Exploring Biological Targets of Magnolol and Honokiol and their Nature-Inspired Synthetic Derivatives: In Silico Identification and Experimental Validation of Estrogen Receptors.

In this work, we describe the results of a computational investigation aimed at identifying potential biological targets of honokiol, magnolol and a series of synthetic prodrug derivatives obtained through esterification of the free hydroxyl groups. The ligand-based and structure-based analyses revealed that these compounds potentially interact with several biological targets, some of which are known while others are new. Honokiol, magnolol, and three of the newly synthesized derivatives may bind to estrogen receptors ERα and ERβ.

Iterative Catalyst-Controlled Diastereoselective Matteson Homologations Enable the Selective Synthesis of Benzestrol Isomers.

We report the development of an iterative Matteson homologation reaction with catalyst-controlled diastereoselectivity through the design of a new catalyst. This reaction was applied to the selective synthesis of each stereoisomer of benzestrol, a bioactive compound with estrogenic activity featuring three contiguous stereocenters. The different stereoisomers were assayed to determine their binding affinity for the estrogen receptor α (ERα), and the absolute configuration of the compound having uniquely high activity was determined.

Asymmetric allostery in estrogen receptor-α homodimers drives responses to the ensemble of estrogens in the hormonal milieu.

The estrogen receptor-α (ER) is thought to function only as a homodimer but responds to a variety of environmental, metazoan, and therapeutic estrogens at subsaturating doses, supporting binding mixtures of ligands as well as dimers that are only partially occupied. Here, we present a series of flexible ER ligands that bind to receptor dimers with individual ligand poses favoring distinct receptor conformations-receptor conformational heterodimers-mimicking the binding of two different ligands. Molecular dynamics simulations showed that the pairs of different ligand poses changed the correlated motion across the dimer interface to generate asymmetric communication between the dimer interface, the ligands, and the surface binding sites for epigenetic regulatory proteins.

Asymmetric Allostery in Estrogen Receptor-α Homodimers Drives Responses to the Ensemble of Estrogens in the Hormonal Milieu.

Unlabelled: The estrogen receptor-α (ER) is thought to function only as a homodimer, but responds to a variety of environmental, metazoan, and therapeutic estrogens at sub-saturating doses, supporting binding mixtures of ligands as well as dimers that are only partially occupied. Here, we present a series of flexible ER ligands that bind to receptor dimers with individual ligand poses favoring distinct receptor conformations -receptor conformational heterodimers-mimicking the binding of two different ligands. Molecular dynamics simulations showed that the pairs of different ligand poses changed the correlated motion across the dimer interface to generate asymmetric communication between the dimer interface, the ligands, and the surface binding sites for epigenetic regulatory proteins.

Skeletal Muscle Endogenous Estrogen Production Ameliorates the Metabolic Consequences of a High-Fat Diet in Male Mice.

Aims: The role of skeletal muscle estrogen and its ability to mitigate the negative impact of a high-fat diet (HFD) on obesity-associated metabolic impairments is unknown. To address this, we developed a novel mouse model to determine the role of endogenous 17β-estradiol (E2) production in males in skeletal muscle via inducible, skeletal muscle-specific aromatase overexpression (SkM-Arom↑).

Methods: Male SkM-Arom↑ mice and littermate controls were fed a HFD for 14 weeks prior to induction of SkM-Arom↑ for a period of 6.

Design, synthesis, biological evaluation and crystal structure determination of dual modulators of carbonic anhydrases and estrogen receptors.

Multi-target compounds have become increasingly important for the development of safer and more effective drug candidates. In this work, we devised a combined ligand-based and structure-based multi-target repurposing strategy and applied it to a series of hexahydrocyclopenta[c]quinoline compounds synthesized previously. The in silico analyses identified human Carbonic Anhydrases (hCA) and Estrogen Receptors (ER) as top scoring candidates for dual modulation.

The SARS-CoV-2 spike protein binds and modulates estrogen receptors.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein binds angiotensin-converting enzyme 2 as its primary infection mechanism. Interactions between S and endogenous proteins occur after infection but are not well understood. We profiled binding of S against >9000 human proteins and found an interaction between S and human estrogen receptor α (ERα).

