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Anand S, Trounce IA, Gangoda L. Role of extracellular vesicles in mitochondrial eye diseases. IUBMB Life 2022; 74:1264-1272. [PMID: 36308309 PMCID: PMC10947567 DOI: 10.1002/iub.2687] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 10/14/2022] [Indexed: 03/20/2024]
Abstract
Extracellular vesicles (EVs) are small packages that are released by almost all types of cells. While the role of EVs in pathogenesis of certain diseases such as cancer is well established, EVs role in ocular health and disease is still at early stages of investigation. Given the significant role of EVs in pathological development and progression of diseases such as cancer, EVs present a similar opportunity for investigation in ocular pathophysiology. Studies have shown the presence of EVs in fluids from the ocular environment have close links with ocular health and disease. Hence, the cargo carried in EVs from ocular fluids can be used for monitoring disease phenotypes or therapeutic outcomes in eye-related disorders. Furthermore, in recent times EVs have increasingly gained attention as therapeutics and drug-delivery vehicles for treatment of eye diseases. There is a close relationship between EVs and mitochondria functioning with mitochondria dysfunction leading to a significant number of ophthalmic disorders. This review discusses the current knowledge of EVs in visual systems with a special focus on eye diseases resulting from dysfunctional mitochondria.
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Affiliation(s)
- Sushma Anand
- Centre for Eye Research AustraliaRoyal Victorian Eye and Ear HospitalEast MelbourneVictoriaAustralia
- Opthalmology, Department of SurgeryUniversity of MelbourneMelbourneVictoriaAustralia
| | - Ian A. Trounce
- Centre for Eye Research AustraliaRoyal Victorian Eye and Ear HospitalEast MelbourneVictoriaAustralia
- Opthalmology, Department of SurgeryUniversity of MelbourneMelbourneVictoriaAustralia
| | - Lahiru Gangoda
- Centre for Eye Research AustraliaRoyal Victorian Eye and Ear HospitalEast MelbourneVictoriaAustralia
- Opthalmology, Department of SurgeryUniversity of MelbourneMelbourneVictoriaAustralia
- The Walter and Eliza Hall Institute of Medical Research (WEHI)MelbourneVictoriaAustralia
- Department of Medical BiologyUniversity of MelbourneMelbourneVictoriaAustralia
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2
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Yu F, Abdelwahid E, Xu T, Hu L, Wang M, Li Y, Mogharbel BF, de Carvalho KAT, Guarita-Souza LC, An Y, Li P. The role of mitochondrial fusion and fission in the process of cardiac oxidative stress. Histol Histopathol 2019; 35:541-552. [PMID: 31820815 DOI: 10.14670/hh-18-191] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Mitochondria are the energy suppliers in the cell and undergo constant fusion and fission to meet metabolic demand during the cell life cycle. Well-balanced mitochondrial dynamics are extremely important and necessary for cell survival as well as for tissue homeostasis. Cardiomyocytes contain large numbers of mitochondria to satisfy the high energy demand. It has been established that deregulated processes of mitochondrial dynamics play a major role in myocardial cell death. Currently, cardiac mitochondrial cell death pathways attract great attention in the cell biology and regenerative medicine fields. Importantly, mitochondrial dynamics are tightly linked to oxidative stress-induced cardiac damage. This review summarizes molecular mechanisms of mitochondrial fusion and fission processes and their potential roles in myocardial cell death triggered by oxidative stress. Advances in understanding the effect of both normal and abnormal mitochondrial dynamics on heart protection will lead to significant improvement of therapeutic discoveries.
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Affiliation(s)
- Fei Yu
- Institute for Translation Medicine, Medical College, Qingdao University, Qingdao, China
| | - Eltyeb Abdelwahid
- Feinberg School of Medicine, Feinberg Cardiovascular Research Institute, Northwestern University, Chicago, IL, USA.
| | - Tao Xu
- Institute for Translation Medicine, Medical College, Qingdao University, Qingdao, China
| | - Longgang Hu
- Department of Cardiology, Affiliated Hospital of Qingdao University, Qingdao, China
| | - Man Wang
- Institute for Translation Medicine, Medical College, Qingdao University, Qingdao, China
| | - Yuzhen Li
- Department of Pathophysiology, Institute of Basic Medical Science, PLA General Hospital, Beijing, China
| | - Bassam Felipe Mogharbel
- Cell Therapy and Biotechnology in Regenerative Medicine Research Group, Pequeno Príncipe Faculty, Pelé Pequeno Príncipe Institute, Curitiba, Brazil
| | | | - Luiz Cesar Guarita-Souza
- Experimental Laboratory of Institute of Biological and Health Sciences of Pontifical Catholic University of Parana, Curitiba, Brazil
| | - Yi An
- Department of cardiology, Affiliated hospital of Qingdao University, Qingdao, China.
| | - Peifeng Li
- Institute for Translation Medicine, Medical College, Qingdao University, Qingdao, China.
