1
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Ulku I, Leung R, Herre F, Walther L, Shobo A, Saftig P, Hancock MA, Liebsch F, Multhaup G. Inhibition of BACE1 affected both its Aβ producing and degrading activities and increased Aβ42 and Aβ40 levels at high-level BACE1 expression. J Biol Chem 2024; 300:107510. [PMID: 38944120 PMCID: PMC11324814 DOI: 10.1016/j.jbc.2024.107510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2024] [Revised: 06/14/2024] [Accepted: 06/20/2024] [Indexed: 07/01/2024] Open
Abstract
The beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) is the predominant β-secretase, cleaving the amyloid precursor protein (APP) via the amyloidogenic pathway. In addition, BACE1 as an amyloid degrading enzyme (ADE), cleaves Aβ to produce the C-terminally truncated non-toxic Aβ fragment Aβ34 which is an indicator of amyloid clearance. Here, we analyzed the effects of BACE1 inhibitors on its opposing enzymatic functions, i.e., amyloidogenic (Aβ producing) and amyloidolytic (Aβ degrading) activities, using cell culture models with varying BACE1/APP ratios. Under high-level BACE1 expression, low-dose inhibition unexpectedly yielded a two-fold increase in Aβ42 and Aβ40 levels. The concomitant decrease in Aβ34 and secreted APPβ levels suggested that the elevated Aβ42 and Aβ40 levels were due to the attenuated Aβ degrading activity of BACE1. Notably, the amyloidolytic activity of BACE1 was impeded at lower BACE1 inhibitor concentrations compared to its amyloidogenic activity, thereby suggesting that the Aβ degrading activity of BACE1 was more sensitive to inhibition than its Aβ producing activity. Under endogenous BACE1 and APP levels, "low-dose" BACE1 inhibition affected both the Aβ producing and degrading activities of BACE1, i.e., significantly increased Aβ42/Aβ40 ratio and decreased Aβ34 levels, respectively. Further, we incubated recombinant BACE1 with synthetic Aβ peptides and found that BACE1 has a higher affinity for Aβ substrates over APP. In summary, our results suggest that stimulating BACE1's ADE activity and halting Aβ production without decreasing Aβ clearance could still be a promising therapeutic approach with new, yet to be developed, BACE1 modulators.
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Affiliation(s)
- Irem Ulku
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada; Integrated Program in Neuroscience, McGill University, Montreal, Quebec, Canada
| | - Rocher Leung
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada
| | - Fritz Herre
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada
| | - Lina Walther
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada
| | - Adeola Shobo
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada
| | - Paul Saftig
- Biochemisches Institut, CAU Kiel, Kiel, Germany
| | - Mark A Hancock
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada
| | - Filip Liebsch
- Department of Chemistry, Institute of Biochemistry, University of Cologne, Cologne, Germany
| | - Gerhard Multhaup
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada; Integrated Program in Neuroscience, McGill University, Montreal, Quebec, Canada.
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2
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Ulku I, Liebsch F, Akerman SC, Schulz JF, Kulic L, Hock C, Pietrzik C, Di Spiezio A, Thinakaran G, Saftig P, Multhaup G. Mechanisms of amyloid-β34 generation indicate a pivotal role for BACE1 in amyloid homeostasis. Sci Rep 2023; 13:2216. [PMID: 36750595 PMCID: PMC9905473 DOI: 10.1038/s41598-023-28846-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Accepted: 01/25/2023] [Indexed: 02/09/2023] Open
Abstract
The beta‑site amyloid precursor protein (APP) cleaving enzyme (BACE1) was discovered due to its "amyloidogenic" activity which contributes to the production of amyloid-beta (Aβ) peptides. However, BACE1 also possesses an "amyloidolytic" activity, whereby it degrades longer Aβ peptides into a non‑toxic Aβ34 intermediate. Here, we examine conditions that shift the equilibrium between BACE1 amyloidogenic and amyloidolytic activities by altering BACE1/APP ratios. In Alzheimer disease brain tissue, we found an association between elevated levels of BACE1 and Aβ34. In mice, the deletion of one BACE1 gene copy reduced BACE1 amyloidolytic activity by ~ 50%. In cells, a stepwise increase of BACE1 but not APP expression promoted amyloidolytic cleavage resulting in dose-dependently increased Aβ34 levels. At the cellular level, a mislocalization of surplus BACE1 caused a reduction in Aβ34 levels. To align the role of γ-secretase in this pathway, we silenced Presenilin (PS) expression and identified PS2-γ-secretase as the main γ-secretase that generates Aβ40 and Aβ42 peptides serving as substrates for BACE1's amyloidolytic cleavage to generate Aβ34.
