201
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Kawahara M, Ohtsuka I, Yokoyama S, Kato-Negishi M, Sadakane Y. Membrane Incorporation, Channel Formation, and Disruption of Calcium Homeostasis by Alzheimer's β-Amyloid Protein. Int J Alzheimers Dis 2011; 2011:304583. [PMID: 21547225 PMCID: PMC3087492 DOI: 10.4061/2011/304583] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2010] [Revised: 12/22/2010] [Accepted: 01/27/2011] [Indexed: 01/09/2023] Open
Abstract
Oligomerization, conformational changes, and the consequent neurodegeneration of Alzheimer's β-amyloid protein (AβP) play crucial roles in the pathogenesis of Alzheimer's disease (AD). Mounting evidence suggests that oligomeric AβPs cause the disruption of calcium homeostasis, eventually leading to neuronal death. We have demonstrated that oligomeric AβPs directly incorporate into neuronal membranes, form cation-sensitive ion channels (“amyloid channels”), and cause the disruption of calcium homeostasis via the amyloid channels. Other disease-related amyloidogenic proteins, such as prion protein in prion diseases or α-synuclein in dementia with Lewy bodies, exhibit similarities in the incorporation into membranes and the formation of calcium-permeable channels. Here, based on our experimental results and those of numerous other studies, we review the current understanding of the direct binding of AβP into membrane surfaces and the formation of calcium-permeable channels. The implication of composition of membrane lipids and the possible development of new drugs by influencing membrane properties and attenuating amyloid channels for the treatment and prevention of AD is also discussed.
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Affiliation(s)
- Masahiro Kawahara
- Department of Analytical Chemistry, School of Pharmaceutical Sciences, Kyushu University of Health and Welfare, 1714-1 Yoshino-cho, Nobeoka-shi, Miyazaki 882-8508, Japan
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202
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Zimmerman LB, Worley BV, Palermo EF, Brender JR, Lee KD, Kuroda K, Ramamoorthy A, Meyerhoff ME. Absorbance-based assay for membrane disruption by antimicrobial peptides and synthetic copolymers using pyrroloquinoline quinone-loaded liposomes. Anal Biochem 2011; 411:194-9. [DOI: 10.1016/j.ab.2011.01.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Revised: 12/20/2010] [Accepted: 01/10/2011] [Indexed: 10/18/2022]
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203
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Laghaei R, Mousseau N, Wei G. Structure and Thermodynamics of Amylin Dimer Studied by Hamiltonian-Temperature Replica Exchange Molecular Dynamics Simulations. J Phys Chem B 2011; 115:3146-54. [DOI: 10.1021/jp108870q] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Rozita Laghaei
- Département de Physique and Groupe de Recherche sur les Protéines Membranaires (GEPROM), Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal (Québec), Canada
| | - Normand Mousseau
- Département de Physique and Groupe de Recherche sur les Protéines Membranaires (GEPROM), Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal (Québec), Canada
| | - Guanghong Wei
- State Key Laboratory of Surface Physics, Key Laboratory for Computational Physical Sciences (Ministry of Education), and Department of Physics, Fudan University, 220 Handan Road, Shanghai 200433, China
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204
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Brender JR, Lee EL, Hartman K, Wong PT, Ramamoorthy A, Steel DG, Gafni A. Biphasic effects of insulin on islet amyloid polypeptide membrane disruption. Biophys J 2011; 100:685-692. [PMID: 21281583 PMCID: PMC3030259 DOI: 10.1016/j.bpj.2010.09.070] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Revised: 09/09/2010] [Accepted: 09/27/2010] [Indexed: 10/18/2022] Open
Abstract
Type II diabetes, in its late stages, is often associated with the formation of extracellular islet amyloid deposits composed of islet amyloid polypeptide (IAPP or amylin). IAPP is stored before secretion at millimolar concentrations within secretory granules inside the β-cells. Of interest, at these same concentrations in vitro, IAPP rapidly aggregates and forms fibrils, yet within secretory granules of healthy individuals, IAPP does not fibrillize. Insulin is also stored within the secretory granules before secretion, and has been shown in vitro to inhibit IAPP fibril formation. Because of insulin's inhibitory effect on IAPP fibrillization, it has been suggested that insulin may also inhibit IAPP-mediated permeabilization of the β-cell plasma membrane in vivo. We show that although insulin is effective at preventing fiber-dependent membrane disruption, it is not effective at stopping the initial phase of membrane disruption before fibrillogenesis, and does not prevent the formation of small IAPP oligomers on the membrane. These results suggest that insulin has a more complicated role in inhibiting IAPP fibrillogenesis, and that other factors, such as the low pH of the secretory granule, may also play a role.
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Affiliation(s)
- Jeffrey R Brender
- Department of Biophysics, University of Michigan, Ann Arbor, Michigan; Department of Chemistry, University of Michigan, Ann Arbor, Michigan
| | - Edgar L Lee
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan
| | - Kevin Hartman
- Department of Biophysics, University of Michigan, Ann Arbor, Michigan; Department of Chemistry, University of Michigan, Ann Arbor, Michigan
| | - Pamela T Wong
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan
| | - Ayyalusamy Ramamoorthy
- Department of Biophysics, University of Michigan, Ann Arbor, Michigan; Department of Chemistry, University of Michigan, Ann Arbor, Michigan
| | - Duncan G Steel
- Department of Biophysics, University of Michigan, Ann Arbor, Michigan; Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan; Department of Physics, University of Michigan, Ann Arbor, Michigan
| | - Ari Gafni
- Department of Biological Chemistry, University of Michigan, Ann Arbor, Michigan; Department of Biophysics, University of Michigan, Ann Arbor, Michigan.
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205
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Membrane cholesterol enrichment prevents Aβ-induced oxidative stress in Alzheimer's fibroblasts. Neurobiol Aging 2011; 32:210-22. [DOI: 10.1016/j.neurobiolaging.2009.02.010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2008] [Revised: 02/05/2009] [Accepted: 02/09/2009] [Indexed: 01/13/2023]
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206
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Butterfield SM, Lashuel HA. Amyloidogenic protein-membrane interactions: mechanistic insight from model systems. Angew Chem Int Ed Engl 2011; 49:5628-54. [PMID: 20623810 DOI: 10.1002/anie.200906670] [Citation(s) in RCA: 483] [Impact Index Per Article: 37.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The toxicity of amyloid-forming proteins is correlated with their interactions with cell membranes. Binding events between amyloidogenic proteins and membranes result in mutually disruptive structural perturbations, which are associated with toxicity. Membrane surfaces promote the conversion of amyloid-forming proteins into toxic aggregates, and amyloidogenic proteins, in turn, compromise the structural integrity of the cell membrane. Recent studies with artificial model membranes have highlighted the striking resemblance of the mechanisms of membrane permeabilization of amyloid-forming proteins to those of pore-forming toxins and antimicrobial peptides.
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Affiliation(s)
- Sara M Butterfield
- Laboratory of Molecular Neurobiology and Neuroproteomics, Swiss Federal Institute of Technology Lausanne (EPFL), SV-BMI-LMNN AI2351, 1015 Lausanne, Switzerland
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207
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Ostroumova OS, Schagina LV, Mosevitsky MI, Zakharov VV. Ion channel activity of brain abundant protein BASP1 in planar lipid bilayers. FEBS J 2010; 278:461-9. [DOI: 10.1111/j.1742-4658.2010.07967.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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208
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Weise K, Radovan D, Gohlke A, Opitz N, Winter R. Interaction of hIAPP with model raft membranes and pancreatic beta-cells: cytotoxicity of hIAPP oligomers. Chembiochem 2010; 11:1280-90. [PMID: 20440729 DOI: 10.1002/cbic.201000039] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Type II diabetes mellitus (T2DM) is associated with beta-cell failure, which correlates with the formation of pancreatic islet amyloid deposits. The human islet amyloid polypeptide (hIAPP) is the major component of islet amyloid and undergoes structural changes followed by self-association and pathological tissue deposition during aggregation in T2DM. There is clear evidence that the aggregation process is accelerated in the presence of particular lipid membranes. Whereas hIAPP aggregation has been extensively studied in homogeneous model membrane systems, especially negatively charged lipid bilayers, information on the interaction of hIAPP with heterogeneous model raft membranes has been missing until now. In the present study, we focus on the principles of aggregation and amyloid formation of hIAPP in the presence of model raft membranes. Time-lapse tapping mode AFM and confocal fluorescence microscopy experiments followed membrane permeabilization and localization of hIAPP in the raft membrane. Together with the ThT and WST-1 assay, the data revealed elevated cytotoxicity of hIAPP oligomers on INS-1E cells.
