Biology subjects

D'Silva, P.

Publications and source records attributed to D'Silva, P..

5 recordsLinked to original sources

bioRxiv2026

Uncovering moonlighting role of mitochondrial presequence translocase machinery in SOD1-mediated ALS pathogenesis

Familial Amyotrophic Lateral Sclerosis (fALS) is a fatal neurodegenerative disease, mainly caused by mutations in the superoxide dismutase 1 (SOD1) protein. Mitochondrial dysfunction is a primary hallmark of ALS pathogenesis. However, the molecular mechanism by which SOD1 mutants impair organellar health remains enigmatic. This study demonstrates that mutant SOD1 associates with the TIM23 complex in Saccharomyces cerevisiae via its intermembrane space (IMS) domain. In ALS-associated SOD1 mutants, both binding and expression of TIM23 complex proteins were downregulated, leading to altered translocation of the substrate protein Sdh3, a component of the electron transport chain (ETC) complex II. Disrupted Sdh3 translocation leads to mitochondrial dysfunction, evidenced by decreased ETC complex II activity, reduced functional mass, and compromised organelle integrity. Overexpression of Tim23 partially rescued mitochondrial integrity by increasing ETC complex activity and functional mass and restoring reticular morphology. Strikingly, the improved mitochondrial homeostasis in Tim23-overexpressing cells partially rescued the growth defects caused by mutant SOD1. Collectively, these findings reveal a previously unrecognized regulatory axis between mutant SOD1 and the mitochondrial pre-sequence translocase machinery, highlighting this pathway as a promising target for future ALS therapies and opening new avenues for mechanistic and translational research. Author SummaryFamilial Amyotrophic Lateral Sclerosis (fALS) is a progressive, fatal neuromuscular disorder marked by motor neuron degeneration. The exact cause of ALS remains unclear. Previous research links familial ALS to mutations in the superoxide dismutase 1 (SOD1) gene. SOD1 mutants in ALS disrupt mitochondrial protein translocation, a key mitochondrial process. The mechanism by which SOD1 mutants affect mitochondrial function and integrity by modulating presequence translocase (TIM23 complex) import is not yet understood. The current study addresses a critical gap in ALS research by demonstrating a novel, direct interaction between SOD1 and Tim23 that regulates mitochondrial function in yeast. We found that SOD1 binds Tim23 via Tim23 IMS domain, stabilizes the Tim23CORE complex, enabling Sdh3 import. Loss of SOD1, Tim23, or Tim50 destabilizes the TIM23CORE complex, leading to impaired Sdh3 import and decreased ETC complex-II activity. These changes disrupt mitochondrial structure, causing fragmentation and a loss of functional mitochondrial mass in {Delta}sod1. ALS-linked SOD1 mutants show similar effects: they diminish Sdh3 import by weakening SOD1-Tim23 interaction and lowering TIM23 complex stability, resulting in punctate mitochondria and reduced mitochondrial mass. Collectively, our study identifies the SOD1-TIM23 interaction as a key regulator of mitochondrial health through Sdh3 import via the TIM23CORE complex and indicates this pathway as a potential early intervention target for ALS therapy.

genetics↗

bioRxiv2024

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

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.

cell biology↗

bioRxiv2024

Control of heat and oxidative stress adaptation by the DJ-1 paralogs in Arabidopsis thaliana

