Localization and functional consequences of a direct interaction between TRIOBP-1 and hERG proteins in the heart

Area of Science:

• Cardiology
• Molecular Biology
• Ion Channel Physiology

Background:

• Reduced cardiac human (h)ERG channel protein levels and I_Kr current are linked to arrhythmia and sudden cardiac death.
• The cellular mechanisms governing hERG surface expression remain incompletely understood.

Purpose of the Study:

• To identify novel proteins interacting with hERG and elucidate their role in regulating hERG surface expression and function.
• To investigate the functional consequences of TRIOBP-1 and hERG interaction on cardiac electrophysiology.

Main Methods:

• Yeast-two hybrid screening of a cardiac library to identify hERG-interacting proteins.
• Förster resonance energy transfer (FRET) and co-immunoprecipitation assays to confirm protein interactions in HEK293 cells and native cardiac tissue.
• Overexpression and shRNA knockdown studies in HEK293 cells and human stem cell-derived cardiomyocytes to assess the impact on hERG levels and function.

Main Results:

• TRIOBP-1 was identified as a direct interactor of hERG.
• TRIOBP-1 overexpression reduced hERG surface expression and I_Kr density, while TRIOBP-1 knockdown increased hERG levels.
• In human cardiomyocytes, TRIOBP-1 overexpression led to hERG co-sequestration, reduced I_Kr, disrupted action potential repolarization, and altered Ca²⁺ currents.

Conclusions:

• TRIOBP-1 directly interacts with the hERG channel.
• TRIOBP-1 plays a significant role in regulating hERG protein levels, I_Kr magnitude, and cardiac membrane excitability.
• These findings provide new insights into the cellular regulation of cardiac repolarization and potential therapeutic targets for arrhythmias.