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Affiliation(s)
- Katrin Weise
- Physical Chemistry I, Biophysical Chemistry, Technische Universität Dortmund, Otto-Hahn-Strasse 6, 44227 Dortmund, Germany.
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209
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Zhang C, Jackson AP, Zhang ZR, Han Y, Yu S, He RQ, Perrett S. Amyloid-like aggregates of the yeast prion protein ure2 enter vertebrate cells by specific endocytotic pathways and induce apoptosis. PLoS One 2010; 5. [PMID: 20824085 PMCID: PMC2932714 DOI: 10.1371/journal.pone.0012529] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Accepted: 07/08/2010] [Indexed: 11/23/2022] Open
Abstract
Background A number of amyloid diseases involve deposition of extracellular protein aggregates, which are implicated in mechanisms of cell damage and death. However, the mechanisms involved remain poorly understood. Methodology/Principal Findings Here we use the yeast prion protein Ure2 as a generic model to investigate how amyloid-like protein aggregates can enter mammalian cells and convey cytotoxicity. The effect of three different states of Ure2 protein (native dimer, protofibrils and mature fibrils) was tested on four mammalian cell lines (SH-SY5Y, MES23.5, HEK-293 and HeLa) when added extracellularly to the medium. Immunofluorescence using a polyclonal antibody against Ure2 showed that all three protein states could enter the four cell lines. In each case, protofibrils significantly inhibited the growth of the cells in a dose-dependent manner, fibrils showed less toxicity than protofibrils, while the native state had no effect on cell growth. This suggests that the structural differences between the three protein states lead to their different effects upon cells. Protofibrils of Ure2 increased membrane conductivity, altered calcium homeostasis, and ultimately induced apoptosis. The use of standard inhibitors suggested uptake into mammalian cells might occur via receptor-mediated endocytosis. In order to investigate this further, we used the chicken DT40 B cell line DKOR, which allows conditional expression of clathrin. Uptake into the DKOR cell-line was reduced when clathrin expression was repressed suggesting similarities between the mechanism of PrP uptake and the mechanism observed here for Ure2. Conclusions/Significance The results provide insight into the mechanisms by which amyloid aggregates may cause pathological effects in prion and amyloid diseases.
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Affiliation(s)
- Chen Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- Graduate University of the Chinese Academy of Sciences, Beijing, China
| | - Antony P. Jackson
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Zai-Rong Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- Graduate University of the Chinese Academy of Sciences, Beijing, China
| | - Yan Han
- Department of Neurobiology and the Sino-Japan Joint Laboratory of Neurodegenerative Diseases, Beijing Institute of Geriatrics, Xuanwu Hospital of the Capital University of Medical Sciences, Beijing, China
| | - Shun Yu
- Department of Neurobiology and the Sino-Japan Joint Laboratory of Neurodegenerative Diseases, Beijing Institute of Geriatrics, Xuanwu Hospital of the Capital University of Medical Sciences, Beijing, China
| | - Rong-Qiao He
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Sarah Perrett
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- * E-mail:
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210
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Abstract
Gut microbiota is an assortment of microorganisms inhabiting the length and width of the mammalian gastrointestinal tract. The composition of this microbial community is host specific, evolving throughout an individual's lifetime and susceptible to both exogenous and endogenous modifications. Recent renewed interest in the structure and function of this "organ" has illuminated its central position in health and disease. The microbiota is intimately involved in numerous aspects of normal host physiology, from nutritional status to behavior and stress response. Additionally, they can be a central or a contributing cause of many diseases, affecting both near and far organ systems. The overall balance in the composition of the gut microbial community, as well as the presence or absence of key species capable of effecting specific responses, is important in ensuring homeostasis or lack thereof at the intestinal mucosa and beyond. The mechanisms through which microbiota exerts its beneficial or detrimental influences remain largely undefined, but include elaboration of signaling molecules and recognition of bacterial epitopes by both intestinal epithelial and mucosal immune cells. The advances in modeling and analysis of gut microbiota will further our knowledge of their role in health and disease, allowing customization of existing and future therapeutic and prophylactic modalities.
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Affiliation(s)
- Inna Sekirov
- Michael Smith Laboratories, Department of Microbiology and Immunology, The University of British Columbia, Vancouver, British Columbia, Canada
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211
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Butterfield S, Lashuel H. Wechselwirkungen zwischen amyloidogenen Proteinen und Membranen: Modellsysteme liefern mechanistische Einblicke. Angew Chem Int Ed Engl 2010. [DOI: 10.1002/ange.200906670] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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212
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Brender JR, Hartman K, Nanga RPR, Popovych N, de la Salud Bea R, Vivekanandan S, Marsh ENG, Ramamoorthy A. Role of zinc in human islet amyloid polypeptide aggregation. J Am Chem Soc 2010; 132:8973-83. [PMID: 20536124 PMCID: PMC2904811 DOI: 10.1021/ja1007867] [Citation(s) in RCA: 190] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Human Islet Amyloid Polypeptide (hIAPP) is a highly amyloidogenic protein found in islet cells of patients with type II diabetes. Because hIAPP is highly toxic to beta-cells under certain conditions, it has been proposed that hIAPP is linked to the loss of beta-cells and insulin secretion in type II diabetics. One of the interesting questions surrounding this peptide is how the toxic and aggregation prone hIAPP peptide can be maintained in a safe state at the high concentrations that are found in the secretory granule where it is stored. We show here zinc, which is found at millimolar concentrations in the secretory granule, significantly inhibits hIAPP amyloid fibrillogenesis at concentrations similar to those found in the extracellular environment. Zinc has a dual effect on hIAPP fibrillogenesis: it increases the lag-time for fiber formation and decreases the rate of addition of hIAPP to existing fibers at lower concentrations, while having the opposite effect at higher concentrations. Experiments at an acidic pH which partially neutralizes the change in charge upon zinc binding show inhibition is largely due to an electrostatic effect at His18. High-resolution structures of hIAPP determined from NMR experiments confirm zinc binding to His18 and indicate zinc induces localized disruption of the secondary structure of IAPP in the vicinity of His18 of a putative helical intermediate of IAPP. The inhibition of the formation of aggregated and toxic forms of hIAPP by zinc provides a possible mechanism between the recent discovery of linkage between deleterious mutations in the SLC30A8 zinc transporter, which transports zinc into the secretory granule, and type II diabetes.
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Affiliation(s)
- Jeffrey R. Brender
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Kevin Hartman
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | | | - Natalya Popovych
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Roberto de la Salud Bea
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Subramanian Vivekanandan
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - E. Neil G. Marsh
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
| | - Ayyalusamy Ramamoorthy
- Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA
- Department of Biophysics, University of Michigan, Ann Arbor, MI 48109-1055, USA
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213
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Khemtémourian L, Engel MFM, Liskamp RMJ, Höppener JWM, Killian JA. The N-terminal fragment of human islet amyloid polypeptide is non-fibrillogenic in the presence of membranes and does not cause leakage of bilayers of physiologically relevant lipid composition. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1798:1805-11. [PMID: 20570648 DOI: 10.1016/j.bbamem.2010.05.022] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Revised: 05/17/2010] [Accepted: 05/24/2010] [Indexed: 10/19/2022]
Abstract
Human islet amyloid polypeptide (hIAPP) forms amyloid fibrils in pancreatic islets of patients with type 2 diabetes mellitus (DM2). The formation of hIAPP fibrils has been shown to cause membrane damage which most likely is responsible for the death of pancreatic islet beta-cells during the pathogenesis of DM2. Previous studies have shown that the N-terminal part of hIAPP, hIAPP(1-19), plays a major role in the initial interaction of hIAPP with lipid membranes. However, the exact role of this N-terminal part of hIAPP in causing membrane damage is unknown. Here we investigate the structure and aggregation properties of hIAPP(1-19) in relation to membrane damage in vitro by using membranes of the zwitterionic lipid phosphatidylcholine (PC), the anionic lipid phosphatidylserine (PS) and mixtures of these lipids to mimic membranes of islet cells. Our data reveal that hIAPP(1-19) is weakly fibrillogenic in solution and not fibrillogenic in the presence of membranes, where it adopts a secondary structure that is dependent on lipid composition and stable in time. Furthermore, hIAPP(1-19) is not able to induce leakage in membranes of PC/PS or PC bilayers, indicating that the membrane interaction of the N-terminal fragment by itself is not responsible for membrane leakage under physiologically relevant conditions. In bilayers of the anionic lipid PS, the peptide does induce membrane damage, but this leakage is not correlated to fibril formation, as it is for mature hIAPP. Hence, membrane permeabilization by the N-terminal fragment of hIAPP in anionic lipids is most likely an aspecific process, occurring via a mechanism that is not relevant for hIAPP-induced membrane damage in vivo.
