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García-Viñuales S, Sciacca MFM, Lanza V, Santoro AM, Grasso G, Tundo GR, Sbardella D, Coletta M, Grasso G, La Rosa C, Milardi D. The interplay between lipid and Aβ amyloid homeostasis in Alzheimer's Disease: risk factors and therapeutic opportunities. Chem Phys Lipids 2021; 236:105072. [PMID: 33675779 DOI: 10.1016/j.chemphyslip.2021.105072] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2020] [Revised: 02/15/2021] [Accepted: 03/01/2021] [Indexed: 12/19/2022]
Abstract
Alzheimer's Diseases (AD) is characterized by the accumulation of amyloid deposits of Aβ peptide in the brain. Besides genetic background, the presence of other diseases and an unhealthy lifestyle are known risk factors for AD development. Albeit accumulating clinical evidence suggests that an impaired lipid metabolism is related to Aβ deposition, mechanistic insights on the link between amyloid fibril formation/clearance and aberrant lipid interactions are still unavailable. Recently, many studies have described the key role played by membrane bound Aβ assemblies in neurotoxicity. Moreover, it has been suggested that a derangement of the ubiquitin proteasome pathway and autophagy is significantly correlated with toxic Aβ aggregation and dysregulation of lipid levels. Thus, studies focusing on the role played by lipids in Aβ aggregation and proteostasis could represent a promising area of investigation for the design of valuable treatments. In this review we examine current knowledge concerning the effects of lipids in Aβ aggregation and degradation processes, focusing on the therapeutic opportunities that a comprehensive understanding of all biophysical, biochemical, and biological processes involved may disclose.
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Affiliation(s)
| | - Michele F M Sciacca
- Consiglio Nazionale delle Ricerche, Istituto di Cristallografia, Catania, Italy
| | - Valeria Lanza
- Consiglio Nazionale delle Ricerche, Istituto di Cristallografia, Catania, Italy
| | - Anna Maria Santoro
- Consiglio Nazionale delle Ricerche, Istituto di Cristallografia, Catania, Italy
| | - Giulia Grasso
- Consiglio Nazionale delle Ricerche, Istituto di Cristallografia, Catania, Italy
| | - Grazia R Tundo
- Department of Clinical Sciences and Translational Medicine, University of Rome Tor Vergata, Rome, Italy
| | | | - Massimiliano Coletta
- Department of Clinical Sciences and Translational Medicine, University of Rome Tor Vergata, Rome, Italy
| | - Giuseppe Grasso
- Department of Chemistry, University of Catania, Catania, Italy
| | - Carmelo La Rosa
- Department of Chemistry, University of Catania, Catania, Italy
| | - Danilo Milardi
- Consiglio Nazionale delle Ricerche, Istituto di Cristallografia, Catania, Italy.
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2
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Liu X, Zhao J, Zhang Y, Ubarretxena-Belandia I, Forth S, Lieberman RL, Wang C. Substrate-Enzyme Interactions in Intramembrane Proteolysis: γ-Secretase as the Prototype. Front Mol Neurosci 2020; 13:65. [PMID: 32508589 PMCID: PMC7248309 DOI: 10.3389/fnmol.2020.00065] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 04/03/2020] [Indexed: 11/15/2022] Open
Abstract
Intramembrane-cleaving proteases (I-CLiPs) catalyze the hydrolysis of peptide bonds within the transmembrane regions of membrane protein substrates, releasing bioactive fragments that play roles in many physiological and pathological processes. Based on their catalytic mechanism and nucleophile, I-CLiPs are classified into metallo, serine, aspartyl, and glutamyl proteases. Presenilin is the most prominent among I-CLiPs, as the catalytic subunit of γ-secretase (GS) complex responsible for cleaving the amyloid precursor protein (APP) and Notch, as well as many other membrane substrates. Recent cryo-electron microscopy (cryo-EM) structures of GS provide new details on how presenilin recognizes and cleaves APP and Notch. First, presenilin transmembrane helix (TM) 2 and 6 are dynamic. Second, upon binding to GS, the substrate TM helix is unwound from the C-terminus, resulting in an intermolecular β-sheet between the substrate and presenilin. The transition of the substrate C-terminus from α-helix to β-sheet is proposed to expose the scissile peptide bond in an extended conformation, leaving it susceptible to protease cleavage. Despite the astounding new insights in recent years, many crucial questions remain unanswered regarding the inner workings of γ-secretase, however. Key unanswered questions include how the enzyme recognizes and recruits substrates, how substrates are translocated from an initial docking site to the active site, how active site aspartates recruit and coordinate catalytic water, and the nature of the mechanisms of processive trimming of the substrate and product release. Answering these questions will have important implications for drug discovery aimed at selectively reducing the amyloid load in Alzheimer's disease (AD) with minimal side effects.
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Affiliation(s)
- Xinyue Liu
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, United States
| | - Jing Zhao
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, United States
| | - Yingkai Zhang
- Department of Chemistry, New York University, New York, NY, United States
| | - Iban Ubarretxena-Belandia
- Instituto Biofisika (UPV/EHU, CSIC), University of the Basque Country, Leioa, Spain
- Ikerbasque, Basque Foundation for Science, Bilbao, Spain
| | - Scott Forth
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, United States
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY, United States
| | - Raquel L. Lieberman
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, United States
| | - Chunyu Wang
- Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY, United States
- Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY, United States
- Department of Chemistry and Chemical Biology, Rensselaer Polytechnic Institute, Troy, NY, United States
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3
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Roitenberg N, Bejerano-Sagie M, Boocholez H, Moll L, Marques FC, Golodetzki L, Nevo Y, Elami T, Cohen E. Modulation of caveolae by insulin/IGF-1 signaling regulates aging of Caenorhabditis elegans. EMBO Rep 2018; 19:embr.201745673. [PMID: 29945933 DOI: 10.15252/embr.201745673] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 05/27/2018] [Accepted: 05/29/2018] [Indexed: 11/09/2022] Open
Abstract
Reducing insulin/IGF-1 signaling (IIS) extends lifespan, promotes protein homeostasis (proteostasis), and elevates stress resistance of worms, flies, and mammals. How these functions are orchestrated across the organism is only partially understood. Here, we report that in the nematode Caenorhabditis elegans, the IIS positively regulates the expression of caveolin-1 (cav-1), a gene which is primarily expressed in neurons of the adult worm and underlies the formation of caveolae, a subtype of lipid microdomains that serve as platforms for signaling complexes. Accordingly, IIS reduction lowers cav-1 expression and lessens the quantity of neuronal caveolae. Reduced cav-1 expression extends lifespan and mitigates toxic protein aggregation by modulating the expression of aging-regulating and signaling-promoting genes. Our findings define caveolae as aging-governing signaling centers and underscore the potential for cav-1 as a novel therapeutic target for the promotion of healthy aging.
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Affiliation(s)
- Noa Roitenberg
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel - Canada, The Hebrew University School of Medicine, Jerusalem, Israel
| | - Michal Bejerano-Sagie
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel - Canada, The Hebrew University School of Medicine, Jerusalem, Israel
| | - Hana Boocholez
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel - Canada, The Hebrew University School of Medicine, Jerusalem, Israel
| | - Lorna Moll
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel - Canada, The Hebrew University School of Medicine, Jerusalem, Israel
| | - Filipa Carvalhal Marques
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel - Canada, The Hebrew University School of Medicine, Jerusalem, Israel
| | - Ludmila Golodetzki
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel - Canada, The Hebrew University School of Medicine, Jerusalem, Israel
| | - Yuval Nevo
- Computation Center, Hebrew University-Hadassah Medical School, Jerusalem, Israel
| | - Tayir Elami
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel - Canada, The Hebrew University School of Medicine, Jerusalem, Israel
| | - Ehud Cohen
- Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel - Canada, The Hebrew University School of Medicine, Jerusalem, Israel
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4
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Aikawa T, Holm ML, Kanekiyo T. ABCA7 and Pathogenic Pathways of Alzheimer's Disease. Brain Sci 2018; 8:E27. [PMID: 29401741 PMCID: PMC5836046 DOI: 10.3390/brainsci8020027] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Revised: 02/01/2018] [Accepted: 02/03/2018] [Indexed: 12/22/2022] Open
Abstract
The ATP-binding cassette (ABC) reporter family functions to regulate the homeostasis of phospholipids and cholesterol in the central nervous system, as well as peripheral tissues. ABCA7 belongs to the A subfamily of ABC transporters, which shares 54% sequence identity with ABCA1. While ABCA7 is expressed in a variety of tissues/organs, including the brain, recent genome-wide association studies (GWAS) have identified ABCA7 gene variants as susceptibility loci for late-onset Alzheimer's disease (AD). More important, subsequent genome sequencing analyses have revealed that premature termination codon mutations in ABCA7 are associated with the increased risk for AD. Alzheimer's disease is a progressive neurodegenerative disease and the most common cause of dementia, where the accumulation and deposition of amyloid-β (Aβ) peptides cleaved from amyloid precursor protein (APP) in the brain trigger the pathogenic cascade of the disease. In consistence with human genetic studies, increasing evidence has demonstrated that ABCA7 deficiency exacerbates Aβ pathology using in vitro and in vivo models. While ABCA7 has been shown to mediate phagocytic activity in macrophages, ABCA7 is also involved in the microglial Aβ clearance pathway. Furthermore, ABCA7 deficiency results in accelerated Aβ production, likely by facilitating endocytosis and/or processing of APP. Taken together, current evidence suggests that ABCA7 loss-of-function contributes to AD-related phenotypes through multiple pathways. A better understanding of the function of ABCA7 beyond lipid metabolism in both physiological and pathological conditions becomes increasingly important to explore AD pathogenesis.
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Affiliation(s)
- Tomonori Aikawa
- Department of Neuroscience, Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL 32224, USA.
| | - Marie-Louise Holm
- Department of Neuroscience, Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL 32224, USA.
| | - Takahisa Kanekiyo
- Department of Neuroscience, Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL 32224, USA.
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5
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Yu Q, Zhong C. Membrane Aging as the Real Culprit of Alzheimer's Disease: Modification of a Hypothesis. Neurosci Bull 2017; 34:369-381. [PMID: 29177767 DOI: 10.1007/s12264-017-0192-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Accepted: 08/05/2017] [Indexed: 01/10/2023] Open
Abstract
Our previous studies proposed that Alzheimer's disease (AD) is a metabolic disorder and hypothesized that abnormal brain glucose metabolism inducing multiple pathophysiological cascades contributes to AD pathogenesis. Aging is one of the great significant risk factors for AD. Membrane aging is first prone to affect the function and structure of the brain by impairing glucose metabolism. We presume that risk factors of AD, including genetic factors (e.g., the apolipoprotein E ε4 allele and genetic mutations) and non-genetic factors (such as fat, diabetes, and cardiac failure) accelerate biomembrane aging and lead to the onset and development of the disease. In this review, we further modify our previous hypothesis to demonstrate "membrane aging" as an initial pathogenic factor that results in functional and structural alterations of membranes and, consequently, glucose hypometabolism and multiple pathophysiological cascades.
