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Marino G, Calabresi P, Ghiglieri V. Alpha-synuclein and cortico-striatal plasticity in animal models of Parkinson disease. HANDBOOK OF CLINICAL NEUROLOGY 2022; 184:153-166. [PMID: 35034731 DOI: 10.1016/b978-0-12-819410-2.00008-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Alpha-synuclein (α-synuclein) is a small, acidic protein containing 140 amino acids, highly expressed in the brain and primarily localized in the presynaptic terminals. It is found in high concentrations in Lewy Bodies, proteinaceous aggregates that constitute a typical histopathologic hallmark of Parkinson's disease. Altered environmental conditions, genetic mutations and post-translational changes can trigger abnormal aggregation processes with the increased frequency of oligomers, protofibrils, and fibrils formation that perturbs the neuronal homeostasis leading to cell death. Relevant to neuronal activity, a function of α-synuclein that has been extensively detailed is its regulatory actions in the trafficking of synaptic vesicles, including the processes of exocytosis, endocytosis and neurotransmitter release. Most recently, increasing attention has been paid to the possible role that α-synuclein plays at a postsynaptic level by interacting with selective subunits of the glutamate N-methyl-d-aspartate receptor, altering the corticostriatal plasticity of distinct neuronal populations.
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Affiliation(s)
- Gioia Marino
- Dipartimento di Neuroscienze, Università Cattolica del Sacro Cuore, Rome, Italy; Dipartimento di Medicina, Università degli Studi di Perugia, Perugia, Italy
| | - Paolo Calabresi
- Dipartimento di Neuroscienze, Università Cattolica del Sacro Cuore, Rome, Italy; UOC Neurologia, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, Rome, Italy
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2
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Ismael S, Sindi G, Colvin RA, Lee D. Activity-dependent release of phosphorylated human tau from Drosophila neurons in primary culture. J Biol Chem 2021; 297:101108. [PMID: 34473990 PMCID: PMC8455371 DOI: 10.1016/j.jbc.2021.101108] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Revised: 08/11/2021] [Accepted: 08/19/2021] [Indexed: 11/23/2022] Open
Abstract
Neuronal activity can enhance tau release and thus accelerate tauopathies. This activity-dependent tau release can be used to study the progression of tau pathology in Alzheimer's disease (AD), as hyperphosphorylated tau is implicated in AD pathogenesis and related tauopathies. However, our understanding of the mechanisms that regulate activity-dependent tau release from neurons and the role that tau phosphorylation plays in modulating activity-dependent tau release is still rudimentary. In this study, Drosophila neurons in primary culture expressing human tau (hTau) were used to study activity-dependent tau release. We found that hTau release was markedly increased by 50 mM KCl treatment for 1 h. A similar level of release was observed using optogenetic techniques, where genetically targeted neurons were stimulated for 30 min using blue light (470 nm). Our results showed that activity-dependent release of phosphoresistant hTauS11A was reduced when compared with wildtype hTau. In contrast, release of phosphomimetic hTauE14 was increased upon activation. We found that released hTau was phosphorylated in its proline-rich and C-terminal domains using phosphorylation site-specific tau antibodies (e.g., AT8). Fold changes in detectable levels of total or phosphorylated hTau in cell lysates or following immunopurification from conditioned media were consistent with preferential release of phosphorylated hTau after light stimulation. This study establishes an excellent model to investigate the mechanism of activity-dependent hTau release and to better understand the role of phosphorylated tau release in the pathogenesis of AD since it relates to alterations in the early stage of neurodegeneration associated with increased neuronal activity.
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Affiliation(s)
- Sazan Ismael
- Neuroscience Program, Department of Biological Sciences, and Molecular and Cellular Biology Interdisciplinary Graduate Program, Ohio University, Athens, Ohio, USA
| | - Ghadir Sindi
- Neuroscience Program, Department of Biological Sciences, and Molecular and Cellular Biology Interdisciplinary Graduate Program, Ohio University, Athens, Ohio, USA
| | - Robert A Colvin
- Neuroscience Program, Department of Biological Sciences, and Molecular and Cellular Biology Interdisciplinary Graduate Program, Ohio University, Athens, Ohio, USA
| | - Daewoo Lee
- Neuroscience Program, Department of Biological Sciences, and Molecular and Cellular Biology Interdisciplinary Graduate Program, Ohio University, Athens, Ohio, USA.
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3
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Blosser JA, Podolsky E, Lee D. L-DOPA-Induced Dyskinesia in a Genetic Drosophila Model of Parkinson's Disease. Exp Neurobiol 2020; 29:273-284. [PMID: 32921640 PMCID: PMC7492844 DOI: 10.5607/en20028] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2020] [Revised: 08/27/2020] [Accepted: 08/31/2020] [Indexed: 01/05/2023] Open
Abstract
Motor symptoms in Parkinson’s disease (PD) are directly related to the reduction of a neurotransmitter dopamine. Therefore, its precursor L-DOPA became the gold standard for PD treatment. However, chronic use of L-DOPA causes uncontrollable, involuntary movements, called L-DOPA-induced dyskinesia (LID) in the majority of PD patients. LID is complicated and very difficult to manage. Current rodent and non-human primate models have been developed to study LID mainly using neurotoxins. Therefore, it is necessary to develop a LID animal model with defects in genetic factors causing PD in order to study the relation between LID and PD genes such as α-synuclein. In this study, we first showed that a low concentration of L-DOPA (100 µM) rescues locomotion defects (i.e., speed, angular velocity, pause time) in Drosophila larvae expressing human mutant α-synuclein (A53T). This A53T larval model of PD was used to further examine dyskinetic behaviors. High concentrations of L-DOPA (5 or 10 mM) causes hyperactivity such as body bending behavior (BBB) in A53T larva, which resembles axial dyskinesia in rodents. Using ImageJ plugins and other third party software, dyskinetic BBB has been accurately and efficiently quantified. Further, we showed that a dopamine agonist pramipexole (PRX) partially rescues BBB caused by high L-DOPA. Our Drosophila genetic LID model will provide an important experimental platform to examine molecular and cellular mechanisms underlying LID, to study the role of PD causing genes in the development of LID, and to identify potential targets to slow/reverse LID pathology.
