Physiology and regulation of T2R bitter taste receptors in enteroendocrine cells

肠内分泌细胞T2R苦味受体的生理学和调节

• 批准号: 8528267
• 负责人: Timothy F Osborne
• 金额: $ 42.41万
• 依托单位: SANFORD BURNHAM PREBYS MEDICAL DISCOVERY INSTITUTE
• 依托单位国家: 美国
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-04-01 至 2017-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8528267
• 关键词: ABCB1 gene; Accidents; Address; Adopted; Agonist; Animals; Area; Biological Assay; Cell Line; Cell Surface Receptors; Cells; Cholecystokinin; Cholesterol; Coupled; Deglutition; Diet; Dietary Cholesterol; Discrimination; Eating; Enterocytes; Enteroendocrine Cell; Enzyme-Linked Immunosorbent Assay; Epithelium; Exons; Family; Food; Gastrins; Gastrointestinal tract structure; Genes; Genetic; Genetic Models; Hepatic; Hormones; Human; In Situ; Individual; Ingestion; Intestinal Secretions; Intestines; Islets of Langerhans; Knock-out; Lovastatin; Lung; Mammals; Measures; Mediating; Methods; Molecular; Monitor; Mus; Mutant Strains Mice; Mutation; Oral; Oral cavity; Organ Culture Techniques; Pancreas; Pathway interactions; Peptides; Physiological; Physiology; Plants; Poison; Polypeptide Hormones; Proteins; Publications; Receptor Cell; Receptor Gene; Receptor Signaling; Regulation; Relative (related person); Rodent; Role; SRE-2 binding protein; Savory; Signal Transduction; Small Intestines; Source; Stomach; Surface; TRPM5 gene; Taste Perception; Testing; Tongue; Toxin; Work; absorption; airway epithelium; base; cell motility; cholesterol absorption; design; detection of nutrient; ezetimibe; feeding; glucagon-like peptide; glucagon-like peptide 1; in vivo; monomer; mouse model; novel; oral tissue; peptide hormone; prevent; promoter; public health relevance; receptor; receptor coupling; response; small molecule; sweet receptor; sweet taste perception; transcription factor; uptake

DESCRIPTION (provided by applicant): Mammals recognize bitter constituents in food through individual small "bitter" molecule agonists stimulation of individual cell surface receptors. These taste 2 receptors (T2Rs) are encoded by a family of single-exon g- protein coupled receptor (GPCR) genes and are predominantly expressed in taste receptor cells (TRCs) on the surface of the tongue and surrounding oral tissue. There is a lone GPCR involved in the majority of sweet taste sensing which is a heterodimer of Taste 1 Receptor (T1R) monomers T1R2 and T1R3. The single sweet and the entire family of bitter T2 receptors are also expressed in areas outside of the oral cavity including the lung, pancreas, and small intestine. Their function in the tongue is obviously to allow taste discrimination between differen potential food sources, however, the physiologic role for taste receptors outside of the oral cavity is not intuitively obvious. In recent publications, we showed that activation of intestinal T2R signaling leads to an increase in secretion of polypeptide hormones cholecystokinin (CCK) and glucagon-like-peptide-1 (GLP-1) from enteroendocrine cells and two major actions of CCK are to limit food intake and slow gastric motility. These results suggest intestinal T2Rs may limit absorption of bitter and potentially toxic molecules that are ingested despite the taste aversion in the mouth. We also showed that intestinal expression and activity of the T2Rs is regulated by the sterol regulatory element binding protein -2 (SREBP-2) transcription factor, which is induced when cellular cholesterol levels are low and activates genes required for accumulating new cell cholesterol. Plant enriched diets are both low in cholesterol and have a higher proportion of bitter tasting and potentially toxic substances relative to diets rich in cholesterol-laden animal flesh. Thus, induction of T2R activity through SREBP-2 on low-cholesterol plant diets provides a mechanism to "sensitize" the gut to the presence of potentially toxic molecules to limit their absorption through CCK dependent suppression of both gut motility and food in take. It should be noted that CCK and the gut peptide hormone gastrin have identical carboxyl termini and the ELISA we used in our early studies detects both hormones with similar sensitivity. Thus, gastrin may be the relevant hormone that is induced by T2R signaling in the gut and our current project is designed to address this key issue. We also showed CCK/gastrin increases expression and activity of the ABCB1 efflux transporter, which is known to prevent cellular uptake of a wide range of toxic organic small molecules. This provides a more active mechanism to limit absorption of toxic molecules consumed during a meal or by accident. Taken together, these studies provide a molecular mechanism connecting nutrient sensing with protection from toxin ingestion. The current proposal combines physiologic studies in select mouse models that have mutations in genes encoding critical proteins of the nutrient sensing and toxin efflux pathways to rigorously test the mechanism. We also propose to adopt a novel in situ assay with isolated small intestine to monitor the connection between T2R signaling and toxin efflux directly.

描述（由申请人提供）：哺乳动物通过单个小的“苦”分子激动剂刺激单个细胞表面受体识别食物中苦味成分。这些味道2受体（T2R）由单外年G-蛋白偶联受体（GPCR）基因的家族编码，并主要在舌头和周围口腔组织的表面上以味觉受体细胞（TRC）表示。大多数甜味感应涉及孤独的GPCR，这是味觉1受体（T1R）单体T1R2和T1R3的异二聚体。单一的甜味和整个苦味T2受体家族也在口腔外的区域表达，包括肺，胰腺和小肠。它们在舌头上的功能显然是为了允许在潜在的食物来源之间识别味道，但是，口腔外的味觉受体的生理作用在直觉上并不明显。在最近的出版物中，我们表明，肠道T2R信号传导的激活导致多肽激素胆囊基蛋白（CCK）和胰甘蓝样肽-1（GLP-1）的分泌增加，而CCK的两种主要作用是限制食物摄入和慢速胃动力。这些结果表明肠道T2R可能会限制 尽管口腔厌恶味道，但吸收苦味和潜在的有毒分子。我们还表明，T2RS的肠道表达和活性受固醇调节元素结合蛋白-2（SREBP -2）转录因子的调节，当细胞胆固醇水平较低并激活基因以积累新的细胞胆固醇所需的基因时，这会引起。相对于富含胆固醇的动物肉的饮食，富含植物的饮食均低胆固醇，苦味和潜在有毒物质的比例较高。因此，通过SREBP-2对低胆固醇植物饮食的诱导T2R活性提供了一种机制，可以将肠道“敏感”到存在潜在有毒分子的存在下，以通过CCK依赖于CCK抑制肠道运动和食物的吸收来限制其吸收。应该注意的是，CCK和肠道肽激素胃癌具有相同的羧基末端，而我们在早期研究中使用的ELISA检测到具有相似敏感性的两种激素。因此，胃蛋白可能是肠道中T2R信号引起的相关激素，而我们当前的项目旨在解决此关键问题。我们还显示CCK/胃蛋白增加了ABCB1外排转运蛋白的表达和活性，该转运蛋白已知可以防止细胞摄取广泛的有毒有机小分子。这提供了一种更积极的机制，以限制在进餐期间或偶然消耗的有毒分子的吸收。综上所述，这些研究提供了一种分子机制，可将营养感传感与毒素摄入的保护联系在一起。当前的建议结合了精选的小鼠模型中的生理研究，这些模型中具有编码营养感应的临界蛋白和毒素外排途径的基因突变，以严格测试该机制。我们还建议采用一种用孤立的小肠的小说原位测定，以直接监测T2R信号传导与毒素外排之间的联系。