Uncovering the Role of Mitochondrial Co-chaperones and Artificial Antioxidants in Cellular Redox Homeostasis

Abstract

Mitochondria play a multidimensional role in cellular physiology, including apoptosis, stress response, and metabolism. Although mitochondria contain their own DNA, most mitochondrial proteins are nuclear-encoded and imported via specialized translocases. Mitochondria generate ATP through oxidative phosphorylation, a process involving five protein complexes in the inner membrane. This electron transfer to oxygen produces water but also generates Reactive Oxygen Species (ROS) such as superoxide (O ), hydrogen peroxide (H O ), and hydroxyl radicals (OH·).

While ROS were once considered purely harmful, they are now recognized as signaling molecules capable of redox-mediated modifications of proteins, lipids, and nucleic acids. However, excessive ROS accumulation leads to oxidative stress, damaging cellular components and contributing to diseases such as diabetes, neurodegeneration, and cancer.

Cells maintain redox balance through antioxidant systems including superoxide dismutase (SOD), glutathione peroxidases (GPx), peroxiredoxins (Prx), catalase, and redox regulators such as glutaredoxin (Grx) and thioredoxin (Trx).

Objectives of the Thesis Identification of novel human mitochondrial regulators of redox homeostasis

Role of NEF in redox sensing (Chapter II)

Function of J-like protein Magmas in ROS regulation (Chapter III)

Characterization of artificial antioxidants as redox therapeutics

Organo-selenium compounds (Chapter IV)

Nanoparticles as enzyme mimics (Chapter V)

Key Findings Chapter II - NEFs and mtHsp70

Mitochondrial Hsp70 (mtHsp70) imports precursor proteins via ATP/ADP cycling.

Nucleotide exchange factors (NEFs) GrpEL1 and GrpEL2 were identified as part of the human mitochondrial import motor.

They form a hetero-subcomplex essential for stability and oxidative stress response.

Chapter III - Magmas as a Redox Regulator

Magmas, a J-like protein, was identified as a novel ROS regulator.

Overexpression enhanced antioxidant enzyme activity, reduced ROS production, and increased tolerance to oxidative stress.

Its ROS-sensing function was independent of protein import, highlighting a dual role in mitochondria.

Magmas provided cytoprotection even in yeast models, making it a candidate for therapeutic exploration.

Chapter IV - Organo-Selenium Antioxidants

Novel isoselenazoles were synthesized with strong GPx and Prx activities.

These compounds showed lower cytotoxicity compared to ebselen, a clinically tested antioxidant.

They provided significant cytoprotection against ROS-mediated damage, suggesting therapeutic potential.

Chapter V - Nanoparticle-Based Antioxidants

Vanadium pentoxide (V O ) nanowires (Vn) functionally mimicked GPx activity using glutathione as a cofactor.

Unlike bulk V O , Vn nanozymes were biocompatible, internalized into mammalian cells, and restored redox balance under stress.

They protected biomolecules against oxidative damage, showing promise for treating ageing, cardiac disorders, and neurodegenerative diseases.