Mouse taste cells with G protein-coupled taste receptors lack voltage-gated calcium channels and SNAP-25
<p>Abstract</p> <p>Background</p> <p>Taste receptor cells are responsible for transducing chemical stimuli from the environment and relaying information to the nervous system. Bitter, sweet and umami stimuli utilize G-protein coupled receptors which activate the phospho...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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BMC
2006-03-01
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| Series: | BMC Biology |
| Online Access: | http://www.biomedcentral.com/1741-7007/4/7 |
| _version_ | 1819027812261036032 |
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| author | Medler Kathryn F Clapp Tod R Damak Sami Margolskee Robert F Kinnamon Sue C |
| author_facet | Medler Kathryn F Clapp Tod R Damak Sami Margolskee Robert F Kinnamon Sue C |
| author_sort | Medler Kathryn F |
| collection | DOAJ |
| description | <p>Abstract</p> <p>Background</p> <p>Taste receptor cells are responsible for transducing chemical stimuli from the environment and relaying information to the nervous system. Bitter, sweet and umami stimuli utilize G-protein coupled receptors which activate the phospholipase C (PLC) signaling pathway in Type II taste cells. However, it is not known how these cells communicate with the nervous system. Previous studies have shown that the subset of taste cells that expresses the T2R bitter receptors lack voltage-gated Ca<sup>2+ </sup>channels, which are normally required for synaptic transmission at conventional synapses. Here we use two lines of transgenic mice expressing green fluorescent protein (GFP) from two taste-specific promoters to examine Ca<sup>2+ </sup>signaling in subsets of Type II cells: T1R3-GFP mice were used to identify sweet- and umami-sensitive taste cells, while TRPM5-GFP mice were used to identify all cells that utilize the PLC signaling pathway for transduction. Voltage-gated Ca<sup>2+ </sup>currents were assessed with Ca<sup>2+ </sup>imaging and whole cell recording, while immunocytochemistry was used to detect expression of SNAP-25, a presynaptic SNARE protein that is associated with conventional synapses in taste cells.</p> <p>Results</p> <p>Depolarization with high K<sup>+ </sup>resulted in an increase in intracellular Ca<sup>2+ </sup>in a small subset of non-GFP labeled cells of both transgenic mouse lines. In contrast, no depolarization-evoked Ca<sup>2+ </sup>responses were observed in GFP-expressing taste cells of either genotype, but GFP-labeled cells responded to the PLC activator <it>m</it>-3M3FBS, suggesting that these cells were viable. Whole cell recording indicated that the GFP-labeled cells of both genotypes had small voltage-dependent Na<sup>+ </sup>and K<sup>+ </sup>currents, but no evidence of Ca<sup>2+ </sup>currents. A subset of non-GFP labeled taste cells exhibited large voltage-dependent Na<sup>+ </sup>and K<sup>+ </sup>currents and a high threshold voltage-gated Ca<sup>2+ </sup>current. Immunocytochemistry indicated that SNAP-25 was expressed in a separate population of taste cells from those expressing T1R3 or TRPM5. These data indicate that G protein-coupled taste receptors and conventional synaptic signaling mechanisms are expressed in separate populations of taste cells.</p> <p>Conclusion</p> <p>The taste receptor cells responsible for the transduction of bitter, sweet, and umami stimuli are unlikely to communicate with nerve fibers by using conventional chemical synapses.</p> |
| first_indexed | 2024-12-21T05:48:25Z |
| format | Article |
| id | doaj.art-21a27d5f702e422e9baf0a5c53b4bc0a |
| institution | Directory Open Access Journal |
| issn | 1741-7007 |
| language | English |
| last_indexed | 2024-12-21T05:48:25Z |
| publishDate | 2006-03-01 |
| publisher | BMC |
| record_format | Article |
| series | BMC Biology |
