201
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Guerreiro S, Florence C, Rousseau E, Hamadat S, Hirsch EC, Michel PP. The Sleep-Modulating Peptide Orexin-B Protects Midbrain Dopamine Neurons from Degeneration, Alone or in Cooperation with Nicotine. Mol Pharmacol 2014; 87:525-32. [DOI: 10.1124/mol.114.095703] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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202
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Celardo I, Martins LM, Gandhi S. Unravelling mitochondrial pathways to Parkinson's disease. Br J Pharmacol 2014; 171:1943-57. [PMID: 24117181 PMCID: PMC3976614 DOI: 10.1111/bph.12433] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Revised: 09/09/2013] [Accepted: 09/17/2013] [Indexed: 02/06/2023] Open
Abstract
Mitochondria are essential for cellular function due to their role in ATP production, calcium homeostasis and apoptotic signalling. Neurons are heavily reliant on mitochondrial integrity for their complex signalling, plasticity and excitability properties, and to ensure cell survival over decades. The maintenance of a pool of healthy mitochondria that can meet the bioenergetic demands of a neuron, is therefore of critical importance; this is achieved by maintaining a careful balance between mitochondrial biogenesis, mitochondrial trafficking, mitochondrial dynamics and mitophagy. The molecular mechanisms that underlie these processes are gradually being elucidated. It is widely recognized that mitochondrial dysfunction occurs in many neurodegenerative diseases, including Parkinson's disease. Mitochondrial dysfunction in the form of reduced bioenergetic capacity, increased oxidative stress and reduced resistance to stress, is observed in several Parkinson's disease models. However, identification of the recessive genes implicated in Parkinson's disease has revealed a common pathway involving mitochondrial dynamics, transport, turnover and mitophagy. This body of work has led to the hypothesis that the homeostatic mechanisms that ensure a healthy mitochondrial pool are key to neuronal function and integrity. In this paradigm, impaired mitochondrial dynamics and clearance result in the accumulation of damaged and dysfunctional mitochondria, which may directly induce neuronal dysfunction and death. In this review, we consider the mechanisms by which mitochondrial dysfunction may lead to neurodegeneration. In particular, we focus on the mechanisms that underlie mitochondrial homeostasis, and discuss their importance in neuronal integrity and neurodegeneration in Parkinson's disease.
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203
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Higher vulnerability and stress sensitivity of neuronal precursor cells carrying an alpha-synuclein gene triplication. PLoS One 2014; 9:e112413. [PMID: 25390032 PMCID: PMC4229205 DOI: 10.1371/journal.pone.0112413] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2013] [Accepted: 10/16/2014] [Indexed: 12/19/2022] Open
Abstract
Parkinson disease (PD) is a multi-factorial neurodegenerative disorder with loss of dopaminergic neurons in the substantia nigra and characteristic intracellular inclusions, called Lewy bodies. Genetic predisposition, such as point mutations and copy number variants of the SNCA gene locus can cause very similar PD-like neurodegeneration. The impact of altered α-synuclein protein expression on integrity and developmental potential of neuronal stem cells is largely unexplored, but may have wide ranging implications for PD manifestation and disease progression. Here, we investigated if induced pluripotent stem cell-derived neuronal precursor cells (NPCs) from a patient with Parkinson's disease carrying a genomic triplication of the SNCA gene (SNCA-Tri). Our goal was to determine if these cells these neuronal precursor cells already display pathological changes and impaired cellular function that would likely predispose them when differentiated to neurodegeneration. To achieve this aim, we assessed viability and cellular physiology in human SNCA-Tri NPCs both under normal and environmentally stressed conditions to model in vitro gene-environment interactions which may play a role in the initiation and progression of PD. Human SNCA-Tri NPCs displayed overall normal cellular and mitochondrial morphology, but showed substantial changes in growth, viability, cellular energy metabolism and stress resistance especially when challenged by starvation or toxicant challenge. Knockdown of α-synuclein in the SNCA-Tri NPCs by stably expressed short hairpin RNA (shRNA) resulted in reversal of the observed phenotypic changes. These data show for the first time that genetic alterations such as the SNCA gene triplication set the stage for decreased developmental fitness, accelerated aging, and increased neuronal cell loss. The observation of this "stem cell pathology" could have a great impact on both quality and quantity of neuronal networks and could provide a powerful new tool for development of neuroprotective strategies for PD.
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204
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Rimessi A, Bonora M, Marchi S, Patergnani S, Marobbio CMT, Lasorsa FM, Pinton P. Perturbed mitochondrial Ca2+signals as causes or consequences of mitophagy induction. Autophagy 2014; 9:1677-86. [DOI: 10.4161/auto.24795] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
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205
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Intracellular processing of disease-associated α-synuclein in the human brain suggests prion-like cell-to-cell spread. Neurobiol Dis 2014; 69:76-92. [DOI: 10.1016/j.nbd.2014.05.020] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Revised: 04/29/2014] [Accepted: 05/17/2014] [Indexed: 01/13/2023] Open
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206
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Rcom-H'cheo-Gauthier A, Goodwin J, Pountney DL. Interactions between calcium and alpha-synuclein in neurodegeneration. Biomolecules 2014; 4:795-811. [PMID: 25256602 PMCID: PMC4192672 DOI: 10.3390/biom4030795] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Revised: 06/25/2014] [Accepted: 07/14/2014] [Indexed: 12/01/2022] Open
Abstract
In Parkinson’s disease and some atypical Parkinson’s syndromes, aggregation of the α-synuclein protein (α-syn) has been linked to neurodegeneration. Many triggers for pathological α-syn aggregation have been identified, including port-translational modifications, oxidative stress and raised metal ions, such as Ca2+. Recently, it has been found using cell culture models that transient increases of intracellular Ca2+ induce cytoplasmic α-syn aggregates. Ca2+-dependent α-syn aggregation could be blocked by the Ca2+ buffering agent, BAPTA-AM, or by the Ca2+ channel blocker, Trimethadione. Furthermore, a greater proportion of cells positive for aggregates occurred when both raised Ca2+ and oxidative stress were combined, indicating that Ca2+ and oxidative stress cooperatively promote α-syn aggregation. Current on-going work using a unilateral mouse lesion model of Parkinson’s disease shows a greater proportion of calbindin-positive neurons survive the lesion, with intracellular α-syn aggregates almost exclusively occurring in calbindin-negative neurons. These and other recent findings are reviewed in the context of neurodegenerative pathologies and suggest an association between raised Ca2+, α-syn aggregation and neurotoxicity.
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Affiliation(s)
- Alex Rcom-H'cheo-Gauthier
- Griffith Health Institute, School of Medical Science, Griffith University, Gold Coast, Queensland 4222, Australia.
| | - Jacob Goodwin
- Griffith Health Institute, School of Medical Science, Griffith University, Gold Coast, Queensland 4222, Australia.
| | - Dean L Pountney
- Griffith Health Institute, School of Medical Science, Griffith University, Gold Coast, Queensland 4222, Australia.