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Affiliation(s)
- Lucie Khemtémourian
- Department of Chemical Biology and Organic Chemistry, Institute of Biomembranes, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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214
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Laghaei R, Mousseau N, Wei G. Effect of the Disulfide Bond on the Monomeric Structure of Human Amylin Studied by Combined Hamiltonian and Temperature Replica Exchange Molecular Dynamics Simulations. J Phys Chem B 2010; 114:7071-7. [DOI: 10.1021/jp100205w] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Rozita Laghaei
- Département de Physique and Regroupement québécois sur les matériaux de pointe, Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal (Québec), Canada
| | - Normand Mousseau
- Département de Physique and Regroupement québécois sur les matériaux de pointe, Université de Montréal, C.P. 6128, succursale Centre-ville, Montréal (Québec), Canada
| | - Guanghong Wei
- Department of Physics and Surface Physics Laboratory (National Key Laboratory), Fudan University, 220 Handan Road, Shanghai 200433, China
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215
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Ebrahim-Habibi MB, Amininasab M, Ebrahim-Habibi A, Sabbaghian M, Nemat-Gorgani M. Fibrillation of α-lactalbumin: Effect of crocin and safranal, two natural small molecules from Crocus sativus. Biopolymers 2010; 93:854-65. [DOI: 10.1002/bip.21477] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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216
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Bartolini M, Andrisano V. Strategies for the Inhibition of Protein Aggregation in Human Diseases. Chembiochem 2010; 11:1018-35. [DOI: 10.1002/cbic.200900666] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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217
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Mazzaglia A, Micali N, Scolaro LM, Attanasio F, Magrí A, Pappalardo G, Villari V. Aggregation properties of the peptide fragments derived from the 17-29 region of the human and rat IAPP: a comparative study with two PEG-conjugated variants of the human sequence. J Phys Chem B 2010; 114:705-13. [PMID: 20039665 DOI: 10.1021/jp908436s] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The amyloidogenic amino acid sequence Ac-VHSSNNFGAILSS-NH(2), corresponding to the 17-29 peptide region of human amylin (hIAPP17-29), was modified by grafting a hydrophilic PEG chain in order to obtain a novel class of peptides to be used as models to study the aggregation process of the full-length IAPP. The amphiphilic feature of the pegylated peptide fragment at the N-terminus (PEG-N-hIAPP17-29) drives the aggregation process toward stable micellar clusters without fibrillogenesis, despite the presence of beta-sheet interaction between peptides at pH values higher than 4.0. The hIAPP17-29-C-PEG, in which the PEG moiety is linked to the C-terminus, does not possess analogous amphiphilic character and the ability of PEG in forming H-bonds with the solvent overcomes that of the peptide chain, thereby causing peptide flocculation. The comparison with the unmodified hIAPP17-29 and the rat's peptide sequence Ac-VRSSNNLGPGLPP-NH(2)(rIAPP17-29) revealed the crucial role of hydrogen bonding between peptide and solvent in determining the aggregate structure and preventing fibril formation, as well as the non-negligible effect of a small amount of organic solvent in the aqueous solution which affects the aggregation process and rate.
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Affiliation(s)
- Antonino Mazzaglia
- CNR-Istituto per lo Studio dei Materiali Nanostrutturati, c/o Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica dell'Universitá di Messina, S.ta Sperone 31, I-98166, Messina, Italy
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218
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Heyl DL, Osborne JM, Pamarthy S, Samisetti S, Gray AW, Jayaprakash A, Konda S, Brown DJ, Miller SR, Eizadkhah R, Milletti MC. Liposome Damage and Modeling of Fragments of Human Islet Amyloid Polypeptide (IAPP) Support a Two-Step Model of Membrane Destruction. Int J Pept Res Ther 2010. [DOI: 10.1007/s10989-010-9202-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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219
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Design and study of peptide-based inhibitors of amylin cytotoxicity. Bioorg Med Chem Lett 2010; 20:1360-2. [DOI: 10.1016/j.bmcl.2010.01.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2009] [Revised: 12/25/2009] [Accepted: 01/04/2010] [Indexed: 11/22/2022]
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220
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Mustata M, Capone R, Jang H, Arce FT, Ramachandran S, Lal R, Nussinov R. K3 fragment of amyloidogenic beta(2)-microglobulin forms ion channels: implication for dialysis related amyloidosis. J Am Chem Soc 2010; 131:14938-45. [PMID: 19824733 DOI: 10.1021/ja9049299] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Beta(2)-microglobulin (beta(2)m) amyloid deposits are linked to dialysis-related amyloidosis (DRA) in hemodialysis patients. The mechanism by which beta(2)m causes DRA is not understood. It is also unclear whether only the full-length beta(2)m induces pathophysiology or if proteolytic fragments are sufficient for inducing this effect. Ser20-Lys41 (K3) is a digestion fragment of full-length beta(2)m. Solid state NMR (ssNMR) combined with X-ray diffraction and atomic force microscopy (AFM) revealed the characteristic oligomeric amyloid conformation of the U-turn beta-strand-turn-beta-strand motif stacked in parallel and stabilized by intermolecular interactions also shown by Abeta(9-40)/Abeta(17-42) and the CA150 WW domain. Here we use the K3 U-turn atomic coordinates and molecular dynamic (MD) simulations to model K3 channels in the membrane. Consistent with previous AFM imaging of other amyloids that show channel-like structures in the membrane, in the simulations K3 also forms ion channels with 3-6 loosely attached mobile subunits. We carry out AFM, single channel electrical recording, and fluorescence imaging experiments. AFM images display 3D ion channel topography with shapes, morphologies, and dimensions consistent with the theoretical model. Electrical conductance measurements indicate multiple single channel conductances, suggesting that various K3 oligomer sizes can constitute the channel structure. Fluorescence measurements in kidney cells show channel-mediated cell calcium uptake. These results suggest that the beta(2)m-induced DRA can be mediated by ion channels formed by its K3 fragment. Because the beta-strand-turn-beta-strand motif appears to be a universal amyloid feature, its ability to form ion channels further suggests that the motif may play a generic role in toxicity.
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Affiliation(s)
- Mirela Mustata
- Center for Nanomedicine and Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA
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221
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Sciacca MFM, Pappalardo M, Attanasio F, Milardi D, La Rosa C, Grasso DM. Are fibrilgrowth and membrane damage linked processes? An experimental and computational study of IAPP12–18and IAPP21–27peptides. NEW J CHEM 2010. [DOI: 10.1039/b9nj00253g] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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222
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Schröder M, Sutcliffe L. Consequences of stress in the secretory pathway: The ER stress response and its role in the metabolic syndrome. Methods Mol Biol 2010; 648:43-62. [PMID: 20700704 DOI: 10.1007/978-1-60761-756-3_3] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The unfolded protein response (UPR) was originally identified as a signaling network coordinating adaptive and apoptotic responses to accumulation of unfolded proteins in the endoplasmic reticulum (ER). More recent work has shown that UPR signaling can be triggered by a multitude of cellular events and that the UPR plays a critical role in the prevention, and also the progression, of a wide variety of diseases. Much attention has been paid to the role of the UPR in neurodegenerative diseases in the past. More recently, important roles for the UPR in diseases associated with the metabolic syndrome have been discovered. Here we review the role of the UPR in these diseases, including type 2 diabetes, atherosclerosis, fatty liver disease, and ischemia.
