AIRE functions as an E3 ubiquitin ligase

Autoimmune regulator (AIRE) gene mutation is responsible for the development of autoimmune-polyendocrinopathy-candidiasis ectodermal dystrophy, an organ-specific autoimmune disease with monogenic autosomal recessive inheritance. AIRE is predominantly expressed in medullary epithelial cells of the thymus and is considered to play important roles in the establishment of self-tolerance. AIRE contains two plant homeodomain (PHD) domains, and the novel role of PHD as an E3 ubiquitin (Ub) ligase has just emerged. Here we show that the first PHD (PHD1) of AIRE mediates E3 ligase activity. The significance of this finding was underscored by the fact that disease-causing missense mutations in the PHD1 (C311Y and P326Q) abolished its E3 ligase activity. These results add a novel enzymatic function for AIRE and suggest an indispensable role of the Ub proteasome pathway in the establishment of self-tolerance, in which AIRE is involved.     

E3泛素连接酶1对SOX2蛋白稳定性的影响

目的 探讨WW结构域的E3泛素蛋白连接酶1(WWP1)和E3泛素蛋白连接酶2(WWP2)对3种转录因子[八聚体结合转录因子4(OCT4)、性别决定区Y-box蛋白2(SOX2)和NANOG蛋白]水平的影响.方法 通过质粒转染,在HEK 293FT细胞中分别共表达OCT4、SOX2、NANOG和WWP1或WWP2.通过免...     

Atrogin-1/muscle atrophy F-box inhibits calcineurin-dependent cardiac hypertrophy by participating in an SCF ubiquitin ligase complex

Calcineurin, which binds to the Z-disc in cardiomyocytes via alpha-actinin, promotes cardiac hypertrophy in response to numerous pathologic stimuli. However, the endogenous mechanisms regulating calcineurin activity in cardiac muscle are not well understood. We demonstrate that a muscle-specific F-box protein called atrogin-1, or muscle atrophy F-box, directly interacts with calcineurin A and alpha-actinin-2 at the Z-disc of cardiomyocytes. Atrogin-1 associates with Skp1, Cul1, and Roc1 to assemble an SCF(atrogin-1) complex with ubiquitin ligase activity. Expression of atrogin-1 decreases levels of calcineurin A and promotes its ubiquitination. Moreover, atrogin-1 attenuates agonist-induced calcineurin activity and represses calcineurin-dependent transactivation and NFATc4 translocation. Conversely, downregulation of atrogin-1 using adenoviral small interfering RNA (siRNA) expression enhances agonist-induced calcineurin activity and cardiomyocyte hypertrophy. Consistent with these cellular observations, overexpression of atrogin-1 in hearts of transgenic mice reduces calcineurin protein levels and blunts cardiac hypertrophy after banding of the thoracic aorta. These studies indicate that the SCF(atrogin-1) ubiquitin ligase complex interacts with and represses calcineurin by targeting calcineurin for ubiquitin-mediated proteolysis, leading to inhibition of cardiac hypertrophy in response to pathologic stimuli.     

肝内胆管细胞癌中E3泛素化连接酶UHRF2的表达及临床意义

目的:探讨E3泛素化连接酶UHRF2在肝内胆管细胞癌(intrahepatic cholangiocarcinoma,ICC)中的表达及其临床意义。方法:采用免疫组织化学法检测UHRF2在138例ICC患者癌组织中的表达,分析其与ICC患者预后及临床病理特征的关系。结果:UHRF2在ICC组织中表达上调。UHRF2在不同甲胎蛋白(AFP)水平(P=0.010)、肿瘤分化程度(P=0.026)、淋巴结转移情况(P=0.001)、TNM分期(P=0.019)患者中差异均有统计学意义。UHRF2高表达组患者5年生存率低于低表达组,5年累计复发率高于低表达组(P0.001)。多因素分析提示UHRF2是ICC的预后指标(P0.05)。结论:UHRF2表达与ICC恶性程度正相关,可作为ICC患者预后和术后复发的预测指标。     

