Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04155 (pS2)
 1,234 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Parabens (4-hydroxybenzoic acid esters) have been recently reported to have oestrogenic activity in yeast cells and animal models. Since the human population is exposed to parabens through their widespread use as preservatives in foods, pharmaceuticals and cosmetics, we have investigated here whether oestrogenic activity of these compounds can also be detected in oestrogen-sensitive human cells. We report on the oestrogenic effects of four parabens (methylparaben, ethylparaben, n-propylparaben, n-butylparaben) in oestrogen-dependent MCF7 human breast cancer cells. Competitive inhibition of [3H]oestradiol binding to MCF7 cell oestrogen receptors could be detected at 1,000,000-fold molar excess of n-butylparaben (86%), n-propylparaben (77%), ethyl-paraben (54%) and methylparaben (21%). At concentrations of 10(-6)M and above, parabens were are able to increase expression of both transfected (ERE-CAT reporter gene) and endogenous (pS2) oestrogen-regulated genes in these cells. They could also increase proliferation of the cells in monolayer culture, which could be inhibited by the antiestrogen ICI 182,780, indicating that the effects were mediated through the oestrogen receptor. However, no antagonist activity of parabens could be detected on regulation of cell proliferation by 17 beta-oestradiol at 10(-10)M. Molecular modelling has indicated the mode by which paraben molecules can bind into the ligand binding pocket of the crystal structure of the ligand binding domain (LBD) of the oestrogen receptor alpha (ERalpha) in place of 17beta-oestradiol; it has furthermore shown that two paraben molecules can bind simultaneously in a mode in which their phenolic hydroxyl groups bind similarly to those of the meso-hexoestrol molecule. Future work will need to address the extent to which parabens can accumulate in hormonally sensitive tissues and also the extent to which their weak oestrogenic activity can add to the more general environmental oestrogen problem.
J Steroid Biochem Mol Biol 2002 Jan
PMID:Oestrogenic activity of parabens in MCF7 human breast cancer cells. 1186 63

Hormone-activated ERs (ERalpha and ERbeta) bind with high affinity to specific DNA sequences, estrogen response elements (EREs), located within the regulatory regions of target genes. Once considered to function solely as receptor tethers, there is an increasing amount of recent evidence to suggest that the sequence of the ERE can influence receptor activity. In this study, we have performed a systematic analysis of the role of different EREs in ER pharmacology. Specifically, by measuring ER activity on the vitellogenin A2, complement 3 gene, pS2, and lactoferrin EREs, we demonstrate that the activities of E2 and xenoestrogen ligands through ERalpha and ERbeta are significantly influenced by the nature of the response element. Using a series of ERalpha and ERbeta interacting peptides that contain the coactivator-binding motif LXXLL, we show that the type of ERE with which the receptor associates regulates the structure of the coactivator pocket on ER. Furthermore, using a novel ELISA developed to measure ER-coactivator interactions revealed that these different conformational states of ERalpha and ERbeta are functionally relevant, as they dictate receptor coactivator binding preference. Together, these results indicate that the DNA response element is a key regulator of receptor structure and biological activity and suggest the ERE sequence influences the recruitment of coactivators to the ER at target gene promoters. We propose that DNA-induced alteration of protein structure and coregulator recruitment may serve as a universal regulatory component for differential gene expression by other nuclear hormone receptors and unrelated transcription factors.
Mol Endocrinol 2002 Mar
PMID:Allosteric regulation of estrogen receptor structure, function, and coactivator recruitment by different estrogen response elements. 1187 5

The estrogen receptor (ER) is a hormone-dependent transcription factor that belongs to the steroid/thyroid hormone receptor superfamily. Since the ER contributes to development and progression in human breast cancer, a number of studies have explored ways to inactivate this receptor. Previous studies have suggested that the 90-kDa heat shock protein (Hsp90) interacts with the ER, thus stabilizing the receptor in an inactive state. Here, we report that radicicol, an Hsp90-specific inhibitor, repressed estrogen-dependent transactivation of the ER as measured by pS2 gene transcription and a reporter gene encoding an estrogen-responsive element. Furthermore, we showed that radicicol induced rapid degradation of ERalpha, while the amount of ubiquitinated ERalpha was increased. A proteasome inhibitor, LLnL, almost completely abrogated the radicicol-induced decrease in expression level, as well as in transcriptional activity of ERalpha. These results suggest that radicicol disrupts the ER-Hsp90 heterodimeric complex, thereby generating ERalpha that is susceptible to ubiquitin/proteasome-induced degradation.
Mol Cell Endocrinol 2002 Feb 25
PMID:Radicicol represses the transcriptional function of the estrogen receptor by suppressing the stabilization of the receptor by heat shock protein 90. 1191 45

