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Lundin B, Comby AC, Berezovska O, Maesako M. Negative Regulation of Cathepsins by β-Amyloid. eNeuro 2024; 11:ENEURO.0258-23.2023. [PMID: 38199815 PMCID: PMC10849021 DOI: 10.1523/eneuro.0258-23.2023] [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: 07/22/2023] [Revised: 11/17/2023] [Accepted: 11/29/2023] [Indexed: 01/12/2024] Open
Abstract
Genome wide association study (GWAS) uncovered Alzheimer's disease (AD) risk genes linked to the endo-lysosomal pathway. This pathway seems to be the gateway of protein aggregates, such as tau and α-synuclein, to the cytoplasm. Furthermore, we and others reported that the amyloid precursor protein (APP) C99 is predominantly processed by γ-secretase in the endo-lysosomal compartments, and β-amyloid (Aβ) peptides are enriched in the same subcellular loci. While the role(s) of APP/Aβ in the endo-lysosomal pathway has not been fully established, a recent study reported that Aβ, in particular Aβ42, inhibits cathepsin D (CTSD) activity. Here, we show using a cell-free in vitro assay that Aβ42 also blocks cathepsin B (CTSB) activity. Furthermore, we uncovered that the autocatalytic processing (i.e., conversion of single chain to heavy/light chains) of CTSB and CTSD is accelerated in APP-deficient cells compared with wild-type controls. Taken together, our findings further support the negative regulation of cathepsins by Aβ.
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Affiliation(s)
- Brianna Lundin
- MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown 02129, Massachusetts
| | - Anne-Claire Comby
- MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown 02129, Massachusetts
| | - Oksana Berezovska
- MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown 02129, Massachusetts
| | - Masato Maesako
- MassGeneral Institute for Neurodegenerative Disease, Massachusetts General Hospital, Harvard Medical School, Charlestown 02129, Massachusetts
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2
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Konings SC, Nyberg E, Martinsson I, Torres-Garcia L, Klementieva O, Guimas Almeida C, Gouras GK. Apolipoprotein E intersects with amyloid-β within neurons. Life Sci Alliance 2023; 6:e202201887. [PMID: 37290814 PMCID: PMC10250689 DOI: 10.26508/lsa.202201887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 05/30/2023] [Accepted: 05/31/2023] [Indexed: 06/10/2023] Open
Abstract
Apolipoprotein E4 (ApoE4) is the most important genetic risk factor for Alzheimer's disease (AD). Among the earliest changes in AD is endosomal enlargement in neurons, which was reported as enhanced in ApoE4 carriers. ApoE is thought to be internalized into endosomes of neurons, whereas β-amyloid (Aβ) accumulates within neuronal endosomes early in AD. However, it remains unknown whether ApoE and Aβ intersect intracellularly. We show that internalized astrocytic ApoE localizes mostly to lysosomes in neuroblastoma cells and astrocytes, whereas in neurons, it preferentially localizes to endosomes-autophagosomes of neurites. In AD transgenic neurons, astrocyte-derived ApoE intersects intracellularly with amyloid precursor protein/Aβ. Moreover, ApoE4 increases the levels of endogenous and internalized Aβ42 in neurons. Taken together, we demonstrate differential localization of ApoE in neurons, astrocytes, and neuron-like cells, and show that internalized ApoE intersects with amyloid precursor protein/Aβ in neurons, which may be of considerable relevance to AD.
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Affiliation(s)
- Sabine C Konings
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
- Medical Microspectroscopy, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Emma Nyberg
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Isak Martinsson
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Laura Torres-Garcia
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Oxana Klementieva
- Medical Microspectroscopy, Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Claudia Guimas Almeida
- iNOVA4Health, NOVA Medical School | Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal
| | - Gunnar K Gouras
- Experimental Dementia Research Unit, Department of Experimental Medical Science, Lund University, Lund, Sweden
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3
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Foley AR, Raskatov J. AN ENANTIOMERIC FRAGMENT PAIR (EFP) APPROACH FOR THE STUDY OF CELLULAR UPTAKE OF INTRINSICALLY DISORDERED PROTEINS. Chembiochem 2022; 23:e202200146. [PMID: 35417609 DOI: 10.1002/cbic.202200146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 04/10/2022] [Indexed: 11/10/2022]
Abstract
The study of intrinsically disordered and amyloidogenic proteins poses a major challenge to researchers: the propensity of the system to aggregate and to form amyloid fibrils and deposits . This intrinsic nature limits the way amyloids can be studied and increases the level of complexity of the techniques needed to study the system of interest. Recent reports suggest that cellular recognition and internalization of pre-fibrillary species of amyloidogenic peptides and proteins may initiate some of its toxic actions. Therefore, developing novels tools to facilitate the understanding and determination of the interactions between intrinsically disordered proteins and the cellular membrane is becoming increasingly valuable. Here, we present and propose an approach for the study of the interactions of intrinsically disordered proteins with the cellular surface based on the use of enantiomeric fragment pairs (EFPs). By following a stepwise methodology in which the amyloidogenic peptide or protein is fragmented into specific segments, we show how this approach can be exploited to differentiate between different types of cellular uptake, to determine the degree of receptor-mediated cellular internalization of intrinsically disordered peptides and proteins, and to pinpoint the specific regions within the amino acid sequence responsible for the cellular recognition. Adopting this approach overcomes aggregation-related challenges and offers a particularly well-suited platform for the elucidation of receptor-intermediated recognition, uptake, and toxicity.
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Affiliation(s)
| | - Jevgenij Raskatov
- UCSC, Chemistry and Biochemistry, 1156 High Street, 95064, Santa Cruz, UNITED STATES
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4
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Shi Y, Andhey PS, Ising C, Wang K, Snipes LL, Boyer K, Lawson S, Yamada K, Qin W, Manis M, Serrano JR, Benitez BA, Schmidt RE, Artyomov M, Ulrich JD, Holtzman DM. Overexpressing low-density lipoprotein receptor reduces tau-associated neurodegeneration in relation to apoE-linked mechanisms. Neuron 2021; 109:2413-2426.e7. [PMID: 34157306 PMCID: PMC8349883 DOI: 10.1016/j.neuron.2021.05.034] [Citation(s) in RCA: 61] [Impact Index Per Article: 20.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 05/03/2021] [Accepted: 05/27/2021] [Indexed: 01/01/2023]
Abstract
APOE is the strongest genetic risk factor for late-onset Alzheimer's disease. ApoE exacerbates tau-associated neurodegeneration by driving microglial activation. However, how apoE regulates microglial activation and whether targeting apoE is therapeutically beneficial in tauopathy is unclear. Here, we show that overexpressing an apoE metabolic receptor, LDLR (low-density lipoprotein receptor), in P301S tauopathy mice markedly reduces brain apoE and ameliorates tau pathology and neurodegeneration. LDLR overexpression (OX) in microglia cell-autonomously downregulates microglial Apoe expression and is associated with suppressed microglial activation as in apoE-deficient microglia. ApoE deficiency and LDLR OX strongly drive microglial immunometabolism toward enhanced catabolism over anabolism, whereas LDLR-overexpressing microglia also uniquely upregulate specific ion channels and neurotransmitter receptors upon activation. ApoE-deficient and LDLR-overexpressing mice harbor enlarged pools of oligodendrocyte progenitor cells (OPCs) and show greater preservation of myelin integrity under neurodegenerative conditions. They also show less reactive astrocyte activation in the setting of tauopathy.
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Affiliation(s)
- Yang Shi
- Department of Neurology, Washington University, St. Louis, MO 63110, USA
| | | | - Christina Ising
- Department of Neurodegenerative Diseases and Geriatric Psychiatry, University Hospital of Bonn and German Center for Neurodegenerative Diseases (DZNE), Bonn 53127, Germany
| | - Kairuo Wang
- Department of Neurology, Washington University, St. Louis, MO 63110, USA
| | - Lisa L Snipes
- Department of Pathology and Immunology, Washington University, St. Louis, MO 63110, USA
| | - Kevin Boyer
- Department of Pathology and Immunology, Washington University, St. Louis, MO 63110, USA
| | - Stephanie Lawson
- Department of Pathology and Immunology, Washington University, St. Louis, MO 63110, USA
| | - Kaoru Yamada
- Department of Neuropathology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
| | - Wei Qin
- Department of Psychiatry, Washington University, St. Louis, MO 63110, USA
| | - Melissa Manis
- Department of Neurology, Washington University, St. Louis, MO 63110, USA
| | | | - Bruno A Benitez
- Department of Psychiatry, Washington University, St. Louis, MO 63110, USA
| | - Robert E Schmidt
- Department of Pathology and Immunology, Washington University, St. Louis, MO 63110, USA
| | - Maxim Artyomov
- Department of Neurodegenerative Diseases and Geriatric Psychiatry, University Hospital of Bonn and German Center for Neurodegenerative Diseases (DZNE), Bonn 53127, Germany
| | - Jason D Ulrich
- Department of Neurology, Washington University, St. Louis, MO 63110, USA.
| | - David M Holtzman
- Department of Neurology, Washington University, St. Louis, MO 63110, USA.
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The Relevance of Amyloid β-Calmodulin Complexation in Neurons and Brain Degeneration in Alzheimer's Disease. Int J Mol Sci 2021; 22:ijms22094976. [PMID: 34067061 PMCID: PMC8125740 DOI: 10.3390/ijms22094976] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 05/02/2021] [Accepted: 05/05/2021] [Indexed: 12/13/2022] Open
Abstract
Intraneuronal amyloid β (Aβ) oligomer accumulation precedes the appearance of amyloid plaques or neurofibrillary tangles and is neurotoxic. In Alzheimer’s disease (AD)-affected brains, intraneuronal Aβ oligomers can derive from Aβ peptide production within the neuron and, also, from vicinal neurons or reactive glial cells. Calcium homeostasis dysregulation and neuronal excitability alterations are widely accepted to play a key role in Aβ neurotoxicity in AD. However, the identification of primary Aβ-target proteins, in which functional impairment initiating cytosolic calcium homeostasis dysregulation and the critical point of no return are still pending issues. The micromolar concentration of calmodulin (CaM) in neurons and its high affinity for neurotoxic Aβ peptides (dissociation constant ≈ 1 nM) highlight a novel function of CaM, i.e., the buffering of free Aβ concentrations in the low nanomolar range. In turn, the concentration of Aβ-CaM complexes within neurons will increase as a function of time after the induction of Aβ production, and free Aβ will rise sharply when accumulated Aβ exceeds all available CaM. Thus, Aβ-CaM complexation could also play a major role in neuronal calcium signaling mediated by calmodulin-binding proteins by Aβ; a point that has been overlooked until now. In this review, we address the implications of Aβ-CaM complexation in the formation of neurotoxic Aβ oligomers, in the alteration of intracellular calcium homeostasis induced by Aβ, and of dysregulation of the calcium-dependent neuronal activity and excitability induced by Aβ.