The E3 ubiquitin ligase Mule acts through the ATM-p53 axis to maintain B lymphocyte homeostasis

Cellular homeostasis is controlled by pathways that balance cell death with survival. Mcl-1 ubiquitin ligase E3 (Mule) is an E3 ubiquitin ligase that targets the proapoptotic molecule p53 for polyubiquitination and degradation. To elucidate the role of Mule in B lymphocyte homeostasis, B cell-specific Mule knockout (BMKO) mice were generated using the Cre-LoxP recombination system. Analysis of BMKO mice showed that Mule was essential for B cell development, proliferation, homeostasis, and humoral immune responses. p53 transactivation was increased by two- to fourfold in Mule-deficient B cells at steady state. Genetic ablation of p53 in BMKO mice restored B cell development, proliferation, and homeostasis. p53 protein was increased in resting Mule-deficient mouse embryonic fibroblasts (MEFs) and embryonic stem (ES) cells. Loss of Mule in both MEFs and B cells at steady state resulted in increased levels of phospho-ataxia telangiectasia mutated (ATM) and the ATM substrate p53. Under genotoxic stress, BMKO B cells were resistant to apoptosis, and control MEFs exhibited evidence of a physical interaction between Mule and phospho-ATM. Phospho-ATM, phospho-p53, and Brca1 levels were reduced in Mule-deficient B cells and MEFs subjected to genotoxic stress. Thus, Mule regulates the ATM-p53 axis to maintain B cell homeostasis under both steady-state and stress conditions.     

去神经支配骨骼肌萎缩的多种治疗

背景:骨骼肌去神经支配后出现肌萎缩和收缩功能的丧失,肌纤维发生与萎缩相关的一系列的形态学和组织学的变化.近年来随着技术水平及理论研究的进展,治疗效果有了较大的提高,但仍未达到满意的效果.目的:总结并讨论近年来有关去神经支配骨骼肌萎缩的治疗新进展,为肌肉功能的恢复提供理论基础.方法:由第一作者用计算机检索中国期刊全文数据库(CNKI:2000/2010)和Medline数据库(2000/2010),检索词分别为"去神经支配,骨骼肌,肌萎缩,治疗"和"denervated,skeletal muscles,atrophy,treatment".共检索到135篇文章,按纳入和排除标准对文献进行筛选,共纳入30篇文章,从物理治疗、神经修复和植入、细胞移植、药物、基因和中药治疗等方面进行总结和分析.结果与结论:近年来去神经支配骨骼肌的治疗取得了很大进展,但这些方法只能在一定程度上缓解骨骼肌萎缩,在一段时间内维持肌肉的生理功能.目前研究随着去神经支配骨骼肌萎缩机制的阐明,针对性的治疗措施将会取得更好的效果.     

去神经支配骨骼肌萎缩的多种治疗

背景：骨骼肌去神经支配后出现肌萎缩和收缩功能的丧失,肌纤维发生与萎缩相关的一系列的形态学和组织学的变化。近年来随着技术水平及理论研究的进展,治疗效果有了较大的提高,但仍未达到满意的效果。目的：总结并讨论近年来有关去神经支配骨骼肌萎缩的治疗新进展,为肌肉功能的恢复提供理论基础。方法：由第一作者用计算机检索中国期刊全文数据库（CNKI：2000/2010）和Medline数据库（2000/2010）,检索词分别为＂去神经支配,骨骼肌,肌萎缩,治疗＂和＂denervated,skeletal muscles,atrophy,treatment＂。共检索到135篇文章,按纳入和排除标准对文献进行筛选,共纳入30篇文章,从物理治疗、神经修复和植入、细胞移植、药物、基因和中药治疗等方面进行总结和分析。结果与结论：近年来去神经支配骨骼肌的治疗取得了很大进展,但这些方法只能在一定程度上缓解骨骼肌萎缩,在一段时间内维持肌肉的生理功能。目前研究随着去神经支配骨骼肌萎缩机制的阐明,针对性的治疗措施将会取得更好的效果。     

