Cysteine redoxome landscape in the liver of male mice fed a high-fat high-sucrose diet.

Reversible cysteine post-translational modifications serve as a "switch" for protein structure-function dynamics. Herein, we applied a comprehensive strategy to map the cysteine redoxome by pinpointing over 5,000 oxidized and reduced cysteine residues in the liver of male mice fed either a normal chow diet (NCD) or a high-fat/high-sucrose diet (HFHSD). The global and subcellular distribution of oxidized and reduced cysteine residues remained stable across both diet groups, indicating that HFHSD does not induce widespread shifts in cysteine redox equilibrium. Proteomic analyses revealed that HFHSD upregulates proteins involved in genomic stability, lipid detoxification, and energy regulation, while downregulating those linked to detoxification and metabolic flexibility. Notably, 169 cysteine residues exhibited dynamic redox changes in response to HFHSD, mapping to 35 KEGG pathways central to redox balance and energy homeostasis. Motif and structural analyses demonstrated that the reactivity of cysteine residues sensitive to redox stress is dictated by distinct electrostatic microenvironments and subcellular localization. Cysteine residues sensitive to HFHSD-induced oxidation were enriched in mitochondria and cytosol, and cysteine residues sensitive to HFHSD-induced reduction in extracellular regions. Furthermore, cysteine residues sensitive to HFHSD-induced reduction mainly participate in disulfide bond formation and are exposed to the surface of the protein, suggesting roles as molecular switches in protein function. The current cysteine redoxome strategy broadens the disease-associated proteome landscape and provides potential therapeutic target cysteine residues critical for regulating protein functions and interactions relevant to pathophysiology.