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Hannan MA, Dash R, Haque MN, Choi SM, Moon IS. Integrated System Pharmacology and In Silico Analysis Elucidating Neuropharmacological Actions of Withania somnifera in the Treatment of Alzheimer's Disease. CNS & NEUROLOGICAL DISORDERS-DRUG TARGETS 2020; 19:541-556. [PMID: 32748763 DOI: 10.2174/1871527319999200730214807] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 06/18/2020] [Accepted: 06/19/2020] [Indexed: 02/08/2023]
Abstract
BACKGROUND Withania somnifera (WS), also referred to as Medhya Rasayana (nootropic or rejuvenating), has traditionally been prescribed for various neurological ailments, including dementia. Despite substantial evidence, pharmacological roles of WS, neither as nootropic nor as an antidementia agent, are well-understood at the cellular and molecular levels. OBJECTIVES We aimed at elucidating the pharmacological action mechanisms of WS root constituents against Alzheimer's Disease (AD) pathology. METHODS Various bioinformatics tools and resources, including DAVID, Cytoscape, NetworkAnalyst and KEGG pathway database were employed to analyze the interaction of WS root bioactive molecules with the protein targets of AD-associated cellular processes. We also used a molecular simulation approach to validate the interaction of compounds with selected protein targets. RESULTS Network analysis revealed that β-sitosterol, withaferin A, stigmasterol, withanolide A, and withanolide D are the major constituents of WS root that primarily target the cellular pathways such as PI3K/Akt signaling, neurotrophin signaling and toll-like receptor signaling and proteins such as Tropomyosin receptor Kinase B (TrkB), Glycogen Synthase Kinase-3β (GSK-3β), Toll-Like Receptor 2/4 (TLR2/4), and β-secretase (BACE-1). Also, the in silico analysis further validated the interaction patterns and binding affinity of the major WS compounds, particularly stigmasterol, withanolide A, withanolide D and β-sitosterol with TrkB, GSK-3β, TLR2/4, and BACE-1. CONCLUSION The present findings demonstrate that stigmasterol, withanolide A, withanolide D and β-sitosterol are the major metabolites that are responsible for the neuropharmacological action of WS root against AD-associated pathobiology, and TrkB, GSK-3β, TLR2/4, and BACE-1 could be the potential druggable targets.
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Affiliation(s)
- Md Abdul Hannan
- Department of Anatomy, Dongguk University College of Medicine, Gyeongju 38066, Korea,Department of Biochemistry and Molecular Biology, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh
| | - Raju Dash
- Department of Anatomy, Dongguk University College of Medicine, Gyeongju 38066, Korea
| | - Md Nazmul Haque
- Departement of Fisheries Biology and Genetics, Patuakhali Science and Technology University Patuakhali-8602, Bangladesh
| | - Sung Min Choi
- Department of Pediatrics, Dongguk University College of Medicine, Gyeongju 38066, Republic of Korea
| | - Il Soo Moon
- Department of Anatomy, Dongguk University College of Medicine, Gyeongju 38066, Korea
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7
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Evidence for aggregation-independent, PrP C-mediated Aβ cellular internalization. Proc Natl Acad Sci U S A 2020; 117:28625-28631. [PMID: 33139554 DOI: 10.1073/pnas.2009238117] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Evidence linking amyloid beta (Aβ) cellular uptake and toxicity has burgeoned, and mechanisms underlying this association are subjects of active research. Two major, interconnected questions are whether Aβ uptake is aggregation-dependent and whether it is sequence-specific. We recently reported that the neuronal uptake of Aβ depends significantly on peptide chirality, suggesting that the process is predominantly receptor-mediated. Over the past decade, the cellular prion protein (PrPC) has emerged as an important mediator of Aβ-induced toxicity and of neuronal Aβ internalization. Here, we report that the soluble, nonfibrillizing Aβ (1-30) peptide recapitulates full-length Aβ stereoselective cellular uptake, allowing us to decouple aggregation from cellular, receptor-mediated internalization. Moreover, we found that Aβ (1-30) uptake is also dependent on PrPC expression. NMR-based molecular-level characterization identified the docking site on PrPC that underlies the stereoselective binding of Aβ (1-30). Our findings therefore identify a specific sequence within Aβ that is responsible for the recognition of the peptide by PrPC, as well as PrPC-dependent cellular uptake. Further uptake stereodifferentiation in PrPC-free cells points toward additional receptor-mediated interactions as likely contributors for Aβ cellular internalization. Taken together, our results highlight the potential of targeting cellular surface receptors to inhibit Aβ cellular uptake as an alternative route for future therapeutic development for Alzheimer's disease.
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8
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Caruso G, Spampinato SF, Cardaci V, Caraci F, Sortino MA, Merlo S. β-amyloid and Oxidative Stress: Perspectives in Drug Development. Curr Pharm Des 2020; 25:4771-4781. [PMID: 31814548 DOI: 10.2174/1381612825666191209115431] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 12/04/2019] [Indexed: 01/08/2023]
Abstract
Alzheimer's Disease (AD) is a slow-developing neurodegenerative disorder in which the main pathogenic role has been assigned to β-amyloid protein (Aβ) that accumulates in extracellular plaques. The mechanism of action of Aβ has been deeply analyzed and several membrane structures have been identified as potential mediators of its effect. The ability of Aβ to modify neuronal activity, receptor expression, signaling pathways, mitochondrial function, and involvement of glial cells have been analyzed. In addition, extensive literature deals with the involvement of oxidative stress in Aβ effects. Herein we focus more specifically on the reciprocal regulation of Aβ, that causes oxidative stress, that favors Aβ aggregation and toxicity and negatively affects the peptide clearance. Analysis of this strict interaction may offer novel opportunities for therapeutic intervention. Both common and new molecules endowed with antioxidant properties deserve attention in this regard.
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Affiliation(s)
| | - Simona F Spampinato
- Department of Biomedical and Biotechnological Sciences, Section of Pharmacology, University of Catania, 95125 Catania, Italy
| | - Vincenzo Cardaci
- Scuola Superiore di Catania, University of Catania, 95123 Catania, Italy.,Department of Drug Sciences, University of Catania, 95125 Catania, Italy
| | - Filippo Caraci
- Oasi Research Institute - IRCCS, 94018 Troina, Italy.,Department of Drug Sciences, University of Catania, 95125 Catania, Italy
| | - Maria A Sortino
- Department of Biomedical and Biotechnological Sciences, Section of Pharmacology, University of Catania, 95125 Catania, Italy
| | - Sara Merlo
- Department of Biomedical and Biotechnological Sciences, Section of Pharmacology, University of Catania, 95125 Catania, Italy
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9
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Oren O, Ben Zichri S, Taube R, Jelinek R, Papo N. Aβ42 Double Mutant Inhibits Aβ42-Induced Plasma and Mitochondrial Membrane Disruption in Artificial Membranes, Isolated Organs, and Intact Cells. ACS Chem Neurosci 2020; 11:1027-1037. [PMID: 32155047 DOI: 10.1021/acschemneuro.9b00638] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Destabilization of plasma and inner mitochondrial membranes by extra- and intracellular amyloid β peptide (Aβ42) aggregates may lead to dysregulated calcium flux through the plasma membrane, mitochondrial-mediated apoptosis, and neuronal cell death in patients with Alzheimer's disease. In the current study, experiments performed with artificial membranes, isolated mitochondria, and neuronal cells allowed us to understand the mechanism by which a nonaggregating Aβ42 double mutant (designated Aβ42DM) exerts its neuroprotective effects. Specifically, we showed that Aβ42DM protected neuronal cells from Aβ42-induced accumulation of toxic intracellular levels of calcium and from apoptosis. Aβ42DM also inhibited Aβ42-induced mitochondrial membrane potential depolarization in the cells and abolished the Aβ42-mediated decrease in cytochrome c oxidase activity in purified mitochondrial particles. These results can be explained in terms of the amelioration by Aβ42DM of Aβ42-mediated changes in membrane fluidity in DOPC and cardiolipin/DOPC phospholipid vesicles, mimicking plasma and mitochondrial membranes, respectively. These observations are also in agreement with the inhibition by Aβ42DM of phospholipid-induced conformational changes in Aβ42 and with the fact that, unlike Aβ42, the Aβ42-Aβ42DM complex could not permeate into cells but instead remained attached to the cell membrane. Although most of the Aβ42DM molecules were localized on the cell membrane, some penetrated into the cytosol in an Aβ42-independent process, and, unlike Aβ42, did not form intracellular inclusion bodies. Overall, we provide a mechanistic explanation for the inhibitory activity of Aβ42DM against Aβ42-induced membrane permeability and cell toxicity and provide confirmatory evidence for its protective function in neuronal cells.
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Affiliation(s)
- Ofek Oren
- The Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences, Ben-Gurion University of the Negev, P.O. Box 653, Beer Sheva 84105, Israel
| | - Shani Ben Zichri
- Department of Chemistry, Ben-Gurion University, P.O. Box 653, Beer Sheva 84105, Israel
| | - Ran Taube
- The Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences, Ben-Gurion University of the Negev, P.O. Box 653, Beer Sheva 84105, Israel
| | - Raz Jelinek
- Department of Chemistry, Ben-Gurion University, P.O. Box 653, Beer Sheva 84105, Israel
| | - Niv Papo
- Avram and Stella Goldstein-Goren Department of Biotechnology Engineering and the National Institute of Biotechnology in the Negev, Ben-Gurion University of the Negev, P.O. Box 653, Beer Sheva 84105, Israel
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10
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Banerjee V, Oren O, Dagan B, Taube R, Engel S, Papo N. An Engineered Variant of the B1 Domain of Protein G Suppresses the Aggregation and Toxicity of Intra- and Extracellular Aβ42. ACS Chem Neurosci 2019; 10:1488-1496. [PMID: 30428260 DOI: 10.1021/acschemneuro.8b00491] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Intra- and extraneuronal deposition of amyloid β (Aβ) peptides have been linked to Alzheimer's disease (AD). While both intra- and extraneuronal Aβ deposits affect neuronal cell viability, the molecular mechanism by which these Aβ structures, especially when intraneuronal, do so is still not entirely understood. This makes the development of inhibitors challenging. To prevent the formation of toxic Aβ structural assemblies so as to prevent neuronal cell death associated with AD, we used a combination of computational and combinatorial-directed evolution approaches to develop a variant of the HTB1 protein (HTB1M2). HTB1M2 inhibits in vitro self-assembly of Aβ42 peptide and shifts the Aβ42 aggregation pathway to the formation of oligomers that are nontoxic to neuroblastoma SH-SY5Y cells overexpressing or treated with Aβ42 peptide. This makes HTB1M2 a potential therapeutic lead in the development of AD-targeted drugs and a tool for elucidating conformational changes in the Aβ42 peptide.
