斯坦利·普鲁辛纳经过多年的研究,终于初步搞清了引起搔痒病的病原体即阮病毒的一些特点。他发现阮病毒大小只有30一50纳米,电镜下见不到病毒粒子的结构;经负染后要见到聚集而成的棒状体,其大小约为10~250 x 100~200纳米。通过研究还发现,朊病毒对多种因素的灭活作用表现出惊人的抗性。对物理因素,如紫外线照射、电离辐射、超声波以及80~100℃高温,均有相当的耐受能力。对化学试剂与生化试剂,如甲醛、羟胺、核酸酶类等表现出强抗性。 对蛋白酶K、尿素、苯酚、氯仿等不具抗性。在生物学特性上,朊病毒能造成慢病毒性感染而不表现出免疫原性,巨噬细胞能降低甚至灭活朊病毒的感染性,但使用免疫学技术又不能检测出有特异性抗体存在,不诱发干扰素的产生,也不受干扰素作用。总体上说,凡能使蛋白质消化、变性、修饰而失活的方法,均可能使朊病毒失活;凡能作用于核酸并使之失活的方法,均不能导致朊病毒失活。由此可见,朊病毒本质上是具有感染性的蛋白质。普鲁辛纳将此种蛋白质单体称为朊病毒蛋白(PrP)。
朊病毒病除上文提到的几种由朊病毒引起的疾病均发生在动物身上外,人的朊病毒病已发现有4种:库鲁病(Ku-rmm)、克——雅氏综合症(CJD)、格斯特曼综合症(GSS)及致死性家庭性失眠症(FFI)。临床变化都局限于人和动物的中枢神经系统。病理研究表明,随着阮病毒的侵入、复制,在神经元树突和细胞本身,尤其是小脑星状细胞和树枝状细胞内发生进行性空泡化,星状细胞胶质增生,灰质中出现海绵状病变。朊病毒病属慢病毒性感染,皆以潜伏期长,病程缓慢,进行性脑功能紊乱,无缓解康复,终至死亡为特征。
朊病毒是一种具有感染性和自我复制能力的因子,也叫做普列昂获蛋白质侵染因子。虽然它们具体的活动和复制机制还不是很清楚,但是它们通常被认为是引起先前一系列人们了解甚少的传染性海绵状脑病的原因,这些脑病包括羊搔痒症和牛绵状脑病(也叫“疯牛病”)。这些疾病对脑组织结构的影响都是致命的和不可医治的。
朊病毒最早由美国旧金山加利福尼亚大学的斯坦利·B·布鲁辛纳(Stanley B. Prusiner)于1982年发现的。 Stanley B. Prusiner of the University of California, San- Francisco
Cited for his discovery of prions, “an entirely new genre of disease-causing agents……” 美国神经学家,因为提出"朊病毒学说"而获得1997年诺贝尔奖
《 朊病毒分子病理学》(Molecular Pathology of the Prions )
Harry F.Baker 编著,2001年Humana Press Inc.出版,279页。
作者系国际公认的朊病毒研究专家,他们在分子水平上综述了朊病毒研究的最新发展,用新的方法去了解朊病毒蛋白质和朊病毒疾病。利用各种关键技术,这些著名的科学家正在探索并阐述朊病毒蛋白质的正常功能,发现和测量对朊病毒疾病的早期免疫反应,尽可能地探索治疗的目标。他们还用转基因大鼠和新的电生理研究去阐明包括朊病毒在内的致病机理。
《朊病毒分子病理学》为基础研究和临床神经病理学家提供了最新的研究发展和方法,以了解朊病毒的发病机理。
本书特点:1. 包括了病理学组织上的显微镜方法分析的技术;2. 提供研究病理学的最新电生理技术;3. 应用转基因方法探索朊病毒疾病的发病机理;4. 概括最新的发展和方法以了解朊病毒疾病;5. 用大脑移植术研究致病过程。
PrpSc形成后,在生物体内选择靶神经元,或选择同源的PrpC.以PrpSc为模板,PrpC——Prp*——PrpSc
*(PrpC是一种膜糖蛋白,其代谢周期从内质网开始.GPI锚和甘露糖在那里迅速附着于PrpC,再沿细胞分裂途径送至高尔基体N-寡糖被修饰并唾液酸化;再由分泌小泡运送至细胞外表面.绝大部分以GPI锚锚定在细胞表面;经过半衰期
3-6个小时后重新进入细胞内.)作者: wood533 时间: 2013-7-19 15:57
相关疾病:
感染朊病毒病
一.朊病毒一般性质:
