RNA干扰技术阻断α-synuclein基因过表达诱导的α-synuclein蛋白病理性积聚的研究

目的 构建并筛选针对帕金森病致病基因α-synuclein特异、高效的RNA干扰载体,观察应用RNA干扰技术阻断α-synuclein过表达导致α-synuclein蛋白病理性积聚的作用.方法 采用携带H1启动子的PBSHH1质粒,设计并构建针对α-synuclein基因4个可有效表达发夹状RNA的特异性α-synuclein基因干扰载体pSYNi-1、pSYNi-2、pSYNi-3、pSYNi-4,通过限制性内切酶酶切、DNA测序证实后,转染HEK293细胞,应用Western印迹、逆转录-PER观察干扰载体的有效性,筛选特异、高效的RNA干扰载体.采用脂质2000将筛选的最佳α-synuelein-pBSHH1 RNA 干扰载体及野生型α-synuclein-pEGFP真核细胞表达载体共转染HEK293细胞,并设立对照组,48h后采用Axiovert200型倒置荧光显微镜、荧光免疫细胞化学观察其在细胞内的表达,HE染色观察细胞质内嗜酸性小体的形成.结果 Western印迹、逆转录-PER结果显示,pSYNi-1载体具有高效的RNA干扰抑制作用,效率达69.6%;将α-synuclein-pBSHH1 RNA干扰载体pSYNi-1及野生型α-synuclein-pEGFP真核细胞表达载体转染HEK293细胞,48h后荧光显微镜下观察细胞在波长488 nm蓝色激发光下发出明亮的绿色荧光,其中对照组某些细胞质内出现绿色荧光物质积聚,而转染pSYNi-1干扰组细胞质内绿色荧光物质分布均匀;免疫荧光细胞化学检测结果显示,转染48h后对照组可见α-synuclein免疫阳性产物在胞浆内聚集,转入RNA干扰载体psYNi-1后胞浆内α-synuclein免疫阳性产物分布均匀;HE结果显示,转染48h后,对照组某些细胞质内出现圆形的嗜酸性小体(类Lewy小体)形成;转入RNA干扰载体pSYNi-1后胞浆内未见类Lewy小体形成.结论 RNA干扰技术通过抑制α-synuclein基因的表达,成功阻断了野生型α-synuclein过表达所诱导的α-synuelein蛋白病理性积聚,为最终应用RNA干扰技术临床治疗帕金森病提供了某些依据.     

α-synuclein基因过度表达诱导HEK293细胞α-synuclein蛋白病理性积聚

目的观察α-synuclein过度表达诱导HEK293细胞α-synuclein蛋白病理性积聚的作用。方法将消除终止密码子α-synuclein基因扩增产物连入pGEM T-easy载体，DNA测序证实后亚克隆入增强型绿色荧光蛋白pEGFP-N1质粒，通过限制性内切酶酶切鉴定重组质粒。采用脂质2000将野生型α-synuclein-EGFP真核表达载体转染HEK293细胞，48h后采用Axiovert200型倒置荧光显微镜、荧光免疫细胞化学观察其在细胞内的表达，HE染色观察细胞胞浆内嗜酸性小体的形成。结果消除终止密码子的扩增序列经测序证实并亚克隆入pEGFP-N1质粒后，限制性内切酶酶切鉴定质粒大小、酶切位点上均符合实验设计。将野生型α-synuclein-EGFP真核表达载体转染HEK293细胞，48h后荧光显微镜下观察细胞在波长488nm蓝色激发光下发出明亮的绿色荧光，其中某些细胞出现绿色荧光物质积聚；免疫荧光细胞化学检测，EGFP阳性细胞同时也表现为α-synuclein免疫反应阳性，某些细胞胞浆内可见α-synuclein免疫阳性产物聚集；HE结果发现一些细胞胞浆内出现圆形的嗜酸性小体形成，约占细胞总数的10．8％。结论野生型α-synuclein基因过表达可诱导α-synuclein蛋白在HEK293细胞内积聚，胞浆内嗜酸性小体形成。     

