Lleó Alberto, Waldron Elaine, von Arnim Christine A F, Herl Lauren, Tangredi Michele M, Peltan Ithan D, Strickland Dudley K, Koo Edward H, Hyman Bradley T, Pietrzik Claus U, Berezovska Oksana
Alzheimer Research Unit, Massachusetts Institute for Neurodegenerative Disorders, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA.
J Biol Chem. 2005 Jul 22;280(29):27303-9. doi: 10.1074/jbc.M413969200. Epub 2005 May 25.
Presenilin 1 (PS1) is a critical component of the gamma-secretase complex, which is involved in the cleavage of several substrates including the amyloid precursor protein (APP) and the Notch receptor. Recently, the low density receptor-related protein (LRP) has been shown to be cleaved by a gamma-secretase-like activity. We postulated that LRP may interact with PS1 and tested its role as a competitive substrate for gamma-secretase. In this report we show that LRP colocalizes and interacts with endogenous PS1 using coimmunoprecipitation and fluorescence lifetime imaging microscopy. In addition, we found that gamma-secretase active site inhibitors do not disrupt the interaction between LRP and PS1, suggesting that the substrate associates with a gamma-secretase docking site located in close proximity to PS1. This is analogous to APP-gamma-secretase interactions. Finally, we show that LRP competes with APP for gamma-secretase activity. Overexpression of a truncated LRP construct consisting of the C terminus, the transmembrane domain, and a short extracellular portion leads to a reduction in the levels of the Abeta40, Abeta42, and p3 peptides without changing the total level of APP expression. In addition, transfection with the beta-chain of LRP causes an increase in uncleaved APP C-terminal fragments and a concomitant decrease in the signaling effects of the APP intracellular domain. In conclusion, LRP is a PS1 interactor and can compete with APP for gamma-secretase enzymatic activity.
早老素1（PS1）是γ-分泌酶复合物的关键组成部分，该复合物参与包括淀粉样前体蛋白（APP）和Notch受体在内的多种底物的切割。最近，低密度受体相关蛋白（LRP）已被证明可被一种类似γ-分泌酶的活性切割。我们推测LRP可能与PS1相互作用，并测试了其作为γ-分泌酶竞争性底物的作用。在本报告中，我们使用免疫共沉淀和荧光寿命成像显微镜表明LRP与内源性PS1共定位并相互作用。此外，我们发现γ-分泌酶活性位点抑制剂不会破坏LRP与PS1之间的相互作用，这表明该底物与位于PS1附近的γ-分泌酶对接位点相关联。这类似于APP与γ-分泌酶的相互作用。最后，我们表明LRP与APP竞争γ-分泌酶活性。由C末端、跨膜结构域和短细胞外部分组成的截短LRP构建体的过表达导致Aβ40、Aβ42和p3肽水平降低，而不改变APP表达的总水平。此外，用LRP的β链转染会导致未切割的APP C末端片段增加，并伴随APP细胞内结构域信号传导效应的降低。总之，LRP是一种PS1相互作用蛋白，可与APP竞争γ-分泌酶的酶活性。
