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Proteolytic processing of Atg32 by the mitochondrial i-AAA protease Yme1 regulates mitophagy
1Life Sciences Institute and Department of Molecular, Cellular and Developmental Biology; University of Michigan; Ann Arbor, MI USA.
Abstract:
Mitophagy, the autophagic removal of mitochondria, occurs through a highly selective mechanism. In the yeast Saccharomyces cerevisiae, the mitochondrial outer membrane protein Atg32 confers selectivity for mitochondria sequestration as a cargo by the autophagic machinery through its interaction with Atg11, a scaffold protein for selective types of autophagy. The activity of mitophagy in vivo must be tightly regulated considering that mitochondria are essential organelles that produce most of the cellular energy, but also generate reactive oxygen species that can be harmful to cell physiology. We found that Atg32 was proteolytically processed at its C terminus upon mitophagy induction. Adding an epitope tag to the C terminus of Atg32 interfered with its processing and caused a mitophagy defect, suggesting the processing is required for efficient mitophagy. Furthermore, we determined that the mitochondrial i-AAA protease Yme1 mediated Atg32 processing and was required for mitophagy. Finally, we found that the interaction between Atg32 and Atg11 was significantly weakened in yme1∆ cells. We propose that the processing of Atg32 by Yme1 acts as an important regulatory mechanism of cellular mitophagy activity.
Insights
Mitophagy, the selective removal of mitochondria, is regulated by the processing of the Atg32 protein. This processing, mediated by the Yme1 protease, is crucial for efficient mitophagy.
Area of Science:
- Cell Biology
- Molecular Biology
- Autophagy Research
Background:
- Mitophagy is a selective form of autophagy responsible for removing damaged or superfluous mitochondria.
- In yeast, the mitochondrial outer membrane protein Atg32 mediates mitophagy by interacting with the scaffold protein Atg11.
- Tight regulation of mitophagy is essential due to the critical roles of mitochondria in energy production and reactive oxygen species generation.
Purpose of the Study:
- To investigate the regulatory mechanisms controlling mitophagy.
- To determine the role of Atg32 processing in mitophagy.
- To identify the protease responsible for Atg32 processing and its impact on the Atg32-Atg11 interaction.
Main Methods:
- Analysis of Atg32 protein processing via C-terminal epitope tagging.
- Investigating mitophagy defects in yeast mutants lacking the Yme1 protease (yme1Δ).
- Assessing the interaction between Atg32 and Atg11 in wild-type and yme1Δ cells.
Main Results:
- Atg32 undergoes C-terminal proteolytic processing upon mitophagy induction.
- Epitope tagging of Atg32's C terminus impaired processing and mitophagy.
- The mitochondrial protease Yme1 mediates Atg32 processing and is essential for mitophagy.
- The Atg32-Atg11 interaction is weakened in yme1Δ cells, indicating impaired mitophagy.
Conclusions:
- Proteolytic processing of Atg32 by Yme1 is a key regulatory step in mitophagy.
- This processing event is required for efficient cargo recognition and autophagic removal of mitochondria.
- Yme1-mediated Atg32 processing fine-tunes cellular mitophagy activity.
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