Estradiol mitigates stress-induced cardiac injury and inflammation by downregulating ADAM17 via the GPER-1/PI3K signaling pathway

Stress-induced cardiovascular diseases characterized by inflammation are among the leading causes of morbidity and mortality in postmenopausal women worldwide. Estradiol (E2) is known to be cardioprotective via the modulation of inflammatory mediators during stress. But the mechanism is unclear. TNFα, a key player in inflammation, is primarily converted to its active form by 'A Disintegrin and Metalloprotease 17' (ADAM17). We investigated if E2 can regulate ADAM17 during stress. Experiments were performed using female FVB wild-type (WT), C57BL/6 WT, and G protein-coupled estrogen receptor 1 knockout (GPER-1 KO) mice and H9c2 cells. The study revealed a significant increase in cardiac injury and inflammation during isoproterenol (ISO)-induced stress in ovariectomized (OVX) mice. Additionally, ADAM17's membrane content (mADAM17) was remarkably increased in OVX and GPER-1 KO mice during stress. However, in vivo supplementation of E2 significantly reduced cardiac injury, mADAM17, and inflammation. Also, administering G1 (GPER-1 agonist) in mice under stress reduced mADAM17. Further experiments demonstrated that E2, via GPER-1/PI3K pathway, localized ADAM17 at the perinuclear region by normalizing β1AR-Gαs, mediating the switch from β2AR-Gαi to Gαs, and reducing phosphorylated kinases, including p38 MAPKs and ERKs. Thus, using G15 and LY294002 to inhibit GPER-1 and its down signaling molecule, PI3K, respectively, in the presence of E2 during stress resulted in the disappearance of E2's modulatory effect on mADAM17. In vitro knockdown of ADAM17 during stress significantly reduced cardiac injury and inflammation, confirming its significant inflammatory role. These interesting findings provide novel evidence that E2 and G1 are potential therapeutic agents for ADAM17-induced inflammatory diseases associated with postmenopausal females.

G protein-coupled estrogen receptor (GPER/GPR30) levels in pelvic floor muscles and its association with estrogen status in female rabbits

Objective: To assess the relative expression of the G-protein coupled estrogen receptor (GPER) in the bulbospongiosus (Bsm) and pubococcygeus (Pcm) muscles in control, ovariectomized (OVX), and OVX with estradiol benzoate supplementation (OVX + EB) rabbits.Methods: We used tissues from C, 1-month OVX, and OVX plus 15-day EB implanted (OVX + EB) groups. The GPER expression was evaluated by Western blot and immunohistochemistry for both Bsm and Pcm. Results: Both muscles showed a GPER immunoreactivity in blood vessels, inside myofibers next to myonuclei, and in polymorphonuclear cells. Four-week ovariectomy did not modify the GPER expression in the Bsm and Pcm, but two-week estradiol benzoate increased it in the latter muscle alone.Conclusions: We demonstrated that the Bsm and Pcm of female rabbits express GPER. High serum estradiol levels elevate GPER relative expression in the Pcm alone. The present study supports the remarkable estrogen sensitivity of the Pcm.

The impact of G protein-coupled oestrogen receptor 1 on male breast cancer: a retrospective analysis

Introduction

The G protein-coupled oestrogen receptor 1 (GPER-1) is a potential prognostic marker in breast cancer. However, its role in male breast cancer (MBC) is still unknown. This study evaluates the expression of GPER-1 in MBC samples and correlates these data with clinical and pathological parameters including patients' survival.

Material and methods

For this retrospective analysis of a prospectively maintained cohort of patients with MBC, we examined 161 specimens for GPER-1 expression using immunohistochemistry. An immunoreactive score (IRS) was calculated based on staining intensity and the percentage of positive tumour cells. Then, we correlated GPER-1 IRS with clinical and pathological parameters, and overall and relapse-free survival.

