蛋白酶体翻译后修饰功能机制研究

蛋白酶体是真核细胞内介导蛋白质特异性降解的主要复合物,在蛋白质质量控制和细胞稳态维持中发挥关键作用。研究发现,蛋白酶体含量或功能的异常会导致癌症、神经退行性疾病等诸多人类恶性疾病。围绕蛋白酶体的活性调控,已经发展了多种靶向药物,加强对蛋白酶体活性精确调控机制的研究具有重要的学术价值与临床意义。蛋白酶体的含量、组装及其活性的调节受多层次的精细调控,本文简要介绍了蛋白酶体的组成亚基、结构特征、转录调控与组装机制,着重阐述磷酸化、泛素化和乙酰化等翻译后修饰对蛋白酶体的调控机制及其生物学意义,以期为深入揭示蛋白酶体调控机制带来新启发。     

蛋白酶体相关翻译后修饰的研究进展

蛋白酶体是具有多种蛋白水解酶活性的蛋白质降解系统,由于细胞内许多关键信号调控分子都是蛋白酶体的降解底物,因此蛋白酶体在细胞周期调控、基因表达、炎症反应等各种关键的生物学活动中都发挥着极其重要的调节作用。蛋白酶体的降解活性也同时受多种机制的调控,其中的翻译后修饰是蛋白酶体降解途径中一个不可忽视的方面。着重阐述蛋白酶体自身及其底物的几种重要的翻译后修饰,探讨最新的进展及其生物学意义。     

原核生物类泛素蛋白Pup-蛋白酶体系统的研究进展

真核泛素-蛋白酶体系统是细胞内蛋白质降解的重要机制,参与细胞生理功能调控,因此泛素-蛋白酶体通路的机制和功能研究备受关注.20世纪80年代,人们就发现放线菌中存在原核蛋白酶体,但是对于原核蛋白酶体的功能和作用机理长期以来了解甚少.2008年,Pearce等在结核分枝杆菌中发现了原核类泛素蛋白(prokaryotic ubiquitin-like protein,Pup).在Dop、PafA、Mpa等辅助因子的作用下,Pup可以共价标记多种功能蛋白,并介导被标记蛋白质通过蛋白酶体降解,Pup-蛋白酶体系统的发现揭示了原核生物中一个崭新的蛋白质降解机制.Pup-蛋白酶体系统的靶蛋白涉及物质中间代谢、信号通路、毒性和抗毒性因子、细胞壁和细胞膜组分等多个方面,并且与结核分枝杆菌的致病性相关,被认为是新的结核病治疗药物靶点.本文就原核Pup-蛋白酶体系统的作用机理及其功能的研究进展作一综述.     

蛋白酶体调节颗粒的结构生物学特征及其功能

蛋白酶体调节颗粒(regulatory particle,RP)参与调控许多重要信号通路的蛋白质降解,在维持细胞稳态中发挥重要作用.近年来,真核细胞蛋白酶体在癌症治疗中的作用机制及药物研发已引起了广泛关注,并有3种蛋白酶体抑制剂已用于临床治疗.随着蛋白酶体功能研究的不断深入,以及晶体学和冷冻电镜技术在其结构生物学研究中...     

POMP与SuFu相互作用调控Hedgehog信号通路的活性

Hedgehog信号通路在胚胎发育、组织再生中发挥重要的作用,且与癌症发生发展密切相关. 其胞内调控组分Suppressor of Fused（SuFu）蛋白通过结合转录因子Gli(s),负调控该信号通路,但其作用的分子机制仍不甚清楚. 在本项研究中,以人SuFu作为诱饵蛋白,利用酵母双杂交技术成功地筛选到1个新的相互作用因子-蛋白酶体成熟蛋白（POMP）. 通过免疫共沉淀、体外GST pull-down和免疫细胞化学实验验证其相互作用. 为了探究POMP与SuFu的相互作用对Hedgehog信号通路的影响,构建了POMP的过表达质粒和干扰质粒（miR-RNAi）以及转录因子Gli活性检测系统,即荧光素酶报告基因法,结果显示,过表达SuFu蛋白时POMP正调控Hedgehog信号通路,而下调POMP的表达则抑制Gli的活性. 该研究结果揭示了POMP新的生物学功能,为阐明Hedgehog信号通路的具体分子机制提供了新的线索.     

