演 題：「ヒトKv1.5チャネルと抗不整脈薬ベプリジルとの相互作用について（中間報告）」
発表者： 松原 一樹（第５学年）
Title:
Interaction
of an antiarrhythmic drug bepridil with human Kv1.5 channel through specific
amino acids within the pore region (progress report).
Abstract:
Because
human Kv1.5 (hKv1.5) channels are highly expressed in cardiac atria but are
scarce in ventricle, pharmacological blockade of hKv1.5 has been regarded as an
effective strategy for prevention and treatment of reentry-based atrial
tachyarrhythmia such as atrial fibrillation. Although the antiarrhythmic drug
bepridil has been reported to inhibit hKv1.5 channel, there is little
information as to the amino acids in the pore region of hKv1.5 which bepridil
interacts with. Thus, this study was undertaken to examine the effect of
bepridil on hKv1.5 channel and to elucidate the underlying molecular
determinants. Site-directed mutagenesis was carried out to introduce single
point mutants (T462C, T479A, T480A, A501V, I502A, V505A, I508A, L510A, V512A
and V516A) into hKv1.5 cDNA by using a QuikChange Ⅱ XL kit. Whole-cell
patch-clamp technique was used to record membrane currents from hKv1.5 wild
type and mutant channels heterologously expressed in Chinese hamster ovary
cells. Bepridil concentration-dependently blocked hKv1.5 current. In addition,
bepridil-induced current block gradually progressed during the depolarizing
pulse, suggesting that bepridil preferentially block the channels as an
open-channel blocker. Moreover, the degree of current block by bepridil was
significantly attenuated in I502A, L510A and V516A, but not in other mutants.
Our results indicate that, several amino acids within the S6 domain (Ile502,
Leu510 and Val516) are critically involved in bepridil-induced inhibitory
effect on hKv1.5 channel. The analysis of other mutant channels (H463C, R487V
and A509G) and the docking simulation are scheduled to be conducted.