Results

About 40% of MBC samples were positive for GPER-1 expression (IRS ≥ 4). There was no significant correlation with clinicopathological parameters, such as hormone receptor status or grading. However, a statistical trend was observed for tumour size (≥ 2 cm, p = 0.093). Kaplan-Meier survival analysis revealed no significant correlation with relapse-free survival. However, there was a significant correlation with overall survival, but when we adjusted the log-rank p-value to compensate for the cut-off point optimization method, it rose above 0.1. Additionally, GPER-1-positive patients were older at diagnosis. When adjusted for age by multivariable Cox regression analysis, the significance of GPER-1 status for survival was further reduced.

Conclusions

We found no significant prognostic value of GPER-1 in this MBC cohort as anticipated from studies on female BC. Future studies with higher sample size are needed to further verify a potential sex-specific role of GPER-1.

Evaluation of serum G protein-coupled estrogen receptor 1 (GPER-1) levels in patients with androgenetic alopecia

The effect of oestrogens in androgenetic alopecia (AGA) pathophysiology has not been clearly understood. However, they are considered to have a place in the AGA pathogenesis as the androgens do. The effects of estrogen occur via the estrogen receptors alpha and beta, and the recently discovered G protein-coupled estrogen receptor 1 (GPER-1). Aim of this study is to examine serum GPER-1 levels of AGA patients and to evaluate the place of them in AGA pathogenesis for the first time through the literature. 40 AGA patients with clinical AGA stage 2-3-4 diagnoses according to the Hamilton-Norwood classification for males, and AGA stage 2 according to Ludwig system for females and with normal serum dihydroepiandrosterone sulfate, estradiol, total testosterone, progesterone, follicle stimulating hormone and luteinizing hormone were included in the study in addition to 40 healthy controls with similar characteristics by means of age and gender. We received the medical history and performed the physical examinations. We measured serum GPER-1 levels. Serum GPER-1 levels of AGA patients and the control group were 30.43 ± 3.83 ng/mL and 14.18 ± 3.61 ng/mL (mean ± SD), respectively. The levels were detected as significantly increased in AGA group compared with the control group (p = 0.007). No serum GPER-1 level differences were found among female and male patients (p = 0.101). Significantly high levels of serum GPER-1 levels in AGA patients without any relationship between gender and GPER-1 Levels compared with healthy controls reminded us that GPER-1 might have a role in AGA pathogenesis independent from the gender.

G protein-coupled estrogen receptor-1: homology modeling approaches and application in screening new GPER-1 modulators

G protein-coupled receptors (GPCRs) belong to the largest family of protein targets comprising over 800 members in which at least 500 members are the therapeutic targets. Among the GPCRs, G protein-coupled estrogen receptor-1 (GPER-1) has shown to have the ability in estrogen signaling. As GPER-1 plays a critical role in several physiological responses, GPER-1 has been considered as a potential therapeutic target to treat estrogen-based cancers and other non-communicable diseases. However, the progress in the understanding of GPER-1 structure and function is relatively slow due to the availability of a only a few selective GPER-1 modulators. As with many GPCRs, the X-ray crystal structure of GPER-1 is yet to be resolved and thus has led the researchers to search for new GPER-1 modulators using homology models of GPER-1. In this review, we aim to summarize various approaches used in the generation of GPER-1 homology model and their applications that have resulted in new GPER-1 ligands.

G Protein-Coupled Estrogen Receptor Mediates Cell Proliferation through the cAMP/PKA/CREB Pathway in Murine Bone Marrow Mesenchymal Stem Cells