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207
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Brini M, Calì T, Ottolini D, Carafoli E. Neuronal calcium signaling: function and dysfunction. Cell Mol Life Sci 2014; 71:2787-814. [PMID: 24442513 PMCID: PMC11113927 DOI: 10.1007/s00018-013-1550-7] [Citation(s) in RCA: 425] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 12/15/2013] [Accepted: 12/30/2013] [Indexed: 01/07/2023]
Abstract
Calcium (Ca(2+)) is an universal second messenger that regulates the most important activities of all eukaryotic cells. It is of critical importance to neurons as it participates in the transmission of the depolarizing signal and contributes to synaptic activity. Neurons have thus developed extensive and intricate Ca(2+) signaling pathways to couple the Ca(2+) signal to their biochemical machinery. Ca(2+) influx into neurons occurs through plasma membrane receptors and voltage-dependent ion channels. The release of Ca(2+) from the intracellular stores, such as the endoplasmic reticulum, by intracellular channels also contributes to the elevation of cytosolic Ca(2+). Inside the cell, Ca(2+) is controlled by the buffering action of cytosolic Ca(2+)-binding proteins and by its uptake and release by mitochondria. The uptake of Ca(2+) in the mitochondrial matrix stimulates the citric acid cycle, thus enhancing ATP production and the removal of Ca(2+) from the cytosol by the ATP-driven pumps in the endoplasmic reticulum and the plasma membrane. A Na(+)/Ca(2+) exchanger in the plasma membrane also participates in the control of neuronal Ca(2+). The impaired ability of neurons to maintain an adequate energy level may impact Ca(2+) signaling: this occurs during aging and in neurodegenerative disease processes. The focus of this review is on neuronal Ca(2+) signaling and its involvement in synaptic signaling processes, neuronal energy metabolism, and neurotransmission. The contribution of altered Ca(2+) signaling in the most important neurological disorders will then be considered.
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Affiliation(s)
- Marisa Brini
- Department of Biology, University of Padova, Via U.Bassi, 58/b, 35131 Padua, Italy
| | - Tito Calì
- Department of Biology, University of Padova, Via U.Bassi, 58/b, 35131 Padua, Italy
| | - Denis Ottolini
- Department of Biology, University of Padova, Via U.Bassi, 58/b, 35131 Padua, Italy
| | - Ernesto Carafoli
- Venetian Institute for Molecular Medicine (VIMM), Via G.Orus, 2, 35129 Padua, Italy
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208
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Abstract
Evolution has exploited the chemical properties of Ca(2+), which facilitate its reversible binding to the sites of irregular geometry offered by biological macromolecules, to select it as a carrier of cellular signals. A number of proteins bind Ca(2+) to specific sites: those intrinsic to membranes play the most important role in the spatial and temporal regulation of the concentration and movements of Ca(2+) inside cells. Those which are soluble, or organized in non-membranous structures, also decode the Ca(2+) message to be then transmitted to the targets of its regulation. Since Ca(2+) controls the most important processes in the life of cells, it must be very carefully controlled within the cytoplasm, where most of the targets of its signaling function reside. Membrane channels (in the plasma membrane and in the organelles) mediate the entrance of Ca(2+) into the cytoplasm, ATPases, exchangers, and the mitochondrial Ca(2+) uptake system remove Ca(2+) from it. The concentration of Ca(2+) in the external spaces, which is controlled essentially by its dynamic exchanges in the bone system, is much higher than inside cells, and can, under conditions of pathology, generate a situation of dangerous internal Ca(2+) overload. When massive and persistent, the Ca(2+) overload culminates in the death of the cell. Subtle conditions of cellular Ca(2+) dyshomeostasis that affect individual systems that control Ca(2+), generate cell disease phenotypes that are particularly severe in tissues in which the signaling function of Ca(2+) has special importance, e.g., the nervous system.
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Affiliation(s)
- Marisa Brini
- Department of Biology, University of Padova, Via U. Bassi 58/B, I-35131, Padova, Italy,
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209
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Kanaan NM, Manfredsson FP. Loss of functional alpha-synuclein: a toxic event in Parkinson's disease? JOURNAL OF PARKINSONS DISEASE 2014; 2:249-67. [PMID: 23938255 PMCID: PMC4736738 DOI: 10.3233/jpd-012138] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The discovery that alpha-synuclein (α-syn) is the primary component of the neuropathological hallmarks of Parkinson's disease (PD) and the identification of α-syn mutations in numerous inherited forms of PD has positioned α-syn at the top of the list of important factors in the pathogenesis of PD. Based on the pathological accumulation of α-syn in the brains of patients, the field is currently focused on therapeutic strategies that aim to reduce or eliminate α-syn. However, recent evidence suggests α-syn is a critical protein in neuron (i.e. dopamine neurons) survival and that maintaining a certain level of biologically functional α-syn is an important consideration in targeting α-syn for therapies. Despite the widespread interest in α-syn, the normal biological functions remain elusive, but a large body of work is focused on addressing this issue. In this review, we will discuss the current evidence related to α-syn function, α-syn folding and aggregation, and α-syn's role in disease. Finally, we will propose a relatively novel hypothesis on the pathogenesis of PD that hinges upon the premises that functional α-syn is critical to cell survival and that a reduction in biologically functional α-syn, whether through aggregation or reduced expression, may lead to the neurodegeneration in PD.
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Affiliation(s)
- Nicholas M Kanaan
- Department of Translational Science & Molecular Medicine, College of Human Medicine, Michigan State University, Grand Rapids, MI 49503, USA
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210
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Luth ES, Stavrovskaya IG, Bartels T, Kristal BS, Selkoe DJ. Soluble, prefibrillar α-synuclein oligomers promote complex I-dependent, Ca2+-induced mitochondrial dysfunction. J Biol Chem 2014; 289:21490-507. [PMID: 24942732 DOI: 10.1074/jbc.m113.545749] [Citation(s) in RCA: 198] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
α-Synuclein (αSyn) aggregation and mitochondrial dysfunction both contribute to the pathogenesis of Parkinson disease (PD). Although recent studies have suggested that mitochondrial association of αSyn may disrupt mitochondrial function, it is unclear what aggregation state of αSyn is most damaging to mitochondria and what conditions promote or inhibit the effect of toxic αSyn species. Because the neuronal populations most vulnerable in PD are characterized by large cytosolic Ca(2+) oscillations that burden mitochondria, we examined mitochondrial Ca(2+) stress in an in vitro system comprising isolated mitochondria and purified recombinant human αSyn in various aggregation states. Using fluorimetry to simultaneously measure four mitochondrial parameters, we observed that soluble, prefibrillar αSyn oligomers, but not monomeric or fibrillar αSyn, decreased the retention time of exogenously added Ca(2+), promoted Ca(2+)-induced mitochondrial swelling and depolarization, and accelerated cytochrome c release. Inhibition of the permeability transition pore rescued these αSyn-induced changes in mitochondrial parameters. Interestingly, the mitotoxic effects of αSyn were specifically dependent upon both electron flow through complex I and mitochondrial uptake of exogenous Ca(2+). Our results suggest that soluble prefibrillar αSyn oligomers recapitulate several mitochondrial phenotypes previously observed in animal and cell models of PD: complex I dysfunction, altered membrane potential, disrupted Ca(2+) homeostasis, and enhanced cytochrome c release. These data reveal how the association of oligomeric αSyn with mitochondria can be detrimental to the function of cells with high Ca(2+)-handling requirements.
