Parkin蛋白及其底物与帕金森病的研究进展

帕金森病(PD)是一种发病率较高的神经退行性疾病,遗传、环境等多种因素均参与其病理生理过程.在PD致病相关蛋白中,PARK2基因编码的Parkin蛋白作为E3泛素连接酶,可与多种底物分子发生相互作用.本文旨在综述 Parkin 蛋白及其底物 septin、Pael-R、Cyclin E、p38、Synphilin-1、...     

热休克同源蛋白70羧基端作用蛋白的功能及其与神经退行性疾病的关系

神经退行性疾病是一组病因不明的慢性进行性神经损害.蛋白质的错误折叠和聚集是这类疾病共同的病理特征.热休克同源蛋白70羧基端作用蛋白(carboxyl-terminus of Hsc70 interacting protein,CHIP)具有双重功能,一方面可作为热休克蛋白的辅助因子,通过氮基端的34肽重复序列结构域与Hsp90和Hsc/Hsp70相互作用,调节热休克蛋白介导的蛋白质异常折叠,同时又可作为E3泛素连接酶,通过羧基端的U-box结构域参与泛素-蛋白酶体系统(ubiqutin-proteasome system,UPS)介导的蛋白质降解过程.CHIP在分子伴侣系统和UPS的交互作用中扮演重要角色,对维持细胞内蛋白质稳态具有重要的作用.本文从CHIP蛋白的分子结构特点、生理功能、在细胞代谢中的作用、与神经退行性疾病的关系等方面进行综述.     

Itch相关免疫调控的研究进展

Itch, one of the main E3 ligases, plays an important role in immune responses as a negative regulator in the ubiquitination of PLC-γ, PKC-θ, JunB,and notch. Itch deficiency leads to sever inflammatory disorders and immunological abnormality. Many efforts have been made in disclosing the Itch-promoted protein ubiquitination, modulation of its ligase, transdution of downstream signals in T cell anergy and differentiation in the past years.     

人睾丸组织TRIM69蛋白具有催化多聚泛素链形成的活性

目的 验证人源TRIM69蛋白是否具有催化多聚泛素链形成的活性.方法 把人源TRIM69基因构建到原核细胞表达载体中,经过转化、诱导、表达和纯化获得TRIM69纯化蛋白,通过细胞外泛素化实验分析其是否具有催化多聚泛素链形成的活性;另外构建了TRIM69基因的全长、RING结构域的点突变、以及RING结构域截短序列的真核细胞表达载体,瞬时转染293T细胞或稳定表达泛素的HeLa细胞株,通过免疫沉淀结合免疫印迹方法检测其是否具有催化多聚泛素链形成的活性.结果 泛素化分析实验表明TRIM69具有催化多聚泛素链形成的活性并且其活性依赖于它的RING结构域.结论 成功鉴定了人源TRIM69蛋白具有催化多聚泛素链形成的活性,为进一步证明其是一个新的E3泛素连接酶提供依据.     

Itch相关免疫调控的研究进展

Itch, one of the main E3 ligases, plays an important role in immune responses as a negative regulator in the ubiquitination of PLC-γ, PKC-θ, JunB,and notch. Itch deficiency leads to sever inflammatory disorders and immunological abnormality. Many efforts have been made in disclosing the Itch-promoted protein ubiquitination, modulation of its ligase, transdution of downstream signals in T cell anergy and differentiation in the past years.     