小泛素样修饰蛋白-1对α-突触核蛋白基因突变或过表达诱导的细胞包涵体形成及细胞凋亡的影响

目的 探讨α-突触核蛋白(α-synuclein)的小泛素样修饰蛋白(small ubiquitin-like modifier,SUMO)-1对α-synuclein基因过表达或突变诱导的细胞包涵体形成及细胞凋亡的影响.方法 构建野生型(WT)、A53T突变型和缺失SUMO-1互作氨基酸的K96R突变型、K96R-A53T突变型α-synuclein真核表达质粒.应用脂质体介导转染方式将构建好的质粒转入HEK293细胞;48 h后Hoechst 33258染色,采用Axiovert200型倒置荧光显微镜观察对细胞的影响,应用四甲基偶氮唑盐检测细胞活力,Annexin V-PE流式细胞仪检测细胞凋亡.结果 将构建所得真核表达质粒经双酶切鉴定及DNA测序证实;将WT型、A53T型、K96R型、K96R-A53T型α-synuclein真核表达质粒转染HEK293细胞,48 h后伊红染色显示转染野生型α-synuclein- pEGFP组及A53T突变型组某些细胞胞浆内出现圆形的嗜酸性小体(类Lewy小体)形成,分别占细胞总数的9.4％和11.7％,转染K96R及K96R-A53T融合表达载体组细胞内嗜酸性小体形成比率为10.2％和9.8％,两两相比差异无统计学意义(P＞0.05).Hoechst染色结果显示,WT组、A53T组细胞核变大,出现着色不均,染色质聚集成斑点状,未见核浓缩或核碎裂.K96R组及K96R-A53T组胞核着色基本均匀.采用四甲基偶氮唑盐法结果显示转染空质粒组细胞活力为96.2％,转染WT组、A53T组细胞活力下降至53.4％及56.1％,转染K96R组及K96R-A53T组细胞活力为72.3％和69.8％;转染48 h后,WT组、A53T组细胞凋亡率分别为32.2％和34.1％,转染K96R组及K96R-A53T突变组细胞凋亡率下降为19.4％和20.3％,两两相比差异有统计学意义(P＜0.05).结论 SUMO-1对α-synuclein基因过度表达及α-synuclein基因致病突变A53T诱导的细胞包涵体的形成无明显影响;SUMO-1可加强α-synuclein基因过度表达及α-synuclein基因致病突变A53T诱导的细胞毒性及细胞凋亡,提示SUMO-1参与了细胞凋亡过程.     

Neuropathology and neurodegeneration in rodent brain induced by lentiviral vector-mediated overexpression of alpha-synuclein

Two mutations in alpha-synuclein, the main constituent of Lewy bodies, have been identified in familial Parkinson's disease. We have stereotactically injected lentiviral vectors encoding wild-type and A30P mutant human alpha-synuclein in different brain regions (striatum, substantia nigra, amygdala) of mice. Overexpression of alpha-synuclein induced time-dependent neuropathological changes reminiscent of Lewy pathology: abnormal accumulation of alpha-synuclein in cell bodies and neurites, alpha-synuclein-positive neuritic varicosities and cytoplasmic inclusions that stained with ubiquitin antibodies and became larger and more frequent with time. After one year, alpha-synuclein- and ubiquitin-positive neurons displayed a degenerative morphology and a significant loss of alpha-synuclein-positive cells was observed. Similar findings were observed with both the wild-type and the A30P mutant form of alpha-synuclein and this in different brain regions. This indicates that overexpression of alpha-synuclein is sufficient to induce Lewy-like pathology and neurodegeneration and that this effect is not restricted to dopaminergic cells. Our data also demonstrate the use of lentiviral vectors to create animal models for neurodegenerative diseases.     

