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Maurer M, Lazaridis T. Transmembrane β-Barrel Models of α-Synuclein Oligomers. J Chem Inf Model 2023; 63:7171-7179. [PMID: 37963823 DOI: 10.1021/acs.jcim.3c00997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2023]
Abstract
The aggregation of α-synuclein is implicated in a number of neurodegenerative diseases, such as Parkinson's and Multiple System Atrophy, but the role of these aggregates in disease development is not clear. One possible mechanism of cytotoxicity is the disturbance or permeabilization of cell membranes by certain types of oligomers. However, no high-resolution structure of such membrane-embedded complexes has ever been determined. Here we construct and evaluate putative transmembrane β-barrels formed by this protein. Examination of the α-synuclein sequence reveals two regions that could form membrane-embedded β-hairpins: 64-92 (the NAC), and 35-56, which harbors many familial Parkinson's mutations. The stability of β-barrels formed by these hairpins is examined first in implicit membrane pores and then by multimicrosecond all-atom simulations. We find that a NAC region barrel remains stably inserted and hydrated for at least 10 μs. A 35-56 barrel remains stably inserted in the membrane but dehydrates and collapses if all His50 are neutral or if His50 is replaced by Q. If half of the His50 are doubly protonated, the barrel takes an oval shape but remains hydrated for at least 10 μs. Possible implications of these findings for α-synuclein pathology are discussed.
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Affiliation(s)
- Manuela Maurer
- Department of Chemistry & Biochemistry, City College of New York/CUNY, 160 Convent Ave, New York, New York 10031, United States
| | - Themis Lazaridis
- Department of Chemistry & Biochemistry, City College of New York/CUNY, 160 Convent Ave, New York, New York 10031, United States
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2
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Battis K, Xiang W, Winkler J. The Bidirectional Interplay of α-Synuclein with Lipids in the Central Nervous System and Its Implications for the Pathogenesis of Parkinson's Disease. Int J Mol Sci 2023; 24:13270. [PMID: 37686080 PMCID: PMC10487772 DOI: 10.3390/ijms241713270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 08/23/2023] [Accepted: 08/24/2023] [Indexed: 09/10/2023] Open
Abstract
The alteration and aggregation of alpha-synuclein (α-syn) play a crucial role in neurodegenerative diseases collectively termed as synucleinopathies, including Parkinson's disease (PD). The bidirectional interaction of α-syn with lipids and biomembranes impacts not only α-syn aggregation but also lipid homeostasis. Indeed, lipid composition and metabolism are severely perturbed in PD. One explanation for lipid-associated alterations may involve structural changes in α-syn, caused, for example, by missense mutations in the lipid-binding region of α-syn as well as post-translational modifications such as phosphorylation, acetylation, nitration, ubiquitination, truncation, glycosylation, and glycation. Notably, different strategies targeting the α-syn-lipid interaction have been identified and are able to reduce α-syn pathology. These approaches include the modulation of post-translational modifications aiming to reduce the aggregation of α-syn and modify its binding properties to lipid membranes. Furthermore, targeting enzymes involved in various steps of lipid metabolism and exploring the neuroprotective potential of lipids themselves have emerged as novel therapeutic approaches. Taken together, this review focuses on the bidirectional crosstalk of α-syn and lipids and how alterations of this interaction affect PD and thereby open a window for therapeutic interventions.
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Affiliation(s)
| | | | - Jürgen Winkler
- Department of Molecular Neurology, University Hospital Erlangen, Friedrich-Alexander-University Erlangen-Nürnberg, 91054 Erlangen, Germany; (K.B.); (W.X.)
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3
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Ramalingam N, Dettmer U. Temperature is a key determinant of alpha- and beta-synuclein membrane interactions in neurons. J Biol Chem 2021; 296:100271. [PMID: 33428933 PMCID: PMC7949061 DOI: 10.1016/j.jbc.2021.100271] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 01/06/2021] [Accepted: 01/07/2021] [Indexed: 02/02/2023] Open
Abstract
Aggregation of α-synuclein (αS) leads to the hallmark neuropathology of Parkinson's disease (PD) and related synucleinopathies. αS has been described to exist in both cytosolic and membrane-associated forms, the relative abundance of which has remained unsettled. To study αS under the most relevant conditions by a quantitative method, we cultured and matured rodent primary cortical neurons for >17 days and determined αS cytosol:membrane distribution via centrifugation-free sequential extractions based on the weak ionic detergent digitonin. We noticed that at lower temperatures (4 °C or room temperature), αS was largely membrane-associated. At 37 °C, however, αS solubility was markedly increased. In contrast, the extraction of control proteins (GAPDH, cytosolic; calnexin, membrane) was not affected by temperature. When we compared the relative distribution of the synuclein homologs αS and β-synuclein (βS) under various conditions that differed in temperature and digitonin concentration (200-1200 μg/ml), we consistently found αS to be more membrane-associated than βS. Both proteins, however, exhibited temperature-dependent membrane binding. Under the most relevant conditions (37 °C and 800 μg/ml digitonin, i.e., the lowest digitonin concentration that extracted cytosolic GAPDH to near completion), cytosolic distribution was 49.8% ± 9.0% for αS and 63.6% ± 6.6% for βS. PD-linked αS A30P was found to be largely cytosolic, confirming previous studies that had used different methods. Our work highlights the dynamic nature of cellular synuclein behavior and has important implications for protein-biochemical and cell-biological studies of αS proteostasis, such as testing the effects of genetic and pharmacological manipulations.
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Affiliation(s)
- Nagendran Ramalingam
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
| | - Ulf Dettmer
- Ann Romney Center for Neurologic Diseases, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
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4
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Yeboah F, Kim TE, Bill A, Dettmer U. Dynamic behaviors of α-synuclein and tau in the cellular context: New mechanistic insights and therapeutic opportunities in neurodegeneration. Neurobiol Dis 2019; 132:104543. [PMID: 31351173 DOI: 10.1016/j.nbd.2019.104543] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Revised: 07/18/2019] [Accepted: 07/22/2019] [Indexed: 10/26/2022] Open
Abstract
α-Synuclein (αS) and tau have a lot in common. Dyshomeostasis and aggregation of both proteins are central in the pathogenesis of neurodegenerative diseases: Parkinson's disease, dementia with Lewy bodies, multi-system atrophy and other 'synucleinopathies' in the case of αS; Alzheimer's disease, frontotemporal dementia, progressive supranuclear palsy and other 'tauopathies' in the case of tau. The aggregated states of αS and tau are found to be (hyper)phosphorylated, but the relevance of the phosphorylation in health or disease is not well understood. Both tau and αS are typically characterized as 'intrinsically disordered' proteins, while both engage in transient interactions with cellular components, thereby undergoing structural changes and context-specific folding. αS transiently binds to (synaptic) vesicles forming a membrane-induced amphipathic helix; tau transiently interacts with microtubules forming an 'extended structure'. The regulation and exact nature of the interactions are not fully understood. Here we review recent and previous insights into the dynamic, transient nature of αS and tau with regard to the mode of interaction with their targets, the dwell-time while bound, and the cis and trans factors underlying the frequent switching between bound and unbound states. These aspects are intimately linked to hypotheses on how subtle changes in the transient behaviors may trigger the earliest steps in the pathogenesis of the respective brain diseases. Based on a deeper understanding of transient αS and tau conformations in the cellular context, new therapeutic strategies may emerge, and it may become clearer why existing approaches have failed or how they could be optimized.
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Affiliation(s)
- Fred Yeboah
- Novartis Institute for Biomedical Research, Chemical Biology and Therapeutics, Cambridge, MA 02139, USA
| | - Tae-Eun Kim
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Anke Bill
- Novartis Institute for Biomedical Research, Chemical Biology and Therapeutics, Cambridge, MA 02139, USA.
| | - Ulf Dettmer
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.
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5
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Dettmer U. Rationally Designed Variants of α-Synuclein Illuminate Its in vivo Structural Properties in Health and Disease. Front Neurosci 2018; 12:623. [PMID: 30319334 PMCID: PMC6167557 DOI: 10.3389/fnins.2018.00623] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Accepted: 08/20/2018] [Indexed: 12/11/2022] Open
Abstract
α-Synuclein (αS) is a conserved and abundant neuronal protein with unusual structural properties. It appears to partition between folded and unstructured states as well as between membrane-bound and aqueously soluble states. In addition, a switch between monomeric and tetrameric/multimeric states has been observed recently. The precise composition, localization and abundance of the multimeric species are under study and remain unsettled. Yet to interfere with disease pathogenesis, we must dissect how small changes in αS homeostasis may give rise to Parkinson’s disease (PD), dementia with Lewy bodies (DLB) and other human synucleinopathies. Rationally designed αS point mutations that prevent the protein from populating all states within its normal folding repertoire have continued to be instrumental in bringing new insights into its biochemistry in vivo. This review summarizes biochemical and cell biological findings about αS homeostasis from different labs, with a special emphasis on intact-cell approaches that may preserve the complex, metastable native states of αS.