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Affiliation(s)
- Qiujian Yu
- Department of Neurology, Zhongshan Hospital, Fudan University, Shanghai, 200032, China
| | - Chunjiu Zhong
- Department of Neurology, Zhongshan Hospital, Fudan University, Shanghai, 200032, China.
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6
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Piedrahita D, Castro-Alvarez JF, Boudreau RL, Villegas-Lanau A, Kosik KS, Gallego-Gomez JC, Cardona-Gómez GP. β-Secretase 1's Targeting Reduces Hyperphosphorilated Tau, Implying Autophagy Actors in 3xTg-AD Mice. Front Cell Neurosci 2016; 9:498. [PMID: 26778963 PMCID: PMC4705306 DOI: 10.3389/fncel.2015.00498] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Accepted: 12/11/2015] [Indexed: 01/08/2023] Open
Abstract
β-site APP cleaving enzyme 1 (BACE1) initiates APP cleavage, which has been reported to be an inducer of tau pathology by altering proteasome functions in Alzheimer’s disease (AD). However, the exact relationship between BACE1 and PHF (Paired Helical Filaments) formation is not clear. In this study, we confirm that BACE1 and Hsc70 are upregulated in the brains of AD patients, and we demonstrate that both proteins show enhanced expression in lipid rafts from AD-affected triple transgenic mouse brains. BACE1 targeting increased Hsc70 levels in the membrane and cytoplasm fractions and downregulated Hsp90 and CHIP in the nucleus in the hippocampi of 3xTg-AD mice. However, these observations occurred in a proteasome-independent manner in vitro. The BACE1miR-induced reduction of soluble hyperphosphorylated tau was associated with a decrease in MAPK activity. However, the BACE1 RNAi-mediated reduction of hyperphosphorylated tau was only blocked by 3-MA (3-methyladenine) in vitro, and it resulted in the increase of Hsc70 and LAMP2 in lipid rafts from hippocampi of 3xTg-AD mice, and upregulation of survival and homeostasis signaling. In summary, our findings suggest that BACE1 silencing neuroprotects reducing soluble hyperphosphorylated tau, modulating certain autophagy-related proteins in aged 3xTg-AD mice.
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Affiliation(s)
- Diego Piedrahita
- Cellular and Molecular Neurobiology Area, Viral Vector Core and Gene Therapy, University of Antioquia Medellin, Antioquia, Colombia
| | - John Fredy Castro-Alvarez
- Cellular and Molecular Neurobiology Area, Viral Vector Core and Gene Therapy, University of Antioquia Medellin, Antioquia, Colombia
| | | | - Andres Villegas-Lanau
- Neurobank, Neuroscience Group of Antioquia, Faculty of Medicine, SIU, University of Antioquia Medellín, Colombia
| | - Kenneth S Kosik
- Department of Molecular Cellular Developmental Biology, Neuroscience Research Institute, University of California Santa Barbara Santa Barbara, CA, USA
| | - Juan Carlos Gallego-Gomez
- Cellular and Molecular Neurobiology Area, Viral Vector Core and Gene Therapy, University of Antioquia Medellin, Antioquia, Colombia
| | - Gloria Patricia Cardona-Gómez
- Cellular and Molecular Neurobiology Area, Viral Vector Core and Gene Therapy, University of Antioquia Medellin, Antioquia, Colombia
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7
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Kandalepas PC, Vassar R. The normal and pathologic roles of the Alzheimer's β-secretase, BACE1. Curr Alzheimer Res 2015; 11:441-9. [PMID: 24893886 DOI: 10.2174/1567205011666140604122059] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 01/15/2014] [Accepted: 01/25/2014] [Indexed: 01/18/2023]
Abstract
As the most common neurodegenerative disease, therapeutic avenues for the treatment and prevention of Alzheimer's Disease are highly sought after. The aspartic protease BACE1 is the initiator enzyme for the formation of Aβ, a major constituent of amyloid plaques that represent one of the hallmark pathological features of this disorder. Thus, targeting BACE1 for disease-modifying AD therapies represents a rationale approach. The collective knowledge acquired from investigations of BACE1 deletion mutants and characterization of BACE1 substrates has downstream significance not only for the discovery of AD drug therapies but also for predicting side effects of BACE1 inhibition. Here we discuss the identification and validation of BACE1 as the β-secretase implicated in AD, in addition to information regarding BACE1 cell biology, localization, substrates and potential physiological functions derived from BACE1 knockout models.
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Affiliation(s)
| | - Robert Vassar
- Northwestern University, Feinberg School of Medicine, Department of Cell & Molecular Biology, 300 E. Superior, Tarry 8-713, IL 60611, Chicago.
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8
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Cellular membrane fluidity in amyloid precursor protein processing. Mol Neurobiol 2014; 50:119-29. [PMID: 24553856 DOI: 10.1007/s12035-014-8652-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Accepted: 01/23/2014] [Indexed: 12/20/2022]
Abstract
The senile plaque is a pathologic hallmark of Alzheimer's disease (AD). Amyloid-β peptide (Aβ), the main constituent of senile plaques, is neurotoxic especially in its oligomeric form. Aβ is derived from the sequential cleavage of amyloid precursor protein (APP) by β- and γ-secretases in the amyloidogenic pathway. Alternatively, APP can be cleaved by α-secretases within the Aβ domain to produce neurotrophic and neuroprotective α-secretase-cleaved soluble APP (sAPPα) in the nonamyloidogenic pathway. Since APP and α-, β-, and γ-secretases are membrane proteins, APP processing should be highly dependent on the membrane composition and the biophysical properties of cellular membrane. In this review, we discuss the role of the biophysical properties of cellular membrane in APP processing, especially the effects of phospholipases A(2) (PLA(2)s), fatty acids, cholesterol, and Aβ on membrane fluidity in relation to their effects on APP processing.
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9
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Trafficking in neurons: Searching for new targets for Alzheimer's disease future therapies. Eur J Pharmacol 2013; 719:84-106. [DOI: 10.1016/j.ejphar.2013.07.019] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 07/11/2013] [Indexed: 11/22/2022]
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10
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WANG JISHENG, WU FENGMING, SHI CHUN. Substitution of membrane cholesterol with β-sitosterol promotes nonamyloidogenic cleavage of endogenous amyloid precursor protein. Neuroscience 2013; 247:227-33. [DOI: 10.1016/j.neuroscience.2013.05.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2012] [Revised: 05/02/2013] [Accepted: 05/14/2013] [Indexed: 10/26/2022]
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11
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Tan JL, Li QX, Ciccotosto GD, Crouch PJ, Culvenor JG, White AR, Evin G. Mild oxidative stress induces redistribution of BACE1 in non-apoptotic conditions and promotes the amyloidogenic processing of Alzheimer's disease amyloid precursor protein. PLoS One 2013; 8:e61246. [PMID: 23613819 PMCID: PMC3629182 DOI: 10.1371/journal.pone.0061246] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2013] [Accepted: 03/07/2013] [Indexed: 12/22/2022] Open
Abstract
BACE1 is responsible for β-secretase cleavage of the amyloid precursor protein (APP), which represents the first step in the production of amyloid β (Aβ) peptides. Previous reports, by us and others, have indicated that the levels of BACE1 protein and activity are increased in the brain cortex of patients with Alzheimer's disease (AD). The association between oxidative stress (OS) and AD has prompted investigations that support the potentiation of BACE1 expression and enzymatic activity by OS. Here, we have established conditions to analyse the effects of mild, non-lethal OS on BACE1 in primary neuronal cultures, independently from apoptotic mechanisms that were shown to impair BACE1 turnover. Six-hour treatment of mouse primary cortical cells with 10-40 µM hydrogen peroxide did not significantly compromise cell viability but it did produce mild oxidative stress (mOS), as shown by the increased levels of reactive radical species and activation of p38 stress kinase. The endogenous levels of BACE1 mRNA and protein were not significantly altered in these conditions, whereas a toxic H2O2 concentration (100 µM) caused an increase in BACE1 protein levels. Notably, mOS conditions resulted in increased levels of the BACE1 C-terminal cleavage product of APP, β-CTF. Subcellular fractionation techniques showed that mOS caused a major rearrangement of BACE1 localization from light to denser fractions, resulting in an increased distribution of BACE1 in fractions containing APP and markers for trans-Golgi network and early endosomes. Collectively, these data demonstrate that mOS does not modify BACE1 expression but alters BACE1 subcellular compartmentalization to favour the amyloidogenic processing of APP, and thus offer new insight in the early molecular events of AD pathogenesis.
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Affiliation(s)
- Jiang-Li Tan
- Department of Pathology, The University of Melbourne, Parkville, Australia
| | - Qiao-Xin Li
- Neuropathology Laboratory, Mental Health Division, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Australia
| | - Giuseppe D. Ciccotosto
- Department of Pathology, The University of Melbourne, Parkville, Australia
- Neuropathology Laboratory, Mental Health Division, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Australia
- BIO21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, Australia
| | - Peter John Crouch
- Department of Pathology, The University of Melbourne, Parkville, Australia
- Neuropathology Laboratory, Mental Health Division, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Australia
| | - Janetta Gladys Culvenor
- Department of Pathology, The University of Melbourne, Parkville, Australia
- Neuropathology Laboratory, Mental Health Division, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Australia
| | - Anthony Robert White
- Department of Pathology, The University of Melbourne, Parkville, Australia
- Neuropathology Laboratory, Mental Health Division, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Australia
| | - Genevieve Evin
- Department of Pathology, The University of Melbourne, Parkville, Australia
- Neuropathology Laboratory, Mental Health Division, The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, Australia
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12
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Holton P, Ryten M, Nalls M, Trabzuni D, Weale ME, Hernandez D, Crehan H, Gibbs JR, Mayeux R, Haines JL, Farrer LA, Pericak-Vance MA, Schellenberg GD, Ramirez-Restrepo M, Engel A, Myers AJ, Corneveaux JJ, Huentelman MJ, Dillman A, Cookson MR, Reiman EM, Singleton A, Hardy J, Guerreiro R. Initial assessment of the pathogenic mechanisms of the recently identified Alzheimer risk Loci. Ann Hum Genet 2013; 77:85-105. [PMID: 23360175 PMCID: PMC3578142 DOI: 10.1111/ahg.12000] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Accepted: 03/05/2012] [Indexed: 12/27/2022]
Abstract
Recent genome wide association studies have identified CLU, CR1, ABCA7 BIN1, PICALM and MS4A6A/MS4A6E in addition to the long established APOE, as loci for Alzheimer's disease. We have systematically examined each of these loci to assess whether common coding variability contributes to the risk of disease. We have also assessed the regional expression of all the genes in the brain and whether there is evidence of an eQTL explaining the risk. In agreement with other studies we find that coding variability may explain the ABCA7 association, but common coding variability does not explain any of the other loci. We were not able to show that any of the loci had eQTLs within the power of this study. Furthermore the regional expression of each of the loci did not match the pattern of brain regional distribution in Alzheimer pathology. Although these results are mainly negative, they allow us to start defining more realistic alternative approaches to determine the role of all the genetic loci involved in Alzheimer's disease.