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Affiliation(s)
- Joshua A Blosser
- Neuroscience Program, Department of Biological Sciences, Ohio University, Athens, OH 45701, USA
| | - Eric Podolsky
- Neuroscience Program, Department of Biological Sciences, Ohio University, Athens, OH 45701, USA
| | - Daewoo Lee
- Neuroscience Program, Department of Biological Sciences, Ohio University, Athens, OH 45701, USA
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Wang L, Yang H, Wang Q, Zhang Q, Wang Z, Zhang Q, Wu S, Li H. Paraquat and MPTP induce alteration in the expression profile of long noncoding RNAs in the substantia nigra of mice: Role of the transcription factor Nrf2. Toxicol Lett 2018; 291:11-28. [PMID: 29627306 DOI: 10.1016/j.toxlet.2018.04.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 04/01/2018] [Accepted: 04/03/2018] [Indexed: 11/27/2022]
Abstract
Parkinson's disease (PD) is a common age-related degenerative disease of the central nervous system caused mainly by hereditary, pesticides, metals, and polychlorinated biphenyls. Paraquat (PQ), a widely used herbicide, causes PD. Long noncoding RNAs (lncRNAs) are nonprotein-coding transcripts, expressed in the brain and play irreplaceable roles in neurodegenerative diseases. NF-E2-related factor-2 (Nrf2) is an important genetic transcription regulator in oxidative stress. We aimed to discover novel PQ or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-Nrf2-related lncRNAs and explore their association with PD. 17157 lncRNAs and 13707 mRNAs (fold change ≥2, P < 0.05) were identified by Microarray. And the expressions of six lncRNAs were confirmed by using qRT-PCR and two by FISH. Coding-noncoding analysis and qRT-PCR were applied to discover the functions of lncRNAs and predict the targeted genes. In mice, PQ and MPTP exposure caused alteration of the lncRNA expression profile, suggesting lncRNAs may be involved in PQ- and MPTP-induced neurotoxicity. The changes in their lncRNA expression were distinct but related. PQ caused lncRNA expression profiling alteration in the substantia nigra (SN) through an interaction with Nrf2, thus changing the NR_027648/Zc3h14/Cybb and NR_030777/Zfp326/Cpne5 mRNA pathways. Similarly, MPTP caused lncRNA expression profiling alteration in SN through an interaction with Nrf2. Nrf2 may be involved in the development of neurodegeneration induced by PQ and MPTP via interaction with lncRNAs as the molecular mechanism. Our findings indicate the potential roles of lncRNAs in the development of PD by PQ or MPTP and provide positive insights into future mechanism studies.
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Affiliation(s)
- Lijin Wang
- Department of Preventive Medicine, Fujian Provincial Key Laboratory of Environment Factors and Cancer, School of Public Health, Fujian Medical University, Fuzhou 350122, China; Department of Endemic Disease Prevention and Control, Fujian Center For Disease Control & Prevention, Fuzhou 350122, China
| | - Hongyu Yang
- Department of Preventive Medicine, Fujian Provincial Key Laboratory of Environment Factors and Cancer, School of Public Health, Fujian Medical University, Fuzhou 350122, China
| | - Qingqing Wang
- Department of Preventive Medicine, Fujian Provincial Key Laboratory of Environment Factors and Cancer, School of Public Health, Fujian Medical University, Fuzhou 350122, China
| | - Qiaohui Zhang
- Department of Preventive Medicine, Fujian Provincial Key Laboratory of Environment Factors and Cancer, School of Public Health, Fujian Medical University, Fuzhou 350122, China
| | - Zhangjing Wang
- Department of Preventive Medicine, Fujian Provincial Key Laboratory of Environment Factors and Cancer, School of Public Health, Fujian Medical University, Fuzhou 350122, China
| | - Qunwei Zhang
- Department of Preventive Medicine, Fujian Provincial Key Laboratory of Environment Factors and Cancer, School of Public Health, Fujian Medical University, Fuzhou 350122, China; Department of Environmental and Occupational Health Sciences, University of Louisville, 485 E. Gray Street, Louisville, KY 40202, USA
| | - Siying Wu
- Department of Epidemiology and Health Statistics, The Key Laboratory of Environment and Health, School of Public Health, Fujian Medical University, Fuzhou 350122, China.
| | - Huangyuan Li
- Department of Preventive Medicine, Fujian Provincial Key Laboratory of Environment Factors and Cancer, School of Public Health, Fujian Medical University, Fuzhou 350122, China.
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Steiner JA, Quansah E, Brundin P. The concept of alpha-synuclein as a prion-like protein: ten years after. Cell Tissue Res 2018; 373:161-173. [PMID: 29480459 DOI: 10.1007/s00441-018-2814-1] [Citation(s) in RCA: 118] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 01/29/2018] [Indexed: 12/18/2022]
Abstract
Parkinson's disease is characterized by the loss of nigrostriatal dopaminergic signaling and the presence of alpha-synuclein aggregates (also called Lewy bodies and neurites) throughout the brain. In 2003, Braak and colleagues created a staging system for Parkinson's disease describing the connection between the alpha-synuclein pathology and disease severity. Later, they suggested that the pathology might initially be triggered by exogenous insults targeting the gut and olfactory system. In 2008, we and other groups documented Lewy pathology in grafted neurons in people with Parkinson's disease who had been transplanted over a decade prior to autopsy. We proposed that the Lewy pathology in the grafted neurons was the result of permissive templating or prion-like spread of alpha-synuclein pathology from neurons in the host to those in the grafts. During the following ten years, several studies described the transmission of alpha-synuclein pathology between neurons, both in cell culture and in experimental animals. Recent research has also begun to identify underlying molecular mechanisms. Collectively, these experimental studies tentatively support the idea that the progression from one Braak stage to the next is the consequence of prion-like propagation of Lewy pathology. However, definitive proof that intercellular propagation of alpha-synuclein pathology occurs in Parkinson's disease cases has proven difficult to secure. In this review, we highlight several open questions that currently prevent us from concluding with certainty that prion-like transfer of alpha-synuclein contributes to the progression of Parkinson's disease.