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Affiliation(s)
- Ulf Dettmer
- Ann Romney Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States
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6
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Sung Y, Eliezer D. Structure and dynamics of the extended-helix state of alpha-synuclein: Intrinsic lability of the linker region. Protein Sci 2018; 27:1314-1324. [PMID: 29663556 PMCID: PMC6032355 DOI: 10.1002/pro.3426] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Revised: 04/11/2018] [Accepted: 04/12/2018] [Indexed: 12/25/2022]
Abstract
The Parkinson's protein alpha-synuclein binds to synaptic vesicles in vivo and adopts a highly extended helical conformation when binding to lipid vesicles in vitro. High-resolution structural analysis of alpha-synuclein bound to small lipid or detergent micelles revealed two helices connected by a non-helical linker, but corresponding studies of the vesicle-bound extended-helix state are hampered by the size and heterogeneity of the protein-vesicle complex. Here we employ fluorinated alcohols (FAs) to induce a highly helical aggregation-resistant state of alpha-synuclein in solution that resembles the vesicle-bound extended-helix state but is amenable to characterization using high-resolution solution-state NMR. Analysis of chemical shift, NOE, coupling constant, PRE and relaxation measurements shows that the lipid-binding domain of alpha-synuclein in FA solutions indeed adopts a single continuous helix and that the ends of this helix do not come into detectable proximity to each other. The helix is well ordered in the center, but features an increase in fast internal motions suggestive of helix fraying approaching the termini. The central region of the helix exhibits slower time scale motions that likely result from flexing of the highly anisotropic structure. Importantly, weak or missing short- and intermediate-range NOEs in the region corresponding to the non-helical linker of micelle-bound alpha-synuclein indicate that the helical structure in this region of the protein is intrinsically unstable. This suggests that conversion of alpha-synuclein from the extended-helix to the broken-helix state represents a functionally relevant structural transition.
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Affiliation(s)
- Yoon‐Hui Sung
- Department of Biochemistry and Program in Structural BiologyWeill Cornell MedicineNew YorkNew York
| | - David Eliezer
- Department of Biochemistry and Program in Structural BiologyWeill Cornell MedicineNew YorkNew York
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7
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Cheng B, Li Y, Ma L, Wang Z, Petersen RB, Zheng L, Chen Y, Huang K. Interaction between amyloidogenic proteins and biomembranes in protein misfolding diseases: Mechanisms, contributors, and therapy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2018; 1860:1876-1888. [PMID: 29466701 DOI: 10.1016/j.bbamem.2018.02.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Revised: 02/12/2018] [Accepted: 02/13/2018] [Indexed: 12/14/2022]
Abstract
The toxic deposition of misfolded amyloidogenic proteins is associated with more than fifty protein misfolding diseases (PMDs), including Alzheimer's disease, Parkinson's disease and type 2 diabetes mellitus. Protein deposition is a multi-step process modulated by a variety of factors, in particular by membrane-protein interaction. The interaction results in permeabilization of biomembranes contributing to the cytotoxicity that leads to PMDs. Different biological and physiochemical factors, such as protein sequence, lipid composition, and chaperones, are known to affect the membrane-protein interaction. Here, we provide a comprehensive review of the mechanisms and contributing factors of the interaction between biomembranes and amyloidogenic proteins, and a summary of the therapeutic approaches to PMDs that target this interaction. 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)
- Biao Cheng
- Department of Pharmacy, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430023, China; Key Laboratory for Molecular Diagnosis of Hubei Province, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430023, China
| | - Yang Li
- Tongji School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Liang Ma
- Tongji School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Zhuoyi Wang
- Tongji School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Robert B Petersen
- Foundational Sciences, Central Michigan University College of Medicine, Mt. Pleasant, MI 48858, USA
| | - Ling Zheng
- Hubei Key Laboratory of Cell Homeostasis, College of Life Sciences, Wuhan 430072, China
| | - Yuchen Chen
- Tongji School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China
| | - Kun Huang
- Tongji School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
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8
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Uchihara T, Giasson BI. Propagation of alpha-synuclein pathology: hypotheses, discoveries, and yet unresolved questions from experimental and human brain studies. Acta Neuropathol 2016; 131:49-73. [PMID: 26446103 PMCID: PMC4698305 DOI: 10.1007/s00401-015-1485-1] [Citation(s) in RCA: 143] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 09/15/2015] [Accepted: 09/26/2015] [Indexed: 12/15/2022]
Abstract
Progressive aggregation of alpha-synuclein (αS) through formation of amorphous pale bodies to mature Lewy bodies or in neuronal processes as Lewy neurites may be the consequence of conformational protein changes and accumulations, which structurally represents "molecular template". Focal initiation and subsequent spread along anatomically connected structures embody "structural template". To investigate the hypothesis that both processes might be closely associated and involved in the progression of αS pathology, which can be observed in human brains, αS amyloidogenic precursors termed "seeds" were experimentally injected into the brain or peripheral nervous system of animals. Although these studies showed that αS amyloidogenic seeds can induce αS pathology, which can spread in the nervous system, the findings are still not unequivocal in demonstrating predominant transsynaptic or intraneuronal spreads either in anterograde or retrograde directions. Interpretation of some of these studies is further complicated by other concurrent aberrant processes including neuroimmune activation, injury responses and/or general perturbation of proteostasis. In human brain, αS deposition and neuronal degeneration are accentuated in distal axon/synapse. Hyperbranching of axons is an anatomical commonality of Lewy-prone systems, providing a structural basis for abundance in distal axons and synaptic terminals. This neuroanatomical feature also can contribute to such distal accentuation of vulnerability in neuronal demise and the formation of αS inclusion pathology. Although retrograde progression of αS aggregation in hyperbranching axons may be a consistent feature of Lewy pathology, the regional distribution and gradient of Lewy pathology are not necessarily compatible with a predictable pattern such as upward progression from lower brainstem to cerebral cortex. Furthermore, "focal Lewy body disease" with the specific isolated involvement of autonomic, olfactory or cardiac systems suggests that spread of αS pathology is not always consistent. In many instances, the regional variability of Lewy pathology in human brain cannot be explained by a unified hypothesis such as transsynaptic spread. Thus, the distribution of Lewy pathology in human brain may be better explained by variable combinations of independent focal Lewy pathology to generate "multifocal Lewy body disease" that could be coupled with selective but variable neuroanatomical spread of αS pathology. More flexible models are warranted to take into account the relative propensity to develop Lewy pathology in different Lewy-prone systems, even without interconnections, compatible with the expanding clinicopathological spectra of Lewy-related disorders. These revised models are useful to better understand the mechanisms underlying the variable progression of Lewy body diseases so that diagnostic and therapeutic strategies are improved.
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Affiliation(s)
- Toshiki Uchihara
- Laboratory of Structural Neuropathology, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo, 156-8506, Japan.
| | - Benoit I Giasson
- Department of Neuroscience, Center for Translational Research in Neurodegenerative Disease, McKinght Brain Institute, University of Florida, 1275 Center Drive, PO Box 100159, Gainesville, FL, 32610-0159, USA.
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9
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Menezes R, Tenreiro S, Macedo D, Santos CN, Outeiro TF. From the baker to the bedside: yeast models of Parkinson's disease. MICROBIAL CELL 2015; 2:262-279. [PMID: 28357302 PMCID: PMC5349099 DOI: 10.15698/mic2015.08.219] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The baker’s yeast Saccharomyces cerevisiae has been extensively explored for our understanding of fundamental cell biology processes highly conserved in the eukaryotic kingdom. In this context, they have proven invaluable in the study of complex mechanisms such as those involved in a variety of human disorders. Here, we first provide a brief historical perspective on the emergence of yeast as an experimental model and on how the field evolved to exploit the potential of the model for tackling the intricacies of various human diseases. In particular, we focus on existing yeast models of the molecular underpinnings of Parkinson’s disease (PD), focusing primarily on the central role of protein quality control systems. Finally, we compile and discuss the major discoveries derived from these studies, highlighting their far-reaching impact on the elucidation of PD-associated mechanisms as well as in the identification of candidate therapeutic targets and compounds with therapeutic potential.
