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Enhancement of hERG channel activity by scFv antibody fragments targeted to the PAS domain
Carol A Harley1, Greg Starek2, David K Jones2
1Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal; Instituto de Investigação e Inovação em Saúde, Universidade do Porto, 4200-135 Porto, Portugal;
Insights
Researchers discovered novel positive modulators for the human ether-à-go-go-related gene (hERG) potassium channel. These molecules bind to the PAS domain, enhancing channel function and reducing cardiac action potential duration in cardiomyocytes.
Area of Science:
- Cardiovascular Physiology
- Molecular Cardiology
- Ion Channel Biology
Background:
- The human ether-à-go-go-related gene (hERG) potassium channel is crucial for cardiac action potential repolarization.
- Dysfunction of hERG channels is linked to long QT syndrome (LQTS), arrhythmias, and sudden cardiac death.
- KCNH channels, including hERG, possess an N-terminal Per-Arnt-Sim (PAS) domain, whose function in these channels remains largely unexplored.
Purpose of the Study:
- To identify novel modulators of hERG channel function.
- To investigate the role of the hERG PAS domain in channel regulation.
- To explore the potential of targeting the PAS domain for therapeutic intervention.
Main Methods:
- Generation of single-chain variable fragments (scFvs) targeting the hERG PAS domain.
- Electrophysiological recordings in human cardiomyocytes to assess hERG channel function.
- Analysis of channel activation, inactivation, and deactivation kinetics.
- Measurement of action potential duration in response to scFv treatment.
Main Results:
- Two distinct scFvs were generated that specifically bind to the hERG PAS domain.
- Both scFvs altered hERG channel deactivation kinetics, with differential effects on activation and inactivation.
- Binding of scFvs to the PAS domain increased the total current through the hERG channel.
- Treatment with these scFvs significantly reduced the action potential duration in human cardiomyocytes.
Conclusions:
- A novel class of positive modulators for the hERG channel has been identified.
- The PAS domain of hERG channels can be allosterically modulated by specific ligands.
- Targeting the hERG PAS domain represents a potential strategy for modulating cardiac electrophysiology and treating related disorders.
Abstract:
The human human ether-à-go-go-related gene (hERG) potassium channel plays a critical role in the repolarization of the cardiac action potential. Changes in hERG channel function underlie long QT syndrome (LQTS) and are associated with cardiac arrhythmias and sudden death. A striking feature of this channel and KCNH channels in general is the presence of an N-terminal Per-Arnt-Sim (PAS) domain. In other proteins, PAS domains bind ligands and modulate effector domains. However, the PAS domains of KCNH channels are orphan receptors. We have uncovered a family of positive modulators of hERG that specifically bind to the PAS domain. We generated two single-chain variable fragments (scFvs) that recognize different epitopes on the PAS domain. Both antibodies increase the rate of deactivation but have different effects on channel activation and inactivation. Importantly, we show that both antibodies, on binding to the PAS domain, increase the total amount of current that permeates the channel during a ventricular action potential and significantly reduce the action potential duration recorded in human cardiomyocytes. Overall, these molecules constitute a previously unidentified class of positive modulators and establish that allosteric modulation of hERG channel function through ligand binding to the PAS domain can be attained.
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