| Project/Area Number |
12670081
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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 |
General pharmacology
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| Research Institution | Yamagata University |
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Principal Investigator |
ISHII Kuniaki Yamagata University, School of Medicine, Associate Professor, 医学部, 助教授 (10184459)
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| Co-Investigator(Kenkyū-buntansha) |
YOMOGIDA Shinichi Yamagata University, School of Medicine, Research assistant, 医学部, 助手 (90250802)
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| Project Period (FY) |
2000 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥3,900,000 (Direct Cost: ¥3,900,000)
Fiscal Year 2001: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2000: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Keywords | Herg / deactivation / amino-terminal region / sixth transmembrane region / tandem / oocyte / 抗不整脈薬 / Herg |
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| Research Abstract |
The pore-forming subunit of human I_<Kr> channel is encoded by HERG. We have investigated influence of the sixth transmembrane segment (S6) on the slow deactivation of HERG channel and possible relationship between the S6 and the ammo-terminal region that is known to be involved in slowing the deactivation. We have also investigated whether changes in the deactivation rate affect the effects of various drugs on the HERG channel. (1) Substitution of Ile at 647 in the S6 with Phe, Tyr or Trp resulted in slowing of the deactivation kinetics. This residue is just next to the gating hinge Gly at which the inner helices bend when the potassium channels open. It might be possible that the bulky aromatic residue at the site next to the hinge interferes closing of the HERG channel. (2) Amino-terminal region of WT and I647F was deleted to generate WTΔ2-354 and I647FΔ2-354. When deactivation kinetics of WT, I647F and their amino-terminal deletion mutants were compared, I647FΔ2-354 deactivated mar
… More
kedly faster than I647F, but slower than WTΔ2-354. This result suggests that the amino-terminal region and the S6 affect the deactivation kinetics through different mechanisms. (3) Effects of various drugs were reduced in I647F, I647Y and I647W that exhibited slowing of the deactivation kinetics. To investigate whether the change in deactivation kinetics itself is responsible for the reduced effects of the drugs, their effects on I647FΔ2-354 were studied. Currents of I647FΔ2-354 were inhibited by the drugs significantly less than I647F, but markedly greater than WT. Thus, although the slower deactivation kinetics might be partly responsible for the reduced effects of the drugs, the mutation of I647 probably affects the binding of the drugs besides changing the deactivation kinetics. (4) We could not investigate how many amino-termini are needed to slow the deactivation kinetics, since no detectable currents were observed through tandem constructs of WT and the amino-terminal deletion mutants. Less
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