Estrogen is an important hormone to regulate skeletal physiology via estrogen receptors. The traditional estrogen receptors are ascribed to two nuclear estrogen receptors (ERs), ERα and ERβ. Moreover, G protein-coupled estrogen receptor-1 (GPER-1) was reported as a membrane receptor for estrogen in recent years. However, whether GPER-1 regulated osteogenic cell biology on skeletal system is still unclear. GPER-1 is expressed in growth plate abundantly before puberty but decreased abruptly since the very late stage of puberty in humans. It indicates GPER-1 might play an important role in skeletal growth regulation. GPER-1 expression has been confirmed in osteoblasts, osteocytes and chondrocytes, but its expression in mesenchymal stem cells (MSCs) has not been confirmed. In this study, we hypothesized that GPER-1 is expressed in bone MSCs (BMSC) and enhances BMSC proliferation. The cultured tibiae of neonatal rat and murine BMSCs were tested in our study. GPER-1-specific agonist (G-1) and antagonist (G-15), and GPER-1 siRNA (siGPER-1) were used to evaluate the downstream signaling pathway and cell proliferation. Our results revealed BrdU-positive cell counts were higher in cultured tibiae in the G-1 group. The G-1 also enhanced the cell viability and proliferation, whereas G-15 and siGPER-1 reduced these activities. The cAMP and phosphorylation of CREB were enhanced by G-1 but inhibited by G-15. We further demonstrated that GPER-1 mediates BMSC proliferation via the cAMP/PKA/p-CREB pathway and subsequently upregulates cell cycle regulators, cyclin D1/cyclin-dependent kinase (CDK) 6 and cyclin E1/CDK2 complex. The present study is the first to report that GPER-1 mediates BMSC proliferation. This finding indicates that GPER-1 mediated signaling positively regulates BMSC proliferation and may provide novel insights into addressing estrogen-mediated bone development.

GPER-1 and sex-hormone levels in patients with otosclerosis

OBJECTIVE

Otosclerosis is a widespread disease but the etiopathogenesis is still not fully understood. Hormonal factors especially estrogens are accused in recent years. The study aimed to evaluate the levels of G-protein associated membrane estrogen receptor-1 (GPER-1) and sex-hormones in patients with otosclerosis.

SUBJECT AND METHODS

The study included 60 people (30 otosclerosis patients, 30 control group). Serum sex-hormone (estradiol, progesterone, prolactin and total testosterone) and GPER-1 levels were measured in otosclerosis patients and compared with the normal population. For the otosclerosis group, air conduction and bone conduction thresholds and air-bone gaps were viewed from audiograms and the relationships between hearing and GPER-1 or sex-hormone levels were also investigated.

RESULTS

Sex-hormone levels were not different between the groups. GPER-1 level was significantly lower in the otosclerosis group [3.1353 (0.76-8.21) ng/mL] than the control group [5.4773 (0.96-20.31) ng/mL] (p =0.017). Differential diagnosis with ROC analysis for the GPER-1 level was also significant (p=0.017). GPER-1 level was significantly lower for the females than the males in the otosclerosis group (p=0.043). Serum estradiol, progesterone, and prolactin levels were significantly higher (p=0.02, p =0.029 and p=0.019 respectively) and the GPER-1 level was significantly lower (p= 0.04) in the female patients compared to the female controls. There was no statistically significant relationship between GPER-1 or sex-hormone levels and hearing parameters.

CONCLUSION

GPER-1 level was lower in the otosclerosis patients compared to healthy volunteers and also lower in females than males in the patient group. Female sex-hormone levels were higher and GPER-1 level was lower in the female patient group than the female control group. Neither GPER-1 nor sex-hormone levels were not predictive of hearing levels. These findings indicate that sex-hormones especially estrogen and GPER-1 might have a potential role in the etiopathogenesis of otosclerosis. This is the first study in the literature that investigates the GPER-1 values in otosclerosis.

GPER-1 expression is associated with a decreased response rate to primary tamoxifen therapy of breast cancer patients

PURPOSE

Endocrine therapies using tamoxifen and/or aromatase inhibitors are important therapeutic options for the targeted treatment of hormone-responsive breast cancer. In addition to nuclear estrogen receptors ERα and β, G-protein-coupled estrogen receptor GPER-1 is a third receptor-mediating estrogen effects in breast cancer cells. The aim of this study was to examine to what extent GPER-1 expression might affect the efficacy of primary endocrine treatment of breast cancer.

METHODS

GPER-1 expression was determined in tissue samples from patients with early breast cancer by means of immunohistochemistry and a GPER-1 score of ≥ 3 was considered to be positive. In a total of 165 patients, the response to a primary therapy with tamoxifen (TAM) or aromatase inhibitors (AI) was assessed by ultrasound imaging for up to 6 months. The primary endpoint of this study was the response to treatment evaluated by RECIST 1.1 criteria.