电针对失神经骨骼肌萎缩及纤维化的影响

目的:观察不同强度电针对失神经支配骨骼肌萎缩及肌纤维化的影响。方法:32只SD大鼠随机等分为4组(n=8):A组(模型组)、B组(0.5m A电针组)、C组(1.0m A电针组)、D组(1.5m A电针组)。切断坐骨神经干造成失神经支配腓肠肌模型,术后1天,B、C、D组术侧分别给予相应强度电针(针刺"足三里"和"承山")治疗,每次治疗10min,隔天1次,每周3次,共治疗4周,A组不行治疗。术后8周,测定术侧腓肠肌湿重比,Masson染色测定腓肠肌结缔组织截面积率、肌纤维直径和截面积,Western blot检测转化生长因子β1(transforming growth factorβ1,TGF-β1)、结缔组织生长因子(connective tissue growth factor,CTGF)、Bcl-2和Bax表达,透射电镜观察腓肠肌超微结构。结果:A组与B、C、D组间,D组与B、C组间腓肠肌湿重比差异均有显著性意义(P0.05),但B、C组间差异无显著性意义(P0.05)。A组与B、C、D组间,以及D组与B、C组间结缔组织截面积率差异均有显著性意义(P0.05),但B、C组间差异无显著性意义(P0.05)。A组与B、C、D组间,以及B、C、D组间肌纤维直径和截面积差异均有显著性意义(P0.01)。A组最高、D组最低,A组与B、C、D组间,以及B、C、D组间TGF-β1、CTGF蛋白表达差异均有显著性意义(P0.01)。Bcl-2蛋白表达,A组最低、D组最高,而Bax蛋白表达,A组最高、D组最低;Bcl-2/Bax比值A组最低,B、C、D组依次升高,且A组与C、D组间,以及B、C、D组间差异均有显著性意义(P0.01)。透射电镜显示,A组肌丝排列紊乱、溶解严重,Z线断裂,线粒体空泡化;B、C、D组肌丝排列基本整齐,肌丝溶解、Z线断裂较轻,B组可见线粒体肿胀、空泡化,但轻于A组。结论:电针可减轻失神经骨骼肌萎缩程度,其机制可能与抑制靶肌肉结缔组织增生,调节Bcl-2、Bax蛋白表达有关。     

骨骼肌萎缩的细胞分子机制与抗萎缩运动模式

目的:回顾骨骼肌萎缩细胞分子机制的研究进展,抗萎缩运动模式和药物干预对骨骼肌萎缩的疗效及机制。资料来源:应用计算机检索PubMed数据库1988-03/2007-03相关骨骼肌萎缩的文献,检索词"skeletal muscle,atrophy,exercise,ubiquitin-proteasome,apoptosis",限定文献语言种类为英文。同时计算机检索万方数据库2002-03/2005-05相关骨骼肌萎缩的文献,检索词"骨骼肌,细胞凋亡,运动",限定文章语言种类为中文。资料选择:对资料进行初审,选取包括骨骼肌萎缩的文献,开始查找全文。纳入标准:涉及骨骼肌萎缩的蛋白质泛化、细胞凋亡、抗萎缩运动、药物干预的文章。排除标准:不涉及上述项目。资料提炼:共检索到61篇关于骨骼肌萎缩的文献,最终纳入33篇符合标准的文献。资料综合:骨骼肌萎缩有衰老性、废用性和病理性3种。去神经支配的动物模型有助于从细胞分子水平认识骨骼肌萎缩,蛋白质同化/泛化研究、细胞增殖/凋亡研究从不同角度揭示了骨骼肌萎缩的机制。废用性模型为开发抗萎缩药物和验证抗萎缩运动模式提供了研究平台,但尚缺少一致性结论,运动抵抗/延缓肌肉萎缩的效应体现于结构蛋白基因表达、细胞信号转导、激素、细胞因子等各个层面。在运动抗萎缩治疗中,药物与物理疗法的辅助作用也不可忽略。结论:骨骼肌萎缩的细胞分子机制与蛋白质泛化和细胞凋亡过甚密切相关,运动抵抗/延缓肌肉萎缩的效应体现于相应的细胞分子水平,药物和理疗对骨骼肌萎缩有一定疗效,但机制不明。     

