Voltage sensor conformations induced by LQTS-associated mutations in hERG potassium channels

Area of Science:

• Molecular and Cellular Biology
• Biophysics
• Cardiovascular Physiology

Background:

• hERG K+ channels are crucial for cardiac rhythm, with voltage sensors mediating electromechanical coupling.
• Mutations in hERG voltage-sensing arginines are linked to Long-QT syndrome, affecting channel gating through unclear mechanisms.

Purpose of the Study:

• To elucidate the structural mechanisms by which mutations in hERG voltage-sensing arginines alter channel gating.
• To identify intermediate voltage-sensor conformations in hERG channels.

Main Methods:

• Live-cell fluorescence lifetime imaging microscopy (FLIM)
• Transition metal FRET with noncanonical amino acid incorporation
• Molecular dynamics (MD) simulations
• Phasor plot analysis of FLIM data

Main Results:

• Neutralization of key arginines in the hERG voltage sensor charge transfer center induced distinct intermediate conformations.
• Mutant hERG channels exhibited multiple voltage-dependent FRET states, unlike the single high-FRET state in controls.
• Intermediate FRET states correlated with predicted voltage-sensor structures from MD simulations.

Conclusions:

• Identified intermediate voltage-sensor conformations as a structural mechanism impairing voltage sensing in hERG channels.
• Provides novel insights into the molecular basis of cardiac channelopathies, including Long-QT syndrome.
• Highlights the role of specific arginine residues in maintaining normal voltage sensor function.