Mitochondria serve as a Holdout Compartment for Aggregation-Prone Proteins hindering Efficient Degradation

Here, we have conducted a genome-wide CRISPR-Cas9 screen to identify cellular factors that regulate the degradation of an aggregation-prone reporter protein. We found that genes encoding proteins involved in mitochondrial homeostasis, including the translation factor eIF5A, were enriched among suppressors of the degradation of the reporter.

Genetic or chemical inhibition of eIF5A led to dissociation of the aggregation-prone substrate from mitochondria, which was accompanied by enhanced ubiquitination at the endoplasmic reticulum. The presence of an aggregation-prone, amphipathic helix that localized the reporter to mitochondria was crucial for the stimulatory effect of eIF5A inhibition on proteasomal degradation. Additionally, inhibition of eIF5A also enhanced degradation of mutant huntingtin and α-synuclein, two disease-associated proteins that contain amphipathic helices and mislocalize to mitochondria.