Selective Activation of Estrogen Receptor-β Transcriptional Pathways by an Herbal Extract

Novel estrogenic therapies are needed that ameliorate menopausal symptoms and have the bone-sparing effects of endogenous estrogens but do not promote breast or uterine cancer. Recent evidence suggests that selective activation of the estrogen receptor (ER)-beta subtype inhibits breast cancer cell proliferation. To establish whether ERbeta-selective ligands represent a viable approach to improve hormone therapy, we investigated whether the estrogenic activities present in an herbal extract, MF101, used to treat hot flashes, are ERbeta selective. MF101 promoted ERbeta, but not ERalpha, activation of an estrogen response element upstream of the luciferase reporter gene. MF101 also selectively regulates transcription of endogenous genes through ERbeta. The ERbeta selectivity was not due to differential binding because MF101 binds equally to ERalpha and ERbeta. Fluorescence resonance energy transfer and protease digestion studies showed that MF101 produces a different conformation in ERalpha from ERbeta when compared with the conformations produced by estradiol. The specific conformational change induced by MF101 allows ERbeta to bind to an estrogen response element and recruit coregulatory proteins that are required for gene activation. MF101 did not activate the ERalpha-regulated proliferative genes, c-myc and cyclin D1, or stimulate MCF-7 breast cancer cell proliferation or tumor formation in a mouse xenograft model. Our results demonstrate that herbal ERbeta-selective estrogens may be a safer alternative for hormone therapy than estrogens that nonselectively activate both ER subtypes

Drug and Cell Type-Specific Regulation of Genes with Different Classes of Estrogen Receptor β-Selective Agonists

Estrogens produce biological effects by interacting with two estrogen receptors, ERα and ERβ. Drugs that selectively target ERα or ERβ might be safer for conditions that have been traditionally treated with non-selective estrogens. Several synthetic and natural ERβ-selective compounds have been identified. One class of ERβ-selective agonists is represented by ERB-041 (WAY-202041) which binds to ERβ much greater than ERα. A second class of ERβ-selective agonists derived from plants include MF101, nyasol and liquiritigenin that bind similarly to both ERs, but only activate transcription with ERβ. Diarylpropionitrile represents a third class of ERβ-selective compounds because its selectivity is due to a combination of greater binding to ERβ and transcriptional activity. However, it is unclear if these three classes of ERβ-selective compounds produce similar biological activities. The goals of these studies were to determine the relative ERβ selectivity and pattern of gene expression of these three classes of ERβ-selective compounds compared to estradiol (E2), which is a non-selective ER agonist. U2OS cells stably transfected with ERα or ERβ were treated with E2 or the ERβ-selective compounds for 6 h. Microarray data demonstrated that ERB-041, MF101 and liquiritigenin were the most ERβ-selective agonists compared to estradiol, followed by nyasol and then diarylpropionitrile. FRET analysis showed that all compounds induced a similar conformation of ERβ, which is consistent with the finding that most genes regulated by the ERβ-selective compounds were similar to each other and E2. However, there were some classes of genes differentially regulated by the ERβ agonists and E2. Two ERβ-selective compounds, MF101 and liquiritigenin had cell type-specific effects as they regulated different genes in HeLa, Caco-2 and Ishikawa cell lines expressing ERβ. Our gene profiling studies demonstrate that while most of the genes were commonly regulated by ERβ-selective agonists and E2, there were some genes regulated that were distinct from each other and E2, suggesting that different ERβ-selective agonists might produce distinct biological and clinical effects

Visualization of Positive Transcription Elongation Factor b (P-TEFb) Activation in Living Cells*

Regulation of transcription elongation by positive transcription elongation factor b (P-TEFb) plays a central role in determining the state of cell activation, proliferation, and differentiation. In cells, P-TEFb exists in active and inactive forms. Its release from the inactive 7SK small nuclear ribonucleoprotein complex is a critical step for P-TEFb to activate transcription elongation. However, no good method exists to analyze this P-TEFb equilibrium in living cells. Only inaccurate and labor-intensive cell-free biochemical assays are currently available. In this study, we present the first experimental system to monitor P-TEFb activation in living cells. We created a bimolecular fluorescence complementation assay to detect interactions between P-TEFb and its substrate, the C-terminal domain of RNA polymerase II. When cells were treated with suberoylanilide hydroxamic acid, which releases P-TEFb from the 7SK small nuclear ribonucleoprotein, they turned green. Other known P-TEFb-releasing agents, including histone deacetylase inhibitors, bromodomain and extraterminal bromodomain inhibitors, and protein kinase C agonists, also scored positive in this assay. Finally, we identified 5'-azacytidine as a new P-TEFb-releasing agent. This release of P-TEFb correlated directly with activation of human HIV and HEXIM1 transcription. Thus, our visualization of P-TEFb activation by fluorescent complementation assay could be used to find new P-TEFb-releasing agents, compare different classes of agents, and assess their efficacy singly and/or in combination

A versatile, bar-coded nuclear marker/reporter for live cell fluorescent and multiplexed high content imaging.