朊病毒的早期认识多源于羊瘙痒病的研究,它是一种具有侵染性且不含核酸的蛋白质。朊病毒蛋白(PrP)分子量为27,000至30,000,是构成朊病毒的基本单位,PrP本身不具有侵染性,由3个PrP分子构成的“朊病毒单位”具有高度侵染性。PrP 还能聚合成杆状颗粒,约由1000个PrP构成的这种杆不单独存在,总是排列成丛。杆和丛都有传染性[7,8]。PrP由17种氨基酸,246个分子组成[7]。它包括两种形式[9]:细胞型(the normal or cellular form of prion protein, PrPc)和异常型(the pathogenic or scrapie form of prion protein , PrPSc)。PrPC分子量33—35KU,含一对二硫键和2个N 型复合寡糖链,二硫键和糖基化残基都在PrP的C端。N端含22个氨基酸残基组成的信号肽序列,C端含由23个氨基酸组成的糖基磷酸肌醇锚受体结合位点(GPI)[10]。PrPC是一种膜蛋白,已证明它是定位于细胞膜的穴样内陷类结构域(CLDS)[11]。PrPSc与PrPC具有下列不同生化特性:(1)在非变性去污剂中PrPSc是不溶的[12];(2)PrPSc具有相对的抗蛋白酶水解特性[13];(3)PrPC和PrPSc都依赖GPI附着在细胞膜表面,经磷酸肌醇脂酶C(PIPLC)酶解后PrPC从膜上释放出来,而PrPSc不释放,TritonX-100进行相分配后,PrPC处于水相,而PrPSc处于TritonX-100相中[14];(4)特异的抗体只与PrPSc有血清反应,而与PrPC无反应,证明两者含有不同的构象表位[15]。(5)糖基化比例和部位不同,PrPSc糖基化比例要低于PrPC[16]。
Peripheral infection is the natural route of transmission in most prion diseases. Peripheral prion infection is followed by rapid prion replication in lymphoid organs, neuroinvasion and progressive neurological disease. Both immune cells and nerves are involved in pathogenesis, but the mechanisms of prion transfer from the immune to the nervous system are unknown. Here we show that ablation of the chemokine receptor CXCR5 juxtaposes follicular dendritic cells (FDCs) to major splenic nerves, and accelerates the transfer of intraperitoneally administered prions into the spinal cord. Neuroinvasion velocity correlated exclusively with the relative locations of FDCs and nerves: transfer of CXCR5-/- bone marrow to wild-type mice induced perineural FDCs and enhanced neuroinvasion, whereas reciprocal transfer to CXCR5-/- mice abolished them and restored normal efficiency of neuroinvasion. Suppression of lymphotoxin signalling depleted FDCs, abolished splenic infectivity, and suppressed acceleration of pathogenesis in CXCR5-/- mice. This suggests that prion neuroimmune transition occurs between FDCs and sympathetic nerves, and relative positioning of FDCs and nerves controls the efficiency of peripheral prion infection.
