Endosomal-dependent mitophagy coordinates mitochondrial nucleoid and mtDNA elimination

Area of Science:

• Cell Biology
• Molecular Biology
• Immunology

Background:

• Mitophagy is a crucial cellular process for removing damaged mitochondria.
• Non-canonical mitophagy pathways, including endosomal-dependent mitophagy, are activated by specific cellular injuries.
• Mitochondrial DNA (mtDNA) damage can trigger cellular dysfunction and inflammatory responses.

Purpose of the Study:

• To elucidate a novel mechanism for mitochondrial nucleoid elimination upon mtDNA damage.
• To identify key proteins involved in the endosomal-mitophagy pathway for mtDNA quality control.
• To understand how this pathway prevents excessive immune activation.

Main Methods:

• Proximity proteomics was employed to identify interacting proteins.
• The study focused on the roles of ATAD3, SAMM50, and VPS35 in mtDNA extraction and sequestration.
• Experiments investigated the endosomal-mitophagy pathway's function in response to mtDNA damage.

Main Results:

• A new pathway was identified where mitochondrial nucleoids are eliminated via endosomal-mitophagy following mtDNA damage.
• ATAD3 and SAMM50 were found to be essential for mtDNA extraction by controlling mitochondrial structure and nucleoid interaction.
• SAMM50, in coordination with VPS35, facilitates the sequestration of mtDNA into endosomes for elimination, thereby mitigating immune responses.

Conclusions:

• This study reveals a previously unknown endosomal-mitophagy pathway for clearing damaged mitochondrial nucleoids.
• The identified proteins, ATAD3, SAMM50, and VPS35, play critical roles in mtDNA quality control and preventing inflammatory signaling.
• This pathway represents a significant addition to our understanding of cellular defense mechanisms against mtDNA damage.