RESULTS

GPER-1 expression was observed in 127 (77.0%) out of 165 cases. Based on GPER-1 expression and the type of endocrine treatment, the patients were divided into 4 groups: GPER-1 negative/TAM (12.1%), GPER-1 negative/AI (10.9%), GPER-1 positive/TAM (44.8%), and GPER-1 positive/AI (32.1%). The groups were well balanced regarding different clinical and pathological factors. After 4 and 6 months of treatment, a high level of stable disease or progressive disease was observed in the GPER-1 positive/TAM group only (p < 0.0001), whereas in the other three groups of patients, the most common objective response was classified as partial response. We observed a continuous reduction of mean tumor size in patients treated with aromatase inhibitors irrespective of the GPER-1 status and in GPER-1 negative patients treated with TAM. In contrast, in GPER-1 positive patients treated with TAM, a reduction of mean tumor size was observed only in the first 2 months after beginning of treatment. Four and six months after start of treatment, no reduction, but even a slight increase of tumor size was observed in this patients group.

CONCLUSIONS

GPER-1 expression is significantly associated with a reduced effect of primary treatment with tamoxifen in breast cancer patients.

Plasma membrane G protein-coupled estrogen receptor 1 (GPER) mediates rapid estradiol facilitation of sexual receptivity through the orphanin-FQ-ORL-1 system in estradiol primed female rats

In estradiol-primed nonreceptive ovariectomized rats, activation of G protein-coupled estrogen receptor 1 (GPER) in the arcuate nucleus of the hypothalamus (ARH) rapidly facilitates sexual receptivity (lordosis). Estradiol priming activates ARH β-endorphin (β-END) neurons that then activate medial preoptic (MPN) μ-opioid receptors (MOP) to inhibit lordosis. ARH infusion of non-esterified 17β-estradiol (E2) 47.5 h after 17β-estradiol benzoate (2 μg EB) priming deactivates MPN MOP and rapidly facilitates lordosis within 30 min via activation of GPER. Since it was unclear where GPERs were located in the neuron, we tested the hypothesis that GPER signaling is initiated at the plasma membrane. Membrane impermeable estradiol (17β-estradiol conjugated to biotin; E-Biotin) infused into the ARH of EB primed rats facilitated lordosis within 30 min, and MPN MOP was deactivated. These actions were blocked by pretreating with GPER antagonist, G-15. Further, we used cell fractionation and western blot techniques to demonstrate that GPER is expressed both in plasma membrane and cytosolic ARH fractions. In previous studies, the orphanin FQ/nociceptin-opioid receptor-like receptor-1 (OFQ/N-ORL-1) system mediated estradiol-only facilitation of lordosis. Therefore, we tested whether the OFQ/N-ORL-1 system mediates E-Biotin-GPER facilitation of lordosis. Pretreatment of UFP-101, an ORL-1 selective antagonist, blocked the facilitation of lordosis and deactivation of MPN MOP by ARH infusion of E-Biotin. Double-label immunohistochemistry revealed that GPER is expressed within approximately 70% of OFQ/N neurons. These data indicate that membrane GPER mediates the E2/E-Biotin facilitation of lordosis by inducing OFQ/N neurotransmission, which inhibits β-END neurotransmission to reduce MPN MOP activation.

Possible role of phytoestrogens in breast cancer via GPER-1/GPR30 signaling

Estrogens generated within endocrine organs and the reproductive system act as ligands for at least three types of estrogen receptors. Estrogen receptors α (ERα) and β (ERβ) belong to the so-called classical family of estrogen receptors, whereas the G protein-coupled receptor GPR30, also known as GPER-1, has been described as a novel estrogen receptor sited in the cell membrane of target cells. Furthermore, these receptors are under stimulation of a family of exogenous estrogens, known as phytoestrogens, which are a diverse group of non-steroidal plant compounds derived from plant food consumed by humans and animals. Because phytoestrogens are omnipresent in our daily diet, they are becoming increasingly important in both human health and disease. Recent evidence indicates that in addition to classical estrogen receptors, phytoestrogens also activate GPER-1 a relevant observation since GPER-1 is involved in several physiopathological disorders and especially in estrogen-dependent diseases such as breast cancer.The first estrogen receptors discovered were the classical ERα and ERβ, but from an evolutionary point of view G protein-coupled receptors trace their origins in history to over a billion years ago suggesting that estrogen receptors like GPER-1 may have been the targets of choice for ancient phytoestrogens and/or estrogens.This review provides a comprehensive and systematic literature search on phytoestrogens and its relationship with classical estrogen receptors and GPER-1 including its role in breast cancer, an issue still under discussion.

