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Chakravorty A, McCalpin SD, Sahoo BR, Ramamoorthy A, Brooks CL. Free Gangliosides Can Alter Amyloid-β Aggregation. J Phys Chem Lett 2022; 13:9303-9308. [PMID: 36174129 PMCID: PMC9700483 DOI: 10.1021/acs.jpclett.2c02362] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A recently proposed lipid-chaperone hypothesis suggests that free lipid molecules, not bound to membranes, affect the aggregation of amyloidogenic peptides such as amyloid-β (Aβ) peptides, whose aggregates are the hallmarks of Alzheimer's disease. Here, we combine experiments with all-atom molecular dynamics simulations in explicit solvent to explore the effects of neuronal ganglioside GM1, abundant in mammalian brains, on the aggregation of two principal isoforms of Aβ, Aβ40 and Aβ42. Our simulations show that free GM1 forms stable, highly water-soluble complexes with both isoforms, and nuclear magnetic resonance experiments support the formation of well-ordered, structurally compact GM1+Aβ complexes. By simulation, we also show that Aβ40 monomers display a preference for binding to GM1-containing hetero-oligomers over GM1-lacking homo-oligomers, while Aβ42 monomers have the opposite preference. These observations explain why GM1 dose-dependently inhibits Aβ40 aggregation but has no effect on Aβ42 aggregation, as assessed by thioflavin T fluorescence.
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Affiliation(s)
- Arghya Chakravorty
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, United States
| | - Samuel D. McCalpin
- Department of Chemistry, Biophysics Program, Biomedical Engineering, Macromolecular Engineering and Science, Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, United States
| | - Bikash R. Sahoo
- Department of Chemistry, Biophysics Program, Biomedical Engineering, Macromolecular Engineering and Science, Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, United States
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, United States
| | - Ayyalusamy Ramamoorthy
- Department of Chemistry, Biophysics Program, Biomedical Engineering, Macromolecular Engineering and Science, Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, United States
| | - Charles L. Brooks
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, United States
- Department of Chemistry, Biophysics Program, Biomedical Engineering, Macromolecular Engineering and Science, Michigan Neuroscience Institute, University of Michigan, Ann Arbor, MI 48109, United States
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2
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Mohamed Asik R, Suganthy N, Aarifa MA, Kumar A, Szigeti K, Mathe D, Gulyás B, Archunan G, Padmanabhan P. Alzheimer's Disease: A Molecular View of β-Amyloid Induced Morbific Events. Biomedicines 2021; 9:biomedicines9091126. [PMID: 34572312 PMCID: PMC8468668 DOI: 10.3390/biomedicines9091126] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 08/22/2021] [Accepted: 08/27/2021] [Indexed: 12/26/2022] Open
Abstract
Amyloid-β (Aβ) is a dynamic peptide of Alzheimer’s disease (AD) which accelerates the disease progression. At the cell membrane and cell compartments, the amyloid precursor protein (APP) undergoes amyloidogenic cleavage by β- and γ-secretases and engenders the Aβ. In addition, externally produced Aβ gets inside the cells by receptors mediated internalization. An elevated amount of Aβ yields spontaneous aggregation which causes organelles impairment. Aβ stimulates the hyperphosphorylation of tau protein via acceleration by several kinases. Aβ travels to the mitochondria and interacts with its functional complexes, which impairs the mitochondrial function leading to the activation of apoptotic signaling cascade. Aβ disrupts the Ca2+ and protein homeostasis of the endoplasmic reticulum (ER) and Golgi complex (GC) that promotes the organelle stress and inhibits its stress recovery machinery such as unfolded protein response (UPR) and ER-associated degradation (ERAD). At lysosome, Aβ precedes autophagy dysfunction upon interacting with autophagy molecules. Interestingly, Aβ act as a transcription regulator as well as inhibits telomerase activity. Both Aβ and p-tau interaction with neuronal and glial receptors elevate the inflammatory molecules and persuade inflammation. Here, we have expounded the Aβ mediated events in the cells and its cosmopolitan role on neurodegeneration, and the current clinical status of anti-amyloid therapy.
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Affiliation(s)
- Rajmohamed Mohamed Asik
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 636921, Singapore; (R.M.A.); (B.G.)
- Cognitive Neuroimaging Centre, 59 Nanyang Drive, Nanyang Technological University, Singapore 636921, Singapore
- Department of Animal Science, Bharathidasan University, Tiruchirappalli 620024, Tamil Nadu, India;
| | - Natarajan Suganthy
- Department of Nanoscience and Technology, Alagappa University, Karaikudi 630003, Tamil Nadu, India;
| | - Mohamed Asik Aarifa
- Department of Animal Science, Bharathidasan University, Tiruchirappalli 620024, Tamil Nadu, India;
| | - Arvind Kumar
- Centre for Cellular and Molecular Biology, Hyderabad 500007, Telangana, India;
| | - Krisztián Szigeti
- Department of Biophysics and Radiation Biology, Semmelweis University, 1094 Budapest, Hungary; (K.S.); (D.M.)
- CROmed Translational Research Centers, 1094 Budapest, Hungary
| | - Domokos Mathe
- Department of Biophysics and Radiation Biology, Semmelweis University, 1094 Budapest, Hungary; (K.S.); (D.M.)
- CROmed Translational Research Centers, 1094 Budapest, Hungary
- In Vivo Imaging Advanced Core Facility, Hungarian Center of Excellence for Molecular Medicine (HCEMM), 1094 Budapest, Hungary
| | - Balázs Gulyás
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 636921, Singapore; (R.M.A.); (B.G.)
- Cognitive Neuroimaging Centre, 59 Nanyang Drive, Nanyang Technological University, Singapore 636921, Singapore
- Department of Clinical Neuroscience, Karolinska Institute, 17176 Stockholm, Sweden
| | - Govindaraju Archunan
- Department of Animal Science, Bharathidasan University, Tiruchirappalli 620024, Tamil Nadu, India;
- Marudupandiyar College, Thanjavur 613403, Tamil Nadu, India
- Correspondence: (G.A.); (P.P.)
| | - Parasuraman Padmanabhan
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore 636921, Singapore; (R.M.A.); (B.G.)
- Cognitive Neuroimaging Centre, 59 Nanyang Drive, Nanyang Technological University, Singapore 636921, Singapore
- Correspondence: (G.A.); (P.P.)
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3
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Kuo YC, Ng IW, Rajesh R. Glutathione- and apolipoprotein E-grafted liposomes to regulate mitogen-activated protein kinases and rescue neurons in Alzheimer's disease. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 2021; 127:112233. [PMID: 34225874 DOI: 10.1016/j.msec.2021.112233] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 05/25/2021] [Accepted: 05/29/2021] [Indexed: 01/29/2023]
Abstract
Neurodegenerative disorders, such as Alzheimer's disease (AD), present biomedical challenges due to inability of pharmaceuticals to permeate the blood-brain barrier (BBB) and lack of therapeutic specificity in definite sites against multiple pathologies. Phosphatidylcholine (PC)-liposomes carrying curcumin (CURC), quercetin (QU), epigallocatechin gallate (EGCG) and rosmarinic acid (RA) with crosslinked glutathione (GSH) and apolipoprotein E (ApoE) were fabricated to recognize brain microvascular endothelial cells and amyloid beta (Aβ), and reduce tau protein hyperphosphorylation for AD management. Addition of stearic acid to liposomal bilayers ameliorated particle stability, promoted drug entrapment efficiency, and prolonged drug release duration. The triple targeting liposomes boosted the capability of CURC, QU, EGCG and RA for crossing the BBB with the assistance of grafted GSH and ApoE and docking Aβ around SK-N-MC cells using ApoE and PC. Moreover, GSH-ApoE-PC-liposomes benefited the 4 medicines in simultaneously transporting to Aβ1-42-insulted neurons, in functioning against hyperphosphorylated mitogen-activated protein kinases, including p-c-Jun N-terminal protein kinase, p-extracellular signal-regulated protein kinase 1/2 and p-p38, in downregulating tau protein at S202, caspase-3 and interleukin-6, and in upregulating p-cyclic adenosine monophosphate response element-binding protein. GSH-ApoE-PC-liposomes can be promising colloidal carriers in delivering CURC, QU, EGCG and RA to degenerated neural tissue in a controlled manner, targeting pathological factors for neuroprotection, and raising preclinical effectualness for AD treatment.
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Affiliation(s)
- Yung-Chih Kuo
- Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 62102, Taiwan, ROC; Advanced Institute of Manufacturing with High-tech Innovations, National Chung Cheng University, Chia-Yi 62102, Taiwan, ROC.
| | - I-Wen Ng
- Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 62102, Taiwan, ROC
| | - Rajendiran Rajesh
- Department of Chemical Engineering, National Chung Cheng University, Chia-Yi 62102, Taiwan, ROC
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Wang Y, Sun S, Yu L, Hu S, Fan W, Leng F, Ma J. Optimization and mechanism exploration for Escherichia coli transformed with plasmid pUC19 by the combination with ultrasound treatment and chemical method. ULTRASONICS SONOCHEMISTRY 2021; 74:105552. [PMID: 33887660 PMCID: PMC8091046 DOI: 10.1016/j.ultsonch.2021.105552] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Revised: 03/28/2021] [Accepted: 04/06/2021] [Indexed: 06/12/2023]
Abstract
As a basic technique of molecular cloning, bio-transformation has been successfully used in the fields of biomedicine and food processing. In this study, we established a transformation system of exogenous DNA into E. coli cells mediated by ultrasound. Under the optimal conditions (i.e. 35 °C, 40 W, 25 s, OD600 = 0.4-0.6) optimized by RSM, the transformation efficiency reached at 1.006 × 107 CFU/μg DNA. The results of membrane permeability, macromolecular substance and cell structure analysis before and after ultrasound treatment showed that the damage of host cells induced by lower (40 W) ultrasound and shorter ultrasound time (25 s) was reversible, and the transformation efficiency and cell survival rate were not significantly affected under this condition. In brief, proper changes in cell membrane and cell wall were the basic conditions for host cells to uptake exogenous DNA, while, whether exogenous DNA could be replicated and expressed in cells depends on the viability of host cells.
