Sharples Robyn A, Vella Laura J, Nisbet Rebecca M, Naylor Ryan, Perez Keyla, Barnham Kevin J, Masters Colin L, Hill Andrew F
Department of Biochemistry and Molecular Biology, The University of Melbourne, Parkville Victoria 3010, Australia.
FASEB J. 2008 May;22(5):1469-78. doi: 10.1096/fj.07-9357com. Epub 2008 Jan 2.
Alzheimer's disease (AD) is the most common form of dementia and is associated with the deposition of the 39- to 43-amino acid beta-amyloid peptide (Abeta) in the brain. C-terminal fragments (CTFs) of amyloid precursor protein (APP) can accumulate in endosomally derived multivesicular bodies (MVBs). These intracellular structures contain intraluminal vesicles that are released from the cell as exosomes when the MVB fuses with the plasma membrane. Here we have investigated the role of exosomes in the processing of APP and show that these vesicles contain APP-CTFs, as well as Abeta. In addition, inhibition of gamma-secretase results in a significant increase in the amount of alpha- and beta-secretase cleavage, further increasing the amount of APP-CTFs contained within these exosomes. We identify several key members of the secretase family of proteases (BACE, PS1, PS2, and ADAM10) to be localized in exosomes, suggesting they may be a previously unidentified site of APP cleavage. These results provide further evidence for a novel pathway in which APP fragments are released from cells and have implications for the analysis of APP processing and diagnostics for Alzheimer's disease.
阿尔茨海默病（AD）是最常见的痴呆形式，与大脑中39至43个氨基酸的β-淀粉样肽（Aβ）沉积有关。淀粉样前体蛋白（APP）的C末端片段（CTF）可在内体来源的多囊泡体（MVB）中积累。这些细胞内结构含有腔内囊泡，当MVB与质膜融合时，这些腔内囊泡作为外泌体从细胞中释放出来。在此，我们研究了外泌体在APP加工过程中的作用，并表明这些囊泡含有APP-CTF以及Aβ。此外，γ-分泌酶的抑制导致α-和β-分泌酶切割量显著增加，进一步增加了这些外泌体中所含APP-CTF的量。我们确定了蛋白酶分泌酶家族的几个关键成员（BACE、PS1、PS2和ADAM10）定位于外泌体中，表明它们可能是APP切割的一个先前未被识别的位点。这些结果为APP片段从细胞中释放的新途径提供了进一步证据，并对APP加工分析和阿尔茨海默病诊断具有启示意义。