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3
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Rosselin M, Santo-Domingo J, Bermont F, Giacomello M, Demaurex N. L-OPA1 regulates mitoflash biogenesis independently from membrane fusion. EMBO Rep 2017; 18:451-463. [PMID: 28174208 PMCID: PMC5331265 DOI: 10.15252/embr.201642931] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 12/19/2016] [Accepted: 12/21/2016] [Indexed: 11/09/2022] Open
Abstract
Mitochondrial flashes mediated by optic atrophy 1 (OPA1) fusion protein are bioenergetic responses to stochastic drops in mitochondrial membrane potential (Δψm) whose origin is unclear. Using structurally distinct genetically encoded pH‐sensitive probes, we confirm that flashes are matrix alkalinization transients, thereby establishing the pH nature of these events, which we renamed “mitopHlashes”. Probes located in cristae or intermembrane space as verified by electron microscopy do not report pH changes during Δψm drops or respiratory chain inhibition. Opa1 ablation does not alter Δψm fluctuations but drastically decreases the efficiency of mitopHlash/Δψm coupling, which is restored by re‐expressing fusion‐deficient OPA1K301A and preserved in cells lacking the outer‐membrane fusion proteins MFN1/2 or the OPA1 proteases OMA1 and YME1L, indicating that mitochondrial membrane fusion and OPA1 proteolytic processing are dispensable. pH/Δψm uncoupling occurs early during staurosporine‐induced apoptosis and is mitigated by OPA1 overexpression, suggesting that OPA1 maintains mitopHlash competence during stress conditions. We propose that OPA1 stabilizes respiratory chain supercomplexes in a conformation that enables respiring mitochondria to compensate a drop in Δψm by an explosive matrix pH flash.
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Affiliation(s)
- Manon Rosselin
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | - Jaime Santo-Domingo
- Nestlé Institute of Health Sciences SA, EPFL Innovation Park, Lausanne, Switzerland
| | - Flavien Bermont
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
| | | | - Nicolas Demaurex
- Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland
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4
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Myers SJ, Malladi CS, Hyland RA, Bautista T, Boadle R, Robinson PJ, Nicholson GA. Mutations in the SPTLC1 protein cause mitochondrial structural abnormalities and endoplasmic reticulum stress in lymphoblasts. DNA Cell Biol 2014; 33:399-407. [PMID: 24673574 DOI: 10.1089/dna.2013.2182] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Mutations in serine palmitoyltransferase long chain subunit 1 (SPTLC1) cause the typical length-dependent axonal degeneration hereditary sensory neuropathy type 1 (HSN1). Transmission electron microscopy studies on SPTLC1 mutant lymphoblasts derived from patients revealed specific structural abnormalities of mitochondria. Swollen mitochondria with abnormal cristae were clustered around the nucleus, with some mitochondria being wrapped in rough endoplasmic reticulum (ER) membranes. Total mitochondrial counts revealed a significant change in mitochondrial numbers between healthy and diseased lymphocytes but did not reveal any change in length to width ratios nor were there any changes to cellular function. However, there was a notable change in ER homeostasis, as assessed using key ER stress markers, BiP and ERO1-Lα, displaying reduced protein expression. The observations suggest that SPTLC1 mutations cause mitochondrial abnormalities and ER stress in HSN1 cells.