G-protein-coupled estrogen receptor GPER-1 expression in hormone receptor-positive breast cancer is associated with poor benefit of tamoxifen

BACKGROUND

The role of G-protein-coupled estrogen receptor 1 (GPER-1) in the development of tamoxifen resistance in breast cancer is a highly controversial issue. The aim of this study was to determine the expression of GPER-1 in the clinical routine under conditions of endocrine treatment.

PATIENTS AND METHODS

GPER-1 expression was analyzed in 442 patients with primary invasive breast cancer. GPER-1 score of > 3 was determined as positive. Expression data were correlated with clinical and pathological characteristics and patient survival.

RESULTS

GPER-1 expression was observed in 352 (80.9%) cases, and positively correlated with estrogen and progesterone receptor status (p = 0.0001). GPER-1 positivity was associated with an increased grade of differentiation (p = 0.0001) and with a low level of Ki-67 expression (p = 0.0001). High GPER-1 expression was associated with a decreased level upon systemic treatment (p = 0.011). In the whole cohort, GPER-1 expression was associated with prolonged disease-free survival (DFS). DFS between tamoxifen- and aromatase inhibitor-treated GPER-1-positive patients was similar (p = 0.090). Notably, after matching the analysis for the most important prognostic factors, DFS for tamoxifen-treated GPER-1-positive patients was 69.1%, which is a percentage that is significantly lower compared to DFS for GPER-1-positive patients treated with aromatase inhibitors (92.7%) (p = 0.005).

CONCLUSION

GPER-1 expression is a favorable prognostic factor in breast cancer patients. Its predictive role for poor benefit form tamoxifen treatment should be investigated in further studies.

Oestrogen Inhibits VEGF Expression And Angiogenesis In Triple-Negative Breast Cancer By Activating GPER-1

Triple-negative breast cancer (TNBC) is the most malignant type of breast cancer with ample vascularisation and high vascular endothelial growth factor (VEGF) expression. The sex steroid hormone oestrogen is involved in several cellular activities associated with TNBC regulation. However, the role of oestrogen in VEGF expression and angiogenesis in TNBC remains unclear. In this study, we found that treatment with 17β-oestradiol (E2) inhibited VEGF mRNA and protein expression in the TNBC cell lines MDA-MB-468 and MDA-MB-436. To further elaborate on the phenomenon of E2-regulated angiogenesis, we showed that conditioned medium from the TNBC cell line MDA-MB-468 treated with E2 inhibits the tube formation ability of human umbilical vein endothelial cells (HUVECs). Additionally, the G-protein-coupled oestrogen receptor-1 (GPER-1)-specific agonist G-1 has a function similar to that of E2. While G-15, the selective antagonist of GPER-1, notably reversed the inhibitory effects of E2 and G-1 on VEGF expression and tube formation, suggesting that GPER-1 is involved in the E2-induced angiogenesis suppression in TNBC cells. Moreover, E2 inhibited in vivo tumour growth and angiogenesis and reduced the expression levels of VEGF, NF-κB/p65, STAT3, and the endothelial marker CD34 in MDA-MB-468 xenograft tumours. Our findings provide important evidence that E2 can inhibit VEGF expression and angiogenesis in TNBC by activating GPER-1, offering additional insight into tumour angiogenesis and targets for drug intervention in TNBC.