The pS2 promoter is complex with binding sites for a number of protein factors that may participate in modulating its activity. The pS2 gene was transcriptionally activated by estrogens in HepG2 cells transformed (HepER3) to express the estrogen receptor alpha (ERalpha). The phorbol ester phorbol 12-myristate 13-acetate (PMA) stimulated pS2 expression in both HepER3 and the parental, non-ER-expressing HepG2 cells, although its activity was substantially less in HepG2 cells. The use of selective protein kinase inhibitors suggested that the MAPK pathway contributes substantially to estrogen stimulation of the pS2 promoter. The activator protein 1 (AP1) site at -332 to -338 in the pS2 promoter had a dominant role in the response to both estrogens and PMA, although the estrogen response element at -393 to -405 was essential to mediate the response to estrogen. The potentiation of pS2 promoter activity by the AP1 motif in response to estrogen was dependent on the ligand binding domain of ERalpha. Furthermore, the presence of an intact AP1 element in the pS2 promoter sustained suppression of pS2 promoter activity by an LXXLL peptide. In summary, the data suggest that the effect of estrogen is mediated through a cross-talk between the estrogen-responsive element and the AP1 response element and that ERalpha plays a crucial role in mediating the effect of both estrogen and PMA.
Mol Pharmacol 2002 Jun
PMID:pS2 Gene expression in HepG2 cells: complex regulation through crosstalk between the estrogen receptor alpha, an estrogen-responsive element, and the activator protein 1 response element. 1202 87

Quantification of estrogen-induced changes in the expression levels of endogenous genes such as pS2 and vitellogenin could be an assay to detect estrogenicity of chemicals. Considering its regulation by estrogen, in the present study, we hypothesize that the calbindin-D(9k) (CaBP-9k) gene has the possibility as a biomarker for estrogenic response of the environmental estrogens. We analyzed the time- and dose-dependent CaBP-9k mRNA expression in the immature rats by 3-day injection of 17beta-estradiol (E2) and alkylphenol acid [octyl-phenol (OP) and nonylphenol (NP)] and bisphenol A(BPA)) which are environmentally persistent and reported to have some estrogenic activity in experimental test systems. The expression of CaBP-9k mRNA was compared with uterotropic response of the compounds. A significant increase in CaBP-9k mRNA expression was observed when treated with 1000 mg/kg body weight (BW) per day of OP (18-fold versus control), NP (17-fold versus control) and BPA (6-fold versus control) for 3 days in dot blot assays. Using Northern blot analysis, a more dramatic increase of CaBP-9k mRNA expression was observed when treated with 1000 mg/kg BW per day of OP (132-fold versus control) and NP (113-fold versus control) for 3 days. Treatment with 10 and 100 mg/kg BW per day of NP and 100 mg/kg BW per day of OP for 3 days induced a small but significant increase in CaBP-9k mRNA expression. As expected, a single dose of E2 (40 microg/kg BW per day) for 3 days induced a significant increase in CaBP-9k mRNA expression as revealed by dot (15-fold versus control) or Northern blot assay (102-fold versus control). In a time response experiment using Northern blot assay, a significant increase in CaBP-9k mRNA expression was observed as early as 3 h, peaked at 6 h and continued until 72 h after treatment with 1000 mg/kg BW per day of OP, NP, and 48 h after treatment with 1000 mg/kg BW per day of BPA. A similar time-dependent response was observed when assessed by dot blot assay. Uterotropic response of the compounds was determined and compared with CaBP-9k mRNA expression. The alkylphenolic compounds induced a significant increase in the uterine wet weight at 1000 mg/kg BW per day of OP and NP, not BPA. A strong correlation between in vivo uterotropic assay and CaBP-9k mRNA expression assay was observed. In order to investigate the possible mechanisms by which the compounds regulate CaBP-9k mRNA expression, we studied the effect of the compound on the ERalpha mRNA level using total RNA from the treated rats. The alkylphenolic compounds as well as E2 stimulate the expression of ERalpha mRNA in a similar pattern to that of CaBP-9k mRNA in terms of dose- and time-dependent response. Strong regulation of CaBP-9k mRNA expression by E2 and the environmental estrogens and its correlation with in vivo uterotropic assay suggest that CaBP-9k gene can be used as a biomarker gene for assaying estrogenicity of putative estrogenic compounds.
Mol Cell Endocrinol 2002 Jun 14
PMID:Stimulation of calbindin-D(9k) mRNA expression in the rat uterus by octyl-phenol, nonylphenol and bisphenol. 1206 1