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Affiliation(s)
- Eric S Luth
- From the Center for Neurologic Diseases, Department of Neurology, and
| | - Irina G Stavrovskaya
- Department of Neurosurgery, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115
| | - Tim Bartels
- From the Center for Neurologic Diseases, Department of Neurology, and
| | - Bruce S Kristal
- Department of Neurosurgery, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115
| | - Dennis J Selkoe
- From the Center for Neurologic Diseases, Department of Neurology, and
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211
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Stoica R, De Vos KJ, Paillusson S, Mueller S, Sancho RM, Lau KF, Vizcay-Barrena G, Lin WL, Xu YF, Lewis J, Dickson DW, Petrucelli L, Mitchell JC, Shaw CE, Miller CCJ. ER-mitochondria associations are regulated by the VAPB-PTPIP51 interaction and are disrupted by ALS/FTD-associated TDP-43. Nat Commun 2014; 5:3996. [PMID: 24893131 PMCID: PMC4046113 DOI: 10.1038/ncomms4996] [Citation(s) in RCA: 445] [Impact Index Per Article: 44.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2014] [Accepted: 04/29/2014] [Indexed: 12/12/2022] Open
Abstract
Mitochondria and the endoplasmic reticulum (ER) form tight structural associations and these facilitate a number of cellular functions. However, the mechanisms by which regions of the ER become tethered to mitochondria are not properly known. Understanding these mechanisms is not just important for comprehending fundamental physiological processes but also for understanding pathogenic processes in some disease states. In particular, disruption to ER-mitochondria associations is linked to some neurodegenerative diseases. Here we show that the ER-resident protein VAPB interacts with the mitochondrial protein tyrosine phosphatase-interacting protein-51 (PTPIP51) to regulate ER-mitochondria associations. Moreover, we demonstrate that TDP-43, a protein pathologically linked to amyotrophic lateral sclerosis and fronto-temporal dementia perturbs ER-mitochondria interactions and that this is associated with disruption to the VAPB-PTPIP51 interaction and cellular Ca(2+) homeostasis. Finally, we show that overexpression of TDP-43 leads to activation of glycogen synthase kinase-3β (GSK-3β) and that GSK-3β regulates the VAPB-PTPIP51 interaction. Our results describe a new pathogenic mechanism for TDP-43.
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Affiliation(s)
- Radu Stoica
- Department of Neuroscience, Institute of Psychiatry, Kings
College London, London
SE5 8AF, UK
- Clinical Neurosciences, Institute of Psychiatry, Kings
College London, London
SE5 8AF, UK
- These authors contributed equally to this work
| | - Kurt J. De Vos
- Department of Neuroscience, Institute of Psychiatry, Kings
College London, London
SE5 8AF, UK
- Clinical Neurosciences, Institute of Psychiatry, Kings
College London, London
SE5 8AF, UK
- These authors contributed equally to this work
- Present address: Sheffield Institute for Translational Neuroscience, University of Sheffield, South Yorkshire S10 2HQ, UK
| | - Sébastien Paillusson
- Department of Neuroscience, Institute of Psychiatry, Kings
College London, London
SE5 8AF, UK
- Clinical Neurosciences, Institute of Psychiatry, Kings
College London, London
SE5 8AF, UK
| | - Sarah Mueller
- Department of Neuroscience, Institute of Psychiatry, Kings
College London, London
SE5 8AF, UK
- Clinical Neurosciences, Institute of Psychiatry, Kings
College London, London
SE5 8AF, UK
| | - Rosa M. Sancho
- Department of Neuroscience, Institute of Psychiatry, Kings
College London, London
SE5 8AF, UK
- Clinical Neurosciences, Institute of Psychiatry, Kings
College London, London
SE5 8AF, UK
- Present address: Alzheimer’s Research UK, Cambridge
CB21 6AD, UK
| | - Kwok-Fai Lau
- Department of Neuroscience, Institute of Psychiatry, Kings
College London, London
SE5 8AF, UK
- Present address: Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR
| | - Gema Vizcay-Barrena
- Centre for Ultrastructural Imaging, King’s
College London, London
SE5 8AF, UK
| | - Wen-Lang Lin
- Department of Neuroscience, Mayo Clinic,
Jacksonville, Florida
32224, USA
| | - Ya-Fei Xu
- Department of Neuroscience, Mayo Clinic,
Jacksonville, Florida
32224, USA
| | - Jada Lewis
- Department of Neuroscience, Mayo Clinic,
Jacksonville, Florida
32224, USA
| | - Dennis W. Dickson
- Department of Neuroscience, Mayo Clinic,
Jacksonville, Florida
32224, USA
| | - Leonard Petrucelli
- Department of Neuroscience, Mayo Clinic,
Jacksonville, Florida
32224, USA
| | - Jacqueline C. Mitchell
- Clinical Neurosciences, Institute of Psychiatry, Kings
College London, London
SE5 8AF, UK
| | - Christopher E. Shaw
- Clinical Neurosciences, Institute of Psychiatry, Kings
College London, London
SE5 8AF, UK
| | - Christopher C. J. Miller
- Department of Neuroscience, Institute of Psychiatry, Kings
College London, London
SE5 8AF, UK
- Clinical Neurosciences, Institute of Psychiatry, Kings
College London, London
SE5 8AF, UK
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212
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Abnormal alpha-synuclein reduces nigral voltage-dependent anion channel 1 in sporadic and experimental Parkinson's disease. Neurobiol Dis 2014; 69:1-14. [PMID: 24825319 DOI: 10.1016/j.nbd.2014.05.003] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 04/09/2014] [Accepted: 05/02/2014] [Indexed: 01/24/2023] Open
Abstract
Both the misfolding of α-synuclein and mitochondrial dysfunction are considered two major contributors to Parkinson's disease (PD). However, the relationship between the two in normal and PD states remains unclear. Here, we report that voltage-dependent anion channel 1 (VDAC1), a major component of the outer mitochondrial membrane known to regulate mitochondrial functions, is down-regulated in response to α-synuclein accumulation and aggregation. Stereological analysis revealed that 58.33% of the neurons were VDAC1 immunoreactive in the remaining neuromelanin laden neurons in the PD group while 87.48% of the nigral neurons were VDAC1 immunoreactive in the age-matched control group. The relative levels of VDAC1 were significantly decreased in PD nigral neurons when compared to age-matched controls. In PD, this decrease was significantly greater in nigral neurons with α-synuclein inclusions. VDAC1 was observed in fibers with granular α-synuclein but not in fibers with aggregated α-synuclein. Viral vector-mediated overexpression of mutant human α-synuclein (A30P) in rats resulted in significantly decreased VDAC1 in nigral neurons and striatal fibers. These results indicate that mitochondrial function associated with VDAC1 is decreased in sporadic and experimental PD, and this decrease is associated with α-synuclein accumulation and aggregation.
