Klement J F, Rice N R, Car B D, Abbondanzo S J, Powers G D, Bhatt P H, Chen C H, Rosen C A, Stewart C L
Roche Institute of Molecular Biology, Roche Research Center, Nutley, New Jersey 07110, USA.
Mol Cell Biol. 1996 May;16(5):2341-9. doi: 10.1128/MCB.16.5.2341.
The ubiquitous transcription factor NF-kappaB is an essential component in signal transduction pathways, in inflammation, and in the immune response. NF-kappaB is maintained in an inactive state in the cytoplasm by protein-protein interaction with IkappaBalpha. Upon stimulation, rapid degradation of IkappaBalpha allows nuclear translocation of NF-kappaB. To study the importance of IkappaBalpha in signal transduction, IkappaBalpha-deficient mice were derived by gene targeting. Cultured fibroblasts derived from IkappaBalpha-deficient embryos exhibit levels of NF-kappaB1, NF-kappaB2, RelA, c-Rel, and IkappaBbeta similar to those of wild-type fibroblasts. A failure to increase nuclear levels of NF-kappaB indicates that cytoplasmic retention of NF-kappaB may be compensated for by other IkappaB proteins. Treatment of wild-type cells with tumor necrosis factor alpha (TNF-alpha) resulted in rapid, transient nuclear localization of NF-kappaB. IkappaBalpha-deficient fibroblasts are also TNF-alpha responsive, but nuclear localization of NF-kappaB is prolonged, thus demonstrating that a major irreplaceable function Of IkappaBalpha is termination of the NF-kappaB response. Consistent with these observations, and with IkappaBalpha and NF-kappaB's role in regulating inflammatory and immune responses, is the normal development Of IkappaBalpha-deficient mice. However, growth ceases 3 days after birth and death usually occurs at 7 to 10 days of age. An increased percentage of monocytes/macrophages was detected in spleen cells taken from 5-, 7-, and 9-day-old pups. Death is accompanied by severe widespread dermatitis and increased levels of TNF-alpha mRNA in the skin.
普遍存在的转录因子核因子κB（NF-κB）是信号转导通路、炎症反应和免疫反应中的重要组成部分。NF-κB通过与IκBα进行蛋白质-蛋白质相互作用而在细胞质中维持无活性状态。受到刺激后，IκBα迅速降解，使得NF-κB能够进行核转位。为了研究IκBα在信号转导中的重要性，通过基因靶向技术培育出了IκBα缺陷型小鼠。从IκBα缺陷型胚胎中获取的培养成纤维细胞，其NF-κB1、NF-κB2、RelA、c-Rel和IκBβ的水平与野生型成纤维细胞相似。NF-κB核水平未能升高表明，NF-κB在细胞质中的滞留可能由其他IκB蛋白进行补偿。用肿瘤坏死因子α（TNF-α）处理野生型细胞会导致NF-κB迅速、短暂地定位于细胞核。IκBα缺陷型成纤维细胞对TNF-α也有反应，但NF-κB的核定位时间延长，这表明IκBα的一个主要不可替代的功能是终止NF-κB反应。与这些观察结果以及IκBα和NF-κB在调节炎症和免疫反应中的作用相一致的是，IκBα缺陷型小鼠发育正常。然而，出生后3天生长停止，通常在7至10日龄时死亡。在取自5日龄、7日龄和9日龄幼崽的脾细胞中，检测到单核细胞/巨噬细胞的比例增加。死亡伴随着严重的广泛性皮炎以及皮肤中TNF-α mRNA水平的升高。
