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Wild-Type Monomeric α-Synuclein Can Impair Vesicle Endocytosis and Synaptic Fidelity via Tubulin Polymerization at the Calyx of Held. J Neurosci 2017; 37:6043-6052. [PMID: 28576942 DOI: 10.1523/jneurosci.0179-17.2017] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 05/08/2017] [Accepted: 05/13/2017] [Indexed: 01/11/2023] Open
Abstract
α-Synuclein is a presynaptic protein the function of which has yet to be identified, but its neuronal content increases in patients of synucleinopathies including Parkinson's disease. Chronic overexpression of α-synuclein reportedly expresses various phenotypes of synaptic dysfunction, but the primary target of its toxicity has not been determined. To investigate this, we acutely loaded human recombinant α-synuclein or its pathological mutants in their monomeric forms into the calyces of Held presynaptic terminals in slices from auditorily mature and immature rats of either sex. Membrane capacitance measurements revealed significant and specific inhibitory effects of WT monomeric α-synuclein on vesicle endocytosis throughout development. However, the α-synuclein A53T mutant affected vesicle endocytosis only at immature calyces, whereas the A30P mutant had no effect throughout. The endocytic impairment by WT α-synuclein was rescued by intraterminal coloading of the microtubule (MT) polymerization blocker nocodazole. Furthermore, it was reversibly rescued by presynaptically loaded photostatin-1, a photoswitcheable inhibitor of MT polymerization, in a light-wavelength-dependent manner. In contrast, endocytic inhibition by the A53T mutant at immature calyces was not rescued by nocodazole. Functionally, presynaptically loaded WT α-synuclein had no effect on basal synaptic transmission evoked at a low frequency, but significantly attenuated exocytosis and impaired the fidelity of neurotransmission during prolonged high-frequency stimulation. We conclude that monomeric WT α-synuclein primarily inhibits vesicle endocytosis via MT overassembly, thereby impairing high-frequency neurotransmission.SIGNIFICANCE STATEMENT Abnormal α-synuclein abundance is associated with synucleinopathies including Parkinson's disease, but neither the primary target of α-synuclein toxicity nor its mechanism is identified. Here, we loaded monomeric α-synuclein directly into mammalian glutamatergic nerve terminals and found that it primarily inhibits vesicle endocytosis and subsequently impairs exocytosis and neurotransmission fidelity during prolonged high-frequency stimulation. Such α-synuclein toxicity could be rescued by blocking microtubule polymerization, suggesting that microtubule overassembly underlies the toxicity of acutely elevated α-synuclein in the nerve terminal.
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Blumenstock S, Rodrigues EF, Peters F, Blazquez-Llorca L, Schmidt F, Giese A, Herms J. Seeding and transgenic overexpression of alpha-synuclein triggers dendritic spine pathology in the neocortex. EMBO Mol Med 2017; 9:716-731. [PMID: 28351932 PMCID: PMC5412764 DOI: 10.15252/emmm.201607305] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Revised: 02/27/2017] [Accepted: 03/02/2017] [Indexed: 12/22/2022] Open
Abstract
Although misfolded and aggregated α-synuclein (α-syn) is recognized in the disease progression of synucleinopathies, its role in the impairment of cortical circuitries and synaptic plasticity remains incompletely understood. We investigated how α-synuclein accumulation affects synaptic plasticity in the mouse somatosensory cortex using two distinct approaches. Long-term in vivo imaging of apical dendrites was performed in mice overexpressing wild-type human α-synuclein. Additionally, intracranial injection of preformed α-synuclein fibrils was performed to induce cortical α-syn pathology. We find that α-synuclein overexpressing mice show decreased spine density and abnormalities in spine dynamics in an age-dependent manner. We also provide evidence for the detrimental effects of seeded α-synuclein aggregates on dendritic architecture. We observed spine loss as well as dystrophic deformation of dendritic shafts in layer V pyramidal neurons. Our results provide a link to the pathophysiology underlying dementia associated with synucleinopathies and may enable the evaluation of potential drug candidates on dendritic spine pathology in vivo.
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Affiliation(s)
- Sonja Blumenstock
- Center for Neuropathology and Prion Research, Ludwig-Maximilians University, Munich, Germany
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
- Munich Cluster of Systems Neurology (SyNergy), Munich, Germany
| | - Eva F Rodrigues
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Finn Peters
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Lidia Blazquez-Llorca
- Departamento de Psicobiología, Universidad Nacional de Educación a Distancia (UNED), Madrid, Spain
| | - Felix Schmidt
- Center for Neuropathology and Prion Research, Ludwig-Maximilians University, Munich, Germany
- Department of Neurology, Ludwig-Maximilians University, Munich, Germany
| | - Armin Giese
- Center for Neuropathology and Prion Research, Ludwig-Maximilians University, Munich, Germany
| | - Jochen Herms
- Center for Neuropathology and Prion Research, Ludwig-Maximilians University, Munich, Germany
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
- Munich Cluster of Systems Neurology (SyNergy), Munich, Germany
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Cartelli D, Cappelletti G. α-Synuclein regulates the partitioning between tubulin dimers and microtubules at neuronal growth cone. Commun Integr Biol 2017. [PMCID: PMC5333521 DOI: 10.1080/19420889.2016.1267076] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The partitioning between tubulin dimers and microtubules is fundamental for the regulation of several neuronal activities, from neuronal polarization and processes extension to growth cone remodelling. This phenomenon is modulated by several proteins, including the well-known microtubule destabilizer Stathmin. We recently demonstrated that α-Synuclein, a presynaptic protein associated to Parkinson's disease, shares structural and functional properties with Stathmin, and we showed that α-Synuclein acts as a foldable dynamase. Here, we pinpoint the impact of wild type α-Synuclein on the partitioning between tubulin dimers and microtubules and show that Parkinson's disease-linked mutants lose this capability. Thus, our results indicate a new role for α-Synuclein in regulating microtubule system and support the concept that microtubules and α-Synuclein are partners in the modulation of neuronal health and degenerative processes. Furthermore, these data strengthen our hypothesis of the existence of a functional redundancy between α-Synuclein and Stathmin.
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Affiliation(s)
- Daniele Cartelli
- Department of Biosciences, Università degli Studi di Milano, Milano, Italy
| | - Graziella Cappelletti
- Department of Biosciences, Università degli Studi di Milano, Milano, Italy
- Center of Excellence on Neurodegenerative Diseases, Università degli Studi di Milano, Milano, Italy
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Vergara D, Ferraro MM, Cascione M, del Mercato LL, Leporatti S, Ferretta A, Tanzarella P, Pacelli C, Santino A, Maffia M, Cocco T, Rinaldi R, Gaballo A. Cytoskeletal Alterations and Biomechanical Properties of parkin-Mutant Human Primary Fibroblasts. Cell Biochem Biophys 2016; 71:1395-404. [PMID: 25399302 DOI: 10.1007/s12013-014-0362-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Parkinson's disease (PD) is one of the most common neurodegenerative diseases. Genes which have been implicated in autosomal-recessive PD include PARK2 which codes for parkin, an E3 ubiquitin ligase that participates in a variety of cellular activities. In this study, we compared parkin-mutant primary fibroblasts, from a patient with parkin compound heterozygous mutations, to healthy control cells. Western blot analysis of proteins obtained from patient's fibroblasts showed quantitative differences of many proteins involved in the cytoskeleton organization with respect to control cells. These molecular alterations are accompanied by changes in the organization of actin stress fibers and biomechanical properties, as revealed by confocal laser scanning microscopy and atomic force microscopy. In particular, parkin deficiency is associated with a significant increase of Young's modulus of null-cells in comparison to normal fibroblasts. The current study proposes that parkin influences the spatial organization of actin filaments, the shape of human fibroblasts, and their elastic response to an external applied force.
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Affiliation(s)
- Daniele Vergara
- Department of Biological and Environmental Sciences and Technologies, University of Salento, Lecce, Italy
- Laboratory of Clinical Proteomic, ''Giovanni Paolo II'' Hospital, ASL-Lecce, Italy
| | - Marzia M Ferraro
- Department of Biological and Environmental Sciences and Technologies, University of Salento, Lecce, Italy
- Institute of Nanoscience-NNL, CNR, Via Arnesano, 16, Lecce, 73100, Italy
| | - Mariafrancesca Cascione
- Institute of Nanoscience-NNL, CNR, Via Arnesano, 16, Lecce, 73100, Italy
- Department of Mathematics and Physics "Ennio De Giorgi", University of Salento, Lecce, Italy
| | | | - Stefano Leporatti
- Institute of Nanoscience-NNL, CNR, Via Arnesano, 16, Lecce, 73100, Italy
| | - Anna Ferretta
- Department of Basic Medical Sciences, Neurosciences and Organs of Senses, University of Bari 'A. Moro', Bari, Italy
| | - Paola Tanzarella
- Department of Basic Medical Sciences, Neurosciences and Organs of Senses, University of Bari 'A. Moro', Bari, Italy
| | - Consiglia Pacelli
- Department of Pharmacology, Faculty of Medicine, Universitè de Montreal, 2900 Boulevard Edouard-Montpetit, Montreal, QC, H3T1J4, Canada
| | - Angelo Santino
- Institute of Science of Food Production, CNR, Lecce, Italy
| | - Michele Maffia
- Department of Biological and Environmental Sciences and Technologies, University of Salento, Lecce, Italy
- Laboratory of Clinical Proteomic, ''Giovanni Paolo II'' Hospital, ASL-Lecce, Italy
| | - Tiziana Cocco
- Department of Basic Medical Sciences, Neurosciences and Organs of Senses, University of Bari 'A. Moro', Bari, Italy
| | - Ross Rinaldi
- Institute of Nanoscience-NNL, CNR, Via Arnesano, 16, Lecce, 73100, Italy
- Department of Mathematics and Physics "Ennio De Giorgi", University of Salento, Lecce, Italy
| | - Antonio Gaballo
- Institute of Nanoscience-NNL, CNR, Via Arnesano, 16, Lecce, 73100, Italy.
