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Mutagenesis and Functional Analysis of Ion Channels Heterologously Expressed in Mammalian Cells
Published on: October 1, 2010
hERG gating microdomains defined by S6 mutagenesis and molecular modeling
Sarah L Wynia-Smith1, Anne Lynn Gillian-Daniel, Kenneth A Satyshur
1Department of Physiology, University of Wisconsin-Madison School of Medicine and Public Health, Madison, WI 53706, USA.
The Journal of General Physiology
|October 29, 2008
Summary
Mutations in the human ether-à-go-go-related gene (hERG) channel S6 domain reveal critical residues for channel closing. This research clarifies the gating mechanism, important for understanding drug-induced arrhythmias.
Area of Science:
- Molecular Biology
- Cardiovascular Physiology
- Ion Channel Function
Background:
- The human ether-à-go-go-related gene (hERG) channel is crucial for cardiac repolarization.
- Dysfunction of hERG channels can lead to acquired long QT syndrome and life-threatening arrhythmias.
- Drug binding sites in the hERG channel S6 domain are known, but the role of specific residues in gating remains unclear.
Purpose of the Study:
- To investigate the role of specific residues in the hERG channel S6 domain in channel gating.
- To elucidate the structural basis of hERG channel closing and drug interactions.
Main Methods:
- Cysteine mutagenesis of the hERG channel S6 domain.
- Electrophysiological measurements of channel gating kinetics and steady-state properties.
- Analysis using energy-minimized molecular models based on related potassium channel structures.
Main Results:
- Most S6 mutations altered channel gating, primarily slowing deactivation and shifting voltage dependence.
- Residues Q664, Y667, and S668 form a ring occluding the pore in the closed state.
- Mutation of V659 suggests its side chain enters a hydrophobic pocket upon closing, but it may not be the primary gate residue.
Conclusions:
- hERG channel S6 mutagenesis significantly impacts the energetics of channel closing.
- Specific residues within the S6 domain are critical for the native hERG channel's gating process.
- Understanding these residues is vital for predicting and mitigating drug-induced hERG channel block.
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