Serum levels of GPER-1 in euthymic bipolar patients

INTRODUCTION

Estrogen and its receptors have been suggested as playing a role in the pathogenesis of bipolar disorder (BD). Estrogen functions through the estrogen receptors alpha and beta and the recently discovered G-protein-coupled estrogen receptor-1 (GPER-1). The aim of this study was to evaluate serum GPER-1 levels in euthymic BD patients.

PATIENTS AND METHODS

The study population consisted of 38 euthymic outpatients meeting the criteria for BD in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition and 35 age- and gender-matched healthy controls. Medical histories were obtained and physical examinations and laboratory tests conducted.

RESULTS

Serum GPER-1 levels were measured in both patients and controls and found to be significantly higher in the BD patients than in controls. These results were not influenced by the medications in use.

CONCLUSION

The results of this study demonstrated that GPER-1 may play a role in BD pathophysiology.

GPER-1/GPR30 a novel estrogen receptor sited in the cell membrane: therapeutic coupling to breast cancer

INTRODUCTION

Breast cancer is clinically classified as 'estrogen-positive' when at least 1% of cancer cells stain for the estrogen receptor alpha (ERα). However, recent research on both basic and clinical aspects of breast cancer suggests that GPER-1 (G protein-coupled estrogen receptor-1) may have an important role in breast cancer. Areas covered: This review provides a comprehensive and systematic literature search on GPER-1. We have focused on the role of GPER-1 in breast cancer and on resistance to endocrine therapy, an unsolved clinical issue still under discussion. Expert opinion: The discovery of GPER-1 as a novel estrogen receptor is unique and the signaling pathways activated by its stimulation, when compared to the classical nuclear ERα, indicate a potential role of GPER-1 in the genesis and mechanisms of drug resistance in breast cancer. Tumors expressing ERα represent the largest group of breast cancer patients indicating that more women eventually die from ERα-positive breast tumors than from other more malignant breast cancer subtypes such as HER2-positive and the triple negative groups. It is important to develop new strategies on endocrine therapy with regard to ERα and GPER-1 receptors to achieve innovative successful therapeutic tools.

Not lost in translation: Emerging clinical importance of the G protein-coupled estrogen receptor GPER

It has been 20years that the G protein-coupled estrogen receptor (GPER) was cloned as the orphan receptor GPR30 from multiple cellular sources, including vascular endothelial cells. Here, I will provide an overview of estrogen biology and the historical background leading to the discovery of rapid vascular estrogen signaling. I will also review the recent advances in the understanding of the mechanisms underlying GPER function, its role in physiology and disease, some of the currently available GPER-targeting drugs approved for clinical use such as SERMs (selective estrogen receptor modulators) and SERDs (selective estrogen receptor downregulators). Many of currently used drugs such as tamoxifen, raloxifene, or faslodex™/fulvestrant were discovered targeting GPER many years after they had been introduced to the clinics for entirely different purposes. This has important implications for the clinical use of these drugs and their modes of action, which I have termed 'reverse translational medicine'. In addition, environmental pollutants known as 'endocrine disruptors' have been found to bind to GPER. This article also discusses recent evidence in these areas as well as opportunities in translational clinical medicine and GPER research, including medical genetics, personalized medicine, prevention, and its theranostic use.

Estrogens and Coronary Artery Disease: New Clinical Perspectives

In premenopausal women, endogenous estrogens are associated with reduced prevalence of arterial hypertension, coronary artery disease, myocardial infarction, and stroke. Clinical trials conducted in the 1990s such as HERS, WHI, and WISDOM have shown that postmenopausal treatment with horse hormone mixtures (so-called conjugated equine estrogens) and synthetic progestins adversely affects female cardiovascular health. Our understanding of rapid (nongenomic) and chronic (genomic) estrogen signaling has since advanced considerably, including identification of a new G protein-coupled estrogen receptor (GPER), which like the "classical" receptors ERα and ERβ is highly abundant in the cardiovascular system. Here, we discuss the role of estrogen receptors in the pathogenesis of coronary artery disease and review natural and synthetic ligands of estrogen receptors as well as their effects in physiology, on cardiovascular risk factors, and atherosclerotic vascular disease. Data from preclinical and clinical studies using nonselective compounds activating GPER, which include selective estrogen receptor modulators such as tamoxifen or raloxifene, selective estrogen receptor downregulators such as Faslodex™ (fulvestrant/ICI 182,780), vitamin B3 (niacin), green tea catechins, and soy flavonoids such as genistein or resveratrol, strongly suggest that activation of GPER may afford therapeutic benefit for primary and secondary prevention in patients with or at risk for coronary artery disease. Evidence from preclinical studies suggest similar efficacy profiles for selective small molecule GPER agonists such as G-1 which are devoid of uterotrophic activity. Further clinical research in this area is warranted to provide opportunities for future cardiovascular drug development.