Neuronal inclusions in sporadic motor neuron disease are negative for alpha-synuclein

Alpha-synuclein has been implicated in neurodegenerative diseases characterized by Lewy bodies. However, we have only scanty information on the immunoreactivity of alpha-synuclein in other inclusion bodies such as the Lewy body-like inclusions and the skein-like inclusions observed in motor neuron disease (MND). In this report, we immunocytochemically investigated inclusion bodies observed in the anterior horn neurons of the spinal cord in 29 patients with sporadic MND. Sixteen age-matched patients without any neurological disease served as controls. In MND patients, we recognized Lewy body-like hyaline inclusions, skein-like inclusions, Bunina bodies, basophilic inclusions, and intracytoplasmic hyaline (colloid) inclusions, but none of them were immunostained for alpha-synuclein. Our findings in this study do not support the hypothesis that MND could be classified as one of the diseases grouped as alpha-synucleinopathies.     

Motor dysfunction and gliosis with preserved dopaminergic markers in human alpha-synuclein A30P transgenic mice

Alpha-synuclein is a major component of Lewy bodies (LBs) in the substantia nigra and cortex in Parkinson's disease (PD) and dementia with Lewy bodies (DLB), and in glial inclusions in multiple systems atrophy (MSA). Mutations in alpha-synuclein have been associated with autosomal dominant forms of PD. We investigated the clinical and neuropathological effects of overexpression of human alpha-synuclein, alpha-synuclein A30P, and alpha-synuclein A53T under the control of the hamster prion protein (PrP) promoter; 5-15x endogenous levels of protein expression were achieved with widespread neuronal, including nigral, transgene expression. High expression of alpha-synuclein A30P in the Tg5093 line was associated with a progressive motor disorder with rigidity, dystonia, gait impairment, and tremor. Histological analysis of this line showed aberrant expression of the protein in cell soma and progressive CNS gliosis, but no discrete Lewy body-like alpha-synuclein inclusions could be identified. Biochemical analysis demonstrated alpha-synuclein fragmentation. Despite strong expression of the transgene in the nigra, there was no specific deterioration of the nigrostriatal dopaminergic system as assessed by quantitation of nigral tyrosine hydroxylase (TH) containing neurons, striatal TH immunoreactivity, dopamine levels, or dopamine receptor number and function. Lower expressing lines had no specific behavioral or histopathological phenotype. Thus, high expression of mutant human alpha-synuclein resulted in a progressive motor and widespread CNS gliotic phenotype independent of dopaminergic dysfunction in the Tg5093 line.     

Expression of mutant alpha-synuclein causes increased susceptibility to dopamine toxicity

Mutations of the alpha-synuclein gene have been identified in autosomal dominant Parkinson's disease (PD). Transgenic mice overexpressing wild-type human alpha-synuclein develop motor impairments, intraneuronal inclusions and loss of dopaminergic terminals in the striatum. To study the mechanism of action through which mutant alpha-synuclein toxicity is mediated, we have generated stable, inducible cell models expressing wild-type or PD-associated mutant (G209A) alpha-synuclein in human-derived HEK293 cells. Increased expression of either wild-type or mutant alpha-synuclein resulted in the formation of cytoplasmic aggregates which were associated with the vesicular (including monoaminergic) compartment. Expression of mutant alpha-synuclein induced a significant increase in sensitivity to dopamine toxicity compared with the wild-type protein expression. These results provide an explanation for the preferential dopaminergic neuronal degeneration seen in both the PD G209A mutant alpha-synuclein families and suggest that similar mechanisms may underlie or contribute to cell death in sporadic PD.     

Alpha-synuclein-enhanced green fluorescent protein fusion proteins form proteasome sensitive inclusions in primary neurons.

