Intercellular mitochondrial transfer and trans-mitophagy in response to protein import dysfunction.

Area of Science:

• Cell Biology
• Mitochondrial Biology
• Organelle Homeostasis

Background:

• Mitochondrial protein import is crucial for cellular energy and homeostasis, especially in high-demand cells like neurons.
• Import failure disrupts cellular energy supplies, leading to cellular damage.
• Previous work showed intercellular mitochondrial transfer (IMT) via tunnelling nanotubes (TNTs) rescues import failure, but the fate and mechanism were unclear.

Purpose of the Study:

• To investigate the fate of transferred mitochondria during intercellular mitochondrial transfer (IMT).
• To elucidate the mechanistic basis for rescue of mitochondrial import failure via IMT.
• To differentiate the regulation and consequences of bidirectional mitochondrial trafficking.

Main Methods:

• Comparative analysis of mitochondrial trafficking between import-defective and import-competent cells.
• Observation of mitochondrial fragmentation and degradation pathways.
• Identification of novel structures involved in mitochondrial accumulation and degradation.

Main Results:

• Import-defective mitochondria are fragmented and undergo lysosomal degradation.
• Reactive oxygen species (ROS)-producing mitochondria are transferred from competent to failing cells.
• Transferred mitochondria accumulate in previously uncharacterized "mitochondrial degradation bodies" (MDBs).

Conclusions:

• Bidirectional mitochondrial trafficking via TNTs exhibits distinct regulatory and consequential pathways.
• A novel noncanonical "trans-mitophagy" process involving MDBs may contribute to mitochondrial regeneration.
• These findings suggest a cooperative mechanism of mitochondrial repair and functional rescue through intercellular exchange.