Monell Chemical Senses Center, Philadelphia, PA, USA.
New York University College of Dentistry, New York, NY, USA.
Chem Senses. 2019 May 29;44(5):289-301. doi: 10.1093/chemse/bjz019.
The peripheral taste and olfactory systems in mammals are separate and independent sensory systems. In the current model of chemosensation, gustatory, and olfactory receptors are genetically divergent families expressed in anatomically distinct locations that project to disparate downstream targets. Although information from the 2 sensory systems merges to form the perception of flavor, the first cross talk is thought to occur centrally, in the insular cortex. Recent studies have shown that gustatory and olfactory receptors are expressed throughout the body and serve as chemical sensors in multiple tissues. Olfactory receptor cDNA has been detected in the tongue, yet the presence of physiologically functional olfactory receptors in taste cells has not yet been demonstrated. Here we report that olfactory receptors are functionally expressed in taste papillae. We found expression of olfactory receptors in the taste papillae of green fluorescent protein-expressing transgenic mice and, using immunocytochemistry and real-time quantitative polymerase chain reaction experiments, the presence of olfactory signal transduction molecules and olfactory receptors in cultured human fungiform taste papilla (HBO) cells. Both HBO cells and mouse taste papilla cells responded to odorants. Knockdown of adenylyl cyclase mRNA by specific small inhibitory RNA and pharmacological block of adenylyl cyclase eliminated these responses, leading us to hypothesize that the gustatory system may receive olfactory information in the periphery. These results provide the first direct evidence of the presence of functional olfactory receptors in mammalian taste cells. Our results also demonstrate that the initial integration of gustatory and olfactory information may occur as early as the taste receptor cells.
哺乳动物的外周味觉和嗅觉系统是独立和分离的感觉系统。在当前的化学感觉模型中，味觉和嗅觉受体是遗传上不同的家族，在解剖上不同的位置表达，并投射到不同的下游靶点。尽管来自 2 种感觉系统的信息融合形成了对味道的感知，但第一次串扰被认为发生在中枢，即岛叶皮层。最近的研究表明，味觉和嗅觉受体在全身表达，并作为多种组织中的化学传感器。在舌头上已经检测到嗅觉受体 cDNA，但味觉细胞中是否存在生理功能的嗅觉受体尚未得到证实。在这里，我们报告嗅觉受体在味觉乳头上具有功能性表达。我们在表达绿色荧光蛋白的转基因小鼠的味觉乳头上发现了嗅觉受体的表达，并通过免疫细胞化学和实时定量聚合酶链反应实验，在培养的人菌状味乳头（HBO）细胞中发现了嗅觉信号转导分子和嗅觉受体的存在。HBO 细胞和小鼠味觉乳突细胞都对气味有反应。特异性小干扰 RNA 下调腺苷酸环化酶 mRNA 并抑制其药理学阻断消除了这些反应，这使我们假设味觉系统可能在外周接收嗅觉信息。这些结果提供了哺乳动物味觉细胞中存在功能性嗅觉受体的直接证据。我们的结果还表明，味觉和嗅觉信息的初始整合可能早在味觉受体细胞中就发生了。
