| Project/Area Number |
10470161
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (B).
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Circulatory organs internal medicine
|
|---|
| Research Institution | Tokyo Meducal and Dental University |
|---|
Principal Investigator |
HIRAOKA Masayasu Tokyo Medical and Dental University, Medical Research Institute, Professor, 難治疾患研究所, 教授 (80014281)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
FURUKAWA Tetsushi Akita University School of Medicine, Associate Professor, 医学部, 助教授 (80251552)
HIRANO Yuji Tokyo Medical and Dental University, Medical Research Institute, Associate Professor, 難治疾患研究所, 助教授 (00181181)
|
|---|
| Project Period (FY) |
1998 – 2000
|
| Project Status |
Completed (Fiscal Year 2000)
|
| Budget Amount *help |
¥15,100,000 (Direct Cost: ¥15,100,000)
Fiscal Year 2000: ¥4,600,000 (Direct Cost: ¥4,600,000)
Fiscal Year 1999: ¥4,800,000 (Direct Cost: ¥4,800,000)
Fiscal Year 1998: ¥5,700,000 (Direct Cost: ¥5,700,000)
|
|---|
| Keywords | long QT syndrome / HERG K channels / mutant channels / activation process / acceleration of inactivation / dominant negative suppression / K current suppression / repolarization / 不活性化過程 / 電位センサー / 女性ホルモン / アシドージス / 遅延整流K電流 / 内向き整流 / 脱活性化の促進 / 遺伝子異変 |
|---|
| Research Abstract |
HERG encodes Ikr current, an important factor for cardiac repolarization and gene defects in HERG cause one form of inherited long QT syndrome (LQT2). HERG/Ikr currents are the targets of various cardiac and non-cardiac drugs that causes drug-induced long QT syndrome. We studied molecular mechanism of HERG current suppression in gene defects found in LQT2 families and by factors known to block Ikr currents. Functional abnormality ofHERG mutations in T474I, A614V and V630L were analyzed using heterologous expression system in Xenopus oocytes. The mutant alone could not express current, but co-injection with wild type and each mutant produced dominant negative suppression (DNS) with its degree increasing in the order of V63OL>A614V>T474I.V60L and A614V further produced negative shift in steady state inactivation curve and fastened inactivation. We next analyzed R534C mutation in S4, presumed voltage sensor. R534C shifted voltage-dependent activation confirming S4 playing as voltage sensor, and produced fast deactivation. But, fast deactivation could not explain the reason for QT prolongation in R534C, suggesting the presence of another unknown factor. The mutation in HERG C-terminus, S818L, did not express the current by mutant alone and co-injection with wild type did not show DNS.However co-injection of wild type and excess amount of cRNA of S818L produced DNS and shifted activation curve with fast activation and deactivation kinetics. The results suggest that S818L can form heteromultimer with wild type to yield functional channels with wild type, and that the C-terminus of HERG may participate in activation process of this channels. Therefore, various types and locations of HERG mutaions cause current suppression with different mechanisms. We also explored acidosis-induced suppression of HERG current due mainly to effects on activation process.
|