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213
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Calcium signaling in Parkinson's disease. Cell Tissue Res 2014; 357:439-54. [PMID: 24781149 DOI: 10.1007/s00441-014-1866-0] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Accepted: 03/06/2014] [Indexed: 12/16/2022]
Abstract
Calcium (Ca(2+)) is an almost universal second messenger that regulates important activities of all eukaryotic cells. It is of critical importance to neurons, which have developed extensive and intricate pathways to couple the Ca(2+) signal to their biochemical machinery. In particular, Ca(2+) participates in the transmission of the depolarizing signal and contributes to synaptic activity. During aging and in neurodegenerative disease processes, the ability of neurons to maintain an adequate energy level can be compromised, thus impacting on Ca(2+) homeostasis. In Parkinson's disease (PD), many signs of neurodegeneration result from compromised mitochondrial function attributable to specific effects of toxins on the mitochondrial respiratory chain and/or to genetic mutations. Despite these effects being present in almost all cell types, a distinguishing feature of PD is the extreme selectivity of cell loss, which is restricted to the dopaminergic neurons in the ventral portion of the substantia nigra pars compacta. Many hypotheses have been proposed to explain such selectivity, but only recently it has been convincingly shown that the innate autonomous activity of these neurons, which is sustained by their specific Cav1.3 L-type channel pore-forming subunit, is responsible for the generation of basal metabolic stress that, under physiological conditions, is compensated by mitochondrial buffering. However, when mitochondria function becomes even partially compromised (because of aging, exposure to environmental factors or genetic mutations), the metabolic stress overwhelms the protective mechanisms, and the process of neurodegeneration is engaged. The characteristics of Ca(2+) handling in neurons of the substantia nigra pars compacta and the possible involvement of PD-related proteins in the control of Ca(2+) homeostasis will be discussed in this review.
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214
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De Bock M, Decrock E, Wang N, Bol M, Vinken M, Bultynck G, Leybaert L. The dual face of connexin-based astroglial Ca(2+) communication: a key player in brain physiology and a prime target in pathology. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:2211-32. [PMID: 24768716 DOI: 10.1016/j.bbamcr.2014.04.016] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Revised: 04/11/2014] [Accepted: 04/12/2014] [Indexed: 12/21/2022]
Abstract
For decades, studies have been focusing on the neuronal abnormalities that accompany neurodegenerative disorders. Yet, glial cells are emerging as important players in numerous neurological diseases. Astrocytes, the main type of glia in the central nervous system , form extensive networks that physically and functionally connect neuronal synapses with cerebral blood vessels. Normal brain functioning strictly depends on highly specialized cellular cross-talk between these different partners to which Ca(2+), as a signaling ion, largely contributes. Altered intracellular Ca(2+) levels are associated with neurodegenerative disorders and play a crucial role in the glial responses to injury. Intracellular Ca(2+) increases in single astrocytes can be propagated toward neighboring cells as intercellular Ca(2+) waves, thereby recruiting a larger group of cells. Intercellular Ca(2+) wave propagation depends on two, parallel, connexin (Cx) channel-based mechanisms: i) the diffusion of inositol 1,4,5-trisphosphate through gap junction channels that directly connect the cytoplasm of neighboring cells, and ii) the release of paracrine messengers such as glutamate and ATP through hemichannels ('half of a gap junction channel'). This review gives an overview of the current knowledge on Cx-mediated Ca(2+) communication among astrocytes as well as between astrocytes and other brain cell types in physiology and pathology, with a focus on the processes of neurodegeneration and reactive gliosis. Research on Cx-mediated astroglial Ca(2+) communication may ultimately shed light on the development of targeted therapies for neurodegenerative disorders in which astrocytes participate. This article is part of a Special Issue entitled: Calcium signaling in health and disease. Guest Editors: Geert Bultynck, Jacques Haiech, Claus W. Heizmann, Joachim Krebs, and Marc Moreau.
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Affiliation(s)
- Marijke De Bock
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Elke Decrock
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium.
| | - Nan Wang
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Mélissa Bol
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
| | - Mathieu Vinken
- Department of Toxicology, Center for Pharmaceutical Research, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, B-1090 Brussels, Belgium
| | - Geert Bultynck
- Department of Cellular and Molecular Medicine, Laboratory of Molecular and Cellular Signalling, KULeuven, Campus Gasthuisberg O/N-I bus 802, B-3000 Leuven, Belgium
| | - Luc Leybaert
- Department of Basic Medical Sciences, Physiology group, Faculty of Medicine and Health Sciences, Ghent University, B-9000 Ghent, Belgium
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215
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Nuber S, Tadros D, Fields J, Overk CR, Ettle B, Kosberg K, Mante M, Rockenstein E, Trejo M, Masliah E. Environmental neurotoxic challenge of conditional alpha-synuclein transgenic mice predicts a dopaminergic olfactory-striatal interplay in early PD. Acta Neuropathol 2014; 127:477-94. [PMID: 24509835 DOI: 10.1007/s00401-014-1255-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 01/31/2014] [Accepted: 02/01/2014] [Indexed: 12/17/2022]
Abstract
The olfactory bulb (OB) is one of the first brain regions in Parkinson's disease (PD) to contain alpha-synuclein (α-syn) inclusions, possibly associated with nonmotor symptoms. Mechanisms underlying olfactory synucleinopathy, its contribution to progressive aggregation pathology and nigrostriatal dopaminergic loss observed at later stages, remain unclear. A second hit, such as environmental toxins, is suggestive for α-syn aggregation in olfactory neurons, potentially triggering disease progression. To address the possible pathogenic role of olfactory α-syn accumulation in early PD, we exposed mice with site-specific and inducible overexpression of familial PD-linked mutant α-syn in OB neurons to a low dose of the herbicide paraquat. Here, we found that olfactory α-syn per se elicited structural and behavioral abnormalities, characteristic of an early time point in models with widespread α-syn expression, including hyperactivity and increased striatal dopaminergic marker. Suppression of α-syn reversed the dopaminergic phenotype. In contrast, paraquat treatment synergistically induced degeneration of olfactory dopaminergic cells and opposed the higher reactive phenotype. Neither neurodegeneration nor behavioral abnormalities were detected in paraquat-treated mice with suppressed α-syn expression. By increasing calpain activity, paraquat induced a pathological cascade leading to inhibition of autophagy clearance and accumulation of calpain-cleaved truncated and insoluble α-syn, recapitulating biochemical and structural changes in human PD. Thus our results underscore the primary role of proteolytic failure in aggregation pathology. In addition, we provide novel evidence that olfactory dopaminergic neurons display an increased vulnerability toward neurotoxins in dependence to presence of human α-syn, possibly mediating an olfactory-striatal dopaminergic network dysfunction in mouse models and early PD.
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Affiliation(s)
- Silke Nuber
- Department of Neurosciences, University of California San Diego, 9500 Gilman Dr., MTF 344, La Jolla, CA, 92093-0624, USA,
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O'Donnell KC, Lulla A, Stahl MC, Wheat ND, Bronstein JM, Sagasti A. Axon degeneration and PGC-1α-mediated protection in a zebrafish model of α-synuclein toxicity. Dis Model Mech 2014; 7:571-82. [PMID: 24626988 PMCID: PMC4007408 DOI: 10.1242/dmm.013185] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
α-synuclein (aSyn) expression is implicated in neurodegenerative processes, including Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). In animal models of these diseases, axon pathology often precedes cell death, raising the question of whether aSyn has compartment-specific toxic effects that could require early and/or independent therapeutic intervention. The relevance of axonal pathology to degeneration can only be addressed through longitudinal, in vivo monitoring of different neuronal compartments. With current imaging methods, dopaminergic neurons do not readily lend themselves to such a task in any vertebrate system. We therefore expressed human wild-type aSyn in zebrafish peripheral sensory neurons, which project elaborate superficial axons that can be continuously imaged in vivo. Axonal outgrowth was normal in these neurons but, by 2 days post-fertilization (dpf), many aSyn-expressing axons became dystrophic, with focal varicosities or diffuse beading. Approximately 20% of aSyn-expressing cells died by 3 dpf. Time-lapse imaging revealed that focal axonal swelling, but not overt fragmentation, usually preceded cell death. Co-expressing aSyn with a mitochondrial reporter revealed deficits in mitochondrial transport and morphology even when axons appeared overtly normal. The axon-protective protein Wallerian degeneration slow (WldS) delayed axon degeneration but not cell death caused by aSyn. By contrast, the transcriptional coactivator PGC-1α, which has roles in the regulation of mitochondrial biogenesis and reactive-oxygen-species detoxification, abrogated aSyn toxicity in both the axon and the cell body. The rapid onset of axonal pathology in this system, and the relatively moderate degree of cell death, provide a new model for the study of aSyn toxicity and protection. Moreover, the accessibility of peripheral sensory axons will allow effects of aSyn to be studied in different neuronal compartments and might have utility in screening for novel disease-modifying compounds.