自噬和泛素-蛋白酶体系统之间的交联

自噬和泛素-蛋白酶体系统作为细胞内最重要的两大降解途径,对细胞稳态及细胞正常生理功能的维持都具有十分重要的作用。目前,越来越多的证据显示,这两大降解途径之间存在多种交联方式。首先,自噬和泛素-蛋白酶体系统都能以泛素作为共同标签,从而将泛素化底物降解;其次,泛素化的蛋白酶体可以通过自噬被清除,自噬相关蛋白质也可以通过蛋白酶体系统被降解;再次,这两条途径在细胞内能协同降解同一种底物;最后,它们之间可以相互调节活性,任一条途径被干扰都将影响另一条途径的活性。自噬和泛素-蛋白酶体系统之间的交联对细胞稳态的维持至关重要。交联失调不仅导致细胞功能异常,还可引起多种疾病的发生。本文主要对自噬和泛素-蛋白酶体系统之间的交联方式及其分子机制进行阐述,有助于深入了解细胞的分解代谢过程,进一步理解细胞稳态的维持机制,继而加深对相关疾病病理机制的认识。     

F-box蛋白家族及其功能

F-box蛋白是一类广泛存在于真核生物中,含有F-box结构域的蛋白家族,在泛素-蛋白酶体途径（ubiquitin-proteasome pathway, UPP）中因特异识别底物蛋白而参与细胞周期调控、转录调控、细胞凋亡、细胞信号转导等生命活动。另外,F-box蛋白还通过其他作用方式参与了体内众多生化过程。本文综述了F-box蛋白的结构和作用途径,以及该蛋白参与的多种生理功能,展示了F-box蛋白家族在生命活动中具有广泛而重要的作用,并指出了F-box蛋白将为阐明疾病发生机制提供新的线索,可望成为疾病治疗中药物作用的靶向位点。     

植物生长素受体蛋白研究现状

受体是研究生长素信号传导链的关键环节,因为只有生长素与生长素受体结合以后才会引起后续的级联反应,生长素受体的发现对探索和了解生长素调控机制是极其重要的.目前所发现的生长素结合蛋白(受体)有TIR1和ABP1.扼要的介绍生长素受体TIR1的结构及其与生长素的结合位点,阐述了TIR1在基因水平上的调控和AUX/IAA被泛素化后最终被26S蛋白酶体降解的过程.概述了ABPI的结构、活性位点、性质以及ABP1的作用机理的模型.     

泛素?蛋白酶体途径在精子生成中的作用

泛素?蛋白酶体途径(Ubiquitin–proteasome pathway,UPP)是真核细胞内蛋白质主要降解途径,通过调节蛋白质相互作用、蛋白活性、蛋白定位及信号转导,进而在细胞周期进程、细胞凋亡、应激反应及机体生长发育等过程发挥重要作用。研究表明,UPP在人和动物精子生成中的顶体生物合成及精子尾部形成过程起着关键的调控作用,精子变态过程中UPP调控异常导致精子畸形及精子活力降低,并引发少精子症、不育及睾丸肿瘤等生殖系统疾病。本文综述了UPP在动物精子生成过程中的信号传导及调节机制,以期为后续相关研究提供参考。     

泛素-蛋白酶体降解途径在细胞周期调控中的作用

细胞周期的进程由一系列细胞周期蛋白依赖性激酶(CDK)和CDK活性调节因子驱动。泛素-蛋白酶体对细胞周期调节因子的降解是细胞调控分裂进程的重要手段。CDK活性抑制因子的降解是细胞分裂所必需的,而细胞周期正调控因子的降解则对维持细胞稳态至关重要。本从参与调控的2类泛素连接酶SCF复合物、APC／C复合物的结构和功能的角度阐述了泛素-蛋白酶体降解途径在整个细胞周期调控中的作用和意义。     

Regulation of proteasome activity in health and disease

The ubiquitin–proteasome system (UPS) is the primary selective degradation system in the nuclei and cytoplasm of eukaryotic cells, required for the turnover of myriad soluble proteins. The hundreds of factors that comprise the UPS include an enzymatic cascade that tags proteins for degradation via the covalent attachment of a poly-ubiquitin chain, and a large multimeric enzyme that degrades ubiquitinated proteins, the proteasome. Protein degradation by the UPS regulates many pathways and is a crucial component of the cellular proteostasis network. Dysfunction of the ubiquitination machinery or the proteolytic activity of the proteasome is associated with numerous human diseases. In this review we discuss the contributions of the proteasome to human pathology, describe mechanisms that regulate the proteolytic capacity of the proteasome, and discuss strategies to modulate proteasome function as a therapeutic approach to ameliorate diseases associated with altered UPS function. This article is part of a Special Issue entitled: Ubiquitin–Proteasome System. Guest Editors: Thomas Sommer and Dieter H. Wolf.     

