BRCA1的泛素连接酶活性与肿瘤

乳腺癌易感基因1(BRCA1)是一种抑癌基因表达产物,参与许多重要的细胞生命过程如细胞周期调控、中心体复制、DNA损伤修复等。近来研究表明,BRCA1基因表达产物具有E3泛素连接酶活性,催化底物蛋白FANCD2、NPM、γ-Tubulin、RNAPII等及其自身的泛素化,从而调控众多生命过程的顺利进行,并且与肿瘤的发生发展密切相关。     

HACE1的生物学特性及其在恶性肿瘤的研究进展

HACE1不仅是一种重要的肿瘤抑制基因,通过介导细胞自噬、Rac1的泛素化等多种作用机制发挥重要的肿瘤抑制作用,而且还涉及到众多的生物学功能,在心脏保护、抗氧化应激和细胞学动力学等方面发挥着关键作用。HACE1基因表达下调或突变在人类多种恶性肿瘤的发生、侵袭转移等过程中扮演重要角色,且与预后密切相关。因此,HACE1可能成为肿瘤治疗的一个新靶标,为恶性肿瘤的治疗提供新的方向和机遇。     

E3泛素连接酶RNF216调控Th1型免疫应答促进肿瘤发生的研究

泛素-蛋白酶体蛋白降解系统是细胞内调控蛋白更新的重要机制,E3泛素连接酶是介导蛋白泛素化修饰的关键分子,可参与调控包括肿瘤发生的多种病理生理过程。E3泛素连接酶RNF216是否可调控肿瘤的发生发展尚不明确。本研究采用WT和RNF216基因缺陷型(RNF216-/-)小鼠,使用EO771乳腺癌细胞建立乳腺癌移植瘤模型,观察乳腺癌细胞在小鼠中的成瘤情况,以明确RNF216在肿瘤发生中的作用及其可能机制。实验结果表明乳腺癌细胞EO771在RNF216-/-小鼠中的成瘤情况和WT小鼠相比显著减小,而且存活率明显升高;腹腔注射CpG可抑制肿瘤的生长,在RNF216-/-小鼠中的抑瘤效果则显著增强。进一步研究表明在乳腺癌细胞EO771移植瘤小鼠模型中,和WT小鼠相比,CpG刺激RNF216-/-小鼠可显著诱导TNF-α、IFN-γ、IL-6等Th1型细胞因子的分泌,而Th2型细胞因子的变化不显著,这提示RNF216可能直接或者间接参与Th1型应答调控。可见,RNF216可通过调控Th1型免疫应答参与肿瘤的发生发展。     

泛素化在TRAF2介导的NF-κB信号通路中的作用

NF-κB(核因子κ增强子结合蛋白)是核转录因子家族成员,具有调节免疫、炎症和细胞存活的功能.它可被TRAF2(tumor necrosis factor receptor associated factor 2,肿瘤坏死因子受体相关因子2)等相关因子活化.TRAF2包含了N-端的环指结构域和C-端的高度保守结构域.它通过与肿瘤坏死因子受体超家族成员相互作用,介导了下游信号通路.而TRAF2的泛素化在过程中是关键的,鞘磷脂作为TRAF2的泛素化连接酶辅助因子,在TRAF2介导的NF-κB信号通路中发挥重要作用.     

细胞焦亡及相关疾病的研究进展

细胞焦亡是由Gasdermin蛋白介导的一种程序性炎性细胞死亡方式,分为依赖caspase-1的经典途径和依赖caspase-4/5/11的非经典途径。炎性小体的激活在此过程中扮演重要角色。细胞焦亡参与肾脏疾病、动脉粥样硬化、神经系统疾病、感染性疾病等的发生发展,并发挥重要作用。通过对细胞焦亡作用机制及相关疾病的研究,为临床疾病的防治提供新思路。     

低氧诱导因子—1与恶性肿瘤的研究进展

肿瘤发生、发展是一个克隆性选择的结果 ,癌基因的激活突变或抑癌基因的失活突变 ,导致HIF 1α的表达和 /或其活性升高 ,后者介导细胞对低氧的适应性反应 ,包括刺激新生血管形成和促进糖酵解过程 ,最终导致细胞在不断增生的同时获得转移和浸润的能力。     