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Affiliation(s)
- Yonggang Wang
- School of Life Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, China.
| | - Shangchen Sun
- School of Petrochemical Engineering, Lanzhou University of Technology, Lanzhou 730050, China
| | - Linmiao Yu
- School of Life Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, China
| | - Shu Hu
- School of Life Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, China
| | - Wenguang Fan
- School of Life Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, China
| | - Feifan Leng
- School of Life Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, China.
| | - Jianzhong Ma
- School of Life Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, China.
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5
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Dehhaghi M, Kazemi Shariat Panahi H, Braidy N, Guillemin GJ. Herpetosiphon Secondary Metabolites Inhibit Amyloid-β Toxicity in Human Primary Astrocytes. J Alzheimers Dis 2021; 76:423-433. [PMID: 32474470 DOI: 10.3233/jad-200116] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
BACKGROUND The accumulation of extracellular plaques containing amyloid-β protein (Aβ) in the brain is one of the main pathological hallmarks of Alzheimer's disease (AD). Aβ peptide can promote the production of highly volatile free radicals and reactive oxygen species (ROS) that can induce oxidative damage to neurons and astrocytes. At present, numerous studies have investigated the neuroprotective and glioprotective effects of natural products derived from plants, animals, and microorganisms. OBJECTIVE We investigated the glioprotective effect of secondary metabolites obtained from Herpetosiphon sp. HM 1988 against Aβ40-induced toxicity in human primary astrocytes. METHODS The protective effect of bacterial secondary metabolites against Aβ40-induced inducible nitric oxide synthase (iNOS) activity was evaluated using the citrulline assay. To confirm the iNOS activity, nitrite production was assessed using the fluorometric Griess diazotization assay. Intracellular NAD+ depletion and lactate dehydrogenase (LDH) release in human primary astrocytes were also examined using well-established spectrophotometric assays. RESULTS Our results indicate that Aβ40 can induce elevation in iNOS and LDH activities, nitrite production, and cellular energy depletion. Importantly, extract of Herpetosiphon sp. HM 1988 decreased iNOS activity, nitrite production, and LDH release. In addition, metabolites of the strain were able to restore cellular energy deficits through inhibition of NAD+ depletion mediated by Aβ40. CONCLUSION These findings suggest that Herpetosiphon metabolites may represent a promising, novel source for the prevention of Aβ toxicity in AD.
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Affiliation(s)
- Mona Dehhaghi
- Neuroinflammation Group, Faculty of Medicine and Health Sciences, Macquarie University, NSW, Australia
| | | | - Nady Braidy
- Centre for Healthy Brain Ageing, School of Psychiatry, University of New South Wales, Faculty of Medicine, Sydney, Australia
| | - Gilles J Guillemin
- Neuroinflammation Group, Faculty of Medicine and Health Sciences, Macquarie University, NSW, Australia
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6
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Xi W, Vanderford EK, Liao Q, Hansmann UHE. Stability of Aβ-fibril fragments in the presence of fatty acids. Protein Sci 2019; 28:1973-1981. [PMID: 31461191 DOI: 10.1002/pro.3719] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 07/10/2019] [Accepted: 08/22/2019] [Indexed: 11/07/2022]
Abstract
We consider the effect of lauric acid on the stability of various fibril-like assemblies of Aβ peptides. For this purpose, we have performed molecular dynamics simulations of these assemblies either in complex with lauric acid or without presence of the ligand. While we do not observe a stabilizing effect on Aβ40 -fibrils, we find that addition of lauric acid strengthens the stability of fibrils built from the triple-stranded S-shaped Aβ42 -peptides considered to be more toxic. Or results may help to understand how the specifics of the brain-environment modulate amyloid formation and propagation.
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Affiliation(s)
- Wenhui Xi
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma
| | - Elliott K Vanderford
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma
| | - Qinxin Liao
- College of Chemistry, Beijing Normal University, Beijing, China
| | - Ulrich H E Hansmann
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma
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7
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Kubánková M, López-Duarte I, Kiryushko D, Kuimova MK. Molecular rotors report on changes in live cell plasma membrane microviscosity upon interaction with beta-amyloid aggregates. SOFT MATTER 2018; 14:9466-9474. [PMID: 30427370 DOI: 10.1039/c8sm01633j] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Amyloid deposits of aggregated beta-amyloid Aβ(1-42) peptides are a pathological hallmark of Alzheimer's disease. Aβ(1-42) aggregates are known to induce biophysical alterations in cells, including disruption of plasma membranes. We investigated the microviscosity of plasma membranes upon interaction with oligomeric and fibrillar forms of Aβ(1-42). Viscosity-sensing fluorophores termed molecular rotors were utilised to directly measure the microviscosities of giant plasma membrane vesicles (GPMVs) and plasma membranes of live SH-SY5Y and HeLa cells. The fluorescence lifetimes of membrane-inserting BODIPY-based molecular rotors revealed a decrease in bilayer microviscosity upon incubation with Aβ(1-42) oligomers, while fibrillar Aβ(1-42) did not significantly affect the microviscosity of the bilayer. In addition, we demonstrate that the neuroprotective peptide H3 counteracts the microviscosity change induced by Aβ(1-42) oligomers, suggesting the utility of H3 as a neuroprotective therapeutic agent in neurodegenerative disorders and indicating that ligand-induced membrane stabilisation may be a possible mechanism of neuroprotection during neurodegenerative disorders such as Alzheimer's disease.
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Affiliation(s)
- Markéta Kubánková
- Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ, UK.
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8
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Rangachari V, Dean DN, Rana P, Vaidya A, Ghosh P. Cause and consequence of Aβ - Lipid interactions in Alzheimer disease pathogenesis. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2018; 1860:1652-1662. [PMID: 29526709 PMCID: PMC6133763 DOI: 10.1016/j.bbamem.2018.03.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/25/2017] [Revised: 02/28/2018] [Accepted: 03/02/2018] [Indexed: 12/14/2022]
Abstract
Self-templating propagation of protein aggregate conformations is increasingly becoming a significant factor in many neurological diseases. In Alzheimer disease (AD), intrinsically disordered amyloid-β (Aβ) peptides undergo aggregation that is sensitive to environmental conditions. High-molecular weight aggregates of Aβ that form insoluble fibrils are deposited as senile plaques in AD brains. However, low-molecular weight aggregates called soluble oligomers are known to be the primary toxic agents responsible for neuronal dysfunction. The aggregation process is highly stochastic involving both homotypic (Aβ-Aβ) and heterotypic (Aβ with interacting partners) interactions. Two of the important members of interacting partners are membrane lipids and surfactants, to which Aβ shows a perpetual association. Aβ-membrane interactions have been widely investigated for more than two decades, and this research has provided a wealth of information. Although this has greatly enriched our understanding, the objective of this review is to consolidate the information from the literature that collectively showcases the unique phenomenon of lipid-mediated Aβ oligomer generation, which has largely remained inconspicuous. This is especially important because Aβ aggregate "strains" are increasingly becoming relevant in light of the correlations between the structure of aggregates and AD phenotypes. Here, we will focus on aspects of Aβ-lipid interactions specifically from the context of how lipid modulation generates a wide variety of biophysically and biochemically distinct oligomer sub-types. This, we believe, will refocus our thinking on the influence of lipids and open new approaches in delineating the mechanisms of AD pathogenesis. This article is part of a Special Issue entitled: Protein Aggregation and Misfolding at the Cell Membrane Interface edited by Ayyalusamy Ramamoorthy.
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Affiliation(s)
- Vijayaraghavan Rangachari
- Department of Chemistry & Biochemistry, University of Southern Mississippi, Hattiesburg, MS 39406, USA.
| | - Dexter N Dean
- Department of Chemistry & Biochemistry, University of Southern Mississippi, Hattiesburg, MS 39406, USA
| | - Pratip Rana
- Department of Computer Science, Virginia Commonwealth University, Richmond, VA 23284, USA
| | - Ashwin Vaidya
- Department of Mathematical Science, Montclair State University, Montclair, NJ 07043, USA
| | - Preetam Ghosh
- Department of Computer Science, Virginia Commonwealth University, Richmond, VA 23284, USA
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9
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Sun M, Zhao Y, Han M, Zhang B, Zhang X, Zhang Q, Lim NKH, Wang WA, Huang FD. TTC7 and Hyccin Regulate Neuronal Aβ42 Accumulation and its Associated Neural Deficits in Aβ42-Expressing Drosophila. J Alzheimers Dis 2018; 65:1001-1010. [PMID: 30103315 DOI: 10.3233/jad-170907] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Neuronal amyloid-β (Aβ) accumulation plays an important role in the pathogenesis of Alzheimer's disease (AD). The conformation and toxicity of Aβ are regulated by lipids on the plasma membrane. Previously, we found downregulation of Rolling Blackout (RBO) or phosphatidylinositol-4-kinase type IIIα (PI4KIIIα) reduces neuronal Aβ accumulation and associated neural deficits in a Drosophila model expressing Aβ42. In mammals, the homologs of RBO and PI4KIIIα were reported to form a plasma membrane-localized complex with a scaffold protein TTC7 and cytosolic protein Hyccin/FAM126A to tightly control the plasmalemmal level of phosphatidylinositol-4-phosphate. Here, we show genetic downregulation of Drosophila TTC7 and Hyccin also reduces neuronal Aβ accumulation and associated synaptic and motor defects as well as premature death in Aβ42-expressing flies, while overexpression of TTC7 and Hyccin produced the opposite effect. These results, together with our previous study, demonstrate that RBO/TTC7/PI4KIIIα/Hyccin regulate neuronal Aβ accumulation and associated neural deficits in the Drosophila model, further supporting the RBO/Efr3-PI4KIIIα complex as a potential therapeutic target for AD.