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Affiliation(s)
- Kelley C O'Donnell
- Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, CA 90095, USA
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217
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Ageing and Parkinson's disease: why is advancing age the biggest risk factor? Ageing Res Rev 2014; 14:19-30. [PMID: 24503004 PMCID: PMC3989046 DOI: 10.1016/j.arr.2014.01.004] [Citation(s) in RCA: 540] [Impact Index Per Article: 54.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Revised: 01/06/2014] [Accepted: 01/24/2014] [Indexed: 12/15/2022]
Abstract
Review of age related processes occurring within substantia nigra neurons. Discussion of why these neurons seem to be susceptible to loss with age. Review of why SN neurons are particularly sensitive to mitochondrial dysfunction. Review of why SN neurons are sensitive to changes in protein degradation pathways. Discussion of relevance to Parkinson's disease pathology.
As the second most common age related neurodegenerative disease after Alzheimer's disease, the health, social and economic impact resulting from Parkinson's disease will continue to increase alongside the longevity of the population. Ageing remains the biggest risk factor for developing idiopathic Parkinson's disease. Although research into the mechanisms leading to cell death in Parkinson's disease has shed light on many aspects of the pathogenesis of this disorder, we still cannot answer the fundamental question, what specific age related factors predispose some individuals to develop this common neurodegenerative disease. In this review we focus specifically on the neuronal population associated with the motor symptoms of Parkinson's disease, the dopaminergic neurons of the substantia nigra, and try to understand how ageing puts these neurons at risk to the extent that a slight change in protein metabolism or mitochondrial function can push the cells over the edge leading to catastrophic cell death and many of the symptoms seen in Parkinson's disease. We review the evidence that ageing is important for the development of Parkinson's disease and how age related decline leads to the loss of neurons within this disease, before describing exactly how advancing age may lead to substantia nigra neuronal loss and Parkinson's disease in some individuals.
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218
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Abstract
Familial Parkinson disease is associated with mutations in α-synuclein (α-syn), a presynaptic protein that has been localized not only to the cytosol, but also to mitochondria. We report here that wild-type α-syn from cell lines, and brain tissue from humans and mice, is present not in mitochondria but rather in mitochondria-associated endoplasmic reticulum (ER) membranes (MAM), a structurally and functionally distinct subdomain of the ER. Remarkably, we found that pathogenic point mutations in human α-syn result in its reduced association with MAM, coincident with a lower degree of apposition of ER with mitochondria, a decrease in MAM function, and an increase in mitochondrial fragmentation compared with wild-type. Although overexpression of wild-type α-syn in mutant α-syn-expressing cells reverted the fragmentation phenotype, neither overexpression of the mitochondrial fusion/MAM-tethering protein MFN2 nor inhibition/ablation of the mitochondrial fission protein DRP1 was able to do so, implying that α-syn operates downstream of the mitochondrial fusion/fission machinery. These novel results indicate that wild-type α-syn localizes to the MAM and modulates mitochondrial morphology, and that these behaviors are impaired by pathogenic mutations in α-syn. We believe that our results have far-reaching implications for both our understanding of α-syn biology and the treatment of synucleinopathies.
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219
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Abstract
Purpose of review The aims of this review is to suggest a new nomenclature and classification system for the diseases currently categorized as neurodegeneration with brain iron accumulation (NBIA) or dystonia-parkinsonism, and to discuss the mechanisms implicated in the pathogenesis of these diseases. Recent findings NBIA is a disease category encompassing syndromes with iron accumulation and prominent dystonia–parkinsonism. However, as there are many diseases with similar clinical presentations but without iron accumulation and/or known genetic cause, the current classification system and nomenclature remain confusing. The pathogenetic mechanisms of these diseases and the causes of gross iron accumulation and significant burden of neuroaxonal spheroids are also elusive. Recent genetic and functional studies have identified surprising links between NBIA, Parkinson's disease and lysosomal storage disorders (LSD) with the common theme being a combined lysosomal–mitochondrial dysfunction. We hypothesize that mitochondria and lysosomes form a functional continuum with a predominance of mitochondrial and lysosomal pathways in NBIA and LSD, respectively, and with Parkinson's disease representing an intermediate form of disease. Summary During the past 18 months, important advances have been made towards understanding the genetic and pathological underpinnings of the pallidopyramidal syndromes with important implications for clinical practice and future treatment developments.
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220
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MAM (mitochondria-associated membranes) in mammalian cells: lipids and beyond. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1841:595-609. [PMID: 24316057 DOI: 10.1016/j.bbalip.2013.11.014] [Citation(s) in RCA: 446] [Impact Index Per Article: 40.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Revised: 11/21/2013] [Accepted: 11/27/2013] [Indexed: 12/15/2022]
Abstract
One mechanism by which communication between the endoplasmic reticulum (ER) and mitochondria is achieved is by close juxtaposition between these organelles via mitochondria-associated membranes (MAM). The MAM consist of a region of the ER that is enriched in several lipid biosynthetic enzyme activities and becomes reversibly tethered to mitochondria. Specific proteins are localized, sometimes transiently, in the MAM. Several of these proteins have been implicated in tethering the MAM to mitochondria. In mammalian cells, formation of these contact sites between MAM and mitochondria appears to be required for key cellular events including the transport of calcium from the ER to mitochondria, the import of phosphatidylserine into mitochondria from the ER for decarboxylation to phosphatidylethanolamine, the formation of autophagosomes, regulation of the morphology, dynamics and functions of mitochondria, and cell survival. This review focuses on the functions proposed for MAM in mediating these events in mammalian cells. In light of the apparent involvement of MAM in multiple fundamental cellular processes, recent studies indicate that impaired contact between MAM and mitochondria might underlie the pathology of several human neurodegenerative diseases, including Alzheimer's disease. Moreover, MAM has been implicated in modulating glucose homeostasis and insulin resistance, as well as in some viral infections.