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Impairment of PDGF-induced chemotaxis by extracellular α-synuclein through selective inhibition of Rac1 activation. Sci Rep 2016; 6:37810. [PMID: 27886249 PMCID: PMC5122898 DOI: 10.1038/srep37810] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 11/02/2016] [Indexed: 01/10/2023] Open
Abstract
Parkinson’s disease (PD) is characterized by α-synuclein (α-Syn)-positive intracytoplasmic inclusions, known as Lewy bodies. Although it is known that extracellular α-Syn is detected in the plasma and cerebrospinal fluid, its physiological significance remains unclear. Here, we show that extracellular α-Syn suppresses platelet-derived growth factor (PDGF)-induced chemotaxis in human neuroblastoma SH-SY5Y cells. The inhibitory effect was stronger in the mutant α-Syn(A53T), found in hereditary PD, and the degree of inhibition was time-dependent, presumably because of the oligomerization of α-Syn. PDGF-induced activation of Akt or Erk was not influenced by α-Syn(A53T). Further studies revealed that α-Syn(A53T) inhibited PDGF-induced Rac1 activation, whereas Cdc42 activation remained unaffected, resulting in unbalanced actin filament remodeling. These results shed light on the understanding of pathological as well as physiological functions of extracellular α-Syn in neuronal cells.
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Identification and Characterization of a Candidate Wolbachia pipientis Type IV Effector That Interacts with the Actin Cytoskeleton. mBio 2016; 7:mBio.00622-16. [PMID: 27381293 PMCID: PMC4958246 DOI: 10.1128/mbio.00622-16] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
UNLABELLED Many bacteria live as intracellular symbionts, causing persistent infections within insects. One extraordinarily common infection is that of Wolbachia pipientis, which infects 40% of insect species and induces reproductive effects. The bacteria are passed from generation to generation both vertically (through the oocyte) and horizontally (by environmental transmission). Maintenance of the infection within Drosophila melanogaster is sensitive to the regulation of actin, as Wolbachia inefficiently colonizes strains hemizygous for the profilin or villin genes. Therefore, we hypothesized that Wolbachia must depend on the host actin cytoskeleton. In this study, we identify and characterize a Wolbachia protein (WD0830) that is predicted to be secreted by the bacterial parasite. Expression of WD0830 in a model eukaryote (the yeast Saccharomyces cerevisiae) induces a growth defect associated with the appearance of aberrant, filamentous structures which colocalize with rhodamine-phalloidin-stained actin. Purified WD0830 bundles actin in vitro and cosediments with actin filaments, suggesting a direct interaction of the two proteins. We characterized the expression of WD0830 throughout Drosophila development and found it to be upregulated in third-instar larvae, peaking in early pupation, during the critical formation of adult tissues, including the reproductive system. In transgenic flies, heterologously expressed WD0830 localizes to the developing oocyte. Additionally, overexpression of WD0830 results in increased Wolbachia titers in whole flies, in stage 9 and 10 oocytes, and in embryos, compared to controls, suggesting that the protein may facilitate Wolbachia's replication or transmission. Therefore, this candidate secreted effector may play a role in Wolbachia's infection of and persistence within host niches. IMPORTANCE The obligate intracellular Wolbachia pipientis is a ubiquitous alphaproteobacterial symbiont of arthropods and nematodes and is related to the rickettsial pathogens Ehrlichia spp. and Anaplasma spp. Studies of Wolbachia cell biology suggest that this bacterium relies on host actin for efficient proliferation and transmission between generations. Here, we identified and characterized a Wolbachia protein that localizes to and manipulates the eukaryotic actin cytoskeleton, is expressed by Wolbachia during host development, and alters Wolbachia titers and localization in transgenic fruit flies. We hypothesize that WD0830 may be utilized by the bacterium to facilitate replication in or invasion of different niches during host development.
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57
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Xuan Q, Zhang YX, Liu DG, Chan P, Xu SL, Cui YQ. Post-translational modifications of α-synuclein contribute to neurodegeneration in the colon of elderly individuals. Mol Med Rep 2016; 13:5077-83. [PMID: 27109489 PMCID: PMC4878562 DOI: 10.3892/mmr.2016.5166] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2015] [Accepted: 02/23/2016] [Indexed: 01/24/2023] Open
Abstract
Synucleinopathies and abnormalities in the nerves of the enteric nervous system are hypothesized to be involved in age-associated motility disorders. The aim of the present study was to investigate the expression of various antigens, including α‑synuclein (Syn) and its post‑translational modified forms, in the human colon at various ages. In addition, the study aimed to correlate the expression of Syn with neurodegeneration. Immunohistochemistry was used to detect the expression of neurofilament (NF), Syn, as well as its nitrated (N) form in the healthy colonic tissue of 12 young (34.08±5.12 years), 10 middle‑aged (51.80±3.52 years), and 11 elderly (75.82±7.70 years) individuals. To the best of our knowledge, the current study is the first to demonstrate the presence of N‑Syn in the colonic tissue. N‑Syn was identified in the upper layer of the mucosa and submucosa layer. Furthermore, Syn (wild‑type) was present in the mucosa and submucosa. The number of NF‑positive neurons in the submucosal layer declined significantly with age (P<0.01). In addition, Syn and N‑Syn significantly increased during aging (P<0.01). Furthermore, a negative correlation was identified between neuron number and synucleinopathies, indicating the abnormal accumulation of both wild-type Syn and N‑Syn in the mucosa, submucosa, muscle layer and myenteric plexus. The present study demonstrates that the Syn pathology may be linked to colic neuronal degeneration during normal aging, and this link may cause functional deficits.
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Affiliation(s)
- Qi Xuan
- Department of Nutrition, Xuanwu Hospital, Capital Medical University, Beijing 100053, P.R. China
| | - Yu-Xian Zhang
- Department of Internal Medicine, Beijing Moslem Hospital, Beijing 100054, P.R. China
| | - Dian-Gang Liu
- Department of General Surgery, Xuanwu Hospital, Capital Medical University, Beijing 100053, P.R. China
| | - Piu Chan
- Department of Neurobiology, Institute of Geriatrics of Beijing, Xuanwu Hospital, Capital Medical University, Key Laboratory for Neurodegenerative Disease of Ministry of Education, Beijing 100053, P.R. China
| | - Sheng-Li Xu
- Department of Neurobiology, Institute of Geriatrics of Beijing, Xuanwu Hospital, Capital Medical University, Key Laboratory for Neurodegenerative Disease of Ministry of Education, Beijing 100053, P.R. China
| | - Ye-Qing Cui
- Department of General Surgery, Xuanwu Hospital, Capital Medical University, Beijing 100053, P.R. China
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58
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Genetic Variants of Microtubule Actin Cross-linking Factor 1 (MACF1) Confer Risk for Parkinson’s Disease. Mol Neurobiol 2016; 54:2878-2888. [DOI: 10.1007/s12035-016-9861-y] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 03/17/2016] [Indexed: 01/12/2023]
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59
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Tilve S, Difato F, Chieregatti E. Cofilin 1 activation prevents the defects in axon elongation and guidance induced by extracellular alpha-synuclein. Sci Rep 2015; 5:16524. [PMID: 26558842 PMCID: PMC4642265 DOI: 10.1038/srep16524] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 10/15/2015] [Indexed: 12/20/2022] Open
Abstract
Impaired adult neurogenesis and axon traumatic injury participate in the severity of neurodegenerative diseases. Alpha-synuclein, a cytosolic protein involved in Parkinson's disease, may be released from neurons, suggesting a role for excess secreted alpha-synuclein in the onset and spread of the pathology. Here we provide evidence that long term exposure of young neurons to extracellular alpha-synuclein hampers axon elongation and growth cone turning. We show that actin turnover and the rate of movement of actin waves along the axon are altered, due to alpha-synuclein-induced inactivation of cofilin. Upon laser disruption of microfilaments, healing of axons is favored by the increased phosphorylation of cofilin, however, at later time points; the defect in neurite extension prevails, being lost the regulation of cofilin activity. Importantly, overexpression of the active form of cofilin in neurons exposed to alpha-synuclein is able to restore the movement of actin waves, physiological axon elongation and growth cone turning. Our study reveals the molecular basis of alpha-synuclein-driven deficits in growth and migration of newborn neurons, and in elongation and regeneration of adult neurons.
