Eraña Hasier, Fernández-Borges Natalia, Elezgarai Saioa R, Harrathi Chafik, Charco Jorge M, Chianini Francesca, Dagleish Mark P, Ortega Gabriel, Millet Óscar, Castilla Joaquín
CIC bioGUNE, Derio, Bizkaia, Spain.
Moredun Research Institute, Penicuik, Scotland, United Kingdom.
J Virol. 2017 Nov 30;91(24). doi: 10.1128/JVI.01543-17. Print 2017 Dec 15.
Prion diseases, or transmissible spongiform encephalopathies (TSEs), are a group of rare progressive neurodegenerative disorders caused by an abnormally folded prion protein (PrP). This is capable of transforming the normal cellular prion protein (PrP) into new infectious PrP Interspecies prion transmissibility studies performed by experimental challenge and the outbreak of bovine spongiform encephalopathy that occurred in the late 1980s and 1990s showed that while some species (sheep, mice, and cats) are readily susceptible to TSEs, others are apparently resistant (rabbits, dogs, and horses) to the same agent. To study the mechanisms of low susceptibility to TSEs of certain species, the mouse-rabbit transmission barrier was used as a model. To identify which specific amino acid residues determine high or low susceptibility to PrP propagation, protein misfolding cyclic amplification (PMCA), which mimics PrP-to-PrP conversion with accelerated kinetics, was used. This allowed amino acid substitutions in rabbit PrP and accurate analysis of misfolding propensities. Wild-type rabbit recombinant PrP could not be misfolded into a protease-resistant self-propagating isoform despite seeding with at least 12 different infectious prions from diverse origins. Therefore, rabbit recombinant PrP mutants were designed to contain every single amino acid substitution that distinguishes rabbit recombinant PrP from mouse recombinant PrP. Key amino acid residue substitutions were identified that make rabbit recombinant PrP susceptible to misfolding, and using these, protease-resistant misfolded recombinant rabbit PrP was generated. Additional studies characterized the mechanisms by which these critical amino acid residue substitutions increased the misfolding susceptibility of rabbit PrP. Prion disorders are invariably fatal, untreatable diseases typically associated with long incubation periods and characteristic spongiform changes associated with neuronal loss in the brain. Development of any treatment or preventative measure is dependent upon a detailed understanding of the pathogenesis of these diseases, and understanding the mechanism by which certain species appear to be resistant to TSEs is critical. Rabbits are highly resistant to naturally acquired TSEs, and even under experimental conditions, induction of clinical disease is not easy. Using recombinant rabbit PrP as a model, this study describes critical molecular determinants that confer this high resistance to transmissible spongiform encephalopathies.
朊病毒病，即传染性海绵状脑病（TSEs），是一组由异常折叠的朊病毒蛋白（PrP）引起的罕见的进行性神经退行性疾病。这种蛋白能够将正常的细胞朊病毒蛋白（PrP）转化为新的传染性PrP。通过实验性攻击进行的种间朊病毒传播性研究以及20世纪80年代末和90年代发生的牛海绵状脑病疫情表明，虽然一些物种（绵羊、小鼠和猫）很容易感染TSEs，但其他物种（兔子、狗和马）对同一病原体显然具有抗性。为了研究某些物种对TSEs低易感性的机制，以小鼠 - 兔子传播屏障为模型。为了确定哪些特定氨基酸残基决定了对PrP传播的高易感性或低易感性，使用了蛋白质错误折叠循环扩增（PMCA）技术，该技术以加速动力学模拟PrP到PrP的转化。这使得能够对兔子PrP进行氨基酸替换并准确分析错误折叠倾向。尽管用至少12种来自不同来源的不同传染性朊病毒进行接种，野生型兔子重组PrP仍不能错误折叠成蛋白酶抗性的自我传播异构体。因此，设计了兔子重组PrP突变体，使其包含区分兔子重组PrP和小鼠重组PrP的每一个氨基酸替换。确定了使兔子重组PrP易于错误折叠的关键氨基酸残基替换，并利用这些替换产生了蛋白酶抗性的错误折叠重组兔子PrP。进一步的研究表征了这些关键氨基酸残基替换增加兔子PrP错误折叠易感性的机制。朊病毒病始终是致命的、无法治疗的疾病，通常与长潜伏期以及与大脑神经元损失相关的特征性海绵状变化有关。任何治疗或预防措施的开发都依赖于对这些疾病发病机制的详细了解，而了解某些物种对TSEs具有抗性的机制至关重要。兔子对自然获得的TSEs具有高度抗性，即使在实验条件下，诱发临床疾病也不容易。以重组兔子PrP为模型，本研究描述了赋予这种对传染性海绵状脑病高度抗性的关键分子决定因素。