失神经支配骨骼肌的萎缩机制

目的:探索失神经支配骨骼肌萎缩的机制已经成为21世纪周围神经领域内的重要任务和研究热点。就血管床重塑、肌细胞凋亡、肌卫星细胞耗竭及成肌因子调控等四个方面对该领域做一归纳。资料来源:应用计算机检索Medline数据库1990-01/2005-01期间的相关文章,检索词为“denervation,muscle atrophy,histology,ultrastructure,motorend-plate,RT-PCRMyoD,myogenin,myostatin,immunohistochemistry,apoptosis”,限定文章语言种类为英文。同时计算机检索中国期刊全文数据库1990-01/2005-01期间的相关文章,检索词“失神经,肌萎缩,形态学,运动终板,超微结构,免疫组化,凋亡”,限定文章语言种类为中文。资料选择:对约330篇文献资料进行初审,纳入研究失神经支配骨骼肌萎缩机制的文献;随机、对照和盲法等论证推荐的文章。排除综述类及重复研究。资料提炼:共收到50余篇关于失神经支配骨骼肌萎缩机制的相关文章。排除20篇综述类及重复研究,对符合标准的27篇文献进行分析。资料综合:失神经支配骨骼肌萎缩机制的研究是多角度、多方面的。血管床重塑、肌细胞凋亡、肌卫星细胞耗竭及成肌因子调控等都是其中重要的作用因素。目前仍不能明确在整个失神经肌萎缩的发生中,是各种因素共同起作用,还是其中哪种因素起主导作用,抑或还有别的什么因素,这些尚待深入研究。结论:血管床重塑、肌细胞凋亡、肌卫星细胞耗竭及成肌因子调控等是骨骼肌失神经支配以后发生萎缩的重要机制。     

Inactivation of SAG/RBX2 E3 ubiquitin ligase suppresses KrasG12D-driven lung tumorigenesis

Cullin-RING ligases (CRLs) are a family of E3 ubiquitin ligase complexes that rely on either RING-box 1 (RBX1) or sensitive to apoptosis gene (SAG), also known as RBX2, for activity. RBX1 and SAG are both overexpressed in human lung cancer; however, their contribution to patient survival and lung tumorigenesis is unknown. Here, we report that overexpression of SAG, but not RBX1, correlates with poor patient prognosis and more advanced disease. We found that SAG is overexpressed in murine Kras^G12D-driven lung tumors and that Sag deletion suppressed lung tumorigenesis and extended murine life span. Using cultured lung cancer cells, we showed that SAG knockdown suppressed growth and survival, inactivated both NF-κB and mTOR pathways, and resulted in accumulation of tumor suppressor substrates, including p21, p27, NOXA, and BIM. Importantly, growth suppression by SAG knockdown was partially rescued by simultaneous knockdown of p21 or the mTOR inhibitor DEPTOR. Treatment with MLN4924, a small molecule inhibitor of CRL E3s, also inhibited the formation of Kras^G12D-induced lung tumors through a similar mechanism involving inactivation of NF-κB and mTOR and accumulation of tumor suppressor substrates. Together, our results demonstrate that Sag is a Kras-cooperating oncogene that promotes lung tumorigenesis and suggest that targeting SAG-CRL E3 ligases may be an effective therapeutic approach for Kras-driven lung cancers.     

