Eckman E A, Reed D K, Eckman C B
Mayo Clinic Jacksonville, 4500 San Pablo Road, Jacksonville, FL 32224, USA.
J Biol Chem. 2001 Jul 6;276(27):24540-8. doi: 10.1074/jbc.M007579200. Epub 2001 May 3.
Deposition of beta-amyloid (Abeta) peptides in the brain is an early and invariant feature of all forms of Alzheimer's disease. As with any secreted protein, the extracellular concentration of Abeta is determined not only by its production but also by its catabolism. A major focus of Alzheimer's research has been the elucidation of the mechanisms responsible for the generation of Abeta. Much less, however, is known about the mechanisms responsible for Abeta removal in the brain. In this report, we describe the identification of endothelin-converting enzyme-1 (ECE-1) as a novel Abeta-degrading enzyme. We show that treatment of endogenous ECE-expressing cell lines with the metalloprotease inhibitor phosphoramidon causes a 2-3-fold elevation in extracellular Abeta concentration that appears to be due to inhibition of intracellular Abeta degradation. Furthermore, we show that overexpression of ECE-1 in Chinese hamster ovary cells, which lack endogenous ECE activity, reduces extracellular Abeta concentration by up to 90% and that this effect is completely reversed by treatment of the cells with phosphoramidon. Finally, we show that recombinant soluble ECE-1 is capable of hydrolyzing synthetic Abeta40 and Abeta42 in vitro at multiple sites.
β-淀粉样蛋白（Aβ）在大脑中的沉积是所有形式阿尔茨海默病的早期且恒定的特征。与任何分泌蛋白一样，Aβ的细胞外浓度不仅取决于其产生，还取决于其分解代谢。阿尔茨海默病研究的一个主要重点是阐明负责Aβ生成的机制。然而，对于大脑中负责Aβ清除的机制了解得要少得多。在本报告中，我们描述了内皮素转化酶-1（ECE-1）作为一种新型Aβ降解酶的鉴定。我们发现，用金属蛋白酶抑制剂磷酰胺处理内源性表达ECE的细胞系会导致细胞外Aβ浓度升高2至3倍，这似乎是由于细胞内Aβ降解受到抑制。此外，我们表明，在中国仓鼠卵巢细胞中过表达ECE-1（这些细胞缺乏内源性ECE活性）可使细胞外Aβ浓度降低多达90%，并且用磷酰胺处理细胞可完全逆转这种效应。最后，我们表明重组可溶性ECE-1能够在体外多个位点水解合成的Aβ40和Aβ42。
