蛋白质错误折叠循环扩增及其在朊病毒蛋白检测中的应用研究进展

朊病毒蛋白（prion protein,PrP）是传染性海绵状脑病的病原体,其检测是该病诊断的重要依据。该文从原理、方法、影响因素和检测应用方面对蛋白质错误折叠循环扩增（protein mis-folding cyclic amplification,PMCA）这种朊病毒蛋白新型检测技术做了介绍,旨在为朊病毒蛋白的检测和发病机制研究提供理论参考。     

朊病毒的分子遗传学研究

院病毒（prion）是一种能引起哺乳动物中枢神经系统退行性疾病,即一般称为传染性海绵状脑病（BE）的病原因子。这些疾病包括人类克雅氏病忙reutrfeltJocob）、致死性家族失眠症、羊瘙痒症和疯牛病等[1]．1982年美国科学家Prusiner从感染了瘙痒症的叙利亚老鼠脑中分离出具有传染性的蛋白因子,并首先提出朊病毒这一名词,以与病毒、类病毒相区别。朊病毒最显著的特征是不含核酸。现已知道朊病毒（prionprotein,PrP是由宿主染色体基因PrP编码的一种正常细胞蛋白,在非患病个体中以低水平存在。这种蛋白在细胞内质网上合成、高尔基小体中…     

朊病毒病

朊病毒是一类可传递的蛋白质感染颗粒,似乎仅仅由一种修饰后的蛋白ＰｒＰ＾ｓｃ构成。ＰｒＰ＾ｓｃ由政党细胞蛋白ＰｒＰ＾ｃ通过翻译后加工、发生构象变化而形成。牛海绵状脑病和人Ｃｒｅｕｔｚｆｅｌｄｔ－Ｊａｃｏｂ病（ＣＪＤ）是朊病毒引起的最名的中枢神经系统变性疾病。ＤＪＤ有散发性、家族性、传染性、医原性等,有语气表明牛朊病毒已传递至人类导致新的变异性ＣＪＤ。针对朊病毒独特的致病机制可得出若干防治策略。     

兔、犬、马抵御朊病毒疾病的研究进展

传染性海绵状脑病(transmissible spongiform encephalopathy)或朊病毒疾病是一类致死的神经退行性疾病,由朊病毒蛋白(prion protein)的错误折叠而引起,影响包括人在内的多种哺乳动物。朊病毒蛋白由宿主基因PRNP编码,正确折叠的蛋白质不仅没有致病性和感染性,还具有重要的生理功能;其错误折叠后则会转变为具有感染性的朊病毒(prion),能够使许多哺乳动物患病。但近年来,也有不少研究报道兔、犬、马可以抵御朊病毒疾病。由于种群内自然病例的缺乏和朊病毒感染动物实验的失败,这三种哺乳动物被公认为具有朊病毒抗性。现简要介绍朊病毒疾病的概念和分类,对抵御朊病毒感染的兔、犬、马可能的抗病机制进行综述,并讨论与展望当前对朊病毒疾病有特殊抗性物种的研究中存在的机遇与挑战。     

疯牛病病原体的研究进展

疯牛病病原体,即朊病毒蛋白（PrionPrP^Sc),是一种不具有核酸的全新致病物质,在动物和人类引起致命性海绵状脑病（Prions疾病）,本文阐述了Prion的含义,Prion蛋白的种类,疾病生物化学以及与Prions疾病的关系。     

哺乳动物中蛋白质折叠异常与朊病毒病

在过去的两年中 ,有关朊病毒 (ｐｒｉｏｎ)蛋白结构的最新ＮＭＲ数据不断扩展 ,这主要是在仓鼠和人体蛋白质中取得的。另外 ,两种朊病毒蛋白的折叠动力学机制亦被阐明。目前已经得到几种朊病毒的样品 ,它们可以在溶液中采取不同的构象。近来所做的有关朊病毒蛋白链分子基础的研究工作进一步巩固了蛋白质独自致病的假说。通过对最小蛋白质片断的辨认 ,疾病与结构的相互关系的研究也取得了重要进展。1 .引言在 2 5种被确证为由动物组织中变性蛋白质沉积而引起的病症中 ,只有传染性海绵状脑病 (ＴＳＥｓ)会产生传染性物质。可能朊病毒疾病最独…     

朊病毒疾病的诊断技术

朊病毒疾病即海绵状脑病,是人的动物中的一类致死性中央神经系统疾病,介绍了朊病毒疾病的诊断技术,病理诊断,基因诊断,免疫诊断和血液检测。     

朊病毒疾病

朊病毒是一种蛋白性质的感染颗粒,它能引起动物的一类大脑功能紊乱疾病:可传染海绵样脑病(TSE)。本文就朊病毒、朊病毒引起的疾病、牛海绵样脑病(BSE)及BSE能否传给人类进行一些讨论。     

