New potential binding determinant for hERG channel inhibitors

Area of Science:

• Cardiovascular pharmacology
• Ion channel biophysics
• Molecular cardiology

Background:

• Human ether-à-go-go related gene (hERG) 1 channels are critical for cardiac action potential repolarization.
• Inhibition of hERG1 channels by drugs can cause life-threatening arrhythmias.
• Known binding sites for hERG1 blockers are on the pore helix and S6 segment.

Purpose of the Study:

• To investigate potential drug binding determinants on the S5 helix of hERG1 channels.
• To identify novel sites that interact with hERG1 channel blockers.

Main Methods:

• Two-microelectrode voltage clamp ionic current measurements.
• Molecular modeling techniques.
• Site-directed mutagenesis (implied by identification of specific residues).

Main Results:

• A novel high-affinity binding determinant, phenylalanine at position 557 (F557), was identified on the S5 helix.
• F557 demonstrated potency comparable to the known residue Y652.
• Molecular modeling supported a direct interaction between F557 and the outer pore helix.

Conclusions:

• The S5 helix contains a previously unrecognized aromatic binding site for hERG1 channel blockers.
• F557 represents a significant determinant for hERG1 channel blockade.
• Findings advance understanding of hERG1 channel-drug interactions and arrhythmia risk.