The Mechanistic Links Between Proteasome Activity,Aging and Age-related Diseases

Damaged and misfolded proteins accumulate during the aging process, impairing cell function and tissue homeostasis. These perturbations to protein homeostasis (proteostasis) are hallmarks of age-related neurodegenerative disorders such as Alzheimer’s, Parkinson’s or Huntington’s disease. Damaged proteins are degraded by cellular clearance mechanisms such as the proteasome, a key component of the proteostasis network. Proteasome activity declines during aging, and proteasomal dysfunction is associated with late-onset disorders. Modulation of proteasome activity extends lifespan and protects organisms from symptoms associated with proteostasis disorders. Here we review the links between proteasome activity, aging and neurodegeneration. Additionally, strategies to modulate proteasome activity and delay the onset of diseases associated to proteasomal dysfunction are discussed herein.     

Oxidative protein damage and the proteasome

Protein damage, caused by radicals, is involved in many diseases and in the aging process. Therefore, it is crucial to understand how protein damage can be limited, repaired or removed. To degrade damaged proteins, several intracellular proteolytic systems exist. One of the most important contributors in intracellular protein degradation of oxidized, aggregated and misfolded proteins is the proteasomal system. The proteasome is not a simple, unregulated structure. It is a more complex proteolytic composition that undergoes diverse regulation in situations of oxidative stress, aging and pathology. In addition to that, numerous studies revealed that the proteasome activity is altered during life time, contributing to the aging process. In addition, in the nervous system, the proteasome plays an important role in maintaining neuronal protein homeostasis. However, alterations in the activity may have an impact on the onset of neurodegenerative diseases. In this review, we discuss what is presently known about protein damage, the role of the proteasome in the degradation of damaged proteins and how the proteasome is regulated. Special emphasis was laid on the role of the proteasome in neurodegenerative diseases.     

抗肺纤维化药物治疗研究进展

特发性肺纤维化是严重危害生命的间质性肺疾病,诊断后半数生存率仅为3年,超过大部分恶性肿瘤.目前所有的抗肺纤维化治疗措施疗效甚微.随着对肺纤维化发病分子细胞机制研究的不断深入,已经发现并确认多种抗肺纤维化的新药靶.本文首先概述抗肺纤维化疾病的临床治疗现状、正在临床实验的新药物,然后重点介绍作用于肺泡上皮细胞、成肌纤维细胞或具有抑制血管新生、调节Th1/Th2细胞因子平衡、阻断氧化应激等作用药物治疗肺纤维化疾病的前景.     

Natural products are an important source for proteasome regulating agents

BackgroundNatural medicines have a long history in the prevention and treatment of various diseases in East Asian region, especially in China. Modern research has proved that the pharmacological effects of numerous natural medicines involve the participation of ubiquitin proteasome system (UPS). UPS can degrade the unwanted and damaged proteins widely distributed in the nucleus and cytoplasm of various eukaryotes.PurposeThe objective of the present study was to review and discuss the regulatory effects of natural products and extracts on proteasome components, which may help to find new proteasome regulators for drug development and clinical applications.MethodsThe related information was compiled using the major scientific databases, such as CNKI, Elsevier, ScienceDirect, PubMed, SpringerLink, Wiley Online, and GeenMedical. The keywords “natural product” and “proteasome” were applied to extract the literature. Nature derived extracts, compounds and their derivatives involved in proteasome regulation were included, and the publications related to synthetic proteasome agents were excluded.ResultsThe pharmacological effects of more than 80 natural products and extracts derived from phytomedicines related to the proteasome regulation were reviewed. These natural products were classified according to their chemical properties. We also summarized some laws of action of natural products as proteasome regulators in the treatment of diseases, and listed the action characteristics of the typical natural products.ConclusionNatural products derived from nature can induce the degradation of damaged proteins through UPS or act as regulators to directly regulate the activity of proteasome. But few proteasome modulators are applied clinically. Summary of known rules for proteasome modulators will contribute to discover, modify and synthesize more proteasome modulators for clinical applications.     

Proteasome Functioning in Breast Cancer: Connection with Clinical-Pathological Factors

Breast cancer is one of four oncology diseases that are most widespread in the world. Moreover, breast cancer is one of leading causes of cancer-related deaths in female population within economically developed regions of the world. So far, detection of new mechanisms of breast cancer development is very important for discovery of novel areas in which therapy approaches may be elaborated. The objective of the present study is to investigate involvement of proteasomes, which cleave up to 90% of cellular proteins and regulate numerous cellular processes, in mechanisms of breast cancer development. Proteasome characteristics in 106 patient breast carcinomas and adjacent tissues, as well as relationships of detected proteasome parameters with clinical-pathological factors, were investigated. Proteasome chymotrypsin-like activity was evaluated by hydrolysis of fluorogenic peptide Suc-LLVY-AMC. The expression of proteasome subunits was studied by Western-blotting and immunohistochemistry. The wide range of chymotrypsin-like activity in tumors was detected. Activity in tumors was higher if compared to adjacent tissues in 76 from 106 patients. Multiple analysis of generalized linear models discovered that in estrogen α-receptor absence, tumor growth was connected with the enhanced expression of proteasome immune subunit LMP2 and proteasome activator PA700 in tumor (at 95% confidence interval). Besides, by this analysis we detected some phenomena in adjacent tissue, which are important for tumor growth and progression of lymph node metastasis in estrogen α-receptor absence. These phenomena are related to the enhanced expression of activator PA700 and immune subunit LMP7. Thus, breast cancer development is connected with functioning of immune proteasome forms and activator PA700 in patients without estrogen α-receptors in tumor cells. These results could indicate a field for search of new therapy approaches for this category of patients, which has the worst prognosis of health recovery.     

