RelA/p65翻译后修饰对NF-κB转录激活的影响

RelA/p65是NF-κB的一个亚单位,其翻译后修饰能够精细地调控NF-κB的转录激活,并在炎症反应及炎症反应相关疾病的发生和发展过程中发挥重要的作用. RelA的翻译后修饰主要包括磷酸化、乙酰化、甲基化以及泛素化等.这些翻译后修饰不仅能在生理和病理的条件下有效地调控NF-κB的转录激活,彼此之间还存在着复杂的相互作用,一种翻译后修饰可以使另一种修饰增强或是抑制,从而综合而完善地调控NF κB的转录活性.本文就近年来RelA的翻译后修饰及这些修饰之间的相互作用对NF-κB信号通路影响的最新研究进展进行综述.     

SIP蛋白调节p65核转位的作用机制

核因子κB（nuclear factor-κB, NF-κB）参与转录调控许多与细胞生长、凋亡、肿瘤形成和转移、胚胎发育及炎症反应相关的基因.它的二聚体与抑制蛋白结合,如抑制蛋白κB（IκBα,β或γ）,而被滞留在细胞质中处于失活状态.然而NF-κB是否还有其它的抑制因子目前还不清楚.本研究结果表明,SIP（steroid receptor coactivator, SRC,SRC-interacting protein）是NF-κB家族的一个新抑制因子,它通过PEST结构域与NF-κB家族的p65蛋白相互作用.当细胞处于静息状态时,SIP将p65蛋白隔离于细胞质中;当有刺激因子TNFα或IL-1作用时,SIP与p65解离继而使p65进入细胞核启动下游靶基因转录激活.该研究为进一步认识NF-κB介导基因转录调控机制和相关疾病的发生发展提供了重要的理论依据.     

抑制LRP16基因的表达显著下调TNF-α介导的NF-κB转录活性

LRP16是1个雌激素(E2)通过其受体α(ERα)诱导表达的靶基因.研究表 明,LRP16可以作为多种核受体（包括AR、ERα）的转录共激活因子.采用荧光素酶报 告检测显示,抑制LRP16基因表达显著削弱了TNF-α(10 ng/mL)介导的NF-κB转录活性;采用免疫荧光和Western印迹法研究抑制LRP16对NF-κB/p65亚基核转位的影响,结果显示,抑制LRP16表达并不能参与影响p65亚基核转位．上述结果提示,LRP16可能以核激活因子角色参与了NF-κB介导的信号途径．RT-PCR实验检测抑制LRP16基因表达对TNF-α诱导NF-κB靶基因调控作用,检测的靶基因包括IκB、A20、IL-8、 FLIP、XIAP.结果表明,在这些靶基因中只有XIAP、cIAP2产生了明显的下调趋势. 因此,LRP16是NF-κB的1个共激活因子,通过调控NF-κB与靶基因的结合能力,从而增强了NF-κB的转录活性.     

TNFα诱导激活NF-κB上调抑癌基因CDKN2B表达

NF-κB通过转录调控其靶基因,在肿瘤发生发展和精准治疗中起关键作用。过表达抑癌基因细胞周期蛋白依赖性激酶抑制剂2B（CDKN2B）可抑制肿瘤细胞增殖并诱导凋亡,但是否受NF-κB调节尚无报道。本文发现,NF-κB直接结合并上调CDKN2B基因：在TNFα处理的HeLa细胞内,CDKN2B的基因区覆盖大量NF-κB结合峰,其中富集倍数大于20的结合峰有14个。TRANSFAC软件分析发现,NF-κB结合峰内包含大量经典的κB位点。ChIP-qPCR证明,TNFα诱导NF-κB结合CDKN2B基因。将NF-κB结合峰中心区DNA片段插入荧光素酶报告基因载体中,发现该DNA片段的插入使荧光素酶相对活性上调至7.88倍,TNFα处理又使其相对活性提高到2.37倍,且NF-κB/p65 siRNA显著干扰其相对活性的升高。免疫荧光检测显示,TNFα诱导激活NF-κB进入细胞核,而NF-κB/p65 siRNA阻止它入核。此结果提示,我们成功构建了具有NF-κB转录活性差异的细胞模型,qPCR检测两个已知的NF-κB靶基因NFKB2和STAT5A的表达,进一步验证该细胞模型构建成功。利用此细胞模型,发现受TNFα诱导激活的NF-κB,能够上调CDKN2B基因。总之,本文发现抑癌基因CDKN2B是NF-κB新的靶基因,NF-κB直接结合并上调CDKN2B基因在转录水平的表达。本研究为抑癌基因CDKN2B的抗肿瘤应用奠定了基础。     

