Inactivation of the mitochondrial protease Afg3l2 results in severely diminished respiratory chain activity and...

Area of Science:

• Mitochondrial biology
• Neurogenetics
• Molecular medicine

Background:

• The m-AAA proteases are essential for maintaining mitochondrial protein homeostasis.
• Mutations in genes encoding m-AAA proteases lead to severe, untreatable neurological disorders.

Purpose of the Study:

• To investigate the biological functions of m-AAA proteases and the pathology of their deficiency.
• To explore the role of the ATPase family gene 3-like 2 (AFG3L2) in mitochondrial proteostasis and neurological disease.

Main Methods:

• Utilized a genetic approach in Drosophila melanogaster to inactivate the AFG3L2 gene.
• Employed RNA interference (RNAi) for partial gene inactivation.
• Assessed developmental viability, neurodegeneration, mitochondrial protein aggregation, respiratory chain activity, mitochondrial transcription/translation, and the mitochondrial unfolded protein response (mito-UPR).

Main Results:

• Complete AFG3L2 inactivation resulted in early developmental lethality.
• Partial AFG3L2 inactivation led to adult flies with behavioral deficits, neurodegeneration, and accumulated unfolded mitochondrial proteins.
• Reduced respiratory chain activity was linked to impaired mitochondrial transcription and translation.
• Mitochondrial unfolded protein response (mito-UPR) and autophagy were activated.
• Overexpression of mito-UPR components partially rescued phenotypes, suggesting protein aggregation contributes to pathology.

Conclusions:

• AFG3L2 deficiency severely impacts mitochondrial function and leads to neurodegeneration.
• Mitochondrial stress pathways, including mito-UPR, are activated in response to AFG3L2 loss.
• Therapeutic strategies targeting mitochondrial stress pathways and gene expression show promise for AFG3L2-related neurological diseases.