朊蛋白PrP~C与神经元的凋亡和存活

朊病毒是不含核酸的一种蛋白质感染颗粒,感染宿主后可诱导细胞固有的同类朊蛋白(PrPC)构象改变、转化成具有蛋白酶抗性的致病性朊粒蛋白(PrPSc),导致可传播性海绵状脑病的发生.PrPC既作为朊病毒复制和疾病发生的分子基础,又是正常的细胞膜蛋白,作为细胞信号转导的参与者调控多条信号通路.因此,揭示PrPC在各条信号途径中发挥的作用将有助于深入了解PrPC的生理功能,进一步理解疾病发生发展过程,为今后的诊断治疗奠定基础.     

疯牛病研究进展

近年来,英国疯牛病成为国内外新闻媒体关注的焦点,它不仅给英国养牛业造成了巨大的经济损失,同时也引起了世界各国政府及农业主管部门的高度重视,疯牛病是对牛海绵状脑病（Bovine Spongiform Encephalopathy BSE)的俗称,它是一种慢性,具有传染性的致死性中枢神经系统疾病,该病临床和组织学病理学特征是病畜神经失常,共济失调,感觉过敏和中枢神经系统灰质空泡化,疯牛病被认为与朊病毒（Prion)有关,因此与克-雅氏病,羊痒病等一起被统称为朊病毒病,朊病毒病是由正常朊病毒蛋白（PrPC)发生蛋白折叠错误变成异常朊病毒蛋白（PrPSC)引起的,BSE主要发生于以英国为中心的欧洲各国家和地区,各国采取了一系列的措施,防制BSE危害人类健康,中国至今尚无疯牛病发生。     

Prion protein glycosylation

The transmissible spongiform encephalopathies (TSE), or prion diseases are a group of transmissible neurodegenerative disorders of humans and animals. Although the infectious agent (the 'prion') has not yet been formally defined at the molecular level, much evidence exists to suggest that the major or sole component is an abnormal isoform of the host encoded prion protein (PrP). Different strains or isolates of the infectious agent exist, which exhibit characteristic disease phenotypes when transmitted to susceptible animals. In the absence of a nucleic acid genome it has been hard to accommodate the existence of TSE strains within the protein-only model of prion replication. Recent work examining the conformation and glycosylation patterns of disease-associated PrP has shown that these post-translational modifications show strain-specific properties and contribute to the molecular basis of TSE strain variation. This article will review the role of glycosylation in the susceptibility of cellular PrP to conversion to the disease-associated conformation and the role of glycosylation as a marker of TSE strain type.     

The role of the prion protein membrane anchor in prion infection

In transmissible spongiform encephalopathies (TSE or prion diseases) such as sheep scrapie, bovine spongiform encephalopathy and human Creutzfeldt-Jakob disease, normally soluble and protease-sensitive prion protein (PrP-sen or PrPC) is converted to an abnormal, insoluble and protease-resistant form termed PrP-res or PrPSc. PrP-res/PrPSc is believed to be the main component of the prion, the infectious agent of the TSE/prion diseases. Its precursor, PrP-sen, is anchored to the cell surface at the C-terminus by a co-translationally added glycophosphatidyl-inositol (GPI) membrane anchor which can be cleaved by the enzyme phosphatidyl-inositol specific phospholipase (PIPLC). The GPI anchor is also present in PrP-res, but is inaccessible to PIPLC digestion suggesting that conformational changes in PrP associated with PrP-res formation have blocked the PIPLC cleavage site. Although the GPI anchor is present in both PrP-sen and PrP-res, its precise role in TSE diseases remains unclear primarily because there are data to suggest that it both is and is not necessary for PrP-res formation and prion infection.     

Formation of protease-resistant prion protein in cell-free systems

In transmissible spongiform encephalopathies (TSE) or prion diseases, the endogenous protease-sensitive prion protein (PrP-sen) of the host is converted to an abnormal pathogenic form that has a characteristic partial protease resistance (PrP-res). Studies with cell-free reactions indicate that the PrP-res itself can directly induce this conversion of PrP-sen. This PrP-res induced conversion reaction is highly specific in ways that might account at the molecular level for TSE species barriers, polymorphism barriers, and strains. Not only has this reaction been observed using mostly purified PrP-sen and PrP-res reactants, but also in TSE-infected brain slices. The conversion mechanism appears to involve both the binding of PrP-sen to polymeric PrP-res and a conformational change that results in incorporation into the PrP-res polymer.     