Alpha-synuclein accumulates in the brains of sporadic Parkinson's disease patients as a major component of Lewy bodies, and mutations in alpha-synuclein are associated with familial forms of Parkinson's disease. The pathogenic mechanisms that precede and promote the aggregation of alpha-synuclein into Lewy bodies in neurons remain to be determined. Here, we constructed a series of alpha-synuclein-enhanced green fluorescent protein (alpha-synucleinEGFP, SynEGFP) fusion proteins to address whether the Parkinson's disease-associated mutations alter the subcellular distribution of alpha-synuclein, and to use as a tool for experimental manipulations to induce aggregate formation. When transfected into mouse cultured primary neurons, the 49-kDa alpha-synucleinEGFP fusion proteins are partially truncated to a approximately 27-kDa form. This non-fluorescent carboxy-terminally modified fusion protein spontaneously forms inclusions in the neuronal cytoplasm. A marked increase in the accumulation of inclusions is detected following treatment with each of three proteasome inhibitors, n-acetyl-leu-leu-norleucinal, lactacystin and MG132. Interestingly, Ala30Pro alpha-synucleinEGFP does not form the cytoplasmic inclusions that are characteristic of wild-type and Ala53Thr alpha-synucleinEGFP, supporting the idea that the Ala30Pro alpha-synuclein protein conformation differs from wild-type alpha-synuclein. Similar inclusions are formed if alpha-synuclein carboxy-terminus is modified by the addition of a V5/6xHistidine epitope tag. By contrast, overexpression of unmodified alpha-synuclein does not lead to aggregate formation. Furthermore, synphilin-1, an alpha-synuclein interacting protein also found in Lewy bodies, colocalizes with the carboxy-terminally truncated alpha-synuclein fusion protein in discrete cytoplasmic inclusions.Our finding that manipulations of the carboxy-terminus of alpha-synuclein lead to inclusion formation may provide a model for studies of the pathogenic mechanisms of alpha-synuclein aggregation in Lewy bodies.     

Beta-synuclein modulates alpha-synuclein neurotoxicity by reducing alpha-synuclein protein expression

Parkinson's disease (PD) is a neurodegenerative disorder characterized by fibrillar aggregates of alpha-synuclein in characteristic inclusions known as "Lewy bodies". As mutations altering alpha-synuclein structure or increasing alpha-synuclein expression level can cause familial forms of PD or related Lewy body disorders, alpha-synuclein is believed to play a central role in the process of neuron toxicity, degeneration and death in "synucleinopathies". beta-synuclein is closely related to alpha-synuclein and has been shown to inhibit alpha-synuclein aggregation and ameliorate alpha-synuclein neurotoxicity. We generated beta-synuclein transgenic mice and observed a marked reduction in alpha-synuclein protein expression in the cortex of mice over-expressing beta-synuclein. This reduction in alpha-synuclein protein expression was not accompanied by decreases in alpha-synuclein mRNA expression. Using the prion protein promoter alpha-synuclein A53T mouse model of PD, we demonstrated that over-expression of beta-synuclein could retard the progression of impaired motor performance, reduce alpha-synuclein aggregation and extend survival in doubly transgenic mice. We attributed the amelioration of alpha-synuclein neurotoxicity in such bigenic mice to the ability of beta-synuclein to reduce alpha-synuclein protein expression based upon I(125) autoradiography quantification. Our findings indicate that increased expression of beta-synuclein protein results in a reduction of alpha-synuclein protein expression. As increased expression of alpha-synuclein may cause or contribute to PD pathogenesis in sporadic and familial forms of disease, this observation has important implications for the development of therapies for PD.     