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Affiliation(s)
- Irem Ulku
- Integrated Program in Neuroscience, McGill University, Montreal, QC, H3G 0B1, Canada
| | - Filip Liebsch
- Integrated Program in Neuroscience, McGill University, Montreal, QC, H3G 0B1, Canada.,Department of Chemistry, Institute of Biochemistry, University of Cologne, 50674, Cologne, Germany
| | - S Can Akerman
- Department of Pharmacology and Therapeutics, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - Jana F Schulz
- Institut Für Chemie Und Biochemie, Freie Universität Berlin, 14195, Berlin, Germany.,Cardiovascular and Metabolic Sciences, Max Delbrück Center for Molecular Medicine in the Helmholtz Association (MDC), 13125, Berlin, Germany
| | - Luka Kulic
- Roche Pharma Research & Early Development, F.Hoffmann-La Roche Ltd., 4070, Basel, Switzerland
| | - Christoph Hock
- Institute for Regenerative Medicine, Un Iversity of Zurich, 8952, Schlieren, Switzerland.,Neurimmune AG, 8952, Schlieren, Switzerland
| | - Claus Pietrzik
- Department Molecular Neurodegeneration, Institute of Pathobiochemistry, University Medical Center of the Johannes Gutenberg-University of Mainz, Duesbergweg 6, 55099, Mainz, Germany
| | | | - Gopal Thinakaran
- Department of Molecular Medicine and Byrd Alzheimer's Institute, University of South Florida, Tampa, FL, 33613, USA
| | - Paul Saftig
- Biochemisches Institut, CAU Kiel, Olshausenstr. 40, 24098, Kiel, Germany
| | - Gerhard Multhaup
- Integrated Program in Neuroscience, McGill University, Montreal, QC, H3G 0B1, Canada. .,Department of Pharmacology and Therapeutics, McGill University, Montreal, QC, H3G 1Y6, Canada.
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3
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Nguyen PH, Derreumaux P. Insights into the Mixture of Aβ24 and Aβ42 Peptides from Atomistic Simulations. J Phys Chem B 2022; 126:10689-10696. [PMID: 36493347 DOI: 10.1021/acs.jpcb.2c07321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Amyloid-β (Aβ) oligomers play a central role in Alzheimer's disease (AD). Plaques of AD patients consist of Aβ40 and Aβ42 peptides and truncated Aβ peptides. The Aβ24 peptide, identified in human AD brains, was found to impair Aβ42 clearance through the brain-blood barrier. The Aβ24 peptide was also shown to reduce Aβ42 aggregation kinetics in pure buffer, but the underlying mechanism is unknown at atomistic level. In this study, we explored the conformational ensemble of the equimolar mixture of Aβ24 and Aβ42 by replica exchange molecular dynamics simulations and compared it to our previous results on the pure Aβ42 dimer. Our simulations demonstrate that the truncation at residue 24 changes the secondary, tertiary, and quaternary structures of the dimer, offering an explanation of the slower aggregation kinetics of the mixture.
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Affiliation(s)
- Phuong H Nguyen
- Université Paris Cité, UPR 9080 CNRS, Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique, Fondation Edmond de Rothschild, 13 rue Pierre et Marie Curie, 75005 Paris, France
| | - Philippe Derreumaux
- Université Paris Cité, UPR 9080 CNRS, Laboratoire de Biochimie Théorique, Institut de Biologie Physico-Chimique, Fondation Edmond de Rothschild, 13 rue Pierre et Marie Curie, 75005 Paris, France.,Institut Universitaire de France (IUF), 75005 Paris, France
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4
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Hanbouch L, Schaack B, Kasri A, Fontaine G, Gkanatsiou E, Brinkmalm G, Camporesi E, Portelius E, Blennow K, Mourier G, Gilles N, Millan MJ, Marquer C, Zetterberg H, Boussicault L, Potier MC. Specific Mutations in the Cholesterol-Binding Site of APP Alter Its Processing and Favor the Production of Shorter, Less Toxic Aβ Peptides. Mol Neurobiol 2022; 59:7056-7073. [PMID: 36076005 PMCID: PMC9525381 DOI: 10.1007/s12035-022-03025-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 08/31/2022] [Indexed: 12/05/2022]
Abstract
Excess brain cholesterol is strongly implicated in the pathogenesis of Alzheimer's disease (AD). Here we evaluated how the presence of a cholesterol-binding site (CBS) in the transmembrane and juxtamembrane regions of the amyloid precursor protein (APP) regulates its processing. We generated nine point mutations in the APP gene, changing the charge and/or hydrophobicity of the amino-acids which were previously shown as part of the CBS. Most mutations triggered a reduction of amyloid-β peptides Aβ40 and Aβ42 secretion from transiently transfected HEK293T cells. Only the mutations at position 28 of Aβ in the APP sequence resulted in a concomitant significant increase in the production of shorter Aβ peptides. Mass spectrometry (MS) confirmed the predominance of Aβx-33 and Aβx-34 with the APPK28A mutant. The enzymatic activity of α-, β-, and γ-secretases remained unchanged in cells expressing all mutants. Similarly, subcellular localization of the mutants in early endosomes did not differ from the APPWT protein. A transient increase of plasma membrane cholesterol enhanced the production of Aβ40 and Aβ42 by APPWT, an effect absent in APPK28A mutant. Finally, WT but not CBS mutant Aβ derived peptides bound to cholesterol-rich exosomes. Collectively, the present data revealed a major role of juxtamembrane amino acids of the APP CBS in modulating the production of toxic Aβ species. More generally, they underpin the role of cholesterol in the pathophysiology of AD.
