Department of Infectology, The Scripps Research Institute, Jupiter, FL 33458, USA.
Proc Natl Acad Sci U S A. 2012 Feb 21;109(8):3113-8. doi: 10.1073/pnas.1118090109. Epub 2012 Feb 7.
Prion diseases are infectious and belong to the group of protein misfolding neurodegenerative diseases. In these diseases, neuronal dysfunction and death are caused by the neuronal toxicity of a particular misfolded form of their cognate protein. The ability to specifically target the toxic protein conformer or the neuronal death pathway would provide powerful therapeutic approaches to these diseases. The neurotoxic forms of the prion protein (PrP) have yet to be defined but there is evidence suggesting that at least some of them differ from infectious PrP (PrP(Sc)). Herein, without making an assumption about size or conformation, we searched for toxic forms of recombinant PrP after dilution refolding, size fractionation, and systematic biological testing of all fractions. We found that the PrP species most neurotoxic in vitro and in vivo (toxic PrP, TPrP) is a monomeric, highly α-helical form of PrP. TPrP caused autophagy, apoptosis, and a molecular signature remarkably similar to that observed in the brains of prion-infected animals. Interestingly, highly α-helical intermediates have been described for other amyloidogenic proteins but their biological significance remains to be established. We provide unique experimental evidence that a monomeric α-helical form of an amyloidogenic protein represents a cytotoxic species. Although toxic PrP has yet to be purified from prion-infected brains, TPrP might be the equivalent of one highly neurotoxic PrP species generated during prion replication. Because TPrP is a misfolded, highly neurotoxic form of PrP reproducing several features of prion-induced neuronal death, it constitutes a useful model to study PrP-induced neurodegenerative mechanisms.
朊病毒病具有传染性，属于蛋白质错误折叠神经退行性疾病。在这些疾病中，神经元功能障碍和死亡是由其同源蛋白的特定错误折叠形式的神经元毒性引起的。特异性靶向毒性蛋白构象或神经元死亡途径的能力将为这些疾病提供强大的治疗方法。朊病毒蛋白（PrP）的神经毒性形式尚未确定，但有证据表明，其中至少一些与传染性 PrP（PrP(Sc)）不同。在此，我们在不假设大小或构象的情况下，在稀释重折叠、大小分级和对所有级分进行系统生物学测试后，寻找重组 PrP 的毒性形式。我们发现，体外和体内最具神经毒性的 PrP 物种（毒性 PrP，TPrP）是 PrP 的单体、高度α-螺旋形式。TPrP 引起自噬、细胞凋亡和分子特征与朊病毒感染动物大脑中观察到的非常相似。有趣的是，其他淀粉样蛋白形成蛋白已经描述了高度α-螺旋中间体，但它们的生物学意义仍有待确定。我们提供了独特的实验证据，证明淀粉样蛋白形成蛋白的单体α-螺旋形式代表了一种细胞毒性物质。尽管尚未从朊病毒感染的大脑中纯化出毒性 PrP，但 TPrP 可能相当于朊病毒复制过程中产生的一种高度神经毒性 PrP 物种。由于 TPrP 是一种错误折叠的、高度神经毒性的 PrP 形式，复制了朊病毒诱导神经元死亡的几个特征，因此它构成了研究 PrP 诱导的神经退行性机制的有用模型。