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Affiliation(s)
- Jennifer A Steiner
- Center for Neurodegenerative Science, Van Andel Research Institute, 333 Bostwick Ave. NE, Grand Rapids, MI, 49503, USA.
| | - Emmanuel Quansah
- Center for Neurodegenerative Science, Van Andel Research Institute, 333 Bostwick Ave. NE, Grand Rapids, MI, 49503, USA
| | - Patrik Brundin
- Center for Neurodegenerative Science, Van Andel Research Institute, 333 Bostwick Ave. NE, Grand Rapids, MI, 49503, USA
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Akan I, Olivier-Van Stichelen S, Bond MR, Hanover JA. Nutrient-driven O-GlcNAc in proteostasis and neurodegeneration. J Neurochem 2017; 144:7-34. [PMID: 29049853 DOI: 10.1111/jnc.14242] [Citation(s) in RCA: 55] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2017] [Revised: 09/28/2017] [Accepted: 10/11/2017] [Indexed: 12/14/2022]
Abstract
Proteostasis is essential in the mammalian brain where post-mitotic cells must function for decades to maintain synaptic contacts and memory. The brain is dependent on glucose and other metabolites for proper function and is spared from metabolic deficits even during starvation. In this review, we outline how the nutrient-sensitive nucleocytoplasmic post-translational modification O-linked N-acetylglucosamine (O-GlcNAc) regulates protein homeostasis. The O-GlcNAc modification is highly abundant in the mammalian brain and has been linked to proteopathies, including neurodegenerative diseases such as Alzheimer's, Parkinson's, and Huntington's. C. elegans, Drosophila, and mouse models harboring O-GlcNAc transferase- and O-GlcNAcase-knockout alleles have helped define the role O-GlcNAc plays in development as well as age-associated neurodegenerative disease. These enzymes add and remove the single monosaccharide from protein serine and threonine residues, respectively. Blocking O-GlcNAc cycling is detrimental to mammalian brain development and interferes with neurogenesis, neural migration, and proteostasis. Findings in C. elegans and Drosophila model systems indicate that the dynamic turnover of O-GlcNAc is critical for maintaining levels of key transcriptional regulators responsible for neurodevelopment cell fate decisions. In addition, pathways of autophagy and proteasomal degradation depend on a transcriptional network that is also reliant on O-GlcNAc cycling. Like the quality control system in the endoplasmic reticulum which uses a 'mannose timer' to monitor protein folding, we propose that cytoplasmic proteostasis relies on an 'O-GlcNAc timer' to help regulate the lifetime and fate of nuclear and cytoplasmic proteins. O-GlcNAc-dependent developmental alterations impact metabolism and growth of the developing mouse embryo and persist into adulthood. Brain-selective knockout mouse models will be an important tool for understanding the role of O-GlcNAc in the physiology of the brain and its susceptibility to neurodegenerative injury.
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Affiliation(s)
- Ilhan Akan
- Laboratory of Cell and Molecular Biology, NIDDK, National Institutes of Health, Bethesda, Maryland, USA
| | | | - Michelle R Bond
- Laboratory of Cell and Molecular Biology, NIDDK, National Institutes of Health, Bethesda, Maryland, USA
| | - John A Hanover
- Laboratory of Cell and Molecular Biology, NIDDK, National Institutes of Health, Bethesda, Maryland, USA
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Zhao J, Liang Q, Sun Q, Chen C, Xu L, Ding Y, Zhou P. (−)-Epigallocatechin-3-gallate (EGCG) inhibits fibrillation, disaggregates amyloid fibrils of α-synuclein, and protects PC12 cells against α-synuclein-induced toxicity. RSC Adv 2017. [DOI: 10.1039/c7ra03752j] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
EGCG protects transduced PC12 cells against α-Syn-induced cytotoxicity by inhibiting the overexpression and fibrillation of α-Syn in the cells.
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Affiliation(s)
- Juan Zhao
- State Key Laboratory of Molecular Engineering of Polymers
- Department of Macromolecular Science
- Fudan University
- Shanghai 200433
- China
| | - Qingnan Liang
- Department of Physiology and Biophysics
- School of Life Sciences
- Fudan University
- Shanghai 200438
- China
| | - Qing Sun
- State Key Laboratory of Molecular Engineering of Polymers
- Department of Macromolecular Science
- Fudan University
- Shanghai 200433
- China
| | - Congheng Chen
- State Key Laboratory of Molecular Engineering of Polymers
- Department of Macromolecular Science
- Fudan University
- Shanghai 200433
- China
| | - Lihui Xu
- State Key Laboratory of Molecular Engineering of Polymers
- Department of Macromolecular Science
- Fudan University
- Shanghai 200433
- China
| | - Yu Ding
- Department of Physiology and Biophysics
- School of Life Sciences
- Fudan University
- Shanghai 200438
- China
| | - Ping Zhou
- State Key Laboratory of Molecular Engineering of Polymers
- Department of Macromolecular Science
- Fudan University
- Shanghai 200433
- China
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8
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Wiemerslage L, Ismael S, Lee D. Early alterations of mitochondrial morphology in dopaminergic neurons from Parkinson's disease-like pathology and time-dependent neuroprotection with D2 receptor activation. Mitochondrion 2016; 30:138-47. [PMID: 27423787 DOI: 10.1016/j.mito.2016.07.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 06/07/2016] [Accepted: 07/12/2016] [Indexed: 01/09/2023]
Abstract
Neuroprotection, to prevent vulnerable cell populations from dying, is perhaps the main strategy for treating Parkinson's disease (PD). Yet in clinical practice, therapy is introduced after the disease is well established and many neurons have already disappeared, while experimentally, treatment is typically added at the same time that PD pathology is instigated. This study uses an already established Drosophila melanogaster model of PD to test for early markers of neurodegeneration and if those markers are reversible following neuroprotective treatment. Specifically, we treat primary neuronal cultures with the neurotoxin 1-methyl-4-phenylpyridinium (MPP(+)) and track neuritic, dopaminergic mitochondria over time, observing a fragmenting change in their morphology before cell death. We then add a neuroprotective treatment (quinpirole, a D2 receptor agonist) at different timepoints to determine if the changes in mitochondrial morphology are reversible. We find that neuroprotective treatment must be added concomitantly to prevent changes in mitochondrial morphology and subsequent cell death. This work further supports Drosophila's use as a model organism and mitochondria's use as a biomarker for neurodegenerative disease. But mainly, this work highlights an import factor for experiments in neuroprotection - time of treatment. Our results highlight the problem that current neuroprotective treatments for PD may not be used the same way that they are tested experimentally.