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Affiliation(s)
- Linda Hanbouch
- Paris Brain Institute, ICM, CNRS UMR7225-INSERM U1127-Sorbonne University Hôpital de La Pitié-Salpêtrière, 47 Bd de l'Hôpital, 75013, Paris, France
| | - Béatrice Schaack
- Univ. Grenoble Alpes, CNRS, INP, TheRex Team, TIMC-IMAG, 38700, La Tronche, France
- Univ. Grenoble Alpes, CEA, CNRS, IBS, 38044, Grenoble, France
| | - Amal Kasri
- Paris Brain Institute, ICM, CNRS UMR7225-INSERM U1127-Sorbonne University Hôpital de La Pitié-Salpêtrière, 47 Bd de l'Hôpital, 75013, Paris, France
| | - Gaëlle Fontaine
- Paris Brain Institute, ICM, CNRS UMR7225-INSERM U1127-Sorbonne University Hôpital de La Pitié-Salpêtrière, 47 Bd de l'Hôpital, 75013, Paris, France
| | - Eleni Gkanatsiou
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience & Physiology, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, S-431 80, Sweden
| | - Gunnar Brinkmalm
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience & Physiology, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, S-431 80, Sweden
| | - Elena Camporesi
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience & Physiology, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, S-431 80, Sweden
| | - Erik Portelius
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience & Physiology, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, S-431 80, Sweden
- Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, S-431 80, Mölndal, Sweden
| | - Kaj Blennow
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience & Physiology, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, S-431 80, Sweden
- Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, S-431 80, Mölndal, Sweden
| | - Gilles Mourier
- Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, S-431 80, Mölndal, Sweden
- Département Médicaments Et Technologies Pour La Santé (DMTS), Université Paris Saclay, CEA, INRAE, SIMoS, 91191, Gif-sur-Yvette, France
| | - Nicolas Gilles
- Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, S-431 80, Mölndal, Sweden
- Département Médicaments Et Technologies Pour La Santé (DMTS), Université Paris Saclay, CEA, INRAE, SIMoS, 91191, Gif-sur-Yvette, France
| | - Mark J Millan
- Neuroscience Inflammation Thérapeutic Area, IDR Servier, 125 Chemin de Ronde, 78290, Croissy-sur-Seine, France
- Institute of Neuroscience and Psychology, College of Medicine, Vet and Life Sciences, Glasgow University, 62 Hillhead Street, Glasgow, G12 8QB, Scotland
| | - Catherine Marquer
- Paris Brain Institute, ICM, CNRS UMR7225-INSERM U1127-Sorbonne University Hôpital de La Pitié-Salpêtrière, 47 Bd de l'Hôpital, 75013, Paris, France
| | - Henrik Zetterberg
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience & Physiology, the Sahlgrenska Academy at the University of Gothenburg, Mölndal, S-431 80, Sweden
- Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, S-431 80, Mölndal, Sweden
- Department of Neurodegenerative Disease, UCL Institute of Neurology, London, WC1N 3BG, UK
- UK Dementia Research Institute at UCL, London, WC1E 6BT, UK
| | - Lydie Boussicault
- Paris Brain Institute, ICM, CNRS UMR7225-INSERM U1127-Sorbonne University Hôpital de La Pitié-Salpêtrière, 47 Bd de l'Hôpital, 75013, Paris, France
| | - Marie-Claude Potier
- Paris Brain Institute, ICM, CNRS UMR7225-INSERM U1127-Sorbonne University Hôpital de La Pitié-Salpêtrière, 47 Bd de l'Hôpital, 75013, Paris, France.
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5
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Busch L, Eggert S, Endres K, Bufe B. The Hidden Role of Non-Canonical Amyloid β Isoforms in Alzheimer's Disease. Cells 2022; 11:3421. [PMID: 36359817 PMCID: PMC9654995 DOI: 10.3390/cells11213421] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 10/18/2022] [Accepted: 10/20/2022] [Indexed: 09/08/2024] Open
Abstract
Recent advances have placed the pro-inflammatory activity of amyloid β (Aβ) on microglia cells as the focus of research on Alzheimer's Disease (AD). Researchers are confronted with an astonishing spectrum of over 100 different Aβ variants with variable length and chemical modifications. With the exception of Aβ1-42 and Aβ1-40, the biological significance of most peptides for AD is as yet insufficiently understood. We therefore aim to provide a comprehensive overview of the contributions of these neglected Aβ variants to microglia activation. First, the impact of Aβ receptors, signaling cascades, scavenger mechanisms, and genetic variations on the physiological responses towards various Aβ species is described. Furthermore, we discuss the importance of different types of amyloid precursor protein processing for the generation of these Aβ variants in microglia, astrocytes, oligodendrocytes, and neurons, and highlight how alterations in secondary structures and oligomerization affect Aβ neurotoxicity. In sum, the data indicate that gene polymorphisms in Aβ-driven signaling pathways in combination with the production and activity of different Aβ variants might be crucial factors for the initiation and progression of different forms of AD. A deeper assessment of their interplay with glial cells may pave the way towards novel therapeutic strategies for individualized medicine.