蛋白质泛素化修饰及其在脓毒症中的研究进展

蛋白质在机体生命活动中扮演关键角色,其降解途径中,泛素-蛋白酶体途径(UPS)通过泛素化修饰调控蛋白降解,同时通过共价修饰底物蛋白参与细胞生理活动。去泛素化酶(DUBs)对蛋白质泛素化具有平衡作用,通过移除泛素化修饰来维持泛素化修饰的动态平衡,它们在脓毒症中发挥着关键作用,通过调控炎症因子的表达,影响机体的炎症反应。脓毒症是导致患者重症监护的主要疾病,涉及复杂炎症反应。蛋白质泛素化修饰参与脓毒症信号转导,影响核因子-κB(NF-κB)信号通路和NOD样受体蛋白3炎症小体(NLRP3)活化。这些调控机制影响细胞内炎症因子的释放,进而影响机体炎症反应的强度和时机。本文探讨了近年来与脓毒症相关关键蛋白的泛素化及去泛素化机制,以期为脓毒症的治疗提供新的靶点和策略。     

泛素羧基末端水解酶L3及其与疾病和肿瘤的相关性

去泛素化酶(deubiquitinating enzymes,DUBs)在调节细胞内稳态、细胞分化和凋亡等过程中,均扮演着重要角色。泛素羧基末端水解酶L3(ubiquitin C-terminal hydrolases L3,UCH-L3)是去泛素化酶家族中,半胱氨酸蛋白酶类的一种,可以催化靶蛋白短肽链上附着的多余的完整泛素分子的脱落,从而实现对靶蛋白的调控以及泛素分子的循环再利用。目前对该水解酶的研究还不充分,但其在多种疾病以及肿瘤中的高表达情况,说明在疾病、肿瘤发生发展中起着重要的作用。本文将针对该水解酶及其与疾病和肿瘤的相关性作一综述。     

SUMO4在甲状腺乳头状癌中的表达及临床意义

目的:探讨小泛素相关修饰因子4(SUMO4)表达与甲状腺乳头状癌(PTC)发生发展的关系。方法:采用real-time PCR、Western blot及免疫组化等方法检测PTC和正常甲状腺组织中SUMO4的mRNA及蛋白表达情况,对比研究SUMO4蛋白表达与PTC及其临床病理特征的关系。结果:SUMO4的mRNA及蛋白表达量在PTC中均明显高于正常甲状腺组织(P0.01)。结论:SUMO4在PTC的高表达提示其在PTC发生发展中扮演着重要的角色,可能与PTC发病的分子机制有关。     

头帕肿瘤综合征蛋白与肿瘤坏死因子受体介导的坏死样凋亡

头帕肿瘤综合征蛋白(cylindromatosis,CYLD)是一种去泛素化酶,其C-末端USP结构域具有催化功能,可移除受体相互作用蛋白激酶1(receptor interacting protein kinase 1,RIPK1)的K63连接泛素链,调节RIPK1的泛素化水平,从而参与调节肿瘤坏死因子受体1(tumor necrosis factor receptor 1, TNFR1)介导的RIPK依赖的细胞坏死样凋亡等病理生理过程。阐明CYLD对RIPK1去泛素化调节的详细机制,寻找针对CYLD的特异性抑制剂,可为与坏死样凋亡相关的损伤与疾病提供治疗的新策略。     

蛋白质SUMO化和泛素化修饰的关系

泛素化和SUMO化是蛋白质翻译后修饰的重要方式,广泛参与调节蛋白质功能和细胞生命活动各个环节.多聚泛素化降解蛋白质,而SUMO化主要调节蛋白质的相互作用和定位等.在不同情况下,SUMO化和泛素化既可协同调节蛋白质功能,也可相互拮抗. 最近研究发现,某些底物的SUMO化能够激活体内一类新发现的SUMO依赖的泛素连接酶,启动泛素-蛋白酶体途径降解底物, 导致蛋白质SUMO化和泛素化的关系进一步精细化和复杂化.     

