Characterisation of Amyloid- B and its Interactions by NMR Exchange Techniques

通过 NMR 交换技术表征淀粉样蛋白 - B 及其相互作用

• 批准号: 2720806
• 金额: --
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2720806
• 关键词: Characterisation; Amyloid; its; Interactions; NMR

Alzheimer's disease is a fatal neurological condition and the leading cause of dementia worldwide. It is characterised by deposits of aggregated peptide, amyloid-B (AB), which form plaques in the brain. AB transitions into aggregated species through three states: monomeric (where the peptide is intrinsically disordered), oligomeric (small aggregates, identified as the primary candidate for toxicity) and highly ordered fibular structures. Most current drug discovery strategies aim to target the aggregated species including oligomers and fibrils. Amyloid precursor protein is proteolytically cleaved into Ab peptides. The 40-residue variant, Ab40, is the predominant form found in biological fluids. In contrast, the 42-residue variant, Ab42, is more commonly found in Alzheimer's disease plaques and has a higher propensity for aggregation. The most striking difference in aggregation rates between the two peptides is found in the first step of aggregation called primary nucleation, suggesting that there are fundamental differences in monomeric AB40 and AB42. It is well known that these peptides are intrinsically disordered in their monomeric forms, but structural studies of the two peptides have found very little chemical or structural differences in their monomeric states. Many suggest that the difference in aggregation propensity is driven by the additional C-terminal hydrophobic amino acids in AB42 or that the aggregation rates differ due to varying structures of oligomeric and fibrillar species. In my 3-month rotation I used CLEAN-EX NMR methods to understand the difference in solvent accessibility between AB40 and AB42. My preliminary data suggests that there is a difference in the solvation rates between the two peptides, not only at the expected C-terminal end of the peptide, but also at an upstream residue (K16) which is surprisingly more protected in AB42. This observation suggests that the additional amino acids in AB42 may be causing some long-range effects that affect the overall structure of the peptide.During my PhD, I will first repeat these CLEAN-EX experiments to confirm my findings and then extend this approach to delve deeper into the monomeric properties of AB. It has been shown that post translationally modifying AB40 on residue K16 (and other residues) results in a different aggregation profile for the peptide and it would be interesting to see if this difference can be detected at the monomer level by CLEAN-EX experiments. Another avenue I plan to explore involves the binding of small, drug-like molecules to AB. I will first conduct aggregation assays identify molecules that alter the aggregation profile of AB and then follow that up with NMR experiments to identify if there are differences in solvation between the bound and unbound states of the monomer. Overall, there are a lot of unanswered questions about the structure of monomeric AB and solvent-based NMR methods would be an interesting and hopefully lucrative method of investigating these questions.

阿尔茨海默病是一种致命的神经系统疾病，也是全球痴呆症的主要原因。其特征在于聚集的肽，淀粉样蛋白-B（AB）的沉积，其在脑中形成斑块。AB通过三种状态转变为聚集物质：单体（其中肽本质上是无序的）、寡聚体（小聚集体，被鉴定为毒性的主要候选物）和高度有序的腓骨结构。目前大多数药物发现策略旨在靶向聚集的物质，包括寡聚体和原纤维。 淀粉样前体蛋白被蛋白水解切割成Ab肽。40个残基的变体Ab 40是在生物液体中发现的主要形式。相比之下，42个残基的变体Ab 42更常见于阿尔茨海默病斑块中，并且具有更高的聚集倾向。两种肽之间聚集速率的最显著差异发现于称为初级成核的聚集的第一步，表明单体AB 40和AB 42存在根本差异。众所周知，这些肽在其单体形式中本质上是无序的，但对这两种肽的结构研究发现它们的单体状态中几乎没有化学或结构差异。许多人认为，聚集倾向的差异是由AB 42中额外的C-末端疏水氨基酸驱动的，或者聚集速率的不同是由于寡聚物和纤维物质的不同结构。在我为期3个月的轮换中，我使用CLEAN-EX NMR方法来了解AB 40和AB 42之间溶剂可及性的差异。我的初步数据表明，两种肽之间的溶剂化速率存在差异，不仅在预期的肽的C末端，而且在上游残基（K16）处，其在AB 42中受到的保护令人惊讶地更多。这一观察结果表明，AB 42中的额外氨基酸可能会引起一些影响肽整体结构的长期效应。在我的博士学位期间，我将首先重复这些CLEAN-EX实验来证实我的发现，然后扩展这种方法以深入研究AB的单体性质。已经表明，在残基K16（和其他残基）上对AB 40进行后修饰导致肽的不同聚集特征，并且观察这种差异是否可以通过CLEAN-EX实验在单体水平上检测到将是有趣的。我计划探索的另一个途径涉及小的药物样分子与AB的结合。我将首先进行聚集测定，确定改变AB聚集特征的分子，然后进行NMR实验，以确定单体的结合态和非结合态之间的溶剂化是否存在差异。总的来说，有很多关于单体AB的结构的未回答的问题，基于溶剂的NMR方法将是一个有趣的，并希望有利可图的方法来研究这些问题。