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Affiliation(s)
- Lyle Wiemerslage
- Uppsala University, Department of Neuroscience, Functional Pharmacology, Biomedicinska Centrum, Husargatan 3, Box 593, 75124 Uppsala, Sweden.
| | - Sazan Ismael
- Ohio University, Neuroscience Program, Department of Biological Sciences, Athens, OH 45701, United States
| | - Daewoo Lee
- Ohio University, Neuroscience Program, Department of Biological Sciences, Athens, OH 45701, United States
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Wiemerslage L, Lee D. Quantification of mitochondrial morphology in neurites of dopaminergic neurons using multiple parameters. J Neurosci Methods 2016; 262:56-65. [PMID: 26777473 DOI: 10.1016/j.jneumeth.2016.01.008] [Citation(s) in RCA: 99] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Revised: 12/12/2015] [Accepted: 01/02/2016] [Indexed: 11/28/2022]
Abstract
BACKGROUND Studies of mitochondrial morphology vary in techniques. Most use one morphological parameter while others describe mitochondria qualitatively. Because mitochondria are so dynamic, a single parameter does not capture the true state of the network and may lead to erroneous conclusions. Thus, a gestalt method of analysis is warranted. NEW METHOD This work describes a method combining immunofluorescence assays with computerized image analysis to measure the mitochondrial morphology within neuritic projections of a specific population of neurons. Six parameters of mitochondrial morphology were examined utilizing ImageJ to analyze colocalized signals. RESULTS Using primary neuronal cultures from Drosophila, we tested mitochondrial morphology in neurites of dopaminergic (DA) neurons. We validate our model using mutants with known defects in mitochondrial morphology. Furthermore, we show a difference in mitochondrial morphology between cells treated as control or with a neurotoxin inducing PD (Parkinson's Disease in humans)-like pathology. We also show interactions between morphological parameters and experimental treatment. COMPARISON WITH EXISTING METHODS Our method is a significant improvement of previously described methods. Six morphometric parameters are quantified, providing a gestalt analysis of mitochondrial morphology. Also it can target specific populations of mitochondria using immunofluorescence assay and image analysis. CONCLUSIONS We found that our method adequately detects differences in mitochondrial morphology between treatment groups. We conclude that some parameters may be unique to a mutation or a disease state, and the relationship between parameters is altered by experimental treatment. We suggest at least four variables should be considered when using mitochondrial structure as an experimental endpoint.
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Affiliation(s)
- Lyle Wiemerslage
- Functional Pharmacology, Department of Neuroscience, Biomedicinska Centrum, Uppsala University, Husargatan 3, Box 593, 75124 Uppsala, Sweden.
| | - Daewoo Lee
- Neuroscience Program, Department of Biological Sciences, Ohio University, Athens, OH 45701, United States.
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Role of Drosophila calcium channel cacophony in dopaminergic neurodegeneration and neuroprotection. Neurosci Lett 2015; 584:342-6. [DOI: 10.1016/j.neulet.2014.11.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 10/17/2014] [Accepted: 11/04/2014] [Indexed: 12/30/2022]
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Parkinson's disease as a member of Prion-like disorders. Virus Res 2014; 207:38-46. [PMID: 25456401 DOI: 10.1016/j.virusres.2014.10.016] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 09/29/2014] [Accepted: 10/14/2014] [Indexed: 12/21/2022]
Abstract
Parkinson's disease is one of several neurodegenerative diseases associated with a misfolded, aggregated and pathological protein. In Parkinson's disease this protein is alpha-synuclein and its neuronal deposits in the form of Lewy bodies are considered a hallmark of the disease. In this review we describe the clinical and experimental data that have led to think of alpha-synuclein as a prion-like protein and we summarize data from in vitro, cellular and animal models supporting this view.
