Makarava Natallia, Savtchenko Regina, Alexeeva Irina, Rohwer Robert G, Baskakov Ilia V
Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland; Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland.
Medical Research Service, Veterans Affairs Medical Center, University of Maryland, Baltimore, Maryland.
Am J Pathol. 2016 Apr;186(4):1006-14. doi: 10.1016/j.ajpath.2015.11.013. Epub 2016 Feb 9.
Previous studies established that transmissible prion diseases could be induced by in vitro-produced recombinant prion protein (PrP) fibrils with structures that are fundamentally different from that of authentic PrP scrapie isoform (PrP(Sc)). To explain evolution of synthetic prions, a new mechanism referred to as deformed templating was introduced. Here, we asked whether an increase in expression level of the cellular form of PrP (PrP(C)) speeds up the evolution of synthetic strains in vivo. We found that in transgenic mice that overexpress hamster PrP(C), PrP(C) overexpression accelerated recombinant PrP fibril-induced conversion of PrP(C) to the abnormal proteinase K-resistant state, referred to as atypical PrPres, which was the first product of PrP(C) misfolding in vivo. However, overexpression of PrP(C) did not facilitate the second step of synthetic strain evolution-transition from atypical PrPres to PrP(Sc), which is attributed to the stochastic nature of rare deformed templating events. In addition, the potential of atypical PrPres to interfere with replication of a short-incubation time prion strain was investigated. Atypical PrPres was found to interfere strongly with replication of 263K in vitro; however, it did not delay prion disease in animals. The rate of deformed templating does not depend on the concentration of substrate and is hence more likely to be controlled by the intrinsic rate of conformational errors in templating alternative self-propagating states.
先前的研究表明，体外产生的重组朊病毒蛋白（PrP）原纤维可诱发可传播的朊病毒疾病，其结构与真实的PrP瘙痒病异构体（PrP(Sc)）的结构根本不同。为了解释合成朊病毒的进化，引入了一种称为变形模板的新机制。在这里，我们询问细胞形式的PrP（PrP(C)）表达水平的增加是否会加速体内合成毒株的进化。我们发现，在过表达仓鼠PrP(C)的转基因小鼠中，PrP(C)的过表达加速了重组PrP原纤维诱导的PrP(C)向异常蛋白酶K抗性状态的转化，即非典型PrPres，这是PrP(C)在体内错误折叠的首个产物。然而，PrP(C)的过表达并未促进合成毒株进化的第二步——从非典型PrPres向PrP(Sc)的转变，这归因于罕见的变形模板事件的随机性。此外，还研究了非典型PrPres干扰短潜伏期朊病毒毒株复制的潜力。发现非典型PrPres在体外强烈干扰263K的复制；然而，它并未延迟动物的朊病毒疾病。变形模板的速率不依赖于底物浓度，因此更有可能由模板化替代自我传播状态时构象错误的内在速率控制。