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Affiliation(s)
- Patrick Holton
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
| | - Mina Ryten
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
| | - Michael Nalls
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, MD
| | - Daniah Trabzuni
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
- Department of Genetics, King Faisal Specialist Hospital and Research Centre, PO Box 3354, Riyadh 11211, Saudi Arabia
| | - Michael E. Weale
- Department of Medical & Molecular Genetics, King’s College London, Guy’s Hospital, London, UK
| | - Dena Hernandez
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, MD
| | - Helen Crehan
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
| | - J. Raphael Gibbs
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, MD
| | - Richard Mayeux
- Gertrude H. Sergievsky Center and Taub Institute on Alzheimer's Disease and the Aging Brain, Department of Neurology, Columbia University, New York, NY
| | - Jonathan L. Haines
- Department of Molecular Physiology and Biophysics and Vanderbilt Center for Human Genetics Research, Vanderbilt University, Nashville, TN
| | - Lindsay A. Farrer
- Departments of Medicine (Biomedical Genetics), Biostatistics, Ophthalmology, Epidemiology, and Neurology, Boston University Schools of Medicine and Public Health, Boston, MA
| | - Margaret A. Pericak-Vance
- The John P. Hussman Institute for Human Genomics and Dr. John T. Macdonald Foundation Department of Human Genetics, University of Miami, Miami, FL
| | - Gerard D. Schellenberg
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA
| | | | - Manuel Ramirez-Restrepo
- Department of Psychiatry and Behavioral Sciences, Miller School of Medicine, University of Miami, Miami, FL
- Johnnie B. Byrd Sr. Alzheimer's Center and Research Institute, Tampa, FL
| | - Anzhelika Engel
- Department of Psychiatry and Behavioral Sciences, Miller School of Medicine, University of Miami, Miami, FL
- Johnnie B. Byrd Sr. Alzheimer's Center and Research Institute, Tampa, FL
| | - Amanda J. Myers
- Department of Psychiatry and Behavioral Sciences, Miller School of Medicine, University of Miami, Miami, FL
- Johnnie B. Byrd Sr. Alzheimer's Center and Research Institute, Tampa, FL
| | - Jason J. Corneveaux
- Neurogenomics Division, Translational Genomics Research Institute and Arizona Alzheimer's Consortium, Phoenix, AZ
| | - Matthew J. Huentelman
- Neurogenomics Division, Translational Genomics Research Institute and Arizona Alzheimer's Consortium, Phoenix, AZ
| | - Allissa Dillman
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, MD
- Department of Neuroscience, Karolinska Institutet, 171 77 Stockholm, Sweden
| | - Mark R. Cookson
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, MD
| | - Eric M. Reiman
- Neurogenomics Division, Translational Genomics Research Institute and Arizona Alzheimer's Consortium, Phoenix, AZ
- Banner Alzheimer's Institute and Department of Psychiatry, University of Arizona, Phoenix, AZ
- Department of Psychiatry, University of Arizona, Tucson, AZ
| | - Andrew Singleton
- Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, MD
| | - John Hardy
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
- Reta Lila Weston Laboratories and Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
| | - Rita Guerreiro
- Department of Molecular Neuroscience, UCL Institute of Neurology, London, UK
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13
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Mencarelli C, Martinez–Martinez P. Ceramide function in the brain: when a slight tilt is enough. Cell Mol Life Sci 2013; 70:181-203. [PMID: 22729185 PMCID: PMC3535405 DOI: 10.1007/s00018-012-1038-x] [Citation(s) in RCA: 168] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Revised: 05/16/2012] [Accepted: 05/21/2012] [Indexed: 12/14/2022]
Abstract
Ceramide, the precursor of all complex sphingolipids, is a potent signaling molecule that mediates key events of cellular pathophysiology. In the nervous system, the sphingolipid metabolism has an important impact. Neurons are polarized cells and their normal functions, such as neuronal connectivity and synaptic transmission, rely on selective trafficking of molecules across plasma membrane. Sphingolipids are abundant on neural cellular membranes and represent potent regulators of brain homeostasis. Ceramide intracellular levels are fine-tuned and alteration of the sphingolipid-ceramide profile contributes to the development of age-related, neurological and neuroinflammatory diseases. The purpose of this review is to guide the reader towards a better understanding of the sphingolipid-ceramide pathway system. First, ceramide biology is presented including structure, physical properties and metabolism. Second, we describe the function of ceramide as a lipid second messenger in cell physiology. Finally, we highlight the relevance of sphingolipids and ceramide in the progression of different neurodegenerative diseases.
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Affiliation(s)
- Chiara Mencarelli
- Department of Neuroscience, School for Mental Health and Neuroscience, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands
| | - Pilar Martinez–Martinez
- Department of Neuroscience, School for Mental Health and Neuroscience, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands
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Ricciarelli R, Canepa E, Marengo B, Marinari UM, Poli G, Pronzato MA, Domenicotti C. Cholesterol and Alzheimer's disease: A still poorly understood correlation. IUBMB Life 2012; 64:931-5. [DOI: 10.1002/iub.1091] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2012] [Accepted: 08/30/2012] [Indexed: 11/08/2022]
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FBL2 regulates amyloid precursor protein (APP) metabolism by promoting ubiquitination-dependent APP degradation and inhibition of APP endocytosis. J Neurosci 2012; 32:3352-65. [PMID: 22399757 DOI: 10.1523/jneurosci.5659-11.2012] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The ubiquitin-proteasome pathway is a major protein degradation pathway whose dysfunction is now widely accepted as a cause of neurodegenerative diseases, including Alzheimer's disease. Here we demonstrate that the F-box and leucine rich repeat protein2 (FBL2), a component of the E3 ubiquitin ligase complex, regulates amyloid precursor protein (APP) metabolism through APP ubiquitination. FBL2 overexpression decreased the amount of secreted amyloid β (Aβ) peptides and sAPPβ, whereas FBL2 mRNA knockdown by siRNA increased these levels. FBL2 overexpression also decreased the amount of intracellular Aβ in Neuro2a cells stably expressing APP with Swedish mutation. FBL2 bound with APP specifically at its C-terminal fragment (CTF), which promoted APP/CTF ubiquitination. FBL2 overexpression also accelerated APP proteasome-dependent degradation and decreased APP protein localization in lipid rafts by inhibiting endocytosis. These effects were not observed in an F-box-deleted FBL2 mutant that does not participate in the E3 ubiquitin ligase complex. Furthermore, a reduced insoluble Aβ and Aβ plaque burden was observed in the hippocampus of 7-month-old FBL2 transgenic mice crossed with double-transgenic mice harboring APPswe and PS1(M146V) transgenes. These findings indicate that FBL2 is a novel and dual regulator of APP metabolism through FBL2-dependent ubiquitination of APP.
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16
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Dislich B, Lichtenthaler SF. The Membrane-Bound Aspartyl Protease BACE1: Molecular and Functional Properties in Alzheimer's Disease and Beyond. Front Physiol 2012; 3:8. [PMID: 22363289 PMCID: PMC3281277 DOI: 10.3389/fphys.2012.00008] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 01/11/2012] [Indexed: 12/31/2022] Open
Abstract
The β-site APP cleaving enzyme 1 (BACE1) is a transmembrane aspartyl protease involved in Alzheimer’s disease (AD) pathogenesis and in myelination. BACE1 initiates the generation of the pathogenic amyloid β-peptide, which makes BACE1 a major drug target for AD. BACE1 also cleaves and activates neuregulin 1, thereby contributing to postnatal myelination, in particular in the peripheral nervous system. Additional proteins are also cleaved by BACE1, but less is known about the physiological consequences of their cleavage. Recently, new phenotypes were described in BACE1-deficient mice. Although it remains unclear through which BACE1 substrates they are mediated, the phenotypes suggest a versatile role of this protease for diverse physiological processes. This review summarizes the enzymatic and cellular properties of BACE1 as well as its regulation by lipids, by transcriptional, and by translational mechanisms. The main focus will be on the recent progress in understanding BACE1 function and its implication for potential mechanism-based side effects upon therapeutic inhibition.
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Affiliation(s)
- Bastian Dislich
- German Center for Neurodegenerative Diseases (DZNE) Munich, Germany
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17
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Abstract
β-Site APP-cleaving enzyme (BACE1) cleaves the amyloid precursor protein (APP) at the β-secretase site to initiate the production of Aβ peptides. These accumulate to form toxic oligomers and the amyloid plaques associated with Alzheimer's disease (AD). An increase of BACE1 levels in the brain of AD patients has been mostly attributed to alterations of its intracellular trafficking. Golgi-associated adaptor proteins, GGA sort BACE1 for export to the endosomal compartment, which is the major cellular site of BACE1 activity. BACE1 undergoes recycling between endosome, trans-Golgi network (TGN), and the plasma membrane, from where it is endocytosed and either further recycled or retrieved to the endosome. Phosphorylation of Ser498 facilitates BACE1 recognition by GGA1 for retrieval to the endosome. Ubiquitination of BACE1 C-terminal Lys501 signals GGA3 for exporting BACE1 to the lysosome for degradation. In addition, the retromer mediates the retrograde transport of BACE1 from endosome to TGN. Decreased levels of GGA proteins and increased levels of retromer-associated sortilin have been associated with AD. Both would promote the co-localization of BACE1 and the amyloid precursor protein in the TGN and endosomes. Decreased levels of GGA3 also impair BACE1 degradation. Further understanding of BACE1 trafficking and its regulation may offer new therapeutic approaches for the treatment of Alzheimer's disease.
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Affiliation(s)
- Jiangli Tan
- Department of Pathology, and Mental Health Research Institute, The University of Melbourne, Parkville, Australia
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18
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Abstract
Our knowledge of the etiology of Alzheimer's disease (AD) has advanced tremendously since the discovery of amyloid beta (Aβ) aggregation in diseased brains. Accumulating evidence suggests that Aβ plays a causative role in AD. The β-secretase enzyme, beta-site APP cleaving enzyme-1 (BACE1), is also implicated in AD pathogenesis, given that BACE1 cleavage of amyloid precursor protein is the initiating step in the formation of Aβ. As a result, BACE1 inhibition has been branded as a potential AD therapy. In this study, we review the identification and basic characteristics of BACE1, as well as the progress in our understanding of BACE1 cell biology, substrates, and phenotypes of BACE1 knockout mice that are informative about the physiological functions of BACE1 beyond amyloid precursor protein cleavage. These data are crucial for predicting potential mechanism-based toxicity that would arise from inhibiting BACE1 for the treatment or prevention of AD.