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Affiliation(s)
- Regina Menezes
- Instituto de Biologia Experimental e Tecnológica, Apartado 12, Oeiras 2781-901, Portugal. ; Instituto de Tecnologia Química e Biológica António Xavier, Av. da República, 2780-157 Oeiras, Universidade Nova de Lisboa, Portugal
| | - Sandra Tenreiro
- Instituto de Medicina Molecular, Av. Prof. Egas Moniz, Lisboa 1649-028, Portugal. ; CEDOC - Chronic Diseases Research Center, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Campo dos Mártires da Pátria, 130, Lisboa 1169-056, Portugal
| | - Diana Macedo
- Instituto de Tecnologia Química e Biológica António Xavier, Av. da República, 2780-157 Oeiras, Universidade Nova de Lisboa, Portugal
| | - Cláudia N Santos
- Instituto de Biologia Experimental e Tecnológica, Apartado 12, Oeiras 2781-901, Portugal. ; Instituto de Tecnologia Química e Biológica António Xavier, Av. da República, 2780-157 Oeiras, Universidade Nova de Lisboa, Portugal
| | - Tiago F Outeiro
- Instituto de Fisiologia, Faculdade de Medicina da Universidade de Lisboa, Lisboa 1649-028, Portugal. ; CEDOC - Chronic Diseases Research Center, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Campo dos Mártires da Pátria, 130, Lisboa 1169-056, Portugal. ; Department of NeuroDegeneration and Restorative Research, University Medical Center Göttingen, Waldweg 33, Göttingen 37073, Germany
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10
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Mechanisms of alpha-synuclein action on neurotransmission: cell-autonomous and non-cell autonomous role. Biomolecules 2015; 5:865-92. [PMID: 25985082 PMCID: PMC4496700 DOI: 10.3390/biom5020865] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2015] [Revised: 04/24/2015] [Accepted: 04/29/2015] [Indexed: 11/23/2022] Open
Abstract
Mutations and duplication/triplication of the alpha-synuclein (αSyn)-coding gene have been found to cause familial Parkinson’s disease (PD), while genetic polymorphisms in the region controlling the expression level and stability of αSyn have been identified as risk factors for idiopathic PD, pointing to the importance of wild-type (wt) αSyn dosage in the disease. Evidence that αSyn is present in the cerebrospinal fluid and interstitial brain tissue and that healthy neuronal grafts transplanted into PD patients often degenerate suggests that extracellularly-released αSyn plays a role in triggering the neurodegenerative process. αSyn’s role in neurotransmission has been shown in various cell culture models in which the protein was upregulated or deleted and in knock out and transgenic animal, with different results on αSyn’s effect on synaptic vesicle pool size and mobilization, αSyn being proposed as a negative or positive regulator of neurotransmitter release. In this review, we discuss the effect of αSyn on pre- and post-synaptic compartments in terms of synaptic vesicle trafficking, calcium entry and channel activity, and we focus on the process of exocytosis and internalization of αSyn and on the spreading of αSyn-driven effects due to the presence of the protein in the extracellular milieu.
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11
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Mbefo MK, Fares MB, Paleologou K, Oueslati A, Yin G, Tenreiro S, Pinto M, Outeiro T, Zweckstetter M, Masliah E, Lashuel HA. Parkinson disease mutant E46K enhances α-synuclein phosphorylation in mammalian cell lines, in yeast, and in vivo. J Biol Chem 2015; 290:9412-27. [PMID: 25657004 DOI: 10.1074/jbc.m114.610774] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Indexed: 12/21/2022] Open
Abstract
Although α-synuclein (α-syn) phosphorylation has been considered as a hallmark of sporadic and familial Parkinson disease (PD), little is known about the effect of PD-linked mutations on α-syn phosphorylation. In this study, we investigated the effects of the A30P, E46K, and A53T PD-linked mutations on α-syn phosphorylation at residues Ser-87 and Ser-129. Although the A30P and A53T mutants slightly affected Ser(P)-129 levels compared with WT α-syn, the E46K mutation significantly enhanced Ser-129 phosphorylation in yeast and mammalian cell lines. This effect was not due to the E46K mutant being a better kinase substrate nor due to alterations in endogenous kinase levels, but was mostly linked with enhanced nuclear and endoplasmic reticulum accumulation. Importantly, lentivirus-mediated overexpression in mice also showed enhanced Ser-129 phosphorylation of the E46K mutant compared to WT α-syn, thus providing in vivo validation of our findings. Altogether, our findings suggest that the different PD-linked mutations may contribute to PD pathogenesis via different mechanisms.
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Affiliation(s)
- Martial Kamdem Mbefo
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute, Ecole Polytechnique Federale de Lausanne, Station 15, 1015 Lausanne, Switzerland
| | - Mohamed-Bilal Fares
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute, Ecole Polytechnique Federale de Lausanne, Station 15, 1015 Lausanne, Switzerland
| | - Katerina Paleologou
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute, Ecole Polytechnique Federale de Lausanne, Station 15, 1015 Lausanne, Switzerland
| | - Abid Oueslati
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute, Ecole Polytechnique Federale de Lausanne, Station 15, 1015 Lausanne, Switzerland
| | - Guowei Yin
- the Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany
| | - Sandra Tenreiro
- the Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, and
| | - Madalena Pinto
- the Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, and
| | - Tiago Outeiro
- the Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, and Instituto de Fisiologia, Faculdade de Medicina, Universidade de Lisboa, Av. Prof. Egas Moniz 1649-028 Lisboa, Portugal, the Department of NeuroDegeneration and Restorative Research, University Medical Center Goettingen and
| | - Markus Zweckstetter
- the Department of NMR-based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany, the German Center for Neurodegenerative Diseases, Am Fassberg 11, 37077 Göttingen, Germany, and
| | - Eliezer Masliah
- the Departments of Pathology and Neurosciences, School of Medicine, University of California at San Diego, San Diego, California 92103
| | - Hilal A Lashuel
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute, Ecole Polytechnique Federale de Lausanne, Station 15, 1015 Lausanne, Switzerland,
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12
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Khalaf O, Fauvet B, Oueslati A, Dikiy I, Mahul-Mellier AL, Ruggeri FS, Mbefo MK, Vercruysse F, Dietler G, Lee SJ, Eliezer D, Lashuel HA. The H50Q mutation enhances α-synuclein aggregation, secretion, and toxicity. J Biol Chem 2014; 289:21856-76. [PMID: 24936070 DOI: 10.1074/jbc.m114.553297] [Citation(s) in RCA: 132] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Over the last two decades, the identification of missense mutations in the α-synuclein (α-Syn) gene SNCA in families with inherited Parkinson disease (PD) has reinforced the central role of α-Syn in PD pathogenesis. Recently, a new missense mutation (H50Q) in α-Syn was described in patients with a familial form of PD and dementia. Here we investigated the effects of this novel mutation on the biophysical properties of α-Syn and the consequences for its cellular function. We found that the H50Q mutation affected neither the structure of free or membrane-bound α-Syn monomer, its interaction with metals, nor its capacity to be phosphorylated in vitro. However, compared with the wild-type (WT) protein, the H50Q mutation accelerated α-Syn fibrillization in vitro. In cell-based models, H50Q mutation did not affect α-Syn subcellular localization or its ability to be phosphorylated by PLK2 and GRK6. Interestingly, H50Q increased α-Syn secretion from SHSY5Y cells into culture medium and induced more mitochondrial fragmentation in hippocampal neurons. Although the transient overexpression of WT or H50Q did not induce toxicity, both species induced significant cell death when added to the culture medium of hippocampal neurons. Strikingly, H50Q exhibited more toxicity, suggesting that the H50Q-related enhancement of α-Syn aggregation and secretion may play a role in the extracellular toxicity of this mutant. Together, our results provide novel insight into the mechanism by which this newly described PD-associated mutation may contribute to the pathogenesis of PD and related disorders.
