Complex I Controls Mitochondrial and Plasma Membrane Potentials in Nerve Terminals

Area of Science:

• Neuroscience
• Cellular Biology
• Biochemistry

Background:

• Mitochondrial electron transport chain (ETC) enzyme dysfunction is linked to neurodegenerative diseases.
• Mitochondrial membrane potential (Δψm) is crucial for ATP production and neuronal survival.

Purpose of the Study:

• To investigate the impact of inhibiting different ETC complexes on Δψm and plasma membrane potential (Δψp) in synaptosomes.
• To determine the sensitivity thresholds of ETC complexes I, II/III, III, and IV to inhibition.

Main Methods:

• Titration of specific inhibitors (rotenone, antimycin A, myxothiazol, KCN) for ETC complexes I, II/III, III, and IV.
• Measurement of Δψm and Δψp in synaptosomal mitochondria.

Main Results:

• Low concentrations of rotenone (complex I inhibitor) caused immediate Δψm depolarization.
• Significant inhibition (>70% for complex II/III, >90% for complex III and IV) was required to affect Δψm.
• Δψp was more sensitive to complex I inhibition (40% threshold) than to complexes III and IV (>90% inhibition).

Conclusions:

• Synaptosomal Δψm and Δψp are more susceptible to complex I activity reduction than other ETC complexes.
• These findings may elucidate the role of reduced complex I activity in neuronal cell death, particularly in Parkinson's disease.