Novel protein complexes containing autophagy and UPS components regulate proteasome-dependent PARK2 recruitment onto mitochondria and PARK2-PARK6 activity during mitophagy

Abstract

Autophagy is an evolutionarily conserved eukaryotic cellular mechanism through which cytosolic fragments, misfolded/aggregated proteins and organelles are degraded and recycled. Priming of mitochondria through ubiquitylation is required for the clearance the organelle by autophagy (mitophagy). Familial Parkinson’s Disease-related proteins, including the E3-ligase PARK2 (PARKIN) and the serine/threonine kinase PARK6 (PINK1) control these ubiquitylation reactions and contribute to the regulation of mitophagy. Here we describe, novel protein complexes containing autophagy protein ATG5 and ubiquitin-proteasome system (UPS) components. We discovered that ATG5 interacts with PSMA7 and PARK2 upon mitochondrial stress. Results suggest that all three proteins translocate mitochondria and involve in protein complexes containing autophagy, UPS and mitophagy proteins. Interestingly, PARK2 and ATG5 recruitment onto mitochondria requires proteasome components PSMA7 and PSMB5. Strikingly, we discovered that subunit of 20 S proteasome, PSMA7, is required for the progression of PARK2-PARK6-mediated mitophagy and the proteasome activity following mitochondrial stress. Our results demonstrate direct, dynamic and functional interactions between autophagy and UPS components that contribute to the regulation of mitophagy.

Interactome of Arabidopsis ATG5 Suggests Functions beyond Autophagy

“…Autophagy is tightly interlinked with another catabolic pathway, governed by the ubiquitin-proteasome system (UPS) [30,31]. Furthermore, mammalian ATG5 was shown to directly interact with UPS components to aid mitophagy [32]. Our affinity purification assay allowed detection of Ubiquitin Fusion Degradation 1 (UFD), a component of the CDC48 complex that was previously suggested to crosstalk with autophagy to help maintenance of chloroplastic proteins during oxidative stress [33] (Table S3).…”