Identification of bitter ligands that specifically activate human T2R receptors and related assays for identifying human bitter taste modulators
The present invention relates to the discovery that specific human taste receptors in the T2R taste receptor family respond to particular bitter compounds. Also, the invention relates to the discovery of specific hT2R9 alleles and their disparate activity in functional assays with the same bitter ligands. The invention further relates to the use of these T2R receptors in assays for identifying ligands that modulate the activation of these taste receptors by specific bitter ligands and related compounds. These compounds may be used as additives and/or removed from foods, beverages, cosmetics and medicinals in order to modify (block) T2R-associated bitter taste. Also T2R ligands may be used as therapeutics to treat and modulate T2R associated gastrointestinal and metabolic functions as well as treat gastrointestinal and metabolic diseases such as eating disorders, food sensing, food absorption, obesity, diabetes, Crohn's disease, celiac disease, et al.
1. An assay for identifying a compound which modulates a human T2R8 bitter taste receptor which comprises a bitter taste receptor polypeptide possessing at least 90% sequence identity to the polypeptide of SEQ ID NO:12, wherein said bitter taste receptor polypeptide specifically responds to sucrose octaacetate, which assay comprises:
i) screening a compound for its effect on at least one bitter compound to induce the activation of a bitter taste receptor polypeptide possessing at least 90% sequence identity to the polypeptide of SEQ ID NO:12, wherein such bitter taste receptor polypeptide is activated by sucrose octaacetate,
ii) determining whether said compound modulates the activation of said bitter taste receptor by sucrose octaacetate; and
iii) identifying said compound as a potential bitter taste modulator if it modulates the activation of said human bitter taste receptor by sucrose octaacetate.
2. The assay of claim 1 , wherein step (ii) detects modulation of the activity of the bitter taste receptor polypeptide by detecting at least one of the following: membrane potential and conductance changes; ion flux changes; changes in intracellular second messengers; changes in intracellular ion levels; or neurotransmitter release.
3. The assay of claim 2 , wherein modulation of the activity of the bitter taste receptor polypeptide is determined by detecting changes in intracellular cation concentrations.
4. The assay of claim 2 , wherein modulation of the activity of the bitter taste receptor polypeptide is determined by detecting changes in intracellular second messengers selected from any of cAMP, cGMP, and inositol triphosphate (IP3).
5. The assay of claim 1 , wherein the bitter taste receptor polypeptide possesses at least 95% sequence identity to a polypeptide comprising the sequence of SEQ ID NO:12.
6. The assay of claim 1 , wherein the bitter taste receptor polypeptide possesses at least 96% sequence identity to the polypeptide of SEQ ID NO:12.
7. The assay of claim 1 , wherein the bitter taste receptor polypeptide possesses at least 97% sequence identity to the polypeptide of SEQ ID NO:12.
8. The assay of claim 1 , wherein the bitter taste receptor polypeptide possesses at least 98% sequence identity to the polypeptide of SEQ ID NO:12.
9. The assay of claim 1 , wherein the bitter taste receptor polypeptide possesses at least 99% sequence identity to a polypeptide to the polypeptide of SEQ ID NO:12.
10. The assay of claim 1 , wherein the bitter taste receptor polypeptide possesses 100% sequence identity to the polypeptide of SEQ ID NO:12.