Wang Haizhi, Sang Nianli, Zhang Can, Raghupathi Ramesh, Tanzi Rudolph E, Saunders Aleister
†Department of Biology, College of Art and Sciences, Drexel University, Philadelphia, Pennsylvania 19104, United States.
‡Department of Neurobiology and Anatomy, College of Medicine, Drexel University, Philadelphia, Pennsylvania 19104, United States.
Biochemistry. 2015 May 12;54(18):2806-16. doi: 10.1021/acs.biochem.5b00329. Epub 2015 Apr 28.
Alzheimer's disease (AD) is characterized by the deposition of amyloid β (Aβ), a peptide generated from proteolytic processing of its precursor, amyloid precursor protein (APP). Canonical APP proteolysis occurs via α-, β-, and γ-secretases. APP is also actively degraded by protein degradation systems. By pharmacologically inhibiting protein degradation with ALLN, we observed an accumulation of several novel APP C-terminal fragments (CTFs). The two major novel CTFs migrated around 15 and 25 kDa and can be observed across multiple cell types. The process was independent of cytotoxicity or protein synthesis. We further determine that the accumulation of the novel CTFs is not mediated by proteasome or calpain inhibition, but by cathepsin L inhibition. Moreover, these novel CTFs are not generated by an increased amount of BACE. Here, we name the CTF of 25 kDa as η-CTF (eta-CTF). Our data suggest that under physiological conditions, a subset of APP undergoes alternative processing and the intermediate products, the 15 kDa CTFs, and the η-CTFs aret rapidly degraded and/or processed via the protein degradation machinery, specifically, cathepsin L.
阿尔茨海默病（AD）的特征是淀粉样蛋白β（Aβ）沉积，Aβ是由其前体淀粉样前体蛋白（APP）经蛋白水解加工产生的一种肽。经典的APP蛋白水解通过α-、β-和γ-分泌酶进行。APP也通过蛋白质降解系统被积极降解。通过用ALLN药理学抑制蛋白质降解，我们观察到几种新型APP C末端片段（CTF）的积累。两种主要的新型CTF在15 kDa和25 kDa左右迁移，并且在多种细胞类型中都能观察到。该过程与细胞毒性或蛋白质合成无关。我们进一步确定，新型CTF的积累不是由蛋白酶体或钙蛋白酶抑制介导的，而是由组织蛋白酶L抑制介导的。此外，这些新型CTF不是由增加的β-分泌酶1（BACE）量产生的。在这里，我们将25 kDa的CTF命名为η-CTF（eta-CTF）。我们的数据表明，在生理条件下，一部分APP经历了替代加工，中间产物、15 kDa的CTF和η-CTF通过蛋白质降解机制，特别是组织蛋白酶L被快速降解和/或加工。