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Affiliation(s)
- Lukas Busch
- Department of Informatics and Microsystems Technology, University of Applied Sciences Kaiserslautern, D-66482 Zweibruecken, Germany
| | - Simone Eggert
- Department of Neurogenetics, Max Planck Institute for Multidisciplinary Sciences, D-37075 Goettingen, Germany
| | - Kristina Endres
- Department of Psychiatry and Psychotherapy, University Medical Centre of the Johannes Gutenberg University, D-55131 Mainz, Germany
| | - Bernd Bufe
- Department of Informatics and Microsystems Technology, University of Applied Sciences Kaiserslautern, D-66482 Zweibruecken, Germany
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6
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N-terminally truncated Aβ4-x proteoforms and their relevance for Alzheimer's pathophysiology. Transl Neurodegener 2022; 11:30. [PMID: 35641972 PMCID: PMC9158284 DOI: 10.1186/s40035-022-00303-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Accepted: 04/21/2022] [Indexed: 01/22/2023] Open
Abstract
Background The molecular heterogeneity of Alzheimer’s amyloid-β (Aβ) deposits extends well beyond the classic Aβ1-40/Aβ1-42 dichotomy, substantially expanded by multiple post-translational modifications that increase the proteome diversity. Numerous truncated fragments consistently populate the brain Aβ peptidome, and their homeostatic regulation and potential contribution to disease pathogenesis are largely unknown. Aβ4-x peptides have been reported as major components of plaque cores and the limited studies available indicate their relative abundance in Alzheimer’s disease (AD). Methods Immunohistochemistry was used to assess the topographic distribution of Aβ4-x species in well-characterized AD cases using custom-generated monoclonal antibody 18H6—specific for Aβ4-x species and blind for full-length Aβ1-40/Aβ1-42—in conjunction with thioflavin-S and antibodies recognizing Aβx-40 and Aβx-42 proteoforms. Circular dichroism, thioflavin-T binding, and electron microscopy evaluated the biophysical and aggregation/oligomerization properties of full-length and truncated synthetic homologues, whereas stereotaxic intracerebral injections of monomeric and oligomeric radiolabeled homologues in wild-type mice were used to evaluate their brain clearance characteristics. Results All types of amyloid deposits contained the probed Aβ epitopes, albeit expressed in different proportions. Aβ4-x species showed preferential localization within thioflavin-S-positive cerebral amyloid angiopathy and cored plaques, strongly suggesting poor clearance characteristics and consistent with the reduced solubility and enhanced oligomerization of their synthetic homologues. In vivo clearance studies demonstrated a fast brain efflux of N-terminally truncated and full-length monomeric forms whereas their oligomeric counterparts—particularly of Aβ4-40 and Aβ4-42—consistently exhibited enhanced brain retention. Conclusions The persistence of aggregation-prone Aβ4-x proteoforms likely contributes to the process of amyloid formation, self-perpetuating the amyloidogenic loop and exacerbating amyloid-mediated pathogenic pathways.
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7
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Is γ-secretase a beneficial inactivating enzyme of the toxic APP C-terminal fragment C99? J Biol Chem 2021; 296:100489. [PMID: 33662398 PMCID: PMC8027268 DOI: 10.1016/j.jbc.2021.100489] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 02/26/2021] [Accepted: 02/26/2021] [Indexed: 12/12/2022] Open
Abstract
Genetic, biochemical, and anatomical grounds led to the proposal of the amyloid cascade hypothesis centered on the accumulation of amyloid beta peptides (Aβ) to explain Alzheimer's disease (AD) etiology. In this context, a bulk of efforts have aimed at developing therapeutic strategies seeking to reduce Aβ levels, either by blocking its production (γ- and β-secretase inhibitors) or by neutralizing it once formed (Aβ-directed immunotherapies). However, so far the vast majority of, if not all, clinical trials based on these strategies have failed, since they have not been able to restore cognitive function in AD patients, and even in many cases, they have worsened the clinical picture. We here propose that AD could be more complex than a simple Aβ-linked pathology and discuss the possibility that a way to reconcile undoubted genetic evidences linking processing of APP to AD and a consistent failure of Aβ-based clinical trials could be to envision the pathological contribution of the direct precursor of Aβ, the β-secretase-derived C-terminal fragment of APP, βCTF, also referred to as C99. In this review, we summarize scientific evidences pointing to C99 as an early contributor to AD and postulate that γ-secretase should be considered as not only an Aβ-generating protease, but also a beneficial C99-inactivating enzyme. In that sense, we discuss the limitations of molecules targeting γ-secretase and propose alternative strategies seeking to reduce C99 levels by other means and notably by enhancing its lysosomal degradation.