Homology Modeling, Validation and Dynamics of the G Protein-coupled Estrogen Receptor 1 (GPER-1)

Estrogens exert their action mainly by binding three receptors, namely estrogen receptors α and β (ERα and ERβ) and GPER-1 (G-protein coupled estrogen receptor 1). While the patho-physiological role of both ERα and ERβ has been deeply investigated, the role of GPER-1 in estrogens' signaling has not been clearly defined yet. Unfortunately, only few GPER-1 selective ligands were discovered so far, and the real efficiency of such compounds is still matter of debate. To better understand the physiological relevance of GPER-1, new selective chemical probes are higly needed. In this scenario, we report herein the generation and validation of a three-dimensional (3-D) GPER-1 homology model by means of docking studies and molecular dynamics simulations. The model thus generated was employed to (i) decipher the structural basis underlying the ability of estrogens and some Selective Estrogen Receptor Modulators (SERMs) to bind GPER-1 and classical ERα and ERβ, and (ii) generate a reliable G1/GPER-1 complex useful in rationalizing the pharmacological profile of G1 reported in the literature. The G1/GPER-1 complex herein reported could be further exploited in drug design approaches aimed at improving the pharmacological profile of G1 or at identifying new chemical entities (NCEs) as potential modulators of GPER-1.

Anatomical location and redistribution of G protein-coupled estrogen receptor-1 during the estrus cycle in mouse kidney and specific binding to estrogens but not aldosterone

Prior studies have linked renoprotective effects of estrogens to G-protein-coupled estrogen receptor-1 (GPER-1) and suggest that aldosterone may also activate GPER-1. Here, the role of GPER-1 in murine renal tissue was further evaluated by examining its anatomical distribution, subcellular distribution and steroid binding specificity. Dual immunofluorescent staining using position-specific markers showed that GPER-1 immunoreactivity primarily resides in distal convoluted tubules and the Loop of Henle (stained with Tamm-Horsfall Protein-1). Lower GPER-1 expression was observed in proximal convoluted tubules marked with megalin, and GPER-1 was not detected in collecting ducts. Plasma membrane fractions prepared from whole kidney tissue or HEK293 cells expressing recombinant human GPER-1 (HEK-GPER-1) displayed high-affinity, specific [(3)H]-17β-estradiol ([(3)H]-E2) binding, but no specific [(3)H]-aldosterone binding. In contrast, cytosolic preparations exhibited specific binding to [(3)H]-aldosterone but not to [(3)H]-E2, consistent with the subcellular distribution of GPER-1 and mineralocorticoid receptor (MR) in these preparations. Aldosterone and MR antagonists, spironolactone and eplerenone, failed to compete for specific [(3)H]-E2 binding to membranes of HEK-GPER-1 cells. Furthermore, aldosterone did not increase [(35)S]-GTP-γS binding to membranes of HEK-GPER-1 cells, indicating that it is not involved in G protein signaling mediated through GPER-1. During the secretory phases of the estrus cycle, GPER-1 is upregulated on cortical epithelia and localized to the basolateral surface during proestrus and redistributed intracellularly during estrus. GPER-1 is down-modulated during luteal phases of the estrus cycle with significantly less receptor on the surface of renal epithelia. Our results demonstrate that GPER-1 is associated with specific estrogen binding and not aldosterone binding and that GPER-1 expression is modulated during the estrus cycle which may suggest a physiological role for GPER-1 in the kidney during reproduction.