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Affiliation(s)
- Ossama Khalaf
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute and
| | - Bruno Fauvet
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute and
| | - Abid Oueslati
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute and
| | - Igor Dikiy
- Department of Biochemistry, Program in Structural Biology, Weill Cornell Medical College, New York, New York 10065, and
| | - Anne-Laure Mahul-Mellier
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute and
| | - Francesco Simone Ruggeri
- Laboratory of Physics of Living Matter, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Martial K Mbefo
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute and
| | - Filip Vercruysse
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute and
| | - Giovanni Dietler
- Laboratory of Physics of Living Matter, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Seung-Jae Lee
- Department of Biomedical Science and Technology, Konkuk University, Seoul 143-701, South Korea
| | - David Eliezer
- Department of Biochemistry, Program in Structural Biology, Weill Cornell Medical College, New York, New York 10065, and
| | - Hilal A Lashuel
- From the Laboratory of Molecular and Chemical Biology of Neurodegeneration, Brain Mind Institute and
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13
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Jain N, Bhasne K, Hemaswasthi M, Mukhopadhyay S. Structural and dynamical insights into the membrane-bound α-synuclein. PLoS One 2013; 8:e83752. [PMID: 24376740 PMCID: PMC3869795 DOI: 10.1371/journal.pone.0083752] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 11/07/2013] [Indexed: 12/31/2022] Open
Abstract
Membrane-induced disorder-to-helix transition of α-synuclein, a presynaptic protein, has been implicated in a number of important neuronal functions as well as in the etiology of Parkinson’s disease. In order to obtain structural insights of membrane-bound α-synuclein at the residue-specific resolution, we took advantage of the fact that the protein is devoid of tryptophan and incorporated single tryptophan at various residue positions along the sequence. These tryptophans were used as site-specific markers to characterize the structural and dynamical aspects of α-synuclein on the negatively charged small unilamellar lipid vesicles. An array of site-specific fluorescence readouts, such as the spectral-shift, quenching efficiency and anisotropy, allowed us to discern various features of the conformational rearrangements occurring at different locations of α-synuclein on the lipid membrane. In order to define the spatial localization of various regions of the protein near the membrane surface, we utilized a unique and sensitive indicator, namely, red-edge excitation shift (REES), which originates when a fluorophore is located in a highly ordered micro-environment. The extent of REES observed at different residue positions allowed us to directly identify the residues that are localized at the membrane-water interface comprising a thin (∼ 15 Å) layer of motionally restrained water molecules and enabled us to construct a dynamic hydration map of the protein. The combination of site-specific fluorescence readouts allowed us to unravel the intriguing molecular details of α-synuclein on the lipid membrane in a direct model-free fashion. Additionally, the combination of methodologies described here are capable of distinguishing subtle but important structural alterations of α-synuclein bound to different negatively charged lipids with varied head-group chemistry. We believe that the structural modulations of α-synuclein on the membrane could potentially be related to its physiological functions as well as to the onset of Parkinson’s diseases.
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Affiliation(s)
- Neha Jain
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER), Mohali, India
| | - Karishma Bhasne
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER), Mohali, India
| | - M. Hemaswasthi
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER), Mohali, India
| | - Samrat Mukhopadhyay
- Department of Biological Sciences, Indian Institute of Science Education and Research (IISER), Mohali, India
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER), Mohali, India
- * E-mail:
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14
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Wietek J, Haralampiev I, Amoussouvi A, Herrmann A, Stöckl M. Membrane bound α-synuclein is fully embedded in the lipid bilayer while segments with higher flexibility remain. FEBS Lett 2013; 587:2572-7. [PMID: 23831067 DOI: 10.1016/j.febslet.2013.06.034] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 05/28/2013] [Accepted: 06/25/2013] [Indexed: 12/15/2022]
Abstract
Cellular pathways involving α-synuclein (αS) seem to be causative for development of Parkinson's disease. Interactions between αS and lipid membranes appear to be important for the physiological function of the protein and influence the pathological aggregation of αS leading to the formation of amyloid plaques. Upon membrane binding the unstructured αS folds into amphipathic helices. In our work we characterized the penetration depth and probed the local environment of Trp-residues introduced along the αS sequence. We could show that while the entire helix is well embedded in the lipid bilayer, segments with a shallower penetration and supposable higher flexibility exist.
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Affiliation(s)
- Jonas Wietek
- Department of Biology, Faculty of Mathematics and Natural Sciences I, Humboldt University Berlin, Invalidenstr. 42, 10115 Berlin, Germany
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15
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Petroi D, Popova B, Taheri-Talesh N, Irniger S, Shahpasandzadeh H, Zweckstetter M, Outeiro TF, Braus GH. Aggregate clearance of α-synuclein in Saccharomyces cerevisiae depends more on autophagosome and vacuole function than on the proteasome. J Biol Chem 2012; 287:27567-79. [PMID: 22722939 DOI: 10.1074/jbc.m112.361865] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Parkinson disease is the second most common neurodegenerative disease. The molecular hallmark is the accumulation of proteinaceous inclusions termed Lewy bodies containing misfolded and aggregated α-synuclein. The molecular mechanism of clearance of α-synuclein aggregates was addressed using the bakers' yeast Saccharomyces cerevisiae as the model. Overexpression of wild type α-synuclein or the genetic variant A53T integrated into one genomic locus resulted in a gene copy-dependent manner in cytoplasmic proteinaceous inclusions reminiscent of the pathogenesis of the disease. In contrast, overexpression of the genetic variant A30P resulted only in transient aggregation, whereas the designer mutant A30P/A36P/A76P neither caused aggregation nor impaired yeast growth. The α-synuclein accumulation can be cleared after promoter shut-off by a combination of autophagy and vacuolar protein degradation. Whereas the proteasomal inhibitor MG-132 did not significantly inhibit aggregate clearance, treatment with phenylmethylsulfonyl fluoride, an inhibitor of vacuolar proteases, resulted in significant reduction in clearance. Consistently, a cim3-1 yeast mutant restricted in the 19 S proteasome regulatory subunit was unaffected in clearance, whereas an Δatg1 yeast mutant deficient in autophagy showed a delayed aggregate clearance response. A cim3-1Δatg1 double mutant was still able to clear aggregates, suggesting additional cellular mechanisms for α-synuclein clearance. Our data provide insight into the mechanisms yeast cells use for clearing different species of α-synuclein and demonstrate a higher contribution of the autophagy/vacuole than the proteasome system. This contributes to the understanding of how cells can cope with toxic and/or aggregated proteins and may ultimately enable the development of novel strategies for therapeutic intervention.
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Affiliation(s)
- Doris Petroi
- Department of Molecular Microbiology and Genetics, Institute of Microbiology and Genetics, Georg-August-Universität Göttingen, Göttingen, Germany
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16
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Bellucci A, Zaltieri M, Navarria L, Grigoletto J, Missale C, Spano P. From α-synuclein to synaptic dysfunctions: new insights into the pathophysiology of Parkinson's disease. Brain Res 2012; 1476:183-202. [PMID: 22560500 DOI: 10.1016/j.brainres.2012.04.014] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2012] [Revised: 03/30/2012] [Accepted: 04/09/2012] [Indexed: 10/28/2022]
Abstract
Alpha-synuclein is a natively unfolded protein playing a key role in the regulation of several neuronal synaptic functions in physiological and pathological conditions. Many studies, over the past years, have shown that it is actively involved in PD pathophysiology. Alpha-synuclein is integrated in a complex network of neuronal processes through the interaction with cytosolic and synaptic proteins. Hence, it is not the sole α-synuclein pathology but its effects on diverse protein partners and specific cellular pathways in the membrane and/or cytosolic districts such as endoplasmic reticulum/Golgi, axonal and synaptic compartments of dopaminergic neurons, that may cause the onset of neuronal cell dysfunction and degeneration which are among the key pathological features of the PD brain. Here we summarize a series of experimental data supporting that α-synuclein aggregation may induce dysfunction and degeneration of synapses via these multiple mechanisms. Taken together, these data add new insights into the complex mechanisms underlying synaptic derangement in PD and other α-synucleinopathies. This article is part of a Special Issue entitled: Brain Integration.
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Affiliation(s)
- Arianna Bellucci
- Division of Pharmacology, Department of Biomedical Sciences and Biotechnologies and National Institute of Neuroscience, University of Brescia, Brescia, Italy.