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Affiliation(s)
- Simon J Myers
- 1 Neuro-Cell Biology Laboratory, School of Science & Health, University of Western Sydney , Campbelltown, NSW, Australia
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Rolland SG, Motori E, Memar N, Hench J, Frank S, Winklhofer KF, Conradt B. Impaired complex IV activity in response to loss of LRPPRC function can be compensated by mitochondrial hyperfusion. Proc Natl Acad Sci U S A 2013; 110:E2967-76. [PMID: 23878239 PMCID: PMC3740885 DOI: 10.1073/pnas.1303872110] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mitochondrial morphology changes in response to various stimuli but the significance of this is unclear. In a screen for mutants with abnormal mitochondrial morphology, we identified MMA-1, the Caenorhabditis elegans homolog of the French Canadian Leigh Syndrome protein LRPPRC (leucine-rich pentatricopeptide repeat containing). We demonstrate that reducing mma-1 or LRPPRC function causes mitochondrial hyperfusion. Reducing mma-1/LRPPRC function also decreases the activity of complex IV of the electron transport chain, however without affecting cellular ATP levels. Preventing mitochondrial hyperfusion in mma-1 animals causes larval arrest and embryonic lethality. Furthermore, prolonged LRPPRC knock-down in mammalian cells leads to mitochondrial fragmentation and decreased levels of ATP. These findings indicate that in a mma-1/LRPPRC-deficient background, hyperfusion allows mitochondria to maintain their functions despite a reduction in complex IV activity. Our data reveal an evolutionary conserved mechanism that is triggered by reduced complex IV function and that induces mitochondrial hyperfusion to transiently compensate for a drop in the activity of the electron transport chain.
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Affiliation(s)
- Stéphane G. Rolland
- Department Biology II, Center for Integrated Protein Science, Ludwig-Maximilians-University Munich, 82152 Planegg-Martinsried, Germany
| | - Elisa Motori
- Department of Neurobiochemistry, Adolf Butenandt Institute, Ludwig-Maximilians-University, 80336 Munich, Germany
- Department of Life Quality Studies–Alma Mater Studiorum, University of Bologna, 40126 Bologna, Italy
| | - Nadin Memar
- Department Biology II, Center for Integrated Protein Science, Ludwig-Maximilians-University Munich, 82152 Planegg-Martinsried, Germany
| | - Jürgen Hench
- Department of Neuropathology, Institute for Pathology, University Hospitals Basel, CH-4031 Basel, Switzerland
| | - Stephan Frank
- Department of Neuropathology, Institute for Pathology, University Hospitals Basel, CH-4031 Basel, Switzerland
| | - Konstanze F. Winklhofer
- Department of Neurobiochemistry, Adolf Butenandt Institute, Ludwig-Maximilians-University, 80336 Munich, Germany
- German Center for Neurodegenerative Diseases, 80336 Munich, Germany
- Munich Cluster for Systems Neurology, 80336 Munich, Germany; and
- Department of Molecular Cell Biology, Institute of Physiological Chemistry, Ruhr University Bochum, 44801 Bochum, Germany
| | - Barbara Conradt
- Department Biology II, Center for Integrated Protein Science, Ludwig-Maximilians-University Munich, 82152 Planegg-Martinsried, Germany
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Loss of OPA1 disturbs cellular calcium homeostasis and sensitizes for excitotoxicity. Cell Death Differ 2012; 20:353-65. [PMID: 23138851 DOI: 10.1038/cdd.2012.128] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Optic atrophy 1 (OPA1) mutations cause dominant optic atrophy (DOA) with retinal ganglion cell (RGC) and optic nerve degeneration. The mechanism for the selective degeneration of RGCs in DOA remains elusive. To address the mechanism, we reduced OPA1 protein expression in cell lines and RGCs by RNA interference. OPA1 loss results in mitochondrial fragmentation, deficiency in oxidative phosphorylation, decreased ATP levels, decreased mitochondrial Ca(2+) retention capacity, reduced mtDNA copy numbers, and sensitization to apoptotic insults. We demonstrate profound cristae depletion and loss of crista junctions in OPA1 knockdown cells, whereas the remaining crista junctions preserve their normal size. OPA1-depleted cells exhibit decreased agonist-evoked mitochondrial Ca(2+) transients and corresponding reduction of NAD(+) to NADH, but the impairment in NADH oxidation leads to an overall more reduced mitochondrial NADH pool. Although in our model OPA1 loss in RGCs has no apparent impact on mitochondrial morphology, it decreases buffering of cytosolic Ca(2+) and sensitizes RGCs to excitotoxic injury. Exposure to glutamate triggers delayed calcium deregulation (DCD), often in a reversible manner, indicating partial resistance of RGCs to this injury. However, when OPA1 is depleted, DCD becomes irreversible. Thus, our data show that whereas OPA1 is required for mitochondrial fusion, maintenance of crista morphology and oxidative phosphorylation, loss of OPA1 also results in defective Ca(2+) homeostasis.
