Tremendous strides have been taken recently in the molecular biology of taste. As a result, a number of G protein-coupled taste receptors, downstream effectors, and ion channels for taste transduction have been identified. Physiological analyses have not progressed as rapidly, due in part to the difficulty in recording signals from taste cells and taste buds. Additionally, physiological studies are sometimes at odds with molecular biological findings. For example, molecular biological investigations suggest that taste cells express only one class of taste receptors such as bitter receptors or sweet receptors, but not both. However, functional studies show that many taste cells respond to multiple classes of taste chemicals. This and other discrepancies remain unreconciled. We have devised a method that promises to overcome many problems in recording physiological signals in taste cells. We will use calcium microfluorometry, confocal laser microscopy, and slices of mouse lingual epithelium to measure calcium transients elicited by chemical stimuli applied to taste cells. This methodology allows one to apply taste stimuli to the apical chemosensory tips of taste receptor cells and record responses in a semi-intact preparation with high spatial resolution (microns) and good time resolution (100s of msec). We will use this method of calcium imaging to obtain detailed information about signal transduction for stimuli believed to activate G protein-coupled taste receptors, namely sweet, bitter, and umami. We will also investigate taste transduction for acid (sour) stimuli in mouse taste cells. We will correlate physiological responses with expression of candidate effector and target molecules downstream of the taste receptors in identified taste cells by using immunocytochemistry. We will take advantage of genetically altered mice to determine whether physiological responses are missing when specific molecules postulated to be involved in taste transduction are absent. For example, we will test whether calcium transients are elicited by bitter stimuli in taste ceils from gustducin knockout mice. Lastly, we will determine whether single taste receptor cells respond to multiple classes of chemicals or instead are """"""""tuned"""""""" to a narrow range of stimuli. Our goal is to bridge the gap between physiological and molecular biological studies and provide a more complete picture of taste transduction mechanisms.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
Research Project (R01)
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Special Emphasis Panel (ZRG1-IFCN-6 (03))
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Davis, Barry
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University of Miami School of Medicine
Schools of Medicine
Coral Gables
United States
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Roper, Stephen D; Chaudhari, Nirupa (2017) Taste buds: cells, signals and synapses. Nat Rev Neurosci 18:485-497
Dando, Robin; Pereira, Elizabeth; Kurian, Mani et al. (2015) A permeability barrier surrounds taste buds in lingual epithelia. Am J Physiol Cell Physiol 308:C21-32
Meredith, Tricia L; Corcoran, Alan; Roper, Stephen D (2015) Leptin's effect on taste bud calcium responses and transmitter secretion. Chem Senses 40:217-22
Roper, Stephen D (2015) The taste of table salt. Pflugers Arch 467:457-63
Roper, Stephen D (2014) TRPs in taste and chemesthesis. Handb Exp Pharmacol 223:827-71
Roper, Stephen D (2013) Taste buds as peripheral chemosensory processors. Semin Cell Dev Biol 24:71-9
Roper, Stephen D (2013) Introduction to signal processing in peripheral sensory organs. Semin Cell Dev Biol 24:1-2
Rodriguez-Diaz, Rayner; Dando, Robin; Huang, Y Anthony et al. (2012) Real-time detection of acetylcholine release from the human endocrine pancreas. Nat Protoc 7:1015-23
Huang, Yijen A; Grant, Jeff; Roper, Stephen (2012) Glutamate may be an efferent transmitter that elicits inhibition in mouse taste buds. PLoS One 7:e30662
Dando, Robin; Roper, Stephen D (2012) Acetylcholine is released from taste cells, enhancing taste signalling. J Physiol 590:3009-17

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