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Affiliation(s)
- Sharada Tilve
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, 16163 Genoa, Italy
| | - Francesco Difato
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, 16163 Genoa, Italy
| | - Evelina Chieregatti
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, 16163 Genoa, Italy
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60
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Bobela W, Aebischer P, Schneider BL. Αlpha-Synuclein as a Mediator in the Interplay between Aging and Parkinson's Disease. Biomolecules 2015; 5:2675-700. [PMID: 26501339 PMCID: PMC4693253 DOI: 10.3390/biom5042675] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 09/22/2015] [Accepted: 10/13/2015] [Indexed: 12/14/2022] Open
Abstract
Accumulation and misfolding of the alpha-synuclein protein are core mechanisms in the pathogenesis of Parkinson's disease. While the normal function of alpha-synuclein is mainly related to the control of vesicular neurotransmission, its pathogenic effects are linked to various cellular functions, which include mitochondrial activity, as well as proteasome and autophagic degradation of proteins. Remarkably, these functions are also affected when the renewal of macromolecules and organelles becomes impaired during the normal aging process. As aging is considered a major risk factor for Parkinson's disease, it is critical to explore its molecular and cellular implications in the context of the alpha-synuclein pathology. Here, we discuss similarities and differences between normal brain aging and Parkinson's disease, with a particular emphasis on the nigral dopaminergic neurons, which appear to be selectively vulnerable to the combined effects of alpha-synuclein and aging.
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Affiliation(s)
- Wojciech Bobela
- Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland.
| | - Patrick Aebischer
- Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne 1015, Switzerland.
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61
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Kevenaar JT, Hoogenraad CC. The axonal cytoskeleton: from organization to function. Front Mol Neurosci 2015; 8:44. [PMID: 26321907 PMCID: PMC4536388 DOI: 10.3389/fnmol.2015.00044] [Citation(s) in RCA: 115] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 07/31/2015] [Indexed: 01/20/2023] Open
Abstract
The axon is the single long fiber that extends from the neuron and transmits electrical signals away from the cell body. The neuronal cytoskeleton, composed of microtubules (MTs), actin filaments and neurofilaments, is not only required for axon formation and axonal transport but also provides the structural basis for several specialized axonal structures, such as the axon initial segment (AIS) and presynaptic boutons. Emerging evidence suggest that the unique cytoskeleton organization in the axon is essential for its structure and integrity. In addition, the increasing number of neurodevelopmental and neurodegenerative diseases linked to defect in actin- and microtubule-dependent processes emphasizes the importance of a properly regulated cytoskeleton for normal axonal functioning. Here, we provide an overview of the current understanding of actin and microtubule organization within the axon and discuss models for the functional role of the cytoskeleton at specialized axonal structures.
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Affiliation(s)
- Josta T. Kevenaar
- Cell Biology, Faculty of Science, Utrecht UniversityUtrecht, Netherlands
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62
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Alpha-Synuclein affects neurite morphology, autophagy, vesicle transport and axonal degeneration in CNS neurons. Cell Death Dis 2015; 6:e1811. [PMID: 26158517 PMCID: PMC4650722 DOI: 10.1038/cddis.2015.169] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Revised: 05/14/2015] [Accepted: 05/15/2015] [Indexed: 12/23/2022]
Abstract
Many neuropathological and experimental studies suggest that the degeneration of dopaminergic terminals and axons precedes the demise of dopaminergic neurons in the substantia nigra, which finally results in the clinical symptoms of Parkinson disease (PD). The mechanisms underlying this early axonal degeneration are, however, still poorly understood. Here, we examined the effects of overexpression of human wildtype alpha-synuclein (αSyn-WT), a protein associated with PD, and its mutant variants αSyn-A30P and -A53T on neurite morphology and functional parameters in rat primary midbrain neurons (PMN). Moreover, axonal degeneration after overexpression of αSyn-WT and -A30P was analyzed by live imaging in the rat optic nerve in vivo. We found that overexpression of αSyn-WT and of its mutants A30P and A53T impaired neurite outgrowth of PMN and affected neurite branching assessed by Sholl analysis in a variant-dependent manner. Surprisingly, the number of primary neurites per neuron was increased in neurons transfected with αSyn. Axonal vesicle transport was examined by live imaging of PMN co-transfected with EGFP-labeled synaptophysin. Overexpression of all αSyn variants significantly decreased the number of motile vesicles and decelerated vesicle transport compared with control. Macroautophagic flux in PMN was enhanced by αSyn-WT and -A53T but not by αSyn-A30P. Correspondingly, colocalization of αSyn and the autophagy marker LC3 was reduced for αSyn-A30P compared with the other αSyn variants. The number of mitochondria colocalizing with LC3 as a marker for mitophagy did not differ among the groups. In the rat optic nerve, both αSyn-WT and -A30P accelerated kinetics of acute axonal degeneration following crush lesion as analyzed by in vivo live imaging. We conclude that αSyn overexpression impairs neurite outgrowth and augments axonal degeneration, whereas axonal vesicle transport and autophagy are severely altered.
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Surgucheva I, He S, Rich MC, Sharma R, Ninkina NN, Stahel PF, Surguchov A. Role of synucleins in traumatic brain injury — an experimental in vitro and in vivo study in mice. Mol Cell Neurosci 2015; 63:114-23. [PMID: 25447944 DOI: 10.1016/j.mcn.2014.10.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 10/16/2014] [Accepted: 10/23/2014] [Indexed: 11/25/2022] Open
Abstract
Synucleins are small prone to aggregate proteins associated with several neurodegenerative diseases (NDDs), however their role in traumatic brain injury (TBI) is an emerging area of investigation. Using in vitro scratch injury model and in vivo mouse weight-drop model we have found that the injury causes alterations in the expression and localization of synucleins near the damaged area. Before injury, α-synuclein is diffused in the cytoplasm of neurons and γ-synuclein is both in the cytoplasm and nucleus of oligodendrocytes. After the scratch injury of the mixed neuronal and glial culture, α-synuclein forms punctate structures in the cytoplasm of neurons and γ-synuclein is almost completely localized to the nucleus of the oligodendrocytes. Furthermore, the amount of post-translationally modified Met38-oxidized γ-synuclein is increased 3.8 fold 24 h after the scratch. α- and γ-synuclein containing cells increased in the initially cell free scratch zone up to 24 h after the scratch.Intracellular expression and localization of synucleins are also changed in a mouse model of focal closed head injury, using a standardized weight drop device. γ-Synuclein goes from diffuse to punctate staining in a piriform cortex near the amygdala, which may reflect the first steps in the formation of deposits/inclusions. Surprisingly, oxidized γ-synuclein co-localizes with cofilin-actin rods in the thalamus, which are absent in all other regions of the brain. These structures reach their peak amounts 7 days after injury. The changes in γ-synuclein localization are accompanied by injury-induced alterations in the morphology of both astrocytes and neurons.
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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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65
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Caesar M, Felk S, Aasly JO, Gillardon F. Changes in actin dynamics and F-actin structure both in synaptoneurosomes of LRRK2(R1441G) mutant mice and in primary human fibroblasts of LRRK2(G2019S) mutation carriers. Neuroscience 2014; 284:311-324. [PMID: 25301747 DOI: 10.1016/j.neuroscience.2014.09.070] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 09/01/2014] [Accepted: 09/02/2014] [Indexed: 12/13/2022]
Abstract
Converging evidence suggests that the Parkinson's disease-linked leucine-rich repeat kinase 2 (LRRK2) modulates cellular function by regulating actin dynamics. In the present study we investigate the role of LRRK2 in functional synaptic terminals of adult LRRK2-knockout and LRRK2(R1441G)-transgenic mice as well as in primary fibroblasts of LRRK2(G2019S) mutation carriers. We show that lack of LRRK2 decreases and overexpression of mutant LRRK2 age-dependently increases the effect of the actin depolymerizing agent Latrunculin A (LatA) on the synaptic cytoskeleton. Similarly, endogenous mutant LRRK2 increases sensitivity to LatA in primary fibroblasts. Under basal conditions however, these fibroblasts show an increase in F-actin bundles and a decrease in filopodial length which can be rescued by LatA treatment. Our data suggest that LRRK2 alters actin dynamics and F-actin structure both in brain neurons and skin fibroblasts. We hypothesize that increased F-actin bundling represents a compensatory mechanism to protect F-actin from the depolymerizing effect of mutant LRRK2 under basal conditions. Our data further indicate that LRRK2-dependent changes in the cytoskeleton might have functional consequences on postsynaptic NMDA receptor localization.
