Apoptosis-inducing factor (AIF), dihydrolipoamide dehydrogenase (DLD), glutathione disulfide reductase (GSR), and thioredoxin reductase (TrxR) in cancer and neurological disorders: Structural insights, redox regulation, and therapeutic potential

FAD/NAD(P)H-dependent dehydrogenases represent a crucial class of enzymes involved in redox reactions, energy metabolism, and the regulation of apoptotic pathways. In this context, apoptosis-inducing factor (AIF), dihydrolipoamide dehydrogenase (DLD), glutathione reductase (GSR), and thioredoxin reductase (TrxR) are central players in mitochondrial and cytosolic redox processes. Aberrant activity or expression of these enzymes has been implicated in cancer progression and neurodegenerative disorders, underscoring their therapeutic relevance. Our structural comparative analysis reveals a conserved overall fold across the four enzymes, with pairwise RMSD values consistently below 3.2 Å. Notably, their FAD and NAD(P)H cofactor-binding pockets are spatially aligned upon superposition, reflecting not only cofactor conservation but also striking structural/functional similarity in the catalytic mechanisms. While this structural similarity raises concerns for selective inhibitor design, the available crystallographic data provide valuable knowledge exploitable for drug-specificity. This review integrates the current knowledge on the structure, function, and pathological relevance of AIF, DLD, GSR, and TrxR, with a focus on their roles in cancer metabolism and neurodegenerative disorders, highlighting recent advances in structural studies.