APOLIPOPROTEINS AND A-BETA CATABOLISM

关于Abeta以其可溶性、低聚物和纤维状形式的催化作用知之甚少。有限的已发表工作和我们自己在实验室动物中的初步数据表明，当全身注射到小鼠中时，Abeta肽在循环中具有短的半衰期，肝脏是主要的分解代谢器官，肝细胞是参与摄取和降解的细胞。细胞表面的结合和剂量依赖性内化表明受体介导的机制。此外，在apoE转基因动物中，Abeta catenase似乎受到转基因表达的apoE同种型的不同影响。 无论脑细胞中是否发生类似的机制，这些发现都引发了各种机制问题，这些问题是本提案的重点。大脑中是否存在受体介导的Abeta摄取？它依赖于肽的结构吗？是否仅限于特定的细胞类型？这种机制与年龄有关吗？载脂蛋白在Abeta的清除和催化中的作用是什么？我们假设，构象转变的Abeta（单体-寡聚体-纤维状）极大地影响其catalysts在脑细胞内，导致在Abeta的积累和伴随形成的淀粉样蛋白沉积物中看到的AD。我们建议（目的1）研究野生型小鼠、人apoES和apoE 4的转基因小鼠、apoE和apoJ的科斯、LRP-1的诱导型科斯以及人apoE和apoJ的转基因小鼠脑中的体内Abeta催化剂。 具有明确的淀粉样病变的转基因动物（即APPsw）使用单体/二聚体、寡聚体和纤维状Abeta物质结合酪胺-纤维二糖细胞捕获技术;和（目的2）使用组织培养技术剖析脑细胞中A β单体/二聚体、寡聚体和原纤维的分解代谢机制，以评估A β表面结合，摄取，和降解以及参与A β-细胞相互作用的推定受体的身份。

Very little is known about the catabolism of Abeta in its soluble, oligomeric and fibrillar forms. Limited published work and our own preliminary data in laboratory animals indicate that Abeta peptides, when systemically injected in mice, have a short half-life in the circulation, being the liver the main catabolic organ and the hepatocytes the cells involved in the uptake and degradation. Binding on the cell surface and dose-dependent internalization suggest a receptor-mediated mechanism. In addition, in apoE transgenic animals, Abeta catabolism seems to be differentially influenced by the apoE isoform expressed by the transgenesis. Whether or not similar mechanisms take place in brain cells, these findings prompted various mechanistic questions that are the focus in this proposal. Is there a receptor-mediated Abeta uptake in the brain? Is it dependent on the peptide's structure? Is it restricted to a particular cell type? Is this mechanism age-related? Which is the role of apolipoproteins in the clearance and catabolism of Abeta? We hypothesize that conformational transitions of Abeta (monomeric-oligomeric-fibrillar) greatly affect their catabolism within brain cells, resulting in Abeta accumulation and the concomitant formation of the amyloid deposits seen in AD. We propose to (aim 1) study Abeta catabolism in vivo in the brain of wild-type mice, transgenics for human apoES and apoE4, KOs for apoE and apoJ, inducible KOs for LRP-1, as well as in transgenic animals with well established amyloid lesions (i.e. APPsw) using monomeric/dimeric, oligomeric and fibrillar Abeta species in conjunction with the tyramine-cellobiose cellular trapping technique; and (aim 2) dissect the catabolic mechanism of Abeta monomers/dimers, oligomers and fibrils in brain cells using tissue culture techniques to assess the mode of Abeta surface binding, uptake, and degradation as well as the identity of the putative receptor(s) involved in the Abeta - cell interaction.