IκBL：IκB家族的成员之一？

IκB家族是一组能够与转录因子NF-κB直接结合并调节NF-κB活力的蛋白.IκB蛋白结构上的普遍特点是拥有负责与NF-κB结合的多个锚蛋白(ankyrin)重复序列.IκBL包含ankyrin的重复序列并且能够抑制LPS诱导的NF-κB激活.然而,IκBL与NF-κB能否直接结合仍不确定.本文综述了IκB家族成员结构和功能上的特点,并分析了IκBL是否应被视为IκB家族成员之一.     

1,6-O,O-diacetylbritannilactones inhibits IκB kinase β-dependent NF-κB activation

To determine the chemical constituents responsible for pharmacological effects of Inula britannica-F., three specific sesquiterpene lactones in Inula britannica were isolated from chloroform extract and identified, including britannilactone (BL), 1-O-acetylbritannilactone (ABLO), and 1,6-O,O-diacetylbritannilactone (ABLOO). Electrophoretic mobility shift assay (EMSA) was performed to detect the nuclear translocation of nuclear factor-κB (NF-κB) p65. The expressions of IκBα, pIκBα, inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), IκB kinase α/β (IKKα/β) and NF-κB kinase (NIK) were detected by Western blot and RT-PCR. We found that acetyl side groups enhanced the inhibitory action of the agents on LPS/IFN-γ-induced iNOS and COX-2 expression. Their inhibiting activity was positive correlation with the acetyl side group number. The effects of LPS/IFN-γ were reversed by ABLOO, and BL without acetyl side groups showed only a weak inhibitory action. Further study indicated that ABLOO markedly inhibited the phosphorylation of IKKβ down to based level, but not IKKα, corresponding with decreased in IκBα degradation and phosphorylation induced by LPS/IFN-γ, resulting in the suppression of NF-κB nuclear translocation and activity. These results suggest that the acetyl moieties add to the lipophilicity, and consequently enhance cellular penetration, so that ABLOO possess the most anti-inflammatory effect and may be a potent lead structure for the development of therapeutic and cytokine-suppressing remedies valuable for the treatment of various inflammatory diseases.     

IκB激酶的研究进展

ＩκＢ激酶的研究进展陈红清（中国医学科学院、中国协和医科大学皮肤病研究所,南京２１００４２关键词ＩκＢ激酶信号转导转录因子中κ基因结合核因子（ＮＦ－κＢ）由属于癌基因ｒｅｌ表达的Ｒｅｌ蛋白家族的２个亚基组成,最常见的形式是由ｐ６５（Ｒｅｌ－Ａ）和ｐ５...     

Inhibition of IκB kinase-β and IκB kinase-α by heterocyclic adamantyl arotinoids

We recently reported on a series of retinoid-related molecules containing an adamantyl group, a.k.a. adamantyl arotinoids (AdArs), that showed significant cancer cell growth inhibitory activity and activated RXRα (NR2B1) in transient transfection assays while devoid of RAR transactivation capacity. We have now explored whether these AdArs could also bind and inhibit IKKβ, a known target that mediates the induction of apoptosis and cancer cell growth inhibition by related AdArs containing a chalcone functional group. In addition, we have prepared and evaluated novel AdArs that incorporate a central heterocyclic ring connecting the adamantyl-phenol and the carboxylic acid at the polar termini. Our results indicate that the majority of the RXRα activating compounds lacked IKKβ inhibitory activity. In contrast, the novel heterocyclic AdArs containing a thiazole or pyrazine ring linked to a benzoic acid motif were potent inhibitors of both IKKα and IKKβ, which in most cases paralleled significant growth inhibitory and apoptosis inducing activities.     

Lipopolysaccharide-Induced NF-κB Activation in Human Endothelial Cells Involves Degradation of IκBα but Not IκBβ

We studied the signal transduction pathways involved in NF-κB activation and the induction of the cytoprotective A20 gene by lipopolysaccharide (LPS) in human umbilical vein endothelial cells (HUVEC). LPS induced human A20 mRNA expression with a maximum level 2 h after stimulation. The proteasome inhibitorN-acetyl-leucinyl-leucinyl-norleucinal-H (ALLN) and the tyrosine kinase inhibitor herbimycin A (HMA) blocked A20 mRNA expression and partially inhibited NF-κB DNA-binding activity induced by LPS treatment. LPS induced IκBα degradation at 30–60 min after treatment, but did not induce IκBβ degradation up to 120 min. In contrast, TNF-α rapidly induced IκBα degradation within 5 min and IκBβ degradation within 15 min. Cycloheximide did not prevent LPS-induced IκBα degradation, indicating that newly synthesized proteins induced by LPS were not involved in LPS-stimulated IκBα degradation. LPS-induced IκBα degradation was inhibited by ALLN, confirming that ALLN inhibits NF-κB activation by preventing IκBα degradation. Of note, HMA also inhibited LPS-induced IκBα degradation. However, tyrosine phosphorylation of IκBα itself was not elicited by LPS stimulation, suggesting that tyrosine phosphorylation of a protein(s) upstream of IκBα is required for subsequent degradation. We conclude that in HUVEC, LPS induces NF-κB-dependent genes through degradation of IκBα, not IκBβ, and propose that this degradation is induced in part by HMA-sensitive kinase(s) upstream of IκBα.     