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8
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Parodi‐Rullán R, Ghiso J, Cabrera E, Rostagno A, Fossati S. Alzheimer's amyloid β heterogeneous species differentially affect brain endothelial cell viability, blood-brain barrier integrity, and angiogenesis. Aging Cell 2020; 19:e13258. [PMID: 33155752 PMCID: PMC7681048 DOI: 10.1111/acel.13258] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 09/02/2020] [Accepted: 09/19/2020] [Indexed: 01/05/2023] Open
Abstract
Impaired clearance in the Alzheimer's Disease (AD) brain is key in the formation of Aβ parenchymal plaques and cerebrovascular deposits known as cerebral amyloid angiopathy (CAA), present in >80% of AD patients and ~50% of non-AD elderly subjects. Aβ deposits are highly heterogeneous, containing multiple fragments mostly derived from catabolism of Aβ40/Aβ42, which exhibit dissimilar aggregation properties. Remarkably, the role of these physiologically relevant Aβ species in cerebrovascular injury and their impact in vascular pathology is unknown. We sought to understand how heterogeneous Aβ species affect cerebral endothelial health and assess whether their diverse effects are associated with the peptides aggregation propensities. We analyzed cerebral microvascular endothelial cell (CMEC) viability, blood-brain barrier (BBB) permeability, and angiogenesis, all relevant aspects of brain microvascular dysfunction. We found that Aβ peptides and fragments exerted differential effects on cerebrovascular pathology. Peptides forming mostly oligomeric structures induced CMEC apoptosis, whereas fibrillar aggregates increased BBB permeability without apoptotic effects. Interestingly, all Aβ species tested inhibited angiogenesis in vitro. These data link the biological effects of the heterogeneous Aβ peptides to their primary structure and aggregation, strongly suggesting that the composition of amyloid deposits influences clinical aspects of the AD vascular pathology. As the presence of predominant oligomeric structures in proximity of the vessel walls may lead to CMEC death and induction of microhemorrhages, fibrillar amyloid is likely responsible for increased BBB permeability and associated neurovascular dysfunction. These results have the potential to unveil more specific therapeutic targets and clarify the multifactorial nature of AD.
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Affiliation(s)
- Rebecca Parodi‐Rullán
- Alzheimer's Center at Temple Lewis Katz School of Medicine Temple University Philadelphia PA USA
| | - Jorge Ghiso
- Department of Pathology New York University School of Medicine New York NY USA
- Department of Psychiatry New York University School of Medicine New York NY USA
| | - Erwin Cabrera
- Department of Pathology New York University School of Medicine New York NY USA
| | - Agueda Rostagno
- Department of Pathology New York University School of Medicine New York NY USA
| | - Silvia Fossati
- Alzheimer's Center at Temple Lewis Katz School of Medicine Temple University Philadelphia PA USA
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9
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Wirths O, Zampar S. Emerging roles of N- and C-terminally truncated Aβ species in Alzheimer’s disease. Expert Opin Ther Targets 2019; 23:991-1004. [DOI: 10.1080/14728222.2019.1702972] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Oliver Wirths
- Department of Psychiatry and Psychotherapy, Molecular Psychiatry, University Medical Center (UMG), Georg-August-University, Göttingen, Germany
| | - Silvia Zampar
- Department of Psychiatry and Psychotherapy, Molecular Psychiatry, University Medical Center (UMG), Georg-August-University, Göttingen, Germany
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10
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Kirabali T, Rigotti S, Siccoli A, Liebsch F, Shobo A, Hock C, Nitsch RM, Multhaup G, Kulic L. The amyloid-β degradation intermediate Aβ34 is pericyte-associated and reduced in brain capillaries of patients with Alzheimer's disease. Acta Neuropathol Commun 2019; 7:194. [PMID: 31796114 PMCID: PMC6892233 DOI: 10.1186/s40478-019-0846-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 11/13/2019] [Indexed: 02/07/2023] Open
Abstract
An impairment of amyloid β-peptide (Aβ) clearance is suggested to play a key role in the pathogenesis of sporadic Alzheimer’s disease (AD). Amyloid degradation is mediated by various mechanisms including fragmentation by enzymes like neprilysin, matrix metalloproteinases (MMPs) and a recently identified amyloidolytic activity of β-site amyloid precursor protein cleaving enzyme 1 (BACE1). BACE1 cleavage of Aβ40 and Aβ42 results in the formation of a common Aβ34 intermediate which was found elevated in cerebrospinal fluid levels of patients at the earliest disease stages. To further investigate the role of Aβ34 as a marker for amyloid clearance in AD, we performed a systematic and comprehensive analysis of Aβ34 immunoreactivity in hippocampal and cortical post-mortem brain tissue from AD patients and non-demented elderly individuals. In early Braak stages, Aβ34 was predominantly detectable in a subset of brain capillaries associated with pericytes, while in later disease stages, in clinically diagnosed AD, this pericyte-associated Aβ34 immunoreactivity was largely lost. Aβ34 was also detected in isolated human cortical microvessels associated with brain pericytes and its levels correlated with Aβ40, but not with Aβ42 levels. Moreover, a significantly decreased Aβ34/Aβ40 ratio was observed in microvessels from AD patients in comparison to non-demented controls suggesting a reduced proteolytic degradation of Aβ40 to Aβ34 in AD. In line with the hypothesis that pericytes at the neurovascular unit are major producers of Aβ34, biochemical studies in cultured human primary pericytes revealed a time and dose dependent increase of Aβ34 levels upon treatment with recombinant Aβ40 peptides while Aβ34 production was impaired when Aβ40 uptake was reduced or BACE1 activity was inhibited. Collectively, our findings indicate that Aβ34 is generated by a novel BACE1-mediated Aβ clearance pathway in pericytes of brain capillaries. As amyloid clearance is significantly reduced in AD, impairment of this pathway might be a major driver of the pathogenesis in sporadic AD.
