von Arnim Christine A F, von Einem Bjoern, Weber Petra, Wagner Michael, Schwanzar Daniel, Spoelgen Robert, Strauss Wolfgang L S, Schneckenburger Herbert
Deparment of Neurology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
Biochem Biophys Res Commun. 2008 May 30;370(2):207-12. doi: 10.1016/j.bbrc.2008.03.047. Epub 2008 Mar 27.
Cleavage of APP by BACE is the first proteolytic step in the production of Amyloid beta (Abeta, which accumulates in senile plaques in Alzheimer's disease. BACE-cleavage of APP is thought to happen in endosomes. However, there are controversial data whether APP and BACE can already interact on the cell surface dependent on the cholesterol level. To examine whether APP and BACE come into close proximity on the cell surface in living cells, we employed a novel technique by combining time-resolved Förster resonance energy transfer (FRET) measurements with total internal reflection microscopy (TIRET microscopy). Our data indicate that BACE and APP come into close proximity within the cell, but probably not on the cell surface. To analyze the impact of alterations in cholesterol level upon BACE-cleavage, we measured sAPP secretion. Alteration of APP processing and BACE proximity by cholesterol might be explained by alterations in cell membrane fluidity.
β-分泌酶（BACE）切割淀粉样前体蛋白（APP）是生成β淀粉样蛋白（Aβ，其在阿尔茨海默病的老年斑中积累）的首个蛋白水解步骤。APP的BACE切割被认为发生在内体中。然而，关于APP和BACE是否能在细胞表面依赖胆固醇水平进行相互作用，存在有争议的数据。为了检测在活细胞中APP和BACE是否在细胞表面紧密靠近，我们采用了一种新技术，即将时间分辨荧光共振能量转移（FRET）测量与全内反射显微镜（TIRET显微镜）相结合。我们的数据表明，BACE和APP在细胞内紧密靠近，但可能不在细胞表面。为了分析胆固醇水平改变对BACE切割的影响，我们测量了可溶性APP（sAPP）的分泌。胆固醇对APP加工和BACE靠近的改变可能是由细胞膜流动性的改变所解释的。
