Fluorescence Polarization Assays: In another embodiment, Fluorescence Polarization ("FP") based assays may be used to detect and monitor ligand binding. Fluorescence polarization is a versatile laboratory technique for measuring equilibrium binding, nucleic acid hybridization, and enzymatic activity. Fluorescence polarization assays are homogeneous in that they do not require a separation step such as centrifugation, filtration, chromatography, precipitation, or electrophoresis. These assays are done in real time, directly in solution and do not require an immobilized phase. Polarization values can be measured repeatedly and after the addition of reagents since measuring the polarization is rapid and does not destroy the sample. Generally, this technique can be used to measure polarization values of fluorophores from low picomolar to micromolar levels.
HTS assay: To determine the effectiveness of an individual antagonist, taste tests were performed with a T2R8 specific agonist, the compound of interest and a reference bitter blocker. We have previously described a good hT2R8 antagonist that was proven to have taste effect. It was shown to reduce bitterness of coffee by itself and in combination with a Broad spectrum bitter blocker.
Antagonist activity at recombinant human TAS2R8 stably expressed in cells co-expressing Galpha16gust44 assessed as inhibition of andrographolide-induced intracellular calcium level at 10 uM measured for 100 secs by fluo-4 dye based FLIPR assay relative to control
Antagonist activity at recombinant human TAS2R8 stably expressed in cells co-expressing Galpha16gust44 assessed as inhibition of andrographolide-induced intracellular calcium level measured for 100 secs by fluo-4 dye based FLIPR assay
Antagonist activity at recombinant human TAS2R8 assessed as inhibition of andrographolide-induced intracellular calcium level at 1 uM preincubated for 60 secs followed by andrographolide addition using Fura-2AM dye by cell-based fluorescent microscopic analysis
Reversible antagonist activity at recombinant human TAS2R8 assessed as recovery of suppression of andrographolide-induced intracellular calcium level at 1 uM preincubated for 60 secs followed by andrographolide addition measured after 5 mins washout period using Fura-2AM dye by cell-based fluorescent microscopic analysis
Competitive antagonist activity at recombinant human TAS2R8 assessed as inhibition of andrographolide-induced intracellular calcium level at 3 to 3000 nM preincubated for 60 secs followed by varying levels of andrographolide addition using Fura-2AM dye by cell-based fluorescent microscopic analysis
Antagonist activity at recombinant human TAS2R8 transiently expressed in HEK293T co-expressing Galpha16gust44 assessed as inhibition of andrographolide-induced intracellular calcium level by measuring remaining activity at 25 uM by fluo-4AM dye based FLIPR assay relative to control
Agonist activity at recombinant human N-terminal rat ST3 receptor-fused TAS2R8 expressed in HEK293T cells co-expressing Galpha16gust44 assessed as increase in intracellular calcium level at 100 uM by FLIPR assay
Antagonist activity at recombinant human N-terminal rat ST3 receptor-fused TAS2R8 expressed in HEK293T cells co-expressing Galpha16gust44 assessed as inhibition of chloramphenicol-induced increase in intracellular calcium level at 100 uM by FLIPR assay
Agonist activity at human TAS2R8 expressed in HEK293T cells co-expressing Galpha15 assessed as increase in intracellular calcium level by Calcium-3 dye based fluorescence assay
Agonist activity at human TAS2R8 expressed in HEK293T cells co-expressing Galpha15 assessed as increase in intracellular calcium level at 20 mM by Calcium-3 dye based fluorescence assay relative to control
Agonist activity at recombinant human N-terminal rat ST3 receptor-fused TAS2R8 expressed in HEK293T cells co-expressing Galpha16gust44 assessed as effect on intracellular calcium level at 100 uM by FLIPR assay
Activity at recombinant human N-terminal rat ST3 receptor-fused TAS2R8 expressed in HEK293T cells co-expressing Galpha16gust44 assessed as effect on chloramphenicol-induced intracellular calcium level at 100 uM by FLIPR assay