TSG101 negatively regulates mitochondrial biogenesis in axons

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 118; no. 20; pp. 1 - 11
• Main Authors: Lin, Tzu-Huai, Bis-Brewer, Dana M., Sheehan, Amy E., Townsend, Louise N., Maddison, Daniel C., Züchner, Stephan, Smith, Gaynor A., Freeman, Marc R.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 18-05-2021
• Subjects: Animals; Animals, Genetically Modified; Autophagy; Axons; Axons - metabolism; Biological Sciences; Biosynthesis; Cytoskeletal Proteins - genetics; Cytoskeletal Proteins - metabolism; Degeneration; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Drosophila melanogaster - genetics; Drosophila melanogaster - metabolism; Drosophila Proteins - genetics; Drosophila Proteins - metabolism; Endosomal Sorting Complexes Required for Transport - genetics; Endosomal Sorting Complexes Required for Transport - metabolism; Female; Genetic screening; GTP-Binding Proteins - genetics; GTP-Binding Proteins - metabolism; Humans; Male; Mitochondria; Mitochondria - genetics; Mitochondria - metabolism; Mitochondrial Dynamics - genetics; Mitophagy - genetics; Mutants; Mutation; Neurodegeneration; Neurodegenerative diseases; Neurons - cytology; Neurons - metabolism; NF-E2-Related Factor 2 - genetics; NF-E2-Related Factor 2 - metabolism; Organelle Biogenesis; Phagocytosis; Phenotypes; TOR protein; Transcription Factors - genetics; Transcription Factors - metabolism; neurodegeneration; TSG101; ESCRT; mitochondrial biogenesis; mitochondria
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.2018770118

There is a tight association between mitochondrial dysfunction and neurodegenerative diseases and axons that are particularly vulnerable to degeneration, but how mitochondria are maintained in axons to support their physiology remains poorly defined. In an in vivo forward genetic screen for mutants altering axonal mitochondria, we identified tsg101. Neurons mutant for tsg101 exhibited an increase in mitochondrial number and decrease in mitochondrial size. TSG101 is best known as a component of the endosomal sorting complexes required for transport (ESCRT) complexes; however, loss of most other ESCRT components did not affect mitochondrial numbers or size, suggesting TSG101 regulates mitochondrial biology in a noncanonical, ESCRT-independent manner. The TSG101-mutant phenotype was not caused by lack of mitophagy, and we found that autophagy blockade was detrimental only to the mitochondria in the cell bodies, arguing mitophagy and autophagy are dispensable for the regulation of mitochondria number in axons. Interestingly, TSG101 mitochondrial phenotypes were instead caused by activation of PGC-1ɑ/Nrf2-dependent mitochondrial biogenesis, which was mTOR independent and TFEB dependent and required the mitochondrial fission–fusion machinery. Our work identifies a role for TSG101 in inhibiting mitochondrial biogenesis, which is essential for the maintenance of mitochondrial numbers and sizes, in the axonal compartment.