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7
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Escobar-Henriques M, Anton F. Mechanistic perspective of mitochondrial fusion: tubulation vs. fragmentation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:162-75. [PMID: 22884630 DOI: 10.1016/j.bbamcr.2012.07.016] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 07/28/2012] [Accepted: 07/30/2012] [Indexed: 01/02/2023]
Abstract
Mitochondrial fusion is a fundamental process driven by dynamin related GTPase proteins (DRPs), in contrast to the general SNARE-dependence of most cellular fusion events. The DRPs Mfn1/Mfn2/Fzo1 and OPA1/Mgm1 are the key effectors for fusion of the mitochondrial outer and inner membranes, respectively. In order to promote fusion, these two DRPs require post-translational modifications and proteolysis. OPA1/Mgm1 undergoes partial proteolytic processing, which results in a combination between short and long isoforms. In turn, ubiquitylation of mitofusins, after oligomerization and GTP hydrolysis, promotes and positively regulates mitochondrial fusion. In contrast, under conditions of mitochondrial dysfunction, negative regulation by proteolysis on these DRPs results in mitochondrial fragmentation. This occurs by complete processing of OPA1 and via ubiquitylation and degradation of mitofusins. Mitochondrial fragmentation contributes to the elimination of damaged mitochondria by mitophagy, and may play a protective role against Parkinson's disease. Moreover, a link of Mfn2 to Alzheimer's disease is emerging and mutations in Mfn2 or OPA1 cause Charcot-Marie-Tooth type 2A neuropathy or autosomal-dominant optic atrophy. Here, we summarize our current understanding on the molecular mechanisms promoting or inhibiting fusion of mitochondrial membranes, which is essential for cellular survival and disease control. This article is part of a Special Issue entitled: Mitochondrial dynamics and physiology.
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Abstract
Apoptosis is a process of programmed cell death that serves as a major mechanism for the precise regulation of cell numbers, and as a defense mechanism to remove unwanted and potentially dangerous cells. Studies in nematode, Drosophila and mammals have shown that, although regulation of the cell death machinery is somehow different from one species to another, it is controlled by homologous proteins and involves mitochondria. In mammals, activation of caspases (cysteine proteases that are the main executioners of apoptosis) is under the tight control of the Bcl-2 family proteins, named in reference to the first discovered mammalian cell death regulator. These proteins mainly act by regulating the release of caspases activators from mitochondria. Although for a long time the absence of mitochondrial changes was considered as a hallmark of apoptosis, mitochondria appear today as the central executioner of apoptosis. In this chapter, we present the current view on the mitochondrial pathway of apoptosis with a particular attention to new aspects of the regulation of the Bcl-2 proteins family control of mitochondrial membrane permeabilization: the mechanisms implicated in their mitochondrial targeting and activation during apoptosis, the function(s) of the oncosuppressive protein p53 at the mitochondria and the role of the processes of mitochondrial fusion and fission.
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9
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Abstract
The structure and function of the mitochondrial network is regulated by mitochondrial biogenesis, fission, fusion, transport and degradation. A well-maintained balance of these processes (mitochondrial dynamics) is essential for neuronal signaling, plasticity and transmitter release. Core proteins of the mitochondrial dynamics machinery play important roles in the regulation of apoptosis, and mutations or abnormal expression of these factors are associated with inherited and age-dependent neurodegenerative disorders. In Parkinson's disease (PD), oxidative stress and mitochondrial dysfunction underlie the development of neuropathology. The recessive Parkinsonism-linked genes PTEN-induced kinase 1 (PINK1) and Parkin maintain mitochondrial integrity by regulating diverse aspects of mitochondrial function, including membrane potential, calcium homeostasis, cristae structure, respiratory activity, and mtDNA integrity. In addition, Parkin is crucial for autophagy-dependent clearance of dysfunctional mitochondria. In the absence of PINK1 or Parkin, cells often develop fragmented mitochondria. Whereas excessive fission may cause apoptosis, coordinated induction of fission and autophagy is believed to facilitate the removal of damaged mitochondria through mitophagy, and has been observed in some types of cells. Compensatory mechanisms may also occur in mice lacking PINK1 that, in contrast to cells and Drosophila, have only mild mitochondrial dysfunction and lack dopaminergic neuron loss. A better understanding of the relationship between the specific changes in mitochondrial dynamics/turnover and cell death will be instrumental to identify potentially neuroprotective pathways steering PINK1-deficient cells towards survival. Such pathways may be manipulated in the future by specific drugs to treat PD and perhaps other neurodegenerative disorders characterized by abnormal mitochondrial function and dynamics.
