Enzyme Fragment Complementation (EFC) is a patented detection technology based on two recombinant β-galactosidase fragments – a large protein fragment (enzyme acceptor) and a small peptide fragment (enzyme donor). Separately, the fragments are inactive, but when combined, they form an active enzyme that hydrolyzes substrate to produce a chemiluminescent signal. Take advantage of this platform using assay ready eXpress or bioassay kits or naturally coupled cAMP Hunter™ stable cell lines with HitHunter® cAMP assays for small molecules or biologics.
ChemiScreen™ stable cell lines and Ready-to-Assay™ frozen cells are based on our proprietary Chem-1 and related host cell backgrounds, which contain endogenous expression of Gα15, a promiscuous G protein, to help funnel signaling to a common calcium readout, regardless of G protein coupling status. Additional second messenger signaling, e.g. cAMP and ERK phosphorylation, has been found for many targets, which can be used to perform orthogonal assay confirmation.
ChemiBrite™ stable cell lines and Ready-to-Assay™ frozen cells are engineered to flash with brilliance upon GPCR activation and developed to provide the greatest readout flexibility, including luminescent and fluorescent calcium flux as well as cAMP. These cells express a proprietary mutant version of clytin, a calcium activated photoprotein.
HitHunter cAMP Assay Principle
Easy-to-use, high throughput immunoassays with a chemiluminescent readout.
HitHunter cAMP assays are competitive immunoassays that utilize the EFC technology where a fragment ß-galactosidase (ß-gal) enzyme donor (ED) is conjugated with cAMP. This ED-cAMP conjugate and cellular cAMP compete for binding to an anti-cAMP antibody (Ab). With low levels of cellular cAMP, most of the ED-cAMP binds to the cAMP Ab, making the ED-cAMP unable to complement with the enzyme acceptor (EA). With high levels of cellular cAMP, the anti-cAMP antibody becomes saturated allowing the ED-cAMP complex to complement with the ß-gal acceptor (EA) and form an active enzyme. The active enzyme then subsequently hydrolyzes a substrate to produce a chemiluminescent signal that is directly proportional to the amount of cAMP in the cells.
HitHunter cAMP Assay Protocol
The HitHunter cAMP Assay kits provide a robust, highly sensitive and easy-to-use, cell-based functional assay to study GPCR activity through cAMP production. The kits contain all the reagents needed for the detection of cAMP from whole cells expressing Gαi
- and Gαs
-coupled receptors induced with a biologic or small molecule ligand. The flexible assay system has been designed to work in agonist or antagonist mode for 96- and 384-well plate formats. After plating and stimulation of cells, the user simply adds the HitHunter cAMP Assay reagents to the cell following the homogeneous, easy-to-use procotol provided.
Assay Ready eXpress and Bioassay Kits
- cAMP Hunter eXpress and bioassay kits includes a specific cell line, optimized reagents, and plates for quick EFC-based chemiluminescent detection. Bioassays include additional optimization for high lot-to-lot reproducibility.
Ready-to-Assay™ Frozen Cells
- HitHunter® cAMP Assays are chemiluminescent EFC-based kits for use with both small molecules and biologics
LeadHunter® GPCR Profiling and Eurofins Discovery Services for GPCRs
Custom Assay Development
cAMP Hunter™ Cell Lines and Assay Ready Kits
- Over 125 stable cell lines with unlimited culture and overexpressed naturally coupled, wild-type GPCRs
- Ultra-convenient, complete eXpress kits for quick assessment without the need for cell culture
- Ready-to-use bioassay kits provide cryopreserved cells and optimized reagents with high lot-to-lot reproducibility to support the lifetime of the biologic drug
HitHunter® cAMP Assays
- Eliminate optimization steps with an assay that has been designed and qualified for use with over 125 cAMP Hunter™ cell lines
- Achieve precise characterization of ligand pharmacology with large assay windows, sensitive detection, and wide dynamic range for ligand bias studies and many more applications
- Reproducible assay performance without fluorescence or serum interference and no need for specialized equipment
ChemiScreen™ Cell Lines
- High functional expression of receptors with the ability to assay both agonist and antagonist in a single well
- Stable cell lines for continuous culture and increased reliability and reproducibility assay results
ChemiBrite™ Cell Lines
- Exceptional high signal-to-background ratio with no assay interference with autofluorescent compounds
- Tool box capabilities allows generation of your own stable cell lines
ChemiScreen™ and ChemiBrite™ Frozen Cells
- Ready-to-Assay™ GPCR frozen cells come with plating media and enough cells to run either 96- or 384-well plate assays in full or half plate formats
- Qualified for cAMP and calcium second messenger assays with results within 24 hours to accelerate your data generation
Optimized for a Variety of Applications
Accurately Rank Molecular Potency of Ligands
- Perform functional screens using small molecules or biologics (antibodies, peptides)
- Detect neutralizing antibodies (immunogenicity studies using serum and plasma)
- Characterize phosphodiesterase inhibitors
- Quantify low levels of cAMP (endogenous receptor studies)
HitHunter cAMP assays provide powerful tools for drug discovery screening and revealing of the correct ligand rank order and pharmacological profile.
Profiling experiment using a cAMP Hunter™ CHO-K1 adrenergic receptor β2 cell line to test five agonists. The data highlights the receptor’s sensitivity to the various agonists, ultimately revealing the correct rank order of the agonists and showing the agonist salbutamol (EC50
of 160 nM) is less potent than the control ligand isoproterenol (EC50
of 1.7 nM).
Easily Determine Pharmacological Profiles of Complex Assay Formats
Large assay windows and sensitive detection makes HitHunter cAMP assays ideal for studying complex assay formats like Gαi
-coupled receptor antagonists.
Comparative study of two antagonists of the Gαi
-coupled metabotropic glutamate receptor 2 (GRM2) using a cAMP Hunter CHO-K1 GRM2 cell line. Results indicate that the Antagonist 2 (IC50
of 8 nM) is a more potent inhibitor compared to Antagonist 1 (IC50
of 24 nM).
Obtain Excellent Reproducibility and High Sensitivity for Testing Biologics
Perform quality control assays, including potency assays for lot release and stability testing in biologics.
(Top) Evaluation of lot-to-lot consistency using a GLP agonist, GLP1(7-36), and the cAMP Hunter Gαs
-coupled GLP1R bioassay that incorporates the HitHunter cAMP Assay for Biologics. Results indicate the assay's excellent reproducibility for all three lots tested with S:B ratios over 10 fold and EC50
’s ranging from only 76 pM to 86 pM. (Bottom) Evaluation of lot-to-lot consistency using a biologic ligand, SDF1α, and the cAMP Hunter Gαi
-coupled CXCR4 receptor (chemokine C-X-C motif receptor 4) cell line. Results show high sensitivity detection and excellent reproducibility with overlapping S:B ratios of ~6 and EC50
’s ranging from only 689 pM to 796 pM.
Identify Allosteric Modulators, Partial Agonists, Inverse Agonists, and Silent Agonists
HitHunter cAMP assays’ superior assay performance, with its large assay window and wide dynamic range, allows for easy identification of a diverse set of pharmacological ligands such as positive allosteric modulators (PAMs), negative allosteric modulators (NAMs), partial agonists, and more.
Easily identify partial agonists. This experiment uses a cAMP Hunter Gαs
-coupled glucagon receptor (GCGR) CHO-K1 cell line to analyze two agonists. Results reveal [des-His1, Glu9]- glucagon exhibits partial agonism (S:B of 9.2; EC50
of 340 nM) compared to the full native agonist, glucagon (S:B of 14.8; EC50
of 11 nM).