Mid51/Fis1 mitochondrial oligomerization complex drives lysosomal untethering and network dynamics.

Area of Science:

• Cell Biology
• Organelle Dynamics
• Mitochondrial-Lysosomal Interactions

Background:

• Lysosomes are crucial organelles involved in cellular waste disposal and are implicated in various diseases.
• Lysosomal dynamics, including tethering and fusion, are essential for maintaining cellular homeostasis.
• Dysregulation of lysosomal networks contributes to the pathogenesis of several human diseases.

Purpose of the Study:

• To investigate the mechanisms governing lysosomal network reorganization.
• To identify the molecular players involved in inter-lysosomal tethering and untethering events.
• To explore the link between mitochondrial dynamics and lysosomal behavior.

Main Methods:

• Live super-resolution microscopy to visualize lysosomal and mitochondrial dynamics in real-time.
• Genetic manipulation of mitochondrial proteins (Mid51, Fis1) and Rab7 GTPase regulators (TBC1D15).
• Analysis of lysosomal network structure and dynamics under various experimental conditions.

Main Results:

• Lysosomal tethering events predominantly lead to untethering rather than fusion, facilitating network reorganization.
• A coupled oligomerization of the mitochondrial Mid51/Fis1 complex drives inter-lysosomal untethering.
• Fis1 oligomerization recruits TBC1D15 (a Rab7-GAP) to mitochondria, promoting Rab7 GTP hydrolysis and lysosomal untethering.
• Inhibition of Fis1 oligomerization disrupts lysosomal network dynamics, with implications for Parkinson's disease-associated mutations.
• Dominant optic atrophy-linked Mid51 mutants do not affect lysosomal dynamics, suggesting specific roles for Mid51/Fis1 complex formation.

Conclusions:

• The study reveals a novel mechanism of lysosomal network reorganization driven by mitochondrial Mid51/Fis1 complex oligomerization.
• This mitochondrial complex couples Drp1 and Rab7 GTP hydrolysis machinery at mitochondria-lysosome contact sites, regulating lysosomal untethering.
• Disruption of this process, particularly through Fis1 oligomerization inhibition, leads to aberrant lysosomal dynamics and has potential links to neurodegenerative diseases like Parkinson's.