p53对乳腺癌耐药蛋白基因的转录调控

乳腺癌耐药蛋白（breast cancer resistance protein,BCRP）是ATP结合盒转运蛋白超家族成员之一,其通过主动外排化疗药物如米托蒽醌、托泊替康和甲氨蝶呤,进而介导肿瘤化疗耐受. 最近有研究发现,在野生型p53（wild type p53, wt-p53）低表达的乳腺癌细胞系MCF-7中,外源性wt-p53通过抑制核转录因子-κB （nuclear factor-κB, NF-κB）的活性进而抑制BCRP的表达,但其详细的分子机制有待进一步阐明. 本研究选用p53缺失的骨肉瘤细胞系Saos-2,通过瞬时转染技术发现,wt-p53可以激活BCRP的表达,而突变型p53的激活作用消失;报告基因试验显示,wt-p53可以上调BCRP启动子活性;通过生物信息学软件MatInspector对BCRP启动子区进行预测,未发现p53结合元件;同时,通过转染IκB抑制Saos-2细胞中NF-κB的活性后发现,Saos-2细胞中NF-κB活性越低,p53对BCRP启动子的激活作用越弱甚至完全消失. 上述结果提示,p53对Saos-2细胞中BCRP的激活作用是NF-κB依赖性的.     

脂质过氧化物酶体增殖物激活受体在心脏生理与病理中的作用

心肌能量代谢状况是其结构与功能的重要决定因素,调节能量代谢是心脏疾病的有效疗法之一.脂质过氧化物酶体增殖物激活受体(PPARs)是一组具有复杂功能的核受体超家族成员,与脂肪形成、糖脂代谢、炎症及肿瘤发生等多种生物过程有关.PPARs可通过调控编码脂肪酸与糖类氧化相关酶的基因转录而调节心肌代谢,在心脏多种疾病病理过程中其表达与活性均有明显变化,因此已被作为心脏病的治疗靶点之一.本文对PPARs在心脏生理与病理中的作用进行简要介绍.     

动物抗低氧胁迫相关基因的表达调控机制

体内氧浓度的稳定是机体维持自身功能的一个必要条件。在低氧条件下,机体内部在低氧信号的刺激下形成一个强大的防御体系以保护自己的组织。在采取防御的过程中,低氧诱导因子-1 (hypoxia inducible factor-1,HIF-1)、血管内皮生长因子(vascular endothelial growth factor, VEGF)、促红细胞生成素(erythropoietin, EPO)、核因子-κB (nuclear factor-κB, NF-κB)等基因表达上调。HIF-1是一个与低氧胁迫相关的转录因子,它的激活与体内氧浓度相关。VEGF是HIF-1下游的一个靶基因,它是至今发现的一个在促血管新生方面起着最关键作用的因子。NF-κB能够抑制由低氧引起的细胞凋亡。以上这些基因在动物抗低氧胁迫方面起着重要作用,综述了低氧条件下HIF-1、VEGF、EPO、NF-κB的功能、表达特性以及调控机制。     