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17
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Abstract
AbstractGenetic, neuropathological and biochemical evidence implicates α-synuclein, a 140 amino acid presynaptic neuronal protein, in the pathogenesis of Parkinson’s disease and other neurodegenerative disorders. The aggregated protein inclusions mainly containing aberrant α-synuclein are widely accepted as morphological hallmarks of α-synucleinopathies, but their composition and location vary between disorders along with neuronal networks affected. α-Synuclein exists physiologically in both soluble and membran-bound states, in unstructured and α-helical conformations, respectively, while posttranslational modifications due to proteostatic deficits are involved in β-pleated aggregation resulting in formation of typical inclusions. The physiological function of α-synuclein and its role linked to neurodegeneration, however, are incompletely understood. Soluble oligomeric, not fully fibrillar α-synuclein is thought to be neurotoxic, main targets might be the synapse, axons and glia. The effects of aberrant α-synuclein include alterations of calcium homeostasis, mitochondrial dysfunction, oxidative and nitric injuries, cytoskeletal effects, and neuroinflammation. Proteasomal dysfunction might be a common mechanism in the pathogenesis of neuronal degeneration in α-synucleinopathies. However, how α-synuclein induces neurodegeneration remains elusive as its physiological function. Genome wide association studies demonstrated the important role for genetic variants of the SNCA gene encoding α-synuclein in the etiology of Parkinson’s disease, possibly through effects on oxidation, mitochondria, autophagy, and lysosomal function. The neuropathology of synucleinopathies and the role of α-synuclein as a potential biomarker are briefly summarized. Although animal models provided new insights into the pathogenesis of Parkinson disease and multiple system atrophy, most of them do not adequately reproduce the cardinal features of these disorders. Emerging evidence, in addition to synergistic interactions of α-synuclein with various pathogenic proteins, suggests that prionlike induction and seeding of α-synuclein could lead to the spread of the pathology and disease progression. Intervention in the early aggregation pathway, aberrant cellular effects, or secretion of α-synuclein might be targets for neuroprotection and disease-modifying therapy.
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18
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Bellucci A, Navarria L, Zaltieri M, Missale C, Spano P. α-Synuclein synaptic pathology and its implications in the development of novel therapeutic approaches to cure Parkinson's disease. Brain Res 2011; 1432:95-113. [PMID: 22153624 DOI: 10.1016/j.brainres.2011.11.031] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2011] [Revised: 11/11/2011] [Accepted: 11/11/2011] [Indexed: 12/24/2022]
Abstract
Parkinson's disease (PD) is characterized by a progressive loss of dopamine (DA) neurons of the nigrostriatal system and by the presence of Lewy bodies (LB), proteinaceous inclusions mainly composed of filamentous α-synuclein aggregates. Alpha-synuclein is a natively unfolded protein which plays a central role in the control of dopaminergic neuronal functions and which is thought to be critically implicated in PD pathophysiology. Indeed, besides the fact that α-synuclein is the main protein component of LB, genetic studies showed that mutations and multiplications of the α-synuclein gene are responsible for the onset of familial forms of PD. A large body of evidence indicates that α-synuclein pathology at dopaminergic synapses may underlie the onset of neuronal cell dysfunction and degeneration in the PD brain. Thus, since the available therapeutic approaches to cure this disease are still limited, we hypothesized that the analysis of the α-synuclein synaptic proteome/lipidome may represent a tool to identify novel potential therapeutic targets to cure this disorder. We thus performed a critical review of studies describing α-synuclein pathophysiology at synaptic sites in experimental models of PD and in this paper we outline the most relevant findings regarding the specific modulatory effects exerted by α-synuclein in the control of synaptic functions in physiological and pathological conditions. The conclusions of these studies allow to single out novel potential therapeutic targets among the α-synuclein synaptic partners. These targets may be considered for the development of new pharmacological and gene-based strategies to cure PD.
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Affiliation(s)
- Arianna Bellucci
- Division of Pharmacology, Department of Biomedical Sciences and Biotechnology and National Institute of Neuroscience - Italy, School of Medicine, University of Brescia, Brescia, Italy.
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19
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Transmission of prion strains in a transgenic mouse model overexpressing human A53T mutated α-synuclein. J Neuropathol Exp Neurol 2011; 70:377-85. [PMID: 21487306 DOI: 10.1097/nen.0b013e318217d95f] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
There is a growing interest in the potential roles of misfolded protein interactions in neurodegeneration. To investigate this issue, we inoculated 3 prion strains intracerebrally into transgenic (TgM83) mice that overexpress human A53T α-synuclein. In comparison to nontransgenic controls, there was a striking decrease in the incubation periods of scrapie, classic and H-type bovine spongiform encephalopathies(C-BSE and H-BSE), with conservation of the histopathologic and biochemical features characterizing these 3 prion strains. TgM83 mice died of scrapie or C-BSE prion diseases before accumulating the insoluble and phosphorylated forms of α-synuclein specific to late stages of synucleinopathy. In contrast, the median incubation time for TgM83 mice inoculated with H-BSE was comparable to that observed when these mice were uninfected, thereby allowing the development of molecular alterations of α-synuclein. The last 4 mice of this cohort exhibited early accumulations of H-BSE prion protein along with α-synuclein pathology. The results indicate that a prion disease was triggered concomitantly with an overt synucleinopathy in some transgenic mice overexpressing human A53T α-synuclein after intracerebral inoculation with an H-BSE prion strain.
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20
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Soper JH, Kehm V, Burd CG, Bankaitis VA, Lee VMY. Aggregation of α-synuclein in S. cerevisiae is associated with defects in endosomal trafficking and phospholipid biosynthesis. J Mol Neurosci 2010; 43:391-405. [PMID: 20890676 DOI: 10.1007/s12031-010-9455-5] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Accepted: 09/17/2010] [Indexed: 01/08/2023]
Abstract
Parkinson's disease is the most common neurodegenerative movement disorder. α-Synuclein is a small synaptic protein that has been linked to familial Parkinson's disease (PD) and is also the primary component of Lewy bodies, the hallmark neuropathology found in the brain of sporadic and familial PD patients. The function of α-synuclein is currently unknown, although it has been implicated in the regulation of synaptic vesicle localization or fusion. Recently, overexpression of α-synuclein was shown to cause cytoplasmic vesicle accumulation in a yeast model of α-synuclein toxicity, but the exact role α-synuclein played in mediating this vesicle aggregation is unclear. Here, we show that α-synuclein induces aggregation of many yeast Rab GTPase proteins, that α-synuclein aggregation is enhanced in yeast mutants that produce high levels of acidic phospholipids, and that α-synuclein colocalizes with yeast membranes that are enriched for phosphatidic acid. Significantly, we demonstrate that α-synuclein expression induces vulnerability to perturbations of Ypt6 and other proteins involved in retrograde endosome-Golgi transport, linking a specific trafficking defect to α-synuclein phospholipid binding. These data suggest new pathogenic mechanisms for α-synuclein neurotoxicity.
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Affiliation(s)
- James H Soper
- Center for Neurodegenerative Disease Research, Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA.
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21
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Fortin DL, Nemani VM, Nakamura K, Edwards RH. The behavior of alpha-synuclein in neurons. Mov Disord 2010; 25 Suppl 1:S21-6. [PMID: 20187244 DOI: 10.1002/mds.22722] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Despite considerable evidence linking alpha-synuclein with membranes in vitro, it has proven difficult to demonstrate membrane association of the protein in vivo. alpha-Synuclein localizes to the nerve terminal, but biochemical experiments have not revealed a tight association with membranes. To address the dynamics of the protein in live cells, we have used photobleaching and found that alpha-synuclein exhibits high mobility, although distinctly less than an entirely soluble protein. Further, neural activity controls the distribution of alpha-synuclein, causing its dispersion from the synapse. In addition to the presumed role of alpha-synuclein dynamics in synaptic function, changes in its physiological behavior may underlie the pathological changes associated with Parkinson's disease.
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Affiliation(s)
- Doris L Fortin
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California, USA
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22
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Vernon AC, Ballard C, Modo M. Neuroimaging for Lewy body disease: is the in vivo molecular imaging of α-synuclein neuropathology required and feasible? ACTA ACUST UNITED AC 2010; 65:28-55. [PMID: 20685363 DOI: 10.1016/j.brainresrev.2010.05.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Revised: 05/26/2010] [Accepted: 05/26/2010] [Indexed: 12/21/2022]
Abstract
Alpha-synuclein aggregation is a neuropathological hallmark of many neurodegenerative diseases including Parkinson's disease (PD), Parkinson's disease with dementia (PDD) and dementia with Lewy bodies (DLB), collectively termed the α-synucleinopathies. Substantial advances in clinical criteria and neuroimaging technology over the last 20 years have allowed great strides in the detection and differential diagnosis of these disorders. Nevertheless, it is clear that whilst the array of different imaging modalities in clinical use allow for a robust diagnosis of α-synucleinopathy in comparison to healthy subjects, there is no clear diagnostic imaging marker that affords a reliable differential diagnosis between the different forms of Lewy body disease (LBD) or that could facilitate tracking of disease progression. This has led to a call for a biomarker based on the pathological hallmarks of these diseases, namely α-synuclein-positive Lewy bodies (LBs). This potentially may be advantageous in terms of early disease detection, but may also be leveraged into a potential marker of disease progression. We here aim to firstly review the current status of neuroimaging biomarkers in PD and related synucleinopathies. Secondly, we outline the rationale behind α-synuclein imaging as a potential novel biomarker as well as the potential benefits and limitations of this approach. Thirdly, we attempt to illustrate the likely technical hurdles to be overcome to permit successful in vivo imaging of α-synuclein pathology in the diseased brain. Our overriding aim is to provide a framework for discussion of how to address this major unmet clinical need.
