Roles for Glucosensors in Taste Function

项目总结 肥胖和糖尿病与长期过量摄入高糖食物和液体有关，这是由 很大程度上是因为他们可口的味道。发现一个异二聚体G蛋白偶联受体(T1R2 3) 哺乳动物的味觉细胞被广泛认为是检测所有单糖的主要方式 并通过味觉系统促进摄取。然而，我们实验室最近的研究表明，啮齿动物 对葡萄糖的口感特性比果糖更积极的反应，当提供 有机会了解它们不同的新陈代谢结果，这种现象不需要 经典的T1R2 3味觉感受器。总体而言，这些已发表的研究表明，以前存在 未知的味觉感受器与葡萄糖胃口有关。这项提案中包含的初步调查结果现在表明 葡萄糖激酶是一种参与其他葡萄糖敏感机制的磷酸化酶，在小鼠体内表达 味觉细胞。我们进一步证明，味觉组织中的葡萄糖激酶水平受能量状态和 饮食中的糖分暴露。此外，舌葡糖激酶的药理激活特别有助于舔舔。 鼓索神经对葡萄糖的行为和神经反应，而不是果糖或水。我们的 工作假说是葡萄糖激酶是T1R2 3独立的味觉感受器的一部分，该感受器转导葡萄糖- 味觉系统中的特定信号。这项提案的总体目标是进一步澄清功能和 这种新型味觉葡萄糖传感器的分子性质。在目标1中，我们将把遗传学和药理学结合起来 选择性地干扰和/或激活典型的“甜味”味觉输入和舌葡萄糖激酶的方法 测量不同“甜味”和“非甜味”品尝者在含糖和露糖的情况下的味觉驱动型舔食 老鼠。通过免疫印迹和定量聚合酶链式反应，我们将进一步量化葡萄糖激酶和其他感官的变化。 作为饮食糖暴露的功能，味觉组织中葡糖激活酶的相关机制。在目标2中，我们将 结合遗传学和药理学方法从心理物理上评估葡萄糖的可识别性， 果糖等在一系列的两个反应操纵子辨别任务中才能充分阐明 行为输出在功能上与味觉葡萄糖感受器相连。在目标3中，我们将结合遗传和 用电生理学的药理学方法来确定T1R2 3非依赖的、葡糖激酶连接的 味觉信号通过神经从舌头传递到大脑。这些目标的结果将确定新的和 营养传感的潜在关键方面，最终目标是确定潜在的新战略，以遏制 胃口。

PROJECT SUMMARY Obesity and diabetes are associated with the chronic overconsumption of high sugar foods and fluids, driven in large part by their palatable taste. A single heterodimeric G-protein coupled receptor (T1R2+3) found in mammalian taste cells is widely considered the principal means through which all simple sugars are detected and promote ingestion via the gustatory system. Yet, recent studies from our laboratory revealed that rodents come to respond more positively to the orosensory properties of glucose over fructose, when provided the opportunity to learn about their divergent metabolic consequences, and this phenomenon does not require the canonical T1R2+3 taste receptor. Collectively, these published studies point to the existence of a previously unknown taste receptor linked to glucose appetite. The preliminary findings included in this proposal now show that glucokinase, a phosphorylating enzyme involved in other glucosensing mechanisms, is expressed in murine taste cells. We further demonstrate that glucokinase levels in the taste tissue are regulated by energy state and dietary sugar exposure. Moreover, pharmacological activation of lingual glucokinase specifically bolsters licking behavior and neural responsiveness in the chorda tympani nerve for glucose, but not fructose or water. Our working hypothesis is that glucokinase is part of a T1R2+3-independent taste receptor that transduces glucose- specific signals in the gustatory system. The overall goal of this proposal is to further clarify the functional and molecular properties of this novel gustatory glucosensor. In Aim 1, we will combine genetic and pharmacological approaches to selectively disrupt and/or activate canonical “sweet” taste inputs and lingual glucokinase while measuring taste-driven licking for various “sweet” and “non-sweet” tastants in sugar-naïve and sugar-exposed mice. With immunoblot and qPCR, we will further quantify changes in glucokinase and other sensory mechanisms linked to glucokinase in taste tissue as a function of dietary sugar exposure. In Aim 2, we will combine genetic and pharmacological approaches to psychophysically assess the discriminability of glucose, fructose, and other tastants in a series of two response operant discrimination tasks in order to fully elucidate the behavioral outputs functionally linked to gustatory glucosensors. In Aim 3, we will combine genetic and pharmacological approaches with electrophysiology to determine how T1R2+3-independent, glucokinase-linked taste signals are neurally-transmitted from tongue to brain. The outcomes of these aims will identify novel and potentially critical aspects of nutrient sensing, with the ultimate goal of identifying potential new strategies to curb appetite.