Background Synaptic degeneration and accumulation of amyloid β-peptides (Aβ) are hallmarks of the Alzheimer diseased brain. Aβ is synaptotoxic and produced by sequential cleavage of the amyloid precursor protein (APP) by the β-secretase BACE1 and by γ-secretase. If APP is instead cleaved by the α-secretase ADAM10, Aβ will not be generated. Although BACE1 is considered to be a presynaptic protein and ADAM10 has been reported to mainly localize to the postsynaptic density, we have previously shown that both ADAM10 and BACE1 are highly enriched in synaptic vesicles of rat brain and mouse primary hippocampal neurons. Results Here, using brightfield proximity ligation assay, we expanded our previous result in primary neurons and investigated the in situ synaptic localization of ADAM10 and BACE1 in rat and human adult brain using both pre- and postsynaptic markers. We found that ADAM10 and BACE1 were in close proximity with both the presynaptic marker synaptophysin and the postsynaptic marker PSD-95. The substrate APP was also detected both pre- and postsynaptically. Subcellular fractionation confirmed that ADAM10 and BACE1 are enriched to a similar degree in synaptic vesicles and as well as in the postsynaptic density. Conclusions We show that the α-secretase ADAM10 and the β-secretase BACE1 are located in both the pre- and postsynaptic compartments in intact brain sections. These findings increase our understanding of the regulation of APP processing, thereby facilitating development of more specific treatment strategies.

中文翻译：

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邻近连接试验揭示了大鼠和成人大脑中 APP 加工酶 ADAM10 和 BACE1 的突触前和突触后定位

背景 突触变性和淀粉样蛋白 β-肽 (Aβ) 的积累是阿尔茨海默病大脑的标志。Aβ 具有突触毒性，由 β-分泌酶 BACE1 和 γ-分泌酶连续裂解淀粉样前体蛋白 (APP) 产生。如果 APP 被 α-分泌酶 ADAM10 切割，则不会生成 Aβ。尽管 BACE1 被认为是一种突触前蛋白，据报道 ADAM10 主要定位于突触后密度，但我们之前已经表明 ADAM10 和 BACE1 在大鼠脑和小鼠原代海马神经元的突触囊泡中高度富集。结果在这里，使用明场邻近连接测定，我们扩展了我们之前在原代神经元中的结果，并使用突触前和突触后标记研究了 ADAM10 和 BACE1 在大鼠和成人大脑中的原位突触定位。我们发现 ADAM10 和 BACE1 与突触前标记突触素和突触后标记 PSD-95 都非常接近。也在突触前和突触后检测到底物 APP。亚细胞分离证实 ADAM10 和 BACE1 在突触小泡和突触后密度中的富集程度相似。结论我们表明α-分泌酶ADAM10 和β-分泌酶BACE1 位于完整脑切片的突触前和突触后隔室中。这些发现增加了我们对 APP 处理调控的理解，