The role of prion heterogeneity in transmission and transport

朊病毒异质性在传播和运输中的作用

• 批准号: RGPIN-2019-05309
• 负责人: Gilch, Sabine
• 金额: $ 3.64万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=766024
• 关键词: role; prion; heterogeneity; transmission; transport

The protein-only hypothesis states that infectious prions consist of a misfolded isoform (PrPSc) of the cellular prion protein (PrPC) without encoding nucleic acid which represents an exceptional biological principle. Prions replicate by inducing conformational conversion of the mainly a-helical PrPC into PrPSc with b-sheet structure, which makes it prone to aggregation and resilient to proteolytic digestion. The conformation of PrPSc can vary despite identical primary structure, and these conformational variants are termed prion strains. Prion strains can evolve or be selected upon passage through different hosts with distinct PrPC primary structures, or in the same host species expressing species-specific allelic variants of PrPC arising from polymorphic codons and subsequent single amino acid substitutions. Prion strains encode and inherit their biological and biochemical properties in their conformations, and consist of a mixture of PrPSc aggregates of different molecular weights, representing fractions of monomeric, oligomeric or fibrillary PrPSc. Oligomeric PrPSc aggregates contain the highest levels of infectivity when injected intracerebrally into rodent models of prion disease. However, the role of PrPSc aggregate size in natural infection at peripheral body sites, and the impact of host factors on the aggregate profile such as the PrP genotype have not been investigated but are critically important to gain a full understanding of how transmissible information is encoded by prions. Interestingly, our preliminary data indicate a role of PrPSc aggregate size in targeting specific brain regions for replication. Our proposed research program addresses the basic questions which information is stored and transmitted by the subsets of PrPSc aggregates that compose prion strains, and how this information is modulated upon interaction with the host organism. Chronic wasting disease (CWD) prions of cervids are a highly relevant model as the disease is spreading among wild cervids in North America and two European countries, and threatens endangered caribou populations in Canada. We will use our newly generated, unique knock-in mouse models expressing wild-type and selected allelic variants of cervid PrP under control of the endogenous PrP promoter for infection with size-fractionated PrPSc aggregates. These will be complemented by innovative cell culture, primary neuron and in vitro prion amplification models to address three objectives: (1) to determine the impact of specific polymorphisms in cervid PrPC on cellular prerequisites for prion conversion, (2) to analyse PrPSc aggregate size profiles of CWD isolates and the role in prion transport and infectivity and (3) to investigate PrPSc aggregate size inheritance and its role in host cell selection in the brain. Results from this research will have a significant impact on our knowledge about prion-host interaction and the range of information that can be encoded by protein structure.

仅蛋白质假说指出，传染性朊病毒由细胞朊病毒蛋白 (PrPC) 的错误折叠异构体 (PrPSc) 组成，不编码核酸，这代表了一种特殊的生物学原理。朊病毒通过诱导主要a螺旋的PrPC构象转换为具有b折叠结构的PrPSc来复制，这使得它易于聚集并且对蛋白水解消化具有弹性。尽管一级结构相同，但 PrPSc 的构象可能有所不同，这些构象变异体被称为朊病毒株。朊病毒菌株可以在通过具有不同 PrPC 一级结构的不同宿主时进化或被选择，或者在表达由多态性密码子和随后的单氨基酸取代产生的 PrPC 物种特异性等位基因变体的同一宿主物种中。朊病毒株在其构象中编码并继承其生物和生化特性，并由不同分子量的 PrPSc 聚集体的混合物组成，代表单体、寡聚或原纤维 PrPSc 的部分。当脑内注射到朊病毒病的啮齿动物模型中时，寡聚 PrPSc 聚集体具有最高水平的感染性。然而，PrPSc 聚集体大小在身体周围部位自然感染中的作用，以及宿主因素对聚集体特征（如 PrP 基因型）的影响尚未得到研究，但对于充分了解朊病毒如何编码可传播信息至关重要。有趣的是，我们的初步数据表明 PrPSc 聚集体大小在针对特定大脑区域进行复制方面发挥着作用。我们提出的研究计划解决了组成朊病毒株的 PrPSc 聚集体子集存储和传输信息的基本问题，以及如何在与宿主生物体相互作用时调节这些信息。鹿科动物的慢性消耗性疾病（CWD）朊病毒是一个高度相关的模型，因为该疾病正在北美和两个欧洲国家的野生鹿科动物中传播，并威胁到加拿大濒临灭绝的驯鹿种群。我们将使用我们新生成的独特的敲入小鼠模型，在内源性 PrP 启动子的控制下表达野生型和选定的鹿 PrP 等位基因变体，以进行大小分级的 PrPSc 聚集体的感染。这些将得到创新细胞培养、原代神经元和体外朊病毒扩增模型的补充，以实现三个目标：(1) 确定鹿 PrPC 中特定多态性对朊病毒转化的细胞先决条件的影响，(2) 分析 CWD 分离株的 PrPSc 聚集体大小概况以及在朊病毒运输和感染性中的作用，(3) 研究 PrPSc 聚集体大小遗传及其遗传性 在大脑中宿主细胞选择中发挥作用。这项研究的结果将对我们关于朊病毒-宿主相互作用的知识以及蛋白质结构编码的信息范围产生重大影响。