泛素蛋白酶体系统与帕金森病

一、概述帕金森病(Parkinson's disease,PD)是一种与年龄有关的神经系统变性疾病,病因和发病机制尚不清楚。从目前研究来看,与遗传、环境因素、感染、衰老、氧化应激、自由基过多形成以及神经营养因子缺乏等有关,是多种机制协同作用的结果。     

泛素-蛋白酶体系统与帕金森病

帕金森病(PD)的病因和发病机制与遗传因素和环境因素共同作用有关,但其内在联系尚不清楚。泛素-蛋白酶体系统功能的损害可能是不同病因作用的共同途径,故泛素-蛋白酶体在PD发病机制中的作用倍受关注,本文就泛素-蛋白酶体系统与帕金森病发病机制的关系做一文献综述。     

帕金森病与泛素蛋白酶体系统

<正> 帕金森病(Parkinson's disease,PD)是以中脑多巴胺(Dopa-mine,DA)能神经元发生退变伴细胞内包含体(LB)形成为主要特征的中枢神经系统变性疾病。LB中聚集了许多蛋白质包括     

蛋白酶体抑制剂对神经细胞的双重作用

目的探索蛋白酶体抑制剂在不同浓度时对多巴胺能神经元的作用及原因。方法用6-羟多巴(6-OHDA)50uM处理的人SH-SY5Y细胞作为细胞受损伤的模型,加用不同浓度的蛋白酶体抑制剂lactacystin,镜下细胞计数和SRB法测定细胞活力,平行对照组测定蛋白酶体活性。用选择性MEKl/2抑制剂PD98059验证蛋白酶体抑制剂是否通过MAPK途径起作用。结果蛋白酶体抑制剂lactacystin在0.1、0.25、0.5uM浓度时提高细胞存活率,在2、5uM时降低细胞存活率,相应的蛋白酶体活性分别是对照组的83.43%、73.84%、66.14%、24.11%、12.36%,加用PD98059后,0.25、0.5uMlactacystin的保护作用被阻断。结论蛋白酶体抑制剂在低浓度时对多巴胺能神经元有保护作用,高浓度时对多巴胺能神经元有毒性作用,这种不同作用的原因可能与蛋白酶体抑制的程度有关。蛋白酶体抑制剂的保护作用可能通过MAPK途径起作用。     

泛素蛋白酶体通路与帕金森病

帕金森病（parkinson’s disease，PD）是一种常见的神经系统退行性疾病，多在中老年人发病。我国65岁以上人群患病率约2．1％，与发达国家基本一致。PD典型临床表现为静止性震颤、肌强直、运动迟缓、姿势步态异常等，主要的病理改变是选择性中脑多巴胺能神经元丢失，残存的神经元中出现路易小体（Lewy bodies，LBs）。     

泛素-蛋白酶体抑制剂诱导细胞内泛素化α-synuclein聚集选择性损伤多巴胺神经元

目的 探讨多巴胺(DA)神经元诱变剂对细胞内泛素化α-synuclein聚集的影响及其细胞损伤作用.方法 应用MPP+、特异性泛素-蛋白酶体系统(UPS)抑制剂lactacystin及H2O2处理神经生长因子(NGF)诱导的PC12细胞株与N2a细胞株16 h后,采用免疫荧光双标记的方法在共聚焦显微镜下观察细胞内泛素化α-synuclein聚集,比较三种诱变剂对这两种细胞株作用的差异.在PC12细胞中加入不同终浓度的lactacystin处理24 h,MTT方法检测PC12细胞活力.10μmol/Llactacystin处理PC12细胞不同时间,流式细胞术检测PC12细胞的早期凋亡率.结果 经三种诱变剂处理后,MPP+和lactacystin选择性地诱发PC12细胞内泛素化α-synuclein聚集且以lactacystin的作用更为显著,N2a细胞则无明显的泛素化α-synuclein聚集.H2O2作用于PC12细胞的效应与MPP+相近,但仅引起N2a细胞内少量泛素化α-synuclein聚集.经lactacystin处理后的PC12细胞活力呈剂量依赖性下降;5 μmol/L、10μmol/L和20 μmol/L lactacystin处理24 h后细胞存活率分别为79.5%±2.1%、49.3%±3.2%和31.2%±2.8%(与对照组相比,均P＜0.01).流式细胞术显示lactacystin处理后PC12细胞早期出现凋亡细胞,并且随着处理时间的延长,细胞凋亡率逐渐增加.结论 特异性UPS和线粒体呼吸链抑制剂选择性作用于DA神经元,诱导细胞内泛素化α-synuclein聚集,终使细胞发生凋亡,而以氧化应激为主要损伤途径的诱变剂的作用则不具有选择性.     

