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Phosphorylation of Serine 114 on Atg32 mediates mitophagy
Yoshimasa Aoki1, Tomotake Kanki, Yuko Hirota
1Department of Clinical Chemistry and Laboratory Medicine, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan.
Abstract:
Mitophagy, which selectively degrades mitochondria via autophagy, has a significant role in mitochondrial quality control. When mitophagy is induced in yeast, mitochondrial residential protein Atg32 binds Atg11, an adaptor protein for selective types of autophagy, and it is recruited into the vacuole along with mitochondria. The Atg11-Atg32 interaction is believed to be the initial molecular step in which the autophagic machinery recognizes mitochondria as a cargo, although how this interaction is mediated is poorly understood. Therefore, we studied the Atg11-Atg32 interaction in detail. We found that the C-terminus region of Atg11, which included the fourth coiled-coil domain, interacted with the N-terminus region of Atg32 (residues 100-120). When mitophagy was induced, Ser-114 and Ser-119 on Atg32 were phosphorylated, and then the phosphorylation of Atg32, especially phosphorylation of Ser-114 on Atg32, mediated the Atg11-Atg32 interaction and mitophagy. These findings suggest that cells can regulate the amount of mitochondria, or select specific mitochondria (damaged or aged) that are degraded by mitophagy, by controlling the activity and/or localization of the kinase that phosphorylates Atg32. We also found that Hog1 and Pbs2, which are involved in the osmoregulatory signal transduction cascade, are related to Atg32 phosphorylation and mitophagy.
Insights
Mitophagy selectively degrades mitochondria for quality control. Researchers found that phosphorylating specific sites on the Atg32 protein is crucial for initiating this process by mediating the interaction between Atg11 and Atg32.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Mitophagy is essential for mitochondrial quality control, involving the selective degradation of mitochondria via autophagy.
- The interaction between mitochondrial protein Atg32 and autophagy adaptor protein Atg11 is critical for initiating mitophagy.
- The precise molecular mechanisms governing the Atg11-Atg32 interaction remain poorly understood.
Purpose of the Study:
- To elucidate the molecular details of the Atg11-Atg32 interaction in yeast mitophagy.
- To identify the specific regions and phosphorylation events involved in mediating this interaction.
Main Methods:
- Investigated protein-protein interactions using yeast models.
- Utilized biochemical assays to map interaction domains between Atg11 and Atg32.
- Analyzed the role of specific serine phosphorylation sites on Atg32 in regulating mitophagy.
Main Results:
- Identified that the C-terminus of Atg11 interacts with residues 100-120 of Atg32.
- Demonstrated that phosphorylation of Ser-114 and Ser-119 on Atg32 is induced upon mitophagy activation.
- Showed that Atg32 phosphorylation, particularly at Ser-114, is essential for the Atg11-Atg32 interaction and subsequent mitophagy.
- Linked the osmoregulatory proteins Hog1 and Pbs2 to Atg32 phosphorylation and mitophagy.
Conclusions:
- Atg32 phosphorylation acts as a key regulatory step controlling the Atg11-Atg32 interaction and mitophagy.
- Cellular regulation of Atg32 phosphorylation provides a mechanism to control mitochondrial degradation.
- The osmoregulatory pathway involving Hog1 and Pbs2 influences mitophagy through Atg32 phosphorylation.
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