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Affiliation(s)
- Victor Banerjee
- Avram and Stella Goldstein-Goren Department of Biotechnology Engineering, Faculty of Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer Sheva 84105, Israel
- The National Institute for Biotechnology in the Negev, P.O. Box 653, Beer Sheva 84105, Israel
| | - Ofek Oren
- The Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Bar Dagan
- Avram and Stella Goldstein-Goren Department of Biotechnology Engineering, Faculty of Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer Sheva 84105, Israel
| | - Ran Taube
- The Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel
| | - Stanislav Engel
- The National Institute for Biotechnology in the Negev, P.O. Box 653, Beer Sheva 84105, Israel
- Department of Clinical Biochemistry, Faculty of Health Sciences, Ben-Gurion University of the Negev, P.O. Box 653, Beer Sheva 84105, Israel
| | - Niv Papo
- Avram and Stella Goldstein-Goren Department of Biotechnology Engineering, Faculty of Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer Sheva 84105, Israel
- The National Institute for Biotechnology in the Negev, P.O. Box 653, Beer Sheva 84105, Israel
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11
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Fong LK, Yang MM, Dos Santos Chaves R, Reyna SM, Langness VF, Woodruff G, Roberts EA, Young JE, Goldstein LSB. Full-length amyloid precursor protein regulates lipoprotein metabolism and amyloid-β clearance in human astrocytes. J Biol Chem 2018; 293:11341-11357. [PMID: 29858247 DOI: 10.1074/jbc.ra117.000441] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Revised: 05/11/2018] [Indexed: 02/05/2023] Open
Abstract
Mounting evidence suggests that alterations in cholesterol homeostasis are involved in Alzheimer's disease (AD) pathogenesis. Amyloid precursor protein (APP) or multiple fragments generated by proteolytic processing of APP have previously been implicated in the regulation of cholesterol metabolism. However, the physiological function of APP in regulating lipoprotein homeostasis in astrocytes, which are responsible for de novo cholesterol biosynthesis and regulation in the brain, remains unclear. To address this, here we used CRISPR/Cas9 genome editing to generate isogenic APP-knockout (KO) human induced pluripotent stem cells (hiPSCs) and differentiated them into human astrocytes. We found that APP-KO astrocytes have reduced cholesterol and elevated levels of sterol regulatory element-binding protein (SREBP) target gene transcripts and proteins, which were both downstream consequences of reduced lipoprotein endocytosis. To elucidate which APP fragments regulate cholesterol homeostasis and to examine whether familial AD mutations in APP affect lipoprotein metabolism, we analyzed an isogenic allelic series harboring the APP Swedish and APP V717F variants. Only astrocytes homozygous for the APP Swedish (APPSwe/Swe) mutation, which had reduced full-length APP (FL APP) due to increased β-secretase cleavage, recapitulated the APP-KO phenotypes. Astrocytic internalization of β-amyloid (Aβ), another ligand for low-density lipoprotein (LDL) receptors, was also impaired in APP-KO and APPSwe/Swe astrocytes. Finally, impairing cleavage of FL APP through β-secretase inhibition in APPSwe/Swe astrocytes reversed the LDL and Aβ endocytosis defects. In conclusion, FL APP is involved in the endocytosis of LDL receptor ligands and is required for proper cholesterol homeostasis and Aβ clearance in human astrocytes.
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Affiliation(s)
- Lauren K Fong
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093; Sanford Consortium for Regenerative Medicine, La Jolla, California 92093
| | - Max M Yang
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093; Sanford Consortium for Regenerative Medicine, La Jolla, California 92093
| | - Rodrigo Dos Santos Chaves
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093; Sanford Consortium for Regenerative Medicine, La Jolla, California 92093
| | - Sol M Reyna
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093; Sanford Consortium for Regenerative Medicine, La Jolla, California 92093
| | - Vanessa F Langness
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093; Sanford Consortium for Regenerative Medicine, La Jolla, California 92093
| | - Grace Woodruff
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093; Sanford Consortium for Regenerative Medicine, La Jolla, California 92093
| | - Elizabeth A Roberts
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093; Sanford Consortium for Regenerative Medicine, La Jolla, California 92093
| | - Jessica E Young
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093; Department of Pathology and Institute of Stem Cell and Regenerative Medicine, University of Washington, Seattle, Washington 98195
| | - Lawrence S B Goldstein
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, California 92093; Sanford Consortium for Regenerative Medicine, La Jolla, California 92093; Department of Neurosciences, University of California at San Diego, La Jolla, California 92093.
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12
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Role of the cell membrane interface in modulating production and uptake of Alzheimer's beta amyloid protein. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1639-1651. [PMID: 29572033 DOI: 10.1016/j.bbamem.2018.03.015] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 03/13/2018] [Accepted: 03/14/2018] [Indexed: 12/22/2022]
Abstract
The beta amyloid protein (Aβ) plays a central role in Alzheimer's disease (AD) pathogenesis and its interaction with cell membranes in known to promote mutually disruptive structural perturbations that contribute to amyloid deposition and neurodegeneration in the brain. In addition to protein aggregation at the membrane interface and disruption of membrane integrity, growing reports demonstrate an important role for the membrane in modulating Aβ production and uptake into cells. The aim of this review is to highlight and summarize recent literature that have contributed insight into the implications of altered membrane composition on amyloid precursor protein (APP) proteolysis, production of Aβ, its internalization in to cells via permeabilization and receptor mediated uptake. Here, we also review the various membrane model systems and experimental tools used for probing Aβ-membrane interactions to investigate the key mechanistic aspects underlying the accumulation and toxicity of Aβ in AD.
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Transcriptional Effects of ApoE4: Relevance to Alzheimer's Disease. Mol Neurobiol 2017; 55:5243-5254. [PMID: 28879423 DOI: 10.1007/s12035-017-0757-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Accepted: 08/24/2017] [Indexed: 10/18/2022]
Abstract
The major genetic risk factor for sporadic Alzheimer's disease (AD) is the lipid binding and transporting carrier protein apolipoprotein E, epsilon 4 allele (ApoE4). One of the unsolved mysteries of AD is how the presence of ApoE4 elicits this age-associated, currently incurable neurodegenerative disease. Recently, we showed that ApoE4 acts as a transcription factor and binds to the promoters of genes involved in a range of processes linked to aging and AD disease pathogenesis. These findings point to novel therapeutic strategies for AD and aging, resulting in an extension of human healthspan, the disease-free and functional period of life. Here, we review the effects and implications of the putative transcriptional role of ApoE4 and propose a model of Alzheimer's disease that focuses on the transcriptional nature of ApoE4 and its downstream effects, with the aim that this knowledge will help to define the role ApoE4 plays as a risk factor for AD, aging, and other processes such as inflammation and cardiovascular disease.
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Rohn TT, Moore ZD. Nuclear Localization of Apolipoprotein E4: A New Trick for an Old Protein. INTERNATIONAL JOURNAL OF NEUROLOGY AND NEUROTHERAPY 2017; 4:067. [PMID: 29264400 PMCID: PMC5734658 DOI: 10.23937/2378-3001/1410067] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
One of the most important genetic risk factors for late-onset Alzheimer's Disease (AD) is harboring the ApoE4 allele. Much is known regarding the functions of the ApoE4 protein including cholesterol transport in the CNS and a critical role in clearing beta-amyloid deposits in the AD brain. However, recent studies demonstrating the nuclear localization suggest a novel function beyond the classical known actions of ApoE4. The purpose of the current review is to examine how this secreted protein traffics to the nucleus and to discuss possible outcomes of nuclear localization in the CNS. It is suggested that proteolytic fragmentation of ApoE4 is a key step leading to nuclear localization and the outcome of this event is to initiate transcription of various genes involved in inflammation and cell death. Therefore, the nuclear localization and induction of gene expression may provide a link between harboring the ApoE4 allele and enhanced dementia risk observed in AD.
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Affiliation(s)
- Troy T Rohn
- Department of Biological Sciences, Boise State University, USA
| | - Zachary D Moore
- Department of Biological Sciences, Boise State University, USA
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15
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Kuo YC, Tsao CW. Neuroprotection against apoptosis of SK-N-MC cells using RMP-7- and lactoferrin-grafted liposomes carrying quercetin. Int J Nanomedicine 2017; 12:2857-2869. [PMID: 28435263 PMCID: PMC5391167 DOI: 10.2147/ijn.s132472] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
A drug delivery system of quercetin (QU)-encapsulated liposomes (LS) grafted with RMP-7, a bradykinin analog, and lactoferrin (Lf) was developed to permeate the blood-brain barrier (BBB) and rescue degenerated neurons, acting as an Alzheimer's disease (AD) pharmacotherapy. This colloidal formulation of QU-encapsulated LS grafted with RMP-7 and Lf (RMP-7-Lf-QU-LS) was used to traverse human brain microvascular endothelial cells (HBMECs) regulated by human astrocytes (HAs) and to treat SK-N-MC cells after an insult with cytotoxic β-amyloid (Aβ) fibrils. We found that surface RMP-7 and Lf enhanced the ability of QU to cross the BBB without inducing strong toxicity and damaging the tight junction. In addition, RMP-7-Lf-QU-LS significantly reduced Aβ-induced neurotoxicity and improved the viability of SK-N-MC cells. Compared with free QU, RMP-7-Lf-QU-LS could also significantly inhibit the expression of phosphorylated c-Jun N terminal kinase, phosphorylated p38, and phosphorylated tau protein at serine 202 by SK-N-MC cells, indicating an important role of RMP-7, Lf, and LS in protecting neurons against apoptosis. RMP-7-Lf-QU-LS is a promising carrier targeting the BBB to prevent Aβ-insulted neurodegeneration and may have potential in managing AD in future clinical applications.
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Affiliation(s)
- Yung-Chih Kuo
- Department of Chemical Engineering, National Chung Cheng University, Chia-Yi, Taiwan, Republic of China
| | - Chien-Wei Tsao
- Department of Chemical Engineering, National Chung Cheng University, Chia-Yi, Taiwan, Republic of China
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Shinohara M, Tachibana M, Kanekiyo T, Bu G. Role of LRP1 in the pathogenesis of Alzheimer's disease: evidence from clinical and preclinical studies. J Lipid Res 2017; 58:1267-1281. [PMID: 28381441 DOI: 10.1194/jlr.r075796] [Citation(s) in RCA: 169] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 04/02/2017] [Indexed: 12/16/2022] Open
Abstract
Among the LDL receptor (LDLR) family members, the roles of LDLR-related protein (LRP)1 in the pathogenesis of Alzheimer's disease (AD), especially late-onset AD, have been the most studied by genetic, neuropathological, and biomarker analyses (clinical studies) or cellular and animal model systems (preclinical studies) over the last 25 years. Although there are some conflicting reports, accumulating evidence from preclinical studies indicates that LRP1 not only regulates the metabolism of amyloid-β peptides (Aβs) in the brain and periphery, but also maintains brain homeostasis, impairment of which likely contributes to AD development in Aβ-independent manners. Several preclinical studies have also demonstrated an involvement of LRP1 in regulating the pathogenic role of apoE, whose gene is the strongest genetic risk factor for AD. Nonetheless, evidence from clinical studies is not sufficient to conclude how LRP1 contributes to AD development. Thus, despite very promising results from preclinical studies, the role of LRP1 in AD pathogenesis remains to be further clarified. In this review, we discuss the potential mechanisms underlying how LRP1 affects AD pathogenesis through Aβ-dependent and -independent pathways by reviewing both clinical and preclinical studies. We also discuss potential therapeutic strategies for AD by targeting LRP1.
