title: Expression of bitter taste receptors of the T2R family in the gastrointestinal tract and enteroendocrine STC-1 cells.
abstract: Although a role for the gastric and intestinal mucosa in molecular sensing has been known for decades, the initial molecular recognition events that sense the chemical composition of the luminal contents has remained elusive. Here we identified putative taste receptor gene transcripts in the gastrointestinal tract. Our results, using reverse transcriptase-PCR, demonstrate the presence of transcripts corresponding to multiple members of the T2R family of bitter taste receptors in the antral and fundic gastric mucosa as well as in the lining of the duodenum. In addition, cDNA clones of T2R receptors were detected in a rat gastric endocrine cell cDNA library, suggesting that these receptors are expressed, at least partly, in enteroendocrine cells. Accordingly, expression of multiple T2R receptors also was found in STC-1 cells, an enteroendocrine cell line. The expression of alpha subunits of G proteins implicated in intracellular taste signal transduction, namely Galpha(gust), and Galpha(t)-(2), also was demonstrated in the gastrointestinal mucosa as well as in STC-1 cells, as revealed by reverse transcriptase-PCR and DNA sequencing, immunohistochemistry, and Western blotting. Furthermore, addition of compounds widely used in bitter taste signaling (e.g., denatonium, phenylthiocarbamide, 6-n-propil-2-thiouracil, and cycloheximide) to STC-1 cells promoted a rapid increase in intracellular Ca(2+) concentration. These results demonstrate the expression of bitter taste receptors of the T2R family in the mouse and rat gastrointestinal tract.
authors.affiliation: Department of Medicine, School of Medicine, Center for Ulcer Research and Education/Digestive Diseases Research Center, Veterans Administration Greater Los Angeles Healthcare System, University of California, Los Angeles, CA 90095, USA.
authors.forename: S Vincent
authors.initials: SV
authors.lastname: Wu
authors.forename: Nora
authors.initials: N
authors.lastname: Rozengurt
authors.forename: Moon
authors.initials: M
authors.lastname: Yang
authors.forename: Steven H
authors.initials: SH
authors.lastname: Young
authors.forename: James
authors.initials: J
authors.lastname: Sinnett-Smith
authors.forename: Enrique
authors.initials: E
authors.lastname: Rozengurt
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002628:Chemoreceptor Cells / Q000737:chemistry* / Q000502:physiology; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D004064:Digestive System / Q000378:metabolism*; D004703:Endocrine System / Q000378:metabolism*; D005753:Gastric Mucosa / Q000378:metabolism; D015723:Gene Library; D007150:Immunohistochemistry; D051379:Mice; D008969:Molecular Sequence Data; D010465:Perception; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011956:Receptors, Cell Surface / Q000096:biosynthesis*; D043562:Receptors, G-Protein-Coupled; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D015398:Signal Transduction; D013649:Taste / Q000502:physiology*; D013650:Taste Buds / Q000737:chemistry* / Q000502:physiology; D013997:Time Factors; D014018:Tissue Distribution; D000098706:Taste Receptors, Type 2
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D000098706:Taste Receptors, Type 2; D002118:Calcium