hERG 1b is critical for human cardiac repolarization

Area of Science:

• Cardiology
• Molecular Biology
• Electrophysiology

Background:

• The human ether-à-go-go-related gene (hERG) encodes potassium channels vital for cardiac repolarization.
• hERG channels are formed by 1a and 1b subunits, which coassemble in heterologous systems.
• The functional role of the hERG 1b subunit in native cardiac tissue remains unclear.

Purpose of the Study:

• To investigate the functional role of the hERG 1b subunit in human cardiac cells.
• To determine if hERG 1b is essential for normal cardiac action potential repolarization and rhythm.

Main Methods:

• Utilized human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs).
• Employed shRNA to specifically knockdown hERG 1b subunit expression.
• Measured ion currents (IKr) and action potentials (APs) at physiological temperatures.
• Expressed a fragment to convert heteromers to 1a homomers.

Main Results:

• Knockdown of hERG 1b significantly reduced 1b mRNA and protein levels, and halved IKr magnitude.
• Reduced hERG 1b expression led to prolonged and more variable AP durations.
• Cells with reduced hERG 1b exhibited early afterdepolarizations, a precursor to arrhythmias.
• Converting channels to 1a homomers mimicked the proarrhythmic effects of 1b loss.

Conclusions:

• The hERG 1b subunit is critical for normal cardiac repolarization.
• Loss of hERG 1b function in human cardiac cells is proarrhythmic.
• These findings highlight the importance of hERG 1b in maintaining cardiac electrical stability.