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Affiliation(s)
- Minghao Sun
- Shanghai Advanced Research Institute, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Yinghui Zhao
- Shanghai Advanced Research Institute, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China.,Laboratory of Molecular Neurobiology, School of Life Sciences, Shanghai University, Shanghai, China
| | - Men Han
- Department of Neurology, Qingdao Municipal Hospital, School of Medicine, Qingdao University, Qingdao, China
| | - Baozhu Zhang
- Shanghai Advanced Research Institute, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Xiao Zhang
- Shanghai Advanced Research Institute, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Qichao Zhang
- Shanghai Advanced Research Institute, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China.,Sino-Danish College, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, China
| | - Nastasia K-H Lim
- Shanghai Advanced Research Institute, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China.,Shanghai Institute of Materia Medica, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China
| | - Wen-An Wang
- Department of Neurology, Xinhua Hospital Chongming Branch Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Fu-De Huang
- Shanghai Advanced Research Institute, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Shanghai, China.,Sino-Danish College, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, China
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10
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Morris C, Cupples S, Kent TW, Elbassal EA, Wojcikiewicz EP, Yi P, Du D. N-Terminal Charged Residues of Amyloid-β Peptide Modulate Amyloidogenesis and Interaction with Lipid Membrane. Chemistry 2018; 24:9494-9498. [PMID: 29738067 PMCID: PMC6035087 DOI: 10.1002/chem.201801805] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 05/07/2018] [Indexed: 11/08/2022]
Abstract
Interactions of amyloid-β (Aβ) peptides and cellular membranes are proposed to be closely related with Aβ neurotoxicity in Alzheimer's disease. In this study, we systematically investigated the effect of the N-terminal hydrophilic region of Aβ40 on its amyloidogenesis and interaction with supported phospholipid bilayer. Our results show that modulation of the charge properties of the dynamic N-terminal region dramatically influences the aggregation properties of Aβ. Furthermore, our results demonstrate that the N-terminal charged residues play a crucial role in driving the early adsorption and latter remobilization of the peptide on membrane bilayer, and mediating the rigidity and viscoelasticity properties of the bound Aβ40 at the membrane interface. The results provide new mechanistic insight into the early Aβ-membrane interactions and binding, which may be critical for elucidating membrane-mediated Aβ amyloidogenesis in a physiological environment and unravelling the origin of Aβ neurotoxicity.
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Affiliation(s)
- Clifford Morris
- Department of Chemistry and Biochemistry, Florida Atlantic University, Boca Raton, FL, 33431, USA
| | - Shirin Cupples
- Department of Civil, Environmental and Geomatics Engineering, Florida Atlantic University, Boca Raton, FL, 33431, USA
- Department of Ocean and Mechanical Engineering, Florida Atlantic University, Boca Raton, FL, 33431, USA
| | - Thomas W Kent
- Department of Chemistry and Biochemistry, Florida Atlantic University, Boca Raton, FL, 33431, USA
| | - Esmail A Elbassal
- Department of Chemistry and Biochemistry, Florida Atlantic University, Boca Raton, FL, 33431, USA
| | - Ewa P Wojcikiewicz
- Department of Biomedical Science, Florida Atlantic University, Boca Raton, FL, 33431, USA
| | - Peng Yi
- Department of Civil, Environmental and Geomatics Engineering, Florida Atlantic University, Boca Raton, FL, 33431, USA
| | - Deguo Du
- Department of Chemistry and Biochemistry, Florida Atlantic University, Boca Raton, FL, 33431, USA
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11
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Cebecauer M, Hof M, Amaro M. Impact of GM 1 on Membrane-Mediated Aggregation/Oligomerization of β-Amyloid: Unifying View. Biophys J 2017; 113:1194-1199. [PMID: 28410623 DOI: 10.1016/j.bpj.2017.03.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 03/02/2017] [Accepted: 03/13/2017] [Indexed: 11/18/2022] Open
Abstract
In this perspective we summarize current knowledge of the effect of monosialoganglioside GM1 on the membrane-mediated aggregation of the β-amyloid (Aβ) peptide. GM1 has been suggested to be actively involved in the development of Alzheimer's disease due to its ability to seed the aggregation of Aβ. However, GM1 is known to be neuroprotective against Aβ-induced toxicity. Here we suggest that the two scenarios are not mutually exclusive but rather complementary, and might depend on the organization of GM1 in membranes. Improving our understanding of the molecular details behind the role of gangliosides in neurodegenerative amyloidoses might help in developing disease-modifying treatments.
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Affiliation(s)
- Marek Cebecauer
- Department of Biophysical Chemistry, J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, v.v.i., Prague, Czech Republic
| | - Martin Hof
- Department of Biophysical Chemistry, J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, v.v.i., Prague, Czech Republic.
| | - Mariana Amaro
- Department of Biophysical Chemistry, J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, v.v.i., Prague, Czech Republic.
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12
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Phosphatidylcholine protects neurons from toxic effects of amyloid β-protein in culture. Brain Res 2016; 1642:376-383. [DOI: 10.1016/j.brainres.2016.04.035] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Revised: 04/11/2016] [Accepted: 04/13/2016] [Indexed: 12/14/2022]
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13
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Han SH, Park JC, Mook-Jung I. Amyloid β-interacting partners in Alzheimer's disease: From accomplices to possible therapeutic targets. Prog Neurobiol 2016; 137:17-38. [DOI: 10.1016/j.pneurobio.2015.12.004] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 12/02/2015] [Accepted: 12/09/2015] [Indexed: 12/20/2022]
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14
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Kim Y, Park JH, Lee H, Nam JM. How Do the Size, Charge and Shape of Nanoparticles Affect Amyloid β Aggregation on Brain Lipid Bilayer? Sci Rep 2016; 6:19548. [PMID: 26782664 PMCID: PMC4726094 DOI: 10.1038/srep19548] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Accepted: 11/13/2015] [Indexed: 11/21/2022] Open
Abstract
Here, we studied the effect of the size, shape, and surface charge of Au nanoparticles (AuNPs) on amyloid beta (Aβ) aggregation on a total brain lipid-based supported lipid bilayer (brain SLB), a fluid platform that facilitates Aβ-AuNP aggregation process. We found that larger AuNPs induce large and amorphous aggregates on the brain SLB, whereas smaller AuNPs induce protofibrillar Aβ structures. Positively charged AuNPs were more strongly attracted to Aβ than negatively charged AuNPs, and the stronger interactions between AuNPs and Aβ resulted in fewer β-sheets and more random coil structures. We also compared spherical AuNPs, gold nanorods (AuNRs), and gold nanocubes (AuNCs) to study the effect of nanoparticle shape on Aβ aggregation on the brain SLB. Aβ was preferentially bound to the long axis of AuNRs and fewer fibrils were formed whereas all the facets of AuNCs interacted with Aβ to produce the fibril networks. Finally, it was revealed that different nanostructures induce different cytotoxicity on neuroblastoma cells, and, overall, smaller Aβ aggregates induce higher cytotoxicity. The results offer insight into the roles of NPs and brain SLB in Aβ aggregation on the cell membrane and can facilitate the understanding of Aβ-nanostructure co-aggregation mechanism and tuning Aβ aggregate structures.
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Affiliation(s)
- Yuna Kim
- Department of Chemistry, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul 151-742, South Korea
| | - Ji-Hyun Park
- Department of Chemistry, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul 151-742, South Korea
| | - Hyojin Lee
- Department of Chemistry, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul 151-742, South Korea
| | - Jwa-Min Nam
- Department of Chemistry, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul 151-742, South Korea
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Tang W, Tam JHK, Seah C, Chiu J, Tyrer A, Cregan SP, Meakin SO, Pasternak SH. Arf6 controls beta-amyloid production by regulating macropinocytosis of the Amyloid Precursor Protein to lysosomes. Mol Brain 2015; 8:41. [PMID: 26170135 PMCID: PMC4501290 DOI: 10.1186/s13041-015-0129-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 06/11/2015] [Indexed: 11/15/2022] Open
Abstract
Alzheimer’s disease (AD) is characterized by the deposition of Beta-Amyloid (Aβ) peptides in the brain. Aβ peptides are generated by cleavage of the Amyloid Precursor Protein (APP) by the β − and γ − secretase enzymes. Although this process is tightly linked to the internalization of cell surface APP, the compartments responsible are not well defined. We have found that APP can be rapidly internalized from the cell surface to lysosomes, bypassing early and late endosomes. Here we show by confocal microscopy and electron microscopy that this pathway is mediated by macropinocytosis. APP internalization is enhanced by antibody binding/crosslinking of APP suggesting that APP may function as a receptor. Furthermore, a dominant negative mutant of Arf6 blocks direct transport of APP to lysosomes, but does not affect classical endocytosis to endosomes. Arf6 expression increases through the hippocampus with the development of Alzheimer’s disease, being expressed mostly in the CA1 and CA2 regions in normal individuals but spreading through the CA3 and CA4 regions in individuals with pathologically diagnosed AD. Disruption of lysosomal transport of APP reduces both Aβ40 and Aβ42 production by more than 30 %. Our findings suggest that the lysosome is an important site for Aβ production and that altering APP trafficking represents a viable strategy to reduce Aβ production.
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Affiliation(s)
- Weihao Tang
- J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada. .,Department of Physiology and Pharmacology, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada.
| | - Joshua H K Tam
- J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada. .,Department of Physiology and Pharmacology, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada.
| | - Claudia Seah
- J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada.
| | - Justin Chiu
- J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada. .,Department of Physiology and Pharmacology, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada.
| | - Andrea Tyrer
- J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada. .,Department of Physiology and Pharmacology, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada.
| | - Sean P Cregan
- J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada. .,Department of Physiology and Pharmacology, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada.
| | - Susan O Meakin
- J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada. .,Department of Biochemistry, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada.
| | - Stephen H Pasternak
- J. Allyn Taylor Centre for Cell Biology, Molecular Medicine Research Group, Robarts Research Institute, 1151 Richmond St, London, ON, N6A 5B8, Canada. .,Department of Clinical Neurological Sciences, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada. .,Department of Physiology and Pharmacology, Schulich School of Medicine, the University of Western Ontario, London, ON, N6A 5B7, Canada.
