2006 Fiscal Year Final Research Report Summary
Assemble of taste transduction mechanism with multifaceted approach
| Project/Area Number |
16380088
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Food science
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| Research Institution | Kyoto University |
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Principal Investigator |
HAYASHI Yukako Kyoto University, Graduate School of Agriculture, Associate Professor, 農学研究科, 助教授 (60212156)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Taste / bitter / Umami / mouse / transduction / second messenger / G protein / channel |
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| Research Abstract |
In this study, we focused in the assembly of transduction cascade in taste cells of C57BL/6Jms Slc strain mouse. Bitterness from food is palatable for human, although bitter substances from toxins and medicines are unpalatable. There might be different mechanisms between acceptable and non-acceptable bitterness. In order to clarify their differences, we focused on isohumulones and caffeine, and investigated their transduction mechanisms. The results indicated that the CT and GL nerves were important for caffeine sensitivity. On the other hand, the recognition of isohumulones had little difference between CTx+GLx and sham. These results apparently suggested that other mechanisms (somatic sensation, olfaction, etc) might be involved in isohumulones sensitivity.
To clarify the involvement of G protein in denatonium signal transduction, we carried out a whole-cell patch-clamp analysis with isolated taste cells in mice. The results suggest dual, G-protein-dependent and-independent mechanisms
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for denatonium. Moreover, the denatonium responses were not attenuated by singly inhibiting the phospholipase C beta2 or phosphodiesterase pathway, implying that both pathways were involved in G-protein-dependent transduction. In the G-protein-independent cells, the response was abolished by the depletion of calcium ions within the intracellular store. These results suggest that Ca2+ release from the intracellular store is an important factor. Our data demonstrate multiple transduction pathways for denatonium in mammalian taste cells.
Recently, candidates for umami receptors have been identified in taste cells, but the precise transduction mechanisms of the downstream receptor remain unknown. To investigate how intracellular Ca(2+) increases in the umami transduction pathway, we measured changes in intracellular Ca(2+) levels in response to umami stimuli monosodium glutamate (MSG), IMP, and MSG + IMP in mouse taste receptor cells (TRCs) by Ca(2+) imaging. We conclude, from the results, that the Ca(2+) influx from extracellular source might play an important role in the synergistic effect between MSG and IMP. Less
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