Structural basis for ApoE4-induced Alzheimer's disease

ApoE4 诱导的阿尔茨海默病的结构基础

• 批准号: 10744482
• 负责人: Gregory R Bowman
• 金额: $ 137万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-02-15 至 2025-01-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10744482
• 关键词: Structural; basis; ApoE4; induced; Alzheimer

Alzheimer's disease (AD) is the 6th leading cause of death in the USA and there are no effective treatments. Moreover, the prevalence of this age-related neurodegenerative disease is likely to increase as the US population ages. Therefore, there is a great need to understand AD and develop therapeutics. ApoE is an appealing target because this lipid transporter is one of the strongest genetic risk factors for AD. ApoE3 is the most common isoform and is considered neutral. Carriers of ApoE4 are up to 15-fold more likely to develop AD, while ApoE2 appears to be protective against AD. Subsequent experiments have confirmed that ApoE4 plays a causal role in AD. However, the mechanism coupling ApoE and AD remains unclear. Strikingly, ApoE4 and ApoE2 each differ from ApoE3 by a single substitution (C112R in ApoE4 and R158C in ApoE2). Neither substitution occurs in a functional site, suggesting they indirectly impact function by altering the protein's conformational preferences. However, characterizing these structural differences remains challenging. Partial crystal structures of the different isoforms are essentially identical and the rest of the protein has largely defied structural characterization because ApoE's role in lipid transport requires it to be partially disordered and prone to oligomerization. This proposal aims to uncover the structural determinants of ApoE-induced neurotoxicity by building and analyzing atomically-detailed Markov state models (MSMs) of neurotoxic and non-toxic variants. The primary focus will be on monomeric, lipid-free ApoE as it is the relevant species for many functional processes, lipid-free ApoE is believed to be the neurotoxic species, and the fluctuations of the monomer are expected to reveal structures whose populations are enhanced/suppressed by binding partners. In Aim 1, new adaptive sampling algorithms will be developed to address the extreme conformational heterogeneity of disordered regions. Then these algorithms will be applied to understand the gross structural properties of representative ApoE variants, such as the extent of domain opening. Computational predictions will be tested with single molecule Förster resonance energy transfer (smFRET) experiments performed with our collaborators. In Aim 2, the allosteric mechanism that couples distant regions of ApoE will be dissected, employing tools once again designed to account for disorder. Resulting insight into the structural differences between neurotoxic and non-toxic isoforms will provide a foundation for the design of new variants to test our models. We will also design `structure correctors' that stabilize non-toxic conformations, providing leads for the future design of drugs that combat AD.

阿尔茨海默病（AD）是美国第六大死因，目前尚无有效的治疗方法。 此外，随着美国的发展，这种与年龄相关的神经退行性疾病的患病率可能会增加。 因此，非常需要了解 AD 并开发 ApoE 治疗方法。 有吸引力的目标，因为这种脂质转运蛋白是 AD 最强的遗传风险因素之一。 最常见的亚型，被认为是中性的，ApoE4 携带者患 AD 的可能性高出 15 倍。 而 ApoE2 似乎对 AD 具有保护作用，随后的实验证实 ApoE4 具有预防 AD 的作用。 然而，ApoE 与 AD 的关联机制仍不清楚。 ApoE2 与 ApoE3 各有一个取代（ApoE4 中的 C112R 和 ApoE2 中的 R158C）。 取代发生在功能位点，表明它们通过改变蛋白质的结构来间接影响功能 然而，表征这些结构差异仍然具有挑战性。 不同同种型的晶体结构本质上是相同的，并且蛋白质的其余部分在很大程度上违反了 结构表征，因为 ApoE 在脂质运输中的作用要求它部分无序且容易发生 该提案旨在通过以下方式揭示 ApoE 诱导的神经毒性的结构决定因素。 构建和分析神经毒性和无毒变体的原子详细马尔可夫状态模型（MSM）。 主要关注点是单体、无脂 ApoE，因为它是许多功能性的相关物种。 过程中，无脂 ApoE 被认为是神经毒性物质，单体的波动为 预计将揭示其种群被结合伙伴增强/抑制的结构。在目标 1 中，新的。 将开发自适应采样算法来解决极端构象异质性问题 然后将应用这些算法来了解无序区域的总体结构特性。 代表性的 ApoE 变体，例如域开放的程度，将被测试。 与我们的合作者进行的单分子福斯特共振能量转移（smFRET）实验。 在目标 2 中，将使用工具一次剖析耦合 ApoE 远距离区域的变构机制 再次旨在解释神经毒性和神经毒性之间的结构差异。 无毒亚型将为设计新变体提供基础，以测试我们的模型。 稳定无毒构象的“结构校正剂”，为未来药物设计提供线索 战斗AD。