Defining molecular contributions of LINE-1 retrotransposons to AD / ADRD

项目摘要：阿尔茨海默病(AD)和与AD相关的痴呆(ADRDS；例如 痴呆症、路易体痴呆症等)是严重的神经退行性疾病。这些疾病的发病 与衰老密切相关。AD和ADRD的治疗仍然难以捉摸；阿尔茨海默氏症已成为第六大 在美国常见的死因。阿尔茨海默病和ADRD的一个新的候选贡献者是L1 逆转座子，它在衰老过程中变得失调，与阿尔茨海默氏症/ADRD的发病相关。一 L1可能导致阿尔茨海默病/ADRD的假设机制是通过它的细胞恶化 衰老。衰老是一种正常细胞停止分裂的现象；这些细胞随着 随着年龄的增长，在与年龄相关的疾病的功能障碍部位被发现。在小鼠中，衰老的细胞 已被证明可以缩短寿命，并积极推动与年龄相关的神经退化；防止细胞衰老 积累可以减少依赖tau的退化和认知能力下降。AD患者表现出增加 细胞衰老的指标。越来越清楚的是，衰老的细胞不是惰性的，而是驱动组织 通过衰老相关的分泌表型而恶化--分泌多种生长因子和促进素 炎性细胞因子。L1反转录转座子最近被证明推动衰老的进展- 相关的分泌表型，因此，L1是细胞衰老的重要因素。L1激活也是 与AD相关的Tau病理有关。L1编码的ORF2p酶(内切酶和反向 转录酶)通常被标记为病理性细胞侮辱的来源，例如通过新的、诱变的L1插入 以及对染色体不稳定的贡献。然而，L1表达的影响超越了DNA 损坏。许多机制可能在起作用，包括滴定正常体内平衡的宿主因子。 远离它们的生理功能，进入L1核糖核蛋白颗粒，以及产生 免疫和炎症触发细胞质L1DNA：RNA杂交体；事实上，后者现在被理解为 是L1‘S在细胞衰老中作用的关键成分。此外，L1还动员Alu和其他非 自主反转录转座子。 目的：在目标1中，我们将使用靶向质谱学来分析L1 ORF1蛋白在 AD/ADRD和认知功能减退患者的脑脊液(CSF)和死后脑组织， 在Aim 2(体外细胞培养)和Aim 3(临床样本)中，我们 将在与目标1相同的生物样本中描述L1相关的蛋白质-蛋白质和蛋白质-RNA相互作用； 在目标4中，我们将采用基于候选对象的方法，使用分子遗传学来剖析 L1在衰老细胞中的作用。

Project Summary: Alzheimer's Disease (AD) and AD-related dementias (ADRDs; e.g. Frontotemporal Dementia, Lewy Body Dementia, etc.) are crippling neurodegenerative disorders. The onset of these diseases is strongly correlated with aging. Cures for AD and ADRDs remain elusive; Alzheimer's has become the 6th most frequent cause of death in the USA. An emerging candidate contributor to Alzheimer's and ADRD is the L1 retrotransposon, which becomes dysregulated during aging and correlates with Alzheimer's / ADRD onset. One hypothetical mechanism by which L1 may contribute to Alzheimer's / ADRD is through its exacerbation of cellular senescence. Senescence is a phenomenon by which normal cells stop dividing; these cells accumulate with advancing age and are found at the locations of dysfunction in age-related diseases. In mice, senescent cells have been shown to shorten life and actively drive age-related neurodegeneration; preventing senescent cell accumulation decreases tau-dependent degeneration and cognitive decline. AD patients exhibit increased indicators of cellular senescence. It is increasingly clear that senescent cells are not inert, but instead drive tissue deterioration via the senescence-associated secretory phenotype - secreting a variety of growth factors and pro- inflammatory cytokines. L1 retrotransposons have recently been shown to drive progression of the senescence- associated secretory phenotype, and thus, L1 is an important agent of cellular senescence. L1 activation is also associated with AD-related Tau pathologies. The L1 encoded ORF2p enzyme (endonuclease and reverse transcriptase) is often flagged as a source of pathological cellular insults, e.g. via new, mutagenic L1 insertions and contributions to chromosomal instability. However, the effects of L1 expression extend beyond DNA damage. Numerous mechanisms may be at play, including the titration of normally homeostatic host factors away from their physiologic functions and into L1 ribonucleoprotein granules, as well as the production of immunity-and-inflammation-triggering cytoplasmic L1 DNA:RNA hybrids; indeed, the latter is now understood to be a key component of L1’s role in cellular senescence. Moreover, L1 also mobilizes Alu and other non- autonomous retrotransposons. Objectives: In Aim 1, we will use targeted mass spectrometry to profile L1 ORF1 protein expression in the cerebrospinal fluid (CSF) and post-mortem brain tissues of patients exhibiting AD/ADRD and cognitive decline, as well as in senescent cells and neuronal iPSCs; in Aim 2 (in vitro cell culture) and Aim 3 (clinical samples) we will profile L1-associated protein-protein and protein-RNA interactions in the same biological samples as Aim 1; and in Aim 4 we will take a candidate-based approach using molecular genetics to dissect the mechanisms of action of L1 in senescent cells.