gal4p transactivation domain (TAD)-co-activator AIB-1, SRC-1 or TIF-2 in Saccharomyces cerevisiae with a chromosome-integrated lacZ reporter gene under the control of CYC1 promoter and Gal4p binding site (GAL4 upstream activating sequence, GAL4$_{UAS}$). Expression of this reporter gene was dependent on the presence of estrogen or EDs in the culture medium. We found that the two-hybrid system with combination of the hER$\beta$ LBD and co-activator SRC-1 was most effective in the xenoestrogen-dependent induction of reporter activity. The extent of transcriptional activation by those chemicals correlated with their estrogenic activities measured by other assay systems, indicating that this assay system is efficient and reliable for measuring estrogenic activity. The data in this research demonstrated that the yeast detection system using steroid hormone receptor and co-activator is a useful tool for identifying chemicals that interact with steroid receptors.s.

• Biomolecules & Therapeutics
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• v.20 no.2
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• pp.183-188
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• 2012

In this study, we examined the estrogenic activity of bavachin, a component of Psoralea corylifolia that has been used as a traditional medicine in Asia. Bavachin was purified from ethanolic extract of Psoralea corylifolia and characterized its estrogenic activity by ligand binding, reporter gene activation, and endogenous estrogen receptor (ER) target gene regulation. Bavachin showed ER ligand binding activity in competitive displacement of [$^3H$] $E_2$ from recombinant ER. The estrogenic activity of bavachin was characterized in a transient transfection system using $ER{\alpha}$ or $ER{\beta}$ and estrogen-responsive luciferase plasmids in CV-1 cells with an $EC_{50}$ of 320 nM and 680 nM, respectively. Bavachin increased the mRNA levels of estrogen-responsive genes such as pS2 and PR, and decreased the protein level of $ER{\alpha}$ by proteasomal pathway. However, bavachin failed to activate the androgen receptor in CV-1 cells transiently transfected with the corresponding receptor and hormone responsive reporter plasmid. These data indicate that bavachin acts as a weak phytoestrogen by binding and activating the ER.