TLR4/NLRP3炎症复合体介导对比剂诱导的肾小管上皮细胞炎症和损伤

目的:探讨Toll样受体4(TLR4)/Nod样受体蛋白3(NLRP3)炎症复合体是否介导了对比剂(CM)引起的肾小管上皮细胞炎症和损伤。方法:本研究运用碘普罗胺作用于大鼠肾小管上皮细胞NRK-52E建立损伤模型。应用CCK-8法测定细胞存活率;Western blot测定TLR4、NLRP3、凋亡相关斑点样蛋白(ASC)、caspase-1和cleaved caspase-3的蛋白水平;ELISA法检测炎症因子白细胞介素1β(IL-1β)和IL-18的水平;Hoechst 33258核染色法检测凋亡率;JC-1染色法测定线粒体膜电位。用小干扰RNA沉默NLRP3表达。结果:CM可降低NRK-52E细胞的存活率并上调cleaved caspase-3的蛋白水平(P0.05);此外,CM可上调细胞TLR4/NLRP3炎症复合体的表达并促进炎症因子IL-1β和IL-18的分泌(P0.05)。沉默NLRP3可以对抗CM诱导的炎症因子分泌;TLR4抑制剂TAK-242及沉默NLRP3能减轻CM引起的细胞凋亡和线粒体功能损伤。结论:TLR4/NLRP3炎症复合体参与了CM致急性肾损伤的发病机制,并介导了CM诱导的肾小管上皮细胞损伤和炎症。     

Itch相关免疫调控的研究进展

Itch是新近发现的泛素连接酶E3之一,其参与细胞内多种信号蛋白如PLC．1、PKC-0、JunB、notch等的泛素化修饰过程,调控细胞表型及功能。Itch缺陷可引起小鼠严重的免疫紊乱和炎症反应,其负向免疫调节作用已在基因敲除动物模型上得以证实。近年来的研究对Itch结构、调控和被调控途径、参与的信号通路等有了更进一步的认识,逐步揭示出Itch在T细胞增殖、分化和诱导免疫耐受中的作用机制。     

参与免疫及炎症反应调控的胞浆蛋白NODs

Nucleotide- binding oligomerization domain (NOD) proteins are members of a growing family of cytosolic factors related to the apoptosis regulator Apaf-1 and a class of plant disease resistance proteins. NOD proteins have been implicated in the induction of NF-κB activity and in the activation of caspases. Biochemical evidence has unraveled the role of NOD1 and NOD2 as intraceUular sensors of bacterial peptidoglycan. Notably, genetic variation in the genes encoding the NOD proteins NOD2, cryopyrin and C Ⅱ TA inhmnans is associated with inflammatory disease or increased susceptibility to bacterial infections. NOD proteins may be involved in the recognition of microorganisms and regulation of inflammatory responses.     

NOD样受体蛋白炎症体亚家族研究进展

炎症体作为固有免疫的一类模式识别受体,在抵抗外来病原微生物和自身非菌性炎症反应中发挥重要作用.NOD样受体(NLR)蛋白炎症体亚家族属于NLRs炎症体家族的一员,随着NLRPs炎症体生理功能的不断外延,它们不仅参与固有免疫的过程,而且参与到其他的常见生理过程,并发挥重要的调控作用.本文主要综述了近年来NLR蛋白炎症体亚家族的研究进展.     

De novo missense variants in the E3 ubiquitin ligase adaptor KLHL20 cause a developmental disorder with intellectual disability,epilepsy, and autism spectrum disorder

PurposeKLHL20 is part of a CUL3-RING E3 ubiquitin ligase involved in protein ubiquitination. KLHL20 functions as the substrate adaptor that recognizes substrates and mediates the transfer of ubiquitin to the substrates. Although KLHL20 regulates neurite outgrowth and synaptic development in animal models, a role in human neurodevelopment has not yet been described. We report on a neurodevelopmental disorder caused by de novo missense variants in KLHL20.MethodsPatients were ascertained by the investigators through Matchmaker Exchange. Phenotyping of patients with de novo missense variants in KLHL20 was performed.ResultsWe studied 14 patients with de novo missense variants in KLHL20, delineating a genetic syndrome with patients having mild to severe intellectual disability, febrile seizures or epilepsy, autism spectrum disorder, hyperactivity, and subtle dysmorphic facial features. We observed a recurrent de novo missense variant in 11 patients (NM_014458.4:c.1069G>A p.[Gly357Arg]). The recurrent missense and the 3 other missense variants all clustered in the Kelch-type β-propeller domain of the KLHL20 protein, which shapes the substrate binding surface.ConclusionOur findings implicate KLHL20 in a neurodevelopmental disorder characterized by intellectual disability, febrile seizures or epilepsy, autism spectrum disorder, and hyperactivity.     

