Molecular genetics of gustatory detection

摘要 该项目具有开发昆虫和昆虫之间味觉机制差异的长期潜力。 哺乳动物将开发新策略来控制感染数亿人的昆虫病媒 每年一次。此外，这项研究探索了昆虫和哺乳动物味道之间出人意料的相似之处 在进化上是保守的。这个项目将利用果蝇提供的大量工具 解决接触式化学传感领域中长期存在的基本问题。这个 AIMS将采用通常不同的方法组合，包括电生理学、钙离子成像、 行为学、分子遗传学和细胞生物学方法。Aim 1测试了存在信号的想法 在检测低水平苦味化合物中起作用的途径，并且以前 与哺乳动物的甜味、苦味和鲜味转导有无法识别的相似性。品味能力 令人厌恶的化合物对于生存是必不可少的，许多有毒化学物质的高浓度是通过 所谓的“味觉受体”，这是昆虫的配基通道，有别于哺乳动物的味觉 感受器。此外，Trp通道也被用来感觉苦味化合物。目标1将测试这样的想法 G蛋白偶联受体与苦味反应性味觉受体中的Trp通道偶联 神经元，使苍蝇能够在低水平下感觉到有毒化学物质。因此，尽管存在显著的差异， 昆虫和人类之间味觉接受的一些机制，目标1是定义一个依赖于GPCR/Trp的 昆虫的味觉传导途径。然而，启动味觉转导的特定GPCRs 在飞行中是非常意想不到的。目标2涉及一种众所周知的高度保守的行为，在这种行为中，动物 被低盐食物吸引，拒绝高盐食物。第一个目标是利用我们最近的发现 在味觉感受器细胞中，低钠味觉和高钠味觉的差异编码有多大，从而 引发不同的行为反应。一种离子亲和性受体(Ir76b)是低盐感受器，但高盐感受器 受体仍不清楚。目标2是定义高Na+受体，并解决它们是否形成多个- 亚基阳离子通道。另一种行为保守但特征不佳的味觉通道是钙离子 品尝一下。目标3是揭示神秘的钙受体，使动物具有品尝钙的能力。最后， 目标4是剖析食物质地影响口味偏好的分子和细胞机制。 这将开辟重要的新领域，因为动物食物质地检测的分子基础尚未 完全没有被开发过。目标4将测试通过果蝇检测食物硬度的想法 “跨膜通道样蛋白”(TMC)的同源蛋白，在哺乳动物中被认为是 听觉毛细胞中的通道复合体。总而言之，在昆虫和人类受体 不同的是，这些差异可以被利用来制定控制病媒的策略。相反，聚焦 也揭示了进化上保守的味觉检测机制。

Abstract This project has the long-term potential to exploit the differences in taste mechanisms between insects and mammals to develop new strategies to control insect disease vectors that infect hundreds of millions of people annually. In addition, this research explores unexpected similarities between insect and mammalian taste that are evolutionarily conserved. This project will exploit the vast array of tools provided by the fruit fly, Drosophila melanogaster, to address fundamental, longstanding questions in the field of contact chemosensation. The aims will employ an usually diverse combination of approaches, including electrophysiology, Ca2+ imaging, behavior, molecular genetics and cell biological approaches. Aim 1 tests the idea that there exists a signaling pathway that functions in the detection of low levels of bitter compounds, and which bears previously unrecognized similarity to mammalian sweet, bitter and umami taste transduction. The capacity to taste aversive compounds is essential for survival, and high levels of many noxious chemicals are detected through so-called “gustatory receptors,” which are insect ligand-gated channels distinct from mammalian taste receptors. In addition, TRP channels are also employed to sense bitter compounds. Aim 1 will test the idea that a G-protein coupled receptor (GPCR) couples to a TRP channel in bitter responsive gustatory receptor neurons, and enables flies to sense noxious chemicals at low levels. Thus, despite the striking differences in some mechanisms of taste reception between insects and humans, aim 1 is to define a GPCR/TRP dependent taste transduction pathway in an insect. However, the specific GPCRs that appear to initiate taste transduction in the fly are highly unexpected. Aim 2 concerns a well-known and highly conserved behavior in which animals are attracted to low salt foods and reject foods with high salt. The first aim leverages our recent discovery as to how low and high Na+ taste perceptions are differentially encoded in gustatory receptor cells, and thereby induce distinct behavioral responses. An ionotropic receptor (IR76b) is the low salt sensor, but the high salt receptor remains unknown. Aim 2 is to define the high Na+ receptors, and address whether they form a multi- subunit cation channel. Another behaviorally conserved, but poorly characterized gustatory modality is Ca2+ taste. Aim 3 is to reveal the enigmatic Ca2+ receptors that endow animals with the ability to taste Ca2+. Finally, aim 4 is to dissect the molecular and cellular mechanism through which food texture affects taste preferences. This would break important new ground since the molecular basis for food texture detection in animals is as yet completely unexplored. Aim 4 will test the idea that the hardness of food is detected through the Drosophila homolog of “transmembrane channel-like” (TMC) proteins, which in mammals are implicated as subunits of a channel complex in auditory hair cells. In summary, in those cases in which insect and human receptors are distinct, the differences can be exploited to develop strategies to control disease vectors. Conversely, focusing on flies also offers to reveal evolutionarily conserved gustatory detection mechanisms.