Beclin 1在阿尔茨海默病样神经元损伤中的调控机制研究

The disturbance of autophagic-lysosomal degradative system commonly occurs early in hippocampus and cortex of patients with Alzheimer’s disease (AD). Dysfunction of such degradative system may lead to the accumulation of amyloid β peptide (Aβ) and subsequent neuronal cell apoptosis or degeneration. Nevertheless, the crosstalk between apoptosis and autophagy in the pathogenesis of AD remains poorly known. Beclin 1 is one of the key genes regulating both autophagic and apoptotic pathways. Under physiological condition, Beclin 1 serves as one of the upstream initiators which contribute to autophagy activation. In certain pathological condition, Beclin 1 can be cleaved by Caspases. The cleaved Beclin 1 fragment turns autophagy off, but turns apoptosis on. Here, we aim to understand the cause of Beclin 1 cleavage and the distribution of cleaved Beclin 1 in neuronal cells with AD-like injury using in vitro cultured neurons, PC12 cells as well as AD animals. The regulatory effects of Beclin 1 on autophagic and apoptotic pathways will be studied before or after cleavage. By interfering with Beclin 1-autophagy/apoptosis pathways, we aim to investigate the potential therapeutic effects of certain interference on the suppression of neuronal cell injury and the improvement of spatial learning and memory in AD animals. These studies may help to better understand the mechanism of neuronal cell injury during early AD and provide valuable insights for the development of novel therapeutic or preventive interventions for AD.

阿尔茨海默病（Alzheimer’s disease, AD）发病早期伴随出现海马、皮层内自噬-溶酶体降解系统的紊乱。该系统功能失常导致β淀粉样蛋白蓄积，致使神经元凋亡、变性。但自噬和凋亡在AD发病机制中的相互关联尚不明确。Beclin 1是介导两通路的关键基因之一：生理情况下，Beclin 1作为启动因子之一，活化自噬途径；病理过程中，Beclin 1受Caspases剪切，关闭自噬通路，启动凋亡程序。本项目将以体外培养的神经元、PC12细胞及AD动物为研究对象，阐明AD样神经元损伤中，Beclin 1剪切体的成因分布，及Beclin 1剪切前后对自噬与凋亡通路的调控作用。通过基因和药物手段干预Beclin 1-自噬/凋亡通路，明确其对神经元损伤的缓解和对模型动物空间学习和记忆可能的改善作用。通过研究，希望能从新的角度阐明AD早期神经元病理损伤机制，为寻找新的干预治疗方法提供依据。

阿尔茨海默病（Alzheimer’s disease, AD）发病早期伴随出现海马、皮层内自噬-溶酶体降解系统的紊乱。该系统功能失常导致β淀粉样蛋白蓄积，致使神经元凋亡、变性。但自噬和凋亡在AD发病机制中的相互关联尚不明确。本研究以体外培养的PC12细胞、原代神经元以及AD小鼠为研究对象，建立了AD样神经元病理损伤模型，研究了Beclin 1在介导自噬和凋亡通路的交互应答以及调控神经元损伤的关键作用。研究结果显示，星胞菌素（STS）可诱导PC12细胞发生急性损伤；Aβ1-42可诱导PC12和神经元发生慢性AD样神经变性。AD样神经元损伤伴随出现自噬流受阻。自噬相关蛋白Beclin 1主要表达在神经元中，且在受损神经细胞内出现核内移现象。细胞内过表达或敲低Beclin 1均不能有效抑制AD样神经元死亡。Beclin 1不同片段在细胞内分布位置不同，受损细胞内Beclin 1剪切体表达增加。运用Caspase广谱抑制剂、Caspase 3抑制剂或对Beclin 1 146/149位点进行定点突变，可抑制Beclin 1的剪切及其在细胞内的重分布。结果提示，受损神经元内Caspase 3可能通过剪切Beclin 1，使Beclin 1失去自噬活化作用，并发生胞内分布改变。与野生型小鼠相比，Beclin 1在APP/PS1转基因动物海马、皮层等脑区神经元内出现核内移。运用自噬激动剂可有效抑制Beclin 1重分布、缓解神经元损伤，提高模型小鼠的学习记忆功能。本研究从新的角度阐明AD早期神经元病理损伤的机制，为以Beclin 1为靶点的干预治疗方法提供依据。