Molecular Genetics of Taste Transduction

描述（由申请人提供）：味道模式不仅对帮助识别食物很重要，而且对避免食用有毒化学物质也很重要。这项研究的长期目标是了解果蝇（Drosophila melanogaster）甜味和苦味转导的分子机制。果蝇已被证明是表征其他感官模式（如视觉和嗅觉）的有价值的模式生物；然而，味觉转导受到的审查较少。最近的研究表明，哺乳动物和果蝇的味觉转导途径是由G蛋白偶联受体启动的。然而，果蝇受体下游的运作机制在很大程度上是未知的。在哺乳动物中，有证据表明味觉转导是通过磷脂酶C介导的信号通路进行的，该信号通路以TRPM5通道的激活为高潮。然而，在适应机制、cAMP信号在味觉转导中的作用、体内味觉通道的调节机制以及调节味觉受体的蛋白质等方面仍存在许多问题。该研究的目标是将遗传学、电生理学、细胞和生物化学方法结合起来，在果蝇中定义由有吸引力或令人厌恶的化合物引发的味觉转导的生物化学基础。本研究的具体目的是验证以下假设：1)参与果蝇视觉的PI信号蛋白也在味觉中起作用；2)cAMP信号蛋白在果蝇的甜味和苦味转导中起作用；3)Gr66a是咖啡因受体，该受体的错误表达可以引发对咖啡因的吸引行为反应；4)TRPA2味觉通道受钙调蛋白和支架蛋白Homer的相互作用调节。考虑到哺乳动物和果蝇味觉转导之间的明显相似之处，这些研究应该为适用于人类味觉受体细胞的味觉转导机制提供重要的新见解。

DESCRIPTION (provided by applicant): The taste modality is critical not only to aid in the identification of food, but also to avoid consuming noxious chemicals. The long-term goal of the proposed research is to understand the molecular mechanisms underlying sweet and bitter taste transduction in the fruitfly, Drosophila melanogaster. The fruitfly has proven to be a valuable model organism for characterizing other sensory modalities, such as vision and olfaction; however, taste transduction has received less scrutiny. Recent studies indicate that the mammalian and Drosophila taste transduction pathways are initiated by G- protein coupled receptors. However, the mechanisms operating downstream of the Drosophila receptors are largely unknown. In mammals, there is evidence that taste transduction operates through a phospholipase C mediated signaling pathway that culminates with the activation of the TRPM5 channel. Nevertheless, many questions remain including the mechanisms of adaptation, the role of cAMP signaling in taste transduction, the mechanisms that regulate the gustatory channel in vivo and the proteins regulating the gustatory receptors. The goal,of the proposed research is to apply a combination of genetic, electrophysiological, cell and biochemical approaches in Drosophila to define the biochemical basis for taste transduction initiated by either attractive or aversive compounds. The specific aims of this proposal are to test the hypotheses that: 1) the PI signaling proteins involved in Drosophila vision also function in taste, 2) cAMP signaling functions in Drosophila sweet and bitter transduction, 3) Gr66a is the caffeine receptor and misexpression of this receptor can elicit an attractive behavioral response to caffeine, and 4) the TRPA2 gustatory channel is regulated by calmodulin and interactions with the scaffold protein Homer. Given the apparent parallels between mammalian and Drosophila taste transduction, these studies should provide important new insights into the mechanisms of gustatory transduction that apply to human taste receptor cells.