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Affiliation(s)
- Patty C Kandalepas
- Northwestern University, Feinberg School of Medicine, Department of Cell and Molecular Biology, Chicago, Illinois, USA
| | - Robert Vassar
- Northwestern University, Feinberg School of Medicine, Department of Cell and Molecular Biology, Chicago, Illinois, USA
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Vassar R, Kandalepas PC. The β-secretase enzyme BACE1 as a therapeutic target for Alzheimer's disease. ALZHEIMERS RESEARCH & THERAPY 2011; 3:20. [PMID: 21639952 PMCID: PMC3226309 DOI: 10.1186/alzrt82] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Amyloid plaques are defining histopathologic lesions in the brains of Alzheimer's disease (AD) patients and are composed of the amyloid-beta peptide, which is widely considered to play a critical role in the pathogenesis of AD. The β-secretase, or β-site amyloid precursor protein cleaving enzyme 1 (BACE1; also called Asp2, memapsin 2), is the enzyme that initiates the generation of amyloid beta. Consequently, BACE1 is an attractive drug target for lowering cerebral levels of amyloid beta for the treatment or prevention of AD. Much has been learned about BACE1 since its discovery over 10 years ago. In the present article, we review BACE1 properties and characteristics, cell biology, in vivo validation, substrates, therapeutic potential, and inhibitor drug development. Studies relating to the physiological functions of BACE1 and the promise of BACE1 inhibition for AD will also be discussed. We conclude that therapeutic inhibition of BACE1 should be efficacious for AD, although careful titration of the drug dose may be necessary to limit mechanism-based side effects.
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Affiliation(s)
- Robert Vassar
- Department of Cell & Molecular Biology, Feinberg School of Medicine, Northwestern University, 300 E, Superior, Tarry 8-713, Chicago, IL 60611, USA.
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20
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Grimm MOW, Grösgen S, Rothhaar TL, Burg VK, Hundsdörfer B, Haupenthal VJ, Friess P, Müller U, Fassbender K, Riemenschneider M, Grimm HS, Hartmann T. Intracellular APP Domain Regulates Serine-Palmitoyl-CoA Transferase Expression and Is Affected in Alzheimer's Disease. Int J Alzheimers Dis 2011; 2011:695413. [PMID: 21660213 PMCID: PMC3109855 DOI: 10.4061/2011/695413] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2010] [Revised: 01/16/2011] [Accepted: 01/20/2011] [Indexed: 12/27/2022] Open
Abstract
Lipids play an important role as risk or protective factors in Alzheimer's disease (AD), a disease biochemically characterized by the accumulation of amyloid beta peptides (Aβ), released by proteolytic processing of the amyloid precursor protein (APP). Changes in sphingolipid metabolism have been associated to the development of AD. The key enzyme in sphingolipid de novo synthesis is serine-palmitoyl-CoA transferase (SPT). In the present study we identified a new physiological function of APP in sphingolipid synthesis. The APP intracellular domain (AICD) was found to decrease the expression of the SPT subunit SPTLC2, the catalytic subunit of the SPT heterodimer, resulting in that decreased SPT activity. AICD function was dependent on Fe65 and SPTLC2 levels are increased in APP knock-in mice missing a functional AICD domain. SPTLC2 levels are also increased in familial and sporadic AD postmortem brains, suggesting that SPT is involved in AD pathology.
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Affiliation(s)
- Marcus O. W. Grimm
- Neurodegeneration and Neurobiology, Deutsches Institut für Demenzprävention (DIDP), Kirrbergerstraße, 66421 Homburg, Germany
| | - Sven Grösgen
- Neurodegeneration and Neurobiology, Deutsches Institut für Demenzprävention (DIDP), Kirrbergerstraße, 66421 Homburg, Germany
| | - Tatjana L. Rothhaar
- Neurodegeneration and Neurobiology, Deutsches Institut für Demenzprävention (DIDP), Kirrbergerstraße, 66421 Homburg, Germany
| | - Verena K. Burg
- Neurodegeneration and Neurobiology, Deutsches Institut für Demenzprävention (DIDP), Kirrbergerstraße, 66421 Homburg, Germany
| | - Benjamin Hundsdörfer
- Neurodegeneration and Neurobiology, Deutsches Institut für Demenzprävention (DIDP), Kirrbergerstraße, 66421 Homburg, Germany
| | - Viola J. Haupenthal
- Neurodegeneration and Neurobiology, Deutsches Institut für Demenzprävention (DIDP), Kirrbergerstraße, 66421 Homburg, Germany
| | - Petra Friess
- Neurodegeneration and Neurobiology, Deutsches Institut für Demenzprävention (DIDP), Kirrbergerstraße, 66421 Homburg, Germany
| | - Ulrike Müller
- Institute of Pharmacy and Molecular Biotechnology (IPMB), University of Heidelberg, Im Neuenheimer Feld 364, 69120 Heidelberg, Germany
| | - Klaus Fassbender
- Neurodegeneration and Neurobiology, Deutsches Institut für Demenzprävention (DIDP), Kirrbergerstraße, 66421 Homburg, Germany
- Department of Neurology, Saarland University, Kirrbergerstraße, 66421 Homburg/Saar, Germany
| | - Matthias Riemenschneider
- Neurodegeneration and Neurobiology, Deutsches Institut für Demenzprävention (DIDP), Kirrbergerstraße, 66421 Homburg, Germany
- Department of Psychiatry, Saarland University, Kirrbergerstraße, 66421 Homburg/Saar, Germany
| | - Heike S. Grimm
- Neurodegeneration and Neurobiology, Deutsches Institut für Demenzprävention (DIDP), Kirrbergerstraße, 66421 Homburg, Germany
| | - Tobias Hartmann
- Neurodegeneration and Neurobiology, Deutsches Institut für Demenzprävention (DIDP), Kirrbergerstraße, 66421 Homburg, Germany
- Department of Psychiatry, Saarland University, Kirrbergerstraße, 66421 Homburg/Saar, Germany
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21
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Schieb H, Weidlich S, Schlechtingen G, Linning P, Jennings G, Gruner M, Wiltfang J, Klafki HW, Knölker HJ. Structural design, solid-phase synthesis and activity of membrane-anchored β-secretase inhibitors on Aβ generation from wild-type and Swedish-mutant APP. Chemistry 2011; 16:14412-23. [PMID: 21132705 DOI: 10.1002/chem.201002878] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Covalent coupling of β-secretase inhibitors to a raftophilic lipid anchor via a suitable spacer by using solid-phase peptide synthesis leads to tripartite structures displaying substantially improved inhibition of cellular secretion of the β-amyloid peptide (Aβ). Herein, we describe a series of novel tripartite structures, their full characterization by NMR spectroscopy and mass spectrometry, and the analysis of their biological activity in cell-based assays. The tripartite structure concept is applicable to different pharmacophores, and the potency in terms of β-secretase inhibition can be optimized by adjusting the spacer length to achieve an optimal distance of the inhibitor from the lipid bilayer. A tripartite structure containing a transition-state mimic inhibitor was found to be less potent on Aβ generation from Swedish-mutant amyloid precursor protein (APP) than from the wild-type protein. Moreover, our observations suggest that specific variants of Aβ are generated from wild-type APP but not from Swedish-mutant APP and are resistant to β-secretase inhibition. Efficient inhibition of Aβ secretion by tripartite structures in the absence of appreciable neurotoxicity was confirmed in a primary neuronal cell culture, thus further supporting the concept.
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Affiliation(s)
- Heinke Schieb
- Department of Psychiatry and Psychotherapy, University of Duisburg-Essen, LVR-Klinikum, Essen, Germany
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22
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Askarova S, Yang X, Lee JCM. Impacts of membrane biophysics in Alzheimer's disease: from amyloid precursor protein processing to aβ Peptide-induced membrane changes. Int J Alzheimers Dis 2011; 2011:134971. [PMID: 21547213 PMCID: PMC3087431 DOI: 10.4061/2011/134971] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Revised: 12/30/2010] [Accepted: 01/21/2011] [Indexed: 12/11/2022] Open
Abstract
An increasing amount of evidence supports the notion that cytotoxic effects of amyloid-β peptide (Aβ), the main constituent of senile plaques in Alzheimer's disease (AD), are strongly associated with its ability to interact with membranes of neurons and other cerebral cells. Aβ is derived from amyloidogenic cleavage of amyloid precursor protein (AβPP) by β- and γ-secretase. In the nonamyloidogenic pathway, AβPP is cleaved by α-secretases. These two pathways compete with each other, and enhancing the non-amyloidogenic pathway has been suggested as a potential pharmacological approach for the treatment of AD. Since AβPP, α-, β-, and γ-secretases are membrane-associated proteins, AβPP processing and Aβ production can be affected by the membrane composition and properties. There is evidence that membrane composition and properties, in turn, play a critical role in Aβ cytotoxicity associated with its conformational changes and aggregation into oligomers and fibrils. Understanding the mechanisms leading to changes in a membrane's biophysical properties and how they affect AβPP processing and Aβ toxicity should prove to provide new therapeutic strategies for prevention and treatment of AD.
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Affiliation(s)
- Sholpan Askarova
- Department of Biological Engineering, University of Missouri, Columbia, MO 65211, USA
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23
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Grimm MOW, Kuchenbecker J, Grösgen S, Burg VK, Hundsdörfer B, Rothhaar TL, Friess P, de Wilde MC, Broersen LM, Penke B, Péter M, Vígh L, Grimm HS, Hartmann T. Docosahexaenoic acid reduces amyloid beta production via multiple pleiotropic mechanisms. J Biol Chem 2011; 286:14028-39. [PMID: 21324907 DOI: 10.1074/jbc.m110.182329] [Citation(s) in RCA: 159] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Alzheimer disease is characterized by accumulation of the β-amyloid peptide (Aβ) generated by β- and γ-secretase processing of the amyloid precursor protein (APP). The intake of the polyunsaturated fatty acid docosahexaenoic acid (DHA) has been associated with decreased amyloid deposition and a reduced risk in Alzheimer disease in several epidemiological trials; however, the exact underlying molecular mechanism remains to be elucidated. Here, we systematically investigate the effect of DHA on amyloidogenic and nonamyloidogenic APP processing and the potential cross-links to cholesterol metabolism in vivo and in vitro. DHA reduces amyloidogenic processing by decreasing β- and γ-secretase activity, whereas the expression and protein levels of BACE1 and presenilin1 remain unchanged. In addition, DHA increases protein stability of α-secretase resulting in increased nonamyloidogenic processing. Besides the known effect of DHA to decrease cholesterol de novo synthesis, we found cholesterol distribution in plasma membrane to be altered. In the presence of DHA, cholesterol shifts from raft to non-raft domains, and this is accompanied by a shift in γ-secretase activity and presenilin1 protein levels. Taken together, DHA directs amyloidogenic processing of APP toward nonamyloidogenic processing, effectively reducing Aβ release. DHA has a typical pleiotropic effect; DHA-mediated Aβ reduction is not the consequence of a single major mechanism but is the result of combined multiple effects.