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Affiliation(s)
| | | | | | - Guojun Bu
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL
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17
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Huynh TPV, Davis AA, Ulrich JD, Holtzman DM. Apolipoprotein E and Alzheimer's disease: the influence of apolipoprotein E on amyloid-β and other amyloidogenic proteins. J Lipid Res 2017; 58:824-836. [PMID: 28246336 DOI: 10.1194/jlr.r075481] [Citation(s) in RCA: 134] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2017] [Revised: 02/25/2017] [Indexed: 12/13/2022] Open
Abstract
Alzheimer's disease (AD) is one of the fastest-growing causes of death and disability in persons 65 years of age or older, affecting more than 5 million Americans alone. Clinical manifestations of AD include progressive decline in memory, executive function, language, and other cognitive domains. Research efforts within the last three decades have identified APOE as the most significant genetic risk factor for late-onset AD, which accounts for >99% of cases. The apoE protein is hypothesized to affect AD pathogenesis through a variety of mechanisms, from its effects on the blood-brain barrier, the innate immune system, and synaptic function to the accumulation of amyloid-β (Aβ). Here, we discuss the role of apoE on the biophysical properties and metabolism of the Aβ peptide, the principal component of amyloid plaques and cerebral amyloid angiopathy (CAA). CAA is characterized by the deposition of amyloid proteins (including Aβ) in the leptomeningeal medium and small arteries, which is found in most AD cases but sometimes occurs as an independent entity. Accumulation of these pathologies in the brain is one of the pathological hallmarks of AD. Beyond Aβ, we will extend the discussion to the potential role of apoE on other amyloidogenic proteins found in AD, and also a number of diverse neurodegenerative diseases.
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Affiliation(s)
- Tien-Phat V Huynh
- Department of Neurology, Hope Center for Neurological Disorders, Knight Alzheimer's Disease Research Center, Washington University, St. Louis, MO 63110
| | - Albert A Davis
- Department of Neurology, Hope Center for Neurological Disorders, Knight Alzheimer's Disease Research Center, Washington University, St. Louis, MO 63110
| | - Jason D Ulrich
- Department of Neurology, Hope Center for Neurological Disorders, Knight Alzheimer's Disease Research Center, Washington University, St. Louis, MO 63110
| | - David M Holtzman
- Department of Neurology, Hope Center for Neurological Disorders, Knight Alzheimer's Disease Research Center, Washington University, St. Louis, MO 63110
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18
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Baker-Nigh AT, Mawuenyega KG, Bollinger JG, Ovod V, Kasten T, Franklin EE, Liao F, Jiang H, Holtzman D, Cairns NJ, Morris JC, Bateman RJ. Human Central Nervous System (CNS) ApoE Isoforms Are Increased by Age, Differentially Altered by Amyloidosis, and Relative Amounts Reversed in the CNS Compared with Plasma. J Biol Chem 2016; 291:27204-27218. [PMID: 27793990 DOI: 10.1074/jbc.m116.721779] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Revised: 10/22/2016] [Indexed: 11/06/2022] Open
Abstract
The risk of Alzheimer's disease (AD) is highly dependent on apolipoprotein-E (apoE) genotype. The reasons for apoE isoform-selective risk are uncertain; however, both the amounts and structure of human apoE isoforms have been hypothesized to lead to amyloidosis increasing the risk for AD. To address the hypothesis that amounts of apoE isoforms are different in the human CNS, we developed a novel isoform-specific method to accurately quantify apoE isoforms in clinically relevant samples. The method utilizes an antibody-free enrichment step and isotope-labeled physiologically relevant lipoprotein particle standards produced by immortalized astrocytes. We applied this method to a cohort of well characterized clinical samples and observed the following findings. The apoE isoform amounts are not different in cerebrospinal fluid (CSF) from young normal controls, suggesting that the amount of apoE isoforms is not the reason for risk of amyloidosis prior to the onset of advanced age. We did, however, observe an age-related increase in both apoE isoforms. In contrast to normal aging, the presence of amyloid increased apoE3, whereas apoE4 was unchanged or decreased. Importantly, for heterozygotes, the apoE4/apoE3 isoform ratio was increased in the CNS, although the reverse was true in the periphery. Finally, CSF apoE levels, but not plasma apoE levels, correlated with CSF β-amyloid levels. Collectively, these findings support the hypothesis that CNS and peripheral apoE are separate pools and differentially regulated. Furthermore, these results suggest that apoE mechanisms for the risk of amyloidosis and AD are related to an interaction between apoE, aging, and the amount of amyloid burden.
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Affiliation(s)
| | | | | | | | | | - Erin E Franklin
- Pathology and Immunology.,Knight Alzheimer's Disease Research Center, and
| | - Fan Liao
- From the Departments of Neurology and
| | | | - David Holtzman
- From the Departments of Neurology and.,Knight Alzheimer's Disease Research Center, and.,Hope Center for Neurological Disorders, Washington University, St. Louis, Missouri 63110
| | - Nigel J Cairns
- From the Departments of Neurology and.,Pathology and Immunology.,Knight Alzheimer's Disease Research Center, and.,Hope Center for Neurological Disorders, Washington University, St. Louis, Missouri 63110
| | - John C Morris
- From the Departments of Neurology and.,Knight Alzheimer's Disease Research Center, and.,Hope Center for Neurological Disorders, Washington University, St. Louis, Missouri 63110
| | - Randall J Bateman
- From the Departments of Neurology and .,Knight Alzheimer's Disease Research Center, and.,Hope Center for Neurological Disorders, Washington University, St. Louis, Missouri 63110
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Improvement of Electroacupuncture on APP/PS1 Transgenic Mice in Spatial Learning and Memory Probably due to Expression of A β and LRP1 in Hippocampus. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2016; 2016:7603975. [PMID: 27829865 PMCID: PMC5088312 DOI: 10.1155/2016/7603975] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 08/22/2016] [Accepted: 09/05/2016] [Indexed: 11/18/2022]
Abstract
Objectives. To explore the alterations of β-amyloid (Aβ) and low density lipoprotein receptor-related protein-1 (LRP1) in APP/PS1 mice after electroacupuncture (EA) treatment and further to explore the mechanism. Methods. Forty 6-month-old APP/PS1 mice were randomly divided into a model group and an EA group, with twenty wild-type mice used as a normal control group. Mice in the EA group were treated with EA at GV 20 (băi huì) and bilateral KI 1 (yŏng quán) acupoints for 6 weeks. The Morris water maze was applied to assess the spatial memory in behavior. Immunohistochemistry (IHC), ELISA, Western blotting, and so forth were used to observe the expression of LRP1 and Aβ. Results. The Morris water maze test showed that, compared with the normal control group, the model group's learning and memory capabilities were significantly decreased (P < 0.05; P < 0.01). The EA group was reversed (P < 0.05; P < 0.01). The hippocampal expression of Aβ in the EA group was significantly decreased compared to the model group (P < 0.01). The expression of LRP1 in the model group was significantly lower than that in the normal control group (P < 0.01); the expression in the EA group was significantly higher than that in the model group (P < 0.01). Conclusions. EA therapy can improve the learning and memory capabilities of APP/PS1 mice. The underlying mechanism may lie in the upregulation of an Aβ transport receptor and LRP1.
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20
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Eugenín J, Vecchiola A, Murgas P, Arroyo P, Cornejo F, von Bernhardi R. Expression Pattern of Scavenger Receptors and Amyloid-β Phagocytosis of Astrocytes and Microglia in Culture are Modified by Acidosis: Implications for Alzheimer’s Disease. J Alzheimers Dis 2016; 53:857-73. [DOI: 10.3233/jad-160083] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Jaime Eugenín
- Laboratory of Neural Systems, Department of Biology, Faculty of Chemistry and Biology, Universidad de Santiago de Chile (USACH), Santiago, Chile
| | - Andrea Vecchiola
- Laboratory of Neuroscience, Department of Neurology, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
- Department of Endocrinology, Faculty of Medicine, Pontificia Universidad Catolica de Chile, Santiago, Chile
| | - Paola Murgas
- Laboratory of Neuroscience, Department of Neurology, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Pablo Arroyo
- Laboratory of Neuroscience, Department of Neurology, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Francisca Cornejo
- Laboratory of Neuroscience, Department of Neurology, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Rommy von Bernhardi
- Laboratory of Neuroscience, Department of Neurology, Faculty of Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile
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21
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Carroll CM, Li YM. Physiological and pathological roles of the γ-secretase complex. Brain Res Bull 2016; 126:199-206. [PMID: 27133790 DOI: 10.1016/j.brainresbull.2016.04.019] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2016] [Revised: 04/19/2016] [Accepted: 04/27/2016] [Indexed: 12/27/2022]
Abstract
Gamma-secretase (GS) is an enzyme complex that cleaves numerous substrates, and it is best known for cleaving amyloid precursor protein (APP) to form amyloid-beta (Aβ) peptides. Aberrant cleavage of APP can lead to Alzheimer's disease, so much research has been done to better understand GS structure and function in hopes of developing therapeutics for Alzheimer's. Therefore, most of the attention in this field has been focused on developing modulators that reduce pathogenic forms of Aβ while leaving Notch and other GS substrates intact, but GS provides multiple avenues of modulation that could improve AD pathology. GS has complex regulation, through its essential subunits and other associated proteins, providing other targets for AD drugs. Therapeutics can also alter GS trafficking and thereby improve cognition, or move beyond Aβ entirely, effecting Notch and neural stem cells. GS also cleaves substrates that affect synaptic morphology and function, presenting another window by which GS modulation could improve AD pathology. Taken together, GS presents a unique cross road for neural processes and an ideal target for AD therapeutics.
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Affiliation(s)
- Courtney M Carroll
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, NY, United States; Program of Neuroscience, Weill Graduate School of Medical Sciences of Cornell University, NY, United States.
| | - Yue-Ming Li
- Chemical Biology Program, Memorial Sloan Kettering Cancer Center, NY, United States; Program of Neuroscience, Weill Graduate School of Medical Sciences of Cornell University, NY, United States; Program of Pharmacology, Weill Graduate School of Medical Sciences of Cornell University, NY, United States
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22
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Xu H, Perreau VM, Dent KA, Bush AI, Finkelstein DI, Adlard PA. Iron Regulates Apolipoprotein E Expression and Secretion in Neurons and Astrocytes. J Alzheimers Dis 2016; 51:471-87. [DOI: 10.3233/jad-150797] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- He Xu
- The Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria, Australia
- The Department of Tissue Engineering, School of Fundamental Science, China Medical University, Shenyang North New Area, Shenyang, Liaoning Province, P.R. China
| | - Victoria M. Perreau
- The Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria, Australia
| | - Krista A. Dent
- The Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria, Australia
| | - Ashley I. Bush
- The Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria, Australia
| | - David I. Finkelstein
- The Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria, Australia
| | - Paul A. Adlard
- The Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria, Australia
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23
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Han SH, Park JC, Mook-Jung I. Amyloid β-interacting partners in Alzheimer's disease: From accomplices to possible therapeutic targets. Prog Neurobiol 2016; 137:17-38. [DOI: 10.1016/j.pneurobio.2015.12.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 12/02/2015] [Accepted: 12/09/2015] [Indexed: 12/20/2022]
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24
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Mitogen-activated protein kinase signaling pathways promote low-density lipoprotein receptor-related protein 1-mediated internalization of beta-amyloid protein in primary cortical neurons. Int J Biochem Cell Biol 2015; 64:252-64. [DOI: 10.1016/j.biocel.2015.04.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 03/30/2015] [Accepted: 04/21/2015] [Indexed: 01/02/2023]
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25
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Suenaga M, Furuta A, Wakabayashi K, Saibara T, Matsunaga Y. Monocytic elastase-mediated apolipoprotein-E degradation: Potential involvement of microglial elastase-like proteases in apolipoprotein-E proteolysis in brains with Alzheimers disease. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:1010-8. [PMID: 25956321 DOI: 10.1016/j.bbapap.2015.04.028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 04/09/2015] [Accepted: 04/28/2015] [Indexed: 01/07/2023]
Abstract
Impaired clearance of soluble Aβ (amyloid-β) promotes Aβ aggregation in brains with Alzheimer's disease (AD), while apolipoprotein-E (ApoE) in microglia mediates Aβ clearance. We studied the protease responsible for ApoE(4) degradation in human peripheral monocyte extracts, which are from the same lineage as microglia. We detected the hydrolytic activity for ApoE(4) in high-salt extracts with 2 M NaCl and found that the activity was inhibited by a serine protease inhibitor and an elastase-specific inhibitor, but not by other protease inhibitors. The extracts exhibited higher activity for the elastase substrate, and we followed the activity with ion-exchange and gel-filtration chromatography. Through silver staining, we partially purified a protein of 28 kDa, which was clarified as elastase by liquid chromatography-tandem mass spectrometry. These observations suggest that elastase is the key protease for ApoE(4) degradation. We also detected ApoE(4) hydrolytic activity in high-salt extracts in mouse microglial (BV-2) cell lysates, and showed that the ApoE(4) fragments by the BV-2 extracts differed from the fragments by the monocyte extracts. Though the ApoE(4) degradation by the extracts was not inhibited with elastase-specific inhibitors, it was inhibited by an elastase-specific monoclonal antibody, suggesting that elastase-like proteases in microglia differ from those of monocytes. Immunohistochemistry revealed that both elastase and ApoE were expressed in the senile plaques of brains with AD. In vitro studies also disclosed the localization of elastase in the microglial cell line, BV-2. Our results suggest that elastase-like proteases in the microglial cells surrounding Aβ plaques are responsible for ApoE degradation in the brain.