The screening of large numbers of compounds or siRNAs is a mainstay of both academic and pharmaceutical research. Most screens test those interventions against a single biochemical or cellular output whereas recording multiple complementary outputs may be more biologically relevant. High throughput, multi-channel fluorescence microscopy permits multiple outputs to be quantified in specific cellular subcompartments. However, the number of distinct fluorescent outputs available remains limited. Here, we describe a cellular bar-code technology in which multiple cell-based assays are combined in one well after which each assay is distinguished by fluorescence microscopy. The technology uses the unique fluorescent properties of assay-specific markers comprised of distinct combinations of different 'red' fluorescent proteins sandwiched around a nuclear localization signal. The bar-code markers are excited by a common wavelength of light but distinguished ratiometrically by their differing relative fluorescence in two emission channels. Targeting the bar-code to cell nuclei enables individual cells expressing distinguishable markers to be readily separated by standard image analysis programs. We validated the method by showing that the unique responses of different cell-based assays to specific drugs are retained when three assays are co-plated and separated by the bar-code. Based upon those studies, we discuss a roadmap in which even more assays may be combined in a well. The ability to analyze multiple assays simultaneously will enable screens that better identify, characterize and distinguish hits according to multiple biologically or clinically relevant criteria. These capabilities also enable the re-creation of complex mixtures of cell types that is emerging as a central area of interest in many fields

A palmitoylation cycle dynamically regulates partitioning of the GABA-synthesizing enzyme GAD65 between ER-Golgi and post-Golgi membranes

GAD65, the smaller isoform of the enzyme glutamic acid decarboxylase, synthesizes GABA for fine-tuning of inhibitory neurotransmission. GAD65 is synthesized as a soluble hydrophilic protein but undergoes a hydrophobic post-translational modification and becomes anchored to the cytosolic face of Golgi membranes. A second hydrophobic modification, palmitoylation of Cys30 and Cys45 in GAD65, is not required for the initial membrane anchoring but is crucial for post-Golgi trafficking of the protein to presynaptic clusters. The mechanism by which palmitoylation directs targeting of GAD65 through and out of the Golgi complex is unknown. Here, we show that prior to palmitoylation, GAD65 anchors to both ER and Golgi membranes. Palmitoylation, however, clears GAD65 from the ER-Golgi, targets it to the trans-Golgi network and then to a post-Golgi vesicular pathway. FRAP analyses of trafficking of GAD65-GFP reveal a rapid and a slow pool of protein replenishing the Golgi complex. The rapid pool represents non-palmitoylated hydrophobic GAD65-GFP, which exchanges rapidly between the cytosol and ER/Golgi membranes. The slow pool represents palmitoylation-competent GAD65-GFP, which replenishes the Golgi complex via a non-vesicular pathway and at a rate consistent with a depalmitoylation step. We propose that a depalmitoylation-repalmitoylation cycle serves to cycle GAD65 between Golgi and post-Golgi membranes and dynamically control levels of enzyme directed to the synapse

Advantages and Limitations of Androgen Receptor-Based Methods for Detecting Anabolic Androgenic Steroid Abuse as Performance Enhancing Drugs.

Testosterone (T) and related androgens are performance enhancing drugs (PEDs) abused by some athletes to gain competitive advantage. To monitor unauthorized androgen abuse, doping control programs use mass spectrometry (MS) to detect androgens, synthetic anabolic-androgenic steroids (AASs) and their metabolites in an athlete's urine. AASs of unknown composition will not be detected by these procedures. Since AASs achieve their anabolic effects by activating the Androgen Receptor (AR), cell-based bioassays that measure the effect of a urine sample on AR activity are under investigation as complementary, pan-androgen detection methods. We evaluated an AR BioAssay as a monitor for androgen activity in urine pre-treated with glucuronidase, which releases T from the inactive T-glucuronide that predominates in urine. AR BioAssay activity levels were expressed as 'T-equivalent' concentrations by comparison to a T dose response curve. The T-equivalent concentrations of androgens in the urine of hypogonadal participants supplemented with T (in whom all androgenic activity should arise from T) were quantitatively identical to the T measurements conducted by MS at the UCLA Olympic Analytical Laboratory (0.96 ± 0.22). All 17 AASs studied were active in the AR BioAssay; other steroids were inactive. 12 metabolites of 10 commonly abused AASs, which are used for MS monitoring of AAS doping because of their prolonged presence in urine, had reduced or no AR BioAssay activity. Thus, the AR BioAssay can accurately and inexpensively monitor T, but its ability to monitor urinary AASs will be limited to a period immediately following doping in which the active AASs remain intact

Bar-Coded FP_NLSFP Nuclear Markers.

<p>Ratio of fluorescence emitted in em1 (635–675 nm) relative to that emitted in em2 (608–648 nm) for the FP-N_NLSFP-C bar-code vectors. Ratios determined in 10x images collected on transiently transfected CHO cells.</p

em1 (635–675 nm) fluorescence channel relative to em2 (608–648 nm) of the indicated red FPs.

a<p>Molar Extinction Coefficient (M⁻¹ cm⁻¹): the ability of the fluorophore to absorb light.</p>b<p>Quantum Yield: proportion of absorbed photons re-emitted as fluorescent photons.</p>c<p>Product of QY and Emol, relative to that of EGFP (100%).</p><p>Ratios determined in 4x images collected on transiently transfected CHO cells.</p