Browsing by Author "Margolskee, Robert F."
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Item Taste Receptor Cell Responses to the Bitter Stimulus Denatonium Involve Ca2+ Influx Via Store-Operated Channels(American Physiological Society (APS), 2002-06-01) Ogura, Tatsuya; Margolskee, Robert F.; Kinnamon, Sue C.Previous studies in rat and mouse have shown that brief exposure to the bitter stimulus denatonium induces an increase in [Ca2+]i due to Ca2+ release from intracellular Ca2+ stores, rather than Ca2+influx. We report here that prolonged exposure to denatonium induces sustained increases in [Ca2+]i that are dependent on Ca2+ influx. Similar results were obtained from taste cells of the mudpuppy, Necturus maculosus, as well as green fluorescent protein (GFP) tagged gustducin-expressing taste cells of transgenic mice. In a subset of mudpuppy taste cells, prolonged exposure to denatonium induced oscillatory Ca2+responses. Depletion of Ca2+ stores by thapsigargin also induced Ca2+ influx, suggesting that Ca2+store-operated channels (SOCs) are present in both mudpuppy taste cells and gustducin-expressing taste cells of mouse. Further, treatment with thapsigargin prevented subsequent responses to denatonium, suggesting that the SOCs were the source of the Ca2+ influx. These data suggest that SOCs may contribute to bitter taste transduction and to regulation of Ca2+ homeostasis in taste cells.Item TRPM5-Expressing Solitary Chemosensory Cells Respond to Odorous Irritants(American Physiological Society (APS), 2008-03-01) Lin, Weihong; Ogura, Tatsuya; Margolskee, Robert F.; Finger, Thomas E.; Restrepo, DiegoInhaled airborne irritants elicit sensory responses in trigeminal nerves innervating the nasal epithelium, leading to protective reflexes. The sensory mechanisms involved in the detection of odorous irritants are poorly understood. We identified a large population of solitary chemosensory cells expressing the transient receptor potential channel M5 (TRPM5) using transgenic mice where the promoter of TRPM5 drives the expression of green fluorescent protein (GFP). Most of these solitary chemosensory cells lie in the anterior nasal cavity. These GFP-labeled solitary chemosensory cells exhibited immunoreactivity for synaptobrevin-2, a vesicle-associated membrane protein important for synaptic transmission. Concomitantly, we found trigeminal nerve fibers apposed closely to the solitary chemosensory cells, indicating potential transmission of sensory information to trigeminal fibers. In addition, stimulation of the nasal cavity with high concentrations (0.5–5 mM) of a variety of odorants elicited event-related potentials (ERPs) in areas rich in TRPM5-expressing solitary chemosensory cells. Furthermore, odorous chemicals and trigeminal stimuli induced changes in intracellular Ca2+ levels in isolated TRPM5-expressing solitary chemosensory cells in a concentration-dependent manner. Together, our data show that the TRPM5-expressing cells respond to a variety of chemicals at high exposure levels typical of irritants and are positioned in the nasal cavity appropriately to monitor inhaled air quality.