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Affiliation(s)
- Hansruedi Büeler
- Department of Anatomy and Neurobiology, University of Kentucky, 800 Rose Street, Lexington, KY 40536, USA.
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10
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Perkins GA, Ellisman MH. Mitochondrial configurations in peripheral nerve suggest differential ATP production. J Struct Biol 2010; 173:117-27. [PMID: 20600951 DOI: 10.1016/j.jsb.2010.06.017] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2010] [Accepted: 06/21/2010] [Indexed: 12/25/2022]
Abstract
Physiological states of mitochondria often correlate with distinctive morphology. Electron microscopy and tomographic reconstruction were used to investigate the three-dimensional structure of axonal mitochondria and mitochondria in the surrounding Schwann cells of the peripheral nervous system (PNS), both in the vicinity of nodes of Ranvier and far from these nodes. Condensed mitochondria were found to be abundant in the axoplasm, but not in the Schwann cell. Uncharacteristic of the classical morphology of condensed mitochondria, the outer and inner boundary membranes are in close apposition and the crista junctions are narrow, consistent with their function as gates for the diffusion of macromolecules. There is also less cristae surface area and lower density of crista junctions in these mitochondria. The density of mitochondria was greater at the paranode-node-paranode (PNP) as was the crista junction opening, yet there were fewer cristae in these organelles compared to those in the internodal region. The greater density of condensed mitochondria in the PNS axoplasm and in particular at the PNP suggests a need for these organelles to operate at a high workload of ATP production.
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Affiliation(s)
- Guy A Perkins
- National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California, San Diego, La Jolla, CA 92093-0608, United States.
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Rolland SG, Lu Y, David CN, Conradt B. The BCL-2-like protein CED-9 of C. elegans promotes FZO-1/Mfn1,2- and EAT-3/Opa1-dependent mitochondrial fusion. ACTA ACUST UNITED AC 2009; 186:525-40. [PMID: 19704021 PMCID: PMC2733758 DOI: 10.1083/jcb.200905070] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The mammalian dynamin-related guanosine triphosphatases Mfn1,2 and Opa1 are required for mitochondrial fusion. However, how their activities are controlled and coordinated is largely unknown. We present data that implicate the BCL-2–like protein CED-9 in the control of mitochondrial fusion in Caenorhabditis elegans. We demonstrate that CED-9 can promote complete mitochondrial fusion of both the outer and inner mitochondrial membrane. We also show that this fusion is dependent on the C. elegans Mfn1,2 homologue FZO-1 and the C. elegans Opa1 homologue EAT-3. Furthermore, we show that CED-9 physically interacts with FZO-1 in vivo and that the ability of CED-9 to interact with FZO-1 is important for its ability to cause mitochondrial fusion. CED-9–induced mitochondrial fusion is not required for the maintenance of mitochondrial morphology during embryogenesis or in muscle cells, at least under normal conditions and in the absence of stress. Therefore, we propose that the BCL-2–like CED-9 acts through FZO-1/Mfn1,2 and EAT-3/Opa1 to promote mitochondrial fusion in response to specific cellular signals.
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Affiliation(s)
- Stéphane G Rolland
- Department of Genetics, Norris Cotton Cancer Center, Dartmouth Medical School, Hanover, NH 03755, USA
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12
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New insights into mitochondrial structure during cell death. Exp Neurol 2009; 218:183-92. [PMID: 19464290 DOI: 10.1016/j.expneurol.2009.05.021] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Revised: 04/30/2009] [Accepted: 05/08/2009] [Indexed: 01/06/2023]
Abstract
Mitochondria play a pivotal role in the cascade of events associated with cell death pathways that are involved with several forms of neurodegeneration. Recent findings show that in the Bax/Bak-dependent pathway of apoptosis, the release of cytochrome c from mitochondria is a consequence of two carefully coordinated events: opening of crista junctions triggered by OPA1 oligomer disassembly and formation of outer membrane pores. Both steps are necessary for the complete release of pro-apoptotic proteins. The remodeling of mitochondrial structure accompanies this pathway, including mitochondrial fission, and cristae and crista junction alterations. Yet, there is controversy surrounding the timing of certain remodeling events and whether they are necessary early events required for the release of pro-apoptotic factors or are simply a downstream after-effect. Here, we analyze the current knowledge of mitochondrial remodeling during cell death and discuss what structural alterations occur to this organelle during neurodegeneration, focusing on the higher resolution structural correlates obtained by electron microscopy and electron tomography.