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Affiliation(s)
- Marcus O W Grimm
- Department of Neurodegeneration and Neurobiology, Deutsches Institut für DemenzPrävention, Saarland University, 66421 Homburg, Germany.
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Effects of fatty acid unsaturation numbers on membrane fluidity and α-secretase-dependent amyloid precursor protein processing. Neurochem Int 2010; 58:321-9. [PMID: 21184792 DOI: 10.1016/j.neuint.2010.12.004] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2010] [Revised: 10/17/2010] [Accepted: 12/07/2010] [Indexed: 12/19/2022]
Abstract
Fatty acids may integrate into cell membranes to change physical properties of cell membranes, and subsequently alter cell functions in an unsaturation number-dependent manner. To address the roles of fatty acid unsaturation numbers in cellular pathways of Alzheimer's disease (AD), we systematically investigated the effects of fatty acids on cell membrane fluidity and α-secretase-cleaved soluble amyloid precursor protein (sAPP(α)) secretion in relation to unsaturation numbers using stearic acid (SA, 18:0), oleic acid (OA, 18:1), linoleic acid (LA, 18:2), α-linolenic acid (ALA, 18:3), arachidonic acid (AA, 20:4), eicosapentaenoic acid (EPA, 20:5), and docosahexaenoic acid (DHA, 22:6). Treatments of differentiated human neuroblastoma (SH-SY5Y cells) with AA, EPA and DHA for 24h increased sAPP(α) secretion and membrane fluidity, whereas those treatments with SA, OA, LA and ALA did not. Treatments with AA and DHA did not alter the total expressions of amyloid precursor protein (APP) and α-secretases in SH-SY5Y cells. These results suggested that not all unsaturated fatty acids but only those with 4 or more double bonds, such as AA, EPA and DHA, are able to increase membrane fluidity and lead to increase in sAPP(α) secretion. This study provides insights into dietary strategies for the prevention of AD.
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Toyn JH, Lin XA, Thompson MW, Guss V, Meredith JE, Sankaranarayanan S, Barrezueta N, Corradi J, Majumdar A, Small DL, Hansard M, Lanthorn T, Westphal RS, Albright CF. Viable mouse gene ablations that robustly alter brain Aβ levels are rare. BMC Neurosci 2010; 11:143. [PMID: 21054826 PMCID: PMC2988800 DOI: 10.1186/1471-2202-11-143] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Accepted: 11/05/2010] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Accumulation of amyloid-β (Aβ) peptide in the brain is thought to play a key pathological role in Alzheimer's disease. Many pharmacological targets have therefore been proposed based upon the biochemistry of Aβ, but not all are equally tractable for drug discovery. RESULTS To search for novel targets that affect brain Aβ without causing toxicity, we screened mouse brain samples from 1930 novel gene knock-out (KO) strains, representing 1926 genes, using Aβ ELISA assays. Although robust Aβ lowering was readily apparent in brains from a BACE1 KO strain, none of the novel strains exhibited robust decreases in brain Aβ, including a GPR3 KO strain, which had previously been proposed as an Aβ target. However, significantly increased Aβ was observed in brain samples from two KO strains, corresponding to genes encoding the glycosylphosphatidylinositol mannosyl transferase PIGZ and quinolinate phosphoribosyltransferase (QPRT). CONCLUSIONS Thus, gene ablations that are permissive for mouse survival and that also have a robust effect on Aβ levels in the brain are rare.
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Affiliation(s)
- Jeremy H Toyn
- Neuroscience Biology, Bristol-Myers Squibb Research and Development, 5 Research Parkway, Wallingford, Connecticut 06492, USA.
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26
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Kodam A, Maulik M, Peake K, Amritraj A, Vetrivel KS, Thinakaran G, Vance JE, Kar S. Altered levels and distribution of amyloid precursor protein and its processing enzymes in Niemann-Pick type C1-deficient mouse brains. Glia 2010; 58:1267-81. [PMID: 20607864 PMCID: PMC2914615 DOI: 10.1002/glia.21001] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Niemann-Pick type C (NPC) disease is an autosomal recessive neurodegenerative disorder characterized by intracellular accumulation of cholesterol and glycosphingolipids in many tissues including the brain. The disease is caused by mutations of either NPC1 or NPC2 gene and is accompanied by a severe loss of neurons in the cerebellum, but not in the hippocampus. NPC pathology exhibits some similarities with Alzheimer's disease, including increased levels of amyloid beta (Abeta)-related peptides in vulnerable brain regions, but very little is known about the expression of amyloid precursor protein (APP) or APP secretases in NPC disease. In this article, we evaluated age-related alterations in the level/distribution of APP and its processing enzymes, beta- and gamma-secretases, in the hippocampus and cerebellum of Npc1(-/-) mice, a well-established model of NPC pathology. Our results show that levels and expression of APP and beta-secretase are elevated in the cerebellum prior to changes in the hippocampus, whereas gamma-secretase components are enhanced in both brain regions at the same time in Npc1(-/-) mice. Interestingly, a subset of reactive astrocytes in Npc1(-/-) mouse brains expresses high levels of APP as well as beta- and gamma-secretase components. Additionally, the activity of beta-secretase is enhanced in both the hippocampus and cerebellum of Npc1(-/-) mice at all ages, while the level of C-terminal APP fragments is increased in the cerebellum of 10-week-old Npc1(-/-) mice. These results, taken together, suggest that increased level and processing of APP may be associated with the development of pathology and/or degenerative events observed in Npc1(-/-) mouse brains.
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Affiliation(s)
- A Kodam
- Department of Psychiatry, Centre for Prions and Protein Folding Diseases, University of Alberta, Edmonton, Alberta, Canada
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27
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Rojo L, Sjöberg MK, Hernández P, Zambrano C, Maccioni RB. Roles of cholesterol and lipids in the etiopathogenesis of Alzheimer's disease. J Biomed Biotechnol 2010; 2006:73976. [PMID: 17047312 PMCID: PMC1559932 DOI: 10.1155/jbb/2006/73976] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Alzheimer's disease is the principal cause of dementia throughout the world and the fourth cause of death in developed economies.This brain disorder is characterized by the formation of brain protein aggregates, namely, the paired helical filaments and senile plaques. Oxidative stress during life, neuroinflamamtion, and alterations in neuron-glia interaction patterns have been also involved in the etiopathogenesis of this disease. In recent years, cumulative evidence has been gained on the involvement of alteration in neuronal lipoproteins activity, as well as on the role of cholesterol and other lipids in the pathogenesis of this neurodegenerative disorder. In this review, we analyze the links between changes in cholesterol homeostasis, and the changes of lipids of major importance for neuronal activity and Alheimer's disease. The investigation on the fine molecular mechanisms underlying the lipids influence in the etiopathogenesis of Alzheimer's disease may shed light into its treatment and medical management.
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Affiliation(s)
- Leonel Rojo
- Laboratory of Cellular and Molecular Biology and Neurosciences, Millennium Institute for Advanced Studies in
Cell Biology and Biotechnology (CBB), Millennium Building, Las Encinas 3370, Ñuñoa, Santiago, Chile
- Department of Chemistry, Arturo Prat University, avenue Arturo Prat 2120, Iquique, Chile
| | - Marcela K. Sjöberg
- Laboratory of Cellular and Molecular Biology and Neurosciences, Millennium Institute for Advanced Studies in
Cell Biology and Biotechnology (CBB), Millennium Building, Las Encinas 3370, Ñuñoa, Santiago, Chile
- Department of Neurological Sciences, Faculty of Medicine, University of Chile, Salvador 486, 750-0922 Providencia,
Santiago, Chile
| | - Paula Hernández
- Laboratory of Cellular and Molecular Biology and Neurosciences, Millennium Institute for Advanced Studies in
Cell Biology and Biotechnology (CBB), Millennium Building, Las Encinas 3370, Ñuñoa, Santiago, Chile
- Department of Neurological Sciences, Faculty of Medicine, University of Chile, Salvador 486, 750-0922 Providencia,
Santiago, Chile
| | - Cristian Zambrano
- Laboratory of Cellular and Molecular Biology and Neurosciences, Millennium Institute for Advanced Studies in
Cell Biology and Biotechnology (CBB), Millennium Building, Las Encinas 3370, Ñuñoa, Santiago, Chile
- Department of Neurological Sciences, Faculty of Medicine, University of Chile, Salvador 486, 750-0922 Providencia,
Santiago, Chile
| | - Ricardo B. Maccioni
- Laboratory of Cellular and Molecular Biology and Neurosciences, Millennium Institute for Advanced Studies in
Cell Biology and Biotechnology (CBB), Millennium Building, Las Encinas 3370, Ñuñoa, Santiago, Chile
- Department of Neurological Sciences, Faculty of Medicine, University of Chile, Salvador 486, 750-0922 Providencia,
Santiago, Chile
- *Ricardo B. Maccioni:
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28
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Membrane biophysics and mechanics in Alzheimer's disease. Mol Neurobiol 2010; 41:138-48. [PMID: 20437210 DOI: 10.1007/s12035-010-8121-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2009] [Accepted: 03/17/2010] [Indexed: 12/12/2022]
Abstract
Alzheimer's disease is a chronic neurodegenerative disorder characterized by neuronal loss, cerebrovascular inflammation, and accumulation of senile plaques in the brain parenchyma and cerebral blood vessels. Amyloid-beta peptide (Abeta), a major component of senile plaques, has been shown to exert multiple toxic effects to neurons, astrocytes, glial cells, and brain endothelium. Oligomeric Abeta can disturb the structure and function of cell membranes and alter membrane mechanical properties, such as membrane fluidity and molecular order. Much of these effects are attributed to their capability to trigger oxidative stress and inflammation. In this review, we discuss the effects of Abeta on neuronal cells, astrocytes, and cerebral endothelial cells with special emphasis on cell membrane properties and cell functions.
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Vassar R, Kovacs DM, Yan R, Wong PC. The beta-secretase enzyme BACE in health and Alzheimer's disease: regulation, cell biology, function, and therapeutic potential. J Neurosci 2009; 29:12787-94. [PMID: 19828790 PMCID: PMC2879048 DOI: 10.1523/jneurosci.3657-09.2009] [Citation(s) in RCA: 410] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Revised: 08/27/2009] [Accepted: 08/28/2009] [Indexed: 01/08/2023] Open
Abstract
The beta-amyloid (Abeta) peptide is the major constituent of amyloid plaques in Alzheimer's disease (AD) brain and is likely to play a central role in the pathogenesis of this devastating neurodegenerative disorder. The beta-secretase, beta-site amyloid precursor protein cleaving enzyme (BACE1; also called Asp2, memapsin 2), is the enzyme responsible for initiating Abeta generation. Thus, BACE is a prime drug target for the therapeutic inhibition of Abeta production in AD. Since its discovery 10 years ago, much has been learned about BACE. This review summarizes BACE properties, describes BACE translation dysregulation in AD, and discusses BACE physiological functions in sodium current, synaptic transmission, myelination, and schizophrenia. The therapeutic potential of BACE will also be considered. This is a summary of topics covered at a symposium held at the 39th annual meeting of the Society for Neuroscience and is not meant to be a comprehensive review of BACE.