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Muñoz G, Urrutia JC, Burgos CF, Silva V, Aguilar F, Sama M, Yeh HH, Opazo C, Aguayo LG. Low concentrations of ethanol protect against synaptotoxicity induced by Aβ in hippocampal neurons. Neurobiol Aging 2015; 36:845-56. [DOI: 10.1016/j.neurobiolaging.2014.10.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Revised: 09/23/2014] [Accepted: 10/08/2014] [Indexed: 12/27/2022]
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17
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van Maarschalkerweerd A, Vetri V, Langkilde AE, Foderà V, Vestergaard B. Protein/lipid coaggregates are formed during α-synuclein-induced disruption of lipid bilayers. Biomacromolecules 2014; 15:3643-54. [PMID: 25210839 DOI: 10.1021/bm500937p] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Amyloid formation is associated with neurodegenerative diseases such as Parkinson's disease (PD). Significant α-synuclein (αSN) deposition in lipid-rich Lewy bodies is a hallmark of PD. Nonetheless, an unraveling of the connection between neurodegeneration and amyloid fibrils, including the molecular mechanisms behind potential amyloid-mediated toxic effects, is still missing. Interaction between amyloid aggregates and the lipid cell membrane is expected to play a key role in the disease progress. Here, we present experimental data based on hybrid analysis of two-photon-microscopy, solution small-angle X-ray scattering and circular dichroism data. Data show in real time changes in liposome morphology and stability upon protein addition and reveal that membrane disruption mediated by amyloidogenic αSN is associated with dehydration of anionic lipid membranes and stimulation of protein secondary structure. As a result of membrane fragmentation, soluble αSN:-lipid coaggregates are formed, hence, suggesting a novel molecular mechanism behind PD amyloid cytotoxicity.
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Affiliation(s)
- Andreas van Maarschalkerweerd
- Department of Drug Design and Pharmacology, University of Copenhagen , Universitetsparken 2, 2100 Copenhagen, Denmark
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18
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Tam JHK, Seah C, Pasternak SH. The Amyloid Precursor Protein is rapidly transported from the Golgi apparatus to the lysosome and where it is processed into beta-amyloid. Mol Brain 2014; 7:54. [PMID: 25085554 PMCID: PMC4237969 DOI: 10.1186/s13041-014-0054-1] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Accepted: 07/23/2014] [Indexed: 01/18/2023] Open
Abstract
BACKGROUND Alzheimer's disease (AD) is characterized by cerebral deposition of β-amyloid peptide (Aβ). Aβ is produced by sequential cleavage of the Amyloid Precursor Protein (APP) by β- and γ-secretases. Many studies have demonstrated that the internalization of APP from the cell surface can regulate Aβ production, although the exact organelle in which Aβ is produced remains contentious. A number of recent studies suggest that intracellular trafficking also plays a role in regulating Aβ production, but these pathways are relatively under-studied. The goal of this study was to elucidate the intracellular trafficking of APP, and to examine the site of intracellular APP processing. RESULTS We have tagged APP on its C-terminal cytoplasmic tail with photoactivatable Green Fluorescent Protein (paGFP). By photoactivating APP-paGFP in the Golgi, using the Golgi marker Galactosyltranferase fused to Cyan Fluorescent Protein (GalT-CFP) as a target, we are able to follow a population of nascent APP molecules from the Golgi to downstream compartments identified with compartment markers tagged with red fluorescent protein (mRFP or mCherry); including rab5 (early endosomes) rab9 (late endosomes) and LAMP1 (lysosomes). Because γ-cleavage of APP releases the cytoplasmic tail of APP including the photoactivated GFP, resulting in loss of fluorescence, we are able to visualize the cleavage of APP in these compartments. Using APP-paGFP, we show that APP is rapidly trafficked from the Golgi apparatus to the lysosome; where it is rapidly cleared. Chloroquine and the highly selective γ-secretase inhibitor, L685, 458, cause the accumulation of APP in lysosomes implying that APP is being cleaved by secretases in the lysosome. The Swedish mutation dramatically increases the rate of lysosomal APP processing, which is also inhibited by chloroquine and L685, 458. By knocking down adaptor protein 3 (AP-3; a heterotetrameric protein complex required for trafficking many proteins to the lysosome) using siRNA, we are able to reduce this lysosomal transport. Blocking lysosomal transport of APP reduces Aβ production by more than a third. CONCLUSION These data suggests that AP-3 mediates rapid delivery of APP to lysosomes, and that the lysosome is a likely site of Aβ production.
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Affiliation(s)
- Joshua HK Tam
- J. Allyn Taylor Centre for Cell Biology, Molecular Brain Research Group, Robarts Research Institute, 100 Perth Drive, London N6A 5K8, Ontario, Canada
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, the University of Western Ontario, London N6A 5K8, Ontario, Canada
| | - Claudia Seah
- J. Allyn Taylor Centre for Cell Biology, Molecular Brain Research Group, Robarts Research Institute, 100 Perth Drive, London N6A 5K8, Ontario, Canada
| | - Stephen H Pasternak
- J. Allyn Taylor Centre for Cell Biology, Molecular Brain Research Group, Robarts Research Institute, 100 Perth Drive, London N6A 5K8, Ontario, Canada
- Department of Clinical Neurological Sciences, London N6A 5K8, Ontario, Canada
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, the University of Western Ontario, London N6A 5K8, Ontario, Canada
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19
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Lauterbach T, Manna M, Ruhnow M, Wisantoso Y, Wang Y, Matysik A, Oglęcka K, Mu Y, Geifman-Shochat S, Wohland T, Kraut R. Weak glycolipid binding of a microdomain-tracer peptide correlates with aggregation and slow diffusion on cell membranes. PLoS One 2012; 7:e51222. [PMID: 23251459 PMCID: PMC3520979 DOI: 10.1371/journal.pone.0051222] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Accepted: 10/30/2012] [Indexed: 11/18/2022] Open
Abstract
Organized assembly or aggregation of sphingolipid-binding ligands, such as certain toxins and pathogens, has been suggested to increase binding affinity of the ligand to the cell membrane and cause membrane reorganization or distortion. Here we show that the diffusion behavior of the fluorescently tagged sphingolipid-interacting peptide probe SBD (Sphingolipid Binding Domain) is altered by modifications in the construction of the peptide sequence that both result in a reduction in binding to ganglioside-containing supported lipid membranes, and at the same time increase aggregation on the cell plasma membrane, but that do not change relative amounts of secondary structural features. We tested the effects of modifying the overall charge and construction of the SBD probe on its binding and diffusion behavior, by Surface Plasmon Resonance (SPR; Biacore) analysis on lipid surfaces, and by Fluorescence Correlation Spectroscopy (FCS) on live cells, respectively. SBD binds preferentially to membranes containing the highly sialylated gangliosides GT1b and GD1a. However, simple charge interactions of the peptide with the negative ganglioside do not appear to be a critical determinant of binding. Rather, an aggregation-suppressing amino acid composition and linker between the fluorophore and the peptide are required for optimum binding of the SBD to ganglioside-containing supported lipid bilayer surfaces, as well as for interaction with the membrane. Interestingly, the strength of interactions with ganglioside-containing artificial membranes is mirrored in the diffusion behavior by FCS on cell membranes, with stronger binders displaying similar characteristic diffusion profiles. Our findings indicate that for aggregation-prone peptides, aggregation occurs upon contact with the cell membrane, and rather than giving a stronger interaction with the membrane, aggregation is accompanied by weaker binding and complex diffusion profiles indicative of heterogeneous diffusion behavior in the probe population.
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Affiliation(s)
- Tim Lauterbach
- School of Biological Sciences, Nanyang Technological University, Singapore
- Institut für Lebensmittel- und Bioverfahrenstechnik, Technische Universität Dresden, Dresden, Germany
| | - Manoj Manna
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Maria Ruhnow
- School of Biological Sciences, Nanyang Technological University, Singapore
- Institut für Lebensmittel- und Bioverfahrenstechnik, Technische Universität Dresden, Dresden, Germany
| | - Yudi Wisantoso
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Yaofeng Wang
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Artur Matysik
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Kamila Oglęcka
- School of Biological Sciences, Nanyang Technological University, Singapore
| | - Yuguang Mu
- School of Biological Sciences, Nanyang Technological University, Singapore
| | | | - Thorsten Wohland
- Department of Chemistry, National University of Singapore, Singapore
- Department of Biological Sciences, National University of Singapore, Singapore
- Centre for Bioimaging Sciences, National University of Singapore, Singapore
| | - Rachel Kraut
- School of Biological Sciences, Nanyang Technological University, Singapore
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20
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Meratan AA, Nemat-Gorgani M. Mitochondrial membrane permeabilization upon interaction with lysozyme fibrillation products: Role of mitochondrial heterogeneity. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2012; 1818:2149-57. [DOI: 10.1016/j.bbamem.2012.04.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 04/18/2012] [Accepted: 04/26/2012] [Indexed: 11/30/2022]
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21
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pH-Dependent Interaction between C-Peptide and Phospholipid Bicelles. JOURNAL OF BIOPHYSICS 2012; 2012:185907. [PMID: 22848213 PMCID: PMC3405660 DOI: 10.1155/2012/185907] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Accepted: 05/22/2012] [Indexed: 12/20/2022]
Abstract
C-peptide is the connecting peptide between the A and B chains of insulin in proinsulin. In this paper, we investigate the interaction between C-peptide and phospholipid bicelles, by circular dichroism and nuclear magnetic resonance spectroscopy, and in particular the pH dependence of this interaction. The results demonstrate that C-peptide is largely unstructured independent of pH, but that a weak structural induction towards a short stretch of β-sheet is induced at low pH, corresponding to the isoelectric point of the peptide. Furthermore, it is demonstrated that C-peptide associates with neutral phospholipid bicelles as well as acidic phospholipid bicelles at this low pH. C-peptide does not undergo a large structural rearrangement as a consequence of lipid interaction, which indicates that the folding and binding are uncoupled. In vivo, local variations in environment, including pH, may cause C-peptide to associate with lipids, which may affect the aggregation state of the peptide.
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Abstract
Alzheimer's disease (AD) is poised to become the most serious healthcare issue of our generation. The leading theory of AD pathophysiology is the Amyloid Cascade Hypothesis, and clinical trials are now proceeding based on this hypothesis. Here, we review the original evidence for the Amyloid Hypothesis, which was originally focused on the extracellular deposition of beta amyloid peptides (Aβ) in large fibrillar aggregates, as well as how this theory has been extended in recent years to focus on highly toxic small soluble amyloid oligomers. We will also examine emerging evidence that Aβ may actually begin to accumulate intracellularly in lysosomes, and the role for intracellular Aβ and lysosomal dysfunction may play in AD pathophysiology. Finally, we will review the clinical implications of these findings.
