| Project/Area Number |
07671243
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Kidney internal medicine
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| Research Institution | Tokyo Medical and Dental University |
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Principal Investigator |
FUSHIMI Kiyohide Tokyo Medical and Dental University, Second Department of Internal Medicine Assistant Professor, 医学部, 助手 (50270913)
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| Co-Investigator(Kenkyū-buntansha) |
SASAKI Sei Tokyo Medical and Dental University, Second Department of Internal Medicine, Ass, 医学部, 助教授 (60170677)
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| Project Period (FY) |
1995 – 1996
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| Project Status |
Completed (Fiscal Year 1996)
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| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1996: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1995: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | AQP2 / aquaporin-2 / water channel / vasopressin / collecting duct / urine concentration / trafficking / exocytosis |
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| Research Abstract |
Methods of molecular biotechnology has been applied to study molecular structure of aquaporin-2 vasopressin water channel. Parts of potentially critical structure of aquaporin-2 were replaced with corresponding parts of other MIP family channels, including GlpF,a glycerol facilitator of E.Coli, and MIP,a non-specific channel of lens. Chimeras were expressed in Xenopus oocytes and mammalian epithelial cells, and structure-function relations of parts of AQP2 were analyzed. It was shown that the aqueous pore of AQP2 was assembled with aligned six transmembrane segments in alpha-helical structure. A constriction that passes only water molecules, thus accounting for selective water permeability, was created with the third and fourth hydrophilic loops in ectoplasmic and endoplasmic side respectively.
In addition, functional expression studies have elucidated that the structure of the endoplasmic domain of AQP2 carboxyl terminus is critically important for plasma membrane expression of AQP2. Especially, it was shown that the carboxyl terminus plays crucial roles in vasopressin-regulated translocation of AQP2, a key feature of vasopressin antidiuresis in the collecting duct cells as revealed in previous studies. The serine 256 in AQP2 carboxyl terminus is phosphorylated by protein kinase A and a mutation in the serine 256 diminished vasopressin-regulated exocytosis of AQP2. Thus, it was proved that phosphorylation of the serine 256 is required for vasopression-regulated trafficking of AQP2. This finding is interesting in that vesicle trafficking system is not only regulated by vesicle-associated proteins but also regulated through modifications on AQP2, a major cargo of vesicles.
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