Ubiquitination of alpha-synuclein by Siah-1 promotes alpha-synuclein aggregation and apoptotic cell death

Point mutations and gene multiplication of alpha-synuclein cause autosomal dominant familial Parkinson's disease (PD). Moreover, alpha-synuclein- and ubiquitin-positive inclusion bodies are the pathological hallmarks of PD and several other neurodegenerative diseases, such as dementia with Lewy bodies and multiple system atrophy. Despite the presence of ubiquitinated alpha-synuclein species in Lewy bodies, the regulation of alpha-synuclein ubiquitination and its role in Lewy body formation and neurodegeneration remain poorly understood. Here, we report that alpha-synuclein interacts and colocalizes with mammalian seven in absentia homologue-1 (Siah-1), a RING-type E3 ubiquitin-protein ligase. Siah-1 binds the brain-enriched E2 ubiquitin-conjugating enzyme UbcH8 and facilitates mono- and di-ubiquitination of alpha-synuclein in vivo. The ubiquitination of alpha-synuclein by Siah-1 is disrupted by the PD-linked A30P mutation but not by A53T mutation. We find that Siah-1-mediated ubiquitination does not target alpha-synuclein for degradation by the proteasome, but rather, it promotes alpha-synuclein aggregation and enhances alpha-synuclein toxicity. Our findings suggest that Siah-1-mediated alpha-synuclein ubiquitination may play a critical role in Lewy body formation and PD pathogenesis.     

A systematic RNAi screen reveals involvement of endocytic pathway in neuronal dysfunction in alpha-synuclein transgenic C. elegans

Mutations or multiplications in alpha-synuclein gene cause familial forms of Parkinson disease or dementia with Lewy bodies (LB), and the deposition of wild-type alpha-synuclein as LB occurs as a hallmark lesion of these disorders, collectively referred to as synucleinopathies, implicating alpha-synuclein in the pathogenesis of synucleinopathy. To identify modifier genes of alpha-synuclein-induced neurotoxicity, we conducted an RNAi screen in transgenic C. elegans (Tg worms) that overexpress human alpha-synuclein in a pan-neuronal manner. To enhance the RNAi effect in neurons, we crossed alpha-synuclein Tg worms with an RNAi-enhanced mutant eri-1 strain. We tested RNAi of 1673 genes related to nervous system or synaptic functions, and identified 10 genes that, upon knockdown, caused severe growth/motor abnormalities selectively in alpha-synuclein Tg worms. Among these were four genes (i.e. apa-2, aps-2, eps-8 and rab-7) related to the endocytic pathway, including two subunits of AP-2 complex. Consistent with the results by RNAi, crossing alpha-synuclein Tg worms with an aps-2 mutant resulted in severe growth arrest and motor dysfunction. alpha-Synuclein Tg worms displayed a decreased touch sensitivity upon RNAi of genes involved in synaptic vesicle endocytosis, and they also showed impaired neuromuscular transmission, suggesting that overexpression of alpha-synuclein caused a failure in uptake or recycling of synaptic vesicles. Furthermore, knockdown of apa-2, an AP-2 subunit, caused an accumulation of phosphorylated alpha-synuclein in neuronal cell bodies, mimicking synucleinopathy. Collectively, these findings raise a novel pathogenic link between endocytic pathway and alpha-synuclein-induced neurotoxicity in synucleinopathy.     

Phosphorylation of alpha-synuclein characteristic of synucleinopathy lesions is recapitulated in alpha-synuclein transgenic Drosophila

alpha-Synuclein is a major component of Lewy bodies in the brains of patients with Parkinson's disease (PD) as well as of neuronal/glial inclusions in a subset of neurodegenerative disorders collectively termed synucleinopathies. Here we studied by immunohistochemistry the accumulation of alpha-synuclein in transgenic (TG) Drosophila overexpressing wild-type (WT) or familial PD-linked mutant (i.e. A30P and A53T) alpha-synuclein in neurons, with special reference to the phosphorylation at Ser129, that is characteristic of human synucleinopathy lesions. Progressive accumulation of human alpha-synuclein was widely observed in the cell bodies and neurites of major neuronal nuclei in TG Drosophila brains, and phosphorylation of alpha-synuclein at Ser129 was detected in a limited subset of neurons approximately 1 week after alpha-synuclein immunoreactivity was first detected. Phosphorylated alpha-synuclein was most abundant in A53T mutant, followed by A30P and WT Drosophila. These results suggest that accumulation and phosphorylation of alpha-synuclein is recapitulated in neurons of alpha-synuclein transgenic Drosophila, that underscores the relevance of this model to human synucleinopatheis.     

