Mitochondrial Complex I and ROS control neuromuscular function through opposing pre- and postsynaptic mechanisms.

Area of Science:

• Neuroscience
• Cell Biology
• Mitochondrial Biology

Background:

• Neurons have high energy demands met by mitochondria.
• Mitochondrial dysfunction causes neuronal problems.
• Mitochondrial Complex I (MCI) subunits are crucial for Drosophila neuromuscular junction (NMJ) function and growth.

Purpose of the Study:

• To investigate tissue-specific adaptations at the Drosophila NMJ upon MCI depletion.
• To identify molecular mechanisms underlying compensatory responses to MCI depletion in neurons.
• To understand the consequences of muscle MCI depletion on synapse integrity and function.

Main Methods:

• Utilized the Drosophila neuromuscular junction (NMJ) as a model system.
• Investigated the effects of MCI depletion in motor neurons and muscles.
• Analyzed mitochondrial reactive oxygen species (ROS) levels.
• Examined cytological defects, synapse function, and neurotransmission.

Main Results:

• In motor neurons, MCI depletion led to cytological defects and increased mitochondrial ROS, which triggered homeostatic signaling to maintain NMJ excitation.
• In muscles, MCI depletion also increased mitochondrial ROS, but this resulted in synapse degeneration, mitochondrial fragmentation, and impaired neurotransmission.
• Identified molecules mediating the compensatory response in neurons.

Conclusions:

• Neuronal and muscle responses to MCI depletion are tissue-specific, involving distinct adaptations and outcomes.
• Neuronal mitochondrial ROS can activate compensatory mechanisms, while muscle mitochondrial ROS leads to pathology.
• Findings in Drosophila offer insights into human neurological and neuromuscular diseases linked to MCI dysfunction.