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Affiliation(s)
- Robert Vassar
- Department of Cell and Molecular Biology, Northwestern University, Chicago, Illinois 60611, USA.
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Yang X, Sheng W, He Y, Cui J, Haidekker MA, Sun GY, Lee JCM. Secretory phospholipase A2 type III enhances alpha-secretase-dependent amyloid precursor protein processing through alterations in membrane fluidity. J Lipid Res 2009; 51:957-66. [PMID: 19805624 DOI: 10.1194/jlr.m002287] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
In the non-amyloidogenic pathway, amyloid precursor protein (APP) is cleaved by alpha-secretases to produce alpha-secretase-cleaved soluble APP (sAPP(alpha)) with neuroprotective and neurotrophic properties; therefore, enhancing the non-amyloidogenic pathway has been suggested as a potential pharmacological approach for the treatment of Alzheimer's disease. Here, we demonstrate the effects of type III secretory phospholipase A(2) (sPLA(2)-III) on sAPP(alpha) secretion. Exposing differentiated neuronal cells (SH-SY5Y cells and primary rat neurons) to sPLA(2)-III for 24 h increased sAPP(alpha) secretion and decreased levels of Abeta(1-42) in SH-SY5Y cells, and these changes were accompanied by increased membrane fluidity. We further tested whether sPLA(2)-III-enhanced sAPP(alpha) release is due in part to the production of its hydrolyzed products, including arachidonic acid (AA), palmitic acid (PA), and lysophosphatidylcholine (LPC). Addition of AA but neither PA nor LPC mimicked sPLA(2)-III-induced increases in sAPP(alpha) secretion and membrane fluidity. Treatment with sPLA(2)-III and AA increased accumulation of APP at the cell surface but did not alter total expressions of APP, alpha-secretases, and beta-site APP cleaving enzyme. Taken together, these results support the hypothesis that sPLA(2)-III enhances sAPP(alpha) secretion through its action to increase membrane fluidity and recruitment of APP at the cell surface.
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Affiliation(s)
- Xiaoguang Yang
- Department of Biological Engineering, University of Missouri, Columbia, MO 65211, USA
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Lu J, Wu DM, Zheng YL, Sun DX, Hu B, Shan Q, Zhang ZF, Fan SH. Trace amounts of copper exacerbate beta amyloid-induced neurotoxicity in the cholesterol-fed mice through TNF-mediated inflammatory pathway. Brain Behav Immun 2009; 23:193-203. [PMID: 18835350 DOI: 10.1016/j.bbi.2008.09.003] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Revised: 09/10/2008] [Accepted: 09/11/2008] [Indexed: 11/29/2022] Open
Abstract
Evidence has been gathered to suggest that trace amounts of copper induce neurotoxicity by interaction with elevated cholesterol in diet. Step-through task and Morris water maze task were used to evaluate cognitive function in the animals. Although a 16-week copper treatment alone in mice showed no significant change in learning and memory performances, cholesterol treatment significantly induced learning and memory impairments, which could be exacerbated by the co-treatment with copper. Immunohistochemical studies revealed that trace amounts of copper further stimulated the amyloid precursor protein (APP) upregulation and contributed to amyloid beta-peptide (Abeta) deposition in the brain of cholesterol-fed mice. Western blot analysis showed that copper also increased the protein expression levels of tumor necrosis factor-alpha (TNF-alpha) and the degradation of IkappaB proteins in the brain of cholesterol-fed mice. Furthermore, increased production of high inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) expressions were detected in the hippocampus and cerebral cortex of copper and cholesterol co-treated mice by immunohistochemical analysis. These findings suggest that trace amounts of copper could induce APP upregulation, activate inflammatory pathway and exacerbate neurotoxicity in cholesterol-fed mice.
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Affiliation(s)
- Jun Lu
- Key Laboratory for Biotechnology on Medicinal Plants of Jiangsu Province, School of Life Science, Xuzhou Normal University, Xuzhou, Jiangsu Province 221116, PR China
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Venugopal C, Demos CM, Rao KSJ, Pappolla MA, Sambamurti K. Beta-secretase: structure, function, and evolution. CNS & NEUROLOGICAL DISORDERS DRUG TARGETS 2008; 7:278-94. [PMID: 18673212 PMCID: PMC2921875 DOI: 10.2174/187152708784936626] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The most popular current hypothesis is that Alzheimer's disease (AD) is caused by aggregates of the amyloid peptide (Abeta), which is generated by cleavage of the Abeta protein precursor (APP) by beta-secretase (BACE-1) followed by gamma-secretase. BACE-1 cleavage is limiting for the production of Abeta, making it a particularly good drug target for the generation of inhibitors that lower Abeta. A landmark discovery in AD was the identification of BACE-1 (a.k.a. Memapsin-2) as a novel class of type I transmembrane aspartic protease. Although BACE-2, a homologue of BACE-1, was quickly identified, follow up studies using knockout mice demonstrated that BACE-1 was necessary and sufficient for most neuronal Abeta generation. Despite the importance of BACE-1 as a drug target, development has been slow due to the incomplete understanding of its function and regulation and the difficulties in developing a brain penetrant drug that can specifically block its large catalytic pocket. This review summarizes the biological properties of BACE-1 and attempts to use phylogenetic perspectives to understand its function. The article also addresses the challenges in discovering a selective drug-like molecule targeting novel mechanisms of BACE-1 regulation.
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Affiliation(s)
| | | | | | | | - Kumar Sambamurti
- Medical University of South Carolina, Charleston, South Carolina
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34
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Chan SL, Kim WS, Kwok JB, Hill AF, Cappai R, Rye KA, Garner B. ATP-binding cassette transporter A7 regulates processing of amyloid precursor protein in vitro. J Neurochem 2008; 106:793-804. [PMID: 18429932 DOI: 10.1111/j.1471-4159.2008.05433.x] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
ATP-binding cassette transporter A7 (ABCA7) is expressed in the brain and, like its closest homolog ABCA1, belongs to the ABCA subfamily of full-length ABC transporters. ABCA1 promotes cellular cholesterol efflux to lipid-free apolipoprotein acceptors and also inhibits the production of neurotoxic beta-amyloid (Abeta) peptides in vitro. The potential functions of ABCA7 in the brain are unknown. This study investigated the ability of ABCA7 to regulate cholesterol efflux to extracellular apolipoprotein acceptors and to modulate Abeta production. The transient expression of ABCA7 in human embryonic kidney cells significantly stimulated cholesterol efflux (fourfold) to apolipoprotein E (apoE) discoidal lipid complexes but not to lipid-free apoE or apoA-I. ABCA7 also significantly inhibited Abeta secretion from Chinese hamster ovary cells stably expressing human amyloid precursor protein (APP) or APP containing the Swedish K670M671-->N670L671 mutations when compared with mock-transfected cells. Studies with fluorogenic substrates indicated that ABCA7 had no impact on alpha-, beta-, or gamma-secretase activities. Live cell imaging of Chinese hamster ovary cells expressing APP-GFP indicated an apparent retention of APP in a perinuclear location in ABCA7 co-transfected cells. These studies indicate that ABCA7 has the capacity to stimulate cellular cholesterol efflux to apoE discs and regulate APP processing resulting in an inhibition of Abeta production.
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Affiliation(s)
- Sharon L Chan
- Prince of Wales Medical Research Institute, Randwick, New South Wales, Australia
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35
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Protein-protein interactions in the assembly and subcellular trafficking of the BACE (beta-site amyloid precursor protein-cleaving enzyme) complex of Alzheimer's disease. Biochem Soc Trans 2008; 35:974-9. [PMID: 17956258 DOI: 10.1042/bst0350974] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The correct assembly of the BACE (beta-site amyloid precursor protein-cleaving enzyme or beta-secretase) complex and its subsequent trafficking to cellular compartments where it associates with the APP (amyloid precursor protein) is essential for the production of Abeta (amyloid beta-peptide), the protein whose aggregation into senile plaques is thought to be responsible for the pathogenesis of AD (Alzheimer's disease). These processes rely upon both transient and permanent BACE-protein interactions. This review will discuss what is currently known about these BACE-protein interactions and how they may reveal novel therapeutic targets for the treatment of AD.
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36
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Wojcik S, Engel WK, Yan R, McFerrin J, Askanas V. NOGO is increased and binds to BACE1 in sporadic inclusion-body myositis and in A beta PP-overexpressing cultured human muscle fibers. Acta Neuropathol 2007; 114:517-26. [PMID: 17764014 DOI: 10.1007/s00401-007-0281-y] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2007] [Revised: 08/06/2007] [Accepted: 08/07/2007] [Indexed: 02/06/2023]
Abstract
Increased amyloid-beta precursor protein (A beta PP) and amyloid-beta (A beta) accumulation appear to be upstream steps in the pathogenesis of sporadic inclusion-body myositis (s-IBM). BACE1, participating in A beta production is also increased in s-IBM muscle fibers. Nogo-B and Nogo-A belong to a family of integral membrane reticulons, and Nogo-B binding to BACE1 blocks BACE1 access to A beta PP, decreasing A beta production. We studied Nogo-B and Nogo-A in s-IBM muscle and in our IBM muscle culture models, based on A beta PP-overexpression or ER-stress-induction in cultured human muscle fibers (CHMFs). We report that: (1) in biopsied s-IBM fibers, Nogo-B is increased, accumulates in aggregates, is immuno-co-localized with BACE1, and binds to BACE1; Nogo-A is undetectable. (2) In CHMFs, (a) A beta PP overexpression increases Nogo-B, Nogo-A, and BACE1, (b) ER stress increases BACE1 but decreases Nogo-B and Nogo-A, (c) Nogo-B and Nogo-A associate with BACE1. Accordingly, two novel mechanisms, A beta PP overexpression and ER stress, are involved in Nogo-B and Nogo-A expression in human muscle. We propose that in s-IBM muscle the Nogo-B increase may represent an attempt by muscle fiber to decrease A beta production. However, the increase of Nogo-B seems insufficient because A beta continues to accumulate and the disease progresses. We propose that manipulations, which increase Nogo-B in s-IBM muscle might offer a new therapeutic opportunity.