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Varga SJ, Qi C, Podolsky E, Lee D. A new Drosophila model to study the interaction between genetic and environmental factors in Parkinson's disease. Brain Res 2014; 1583:277-86. [PMID: 25130663 DOI: 10.1016/j.brainres.2014.08.021] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Revised: 08/08/2014] [Accepted: 08/09/2014] [Indexed: 12/21/2022]
Abstract
The fruit fly Drosophila melanogaster has long been used as a model organism for human diseases, including Parkinson׳s disease (PD). Its short lifespan, simple maintenance, and the widespread availability of genetic tools allow researchers to study disease mechanisms as well as potential drug therapies. Many different PD models have already been developed, including ones utilizing mutated α-Syn and chronic exposure to rotenone. However, few animal models have been used to study interaction between the PD causing factors. In this study, we developed a new model of PD for use in the larval stage in order to study interaction between genetic and environmental factors. First, the 3rd instar larvae (90-94 hours after egg laying) expressing a mutated form of human α-Syn (A53T) in dopaminergic (DA) neurons were video-taped and quantified for locomotion (e.g. crawling pattern and speed) using ImageJ software. A53T mutant larvae showed locomotion deficits and also loss of DA neurons in age-dependent manner. Similarly, larvae chronically exposed to rotenone (10 μM in food) showed age-dependent decline in locomotion accompanied by loss of DA neurons. We further show that combining the two models, by exposing A53T mutant larvae to rotenone, causes a much more severe PD phenotype (i.e. locomotor deficit). Our finding shows interaction between genetic and environmental factors underlying development of PD symptoms. This model can be used to further study mechanisms underlying the interaction between genes and different environmental PD factors, as well as to explore potential therapies for PD treatment.
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Affiliation(s)
- Scott J Varga
- Neuroscience Program, Department of Biological Sciences, Ohio University, Athens, OH 45701, USA
| | - Cheng Qi
- Neuroscience Program, Department of Biological Sciences, Ohio University, Athens, OH 45701, USA
| | - Eric Podolsky
- Neuroscience Program, Department of Biological Sciences, Ohio University, Athens, OH 45701, USA
| | - Daewoo Lee
- Neuroscience Program, Department of Biological Sciences, Ohio University, Athens, OH 45701, USA.
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The neuroprotective effect of human uncoupling protein 2 (hUCP2) requires cAMP-dependent protein kinase in a toxin model of Parkinson's disease. Neurobiol Dis 2014; 69:180-91. [PMID: 24965893 DOI: 10.1016/j.nbd.2014.05.032] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2013] [Revised: 05/06/2014] [Accepted: 05/26/2014] [Indexed: 11/20/2022] Open
Abstract
Parkinson's disease (PD), caused by selective loss of dopaminergic (DA) neurons in the substantia nigra, is the most common movement disorder with no cure or effective treatment. Exposure to the mitochondrial complex I inhibitor rotenone recapitulates pathological hallmarks of PD in rodents and selective loss of DA neurons in Drosophila. However, mechanisms underlying rotenone toxicity are not completely resolved. We previously reported a neuroprotective effect of human uncoupling protein 2 (hUCP2) against rotenone toxicity in adult fly DA neurons. In the current study, we show that increased mitochondrial fusion is protective from rotenone toxicity whereas increased fission sensitizes the neurons to rotenone-induced cell loss in vivo. In primary DA neurons, rotenone-induced mitochondrial fragmentation and lethality is attenuated as the result of hucp2 expression. To test the idea that the neuroprotective mechanism of hUCP2 involves modulation of mitochondrial dynamics, we detect preserved mitochondrial network, mobility and fusion events in hucp2 expressing DA neurons exposed to rotenone. hucp2 expression also increases intracellular cAMP levels. Thus, we hypothesize that cAMP-dependent protein kinase (PKA) might be an effector that mediates hUCP2-associated neuroprotection against rotenone. Indeed, PKA inhibitors block preserved mitochondrial integrity, movement and cell survival in hucp2 expressing DA neurons exposed to rotenone. Taken together, we present strong evidence identifying a hUCP2-PKA axis that controls mitochondrial dynamics and survival in DA neurons exposed to rotenone implicating a novel therapeutic strategy in modifying the progression of PD pathogenesis.
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Wiemerslage L, Schultz BJ, Ganguly A, Lee D. Selective degeneration of dopaminergic neurons by MPP(+) and its rescue by D2 autoreceptors in Drosophila primary culture. J Neurochem 2013; 126:529-40. [PMID: 23452092 DOI: 10.1111/jnc.12228] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 01/10/2013] [Accepted: 02/14/2013] [Indexed: 11/29/2022]
Abstract
Drosophila melanogaster is widely used to study genetic factors causing Parkinson's disease (PD) largely because of the use of sophisticated genetic approaches and the presence of a high conservation of gene sequence/function between Drosophila and mammals. However, in Drosophila, little has been done to study the environmental factors which cause over 90% of PD cases. We used Drosophila primary neuronal culture to study degenerative effects of a well-known PD toxin MPP(+) . Dopaminergic (DA) neurons were selectively degenerated by MPP(+) , whereas cholinergic and GABAergic neurons were not affected. This DA neuronal loss was because of post-mitotic degeneration, not by inhibition of DA neuronal differentiation. We also found that MPP(+) -mediated neurodegeneration was rescued by D2 agonists quinpirole and bromocriptine. This rescue was through activation of Drosophila D2 receptor DD2R, as D2 agonists failed to rescue MPP(+) -toxicity in neuronal cultures prepared from both a DD2R deficiency line and a transgenic line pan-neuronally expressing DD2R RNAi. Furthermore, DD2R autoreceptors in DA neurons played a critical role in the rescue. When DD2R RNAi was expressed only in DA neurons, MPP(+) toxicity was not rescued by D2 agonists. Our study also showed that rescue of DA neurodegeneration by Drosophila DD2R activation was mediated through suppression of action potentials in DA neurons.