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Affiliation(s)
- Midori Suenaga
- Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Nishihama, Yamashiro-cho, Tokushima 770-8514, Japan
| | - Akiko Furuta
- Department of Cellular and Molecular Neuropathology, Juntendo University, School of Medicine, Hongo 2-1-1, Bunkyou-ku, Tokyo 113-8421, Japan
| | - Koichi Wakabayashi
- Department of Neuropathology, Institute of Brain Science, Hirosaki University, Graduate School of Medicine, 5 Zaifu-cho, Hirosaki 036-8562, Japan
| | - Toshiji Saibara
- Department of Gastroenterology and Hepatology, Kochi Medical School, Kochi University, Nankoku, Kochi 783-8505, Japan
| | - Yoichi Matsunaga
- Faculty of Pharmaceutical Sciences, Tokushima Bunri University, Nishihama, Yamashiro-cho, Tokushima 770-8514, Japan.
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26
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Cholesterol overload impairing cerebellar function: The promise of natural products. Nutrition 2015; 31:621-30. [DOI: 10.1016/j.nut.2014.10.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Revised: 10/19/2014] [Accepted: 10/21/2014] [Indexed: 11/20/2022]
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27
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Hu WT, Watts KD, Shaw LM, Howell JC, Trojanowski JQ, Basra S, Glass JD, Lah JJ, Levey AI. CSF beta-amyloid 1-42 - what are we measuring in Alzheimer's disease? Ann Clin Transl Neurol 2014; 2:131-9. [PMID: 25750918 PMCID: PMC4338954 DOI: 10.1002/acn3.160] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Revised: 11/19/2014] [Accepted: 11/11/2014] [Indexed: 01/09/2023] Open
Abstract
Objective To characterize biological and technical factors which influence cerebrospinal fluid (CSF) Alzheimer's disease (AD) biomarker levels, including the presence of apolipoprotein E (APOE) ε4 allele, AD diagnosis, Aβ-binding proteins, sample processing, and preanalytical handling. Methods CSF was collected from 140 subjects with normal cognition, mild cognitive impairment, AD, and non-AD dementia. CSF levels of beta-amyloid 1–42 (Aβ42), total Tau (t-Tau), and Tau phosphorylated at threonine 181 (p-Tau181) were analyzed following the standard and modified protocols. CSF levels of apoJ, apoE, albumin, and α-synuclein were measured in a subgroup (n = 69), and their effects on measured AD biomarker levels were also determined in vitro using human CSF samples. Results CSF Aβ42 levels measured using the AD Neuro-imaging Initiative (ADNI) protocol (which we call suspended Aβ42 or susAβ) were lower than total measurable CSF Aβ42 in all groups, and on average represents 57% of the latter. Logistic regression analysis showed this proportion (% susAβ) to be directly correlated with CSF Aβ42 and apoJ levels, but inversely correlated with CSF t-Tau levels. Finally, we showed in vitro that increasing apoE and apoJ levels directly increased % susAβ. Conclusion CSF susAβ levels are influenced by biological and technical factors, and may represent a marker of Aβ susceptible to lipoprotein-mediated clearance. Clinical trials should include total measurable Aβ42 and susAβ to better inform outcomes.
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Affiliation(s)
- William T Hu
- Department of Neurology, Emory University Atlanta, Georgia ; Center for Neurodegenerative Diseases, Emory University Atlanta, Georgia ; Alzheimer's Disease Research Center, Emory University Atlanta, Georgia
| | - Kelly D Watts
- Department of Neurology, Emory University Atlanta, Georgia ; Center for Neurodegenerative Diseases, Emory University Atlanta, Georgia
| | - Leslie M Shaw
- Department of Pathology and Laboratory Medicine, University of Pennsylvania Philadelphia, Pennsylvania
| | - Jennifer C Howell
- Department of Neurology, Emory University Atlanta, Georgia ; Center for Neurodegenerative Diseases, Emory University Atlanta, Georgia ; Alzheimer's Disease Research Center, Emory University Atlanta, Georgia
| | - John Q Trojanowski
- Department of Pathology and Laboratory Medicine, University of Pennsylvania Philadelphia, Pennsylvania
| | - Sundeep Basra
- Department of Neurology, Emory University Atlanta, Georgia ; Center for Neurodegenerative Diseases, Emory University Atlanta, Georgia
| | - Jonathan D Glass
- Department of Neurology, Emory University Atlanta, Georgia ; Center for Neurodegenerative Diseases, Emory University Atlanta, Georgia ; Alzheimer's Disease Research Center, Emory University Atlanta, Georgia
| | - James J Lah
- Department of Neurology, Emory University Atlanta, Georgia ; Center for Neurodegenerative Diseases, Emory University Atlanta, Georgia ; Alzheimer's Disease Research Center, Emory University Atlanta, Georgia
| | - Allan I Levey
- Department of Neurology, Emory University Atlanta, Georgia ; Center for Neurodegenerative Diseases, Emory University Atlanta, Georgia ; Alzheimer's Disease Research Center, Emory University Atlanta, Georgia
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Abstract
Members of the low-density lipoprotein (LDL) receptor gene family have a diverse set of biological functions that transcend lipid metabolism. Lipoprotein receptors have broad effects in both the developing and adult brain and participate in synapse development, cargo trafficking, and signal transduction. In addition, several family members play key roles in Alzheimer's disease (AD) pathogenesis and neurodegeneration. This Review summarizes our current understanding of the role lipoprotein receptors play in CNS function and AD pathology, with a special emphasis on amyloid-independent roles in endocytosis and synaptic dysfunction.
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29
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Kam TI, Gwon Y, Jung YK. Amyloid beta receptors responsible for neurotoxicity and cellular defects in Alzheimer's disease. Cell Mol Life Sci 2014; 71:4803-13. [PMID: 25151011 PMCID: PMC11113744 DOI: 10.1007/s00018-014-1706-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 07/24/2014] [Accepted: 08/13/2014] [Indexed: 01/11/2023]
Abstract
Alzheimer's disease (AD) is the most common neurodegenerative disease. Although a major cause of AD is the accumulation of amyloid-β (Aβ) peptide that induces neuronal loss and cognitive impairments, our understanding of its neurotoxic mechanisms is limited. Recent studies have identified putative Aβ-binding receptors that mediate Aβ neurotoxicity in cells and models of AD. Once Aβ interacts with a receptor, a toxic signal is transduced into neurons, resulting in cellular defects including endoplasmic reticulum stress and mitochondrial dysfunction. In addition, Aβ can also be internalized into neurons through unidentified Aβ receptors and induces malfunction of subcellular organelles, which explains some part of Aβ neurotoxicity. Understanding the neurotoxic signaling initiated by Aβ-receptor binding and cellular defects provide insight into new therapeutic windows for AD. In the present review, we summarize the findings on Aβ-binding receptors and the neurotoxicity of oligomeric Aβ.
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Affiliation(s)
- Tae-In Kam
- Global Research Laboratory, School of Biological Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 151-747 Korea
| | - Youngdae Gwon
- Global Research Laboratory, School of Biological Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 151-747 Korea
| | - Yong-Keun Jung
- Global Research Laboratory, School of Biological Sciences, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 151-747 Korea
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Kanekiyo T, Bu G. The low-density lipoprotein receptor-related protein 1 and amyloid-β clearance in Alzheimer's disease. Front Aging Neurosci 2014; 6:93. [PMID: 24904407 PMCID: PMC4033011 DOI: 10.3389/fnagi.2014.00093] [Citation(s) in RCA: 188] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 04/28/2014] [Indexed: 11/24/2022] Open
Abstract
Accumulation and aggregation of amyloid-β (Aβ) peptides in the brain trigger the development of progressive neurodegeneration and dementia associated with Alzheimer’s disease (AD). Perturbation in Aβ clearance, rather than Aβ production, is likely the cause of sporadic, late-onset AD, which accounts for the majority of AD cases. Since cellular uptake and subsequent degradation constitute a major Aβ clearance pathway, the receptor-mediated endocytosis of Aβ has been intensely investigated. Among Aβ receptors, the low-density lipoprotein receptor-related protein 1 (LRP1) is one of the most studied receptors. LRP1 is a large endocytic receptor for more than 40 ligands, including apolipoprotein E, α2-macroglobulin and Aβ. Emerging in vitro and in vivo evidence demonstrates that LRP1 is critically involved in brain Aβ clearance. LRP1 is highly expressed in a variety of cell types in the brain including neurons, vascular cells and glial cells, where LRP1 functions to maintain brain homeostasis and control Aβ metabolism. LRP1-mediated endocytosis regulates cellular Aβ uptake by binding to Aβ either directly or indirectly through its co-receptors or ligands. Furthermore, LRP1 regulates several signaling pathways, which also likely influences Aβ endocytic pathways. In this review, we discuss how LRP1 regulates the brain Aβ clearance and how this unique endocytic receptor participates in AD pathogenesis. Understanding of the mechanisms underlying LRP1-mediated Aβ clearance should enable the rational design of novel diagnostic and therapeutic strategies for AD.
