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From the Cover: Activation and intrinsic -secretase activity of presenilin 1

Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 12/2010; 107(50):21435-21440. DOI: 10.1073/pnas.1013246107

ABSTRACT A complex composed of presenilin (PS), nicastrin, PEN-2, and APH-1 is absolutely required for γ-secretase activity in vivo. Evidence has emerged to suggest a role for PS as the catalytic subunit of γ-secretase, but it has not been established that PS is catalytically active in the absence of associated subunits. We now report that bacterially synthesized, recombinant PS (rPS) reconstituted into liposomes exhibits γ-secretase activity. Moreover, an rPS mutant that lacks a catalytic aspartate residue neither exhibits reconstituted γ-secretase activity nor interacts with a transition-state γ-secretase inhibitor. Importantly, we demonstrate that rPS harboring mutations that cause early onset familial Alzheimer's disease (FAD) lead to elevations in the ratio of Aβ42 to Aβ40 peptides produced from a wild-type APP substrate and that rPS enhances the Aβ42/Aβ40 peptide ratio from FAD-linked mutant APP substrates, findings that are entirely consistent with the results obtained in in vivo settings. Thus, γ-secretase cleavage specificity is an inherent property of the polypeptide. Finally, we demonstrate that PEN2 is sufficient to promote the endoproteolysis of PS1 to generate the active form of γ-secretase. Thus, we conclusively establish that activated PS is catalytically competent and the bimolecular interaction of PS1 and PEN2 can convert the PS1 zymogen to an active protease.

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Available from: Malcolm Lane Gilchrist, Sep 03, 2015
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    • "Mutations of g-secretase subunits have been associated with Alzheimer's disease (Levy-Lahad et al., 1995; Sherrington et al., 1995), acne inversa (Wang et al., 2010), and acute myeloid leukemia (Klinakis et al., 2011). Although cellular reconstitution studies suggest that all four integral membrane proteins are required for g-secretase activity (Edbauer et al., 2003), multiple reports indicate that only a fraction of the steady-state complexes existing in mammalian cells are catalytically active and that g-secretase activity is not always correlated with the levels of presenilin (Beher et al., 2003; Gu et al., 2004; Lai et al., 2003; Placanica et al., 2009), the catalytic subunit of g-secretase (Ahn et al., 2010). Thus, the function of the inactive complexes remains poorly understood. "
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    ABSTRACT: γ-Secretase is composed of four proteins that are obligatory for protease activity: presenilin, nicastrin, Aph1, and Pen-2. Despite the progress toward understanding the function of these individual subunits, there is no information available pertaining to the modulation of γ-secretase in response to environmental changes in cells. Here, we show that hypoxia upregulates γ-secretase activity through a direct interaction with Hif-1α, revealing an unconventional function for Hif-1α as an enzyme subunit, which is distinct from its canonical role as a transcription factor. Moreover, hypoxia-induced cell invasion and metastasis are alleviated by either γ-secretase inhibitors or a dominant-negative Notch coactivator, indicating that γ-secretase/Notch signaling plays an essential role in controlling these cellular processes. The present study reveals a mechanism in which γ-secretase can achieve temporal control through conditional interactions with regulatory proteins, such as Hif-1α, under select physiological and pathological conditions.
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    • "Nicastrin may also act as the γ-secretase receptor [144]. The seven-transmembrane APH-1 interacts with nicastrin to form a stable intermediate in an early assembly stage of the γ-secretase complex [140,141], whereas the two-pass transmembrane component PEN2 regulates PS endoproteolysis [145,146]. Each of these four components is necessary for γ-secretase activity and deficiency in any of these factors dramatically impairs the enzymatic activity. "
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    ABSTRACT: The beta-amyloid (Abeta) peptide has been postulated to be a key determinant in the pathogenesis of Alzheimer's disease (AD). Abeta is produced through sequential cleavage of the beta-amyloid precursor protein (APP) by beta- and gamma-secretases. APP and relevant secretases are transmembrane proteins and traffic through the secretory pathway in a highly regulated fashion. Perturbation of their intracellular trafficking may affect dynamic interactions among these proteins, thus altering Abeta generation and accelerating disease pathogenesis. Herein, we review recent progress elucidating the regulation of intracellular trafficking of these essential protein components in AD.
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    • "A number of studies have suggested that ncstn forms with Aph-1, an initial scaffolding precomplex, upon which the active c-secretase complex is formed (Yu et al., 2000), and ncstn has also been implicated in PS1 regulation and stability (Edbauer et al., 2002). Although it has been demonstrated in different studies that ncstn is essential in APP processing and Ab production (Kimberly et al., 2003; Li et al., 2003a), recent reports have supported that ncstn might be dispensable for Ab production (Futai et al., 2009; Ahn et al., 2010; Zhao et al., 2010). "
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    ABSTRACT: Production of Aβ by γ-secretase is a key event in Alzheimer's disease (AD). The γ-secretase complex consists of Presenilin (PS) 1 or 2, Nicastrin (ncstn), Pen-2 and Aph-1 and cleaves type I transmembrane proteins, including the amyloid precursor protein (APP). Although ncstn is widely accepted as an essential component of the complex required for γ-secretase activity, recent in vitro studies have suggested that ncstn is dispensable for APP processing and Aβ production. The focus of this study was to answer this controversy and evaluate the role of ncstn in Aβ generation and the development of the amyloid-related phenotype in the mouse brain. To eliminate ncstn expression in the mouse brain we used a ncstn conditional knock-out mouse that we mated with an established AD transgenic mouse model (5XFAD) and a neuronal Cre expressing transgenic mouse (CamKIIα-iCre), to generate AD mice (5XFAD/CamKIIα-iCre/ncstn(f/f) mice) where ncstn was conditionally inactivated in the brain. 5XFAD/CamKIIα-iCre/ncstn(f/f) mice at 10 week of age developed a neurodegenerative phenotype with a significant reduction in Aβ production and formation of Aβ aggregates, and absence of amyloid plaques. Inactivation of nctsn resulted in substantial accumulation of APP-CTFs and altered PS1 expression. These results reveal a key role for ncstn in modulating Aβ production and amyloid plaque formation in vivo and suggest ncstn as a target in AD therapeutics. This article is protected by copyright. All rights reserved.
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