Calpain 3 participates in sarcomere remodeling by acting upstream of the ubiquitin-proteasome pathway

Mutations in the non-lysosomal cysteine protease calpain 3 cause limb-girdle muscular dystrophy type 2A (LGMD2A). Our previous studies of the calpain 3 knockout mouse (C3KO) suggested a role for calpain 3 in sarcomere formation and remodeling. Calpain 3 may mediate remodeling by cleavage and release of myofibrillar proteins, targeting them for ubiquitination and proteasomal degradation. Loss of proper protein turnover may be the basis for this muscle disease. To test this hypothesis in vivo, we used an experimental model of hindlimb unloading and reloading that has been shown to induce sarcomere remodeling. We showed that the rate of atrophy and especially the rate of growth are decreased in C3KO muscles under conditions promoting sarcomere remodeling. In wild-type mice, an elevated level of ubiquitinated proteins was observed during muscle reloading, which is presumably necessary to remove atrophy-specific and damaged proteins. This increase in ubiquitination correlated with an increase in calpain 3 expression. C3KO muscles did not show any increase in ubiquitination at the reloading stage, suggesting that calpain 3 is necessary for ubiquitination and that it acts upstream of the ubiquitination machinery. We found upregulation of heat shock proteins in C3KO muscles following challenge with a physiological condition that requires highly increased protein degradation. Furthermore, old C3KO mice show evidence of insoluble protein aggregate formation in skeletal muscles. These studies suggest that accumulation of aged and damaged proteins can lead to cellular toxicity and a cell stress response in C3KO muscles, and that these characteristics are pathological features of LGMD2A.     

泛素连接酶LNX1促进外源PBK的泛素化和降解

 目的 研究LNX1对其相互作用蛋白PBK的泛素化和降解。方法 克隆、原核表达、纯化了一系列重组人LNX1截断体蛋白和LNX1全长蛋白;在体外泛素化体系中研究其对PBK的泛素化,哺乳动物细胞内研究其对外源PBK的泛素化和降解。结果 在体外泛素化体系中LNX1泛素化PBK,并研究了不同LNX1截断体对PBK泛素化的影响;发现在哺乳动物细胞内外源LNX1促进外源PBK的泛素化,进而导致其通过蛋白酶体降解。结论 研究发现了LNX1对外源PBK的泛素化和降解,为研究LNX1的生理功能提供了重要线索。     

Acute myelogenous leukemia-derived SMAD4 mutations target the protein to ubiquitin-proteasome degradation

Disruption of transforming growth factor-beta (TGFB1/TGF-beta) signaling contributes to the formation of human hematological malignancies. Smad4, a tumor suppressor, functions as an essential intracellular signal transducer of the TGF-beta signaling pathway. Recent studies have demonstrated that some tumor-derived mutations of Smad4 are associated with protein instability; however, the precise mechanism by which mutated Smad4 proteins undergo rapid degradation remains to be elucidated. A missense mutation of the SMAD4 gene in the Mad homology 1 (MH1) domain (c.305C>T, Pro102Leu) and one frameshift mutation resulting in termination in the Mad homology 2 (MH2) domain (c.1447_1448insAATA, Delta483-552) have been identified in acute myelogenous leukemia. It is not known whether protein instability of these SMAD4 mutants is one of the contributors to TGF-beta signaling disruption in acute myelogenous leukemia. Here we report that these two acute myelogenous leukemia-derived SMAD4 mutants are degraded rapidly when compared to their wild-type counterpart. We have demonstrated that both mutated proteins exhibit enhanced polyubiquitination (or polyubiquitylation) and proteasomal degradation. Importantly, we found that beta-transducin-repeat-containing protein 1 (beta-TrCP1), an F-box protein in the ubiquitin E3 ligase Skp1-Cullin-F-box protein (SCF) complex, directly interacts with and acts as a critical determinant for degradation of both mutated SMAD4 proteins. In addition, small interference RNA (siRNA)-triggered endogenous beta-TrCP1 suppression increased the protein expression level of both overexpressed SMAD4 mutants and endogenous mutated SMAD4 protein in acute myelogenous leukemia cells. These data suggest that mutated SMAD4 proteins undergo rapid degradation in acute myelogenous leukemia cells via SCF(beta-TrCP1) E3 ligase-mediated protein ubiquitination (or ubiquitylation) and subsequent proteasomal degradation.     

