Estrogen Receptor Alpha Splice Variants, Post-Translational Modifications, and Their Physiological Functions

Change in selectivity of estrogen receptor alpha ligand-binding domain by mutations at residues H524/L525

The estrogen receptor alpha (ERα) features a large ligand-binding pocket capable of accommodating a variety of conformationally diverse molecules, each eliciting unique cellular responses. This structural plasticity facilitates various conformational changes, exposing different interaction surfaces for cellular proteins, triggering a myriad of biological outcomes. Alterations in the ligand-binding domain, particularly through amino acid substitutions, can modify the recognition and selectivity of ERα for agonists versus antagonists. In our study, we engineered a small library of ERα variants by modifying residues 524 and 525. These modifications resulted in variants with up to seventy-fold increased selectivity for the antagonist endoxifen and up to fifty-fold increased selectivity for the antagonist 4-hydroxytamoxifen (4-OHT) over the natural ligand estradiol. Analyzing these variants elucidates the critical roles of residues 524 and 525 in determining agonist specificity for estradiol. This advancement holds significant potential for developing selective recognition molecules, a crucial step towards creating a biosensor for endoxifen, the active metabolite used in breast cancer treatment.

Menopause-related changes in vascular signaling by sex hormones

Cardiovascular disease (CVD), such as hypertension and coronary artery disease, involves pathological changes in vascular signaling, function, and structure. Vascular signaling is regulated by multiple intrinsic and extrinsic factors that influence endothelial cells, vascular smooth muscle, and extracellular matrix. Vascular function is also influenced by environmental factors including diet, exercise, and stress, as well as genetic background, sex differences, and age. CVD is more common in adult men and postmenopausal women than in premenopausal women. Specifically, women during menopausal transition, with declining ovarian function and production of estrogen (E2) and progesterone, show marked increase in the incidence of CVD and associated vascular dysfunction. Mechanistic research suggests that E2 and E2 receptor signaling have beneficial effects on vascular function including vasodilation, decreased blood pressure, and cardiovascular protection. Also, the tangible benefits of E2 supplementation in improving menopausal symptoms have prompted clinical trials of menopausal hormone therapy (MHT) in CVD, but the results have been inconsistent. The inadequate benefits of MHT in CVD could be attributed to the E2 type, dose, formulation, route, timing, and duration as well as menopausal changes in E2/E2 receptor vascular signaling. Other factors that could affect the responsiveness to MHT are the integrated hormonal milieu including gonadotropins, progesterone, and testosterone, vascular health status, preexisting cardiovascular conditions, and menopause-related dysfunction in the renal, gastrointestinal, endocrine, immune, and nervous systems. Further analysis of these factors should enhance our understanding of menopause-related changes in vascular signaling by sex hormones and provide better guidance for management of CVD in postmenopausal women. SIGNIFICANCE STATEMENT: Cardiovascular disease is more common in adult men and postmenopausal women than premenopausal women. Earlier observations of vascular benefits of menopausal hormone therapy did not materialize in randomized clinical trials. Further examination of the cardiovascular effects of sex hormones in different formulations and regimens, and the menopausal changes in vascular signaling would help to adjust the menopausal hormone therapy protocols in order to enhance their effectiveness in reducing the risk and the management of cardiovascular disease in postmenopausal women.

Progerin mRNA Is Associated with Smoking and Signs of Increased Microvascular Damage in Patients with Diabetic Macular Edema