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Affiliation(s)
- Lyle Wiemerslage
- Neuroscience Program, Department of Biological Sciences, Ohio University, Athens, Ohio 45701, USA
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Ganguly A, Lee D. Suppression of inhibitory GABAergic transmission by cAMP signaling pathway: alterations in learning and memory mutants. Eur J Neurosci 2013; 37:1383-93. [PMID: 23387411 DOI: 10.1111/ejn.12144] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2012] [Revised: 12/12/2012] [Accepted: 01/05/2013] [Indexed: 01/29/2023]
Abstract
The cAMP signaling pathway mediates synaptic plasticity and is essential for memory formation in both vertebrates and invertebrates. In the fruit fly Drosophila melanogaster, mutations in the cAMP pathway lead to impaired olfactory learning. These mutant genes are preferentially expressed in the mushroom body (MB), an anatomical structure essential for learning. While cAMP-mediated synaptic plasticity is known to be involved in facilitation at the excitatory synapses, little is known about its function in GABAergic synaptic plasticity and learning. In this study, using whole-cell patch-clamp techniques on Drosophila primary neuronal cultures, we demonstrate that focal application of an adenylate cyclase activator forskolin (FSK) suppressed inhibitory GABAergic postsynaptic currents (IPSCs). We observed a dual regulatory role of FSK on GABAergic transmission, where it increases overall excitability at GABAergic synapses, while simultaneously acting on postsynaptic GABA receptors to suppress GABAergic IPSCs. Further, we show that cAMP decreased GABAergic IPSCs in a PKA-dependent manner through a postsynaptic mechanism. PKA acts through the modulation of ionotropic GABA receptor sensitivity to the neurotransmitter GABA. This regulation of GABAergic IPSCs is altered in the cAMP pathway and short-term memory mutants dunce and rutabaga, with both showing altered GABA receptor sensitivity. Interestingly, this effect is also conserved in the MB neurons of both these mutants. Thus, our study suggests that alterations in cAMP-mediated GABAergic plasticity, particularly in the MB neurons of cAMP mutants, account for their defects in olfactory learning.
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Affiliation(s)
- Archan Ganguly
- Department of Biological Sciences, Neuroscience Program, Ohio University, 213 Life Science Building, Athens, OH, 45701, USA.
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16
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Trinh K, Andrews L, Krause J, Hanak T, Lee D, Gelb M, Pallanck L. Decaffeinated coffee and nicotine-free tobacco provide neuroprotection in Drosophila models of Parkinson's disease through an NRF2-dependent mechanism. J Neurosci 2010; 30:5525-32. [PMID: 20410106 PMCID: PMC3842467 DOI: 10.1523/jneurosci.4777-09.2010] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2009] [Revised: 01/07/2010] [Accepted: 02/17/2010] [Indexed: 11/21/2022] Open
Abstract
Epidemiological studies have revealed a significantly reduced risk of Parkinson's disease (PD) among coffee and tobacco users, although it is unclear whether these correlations reflect neuroprotective/symptomatic effects of these agents or preexisting differences in the brains of tobacco and coffee users. Here, we report that coffee and tobacco, but not caffeine or nicotine, are neuroprotective in fly PD models. We further report that decaffeinated coffee and nicotine-free tobacco are as neuroprotective as their caffeine and nicotine-containing counterparts and that the neuroprotective effects of decaffeinated coffee and nicotine-free tobacco are also evident in Drosophila models of Alzheimer's disease and polyglutamine disease. Finally, we report that the neuroprotective effects of decaffeinated coffee and nicotine-free tobacco require the cytoprotective transcription factor Nrf2 and that a known Nrf2 activator in coffee, cafestol, is also able to confer neuroprotection in our fly models of PD. Our findings indicate that coffee and tobacco contain Nrf2-activating compounds that may account for the reduced risk of PD among coffee and tobacco users. These compounds represent attractive candidates for therapeutic intervention in PD and perhaps other neurodegenerative diseases.
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Affiliation(s)
| | | | - James Krause
- Chemistry, University of Washington, Seattle, Washington 98195, and
| | - Tyler Hanak
- Neuroscience Program, Department of Biological Sciences, Ohio University, Athens, Ohio 45701
| | - Daewoo Lee
- Neuroscience Program, Department of Biological Sciences, Ohio University, Athens, Ohio 45701
| | - Michael Gelb
- Chemistry, University of Washington, Seattle, Washington 98195, and
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17
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Cao P, Yuan Y, Pehek EA, Moise AR, Huang Y, Palczewski K, Feng Z. Alpha-synuclein disrupted dopamine homeostasis leads to dopaminergic neuron degeneration in Caenorhabditis elegans. PLoS One 2010; 5:e9312. [PMID: 20174477 PMCID: PMC2824852 DOI: 10.1371/journal.pone.0009312] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Accepted: 01/28/2010] [Indexed: 12/01/2022] Open
Abstract
Disruption of dopamine homeostasis may lead to dopaminergic neuron degeneration, a proposed explanation for the specific vulnerability of dopaminergic neurons in Parkinson's disease. While expression of human α-synuclein in C. elegans results in dopaminergic neuron degeneration, the effects of α-synuclein on dopamine homeostasis and its contribution to dopaminergic neuron degeneration in C. elegans have not been reported. Here, we examined the effects of α-synuclein overexpression on worm dopamine homeostasis. We found that α-synuclein expression results in upregulation of dopamine synthesis and content, and redistribution of dopaminergic synaptic vesicles, which significantly contribute to dopaminergic neuron degeneration. These results provide in vivo evidence supporting a critical role for dopamine homeostasis in supporting dopaminergic neuron integrity.
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Affiliation(s)
- Pengxiu Cao
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Yiyuan Yuan
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Elizabeth A. Pehek
- Departments of Psychiatry and Neurosciences, School of Medicine, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Veterans Affairs, Louis Stokes Cleveland Veterans Affairs Medical Center, Cleveland, Ohio, United States of America
| | - Alex R. Moise
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Ying Huang
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Krzysztof Palczewski
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Zhaoyang Feng
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Physiology, College of Medicine, Xi'an Jiaotong University, Xi'an, Shaanxi, China
- * E-mail:
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18
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Martin I, Dawson VL, Dawson TM. The impact of genetic research on our understanding of Parkinson's disease. PROGRESS IN BRAIN RESEARCH 2010; 183:21-41. [PMID: 20696313 DOI: 10.1016/s0079-6123(10)83002-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Until recently, genetics was thought to play a minor role in the development of Parkinson's disease (PD). Over the last decade, a number of genes that definitively cause PD have been identified, which has led to the generation of disease models based on pathogenic gene variants that recapitulate many features of the disease. These genetic studies have provided novel insight into potential mechanisms underlying the aetiology of PD. This chapter will provide a profile of the genes conclusively linked to PD and will outline the mechanisms of PD pathogenesis implicated by genetic studies. Mitochondrial dysfunction, oxidative stress and impaired ubiquitin-proteasome system function are disease mechanisms that are particularly well supported by genetic studies and are therefore the focus of this chapter.