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221
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Phillipson OT. Management of the aging risk factor for Parkinson's disease. Neurobiol Aging 2013; 35:847-57. [PMID: 24246717 DOI: 10.1016/j.neurobiolaging.2013.10.073] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 10/02/2013] [Accepted: 10/04/2013] [Indexed: 01/12/2023]
Abstract
The aging risk factor for Parkinson's disease is described in terms of specific disease markers including mitochondrial and gene dysfunctions relevant to energy metabolism. This review details evidence for the ability of nutritional agents to manage these aging risk factors. The combination of alpha lipoic acid, acetyl-l-carnitine, coenzyme Q10, and melatonin supports energy metabolism via carbohydrate and fatty acid utilization, assists electron transport and adenosine triphosphate synthesis, counters oxidative and nitrosative stress, and raises defenses against protein misfolding, inflammatory stimuli, iron, and other endogenous or xenobiotic toxins. These effects are supported by gene expression via the antioxidant response element (ARE; Keap/Nrf2 pathway), and by peroxisome proliferator-activated receptor gamma co-activator 1 alpha (PGC-1 alpha), a transcription coactivator, which regulates gene expression for energy metabolism and mitochondrial biogenesis, and maintains the structural integrity of mitochondria. The effectiveness and synergies of the combination against disease risks are discussed in relation to gene action, dopamine cell loss, and the accumulation and spread of pathology via misfolded alpha-synuclein. In addition there are potential synergies to support a neurorestorative role via glial derived neurotrophic factor expression.
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Affiliation(s)
- Oliver T Phillipson
- School of Medical Sciences, University of Bristol, University Walk, Bristol, UK.
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222
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Rousseau E, Michel PP, Hirsch EC. The iron-binding protein lactoferrin protects vulnerable dopamine neurons from degeneration by preserving mitochondrial calcium homeostasis. Mol Pharmacol 2013; 84:888-98. [PMID: 24077968 DOI: 10.1124/mol.113.087965] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Previous studies on postmortem human brain tissue have shown that the iron-binding glycoprotein lactoferrin is upregulated in dopamine (DA) neurons resistant to degeneration in Parkinson disease (PD). To study how this could possibly relate to disease progression, we used midbrain cultures and experimental settings that model the progressive loss of DA neurons in this disorder. Human lactoferrin of either recombinant or natural origin provided robust protection to vulnerable DA neurons in a culture paradigm in which these neurons die spontaneously and selectively as they mature. The efficacy of lactoferrin was comparable to that of glial cell line-derived neurotrophic factor, a prototypical neurotrophic factor for DA neurons. Neuroprotection by lactoferrin was attributable to its binding to heparan sulfate proteoglycans on the cell surface of DA neurons and subsequently to partial inactivation of focal adhesion kinase (FAK), a major effector kinase of integrins. We established that FAK inactivation served to unmask a prosurvival phosphoinositide 3-kinase/AKT-dependent signaling pathway that stimulates calcium shuttling from endoplasmic reticulum to mitochondria. DA neurons exposed to the mitochondrial toxin 1-methyl-4-phenylpyridinium were also partially protected by lactoferrin, further supporting the view that mitochondria may represent a downstream target for lactoferrin protective actions. Finally, we found that the iron binding capability of lactoferrin intervened in DA cell rescue only when neurodegeneration was consecutive to iron-catalyzed oxidative stress. Overall, our data suggest that the accumulation of lactoferrin in PD brains might be evidence of an attempt by the brain to minimize the consequences of neurodegeneration.
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Affiliation(s)
- Erwann Rousseau
- Université Pierre et Marie Curie-Paris 6, Unité Mixte de Recherche (UMR) S975, Institut du Cerveau et de la Moelle Epinière, Paris, France; Institut National de la Santé et de la Recherche Médicale, U975, Paris, France; and Centre National de la Recherche Scientifique, UMR 7225, Paris, France
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223
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Melachroinou K, Xilouri M, Emmanouilidou E, Masgrau R, Papazafiri P, Stefanis L, Vekrellis K. Deregulation of calcium homeostasis mediates secreted α-synuclein-induced neurotoxicity. Neurobiol Aging 2013; 34:2853-65. [PMID: 23891486 DOI: 10.1016/j.neurobiolaging.2013.06.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Revised: 06/04/2013] [Accepted: 06/14/2013] [Indexed: 01/24/2023]
Abstract
α-Synuclein (AS) plays a crucial role in Parkinson's disease pathogenesis. AS is normally secreted from neuronal cells and can thus exert paracrine effects. We have previously demonstrated that naturally secreted AS species, derived from SH-SY5Y cells inducibly overexpressing human wild type AS, can be toxic to recipient neuronal cells. In the current study, we show that application of secreted AS alters membrane fluidity and increases calcium (Ca2+) entry. This influx is reduced on pharmacological inhibition of voltage-operated Ca2+ channels. Although no change in free cytosolic Ca2+ levels is observed, a significantly increased mitochondrial Ca2+ sequestration is found in recipient cells. Application of voltage-operated Ca2+ channel blockers or Ca2+ chelators abolishes AS-mediated toxicity. AS-treated cells exhibit increased calpain activation, and calpain inhibition greatly alleviates the observed toxicity. Collectively, our data suggest that secreted AS exerts toxicity through engagement, at least in part, of the Ca2+ homeostatic machinery. Therefore, manipulating Ca2+ signaling pathways might represent a potential therapeutic strategy for Parkinson's disease.
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Affiliation(s)
- Katerina Melachroinou
- Division of Basic Neurosciences, Biomedical Research Foundation of the Academy of Athens, Athens, Greece
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224
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Jia W, He MX, McLeod IX, He YW. Autophagy, a novel pathway to regulate calcium mobilization in T lymphocytes. Front Immunol 2013; 4:179. [PMID: 23847620 PMCID: PMC3701145 DOI: 10.3389/fimmu.2013.00179] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 06/21/2013] [Indexed: 01/10/2023] Open
Abstract
The T lymphocyte response initiates with the recognition of MHC/peptides on antigen presenting cells by the T cell receptor (TCR). After the TCR engagement, the proximal signaling pathways are activated for downstream cellular events. Among these pathways, the calcium-signaling flux is activated through the depletion of endoplasmic reticulum (ER) calcium stores and plays pivotal roles in T cell proliferation, cell survival, and apoptosis. In studying the roles of macroautophagy (hereafter referred to as autophagy) in T cell function, we found that a pathway for intracellular degradation, autophagy, regulates calcium signaling by developmentally maintaining the homeostasis of the ER. Using mouse genetic models with specific deletion of autophagy-related genes in T lymphocytes, we found that the calcium influx is defective and the calcium efflux is increased in autophagy-deficient T cells. The abnormal calcium flux is related to the expansion of the ER and higher calcium stores in the ER. Because of this, treatment with the ER sarco/ER Ca2+-ATPase pump inhibitor, thapsigargin, rescues the calcium influx defect in autophagy-deficient T cells. Therefore, autophagy regulates calcium mobilization in T lymphocytes through ER homeostasis.
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Affiliation(s)
- Wei Jia
- Department of Immunology, Duke University Medical Center Durham, NC, USA
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225
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Ca2+ homeostasis in the endoplasmic reticulum measured with a new low-Ca2+-affinity targeted aequorin. Cell Calcium 2013; 54:37-45. [DOI: 10.1016/j.ceca.2013.04.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Revised: 02/27/2013] [Accepted: 04/04/2013] [Indexed: 11/18/2022]
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226
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Abstract
Increased α-synuclein levels and mutations in mitochondria-associated proteins both cause familial Parkinson's disease (PD), and synuclein and mitochondria also play central, but poorly understood, roles in the pathogenesis of idiopathic PD. A fraction of synuclein interacts with mitochondria, and synuclein can produce mitochondrial fragmentation and impair mitochondrial complex I activity. However, the consequences of these mitochondrial changes for bioenergetic and other mitochondrial functions remain poorly defined, as does the role of synuclein-mitochondria interactions in the normal and pathologic effects of synuclein. Understanding the functional consequences of synuclein's interactions with mitochondria is likely to provide important insights into disease pathophysiology, and may also reveal therapeutic strategies.