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Affiliation(s)
| | - Guojun Bu
- Department of Neuroscience, Mayo Clinic, Jacksonville FL, USA
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31
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Kanekiyo T, Xu H, Bu G. ApoE and Aβ in Alzheimer's disease: accidental encounters or partners? Neuron 2014; 81:740-54. [PMID: 24559670 DOI: 10.1016/j.neuron.2014.01.045] [Citation(s) in RCA: 432] [Impact Index Per Article: 43.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/21/2014] [Indexed: 12/26/2022]
Abstract
Among the three human apolipoprotein E (apoE) isoforms, apoE4 increases the risk of Alzheimer's disease (AD). While transporting cholesterol is a primary function, apoE also regulates amyloid-β (Aβ) metabolism, aggregation, and deposition. Although earlier work suggests that different affinities of apoE isoforms to Aβ might account for their effects on Aβ clearance, recent studies indicate that apoE also competes with Aβ for cellular uptake through apoE receptors. Thus, several factors probably determine the variable effects apoE has on Aβ. In this Review, we examine biochemical, structural, and functional studies and propose testable models that address the complex mechanisms underlying apoE-Aβ interaction and how apoE4 may increase AD risk and also serve as a target pathway for therapy.
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Affiliation(s)
- Takahisa Kanekiyo
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA
| | - Huaxi Xu
- Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, College of Medicine, Xiamen University, Xiamen 361005, China
| | - Guojun Bu
- Department of Neuroscience, Mayo Clinic, Jacksonville, FL 32224, USA; Fujian Provincial Key Laboratory of Neurodegenerative Disease and Aging Research, College of Medicine, Xiamen University, Xiamen 361005, China.
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Schmidt V, Carlo AS, Willnow TE. Apolipoprotein E receptor pathways in Alzheimer disease. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2014; 6:255-70. [PMID: 24604742 DOI: 10.1002/wsbm.1262] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Revised: 12/31/2013] [Accepted: 01/03/2014] [Indexed: 11/07/2022]
Abstract
UNLABELLED Alzheimer disease (AD) is the most common neurodegenerative disease affecting millions of patients worldwide. According to the amyloid cascade hypothesis, the formation of neurotoxic oligomers composed of amyloid-β (Aβ) peptides is the main mechanism that causes synaptic dysfunction and, eventually, neuronal cell death in this condition. Intriguingly, apolipoprotein E (apoE), the most important genetic risk factor for sporadic AD, emerges as a key factor that contributes to many aspects of the amyloid cascade including the clearance of Aβ from brain interstitial fluid and the ability of this peptide to form neurotoxic oligomers. Central to the activity of apoE in the healthy and in the diseased brain are apoE receptors that interact with this protein to mediate its multiple cellular and systemic effects. This review describes the molecular interactions that link apoE and its cellular receptors with neuronal viability and function, and how defects in these pathways in the brain promote neurodegeneration. For further resources related to this article, please visit the WIREs website. CONFLICT OF INTEREST The authors have declared no conflicts of interest for this article.
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Affiliation(s)
- Vanessa Schmidt
- Max-Delbrueck-Center for Molecular Medicine, Berlin, Germany
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Rohn TT, McCarty KL, Love JE, Head E. Is Apolipoprotein E4 an Important Risk Factor for Dementia in Persons with Down Syndrome? ACTA ACUST UNITED AC 2014; 1. [PMID: 25594074 DOI: 10.13188/2376-922x.1000004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Down syndrome is one of the most common genetic causes of intellectual disability and is characterized by a number of behavioral as well as cognitive symptoms. Triplication of all or part of human chromosome 21 has been considered as the main cause of Down syndrome. Due to the location of the amyloid precursor protein on chromosome 21, many of the neuropathological features of early-onset Alzheimer's disease including senile plaques and neurofibrillary tangles are also present in Down syndrome patients who are either demented or nondemented. Significant advances in medical treatment have increased longevity in people with Down syndrome resulting in an increased population that may be subjected to many of the same risk factors as those with Alzheimer's disease. It is well established that harboring one or both apolipoprotein E4 alleles greatly increases the risk for Alzheimer's disease. However, whether apolipoprotein E4 contributes to an earlier onset of dementia or increased mortality in Down syndrome patients is still a matter of debate. The purpose of this mini review is to provide an updated assessment on apolipoprotein E4 status and risk potential of developing dementia and mortality associated with Down syndrome.
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Affiliation(s)
- Troy T Rohn
- Department of Biological Sciences, Science Building, Boise State University, USA
| | - Katie L McCarty
- University of Kentucky, Department of Pharmacology & Nutritional Sciences, Sanders-Brown Center on Aging, Lexington, KY
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Abstract
In the brain, apolipoprotein E (APOE) delivers cholesterol-rich lipoproteins to neurons to support synaptogenesis and maintenance of synaptic connections. Three APOE alleles exist in the human population with ε4 being an Alzheimer disease (AD) risk gene and ε2 being protective relative to the common ε3 variant. Many hypotheses have been advanced concerning allele-specific effects of APOE on neurodegeneration including effects on Aβ clearance, synaptic transmission, or neurotoxicity. Central to most proposed APOE functions is its interaction with receptors that mediate cellular uptake of this ligand. Several members of the LDL receptor gene family have been implicated as APOE receptors in the (patho)physiology of APOE in the brain, yet their specific modes of action in AD remain controversial. Recently, the pro-neurotrophin receptor sortilin has been identified as a novel APOE receptor in neurons. Ablation of sortilin expression in mice results in accumulation of APOE and Aβ in the brain. Moreover, primary neurons lacking sortilin exhibit significantly impaired uptake of APOE/Aβ complexes. Despite increased brain APOE levels, sortilin-deficient animals recapitulate anomalies in brain lipid homeostasis seen in APOE null mice, indicating functional deficiency in APOE uptake pathways. Taken together, these findings suggest a link between Aβ catabolism and pro-neurotrophin signaling converging on this receptor pathway.
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35
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Holtzman DM, Herz J, Bu G. Apolipoprotein E and apolipoprotein E receptors: normal biology and roles in Alzheimer disease. Cold Spring Harb Perspect Med 2013; 2:a006312. [PMID: 22393530 DOI: 10.1101/cshperspect.a006312] [Citation(s) in RCA: 578] [Impact Index Per Article: 52.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Apolipoprotein E (APOE) genotype is the major genetic risk factor for Alzheimer disease (AD); the ε4 allele increases risk and the ε2 allele is protective. In the central nervous system (CNS), apoE is produced by glial cells, is present in high-density-like lipoproteins, interacts with several receptors that are members of the low-density lipoprotein receptor (LDLR) family, and is a protein that binds to the amyloid-β (Aβ) peptide. There are a variety of mechanisms by which apoE isoform may influence risk for AD. There is substantial evidence that differential effects of apoE isoform on AD risk are influenced by the ability of apoE to affect Aβ aggregation and clearance in the brain. Other mechanisms are also likely to play a role in the ability of apoE to influence CNS function as well as AD, including effects on synaptic plasticity, cell signaling, lipid transport and metabolism, and neuroinflammation. ApoE receptors, including LDLRs, Apoer2, very low-density lipoprotein receptors (VLDLRs), and lipoprotein receptor-related protein 1 (LRP1) appear to influence both the CNS effects of apoE as well as Aβ metabolism and toxicity. Therapeutic strategies based on apoE and apoE receptors may include influencing apoE/Aβ interactions, apoE structure, apoE lipidation, LDLR receptor family member function, and signaling. Understanding the normal and disease-related biology connecting apoE, apoE receptors, and AD is likely to provide novel insights into AD pathogenesis and treatment.
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Affiliation(s)
- David M Holtzman
- Department of Neurology, Alzheimer's Disease Research Center, Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
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36
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Proteolytic cleavage of apolipoprotein E4 as the keystone for the heightened risk associated with Alzheimer's disease. Int J Mol Sci 2013; 14:14908-22. [PMID: 23867607 PMCID: PMC3742279 DOI: 10.3390/ijms140714908] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 06/26/2013] [Accepted: 07/12/2013] [Indexed: 11/20/2022] Open
Abstract
Alzheimer’s disease (AD) is a progressive neurodegenerative disease characterized by microscopic lesions consisting of beta-amyloid plaques and neurofibrillary tangles (NFTs). The majority of cases are defined as sporadic and are likely caused by a combination of both genetic and environmental factors. Of the genetic risk factors identified, the 34 kDa protein, apolipoprotein (apo) E4, is of significant importance as APOE4 carriers account for 65%–80% of all AD cases. Although apoE4 plays a normal role in lipoprotein transport, how it contributes to AD pathogenesis is currently unknown. One potential mechanism by which apoE4 contributes to disease risk is its propensity to undergo proteolytic cleavage generating N- and C-terminal fragments. The purpose of this review will be to examine the mechanisms by which apoE4 contributes to AD pathogenesis focusing on the potential loss or gain of function that may occur following cleavage of the full-length protein. In this context, a discussion of whether targeting apoE4 therapeutically is a rationale approach to treating this disease will be assessed.
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37
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The cell biology of prion-like spread of protein aggregates: mechanisms and implication in neurodegeneration. Biochem J 2013; 452:1-17. [DOI: 10.1042/bj20121898] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The misfolding and aggregation of specific proteins is a common hallmark of many neurodegenerative disorders, including highly prevalent illnesses such as Alzheimer's and Parkinson's diseases, as well as rarer disorders such as Huntington's and prion diseases. Among these, only prion diseases are ‘infectious’. By seeding misfolding of the PrPC (normal conformer prion protein) into PrPSc (abnormal disease-specific conformation of prion protein), prions spread from the periphery of the body to the central nervous system and can also be transmitted between individuals of the same or different species. However, recent exciting data suggest that the transmissibility of misfolded proteins within the brain is a property that goes way beyond the rare prion diseases. Evidence indicates that non-prion aggregates [tau, α-syn (α-synuclein), Aβ (amyloid-β) and Htt (huntingtin) aggregates] can also move between cells and seed the misfolding of their normal conformers. These findings have enormous implications. On the one hand they question the therapeutical use of transplants, and on the other they indicate that it may be possible to bring these diseases to an early arrest by preventing cell-to-cell transmission. To better understand the prion-like spread of these protein aggregates it is essential to identify the underlying cellular and molecular factors. In the present review we analyse and discuss the evidence supporting prion-like spreading of amyloidogenic proteins, especially focusing on the cellular and molecular mechanisms and their significance.
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38
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Martiskainen H, Haapasalo A, Kurkinen KMA, Pihlajamäki J, Soininen H, Hiltunen M. Targeting ApoE4/ApoE receptor LRP1 in Alzheimer's disease. Expert Opin Ther Targets 2013; 17:781-94. [PMID: 23573918 DOI: 10.1517/14728222.2013.789862] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
INTRODUCTION Progressive neuronal loss is a key feature in Alzheimer's disease (AD), which is the most common neurodegenerative disorder in the aging population. Currently, there are no therapeutic means to intervene neuronal damage in AD and therefore innovative approaches to discover novel strategies for the treatment of AD are needed. Based on the prevailing amyloid cascade hypothesis, it is conceivable that lowering the β-amyloid (Aβ) levels is sufficient to slow down the disease process, if started early enough. AREAS COVERED Here, we review genetic and biological functions related to apolipoprotein E (ApoE) and low-density lipoprotein receptor-related protein 1 receptor (LRP1)-mediated clearance of Aβ. Furthermore, we discuss the AD-related therapeutic potential of targeting to ApoE receptor LRP1 at the blood-brain barrier (BBB) and in the periphery. EXPERT OPINION Due to the recent setbacks in the clinical trials targeting AD, it is instrumental to seek alternative therapeutic approaches, which aim to reduce the accumulation of Aβ in the brain tissue. As the ApoE/LRP1-mediated clearance of Aβ across the BBB is the key event in the regulation of Aβ transcytosis from brain to periphery, direct targeting of this protein entity at the BBB holds a great potential in the treatment of AD.
