Ghosh S, Baltimore D
Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142.
Nature. 1990 Apr 12;344(6267):678-82. doi: 10.1038/344678a0.
Nuclear factor kappa B (NF-kappa B), which was first detected by its binding to the kappa B site in the immunoglobulin kappa-gene enhancer, is important for the regulated expression of the kappa-gene and is partly responsible for the induction in appropriate cells of interleukin-2 (IL-2), IL-2 alpha receptor, beta-interferon and serum amyloid A protein. NF-kappa B is present as a nuclear DNA-binding protein in B lymphocytes and mature macrophages, but is found in the cytoplasm of many cells in a form unable to bind to DNA. The cytoplasmic form is bound to an inhibitor protein, I kappa B, from which it can be released in vitro by deoxycholate and other agents. Activation of cells by various agents, notably the phorbol esters that stimulate protein kinase C (PKC), leads to dissociation in vivo of the NF-kappa B/I kappa B complex and migration of NF-kappa B to the nucleus. Therefore, it acts as a second messenger system, transducing activation signals from the cytoplasm to the nucleus. To elucidate the mechanism of signal transfer, we have used an in vitro system in which addition of purified protein kinases to a partially purified NF-kappa B/I kappa B complex leads to the activation of the DNA-binding activity of NF-kappa B. Using gel retardation assays we found that PKC, cyclic AMP-dependent protein kinase (PKA) and a haem-regulated eIF-2 kinase (HRI) could activate NF-kappa B in vitro, whereas casein kinase II was ineffective. To determine the target for the protein kinases we purified and characterized both NF-kappa B and I kappa B and found that I kappa B is phosphorylated and inactivated in the presence of PKC and HRI but not PKA.
核因子κB（NF-κB）最初是因其与免疫球蛋白κ基因增强子中的κB位点结合而被发现的，它对于κ基因的调控表达很重要，并且部分负责在适当细胞中诱导白细胞介素-2（IL-2）、IL-2α受体、β干扰素和血清淀粉样蛋白A的表达。NF-κB在B淋巴细胞和成熟巨噬细胞中以核DNA结合蛋白的形式存在，但在许多细胞的细胞质中以无法与DNA结合的形式被发现。细胞质形式与一种抑制蛋白IκB结合，在体外可通过脱氧胆酸盐和其他试剂将其从IκB中释放出来。各种试剂，特别是刺激蛋白激酶C（PKC）的佛波酯对细胞的激活，导致体内NF-κB/IκB复合物的解离以及NF-κB向细胞核的迁移。因此，它作为一种第二信使系统，将激活信号从细胞质传递到细胞核。为了阐明信号传递的机制，我们使用了一种体外系统，在该系统中，向部分纯化的NF-κB/IκB复合物中添加纯化的蛋白激酶会导致NF-κB的DNA结合活性被激活。使用凝胶阻滞分析，我们发现PKC、环磷酸腺苷依赖性蛋白激酶（PKA）和血红素调节的真核起始因子2激酶（HRI）在体外可激活NF-κB，而酪蛋白激酶II则无效。为了确定蛋白激酶的作用靶点，我们对NF-κB和IκB进行了纯化和表征，发现IκB在PKC和HRI存在的情况下会被磷酸化并失活，但在PKA存在的情况下不会。