Intranasal administration of hormone replacement therapy presents an original plasma kinetic profile with transient estrogen levels giving rise to the concept of pulsed therapy. To further understand the molecular effects of this new therapy, we have compared the effects of pulsed and continuous estradiol treatments on two critical aspects of estradiol action: gene expression and cell proliferation. Cells were stimulated with estradiol as 1-h pulsed or 24-h continuous treatments at concentrations such that the 24-h exposure (concentration x time) was identical in both conditions. In MCF7 cells, the transcriptional activity of estrogen receptors (ER) on a transiently transfected responsive estrogen response element-luciferase reporter construct was shown to be drastically (approximately 10-fold) and similarly stimulated after both treatments. Moreover, the increased mRNA expression of three representative estradiol-sensitive genes (pS2, cathepsin D, progesterone receptor), evaluated by Northern blot, was identical after 1-h pulse with 7 nM estradiol or continuous treatment with 0.29 nM estradiol with the same kinetic profile over 48 h. Proliferation was quantified by a histomorphometric method on primary cultures of human normal breast cells from reduction mammoplasties and using a fluorescence DNA assay in six human breast cancer cell lines which were ER positive or negative. After a 7-day treatment period, estradiol had no effect on the proliferation of the three ER negative cell lines (BT20, MDA MB231, SK BR3) but significantly stimulated the proliferation of the normal cells and of the three tumoral hormone-sensitive cell lines (MCF7, T47D, ZR 75-1); both hormone treatments producing the same increases in cell growth. In conclusion, we have shown that the genomic or proliferative effects of estradiol were identical with pulsed or continuous treatments, thus indicating that estrogenic effects are not strictly related to concentrations but rather to total hormone exposure.
J Mol Endocrinol 2002 Jun
PMID:Comparative activity of pulsed or continuous estradiol exposure on gene expression and proliferation of normal and tumoral human breast cells. 1206 83

Melatonin inhibits the proliferation of estrogen receptor alpha (ERalpha)-positive (MCF-7), but not ERalpha-negative (MDA-MB-231) breast cancer cells. Here, we assessed the effect of MT(1) melatonin receptor stable overexpression in MCF-7 and MDA-MB-231 breast cancer cells on the growth-suppressive effects of melatonin. Parental and vector-transfected MCF-7 cells demonstrated a modest, but significant, growth-suppressive response to melatonin; however, melatonin treatment of MT(1)-transfected MCF-7 cells resulted in significantly enhanced growth-suppression. This response was blocked by an MT1/MT2 melatonin receptor antagonist. Interestingly, MT(1)-overexpression did not induce a melatonin-sensitive phenotype in melatonin-insensitive MDA-MB-231 cells. Finally, Northern blot analysis demonstrated an enhanced inhibition of ERalpha mRNA expression and an enhanced induction of pancreatic spasmolytic polypeptide (pS2) by melatonin in MT(1)-transfected MCF-7 cells relative to vector-transfected MCF-7 cells. These data suggest the involvement of the MT(1) melatonin receptor in mediation of melatonin effects on growth-suppression and gene-modulation in breast cancer cells.
Mol Cell Endocrinol 2002 Jun 28
PMID:MT(1) melatonin receptor overexpression enhances the growth suppressive effect of melatonin in human breast cancer cells. 1208 76