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Affiliation(s)
- Ian Martin
- NeuroRegeneration and Stem Cell Programs, Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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19
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Darya K, Ganguly A, Lee D. Quantitative analysis of synaptic boutons in Drosophila primary neuronal cultures. Brain Res 2009; 1280:1-12. [PMID: 19460362 DOI: 10.1016/j.brainres.2009.05.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Revised: 05/11/2009] [Accepted: 05/12/2009] [Indexed: 11/25/2022]
Abstract
Little information is currently available for structural and quantitative aspects of Drosophila central synapses due to difficulties in accessing those synapses in the tiny fly brain. Here, we developed a new approach to quantitatively analyze central synapses using Drosophila primary neuronal cultures. Two different markers were used to identify synaptic boutons: GFP marking with a synaptotagmin (Syt)::eGFP transgene and anti-Syt antibody. These markers clearly recognized puncta-like synaptic boutons and both signals were well overlapped. In addition, these puncta signals were completely absent in neuronal cultures derived from a Syt null mutant Syt(AD4), firmly demonstrating that anti-Syt(+) puncta are presynaptic terminals. Since anti-Syt signals were stronger and extensive, it was chosen to quantify synaptic boutons in the neuronal culture. Using an image analysis software Image J, synaptic boutons were quantified on the basis of the size and intensity of anti-Syt(+) signals. The number of synaptic boutons in wild type neurons increased by 27% between 3 and 9 days in culture. This increase was much greater (142%) in neuronal cultures derived from a FasII(e86) mutant known to show alterations in synapse growth and stabilization. A parallel increase in neurite length was also observed in both wild type and FasII(e86) neurons. Interestingly, the number of GABAergic synaptic boutons did not increase during this time, indicating distinctive mechanisms underlying development and maintenance of specific types of boutons. Our results successfully showed that Drosophila synaptic boutons can be quantified and thus we can examine genes and signaling pathways regulating structural properties of central synapses in Drosophila.
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Affiliation(s)
- Kauroon Darya
- Department of Biological Sciences, Ohio University, Athens, OH 45701, USA
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20
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Cookson MR. alpha-Synuclein and neuronal cell death. Mol Neurodegener 2009; 4:9. [PMID: 19193223 PMCID: PMC2646729 DOI: 10.1186/1750-1326-4-9] [Citation(s) in RCA: 256] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2008] [Accepted: 02/04/2009] [Indexed: 11/16/2022] Open
Abstract
α-Synuclein is a small protein that has special relevance for understanding Parkinson disease and related disorders. Not only is α-synuclein found in Lewy bodies characteristic of Parkinson disease, but also mutations in the gene for α-synuclein can cause an inherited form of Parkinson disease and expression of normal α-synuclein can increase the risk of developing Parkinson disease in sporadic, or non-familial, cases. Both sporadic and familial Parkinson disease are characterized by substantial loss of several groups of neurons, including the dopaminergic cells of the substantia nigra that are the target of most current symptomatic therapies. Therefore, it is predicted that α-synuclein, especially in its mutant forms or under conditions where its expression levels are increased, is a toxic protein in the sense that it is associated with an increased rate of neuronal cell death. This review will discuss the experimental contexts in which α-synuclein has been demonstrated to be toxic. I will also outline what is known about the mechanisms by which α-synuclein triggers neuronal damage, and identify some of the current gaps in our knowledge about this subject. Finally, the therapeutic implications of toxicity of α-synuclein will be discussed.
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Affiliation(s)
- Mark R Cookson
- Laboratory of Neurogenetics, National Institute on Aging, NIH, Building 35, Room 1A116, MSC 3707, 35 Convent Drive, Bethesda, MD 20982-3707, USA.
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21
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Sepp KJ, Hong P, Lizarraga SB, Liu JS, Mejia LA, Walsh CA, Perrimon N. Identification of neural outgrowth genes using genome-wide RNAi. PLoS Genet 2008; 4:e1000111. [PMID: 18604272 PMCID: PMC2435276 DOI: 10.1371/journal.pgen.1000111] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Accepted: 05/28/2008] [Indexed: 12/13/2022] Open
Abstract
While genetic screens have identified many genes essential for neurite outgrowth, they have been limited in their ability to identify neural genes that also have earlier critical roles in the gastrula, or neural genes for which maternally contributed RNA compensates for gene mutations in the zygote. To address this, we developed methods to screen the Drosophila genome using RNA-interference (RNAi) on primary neural cells and present the results of the first full-genome RNAi screen in neurons. We used live-cell imaging and quantitative image analysis to characterize the morphological phenotypes of fluorescently labelled primary neurons and glia in response to RNAi-mediated gene knockdown. From the full genome screen, we focused our analysis on 104 evolutionarily conserved genes that when downregulated by RNAi, have morphological defects such as reduced axon extension, excessive branching, loss of fasciculation, and blebbing. To assist in the phenotypic analysis of the large data sets, we generated image analysis algorithms that could assess the statistical significance of the mutant phenotypes. The algorithms were essential for the analysis of the thousands of images generated by the screening process and will become a valuable tool for future genome-wide screens in primary neurons. Our analysis revealed unexpected, essential roles in neurite outgrowth for genes representing a wide range of functional categories including signalling molecules, enzymes, channels, receptors, and cytoskeletal proteins. We also found that genes known to be involved in protein and vesicle trafficking showed similar RNAi phenotypes. We confirmed phenotypes of the protein trafficking genes Sec61alpha and Ran GTPase using Drosophila embryo and mouse embryonic cerebral cortical neurons, respectively. Collectively, our results showed that RNAi phenotypes in primary neural culture can parallel in vivo phenotypes, and the screening technique can be used to identify many new genes that have important functions in the nervous system. Development and function of the brain requires the coordinated action of thousands of genes, and currently we understand the roles of only a small fraction of them. Recent advances in genomics, such as the sequencing of entire genomes and the discovery of RNA-interference as a means of testing the effects of gene loss, have opened up the possibility to systematically analyze the function of all known and predicted genes in an organism. Until now, this type of functional genomics approach has not been applied to the study of very complex cells, such as the brain's neurons, on a full-genome scale. In this work, we developed techniques to test all genes, one by one in a rapid manner, for their potential role in neuronal development using neurons isolated from fruit fly embryos. These results yielded a global perspective of what types of genes are necessary for brain development; importantly, they show that a large variety of genes can be studied in this way.