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Affiliation(s)
- Henna Martiskainen
- Kuopio University Hospital, Institute of Clinical Medicine-Neurology, University of Eastern Finland and Department of Neurology, Kuopio, Finland
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Kuszczyk MA, Sanchez S, Pankiewicz J, Kim J, Duszczyk M, Guridi M, Asuni AA, Sullivan PM, Holtzman DM, Sadowski MJ. Blocking the interaction between apolipoprotein E and Aβ reduces intraneuronal accumulation of Aβ and inhibits synaptic degeneration. THE AMERICAN JOURNAL OF PATHOLOGY 2013; 182:1750-68. [PMID: 23499462 DOI: 10.1016/j.ajpath.2013.01.034] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 01/15/2013] [Accepted: 01/17/2013] [Indexed: 01/09/2023]
Abstract
Accumulation of β-amyloid (Aβ) in the brain is a key event in Alzheimer disease pathogenesis. Apolipoprotein (Apo) E is a lipid carrier protein secreted by astrocytes, which shows inherent affinity for Aβ and has been implicated in the receptor-mediated Aβ uptake by neurons. To characterize ApoE involvement in the intraneuronal Aβ accumulation and to investigate whether blocking the ApoE/Aβ interaction could reduce intraneuronal Aβ buildup, we used a noncontact neuronal-astrocytic co-culture system, where synthetic Aβ peptides were added into the media without or with cotreatment with Aβ12-28P, which is a nontoxic peptide antagonist of ApoE/Aβ binding. Compared with neurons cultured alone, intraneuronal Aβ content was significantly increased in neurons co-cultured with wild-type but not with ApoE knockout (KO) astrocytes. Neurons co-cultured with astrocytes also showed impaired intraneuronal degradation of Aβ, increased level of intraneuronal Aβ oligomers, and marked down-regulation of several synaptic proteins. Aβ12-28P treatment significantly reduced intraneuronal Aβ accumulation, including Aβ oligomer level, and inhibited loss of synaptic proteins. Furthermore, we showed significantly reduced intraneuronal Aβ accumulation in APPSW/PS1dE9/ApoE KO mice compared with APPSW/PS1dE9/ApoE targeted replacement mice that expressed various human ApoE isoforms. Data from our co-culture and in vivo experiments indicate an essential role of ApoE in the mechanism of intraneuronal Aβ accumulation and provide evidence that ApoE/Aβ binding antagonists can effectively prevent this process.
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Affiliation(s)
- Magdalena A Kuszczyk
- Department of Neurology, New York University School of Medicine, New York, NY 10016, USA
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The pro-neurotrophin receptor sortilin is a major neuronal apolipoprotein E receptor for catabolism of amyloid-β peptide in the brain. J Neurosci 2013; 33:358-70. [PMID: 23283348 DOI: 10.1523/jneurosci.2425-12.2013] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Apolipoprotein E (APOE) is the major risk factor for sporadic Alzheimer's disease. Among other functions, APOE is proposed to sequester neurotoxic amyloid-β (Aβ) peptides in the brain, delivering them to cellular catabolism via neuronal APOE receptors. Still, the receptors involved in this process remain controversial. Here, we identified the pro-neurotrophin receptor sortilin as major endocytic pathway for clearance of APOE/Aβ complexes in neurons. Sortilin binds APOE with high affinity. Lack of receptor expression in mice results in accumulation of APOE and of Aβ in the brain and in aggravated plaque burden. Also, primary neurons lacking sortilin exhibit significantly impaired uptake of APOE/Aβ complexes despite proper expression of other APOE receptors. Despite higher than normal brain APOE levels, sortilin-deficient animals display anomalies in brain lipid metabolism (e.g., accumulation of sulfatides) seen in APOE-deficient mice, indicating functional deficiency in cellular APOE uptake pathways. Together, our findings identified sortilin as an essential neuronal pathway for APOE-containing lipoproteins in vivo and suggest an intriguing link between Aβ catabolism and pro-neurotrophin signaling converging on this receptor.
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Takahashi RH, Capetillo-Zarate E, Lin MT, Milner TA, Gouras GK. Accumulation of intraneuronal β-amyloid 42 peptides is associated with early changes in microtubule-associated protein 2 in neurites and synapses. PLoS One 2013; 8:e51965. [PMID: 23372648 PMCID: PMC3553177 DOI: 10.1371/journal.pone.0051965] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2012] [Accepted: 11/09/2012] [Indexed: 11/19/2022] Open
Abstract
Pathologic aggregation of β-amyloid (Aβ) peptide and the axonal microtubule-associated protein tau protein are hallmarks of Alzheimer's disease (AD). Evidence supports that Aβ peptide accumulation precedes microtubule-related pathology, although the link between Aβ and tau remains unclear. We previously provided evidence for early co-localization of Aβ42 peptides and hyperphosphorylated tau within postsynaptic terminals of CA1 dendrites in the hippocampus of AD transgenic mice. Here, we explore the relation between Aβ peptide accumulation and the dendritic, microtubule-associated protein 2 (MAP2) in the well-characterized amyloid precursor protein Swedish mutant transgenic mouse (Tg2576). We provide evidence that localized intraneuronal accumulation of Aβ42 peptides is spatially associated with reductions of MAP2 in dendrites and postsynaptic compartments of Tg2576 mice at early ages. Our data support that reduction in MAP2 begins at sites of Aβ42 monomer and low molecular weight oligomer (M/LMW) peptide accumulation. Cumulative evidence suggests that accumulation of M/LMW Aβ42 peptides occurs early, before high molecular weight oligomerization and plaque formation. Since synaptic alteration is the best pathologic correlate of cognitive dysfunction in AD, the spatial association of M/LMW Aβ peptide accumulation with pathology of MAP2 within neuronal processes and synaptic compartments early in the disease process reinforces the importance of intraneuronal Aβ accumulation in AD pathogenesis.
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Affiliation(s)
- Reisuke H. Takahashi
- Department of Anatomic Pathology, Tokyo Medical University, Tokyo, Japan
- Department of Neurology and Neuroscience, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail: (RHT); (GKG)
| | - Estibaliz Capetillo-Zarate
- Department of Neurology and Neuroscience, Weill Cornell Medical College, New York, New York, United States of America
| | - Michael T. Lin
- Department of Neurology and Neuroscience, Weill Cornell Medical College, New York, New York, United States of America
| | - Teresa A. Milner
- Department of Neurology and Neuroscience, Weill Cornell Medical College, New York, New York, United States of America
- Laboratory of Neuroendocrinology, The Rockefeller University, New York, New York, United States of America
| | - Gunnar K. Gouras
- Department of Neurology and Neuroscience, Weill Cornell Medical College, New York, New York, United States of America
- Wallenberg Neuroscience Center, Department of Experimental Medical Science, Lund University, Lund, Sweden
- * E-mail: (RHT); (GKG)
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42
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Russell CL, Semerdjieva S, Empson RM, Austen BM, Beesley PW, Alifragis P. Amyloid-β acts as a regulator of neurotransmitter release disrupting the interaction between synaptophysin and VAMP2. PLoS One 2012; 7:e43201. [PMID: 22905234 PMCID: PMC3419646 DOI: 10.1371/journal.pone.0043201] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Accepted: 07/18/2012] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND It is becoming increasingly evident that deficits in the cortex and hippocampus at early stages of dementia in Alzheimer's disease (AD) are associated with synaptic damage caused by oligomers of the toxic amyloid-β peptide (Aβ42). However, the underlying molecular and cellular mechanisms behind these deficits are not fully understood. Here we provide evidence of a mechanism by which Aβ42 affects synaptic transmission regulating neurotransmitter release. METHODOLOGY/FINDINGS We first showed that application of 50 nM Aβ42 in cultured neurones is followed by its internalisation and translocation to synaptic contacts. Interestingly, our results demonstrate that with time, Aβ42 can be detected at the presynaptic terminals where it interacts with Synaptophysin. Furthermore, data from dissociated hippocampal neurons as well as biochemical data provide evidence that Aβ42 disrupts the complex formed between Synaptophysin and VAMP2 increasing the amount of primed vesicles and exocytosis. Finally, electrophysiology recordings in brain slices confirmed that Aβ42 affects baseline transmission. CONCLUSIONS/SIGNIFICANCE Our observations provide a necessary and timely insight into cellular mechanisms that underlie the initial pathological events that lead to synaptic dysfunction in Alzheimer's disease. Our results demonstrate a new mechanism by which Aβ42 affects synaptic activity.
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Affiliation(s)
- Claire L. Russell
- School of Biological Sciences, Royal Holloway University London, Surrey, United Kingdom
| | - Sophia Semerdjieva
- School of Biological Sciences, Royal Holloway University London, Surrey, United Kingdom
| | - Ruth M. Empson
- School of Biological Sciences, Royal Holloway University London, Surrey, United Kingdom
- Department of Physiology, University of Otago School of Medical Sciences, Dunedin, New Zealand
| | - Brian M. Austen
- Neurodegeneration Unit, Basic Medical Sciences, St George’s, University of London, Cranmer Terrace, London, United Kingdom
| | - Philip W. Beesley
- School of Biological Sciences, Royal Holloway University London, Surrey, United Kingdom
| | - Pavlos Alifragis
- School of Biological Sciences, Royal Holloway University London, Surrey, United Kingdom
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Viana RJS, Nunes AF, Rodrigues CMP. Endoplasmic reticulum enrollment in Alzheimer's disease. Mol Neurobiol 2012; 46:522-34. [PMID: 22815194 DOI: 10.1007/s12035-012-8301-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Accepted: 07/05/2012] [Indexed: 12/26/2022]
Abstract
Alzheimer's disease (AD) poses a huge challenge for society and health care worldwide as molecular pathogenesis of the disease is poorly understood and curative treatment does not exist. The mechanisms leading to accelerated neuronal cell death in AD are still largely unknown, but accumulation of misfolded disease-specific proteins has been identified as potentially involved. In the present review, we describe the essential role of endoplasmic reticulum (ER) in AD. Despite the function that mitochondria may play as the central major player in the apoptotic process, accumulating evidence highlights ER as a critical organelle in AD. Stress that impairs ER physiology leads to accumulation of unfolded or misfolded proteins, such as amyloid β (Aβ) peptide, the major component of amyloid plaques. In an attempt to ameliorate the accumulation of unfolded proteins, ER stress triggers a protective cellular mechanism, which includes the unfolded protein response (UPR). However, when activation of the UPR is severe or prolonged enough, the final cellular outcome is pathologic apoptotic cell death. Distinct pathways can be activated in this process, involving stress sensors such as the JNK pathway or ER chaperones such as Bip/GRP94, stress modulators such as Bcl-2 family proteins, or even stress effectors such as caspase-12. Here, we detail the involvement of the ER and associated stress pathways in AD and discuss potential therapeutic strategies targeting ER stress.
