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Human FXR Reporter Assay Kit

SIZES SKU
1 x 96-well format assays IB00601
3 x 32 assays in 96-well format IB00601-32
1 x 384-well format assays IB00602

Product Description and Product Data

This is an all-inclusive cell-based luciferase reporter assay kit targeting the Human Farnesoid X Receptor (FXR). INDIGO’s FXR reporter assay utilizes proprietary mammalian cells that have been engineered to provide constitutive expression of the Human FXR. In addition to FXR Reporter Cells, this kit provides two optimized media for use during cell culture and in diluting the user’s test samples, a reference agonist, Luciferase Detection Reagent, and a cell culture-ready assay plate. The principal application of this assay is in the screening of test samples to quantify any functional activity, either agonist or antagonist, that they may exert against human FXR. This kit provides researchers with clear, reproducible results, exceptional cell viability post-thaw, and consistent results lot to lot. Kits must be stored at -80C. Do not store in liquid nitrogen. Note: reporter cells cannot be refrozen or maintained in extended culture.

Features

  • Clear, Reproducible Results

  • All-Inclusive Assay Systems
  • Exceptional Cell Viability Post-Thaw
  • Consistent Results Lot to Lot

Product Specifications

Target TypeNuclear Hormone Receptor
SpeciesHuman
Receptor FormHybrid
Assay ModeAgonist, Antagonist
Kit Components
  • FXR Reporter Cells
  • Cell Recovery Medium (CRM)
  • Compound Screening Medium (CSM)
  • GW4064, (ref. agonist; in DMSO)
  • Detection Substrate
  • Detection Buffer
  • White, sterile, cell-culture ready assay plate
Shelf Life6 months
Orthologs AvailableYes
Shipping RequirementsDry Ice
Storage temperature-80C

Data

Agonist and Antagonist dose-responses of the FXR Assay. Dose-response assays were performed as described in the assay Technical Manual. FXR reference agonists GW4064 (provided), Fexaramine and CDCA (Cayman Chemical), Obeticholic acid (OCA) and WAY-362450 (Selleckchem) were analyzed. For antagonist analyses the suspension of FXR reporter cells were pre-treated with a sub-maximal (~ EC80) concentration of the agonist GW4064; prepared treatment media supplemented with the antagonist references Z-Guggulsterone (Cayman Chemical) and DY 268 (Tocris) were dispensed into assay wells. Luminescence was quantified using a GloMax-Multi+ luminometer (Promega). Average relative light units (RLU) and corresponding standard deviation (SD) values were determined for each treatment concentration. Z’ values were calculated as described by Zhang, et al. (1999). Non-linear regression and EC50 analyses were performed using GraphPad Prism software. RESULTS: The large response range and high Z' values confirm the robust performance of both agonist-mode and antagonist-mode setups for this FXR assay, and demonstrate its suitability for use in HTS applications.

Target Background

The farnesoid X receptor (FXR), also known as NR1H4 is a nuclear hormone receptor with activity similar to that seen in other steroid receptors such as estrogen or progesterone receptor, but more similar in form to PPAR, LXR and RXR. Encoded by the NR1H4 gene, FXR is expressed at high levels in the liver and intestine. Chenodeoxycholic acid and other bile acids are natural ligands for FXR.

Like other steroid receptors, when activated, FXR translocates to the cell nucleus, forms a heterodimer with RXR and binds to hormone response elements on DNA (FXEs) to elicit expression or transrepression of gene products. One of the primary functions of FXR activation is the suppression of cholesterol 7 alpha-hydroxylase (CYP7A1), the rate-limiting enzyme in bile acid synthesis from cholesterol. FXR does not directly bind to the CYP7A1 promoter. Rather, FXR induces expression of small heterodimer partner (SHP) which then functions to inhibit transcription of the CYP7A1 gene. In this way a negative feedback pathway is established in which synthesis of bile acids is inhibited when cellular levels is already high.

INDIGO’s FXR Reporter Assay Systems utilize proprietary mammalian cells engineered to express human NR1H4 protein, commonly referred to as FXR.

The principle application of this FXR assay is in the screening of test samples to quantify functional activities, either as agonist or antagonist, that they may exert against the human farnesoid x receptor.

Citations

Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) is an organophosphate flame retardant. The primary TDCPP metabolite, bis(1,3-dichloro-2-propyl) phosphate (BDCPP), is detectable in the urine of over 90 % of Americans. Epidemiological studies show sex-specific associations between urinary BDCPP levels and metabolic syndrome, which is an established risk factor for type 2 diabetes, heart disease, and stroke. We used a mouse model to determine whether TDCPP exposure disrupts glucose homeostasis. Six-week old male and female C57BL/6J mice were given ad libitum access to diets containing vehicle (0.1 % DMSO) and TDCPP resulting in the following treatment groups: 0 mg/kg/day, 0.02 mg/kg/day, 1 mg/kg/day, or 100 mg/kg/day. After being on the experimental diet for five weeks without interruption, body composition was analyzed, glucose and insulin tolerance tests were performed, and fasting glucose and insulin levels were quantified. TDCPP at 100 mg/kg/day caused male sex-specific adiposity, fasting hyperglycemia, and insulin resistance. TDCPP-induced modulation of nuclear receptor activation was investigated using an in vitro screen to identify potential mechanisms of metabolic disruption. TDCPP activated farnesoid X receptor (FXR) and pregnane X receptor (PXR), and inhibited the androgen receptor (AR). PXR target genes, but not FXR target genes, were upregulated in livers from mice exposed to 100 mg TDCPP/kg/day. Interestingly, PXR target genes were differentially expressed in livers from both males and females. It remains to be determined whether TDCPP-induced metabolic disruption occurs via modulation of nuclear receptor activity. Taken together, these studies build upon the association of TDCPP exposure and metabolic syndrome in humans by identifying sex-specific effects of TDCPP on glucose homeostasis in mice.
2022-12-07
Nonalcoholic steatohepatitis (NASH) is associated with obesity, metabolic syndrome, and dysbiosis of the gut microbiome. Cholecystokinin (CCK) is released by saturated fats and plays an important role in bile acid secretion. CCK receptors are expressed on cholangiocytes, and CCK-B receptor expression increases in the livers of mice with NASH. The farnesoid X receptor (FXR) is involved in bile acid transport and is a target for novel therapeutics for NASH. The aim of this study was to examine the role of proglumide, a CCK receptor inhibitor, in a murine model of NASH and its interaction at FXR. Mice were fed a choline deficient ethionine (CDE) diet to induce NASH. Some CDE-fed mice received proglumide-treated drinking water. Blood was collected and liver tissues were examined histologically. Proglumide’s interaction at FXR was evaluated by computer modeling, a luciferase reporter assay, and tissue FXR expression. Stool microbiome was analyzed by RNA-Sequencing. CDE-fed mice developed NASH and the effect was prevented by proglumide. Computer modeling demonstrated specific binding of proglumide to FXR. Proglumide binding in the reporter assay was consistent with a partial agonist at the FXR with a mean binding affinity of 215 nM. FXR expression was significantly decreased in livers of CDE-fed mice compared to control livers, and proglumide restored FXR expression to normal levels. Proglumide therapy altered the microbiome signature by increasing beneficial and decreasing harmful bacteria. These data highlight the potential novel mechanisms by which proglumide therapy may improve NASH through interaction with the FXR and consequent alteration of the gut microbiome.
2022-02-08

Also available as a service

Farnesoid X Receptor (FXR, NR1H4)