Functional interactions between KCNE1 C-terminus and the KCNQ1 channel

Area of Science:

• Molecular biology
• Cardiovascular physiology
• Genetics

Background:

• The KCNE1 protein (minK) and KCNQ1 channel form the cardiac I(Ks) potassium channel, crucial for heart rhythm.
• Mutations in KCNE1 and KCNQ1 cause Long QT Syndrome (LQTS), a hereditary arrhythmia disorder.
• KCNE1 regulates KCNQ1 via membrane segment interactions, but the C-terminus role is less understood.

Purpose of the Study:

• To investigate the impact of KCNE1 C-terminus mutations on KCNQ1 channel function, assembly, and interaction.
• To elucidate the role of the KCNE1 C-terminus in regulating I(Ks) channel kinetics and properties.

Main Methods:

• Analysis of KCNE1 mutations (D76N point mutation and Delta70 C-terminal truncation) in KCNQ1 channels.
• Electrophysiological recordings to assess channel activation, deactivation, and current density.
• Investigation of channel assembly and surface expression.

Main Results:

• KCNE1 C-terminus mutations shifted KCNQ1 activation voltage-dependently and reduced I(Ks) current density.
• Mutations accelerated deactivation but not activation kinetics.
• C-terminal truncation impaired KCNE1-KCNQ1 interaction, reducing channel formation and surface presentation.
• Rate-dependent facilitation of K(+) conductance was defective, potentially linking to LQTS arrhythmias.

Conclusions:

• The KCNE1 C-terminus is critical for KCNQ1 channel assembly and proper surface expression.
• It plays a key role in regulating channel deactivation kinetics and open-state stability.
• Defects in the KCNE1 C-terminus function contribute to LQTS pathophysiology, particularly arrhythmias triggered by increased heart rate.