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13
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OPA1 functions in mitochondria and dysfunctions in optic nerve. Int J Biochem Cell Biol 2009; 41:1866-74. [PMID: 19389483 DOI: 10.1016/j.biocel.2009.04.013] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2008] [Revised: 04/11/2009] [Accepted: 04/14/2009] [Indexed: 11/23/2022]
Abstract
OPA1 is the major gene responsible for Dominant Optic Atrophy (DOA), a blinding disease that affects specifically the retinal ganglion cells (RGCs), which function consists in connecting the neuro-retina to the brain. OPA1 encodes an intra-mitochondrial dynamin, involved in inner membrane structures and ubiquitously expressed, raising the critical question of the origin of the disease pathophysiology. Here, we review the fundamental knowledge on OPA1 functions and regulations, highlighting their involvements in mitochondrial respiration, membrane dynamic and apoptosis. In light of these functions, we then describe the remarkable RGC mitochondrial network physiology and analyse data collected from animal models expressing OPA1 mutations. If, to date RGC mitochondria does not present any peculiarity at the molecular level, they represent possible targets of numerous assaults, like light, pressure, oxidative stress and energetic impairment, which jeopardize their function and survival, as observed in OPA1 mouse models. Although fascinating fields of investigation are still to be addressed on OPA1 functions and on DOA pathophysiology, we have reached a conspicuous state of knowledge with pertinent cell and animal models, from which therapeutic trials can be initiated and deeply evaluated.
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14
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Yamaguchi R, Perkins G. Dynamics of mitochondrial structure during apoptosis and the enigma of Opa1. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:963-72. [PMID: 19245786 DOI: 10.1016/j.bbabio.2009.02.005] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Revised: 02/07/2009] [Accepted: 02/10/2009] [Indexed: 01/06/2023]
Abstract
"The large scale remodeling of mitochondria during apoptosis is a necessary step for the complete release of cytochrome c" has been a tenet since 2002. However, more recent findings strongly indicate that the large-scale remodeling previously described actually takes place after the release of cytochrome c and in a caspase-dependent manner, bringing into question whether mitochondria remodeling is necessary. In a more recent article, however, it was shown that a much more subtle form of remodeling is taking place which is only observable by electron tomography. In the Bcl-2 inhibitable Bax/Bak-dependent intrinsic pathway of apoptosis, the release of cytochrome c from mitochondria is a consequence of two carefully coordinated events: formation of outer membrane pores and opening of crista junctions triggered by Opa1 oligomer disassembly, and both steps are necessary for the complete release of cytochrome c. We review the recent literature pertaining to the coordinated release of cytochrome c during cell death.
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Affiliation(s)
- Ryuji Yamaguchi
- Burnham Institute for Medical Science, 10901 N. Torrey Pines Rd., La Jolla, CA 92037, USA.
