Distinct roles of thioredoxin in the cytoplasm and in the nucleus. A two-step mechanism of redox regulation of transcription factor NF-kappaB.
Oxidative stresses such as UV irradiation to mammalian cells triggers a variety of oxistress responses including activation of transcription factors. Recently, activation of nuclear factor-kappaB (NF-kappaB) has been shown to be under oxidoreduction (redox) regulation controlled by thioredoxin (TRX), which is one of major endogenous redox-regulating molecules with thiol reducing activity. In order to elucidate where in the cellular compartment TRX participates in NF-kappaB regulation, we investigated the intracellular localization of TRX. UVB irradiation induced translocation of TRX from the cytoplasm into the nucleus. In our in vitro diamide-induced cross-linking study, we showed that TRX can associate directly with NF-kappaB p50. Overexpression of wild-type TRX suppressed induction of luciferase activity under NF-kappaB-binding sites in response to UV irradiation compared with the mock transfectant. In contrast, overexpression of nuclear-targeted TRX enhanced the luciferase activity. Thus, TRX seems to play dual and opposing roles in the regulation of NF-kappaB. In the cytoplasm, it interferes with the signals to IkappaB kinases and blocks the degradation of IkappaB. In the nucleus, however, TRX enhances NF-kappaB transcriptional activities by enhancing its ability to bind DNA. This two-step TRX-dependent regulation of the NF-kappaB complex may be a novel activation mechanism of redox-sensitive transcription factors.
Hirota
K
K
Department of Anesthesia, Kyoto University Hospital, Institute for Virus Research, Kyoto University, 53 Shogoin-Kawaharacho, Sakyo-Ku, Kyoto, 606-01, Japan.
Murata
M
M
Sachi
Y
Y
Nakamura
H
H
Takeuchi
J
J
Mori
K
K
Yodoi
J
J
D002461:Cell Line, Transformed; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D003593:Cytoplasm / Q000187:drug effects / Q000378:metabolism; D017930:Genes, Reporter; D006367:HeLa Cells; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D008156:Luciferases / Q000235:genetics; D018613:Microscopy, Confocal; D016328:NF-kappa B / Q000378:metabolism* / Q000528:radiation effects; D010084:Oxidation-Reduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013879:Thioredoxins / Q000378:metabolism*; D014162:Transfection; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D014466:Ultraviolet Rays
D016328:NF-kappa B; D014409:Tumor Necrosis Factor-alpha; D013879:Thioredoxins; D008156:Luciferases; D013755:Tetradecanoylphorbol Acetate