CD2AP通过网格蛋白介导的内吞途径参与阿尔兹海默症中Tau蛋白转运的作用机制

In Alzheimer’s disease (AD), Tau pathology progresses like prion in a temporospatial pattern throughout connected brain structures involved in learning and memory. One way of internalization of Tau aggregates has been suggested to occur through endocytic routes, but the mechanism underlying is unclear. Recently, many large-scale genome-wide association studies (GWAS) indicate that variants upstream of the CD2-associated protein (CD2AP) gene are a genetic determinant of late onset AD susceptibility. CD2AP plays an important role in numerous cellular processes, including endocytosis, intracellular transport and regulation of cytoskeletal dynamics. In drosophila, genetic manipulation of cindr, the fly ortholog of human CD2AP, robustly enhanced Tau toxicity. In this study, we intend to investigate whether CD2AP colocalizes with neurofibrillary tangles in the involved brain structures affected in AD. Then we plan to study whether CD2AP is involved in interneuronal Tau pathology propagation through clathrin-mediated endocytosis by using in vitro models consists of co-culture of HEK293 persistently harboring intracellular TauP301L-GFP with rat hippocampal neurons expressing soluble hemagglutinin(HA)-tagged TauP301L and in vivo rTgTauEC mice model. This study will help to understand the mechanisms of the “spread” of Tau in AD and may identify potential therapeutic targets for preventing the propagation of Tau pathology in the early stage of the disease.

在阿尔兹海默症（AD）患者大脑中，Tau聚体以一种类似“朊病毒”传播的模式播散，按特定顺序通过神经环路侵犯各个影响学习和记忆功能的脑区。而内吞途径可能参与了Tau聚体在神经元之间的传播，其具体机制不明。近年来的GWAS研究发现CD2相关蛋白（CD2AP）基因上游位点是晚发型AD易感性的重要的遗传因素。CD2AP在细胞内吞、细胞内转运、细胞骨架调节等方面具有重要作用；在果蝇中下调人CD2AP的同源基因后会引起突变形式Tau蛋白的神经毒性增加。本研究将在人脑中研究CD2AP是否与Tau聚体在AD进程中接连侵犯的脑区存在共定位，然后在Tau聚集 的HEK293细胞与表达TauP301L的大鼠海马神经元共培养及 rTgTauEC小鼠中进行离体和在体研究，探讨CD2AP是否通过影响网格蛋白介导的内吞途径参与AD病程中Tau在神经元间的转运，可能为在疾病早期打破Tau病理的播散提供潜在的治疗靶点。

在阿尔兹海默症（AD）患者大脑中，Tau聚体以一种类似“朊病毒”传播的模式播散。而内吞途径可能参与了Tau聚体在神经元之间的传播，但其机制不明。近年来的GWAS研究发现CD2相关蛋白（CD2AP）基因上游位点是晚发型AD易感性的重要的遗传因素。我们在覆盖AD全进程的15例死亡后人脑中发现，CD2AP在AD临床前期的内嗅皮层中表达下降，到AD晚期又再次升高。但CD2AP与过度磷酸化的Tau在内嗅皮层的表达并未发现相关性。我们在稳定表达Tau聚体的HEK293细胞与表达TauP301L的大鼠海马神经元共培养的细胞模型中发现，上调和下调CD2AP都会导致聚集的 HA-TauP301L 相对增多；在微神经环路中上调 CD2AP 也引起聚集的 HA-TauP301L 相对增多，提示CD2AP影响Tau 聚体在神经元间的转运。机制方面，尽管既往研究提示CD2AP可通过FxDxF 结构域与 AP2 适配器结合从而参与网格蛋白的调节，但我们在SY5Y细胞系中发现上调CD2AP并不影响网格蛋白介导的内吞途径经典标记物转铁蛋白的内吞，推测CD2AP可能参与了内吞的后面过程，可能是参与Tau聚体在细胞内的运输。本研究结果提示CD2AP参与AD病程中Tau在神经元间的转运，可能为在疾病早期打破Tau病理的播散提供潜在的治疗靶点。

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