Illuminating the structure and function of Type I taste cells

摘要 味蕾是报告味道的多细胞传感器，它反映了味觉的质量和潜在的毒性。 吃的东西。组成味蕾的3种细胞类型中的两种(类型II和类型III)用以下术语描述得很好 不同口味的转导和传递的分子特征，而I型细胞是 被描述为支撑性的或胶质样的。在这个提议中，我们检验了I型味觉细胞服务的假设 两个关键功能。首先，我们对味蕾的初步重建表明，I型细胞完全 在味蕾中包围和分离其他类型的细胞；因此，I型细胞必须对信号和 味觉信息在花蕾中的整合。第二，我们的超微结构分析进一步表明，一些 I型细胞通过味孔延伸尖突，采样口腔内容物，因此可能会转导 咸味的一些成分。我们建议使用相关的解剖学、功能和分子手段来 对小鼠味蕾中的I型细胞进行分类和鉴定。第一组实验将延长我们的 环状味蕾中I型细胞检测菌样味觉的初步分析 类似地，芽将II型和III型细胞彼此分开。此外，我们还测试了I型细胞 通过释放GABA或其他神经递质参与芽内信号传递，以响应释放的ATP 通过刺激的II型(甜-苦-鲜味)细胞。然后，GABA可以作用于相邻的II型细胞以终止 发出信号，并降低随后对品尝者的反应。在目标2中，我们测试是否有形态上的 I型细胞亚型表达功能性阿米洛利敏感盐(ENaC)受体，如果是，确定 这些细胞与感觉神经纤维的关系。常规扫描电子显微镜显示I型细胞不形成 突触留下了一个悬而未决的问题，即任何I型细胞的反应如何与神经细胞沟通 系统。我们认为I型细胞，就像中枢神经系统中的神经胶质细胞一样，可以通过逆转 GABA或谷氨酸的膜转运体或大孔道的开放。最终，我们将拥有 通过界定味觉信息的性质，解决了味觉信息传递中的两个重要问题 受体细胞类型之间的芽内信号传递，第二，最终决定潜在细胞的身份 阿米洛利敏感的盐转导。

Abstract Taste buds are multicellular sensors reporting taste, which reflects quality and potential toxicity for potential food items. Two of the 3 cell types (Type II and Type III) comprising a taste bud are well described in terms of molecular features for transduction and transmission of different taste qualities whereas Type I cells are described as being supporting or glial-like. In this proposal we test the hypothesis that Type I taste cells serve two critical functions. First, our preliminary reconstructions of taste buds show that Type I cells completely surround and separate other cell types in a taste bud; thus Type I cells must be important for signaling and integration of taste information within the bud. Second, our ultrastructural analysis further shows that some Type I cells extend an apical process through the taste pore to sample the oral contents and so may transduce some components of salty taste. We propose to use correlated anatomical, functional and molecular means to classify and characterize Type I cells in taste buds from mice. The first set of experiments will extend our preliminary analysis of Type I cells in circumvallate taste buds to test whether Type I cells in fungiform taste buds similarly separate Type II and Type III cells from one another. Further we test whether the Type I cells participate in intrabud signaling by releasing GABA or other neurotransmitters in response to the ATP released by stimulated Type II (sweet-bitter-umami) cells. The GABA can then act on adjacent Type II cells to terminate signaling and reduce subsequent responsiveness to tastants. In Aim 2, we test whether any morphological subtype of Type I cells expresses functional amiloride-sensitive salt (ENaC) receptors and if so, determine the relationship of these cells to sensory nerve fibers. Conventional EM indicates that Type I cells do not form synapses leaving open the question of how any Type I cell response could be communicated to the nervous system. We suggest that Type I cells, like glial cells in the CNS, can release neurotransmitter by reversal of membrane transporters for GABA or glutamate or opening of large pore channels. In the end we will have resolved two important questions in transduction and transmission of taste information by defining the nature of intrabud signaling between receptor cell types, and secondly finally determining the identity of cells underlying amiloride-sensitive salt transduction.