Storey E, Spurck T, Pickett-Heaps J, Beyreuther K, Masters C L
Department of Pathology, University of Melbourne, Parkville, Victoria, Australia.
Brain Res. 1996 Sep 30;735(1):59-66. doi: 10.1016/0006-8993(96)00609-9.
We have previously found that the amyloid precursor protein (APP) of Alzheimer's disease is present on the surface of rat cortical neurons in culture, in a segmental pattern which first becomes evident after 24 hours and is fully developed by five days. As APP has previously been reported to have a short half-life in neuronal cell lines, and has been shown to contain binding sites for various extracellular matrix components within its extracellular domain, we hypothesized that APP would be associated with portions of neurites undergoing rapid structural change, such as growth cones. To test this hypothesis, we observed selected neurons by video time-lapse differential interference microscopy on 24-hour-old primary rat neuronal cultures for up to 45 minutes, followed by fixation and immunocytochemistry to ascertain surface APP distribution on those same neurons. In contrast to our predictions, surface APP was not found on active portions of neurites, even if the activity produced no net translational movement. This result indicates that surface APP is actually associated with stable portions of neurites, a conclusion that tallies with other recent results showing that neuronal surface APP has a longer half-life than general cellular APP, and is associated with markers of adhesion patches, which themselves are relatively stable structures.
我们之前发现，阿尔茨海默病的淀粉样前体蛋白（APP）存在于培养的大鼠皮质神经元表面，呈节段性分布模式，该模式在24小时后首次变得明显，并在五天时完全形成。由于之前有报道称APP在神经元细胞系中的半衰期较短，且已显示其细胞外结构域内含有各种细胞外基质成分的结合位点，我们推测APP会与经历快速结构变化的神经突部分相关，比如生长锥。为了验证这一假设，我们在24小时龄的原代大鼠神经元培养物中，通过视频延时微分干涉显微镜观察选定的神经元长达45分钟，然后进行固定和免疫细胞化学，以确定这些相同神经元表面APP的分布。与我们的预测相反，即使神经突的活动没有产生净平移运动，在神经突的活跃部分也未发现表面APP。这一结果表明，表面APP实际上与神经突的稳定部分相关，这一结论与最近的其他结果一致，这些结果表明神经元表面APP的半衰期比一般细胞APP长，并且与黏附斑的标记物相关，而黏附斑本身就是相对稳定的结构。