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223
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Amyloid peptide pores and the beta sheet conformation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 677:150-67. [PMID: 20687488 DOI: 10.1007/978-1-4419-6327-7_13] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Over 20 clinical syndromes have been described as amyloid diseases. Pathologically, these illnesses are characterized by the deposition in various tissues of amorphous, Congo red stainingdeposits, referred to as amyloid. Under polarizing light microscopy, these deposits exhibit characteristic green birefringence. X-ray diffraction reveals cross-beta structure of extended amyloid fibrils. Although there is always a major protein in amyloid deposits, the predominant protein differs in each ofthe clinical syndromes. All the proteins exhibit the characteristic nonnative beta-sheet state. These proteins aggregate spontaneously into extended fibrils and precipitate out of solution. At least a dozen of these peptides have been demonstrated to be capable of channel formation in lipid bilayers and it has been proposed that this represents a pathogenic mechanism. Remarkably, the channels formed by these various peptides exhibit a number of common properties including irreversible, spontaneous insertion into membranes, production oflarge, heterogeneous single-channel conductances, relatively poor ion selectivity, inhibition of channel formation by Congo red and related dyes and blockade of inserted channels by zinc. In vivo amyloid peptides have been shown to disrupt intracellular calcium regulation, plasma membrane potential, mitochondrial membrane potential and function and long-term potentiation in neurons. Amyloid peptides also cause cytotoxicity. Formation of the beta sheet conformation from native protein structures can be induced by high protein concentrations, metal binding, acidic pH, amino acid mutation and interaction with lipid membranes. Most amyloid peptides interact strongly with membranes and this interaction is enhanced by conditions which favor beta-sheet formation. Formation of pores in these illnesses appears to be a spontaneous process and available evidence suggests several steps are critical. First, destabilization of the native structure and formation of the beta-sheet conformation must occur. This may occur in solution or may be facilitated by contact with lipid membranes. Oligomerization of the amyloid protein is then mediated by the beta strands. Amyloid monomers and extended fibrils appear to have little potential for toxicity whereas there is much evidence implicating amyloid oligomers of intermediate size in the pathogenesis of amyloid disease. Insertion of the oligomer appears to take place spontaneously although there may be a contribution of acidic pH and/or membrane potential. Very little is known about the structure of amyloid pores, but given that the amyloid peptides must acquire beta-sheet conformation to aggregate and polymerize, it has been hypothesized that amyloid pores may in fact be beta-sheet barrels similar to the pores formed by alpha-latrotoxin, Staphylococcal alpha-hemolysin, anthrax toxin and clostridial perfringolysin.
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224
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Stefani M. Protein aggregation diseases: toxicity of soluble prefibrillar aggregates and their clinical significance. Methods Mol Biol 2010; 648:25-41. [PMID: 20700703 DOI: 10.1007/978-1-60761-756-3_2] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Amyloid diseases, the most clinically relevant protein misfolding pathologies due to the high prevalence of some of them in the population, are characterized by the presence, in specific tissues and organs, of fibrillar deposits of specific peptides or proteins. Increasing efforts are presently dedicated at investigating the structural features and the structure-toxicity relation of the soluble oligomeric precursors arising in the path of fibril formation. In fact, it is increasingly recognised that these unstable, dynamic assemblies are remarkably toxic to cells thus featuring these as the main factor responsible for cell impairment in amyloid diseases. This chapter will review shortly the data presently available on the structural and biochemical features of these assemblies, as well as on their biological and clinical significance.
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225
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Pathuri G, Agashe HB, Awasthi V, Gali H. Radiosynthesis and in vivoevaluation of a F-18-labeled pancreatic islet amyloid inhibitor. J Labelled Comp Radiopharm 2010. [DOI: 10.1002/jlcr.1748] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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226
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Bedrood S, Jayasinghe S, Sieburth D, Chen M, Erbel S, Butler PC, Langen R, Ritzel RA. Annexin A5 directly interacts with amyloidogenic proteins and reduces their toxicity. Biochemistry 2009; 48:10568-76. [PMID: 19810772 DOI: 10.1021/bi900608m] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Protein misfolding is a central mechanism for the development of neurodegenerative diseases and type 2 diabetes mellitus. The accumulation of misfolded alpha-synuclein protein inclusions in the Lewy bodies of Parkinson's disease is thought to play a key role in pathogenesis and disease progression. Similarly, the misfolding of the beta-cell hormone human islet amyloid polypeptide (h-IAPP) into toxic oligomers plays a central role in the induction of beta-cell apoptosis in the context of type 2 diabetes. In this study, we show that annexin A5 plays a role in interacting with and reducing the toxicity of the amyloidogenic proteins, h-IAPP and alpha-synuclein. We find that annexin A5 is coexpressed in human beta-cells and that exogenous annexin A5 reduces the level of h-IAPP-induced apoptosis in human islets by approximately 50% and in rodent beta-cells by approximately 90%. Experiments with transgenic expression of alpha-synuclein in Caenorhabditis elegans show that annexin A5 reduces alpha-synuclein inclusions in vivo. Using thioflavin T fluorescence, electron microscopy, and electron paramagnetic resonance, we provide evidence that substoichiometric amounts of annexin A5 inhibit h-IAPP and alpha-synuclein misfolding and fibril formation. We conclude that annexin A5 might act as a molecular safeguard against the formation of toxic amyloid aggregates.
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Affiliation(s)
- Sahar Bedrood
- Department of Biochemistry and Molecular Biology, Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern California, Los Angeles, California 90033, USA
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227
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Huang CJ, Gurlo T, Haataja L, Costes S, Daval M, Ryazantsev S, Wu X, Butler AE, Butler PC. Calcium-activated calpain-2 is a mediator of beta cell dysfunction and apoptosis in type 2 diabetes. J Biol Chem 2009; 285:339-48. [PMID: 19861418 DOI: 10.1074/jbc.m109.024190] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The islet in type 2 diabetes (T2DM) and the brain in neurodegenerative diseases share progressive cell dysfunction, increased apoptosis, and accumulation of locally expressed amyloidogenic proteins (islet amyloid polypeptide (IAPP) in T2DM). Excessive activation of the Ca(2+)-sensitive protease calpain-2 has been implicated as a mediator of oligomer-induced cell death and dysfunction in neurodegenerative diseases. To establish if human IAPP toxicity is mediated by a comparable mechanism, we overexpressed human IAPP in rat insulinoma cells and freshly isolated human islets. Pancreas was also obtained at autopsy from humans with T2DM and nondiabetic controls. We report that overexpression of human IAPP leads to the formation of toxic oligomers and increases beta cell apoptosis mediated by increased cytosolic Ca(2+) and hyperactivation of calpain-2. Cleavage of alpha-spectrin, a marker of calpain hyperactivation, is increased in beta cells in T2DM. We conclude that overactivation of Ca(2+)-calpain pathways contributes to beta cell dysfunction and apoptosis in T2DM.
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Affiliation(s)
- Chang-jiang Huang
- Larry Hillblom Islet Research Center, David Geffen School of Medicine, California Nano Systems Institute, UCLA, Los Angeles, California 90024-2852, USA
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228
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Dvir H, Lundberg ME, Maji SK, Riek R, Choe S. Mistic: cellular localization, solution behavior, polymerization, and fibril formation. Protein Sci 2009; 18:1564-70. [PMID: 19475664 DOI: 10.1002/pro.148] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Mistic represents a family of unique membrane-associating proteins originally found in Bacillus subtilis (M110). As a fusion partner, it has been shown to assist overexpression of foreign integral membrane proteins in E. coli. We have expressed shorter Mistic homologs from other Bacillus species and surprisingly, unlike M110, found them abundant in the cytoplasm. These Mistic homologs including the corresponding shorter sequence (amino acids 27 through 110 of M110) exist as multimeric assemblies in solution in the absence of detergent. Crystals of Mistic from B. leicheniformis (M2) diffracted to 3.2 A resolution, indicating that it exists as a multimer in the crystalline state as well. Moreover, we show that although M2 is mostly alpha-helical, it tends to polymerize and form fibrils. Such oligomerization could potentially mask the charged surface of the monomeric Mistic to assist membrane integration.