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23
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Zheng L, Terman A, Hallbeck M, Dehvari N, Cowburn RF, Benedikz E, Kågedal K, Cedazo-Minguez A, Marcusson J. Macroautophagy-generated increase of lysosomal amyloid β-protein mediates oxidant-induced apoptosis of cultured neuroblastoma cells. Autophagy 2011; 7:1528-45. [PMID: 22108004 PMCID: PMC3288025 DOI: 10.4161/auto.7.12.18051] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Increasing evidence suggests the toxicity of intracellular amyloid β-protein (Aβ) to neurons, as well as the involvement of oxidative stress in Alzheimer disease (AD). Here we show that normobaric hyperoxia (exposure of cells to 40% oxygen for five days), and consequent activation of macroautophagy and accumulation of Aβ within lysosomes, induced apoptosis in differentiated SH-SY5Y neuroblastoma cells. Cells under hyperoxia showed: (1) increased numbers of autophagic vacuoles that contained amyloid precursor protein (APP) as well as Aβ monomers and oligomers, (2) increased reactive oxygen species production, and (3) enhanced apoptosis. Oxidant-induced apoptosis positively correlated with cellular Aβ production, being the highest in cells that were stably transfected with APP Swedish KM670/671NL double mutation. Inhibition of γ-secretase, prior and/or in parallel to hyperoxia, suggested that the increase of lysosomal Aβ resulted mainly from its autophagic uptake, but also from APP processing within autophagic vacuoles. The oxidative stress-mediated effects were prevented by macroautophagy inhibition using 3-methyladenine or ATG5 downregulation. Our results suggest that upregulation of macroautophagy and resulting lysosomal Aβ accumulation are essential for oxidant-induced apoptosis in cultured neuroblastoma cells and provide additional support for the interactive role of oxidative stress and the lysosomal system in AD-related neurodegeneration.
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Affiliation(s)
- Lin Zheng
- Division of Geriatric Medicine, Department of Clinical and Experimental Medicine, IKE, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
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24
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LaDu MJ, Munson GW, Jungbauer L, Getz GS, Reardon CA, Tai LM, Yu C. Preferential interactions between ApoE-containing lipoproteins and Aβ revealed by a detection method that combines size exclusion chromatography with non-reducing gel-shift. Biochim Biophys Acta Mol Cell Biol Lipids 2011; 1821:295-302. [PMID: 22138302 DOI: 10.1016/j.bbalip.2011.11.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2011] [Revised: 10/29/2011] [Accepted: 11/02/2011] [Indexed: 01/06/2023]
Abstract
The association between apolipoprotein E (apoE) and amyloid-β peptide (Aβ) may significantly impact the function of both proteins, thus affecting the etiology of Alzheimer's disease (AD). However, apoE/Aβ interactions remain fundamentally defined by the stringency of the detection method. Here we use size exclusion chromatography (SEC) as a non-stringent approach to the detection of apoE/Aβ interactions in solution, specifically apoE and both endogenous and exogenous Aβ from plasma, CSF and astrocyte conditioned media. By SEC analysis, Aβ association with plasma and CNS lipoproteins is apoE-dependent. While endogenous Aβ elutes to specific human plasma lipoproteins distinct from those containing apoE, it is the apoE-containing lipoproteins that absorb excess amounts of exogenous Aβ40. In human CSF, apoE, endogenous Aβ and phospholipid elute in an almost identical profile, as do apoE, exogenous Aβ and phospholipid from astrocyte conditioned media. Combining SEC fractionation with subsequent analysis for SDS-stable apoE/Aβ complex reveals that apoE-containing astrocyte lipoproteins exhibit the most robust interactions with Aβ. Thus, standardization of the methods for detecting apoE/Aβ complex is necessary to determine its functional significance in the neuropathology characteristic of AD. Importantly, a systematic understanding of the role of apoE-containing plasma and CNS lipoproteins in Aβ homeostasis could potentially contribute to identifying a plasma biomarker currently over-looked because it has multiple components.
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Affiliation(s)
- Mary Jo LaDu
- Department of Anatomy and Cell Biology, University of Illinois, Chicago, IL 60612, USA.
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25
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Axelsen PH, Komatsu H, Murray IVJ. Oxidative stress and cell membranes in the pathogenesis of Alzheimer's disease. Physiology (Bethesda) 2011; 26:54-69. [PMID: 21357903 DOI: 10.1152/physiol.00024.2010] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Amyloid β proteins and oxidative stress are believed to have central roles in the development of Alzheimer's disease. Lipid membranes are among the most vulnerable cellular components to oxidative stress, and membranes in susceptible regions of the brain are compositionally distinct from those in other tissues. This review considers the evidence that membranes are either a source of neurotoxic lipid oxidation products or the target of pathogenic processes involving amyloid β proteins that cause permeability changes or ion channel formation. Progress toward a comprehensive theory of Alzheimer's disease pathogenesis is discussed in which lipid membranes assume both roles and promote the conversion of monomeric amyloid β proteins into fibrils, the pathognomonic histopathological lesion of the disease.
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Affiliation(s)
- Paul H Axelsen
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA
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26
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Belinson H, Kariv-Inbal Z, Kayed R, Masliah E, Michaelson DM. Following activation of the amyloid cascade, apolipoprotein E4 drives the in vivo oligomerization of amyloid-β resulting in neurodegeneration. J Alzheimers Dis 2011; 22:959-70. [PMID: 20858958 DOI: 10.3233/jad-2010-101008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
According to the amyloid hypothesis, the accumulation of oligomerized amyloid-β (Aβ) is a primary event in the pathogenesis of Alzheimer's disease (AD). The trigger of the amyloid cascade and of Aβ oligomerization in sporadic AD, the most prevalent form of the disease, remains elusive. Here, we examined the hypothesis that apolipoprotein E4 (ApoE4), the most prevalent genetic risk factor for AD, triggers the accumulation of intraneuronal oligomerized Aβ following activation of the amyloid cascade. We investigated the intracellular organelles that are targeted by these processes and govern their pathological consequences. This revealed that activation of the amyloid cascade in vivo by inhibition of the Aβ degrading enzyme neprilysin specifically results in accumulation of Aβ and oligomerized Aβ and of ApoE4 in the CA1 neurons of ApoE4 mice. This was accompanied by lysosomal and mitochondrial pathology and the co-localization of Aβ, oligomerized Aβ, and ApoE4 with enlarged lysosomes and of Aβ and oligomerized Aβ with mitochondria. The time course of the lysosomal effects paralleled that of the loss of CA1 neurons, whereas the mitochondrial effects reached an earlier plateau. These findings suggest that ApoE4 potentiates the pathological effects of Aβ and the amyloid cascade by triggering the oligomerization of Aβ, which in turn, impairs intraneuronal mitochondria and lysosomes and drives neurodegeneration.
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Affiliation(s)
- Haim Belinson
- Department of Neurobiology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
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27
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Aluminum enhances the toxic effects of amyloid β-peptide on cell membranes and a molecular model. MONATSHEFTE FUR CHEMIE 2011. [DOI: 10.1007/s00706-011-0471-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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28
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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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29
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Dafnis I, Stratikos E, Tzinia A, Tsilibary EC, Zannis VI, Chroni A. An apolipoprotein E4 fragment can promote intracellular accumulation of amyloid peptide beta 42. J Neurochem 2010; 115:873-84. [PMID: 20412390 DOI: 10.1111/j.1471-4159.2010.06756.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Apolipoprotein E (apoE) plays a crucial role in lipid transport in circulation and the brain. The apoE4 isoform is a major risk factor for Alzheimer's disease (AD). ApoE4 is more susceptible to proteolysis than other apoE isoforms and apoE4 fragments have been found in brains of AD patients. These apoE4 fragments have been hypothesized to be involved in the pathogenesis of AD, although the mechanism is not clear. In this study we examined the effect of lipid-free apoE4 on amyloid precursor protein processing and 40-amino-acid Aβ variant and 42-amino-acid Aβ variant levels in human neuroblastoma SK-N-SH cells. We discovered that a specific apoE4 fragment, apoE4[Δ(166-299)], can promote the cellular uptake of extracellular 40-amino-acid Aβ variant and 42-amino-acid Aβ variant either generated after amyloid precursor protein transfection or added exogenously. A longer length fragment, apoE4[Δ(186-299)], or full-length apoE4 failed to elicit this effect. ApoE4[Δ(166-299)] effected a 20% reduction of cellular sphingomyelin levels, as well as changes in cellular membrane micro-fluidity. Following uptake, approximately 50% of 42-amino-acid Aβ variant remained within the cell for at least 24 h, and led to increased formation of reactive oxygen species. Overall, our findings suggest a direct link between two early events in the pathogenesis of AD, apoE4 proteolysis and intraneuronal presence of amyloid beta peptide.
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Affiliation(s)
- Ioannis Dafnis
- Institute of Biology, National Center for Scientific Research Demokritos, Athens, Greece
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Molecular insights into amyloid regulation by membrane cholesterol and sphingolipids: common mechanisms in neurodegenerative diseases. Expert Rev Mol Med 2010; 12:e27. [PMID: 20807455 PMCID: PMC2931503 DOI: 10.1017/s1462399410001602] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Alzheimer, Parkinson and other neurodegenerative diseases involve a series of brain
proteins, referred to as ‘amyloidogenic proteins’, with exceptional
conformational plasticity and a high propensity for self-aggregation. Although the
mechanisms by which amyloidogenic proteins kill neural cells are not fully understood, a
common feature is the concentration of unstructured amyloidogenic monomers on
bidimensional membrane lattices. Membrane-bound monomers undergo a series of
lipid-dependent conformational changes, leading to the formation of oligomers of varying
toxicity rich in β-sheet structures (annular pores, amyloid fibrils) or in
α-helix structures (transmembrane channels). Condensed membrane nano- or
microdomains formed by sphingolipids and cholesterol are privileged sites for the binding
and oligomerisation of amyloidogenic proteins. By controlling the balance between
unstructured monomers and α or β conformers (the chaperone effect),
sphingolipids can either inhibit or stimulate the oligomerisation of amyloidogenic
proteins. Cholesterol has a dual role: regulation of protein–sphingolipid
interactions through a fine tuning of sphingolipid conformation (indirect effect), and
facilitation of pore (or channel) formation through direct binding to amyloidogenic
proteins. Deciphering this complex network of molecular interactions in the context of
age- and disease-related evolution of brain lipid expression will help understanding of
how amyloidogenic proteins induce neural toxicity and will stimulate the development of
innovative therapies for neurodegenerative diseases.