EWS蛋白质抑制核因子κB的转录活性

目的:研究EWS蛋白质是否参与核因子κB(NF-κB)信号通路,以及EWS蛋白质对NF-κB转录活性的影响。方法:在真核细胞中表达Flag-EWS,利用Western印迹检测其表达;通过双萤光素酶光报告系统,研究EWS蛋白质对NF-κB转录活性的影响及其发挥作用的分子水平。结果:Western印迹检测到相对分子质量为95×103的Flag-EWS能够在真核细胞中正确表达,过表达EWS蛋白质能够抑制TNFα、IL-1β及poly(I:C)激活的NF-κB转录活性;EWS蛋白质能够抑制由过表达HA-TRAF2或HA-p65激活的NF-κB转录活性,其抑制NF-κB转录活性发生在p65转录因子水平。结论:过表达EWS能够抑制多种刺激激活的NF-κB转录活性,这种抑制作用发生在p65转录因子水平。     

离心力和剪应力应答蛋白1是肿瘤坏死因子受体1的新调控因子

离心力和剪应力应答基因1(responsive to centrifugal force and shear stress gene 1,RECS1)被剔除的小鼠易患囊性内侧坏死和动脉扩张症,伴随着血管组织基质金属蛋白酶9表达水平的增强.本室前期研究发现,稳定表达RECS1的小鼠成纤维细胞对肿瘤坏死因子受体2激动性抗体的敏感性被明显弱化,显示RECS1参与肿瘤坏死因子信号的调控.本文研究了RECS1对肿瘤坏死因子受体1（tumor necrosis factor receptor-1, TNFR1）的调控作用.结果显示,RECS1结合TNFR1,并抑制过量表达TNFR1诱导的核转录因子-κB (NF-κB)活化.缺失突变研究发现,RECS1分子上有NPLY和SPEDY两个模体是其抑制TNFR1信号所必需的.免疫共沉淀实验发现,NPLY是RECS1与TNFR1结合所必需的.而SPEDY的缺失不影响RECS1与TNFR1的结合.另外,免疫共染色实验显示,RECS1与TNFR1共定位于细胞内核体.这些实验结果进一步揭示了RECS1负调控肿瘤坏死因子-α(tumor necrosis factor-α, TNF-α)信号进而参与调控血管发育与重塑的生物功能及可能机理.     

TXLNA enhances TBK1 phosphorylation by suppressing PPM1B recruitment

In recent years, there has been a notable increase in cancer incidence and mortality, and immune abnormalities have been closely linked to malignancy development. TANK-binding kinase 1 (TBK1) is a non-classical IκB kinase that regulates interferon and NF-κB signaling pathways and plays a crucial role in innate immunity. Recent studies have shown high expression levels of TBK1 and increased activity in various tumor cells, suggesting its involvement in the development and progression of multiple cancers. Targeting TBK1 for tumor therapy may be a possibility. However, little is known about the abnormal activation and dynamic regulation of TBK1 in cancer. First, we utilized the BioID biotinylation technique combined with TMT-based quantitative proteomics to analyze the TBK1 interacting proteins. Our results revealed that TXLNA interacts with TBK1 and binds to the α-helical scaffold of TBK1. The expression of TXLNA could affect the S172 phosphorylation of TBK1. PPM1B is a phosphatase that can dephosphorylate TBK1 S172, so we used the APEX2 proximity labeling technique combined with TMT-based quantitative proteomics to explore the interacting proteins of PPM1B and search for the regulatory pathway of TXLNA on TBK1 phosphorylation. We found that PPM1B interacts with TXLNA. Based on these results, we further found that TXLNA impairs the binding of PPM1B to TBK1, inhibiting the dephosphorylation of TBK1 and contributing to the abnormal enhancement of TBK1 activity in cancer cells. This study sheds light on the potential mechanism of aberrant activation and dynamic regulation of TBK1 in tumors and provides a potential target for tumor therapy.     

Impact of bile acids on the growth of human cholangiocarcinoma via FXR

Mast cell activation disease comprises disorders characterized by accumulation of genetically altered mast cells and/or abnormal release of these cells' mediators, affecting functions in potentially every organ system, often without causing abnormalities in routine laboratory or radiologic testing. In most cases of mast cell activation disease, diagnosis is possible by relatively non-invasive investigation. Effective therapy often consists simply of antihistamines and mast cell membrane-stabilising compounds supplemented with medications targeted at specific symptoms and complications. Mast cell activation disease is now appreciated to likely be considerably prevalent and thus should be considered routinely in the differential diagnosis of patients with chronic multisystem polymorbidity or patients in whom a definitively diagnosed major illness does not well account for the entirety of the patient's presentation.     