VHL-box and SOCS-box domains determine binding specificity for Cul2-Rbx1 and Cul5-Rbx2 modules of ubiquitin ligases

The ECS (Elongin B/C-Cul2/Cul5-SOCS-box protein) complex is a member of a family of ubiquitin ligases that share a Cullin-Rbx module. SOCS-box proteins recruit substrates to the ECS complex and are linked to Cullin-Rbx via Elongin B/C. VHL has been implicated as a SOCS-box protein, but lacks a C-terminal sequence (downstream of the BC box) of the SOCS box. We now show that VHL specifically interacts with endogenous Cul2-Rbx1 in mammalian cells, whereas SOCS-box proteins associate with Cul5-Rbx2. We also identify LRR-1 and FEM1B as proteins that share a region of homology with VHL (the VHL box, including the BC box and downstream residues) and associate with Cul2-Rbx1. ECS complexes can thus be classified into two distinct protein assemblies, that is, those that contain a subunit with a VHL box (composed of the BC box and a downstream Cul2 box) that interacts with Cul2-Rbx1, and those that contain a subunit with a SOCS box (BC box and downstream Cul5 box) that interacts with Cul5-Rbx2. Domain-swapping analyses showed that the specificity of interaction of VHL-box and SOCS-box proteins with Cullin-Rbx modules is determined by the Cul2 and Cul5 boxes, respectively. Finally, RNAi-mediated knockdown of the Cul2-Rbx1 inhibited the VHL-mediated degradation of HIF-2alpha, whereas knockdown of Cul5-Rbx2 did not affect it. These data suggest that the functions of the Cul2-Rbx1 and Cul5-Rbx2 modules are distinct.     

Itch attenuates CD4 T-cell proliferation in mice by limiting WBP2 protein stability

To mount an antipathogen response, CD4 T cells must undergo rapid cell proliferation; however, poorly controlled expansion can result in diseases such as autoimmunity. One important regulator of T-cell activity is the E3 ubiquitin ligase Itch. Itch deficient patients suffer from extensive autoinflammation. Similarly, Itch deficient mice exhibit inflammation characterized by high numbers of activated CD4 T cells. While the role of Itch in limiting CD4 T-cell cytokine production has been extensively studied, it is less clear whether and how Itch regulates proliferation of these cells. We determined that Itch deficient CD4 T cells are hyperproliferative in vitro and in vivo, due to increased S phase entry. Whole cell proteomics analysis of Itch deficient primary mouse CD4 T cells revealed increased abundance of the β-catenin coactivator WW domain-binding protein 2 (WBP2). Furthermore, Itch deficient cells demonstrate increased WBP2 protein stability, and Itch and WBP2 interact in CD4 T cells. Knockdown of WBP2 in CD4 T cells caused reduced proliferation. Together, our data support that Itch attenuates CD4 T cell proliferation by promoting WBP2 degradation. This study identifies novel roles for Itch and WBP2 in regulating CD4 T cell proliferation, providing insight into how Itch may prevent inflammation.     

Regulated expression of the ubiquitin protein ligase, E3(Histone)/LASU1/Mule/ARF-BP1/HUWE1, during spermatogenesis.

