Wu S Vincent, Rozengurt Nora, Yang Moon, Young Steven H, Sinnett-Smith James, Rozengurt Enrique
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.
Proc Natl Acad Sci U S A. 2002 Feb 19;99(4):2392-7. doi: 10.1073/pnas.042617699.
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.
尽管胃和肠黏膜在分子感知中的作用已为人所知数十年，但感知管腔内容物化学成分的初始分子识别事件仍不清楚。在这里，我们在胃肠道中鉴定出了假定的味觉受体基因转录本。我们使用逆转录酶 - PCR的结果表明，在胃窦和胃底黏膜以及十二指肠内衬中存在与苦味受体T2R家族多个成员相对应的转录本。此外，在大鼠胃内分泌细胞cDNA文库中检测到了T2R受体的cDNA克隆，这表明这些受体至少部分地在肠内分泌细胞中表达。因此，在肠内分泌细胞系STC - 1细胞中也发现了多种T2R受体的表达。逆转录酶 - PCR、DNA测序、免疫组织化学和蛋白质印迹显示，参与细胞内味觉信号转导的G蛋白α亚基，即Gα(gust)和Gα(t)-(2)，在胃肠道黏膜以及STC - 1细胞中也有表达。此外，向STC - 1细胞中添加广泛用于苦味信号传导的化合物（如苯甲地那铵、苯硫脲、6 - n - 丙基 - 2 - 硫尿嘧啶和环己酰亚胺）会促使细胞内Ca(2+)浓度迅速升高。这些结果证明了T2R家族苦味受体在小鼠和大鼠胃肠道中的表达。
