A unique subpopulation of wild-type neurons recapitulating FAD phenotypes

野生型神经元的独特亚群再现了 FAD 表型

• 批准号: 10559827
• 负责人: Masato Maesako
• 金额: $ 51.87万
• 依托单位: MASSACHUSETTS GENERAL HOSPITAL
• 依托单位国家: 美国
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-03-01 至 2027-11-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10559827
• 关键词: Age of Onset; Alzheimer' s Disease; Alzheimer' s disease brain; Amyloid beta-Protein; Autopsy; Binding; Biological Assay; Biological Models; Biosensor; Brain; Cell Separation; Cells; Characteristics; Clinical; Cyclic AMP-Dependent Protein Kinases; Data; Data Set; Databases; Development; Disease; FDA approved; Fluorescence Resonance Energy Transfer; Genetic; Genetic Transcription; Goals; Grant; Heterogeneity; Human; Impairment; In Vitro; Individual; Knock-in; Knowledge Portal; Link; Mediating; Molecular; Molecular Conformation; Mus; Mutation; Nerve Degeneration; Neurons; PKA inhibitor; Pathologic; Pathology; Pathway interactions; Persons; Pharmacologic Substance; Phenotype; Phosphorylation; Physiological; Play; Population; Post-Translational Protein Processing; Production; Proteomics; Role; Site; Tg2576; Therapeutic; Time; Tissues; Transgenic Mice; Transgenic Organisms; Vulnerable Populations; brain tissue; early onset; enzyme substrate; familial Alzheimer disease; gamma secretase; in vivo; induced pluripotent stem cell; mouse model; mutant; non-demented; novel; novel therapeutic intervention; novel therapeutics; pharmacologic; presenilin; presenilin-1; resilience; response; sensor; tau Proteins; transcriptomics

Abstract People with late-onset sporadic Alzheimer’s disease (SAD) display overall the same clinical and pathological features as those with early-onset familial AD (FAD). However, the mechanism(s) underlying the clinicopathologic commonality between these two genetically distinct AD forms is unclear. Our overall hypothesis is that a subpopulation of wild-type neurons in the brain strikingly recapitulates the phenotypes of neurons expressing FAD mutant Presenilin (PSEN) (perhaps via post-translational modification of wild-type PSEN1), and this selective cell population plays a role in SAD neurodegeneration. Several pieces of evidence support this hypothesis. First, we showed that wild-type PSEN1 in a subset of neurons within the SAD brain displays a conformation similar to FAD mutant PSEN1 (Wahlster et al. Acta Neuropathol 2013). Second, we uncovered that PKA-mediated PSEN1 phosphorylation at Ser310 is significantly upregulated in SAD brains, and this post translational modification, together with phosphorylation of two other sites, steers wild-type PSEN1 conformation towards that of FAD mutant PSEN1 (Maesako et al. eLife 2017). Lastly, we have recently developed novel genetically encoded FRET-based biosensors that for the first time allow quantitative recording of the gamma-secretase activity over time, on a cell-by-cell basis, in live neurons (Maesako et al. iScience 2020, Houser et al. Sensors 2020, Houser et al. Biosensors 2021, Maesako et al. J Neurosci 2022). Surprisingly, these biosensors have enabled us to discover a unique subpopulation of wild-type neurons displaying diminished endogenous gamma-secretase activity. More importantly, our strong preliminary data show that this cell population recapitulates several key characteristics that have been identified in neurons expressing FAD mutant PSEN; these include impaired gamma-secretase “processivity” and thus predominant production of long Aβ, endo-lysosomal abnormalities, and vulnerability phenotypes in response to toxic insults. Therefore, this proposal will further employ multiple model systems and complementary assays to establish the molecular basis and physiological relevance that support our hypothesis. Aim 1 will elucidate the molecular mechanism(s) underlying the heterogeneity in endogenous gamma-secretase activity and its consequences in neurons. Aim 2 will further verify the cause-and-effect relationship between dysfunctional gamma-secretase, endo-lysosomal abnormalities, and neuronal vulnerability. More importantly, we will explore the therapeutic potential of the US FDA-approved compounds that could potentially function as gamma-secretase modulators (GSMs) or gamma-secretase activators (GSAs). Aim 3 will determine if the unique FAD-like neuronal population exists in “AD” mouse models endogenously expressing wild-type PSEN, as our preliminary results indicate, in iPSCs derived human neurons and post-mortem brains from SAD cases. Given that promoting neuronal resilience could be a new therapeutic strategy for AD, a better understanding of the molecular basis behind the newly discovered selectively vulnerable cell population will open a new path for developing novel therapeutic opportunities.

摘要 晚发性散发性阿尔茨海默病（SAD）患者与早发性家族性AD（FAD）患者的临床和病理特征基本相同。然而，这两种遗传学上不同的AD形式之间的临床病理学共性的机制尚不清楚。我们的总体假设是，大脑中野生型神经元的亚群惊人地再现了表达FAD突变体早老素（PSEN）的神经元的表型（可能通过野生型PSEN 1的翻译后修饰），并且这种选择性细胞群在SAD神经变性中起作用。有几个证据支持这一假设。首先，我们表明SAD脑内神经元亚组中的野生型PSEN 1显示出与FAD突变体PSEN 1相似的构象（Wahlster et al. Acta Neuropathol 2013）。其次，我们发现，在SAD脑中，PKA介导的PSEN 1在Ser 310处的磷酸化显著上调，并且这种翻译后修饰与其他两个位点的磷酸化一起，将野生型PSEN 1构象转向FAD突变体PSEN 1的构象（Maesako et al. eLife 2017）。最后，我们最近开发了新的基于基因编码的FRET的生物传感器，其首次允许在活神经元中以细胞为基础定量记录γ-分泌酶随时间的活性（Maesako et al. iScience 2020，Houser et al. Sensors 2020，Houser et al. Biosensors 2021，Maesako et al. J Neurosci 2022）。令人惊讶的是，这些生物传感器使我们能够发现一个独特的野生型神经元亚群显示内源性γ分泌酶活性降低。更重要的是，我们强有力的初步数据表明，该细胞群重现了在表达FAD突变体PSEN的神经元中已鉴定的几个关键特征;这些特征包括受损的γ-分泌酶“持续合成能力”，从而主要产生长Aβ、内溶酶体异常和响应毒性损伤的脆弱性表型。因此，本提案将进一步采用多个模型系统和互补测定来建立支持我们假设的分子基础和生理相关性。目的1将阐明内源性γ-分泌酶活性的异质性及其在神经元中的后果的分子机制。目的2将进一步验证γ-分泌酶功能障碍、内-溶酶体异常和神经元易损性之间的因果关系。更重要的是，我们将探索美国FDA批准的化合物的治疗潜力，这些化合物可能作为γ-分泌酶调节剂（GSM）或γ-分泌酶激活剂（GSA）发挥作用。目的3将确定独特的FAD样神经元群体是否存在于内源性表达野生型PSEN的“AD”小鼠模型中，如我们的初步结果所示，在来自SAD病例的iPSC衍生的人神经元和死后脑中。鉴于促进神经元恢复可能是AD的一种新的治疗策略，更好地了解新发现的选择性脆弱细胞群背后的分子基础将为开发新的治疗机会开辟一条新的道路。