Elucidation of thioredoxin target protein networks in mouse

Thioredoxin 1 (Trx1) is a key redox modulator that is functionally conserved across a wide range of species, including plants, bacteria, and mammals. Using a conserved CXXC motif, Trx1 catalyzes the reduction of cysteine disulfides and S-nitrosothiols. In contrast to small molecular reductants such as glutathione and cysteine that can reduce a wide range of oxidized proteins, Trx1 reduces only selected proteins via specific protein-protein interaction. Trx1 has been shown to regulate numerous signal transduction pathways, and its dysfunctions have been implicated in several diseases, including cancer, inflammation, and neurodegenerative and cardiovascular diseases. Identification of Trx1 target proteins may help to identify novel signaling mechanisms that are important for Trx1 antistress responses. In this study, we performed an ICAT proteomics study for the identification of Trx1 target proteins from the hearts of a cardiac specific Trx1-overexpressing transgenic mouse model (Tg-Trx1). Trx1-reduced proteins were distinguished from Trx1-induced proteins by comparison of the ICAT results with those obtained using a parallel iTRAQ (isobaric tags for relative and absolute quantitation) protein expression analysis. We were able to identify 78 putative Trx1 reductive sites in 55 proteins. Interestingly we identified a few protein functional networks that had not been shown previously to be regulated by Trx1, including the creatine-phosphocreatine shuttle, the mitochondrial permeability transition pore complex, and the cardiac contractile apparatus. The results presented here suggest that in addition to a general antioxidant function, Trx1 may be involved in the coordination of a wide array of cellular functions for maintaining proper cardiac energy dynamics and facilitating muscle contraction.