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11
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Liebsch F, Kulic L, Teunissen C, Shobo A, Ulku I, Engelschalt V, Hancock MA, van der Flier WM, Kunach P, Rosa-Neto P, Scheltens P, Poirier J, Saftig P, Bateman RJ, Breitner J, Hock C, Multhaup G. Aβ34 is a BACE1-derived degradation intermediate associated with amyloid clearance and Alzheimer's disease progression. Nat Commun 2019; 10:2240. [PMID: 31110178 PMCID: PMC6527709 DOI: 10.1038/s41467-019-10152-w] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 04/17/2019] [Indexed: 12/13/2022] Open
Abstract
The beta-site APP cleaving enzyme 1 (BACE1) is known primarily for its initial cleavage of the amyloid precursor protein (APP), which ultimately leads to the generation of Aβ peptides. Here, we provide evidence that altered BACE1 levels and activity impact the degradation of Aβ40 and Aβ42 into a common Aβ34 intermediate. Using human cerebrospinal fluid (CSF) samples from the Amsterdam Dementia Cohort, we show that Aβ34 is elevated in individuals with mild cognitive impairment who later progressed to dementia. Furthermore, Aβ34 levels correlate with the overall Aβ clearance rates in amyloid positive individuals. Using CSF samples from the PREVENT-AD cohort (cognitively normal individuals at risk for Alzheimer’s disease), we further demonstrate that the Aβ34/Aβ42 ratio, representing Aβ degradation and cortical deposition, associates with pre-clinical markers of neurodegeneration. We propose that Aβ34 represents a marker of amyloid clearance and may be helpful for the characterization of Aβ turnover in clinical samples. Aβ34 is generated from degradation of Aβ40 and Aβ42 by β-secretase. Here, the authors show that Aβ34 is a marker for amyloid clearance and is elevated in the CSF of patients that go on to convert from mild cognitive impairment to Alzheimer’s disease, suggesting it may be a useful biomarker.
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Affiliation(s)
- Filip Liebsch
- Department of Pharmacology and Therapeutics and Integrated Program in Neuroscience, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - Luka Kulic
- Institute for Regenerative Medicine, University of Zurich, CH-8952, Schlieren, Switzerland
| | - Charlotte Teunissen
- Department of Clinical Chemistry, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, 1081HZ, Amsterdam, The Netherlands
| | - Adeola Shobo
- Department of Pharmacology and Therapeutics and Integrated Program in Neuroscience, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - Irem Ulku
- Department of Pharmacology and Therapeutics and Integrated Program in Neuroscience, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - Vivienne Engelschalt
- Institut für Chemie und Biochemie, Freie Universität Berlin, 14195, Berlin, Germany
| | - Mark A Hancock
- SPR-MS Facility, McGill University, Montreal, QC, H3G 1Y6, Canada
| | - Wiesje M van der Flier
- Alzheimer Center Amsterdam, Department of Neurology, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, 1081HZ, The Netherlands
| | - Peter Kunach
- Translational Neuroimaging Laboratory, The McGill University Research Centre for Studies in Aging, Alzheimer's Disease Research Unit, Douglas Research Institute, McGill University, Montreal, H4H 1R3, QC, Canada
| | - Pedro Rosa-Neto
- Translational Neuroimaging Laboratory, The McGill University Research Centre for Studies in Aging, Alzheimer's Disease Research Unit, Douglas Research Institute, McGill University, Montreal, H4H 1R3, QC, Canada
| | - Philip Scheltens
- Alzheimer Center Amsterdam, Department of Neurology, Amsterdam Neuroscience, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, 1081HZ, The Netherlands
| | - Judes Poirier
- Department of Psychiatry, McGill University, Montreal, QC, H4H 1R3, Canada
| | - Paul Saftig
- Biochemisches Institut, Christian-Albrechts-Universität-Kiel, 24118, Kiel, Germany
| | - Randall J Bateman
- Department of Neurology, Washington University in St. Louis, St. Louis, MO, 63110, USA
| | - John Breitner
- Department of Psychiatry, McGill University, Montreal, QC, H4H 1R3, Canada
| | - Christoph Hock
- Institute for Regenerative Medicine, University of Zurich, CH-8952, Schlieren, Switzerland.,Neurimmune, CH-8952, Schlieren, Switzerland
| | - Gerhard Multhaup
- Department of Pharmacology and Therapeutics and Integrated Program in Neuroscience, McGill University, Montreal, QC, H3G 1Y6, Canada.