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Affiliation(s)
- Anthony C Vernon
- Kings College London, Institute of Psychiatry, Department of Neuroscience, Denmark Hill campus, London, UK
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23
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Jang A, Lee HJ, Suk JE, Jung JW, Kim KP, Lee SJ. Non-classical exocytosis of alpha-synuclein is sensitive to folding states and promoted under stress conditions. J Neurochem 2010; 113:1263-74. [PMID: 20345754 DOI: 10.1111/j.1471-4159.2010.06695.x] [Citation(s) in RCA: 161] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Parkinson's disease is characterized by deposition of misfolded/aggregated alpha-synuclein proteins in multiple regions of the brain. Neurons can release alpha-synuclein; through this release, pathological forms of alpha-synuclein are propagated between neurons, and also cause neuroinflammation. In this study, we demonstrate that release of alpha-synuclein is consistently increased under various protein misfolding stress conditions in both neuroblastoma and primary neuron models. This release is mediated by a non-classical, endoplasmic reticulum (ER)/Golgi-independent exocytosis, and stress-induced release coincides with increased translocation of alpha-synuclein into vesicles. Both vesicle translocation and secretion were blocked by attachment of a highly stable, globular protein to alpha-synuclein, whereas forced protein misfolding resulted in an increase in both of these activities. Mass spectrometry analysis showed a higher degree of oxidative modification in secreted alpha-synuclein than in the cellular protein. Together, these results suggest that structurally abnormal, damaged alpha-synuclein proteins translocate preferentially into vesicles and are released from neuronal cells via exocytosis.
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Affiliation(s)
- Ara Jang
- Department of Anatomy, School of Medicine, Konkuk University, Seoul, Korea
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24
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Sen S, West AB. The therapeutic potential of LRRK2 and alpha-synuclein in Parkinson's disease. Antioxid Redox Signal 2009; 11:2167-87. [PMID: 19271991 PMCID: PMC2787962 DOI: 10.1089/ars.2009.2430] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Current treatments for Parkinson's disease fail to modify disease progression, and the underlying pathogenic mechanisms remain elusive. The identification of specific targets responsible for disease will aid in the development of relevant model systems and the discovery of neuroprotective and neurorestorative therapies. Two promising protein candidates, alpha-synuclein and LRRK2, offer unique insight into the molecular basis of disease and the potential to intervene in pathogenesis. Although multiple lines of evidence support alpha-synuclein and LRRK2 as robust targets for therapy, the connection between protein function and neurodegeneration is unclear. Technology capable of mitigating alpha-synuclein and LRRK2 disease-associated function will ultimately be required before the true value of these proteins as therapeutic targets can be discerned.
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Affiliation(s)
- Saurabh Sen
- Center for Neurodegeneration and Experimental Therapeutics, Department of Neurology, University of Alabama School of Medicine, Birmingham, Alabama 35294, USA
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25
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Kjaer L, Giehm L, Heimburg T, Otzen D. The influence of vesicle size and composition on alpha-synuclein structure and stability. Biophys J 2009; 96:2857-70. [PMID: 19348768 DOI: 10.1016/j.bpj.2008.12.3940] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Revised: 12/30/2008] [Accepted: 12/30/2008] [Indexed: 12/22/2022] Open
Abstract
Monomeric alpha-synuclein (alphaSN), which has no persistent structure in aqueous solution, is known to bind to anionic lipids with a resulting increase in alpha-helix structure. Here we show that at physiological pH and ionic strength, alphaSN incubated with different anionic lipid vesicles undergoes a marked increase in alpha-helical content at a temperature dictated either by the temperature of the lipid phase transition, or (in 1,2-DilauroylSN-Glycero-3-[Phospho-rac-(1-glycerol)] (DLPG), which is fluid down to 0 degrees C) by an intrinsic cold denaturation that occurs around 10-20 degrees C. This structure is subsequently lost in a thermal transition around 60 degrees C. Remarkably, this phenomenon is only observed for vesicles >100 nm in diameter and is sensitive to lipid chain length, longer chain lengths, and larger vesicles giving more cooperative unfolding transitions and a greater degree of structure. For both vesicle size and chain length, a higher degree of compressibility or permeability in the lipid thermal transition region is associated with a higher degree of alphaSN folding. Furthermore, the degree of structural change is strongly reduced by an increase in ionic strength or a decrease in the amount of anionic lipid. A simple binding-and-folding model that includes the lipid phase transition, exclusive binding of alphaSN to the liquid disordered phase, the thermodynamics of unfolding, and the electrostatics of binding of alphaSN to lipids is able to reproduce the two thermal transitions as well as the effect of ionic strength and anionic lipid. Thus the nature of alphaSN's binding to phospholipid membranes is intimately tied to the lipids' physico-chemical properties.
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Affiliation(s)
- Lars Kjaer
- Department of Life Sciences, Aalborg University, Aalborg, Denmark
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26
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Vamvaca K, Volles MJ, Lansbury PT. The first N-terminal amino acids of alpha-synuclein are essential for alpha-helical structure formation in vitro and membrane binding in yeast. J Mol Biol 2009; 389:413-24. [PMID: 19285989 DOI: 10.1016/j.jmb.2009.03.021] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2008] [Revised: 02/25/2009] [Accepted: 03/09/2009] [Indexed: 12/31/2022]
Abstract
Alpha-synuclein (alpha-syn), a protein implicated in Parkinson's disease, is structurally diverse. In addition to its random-coil state, alpha-syn can adopt an alpha-helical structure upon lipid membrane binding or a beta-sheet structure upon aggregation. We used yeast biology and in vitro biochemistry to detect how sequence changes alter the structural propensity of alpha-syn. The N-terminus of the protein, which adopts an alpha-helical conformation upon lipid binding, is essential for membrane binding in yeast, and variants that are more prone to forming an alpha-helical structure in vitro are generally more toxic to yeast. beta-Sheet structure and inclusion formation, on the other hand, appear to be protective, possibly by sequestering the protein from the membrane. Surprisingly, sequential deletion of residues 2 through 11 caused a dramatic drop in alpha-helical propensity, vesicle binding in vitro, and membrane binding and toxicity in yeast, part of which could be mimicked by mutating aspartic acid at position 2 to alanine. Variants with distinct structural preferences, identified here by a reductionist approach, provide valuable tools for elucidating the nature of toxic forms of alpha-syn in neurons.
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Affiliation(s)
- Katherina Vamvaca
- Center for Neurologic Diseases, Brigham and Women's Hospital and Department of Neurology, Harvard Medical School, 65 Landsdowne Street, Cambridge, MA 02139, USA
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27
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Bisaglia M, Mammi S, Bubacco L. Structural insights on physiological functions and pathological effects of alpha-synuclein. FASEB J 2008; 23:329-40. [PMID: 18948383 DOI: 10.1096/fj.08-119784] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Alpha-synuclein is an intrinsically unfolded protein that can adopt a partially helical structure when it interacts with different lipid membranes. Its pathological relevance is linked to its involvement in several neurodegenerative disorders including Parkinson's disease, Alzheimer's disease, and dementia with Lewy bodies. Typical of such ailments is the presence of alpha-synuclein aggregates in a beta-structure that can be soluble or precipitate. This review focuses on the structural knowledge acquired in recent years on the various conformations accessible to alpha-synuclein and to its pathologically relevant mutants. Furthermore, the role of the different variables of the chemical environments that govern the equilibria among the accessible conformations is also reviewed. The hypotheses that rationalize the relevance of the individual structural features and conformations for the physiological function of the protein or for its purported pathological role are described and compared.