传染性泡状脑炎(TSEs-transmissible spongiform encephalopathies)的临床诊断一直是一个很困难的问题,因为往往要到疾病发展到晚期的时候病人才能表现出临床症状来。Dell'Omo et al.在European Journal of Neuroscience上报道的最新研究发现被不同prion种系所感染的小鼠在临床症状产生之前就表现出生物钟活性的显著改变,而且这些改变是与prion的种系有关的。
研究者将小鼠用三种prion种系进行感染,分别是139A、ME7和牛的泡状脑炎BSE种系301C。用一个自动的跟踪系统,小鼠的活动被连续的监控了七个星期。最显著的活动改变出现的夜间,小鼠最活跃的时期。注射了301C和ME7的小鼠表现出夜间活性的持续抑制,从开始监控时就产生。而139A种系注射小鼠则一开始表现出正常的活性,但在临床症状开始产生后表现出异常的活跃。在11周后,301C注射小鼠表现出比ME7注射小鼠活动少的多。
研究者认为这种监控的系统同样适用与大型动物,这显然是早期诊断的一个重要指标,而且如果活性改变还与病毒种系有关的话,检测出受感染动物是受何种病毒感染也是十分可能的了。
相关文章及链接:
ORIGINAL RESEARCH PAPERS
Dell'Omo, G. et al. Automated home cage monitoring of mice infected with BSE and scrapie differentiates early behavioural changes according to prion strain. Eur. J. Neurosci. 2002 (doi:10.1046/j.1460-9568.2002.02128.x)
FURTHER READING
Collinge, J. Prion diseases of humans and animals: their causes and molecular basis. Annu. Rev. Neurosci. 24, 519-550 (2001) | Article | PubMed |
WEB SITES
Encyclopedia of Life Sciences: prion diseases作者: nut6694 时间: 2013-7-19 15:59
题目:RNA molecules stimulate prion protein conversion
先把我上面的问题 hang on 着,欢迎大家在文章讨论的同时随时提出宝贵意见,您的参与是对我最大的支持和鼓励!一篇文章的讨论并不是最重要的,最重要的是想通过这种形式,来帮助大家学会怎么阅读论文,怎样通过阅读别人的文章来build up 自己的科研思维。(也许话说得大了些,大体上是这个意思吧)
下面我就简单介绍一下这篇文章的内容。
文章的假设直接指向:具有感染性的朊病毒的复制需要小分子特异性RNA的参与
文章所用条件:体外
(对体外模型当然有不周到的地方,对此,在文章介绍中第一句就提到:We previously showed that PrPres amplification in vitro shares many specific features with the pathogenic process of prion propagation in vivo, including strain and species specificity. 这里还特意指明了,研究结果表明不同种属来源的朊病毒和朊病毒的不同strain 性质相似。附件的图版是不同鼠体内朊病毒的构象相似状况,请看一下)
文章based on 的一些理论依据是:有感染能力的朊病毒的复制不需要核酸(一些实验证据表明的);构象翻转机制现在还不清楚。
文章的思路:被朊病毒感染的Hamster (一种大鼠,仓鼠?)的脑匀浆与健脑匀浆混合,三十七度过夜,测具有感染性的朊病毒蛋白的增殖(diluted prion-infected brain homogenate (0.1% w/v) is mixed with either 5% (w/v) normal brain homogenate or buffer control and incubated overnight at 37 oC. Hamster Sc237 PrPres is amplified about sixfold under these conditions );为了证明不是蛋白酶、核酸酶、双链小RNA、DNA与RNA杂交体、单核苷酸的作用,分别把它们的抑制剂或降解试剂加入,再跑胶,看是否对复制有影响
<enzyme> Product of genetic engineering which hydrolyzes both DNA and RNA; from serratia marcescens(粘质沙雷氏菌);both Dnase and Rnase activity.
Synonym: benzon nuclease, ben endonuclease
Benzonase® - The smart solution for DNA removal
For the first time, an effective biochemical method is available for removing DNA and RNA from laboratory and industrial scale bioprocesses. It is called Benzonase® endonuclease.
Benzonase® is a unique, genetically engineered endonuclease offering a variety of advantages over existing methods of nucleic acid removal.
Benzonase® endonuclease has proven its value in the laboratory for well over ten years and is successfully applied in the pharmaceutical and biotechnological industry in the downstream processing of biopharmaceutical actives e.g. monoclonal antibodies, virus vaccines, gene therapy and recombinant proteins from E.coli.
Benzonase® is applied whenever the presence of nucleic acids might cause interference i.e.
• Purification and characterisation of proteins, and peptides
• Purification of antibodies and viruses for therapeutic use
• Safety of biopharmaceuticals
FDA guidelines for the manufacture of recombinant biological entities for therapeutic use demand that nucleic acid contamination should be limited to 10 pg per dose. Benzonase® - alone or in combination with other steps - offers a powerful and well-accepted tool to achieve regulatory requirements.