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Affiliation(s)
- Ken Nakamura
- Gladstone Institute of Neurological Disease, 1650 Owens Street, San Francisco, CA 94158, USA.
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227
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Yang W, Wang X, Duan C, Lu L, Yang H. Alpha-synuclein overexpression increases phospho-protein phosphatase 2A levels via formation of calmodulin/Src complex. Neurochem Int 2013; 63:180-94. [PMID: 23796501 DOI: 10.1016/j.neuint.2013.06.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 06/01/2013] [Accepted: 06/14/2013] [Indexed: 11/28/2022]
Abstract
Alpha-synuclein (α-Syn) is the principal protein component of Lewy bodies, a pathological hallmark of Parkinson's disease (PD). This protein may regulate protein phosphatase 2A (PP2A) activity, although the molecular mechanisms for α-Syn-mediated regulation of PP2A and the potential neuroprotective actions of PP2A against PD-associated pathology remain largely unexplored. We found that α-Syn gene overexpression in SK-N-SH cells and primary neurons led to PP2A/C phosphorylation at Y307, a known target of Src kinase, and consequent phosphatase inhibition. In addition, phospho-activated Src (p-Y416 Src, pSrc) was higher in SK-N-SH cells and primary neurons overexpressing α-Syn. Thus, α-Syn may promote Src activation and PP2A inactivation, leading to hyperphosphorylation of proteins. Immunoprecipitation revealed higher calmodulin/Src complex formation in α-Syn-overexpressing cells and α-Syn transgenic mice. A TUNEL apoptosis assay and an MTT cell viability assay demonstrated that the PP2A activator C2-ceramide protected neurons against α-Syn-induced cell injury. Buffering the Ca(2+) elevations induced by α-Syn overexpression ameliorated the cytotoxicity of α-Syn. Our findings define a potential molecular mechanism for α-Syn-mediated regulation of PP2A through formation of the calmodulin/Src complex, activation of Src, and Src-mediated phospho-inhibition of PP2A. Overexpression of α-Syn may lead to neurodegeneration in PD in part by suppressing the endogenous neuroprotective activity of PP2A.
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Affiliation(s)
- W Yang
- Beijing Institute of Brain Disorders, Capital Medical University, Key Laboratory for Neurodegenerative Disease of the Ministry of Education, Beijing Center of Neural Regeneration and Repair, Beijing 100069, China
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228
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Crosstalk between Endoplasmic Reticulum Stress and Protein Misfolding in Neurodegenerative Diseases. ACTA ACUST UNITED AC 2013. [DOI: 10.1155/2013/256404] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Under physiological conditions, the endoplasmic reticulum (ER) is a central subcellular compartment for protein quality control in the secretory pathway that prevents protein misfolding and aggregation. Instrumental in protein quality control in the ER is the unfolded protein response (UPR), which is activated upon ER stress to reestablish homeostasis through a sophisticated transcriptionally and translationally regulated signaling network. However, this response can lead to apoptosis if the stress cannot be alleviated. The presence of abnormal protein aggregates containing specific misfolded proteins is recognized as the basis of numerous human conformational disorders, including neurodegenerative diseases. Here, I will highlight the overwhelming evidence that the presence of specific aberrant proteins in Alzheimer’s disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD), prion diseases, and Amyotrophic Lateral Sclerosis (ALS) is intimately associated with perturbations in the ER protein quality control machinery that become incompetent to restore protein homeostasis and shift adaptive programs toward the induction of apoptotic signaling to eliminate irreversibly damaged neurons. Increasing our understanding about the deadly crosstalk between ER dysfunction and protein misfolding in these neurodegenerative diseases may stimulate the development of novel therapeutic strategies able to support neuronal survival and ameliorate disease progression.
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229
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Michel PP, Toulorge D, Guerreiro S, Hirsch EC. Specific needs of dopamine neurons for stimulation in order to survive: implication for Parkinson disease. FASEB J 2013; 27:3414-23. [PMID: 23699175 DOI: 10.1096/fj.12-220418] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Parkinson disease (PD) is a degenerative brain disorder characterized by motor symptoms that are unequivocally associated with the loss of dopaminergic (DA) neurons in the substantia nigra (SN). Although our knowledge of the mechanisms that contribute to DA cell death in both hereditary and sporadic forms of the disease has advanced significantly, the nature of the pathogenic process remains poorly understood. In this review, we present evidence that neurodegeneration occurs when the electrical activity and excitability of these neurons is reduced. In particular, we will focus on the specific need these neurons may have for stimulation in order to survive and on the molecular and cellular mechanisms that may be compromised when this need is no longer met in PD.
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Affiliation(s)
- Patrick P Michel
- Université Pierre et Marie Curie-Paris 6, Centre de Recherche de l'Institut du Cerveau et de la Moelle Epinière, Unité Mixte de Recherche (UMR) S975, Paris, France.
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230
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Calì T, Ottolini D, Brini M. Calcium and Endoplasmic Reticulum-Mitochondria Tethering in Neurodegeneration. DNA Cell Biol 2013; 32:140-6. [DOI: 10.1089/dna.2013.2011] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Affiliation(s)
- Tito Calì
- Department of Comparative Biomedicine and Food Science, University of Padova, Padova, Italy
| | - Denis Ottolini
- Department of Comparative Biomedicine and Food Science, University of Padova, Padova, Italy
| | - Marisa Brini
- Department of Comparative Biomedicine and Food Science, University of Padova, Padova, Italy
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231
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Ottolini D, Cali T, Negro A, Brini M. The Parkinson disease-related protein DJ-1 counteracts mitochondrial impairment induced by the tumour suppressor protein p53 by enhancing endoplasmic reticulum-mitochondria tethering. Hum Mol Genet 2013; 22:2152-68. [DOI: 10.1093/hmg/ddt068] [Citation(s) in RCA: 154] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
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232
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Calì T, Ottolini D, Negro A, Brini M. Enhanced parkin levels favor ER-mitochondria crosstalk and guarantee Ca(2+) transfer to sustain cell bioenergetics. Biochim Biophys Acta Mol Basis Dis 2013; 1832:495-508. [PMID: 23313576 DOI: 10.1016/j.bbadis.2013.01.004] [Citation(s) in RCA: 174] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Revised: 11/30/2012] [Accepted: 01/02/2013] [Indexed: 12/01/2022]
Abstract
Loss-of-function mutations in PINK1 or parkin genes are associated with juvenile-onset autosomal recessive forms of Parkinson disease. Numerous studies have established that PINK1 and parkin participate in a common mitochondrial-quality control pathway, promoting the selective degradation of dysfunctional mitochondria by mitophagy. Upregulation of parkin mRNA and protein levels has been proposed as protective mechanism against mitochondrial and endoplasmic reticulum (ER) stress. To better understand how parkin could exert protective function we considered the possibility that it could modulate the ER-mitochondria inter-organelles cross talk. To verify this hypothesis we investigated the effects of parkin overexpression on ER-mitochondria crosstalk with respect to the regulation of two key cellular parameters: Ca(2+) homeostasis and ATP production. Our results indicate that parkin overexpression in model cells physically and functionally enhanced ER-mitochondria coupling, favored Ca(2+) transfer from the ER to the mitochondria following cells stimulation with an 1,4,5 inositol trisphosphate (InsP(3)) generating agonist and increased the agonist-induced ATP production. The overexpression of a parkin mutant lacking the first 79 residues (ΔUbl) failed to enhance the mitochondrial Ca(2+) transients, thus highlighting the importance of the N-terminal ubiquitin like domain for the observed phenotype. siRNA-mediated parkin silencing caused mitochondrial fragmentation, impaired mitochondrial Ca(2+) handling and reduced the ER-mitochondria tethering. These data support a novel role for parkin in the regulation of mitochondrial homeostasis, Ca(2+) signaling and energy metabolism under physiological conditions.
