Mechanisms of prion aggregation and species barriers

描述(申请人提供)：Pron病是一种传染性和致命性神经退行性疾病，没有可用的治疗方法。由于牛海绵状脑病(BSE)疫情已导致近200例人类感染Prion，人畜共患病的Prion传播令人担忧。最近在食用动物和野鹿中出现了新的Prion疾病，其传播给人类的可能性尚不清楚。Pron聚集、物种间传播和Pron菌株的分子机制仍然知之甚少。我们的长期目标是确定控制物种障碍和菌株构象的Pron蛋白的关键残基。Pron蛋白(氨基酸165-175)的2-a2环是一个序列变异性极高的位置。微晶学研究表明，相邻的2-a2环可以与侧链对齐，侧链作为淀粉样蛋白核心的一部分交织在干燥的界面上。我们已经证明，在转基因小鼠中，小鼠Pron蛋白2-a2环中的两个氨基酸替换导致了新的Prion病。在初步研究中，这些替换显著改变了小鼠的物种间传播障碍。在这里，我们提出？2-a2环在普恩病毒向人和牛的传播中也起着重要的作用。在这项提案中，我们将评估2-a2环残基对Pron聚集、物种障碍和菌株的影响。在目标1中，我们将确定关键残基在体内和体外对Pron聚集和构象转换的作用。在目标2中，我们将使用仅在环上不同的小鼠模型来评估？2-a2环区对于人和牛感染普恩病毒的重要性。这些研究的结果将有助于我们理解PrP蛋白聚集的基本机制，有助于我们对Pron向人类传播的风险评估，以及促进合理设计阻断Pron聚集的治疗方法。

DESCRIPTION (provided by applicant): Prion diseases are infectious and fatal neurodegenerative disorders with no available treatment. Zoonotic prion transmission is of concern, as the bovine spongiform encephalopathy (BSE) epidemic has led to nearly 200 cases of prion infection in humans. New prion diseases have recently emerged in food animals and wild deer with unknown potential for spread to humans. The molecular mechanisms that underlie prion aggregation, transmission between species, and the prion strains are still poorly understood. Our long term goal is to identify the key residues of the prion protein that govern species barriers and strain conformation. The ¿2-a2 loop of the prion protein (amino acids 165-175) is a site of exceptionally high sequence variability. Microcrystallography has shown that adjacent ¿2-a2 loops can align as ¿-sheets with side chains that intermesh in a dry interface as part of the amyloid core. We have shown that two amino acid substitutions in the ¿2-a2 loop of the mouse prion protein lead to de novo prion disease in transgenic mice. In preliminary studies, these substitutions markedly change the interspecies transmission barriers in mice. Here we propose that the ¿2-a2 loop also plays an important role for prion transmission to humans and cattle. In this proposal, we will evaluate the impact of the ¿2-a2 loop residues on prion aggregation, species barriers, and strains. In Aim 1, we will determine the role of critical residues for prion aggregation and conformational conversion in vitro and in vivo. In Aim 2, we will assess the importance of the ¿2-a2 loop region for prion infection of humans and cattle using mouse models that differ only at the loop. Results from these studies will contribute to our understanding of the fundamental mechanisms of prion protein aggregation, aid in our risk assessment of prion transmission to humans, as well as advance the rational design of therapeutics to block prion aggregation.