泛素-蛋白酶体系统在帕金森病研究中的进展

泛素-蛋白酶体系统（ubiquitin-proteasome system, UPS）是体内蛋白降解的重要通路.许多证据表明帕金森病（Parkinson disease, PD）以及其他神经变性病可能是一类蛋白降解障碍疾病.家族性PD的致病基因与UPS密切相关.此外,在散发性PD患者脑中黑质的UPS功能选择性受损,线粒体复合物Ⅰ抑制剂1-甲基4-苯基-吡啶离子（MPP＋）、鱼藤酮（rotenone）等所造成的能量代谢障碍也会影响UPS的正常功能.所有这些发现都表明,UPS功能障碍在PD的发病机制中有重要的作用,这方面的研究已经有了相关的综述,近年来这方面的研究取得了一些新的进展,我们对该方面最近的研究作一综述。     

帕金森病大鼠模型泛素连接酶hHrd1表达水平的研究

目的探讨泛素-蛋白酶体系统关键酶泛素连接酶hHrd1在帕金森病动物模型中的表达，并探讨其意义。方法应用立体定向仪，经大鼠黑质和内侧前脑束两靶点微量注射6-羟多巴制作帕金森病模型-2周后阿扑吗啡腹腔注射，筛选成功模型。免疫组化检测泛素连接酶hHrd1在帕金森病模型大鼠中脑的表达．并行Western blot定量分析。结果注射6-羟多巴到黑质和内侧前脑束双靶点，通过大鼠旋转实验测试，造模成功率为57．9％。泛素连接酶hHrd1在帕金森病模型中呈高表达。且呈区域性，如黑质、红核、中缝核及缰内侧核呈强阳性。结论泛素连接酶hHrd1在帕金森病模型中高表达。揭示泛素-蛋白酶体系统功能异常与帕金森病发病过程有着极其密切的关系．可能成为帕金森病治疗的又一途径。     

认知功能障碍中泛素蛋白酶体通路的作用

众多信号转导通路功能稳定是保持正常认知的生物学基础,其中,泛素蛋白酶体通路（UPP）功能障碍会导致蛋白质降解出现障碍,神经元稳定性遭到破坏,出现神经元变性坏死。现通过介绍突触可塑性中起关键作用的分子与UPP的相互关系,阐述认知功能障碍中UPP的作用机制。     

阻断泛素-蛋白酶体通路诱导PC12细胞死亡和泛素阳性包涵体生成

目的探讨泛素蛋白酶体通路的功能障碍对于多巴胺能细胞的活力以及胞质内包涵体生成的影响。方法应用蛋白酶体抑制剂lactacystin(5μmol/L、10μmol/L、15μmol/L和20μmol/L)处理PC12细胞24h,MTT方法检测细胞活力,WesternBlot方法测定细胞内泛素化蛋白质水平,免疫荧光细胞化学染色观察泛素免疫阳性包涵体的生成。结果经5μmol/L、10μmol/L、15μmol/L和20μmol/Llactacystin处理24h后,PC12细胞的活力显著降低(细胞存活率分别为81.5%±3.6%、75.4%±2.4%、70.2%±2.7%和60.4%±3.9%),呈现剂量依赖性。WesternBlot证实对照组细胞内未检测到相对高分子质量的泛素化蛋白质;随着lactacystin作用浓度的增加,细胞内相对高分子质量泛素化蛋白质的含量逐渐增高。免疫荧光染色显示对照组中仅有极少数细胞内含有泛素阳性包涵体;20μmol/Llactacystin处理组中含有泛素阳性包涵体的细胞数目显著增多(P<0.01)。结论泛素蛋白酶体通路的功能缺失能诱导多巴胺能细胞死亡,造成细胞内泛素化蛋白质积聚,促进胞质内泛素阳性包涵体的生成,可能在帕金森病黑质多巴胺能神经元变性死亡和Lewy小体形成中发挥重要作用。     