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15
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Hunsucker SW, Solomon B, Gawryluk J, Geiger JD, Vacano GN, Duncan MW, Patterson D. Assessment of post-mortem-induced changes to the mouse brain proteome. J Neurochem 2008; 105:725-37. [DOI: 10.1111/j.1471-4159.2007.05183.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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16
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Yarosh W, Monserrate J, Tong JJ, Tse S, Le PK, Nguyen K, Brachmann CB, Wallace DC, Huang T. The molecular mechanisms of OPA1-mediated optic atrophy in Drosophila model and prospects for antioxidant treatment. PLoS Genet 2008; 4:e6. [PMID: 18193945 PMCID: PMC2174975 DOI: 10.1371/journal.pgen.0040006] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2007] [Accepted: 11/27/2007] [Indexed: 11/18/2022] Open
Abstract
Mutations in optic atrophy 1 (OPA1), a nuclear gene encoding a mitochondrial protein, is the most common cause for autosomal dominant optic atrophy (DOA). The condition is characterized by gradual loss of vision, color vision defects, and temporal optic pallor. To understand the molecular mechanism by which OPA1 mutations cause optic atrophy and to facilitate the development of an effective therapeutic agent for optic atrophies, we analyzed phenotypes in the developing and adult Drosophila eyes produced by mutant dOpa1 (CG8479), a Drosophila ortholog of human OPA1. Heterozygous mutation of dOpa1 by a P-element or transposon insertions causes no discernable eye phenotype, whereas the homozygous mutation results in embryonic lethality. Using powerful Drosophila genetic techniques, we created eye-specific somatic clones. The somatic homozygous mutation of dOpa1 in the eyes caused rough (mispatterning) and glossy (decreased lens and pigment deposition) eye phenotypes in adult flies; this phenotype was reversible by precise excision of the inserted P-element. Furthermore, we show the rough eye phenotype is caused by the loss of hexagonal lattice cells in developing eyes, suggesting an increase in lattice cell apoptosis. In adult flies, the dOpa1 mutation caused an increase in reactive oxygen species (ROS) production as well as mitochondrial fragmentation associated with loss and damage of the cone and pigment cells. We show that superoxide dismutase 1 (SOD1), Vitamin E, and genetically overexpressed human SOD1 (hSOD1) is able to reverse the glossy eye phenotype of dOPA1 mutant large clones, further suggesting that ROS play an important role in cone and pigment cell death. Our results show dOpa1 mutations cause cell loss by two distinct pathogenic pathways. This study provides novel insights into the pathogenesis of optic atrophy and demonstrates the promise of antioxidants as therapeutic agents for this condition. Optic atrophies are a group of neurodegenerative disorders characterized by a gradual loss of vision, color vision defects, and temporal optic pallor. Autosomal dominant optic atrophy (DOA), a type of optic atrophy, contributes to a large portion of optic atrophy cases. Mutations of the optic atrophy 1 (OPA1) gene are responsible for this condition. Here we describe mutant Drosophila that contain insertions in the Drosophila OPA1 ortholog, dOpa1. Heterozygous mutation causes no discernable eye phenotype, and homozygous mutation results in embryonic lethality. Using the powerful Drosophila genetic techniques, we created eye-specific mutants, giving rise to cells with two mutant copies of dOpa1 only in the Drosophila eye, and found that these eyes were rough (mispatterned) and glossy (decreased lens and pigment deposition). We found that these phenotypes were associated with fragmented mitochondria and were caused by elevated reactive oxygen species. The administration of antioxidants could ameliorate the phenotypes caused by mutation of dOpa1, offering new insight into treatment of this disease.
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MESH Headings
- Amino Acid Sequence
- Animals
- Antioxidants/therapeutic use
- DNA Transposable Elements/genetics
- Disease Models, Animal
- Drosophila
- Drosophila Proteins/chemistry
- Drosophila Proteins/genetics
- Drosophila Proteins/metabolism
- Eye/ultrastructure
- GTP Phosphohydrolases/chemistry
- GTP Phosphohydrolases/genetics
- GTP Phosphohydrolases/metabolism
- Gene Dosage
- Genes, Dominant
- Genes, Insect
- Genetic Techniques
- Homozygote
- Humans
- Membrane Proteins/chemistry
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Molecular Sequence Data
- Mutagenesis, Insertional
- Mutation
- Optic Atrophy, Autosomal Dominant/etiology
- Optic Atrophy, Autosomal Dominant/genetics
- Optic Atrophy, Autosomal Dominant/pathology
- Optic Atrophy, Autosomal Dominant/therapy
- Penetrance
- Protein Structure, Tertiary
- Sequence Homology, Amino Acid
- Superoxide Dismutase/therapeutic use
- Vitamin E/therapeutic use
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Affiliation(s)
- Will Yarosh
- Department of Pediatrics, Division of Human Genetics, University of California Irvine, Irvine, California, United States of America
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, California, United States of America
| | - Jessica Monserrate
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, California, United States of America
| | - James Jiayuan Tong
- Department of Biological Chemistry, University of California Irvine, Irvine, California, United States of America
- Center for Molecular and Mitochondrial Medicine and Genetics, University of California Irvine, Irvine, California, United States of America