Abnormal alpha-synuclein solubility, aggregation and nitration in the frontal cortex in Pick's disease

Abnormal solubility and aggregation of alpha-synuclein have been observed in the frontal cortex in three cases with Pick's disease (PiD) when compared with age-matched controls. Bands of 45 kDa and higher molecular weight were detected in the SDS-soluble fractions only in PiD. Patterns in PiD differed from that observed in the cerebral cortex in Lewy body diseases which were examined in parallel. Immunoblots to alpha-synuclein nitrated in tyrosines revealed bands of 45 and 60 kDa in Dxc- and SDS-soluble fractions in the frontal cortex (which is vulnerable to PiD) but not in the occipital cortex (which is resistant to this degenerative disease). Moreover, nitrated alpha-synuclein was found in Lewy bodies and neurites in synucleinopathies but diffusely in the cytoplasm of scattered neurons in PiD. These findings demonstrate abnormal and distinct alpha-synuclein solubility and aggregation, and alpha-synuclein nitration without formation of Lewy bodies in the frontal cortex in PiD.     

Polyunsaturated fatty acids induce alpha-synuclein-related pathogenic changes in neuronal cells

The misfolding and aggregation of normally soluble proteins has emerged as a key feature of several neurodegenerative diseases. In Parkinson's disease, progressive loss of dopaminergic neurons is accompanied by polymerization of the cytoplasmic protein alpha-synuclein (alphaS) into filamentous inclusions found in neuronal somata (Lewy bodies) and dendrites (Lewy neurites). Similar alphaS aggregates occur in cortical neurons in dementia with Lewy bodies. Numerous reports now indicate that alphaS can interact with lipids. We previously found that treating dopaminergic cells expressing alphaS with polyunsaturated fatty acids (PUFAs) induced the formation of soluble, sodium dodecyl sulfate-stable oligomers whereas treatment with saturated fatty acids did not. Here, we examine the relevance of alphaS-PUFA interactions to the development of Parkinson's disease-like cytopathology. Exposure of alphaS-overexpressing dopaminergic or neuronal cell lines to physiological levels of a PUFA induced the formation of proteinaceous inclusions in the cytoplasm. Kinetic experiments indicated that PUFA-induced soluble oligomers of alphaS precede these Lewy-like inclusions. Importantly, we found that alphaS oligomers were associated with cyto-toxicity, whereas the development of Lewy-like inclusions appeared to be protective. We conclude that alterations in PUFA levels can lead to aggregation of alphaS and subsequent deposition into potentially cyto-toxic oligomers that precede inclusions in dopaminergic cells.     

Alpha-synuclein degradation by serine protease neurosin: implication for pathogenesis of synucleinopathies

Accumulation of insoluble alpha-synuclein aggregates in the brain is characteristic of Parkinson's disease, dementia with Lewy bodies and multiple system atrophy. Although numerous studies on the aggregation properties of alpha-synuclein have been reported, little is known about its degradation so far. In view of proteolytic degradation, we have found that the serine protease neurosin (kallikrein-6) degrades alpha-synuclein and co-localizes with pathological inclusions such as Lewy bodies and glial cytoplasmic inclusions. In vitro study showed that neurosin prevented alpha-synuclein polymerization by reducing the amount of monomer and also by generating fragmented alpha-synucleins that themselves inhibited the polymerization. Upon cellular stress, neurosin was released from mitochondria to the cytosol, which resulted in the increase of degraded alpha-synuclein species. Down-regulation of neurosin caused accumulation of alpha-synuclein within cultured cells. Thus we concluded that neurosin plays a significant role in physiological alpha-synuclein degradation and also in the pathogenesis of synucleinopathies.     

