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Chaperone-like Protein P32 Regulates ULK1 Stability and Autophagy

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Specialty Cell Biology
Date 2015 Apr 25
PMID 25909887
Citations 29
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Abstract

Mitophagy mediates clearance of dysfunctional mitochondria, and represents one type of mitochondrial quality control, which is essential for optimal mitochondrial bioenergetics. p32, a chaperone-like protein, is crucial for maintaining mitochondrial membrane potential and oxidative phosphorylation. However, the relationship between p32 and mitochondrial homeostasis has not been addressed. Here, we identified p32 as a key regulator of ULK1 stability by forming complex with ULK1. p32 depletion potentiated K48-linked but impaired K63-linked polyubiquitination of ULK1, leading to proteasome-mediated degradation of ULK1. As a result, silencing p32 profoundly impaired starvation-induced autophagic flux and the clearance of damaged mitochondria caused by mitochondrial uncoupler. Importantly, restoring ULK1 expression in p32-depleted cells rescued autophagy and mitophagy defects. Our findings highlight a cytoprotective role of p32 under starvation conditions by regulating ULK1 stability, and uncover a crucial role of the p32-ULK1-autophagy axis in coordinating stress response, cell survival and mitochondrial homeostasis.

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