Mitochondrial dysfunction reduces the activity of KIR2.1 K⁺ channel in myoblasts via impaired oxidative...

Area of Science:

• Cellular Biology
• Muscle Physiology
• Mitochondrial Biology

Background:

• Myoblast fusion is crucial for muscle development and repair.
• Intracellular calcium ([Ca2+]i) signaling and mitochondrial integrity are key regulators.
• Ion channels play a vital role in maintaining cellular homeostasis during myogenesis.

Purpose of the Study:

• To investigate the ionic currents involved in [Ca2+]i regulation in normal and mitochondrial DNA-depleted (ρ0) L6 myoblasts.
• To determine the impact of mitochondrial dysfunction on ion channel activity and myoblast fusion.

Main Methods:

• Electrophysiological recordings to measure ionic currents (I_Kir, voltage-operated Ca2+ channels, Ca2+-activated K+ channels).
• Quantitative analysis of KIR2.1 expression.
• Measurement of resting membrane potential and basal [Ca2+]i.
• Treatment with antimycin A to inhibit mitochondrial electron transport.

Main Results:

• ρ0 myoblasts exhibited impaired myotube formation.
• A significant decrease in inwardly rectifying K+ current (I_Kir) and KIR2.1 expression was observed in ρ0 myoblasts.
• Voltage-operated Ca2+ channel and Ca2+-activated K+ channel currents remained intact.
• Mitochondrial electron transport inhibition by antimycin A also reduced I_Kir.
• ρ0 myoblasts displayed depolarized resting membrane potential and elevated basal [Ca2+]i.

Conclusions:

• Dysfunctional mitochondria specifically downregulate I_Kir in L6 myoblasts.
• The observed depolarization and altered [Ca2+]i signaling due to reduced I_Kir may contribute to impaired myoblast fusion in ρ0 cells.
• Mitochondrial integrity is essential for maintaining proper ion channel function and calcium homeostasis during myogenesis.