Gamma-secretase: structure, function, and modulation for Alzheimer's disease.
ABSTRACT Gamma-secretase proteolyzes a variety of membrane-associated fragments derived from type I integral membrane proteins, including the amyloid beta-protein precursor, involved in Alzheimer's disease, and the Notch receptor, critical for cellular differentiation. This protease is composed of four integral membrane proteins: presenilin, nicastrin, Aph-1 and Pen-2. Assembly of these four components leads to presenilin autoproteolysis into two subunits, each of which contributes one aspartate to the active site of an aspartyl protease. The protease contains an initial docking site for substrate, where it binds prior to passing between the two presenilin subunits to the internal water-containing active site. The extracellular region of nicastrin also interacts with the N-terminus of the substrate as an essential step in substrate recognition and processing. Modulation of APP processing without interfering with Notch signaling is an important therapeutic goal, and allosteric sites on the protease allow such selective modulation. A better structural and mechanistic understanding of gamma-secretase should ultimately allow structure-based design of more potent and selective modulators.
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- "These findings suggest a pathway for γ-secretase substrate from docking site to active site: upon binding to the outer surface of presenilin at the NTF/CTF interface, the substrate can pass between these two presenilin subunits to access the internal active site. γ-Secretase has in many ways been an attractive target for Alzheimer therapeutics (Wolfe, 2008), with one inhibitor (compound 3, Figure 2) now in advanced clinical trials (Siemers et al., 2007). However, interference with Notch processing and signalling may lead to toxicities that preclude clinical use of such inhibitors. "
ABSTRACT: Presenilin is the catalytic component of gamma-secretase, a complex aspartyl protease and a founding member of intramembrane-cleaving proteases. gamma-Secretase is involved in the pathogenesis of Alzheimer's disease and a top target for therapeutic intervention. However, the protease complex processes a variety of transmembrane substrates, including the Notch receptor, raising concerns about toxicity. Nevertheless, gamma-secretase inhibitors and modulators have been identified that allow Notch processing and signaling to continue, and promising compounds are entering clinical trials. Molecular and biochemical studies offer a model for how this protease hydrolyzes transmembrane domains in the confines of the lipid bilayer. Progress has also been made toward structure elucidation of presenilin and the gamma-secretase complex by electron microscopy as well as by studying cysteine-mutant presenilins. The signal peptide peptidase (SPP) family of proteases are distantly related to presenilins. However, the SPPs work as single polypeptides without the need for cofactors and otherwise appear to be simple model systems for presenilin in the gamma-secretase complex. SPP biology, structure, and inhibition will also be discussed.Biological Chemistry 08/2010; 391(8):839-47. DOI:10.1515/BC.2010.086 · 2.69 Impact Factor
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- "This is in sharp contrast to mice with deficiencies in components of the γ-secretase complex . For example, mice deficient in presenilin-1 , nicastrin , or APH-1  all exhibit serious developmental defects and die at early embryonic stages because γ-secretase is required to process Notch, a signaling molecule that controls cell fate in embryonic and adult myelopoiesis   . Therefore, compared with γ-secretase, BACE1 is viewed as a better drug target whose inhibition should cause less serious biological dysfunction. "
ABSTRACT: Since BACE1 was reported as the beta-secretase in Alzheimer's disease (AD) over ten years ago, encouraging progress has been made toward understanding the cellular functions of BACE1. Genetic studies have further confirmed that BACE1 is essential for processing amyloid precursor protein (APP) at the beta-secretase site. Only after this cleavage can the membrane-bound APP C-terminal fragment be subsequently cleaved by gamma-secretase to release so-called AD-causing Abeta peptides. Hence, in the past decade, a wide variety of BACE1 inhibitors have been developed for AD therapy. This review will summarize the major historical events during the evolution of BACE1 inhibitors designed through different strategies of drug discovery. Although BACE1 inhibitors are expected to be safe in general, careful titration of drug dosage to avoid undesirable side effects in BACE1-directed AD therapy is also emphasized.International journal of clinical and experimental pathology 01/2010; 3(6):618-28. · 1.78 Impact Factor
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ABSTRACT: Genetic, biochemical and pathological evidence support that self-assembly of amyloid-beta (Aβ) peptide into toxic aggregates is implicated as the cause of Alzheimer’s disease. An attractive therapeutic strategy for the treatment of AD is to prevent or interfere with Aβ aggregation. A systematic investigation of the effects of proline-, glycine-, arginine- and lysine- containing peptides (PGKLVYA, KKLVFFARRRRA and KKLVFFA) on the beta-amyloid aggregation was made using FTIR, circular dichroism, ANS binding, ThT binding and TEM analysis. These peptides are based on the central hydrophobic region of Aβ (residues 16–20), which is believed to be crucial in Aβ self-association. There is increasing evidence to suggest that protein aggregation, including amyloid fibril formation results from the strong self-association tendency of the partially folded intermediates. Addition of PGKLVYA and KKLVFFARRRRA resulted in increase in ANS fluorescence intensity, suggesting enhanced exposure of hydrophobic surface area. As observed by ThT and TEM analysis PGKLVYA and KKLVFFARRRRA promote non-fibrillar ensembles, while peptide KKLVFFA accelerated the fibrillization of Aβ peptide by stabilizing intermolecular interactions. Circular dichroism and FTIR data showed that PGKLVYA and KKLVFFARRRRA effectively prevented amyloid-beta (Aβ) peptide adopting the beta-sheet secondary structure correlated with fibrillogenesis. This result indicates that PGKLVYA and KKLVFFARRRRA might have triggered another mechanism of Aβ assembly.International Journal of Peptide Research and Therapeutics 03/2011; 18(1). DOI:10.1007/s10989-011-9278-4 · 0.83 Impact Factor