Identification and characterization of a novel estrogenic ligand actinopolymorphol A

Abstract

Xenoestrogenic compounds are abundant in the modern environment including phytoestrogens from plants, chemical by-products from industry, and secondary metabolites from microbes; all can profoundly affect human health. Consequently mechanism-based screens are urgently needed to improve the rate at which the xenoestrogens are discovered. Estrogen Receptor (ER) dimerization is required for target gene transcription. The three ER dimer pairs (ERα/α homodimers, ERβ/β homodimers, and ERα/β heterodimers) exhibit diverse physiological responses in response to ligand-dependent activation with ERα/α homodimers being pro-proliferative and ERβ/β homodimers being anti-proliferative. The biological role of the ERα/β heterodimer remains unclear. We previously developed a cell-based, bioluminescence resonance energy transfer (BRET) assay that can distinguish natural estrogenic compounds based on their abilities to activate the three diverse ER dimer pairs. Using BRET assays, we sought to identify novel xenoestrogens from soil bacteria that preferentially activate ERα/β heterodimer with hopes of shedding light on the biological function of this elusive dimer pair. Here we describe the application of BRET assays in high throughput screens of crude bacterial extracts not previously screened for ER modulatory function and originating from unique ecological niches. Here we report the discovery and biological evaluation of a new natural product, actinopolymorphol A (1), that preferentially induces ERα/β dimerization. Actinopolymorphol A represents the first representative of a new ER modulatory scaffold.

Δ9-Tetrahydrocannabinol Disrupts Estrogen-Signaling through Up-Regulation of Estrogen Receptor β (ERβ)

“…The possible binding of Δ 9 -THC to ER α /ER β was measured using PolarScreen Estrogen Receptor Competitor Assays from Life Technologies (Carlsbad, CA, USA) (Part # P2698 for ER α ; Part # P2700 for ER β ) according to the manufacturer’s instructions and the report by Powell et al 11 …”

Recent insights into the effect of natural and environmental estrogens on mammary development and carcinogenesis

“…This property does not necessarily hold for nonsteroidal estrogens of natural or synthetic origin. The small difference in aminoacids sequence between ERa and ERb is indeed sufficient to generate a potential anchorage selectivity to a large panel of natural and synthetic molecules (Lorand et al, 2010) allowing the design of compounds to modulate the action of only one receptor isoform (Harrington et al, 2003, Kraichely et al, 2000, as well as impede ERa/ERb heteroassociation (receptors usually act as dimers) when they are simultaneously expressed at the cellular level (Powell et al, 2010).…”

Generation of stable reporter breast cancer cell lines for the identification of ER subtype selective ligands

“…Competitive ligand binding assays provide insight into binding affinities and are useful for high throughput small molecule screening [37], but they are limited because ligands can act as agonists or antagonists and binding affinity does not often reflect transcriptional potency. BRET assays to measure receptor dimerization have been used to identify subtype selective ligands [38], but also cannot differentiate between agonists or antagonists [39]. Agonists can be characterized using proliferation assays in MCF7 cells, which are highly sensitive and provide a biologically relevant endpoint in the context of estrogen-sensitive cells [40].…”