Rapid presymptomatic detection of PrPSc via conformationally responsive palindromic PrP peptides

Structurally unique, synthetic prion peptides provide the basis of a simple assay to serve as both a detection and signal amplification system that distinguishes the normal prion protein, PrPC, from the misfolded prion protein, PrPSc, that is associated with the occurrence of transmissible spongiform encephalopathies (TSE). Proof-of-principle has been shown on brain samples from an experimental scrapie hamster model. The assay demonstrates very sensitive detection of PrPSc in animal brain tissue with potential application for early presymptomatic detection in animal screening. Furthermore, the sensitivity of the assay could enable blood tests for this TSE disease as well as other amyloid and/or misfolded protein diseases.     

Recombinant human prion protein fragment 90-231, a useful model to study prion neurotoxicity

Transmissible spongiform encephalopathies (TSE), or prion diseases, are a group of fatal neurodegenerative disorders of animals and humans. Human diseases include Creutzfeldt-Jakob (CJD) and Gerstmann-Straussler-Scheinker (GSSD) diseases, fatal familial insomnia, and Kuru. Human and animal TSEs share a common histopathology with a pathognomonic triad: spongiform vacuolation of the grey matter, neuronal death, glial proliferation, and, more inconstantly, amyloid deposition. According to the "protein only" hypothesis, TSEs are caused by a unique post-translational conversion of normal, host-encoded, protease-sensitive prion protein (PrP(sen) or PrP(C)) to an abnormal disease-associated isoform (PrP(res) or PrP(Sc)). To investigate the molecular mechanism of neurotoxicity induced by PrP(Sc) we developed a protocol to obtain millimolar amounts of soluble recombinant polypeptide encompassing the amino acid sequence 90-231 of human PrP (hPrP90-231). This protein corresponds to the protease-resistant prion protein fragment that originates after amino-terminal truncation. Importantly, hPrP90-231 has a flexible backbone that, similar to PrP(C), can undergo to structural rearrangement. This peptide, structurally resembling PrP(C), can be converted in a PrP(Sc)-like conformation, and thus represents a valuable model to study prion neurotoxicity. In this article we summarized our experimental evidence on the molecular and structural mechanisms responsible of hPrP90-231 neurotoxicity on neuroectodermal cell line SHSY5Y and the effects of some PrP pathogen mutations identified in familial TSE.     

Distinct Transmissibility Features of TSE Sources Derived from Ruminant Prion Diseases by the Oral Route in a Transgenic Mouse Model (TgOvPrP4) Overexpressing the Ovine Prion Protein

Transmissible spongiform encephalopathies (TSEs) are a group of fatal neurodegenerative diseases associated with a misfolded form of host-encoded prion protein (PrP). Some of them, such as classical bovine spongiform encephalopathy in cattle (BSE), transmissible mink encephalopathy (TME), kuru and variant Creutzfeldt–Jakob disease in humans, are acquired by the oral route exposure to infected tissues. We investigated the possible transmission by the oral route of a panel of strains derived from ruminant prion diseases in a transgenic mouse model (TgOvPrP4) overexpressing the ovine prion protein (A₁₃₆R₁₅₄Q₁₇₁) under the control of the neuron-specific enolase promoter. Sources derived from Nor98, CH1641 or 87V scrapie sources, as well as sources derived from L-type BSE or cattle-passaged TME, failed to transmit by the oral route, whereas those derived from classical BSE and classical scrapie were successfully transmitted. Apart from a possible effect of passage history of the TSE agent in the inocula, this implied the occurrence of subtle molecular changes in the protease-resistant prion protein (PrPres) following oral transmission that can raises concerns about our ability to correctly identify sheep that might be orally infected by the BSE agent in the field. Our results provide proof of principle that transgenic mouse models can be used to examine the transmissibility of TSE agents by the oral route, providing novel insights regarding the pathogenesis of prion diseases.     

Molecular aspects of disease pathogenesis in the transmissible spongiform encephalopathies

The transmissible spongiform encephalopathies (TSE), or prion diseases, are a group of rare, fatal, and transmissible neurodegenerative diseases of mammals for which there are no known viral or bacterial etiological agents. The bovine form of these diseases, bovine spongiform encephalopathy (BSE), has crossed over into humans to cause variant Creutzfeldt-Jakob disease. As a result, BSE and the TSE diseases are now considered a significant threat to human health. Understanding the basic mechanisms of TSE pathogenesis is essential for the development of effective TSE diagnostic tests and anti-TSE therapeutic regimens. This review provides an overview of the molecular mechanisms that underlie this enigmatic group of diseases.     

Prion protein interconversions

The transmissible spongiform encephalopathies (TSEs), or prion diseases, remain mysterious neurodegenerative diseases that involve perturbations in prion protein (PrP) structure. This article summarizes our use of in vitro models to describe how PrP is converted to the disease-associated, protease-resistant form. These models reflect many important biological parameters of TSE diseases and have been used to identify inhibitors of the PrP conversion as lead compounds in the development of anti-TSE drugs.