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Affiliation(s)
- Hay Dvir
- Structural Biology Laboratory, The Salk Institute for Biological Studies, San Diego, California 92037, USA
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229
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Cho WJ, Trikha S, Jeremic AM. Cholesterol regulates assembly of human islet amyloid polypeptide on model membranes. J Mol Biol 2009; 393:765-75. [PMID: 19720065 DOI: 10.1016/j.jmb.2009.08.055] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 08/18/2009] [Accepted: 08/23/2009] [Indexed: 01/25/2023]
Abstract
Amylin, a 37-aa pancreatic hormone, is the major constituent of islet amyloid, a hallmark of type II diabetes mellitus. Recent studies have revealed a pivotal role of anionic phospholipids in membrane-catalyzed amylin fibrillogenesis and aggregation. However, cholesterol, an integral component of eukaryotic cell membranes, also could have a role. In this study, we have examined the effect of cholesterol on amylin polymerization both on planar membranes and in solution. Using time-lapse atomic force microscopy, we have studied the dynamics and macromolecular organization of amylin on anionic and neutral planar membranes that lack or include cholesterol. On cholesterol-depleted planar membranes, amylin formed highly symmetrical tetrameric and pentameric pore-like supramolecular structures composed of 25- to 35-nm intermediate-sized globular structures or oligomers. Conversely, on membranes incorporating cholesterol, amylin formed highly compact approximately 200- to 500-nm protein clusters that constituted seeds or nuclei for continuing amylin binding and aggregation. However, cholesterol inhibited amylin nucleation with a 7-fold decrease in the number of amylin particles. Consequently, cholesterol-containing membranes accumulated significantly less amyloid with some membrane areas completely free of amyloid particles. The inhibitory effect of cholesterol on amylin aggregation in solution was also demonstrated as a 16-fold decrease in the aggregation rate. Consistent with this, circular dichroism spectroscopy revealed a stable, soluble random-coil conformation for amylin in the presence of cholesterol that could explain the inhibitory effect of cholesterol on amylin polymerization in solution and on membranes. The modulatory effect of cholesterol was largely independent of membrane charge or phospholipids, suggesting a novel cholesterol-regulated amylin polymerization process.
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Affiliation(s)
- Won-Jin Cho
- Department of Physiology, Wayne State University School of Medicine, 540 East Canfield, Detroit, MI 48201, USA
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230
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Yu JT, Chang RCC, Tan L. Calcium dysregulation in Alzheimer's disease: from mechanisms to therapeutic opportunities. Prog Neurobiol 2009; 89:240-55. [PMID: 19664678 DOI: 10.1016/j.pneurobio.2009.07.009] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2009] [Revised: 07/28/2009] [Accepted: 07/31/2009] [Indexed: 11/28/2022]
Abstract
Calcium is involved in many facets of neuronal physiology, including activity, growth and differentiation, synaptic plasticity, and learning and memory, as well as pathophysiology, including necrosis, apoptosis, and degeneration. Though disturbances in calcium homeostasis in cells from Alzheimer's disease (AD) patients have been observed for many years, much more attention was focused on amyloid-beta (Abeta) and tau as key causative factors for the disease. Nevertheless, increasing lines of evidence have recently reported that calcium dysregulation plays a central role in AD pathogenesis. Systemic calcium changes accompany almost the whole brain pathology process that is observed in AD, including synaptic dysfunction, mitochondrial dysfunction, presenilins mutation, Abeta production and Tau phosphorylation. Given the early and ubiquitous involvement of calcium dysregulation in AD pathogenesis, it logically presents a variety of potential therapeutic targets for AD prevention and treatment, such as calcium channels in the plasma membrane, calcium channels in the endoplasmic reticulum membrane, Abeta-formed calcium channels, calcium-related proteins. The review aims to provide an overview of the current understanding of the molecular mechanisms involved in calcium dysregulation in AD, and an insight on how to exploit calcium regulation as therapeutic opportunities in AD.
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Affiliation(s)
- Jin-Tai Yu
- Department of Neurology, Qingdao Municipal Hospital, School of Medicine, Qingdao University, No. 5 Donghai Middle Road, Qingdao, Shandong Province 266071, China
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231
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Pancreatic islet amyloidosis, beta-cell apoptosis, and alpha-cell proliferation are determinants of islet remodeling in type-2 diabetic baboons. Proc Natl Acad Sci U S A 2009; 106:13992-7. [PMID: 19666551 DOI: 10.1073/pnas.0906471106] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
beta-Cell dysfunction is an important factor in the development of hyperglycemia of type-2 diabetes mellitus, and pancreatic islet amyloidosis (IA) has been postulated to be one of the main contributors to impaired insulin secretion. The aim of this study was to evaluate the correlation of IA with metabolic parameters and its effect on islets of Langerhans remodeling and relative endocrine-cell volume in baboons. We sequenced the amylin peptide, determined the fibrillogenic propensities, and evaluated pancreatic histology, clinical and biochemical characteristics, and endocrine cell proliferation and apoptosis in 150 baboons with different metabolic status. Amylin sequence in the baboon was 92% similar to humans and showed superimposable fibrillogenic propensities. IA severity correlated with fasting plasma glucose (FPG) (r = 0.662, P < 0.001) and HbA1c (r = 0.726, P < 0.001), as well as with free fatty acid, glucagon values, decreased homeostasis model assessment (HOMA) insulin resistance, and HOMA-B. IA severity was associated with a decreased relative beta-cell volume, and increased relative alpha-cell volume and hyperglucagonemia. These results strongly support the concept that IA and beta-cell apoptosis in concert with alpha-cell proliferation and hypertrophy are key determinants of islets of Langerhans "dysfunctional remodeling" and hyperglycemia in the baboon, a nonhuman primate model of type-2 diabetes mellitus. The most important determinants of IA were age and FPG (R(2) = 0.519, P < 0.0001), and different FPG levels were sensitive and specific to predict IA severity. Finally, a predictive model for islet amyloid severity was generated with age and FPG as required variables.
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232
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Hebda JA, Miranker AD. The interplay of catalysis and toxicity by amyloid intermediates on lipid bilayers: insights from type II diabetes. Annu Rev Biophys 2009; 38:125-52. [PMID: 19416063 DOI: 10.1146/annurev.biophys.050708.133622] [Citation(s) in RCA: 196] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The dynamics, energies, and structures governing protein folding are critical to biological function. Amyloidoses are a class of disease defined, in part, by the misfolding and aggregation of functional protein precursors into fibrillar states. Amyloid fibers contribute to the pathology of many diseases, including type II diabetes, Alzheimer's, and Parkinson's. In these disorders, amyloid fibers are present in affected tissues. However, it has become clear that intermediate states, rather than mature fibers, represent the cytotoxic species. In this review, we focus particularly on lipid bilayer-bound intermediates. Remarkably, the precursors of these fibers are intrinsically disordered, and yet catalysis of beta-sheet formation appears to be mediated by the stabilization of alpha-helical states. On the lipid bilayer, these intermediate species have been implicated as cytotoxic through elimination of ionic homeostasis. Recent advances are enabling insights at a molecular level that promise to provide meaningful targets for the development of therapeutics.
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Affiliation(s)
- James A Hebda
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA
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233
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Ahmad A, Muzaffar M, Ingram VM. Ca(2+), within the physiological concentrations, selectively accelerates Abeta42 fibril formation and not Abeta40 in vitro. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2009; 1794:1537-48. [PMID: 19595795 DOI: 10.1016/j.bbapap.2009.06.022] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/01/2009] [Revised: 06/06/2009] [Accepted: 06/29/2009] [Indexed: 01/14/2023]
Abstract
Alzheimer's disease (AD) in humans is a common progressive neurodegenerative disease, associated with cognitive dysfunction, memory loss and neuronal loss. Alzheimer peptides Abeta40 and Abeta42 are precursors of the amyloid fibers that accumulate in the brain of patients. These peptides misfold and the monomers aggregate to neurotoxic oligomers and fibrils. Thus, the aggregation kinetics of these peptides is central to understanding the etiology of AD. Using size exclusion chromatography as well as filtration methods, we report here that Ca(2+) ions at physiological concentrations greatly accelerate the rate of aggregation of Abeta42 to form intermediate soluble associated species and fibrils. In the presence of 1 or 2 mM Ca(2+), CD spectra indicated that the secondary structure of Abeta42 changed from an unfolded to a predominantly beta-sheet conformation. These concentrations of Ca(2+) greatly decreased the lag time for Abeta42 fibril formation, measured with thioflavin T. However, the elongation rate was apparently unaffected. Ca(2+) appears to predominantly accelerate the nucleation stage of Abeta42 on pathway to the Alzheimer's fibril formation. Unlike Abeta42, Ca(2+) was not observed to trigger similar effect at any stage during the study of fibrillation kinetics of Abeta40 by any techniques. Abeta40 and Abeta42 seem to have distinct aggregation pathways.