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Affiliation(s)
- M Caesar
- Boehringer Ingelheim Pharma GmbH & Co. KG, CNS Diseases Research, Biberach an der Riss, Germany.
| | - S Felk
- Boehringer Ingelheim Pharma GmbH & Co. KG, CNS Diseases Research, Biberach an der Riss, Germany
| | - J O Aasly
- St. Olav's University Hospital, Department of Neurology, Trondheim, Norway
| | - F Gillardon
- Boehringer Ingelheim Pharma GmbH & Co. KG, CNS Diseases Research, Biberach an der Riss, Germany.
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Tönges L, Szegö EM, Hause P, Saal KA, Tatenhorst L, Koch JC, D Hedouville Z, Dambeck V, Kügler S, Dohm CP, Bähr M, Lingor P. Alpha-synuclein mutations impair axonal regeneration in models of Parkinson's disease. Front Aging Neurosci 2014; 6:239. [PMID: 25309425 PMCID: PMC4159996 DOI: 10.3389/fnagi.2014.00239] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2014] [Accepted: 08/21/2014] [Indexed: 12/27/2022] Open
Abstract
The dopaminergic (DAergic) nigrostriatal tract has an intrinsic regenerative capacity which can be impaired in Parkinson's disease (PD). Alpha-synuclein (aSyn) is a major pathogenic component in PD but its impact on DAergic axonal regeneration is largely unknown. In this study, we expressed pathogenic variants of human aSyn by means of recombinant adeno-associated viral vectors in experimental paradigms of DAergic regeneration. In a scratch lesion model in vitro, both aSyn(A30P) and aSyn(A53T) significantly reduced DAergic neurite regeneration and induced loss of TH-immunopositive cells while aSyn(WT) showed only minor cellular neurotoxic effects. The striatal density of TH-immunopositive axons in the striatal 6-OHDA lesion mouse model was attenuated only by aSyn(A30P). However, striatal expression levels of the regeneration marker GAP-43 in TH-immunopositive fibers were reduced by both aSyn(A30P) and aSyn(A53T), but not by aSyn(WT), which was associated with an activation of the ROCK signaling pathway. Nigral DAergic cell loss was only mildly enhanced by additional overexpression of aSyn variants. Our findings indicate that mutations of aSyn have a strong impact on the regenerative capacity of DAergic neurons, which may contribute to their pathogenic effects.
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Affiliation(s)
- Lars Tönges
- Department of Neurology, University Medicine Göttingen Göttingen, Germany ; Nanoscale Microscopy and Molecular Physiology of the Brain, Cluster of Excellence 171-DFG Research Center 103 (CNMPB) Göttingen, Germany
| | - Eva M Szegö
- Department of Neurodegeneration and Restorative Research, University Medicine Göttingen Göttingen, Germany
| | - Patrizia Hause
- Department of Neurology, University Medicine Göttingen Göttingen, Germany
| | - Kim-Ann Saal
- Department of Neurology, University Medicine Göttingen Göttingen, Germany
| | - Lars Tatenhorst
- Department of Neurology, University Medicine Göttingen Göttingen, Germany
| | - Jan Christoph Koch
- Department of Neurology, University Medicine Göttingen Göttingen, Germany ; Nanoscale Microscopy and Molecular Physiology of the Brain, Cluster of Excellence 171-DFG Research Center 103 (CNMPB) Göttingen, Germany
| | - Zara D Hedouville
- Department of Neurology, University Medicine Göttingen Göttingen, Germany
| | - Vivian Dambeck
- Department of Neurology, University Medicine Göttingen Göttingen, Germany
| | - Sebastian Kügler
- Department of Neurology, University Medicine Göttingen Göttingen, Germany ; Nanoscale Microscopy and Molecular Physiology of the Brain, Cluster of Excellence 171-DFG Research Center 103 (CNMPB) Göttingen, Germany
| | - Christoph P Dohm
- Department of Neurology, University Medicine Göttingen Göttingen, Germany ; Nanoscale Microscopy and Molecular Physiology of the Brain, Cluster of Excellence 171-DFG Research Center 103 (CNMPB) Göttingen, Germany
| | - Mathias Bähr
- Department of Neurology, University Medicine Göttingen Göttingen, Germany
| | - Paul Lingor
- Department of Neurology, University Medicine Göttingen Göttingen, Germany ; Nanoscale Microscopy and Molecular Physiology of the Brain, Cluster of Excellence 171-DFG Research Center 103 (CNMPB) Göttingen, Germany
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Bellani S, Mescola A, Ronzitti G, Tsushima H, Tilve S, Canale C, Valtorta F, Chieregatti E. GRP78 clustering at the cell surface of neurons transduces the action of exogenous alpha-synuclein. Cell Death Differ 2014; 21:1971-83. [PMID: 25124556 DOI: 10.1038/cdd.2014.111] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2014] [Revised: 06/02/2014] [Accepted: 07/01/2014] [Indexed: 01/07/2023] Open
Abstract
Mutation or multiplication of the alpha-synuclein (Syn)-encoding gene is frequent cause of early onset Parkinson's disease (PD). Recent evidences point to the pathogenic role of excess Syn also in sporadic PD. Syn is a cytosolic protein, which has been shown to be released from neurons. Here we provide evidence that extracellular Syn induces an increase in surface-exposed glucose-related protein of 78 kDa (GRP78), which becomes clustered in microdomains of the neuronal plasma membrane. Upon interacting with Syn, GRP78 activates a signaling cascade leading to cofilin 1 inactivation and stabilization of microfilaments, thus affecting morphology and dynamics of actin cytoskeleton in cultured neurons. Downregulation of GRP78 abolishes the activity of exogenous Syn, indicating that it is the primary target of Syn. Inactivation of cofilin 1 and stabilization of actin cytoskeleton are present also in fibroblasts derived from genetic PD patients, which show a dramatic increase in stress fibers. Similar changes are displayed by control cells incubated with the medium of PD fibroblasts, only when Syn is present. The accumulation of Syn in the extracellular milieu, its interaction with the plasma membrane and Syn-driven clustering of GRP78 appear, therefore, responsible for the dysregulation of actin turnover, leading to early deficits in synaptic function that precede neurodegeneration.
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Affiliation(s)
- S Bellani
- Division of Neuroscience, San Raffaele Scientific Institute and Vita-Salute University, Milan 20132, Italy
| | - A Mescola
- Department of Nanophysics and Brain Technologies, Istituto Italiano di Tecnologia, Genoa 16163, Italy
| | - G Ronzitti
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, Genoa 16163, Italy
| | - H Tsushima
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, Genoa 16163, Italy
| | - S Tilve
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, Genoa 16163, Italy
| | - C Canale
- Department of Nanophysics and Brain Technologies, Istituto Italiano di Tecnologia, Genoa 16163, Italy
| | - F Valtorta
- Division of Neuroscience, San Raffaele Scientific Institute and Vita-Salute University, Milan 20132, Italy
| | - E Chieregatti
- Department of Neuroscience and Brain Technologies, Istituto Italiano di Tecnologia, Genoa 16163, Italy
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Neuner J, Ovsepian SV, Dorostkar M, Filser S, Gupta A, Michalakis S, Biel M, Herms J. Pathological α-synuclein impairs adult-born granule cell development and functional integration in the olfactory bulb. Nat Commun 2014; 5:3915. [PMID: 24867427 PMCID: PMC4050256 DOI: 10.1038/ncomms4915] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Accepted: 04/18/2014] [Indexed: 12/21/2022] Open
Abstract
Although the role of noxious α-synuclein (α-SYN) in the degeneration of midbrain dopaminergic
neurons and associated motor deficits of Parkinson’s disease is
recognized, its impact on non-motor brain circuits and related symptoms remains
elusive. Through combining in vivo two-photon imaging with time-coded
labelling of neurons in the olfactory bulb of A30P α-SYN transgenic mice, we show impaired growth and
branching of dendrites of adult-born granule cells (GCs), with reduced gain and
plasticity of dendritic spines. The spine impairments are especially pronounced
during the critical phase of integration of new neurons into existing circuits.
Functionally, retarded dendritic expansion translates into reduced electrical
capacitance with enhanced intrinsic excitability and responsiveness of GCs to
depolarizing inputs, while the spine loss correlates with decreased frequency of
AMPA-mediated miniature EPSCs.
Changes described here are expected to interfere with the functional integration and
survival of new GCs into bulbar networks, contributing towards olfactory deficits
and related behavioural impairments. Aggregation-prone forms of α-synuclein lead to
degeneration of midbrain dopaminergic neurons, as seen in Parkinson’s
disease, but less is known about the effects that the noxious protein has in other brain
regions. Here, the authors investigate the effect of a pathological form of
α-synuclein on the functional integration of new neurons into the olfactory
bulb of adult mice.