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Affiliation(s)
- Ricardo J S Viana
- Research Institute for Medicines and Pharmaceutical Sciences, University of Lisbon, Lisbon 1649-003, Portugal
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44
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Omtri RS, Davidson MW, Arumugam B, Poduslo JF, Kandimalla KK. Differences in the cellular uptake and intracellular itineraries of amyloid beta proteins 40 and 42: ramifications for the Alzheimer's drug discovery. Mol Pharm 2012; 9:1887-97. [PMID: 22574751 DOI: 10.1021/mp200530q] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Mounting evidence suggests that the pathological hallmarks of Alzheimer's disease (AD), neurofibrillary tangles and parenchymal amyloid plaques, are downstream reflections of neurodegeneration caused by the intraneuronal accumulation of amyloid-β proteins (Aβ), particularly Aβ42 and Aβ40. While the neurotoxicity of more amyloidogenic but less abundant Aβ42 is well documented, the effect of Aβ40 on neurons has been understudied. The Aβ40 expression in the presymptomatic AD brain is ten times greater than that of Aβ42. However, the Aβ40:42 ratio decreases with AD progression and coincides with increased amyloid plaque deposition in the brain. Hence, it is thought that Aβ40 protects neurons from the deleterious effects of Aβ42. The pathophysiological pathways involved in the neuronal uptake of Aβ40 or Aβ42 have not been clearly elucidated. Lack of such critical information obscures therapeutic targets and thwarts rational drug development strategies aimed at preventing neurodegeneration in AD. The current study has shown that fluorescein labeled Aβ42 (F-Aβ42) is internalized by neurons via dynamin dependent endocytosis and is sensitive to membrane cholesterol, whereas the neuronal uptake of F-Aβ40 is energy independent and nonendocytotic. Following their uptake, both F-Aβ40 and F-Aβ42 did not accumulate in early/recycling endosomes; F-Aβ42 but not F-Aβ40 accumulated in late endosomes and in the vesicles harboring caveolin-1. Furthermore, F-Aβ42 demonstrated robust accumulation in the lysosomes and damaged their integrity, whereas F-Aβ40 showed only a sparse lysosomal accumulation. Such regulated trafficking along distinct pathways suggests that Aβ40 and Aβ42 exercise differential effects on neurons. These differences must be carefully considered in the design of a pharmacological agent intended to block the neurodegeneration triggered by Aβ proteins.
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Affiliation(s)
- Rajesh S Omtri
- Division of Basic Pharmaceutical Sciences, Florida A&M University College of Pharmacy and Pharmaceutical Sciences, Tallahassee, Florida, United States
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Posse de Chaves E. Reciprocal regulation of cholesterol and beta amyloid at the subcellular level in Alzheimer's disease. Can J Physiol Pharmacol 2012; 90:753-64. [PMID: 22626060 DOI: 10.1139/y2012-076] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Since the discovery that apolipoprotein E, a cholesterol transport protein, is a major risk factor for Alzheimer's disease (AD) development, there has been a remarkable interest in understanding the many facets of the relationship between cholesterol and AD. Several lines of evidence have demonstrated the importance of cholesterol in amyloid beta peptide (Aβ) production and metabolism, as well as the involvement of Aβ in cholesterol homeostasis. The emerging picture is complex and still incomplete. This review discusses findings that indicate that a reciprocal regulation exists between Aβ and cholesterol at the subcellular level. The pathological impact of such regulation is highlighted.
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Affiliation(s)
- Elena Posse de Chaves
- Department of Pharmacology, 9-31 Medical Sciences Building, University of Alberta, Edmonton, AB T6G 2H7, Canada.
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Reddy PH. Abnormal tau, mitochondrial dysfunction, impaired axonal transport of mitochondria, and synaptic deprivation in Alzheimer's disease. Brain Res 2011; 1415:136-48. [PMID: 21872849 DOI: 10.1016/j.brainres.2011.07.052] [Citation(s) in RCA: 199] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2011] [Revised: 07/20/2011] [Accepted: 07/26/2011] [Indexed: 01/01/2023]
Abstract
Growing evidence suggests that amyloid beta (Aβ) and tau pathologies are strongly associated with mitochondrial dysfunction and neuronal damage in Alzheimer's disease (AD). Extensive research of AD postmortem brains, mouse and fly models, including triple transgenic AD mice and mutant tau mice, and cell culture studies revealed that tau hyperphosphorylation is caused by multiple factors, including intraneuronal Aβ-oligomers, chronic oxidative stress, reduced insulin-like growth factor 1, and astrocytic mediated-Aβ and caspase activation. Overexpressed and phosphorylated tau appears to impair axonal transport of organelles causing synapse starvation, depletion of ATP, and ultimately neuronal damage. This article evaluates the role of tau in mitochondrial dysfunction and assesses how hyperphosphorylated tau impairs axonal transport of organelles in AD neurons.
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Affiliation(s)
- P Hemachandra Reddy
- Neurogenetics Laboratory, Division of Neuroscience, Oregon National Primate Research Center, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, OR 97006, USA.
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Pfrieger FW, Ungerer N. Cholesterol metabolism in neurons and astrocytes. Prog Lipid Res 2011; 50:357-71. [PMID: 21741992 DOI: 10.1016/j.plipres.2011.06.002] [Citation(s) in RCA: 332] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 06/11/2011] [Accepted: 06/22/2011] [Indexed: 12/20/2022]
Abstract
Cells in the mammalian body must accurately maintain their content of cholesterol, which is an essential membrane component and precursor for vital signalling molecules. Outside the brain, cholesterol homeostasis is guaranteed by a lipoprotein shuttle between the liver, intestine and other organs via the blood circulation. Cells inside the brain are cut off from this circuit by the blood-brain barrier and must regulate their cholesterol content in a different manner. Here, we review how this is accomplished by neurons and astrocytes, two cell types of the central nervous system, whose cooperation is essential for normal brain development and function. The key observation is a remarkable cell-specific distribution of proteins that mediate different steps of cholesterol metabolism. This form of metabolic compartmentalization identifies astrocytes as net producers of cholesterol and neurons as consumers with unique means to prevent cholesterol overload. The idea that cholesterol turnover in neurons depends on close cooperation with astrocytes raises new questions that need to be addressed by new experimental approaches to monitor and manipulate cholesterol homeostasis in a cell-specific manner. We conclude that an understanding of cholesterol metabolism in the brain and its role in disease requires a close look at individual cell types.
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Affiliation(s)
- Frank W Pfrieger
- CNRS UPR 3212, University of Strasbourg, Institute of Cellular and Integrative Neurosciences (INCI), 67084 Strasbourg Cedex, France.
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Axelsen PH, Komatsu H, Murray IVJ. Oxidative stress and cell membranes in the pathogenesis of Alzheimer's disease. Physiology (Bethesda) 2011; 26:54-69. [PMID: 21357903 DOI: 10.1152/physiol.00024.2010] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Amyloid β proteins and oxidative stress are believed to have central roles in the development of Alzheimer's disease. Lipid membranes are among the most vulnerable cellular components to oxidative stress, and membranes in susceptible regions of the brain are compositionally distinct from those in other tissues. This review considers the evidence that membranes are either a source of neurotoxic lipid oxidation products or the target of pathogenic processes involving amyloid β proteins that cause permeability changes or ion channel formation. Progress toward a comprehensive theory of Alzheimer's disease pathogenesis is discussed in which lipid membranes assume both roles and promote the conversion of monomeric amyloid β proteins into fibrils, the pathognomonic histopathological lesion of the disease.
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Affiliation(s)
- Paul H Axelsen
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
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Fujiyoshi M, Tachikawa M, Ohtsuki S, Ito S, Uchida Y, Akanuma SI, Kamiie J, Hashimoto T, Hosoya KI, Iwatsubo T, Terasaki T. Amyloid-β peptide(1-40) elimination from cerebrospinal fluid involves low-density lipoprotein receptor-related protein 1 at the blood-cerebrospinal fluid barrier. J Neurochem 2011; 118:407-15. [PMID: 21585370 DOI: 10.1111/j.1471-4159.2011.07311.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Amyloid-β peptide (Aβ) concentration in CSF is potentially a diagnostic and therapeutic target for Alzheimer's disease (AD). The purpose of this study was to clarify the elimination mechanism of human Aβ(1-40) [hAβ (1-40)] from CSF. After intracerebroventricular (ICV) administration, [(125) I]hAβ(1-40) was eliminated from the rat CSF with a half-life of 17.3 min. The elimination of [(125) I]hAβ(1-40) was significantly inhibited by human receptor-associated protein (RAP) and the elimination was attenuated in either anti-low-density lipoprotein receptor-related protein (LRP)1 antibody-treated or RAP-deficient mice, suggesting that a member(s) of the low-density lipoprotein receptor gene family is involved in the elimination of hAβ(1-40) from CSF. The amounts of LRP1 and LRP2 proteins were determined by means of liquid chromatography-tandem mass spectrometry, and the LRP1 content in rat choroid plexus was determined to be 3.7 fmol/μg protein, whereas the LRP2 content was below the detection limit (<0.2 fmol/μg protein). Conditionally, immortalized rat choroid plexus epithelial cells exhibited predominant apical-to-basal and apical-to-cell transport of [(125) I]hAβ(1-40). These results indicated that hAβ(1-40) is actively eliminated from CSF and this process is at least partly mediated by LRP1 expressed at choroid plexus epithelial cells, which therefore play a role in determining CSF concentrations of hAβ(1-40).
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Affiliation(s)
- Masachika Fujiyoshi
- Division of Membrane Transport and Drug Targeting, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
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Association of ApoE and LRP mRNA levels with dementia and AD neuropathology. Neurobiol Aging 2011; 33:628.e1-628.e14. [PMID: 21676498 DOI: 10.1016/j.neurobiolaging.2011.04.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Revised: 03/21/2011] [Accepted: 04/29/2011] [Indexed: 11/21/2022]
Abstract
Inheritance of the ε4 allele of apolipoprotein E (ApoE) is the only confirmed and consistently replicated risk factor for late onset Alzheimer's disease (AD). ApoE is also a key ligand for low-density lipoprotein (LDL) receptor-related protein (LRP), a major neuronal low-density lipoprotein receptor. Despite the considerable converging evidence that implicates ApoE and LRP in the pathogenesis of AD, the precise mechanism by which ApoE and LRP modulate the risk for AD remains elusive. Moreover, studies investigating expression of ApoE and LRP in AD brain have reported variable and contradictory results. To overcome these inconsistencies, we studied the mRNA expression of ApoE and LRP in the postmortem brain of persons who died at different stages of dementia and AD-associated neuropathology relative to controls by quantitative polymerase chain reaction (qPCR) and Western blotting analyses. Clinical dementia rating scores were used as a measure of dementia severity, whereas, Braak neuropathological staging and neuritic plaque density were used as indexes of the neuropathological progression of AD. ApoE and LRP mRNA expression was significantly elevated in the postmortem inferior temporal gyrus (area 20) and the hippocampus from individuals with dementia compared with those with intact cognition. In addition to their strong association with the progression of cognitive dysfunction, LRP and ApoE mRNA levels were also positively correlated with increasing neuropathological hallmarks of AD. Additionally, Western blot analysis of ApoE protein expression in the hippocampus showed that the differential expression observed at the transcriptional level is also reflected at the protein level. Given the critical role played by LRP and ApoE in amyloid beta (Aβ) and cholesterol trafficking, increased expression of LRP and ApoE may not only disrupt cholesterol homeostasis but may also contribute to some of the neurobiological features of AD, including plaque deposition.
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