Plants have an unusually complex complement of Trx's composed of six well-defined types (Trxs f, m, x, y, h, and o) that reside in diverse cell compartments and function in an array of processes. Thioredoxin proteins move from cell to cell, representing a novel form of cellular communication in plants. Interactions Thioredoxin has been shown to interact with: ASK1, Collagen, type I, alpha 1, Glucocorticoid receptor, SENP1, TXNIP. NF-κB – by reducing a disulfide bond in NF-κB, Trx1 promotes binding of this transcription factor to DNA. AP1 via Ref1 – Trx1 indirectly increases the DNA-binding activity of activator protein 1 (AP1) by reducing the DNA repair enzyme redox factor 1 (Ref-1), which in turn reduces AP1 in an example of a redox regulation cascade. AMPK – AMPK function in cardiomyocytes is preserved during oxidative stress due to an interaction between AMPK and Trx1. By forming a disulfide bridge between the two proteins, Trx1 prevents the formation and aggregation of oxidized AMPK, thereby allowing AMPK to function normally and participate in signaling cascades. Effect on cardiac hypertrophy Trx1 has been shown to downregulate cardiac hypertrophy, the thickening of the walls of the lower heart chambers, by interactions with several different targets. Trx1 upregulates the transcriptional activity of nuclear respiratory factors 1 and 2 (NRF1 and NRF2) and stimulates the expression of peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α). Furthermore, Trx1 reduces two cysteine residues in histone deacetylase 4 (HDAC4), which allows HDAC4 to be imported from the cytosol, where the oxidized form resides, into the nucleus. Once in the nucleus, reduced HDAC4 downregulates the activity of transcription factors such as NFAT that mediate cardiac hypertrophy. Trx 1 also controls microRNA levels in the heart and has been found to inhibit cardiac hypertrophy by upregulating miR-98/let-7. Trx1 can regulate the expression level of SMYD1, thus may indirectly modulate protein methylation for purpose of cardiac protection. Thioredoxin in skin care Thioredoxin is used in skin care products as an antioxidant in conjunction with glutaredoxin and glutathione. See also RuBisCO - enzyme activity regulated by thioredoxin Peroxiredoxin - enzyme activity regulated by thioredoxin Thioredoxin fold Thioredoxin reductase References Further reading External links Single-pass transmembrane proteins Moonlighting proteins