IκB 激酶及相关信号转导研究进展

NF-κB（nuclear factor-κB）是一种广泛存在的核转录因子，它参 与多种基因的转录调控，与许多重要的生理病理过程关系密切。许多细胞外刺激可诱导NF- κB的活性，位点特异的NF-κB抑制蛋白（IκB）的磷酸化对于激活NF-κB有重要意义。I κK（IκB kinase）的发现为进一步了解NF-κB的功能和调控提供了线索。本文综述了Iκ K的结构、功能及相关信号转导研究进展。     

IκB激酶的结构和功能

ＮＦκＢ是细胞活化和产生细胞因子的重要转录调控因子。在静止细胞胞液中,ＮＦκＢ与ＩκＢ(κＢ的抑制剂)结合,处于失活状态。细胞活化传递的信号激活ＩκＢ激酶(ＩＫＫ),ＩＫＫ催化ＩκＢα(Ｓｅｒ32、Ｓｅｒ36)和ＩκＢβ(Ｓｅｒ19、Ｓｅｒ32)磷酸化,使ＩκＢ与ＮＦκＢ解离后被降解,于是ＮＦκＢ进入核内,调节多种基因转录[1]。1.ＩＫＫ的结构及其与功能的关系ＩＫＫ复合物的分子量约600～900ｋＤ,主要由3个亚单位组成:ＩＫＫα、ＩＫＫβ和ＩＫＫγ[2]。其中ＩＫＫα和ＩＫＫβ组成功能性异二聚体并以二聚体表现活性,在一定条件下(如…     

Mustard NPR1, a mammalian IκB homologue inhibits NF-κB activation in human GBM cell lines

NF-κB activity is tightly regulated by IκB class of proteins. IκB proteins possess ankyrin repeats for binding to and inhibiting NF-κB. The regulatory protein, NPR1 from Brassica juncea possesses ankyrin repeats with sequence similarity to IκBα subgroup. Therefore, we examined whether stably expressed BjNPR1 could function as IκB in inhibiting NF-κB in human glioblastoma cell lines. We observed that BjNPR1 bound to NF-κB and inhibited its nuclear translocation. Further, BjNPR1 expression down-regulated the NF-κB target genes iNOS, Cox-2, c-Myc and cyclin D1 and reduced the proliferation rate of U373 cells. Finally, BjNPR1 decreased the levels of pERK, pJNK and PKCα and increased the Caspase-3 and Caspase-8 activities. These results suggested that inhibition of NF-κB activation by BjNPR1 can be a promising therapy in NF-κB dependent pathologies.     

The IκB kinase complex in NF-κB regulation and beyond

The IκB kinase (IKK) complex is the signal integration hub for NF-κB activation. Composed of two serine-threonine kinases (IKKα and IKKβ) and the regulatory subunit NEMO (also known as IKKγ), the IKK complex integrates signals from all NF-κB activating stimuli to catalyze the phosphorylation of various IκB and NF-κB proteins, as well as of other substrates. Since the discovery of the IKK complex components about 15 years ago, tremendous progress has been made in the understanding of the IKK architecture and its integration into signaling networks. In addition to the control of NF-κB, IKK subunits mediate the crosstalk with other pathways, thereby extending the complexity of their biological function. This review summarizes recent advances in IKK biology and focuses on emerging aspects of IKK structure, regulation and function.     

Immune role of MrNFκBI-α, an IκB family member characterized in prawn M. rosenbergii

NF kappa B inhibitor alpha (MrNFκBI-α) was sequenced from a freshwater prawn Macrobrachium rosenbergii. The MrNFκBI-α protein contains a long ankyrin repeat region circular domain between 193 and 413 along with its 6 repeats (ankyrin repeat 1,2,3,4,5 and 6). An IκB degradation motif and a putative PEST motif is present at 37-64 and 418-471 of the N- and C-terminal regions of MrNFκBI-α respectively. The gene expressions of MrNFκBI-α in healthy and infectious hematopoietic and hypodermal necrosis virus (IHHNV), poly I:C, Aeromonas hydrophila and Enterococcus faecium injected M.?rosenbergii were examined using quantitative real time PCR. The MrNFκBI-α is expressed in all the tissues taken for examination and the highest is observed in hemocytes. The MrNFκBI-α gene expression is strongly up-regulated in hemocytes of prawn after IHHNV, poly I:C, A.?hydrophila and E.?faecium infection. This result indicates an important role of MrNFκBI-α in M.?rosenbergii immune system. This, however, remains to be verified by further studies.     

Beyond NF-κB activation: nuclear functions of IκB kinase α

IκB kinase (IKK) complex, the master kinase for NF-κB activation, contains two kinase subunits, IKKα and IKKβ. In addition to mediating NF-κB signaling by phosphorylating IκB proteins during inflammatory and immune responses, the activation of the IKK complex also responds to various stimuli to regulate diverse functions independently of NF-κB. Although these two kinases share structural and biochemical similarities, different sub-cellular localization and phosphorylation targets between IKKα and IKKβ account for their distinct physiological and pathological roles. While IKKβ is predominantly cytoplasmic, IKKα has been found to shuttle between the cytoplasm and the nucleus. The nuclear-specific roles of IKKα have brought increasing complexity to its biological function. This review highlights major advances in the studies of the nuclear functions of IKKα and the mechanisms of IKKα nuclear translocation. Understanding the nuclear activity is essential for targeting IKKα for therapeutics.     

Rel／NF—κB／IκB／IKK信号转导途径研究进展

真核细胞枋转导因子Ｒｅｌ／ＮＦ－κＢ家族广泛调控着自昆虫至人类的免疫和炎症反应中一系列基因的表达。静息状态下,ＮＦ－κＢ二聚体与抑制性蛋白ＩκＢ结合而存在于胞质中,当细胞受外源性刺激哩,ＮＦ－κＢ活化进入核内发挥其功能。目前,外源性信号活化ＮＦ－κＢ的机制已初步阐明,Ｒｅｌ／ＮＦ－κＢ／ＩκＢ／ＩＫＫ信号转导途径在蛋白质水平的相互调控,以及在肿瘤发生中的意义的研究也已获得一定进展。本文综述了近年来