A ubiquitin protein ligase (E3), E3(Histone)/LASU1 (Mule/ARF-BP1/HUWE1), was recently identified that mediates ubiquitination of core histones, the Mcl-1 anti-apoptotic protein, and the p53 tumor suppressor protein. However, the expression of E3(Histone)/LASU1 remains poorly studied. Because we identified E3(Histone)/LASU1 from the testis, we explored its regulation during spermatogenesis. In the first wave of rat spermatogenesis, E3(Histone)/LASU1 mRNA and protein had peak expression at days 10 and 20, respectively, and decreased with age. Consistent with these findings, immunohistochemistry revealed that E3(Histone)/LASU1 was highly expressed in nuclei from spermatogonia to mid-pachytene spermatocytes. There was no obvious staining in spermatids, when histones are ubiquitinated and degraded. E3(Histone)/LASU1 was also expressed in other tissues. However, except in neuronal cells of the brain, expression was cytoplasmic. Thus, E3(Histone)/LASU1 may play a role in chromatin modification in early germ cells of the testis, but also has functions in other tissues.     

Myc protein is stabilized by suppression of a novel E3 ligase complex in cancer cells

Rapid Myc protein turnover is critical for maintaining basal levels of Myc activity in normal cells and a prompt response to changing growth signals. We characterize a new Myc-interacting factor, TRPC4AP (transient receptor potential cation channel, subfamily C, member 4-associated protein)/TRUSS (tumor necrosis factor receptor-associated ubiquitous scaffolding and signaling protein), which is the receptor for a DDB1 (damage-specific DNA-binding protein 1)–CUL4 (Cullin 4) E3 ligase complex for selective Myc degradation through the proteasome. TRPC4AP/TRUSS binds specifically to the Myc C terminus and promotes its ubiquitination and destruction through the recognition of evolutionarily conserved domains in the Myc N terminus. TRPC4AP/TRUSS suppresses Myc-mediated transactivation and transformation in a dose-dependent manner. Finally, we found that TRPC4AP/TRUSS expression is strongly down-regulated in most cancer cell lines, leading to Myc protein stabilization. These studies identify a novel pathway targeting Myc degradation that is suppressed in cancer cells.     

Reconstruction of an active SOCS3-based E3 ubiquitin ligase complex in vitro: identification of the active components and JAK2 and gp130 as substrates

Abstract

SOCS3 (suppressor of cytokine signaling 3) inhibits the intracellular signaling cascade initiated by exposure of cells to cytokines. SOCS3 regulates signaling via two distinct mechanisms: directly inhibiting the catalytic activity of Janus kinases (JAKs) that initiate the intracellular signaling cascade and catalysing the ubiquitination of signaling components by recruiting components of an E3 ubiquitin ligase complex. Here we investigate the latter mode-of-action biochemically by reconstructing a SOCS3-based E3 ubiquitin ligase complex in vitro using fully purified, recombinant components and examining its ability to promote the ubiquitination of molecules involved in the cytokine signaling cascade. We show that SOCS3 is an active substrate recruitment module for a Cullin5-based E3 ligase and have defined the core protein components required for ubiquitination. SOCS3-induced polyubiquitination was rapid and could proceed through a number of different ubiquitin lysines. SOCS3 catalyzed the ubiquitination of both the IL-6 receptor common chain (gp130) and JAK2.     

Selective assembly of HIV-1 Vif-Cul5-ElonginB-ElonginC E3 ubiquitin ligase complex through a novel SOCS box and upstream cysteines

APOBEC3G, which induces hypermutations in newly synthesized viral DNA, is suppressed by HIV-1 Vif, acting through Cul5-ElonginB-ElonginC E3 ubiquitin ligase. We have now characterized a novel SOCS box in HIV-1 Vif that mediates its interaction with ElonginC. In this SOCS box, alanine replaces the consensus cysteine in the previously identified SOCS box. This new motif was necessary but insufficient for interaction with Cul5-ElonginB-ElonginC, as two highly conserved Cys residues outside the SOCS box were required to interact with Cul5 but not ElonginC. Therefore, selective assembly with Cul5 versus Cul2 E3 may require protein interfaces besides the SOCS-box-ElonginC interaction.