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Affiliation(s)
- Slawomir Wojcik
- USC Neuromuscular Center, Department of Neurology, University of Southern California Keck School of Medicine, Good Samaritan Hospital, 637 S. Lucas Ave, Los Angeles, CA 90017-1912, USA
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37
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Comparison of biochemical effects of statins and fish oil in brain: the battle of the titans. ACTA ACUST UNITED AC 2007; 56:443-71. [PMID: 17959252 DOI: 10.1016/j.brainresrev.2007.09.004] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2007] [Revised: 09/16/2007] [Accepted: 09/17/2007] [Indexed: 11/20/2022]
Abstract
Neural membranes are composed of glycerophospholipids, sphingolipids, cholesterol and proteins. The distribution of these lipids within the neural membrane is not random but organized. Neural membranes contain lipid rafts or microdomains that are enriched in sphingolipids and cholesterol. These rafts act as platforms for the generation of glycerophospholipid-, sphingolipid-, and cholesterol-derived second messengers, lipid mediators that are necessary for normal cellular function. Glycerophospholipid-derived lipid mediators include eicosanoids, docosanoids, lipoxins, and platelet-activating factor. Sphingolipid-derived lipid mediators include ceramides, ceramide 1-phosphates, and sphingosine 1-phosphate. Cholesterol-derived lipid mediators include 24-hydroxycholesterol, 25-hydroxycholesterol, and 7-ketocholesterol. Abnormal signal transduction processes and enhanced production of lipid mediators cause oxidative stress and inflammation. These processes are closely associated with the pathogenesis of acute neural trauma (stroke, spinal cord injury, and head injury) and neurodegenerative diseases such as Alzheimer disease. Statins, the HMG-CoA reductase inhibitors, are effective lipid lowering agents that significantly reduce risk for cardiovascular and cerebrovascular diseases. Beneficial effects of statins in neurological diseases are due to their anti-excitotoxic, antioxidant, and anti-inflammatory properties. Fish oil omega-3 fatty acids, eicosapentaenoic acid and docosahexaenoic acid, have similar anti-excitotoxic, antioxidant and anti-inflammatory effects in brain tissue. Thus the lipid mediators, resolvins, protectins, and neuroprotectins, derived from eicosapentaenoic acid and docosahexaenoic acid retard neuroinflammation, oxidative stress, and apoptotic cell death in brain tissue. Like statins, ingredients of fish oil inhibit generation of beta-amyloid and provide protection from oxidative stress and inflammatory processes. Collective evidence suggests that antioxidant, anti-inflammatory, and anti-apoptotic properties of statins and fish oil contribute to the clinical efficacy of treating neurological disorders with statins and fish oil. We speculate that there is an overlap between neurochemical events associated with neural cell injury in stroke and neurodegenerative diseases. This commentary compares the neurochemical effects of statins with those of fish oil.
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Poli M, Gatta LB, Lovati C, Mariani C, Galimberti D, Scarpini E, Biunno I, Musicco M, Dominici R, Albertini A, Finazzi D. Interaction between the APOE epsilon4 allele and the APH-1b c + 651T > G SNP in Alzheimer's disease. Neurobiol Aging 2007; 29:1494-501. [PMID: 17466415 DOI: 10.1016/j.neurobiolaging.2007.03.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/10/2007] [Indexed: 10/23/2022]
Abstract
The gamma-secretase complex is a multimeric aspartyl protease which plays a pivotal role in the production of amyloid beta-peptide, the main component of senile plaques in Alzheimer's disease (AD). APH-1a and APH-1b have been recently identified as important subunits of the gamma-secretase complex. We previously studied sequence variations in both genes and their association with AD in a small Italian population. The rare polymorphism c + 651T > G in APH-1b showed a possible interaction with the Apolipoprotein E (APOE) epsilon4 allele in the AD population sample. We extended our genetic analysis to 449 AD patients and 435 controls and, in AD cases, we found a significant interaction (P=0.001) between the allelic variants in the two genes, resulting in a marked increase of the relative risk for AD (OR=28.6). Despite the amino acid substitution does not seem to modify either the intracellular localization or the half-life of APH-1b protein, these data suggest that a cooperative mechanism involving APOE and APH-1b plays a role in the susceptibility to develop AD.
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Affiliation(s)
- Maura Poli
- Section of Chemistry, Faculty of Medicine, University of Brescia, viale Europa 11, 25123 Brescia, Italy
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39
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Kim WS, Rahmanto AS, Kamili A, Rye KA, Guillemin GJ, Gelissen IC, Jessup W, Hill AF, Garner B. Role of ABCG1 and ABCA1 in regulation of neuronal cholesterol efflux to apolipoprotein E discs and suppression of amyloid-beta peptide generation. J Biol Chem 2006; 282:2851-61. [PMID: 17121837 DOI: 10.1074/jbc.m607831200] [Citation(s) in RCA: 137] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Maintenance of an adequate supply of cholesterol is important for neuronal function, whereas excess cholesterol promotes amyloid precursor protein (APP) cleavage generating toxic amyloid-beta (Abeta) peptides. To gain insights into the pathways that regulate neuronal cholesterol level, we investigated the potential for reconstituted apolipoprotein E (apoE) discs, resembling nascent lipoprotein complexes in the central nervous system, to stimulate neuronal [3H]cholesterol efflux. ApoE discs potently accelerated cholesterol efflux from primary human neurons and cell lines. The process was saturable (17.5 microg of apoE/ml) and was not influenced by APOE genotype. High performance liquid chromatography analysis of cholesterol and cholesterol metabolites effluxed from neurons indicated that <25% of the released cholesterol was modified to polar products (e.g. 24-hydroxycholesterol) that diffuse from neuronal membranes. Thus, most cholesterol (approximately 75%) appeared to be effluxed from neurons in a native state via a transporter pathway. ATP-binding cassette transporters ABCA1, ABCA2, and ABCG1 were detected in neurons and neuroblastoma cell lines and expression of these cDNAs revealed that ABCA1 and ABCG1 stimulated cholesterol efflux to apoE discs. In addition, ABCA1 and ABCG1 expression in Chinese hamster ovary cells that stably express human APP significantly reduced Abeta generation, whereas ABCA2 did not modulate either cholesterol efflux or Abeta generation. These data indicate that ABCA1 and ABCG1 play a significant role in the regulation of neuronal cholesterol efflux to apoE discs and in suppression of APP processing to generate Abeta peptides.
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Affiliation(s)
- Woojin Scott Kim
- Prince of Wales Medical Research Institute, Sydney, New South Wales 2031, Australia
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40
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Stockley JH, Ravid R, O'Neill C. Altered beta-secretase enzyme kinetics and levels of both BACE1 and BACE2 in the Alzheimer's disease brain. FEBS Lett 2006; 580:6550-60. [PMID: 17113083 DOI: 10.1016/j.febslet.2006.10.076] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Revised: 09/19/2006] [Accepted: 10/31/2006] [Indexed: 10/23/2022]
Abstract
beta-Secretase is the rate limiting enzymatic activity in the production of amyloid-beta peptide, the primary component of senile plaque pathology in Alzheimer's disease (AD). This study performed the first comparative analysis of beta-secretase enzyme kinetics in AD and control brain tissue. Results found V(max) values for beta-secretase to be significantly increased, and K(m) values unchanged in AD temporal cortex compared to matched control temporal cortex. The increased V(max) in AD cases, did not correlate with levels of BACE1, and decreased BACE1 and BACE2 levels correlated with the severity of neurofibrillary pathology (I-VI), and synaptic loss in AD. These results indicate that increased V(max) for beta-secretase is a feature of AD pathogenesis and this increase does not correlate directly with levels of BACE1, the principal beta-secretase in brain.
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Affiliation(s)
- John H Stockley
- Department of Biochemistry, BioSciences Institute, University College Cork, Cork, Ireland
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41
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Parsons RB, Price GC, Farrant JK, Subramaniam D, Adeagbo-Sheikh J, Austen BM. Statins inhibit the dimerization of beta-secretase via both isoprenoid- and cholesterol-mediated mechanisms. Biochem J 2006; 399:205-14. [PMID: 16803455 PMCID: PMC1609905 DOI: 10.1042/bj20060655] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We have previously reported that protein lipidation in the form of palmitoylation and farnesylation is critical for the production of Abeta (amyloid beta-peptide), the dimerization of beta-secretase and its trafficking into cholesterol-rich microdomains. As statins influence these lipid modifications in addition to their effects on cholesterol biosynthesis, we have investigated the effects of lovastatin and SIMVA (simvastatin) at a range of concentrations chosen to distinguish different cellular effects on Abeta production and beta-secretase structure and its localization in bHEK cells [HEK-293 cells (human embryonic kidney cells) transfected with the Asp-2 gene plus a polyhistidine coding tag] cells. We have compared the changes brought about by statins with those brought about by the palmitoylation inhibitor cerulenin and the farnesyltransferase inhibitor CVFM (Cys-Val-Phe-Met). The statin-mediated reduction in Abeta production correlated with an inhibition of beta-secretase dimerization into its more active form at all concentrations of statin investigated. These effects were reversed by the administration of mevalonate, showing that these effects were mediated via 3-hydroxy-3-methylglutaryl-CoA-dependent pathways. At low (1 microM) statin concentrations, reduction in Abeta production and inhibition of beta-secretase dimerization were mediated by inhibition of isoprenoid synthesis. At high (>10 microM) concentrations of statins, inhibition of beta-secretase palmitoylation occurred, which we demonstrated to be regulated by intracellular cholesterol levels. There was also a concomitant concentration-dependent change in beta-secretase subcellular trafficking. Significantly, Abeta release from cells was markedly higher at 50 microM SIMVA than at 1 microM, whereas these concentrations resulted in similar reductions in total Abeta production, suggesting that low-dose statins may be more beneficial than high doses for the therapeutic treatment of Alzheimer's disease.
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Affiliation(s)
- Richard B Parsons
- Department of Basic Medical Sciences, St. Georges, University of London, Cranmer Terrace, London SW17 0RE, UK.
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42
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Dominguez DI, Hartmann D, De Strooper B. BACE1 and presenilin: two unusual aspartyl proteases involved in Alzheimer's disease. NEURODEGENER DIS 2006; 1:168-74. [PMID: 16908986 DOI: 10.1159/000080982] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Two enzymatic activities are required to generate the pathogenic beta-amyloid (Abeta) peptide that accumulates in the brain of Alzheimer's disease patients. Both activities are carried out by two unusual aspartyl proteases known as beta- and gamma-secretase. Their therapeutic inhibition appears, therefore, a promising strategy to treat the disease. Transgenic mouse models in which the genes encoding the secretases have been ablated offer an invaluable tool, on the one hand, to gain more insights into the biological function of these proteases and, on the other hand, to predict the consequences that might be associated with enzyme inhibition in vivo.
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Affiliation(s)
- Diana-Ines Dominguez
- Neuronal Cell Biology and Gene Transfer Laboratory, Department of Human Genetics, KU Leuven and VIB4, Leuven, Belgium.