Hydroxychloroquine blocks SARS-CoV-2 entry into the endocytic pathway in mammalian cell culture.

Hydroxychloroquine (HCQ), a drug used to treat lupus and malaria, was proposed as a treatment for SARS-coronavirus-2 (SARS-CoV-2) infection, albeit with controversy. In vitro, HCQ effectively inhibits viral entry, but its use in the clinic has been hampered by conflicting results. A better understanding of HCQ's mechanism of actions in vitro is needed.

The SARS-CoV-2 spike protein binds and modulates estrogen receptors.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike (S) protein binds angiotensin-converting enzyme 2 (ACE2) at the cell surface, which constitutes the primary mechanism driving SARS-CoV-2 infection. Molecular interactions between the transduced S and endogenous proteins likely occur post-infection, but such interactions are not well understood. We used an unbiased primary screen to profile the binding of full-length S against >9,000 human proteins and found significant S-host protein interactions, including one between S and human estrogen receptor alpha (ERα).

Activation of Crtc2/Creb1 in skeletal muscle enhances weight loss during intermittent fasting.

The Creb-Regulated Transcriptional Coactivator (Crtc) family of transcriptional coregulators drive Creb1-mediated transcription effects on metabolism in many tissues, but the in vivo effects of Crtc2/Creb1 transcription on skeletal muscle metabolism are not known. Skeletal muscle-specific overexpression of Crtc2 (Crtc2 mice) induced greater mitochondrial activity, metabolic flux capacity for both carbohydrates and fats, improved glucose tolerance and insulin sensitivity, and increased oxidative capacity, supported by upregulation of key metabolic genes. Crtc2 overexpression led to greater weight loss during alternate day fasting (ADF), selective loss of fat rather than lean mass, maintenance of higher energy expenditure during the fast and reduced binge-eating during the feeding period.

Dual-mechanism estrogen receptor inhibitors.

Efforts to improve estrogen receptor-α (ER)-targeted therapies in breast cancer have relied upon a single mechanism, with ligands having a single side chain on the ligand core that extends outward to determine antagonism of breast cancer growth. Here, we describe inhibitors with two ER-targeting moieties, one of which uses an alternate structural mechanism to generate full antagonism, freeing the side chain to independently determine other critical properties of the ligands. By combining two molecular targeting approaches into a single ER ligand, we have generated antiestrogens that function through new mechanisms and structural paradigms to achieve antagonism.

Suppression of breast cancer metastasis and extension of survival by a new antiestrogen in a preclinical model driven by mutant estrogen receptors.

Purpose: Many human breast tumors become resistant to endocrine therapies and recur due to estrogen receptor (ERα) mutations that convey constitutive activity and a more aggressive phenotype. Here, we examined the effectiveness of a novel adamantyl antiestrogen, K-07, in suppressing the growth of breast cancer metastases containing the two most frequent ER-activating mutations, Y537S and D538G, and in extending survival in a preclinical metastatic cancer model.

Methods: MCF7 breast cancer cells expressing luciferase and Y537S or D538G ER were injected into NOD-SCID-gamma female mice, and animals were treated orally with the antiestrogen K-07 or control vehicle.

Pocket similarity identifies selective estrogen receptor modulators as microtubule modulators at the taxane site.

Taxanes are a family of natural products with a broad spectrum of anticancer activity. This activity is mediated by interaction with the taxane site of beta-tubulin, leading to microtubule stabilization and cell death. Although widely used in the treatment of breast cancer and other malignancies, existing taxane-based therapies including paclitaxel and the second-generation docetaxel are currently limited by severe adverse effects and dose-limiting toxicity.

Unexpected equivalent potency of a constrained chromene enantiomeric pair rationalized by co-crystal structures in complex with estrogen receptor alpha.

Despite tremendous progress made in the understanding of the ERα signaling pathway and the approval of many therapeutic agents, ER+ breast cancer continues to be a leading cause of cancer death in women. We set out to discover compounds with a dual mechanism of action in which they not only compete with estradiol for binding with ERα, but also can induce the degradation of the ERα protein itself. We were attracted to the constrained chromenes containing a tetracyclic benzopyranobenzoxepine scaffold, which were reported as potent selective estrogen receptor modulators (SERMs).

