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)是美国第六大死亡原因，目前还没有有效的治疗方法。 此外，这种与年龄相关的神经退行性疾病的患病率可能会随着美国的增长而增加 人口老龄化。因此，对AD的认识和治疗方法的发展十分必要。APOE是一种 吸引人的靶子是因为这种脂质转运蛋白是AD最强烈的遗传风险因素之一。APOE3是 最常见的异构体，被认为是中性的。载脂蛋白E4携带者患AD的可能性高达15倍， 而APOE2似乎对AD有保护作用。随后的实验已经证实，载脂蛋白E4在 在AD中的因果作用。然而，载脂蛋白E和AD的偶联机制尚不清楚。引人注目的是，ApoE4和 APOE2与ApoE3各有一处不同(ApoE4中的C112R和APOE2中的R158C)。都不是 替代发生在一个功能部位，这表明它们通过改变蛋白质的 构象偏好。然而，确定这些结构性差异的特征仍然具有挑战性。部分 不同亚型的晶体结构基本相同，蛋白质的其余部分在很大程度上是不同的 结构特征，因为载脂蛋白E在脂质运输中的作用要求它部分无序和倾向于 到寡聚化。这项提议旨在通过以下方式揭示载脂蛋白E诱导的神经毒性的结构决定因素 建立和分析神经毒性和无毒变体的原子详细的马尔可夫状态模型(MSM)。 主要的焦点将放在单体、无脂的载脂蛋白E上，因为它是许多功能的相关物种 过程中，脱脂ApoE被认为是神经毒性物种，单体的波动是 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 自适应采样算法将被开发来解决极端的构象异质性 无序的区域。然后，这些算法将被应用于理解 有代表性的ApoE变体，如结构域开放的程度。计算预测将得到检验 与我们的合作者一起进行了单分子Förster共振能量转移(SmFRET)实验。 在目标2中，将使用一次工具来剖析连接载脂蛋白E远端区域的变构机制 又一次被设计来解释混乱。由此洞察到神经毒性和神经毒性之间的结构差异 无毒的亚型将为设计新的变种来测试我们的模型提供基础。我们还将设计 稳定无毒构象的“结构校正器”，为未来药物的设计提供线索 战斗广告。