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43
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Sjögren M, Mielke M, Gustafson D, Zandi P, Skoog I. Cholesterol and Alzheimer's disease—is there a relation? Mech Ageing Dev 2006; 127:138-47. [PMID: 16332384 DOI: 10.1016/j.mad.2005.09.020] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2004] [Revised: 05/16/2005] [Accepted: 09/15/2005] [Indexed: 11/25/2022]
Abstract
The predominating theory on the pathophysiology of Alzheimer's disease (AD) concerns the mis-metabolism of amyloid precursor protein (APP). As a result of this mis-metabolism, there is an increased production of the 42 amino acid form of beta-amyloid (Abeta42) that rapidly will form oligomers that initiates a cascade of events leading to the accumulation of amyloid plaques. Commonly recognised as vascular factors, hypertension, hypercholesterolemia and diabetes and the inheritance of the epsilon4 allele of the APOE gene, are also risk factors for AD. These risks have been found to promote the production of Abeta42. An association between cholesterol and the development of AD was suggested in the early 1990s and ever since, an increasing amount of research has confirmed that there is a link between cholesterol and the development of AD. A high cholesterol levels in mid-life is a risk for AD and statins, i.e., cholesterol-lowering drugs, reduce this risk. Statins may not only inhibit enzymes involved in the endogenous synthesis of cholesterol but also affect enzymes involved in Abeta metabolism, i.e., alpha-secretase and beta-secretase. This normalises the breakdown of APP thereby promoting the non-amyloidogenic pathway. In this review, investigations focusing on cholesterol and Alzheimer's disease are presented.
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Affiliation(s)
- Magnus Sjögren
- Department of Experimental Geriatrics, Neurotec, Karolinska Institute, Huddinge, Sweden.
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44
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Dillen K, Annaert W. A Two Decade Contribution of Molecular Cell Biology to the Centennial of Alzheimer's Disease: Are We Progressing Toward Therapy? INTERNATIONAL REVIEW OF CYTOLOGY 2006; 254:215-300. [PMID: 17148000 DOI: 10.1016/s0074-7696(06)54005-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Alzheimer's disease (AD), described for the first time 100 years ago, is a neurodegenerative disease characterized by two neuropathological hallmarks: neurofibrillary tangles containing hyperphosphorylated tau and senile plaques. These lesions are likely initiated by an imbalance between production and clearance of amyloid beta, leading to increased oligomerization of these peptides, formation of amyloid plaques in the brain of the patient, and final dementia. Amyloid beta is generated from amyloid precursor protein (APP) by subsequent beta- and gamma-secretase cleavage, the latter being a multiprotein complex consisting of presenilin-1 or -2, nicastrin, APH-1, and PEN-2. Alternatively, APP can be cleaved by alpha- and gamma-secretase, precluding the production of Abeta. In this review, we discuss the major breakthroughs during the past two decades of molecular cell biology and the current genetic and cell biological state of the art on APP proteolysis, including structure-function relationships and subcellular localization. Finally, potential directions for cell biological research toward the development of AD therapies are briefly discussed.
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Affiliation(s)
- Katleen Dillen
- Laboratory for Membrane Trafficking, Center for Human Genetics/VIB1104 & KULeuven, Gasthuisberg O&N1, B-3000 Leuven, Belgium
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45
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Abstract
A leading hypothesis on the pathophysiology of Alzheimer's disease (AD) is the mis-metabolism of amyloid precursor protein. This mis-metabolism causes the 42-amino acid form of A beta(Abeta42) to form oligomers that in turn start a chain of events leading to the accumulation of amyloid plaques. Vascular factors such as hypertension, hypercholesterolemia and diabetes as well as the inheritance of the epsilon4 allele of the ApoE gene are risk factors for AD. These risks are thought to promote the production of beta-amyloid (Abeta). An association between cholesterol and the development of AD was suggested in 1994 and since then, research has confirmed a link between cholesterol and the development of AD. A high cholesterol level in mid-life is a risk for AD and statins i.e. cholesterol-lowering drugs, reduce this risk. Statins inhibit enzymes involved in the endogenous synthesis of cholesterol and evidence is mounting that they also affect enzymes in Abeta metabolism i.e. beta-secretase. This normalises the breakdown of the precursor of Abeta, amyloid precursor protein, thereby promoting the nonamyloidogenic pathway. This review focusses on the link between cholesterol and Alzheimer's disease.
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Affiliation(s)
- Magnus Sjögren
- Section of Experimental Geriatrics, Neurotec, Karolinska Institute KFC, Novum Plan 4, SE-14186 Huddinge, Sweden.
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46
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Cottrell BA, Galvan V, Banwait S, Gorostiza O, Lombardo CR, Williams T, Schilling B, Peel A, Gibson B, Koo EH, Link CD, Bredesen DE. A pilot proteomic study of amyloid precursor interactors in Alzheimer's disease. Ann Neurol 2005; 58:277-89. [PMID: 16049941 PMCID: PMC1847583 DOI: 10.1002/ana.20554] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Several approaches have been used in an effort to identify proteins that interact with beta-amyloid precursor protein (APP). However, few studies have addressed the identification of proteins associated with APP in brain tissue from patients with Alzheimer's disease. We report the results of a pilot proteomic study performed on complexes immunoprecipitated with APP in brain samples of patients with Alzheimer's disease and normal control subjects. The 21 proteins identified could be grouped into five functional classes: molecular chaperones, cytoskeletal and structural proteins, proteins involved in trafficking, adaptors, and enzymes. Among the proteins identified, six had been reported previously as direct, indirect, or genetically inferred APP interactors. The other 15 proteins immunoprecipitated with APP were novel potential partners. We confirmed the APP interaction by Western blotting and coimmunolocalization in brain tissues, for 5 of the 21 interactors. In agreement with previous studies, our results are compatible with an involvement of APP in axonal transport and vesicular trafficking, and with a potential association of APP with cellular protein folding/protein degradation systems.
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Lane RM, Farlow MR. Lipid homeostasis and apolipoprotein E in the development and progression of Alzheimer's disease. J Lipid Res 2005; 46:949-68. [PMID: 15716586 DOI: 10.1194/jlr.m400486-jlr200] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Extracellular amyloid plaques, intracellular neurofibrillary tangles, and loss of basal forebrain cholinergic neurons in the brains of Alzheimer's disease (AD) patients may be the end result of abnormalities in lipid metabolism and peroxidation that may be caused, or exacerbated, by beta-amyloid peptide (Abeta). Apolipoprotein E (apoE) is a major apolipoprotein in the brain, mediating the transport and clearance of lipids and Abeta. ApoE-dependent dendritic and synaptic regeneration may be less efficient with apoE4, and this may result in, or unmask, age-related neurodegenerative changes. The increased risk of AD associated with apoE4 may be modulated by diet, vascular risk factors, and genetic polymorphisms that affect the function of other transporter proteins and enzymes involved in brain lipid homeostasis. Diet and apoE lipoproteins influence membrane lipid raft composition and the properties of enzymes, transporter proteins, and receptors mediating Abeta production and degradation, tau phosphorylation, glutamate and glucose uptake, and neuronal signal transduction. The level and isoform of apoE may influence whether Abeta is likely to be metabolized or deposited. This review examines the current evidence for diet, lipid homeostasis, and apoE in the pathogenesis of AD. Effects on the cholinergic system and response to cholinesterase inhibitors by APOE allele carrier status are discussed briefly.
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Affiliation(s)
- Roger M Lane
- Novartis Pharmaceuticals Corporation, East Hanover, NJ, USA.
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Wickham L, Benjannet S, Marcinkiewicz E, Chretien M, Seidah NG. Beta-amyloid protein converting enzyme 1 and brain-specific type II membrane protein BRI3: binding partners processed by furin. J Neurochem 2005; 92:93-102. [PMID: 15606899 DOI: 10.1111/j.1471-4159.2004.02840.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Using a yeast two-hybrid system, we screened a human brain cDNA library for possible interacting proteins with the C-terminal cytosolic tail of the beta-secretase beta-amyloid protein converting enzyme (BACE)1. This identified seven potential candidates, including the brain-specific type II membrane protein BRI3. Co-localization and co-immunoprecipitation experiments confirmed that BACE1 and BRI3 co-localize and interact with each other via the cytosolic tail of BACE1. Furthermore, pulse and pulse-chase analyses revealed that the pro-protein convertases furin, and to a lesser extent PC7 and PC5A, process BRI3 into a C-terminal secreted approximately 4-kDa product. Thus, furin efficiently processes both pro-BACE1 and its novel interacting protein pro-BRI3.
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Affiliation(s)
- Louise Wickham
- Laboratory of Biochemical Neuroendocrinology, Clinical Research Institute of Montreal, Montreal, Quebec, Canada
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BACE Inhibitors for the Treatment of Alzheimer's Disease. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 2005. [DOI: 10.1016/s0065-7743(05)40003-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/08/2023]
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Igbavboa U, Eckert GP, Malo TM, Studniski AE, Johnson LNA, Yamamoto N, Kobayashi M, Fujita SC, Appel TR, Müller WE, Wood WG, Yanagisawa K. Murine synaptosomal lipid raft protein and lipid composition are altered by expression of human apoE 3 and 4 and by increasing age. J Neurol Sci 2004; 229-230:225-32. [PMID: 15760644 DOI: 10.1016/j.jns.2004.11.037] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Apolipoprotein E (apoE) 4 and aging are risk factors for Alzheimer's disease (AD). Mice expressing human apoE4 and aged wild-type mice show a similarity in the transbilayer distribution of cholesterol in synaptic plasma membranes (SPMs) but differ markedly compared with apoE3 mice and young mice. The largest changes in cholesterol distribution were observed in the SPM exofacial leaflet where there was a doubling of cholesterol. Lipid rafts are thought to be associated with the exofacial leaflet, and we proposed that lipid raft protein and lipid composition would be associated with apoE genotype and age. Lipid rafts were isolated from synaptosomes of different age groups (2, 12, 24 months) of mice expressing human apoE3 and apoE4. Lipid raft markers, alkaline phosphatase (ALP), flotillin-1, cholesterol and sphingomyelin (SM) were examined. Lipid rafts of young apoE4 mice were more similar to older mice as compared with young apoE3 mice in reductions in alkaline phosphatase activity and flotillin-1 abundance. Lipid raft cholesterol and sphingomyelin levels were not significantly different between the young apoE3 and apoE4 mice but cholesterol levels of lipid rafts did increase with age in both genotypes. Results of the present study demonstrate that the two risk factors for Alzheimer's disease, apoE4 genotype and increasing age have similar effects on brain lipid raft protein markers and these findings support the notion that the transbilayer distribution of cholesterol is associated with lipid raft function.
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Affiliation(s)
- U Igbavboa
- Department of Pharmacology, University of Minnesota School of Medicine, and Geriatric Research, Education and Clinical Center, VA Medical Center, 11G, Minneapolis, Minnesota 55417, USA
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