Benzonase® is covered by several patents, i.e. US Patent No.5,173,418, EP Patent No.0229866 B1作者: nut6694 时间: 2013-7-19 16:23
活性定义: 以热变性小牛胸腺DNA作底物,在37℃,pH8.0的条件下,30分钟内生成1 OD260的酸可溶性物质的酶的活性定义为1 U。
纯度 50 U的本酶和1 μg的λ-DNA在Mg2+存在下37℃反应10分钟,DNA的电泳谱带不发生变化 .SDS电泳表现95%以上的纯度。
使用注意 : 本酶的活性严格依赖于Ca2+的存在,用EDTA或EGTA可以终止反应。
用途: 细胞粗抽提液中核酸的水解。
为制备核小体 (Nucleosome) 时消化分解染色质 (Chromatin)
参考资料:
Pelham, H. R. and Jackson, R. J., Eur. J. Biochem. 67, 247 (1976).
Noll, M., Nature 251, 249 (1974).
Heins, J. N. et al., Proc. Nucl. Acids Res. 1, 79 (1976).
Ye, X. et al. Defective S phase chromatin assembly causes DNA damage, activation of the S phase checkpoint, and S phase arrest. Mol. Cell 11, 341-351 (2003) | PubMed |
Mujun Zhao*, Zhenyu Wu, Wenlin Chen, Tsaiping Li:“The Biological Significance of Micrococcal Nuclease (MNase) hypersensitive sites of rRNA chromatin template of Silkworm Attacus ricini”, Molecolar Biology of the Cell. Vol.10, (Sup) pp.282a, 1999作者: lixi559 时间: 2013-7-19 16:30
Benzonase is a genetically engineered endonuclease which degrades both DNA and RNA strands in many forms to small oligonucleotides. It promotes quick reduction of the viscosity of cell lysates, which facilitates ultracentrifugation and increases the capacity and life of chromatography columns. It saves time, reducing proteolysis and increasing the yield in targeted protein and offers complete elimination of nucleic acids from recombinant proteins.
来源:cuturl('http://www.oswel.com/code/en/mod_38.htm')作者: pencil菲 时间: 2013-7-19 16:31
RNase A cleaves 3' of single-stranded C and U residues. RNase V1 cleaves base-paired nucleotides
Ribonuclease T1 (RNase T1) is an endoribonuclease that specifically cuts RNA or deaminated RNA at the 3’-end of guanosine residues and adjacent nucleotides through a 2’, 3’-cyclic phosphate intermediate mechanism. Epicentre’s RNase T1 is cloned from Aspergillus oryzae and over expressed in E. coli to produce a highly pure enzyme without contaminating DNase or non-specific RNase activity. [icesugar75 补充]
这是一个例子(附件中):Structural Analysis of an RNA.
The RNA molecule shown above was end-labeled and subjected to digestion with RNases A, TI, and VI. The resulting fragments were visualized by denaturing PAGE.
heparinase III是一种葡萄糖醛酸酯酶,是能降解硫酸乙酰肝素的葡萄糖苷酸内切酶(endosluconidase)。 该酶 cleaves selectively, via an elimination mechanism, sulfated polysaccharide chains containing 1-4 linkages between hexosamines and glucuronic acid residues. The reaction yields oligosaccharide products (mainly disaccharides) containing unsaturated uronic acids which can be detected by UV spectroscopy at 232 nm. The enzyme is active only towards heparan sulfate and does not cleave heparin or low molecular weight heparins.
这种酶常应用于糖生物学(99年Nobel Price),寡糖文库的制备,从heparan sulfate制备二糖.
(受启发rPsc似乎有分子伴侣的作用,在它的作用下,原本应该正常的PrPc都折叠成了PrPsc的形式),糖生物学研究表明:有的分子伴侣发挥功能需要靠蛋白上的寡糖链识别(具体文献忘了,见附件文献提到的这样的意思),而heparinase III可去除糖蛋白的可寡糖链.(Prion是一分子量为33kD~ 35kD的糖蛋白,)因此,我认为,此处可能是排除PrPsc自身作为分子伴侣辅助PrP的复制或折叠. 作者: one 时间: 2013-7-19 16:46
原始論文:
Mallucci, G. et al. Depleting neuronal PrP in prion infection prevents disease and reverses spongiosis. Science, 302, 871 - 874, (2003).