Clinical observations suggest that human breast tumors can adapt in response to endocrine therapy by developing hypersensitivity to estradiol. To understand the mechanisms responsible, we examined estrogenic stimulation of cell proliferation in a model system and provided evidence that long-term deprivation of estradiol causes adaptive hypersensitivity. The enhanced responses to estradiol do not involve mechanisms acting at the level of transcription of estrogen regulated genes. We found no evidence of hypersensitivity when examining the effects of estradiol on regulation of c-myc, pS2, progesterone receptor, several ER reporter genes or c-myb in hypersensitive cells. On the other hand, deprivation of breast cells long term was found to up-regulate a separate pathway whereby the estrogen receptor co-opts a classical growth factor pathway and induces rapid non-genomic effects. Through this pathway, estradiol caused rapid activation of mitogen-activated protein (MAP) kinase. In exploring the mechanisms mediating this event, we found that estradiol binds to cell membrane associated estrogen receptors and causes phosphorylation of Shc, an adaptor protein usually involved in growth factor signaling pathways. ERalpha was found to complex with Shc under these conditions. In turn, Shc bound Grb-2 and Sos which resulted in the activation of MAP kinase. The pure antiestrogen, ICI 182,780, blocked several steps in the rapidly responding ER alpha, Shc, MAP kinase pathway. These non-genomic effects of estradiol produced biologic effects by activating Elk and by inducing morphologic changes in cell membranes. Using confocal microscopy, we demonstrated that estradiol caused a rapid alteration in membrane ruffling, the formation of pseudopodia and translocation of ER alpha to regions contiguous with the cell membrane. These morphologic effects could be blocked with a pure anti-estrogen. We conclude that long-term estradiol deprived cells utilize both genomic (transcriptional) and rapid, non-genomic estradiol induced pathways. We postulate that synergy between these two pathways acting at the level of the cell cycle is responsible for adaptive hypersensitivity.
Mol Cell Endocrinol 2002 Jul 31
PMID:Adaptive mechanisms induced by long-term estrogen deprivation in breast cancer cells. 1216 Sep 99

Regulation of estrogen receptor alpha (ERalpha) plays an important role in hormone responsiveness and growth of ER-positive breast cancer cells and tumors. ZR-75 breast cancer cells were grown under conditions of normoxia (21% O(2)) or hypoxia (1% O(2) or cobaltous chloride), and hypoxia significantly increased hypoxia-inducible factor 1alpha protein within 3 h after treatment, whereas ERalpha protein levels were dramatically decreased within 6-12 h, and this response was blocked by the proteasome inhibitor MG-132. In contrast, hypoxia induced only minimal decreases in cellular Sp1 protein and did not affect ERalpha mRNA; however, hypoxic conditions decreased basal and 17beta-estradiol-induced pS2 gene expression (mRNA levels) and estrogen response element-dependent reporter gene activity in ZR-75 cells. Although 17beta-estradiol and hypoxia induce proteasome-dependent degradation of ERalpha, their effects on transactivation are different, and this may have implications for clinical treatment of mammary tumors.
Mol Endocrinol 2002 Oct
PMID:Hypoxia induces proteasome-dependent degradation of estrogen receptor alpha in ZR-75 breast cancer cells. 1235 89

The pS2 gene is estrogen responsive in hepatocarcinoma cells (HepG2) in the presence of estrogen receptor alpha (ERalpha). The estrogenic activity is mediated through an estrogen response element (ERE) in the 5'-flanking region of the pS2 gene; however, an activator protein 1 (AP1) response element located close to the ERE in the pS2 promoter has also proven essential for a maximum response to estrogen. In the present study, we show estrogen-induced synergistic activity by the p160 coactivator steroid receptor coactivator-1 (SRC-1), mediated via the ERE and the AP1 response element in the pS2 promoter. In addition, we present data that support an interaction between the ERE and the AP1 motif via SRC-1. The related but distinct p160 coactivator, transcriptional intermediary factor-2, was a more potent activator of pS2 gene expression. In addition, transcriptional intermediary factor-2 was less dependent on an intact AP1 response element in the pS2 promoter than SRC-1. Furthermore, the type of ERE in the pS2 promoter influenced the potentiation by SRC-1, supported by less dependence on the AP1 motif when the natural ERE was substituted for by a consensus ERE. These results highlight several mechanisms whereby fine-tuning of estrogen responsiveness of an individual gene may be achieved.
Mol Endocrinol 2002 Nov
PMID:Transcriptional synergism on the pS2 gene promoter between a p160 coactivator and estrogen receptor-alpha depends on the coactivator subtype, the type of estrogen response element, and the promoter context. 1240 46


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