2000 Fiscal Year Final Research Report Summary
Cloning and functional analysis of taste receptors for sourness and saltiness
| Project/Area Number |
10480220
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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 |
Neurochemistry/Neuropharmacology
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| Research Institution | Nagoya City University |
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Principal Investigator |
SHIMADA Shoichi Nagoya City University, Medical School, Professor, 医学部, 教授 (20216063)
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| Co-Investigator(Kenkyū-buntansha) |
UEDA Takashi Nagoya City University, Medical School, Research Associate, 医学部, 助手 (90244540)
HIRABAYASHI Yoshifumi Nagoya City University, Medical School, Assistant Professor, 医学部, 講師 (30181184)
FUJIMORI Osamu Nagoya City University, Medical School, Associate Professor, 医学部, 助教授 (30128350)
UGAWA Shinya Nagoya City University, Medical School, Research Associate, 医学部, 助手 (20326135)
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| Project Period (FY) |
1998 – 2000
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| Keywords | Sour Receptor / Taste sensation / Receptor / Cloning / Gene / Adaptation |
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| Research Abstract |
We have identifieda cDNA encoding a taste receptor for sourness (MDEG1) from a rat circumvallate papilla cDNA library by combined cDNA homology and functional expression approaches. When expressed in Xenopus laevis oocytes, MDEG1 showed characteristics of a proton-gated amiloride-sensitive cation channel. Interestingly, acidic stimulation by acetic acid, the chief ingredient of vinegar, generatedlarger inwardcurrents than that by hydrochloric acidat equal pH.In situ hybridization revealed that the mRNA of MDEG1 was exclusively localized in taste buds. MDEG1 immunoreactivity was found on the cell surface and in the apical portion of taste bud cells, especially in type III cells which are classifiedas gustatory receptor cells. This is the first taste receptor cDNA to be cloned. To isolate another subunit of the sour-taste receptor, we screened a rat circumvallate papilla cDNA library and iden tified MDEG2. Immunohistochemical and electrophysiological studies demonstrated that MDEG2 formed heterooligomeric channels with MDIEG1 at the apical portion of single taste-cells and modified the desensitization of MDEG1 channel. The desensitization rate of the heterooligomer was dramatically altered by a single amino acid substitution of Gly481 in MDEG2 without changing other channel properties. These findings suggest that MDEG2 regulates the sour-taste receptor desensitization contributing to sour-taste adaptation and that Gly481 in MDEG2 is the key amino acidresidue that controls the duration of sourtaste sensation.
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