E3 ubiquitin ligase CHIP facilitates Toll-like receptor signaling by recruiting and polyubiquitinating Src and atypical PKC{zeta}

The carboxyl terminus of constitutive heat shock cognate 70 (HSC70)-interacting protein (CHIP, also known as Stub1) is a U box-containing E3 ubiquitin ligase that is important for protein quality control. The role of CHIP in innate immunity is not known. Here, we report that CHIP knockdown inhibits Toll-like receptor (TLR) 4- and TLR9-driven signaling, but not TLR3-driven signaling; proinflammatory cytokine and type 1 interferon (IFN) production; and maturation of antigen-presenting cells, including macrophages and dendritic cells. We demonstrate that CHIP can recruit the tyrosine kinase Src and atypical protein kinase C ζ (PKCζ) to the TLR complex, thereby leading to activation of IL-1 receptor-associated kinase 1, TANK-binding kinase 1, and IFN regulatory factors 3 and 7. CHIP acts as an E3 ligase for Src and PKCζ during TLR signaling. CHIP-mediated enhancement of TLR signaling is inhibited by IFNAR deficiency or expression of ubiquitination resistant mutant forms of Src or PKCζ. These findings suggest that CHIP facilitates the formation of a TLR signaling complex by recruiting, ubiquitinating, and activating Src and PKCζ.     

成人型脊髓性肌萎缩症的骨骼肌病理与肌萎缩的关系

背景:脊髓性肌萎缩症是运动神经元疾病中病变仅影响下运动神经元的一组疾病。成人型少见,目前对其研究较少。目的:总结成人型脊髓性肌萎缩症骨骼肌病理学特征。设计:以诊断为依据的回顾性研究。地点和对象:收集1998-02/2002-02在解放军第八一医院南京医学院第二附属医院和南京军区总医院经肌肉活检确诊的、有完整临床资料的门诊和住院患者共46例。方法:结合临床特征及病理学改变进行分析。主要观察指标:病史、家族史、完整体格检查、相关血液及血生化、肌电图和肌肉活检。结果:临床表现为进行性对称性肢体近端肌萎缩,肌无力,实验室检查血肌酸磷酸肌酶12例中轻度升高,肌电图检查2例正常,3例呈轻度肌源性损害,余37例呈神经元性损害,肌活检主要为小群性肌萎缩,腺苷三磷酸酶染色见同型肌群化及肌纤维代偿性肥大。结论:肌活检对成人型脊髓性肌萎缩症具有诊断和鉴别诊断意义。适当、持久的康复锻炼可能对维持患者的运动功能有帮助。     

Disruption of either the Nfkb1 or the Bcl3 gene inhibits skeletal muscle atrophy

The intracellular signals that mediate skeletal muscle protein loss and functional deficits due to muscular disuse are just beginning to be elucidated. Previously we showed that the activity of an NF-kappaB-dependent reporter gene was markedly increased in unloaded muscles, and p50 and Bcl-3 proteins were implicated in this induction. In the present study, mice with a knockout of the p105/p50 (Nfkb1) gene are shown to be resistant to the decrease in soleus fiber cross-sectional area that results from 10 days of hindlimb unloading. Furthermore, the marked unloading-induced activation of the NF-kappaB reporter gene in soleus muscles from WT mice was completely abolished in soleus muscles from Nfkb1 knockout mice. Knockout of the B cell lymphoma 3 (Bcl3) gene also showed an inhibition of fiber atrophy and an abolition of NF-kappaB reporter activity. With unloading, fast fibers from WT mice atrophied to a greater extent than slow fibers. Resistance to atrophy in both strains of knockout mice was demonstrated clearly in fast fibers, while slow fibers from only the Bcl3(-/-) mice showed atrophy inhibition. The slow-to-fast shift in myosin isoform expression due to unloading was also abolished in both Nfkb1 and Bcl3 knockout mice. Like the soleus muscles, plantaris muscles from Nfkb1(-/-) and Bcl3(-/-) mice also showed inhibition of atrophy with unloading. Thus both the Nfkb1 and the Bcl3 genes are necessary for unloading-induced atrophy and the associated phenotype transition.