The c-Cbl proto-oncoprotein downregulates EBV LMP2A signaling

Latent membrane protein 2A (LMP2A) of Epstein-Barr virus (EBV) plays a key role in regulating viral latency and EBV pathogenesis by functionally mimicking signals induced by the B-cell receptor (BCR) altering normal B cell development. As c-Cbl ubiquitin ligase (E3) is a critical negative regulator in the BCR signal pathway, the role of c-Cbl in the function and formation of the LMP2A signalosome was examined. c-Cbl promoted LMP2A degradation through ubiquitination, specifically degraded the Syk protein tyrosine kinase in the presence of LMP2A, and inhibited LMP2A induction of the EBV lytic cycle. Our earlier studies indicated that LMP2A-dependent Lyn degradation was mediated by Nedd4-family E3s in LMP2A expressing cells. Combine with these new findings, we propose a model in which c-Cbl and Nedd4-family E3s cooperate to degrade target proteins at discrete steps in the function of the LMP2A signalosome.     

The ubiquitin-mediated proteolytic pathway as a therapeutic area

 Ubiquitin-mediated proteolysis is involved in the turnover of many short-lived regulatory proteins. This pathway leads to the covalent attachment of one or more multiubiquitin chains to target substrates which are then degraded by the 26S multicatalytic proteasome complex. Multiple classes of regulatory enzymes have been identified that mediate either ubiquitin conjugation or ubiquitin deconjugation from target substrates. Timed destruction of cellular regulators by the ubiquitin-proteasome pathway plays a critical role in ensuring normal cellular processes. This review provides multiple examples of key growth regulatory proteins whose levels are regulated by ubiquitin-mediated proteolysis. Pharmacological intervention which alters the half-lives of these cellular proteins may have wide therapeutic potential. Specifically, prevention of p53 ubiquitination (and subsequent degradation) in human papilloma virus positive tumors, and perhaps all tumors retaining wild-type p53 but lacking the retinoblastoma gene function, should lead to programmed cell death. Specific inhibitors of p27 and cyclin B ubiquitination are predicted to be potent antiproliferative agents. Inhibitors of IκB ubiquitination should prevent NFκB activation and may have utility in a variety of autoimmune and inflammatory conditions. Finally, we present a case for deubiquitination enzymes as novel, potential drug targets. Received: 14 May 1996 / Accepted: 11 July 1996     

E3泛素连接酶RFWD家族成员在肿瘤中的作用研究进展

环指和WD重复结构域 (RING Finger and WD Repeat Domain,RFWD) 蛋白属于E3泛素连接酶,在细胞增殖、 凋亡和DNA损伤修复的调控中发挥重要作用。越来越多的证据表明,RFWD蛋白通过靶向其底物泛素化降解参与肿瘤的发生发展。RFWD蛋白在不同类型的人类恶性肿瘤中具有抑癌和促癌的不同作用,可能与其底物蛋白的功能有关。本文分析了RFWD蛋白家族成员 (RFWD1,RFWD2,RFWD3) 的结构和功能,总结了RFWD蛋白家族成员的已知底物,并阐明其在不同肿瘤中的不同功能。此外,本文还讨论了RFWD家族成员作为癌症治疗潜在靶点的可能及策略。     

The autosomal recessive juvenile Parkinson disease gene product,parkin, interacts with and ubiquitinates synaptotagmin XI

Inactivating mutations of the gene encoding parkin are responsible for some forms of autosomal recessive juvenile Parkinson disease. Parkin is a ubiquitin ligase that ubiquitinates misfolded proteins targeted for the proteasome-dependent protein degradation pathway. Using the yeast two-hybrid system and co-immunoprecipitation methods, we identified synaptotagmin XI as a protein that interacts with parkin. Parkin binds to the C2A and C2B domains of synaptotagmin XI resulting in the polyubiquitination of synaptotagmin XI. Truncated and missense mutated parkins reduce parkin-sytXI binding affinity and ubiquitination. Parkin-mediated ubiquitination also enhances the turnover of sytXI. In sporadic PD brain sections, sytXI was found in the core of the Lewy bodies. Since synaptotagmin XI is a member of the synaptotagmin family that is well characterized in their importance for vesicle formation and docking, the interaction with this protein suggests a role for parkin in the regulation of the synaptic vesicle pool and in vesicle release. Loss of parkin could thus affect multiple proteins controlling vesicle pools, docking and release and explain the deficits in dopaminergic function seen in patients with parkin mutations.