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Affiliation(s)
- Atta Ahmad
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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234
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Kawahara M, Negishi-Kato M, Sadakane Y. Calcium dyshomeostasis and neurotoxicity of Alzheimer's beta-amyloid protein. Expert Rev Neurother 2009; 9:681-93. [PMID: 19402778 DOI: 10.1586/ern.09.28] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Neurotoxicity of Alzheimer's beta-amyloid protein (AbetaP) is central to the pathogenesis of Alzheimer's disease (AD). Recent approaches have emphasized the importance of AbetaP oligomerization, which causes synaptic degeneration and neuronal loss, finally leading to the pathogenesis of AD. Although the precise molecular mechanism of AbetaP neurotoxicity remains elusive, our and other numerous findings have demonstrated that AbetaP directly incorporated into neuronal membranes formed calcium-permeable ion channels (amyloid channels) and resulted in an abnormal elevation of the intracellular calcium levels. The formation of amyloid channels and the abnormal increase of intracellular Ca(2+) have also been commonly observed in other neurodegenerative diseases, including conformational diseases such as prion disease or dementia with Lewy bodies. This article reviews the current understanding of the pathology of AD based on the hypothesis that the disruption of calcium homeostasis through amyloid channels may be the molecular basis of AbetaP neurotoxicity. The potential development of preventive agents is also discussed.
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Affiliation(s)
- Masahiro Kawahara
- Department of Analytical Chemistry, School of Pharmaceutical Sciences, Kyushu University of Health and Welfare, Nobeoka-shi, Miyazaki, Japan.
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235
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Li XL, Xu G, Chen T, Wong YS, Zhao HL, Fan RR, Gu XM, Tong PC, Chan JC. Phycocyanin protects INS-1E pancreatic beta cells against human islet amyloid polypeptide-induced apoptosis through attenuating oxidative stress and modulating JNK and p38 mitogen-activated protein kinase pathways. Int J Biochem Cell Biol 2009; 41:1526-35. [PMID: 19166964 DOI: 10.1016/j.biocel.2009.01.002] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2008] [Revised: 12/22/2008] [Accepted: 01/05/2009] [Indexed: 12/20/2022]
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236
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Soong R, Brender JR, Macdonald PM, Ramamoorthy A. Association of highly compact type II diabetes related islet amyloid polypeptide intermediate species at physiological temperature revealed by diffusion NMR spectroscopy. J Am Chem Soc 2009; 131:7079-85. [PMID: 19405534 DOI: 10.1021/ja900285z] [Citation(s) in RCA: 127] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Self-association of human islet amyloid polypeptide (hIAPP) is correlated with the development of type II diabetes by the disruption of cellular homeostasis in islet cells through the formation of membrane-active oligomers. The toxic species of hIAPP responsible for membrane damage has not been identified. In this study, we show by pulsed field gradient NMR spectroscopy that the monomeric form of the toxic, amyloidogenic human variant of IAPP (hIAPP) adopts a temperature dependent compact folded conformation that is absent in both the nontoxic and nonamyloidogenic rat variant of IAPP and absent in hIAPP at low temperatures, suggesting this compact form of monomeric hIAPP may be linked to its later aggregation and cytotoxicity. In addition to the monomeric form of hIAPP, a large oligomeric species greater than 100 nm in diameter is also present but does not trigger the nucleation-dependent aggregation of IAPP at 4 degrees C, indicating the large oligomeric species may be an off-pathway intermediate that has been predicted by kinetic models of IAPP fiber formation. Furthermore, analysis of the polydispersity of the calculated diffusion values indicates small oligomeric species of hIAPP are absent in agreement with a recent ultracentrifugation study. The absence of small oligomeric species in solution suggests the formation of small, well-defined ion channels by hIAPP may proceed by aggregation of monomeric IAPP on the membrane, rather than by the insertion of preformed structured oligomers from the solution state as has been proposed for other amyloidogenic proteins.
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Affiliation(s)
- Ronald Soong
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
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237
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Pieri L, Bucciantini M, Guasti P, Savistchenko J, Melki R, Stefani M. Synthetic lipid vesicles recruit native-like aggregates and affect the aggregation process of the prion Ure2p: insights on vesicle permeabilization and charge selectivity. Biophys J 2009; 96:3319-30. [PMID: 19383475 DOI: 10.1016/j.bpj.2008.12.3958] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2008] [Revised: 12/19/2008] [Accepted: 12/23/2008] [Indexed: 10/20/2022] Open
Abstract
The yeast prion Ure2p polymerizes into native-like fibrils, retaining the overall structure and binding properties of the soluble protein. Recently we have shown that, similar to amyloid oligomers, the native-like Ure2p fibrils and their precursor oligomers are highly toxic to cultured mammalian cells when added to the culture medium, whereas Ure2p amyloid fibrils generated by heating the native-like fibrils are substantially harmless. We show here that, contrary to the nontoxic amyloid fibrils, the toxic, native-like Ure2p assemblies induce a significant calcein release from negatively charged phosphatidylserine vesicles. A minor and less-specific effect was observed with zwitterionic phosphatidylcholine vesicles, suggesting that the toxic aggregates preferentially bind to negatively charged sites on lipid membranes. We also found that cholesterol-enriched phospholipid membranes are protected against permeabilization by native-like Ure2p assemblies. Moreover, vesicle permeabilization appears charge-selective, allowing calcium, but not chloride, influx to be monitored. Finally, we found that the interaction with phosphatidylserine membranes speeds up Ure2p polymerization into oligomers and fibrils structurally and morphologically similar to the native-like Ure2p assemblies arising in free solution, although less cytotoxic. These data suggest that soluble Ure2p oligomers and native-like fibrils, but not amyloid fibrils, interact intimately with negatively charged lipid membranes, where they allow selective cation influx.
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Affiliation(s)
- Laura Pieri
- Department of Biochemical Sciences, University of Florence, Italy; Research Centre on the Molecular Basis of Neurodegeneration, University of Florence, Italy
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238
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Lindner AB, Demarez A. Protein aggregation as a paradigm of aging. Biochim Biophys Acta Gen Subj 2009; 1790:980-96. [PMID: 19527771 DOI: 10.1016/j.bbagen.2009.06.005] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Revised: 06/08/2009] [Accepted: 06/09/2009] [Indexed: 12/23/2022]
Abstract
The process of physiological decline leading to death of the individual is driven by the deteriorating capacity to withstand extrinsic and intrinsic hazards, resulting in damage accumulation with age. The dynamic changes with time of the network governing the outcome of misfolded proteins, exemplifying as intrinsic hazards, is considered here as a paradigm of aging. The main features of the network, namely, the non-linear increase of damage and the presence of amplifying feedback loops within the system are presented through a survey of the different components of the network and related cellular processes in aging and disease.
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Affiliation(s)
- Ariel B Lindner
- INSERM U571, Paris Descartes University, Paris, F-75015, France.
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239
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Mina EW, Lasagna-Reeves C, Glabe CG, Kayed R. Poloxamer 188 copolymer membrane sealant rescues toxicity of amyloid oligomers in vitro. J Mol Biol 2009; 391:577-85. [PMID: 19524592 DOI: 10.1016/j.jmb.2009.06.024] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2009] [Revised: 06/08/2009] [Accepted: 06/08/2009] [Indexed: 10/20/2022]
Abstract
Amyloid oligomers and protofibrils increase cell membrane permeability, eventually leading to cell death. Here, we demonstrate that amyloid oligomer toxicity and membrane permeabilization can be reversed using the membrane sealant copolymer poloxamer 188. The data indicate that amyloid oligomer toxicity is caused by defects in the lipid bilayer of the type that are sealed by poloxamer 188. Our results also suggest the possibility of using polymer-based membrane sealants to prevent or reverse amyloid oligomer toxicity in vivo. Because the ability to permeabilize membranes is a generic property of amyloid oligomers, this therapeutic approach may be effective for the treatment of many degenerative diseases caused in part by the interaction of misfolded proteins with cell membranes, as in Alzheimer's disease, type II diabetes, and a host of others.
