Physicochemical Investigation of Taste

生物体已经进化出控制其细胞内和细胞外液酸度的机制 在狭窄的生理范围内。在系统水平上，作为氢离子的细胞 大脑、心脏、肠道和舌头中的传感器会引起反射性反应， 最终消除酸性挑战。酸味受体检测到细胞内pH值的降低，但在细胞内pH值的降低。 在强酸如胃酸（HCI）的情况下，质子进入味觉细胞的机制仍然存在 未知来自NADPH氧化酶敲除小鼠的初步数据表明，质子穿过顶端 味觉细胞膜通过两个氢离子通道。1)大约60%的味觉神经对 与对照组相比，NADPH氧化酶敲除小鼠中不存在HCl，这表明一个味觉质子 通道与NADPH氧化酶活性有关。2)NADPH氧化酶基因敲除后对盐酸的剩余反应 小鼠通过环AMP增强。我们将详细研究这两个通道的功能， 在电压钳条件下麻醉的野生型和NADPH氧化酶敲除小鼠的味觉神经， 并通过测量穿过味觉细胞的顶膜和基底膜的氢离子通量 使用具有荧光成像方法的偏振单一味蕾制备物。翻译为 酸味反应的阶段性部分不依赖于钙，而紧张性部分依赖于钙。新数据 表明阶段性转导涉及由味觉细胞体积的减少诱导的味觉细胞体积的减少。 pH诱导的体积减小依赖于细胞骨架肌动蛋白。化学破坏 细胞骨架或螺旋预收缩细胞阻断了相位反应，但不阻断强直反应。我们将 详细探索阶段性酸反应和细胞体积变化之间的联系。pH恢复 味觉细胞中的机制形成酸味反应。我们有证据表明其中之一是pendrin， 氯化物-碳酸氢盐交换器。我们将研究它的作用和相关的转运蛋白在酸性磷酸酶中的作用。 对二氧化碳的反应。由于pendrin也运输甲酸，我们将调查其在甲酸的作用 味觉反应该提案研究了酸味的三个关键过程：1）酸进入机制， 2)单独的阶段性和紧张性转导机制，以及3）pH恢复和适应机制。 这项研究将揭示酸味防御机制如何发挥作用，以防止摄入酸。

Organisms have evolved mechanisms for controlling the acidity of their intracellular and extracellular fluid compartments to within narrow physiological limits. On the systemic level, cells that function as hydrogen ion sensors in the brain, the heart, the gut,and the tongue evoke reflexive responses that serve to mitigate and ultimately eliminate the acidic challenge. Sour taste receptors detect a decrease in intracellular pH, but in the case of strong acids such as gastric acid (HCI) the mechanism by which protons enter taste cells remains unknown. Preliminary data from NADPH oxidase knockout mice indicate that protons cross the apical membranes of taste cells through two hydrogen ion channels. 1) About 60% of the taste neural response to HCI is absent in NADPH oxidase knockout mice relative to controls, suggesting that one taste proton channel is linked to NADPH oxidase activity. 2) The remaining response to HCI in NADPH oxidase knockout mice is enhanced by cyclic AMP. We will investigate the function of both channels in detail by recording from taste nerves in anesthetized wild type and NADPH oxidase knockout mice under voltage clamp conditions, and by making hydrogen ion flux measurements across the apical and basolateral membranes of taste cells using a polarized single taste bud preparation with fluorescence imaging methods. Transdaction for the phasic part of the sour response is calcium-independent while the tonic part depends on calcium. New data indicate that the phasic transduction involves a decrease in taste cell volume induced by a decrease in intracellular pH. The pH-induced volume decrease depends on cytoskeletal actin. Chemical disruption of the cytoskeleton or osmotically pre-shrinking the cells blocks the phasic response, but not the tonic. We shall explore the link between the phasic sour response and cell volume changes in detail. pH recovery mechanisms in taste cells shape the sour taste response. We have evidence that one of these is pendrin, a chloride-bicarbonate exchanger. We will investigate its role and the role of related transporters in sour responses to carbon dioxide. Since pendrin also transports formate, we will investigate its role in formic acid taste responses. The proposal investigates the three key processes in sour taste: 1) acid entry mechanisms, 2) separate phasic and tonic transduction mechanisms, and 3) pH recovery and adaptation mechanisms. The research will reveal how the sour taste defense mechanism functions to prevent the ingestion of acids.