Plant growth and development are highly regulated processes and are majorly controlled by various environmental factors, whose extreme exposures lead to chronic stress conditions promoting reactive oxygen species (ROS) and carbonyl species (RCS) production. ROS and RCS extensively damage cellular biomolecules and organelles, affecting plants viability and development. Emerging reports highlight that the multi-stress responding DJ-1 superfamily proteins are critical in attenuating cytotoxic effects associated with abiotic stress. The current report, validated in yeast and plant models, shows that AtDJ-1C and AtDJ-1E are robust antioxidants that scavenge ROS and improve survival under oxidative stress. Although they lack conventional glyoxalases and do not attenuate the glycation of proteins, AtDJ-1C and AtDJ-1E preserve the GSH pool and regulate redox homeostasis. Moreover, transcriptome profiling indicates that levels of AtDJ-1C and AtDJ-1E are rapidly established to counter heat and oxidative stress conditions. Notably, the knockdown of AtDJ-1C and AtDJ-1E promotes detrimental alterations such as reduced chlorophyll retention, impaired root morphogenesis, and induced sensitivity to heat stress due to ROS elevation. Contrastingly, overexpression of AtDJ-1C and AtDJ-1E improved plant height and rosette formation under physiological conditions. In conclusion, our study unravels the pivotal functions of Arabidopsis thaliana DJ-1C and DJ-1E in governing plant health and survival under heat and oxidative stress conditions.

plant biology↗

bioRxiv2022

Saccharomyces cerevisiae DJ-1 paralogs maintain genome integrity through glycation repair of nucleic acids and proteins

Reactive carbonyl species (RCS) such as methylglyoxal and glyoxal are potent glycolytic intermediates that extensively damage cellular biomolecules leading to genetic aberration and protein misfolding. Hence, RCS levels are crucial indicators in the progression of various pathological diseases. Besides the glyoxalase system, emerging studies report highly conserved DJ-1/ThiJ/PfpI superfamily proteins as critical regulators of RCS. DJ-1 superfamily proteins, including the human DJ-1, a genetic determinant of Parkinsons disease possess diverse physiological functions paramount for combating multiple stressors. Although S. cerevisiae retains four DJ-1 orthologs (namely Hsp31, Hsp32, Hsp33, and Hsp34), their physiological relevance and collective requirement are still obscure due to their close sequence similarity. Here, we report for the first time that the yeast DJ-1 orthologs function as novel enzymes involved in the preferential scavenge of glyoxal and methylglyoxal, toxic metabolites, and genotoxic agents. At the cellular level, their collective loss induces chronic glycation of the proteome, and nucleic acids, resulting in a spectrum of genetic mutations and reduced mRNA translational efficiency. Furthermore, the Hsp31 paralogs efficiently repair severely glycated macromolecules derived from carbonyl modifications. They also participate in genome maintenance as their absence upregulates DNA damage response pathways when exposed to different genotoxins. Interestingly, yeast DJ-1 orthologs provide robust organellar protection by redistributing into mitochondria to alleviate the glycation damage of mitochondrial DNA and proteins. Taken together, our study uncovers the existence of a novel glycation repair pathway in S. cerevisiae and a possible neuroprotective mechanism of how hDJ-1 confers mitochondrial health during carbonyl stress.

biochemistry↗

bioRxiv2022

Functional crosstalk between the carrier translocase machinery and YME1 complex maintains mitochondrial proteostasis and integrity

The TIM22 pathway cargos are essential for sustaining mitochondrial proteostasis as an excess of these proteins leads to proteostatic stress and cell death. Yme1 is an inner membrane metalloprotease that regulates proteostasis with its chaperone-like and proteolytic activities. Although the mitochondrial translocase and protease machinery are critical for organelle health, the functional link between these complexes remains unexplored. The present study unravels a novel genetic connection between the TIM22 complex and YME1 machinery in maintaining mitochondrial proteostasis and quality control. Our genetic analyses indicate that impairment in the TIM22 complex rescues the respiratory growth defects of cells without Yme1. We further demonstrate that Yme1 is essential for the stability of the TIM22 complex and regulating the proteostasis of the TIM22 pathway substrates. Moreover, impairment in the TIM22 complex suppressed the mitochondrial structural and functional defects of Yme1 devoid cells. Notably, the functional dependence between the TIM22 and YME1 complexes remains functionally conserved from yeast to humans. Our findings suggest that excessive levels of the TIM22 pathway substrates could be one of the reasons for the respiratory growth defects of cells lacking Yme1 and compromising the TIM22 complex compensate for the imbalance in mitochondrial proteostasis caused by loss of Yme1.

cell biology↗