转自Sciscape 作者: langlang 时间: 2013-7-19 16:47
How to distinguish PrPsc from PrPc? (From FEBS Letters, 2001, 451)
a。PrPSc is partially resistant to proteolytic degradation,
whereas PrPC is sensitive to proteolysis;
b。 PrPC is a soluble protein, while PrPSc is stubbornly insoluble and becomes deposited in infected brain parenchyma;
c。PrPC is mainly composed of K-helical conformation, while PrPSc is rich in L-sheet secondary structure;
d。PrPSc is able to replicate itself in vitro and in vivo by converting PrPC into PrPSc .作者: nut6694 时间: 2013-7-19 16:48
PrPSc is able to replicate itself in vitro and in vivo by converting PrPC into PrPSc .
根据我所看到的资料,prion是Proteinaceous infectious particle(蛋白质样感染颗粒)的缩写修改而成,念成[pri:^n],prion国内学者译成朊病毒,而相应的朊病毒蛋白(PrP,Prion Protein)又称朊蛋白,它有两种形式,细胞型(Prion Protein of Normal Cell,PrPC)和致病型(Prion Protein of Scrapie,PrPSc),PrPC的C和PrPSc中的Sc是上标。通常我们所说的朊病毒应该是致病型朊病毒。作者: linlinstar 时间: 2013-7-19 16:57
Antibody to DNA detects scrapie but not normal prion protein
Communicated by Lynn T. Landmesser, Case Western Reserve University, Cleveland, OH, November 25, 2003 (received for review June 10, 2003)
A conformational change is
believed to convert the normal cellular prion protein into PrPSc.
Detection of PrPSc for diagnosis and prophylaxis is impaired because
available Abs recognizing epitopes on PrP fail to distinguish
between PrPSc and normal cellular prion protein. Here, we report
that an anti-DNA Ab, OCD4, as well as gene 5 protein, a well
established DNA-binding protein, capture PrP from brains affected
by prion diseases in both humans and animals but not from
unaffected controls. OCD4 appears to immunoreact with DNA (or
a DNA-associated molecule) that forms a conformation-dependent
complex with PrP in prion diseases. Whereas PrP immunocaptured
by OCD4 is largely protease-resistant, a fraction of it remains
protease-sensitive. Moreover, OCD4 detects disease-associated PrP
>10 times more efficiently than a widely used Ab to PrP. Our
finding that anti-DNA Abs and gene 5 protein specifically target
disease-associated DNA–PrP complexes in a wide variety of species
and disease phenotypes opens new avenues in the study and
diagnosis of prion diseases.
使用計算機糢擬的手段 糢擬低Ph條件誘導的倉鼠PrPD147N從prpc到prpsc
的轉變
From conversion to aggregation: Protofibril formation of the prion protein
PNAS February 24, 2004 vol. 101 no. 8 2293–2298
1. What is the nature of the infectious agent?
(1) Is PrPSc identical with the prion?
(2) How does PrPSc promote PrPC conversion into further PrPSc?
(3) Which other proteins assist in this process?
(4) Can we cure prion diseases by interfering with the conversion process?
(5) What are prion strains, molecularly speaking? How are the strain-speci.c properties encoded?
2. How do peripherally administered prions travel to the brain?
(1) Which molecules and cells are involved in neuroinvasion?
(2) Which inhibitory strategies have a realistic chance of succeeding?
3. What are the mechanisms of spongiform neurodegeneration?
(1) Which pathogenetic cascades are activated?
(2) What are the biochemical executioners of brain damage?
4. What is the physiological function of the normal prion protein, PrPC?
(1) PrPC is highly conserved, so it is probably useful.
(2) The Prnp gene was identi.ed in 1985, and Prnp knockout mice in 1992, yet the function of PrPC remains unknown.
(3) None of the phenotypes ascribed to the absence of PrPC has been explained in molecular terms.
(4) Is abnormal function of PrPC involved in prion disease pathogenesis?
5.why do we have prions?作者: u76mp 时间: 2013-7-19 17:17