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Affiliation(s)
- Tito Calì
- Department of Comparative Biomedicine and Food Science, University of Padova, Padova, Italy
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233
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Dunning CJR, George S, Brundin P. What's to like about the prion-like hypothesis for the spreading of aggregated α-synuclein in Parkinson disease? Prion 2013; 7:92-7. [PMID: 23360753 PMCID: PMC3609056 DOI: 10.4161/pri.23806] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
α-Synuclein is a key protein in Parkinson disease. Not only is it the major protein component of Lewy bodies, but it is implicated in several cellular processes that are disrupted in Parkinson disease. Misfolded α-synuclein has also been shown to spread from cell-to-cell and, in a prion-like fashion, trigger aggregation of α-synuclein in the recipient cell. In this mini-review we explore the evidence that misfolded α-synuclein underlies the spread of pathology in Parkinson disease and discuss why it should be considered a prion-like protein.
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234
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Over-expression of N-type calcium channels in cortical neurons from a mouse model of Amyotrophic Lateral Sclerosis. Exp Neurol 2012; 247:349-58. [PMID: 23142186 DOI: 10.1016/j.expneurol.2012.11.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2012] [Revised: 10/24/2012] [Accepted: 11/02/2012] [Indexed: 12/13/2022]
Abstract
Voltage-gated Ca(2+) channels (VGCCs) mediate calcium entry into neuronal cells in response to membrane depolarisation and play an essential role in a variety of physiological processes. In Amyotrophic Lateral Sclerosis (ALS), a fatal neurodegenerative disease caused by motor neuron degeneration in the brain and spinal cord, intracellular calcium dysregulation has been shown, while no studies have been carried out on VGCCs. Here we show that the subtype N-type Ca(2+) channels are over expressed in G93A cultured cortical neurons and in motor cortex of G93A mice compared to Controls. In fact, by western blotting, immunocytochemical and electrophysiological experiments, we observe higher membrane expression of N-type Ca(2+) channels in G93A neurons compared to Controls. G93A cortical neurons filled with calcium-sensitive dye Fura-2, show a net calcium entry during membrane depolarization that is significantly higher compared to Control. Analysis of neuronal vitality following the exposure of neurons to a high K(+) concentration (25 mM, 5h), shows a significant reduction of G93A cellular survival compared to Controls. N-type channels are involved in the G93A higher mortality because ω-conotoxin GVIA (1 μM), which selectively blocks these channels, is able to abolish the higher G93A mortality when added to the external medium. These data provide robust evidence for an excess of N-type Ca(2+) expression in G93A cortical neurons which induces a higher mortality following membrane depolarization. These results may be central to the understanding of pathogenic pathways in ALS and provide novel molecular targets for the design of rational therapies for the ALS disorder.
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235
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Nikoletopoulou V, Tavernarakis N. Calcium homeostasis in aging neurons. Front Genet 2012; 3:200. [PMID: 23060904 PMCID: PMC3462315 DOI: 10.3389/fgene.2012.00200] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 09/19/2012] [Indexed: 11/13/2022] Open
Abstract
The nervous system becomes increasingly vulnerable to insults and prone to dysfunction during aging. Age-related decline of neuronal function is manifested by the late onset of many neurodegenerative disorders, as well as by reduced signaling and processing capacity of individual neuron populations. Recent findings indicate that impairment of Ca(2+) homeostasis underlies the increased susceptibility of neurons to damage, associated with the aging process. However, the impact of aging on Ca(2+) homeostasis in neurons remains largely unknown. Here, we survey the molecular mechanisms that mediate neuronal Ca(2+) homeostasis and discuss the impact of aging on their efficacy. To address the question of how aging impinges on Ca(2+) homeostasis, we consider potential nodes through which mechanisms regulating Ca(2+) levels interface with molecular pathways known to influence the process of aging and senescent decline. Delineation of this crosstalk would facilitate the development of interventions aiming to fortify neurons against age-associated functional deterioration and death by augmenting Ca(2+) homeostasis.
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Affiliation(s)
- Vassiliki Nikoletopoulou
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology - Hellas Heraklion, Crete, Greece
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236
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Calì T, Ottolini D, Brini M. Mitochondrial Ca(2+) and neurodegeneration. Cell Calcium 2012; 52:73-85. [PMID: 22608276 PMCID: PMC3396847 DOI: 10.1016/j.ceca.2012.04.015] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2012] [Revised: 04/18/2012] [Accepted: 04/20/2012] [Indexed: 12/16/2022]
Abstract
Mitochondria are essential for ensuring numerous fundamental physiological processes such as cellular energy, redox balance, modulation of Ca2+ signaling and important biosynthetic pathways. They also govern the cell fate by participating in the apoptosis pathway. The mitochondrial shape, volume, number and distribution within the cells are strictly controlled. The regulation of these parameters has an impact on mitochondrial function, especially in the central nervous system, where trafficking of mitochondria is critical to their strategic intracellular distribution, presumably according to local energy demands. Thus, the maintenance of a healthy mitochondrial population is essential to avoid the impairment of the processes they regulate: for this purpose, cells have developed mechanisms involving a complex system of quality control to remove damaged mitochondria, or to renew them. Defects of these processes impair mitochondrial function and lead to disordered cell function, i.e., to a disease condition. Given the standard role of mitochondria in all cells, it might be expected that their dysfunction would give rise to similar defects in all tissues. However, damaged mitochondrial function has pleiotropic effects in multicellular organisms, resulting in diverse pathological conditions, ranging from cardiac and brain ischemia, to skeletal muscle myopathies to neurodegenerative diseases. In this review, we will focus on the relationship between mitochondrial (and cellular) derangements and Ca2+ dysregulation in neurodegenerative diseases, emphasizing the evidence obtained in genetic models. Common patterns, that recognize the derangement of Ca2+ and energy control as a causative factor, have been identified: advances in the understanding of the molecular regulation of Ca2+ homeostasis, and on the ways in which it could become perturbed in neurological disorders, may lead to the development of therapeutic strategies that modulate neuronal Ca2+ signaling.
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Affiliation(s)
- Tito Calì
- Department of Comparative Biomedicine and Food Science, University of Padova, Padova, Italy
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