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Affiliation(s)
- Erene W Mina
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900, USA
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240
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Hull RL, Zraika S, Udayasankar J, Aston-Mourney K, Subramanian SL, Kahn SE. Amyloid formation in human IAPP transgenic mouse islets and pancreas, and human pancreas, is not associated with endoplasmic reticulum stress. Diabetologia 2009; 52:1102-11. [PMID: 19352619 PMCID: PMC2734275 DOI: 10.1007/s00125-009-1329-4] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Accepted: 02/19/2009] [Indexed: 12/31/2022]
Abstract
AIMS/HYPOTHESIS Supraphysiological levels of the amyloidogenic peptide human islet amyloid polypeptide have been associated with beta cell endoplasmic reticulum (ER) stress. However, in human type 2 diabetes, levels of human IAPP are equivalent or decreased relative to matched controls. Thus, we sought to investigate whether ER stress is induced during amyloidogenesis at physiological levels of human IAPP. METHODS Islets from human IAPP transgenic mice that develop amyloid, and non-transgenic mice that do not, were cultured for up to 7 days in 11.1, 16.7 and 33.3 mmol/l glucose. Pancreases from human IAPP transgenic and non-transgenic mice and humans with or without type 2 diabetes were also evaluated. Amyloid formation was determined histologically. ER stress was determined in islets by quantifying mRNA levels of Bip, Atf4 and Chop (also known as Ddit3) and alternate splicing of Xbp1 mRNA, or in pancreases by immunostaining for immunoglobulin heavy chain-binding protein (BIP), C/EBP homologous protein (CHOP) and X-box binding protein 1 (XBP1). RESULTS Amyloid formation in human IAPP transgenic islets was associated with reduced beta cell area in a glucose- and time-dependent manner. However, amyloid formation was not associated with significant increases in expression of ER stress markers under any culture condition. Thapsigargin treatment, a positive control, did result in significant ER stress. Amyloid formation in vivo in pancreas samples from human IAPP transgenic mice or humans was not associated with upregulation of ER stress markers. CONCLUSIONS/INTERPRETATION Our data suggest that ER stress is not an obligatory pathway mediating the toxic effects of amyloid formation at physiological levels of human IAPP.
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Affiliation(s)
- R L Hull
- Division of Metabolism, Endocrinology and Nutrition, VA Puget Sound Health Care System (151), Seattle, WA 98108, USA.
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241
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Ling YL, Strasfeld DB, Shim SH, Raleigh DP, Zanni MT. Two-dimensional infrared spectroscopy provides evidence of an intermediate in the membrane-catalyzed assembly of diabetic amyloid. J Phys Chem B 2009; 113:2498-505. [PMID: 19182939 DOI: 10.1021/jp810261x] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Islet amyloid polypeptide (IAPP, also known as amylin) is responsible for pancreatic amyloid deposits in type 2 diabetes. The deposits, as well as intermediates in their assembly, are cytotoxic to pancreatic beta-cells and contribute to the loss of beta-cell mass associated with type 2 diabetes. The factors that trigger islet amyloid deposition in vivo are not well understood, but peptide membrane interactions have been postulated to play an important role in islet amyloid formation. To better understand the role of membrane interactions in amyloid formation, two-dimensional infrared (2D IR) spectroscopy was used to compare the kinetics of amyloid formation for human IAPP both in the presence and in the absence of negatively charged lipid vesicles. Comparison of spectral features and kinetic traces from the two sets of experiments provides evidence for the formation of an ordered intermediate during the membrane-mediated assembly of IAPP amyloid. A characteristic transient spectral feature is detected during amyloid formation in the presence of vesicles that is not observed in the absence of vesicles. The spectral feature associated with the intermediate raises in intensity during the self-assembly process and subsequently decays in intensity in the classic manner of a kinetic intermediate. Studies with rat IAPP, a variant that is known to interact with membranes but does not form amyloid, confirm the presence of an intermediate. The analysis of 2D IR spectra in terms of specific structural features is discussed. The unique combination of time and secondary structure resolution of 2D IR spectroscopy has enabled the time-evolution of a hIAPP intermediate to be directly monitored for the first time. The data presented here demonstrates the utility of 2D IR spectroscopy for studying membrane-catalyzed amyloid formation.
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Affiliation(s)
- Yun L Ling
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706-1396, USA
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242
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Marambaud P, Dreses-Werringloer U, Vingtdeux V. Calcium signaling in neurodegeneration. Mol Neurodegener 2009; 4:20. [PMID: 19419557 PMCID: PMC2689218 DOI: 10.1186/1750-1326-4-20] [Citation(s) in RCA: 232] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Accepted: 05/06/2009] [Indexed: 12/16/2022] Open
Abstract
Calcium is a key signaling ion involved in many different intracellular and extracellular processes ranging from synaptic activity to cell-cell communication and adhesion. The exact definition at the molecular level of the versatility of this ion has made overwhelming progress in the past several years and has been extensively reviewed. In the brain, calcium is fundamental in the control of synaptic activity and memory formation, a process that leads to the activation of specific calcium-dependent signal transduction pathways and implicates key protein effectors, such as CaMKs, MAPK/ERKs, and CREB. Properly controlled homeostasis of calcium signaling not only supports normal brain physiology but also maintains neuronal integrity and long-term cell survival. Emerging knowledge indicates that calcium homeostasis is not only critical for cell physiology and health, but also, when deregulated, can lead to neurodegeneration via complex and diverse mechanisms involved in selective neuronal impairments and death. The identification of several modulators of calcium homeostasis, such as presenilins and CALHM1, as potential factors involved in the pathogenesis of Alzheimer's disease, provides strong support for a role of calcium in neurodegeneration. These observations represent an important step towards understanding the molecular mechanisms of calcium signaling disturbances observed in different brain diseases such as Alzheimer's, Parkinson's, and Huntington's diseases.
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Affiliation(s)
- Philippe Marambaud
- Litwin-Zucker Research Center for the Study of Alzheimer's Disease, The Feinstein Institute for Medical Research, North Shore-LIJ, Manhasset, New York 11030, USA.
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243
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Engel MFM. Membrane permeabilization by Islet Amyloid Polypeptide. Chem Phys Lipids 2009; 160:1-10. [PMID: 19501206 DOI: 10.1016/j.chemphyslip.2009.03.008] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2009] [Revised: 03/26/2009] [Accepted: 03/27/2009] [Indexed: 01/14/2023]
Abstract
Membrane permeabilization by Islet Amyloid Polypeptide (IAPP) is suggested to be the main mechanism for IAPP-induced cytotoxicity and death of insulin-producing beta-cells in type 2 diabetes mellitus (T2DM). The insoluble fibrillar IAPP deposits (amyloid) present in the pancreas of most T2DM patients are not the primary suspects responsible for permeabilization of beta-cell membranes. Instead, soluble IAPP oligomers are thought to be cytotoxic by forming membrane channels or by inducing bilayer disorder. In addition, the elongation of IAPP fibrils at the membrane, but not the fibrils themselves, could cause membrane disruption. Recent reports substantiate the formation of an alpha-helical, membrane-bound IAPP monomer as possible intermediate on the aggregation pathway. Here, the structures and membrane interactions of various IAPP species will be reviewed, and the proposed hypotheses for IAPP-induced membrane permeabilization and cytotoxicity will be discussed.
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Affiliation(s)
- Maarten F M Engel
- Astbury Centre for Structural Molecular Biology and Institute of Molecular and Cellular Biology, University of Leeds, UK.
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244
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Smith PES, Brender JR, Ramamoorthy A. Induction of negative curvature as a mechanism of cell toxicity by amyloidogenic peptides: the case of islet amyloid polypeptide. J Am Chem Soc 2009; 131:4470-8. [PMID: 19278224 PMCID: PMC2665920 DOI: 10.1021/ja809002a] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The death of insulin-producing beta-cells is a key step in the pathogenesis of type 2 diabetes. The amyloidogenic peptide Islet Amyloid Polypeptide (IAPP, also known as amylin) has been shown to disrupt beta-cell membranes leading to beta-cell death. Despite the strong evidence linking IAPP to the destruction of beta-cell membrane integrity and cell death, the mechanism of IAPP toxicity is poorly understood. In particular, the effect of IAPP on the bilayer structure has largely been uncharacterized. In this study, we have determined the effect of the amyloidogenic and toxic hIAPP(1-37) peptide and the nontoxic and nonamyloidogenic rIAPP(1-37) peptide on membranes by a combination of DSC and solid-state NMR spectroscopy. We also characterized the toxic but largely nonamyloidogenic rIAPP(1-19) and hIAPP(1-19) fragments. DSC shows that both amyloidogenic (hIAPP(1-37)) and largely nonamyloidogenic (hIAPP(1-19) and rIAPP(1-19)) toxic versions of the peptide strongly favor the formation of negative curvature in lipid bilayers, while the nontoxic full-length rat IAPP(1-37) peptide does not. This result was confirmed by solid-state NMR spectroscopy which shows that in bicelles composed of regions of high curvature and low curvature, nontoxic rIAPP(1-37) binds to the regions of low curvature while toxic rIAPP(1-19) binds to regions of high curvature. Similarly, solid-state NMR spectroscopy shows that the toxic rIAPP(1-19) peptide significantly disrupts the lipid bilayer structure, whereas the nontoxic rIAPP(1-37) does not have a significant effect. These results indicate IAPP may induce the formation of pores by the induction of excess membrane curvature and can be used to guide the design of compounds that can prevent the cell-toxicity of IAPP. This mechanism may be important to understand the toxicity of other amyloidogenic proteins. Our solid-state NMR results also demonstrate the possibility of using bicelles to measure the affinity of biomolecules for negatively or positively curved regions of the membrane, which we believe will be useful in a variety of biochemical and biophysical investigations related to the cell membrane.