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Affiliation(s)
- Johanna Neuner
- Center for Neuropathology and Prion Research, Department for Translationsal Brain Research, Ludwig Maximilian University, Feodor-Lynen-Strassee 23, Munich 81377, Germany
| | - Saak V Ovsepian
- German Center for Neurodegeneratione Diseases (DZNE), Department for Translational Brain Research, Feodor-Lynen-Strasse 23, Munich 81377, Germany
| | - Mario Dorostkar
- Center for Neuropathology and Prion Research, Department for Translationsal Brain Research, Ludwig Maximilian University, Feodor-Lynen-Strassee 23, Munich 81377, Germany
| | - Severin Filser
- German Center for Neurodegeneratione Diseases (DZNE), Department for Translational Brain Research, Feodor-Lynen-Strasse 23, Munich 81377, Germany
| | - Aayush Gupta
- Center for Neuropathology and Prion Research, Department for Translationsal Brain Research, Ludwig Maximilian University, Feodor-Lynen-Strassee 23, Munich 81377, Germany
| | - Stylianos Michalakis
- Center for Integrated Protein Science Munich, (CiPSM) and Department of Pharmacy-Center for Drug Research, Ludwig Maximilian University, Butenandtstrasse 5-13, Munich 81377, Germany
| | - Martin Biel
- Center for Integrated Protein Science Munich, (CiPSM) and Department of Pharmacy-Center for Drug Research, Ludwig Maximilian University, Butenandtstrasse 5-13, Munich 81377, Germany
| | - Jochen Herms
- 1] German Center for Neurodegeneratione Diseases (DZNE), Department for Translational Brain Research, Feodor-Lynen-Strasse 23, Munich 81377, Germany [2] Munich Cluster of Systems Neurology (SyNergy), Ludwig Maximilian University, Feodor-Lynen-Strasse 23, Munich 81377, Germany
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69
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Chapman MA. Interactions between cell adhesion and the synaptic vesicle cycle in Parkinson's disease. Med Hypotheses 2014; 83:203-7. [PMID: 24837686 DOI: 10.1016/j.mehy.2014.04.029] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 04/21/2014] [Indexed: 12/27/2022]
Abstract
Synaptic dysfunction has been identified as an early neuropathologic event in Parkinson's disease. Synapses depend critically on the adhesion of neurons to one another, glial cells, and the extracellular matrix. Cell-cell and cell-matrix adhesions regulate the structure and function of synapses, in part, through interactions with structural elements such as actin and microtubule proteins. These proteins are critical not only for neuronal structure and polarity, but also for the synaptic vesicle cycle, including maintenance of and transfer between vesicle pools, exocytosis, and vesicle recycling. Pathway analyses of genome wide association studies (GWAS) in Parkinson's disease have identified frequent single nucleotide polymorphisms (SNPs) in cell adhesion pathways, suggesting that dysfunction in cell adhesion may play a role in disease pathology. Based on these observations, it may be hypothesized that Parkinson's disease is due to synaptic dysfunction caused by genetic variations in cell adhesion pathways that affect actin and/or microtubule-mediated events in the synaptic vesicle cycle. Furthermore, it is hypothesized that cells with pacemaker-like activity-a characteristic of neurons that degenerate in Parkinson's disease-may depend more on actin for recruiting synaptic vesicles for release than do less active neurons, thereby enhancing their sensitivity to SNPs in cell adhesion pathways and explaining the selectivity of neurodegeneration. Cells may ultimately die due to detachment from the extracellular matrix. This hypothesis suggests that further exploration of cell adhesion pathways and their linkage to neurotransmitter release through cell structural proteins such as actin and microtubules may provide important insights into Parkinson's disease.
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Licker V, Turck N, Kövari E, Burkhardt K, Côte M, Surini-Demiri M, Lobrinus JA, Sanchez JC, Burkhard PR. Proteomic analysis of human substantia nigra identifies novel candidates involved in Parkinson's disease pathogenesis. Proteomics 2014; 14:784-94. [DOI: 10.1002/pmic.201300342] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Revised: 12/13/2013] [Accepted: 12/15/2013] [Indexed: 11/09/2022]
Affiliation(s)
- Virginie Licker
- Neuroproteomics Group; University Medical Center; Faculty of Medicine; Geneva University; Geneva Switzerland
- Translational Biomarker Group; University Medical Center; Faculty of Medicine; Geneva University; Geneva Switzerland
| | - Natacha Turck
- Translational Biomarker Group; University Medical Center; Faculty of Medicine; Geneva University; Geneva Switzerland
| | - Enikö Kövari
- Department of Psychiatry; Geneva University Hospitals; Geneva Switzerland
| | - Karim Burkhardt
- Department of Pathology; Geneva University Hospitals; Geneva Switzerland
| | - Mélanie Côte
- Neuroproteomics Group; University Medical Center; Faculty of Medicine; Geneva University; Geneva Switzerland
- Translational Biomarker Group; University Medical Center; Faculty of Medicine; Geneva University; Geneva Switzerland
| | | | | | - Jean-Charles Sanchez
- Translational Biomarker Group; University Medical Center; Faculty of Medicine; Geneva University; Geneva Switzerland
| | - Pierre R. Burkhard
- Neuroproteomics Group; University Medical Center; Faculty of Medicine; Geneva University; Geneva Switzerland
- Translational Biomarker Group; University Medical Center; Faculty of Medicine; Geneva University; Geneva Switzerland
- Department of Neurology; Geneva University Hospitals; Geneva Switzerland
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Biophysical groundwork as a hinge to unravel the biology of α-synuclein aggregation and toxicity. Q Rev Biophys 2014; 47:1-48. [PMID: 24443929 DOI: 10.1017/s0033583513000097] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Alpha-synuclein (aS) and its aggregation properties are central in the development and spread of Parkinson's disease. Point mutations and multiplications of the SNCA gene encoding aS cause autosomal dominant forms of the disorder. Moreover, protein inclusions found in the surviving neurons of parkinsonian brains consist mainly of a fibrillar form of aS. Aggregates of aS, which form a transient, complex and heterogeneous ensemble, participate in a wide variety of toxic mechanisms that may be amplified by aS spreading among neighbouring neurons. Recently, significant effort has been directed into the study of the aS aggregation process and the impact of aS aggregates on neuron survival. In this review, we present state-of-the-art biophysical studies on the aS aggregation process in vitro and in cellular models. We comprehensively review the new insights generated by the recent biophysical investigations, which could provide a solid basis from which to design future biomedical studies. The diverse cellular models of aS toxicity and their potential use in the biophysical investigation are also discussed.
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72
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Roy B, Jackson GR. Interactions between Tau and α-synuclein augment neurotoxicity in a Drosophila model of Parkinson's disease. Hum Mol Genet 2014; 23:3008-23. [PMID: 24430504 DOI: 10.1093/hmg/ddu011] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Clinical and pathological studies have suggested considerable overlap between tauopathies and synucleinopathies. Several genome-wide association studies have identified alpha-Synuclein (SNCA) and Tau (MAPT) polymorphisms as common risk factors for sporadic Parkinson's disease (PD). However, the mechanisms by which subtle variations in the expression of wild-type SNCA and MAPT influence risk for PD and the underlying cellular events that effect neurotoxicity remain unclear. To examine causes of neurotoxicity associated with the α-Syn/Tau interaction, we used the fruit fly as a model. We utilized misexpression paradigms in three different tissues to probe the α-Syn/Tau interaction: the retina, dopaminergic neurons and the larval neuromuscular junction. Misexpression of Tau and α-Syn enhanced a rough eye phenotype and loss of dopaminergic neurons in fly tauopathy and synucleinopathy models, respectively. Our findings suggest that interactions between α-Syn and Tau at the cellular level cause disruption of cytoskeletal organization, axonal transport defects and aberrant synaptic organization that contribute to neuronal dysfunction and death associated with sporadic PD. α-Syn did not alter levels of Tau phosphorylated at the AT8 epitope. However, α-Syn and Tau colocalized in ubiquitin-positive aggregates in eye imaginal discs. The presence of Tau also led to an increase in urea soluble α-Syn. Our findings have important implications in understanding the cellular and molecular mechanisms underlying α-Syn/Tau-mediated synaptic dysfunction, which likely arise in the early asymptomatic phase of sporadic PD.
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Affiliation(s)
- Bidisha Roy
- Mitchell Center for Neurodegenerative Diseases
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73
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74
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Abstract
α-Synuclein is a presynaptic neuronal protein that is linked genetically and neuropathologically to Parkinson's disease (PD). α-Synuclein may contribute to PD pathogenesis in a number of ways, but it is generally thought that its aberrant soluble oligomeric conformations, termed protofibrils, are the toxic species that mediate disruption of cellular homeostasis and neuronal death, through effects on various intracellular targets, including synaptic function. Furthermore, secreted α-synuclein may exert deleterious effects on neighboring cells, including seeding of aggregation, thus possibly contributing to disease propagation. Although the extent to which α-synuclein is involved in all cases of PD is not clear, targeting the toxic functions conferred by this protein when it is dysregulated may lead to novel therapeutic strategies not only in PD, but also in other neurodegenerative conditions, termed synucleinopathies.