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31
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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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32
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Lorenzen A, Samosh J, Vandewark K, Anborgh PH, Seah C, Magalhaes AC, Cregan SP, Ferguson SSG, Pasternak SH. Rapid and direct transport of cell surface APP to the lysosome defines a novel selective pathway. Mol Brain 2010; 3:11. [PMID: 20409323 PMCID: PMC2868040 DOI: 10.1186/1756-6606-3-11] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Accepted: 04/21/2010] [Indexed: 12/03/2022] Open
Abstract
Background A central feature of Alzheimer's disease is the cleavage of the amyloid precursor protein (APP) to form beta-amyloid peptide (Aβ) by the β-secretase and γ-secretase enzymes. Although this has been shown to occur after endocytosis of APP from the cell surface, the exact compartments of APP processing are not well defined. We have previously demonstrated that APP and γ-secretase proteins and activity are highly enriched in purified rat liver lysosomes. In order to examine the lysosomal distribution and trafficking of APP in cultured cells, we generated constructs containing APP fused to a C-terminal fluorescent protein tag and N-terminal HA-epitope tag. These were co-transfected with a panel of fluorescent-protein tagged compartment markers. Results Here we demonstrate using laser-scanning confocal microscopy that although APP is present throughout the endosomal/lysosomal system in transfected Cos7 and neuronal SN56 cell lines as well as in immunostained cultured mouse neurons, it is enriched in the lysosome. We also show that the Swedish and London mutations reduce the amount of APP in the lysosome. Surprisingly, in addition to its expected trafficking from the cell surface to the early and then late endosomes, we find that cell-surface labelled APP is transported rapidly and directly from the cell surface to lysosomes in both Cos7 and SN56 cells. This rapid transit to the lysosome is blocked by the presence of either the London or Swedish mutations. Conclusions These results demonstrate the presence of a novel, rapid and specific transport pathway from the cell surface to the lysosomes. This suggests that regulation of lysosomal traffic could regulate APP processing and that the lysosome could play a central role in the pathophysiology of Alzheimer's disease.
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Affiliation(s)
- Angela Lorenzen
- J, Allyn Taylor Centre for Cell Biology, Molecular Brain Research Group, Robarts Research Institute, Schulich School of Medicine, the University of Western Ontario, London, Ontario, N6A 5K8, Canada
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33
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Ravault S, Flore C, Saurel O, Milon A, Brasseur R, Lins L. Study of the specific lipid binding properties of Abeta 11-22 fragment at endosomal pH. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:10948-10953. [PMID: 19735146 DOI: 10.1021/la901544g] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Increasing evidence implicates interactions between Abeta peptide and lipids in the development of Alzheimer's disease. More generally, Abeta peptide interactions with membranes seem to depend on the composition of the lipid bilayer and the structural features of the peptide. One key parameter should be pH, since one site of intracellular Abeta peptide production and/or accumulation is likely to be endosomes. This intracellular endosomal accumulation was suggested to contribute to disease progression. In this paper, we report a study on the 11-22 amphiphilic domain of Abeta in interaction with model membrane; this region contains most of the charged residues of the N-terminal domain of Abeta. We show that the peptide charge, and more precisely the protonation state of histidines 13 and/or 14, is important for the interaction with lipids. Hence, it is only at endosomal pH that a conformational change of the peptide is observed in the presence of negatively charged lipid vesicles, that is, when both lipid headgroups and histidines can interact through electrostatic interactions. Specific interactions of the fragment with phosphatidylserine and to a lesser extent with phosphatidylcholine, but not phosphatidylethanolamine, are further evidenced by the Langmuir monolayer technique. From our results, we suggest that the protonation state of His residues could have a role in the pathogenic surface interaction of the whole Abeta peptide with membranes.
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Affiliation(s)
- S Ravault
- Centre de Biophysique Moléculaire Numérique, Agricultural University of Gembloux, 5030 Gembloux, Belgium
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34
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Qiu L, Lewis A, Como J, Vaughn MW, Huang J, Somerharju P, Virtanen J, Cheng KH. Cholesterol modulates the interaction of beta-amyloid peptide with lipid bilayers. Biophys J 2009; 96:4299-307. [PMID: 19450500 DOI: 10.1016/j.bpj.2009.02.036] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2008] [Revised: 01/10/2009] [Accepted: 02/17/2009] [Indexed: 11/29/2022] Open
Abstract
The interaction of an amphiphilic, 40-amino acid beta-amyloid (Abeta) peptide with liposomal membranes as a function of sterol mole fraction (X(sterol)) was studied based on the fluorescence anisotropy of a site-specific membrane sterol probe, dehydroergosterol (DHE), and fluorescence resonance energy transfer (FRET) from the native Tyr-10 residue of Abeta to DHE. Without Abeta, peaks or kinks in the DHE anisotropy versus X(sterol) plot were detected at X(sterol) approximately 0.25, 0.33, and 0.53. Monomeric Abeta preserved these peaks/kinks, but oligomeric Abeta suppressed them and created a new DHE anisotropy peak at X(sterol) approximately 0.38. The above critical X(sterol) values coincide favorably with the superlattice compositions predicted by the cholesterol superlattice model, suggesting that membrane cholesterol tends to adopt a regular lateral arrangement, or domain formation, in the lipid bilayers. For FRET, a peak was also detected at X(sterol) approximately 0.38 for both monomeric and oligomeric Abeta, implying increased penetration of Abeta into the lipid bilayer at this sterol mole fraction. We conclude that the interaction of Abeta with membranes is affected by the lateral organization of cholesterol, and hypothesize that the formation of an oligomeric Abeta/cholesterol domain complex may be linked to the toxicity of Abeta in neuronal membranes.
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Affiliation(s)
- Liming Qiu
- Department of Physics, Texas Tech University, Lubbock, Texas, USA
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35
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Li Y, Qin HQ, Chen QS, Wang JJ. BEHAVIORAL AND NEUROCHEMICAL EFFECTS OF THE INTRAHIPPOCAMPAL CO-INJECTION OF ß-AMYLOID PROTEIN1-40 AND IBOTENIC ACID IN RATS. Int J Neurosci 2009; 114:1521-31. [PMID: 15512836 DOI: 10.1080/00207450490509159] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The authors investigated the effects of bilateral intrahippocampal co-injection of Abeta1-40 (4 microg for each side) with ibotenic acid (Ibo, 2 microg for each side) on rats' performance in the open field behavior, Y-maze, and passive avoidance task, and also examined some neurochemical changes in hippocampus two weeks after the co-injection. The results showed that the co-injection of Abeta1-40 with Ibo induced a decrease in exploratory activity and a significant decline in learning-memory ability of the tested rats (p < .01). The neurochemistry changes induced by the co-injection included a significant decreased in membrane fluidity of hippocampal mitochondria (p < .01), a significant decrease in the activity of SOD (p < .01), and a remarkable increase in the content of MDA (p < .01). These results suggest that the co-injection of Abeta1-40 with Ibo may induce an increase of hippocampal damage by peroxidation, and a serious learning and memory impairment of the rats. The results also suggest that the co-injection of Abeta1-40 with Ibo may provide a useful animal model for Alzheimer's disease (AD) research.
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Affiliation(s)
- Ya Li
- Department of Biological Science and Technology, Nanjing University, China.
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36
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Pistolesi S, Rossini L, Ferro E, Basosi R, Trabalzini L, Pogni R. Humanin Structural Versatility and Interaction with Model Cerebral Cortex Membranes. Biochemistry 2009; 48:5026-33. [DOI: 10.1021/bi900187s] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sara Pistolesi
- Department of Chemistry, University of Siena, Via A. De Gasperi, 53100 Siena, Italy
| | - Lara Rossini
- Department of Molecular Biology, University of Siena, Via Fiorentina 1, 53100 Siena, Italy
| | - Elisa Ferro
- Department of Molecular Biology, University of Siena, Via Fiorentina 1, 53100 Siena, Italy
| | - Riccardo Basosi
- Department of Chemistry, University of Siena, Via A. De Gasperi, 53100 Siena, Italy
| | - Lorenza Trabalzini
- Department of Molecular Biology, University of Siena, Via Fiorentina 1, 53100 Siena, Italy
| | - Rebecca Pogni
- Department of Chemistry, University of Siena, Via A. De Gasperi, 53100 Siena, Italy
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37
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Hawkes CA, Ng V, McLaurin J. Small molecule inhibitors of Aβ-aggregation and neurotoxicity. Drug Dev Res 2009. [DOI: 10.1002/ddr.20290] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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38
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Kandimalla KK, Scott OG, Fulzele S, Davidson MW, Poduslo JF. Mechanism of neuronal versus endothelial cell uptake of Alzheimer's disease amyloid beta protein. PLoS One 2009; 4:e4627. [PMID: 19247480 PMCID: PMC2645672 DOI: 10.1371/journal.pone.0004627] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Accepted: 01/01/2009] [Indexed: 01/08/2023] Open
Abstract
Alzheimer's disease (AD) is characterized by significant neurodegeneration in the cortex and hippocampus; intraneuronal tangles of hyperphosphorylated tau protein; and accumulation of β-amyloid (Aβ) proteins 40 and 42 in the brain parenchyma as well as in the cerebral vasculature. The current understanding that AD is initiated by the neuronal accumulation of Aβ proteins due to their inefficient clearance at the blood-brain-barrier (BBB), places the neurovascular unit at the epicenter of AD pathophysiology. The objective of this study is to investigate cellular mechanisms mediating the internalization of Aβ proteins in the principle constituents of the neurovascular unit, neurons and BBB endothelial cells. Laser confocal micrographs of wild type (WT) mouse brain slices treated with fluorescein labeled Aβ40 (F-Aβ40) demonstrated selective accumulation of the protein in a subpopulation of cortical and hippocampal neurons via nonsaturable, energy independent, and nonendocytotic pathways. This groundbreaking finding, which challenges the conventional belief that Aβ proteins are internalized by neurons via receptor mediated endocytosis, was verified in differentiated PC12 cells and rat primary hippocampal (RPH) neurons through laser confocal microscopy and flow cytometry studies. Microscopy studies have demonstrated that a significant proportion of F-Aβ40 or F-Aβ42 internalized by differentiated PC12 cells or RPH neurons is located outside of the endosomal or lysosomal compartments, which may accumulate without degradation. In contrast, BBME cells exhibit energy dependent uptake of F-Aβ40, and accumulate the protein in acidic cell organelle, indicative of endocytotic uptake. Such a phenomenal difference in the internalization of Aβ40 between neurons and BBB endothelial cells may provide essential clues to understanding how various cells can differentially regulate Aβ proteins and help explain the vulnerability of cortical and hippocampal neurons to Aβ toxicity.