The SERM/SERD bazedoxifene disrupts ESR1 helix 12 to overcome acquired hormone resistance in breast cancer cells.

Acquired resistance to endocrine therapy remains a significant clinical burden for breast cancer patients. Somatic mutations in the (estrogen receptor alpha (ERα)) gene ligand-binding domain (LBD) represent a recognized mechanism of acquired resistance. Antiestrogens with improved efficacy versus tamoxifen might overcome the resistant phenotype in ER +breast cancers.

Cryptic glucocorticoid receptor-binding sites pervade genomic NF-κB response elements.

Glucocorticoids (GCs) are potent repressors of NF-κB activity, making them a preferred choice for treatment of inflammation-driven conditions. Despite the widespread use of GCs in the clinic, current models are inadequate to explain the role of the glucocorticoid receptor (GR) within this critical signaling pathway. GR binding directly to NF-κB itself-tethering in a DNA binding-independent manner-represents the standing model of how GCs inhibit NF-κB-driven transcription.

Structurally Novel Antiestrogens Elicit Differential Responses from Constitutively Active Mutant Estrogen Receptors in Breast Cancer Cells and Tumors.

Many estrogen receptor α (ERα)-positive breast cancers develop resistance to endocrine therapy via mutation of ERs whose constitutive activation is associated with shorter patient survival. Because there is now a clinical need for new antiestrogens (AE) against these mutant ERs, we describe here our development and characterization of three chemically novel AEs that effectively suppress proliferation of breast cancer cells and tumors. Our AEs are effective against wild-type and Y537S and D538G ERs, the two most commonly occurring constitutively active ERs.

Adamantyl Antiestrogens with Novel Side Chains Reveal a Spectrum of Activities in Suppressing Estrogen Receptor Mediated Activities in Breast Cancer Cells.

To search for new antiestrogens more effective in treating breast cancers, we explored alternatives to the acrylic acid side chain used in many antiestrogens. To facilitate our search, we used a simple adamantyl ligand core that by avoiding stereochemical issues enabled rapid synthesis of acrylate ketone, ester, and amide analogs. All compounds were high affinity estrogen receptor α (ERα) ligands but displayed a range of efficacies and potencies as antiproliferative and ERα-downregulating agents.

Tethering not required: the glucocorticoid receptor binds directly to activator protein-1 recognition motifs to repress inflammatory genes.

The glucocorticoid receptor (GR) is a ligand-regulated transcription factor that controls the expression of extensive gene networks, driving both up- and down-regulation. GR utilizes multiple DNA-binding-dependent and -independent mechanisms to achieve context-specific transcriptional outcomes. The DNA-binding-independent mechanism involves tethering of GR to the pro-inflammatory transcription factor activator protein-1 (AP-1) through protein-protein interactions.

Structural and Molecular Mechanisms of Cytokine-Mediated Endocrine Resistance in Human Breast Cancer Cells.

Human breast cancers that exhibit high proportions of immune cells and elevated levels of pro-inflammatory cytokines predict poor prognosis. Here, we demonstrate that treatment of human MCF-7 breast cancer cells with pro-inflammatory cytokines results in ERα-dependent activation of gene expression and proliferation, in the absence of ligand or presence of 4OH-tamoxifen (TOT). Cytokine activation of ERα and endocrine resistance is dependent on phosphorylation of ERα at S305 in the hinge domain.

Systems Structural Biology Analysis of Ligand Effects on ERα Predicts Cellular Response to Environmental Estrogens and Anti-hormone Therapies.

Environmental estrogens and anti-hormone therapies for breast cancer have diverse tissue- and signaling-pathway-selective outcomes, but how estrogen receptor alpha (ERα) mediates this phenotypic diversity is poorly understood. We implemented a statistical approach to allow unbiased, parallel analyses of multiple crystal structures, and identified subtle perturbations of ERα structure by different synthetic and environmental estrogens. Many of these perturbations were in the sub-Å range, within the noise of the individual structures, but contributed significantly to the activities of synthetic and environmental estrogens.