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Affiliation(s)
- Leonidas Stefanis
- Laboratory of Neurodegenerative Diseases, Biomedical Research Foundation of the Academy of Athens, and Second Department of Neurology, University of Athens Medical School, Athens 11527, Greece.
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75
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Liu G, Wang P, Li X, Li Y, Xu S, Uéda K, Chan P, Yu S. Alpha-synuclein promotes early neurite outgrowth in cultured primary neurons. J Neural Transm (Vienna) 2013; 120:1331-43. [PMID: 23443897 DOI: 10.1007/s00702-013-0999-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 02/09/2013] [Indexed: 12/28/2022]
Abstract
We previously showed that alpha-synuclein (α-Syn), a protein implicated in the pathogenesis of several neurodegenerative diseases, is a microtubule-associated protein (MAP), facilitating the polymerization of tubulin into microtubules. Therefore, we hypothesized that α-Syn might promote neurite outgrowth, a process that requires microtubule assembly. To test this hypothesis, recombinant human wild type (WT) and mutant (A30P and A53T) α-Syn proteins were added to cultured primary rat cortical neurons, and their effects on early neurite outgrowth were observed. The WT and mutant α-Syn proteins entered the neurons after 1-4 h of incubation. However, a significant increase in neurite outgrowth was observed only in neurons treated with WT α-Syn. MES23.5 dopaminergic neuronal cells overexpressing WT α-Syn also exhibited enhanced neurite outgrowth, indicating that the ability of α-Syn to promote neurite outgrowth was not due to a direct action on the cell membrane or by the membrane translocation process. Co-immunoprecipitation demonstrated that the recombinant human α-Syn was bound to tubulin. In addition, the α-Syn-treated neurons displayed increased levels of polymerized tubulin. Because α-Syn's MAP functionality is mediated by specific domains, we generated N-terminal (a.a. 1-65), non-amyloid-β (non-Aβ) component (NAC) (a.a. 61-95) and C-terminal (a.a. 96-140) fragments and added them to the primary neurons. After 1-4 h of incubation, the various α-Syn fragments had entered the neurons. However, only the NAC and C-terminal fragments, which have been previously shown to mediate MAP functionality, promoted neurite outgrowth. These results suggest that α-Syn promotes neurite outgrowth by facilitating the polymerization of tubulin into microtubules.
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Affiliation(s)
- Guangwei Liu
- Department of Neurobiology, Beijing Institute of Geriatrics, Xuanwu Hospital of China Capital Medical University, No. 45 Changchun Street, Beijing, 100053, China
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76
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Gonçalves S, Outeiro TF. Assessing the subcellular dynamics of alpha-synuclein using photoactivation microscopy. Mol Neurobiol 2013; 47:1081-92. [PMID: 23389286 PMCID: PMC3637893 DOI: 10.1007/s12035-013-8406-x] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Accepted: 01/08/2013] [Indexed: 11/27/2022]
Abstract
Alpha-synuclein (aSyn) is implicated in Parkinson’s disease and several other neurodegenerative disorders. To date, the function and intracellular dynamics of aSyn are still unclear. Here, we tracked the dynamics of aSyn using photoactivatable green fluorescent protein as a reporter. We found that the availability of the aSyn N terminus modulates its shuttling into the nucleus. Interestingly, familial aSyn mutations altered the dynamics at which the protein distributes throughout the cell. Both the A30P and A53T aSyn mutations increase the speed at which the protein moves between the nucleus and cytoplasm, respectively. We also found that specific kinases potentiate the shuttling of aSyn between nucleus and cytoplasm. A mutant aSyn form that blocks S129 phosphorylation, S129A, results in the formation of cytoplasmic inclusions, suggesting phosphorylation modulates aggregation in addition to modulating aSyn intracellular dynamics. Finally, we found that the molecular chaperone HSP70 accelerates the entry of aSyn into the nuclear compartment.
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Affiliation(s)
- Susana Gonçalves
- Cell and Molecular Neuroscience Unit, Instituto de Medicina Molecular, Av. Prof. Egas Moniz, 1649-028 Lisboa, Portugal
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77
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Caesar M, Zach S, Carlson CB, Brockmann K, Gasser T, Gillardon F. Leucine-rich repeat kinase 2 functionally interacts with microtubules and kinase-dependently modulates cell migration. Neurobiol Dis 2013; 54:280-8. [PMID: 23318930 DOI: 10.1016/j.nbd.2012.12.019] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 11/29/2012] [Accepted: 12/21/2012] [Indexed: 11/24/2022] Open
Abstract
Recent studies indicate that the Parkinson's disease-linked leucine-rich repeat kinase 2 (LRRK2) modulates cytoskeletal functions by regulating actin and tubulin dynamics, thereby affecting neurite outgrowth. By interactome analysis we demonstrate that the binding of LRRK2 to tubulins is significantly enhanced by pharmacological LRRK2 inhibition in cells. Co-incubation of LRRK2 with microtubules increased the LRRK2 GTPase activity in a cell-free assay. Destabilization of microtubules causes a rapid decrease in cellular LRRK2(S935) phosphorylation indicating a decreased LRRK2 kinase activity. Moreover, both human LRRK2(G2019S) fibroblasts and mouse LRRK2(R1441G) fibroblasts exhibit alterations in cell migration in culture. Treatment of mouse fibroblasts with the selective LRRK2 inhibitor LRRK2-IN1 reduces cell motility. These findings suggest that LRRK2 and microtubules mutually interact both in non-neuronal cells and in neurons, which might contribute to our understanding of its pathogenic effects in Parkinson's disease.
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Affiliation(s)
- Mareike Caesar
- Boehringer Ingelheim Pharma GmbH & Co. KG, CNS Diseases Research, 88397 Biberach an der Riss, Germany
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Szegő ÉM, Outeiro TF, Kermer P, Schulz JB. Impairment of the septal cholinergic neurons in MPTP-treated A30P α-synuclein mice. Neurobiol Aging 2012; 34:589-601. [PMID: 22579457 DOI: 10.1016/j.neurobiolaging.2012.04.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Revised: 03/28/2012] [Accepted: 04/21/2012] [Indexed: 01/09/2023]
Abstract
Dementia in Parkinson's disease (PDD) and dementia with Lewy bodies (DLB) are characterized by loss of acetylcholine (ACh) from cortical areas. Clinical studies report positive effects of acetylcholine esterase (AChE) inhibitors in PDD and dementia with Lewy bodies. We here report that the number of neurons expressing a cholinergic marker in the medial septum-diagonal band of Broca complex decreases in A30P α-synuclein-expressing mice during aging, paralleled by a lower AChE fiber density in the dentate gyrus and in the hippocampal CA1 field. After inducing dopamine depletion by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride (MPTP), no acute but a delayed loss of cholinergic neurons and AChE-positive fibers was observed, which was attenuated by L-3,4-dihydroxyphenylalanine (DOPA) treatment. Expression of nerve growth factor (NGF) and tyrosine receptor kinase A (TrkA) genes was upregulated in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride-treated wild type mice, but not in A30P α-synuclein expressing animals. In contrast, upregulation of sortilin and p75(NTR) genes was found in the A30P α-synuclein-expressing mice. These results suggest that dopamine deficiency may contribute to the impairment of the septohippocampal system in patients with PDD and that L-3,4-dihydroxyphenylalanine may not only result in symptomatic treatment of the akinetic-rigid syndrome but may also alleviate the degeneration of basal forebrain cholinergic system and the cognitive decline.
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Affiliation(s)
- Éva M Szegő
- Department of NeuroDegeneration and Restorative Research, Georg-August University, DFG Research Center, Molecular Physiology of Brain, Göttingen, Germany.
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79
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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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80
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Liu G, Aliaga L, Cai H. α-synuclein, LRRK2 and their interplay in Parkinson's disease. FUTURE NEUROLOGY 2012; 7:145-153. [PMID: 22563296 DOI: 10.2217/fnl.12.2] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Of the various genetic factors contributing to the pathogenesis of Parkinson's disease (PD), only mutations in α-synuclein (α-syn) and LRRK2 genes cause clinical and neuropathological phenotypes closely resembling the sporadic cases. Therefore, studying the pathophysiological functions of these two PD-related genes is particularly informative in understanding the underlying molecular pathogenic mechanism of the disease. PD-related missense and multiplication mutations in α-syn may cause both early- and late-onset PD, whereas various PD-related LRRK2 missense mutations may contribute to the more common late-onset PD. While intensive studies have been carried out to elucidate the pathogenic properties of PD-related mutant α-syn and LRRK2, our knowledge of their normal functions and their potential genetic interplay remains rudimental. In this review, we summarize the progress made regarding the pathophysiological functions of α-syn, LRRK2 and their interaction in PD, based on the available literature and our unpublished observations.
