Fitness defects due to cytosolic protein misfolding in S. cerevisiae can be alleviated by decreasing mitochondrial protein import capacity

Abstract

Protein misfolding affects cellular fitness. This can be caused due to the toxic aggregation of one species of protein or global protein misfolding events. Since the fitness defect arises due to the multi-modal effect of misfolding, there is no consensus mechanism to alleviate this fitness defect. Here, we used adaptive laboratory evolution of thermotolerance to identify pathways contributing to proteotoxic stress resistance in S. cerevisiae. Our results suggest a link between thermotolerance and proteotoxicity resistance, majorly routed through the loss of mitochondrial DNA. Loss of mitochondrial DNA decreased the association of mistargeted misfolded proteins on the mitochondrial surface and altered the cellular response to proteostasis to enhance protein quality control associated degradation. We show that a decrease in the abundance of import channels is sufficient to mimic the loss of mtDNA and increase cellular proteostasis. Thus, we uncover a cryptic interorganellar cooperation in combating proteotoxicity in yeast.