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Updated: Sep 11, 2025
Real Time Monitoring of Intracellular Bile Acid Dynamics Using a Genetically Encoded FRET-based Bile Acid Sensor
Published on: January 4, 2016
Structural Basis of Novel Bile Acid-Based Modulators of FXR
D Kydd-Sinclair1, G L Packer2, A C Weymouth-Wilson3
1School of Biological Sciences, Health and Life Sciences Building, Whiteknights Campus, University of Reading, Reading, Berkshire RG6 6EX, UK.
Abstract:
Following its deorphanisation in the early 2000s, the farnesoid X receptor (FXR) attracted significant attention for regulating genes involved in bile acid, lipid and glucose metabolism and inflammation, pathways central to many liver diseases. As such, pharmaceutical efforts targeted FXR for their treatment. However, while FXR agonists, such as obeticholic acid, have been studied in clinical trials, many were associated with adverse effects arising from the promiscuity of systemic FXR activation, thus efforts to limit or selectively modulate the downstream effects of FXR are crucially important. In work here, two novel bile acid derivatives, previously identified via molecular docking and cell-based screening, were validated by X-ray crystallography and tested in LanthaScreen coactivator recruitment assays. Their effects on downstream FXR signalling were assessed in vitro in hepatocellular carcinoma cells, and in vivo in C57BL/6 mice, by RNA sequencing and RT-qPCR. The novel compounds exhibited potent and selective FXR agonist activity. Co-crystal structures of FXR LBD with both compounds, demonstrated distinctive binding modes for each, including occupancy of a receptor sub-pocket associated with allosteric activation, not observed with classic bile acids. Both compounds were up to four-fold more potent than obeticholic acid and demonstrated ligand-dependent differences in coactivator recruitment assays. In vitro, both compounds induced greater changes in the expression of FXR target genes, at lower doses than obeticholic acid. In vivo, compound-dependent differential gene expression was observed. These findings suggest that the novel compounds may enable gene-specific FXR regulation through differential coactivator usage and hold potential to overcome the shortcomings of current bile acid drugs, thus representing promising candidates for further research.
Insights
Two novel bile acid derivatives show potent and selective farnesoid X receptor (FXR) activation, offering potential for gene-specific regulation in liver diseases and overcoming limitations of current drugs.
Area of Science:
- Hepatology and Pharmacology
- Molecular Biology and Biochemistry
- Drug Discovery and Development
Background:
- Farnesoid X receptor (FXR) regulates key metabolic and inflammatory pathways implicated in liver diseases.
- Current FXR agonists like obeticholic acid face challenges due to systemic activation and adverse effects.
- Selective modulation of FXR signaling is crucial for developing safer and more effective therapeutics.
Purpose of the Study:
- To validate and characterize two novel bile acid derivatives as selective FXR agonists.
- To investigate their binding modes, coactivator recruitment, and downstream signaling effects in vitro and in vivo.
- To assess their potential to overcome the limitations of existing FXR-targeting drugs.
Main Methods:
- X-ray crystallography to determine co-crystal structures of FXR ligand-binding domain (LBD) with novel compounds.
- LanthaScreen coactivator recruitment assays to assess ligand-dependent activation.
- In vitro studies using hepatocellular carcinoma cells to analyze gene expression changes (RNA sequencing, RT-qPCR).
- In vivo studies in C57BL/6 mice to evaluate compound effects on FXR signaling pathways.
Main Results:
- Novel compounds demonstrated potent and selective FXR agonist activity, exceeding obeticholic acid in potency.
- Distinct binding modes were observed, including allosteric activation via a receptor sub-pocket.
- Compounds induced greater FXR target gene expression changes at lower doses compared to obeticholic acid.
- Differential gene expression patterns were observed in vivo, suggesting compound-specific regulatory effects.
Conclusions:
- The novel bile acid derivatives exhibit unique binding and activation properties, enabling gene-specific FXR regulation.
- These compounds hold promise for developing improved therapeutics for liver diseases by overcoming the adverse effects of systemic FXR activation.
- Further research is warranted to explore their full therapeutic potential.
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