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Affiliation(s)
- Guoxiang Liu
- Transgenics Section, Laboratory of Neurogenetics, National Institute on Aging, National Institutes of Health, Bethesda, MD 20892, USA
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81
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Bellucci A, Navarria L, Falarti E, Zaltieri M, Bono F, Collo G, Spillantini MG, Missale C, Spano P. Redistribution of DAT/α-synuclein complexes visualized by "in situ" proximity ligation assay in transgenic mice modelling early Parkinson's disease. PLoS One 2011; 6:e27959. [PMID: 22163275 PMCID: PMC3233557 DOI: 10.1371/journal.pone.0027959] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2011] [Accepted: 10/28/2011] [Indexed: 01/09/2023] Open
Abstract
Alpha-synuclein, the major component of Lewy bodies, is thought to play a central role in the onset of synaptic dysfunctions in Parkinson's disease (PD). In particular, α-synuclein may affect dopaminergic neuron function as it interacts with a key protein modulating dopamine (DA) content at the synapse: the DA transporter (DAT). Indeed, recent evidence from our “in vitro” studies showed that α-synuclein aggregation decreases the expression and membrane trafficking of the DAT as the DAT is retained into α-synuclein-immunopositive inclusions. This notwithstanding, “in vivo” studies on PD animal models investigating whether DAT distribution is altered by the pathological overexpression and aggregation of α-synuclein are missing. By using the proximity ligation assay, a technique which allows the “in situ” visualization of protein-protein interactions, we studied the occurrence of alterations in the distribution of DAT/α-synuclein complexes in the SYN120 transgenic mouse model, showing insoluble α-synuclein aggregates into dopaminergic neurons of the nigrostriatal system, reduced striatal DA levels and an altered distribution of synaptic proteins in the striatum. We found that DAT/α-synuclein complexes were markedly redistributed in the striatum and substantia nigra of SYN120 mice. These alterations were accompanied by a significant increase of DAT striatal levels in transgenic animals when compared to wild type littermates. Our data indicate that, in the early pathogenesis of PD, α-synuclein acts as a fine modulator of the dopaminergic synapse by regulating the subcellular distribution of key proteins such as the DAT.
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Affiliation(s)
- Arianna Bellucci
- Division of Pharmacology, Department of Biomedical Sciences and Biotechnologies and National Institute of Neuroscience-Italy, School of Medicine, University of Brescia, Brescia, Italy.
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82
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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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83
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Szego ÉM, Gerhardt E, Kermer P, Schulz JB. A30P α-synuclein impairs dopaminergic fiber regeneration and interacts with L-DOPA replacement in MPTP-treated mice. Neurobiol Dis 2011; 45:591-600. [PMID: 22001606 DOI: 10.1016/j.nbd.2011.09.017] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 08/29/2011] [Accepted: 09/29/2011] [Indexed: 11/18/2022] Open
Abstract
Parkinson's disease (PD) is the most common neurodegenerative movement disorder and is characterized by the loss of dopaminergic neurons from the substantia nigra pars compacta (SNpc). α-synuclein (αsyn) has been linked to the pathophysiology of PD, because of its mutations causing familial PD and its accumulation in brains of patients with familial and sporadic PD. Dopamine (DA) replacement is the most effective therapy for ameliorating the motor symptoms of PD; however, it remains controversial whether DA-replacement boosts regeneration in the dopaminergic system or accelerates disease progression and enhances neuronal loss. Here, we studied the effect of chronic L-DOPA treatment on dopaminergic neurons in wild-type (WT) and A30P αsyn transgenic mice after MPTP treatment. Acute MPTP intoxication induced degeneration of dopaminergic neurons in both WT and A30P αsyn transgenic mice. A strong regeneration of dopaminergic fibers at 90 days after MPTP was observed in WT mice. In contrast, regeneration was less pronounced in A30P αsyn mice. Chronic L-DOPA treatment after MPTP intoxication did not only reduce the regeneration of nigrostriatal fibers but also led to an increased apoptotic gene-expression profile in the SNpc and to a decline of TH-positive neurons in A30P αsyn. Our findings reveal that the presence of A30P αsyn inhibits the regeneration of nigrostriatal dopaminergic fibers, and that L-DOPA treatment might interact with the pathogenesis in PD.
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Affiliation(s)
- Éva M Szego
- Department of Neurodegeneration and Restorative Research, Georg-August University, DFG Research Center: Molecular Physiology of the Brain (CMPB), Göttingen, 37073, Germany.
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84
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Elcoroaristizabal Martín X, Gómez Busto F, González Fernández MC, de Pancorbo MM. [Role of genetics in the etiology of synucleinopathies]. Rev Esp Geriatr Gerontol 2011; 46 Suppl 1:3-11. [PMID: 22152908 DOI: 10.1016/j.regg.2011.10.002] [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: 05/31/2023]
Abstract
The protein family known as synucleins is composed of α-, β- and γ-synuclein. The most widely studied is the α-synuclein protein due to its participation in essential processes of the central nervous system. Neurotoxicity of this protein is related to the presence of multiplications (duplications and triplications) and point mutations in the gene sequence of the α-synuclein gene (SNCA), differential expression of its isoforms and variations in post-transductional modifications. Neurotoxicity is also related to cytoplasmic inclusions known as Lewy bodies (LBs) and Lewy neurites (LNs), which are also present in α-synucleinopathies. In general, the β-synuclein protein, codified by the SNCB gene, acts as a regulator of processes triggered by α-synuclein and its function is altered by variations in the gene sequence, while γ-synuclein, codified by the SNCG gene, seems to play a major role in certain tumoral processes.
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Affiliation(s)
- Xabier Elcoroaristizabal Martín
- Grupo de Investigación BIOMICS, Departamento de Biología Celular A, Centro de Investigación y Estudios Avanzados Lucio Lascaray, Universidad del País Vasco UPV/EHU, Vitoria-Gasteiz, España
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85
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Bellani S, Sousa VL, Ronzitti G, Valtorta F, Meldolesi J, Chieregatti E. The regulation of synaptic function by alpha-synuclein. Commun Integr Biol 2011; 3:106-9. [PMID: 20585500 DOI: 10.4161/cib.3.2.10964] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2009] [Accepted: 12/17/2009] [Indexed: 11/19/2022] Open
Abstract
The cytosolic protein alpha-synuclein is enriched at the pre-synaptic terminals of almost all types of neurons in the central nervous system. alpha-Synuclein overexpression and the expression of three different mutants have been shown to sustain the pathogenesis of selected forms of Parkinson's disease. The localization of the protein and the defects found in knocked out or transgenic animals suggest a role of alpha-synuclein in the regulation of synaptic efficiency. However, the precise function of the protein and the molecular mechanisms of its action are still unclear. At synapses the synaptic vesicle release cycle is a finely tuned process composed of sequential steps that require the interconnected participation of several proteins and cytoskeletal elements. Actin microfilaments are required for the regulation of synaptic vesicle mobilization between different functional pools, for their organization at the active zone and influence the exocytotic process. We recently identified actin as a possible target of alpha-synuclein function. Through its binding to actin and the regulation of actin dynamics, alpha-synuclein could participate in the tuning of the vesicle release process, thereby modulating synaptic function and plasticity.
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86
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Parisiadou L, Cai H. LRRK2 function on actin and microtubule dynamics in Parkinson disease. Commun Integr Biol 2011; 3:396-400. [PMID: 21057624 DOI: 10.4161/cib.3.5.12286] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Accepted: 05/05/2010] [Indexed: 01/11/2023] Open
Abstract
The mutations in the LRRK2 gene cause clinically typical, late-onset Parkinson disease, strengthening the idea that the familial forms of the disease represent an important tool for the study of the idiopathic forms. Despite the great effort to describe and functionally characterize the LRRK2 gene product, its physiological role remains elusive. In this article, we will discuss along with other references, our recent findings that assigned a critical role of LRRK2 protein on cytosleketal dynamics and how this direction could provide a valuable platform to further appreciate the mechanism underlying LRRK2-mediated pathophysiology of the disease.
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Affiliation(s)
- Loukia Parisiadou
- Unit of Transgenesis; Laboratory of Neurogenetics; National Institute on Aging; National Institutes of Health; Bethesda, MD USA
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87
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Kang DE, Roh SE, Woo JA, Liu T, Bu JH, Jung AR, Lim Y. The Interface between Cytoskeletal Aberrations and Mitochondrial Dysfunction in Alzheimer's Disease and Related Disorders. Exp Neurobiol 2011; 20:67-80. [PMID: 22110363 PMCID: PMC3213703 DOI: 10.5607/en.2011.20.2.67] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Accepted: 05/17/2011] [Indexed: 01/19/2023] Open
Abstract
The major defining pathological hallmarks of Alzheimer's disease (AD) are the accumulations of Aβ in senile plaques and hyperphosphorylated tau in neurofibrillary tangles and neuropil threads. Recent studies indicate that rather than these insoluble lesions, the soluble Aβ oligomers and hyperphosphorylated tau are the toxic agents of AD pathology. Such pathological protein species are accompanied by cytoskeletal changes, mitochondrial dysfunction, Ca2+ dysregulation, and oxidative stress. In this review, we discuss how the binding of Aβ to various integrins, defects in downstream focal adhesion signaling, and activation of cofilin can impact mitochondrial dysfunction, cytoskeletal changes, and tau pathology induced by Aβ oligomers. Such pathological consequences can also feedback to further activate cofilin to promote cofilin pathology. We also suggest that the mechanism of Aβ generation by the endocytosis of APP is mechanistically linked with perturbations in integrin-based focal adhesion signaling, as APP, LRP, and β-integrins are physically associated with each other.
