Mechanisms of prion aggregation and species barriers

描述（由申请人提供）：朊病毒疾病是传染性和致命的神经退行性疾病，目前尚无治疗方法。由于牛海绵状脑病（BSE）流行已导致近200例人类感染朊病毒，人畜共患朊病毒传播引起关注。最近在食用动物和野鹿中出现了新的朊病毒疾病，其传播给人类的可能性未知。朊病毒聚集、物种间传播和朊病毒毒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屏障和菌株构象的朊病毒蛋白的关键残基。朊病毒蛋白的¿2-a2环（氨基酸165-175）是一个序列变异性异常高的位点。微晶体学表明，相邻的¿2-a2环可以排列成¿2-片，侧链在干燥的界面上相互交织，作为淀粉样蛋白核心的一部分。我们已经证明，小鼠朊病毒蛋白的¿2-a2环中的两个氨基酸替换导致转基因小鼠的从头朊病毒疾病。在初步研究中，这些替换显著改变了小鼠的种间传播屏障。在这里，我们提出¿2-a2环在人类和牛的朊病毒传播中也起着重要作用。在本提案中，我们将评估¿2-a2环残基对朊病毒聚集，物种屏障和菌株的影响。在目标1中，我们将确定体外和体内朊病毒聚集和构象转化的关键残基的作用。在目标2中，我们将使用仅在环上不同的小鼠模型，评估¿2-a2环区域对人类和牛朊病毒感染的重要性。这些研究结果将有助于我们了解朊病毒蛋白聚集的基本机制，有助于我们评估朊病毒向人类传播的风险，并促进合理设计阻断朊病毒聚集的治疗方法。

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. PUBLIC HEALTH RELEVANCE: Prion infections have the potential to spread from animals to humans and have caused deaths as well as enormous economic losses in the UK. Chronic wasting disease (CWD) is an emerging prion disease in deer and elk, transmitted at a rate unparalleled by any other prion disease, and thus may present a risk of infecting humans, our food animals, and other wildlife. We propose to investigate the underlying mechanisms for when and how prions can infect a new host.