The proteasome regulates the interaction between Cx43 and ZO-1

Gap junction (GJ) intercellular communication (GJIC) is vital to ensure proper cell and tissue function. GJ are multimeric structures composed of proteins called connexins. Modifications on stability or subcellular distribution of connexins have a direct impact on the extent of GJIC. In this study we have investigated the role of the proteasome in regulation of connexin 43 (Cx43) internalization. Although the participation of both the proteasome and lysosome has long been suggested in Cx43 degradation, the molecular mechanisms whereby proteasome contributes to regulate Cx43 internalization and intercellular communication are still unclear. The results presented in this study envision a new mechanism whereby proteasome regulates GJIC by modulating interaction between Cx43 and ZO-1. Immunoprecipitation experiments, in the presence of proteasome inhibitors, together with immunofluorescence data indicate that the proteasome regulates interaction between Cx43 and ZO-1. Overexpression of the PDZ2 domain of ZO-1 and the expression of Cx-43 fused in frame with a V5/HIS tag, suggest that interaction between the two proteins occurs through the PDZ2 domain of ZO-1 and the C-terminus of Cx43. When interaction between Cx43 and ZO-1 is reduced, as in the presence of proteasome inhibitors, Cx43 accumulates, forming large GJ plaques at plasma membrane. Data presented in this article suggest a new pathway whereby alterations in proteasome activity may impact on GJIC as well as on non-junctional communication with extracellular environment, contributing to cell and tissue dysfunction.     

Could Dysregulation of UPS be a Common Underlying Mechanism for Cancer and Neurodegeneration? Lessons from UCHL1

Ubiquitin proteasome system (UPS) determines the timing and extent of protein turnover in cells, and it is one of the most strictly controlled cellular mechanisms. Lack of proper control over UPS is attributed to both cancer and to neurodegenerative diseases, yet in different context and direction. Cancerous cells have altered cellular metabolisms, uncontrolled cellular division, and increased proteasome activity. The specialized function prevent neurons from undergoing cellular division but allow them to extend an axon over long distances, establish connections, and to form stable neuronal circuitries. Neurons heavily depend on the proper function of the proteasome and the UPS for their proper function. Reduction of UPS function in vulnerable neurons results in protein aggregation, increased ER stress, and cell death. Identification of compounds that selectively block proteasome function in distinct set of malignancies added momentum to drug discovery efforts, and deubiquitinases (DUBs) gained much attention. This review will focus on ubiquitin carboxy-terminal hydrolase L1 (UCHL1), a DUB that is attributed to both cancer and neurodegeneration. The potential of developing effective treatment strategies for two major health problems by controlling the function of UPS opens up new avenues for innovative approaches and therapeutic interventions.     

ASK1 Negatively Regulates the 26 S Proteasome

The 26 S proteasome, composed of the 20 S core and 19 S regulatory particle, plays a central role in ubiquitin-dependent proteolysis. Disruption of this process contributes to the pathogenesis of the various diseases; however, the mechanisms underlying the regulation of 26 S proteasome activity remain elusive. Here, cell culture experiments and in vitro assays demonstrated that apoptosis signal-regulating kinase 1 (ASK1), a member of the MAPK kinase kinase family, negatively regulated 26 S proteasome activity. Immunoprecipitation/Western blot analyses revealed that ASK1 did not interact with 20 S catalytic core but did interact with ATPases making up the 19 S particle, which is responsible for recognizing polyubiquitinated proteins, unfolding them, and translocating them into the 20 S catalytic core in an ATP-dependent process. Importantly, ASK1 phosphorylated Rpt5, an AAA ATPase of the 19 S proteasome, and inhibited its ATPase activity, an effect that may underlie the ability of ASK1 to inhibit 26 S proteasome activity. The current findings point to a novel role for ASK1 in the regulation of 26 S proteasome and offer new strategies for treating human diseases caused by proteasome malfunction.