泛素羧基末端水解酶-1抑制剂对多巴胺能神经元的神经毒性作用

目的 利用人神经母细胞瘤SK-N-SH细胞观察泛素羧基末端水解酶-1(OCH-L1)抑制剂对多巴胺能神经元的毒性作用并探讨其可能的毒性机制. 方法 用不同浓度(5、10、25、50、75、100 μmol/L)的UCH-L1抑制剂作用SK-N-SH细胞24h,MTT法检测细胞活力、Hoechst染色检测凋亡的细胞核及Western blot检测UCH-L1蛋白、单个泛素分子及多聚化泛素蛋白的表达、荧光检测泛素蛋白酶体系统(UPS)的功能. 结果经UCH-L1抑制剂处理24 h后SK-N-SH细胞突起样结构消失,细胞体积变小、形态变圆;随着UCH-L1抑制剂浓度的增加,细胞活性进一步下降;与对照组比较,细胞活力在抑制剂浓度为50μmol/L时.作用24h后即出现明显下降,差异有统计学意义(P<0.05);Hoechst染色可见凋亡细胞碎裂的细胞核;Western blot检测到细胞内UCH-L1蛋白表达没有变化、单个泛素分子水平下降、多聚泛素化蛋白增加;荧光检测显示UPS功能下降.结论 UCH-L1抑制剂在体外对多巴胺能神经元有毒性作用,可诱导细胞凋亡.在凋亡过程中,UPS功能下降、细胞内多聚泛素化蛋白堆积可能发挥了作用.     

姜黄素对多巴胺能细胞的保护作用研究

目的探讨姜黄素对多巴胺能细胞的保护作用及机制。方法采用神经毒素鱼藤酮(1μmol/L)处理经神经生长因子(NGF)(50 ng/ml×7)诱导分化过的PC12细胞,并在处理前6 h加入1μmol/L的姜黄素进行干预,MTT法检测细胞活力,荧光分光光度法检测细胞内活性氧水平,比色法检测还原型谷胱甘肽(GSH)含量。结果 NGF诱导后的PC12细胞经1μmol/L鱼藤酮处理24 h后,细胞活力下降至对照组的57.1%,细胞内活性氧水平为对照组的189%,而GSH水平显著下降(P<0.05);姜黄素干预后,与鱼藤酮组相比,细胞活力和GSH含量显著提高,活性氧水平显著降低(P<0.05)。结论姜黄素对多巴胺细胞具有保护作用,其机制与抗氧化活性有关。     

泛素羧基末端水解酶-1抑制剂对多巴胺能神经元的神经毒性作用

Objective To investigate the neurotoxic effects ofLDN-57444, a specific ubiquitin C-termiual hydrolase L1 (UCH-L1) inhibitor, on dopaminergic neurons and the possible mechanism. Methods The viability of SK-N-SH cells exposed to 5, 10, 25, 50, 75 or 100 μmol/L LDN-57444 for 24 h was assessed using MTT assay, and the cell apoptosis was detected with Hoechst staining. Western blot was performed to identify the expressions of UCH-L1 protein, ubiquitin monomer and polyubiquitinated proteins, and the activity of the ubiquitin-proteasome system (UPS) was evaluated with fluorometry. Results After exposure to UCH-LI inhibitor for 24 h, the cell process-like structures of SK-N-SH cells diminished, and the cell body shrank and became spherical. Exposure to LDN-57444 resulted in concentration-dependent reduction of the cell viability, and the reduction became statistically significant following the exposure to 50 μmol/L LDN-57444, as compared with that in the control group (P<0.05). The exposure also resulted in obvious cell apoptosis as shown by nuclear fragmentation and presence of the apoptotie bodies. Western blot detected no obvious changes in UCH-L1 protein expression but identified reduced ubiquitin monomer and increased polyubiquitinated protein expression in the cells. Fluorometry showed reduced activity of UPS in the exposed cells. Conclusion UCH-L1 inhibitor produces neurotoxicity to dopaminergie neurons and induces cell apoptosis possibly as the result of impaired UPS activity and intracellular accumulation of polyubiquitinated proteins following the exposure.     

