Ubp2 modulates DJ-1-mediated redox-dependent mitochondrial dynamics in Saccharomyces cerevisiae

Abstract

Mitochondrial integrity is a crucial determinant of overall cellular health. Mitochondrial dysfunction and impediments in regulating organellar homeostasis contribute majorly to the pathophysiological manifestation of several neurological disorders. Mutations in human DJ-1 (PARK7) have been implicated in the deregulation of mitochondrial homeostasis, a critical cellular etiology observed in Parkinsons disease progression. DJ-1 is a multifunctional protein belonging to the DJ-1/ThiJ/PfpI superfamily, conserved across the phylogeny. Although the pathophysiological significance of DJ-1 has been well-established, the underlying molecular mechanism(s) by which DJ-1 paralogs modulate mitochondrial maintenance and other cellular processes remains elusive. Using Saccharomyces cerevisiae as the model organism, we unravel the intricate mechanism by which yeast DJ-1 paralogs (collectively called Hsp31 paralogs) modulate mitochondrial homeostasis. Our study establishes a genetic synthetic interaction between Ubp2, a cysteine-dependent deubiquitinase, and DJ-1 paralogs. In the absence of DJ-1 paralogs, mitochondria adapt to a highly tubular network due to enhanced expression of Fzo1. Intriguingly, the loss of Ubp2 restores the mitochondrial integrity in the DJ-1 deletion background by modulating the ubiquitination status of Fzo1. Besides, the loss of Ubp2 in the absence of DJ-1 restores mitochondrial respiration and functionality by regulating the mitophagic flux. Further, Ubp2 deletion makes cells resistant to oxidative stress without DJ-1 paralogs. For the first time, our study deciphers functional crosstalk between Ubp2 and DJ-1 in regulating mitochondrial homeostasis and cellular health. Author SummaryMitochondria are dynamic organelles essential for generating the energy required to maintain cellular viability and drive biological processes. Mitochondrial structures undergo continuous remodeling, modulating their function in response to cellular cues. The plasticity of mitochondrial structures is due to conserved fusion-fission proteins, thus enabling cells to adapt to metabolic changes. Mutations in PARK7, encoding for DJ-1, lead to an imbalance in mitochondrial dynamics and culminate in the progression of neurodegenerative disorders such as Parkinsons disease (PD). DJ-1 belongs to the highly conserved DJ-1/ThiJ/Pfp superfamily of multifunctional proteins. Saccharomyces cerevisiae encodes for four paralogs, which belong to the DJ-1 superfamily. Recent studies demonstrate the role of yeast DJ-1 members in regulating mitochondrial integrity and oxidative stress response. However, the mechanism(s) by which the paralogs mediate cytoprotective action remains elusive. The current study addresses the mechanistic lacuna by delineating cross-talk between Ubp2, a deubiquitinase, and redox-sensitive DJ-1 paralogs in regulating mitochondrial health. Our results suggest that elevated expression of Ubp2 in cells lacking DJ-1 paralogs promotes hyperfused mitochondrial structures. At the same time, in the absence of DJ-1 paralogs, the levels of Fzo1 expression are enhanced significantly due to its altered ubiquitination status. Intriguingly, mitochondrial dynamics and cellular health were reinstated upon deletion of Ubp2, particularly in cells with combinatorial deletion of DJ-1 paralogs in yeast. The study thus provides evidence linking the role of DJ-1 and deubiquitinase in the maintenance of mitochondrial dynamics, which can further aid in understanding the mechanism causing PD progression.