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12
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Scholz D, Chernyshova Y, Ückert AK, Leist M. Reduced Aβ secretion by human neurons under conditions of strongly increased BACE activity. J Neurochem 2018; 147:256-274. [PMID: 29804308 DOI: 10.1111/jnc.14467] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 05/06/2018] [Accepted: 05/23/2018] [Indexed: 12/20/2022]
Abstract
The initial step in the amyloidogenic cascade of amyloid precursor protein (APP) processing is catalyzed by beta-site APP-cleaving enzyme (BACE), and this protease has increased activities in affected areas of Alzheimer's disease brains. We hypothesized that altered APP processing, because of augmented BACE activity, would affect the actions of direct and indirect BACE inhibitors. We therefore compared post-mitotic human neurons (LUHMES) with their BACE-overexpressing counterparts (BLUHMES). Although β-cleavage of APP was strongly increased in BLUHMES, they produced less full-length and truncated amyloid beta (Aβ) than LUHMES. Moreover, low concentrations of BACE inhibitors decreased cellular BACE activity as expected, but increased Aβ1-40 levels. Several other approaches to modulate BACE activity led to a similar, apparently paradoxical, behavior. For instance, reduction in intracellular acidification by bepridil increased Aβ production in parallel with decreased BACE activity. In contrast to BLUHMES, the respective control cells (LUHMES or BLUHMES with catalytically inactive BACE) showed conventional pharmacological responses. Other non-canonical neurochemical responses (so-called 'rebound effects') are well-documented for the Aβ pathway, especially for γ-secretase: a partial block of its activity leads to an increased Aβ secretion by some cell types. We therefore compared LUHMES and BLUHMES regarding rebound effects of γ-secretase inhibitors and found an Aβ rise in LUHMES but not in BLUHMES. Thus, different cellular factors are responsible for the γ-secretase- versus BACE-related Aβ rebound. We conclude that increased BACE activity, possibly accompanied by an altered cellular localization pattern, can dramatically influence Aβ generation in human neurons and affect pharmacological responses to secretase inhibitors. OPEN PRACTICES: Open Science: This manuscript was awarded with the Open Materials Badge. For more information see: https://cos.io/our-services/open-science-badges/.
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Affiliation(s)
- Diana Scholz
- Chair for in vitro Toxicology and Biomedicine, University of Konstanz, Konstanz, Germany
| | - Yana Chernyshova
- Chair for in vitro Toxicology and Biomedicine, University of Konstanz, Konstanz, Germany
| | - Anna-Katharina Ückert
- Chair for in vitro Toxicology and Biomedicine, University of Konstanz, Konstanz, Germany
| | - Marcel Leist
- Chair for in vitro Toxicology and Biomedicine, University of Konstanz, Konstanz, Germany
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13
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Dunys J, Valverde A, Checler F. Are N- and C-terminally truncated Aβ species key pathological triggers in Alzheimer's disease? J Biol Chem 2018; 293:15419-15428. [PMID: 30143530 DOI: 10.1074/jbc.r118.003999] [Citation(s) in RCA: 83] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The histopathology of Alzheimer's disease (AD) is characterized by neuronal loss, neurofibrillary tangles, and senile plaque formation. The latter results from an exacerbated production (familial AD cases) or altered degradation (sporadic cases) of 40/42-amino acid-long β-amyloid peptides (Aβ peptides) that are produced by sequential cleavages of Aβ precursor protein (βAPP) by β- and γ-secretases. The amyloid cascade hypothesis proposes a key role for the full-length Aβ42 and the Aβ40/42 ratio in AD etiology, in which soluble Aβ oligomers lead to neurotoxicity, tau hyperphosphorylation, aggregation, and, ultimately, cognitive defects. However, following this postulate, during the last decade, several clinical approaches aimed at decreasing full-length Aβ42 production or neutralizing it by immunotherapy have failed to reduce or even stabilize AD-related decline. Thus, the Aβ peptide (Aβ40/42)-centric hypothesis is probably a simplified view of a much more complex situation involving a multiplicity of APP fragments and Aβ catabolites. Indeed, biochemical analyses of AD brain deposits and fluids have unraveled an Aβ peptidome consisting of additional Aβ-related species. Such Aβ catabolites could be due to either primary enzymatic cleavages of βAPP or secondary processing of Aβ itself by exopeptidases. Here, we review the diversity of N- and C-terminally truncated Aβ peptides and their biosynthesis and outline their potential function/toxicity. We also highlight their potential as new pharmaceutical targets and biomarkers.
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Affiliation(s)
- Julie Dunys
- From the Université Côte d'Azur, INSERM, CNRS, IPMC, Team labeled "Laboratory of Excellence (LABEX) Distalz," 660 Route des Lucioles, Sophia-Antipolis, 06560 Valbonne, France
| | - Audrey Valverde
- From the Université Côte d'Azur, INSERM, CNRS, IPMC, Team labeled "Laboratory of Excellence (LABEX) Distalz," 660 Route des Lucioles, Sophia-Antipolis, 06560 Valbonne, France
| | - Frédéric Checler
- From the Université Côte d'Azur, INSERM, CNRS, IPMC, Team labeled "Laboratory of Excellence (LABEX) Distalz," 660 Route des Lucioles, Sophia-Antipolis, 06560 Valbonne, France
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14
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Multi-scale simulations of biological systems using the OPEP coarse-grained model. Biochem Biophys Res Commun 2017; 498:296-304. [PMID: 28917842 DOI: 10.1016/j.bbrc.2017.08.165] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 08/31/2017] [Indexed: 12/14/2022]
Abstract
Biomolecules are complex machines that are optimized by evolution to properly fulfill or contribute to a variety of biochemical tasks in the cellular environment. Computer simulations based on quantum mechanics and atomistic force fields have been proven to be a powerful microscope for obtaining valuable insights into many biological, physical, and chemical processes. Many interesting phenomena involve, however, a time scale and a number of degrees of freedom, notably if crowding is considered, that cannot be explored at an atomistic resolution. To bridge the gap between reality and simulation, many different advanced computational techniques and coarse-grained (CG) models have been developed. Here, we report some applications of the CG OPEP protein model to amyloid fibril formation, the response of catch-bond proteins to two types of fluid flow, and interactive simulations to fold peptides with well-defined 3D structures or with intrinsic disorder.