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Affiliation(s)
- Marco Bisaglia
- Department of Biology, University of Padova, Via U. Bassi 58B, 35121, Padova, Italy
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28
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Waxman EA, Giasson BI. Molecular mechanisms of alpha-synuclein neurodegeneration. Biochim Biophys Acta Mol Basis Dis 2008; 1792:616-24. [PMID: 18955133 DOI: 10.1016/j.bbadis.2008.09.013] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Revised: 09/18/2008] [Accepted: 09/24/2008] [Indexed: 12/31/2022]
Abstract
alpha-Synuclein is an abundant highly charged protein that is normally predominantly localized around synaptic vesicles in presynaptic terminals. Although the function of this protein is still ill-defined, genetic studies have demonstrated that point mutations or genetic alteration (duplications or triplications) that increase the number of copies of the alpha-synuclein (SCNA) gene can cause Parkinson's disease or the related disorder dementia with Lewy bodies. alpha-Synuclein can aberrantly polymerize into fibrils with typical amyloid properties, and these fibrils are the major component of many types of pathological inclusions, including Lewy bodies, which are associated with neurodegenerative diseases, such as Parkinson's disease. Although there is substantial evidence supporting the toxic nature of alpha-synuclein inclusions, other modes of toxicity such as oligomers have been proposed. In this review, some of the evidence for the different mechanisms of alpha-synuclein toxicity is presented and discussed.
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Affiliation(s)
- Elisa A Waxman
- Department of Pharmacology, University of Pennsylvania School of Medicine, 125 John Morgan Building, Philadelphia, PA 19104-6084, USA
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29
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Wislet-Gendebien S, Visanji NP, Whitehead SN, Marsilio D, Hou W, Figeys D, Fraser PE, Bennett SAL, Tandon A. Differential regulation of wild-type and mutant alpha-synuclein binding to synaptic membranes by cytosolic factors. BMC Neurosci 2008; 9:92. [PMID: 18808659 PMCID: PMC2562387 DOI: 10.1186/1471-2202-9-92] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2008] [Accepted: 09/22/2008] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Alpha-Synuclein (alpha-syn), a 140 amino acid protein associated with presynaptic membranes in brain, is a major constituent of Lewy bodies in Parkinson's disease (PD). Three missense mutations (A30P, A53T and E46K) in the alpha-syn gene are associated with rare autosomal dominant forms of familial PD. However, the regulation of alpha-syn's cellular localization in neurons and the effects of the PD-linked mutations are poorly understood. RESULTS In the present study, we analysed the ability of cytosolic factors to regulate alpha-syn binding to synaptic membranes. We show that co-incubation with brain cytosol significantly increases the membrane binding of normal and PD-linked mutant alpha-syn. To characterize cytosolic factor(s) that modulate alpha-syn binding properties, we investigated the ability of proteins, lipids, ATP and calcium to modulate alpha-syn membrane interactions. We report that lipids and ATP are two of the principal cytosolic components that modulate Wt and A53T alpha-syn binding to the synaptic membrane. We further show that 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (C16:0 PAF) is one of the principal lipids found in complex with cytosolic proteins and is required to enhance alpha-syn interaction with synaptic membrane. In addition, the impaired membrane binding observed for A30P alpha-syn was significantly mitigated by the presence of protease-sensitive factors in brain cytosol. CONCLUSION These findings suggest that endogenous brain cytosolic factors regulate Wt and mutant alpha-syn membrane binding, and could represent potential targets to influence alpha-syn solubility in brain.
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Affiliation(s)
- Sabine Wislet-Gendebien
- Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, Ontario, M5S 3H2 Canada.
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Cole NB, Dieuliis D, Leo P, Mitchell DC, Nussbaum RL. Mitochondrial translocation of alpha-synuclein is promoted by intracellular acidification. Exp Cell Res 2008; 314:2076-89. [PMID: 18440504 DOI: 10.1016/j.yexcr.2008.03.012] [Citation(s) in RCA: 150] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Revised: 03/11/2008] [Accepted: 03/12/2008] [Indexed: 10/22/2022]
Abstract
Mitochondrial dysfunction plays a central role in the selective vulnerability of dopaminergic neurons in Parkinson's disease (PD) and is influenced by both environmental and genetic factors. Expression of the PD protein alpha-synuclein or its familial mutants often sensitizes neurons to oxidative stress and to damage by mitochondrial toxins. This effect is thought to be indirect, since little evidence physically linking alpha-synuclein to mitochondria has been reported. Here, we show that the distribution of alpha-synuclein within neuronal and non-neuronal cells is dependent on intracellular pH. Cytosolic acidification induces translocation of alpha-synuclein from the cytosol onto the surface of mitochondria. Translocation occurs rapidly under artificially-induced low pH conditions and as a result of pH changes during oxidative or metabolic stress. Binding is likely facilitated by low pH-induced exposure of the mitochondria-specific lipid cardiolipin. These results imply a direct role for alpha-synuclein in mitochondrial physiology, especially under pathological conditions, and in principle, link alpha-synuclein to other PD genes in regulating mitochondrial homeostasis.
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Affiliation(s)
- Nelson B Cole
- Genetic Diseases Research Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland 20892, USA.
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Soper JH, Roy S, Stieber A, Lee E, Wilson RB, Trojanowski JQ, Burd CG, Lee VMY. Alpha-synuclein-induced aggregation of cytoplasmic vesicles in Saccharomyces cerevisiae. Mol Biol Cell 2008; 19:1093-103. [PMID: 18172022 DOI: 10.1091/mbc.e07-08-0827] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Aggregated alpha-synuclein (alpha-syn) fibrils form Lewy bodies (LBs), the signature lesions of Parkinson's disease (PD) and related synucleinopathies, but the pathogenesis and neurodegenerative effects of LBs remain enigmatic. Recent studies have shown that when overexpressed in Saccharomyces cerevisiae, alpha-syn localizes to plasma membranes and forms cytoplasmic accumulations similar to human alpha-syn inclusions. However, the exact nature, composition, temporal evolution, and underlying mechanisms of yeast alpha-syn accumulations and their relevance to human synucleinopathies are unknown. Here we provide ultrastructural evidence that alpha-syn accumulations are not comprised of LB-like fibrils, but are associated with clusters of vesicles. Live-cell imaging showed alpha-syn initially localized to the plasma membrane and subsequently formed accumulations in association with vesicles. Imaging of truncated and mutant forms of alpha-syn revealed the molecular determinants and vesicular trafficking pathways underlying this pathological process. Because vesicular clustering is also found in LB-containing neurons of PD brains, alpha-syn-mediated vesicular accumulation in yeast represents a model system to study specific aspects of neurodegeneration in PD and related synucleinopathies.
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Affiliation(s)
- James H Soper
- Center for Neurodegenerative Disease Research and Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
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Eliezer D. Protein Folding and Aggregation in in vitro Models of Parkinson's Disease. PARKINSON'S DISEASE 2008. [DOI: 10.1016/b978-0-12-374028-1.00042-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Assayag K, Yakunin E, Loeb V, Selkoe DJ, Sharon R. Polyunsaturated fatty acids induce alpha-synuclein-related pathogenic changes in neuronal cells. THE AMERICAN JOURNAL OF PATHOLOGY 2007; 171:2000-11. [PMID: 18055555 DOI: 10.2353/ajpath.2007.070373] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The misfolding and aggregation of normally soluble proteins has emerged as a key feature of several neurodegenerative diseases. In Parkinson's disease, progressive loss of dopaminergic neurons is accompanied by polymerization of the cytoplasmic protein alpha-synuclein (alphaS) into filamentous inclusions found in neuronal somata (Lewy bodies) and dendrites (Lewy neurites). Similar alphaS aggregates occur in cortical neurons in dementia with Lewy bodies. Numerous reports now indicate that alphaS can interact with lipids. We previously found that treating dopaminergic cells expressing alphaS with polyunsaturated fatty acids (PUFAs) induced the formation of soluble, sodium dodecyl sulfate-stable oligomers whereas treatment with saturated fatty acids did not. Here, we examine the relevance of alphaS-PUFA interactions to the development of Parkinson's disease-like cytopathology. Exposure of alphaS-overexpressing dopaminergic or neuronal cell lines to physiological levels of a PUFA induced the formation of proteinaceous inclusions in the cytoplasm. Kinetic experiments indicated that PUFA-induced soluble oligomers of alphaS precede these Lewy-like inclusions. Importantly, we found that alphaS oligomers were associated with cyto-toxicity, whereas the development of Lewy-like inclusions appeared to be protective. We conclude that alterations in PUFA levels can lead to aggregation of alphaS and subsequent deposition into potentially cyto-toxic oligomers that precede inclusions in dopaminergic cells.