The premature aging disease Hutchinson-Gilford Syndrome (HGPS) is caused by defined mutations in the LMNA gene, resulting in the activation of a cryptic splice donor site, which leads to a defective truncated prelamin A protein called progerin. Notably, progerin expression has also been detected in non-mutated healthy individuals, and therefore, its involvement in the physiological aging process has been widely discussed. Since diabetes mellitus is associated with premature aging and increased cardiovascular mortality, we aimed to investigate the role of progerin expression in patients with diabetic retinopathy (DR). mRNA expression of progerin was analyzed in blood samples from 140 patients with DR who received anti-vascular endothelial growth factor (VEGF) therapy. Progerin mRNA levels were significantly lower in female compared to male patients (n = 42 vs. n = 98; 0.67 ± 0.19 vs. 0.89 ± 0.51, p = 0.006) and higher in patients with non-proliferative (NP)DR (n = 87 vs. n = 53; 0.9 ± 0.51 vs. 0.71 ± 0.29, p = 0.013) compared to those with proliferative (P)DR. Additionally, a positive correlation was found between progerin mRNA expression and the number of intravitreal anti-VEGF applications (n = 139, r = 0.21, p = 0.015), central macula thickness (CMT), (n = 137, r = 0.18, p = 0.036) and nicotine consumption (n = 105, r = 0.235, p = 0.002). The nuclear localization and significant upregulation of progerin mRNA and protein levels in dermal fibroblasts from HGPS donors emphasize its role in cellular aging mechanisms. Progerin mRNA levels were higher in patients with NPDR. CMT, number of intravitreal anti-VEGF therapy treatments, and cigarette consumption were positively related to progerin mRNA, suggesting an association with disease progression and premature aging.

Endometrial expression of ERRβ and ERRγ: prognostic significance and clinical correlations in severe endometriosis

Background

Endometriosis (EMs) results in approximately 50% of reproductive-age women facing infertility. Currently, no precise model is available to predict successful postoperative pregnancy.

Methods

This study involved 81 patients with severe EMs (stages III and IV) and 38 controls with benign gynecological conditions, matched by age and BMI, diagnosis at Fujian Maternity and Child Health Hospital from January 2018 to December 2019. Relative expression levels of ERRβ and ERRγ mRNA in ectopic and ectopic endometrial tissues were measured using fluorescence quantitative PCR. Serum levels of ERRβ, ERRγ, and fertility-related hormones (AMH, FSH, LH, CA125) were assessed. Correlations were analyzed, and the predictive value of ERRγ for postoperative pregnancy was evaluated using a nomogram based on LASSO and multivariate logistic regression. Internal validation using bootstrapping techniques assessed the nomograms performance, including calibration and DCA.

Results

ERRβ and ERRγ mRNA levels from ectopic tissues were significantly reduced in patients with severe EMs compared to controls. High serum CA125 correlated with increased ERRγ mRNA expression in ectopic tissues. ERRγ mRNA expression in ectopic endometrial tissues was negatively correlated with age, BMI, and FSH levels, and positively with AMH and LH/FSH ratio. ERRγ mRNA and FSH were significant predictors of postoperative pregnancy, with the nomogram model showing a Brier score of 0.175 and a consistency statistic of 0.811.

Conclusions

ERRβ and ERRγ are downregulated in ectopic tissues from severe EMs. Elevated ERRγ mRNA expression and lower FSH levels are predictive factors for successful postoperative pregnancy.

Estrogen-insensitivity syndrome (EIS) in a female adolescent patient - a case report

OBJECTIVES

Estrogen insensitivity syndrome (EIS) is a rare genetic disorder characterized by an autosomal dominant inheritance pattern. The disease results from a pathogenic variant in the ESR1 (estrogen receptor 1) gene, leading to estrogen resistance in individuals possessing the 46, XX karyotype. The alpha receptor, which is predominant in peripheral tissues, is responsible for estrogen action. As a result, pathogenic variants in the ESR1 gene can cause various disorders, such as changes in secondary sexual characteristics, increased concentrations of estrogen and gonadotropins, and delayed bone maturation.

CASE PRESENTATION

Here, the case of a 13-year-old girl, with high estrogen and gonadotropin concentrations, lack of breast development, uterine growth and delayed bone age is described. The patient's parents were related. She was found to have a homozygous pathogenic variant in the ESR1 gene located on chromosome 6q25, which interferes with estrogen signaling.

CONCLUSIONS

This case supports that disruption of ESR1 causes profound estrogen resistance in females.