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Affiliation(s)
- Karunya K Kandimalla
- Department of Basic Pharmaceutical Sciences, College of Pharmacy and Pharmaceutical Sciences, Florida A&M University, Tallahassee, Florida, United States of America.
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39
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Berrocal M, Marcos D, Sepúlveda MR, Pérez M, Ávila J, Mata AM. Altered Ca
2+
dependence of synaptosomal plasma membrane Ca
2+
‐ATPase in human brain affected by Alzheimer's disease. FASEB J 2009; 23:1826-34. [DOI: 10.1096/fj.08-121459] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- María Berrocal
- Departamento de Bioquímica y Biología Molecular y GenéticaFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - Daniel Marcos
- Departamento de Bioquímica y Biología Molecular y GenéticaFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - M. Rosario Sepúlveda
- Departamento de Bioquímica y Biología Molecular y GenéticaFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
| | - Mar Pérez
- Centro de Biología Molecular “Severo Ochoa,”Autónoma de MadridCampus de CantoblancoMadridSpain
| | - Jesuús Ávila
- Centro de Biología Molecular “Severo Ochoa,”Autónoma de MadridCampus de CantoblancoMadridSpain
| | - Ana M. Mata
- Departamento de Bioquímica y Biología Molecular y GenéticaFacultad de CienciasUniversidad de ExtremaduraBadajozSpain
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40
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Yoda M, Miura T, Takeuchi H. Non-electrostatic binding and self-association of amyloid β-peptide on the surface of tightly packed phosphatidylcholine membranes. Biochem Biophys Res Commun 2008; 376:56-9. [DOI: 10.1016/j.bbrc.2008.08.093] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2008] [Accepted: 08/18/2008] [Indexed: 10/21/2022]
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41
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Hicks JB, Lai Y, Sheng W, Yang X, Zhu D, Sun GY, Lee JCM. Amyloid-beta peptide induces temporal membrane biphasic changes in astrocytes through cytosolic phospholipase A2. BIOCHIMICA ET BIOPHYSICA ACTA 2008; 1778:2512-9. [PMID: 18725190 PMCID: PMC2592609 DOI: 10.1016/j.bbamem.2008.07.027] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2008] [Revised: 07/21/2008] [Accepted: 07/22/2008] [Indexed: 11/21/2022]
Abstract
Oligomeric amyloid-beta peptide (Abeta) is known to induce cytotoxic effects and to damage cell functions in Alzheimer's disease. However, mechanisms underlying the effects of Abeta on cell membranes have yet to be fully elucidated. In this study, Abeta 1-42 (Abeta(42)) was shown to cause a temporal biphasic change in membranes of astrocytic DITNC cells using fluorescence microscopy of Laurdan. Abeta(42) made astrocyte membranes became more molecularly-disordered within the first 30 min to 1 h, but gradually changed to more molecularly-ordered after 3 h. However, Abeta(42) caused artificial membranes of vesicles made of rat whole brain lipid extract to become more disordered only. The trend for more molecularly-ordered membranes in astrocytes induced by Abeta(42) was abrogated by either an NADPH oxidase inhibitor, apocynin, or an inhibitor of cytosolic phospholipase A(2) (cPLA(2)), but not by an inhibitor of calcium-independent PLA(2) (iPLA(2)). Apocynin also suppressed the increased production of superoxide anions (O(2)(-)) and phosphorylation of cPLA(2) induced by Abeta(42). In addition, hydrolyzed products of cPLA(2), arachidonic acid (AA), but not lysophosphatidylcholine (LPC) caused astrocyte membranes to become more molecularly-ordered. These results suggest (1) a direct interaction of Abeta(42) with cell membranes making them more molecularly-disordered, and (2) Abeta(42) also indirectly makes membranes become more molecularly-ordered by triggering the signaling pathway involving NADPH oxidase and cPLA(2) in astrocytes.
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Affiliation(s)
- Jacob B. Hicks
- Department of Biological Engineering, University of Missouri, Columbia, Missouri 65211, USA
| | - Yinzhi Lai
- Department of Biological Engineering, University of Missouri, Columbia, Missouri 65211, USA
| | - Wenwen Sheng
- Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, Missouri 65211, USA
| | - Xiaoguang Yang
- Department of Biological Engineering, University of Missouri, Columbia, Missouri 65211, USA
| | - Donghui Zhu
- Department of Biological Engineering, University of Missouri, Columbia, Missouri 65211, USA
| | - Grace Y. Sun
- Department of Biochemistry, University of Missouri, Columbia, Missouri 65211, USA
| | - James C-M Lee
- Department of Biological Engineering, University of Missouri, Columbia, Missouri 65211, USA
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42
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Byström R, Aisenbrey C, Borowik T, Bokvist M, Lindström F, Sani MA, Olofsson A, Gröbner G. Disordered proteins: biological membranes as two-dimensional aggregation matrices. Cell Biochem Biophys 2008; 52:175-89. [PMID: 18975139 DOI: 10.1007/s12013-008-9033-4] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/08/2008] [Indexed: 01/05/2023]
Abstract
Aberrant folded proteins and peptides are hallmarks of amyloidogenic diseases. However, the molecular processes that cause these proteins to adopt non-native structures in vivo and become cytotoxic are still largely unknown, despite intense efforts to establish a general molecular description of their behavior. Clearly, the fate of these proteins is ultimately linked to their immediate biochemical environment in vivo. In this review, we focus on the role of biological membranes, reactive interfaces that not only affect the conformational stability of amyloidogenic proteins, but also their aggregation rates and, probably, their toxicity. We first provide an overview of recent work, starting with findings regarding the amphiphatic amyloid-beta protein (Abeta), which give evidence that membranes can directly promote aggregation, and that the effectiveness in this process can be related to the presence of specific neuronal ganglioside lipids. In addition, we discuss the implications of recent research (medin as an detailed example) regarding putative roles of membranes in the misfolding behavior of soluble, non-amphiphatic proteins, which are attracting increasing interest. The potential role of membranes in exerting the toxic action of misfolded proteins will also be highlighted in a molecular context. In this review, we discuss novel NMR-based approaches for exploring membrane-protein interactions, and findings obtained using them, which we use to develop a molecular concept to describe membrane-mediated protein misfolding as a quasi-two-dimensional process rather than a three-dimensional event in a biochemical environment. The aim of the review is to provide researchers with a general understanding of the involvement of membranes in folding/misfolding processes in vivo, which might be quite universal and important for future research concerning amyloidogenic and misfolding proteins, and possible ways to prevent their toxic actions.
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Affiliation(s)
- Roberth Byström
- Department of Chemistry, Umeå University, 90187, Umeå, Sweden
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43
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Panja S, Aich P, Jana B, Basu T. How does plasmid DNA penetrate cell membranes in artificial transformation process of Escherichia coli? Mol Membr Biol 2008; 25:411-22. [PMID: 18651316 DOI: 10.1080/09687680802187765] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Artificial transformation of Escherichia coli with plasmid DNA in presence of CaCl2 is a widely used technique in recombinant DNA technology. However, exact mechanism of DNA transfer across cell membranes is largely obscure. In this study, measurements of both steady state and time-resolved anisotropies of fluorescent dye trimethyl ammonium diphenyl hexatriene (TMA-DPH), bound to cellular outer membrane, indicated heat-pulse (0 degrees C42 degrees C) step of the standard transformation procedure had lowered considerably outer membrane fluidity of cells. The decrease in fluidity was caused by release of lipids from cell surface to extra-cellular medium. A subsequent cold-shock (42 degrees C0 degrees C) to the cells raised the fluidity further to its original value and this was caused by release of membrane proteins to extra-cellular medium. When the cycle of heat-pulse and cold-shock steps was repeated, more release of lipids and proteins respectively had taken place, which ultimately enhanced transformation efficiency gradually up to third cycle. Study of competent cell surface by atomic force microscope showed release of lipids had formed pores on cell surface. Moreover, the heat-pulse step almost depolarized cellular inner membrane. In this communication, we propose heat-pulse step had two important roles on DNA entry: (a) Release of lipids and consequent formation of pores on cell surface, which helped DNA to cross outer membrane barrier, and (b) lowering of membrane potential, which facilitated DNA to cross inner membrane of E. coli.
