# A New biosensor illuminates the driving force behind mitochondrial outer membrane rupture

## TL;DR

A new biosensor helps track mitochondrial membrane rupture during mitophagy, revealing that VCP and related proteins are essential for this process.

## Contribution

A novel fluorescent biosensor was developed to directly visualize and study mitochondrial outer membrane rupture during mitophagy.

## Key findings

- The biosensor enables detailed observation of outer mitochondrial membrane rupture during mitophagy.
- VCP and its recruitment factors are required for outer mitochondrial membrane rupture.
- The study provides a platform to dissect the mechanisms of mitophagy.

## Abstract

In PINK1 (PTEN induced kinase 1)/PRKN (Parkin)-mediated mitophagy, the rupture of the outer mitochondrial membrane (OMM) emerges as a crucial event required for efficient mitochondrial clearance. Mechanistically, OMM rupture exposes inner mitochondrial membrane (IMM) mitophagy receptors, facilitating subsequent autophagic removal. Despite the important role of OMM rupture in mitophagy, the underlying mechanism remains elusive and technically difficult to monitor. In a recent study, we developed a novel fluorescent biosensor to directly visualize OMM rupture. This technique enables temporal and spatial characterization of OMM rupture and provides a powerful platform to dissect the underlying mechanism. Using this tool, we revealed that VCP (valosin containing protein) and its recruitment factors are required for OMM rupture, suggesting that VCP-dependent remodeling of the OMM proteome primes the rupture of OMM during mitophagy.

Abbreviations: ARIH1, Ariadne RBR E3 ubiquitin protein Ligase 1; AMFR, autocrine motility factor receptor; ANKRD13A, ankyrin repeat domain-containing protein 13 A; FUNDC1, FUN14 domain containing 1; OA, oligomycin and antimycin; CID, chemical-induced dimerization; IMM, nner mitochondrial membrane; LC3, microtubule-associated protein 1 light chain 3; MUL1, mitochondrial E3 ubiquitin protein ligase 1; NIX, BCL2 interacting protein 3 like; OMM, outer mitochondrial membrane; UBXN1, ubiquitin regulatory X domain-containing protein 1; UBXN6, ubiquitin regulatory X domain-containing protein 6; VCP, valosin-containing protein; WIPI2, WD repeat domain phosphoinositide interacting protein 2.