The N-terminal activation function AF-1 domain of ERα interacts directly with the C-terminal AF-2-holding ligand-binding domain to recruit the coactivator proteins

Cryoelectron microscopy (cryo-EM) clarified the quaternary structure of the DNA complex of coactivator-bound estrogen receptor alpha (ERα), revealing the adjacency of the N-terminal domain (NTD) and C-terminal ligand-binding domain (LBD). ERα-NTD and LBD constitute activation function 1 (AF-1) and activation function 2 (AF-2), respectively. These domains are essential for transcription activation. Their spatial proximity was judged to be essential for ERα to recruit the SRC coactivator proteins. In the present study, we first evaluated untethered free ERα-NTD(AF-1) [residues 1-180] and its-truncated desNTD(AF-1)-ERα [residues 181-595] in a luciferase reporter gene assay. ERα-NTD(AF-1) was completely inactive, whereas desNTD(AF-1)-ERα exhibited 66% activity of wild-type ERα. Surprisingly, ERα-NTD(AF-1) was found to inhibit desNTD(AF-1)-ERα markedly. Therefore, assuming that ERα-NTD(AF-1) must also inhibit wild-type full-length ERα, we co-expressed ERα-NTD(AF-1) and full-length ERα. As expected, ERα-NTD(AF-1) inhibited ERα in a dose-dependent manner, but non-competitively for 17β-estradiol. When their intracellular transport was examined immunocytochemically, ERα-NTD(AF-1) showed a distinct translocation from the cytoplasm to the nucleus, despite being expressed solely in the cytoplasm without full-length ERα. This nuclear translocation was attributable to a direct interaction between ERα-NTD(AF-1) and full-length ERα consisting of the nuclear localization signal. The present results demonstrated that, in full-length ERα, the N-terminally tethered NTD(AF-1) domain collaborates with the C-terminal LBD(AF-2) for coactivator recruitment.

A Positive Feedback Loop Exists between Estradiol and IL-6 and Contributes to Dermal Fibrosis

Systemic sclerosis (SSc) is characterized by dermal fibrosis with a female predominance, suggesting a hormonal influence. Patients with SSc have elevated interleukin (IL)-6 levels, and post-menopausal women and older men also have high estradiol (E2) levels. In the skin, IL-6 increases the enzymatic activity of aromatase, thereby amplifying the conversion of testosterone to E2. Therefore, we hypothesized that an interplay between E2 and IL-6 contributes to dermal fibrosis. We used primary dermal fibroblasts from healthy donors and patients with diffuse cutaneous (dc)SSc, and healthy donor skin tissues stimulated with recombinant IL-6 and its soluble receptor (sIL-6R) or E2. Primary human dermal fibroblasts and tissues from healthy donors stimulated with IL-6+sIL-6R produced E2, while E2-stimulated dermal tissues and fibroblasts produced IL-6. Primary dermal fibroblasts from healthy donors treated with IL-6+sIL-6R and the aromatase inhibitor anastrozole (ANA) and dcSSc fibroblasts treated with ANA produced less fibronectin (FN), type III collagen A1 (Col IIIA1), and type V collagen A1 (Col VA1). Finally, dcSSc dermal fibroblasts treated with the estrogen receptor inhibitor fulvestrant also generated less FN, Col IIIA1, and Col VA1. Our data show that IL-6 exerts its pro-fibrotic influence in human skin in part through E2 and establish a positive feedback loop between E2 and IL-6.

Breast cancer cells are sensitized by piperine to radiotherapy through estrogen receptor-α mediated modulation of a key NHEJ repair protein- DNA-PK

BACKGROUND

Non-homologous end joining, an important DNA-double-stranded break repair pathway, plays a prominent role in conferring resistance to radiotherapeutic agents, resulting in cancer progression and relapse.

PURPOSE

The molecular players involved in the radio-sensitizing effects of piperine and many other phytocompounds remain evasive to a great extent. The study is designed to assess if piperine, a plant alkaloid can alter the radioresistance by modulating the expression of non-homologous end-joining machinery.