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Affiliation(s)
- Subrata Panja
- Department of Biochemistry and Biophysics, University of Kalyani, West Bengal, India
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44
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Bate C, Tayebi M, Williams A. Ginkgolides protect against amyloid-beta1-42-mediated synapse damage in vitro. Mol Neurodegener 2008; 3:1. [PMID: 18179689 PMCID: PMC2254622 DOI: 10.1186/1750-1326-3-1] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2007] [Accepted: 01/07/2008] [Indexed: 12/23/2022] Open
Abstract
Background The early stages of Alzheimer's disease (AD) are closely associated with the production of the Aβ1–42 peptide, loss of synapses and gradual cognitive decline. Since some epidemiological studies showed that EGb 761, an extract from the leaves of the Ginkgo biloba tree, had a beneficial effect on mild forms of AD, the effects of some of the major components of the EGb 761 extract (ginkgolides A and B, myricetin and quercetin) on synapse damage in response to Aβ1–42 were examined. Results The addition of Aβ1–42 to cortical or hippocampal neurons reduced the amounts of cell associated synaptophysin, a pre-synaptic membrane protein that is essential for neurotransmission, indicating synapse damage. The effects of Aβ1–42 on synapses were apparent at concentrations approximately 100 fold less than that required to kill neurons; the synaptophysin content of neuronal cultures was reduced by 50% by 50 nM Aβ1–42. Pre-treatment of cortical or hippocampal neuronal cultures with ginkgolides A or B, but not with myrecitin or quercetin, protected against Aβ1–42-induced loss of synaptophysin. This protective effect was achieved with nanomolar concentrations of ginkgolides. Previous studies indicated that the ginkgolides are platelet-activating factor (PAF) receptor antagonists and here we show that Aβ1–42-induced loss of synaptophysin from neuronal cultures was also reduced by pre-treatment with other PAF antagonists (Hexa-PAF and CV6209). PAF, but not lyso-PAF, mimicked the effects Aβ1–42 and caused a dose-dependent reduction in the synaptophysin content of neurons. This effect of PAF was greatly reduced by pre-treatment with ginkgolide B. In contrast, ginkgolide B did not affect the loss of synaptophysin in neurons incubated with prostaglandin E2. Conclusion Pre-treatment with ginkgolides A or B protects neurons against Aβ1–42-induced synapse damage. These ginkgolides also reduced the effects of PAF, but not those of prostaglandin E2, on the synaptophysin content of neuronal cultures, results consistent with prior reports that ginkgolides act as PAF receptor antagonists. Such observations suggest that the ginkgolides are active components of Ginkgo biloba preparations and may protect against the synapse damage and the cognitive loss seen during the early stages of AD.
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Affiliation(s)
- Clive Bate
- Department of Pathology and Infectious Diseases, Royal Veterinary College, Hawkshead Lane, North Mymms, Herts, AL9 7TA, UK.
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45
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Rak M, Del Bigio MR, Mai S, Westaway D, Gough K. Dense-core and diffuse Abeta plaques in TgCRND8 mice studied with synchrotron FTIR microspectroscopy. Biopolymers 2007; 87:207-17. [PMID: 17680701 DOI: 10.1002/bip.20820] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Plaques composed of the Abeta peptide are the main pathological feature of Alzheimer's disease. Dense-core plaques are fibrillar deposits of Abeta, showing all the classical properties of amyloid including beta-sheet secondary structure, while diffuse plaques are amorphous deposits. We studied both plaque types, using synchrotron infrared (IR) microspectroscopy, a technique that allows the chemical composition and average protein secondary structure to be investigated in situ. We examined plaques in hippocampal, cortical and caudal tissue from 5- to 21-month-old TgCRND8 mice, a transgenic model expressing doubly mutant amyloid precursor protein, and displaying impaired hippocampal function and robust pathology from an early age. Spectral analysis confirmed that the congophilic plaque cores were composed of protein in a beta-sheet conformation. The amide I maximum of plaque cores was at 1623 cm(-1), and unlike for in vitro Abeta fibrils, the high-frequency (1680-1690 cm(-1)) component attributed to antiparallel beta-sheet was not observed. A significant elevation in phospholipids was found around dense-core plaques in TgCRND8 mice ranging in age from 5 to 21 months. In contrast, diffuse plaques were not associated with IR detectable changes in protein secondary structure or relative concentrations of any other tissue components.
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Affiliation(s)
- Margaret Rak
- Department of Chemistry, University of Manitoba, Winnipeg, MB, Canada R3T 2N2
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46
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Aisenbrey C, Borowik T, Byström R, Bokvist M, Lindström F, Misiak H, Sani MA, Gröbner G. How is protein aggregation in amyloidogenic diseases modulated by biological membranes? EUROPEAN BIOPHYSICS JOURNAL: EBJ 2007; 37:247-55. [PMID: 18030461 DOI: 10.1007/s00249-007-0237-0] [Citation(s) in RCA: 141] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 08/31/2007] [Revised: 10/19/2007] [Accepted: 10/19/2007] [Indexed: 10/22/2022]
Abstract
The fate of proteins with amyloidogenic properties depends critically on their immediate biochemical environment. However, the role of biological interfaces such as membrane surfaces, as promoters of pathological aggregation of amyloidogenic proteins, is rarely studied and only established for the amyloid-beta protein (A beta) involved in Alzheimer's disease, and alpha-synuclein in Parkinsonism. The occurrence of binding and misfolding of these proteins on membrane surfaces, is poorly understood, not at least due to the two-dimensional character of this event. Clearly, the nature of the folding pathway for A beta protein adsorbed upon two-dimensional aggregation templates, must be fundamentally different from the three-dimensional situation in solution. Here, we summarize the current research and focus on the function of membrane interfaces as aggregation templates for amyloidogenic proteins (and even prionic ones). One major aspect will be the relationship between membrane properties and protein association and the consequences for amyloidogenic products. The other focus will be on a general understanding of protein folding pathways on two-dimensional templates on a molecular level. Finally, we will demonstrate the potential importance of membrane-mediated aggregation for non-amphiphatic soluble amyloidogenic proteins, by using the SOD1 protein involved in the amyotrophic lateral sclerosis syndrome.
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LaFerla FM, Green KN, Oddo S. Intracellular amyloid-beta in Alzheimer's disease. Nat Rev Neurosci 2007; 8:499-509. [PMID: 17551515 DOI: 10.1038/nrn2168] [Citation(s) in RCA: 1446] [Impact Index Per Article: 85.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The primal role that the amyloid-beta (Abeta) peptide has in the development of Alzheimer's disease is now almost universally accepted. It is also well recognized that Abeta exists in multiple assembly states, which have different physiological or pathophysiological effects. Although the classical view is that Abeta is deposited extracellularly, emerging evidence from transgenic mice and human patients indicates that this peptide can also accumulate intraneuronally, which may contribute to disease progression.
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Affiliation(s)
- Frank M LaFerla
- Department of Neurobiology and Behaviour, and Institute for Brain Aging and Dementia, University of California, Irvine, California 92697-4545, USA.
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Marushchak D, Gretskaya N, Mikhalyov I, Johansson LBA. Self-aggregation--an intrinsic property of G(M1) in lipid bilayers. Mol Membr Biol 2007; 24:102-12. [PMID: 17453417 DOI: 10.1080/09687860600995235] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
We demonstrate that the ganglioside G(M1) in lipid bilayers of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) exhibits a non-uniform lateral distribution, i.e., enriched regions of GM(1) molecules are formed, which is an argument in favour of self-aggregation of G(M1) being an intrinsic property of G(M1) ganglioside. This was concluded from energy transfer/migration studies of BODIPY-labelled gangliosides by means of time-resolved fluorescence lifetime and depolarization experiments. Three fluorophore-labelled gangliosides were synthesized to include either of two spectroscopically different BODIPY groups. These were specifically localized either in the polar headgroup region or in the non-polar region of the lipid bilayer. An eventual ganglioside-ganglioside affinity/aggregation induced by the BODIPY groups was experimentally excluded, which suggests their use in examining the influence of G(M1) in more complex systems.
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Affiliation(s)
- Denys Marushchak
- Department of Chemistry, Biophysical Chemistry, Umeå University, Umeå, Sweden
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Widenbrant MJO, Rajadas J, Sutardja C, Fuller GG. Lipid-induced beta-amyloid peptide assemblage fragmentation. Biophys J 2007; 91:4071-80. [PMID: 17098805 PMCID: PMC1635663 DOI: 10.1529/biophysj.106.085944] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Alzheimer's disease is the most common cause of dementia and is widely believed to be due to the accumulation of beta-amyloid peptides (Abeta) and their interaction with the cell membrane. Abetas are hydrophobic peptides derived from the amyloid precursor proteins by proteolytic cleavage. After cleavage, these peptides are involved in a self-assembly-triggered conformational change. They are transformed into structures that bind to the cell membrane, causing cellular degeneration. However, it is not clear how these peptide assemblages disrupt the structural and functional integrity of the membrane. Membrane fluidity is one of the important parameters involved in pathophysiology of disease-affected cells. Probing the Abeta aggregate-lipid interactions will help us understand these processes with structural detail. Here we show that a fluid lipid monolayer develop immobile domains upon interaction with Abeta aggregates. Atomic force microscopy and transmission electron microscopy data indicate that peptide fibrils are fragmented into smaller nano-assemblages when interacting with the membrane lipids. Our findings could initiate reappraisal of the interactions between lipid assemblages and Abeta aggregates involved in Alzheimer's disease.
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Choucair A, Chakrapani M, Chakravarthy B, Katsaras J, Johnston LJ. Preferential accumulation of Aβ(1−42) on gel phase domains of lipid bilayers: An AFM and fluorescence study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:146-54. [PMID: 17052685 DOI: 10.1016/j.bbamem.2006.09.005] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2006] [Revised: 09/07/2006] [Accepted: 09/08/2006] [Indexed: 01/09/2023]
Abstract
Peptide-membrane interactions have been implicated in both the toxicity and aggregation of beta-amyloid (Abeta) peptides. Recent studies have provided evidence for the involvement of liquid-ordered membrane domains known as lipid rafts in the formation and aggregation of Abeta. As a model, we have examined the interaction of Abeta(1-42) with phase separated DOPC/DPPC lipid bilayers using a combination of atomic force microscopy (AFM) and total internal reflection fluorescence microscopy (TIRF). AFM images show that addition of Abeta to preformed supported bilayers leads to accumulation of small peptide aggregates exclusively on the gel phase DPPC domains. Initial aggregates are observed approximately 90 min after peptide addition and increase in diameter to 45-150 nm within 24 h. TIRF studies with a mixture of Abeta and Abeta-Fl demonstrate that accumulation of the peptide on the gel phase domains occurs as early as 15 min after Abeta addition and is maintained for over 24 h. By contrast, Abeta is randomly distributed throughout both fluid and gel phases when the peptide is reconstituted into DOPC/DPPC vesicles prior to formation of a supported bilayer. The preferential accumulation of Abeta on DPPC domains suggests that rigid domains may act as platforms to concentrate peptide and enhance its aggregation and may be relevant to the postulated involvement of lipid rafts in modulating Abeta activity in vivo.
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Affiliation(s)
- A Choucair
- Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, ON, Canada K1A 0R6
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