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Updated: May 29, 2026
High-throughput Screening for Chemical Modulators of Post-transcriptionally Regulated Genes
Published on: March 3, 2015
Use of comprehensive screening methods to detect selective human CAR activators
Jenni Küblbeck1, Tuomo Laitinen, Johanna Jyrkkärinne
1University of Eastern Finland, School of Pharmacy and Biocenter Kuopio, Yliopistonranta 1C, FI-70211 Kuopio, Finland. Jenni.Kublbeck@uef.fi
Abstract:
The so-called human xenosensors, constitutive androstane receptor (hCAR), pregnane X receptor (hPXR) and aryl hydrocarbon receptor (hAhR), participate in drug metabolism and transport as well as in several endogenous processes by regulating the expression of their target genes. While the ligand specificities for hPXR and hAhR are relatively well described, this property of hCAR still remains fairly unclear. Identifying hCAR agonists for drug development and for studying hCAR biology are hindered mainly by the unique properties of the receptor, such as the high constitutive activity and complex signaling network but also by the lack of robust and reliable assays and cellular models. Here, validated reporter assays for these three xenosensors are presented and thereafter used to screen a large set of chemicals in order to find novel selective hCAR ligands. We introduce a novel selective hCAR agonist, FL81, which can be used as a stable positive control in hCAR activity assays. Our established receptor-selective ligand identification methods consisting of supporting biological assays and molecular modeling techniques are then used to study FL81 as well as other discovered ligands, such as diethylstilbestrol, o,p'-DDT, methoxychlor and permethrin, for their ability to specifically activate hCAR and to regulate the CYP enzyme expression and function.
Insights
Researchers identified a new selective agonist, FL81, for the human constitutive androstane receptor (hCAR). This discovery aids drug development and understanding of hCAR
Area of Science:
- Pharmacology
- Molecular Biology
- Biochemistry
Background:
- Human xenosensors, including constitutive androstane receptor (hCAR), pregnane X receptor (hPXR), and aryl hydrocarbon receptor (hAhR), regulate drug metabolism and endogenous processes.
- Ligand specificities for hPXR and hAhR are understood, but hCAR ligand binding remains unclear.
- Challenges in hCAR research include its high constitutive activity, complex signaling, and lack of reliable assays and cellular models.
Purpose of the Study:
- To develop and validate reporter assays for hCAR, hPXR, and hAhR.
- To screen a large chemical set for novel selective hCAR ligands.
- To characterize identified ligands, including a novel agonist FL81, for hCAR activation and regulation of CYP enzymes.
Main Methods:
- Development and validation of reporter gene assays for three human xenosensors.
- High-throughput screening of a diverse chemical library to identify selective ligands.
- Utilized biological assays and molecular modeling for ligand characterization and mechanism studies.
Main Results:
- Validated reporter assays for hCAR, hPXR, and hAhR were established.
- A novel selective hCAR agonist, FL81, was identified and validated as a stable positive control.
- Several other ligands, including diethylstilbestrol, o,p'-DDT, methoxychlor, and permethrin, were characterized for their hCAR-specific activation and impact on CYP enzyme expression.
Conclusions:
- The study presents robust assays for xenosensor activity screening.
- FL81 is introduced as a valuable tool for hCAR research and drug development.
- Established methods enable the discovery and characterization of selective xenosensor ligands, advancing the understanding of their biological roles and therapeutic potential.
