Structural basis for ApoE4-induced Alzheimer's disease

阿尔茨海默病（AD）是美国第六大死亡原因，目前尚无有效的治疗方法。 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，非常需要了解AD并开发治疗方法。ApoE是一种 这是一个有吸引力的目标，因为这种脂质转运蛋白是AD最强的遗传风险因素之一。ApoE 3是 最常见的同种型，被认为是中性的。ApoE 4携带者患AD的可能性高达15倍， 而ApoE 2似乎对AD具有保护作用。随后的实验证实，ApoE 4发挥了重要作用。 在AD中的作用然而，ApoE和AD的耦合机制仍不清楚。值得注意的是，ApoE 4和 ApoE 2与ApoE 3的不同之处在于单个取代（ApoE 4中的C112 R和ApoE 2中的R158 C）。既不 取代发生在功能位点，这表明它们通过改变蛋白质的 构象偏好然而，描述这些结构性差异仍然具有挑战性。部分 不同同种型的晶体结构基本相同，蛋白质的其余部分在很大程度上不相同。 结构表征，因为ApoE在脂质转运中的作用要求其部分无序且倾向于 低聚化。该提案旨在揭示ApoE诱导的神经毒性的结构决定因素， 建立和分析神经毒性和非毒性变体的原子详细马尔可夫状态模型（MSM）。 主要重点将是单体、无脂质的Apoe，因为它是许多功能的相关物种 过程中，无脂质ApoE被认为是神经毒性物质，单体的波动是 预期揭示其群体被结合伴侣增强/抑制的结构。在目标1中，新 自适应采样算法将被开发，以解决极端的构象异质性 无序区域然后，这些算法将被应用于了解的总结构特性， 代表性ApoE变体，如结构域开放的程度。计算预测将得到检验 与我们的合作者进行的单分子Förster共振能量转移（smFRET）实验。 在目标2中，耦合ApoE远端区域的变构机制将被解剖，使用工具一次， 也是为了解释混乱。从而深入了解神经毒性和神经毒性之间的结构差异， 无毒同种型将为设计新变体以测试我们的模型提供基础。我们还将设计 稳定无毒构象的“结构矫正剂”，为今后设计药物提供线索， 战斗AD

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.