Owing to a worldwide epidemic of obesity, there is enormous interest in understanding physiological mechanisms that regulate body weight. Sweet taste sensitivity is likely to play a significant role in food selection, calorie balance and the onset and progression of disorders such as type II diabetes and obesity. In recent years, taste research has focused on the identity of sweet taste receptors, T1R2+T1R3, and their binding sites for sugars and other natural and synthetic sweeteners. Yet, the downstream transduction events within taste cells following sweet receptor activation are incompletely understood. And, mechanisms modulating the primary sensory signal to produce adaptation are unexplored. In this competing renewal, we will extend studies begun during the previous funding period on mechanisms of sweet transduction. These provide a foundation for understanding the interplay of signaling pathways for sweet taste. In particular, we will focus on the role of cAMP in both transduction and adaptation for sweet stimuli. We will achieve this through the use of a novel transgenic mouse, that we developed, that expresses an inducible fluorescent reporter for cAMP in selected populations of cells. Functional studies on taste buds will include real-time imaging for cAMP in individual taste cells, patch-clamp recordings, and Ca2+ imaging (taste buds that are either isolated from the tongue, or retained in a semi-intact preparation). These will reveal cellular functions in individual taste cells as they respond to sucrose and synthetic sweeteners. We will answer the following questions in two specific aims: 1. Is cAMP modulated in sweet-sensitive taste cells? Our transgenic, inducible cAMP reporter will allow us gain spatial and temporal resolution of cAMP modulation in mammalian taste cells. 2. How is the cAMP signal produced and what is its downstream consequence for sweet sensing? We will test whether the cAMP opposes, complements, or refines the well-characterized Ca2+ signal, and whether cAMP plays a role in sweet taste adaptation. These studies will provide important new information about the relative roles of cAMP and phospho- inositide signaling in sweet taste transduction and adaptation, and should provide a foundation for future studies on the role of sweet taste in obesity.

R01DC006021

2003-04-04

2013-06-30