小泛素样修饰蛋白对α-突触核蛋白线粒体亚细胞定位及α-突触核蛋白经泛素系统降解的影响

目的 探讨α-突触核蛋白(α-synuclein)的小泛素样修饰蛋白1(small ubiquitin-like modifier1,SUMO-1)化修饰对α-synuclein蛋白亚细胞线粒体定位及α-synuelein蛋白经泛素系统降解的影响.方法 构建野生型、A53T突变型和缺失SUMO-1互作氨基酸的K96R突变型α-synuclein真核表达质粒.将野生型、A53T突变型和K96R突变型α-synuclein真核表达质粒分别转染HEK293细胞;在转染后48 h通过应用线粒体染色剂和激光共聚焦技术,观察野生型、A53T突变型及缺失SUMO-1修饰的α-synuclein蛋白的亚细胞线粒体定位和蛋白聚集情况.在转染后48 h应用anti-ubiquitin抗体进行Western印迹分析,明确野生型、A53T突变型及缺失SUMO-1修饰的α-synuclein蛋白泛素化程度有无差别.结果 将构建所得EGFP-α-synuclein-WT、EGFP-α-synuclein-A53T、EGFP-α-synuclein-K96R真核表达质粒经双酶切鉴定及DNA测序证实;激光共聚焦结果显示野生型、A53T突变型、K96R突变型α-synuclein蛋白均广泛分布于细胞质和细胞核中,以细胞质为主,野生型、A53T型细胞可见绿色荧光物质在胞质积聚,形成强荧光斑块,K96R型胞质内绿色荧光物质聚集少;野生型、A53T突变型、K96R突变型α-synuclein均与线粒体存在共定位,A53T突变型、K96R突变型α-synuclein在SUMO-1修饰或缺失的情况下对α-synuclein蛋白的线粒体亚细胞定位无明显影响.Western印迹结果显示转染缺失SUMO-1互作氨基酸的K96R突变型α-synuclein真核表达质粒组的细胞泛素蛋白的含量与转染空质粒组相比无明显变化,转染野生型、A53T突变型α-synuclein真核表达质粒组HEK293细胞中泛素蛋白的含量减少.结论 α-synuclein基因过度表达及致病突变A53T对α-synuclein蛋白的线粒体亚细胞定位无明显影响;SUMO-1修饰对α-synuclein蛋白的线粒体亚细胞定位也无明显影响;SUMO-1对a-αsynuclein基因过度表达及A53T突变型α-synuclein细胞内泛素化蛋白数量产生影响.     

Salusin-a基因真核表达载体的构建及在HEK293细胞中的表达

目的:研究增强型绿色荧光蛋白真核表达载体Salusin-a(pEG-FP-Salusin-a)的构建及在人胚胎肾细胞系293细胞(HEK293)中的表达。方法:提取人单核细胞系THP-1细胞Salusin-a的mRNA,逆转录多聚酶链反应(RT-PCR)扩增Salusin-a基因,克隆入pEGFP-N3载体,双酶切、菌落PCR及测序鉴定pEGFP-Salusin-a质粒。用脂质体转染pEGFP-Salusin-a入HEK293细胞,分为转染细胞组、质粒对照组和空白对照组,检测分析各组荧光蛋白和Salusin-a基因的表达。结果:成功构建pEGFP-Salusin-a质粒,并转染HEK293,细胞转染效率86%,转染细胞组和质粒对照组绿色荧光蛋白的表达明显高于空白对照组(P0.05);转染细胞组Salusin-amRNA的表达明显高于质粒对照组和空白对照组(P0.05)。结论:重组pEGFP-Salusin-a质粒能转染HEK293细胞并表达Salusin-a,为Salusin-a基因功能的进一步研究提供了实验基础。     

