The ubiquitin-binding protein ANKRD13A mediates VCP-dependent mitochondrial outer membrane rupture during PINK1/Parkin-mediated mitophagy.

PINK1/Parkin-mediated mitophagy is a major homeostatic mechanism by which cells selectively remove damaged, depolarized mitochondria. A signature event in this form of mitophagy is the rupture of the mitochondrial outer membrane (OMM), a process required for proper disposal of mitochondria. The OMM rupture results in the topological exposure of the mitochondrial inner membrane (IMM) mitophagy receptors, which are recognized by autophagy machinery, thus promoting the turnover of the depolarized mitochondria. However, due to the lack of efficient tools to measure OMM rupture, our mechanistic understanding of this process has been limited. In this study, we identified ankyrin repeat domain-containing protein 13 A (ANKRD13A) as a novel mitophagy factor that interacts with multiple mitochondrial proteins and relocalizes to the depolarized mitochondria. ANKRD13A promotes PINK1/Parkin-mediated mitophagy by recruiting valosin-containing protein (VCP), an AAA-ATPase that functions to remodel protein complexes or membranes via the extraction of protein substrates. Through the development of a novel biosensor that fluorescently marks the sites of OMM rupture, we visualized the OMM rupture events in cellulo and revealed that VCP and its recruitment factors, including ANKRD13A, are required for the rupture of OMM. This finding demonstrated that VCP-dependent remodeling of OMM during PINK1/Parkin-mediated mitophagy is a key driving force behind the OMM rupture. Furthermore, our newly developed biosensor represents an effective, reliable method to detect OMM rupture during PINK1/Parkin-mediated mitophagy, and it is valuable for future mechanistic investigation of this process.