# A long-lived pool of PINK1 imparts a molecular memory of depolarization-induced activity

## TL;DR

The study shows that PINK1, a protein linked to Parkinson's disease, forms a long-lasting active pool after mitochondrial stress, which can later help activate new PINK1.

## Contribution

The discovery of a long-lived, active PINK1 pool that persists after mitochondrial recovery is novel.

## Key findings

- PINK1 accumulates on mitochondria under depolarizing conditions and remains active after recovery.
- A residual pool of active PINK1 can seed new PINK1 activation after a 16-hour recovery period.
- Free phospho-ubiquitin levels serve as a proxy for PINK1 activity in the presence of TAK-243.

## Abstract

The Parkinson’s disease–linked kinase, PINK1, is a short-lived protein that undergoes cleavage upon mitochondrial import leading to its proteasomal degradation. Under depolarizing conditions, it accumulates on mitochondria where it becomes activated, phosphorylating both ubiquitin and the ubiquitin E3 ligase Parkin, at Ser65. Our experiments reveal that in retinal pigment epithelial cells, only a fraction of PINK1 becomes stabilized after depolarization by electron transport chain inhibitors. Furthermore, the observed accrual of PINK1 cannot be completely accounted for without an accompanying increase in biosynthesis. We have used a ubiquitylation inhibitor TAK-243 to accumulate cleaved PINK1. Under these conditions, generation of unconjugated “free” phospho-ubiquitin serves as a proxy readout for PINK1 activity. This has enabled us to find a preconditioning phenomenon, whereby an initial depolarizing treatment leaves a residual pool of active PINK1 that remains competent to seed the activation of nascent cleaved PINK1 following a 16-hour recovery period.

Mitochondrial stress activates a long-lived pool of PINK1 that retains activity long after mitochondria have recovered.