Cyclic Stretch Induces Inflammatory Cytokines via the Oxidative Stress and NF-ΚB Pathways Activation in Human Keratoconic Fibroblasts

The cornea is a load-bearing tissue. Lower biomechanical properties in the local tissue of keratoconic cornea evoke mechanical stress increase. Inflammatory cytokines have been shown to be over-expressed in patients with keratoconus. However, how mechanical stimuli are involved in the production of inflammatory cytokines in keratoconus remains unclear. The objective of the study is to determine the role of mechanical stretch in the regulation of inflammatory cytokines and the underlying mechanisms in keratoconus. Human keratoconic fibroblasts (hKCFs) were subjected to 12% cyclic mechanical stretch at 0.1 Hz or in static conditions as controls. N-acetyl cysteine (NAC) and pyrrolidine dithiocarbamate and pyrrolidine dithiocarbamate (PDTC) were used to inhibit reactive oxygen species (ROS) production and NF-κB pathway respectively. ROS production was measured using 2’,7’-dichlorodihydrofluorescindiacetate probe. Conditioned media and cell lysates were collected for protein assessment. Cyclic stretch-induced a higher production of intercellular cell adhesion molecule-1 (ICAM-1), tumor necrosis factor α (TNF-α), interleukin (IL)-6, and IL-8 in hKCFs than static controls. ROS was also elevated in response to cyclic stretch. Inhibition of ROS or NF-κB attenuated stretch-induced ICAM-1, TNF-α, IL-6, and IL-8. Inhibition of stretch-induced ROS production by NAC also attenuated NF-κB activation. Our findings suggest that mechanical stretch may induce the release of inflammatory cytokines by activating oxidative stress and NF-kB pathway, and ROS may positively control NF-κB signaling. Over-expression of inflammatory cytokines induced by mechanical stretch may play a role in progression of keratoconus.     

TSA通过抑制STAT1磷酸化与核转位下调人肝癌细胞HepG2内 IDO的表达

目的:研究曲古抑菌素A (Trichostatin A, TSA)下调γ干扰素(interferon-gamma, IFN-γ)诱导的人肝癌细胞HepG2内吲哚胺2, 3-双加氧酶(indoleamine 2, 3-dioxygenase, IDO)表达的分子机制。方法: Western blot 检测TSA在IFN-γ诱导的HepG2细胞中IDO的表达、信号转导及转录激活子1(STAT1)的磷酸化和干扰素调节因子1(IRF-1)的诱导表达情况。用免疫细胞化学法检测TSA处理HepG2细胞后对IDO表达的影响。流式细胞术分析TSA处理后IFN-γ受体2表达量的变化,进一步在激光共聚焦显微镜下观察TSA对STAT1核转位的影响,利用双荧光素酶报告基因系统检测TSA对IFN-γ激活位点(γ-activated sites, GAS)、干扰素刺激应答元件(interferon stimulated response elements, ISRE)和核因子-κB (NF-κB)的激活的影响。结果:TSA以剂量依赖方式下调HepG2细胞内IFN-γ诱导的IDO表达、能明显抑制STAT1第701位酪氨酸的磷酸化和STAT1的核转位,但是上调IFN-γ受体2受体的表达。双荧光素酶报告基因分析和Western blot结果表明:TSA能显著抑制GAS和IRF-1 的激活却不能抑制NF-κB和ISRE的激活。 结论:TSA能下调IFN-γ诱导的HepG2细胞中IDO的表达,其机制可能是与其抑制STAT1的磷酸化和核转位,以及抑制STAT1与GAS的结合有关,而不是通过下调IFN-γ受体的表达来实现的。