Acacetin causes a frequency- and use-dependent blockade of hKv1.5 channels by binding to the S6 domain.

Abstract

We have demonstrated that the natural flavone acacetin selectively inhibits ultra-rapid delayed rectifier potassium current (I(Kur)) in human atria. However, molecular determinants of this ion channel blocker are unknown. The present study was designed to investigate the molecular determinants underlying the ability of acacetin to block hKv1.5 channels (coding I(Kur)) in human atrial myocytes using the whole-cell patch voltage-clamp technique to record membrane current in HEK 293 cells stably expressing the hKv1.5 gene or transiently expressing mutant hKv1.5 genes generated by site-directed mutagenesis. It was found that acacetin blocked hKv1.5 channels by binding to both closed and open channels. The blockade of hKv1.5 channels by acacetin was use- and frequency-dependent, and the IC(50) of acacetin for inhibiting hKv1.5 was 3.5, 3.1, 2.9, 2.1, and 1.7μM, respectively, at 0.2, 0.5, 1, 3, and 4Hz. The mutagenesis study showed that the hKv1.5 mutants V505A, I508A, and V512A in the S6-segment remarkably reduced the channel blocking properties by acacetin (IC(50), 29.5μM for V505A, 19.1μM for I508A, and 6.9μM for V512A). These results demonstrate the novel information that acacetin mainly blocks open hKv1.5 channels by binding to their S6 domain. The use- and rate-dependent blocking of hKv1.5 by acacetin is beneficial for anti-atrial fibrillation.

• Authors: Hui-Jun Wu, Wei Wu, Hai-Ying Sun, Guo-Wei Qin, Hong-Bing Wang, Panwen Wang, Hari Krishna Yalamanchili, Junwen Wang, Hung-Fat Tse, Chu-Pak Lau, Paul M Vanhoutte, Gui-Rong Li
• Journal: Journal of molecular and cellular cardiology (J Mol Cell Cardiol) Vol. 51 Issue 6 Pg. 966-73 (Dec 2011) ISSN: 1095-8584 [Electronic] England
• PMID: 21906601 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: 2011 Elsevier Ltd. All rights reserved.

Chemical References

• Flavones
• Kv1.5 Potassium Channel
• Potassium Channel Blockers
• acacetin

Topics

• Amino Acid Substitution
• Cell Line
• Flavones (metabolism, pharmacology)
• HEK293 Cells
• Heart Atria (drug effects, metabolism)
• Humans
• Kv1.5 Potassium Channel (antagonists & inhibitors, chemistry, genetics)
• Membrane Potentials
• Models, Molecular
• Mutagenesis, Site-Directed
• Mutation
• Myocytes, Cardiac (drug effects, metabolism)
• Potassium Channel Blockers (metabolism, pharmacology)
• Protein Binding
• Protein Conformation
• Protein Structure, Tertiary (genetics)