| | - Stephanie Tse
- Department of Pediatrics, Division of Human Genetics, University of California Irvine, Irvine, California, United States of America
| | - Phung Khanh Le
- Department of Pediatrics, Division of Human Genetics, University of California Irvine, Irvine, California, United States of America
| | - Kimberly Nguyen
- Department of Pediatrics, Division of Human Genetics, University of California Irvine, Irvine, California, United States of America
| | - Carrie B Brachmann
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, California, United States of America
| | - Douglas C Wallace
- Department of Biological Chemistry, University of California Irvine, Irvine, California, United States of America
- Center for Molecular and Mitochondrial Medicine and Genetics, University of California Irvine, Irvine, California, United States of America
| | - Taosheng Huang
- Department of Pediatrics, Division of Human Genetics, University of California Irvine, Irvine, California, United States of America
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, California, United States of America
- Department of Pathology, University of California Irvine, Irvine, California, United States of America
- * To whom correspondence should be addressed. E-mail:
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17
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Chung S, Dzeja PP, Faustino RS, Perez-Terzic C, Behfar A, Terzic A. Mitochondrial oxidative metabolism is required for the cardiac differentiation of stem cells. ACTA ACUST UNITED AC 2007; 4 Suppl 1:S60-7. [PMID: 17230217 PMCID: PMC3232050 DOI: 10.1038/ncpcardio0766] [Citation(s) in RCA: 393] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2006] [Accepted: 11/13/2006] [Indexed: 12/15/2022]
Abstract
Cardiogenesis within embryos or associated with heart repair requires stem cell differentiation into energetically competent, contracting cardiomyocytes. While it is widely accepted that the coordination of genetic circuits with developmental bioenergetics is critical to phenotype specification, the metabolic mechanisms that drive cardiac transformation are largely unknown. Here, we aim to define the energetic requirements for and the metabolic microenvironment needed to support the cardiac differentiation of embryonic stem cells. We demonstrate that anaerobic glycolytic metabolism, while sufficient for embryonic stem cell homeostasis, must be transformed into the more efficient mitochondrial oxidative metabolism to secure cardiac specification and excitation-contraction coupling. This energetic switch was programmed by rearrangement of the metabolic transcriptome that encodes components of glycolysis, fatty acid oxidation, the Krebs cycle, and the electron transport chain. Modifying the copy number of regulators of mitochondrial fusion and fission resulted in mitochondrial maturation and network expansion, which in turn provided an energetic continuum to supply nascent sarcomeres. Disrupting respiratory chain function prevented mitochondrial organization and compromised the energetic infrastructure, causing deficient sarcomerogenesis and contractile malfunction. Thus, establishment of the mitochondrial system and engagement of oxidative metabolism are prerequisites for the differentiation of stem cells into a functional cardiac phenotype. Mitochondria-dependent energetic circuits are thus critical regulators of de novo cardiogenesis and targets for heart regeneration.
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Affiliation(s)
| | | | | | | | | | - Andre Terzic
- Correspondence: Marriott Heart Disease Research Program, Division of Cardiovascular Diseases, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA
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18
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Meeusen S, DeVay R, Block J, Cassidy-Stone A, Wayson S, McCaffery JM, Nunnari J. Mitochondrial inner-membrane fusion and crista maintenance requires the dynamin-related GTPase Mgm1. Cell 2006; 127:383-95. [PMID: 17055438 DOI: 10.1016/j.cell.2006.09.021] [Citation(s) in RCA: 361] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2006] [Revised: 06/19/2006] [Accepted: 09/04/2006] [Indexed: 11/15/2022]
Abstract
Mitochondrial outer- and inner-membrane fusion events are coupled in vivo but separable and mechanistically distinct in vitro, indicating that separate fusion machines exist in each membrane. Outer-membrane fusion requires trans interactions of the dynamin-related GTPase Fzo1, GTP hydrolysis, and an intact inner-membrane proton gradient. Inner-membrane fusion also requires GTP hydrolysis but distinctly requires an inner-membrane electrical potential. The protein machinery responsible for inner-membrane fusion is unknown. Here, we show that the conserved intermembrane-space dynamin-related GTPase Mgm1 is required to tether and fuse mitochondrial inner membranes. We observe an additional role of Mgm1 in inner-membrane dynamics, specifically in the maintenance of crista structures. We present evidence that trans Mgm1 interactions on opposing inner membranes function similarly to tether and fuse inner membranes as well as maintain crista structures and propose a model for how the mitochondrial dynamins function to facilitate fusion.
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Affiliation(s)
- Shelly Meeusen
- Section of Molecular and Cellular Biology, Center of Genetics and Development, University of California, Davis, 95616, USA
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