Mukherjee Soumya, Coyle Reid, Dubois Celine, Perez Keyla, McLean Catriona, Masters Colin L, Roberts Blaine R
The Tracy Family SILQ Center, Washington University School of Medicine, St. Louis, MO, 63110, USA.
Department of Neurology, Washington University School of Medicine, St. Louis, MO, 63110, USA.
Acta Neuropathol. 2025 Jul 22;150(1):7. doi: 10.1007/s00401-025-02914-2.
Extracellular amyloid plaques, the pathognomonic hallmark of Alzheimer's disease (AD), are also observed in cognitively unimpaired subjects in the preclinical stages. Progressive accumulation of fibrillar amyloid-β (Aβ) as plaques and perivascular deposits occur two decades before clinical onset, making Aβ a long-lived peptide. To characterize the amyloid plaques biochemically, both the Aβ-load as well the post-translational modifications (PTMs) could serve as markers for distinguishing the pre-clinical stage compared to later prodromal and clinical stages of AD. Recently, we described the presence of extensive isomerization of the Aβ N-terminus in AD post-mortem brains that is significantly increased compared to the age-matched non-AD control brains with Aβ aggregates. In this report, we performed Lys-N enzymatic digestion followed by mass spectrometry-based quantitative analysis of the most common PTMs associated with plaque Aβ. We focused on pyroglutamation (pGlu3), citrullination (cit5), N-terminal truncation (Aβ), C-terminal isoforms (Aβ and Aβ), and isomerization of aspartic acid residues (Asp-1 and Asp-7) in postmortem human brain tissue from pathologically negative (no Aβ plaques) controls (n = 23), controls with Aβ plaques (n = 35), Parkinson's disease (PD) with (n = 28) and without Aβ accumulation/plaques (n = 30) and symptomatic AD (n = 60). The AD cases contained statistically significant amounts of Asp-1 and Asp-7 isomerized Aβ (~ 90%) compared to controls (preclinical AD) and PD brains with fibrillar Aβ aggregates/deposits. We find that the ratio of isomerized N-terminus Aβ (Aβ) species in the brain detergent soluble pool differentiates older fibrillar Aβ deposits in symptomatic AD brain compared to Aβ deposits detected in preclinical AD and PD. Citrullinated pGlu3-Aβ was increased only in symptomatic AD, highlighting this Aβ PTM is a unique feature of parenchymal plaques in advanced AD. Our results have implications for early therapeutic targeting of these modified species as well as potential for better biofluid biomarker development for drug efficacy monitoring.
细胞外淀粉样斑块是阿尔茨海默病（AD）的特征性标志，在临床前期认知未受损的个体中也可观察到。作为斑块和血管周围沉积物的纤维状淀粉样β蛋白（Aβ）的渐进性积累在临床发病前二十年就已发生，这使得Aβ成为一种长寿肽。为了从生化角度表征淀粉样斑块，Aβ负荷以及翻译后修饰（PTM）都可作为区分AD临床前期与后期前驱期和临床期的标志物。最近，我们描述了AD尸检大脑中Aβ N端存在广泛的异构化，与有Aβ聚集物的年龄匹配的非AD对照大脑相比，这种异构化显著增加。在本报告中，我们进行了赖氨酰-N酶消化，然后基于质谱对与斑块Aβ相关的最常见PTM进行定量分析。我们重点研究了来自病理阴性（无Aβ斑块）对照（n = 23）、有Aβ斑块的对照（n = 35）、有（n = 28）和无Aβ积累/斑块（n = 30）的帕金森病（PD）以及有症状AD（n = 60）的人死后脑组织中焦谷氨酸化（pGlu3）、瓜氨酸化（cit5）、N端截短（Aβ）、C端异构体（Aβ和Aβ）以及天冬氨酸残基（Asp-1和Asp-7）的异构化情况。与对照（临床前期AD）和有纤维状Aβ聚集物/沉积物的PD大脑相比，AD病例中含有统计学上显著量的Asp-1和Asp-7异构化Aβ（约90%）。我们发现，与临床前期AD和PD中检测到的Aβ沉积物相比，脑去污剂可溶性池中异构化N端Aβ（Aβ）物种的比例可区分有症状AD大脑中较老的纤维状Aβ沉积物。瓜氨酸化的pGlu3-Aβ仅在有症状AD中增加，突出了这种Aβ PTM是晚期AD实质斑块的独特特征。我们的结果对于这些修饰物种的早期治疗靶点以及开发用于药物疗效监测的更好的生物流体生物标志物具有重要意义。