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Affiliation(s)
- Karen Assayag
- Department of Cellular Biochemistry and Human Genetics, Hebrew University, Hadassah Medical School, Jerusalem, Israel
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Stöckl M, Fischer P, Wanker E, Herrmann A. Alpha-synuclein selectively binds to anionic phospholipids embedded in liquid-disordered domains. J Mol Biol 2007; 375:1394-404. [PMID: 18082181 DOI: 10.1016/j.jmb.2007.11.051] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2007] [Revised: 10/15/2007] [Accepted: 11/15/2007] [Indexed: 11/27/2022]
Abstract
Previous studies indicate that binding of alpha-synuclein to membranes is critical for its physiological function and the development of Parkinson's disease (PD). Here, we have investigated the association of fluorescence-labeled alpha-synuclein variants with different types of giant unilamellar vesicles using confocal microscopy. We found that alpha-synuclein binds with high affinity to anionic phospholipids, when they are embedded in a liquid-disordered as opposed to a liquid-ordered environment. This indicates that not only electrostatic forces but also lipid packing and hydrophobic interactions are critical for the association of alpha-synuclein with membranes in vitro. When compared to wild-type alpha-synuclein, the disease-causing alpha-synuclein variant A30P bound less efficiently to anionic phospholipids, while the variant E46K showed enhanced binding. This suggests that the natural association of alpha-synuclein with membranes is altered in the inherited forms of Parkinson's disease.
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Affiliation(s)
- Martin Stöckl
- Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, Institut für Biologie/Biophysik, Invalidenstr. 43, D-10115 Berlin, Germany
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Wang Y, Guo X, Guo R. Interaction of methemoglobin with GDA/n-C5H11OH/water assemblies. J Colloid Interface Sci 2007; 317:568-76. [PMID: 17963777 DOI: 10.1016/j.jcis.2007.09.040] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2007] [Revised: 09/15/2007] [Accepted: 09/18/2007] [Indexed: 01/29/2023]
Abstract
In the present paper, we studied the interaction between n-dodecylammonium alpha-glutamate (GDA)/n-C5H11OH/H2O assemblies and methemoglobin by UV-vis spectroscopy, X-ray diffraction, electron spin resonance (ESR), rheology, and freeze-fractured transmission electron microscopy (FF-TEM). It is found that W/O microemulsion forms at a lower n-pentanol content and O/W microemulsion forms at a lower water content with the addition of methemoglobin. The existence of methemoglobin reduces the hexagonal liquid crystal region, while the lamellar liquid crystal region is little changed in the presence of methemoglobin. Moreover, methemoglobin and GDA/n-C5H11OH/H2O assemblies can affect their structures and properties and the change in behavior is dependent on the content of methemoglobin and the composition and structure of the GDA/n-C5H11OH/H2O system. The relationship among the changes in the structure and properties of GDA/n-C5H11OH/H2O assemblies, the content of methemoglobin, and the composition and structure of GDA/n-C5H11OH/H2O assemblies may provide some important theoretical information for elucidation of the interaction between methemoglobin and blood cell membrane and may also be helpful for the cure of some blood diseases.
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Affiliation(s)
- Yongsheng Wang
- School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, 225002, People's Republic of China
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Beyer K. Mechanistic aspects of Parkinson's disease: alpha-synuclein and the biomembrane. Cell Biochem Biophys 2007; 47:285-99. [PMID: 17652776 DOI: 10.1007/s12013-007-0014-9] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 01/07/2023]
Abstract
AA key feature in Parkinson's disease is the deposition of Lewy bodies. The major protein component of these intracellular deposits is the 140-amino acid protein alpha-synuclein that is widely distributed throughout the brain. alpha-synuclein was identified in presynaptic terminals and in synaptosomal preparations. The protein is remarkable for its structural variability. It is almost unstructured as a monomer in aqueous solution. Self-aggregation leads to a variety of beta-structures, while membrane association may result in the formation of an amphipathic helical structure. The present article strives to give an overview of what is currently known on the interaction of alpha-synuclein with lipid membranes, including synthetic lipid bilayers, membraneous cell fractions, synaptic vesicles and intact cells. Manifestations of a functional relevance of the alpha-synuclein-lipid interaction will be discussed and the potential pathogenicity of oligomeric alpha-synuclein aggregates will be briefly reviewed.
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Affiliation(s)
- Klaus Beyer
- Laboratory of Alzheimer's and Parkinson's Disease Research, Department of Biochemistry, Ludwig Maximilian University, 80336 Munich, Germany.
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Abstract
Aggregation of alpha-synuclein, an abundant and conserved pre-synaptic brain protein, is implicated as a critical factor in several neurodegenerative diseases. These diseases, known as synucleinopathies, include Parkinson's disease, dementia with Lewy bodies (LBs), diffuse LB disease, the LB variant of Alzheimer's disease, multiple system atrophy, and neurodegeneration with brain iron accumulation type I. Although the precise nature of in vivoalpha-synuclein function remains elusive, considerable knowledge has been accumulated about its structural properties and conformational behavior. alpha-Synuclein is a typical natively unfolded protein. It is characterized by the lack of rigid, well-defined, 3-D structure and possesses remarkable conformational plasticity. The structure of this protein depends dramatically on its environment and it accommodates a number of unrelated conformations. This paper provides an overview of the biochemistry, biophysics, and neuropathology of alpha-synuclein aggregation.
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Affiliation(s)
- Vladimir N Uversky
- Department of Biochemistry and Molecular Biology, Center for Computational Biology and Bioinformatics, Indiana University School of Medicine, Indianapolis, Indiana, USA.
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Origins and effects of extracellular alpha-synuclein: implications in Parkinson's disease. J Mol Neurosci 2007; 34:17-22. [PMID: 18157654 DOI: 10.1007/s12031-007-0012-9] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2006] [Accepted: 01/29/2007] [Indexed: 10/23/2022]
Abstract
Misfolding and abnormal aggregation of the neuronal protein alpha-synuclein has been implicated in the pathogenesis of Parkinson's disease and related neurological disorders, such as dementia with Lewy bodies. alpha-synuclein is a conventional cytosolic protein and is thought to exert its pathogenic function exclusively in the neuronal cytoplasm in a cell-autonomous manner. However, the current model is being challenged by a series of new observations that demonstrate the presence of alpha-synuclein and its aggregated forms in the extracellular fluid both in vivo and in vitro. Extracellular alpha-synuclein appears to be delivered by unconventional exocytosis of intravesicular alpha-synuclein, although the exact mechanism has not been characterized. Compared to the cytosolic alpha-synuclein, intravesicular alpha-synuclein is prone to aggregation and the potential source of extracellular aggregates. A number of tissue culture studies suggest that exposure to extracellular alpha-synuclein aggregates induces microglial activation, release of pro-inflammatory cytokines from astrocytes, and neurotoxicity. Thus, exocytosis of alpha-synuclein may be an important mechanism for amplifying and spreading degenerative changes from a small group of cells to its surrounding tissues, and it potentially provides therapeutic targets for halting the progression of the disease.
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Chowdary T, Raman B, Ramakrishna T, Rao C. Interaction of mammalian Hsp22 with lipid membranes. Biochem J 2007; 401:437-45. [PMID: 17020537 PMCID: PMC1820815 DOI: 10.1042/bj20061046] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Hsp22/HspB8 is a member of the small heat-shock protein family, whose function is not yet completely understood. Our immunolocalization studies in a human neuroblastoma cell line, SK-N-SH, using confocal microscopy show that a significant fraction of Hsp22 is localized to the plasma membrane. We therefore investigated its interactions with lipid vesicles in vitro. Intrinsic tryptophan fluorescence is quenched in the presence of lipid vesicles derived from either bovine brain lipid extract or purified lipids. Time-resolved fluorescence studies show a decrease in the lifetimes of the tryptophan residues. Both of these results indicate burial of some tryptophan residues of Hsp22 upon interaction with lipid vesicles. Membrane interactions also lead to increase in fluorescence polarization of Hsp22. Gel-filtration chromatography shows that Hsp22 binds stably with lipid vesicles; the extent of binding depends on the nature of the lipid. Hsp22 binds more strongly to vesicles made of lipids containing a phosphatidic acid, phosphatidylinositol or phosphatidylserine headgroup (known to be present in the inner leaflet of plasma membrane) compared with lipid vesicles made of a phosphatidylcholine head-group alone. Far-UV CD spectra reveal conformational changes upon binding to the lipid vesicles or in membrane-mimetic solvent, trifluoroethanol. Thus our fluorescence, CD and gel-filtration studies show that Hsp22 interacts with membrane and this interaction leads to stable binding and conformational changes. The present study therefore clearly demonstrates that Hsp22 exhibits potential membrane interaction that may play an important role in its cellular functions.
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Affiliation(s)
| | - Bakthisaran Raman
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
| | - Tangirala Ramakrishna
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
- Correspondence may be addressed to either of these authors (email or )
| | - Ch. Mohan Rao
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
- Correspondence may be addressed to either of these authors (email or )
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