Aggregation and catabolism of disease-associated intra-Aβ mutations:: reduced proteolysis of AβA21G by neprilysin
Aggregation and catabolism of disease-associated intra-Aβ mutations:: reduced proteolysis of AβA21G by neprilysin
复制标题
DOI：
10.1016/j.nbd.2008.06.001
复制
发表时间：
2008-09-01
影响因子：
6.1
通讯作者：
Walsh, Dominic M.
中科院分区：
文献类型：
--
作者：
Betts, Vicki;Leissring, Malcolm A.;Walsh, Dominic M.
APP基因的淀粉样β蛋白(Aβ)序列中的五个点突变与类似或相同于阿尔茨海默病的遗传性疾病有关，并编码：A21G(佛兰德人)、E22G(北极人)、E22K(意大利人)、E22Q(荷兰人)和D23N(爱荷华州)氨基酸替换。尽管存在大量关于这些突变对Aβ产生的影响的数据，但Aβ内突变是否会改变降解及其与其聚集状态的关系仍不清楚。在这里，我们报告了E22G、E22Q和D23N替换显著增加了纤维形核和伸长，而E22K替换只表现出更高的伸长速率，而A21G替换实际上导致了伸长率的下降。这些在聚集方面的实质性差异，加上我们观察到聚集的野生型Aβ(1-0)比单体野生型Aβ(1-40)的降解要好得多，促使我们评估与疾病相关的Aβ内突变是否改变了蛋白质分解，而不是独立于它们对聚集的影响。奈普利辛(NEP)、胰岛素降解酶(IDE)和纤溶酶在Aβ分解代谢中起主要作用，因此我们比较了这些酶对野生型和突变型单体Aβ多肽的降解能力。蛋白质降解实验表明，IDE和纤溶酶对所有单体多肽的降解都是相似的，但NEP对佛兰德多肽的降解速度明显慢于野生型Aβ或任何其他突变多肽。这一发现表明，对NEP介导的蛋白分解的抗性可能是与A21G突变相关的致病性的基础。(C)2008 Elsevier Inc.保留所有权利。
Five point mutations within the amyloid beta-protein (A beta) sequence of the APP gene are associated with hereditary diseases which are similar or identical to Alzheimer's disease and encode: the A21G (Flemish), E22G (Arctic), E22K (Italian), E22Q (Dutch) and the D23N (Iowa) amino acid substitutions. Although a substantial body of data exists on the effects of these mutations on A beta production, whether or not intra-A beta mutations alter degradation and how this relates to their aggregation state remain unclear. Here we report that the E22G, E22Q and the D23N substitutions significantly increase fibril nucleation and extension, whereas the E22K substitution exhibits only an increased rate of extension and the A21G substitution actually causes a decrease in the extension rate.These substantial differences in aggregation together with our observation that aggregated wild type A beta(1-0) was much less well degraded than monomeric wild type A beta(1-40), prompted us to assess whether or not disease-associated intra-A beta mutations alter proteolysis independent of their effects on aggregation. Neprilysin (NEP), insulin degrading enzyme (IDE) and plasmin play a major role in A beta catabolism, therefore we compared the ability of these enzymes to degrade wild type and mutant monomeric A beta peptides. Experiments investigating proteolysis revealed that all monomeric peptides are degraded similarly by IDE and plasmin, but that the Flemish peptide was degraded significantly more slowly by NEP than wild type A beta or any of the other mutant peptides. This finding suggests that resistance to NEP-mediated proteolysis may underlie the pathogenicity associated with the A21G mutation. (C) 2008 Elsevier Inc. All rights reserved.