泛素羧基末端水解酶-1抑制剂对多巴胺能神经元的神经毒性作用

Objective To investigate the neurotoxic effects ofLDN-57444, a specific ubiquitin C-termiual hydrolase L1 (UCH-L1) inhibitor, on dopaminergic neurons and the possible mechanism. Methods The viability of SK-N-SH cells exposed to 5, 10, 25, 50, 75 or 100 μmol/L LDN-57444 for 24 h was assessed using MTT assay, and the cell apoptosis was detected with Hoechst staining. Western blot was performed to identify the expressions of UCH-L1 protein, ubiquitin monomer and polyubiquitinated proteins, and the activity of the ubiquitin-proteasome system (UPS) was evaluated with fluorometry. Results After exposure to UCH-LI inhibitor for 24 h, the cell process-like structures of SK-N-SH cells diminished, and the cell body shrank and became spherical. Exposure to LDN-57444 resulted in concentration-dependent reduction of the cell viability, and the reduction became statistically significant following the exposure to 50 μmol/L LDN-57444, as compared with that in the control group (P<0.05). The exposure also resulted in obvious cell apoptosis as shown by nuclear fragmentation and presence of the apoptotie bodies. Western blot detected no obvious changes in UCH-L1 protein expression but identified reduced ubiquitin monomer and increased polyubiquitinated protein expression in the cells. Fluorometry showed reduced activity of UPS in the exposed cells. Conclusion UCH-L1 inhibitor produces neurotoxicity to dopaminergie neurons and induces cell apoptosis possibly as the result of impaired UPS activity and intracellular accumulation of polyubiquitinated proteins following the exposure.     

泛素羧基末端水解酶-1抑制剂对多巴胺能神经元的神经毒性作用

Objective To investigate the neurotoxic effects ofLDN-57444, a specific ubiquitin C-termiual hydrolase L1 (UCH-L1) inhibitor, on dopaminergic neurons and the possible mechanism. Methods The viability of SK-N-SH cells exposed to 5, 10, 25, 50, 75 or 100 μmol/L LDN-57444 for 24 h was assessed using MTT assay, and the cell apoptosis was detected with Hoechst staining. Western blot was performed to identify the expressions of UCH-L1 protein, ubiquitin monomer and polyubiquitinated proteins, and the activity of the ubiquitin-proteasome system (UPS) was evaluated with fluorometry. Results After exposure to UCH-LI inhibitor for 24 h, the cell process-like structures of SK-N-SH cells diminished, and the cell body shrank and became spherical. Exposure to LDN-57444 resulted in concentration-dependent reduction of the cell viability, and the reduction became statistically significant following the exposure to 50 μmol/L LDN-57444, as compared with that in the control group (P<0.05). The exposure also resulted in obvious cell apoptosis as shown by nuclear fragmentation and presence of the apoptotie bodies. Western blot detected no obvious changes in UCH-L1 protein expression but identified reduced ubiquitin monomer and increased polyubiquitinated protein expression in the cells. Fluorometry showed reduced activity of UPS in the exposed cells. Conclusion UCH-L1 inhibitor produces neurotoxicity to dopaminergie neurons and induces cell apoptosis possibly as the result of impaired UPS activity and intracellular accumulation of polyubiquitinated proteins following the exposure.     

泛素羧基末端水解酶-1抑制剂对多巴胺能神经元的神经毒性作用

Objective To investigate the neurotoxic effects ofLDN-57444, a specific ubiquitin C-termiual hydrolase L1 (UCH-L1) inhibitor, on dopaminergic neurons and the possible mechanism. Methods The viability of SK-N-SH cells exposed to 5, 10, 25, 50, 75 or 100 μmol/L LDN-57444 for 24 h was assessed using MTT assay, and the cell apoptosis was detected with Hoechst staining. Western blot was performed to identify the expressions of UCH-L1 protein, ubiquitin monomer and polyubiquitinated proteins, and the activity of the ubiquitin-proteasome system (UPS) was evaluated with fluorometry. Results After exposure to UCH-LI inhibitor for 24 h, the cell process-like structures of SK-N-SH cells diminished, and the cell body shrank and became spherical. Exposure to LDN-57444 resulted in concentration-dependent reduction of the cell viability, and the reduction became statistically significant following the exposure to 50 μmol/L LDN-57444, as compared with that in the control group (P<0.05). The exposure also resulted in obvious cell apoptosis as shown by nuclear fragmentation and presence of the apoptotie bodies. Western blot detected no obvious changes in UCH-L1 protein expression but identified reduced ubiquitin monomer and increased polyubiquitinated protein expression in the cells. Fluorometry showed reduced activity of UPS in the exposed cells. Conclusion UCH-L1 inhibitor produces neurotoxicity to dopaminergie neurons and induces cell apoptosis possibly as the result of impaired UPS activity and intracellular accumulation of polyubiquitinated proteins following the exposure.     