| spelling | doaj.art-21a27d5f702e422e9baf0a5c53b4bc0a2022-12-21T19:14:03ZengBMCBMC Biology1741-70072006-03-0141710.1186/1741-7007-4-7Mouse taste cells with G protein-coupled taste receptors lack voltage-gated calcium channels and SNAP-25Medler Kathryn FClapp Tod RDamak SamiMargolskee Robert FKinnamon Sue C<p>Abstract</p> <p>Background</p> <p>Taste receptor cells are responsible for transducing chemical stimuli from the environment and relaying information to the nervous system. Bitter, sweet and umami stimuli utilize G-protein coupled receptors which activate the phospholipase C (PLC) signaling pathway in Type II taste cells. However, it is not known how these cells communicate with the nervous system. Previous studies have shown that the subset of taste cells that expresses the T2R bitter receptors lack voltage-gated Ca<sup>2+ </sup>channels, which are normally required for synaptic transmission at conventional synapses. Here we use two lines of transgenic mice expressing green fluorescent protein (GFP) from two taste-specific promoters to examine Ca<sup>2+ </sup>signaling in subsets of Type II cells: T1R3-GFP mice were used to identify sweet- and umami-sensitive taste cells, while TRPM5-GFP mice were used to identify all cells that utilize the PLC signaling pathway for transduction. Voltage-gated Ca<sup>2+ </sup>currents were assessed with Ca<sup>2+ </sup>imaging and whole cell recording, while immunocytochemistry was used to detect expression of SNAP-25, a presynaptic SNARE protein that is associated with conventional synapses in taste cells.</p> <p>Results</p> <p>Depolarization with high K<sup>+ </sup>resulted in an increase in intracellular Ca<sup>2+ </sup>in a small subset of non-GFP labeled cells of both transgenic mouse lines. In contrast, no depolarization-evoked Ca<sup>2+ </sup>responses were observed in GFP-expressing taste cells of either genotype, but GFP-labeled cells responded to the PLC activator <it>m</it>-3M3FBS, suggesting that these cells were viable. Whole cell recording indicated that the GFP-labeled cells of both genotypes had small voltage-dependent Na<sup>+ </sup>and K<sup>+ </sup>currents, but no evidence of Ca<sup>2+ </sup>currents. A subset of non-GFP labeled taste cells exhibited large voltage-dependent Na<sup>+ </sup>and K<sup>+ </sup>currents and a high threshold voltage-gated Ca<sup>2+ </sup>current. Immunocytochemistry indicated that SNAP-25 was expressed in a separate population of taste cells from those expressing T1R3 or TRPM5. These data indicate that G protein-coupled taste receptors and conventional synaptic signaling mechanisms are expressed in separate populations of taste cells.</p> <p>Conclusion</p> <p>The taste receptor cells responsible for the transduction of bitter, sweet, and umami stimuli are unlikely to communicate with nerve fibers by using conventional chemical synapses.</p>http://www.biomedcentral.com/1741-7007/4/7 |
| spellingShingle | Medler Kathryn F Clapp Tod R Damak Sami Margolskee Robert F Kinnamon Sue C Mouse taste cells with G protein-coupled taste receptors lack voltage-gated calcium channels and SNAP-25 BMC Biology |
| title | Mouse taste cells with G protein-coupled taste receptors lack voltage-gated calcium channels and SNAP-25 |
| title_full | Mouse taste cells with G protein-coupled taste receptors lack voltage-gated calcium channels and SNAP-25 |
| title_fullStr | Mouse taste cells with G protein-coupled taste receptors lack voltage-gated calcium channels and SNAP-25 |
| title_full_unstemmed | Mouse taste cells with G protein-coupled taste receptors lack voltage-gated calcium channels and SNAP-25 |
| title_short | Mouse taste cells with G protein-coupled taste receptors lack voltage-gated calcium channels and SNAP-25 |
| title_sort | mouse taste cells with g protein coupled taste receptors lack voltage gated calcium channels and snap 25 |
| url | http://www.biomedcentral.com/1741-7007/4/7 |
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