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Affiliation(s)
- David E Kang
- Department of Neurosciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
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88
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Kondo K, Obitsu S, Teshima R. .ALPHA.-Synuclein Aggregation and Transmission Are Enhanced by Leucine-Rich Repeat Kinase 2 in Human Neuroblastoma SH-SY5Y Cells. Biol Pharm Bull 2011; 34:1078-83. [DOI: 10.1248/bpb.34.1078] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Kazunari Kondo
- Division of Novel Foods and Immunochemistry, National Institute of Health Sciences
| | - Saemi Obitsu
- Division of Novel Foods and Immunochemistry, National Institute of Health Sciences
| | - Reiko Teshima
- Division of Novel Foods and Immunochemistry, National Institute of Health Sciences
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89
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Alberio T, Bossi AM, Milli A, Parma E, Gariboldi MB, Tosi G, Lopiano L, Fasano M. Proteomic analysis of dopamine and α-synuclein interplay in a cellular model of Parkinson’s disease pathogenesis. FEBS J 2010; 277:4909-19. [DOI: 10.1111/j.1742-4658.2010.07896.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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90
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Gauthier A, Brandt R. Live cell imaging of cytoskeletal dynamics in neurons using fluorescence photoactivation. Biol Chem 2010; 391:639-43. [PMID: 20370315 DOI: 10.1515/bc.2010.060] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Alzheimer's disease and other neurodegenerative disorders share some common features at the cellular level, which are often associated with a change in cytoskeletal dynamics. Live cell imaging has been applied to study various aspects of cell physiology including cytoskeletal dynamics. Recently, fluorescence photoactivation (FPA) has been developed as a novel approach to analyze protein dynamics in living cells with high sensitivity. Here, we describe the application of FPA to determine interactions and mobility of the microtubule-associated protein tau in neurons as an example for a disease-related cytoskeletal protein and discuss further applications of FPA to study cytoskeletal dynamics in neurodegenerative diseases.
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Affiliation(s)
- Anne Gauthier
- Department of Neurobiology, University of Osnabrück, Barbarastrasse 11, D-49076 Osnabrück, Germany
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91
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A pathologic cascade leading to synaptic dysfunction in alpha-synuclein-induced neurodegeneration. J Neurosci 2010; 30:8083-95. [PMID: 20554859 DOI: 10.1523/jneurosci.1091-10.2010] [Citation(s) in RCA: 250] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Several neurodegenerative diseases are typified by intraneuronal alpha-synuclein deposits, synaptic dysfunction, and dementia. While even modest alpha-synuclein elevations can be pathologic, the precise cascade of events induced by excessive alpha-synuclein and eventually culminating in synaptotoxicity is unclear. To elucidate this, we developed a quantitative model system to evaluate evolving alpha-synuclein-induced pathologic events with high spatial and temporal resolution, using cultured neurons from brains of transgenic mice overexpressing fluorescent-human-alpha-synuclein. Transgenic alpha-synuclein was pathologically altered over time and overexpressing neurons showed striking neurotransmitter release deficits and enlarged synaptic vesicles; a phenotype reminiscent of previous animal models lacking critical presynaptic proteins. Indeed, several endogenous presynaptic proteins involved in exocytosis and endocytosis were undetectable in a subset of transgenic boutons ("vacant synapses") with diminished levels in the remainder, suggesting that such diminutions were triggering the overall synaptic pathology. Similar synaptic protein alterations were also retrospectively seen in human pathologic brains, highlighting potential relevance to human disease. Collectively the data suggest a previously unknown cascade of events where pathologic alpha-synuclein leads to a loss of a number of critical presynaptic proteins, thereby inducing functional synaptic deficits.
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92
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Alpha-synuclein sequesters arachidonic acid to modulate SNARE-mediated exocytosis. EMBO Rep 2010; 11:528-33. [PMID: 20489724 DOI: 10.1038/embor.2010.66] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Revised: 03/22/2010] [Accepted: 04/14/2010] [Indexed: 01/06/2023] Open
Abstract
Alpha-synuclein is a synaptic modulatory protein implicated in the pathogenesis of Parkinson disease. The precise functions of this small cytosolic protein are still under investigation. alpha-Synuclein has been proposed to regulate soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins involved in vesicle fusion. Interestingly, alpha-synuclein fails to interact with SNARE proteins in conventional protein-binding assays, thus suggesting an indirect mode of action. As the structural and functional properties of both alpha-synuclein and the SNARE proteins can be modified by arachidonic acid, a common lipid regulator, we analysed this possible tripartite link in detail. Here, we show that the ability of arachidonic acid to stimulate SNARE complex formation and exocytosis can be controlled by alpha-synuclein, both in vitro and in vivo. Alpha-synuclein sequesters arachidonic acid and thereby blocks the activation of SNAREs. Our data provide mechanistic insights into the action of alpha-synuclein in the modulation of neurotransmission.
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93
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Sun F, Cavalli V. Neuroproteomics approaches to decipher neuronal regeneration and degeneration. Mol Cell Proteomics 2010; 9:963-75. [PMID: 20019051 PMCID: PMC2871427 DOI: 10.1074/mcp.r900003-mcp200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Revised: 12/14/2009] [Indexed: 01/02/2023] Open
Abstract
Given the complexity of brain and nerve tissues, systematic approaches are essential to understand normal physiological conditions and functional alterations in neurological diseases. Mass spectrometry-based proteomics is increasingly used in neurosciences to determine both basic and clinical differential protein expression, protein-protein interactions, and post-translational modifications. Proteomics approaches are especially useful to understand the mechanisms of nerve regeneration and degeneration because changes in axons following injury or in disease states often occur without the contribution of transcriptional events in the cell body. Indeed, the current understanding of axonal function in health and disease emphasizes the role of proteolysis, local axonal protein synthesis, and a broad range of post-translational modifications. Deciphering how axons regenerate and degenerate has thus become a postgenomics problem, which depends in part on proteomics approaches. This review focuses on recent proteomics approaches designed to uncover the mechanisms and molecules involved in neuronal regeneration and degeneration. It emerges that the principal degenerative mechanisms converge to oxidative stress, dysfunctions of axonal transport, mitochondria, chaperones, and the ubiquitin-proteasome systems. The mechanisms regulating nerve regeneration also impinge on axonal transport, cytoskeleton, and chaperones in addition to changes in signaling pathways. We also discuss the major challenges to proteomics work in the nervous system given the complex organization of the brain and nerve tissue at the anatomical, cellular, and subcellular levels.
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Affiliation(s)
- Faneng Sun
- From the Department of Anatomy and Neurobiology, Washington University, St. Louis, Missouri 63110
| | - Valeria Cavalli
- From the Department of Anatomy and Neurobiology, Washington University, St. Louis, Missouri 63110
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94
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Reduced expression of peroxisome-proliferator activated receptor gamma coactivator-1alpha enhances alpha-synuclein oligomerization and down regulates AKT/GSK3beta signaling pathway in human neuronal cells that inducibly express alpha-synuclein. Neurosci Lett 2010; 473:120-5. [PMID: 20178833 DOI: 10.1016/j.neulet.2010.02.034] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2009] [Revised: 02/05/2010] [Accepted: 02/15/2010] [Indexed: 02/03/2023]
Abstract
Intracellular accumulation of filamentous alpha-synuclein (alpha-Syn) aggregates to form Lewy bodies is a pathologic hallmark of Parkinson's disease. To determine whether mitochondrial impairment plays a role in the accumulation of alpha-Syn oligomer, we used 3D5 cell culture model of human neuronal type whereby conditional overexpression of wild-type alpha-Syn via the tetracycline-off (TetOff) induction mechanism results in formation of inclusions that exhibit many characteristics of Lewy bodies. In the present study, we compromised mitochondrial function in 3D5 cells by using shRNA to knockdown peroxisome-proliferator activated receptor gamma coactivator-1alpha (PGC-1alpha), a key regulator of mitochondrial biogenesis and cellular energy metabolism and found that PGC-1alpha suppression at both protein and mRNA levels results in alpha-Syn accumulation (i.e. monomeric and oligomeric species in the TetOff-induced cells and monomeric only in the non-induced). These changes were accompanied with reduced mitochondrial potential as well as decreased levels of AKT, GSK3beta (total and Ser(9)-phosphorylated) and p53 that are important for cell survival. The extent to which these proteins decreased following PGC-1alpha knockdown, in contrast to what was demonstrable with the viability assay, is greater in the induced than the non-induced. Together these findings indicate that such knockdown increases the propensity to accumulate alpha-Syn oligomers, but the accumulation appears to have very little toxic impact to the neuronal cells.
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