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Affiliation(s)
- Pieter E S Smith
- Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109-1055, USA
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245
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Fluorescence microscopy studies on islet amyloid polypeptide fibrillation at heterogeneous and cellular membrane interfaces and its inhibition by resveratrol. FEBS Lett 2009; 583:1439-45. [DOI: 10.1016/j.febslet.2009.03.059] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2009] [Revised: 03/09/2009] [Accepted: 03/24/2009] [Indexed: 02/01/2023]
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246
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Zraika S, Hull RL, Udayasankar J, Aston-Mourney K, Subramanian SL, Kisilevsky R, Szarek WA, Kahn SE. Oxidative stress is induced by islet amyloid formation and time-dependently mediates amyloid-induced beta cell apoptosis. Diabetologia 2009; 52:626-35. [PMID: 19148619 PMCID: PMC2719780 DOI: 10.1007/s00125-008-1255-x] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2008] [Accepted: 12/12/2008] [Indexed: 01/09/2023]
Abstract
AIMS/HYPOTHESIS Islet amyloid in type 2 diabetes contributes to loss of beta cell mass and function. Since islets are susceptible to oxidative stress-induced toxicity, we sought to determine whether islet amyloid formation is associated with induction of oxidative stress. METHODS Human islet amyloid polypeptide transgenic and non-transgenic mouse islets were cultured for 48 or 144 h with or without the antioxidant N-acetyl-L: -cysteine (NAC) or the amyloid inhibitor Congo Red. Amyloid deposition, reactive oxygen species (ROS) production, beta cell apoptosis, and insulin secretion, content and mRNA were measured. RESULTS After 48 h, amyloid deposition was associated with increased ROS levels and increased beta cell apoptosis, but no change in insulin secretion, content or mRNA levels. Antioxidant treatment prevented the rise in ROS, but did not prevent amyloid formation or beta cell apoptosis. In contrast, inhibition of amyloid formation prevented the induction of oxidative stress and beta cell apoptosis. After 144 h, amyloid deposition was further increased and was associated with increased ROS levels, increased beta cell apoptosis and decreased insulin content. At this time-point, antioxidant treatment and inhibition of amyloid formation were effective in reducing ROS levels, amyloid formation and beta cell apoptosis. Inhibition of amyloid formation also increased insulin content. CONCLUSIONS/INTERPRETATION Islet amyloid formation induces oxidative stress, which in the short term does not mediate beta cell apoptosis, but in the longer term may feed back to further exacerbate amyloid formation and contribute to beta cell apoptosis.
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Affiliation(s)
- S Zraika
- Division of Metabolism, Endocrinology and Nutrition, Department of Medicine, University of Washington and VA Puget Sound Health Care System, 1660 South Columbian Way (151), Seattle, WA 98108, USA.
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Korol’ TY, Korol’ SV, Kostyuk EP, Kostyuk PG. Disruption of Calcium Homeostasis in Alzheimer’s Disease. NEUROPHYSIOLOGY+ 2009. [DOI: 10.1007/s11062-009-9064-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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248
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Exploring the mechanism of beta-amyloid toxicity attenuation by multivalent sialic acid polymers through the use of mathematical models. J Theor Biol 2009; 258:189-97. [PMID: 19217912 DOI: 10.1016/j.jtbi.2009.02.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Revised: 12/11/2008] [Accepted: 02/05/2009] [Indexed: 01/17/2023]
Abstract
beta-Amyloid peptide (A beta), the primary protein component in senile plaques associated with Alzheimer's disease (AD), has been implicated in neurotoxicity associated with AD. Previous studies have shown that the A beta-neuronal membrane interaction plays a role in the mechanism of A beta toxicity. More specifically, it is thought that A beta interacts with ganglioside rich and sialic acid rich regions of cell surfaces. In light of such evidence, we have used a number of different sialic acid compounds of different valency or number of sialic acid moieties per molecule to attenuate A beta toxicity in a cell culture model. In this work, we proposed various mathematical models of A beta interaction with both the cell membrane and with the multivalent sialic acid compounds, designed to act as membrane mimics. These models allow us to explore the mechanism of action of this class of sialic acid membrane mimics in attenuating the toxicity of A beta. The mathematical models, when compared with experimental data, facilitate the discrimination between different modes of action of these materials. Understanding the mechanism of action of A beta toxicity inhibitors should provide insight into the design of the next generation of molecules that could be used to prevent A beta toxicity associated with AD.
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249
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Hartley T, Brumell J, Volchuk A. Emerging roles for the ubiquitin-proteasome system and autophagy in pancreatic beta-cells. Am J Physiol Endocrinol Metab 2009; 296:E1-10. [PMID: 18812463 DOI: 10.1152/ajpendo.90538.2008] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Protein degradation in eukaryotic cells is mediated primarily by the ubiquitin-proteasome system and autophagy. Turnover of protein aggregates and other cytoplasmic components, including organelles, is another function attributed to autophagy. The ubiquitin-proteasome system and autophagy are essential for normal cell function but under certain pathological conditions can be overwhelmed, which can lead to adverse effects in cells. In this review we will focus primarily on the insulin-producing pancreatic beta-cell. Pancreatic beta-cells respond to glucose levels by both producing and secreting insulin. The inability of beta-cells to secrete sufficient insulin is a major contributory factor in the development of type 2 diabetes. The aim of this review is to examine some of the crucial roles of the ubiquitin-proteasome system and autophagy in normal pancreatic beta-cell function and how these pathways may become dysfunctional under pathological conditions associated with metabolic syndromes.
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Affiliation(s)
- Taila Hartley
- Division of Cell and Molecular Biology, Toronto General Research Institute, University Health Network, Toronto, ON, M5G 1L7 Canada
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250
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Udayasankar J, Kodama K, Hull RL, Zraika S, Aston-Mourney K, Subramanian SL, Tong J, Faulenbach MV, Vidal J, Kahn SE. Amyloid formation results in recurrence of hyperglycaemia following transplantation of human IAPP transgenic mouse islets. Diabetologia 2009; 52:145-53. [PMID: 19002432 PMCID: PMC4950742 DOI: 10.1007/s00125-008-1185-7] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Accepted: 09/26/2008] [Indexed: 10/21/2022]
Abstract
AIMS/HYPOTHESIS Islet transplantation is a potential cure for diabetes; however, rates of graft failure remain high. The aim of the present study was to determine whether amyloid deposition is associated with reduced beta cell volume in islet grafts and the recurrence of hyperglycaemia following islet transplantation. METHODS We transplanted a streptozotocin-induced mouse model of diabetes with 100 islets from human IAPP (which encodes islet amyloid polypeptide) transgenic mice that have the propensity to form islet amyloid (n = 8-12) or from non-transgenic mice that do not develop amyloid (n = 6-10) in sets of studies that lasted 1 or 6 weeks. RESULTS Plasma glucose levels before and for 1 week after transplantation were similar in mice that received transgenic or non-transgenic islets, and at that time amyloid was detected in all transgenic grafts and, as expected, in none of the non-transgenic grafts. However, over the 6 weeks following transplantation, plasma glucose levels increased in transgenic but remained stable in non-transgenic islet graft recipients (p < 0.05). At 6 weeks, amyloid was present in 92% of the transgenic grafts and in none of the non-transgenic grafts. Beta cell volume was reduced by 30% (p < 0.05), beta cell apoptosis was twofold higher (p < 0.05), and beta cell replication was reduced by 50% (p < 0.001) in transgenic vs non-transgenic grafts. In summary, amyloid deposition in islet grafts occurs prior to the recurrence of hyperglycaemia and its accumulation over time is associated with beta cell loss. CONCLUSIONS/INTERPRETATION Islet amyloid formation may explain, in part, the non-immune loss of beta cells and recurrence of hyperglycaemia following clinical islet transplantation.
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Affiliation(s)
- J Udayasankar
- VA Puget Sound Health Care System 151, Seattle, WA 98108, USA
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