泛素羧基末端水解酶-1抑制剂对多巴胺能神经元的神经毒性作用

Objective To investigate the neurotoxic effects ofLDN-57444, a specific ubiquitin C-termiual hydrolase L1 (UCH-L1) inhibitor, on dopaminergic neurons and the possible mechanism. Methods The viability of SK-N-SH cells exposed to 5, 10, 25, 50, 75 or 100 μmol/L LDN-57444 for 24 h was assessed using MTT assay, and the cell apoptosis was detected with Hoechst staining. Western blot was performed to identify the expressions of UCH-L1 protein, ubiquitin monomer and polyubiquitinated proteins, and the activity of the ubiquitin-proteasome system (UPS) was evaluated with fluorometry. Results After exposure to UCH-LI inhibitor for 24 h, the cell process-like structures of SK-N-SH cells diminished, and the cell body shrank and became spherical. Exposure to LDN-57444 resulted in concentration-dependent reduction of the cell viability, and the reduction became statistically significant following the exposure to 50 μmol/L LDN-57444, as compared with that in the control group (P<0.05). The exposure also resulted in obvious cell apoptosis as shown by nuclear fragmentation and presence of the apoptotie bodies. Western blot detected no obvious changes in UCH-L1 protein expression but identified reduced ubiquitin monomer and increased polyubiquitinated protein expression in the cells. Fluorometry showed reduced activity of UPS in the exposed cells. Conclusion UCH-L1 inhibitor produces neurotoxicity to dopaminergie neurons and induces cell apoptosis possibly as the result of impaired UPS activity and intracellular accumulation of polyubiquitinated proteins following the exposure.     

泛素羧基末端水解酶-1抑制剂对多巴胺能神经元的神经毒性作用

Objective To investigate the neurotoxic effects ofLDN-57444, a specific ubiquitin C-termiual hydrolase L1 (UCH-L1) inhibitor, on dopaminergic neurons and the possible mechanism. Methods The viability of SK-N-SH cells exposed to 5, 10, 25, 50, 75 or 100 μmol/L LDN-57444 for 24 h was assessed using MTT assay, and the cell apoptosis was detected with Hoechst staining. Western blot was performed to identify the expressions of UCH-L1 protein, ubiquitin monomer and polyubiquitinated proteins, and the activity of the ubiquitin-proteasome system (UPS) was evaluated with fluorometry. Results After exposure to UCH-LI inhibitor for 24 h, the cell process-like structures of SK-N-SH cells diminished, and the cell body shrank and became spherical. Exposure to LDN-57444 resulted in concentration-dependent reduction of the cell viability, and the reduction became statistically significant following the exposure to 50 μmol/L LDN-57444, as compared with that in the control group (P<0.05). The exposure also resulted in obvious cell apoptosis as shown by nuclear fragmentation and presence of the apoptotie bodies. Western blot detected no obvious changes in UCH-L1 protein expression but identified reduced ubiquitin monomer and increased polyubiquitinated protein expression in the cells. Fluorometry showed reduced activity of UPS in the exposed cells. Conclusion UCH-L1 inhibitor produces neurotoxicity to dopaminergie neurons and induces cell apoptosis possibly as the result of impaired UPS activity and intracellular accumulation of polyubiquitinated proteins following the exposure.     

Expression of expanded polyglutamine targets profilin for degradation and alters actin dynamics

Huntington's disease is caused by polyglutamine expansion in the huntingtin protein. Huntingtin directly interacts with profilin, a major actin monomer sequestering protein and a key integrator of signals leading to actin polymerization. We observed a progressive loss of profilin in the cerebral cortex of Huntington's disease patients, and in cell culture and Drosophila models of polyglutamine disease. This loss of profilin is likely due to increased degradation through the ubiquitin proteasome system. Profilin loss reduces the F/G actin ratio, indicating a shift in actin polymerization. Overexpression of profilin abolishes mutant huntingtin toxicity in cells and partially ameliorates the morphological and functional eye phenotype and extends lifespan in a transgenic polyglutamine Drosophila model. These results indicate a link between huntingtin and profilin and implicate profilin in Huntington's disease pathogenesis.