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Affiliation(s)
- Katharine J Sepp
- Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America.
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22
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Yuan N, Lee D. Suppression of excitatory cholinergic synaptic transmission by Drosophila dopamine D1-like receptors. Eur J Neurosci 2008; 26:2417-27. [PMID: 17986026 DOI: 10.1111/j.1460-9568.2007.05870.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The physiological function of dopamine is mediated through its G-protein-coupled receptor family. In Drosophila, four dopamine receptors have been molecularly characterized so far. However, due largely to the absence of a suitable preparation, the role of Drosophila dopamine receptors in modulating central synaptic transmission has not been examined. The present study investigated mechanisms by which dopamine modulates excitatory cholinergic synaptic transmission in Drosophila using primary neuronal cultures. Whole-cell recordings demonstrated that cholinergic excitatory postsynaptic currents (EPSCs) were down-regulated by focally applied dopamine (10-500 microm). The vertebrate D1 specific agonists SKF38393 and 6-chloro-APB (10 microm) mimicked dopamine-mediated suppression of cholinergic synaptic transmission with higher potency. In contrast, the D2 agonists quinpirole and bromocriptine did not alter cholinergic EPSCs, demonstrating that dopamine-mediated suppression of cholinergic synaptic transmission is specifically through activation of Drosophila D1-like receptors. Biophysical analysis of miniature EPSCs indicated that cholinergic suppression by activation of D1-like receptors is presynaptic in origin. Dopamine modulation of cholinergic transmission is not mediated through the cAMP/protein kinase A signaling pathway as cholinergic suppression by dopamine occurred in the presence of the protein kinase A inhibitor H-89. In addition, an adenylate cyclase activator, forskolin, led to an increase, not a decrease, of cholinergic EPSC frequency. Finally, we showed that activation of D1-like receptors decreased the frequency of action potentials in cultured Drosophila neurons by inhibiting excitatory cholinergic transmission. All our data demonstrated that activation of D1-like receptors in Drosophila neurons negatively modulates excitatory cholinergic synaptic transmission and thus inhibits neuronal excitability.
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Affiliation(s)
- Ning Yuan
- Neuroscience Program, Department of Biological Sciences, Ohio University, Athens, OH 45701, USA
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23
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Doronkin S, Reiter LT. Drosophila orthologues to human disease genes: an update on progress. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 2008; 82:1-32. [PMID: 18929137 DOI: 10.1016/s0079-6603(08)00001-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- Sergey Doronkin
- Department of Neurology, Univeristy of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
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24
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Park SS, Schulz EM, Lee D. Disruption of dopamine homeostasis underlies selective neurodegeneration mediated by alpha-synuclein. Eur J Neurosci 2007; 26:3104-12. [PMID: 18005066 DOI: 10.1111/j.1460-9568.2007.05929.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
A key challenge in Parkinson's disease research is to understand mechanisms underlying selective degeneration of dopaminergic neurons mediated by genetic factors such as alpha-synuclein (alpha-Syn). The present study examined whether dopamine (DA)-dependent oxidative stress underlies alpha-Syn-mediated neurodegeneration using Drosophila primary neuronal cultures. Green fluorescent protein (GFP) was used to identify live dopaminergic neurons in primary cultures prepared on a marked photoetched coverslip, which allowed us to repeatedly access preidentified dopaminergic neurons at different time points in a non-invasive manner. This live tracking of GFP-marked dopaminergic neurons revealed age-dependent neurodegeneration mediated by a mutant human alpha-Syn (A30P). Degeneration was rescued when alpha-Syn neuronal cultures were incubated with 1 mm glutathione from Day 3 after culturing. Furthermore, depletion of cytoplasmic DA by 100 microm alpha-methyl-p-tyrosine completely rescued the early stage of alpha-Syn-mediated dopaminergic cell loss, demonstrating that DA plays a major role in oxidative stress-dependent neurodegeneration mediated by alpha-Syn. In contrast, overexpression of a Drosophila tyrosine hydroxylase gene (dTH1) alone caused DA neurodegeneration by enhanced DA synthesis in the cytoplasm. Age-dependent dopaminergic cell loss was comparable in alpha-Syn vs dTH1-overexpressed neuronal cultures, indicating that increased DA levels in the cytoplasm is a critical change downstream of mutant alpha-Syn function. Finally, overexpression of a Drosophila vesicular monoamine transporter rescued alpha-Syn-mediated neurodegeneration through enhanced sequestration of cytoplasmic DA into synaptic vesicles, further indicating that a main cause of selective neurodegeneration is alpha-Syn-induced disruption of DA homeostasis. All of these results demonstrate that elevated cytoplasmic DA is a main factor underlying the early stage of alpha-Syn-mediated neurodegeneration.
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Affiliation(s)
- Soon S Park
- Neuroscience Program, Department of Biological Sciences, Ohio University, Athens, OH 45701, USA
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