Placanica Lisa, Tarassishin Leonid, Yang Guangli, Peethumnongsin Erica, Kim Seong-Hun, Zheng Hui, Sisodia Sangram S, Li Yue-Ming
Molecular Pharmacology and Chemistry Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065; Department of Pharmacology, Weill Graduate School of Medical Science of Cornell University, New York, New York 10065.
Molecular Pharmacology and Chemistry Program, Memorial Sloan Kettering Cancer Center, New York, New York 10065.
J Biol Chem. 2009 Jan 30;284(5):2967-2977. doi: 10.1074/jbc.M807269200. Epub 2008 Nov 25.
gamma-Secretase is known to play a pivotal role in the pathogenesis of Alzheimer disease through production of amyloidogenic Abeta42 peptides. Early onset familial Alzheimer disease mutations in presenilin (PS), the catalytic core of gamma-secretase, invariably increase the Abeta42:Abeta40 ratio. However, the mechanism by which these mutations affect gamma-secretase complex formation and cleavage specificity is poorly understood. We show that our in vitro assay system recapitulates the effect of PS1 mutations on the Abeta42:Abeta40 ratio observed in cell and animal models. We have developed a series of small molecule affinity probes that allow us to characterize active gamma-secretase complexes. Furthermore we reveal that the equilibrium of PS1- and PS2-containing active complexes is dynamic and altered by overexpression of Pen2 or PS1 mutants and that formation of PS2 complexes is positively correlated with increased Abeta42:Abeta40 ratios. These data suggest that perturbations to gamma-secretase complex equilibrium can have a profound effect on enzyme activity and that increased PS2 complexes along with mutated PS1 complexes contribute to an increased Abeta42:Abeta40 ratio.
已知γ-分泌酶通过产生淀粉样β-淀粉样蛋白42肽（Aβ42）在阿尔茨海默病的发病机制中起关键作用。早发性家族性阿尔茨海默病中早老素（PS）（γ-分泌酶的催化核心）的突变总是会增加Aβ42与Aβ40的比例。然而，这些突变影响γ-分泌酶复合物形成和切割特异性的机制尚不清楚。我们表明，我们的体外检测系统概括了PS1突变对在细胞和动物模型中观察到的Aβ42与Aβ40比例的影响。我们开发了一系列小分子亲和探针，使我们能够表征活性γ-分泌酶复合物。此外，我们发现含PS1和PS2的活性复合物的平衡是动态的，并且会因Pen2或PS1突变体的过表达而改变，并且PS2复合物的形成与Aβ42与Aβ40比例的增加呈正相关。这些数据表明，γ-分泌酶复合物平衡的扰动可对酶活性产生深远影响，并且增加的PS2复合物以及突变的PS1复合物导致Aβ42与Aβ40比例增加。
