Hirota K, Murata M, Sachi Y, Nakamura H, Takeuchi J, Mori K, Yodoi J
Department of Anesthesia, Kyoto University Hospital, Institute for Virus Research, Kyoto University, 53 Shogoin-Kawaharacho, Sakyo-Ku, Kyoto, 606-01, Japan.
J Biol Chem. 1999 Sep 24;274(39):27891-7. doi: 10.1074/jbc.274.39.27891.
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.
诸如紫外线照射等氧化应激会引发哺乳动物细胞的多种氧化应激反应，包括转录因子的激活。最近研究表明，核因子-κB（NF-κB）的激活受硫氧还蛋白（TRX）控制的氧化还原调节，TRX是具有巯基还原活性的主要内源性氧化还原调节分子之一。为了阐明TRX在细胞区室中参与NF-κB调节的位置，我们研究了TRX的细胞内定位。紫外线B照射诱导TRX从细胞质转运到细胞核。在我们的体外二硫苏糖醇诱导的交联研究中，我们表明TRX可以直接与NF-κB p50结合。与空载体转染细胞相比，野生型TRX的过表达抑制了紫外线照射后NF-κB结合位点下游荧光素酶活性的诱导。相反，核靶向TRX的过表达增强了荧光素酶活性。因此，TRX似乎在NF-κB的调节中发挥双重且相反的作用。在细胞质中，它干扰IκB激酶的信号并阻止IκB的降解。然而，在细胞核中，TRX通过增强其结合DNA的能力来增强NF-κB的转录活性。NF-κB复合物的这种两步TRX依赖性调节可能是氧化还原敏感转录因子的一种新的激活机制。