METHODS AND MATERIALS

Estrogen receptor-positive/negative, breast cancer cells were cultured to understand the synergetic effects of piperine with radiotherapy. Cisplatin and Bazedoxifene were used as positive controls. Cells were exposed to γ- radiation using Low Dose gamma Irradiator-2000. The piperine effect on Estrogen receptor modulation, DNA-Damage, DNA-Damage-Response, and apoptosis was done by western blotting, immunofluorescence, yeast-based-estrogen-receptor-LacZ-reporter assay, and nuclear translocation analysis. Micronuclei assay was done for DNA damage and genotoxicity, and DSBs were quantified by γH2AX-foci-staining using confocal microscopy. Flow cytometry analysis was done to determine the cell cycle, mitochondrial membrane depolarization, and Reactive oxygen species generation. Pharmacophore analysis and protein-ligand interaction studies were done using Schrodinger software. Synergy was computed by compusyn-statistical analysis. Standard errors/deviation/significance were computed with GraphPad prism.

RESULTS

Using piperine, we propose a new strategy for overcoming acquired radioresistance through estrogen receptor-mediated modulation of the NHEJ pathway. This is the first comprehensive study elucidating the mechanism of radio sensitizing potential of piperine. Piperine enhanced the radiation-induced cell death and enhanced the expression and activation of Estrogen receptor β, while Estrogen receptor α expression and activation were reduced. In addition, piperine shares common pharmacophore features with most of the known estrogen agonists and antagonists. It altered the estrogen receptor α/β ratio and the expression of estrogen-responsive proteins of DDR and NHEJ pathway. Enhanced expression of DDR proteins, ATM, p53, and P-p53 with low DNA-PK repair complex (comprising of DNA-PKcs/Ku70/Ku80), resulted in the accumulation of radiation-induced DNA double-stranded breaks (as evidenced by MNi and γH2AX-foci) culminating in cell cycle arrest and mitochondrial-pathway of apoptosis.

CONCLUSION

In conclusion, our study for the first time reported that piperine sensitizes breast cancer cells to radiation by accumulating DNA breaks, through altering the expression of DNA-PK Complex, and DDR proteins, via selective estrogen receptor modulation, offering a novel strategy for combating radioresistance.

Sex Differences in Colon Cancer: Genomic and Nongenomic Signalling of Oestrogen

Colon cancer (CRC) is a prevalent malignancy that exhibits distinct differences in incidence, prognosis, and treatment responses between males and females. These disparities have long been attributed to hormonal differences, particularly the influence of oestrogen signalling. This review aims to provide a comprehensive analysis of recent advances in our understanding of the molecular mechanisms underlying sex differences in colon cancer and the protective role of membrane and nuclear oestrogen signalling in CRC development, progression, and therapeutic interventions. We discuss the epidemiological and molecular evidence supporting sex differences in colon cancer, followed by an exploration of the impact of oestrogen in CRC through various genomic and nongenomic signalling pathways involving membrane and nuclear oestrogen receptors. Furthermore, we examine the interplay between oestrogen receptors and other signalling pathways, in particular the Wnt/β-catenin proliferative pathway and hypoxia in shaping biological sex differences and oestrogen protective actions in colon cancer. Lastly, we highlight the potential therapeutic implications of targeting oestrogen signalling in the management of colon cancer and propose future research directions to address the current gaps in our understanding of this complex phenomenon.

Role of Estrogen Receptor α in Aging and Chronic Disease

Estrogen receptor alpha (ERα) plays a crucial role in reproductive function in both sexes. It also mediates cellular responses to estrogens in multiple nonreproductive organ systems, many of which regulate systemic metabolic homeostasis and inflammatory processes in mammals. The loss of estrogens and/or ERα agonism during aging is associated with the emergence of several comorbid conditions, particularly in females undergoing the menopausal transition. Emerging data also suggests that male mammals likely benefit from ERα agonism if done in a way that circumvents feminizing characteristics. This has led us, and others, to speculate that tissue-specific ERα agonism may hold therapeutic potential for curtailing aging and chronic disease burden in males and females that are at high-risk of cancer and/or cardiovascular events with traditional estrogen replacement therapies. In this mini-review, we emphasize the role of ERα in the brain and liver, summarizing recent evidence that indicates these two organs systems mediate the beneficial effects of estrogens on metabolism and inflammation during aging. We also discuss how 17α-estradiol administration elicits health benefits in an ERα-dependent manner, which provides proof-of-concept that ERα may be a druggable target for attenuating aging and age-related disease burden.