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15
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Aβ truncated species: Implications for brain clearance mechanisms and amyloid plaque deposition. Biochim Biophys Acta Mol Basis Dis 2017; 1864:208-225. [PMID: 28711595 DOI: 10.1016/j.bbadis.2017.07.005] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 06/24/2017] [Accepted: 07/11/2017] [Indexed: 12/14/2022]
Abstract
Extensive parenchymal and vascular Aβ deposits are pathological hallmarks of Alzheimer's disease (AD). Besides classic full-length peptides, biochemical analyses of brain deposits have revealed high degree of Aβ heterogeneity likely resulting from the action of multiple proteolytic enzymes. In spite of the numerous studies focusing in Aβ, the relevance of N- and C-terminal truncated species for AD pathogenesis remains largely understudied. In the present work, using novel antibodies specifically recognizing Aβ species N-terminally truncated at position 4 or C-terminally truncated at position 34, we provide a clear assessment of the differential topographic localization of these species in AD brains and transgenic models. Based on their distinct solubility, brain N- and C-terminal truncated species were extracted by differential fractionation and identified via immunoprecipitation coupled to mass spectrometry analysis. Biochemical/biophysical studies with synthetic homologues further confirmed the different solubility properties and contrasting fibrillogenic characteristics of the truncated species composing the brain Aβ peptidome. Aβ C-terminal degradation leads to the production of more soluble fragments likely to be more easily eliminated from the brain. On the contrary, N-terminal truncation at position 4 favors the formation of poorly soluble, aggregation prone peptides with high amyloidogenic propensity and the potential to exacerbate the fibrillar deposits, self-perpetuating the amyloidogenic loop. Detailed assessment of the molecular diversity of Aβ species composing interstitial fluid and amyloid deposits at different disease stages, as well as the evaluation of the truncation profile during various pharmacologic approaches will provide a comprehensive understanding of the still undefined contribution of Aβ truncations to the disease pathogenesis and their potential as novel therapeutic targets.
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16
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Kimura A, Hata S, Suzuki T. Alternative Selection of β-Site APP-Cleaving Enzyme 1 (BACE1) Cleavage Sites in Amyloid β-Protein Precursor (APP) Harboring Protective and Pathogenic Mutations within the Aβ Sequence. J Biol Chem 2016; 291:24041-24053. [PMID: 27687728 DOI: 10.1074/jbc.m116.744722] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Revised: 09/21/2016] [Indexed: 11/06/2022] Open
Abstract
β-Site APP-cleaving enzyme 1 (BACE1) cleaves amyloid β-protein precursor (APP) at the bond between Met671 and Asp672 (β-site) to generate the carboxyl-terminal fragment (CTFβ/C99). BACE1 also cleaves APP at another bond between Thr681 and Gln682 (β'-site), yielding CTFβ'/C89. Cleavage of CTFβ/C99 by γ-secretase generates Aβ(1-XX), whereas cleavage of CTFβ'/C89 generates Aβ(11-XX). Thus, β'-site cleavage by BACE1 is amyloidolytic rather than amyloidogenic. β' cleavage of mouse APP is more common than the corresponding cleavage of human APP. We found that the H684R substitution within human Aβ, which replaces the histidine in the human protein with the arginine found at the corresponding position in mouse, facilitated β' cleavage irrespective of the species origin of BACE1, thereby significantly increasing the level of Aβ(11-XX) and decreasing the level of Aβ(1-XX). Thus, amino acid substitutions within the Aβ sequence influenced the selectivity of alternative β- or β'-site cleavage of APP by BACE1. In familial Alzheimer's disease (FAD), the APP gene harbors pathogenic variations such as the Swedish (K670N/M671L), Leuven (E682K), and A673V mutations, all of which decrease Aβ(11-40) generation, whereas the protective Icelandic mutation (A673T) increases generation of Aβ(11-40). Thus, A673T promotes β' cleavage of APP and protects subjects against AD. In addition, CTFβ/C99 was cleaved by excess BACE1 activity to generate CTFβ'/C89, followed by Aβ(11-40), even if APP harbored pathogenic mutations. The resultant Aβ(11-40) was more metabolically labile in vivo than Aβ(1-40). Our analysis suggests that some FAD mutations in APP are amyloidogenic and/or amyloidolytic via selection of alternative BACE1 cleavage sites.
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Affiliation(s)
- Ayano Kimura
- From the Laboratory of Neuroscience, Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita 12-Nishi 6, Kita-ku, Sapporo 060-0812, Japan
| | - Saori Hata
- From the Laboratory of Neuroscience, Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita 12-Nishi 6, Kita-ku, Sapporo 060-0812, Japan
| | - Toshiharu Suzuki
- From the Laboratory of Neuroscience, Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita 12-Nishi 6, Kita-ku, Sapporo 060-0812, Japan
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