Ubiquitination of alpha-synuclein is not required for formation of pathological inclusions in alpha-synucleinopathies

alpha-Synucleinopathies, including Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy, are neurodegenerative disorders in which abnormal inclusions containing alpha-synuclein accumulate in selectively vulnerable neurons and glia. In this report, immunohistochemistry demonstrates ubiquitin in subsets of alpha-synuclein inclusions in dementia with Lewy bodies and multiple system atrophy. Biochemistry demonstrates that alpha-synuclein in the sodium dodecyl sulfate-soluble fractions of diseased brains is ubiquitinated, with mono- and di-ubiquitinated species predominating over polyubiquitinated forms. Similar immunohistochemical and biochemical characteristics were observed in an A53T mutant human alpha-synuclein transgenic mouse model of neurodegenerative alpha-synucleinopathies. Furthermore, in vitro ubiquitination of alpha-synuclein fibrils recapitulated the pattern of alpha-synuclein ubiquitination observed in human disease and the A53T alpha-synuclein mouse model. These results suggest that ubiquitination of alpha-synuclein is not required for inclusion formation and follows the fibrillization of alpha-synuclein.     

Mitochondrial localization of alpha-synuclein protein in alpha-synuclein overexpressing cells

Alpha-synuclein (alpha-syn) is implicated in the pathogenesis of Parkinson's disease (PD). Mutations in alpha-syn gene or alpha-syn locus (SNCA) triplication are associated with mitochondrial abnormalities and early onset of familial PD. The goals of the present study were to examine whether alpha-syn is localized in the mitochondria of alpha-syn overexpressing cells (HEK-syn cells); and whether alpha-syn overexpression causes cells to be more vulnerable to mitochondrial toxin, rotenone. Western blotting and confocal microscopy techniques were employed to assess localization of alpha-syn in the mitochondria of HEK-293 cells that were stably transfected with human wild-type alpha-syn. The results demonstrated that the mitochondrial fractions that were isolated from HEK-syn cells showed the presence of alpha-syn, whereas, no alpha-syn was detected in the mitochondrial fractions of control HEK cells. The mitochondria of HEK-syn cells were found to be more susceptible to rotenone-induced toxicity when compared to control HEK cells. The intracellular ATP levels were significantly decreased in HEK-syn cells in response to sub toxic concentrations of rotenone. These results suggest that under overexpression conditions, alpha-syn may translocate to mitochondria and cause enhanced toxicity in response to sub toxic concentrations of mitochondrial toxins. This study has implications to the pathogenesis of familial PD where alpha-syn overexpression is mainly involved.     

Expression of alpha-synuclein in non-apoptotic,slowly degenerating facial motoneurones

The discovery that missense mutations in the alpha-synuclein gene represent a rare genetic cause of Parkinson's disease (PD) has had significant impact on the development of research into neurodegenerative disorders. It is becoming increasingly clear that alpha-synuclein plays a central role in the pathological process, which causes Lewy body formation and neurodegeneration in PD. Importantly, there is evidence to suggest that mutated alpha-synuclein is toxic to both nerve cells and glia. However, the regulation and function of wild-type alpha-synuclein are as yet ill defined. Using the facial nerve axotomy model, we have addressed the question whether the expression of alpha-synuclein in nerve cells may change in response to injury. We were particularly interested in testing the hypothesis that the severity of neuronal injury had an effect on alpha-synuclein metabolism. Facial nerve cut and crush, respectively, were performed in adult rats where normal facial motoneurones do not express alpha-synuclein. Following axotomy, a subset of facial motoneurones newly expressed high levels of alpha-synuclein immunoreactivity in their cell body and, occasionally, their nucleus. Significantly more nerve cells were labelled following facial nerve transection than following facial nerve crush. Confocal microscopy revealed a granular pattern of alpha-synuclein aggregation in degenerating nerve cells. Interestingly, the observed cell death phenotype was clearly non-apoptotic and developed over days or weeks rather than hours. Thus, axotomy of adult rat facial motoneurones triggers de novo expression of alpha-synuclein and this expression is associated with a non-apoptotic, slow form a neurodegeneration. In addition, the extent of alpha-synuclein expression is related to the severity of neuronal injury.