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: 9.67). 12/2010; 107(50):21435-21440. DOI: 10.1073/pnas.1013246107


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
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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.
    Full-text · Article · Aug 2014 · Cell Reports
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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.
    Full-text · Article · Jan 2014 · Molecular Neurodegeneration
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    • "The following evidence supports that Pen-2 is indispensable for endoproteolysis of PS: first, knock-down of Pen-2 by RNAi resulted in a decrease of PS1- NTF/CTF and a stabilization of the PS1 holoprotein in the Nct- Aph-1 complex, while transient overexpression of Pen-2 in Pen-2 deficient cells led to the recovery of PS fragments (Takasugi et al., 2003). Second, coincorporation of recombinant PS1 and Pen-2 in liposomes showed Pen-2 to be necessary and sufficient for endoproteolysis of PS1 (Ahn et al., 2010). Pen-2 is also required for γ-secretase activity: Pen-2 knockdown in mammalian cells resulted not only in an accumulation of the PS1 holoprotein, but also in a drastic decrease in γ-secretase activity (Takasugi et al., 2003). "
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    ABSTRACT: γ-Secretase is a four subunit, 19-pass transmembrane enzyme that cleaves amyloid precursor protein (APP), catalyzing the formation of amyloid beta (Aβ) peptides that form amyloid plaques, which contribute to Alzheimer's disease (AD) pathogenesis. γ-Secretase also cleaves Notch, among many other type I transmembrane substrates. Despite its seemingly promiscuous enzymatic capacity, γ-secretase activity is tightly regulated. This regulation is a function of many cellular entities, including but not limited to the essential γ-secretase subunits, nonessential (modulatory) subunits, and γ-secretase substrates. Regulation is also accomplished by an array of cellular events, such as presenilin (active subunit of γ-secretase) endoproteolysis and hypoxia. In this review we discuss how γ-secretase is regulated with the hope that an advanced understanding of these mechanisms will aid in the development of effective therapeutics for γ-secretase-associated diseases like AD and Notch-addicted cancer.
    Full-text · Article · Jan 2014 · Frontiers in Aging Neuroscience
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