Department of Neuroscience, Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL, 32224, USA.
Division of Biomedical Statistics and Informatics, Mayo Clinic, Jacksonville, FL, 32224, USA.
Acta Neuropathol. 2022 Jun;143(6):641-662. doi: 10.1007/s00401-022-02421-8. Epub 2022 Apr 26.
Approximately half of Alzheimer's disease (AD) brains have concomitant Lewy pathology at autopsy, suggesting that α-synuclein (α-SYN) aggregation is a regulated event in the pathogenesis of AD. Genome-wide association studies revealed that the ε4 allele of the apolipoprotein E (APOE4) gene, the strongest genetic risk factor for AD, is also the most replicated genetic risk factor for Lewy body dementia (LBD), signifying an important role of APOE4 in both amyloid-β (Aβ) and α-SYN pathogenesis. How APOE4 modulates α-SYN aggregation in AD is unclear. In this study, we aimed to determine how α-SYN is associated with AD-related pathology and how APOE4 impacts α-SYN seeding and toxicity. We measured α-SYN levels and their association with other established AD-related markers in brain samples from autopsy-confirmed AD patients (N = 469), where 54% had concomitant LB pathology (AD + LB). We found significant correlations between the levels of α-SYN and those of Aβ40, Aβ42, tau and APOE, particularly in insoluble fractions of AD + LB. Using a real-time quaking-induced conversion (RT-QuIC) assay, we measured the seeding activity of soluble α-SYN and found that α-SYN seeding was exacerbated by APOE4 in the AD cohort, as well as a small cohort of autopsy-confirmed LBD brains with minimal Alzheimer type pathology. We further fractionated the soluble AD brain lysates by size exclusion chromatography (SEC) ran on fast protein liquid chromatography (FPLC) and identified the α-SYN species (~ 96 kDa) that showed the strongest seeding activity. Finally, using human induced pluripotent stem cell (iPSC)-derived neurons, we showed that amplified α-SYN aggregates from AD + LB brain of patients with APOE4 were highly toxic to neurons, whereas the same amount of α-SYN monomer was not toxic. Our findings suggest that the presence of LB pathology correlates with AD-related pathologies and that APOE4 exacerbates α-SYN seeding activity and neurotoxicity, providing mechanistic insight into how APOE4 affects α-SYN pathogenesis in AD.
大约有一半的阿尔茨海默病（AD）大脑在尸检时同时存在路易体病理学，这表明α-突触核蛋白（α-SYN）聚集是 AD 发病机制中的一个受调控事件。全基因组关联研究表明，载脂蛋白 E（APOE）基因的 ε4 等位基因是 AD 最强的遗传风险因素，也是路易体痴呆（LBD）最具复制性的遗传风险因素，这表明 APOE4 在淀粉样蛋白-β（Aβ）和 α-SYN 发病机制中都起着重要作用。APOE4 如何调节 AD 中的 α-SYN 聚集尚不清楚。在这项研究中，我们旨在确定 α-SYN 如何与 AD 相关的病理学相关，以及 APOE4 如何影响 α-SYN 接种和毒性。我们测量了尸检证实的 AD 患者（n=469）大脑样本中的 α-SYN 水平及其与其他已建立的 AD 相关标志物的关联，其中 54%的患者同时存在 LB 病理学（AD+LB）。我们发现 α-SYN 水平与 Aβ40、Aβ42、tau 和 APOE 水平之间存在显著相关性，特别是在 AD+LB 的不溶性部分。使用实时震颤诱导转化（RT-QuIC）测定法，我们测量了可溶性 α-SYN 的接种活性，发现 APOE4 在 AD 队列以及一小部分尸检证实的具有最小阿尔茨海默病类型病理学的 LBD 大脑中加剧了 α-SYN 接种。我们进一步通过快速蛋白质液相色谱（FPLC）上的大小排阻色谱（SEC）对可溶性 AD 脑裂解物进行分级，并鉴定出具有最强接种活性的 α-SYN 物种（~96 kDa）。最后，使用人诱导多能干细胞（iPSC）衍生的神经元，我们表明来自 AD+LB 脑的放大的 α-SYN 聚集体对神经元具有高度毒性，而相同量的 α-SYN 单体没有毒性。我们的研究结果表明，LB 病理学的存在与 AD 相关病理学相关，APOE4 加剧了 α-SYN 的接种活性和神经毒性，为 APOE4 如何影响 AD 中的 α-SYN 发病机制提供了机制上的见解。
