101
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Huang P, Yu T, Yoon Y. Mitochondrial clustering induced by overexpression of the mitochondrial fusion protein Mfn2 causes mitochondrial dysfunction and cell death. Eur J Cell Biol 2007; 86:289-302. [PMID: 17532093 DOI: 10.1016/j.ejcb.2007.04.002] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Revised: 03/15/2007] [Accepted: 04/16/2007] [Indexed: 10/23/2022] Open
Abstract
Mitochondria change their shapes dynamically mainly through fission and fusion. Dynamin-related GTPases have been shown to mediate remodeling of mitochondrial membranes during these processes. One of these GTPases, mitofusin, is anchored at the outer mitochondrial membrane and mediates fusion of the outer membrane. We found that overexpression of a mitofusin isoform, Mfn2, drastically changes mitochondrial morphology, forming mitochondrial clusters. High-resolution microscopic examination indicated that the mitochondrial clusters consisted of small fragmented mitochondria. Inhibiting mitochondrial fission prevented the cluster formation, supporting the notion that mitochondrial clusters are formed by fission-mediated mitochondrial fragmentation and aggregation. Mitochondrial clusters displayed a decreased inner membrane potential and mitochondrial function, suggesting a functional compromise of small fragmented mitochondria produced by Mfn2 overexpression; however, mitochondrial clusters still retained mitochondrial DNA. We found that cells containing clustered mitochondria lost cytochrome c from mitochondria and underwent caspase-mediated apoptosis. These results demonstrate that mitochondrial deformation impairs mitochondrial function, leading to apoptotic cell death and suggest the presence of an intricate form-function relationship in mitochondria.
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Affiliation(s)
- Pinwei Huang
- Department of Pharmacology and Physiology, University of Rochester, School of Medicine and Dentistry, 601 Elmwood Avenue, P.O. Box 604, Rochester, NY 14642, USA
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102
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Bantseev V, Youn HY. Mitochondrial "movement" and lens optics following oxidative stress from UV-B irradiation: cultured bovine lenses and human retinal pigment epithelial cells (ARPE-19) as examples. Ann N Y Acad Sci 2007; 1091:17-33. [PMID: 17341599 DOI: 10.1196/annals.1378.051] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Mitochondria provide energy generated by oxidative phosphorylation and at the same time play a central role in apoptosis and aging. As a byproduct of respiration, the electron transport chain is known to be the major intracellular site for the generation of reactive oxygen species (ROS). Exposure to solar and occupational ultraviolet (UV) radiation, and thus production of ROS and subsequent cell death, has been implicated in a large spectrum of skin and ocular pathologies, including cataract. Retinal pigment epithelial cell apoptosis generates photoreceptor dysfunction and ultimately visual impairment. The purpose of this article was to characterize in vitro changes following oxidative stress with UV-B radiation in (a) ocular lens optics and cellular function in terms of mitochondrial dynamics of bovine lens epithelium and superficial cortical fiber cells and (b) human retinal pigment epithelial (ARPE-19) cells. Cultured bovine lenses and confluent cultures of ARPE-19 cells were irradiated with broadband UV-B radiation at energy levels of 0.5 and 1.0 J/cm(2). Lens optical function (spherical aberration) was monitored daily up to 14 days using an automated laser scanning system that was developed at the University of Waterloo. This system consists of a single collimated scanning helium-neon laser source that projects a thin (0.05 mm) laser beam onto a plain mirror mounted at 45 degrees on a carriage assembly. This mirror reflects the laser beam directly up through the scanner table surface and through the lens under examination. A digital camera captures the actual position and slope of the laser beam at each step. When all steps have been made, the captured data for each step position is used to calculate the back vertex distance for each position and the difference in that measurement between beams. To investigate mitochondrial movement, the mitochondria-specific fluorescent dye Rhodamine 123 was used. Time series were acquired with a Zeiss 510 (configuration Meta 18) confocal laser scanning microscope equipped with an inverted Axiovert 200 M microscope and 40-x water-immersion C-Apochromat objective (NA 1.2). The optical analysis showed energy level-dependent increases in back vertex distance variability (loss of sharp focus) from 0.39 +/- 0.04 mm (control, n = 11) to 1.63 +/- 0.33 mm (1.0 J/cm(2), n = 10) and 0.63 +/- 0.13 mm (0.5 J/cm(2), n = 9). Confocal laser scanning microscopy analysis of both bovine lenses and ARPE-19 cells showed that following treatment at 0.5 J/cm(2) the mitochondria stopped moving immediately whereas at 1.0 J/cm(2) not only did the mitochondria stop moving, but fragmentation and swelling was seen. Untreated control tissue exhibited up to 15 microm/min of movement of the mitochondria. This could represent normal morphological change, presumably allowing energy transmission across the cell from regions of low to regions of high ATP demand. Lack of mitochondrial movement, fragmentation, and swelling of mitochondria may represent early morphological changes following oxidative stress that may lead to activation of caspase-mediated apoptotic pathways.
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Affiliation(s)
- Vladimir Bantseev
- School of Optometry, University of Waterloo, Waterloo, Ontario N2L 3G1 Canada.
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103
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Busch KB, Bereiter-Hahn J, Wittig I, Schagger H, Jendrach M. Mitochondrial dynamics generate equal distribution but patchwork localization of respiratory Complex I. Mol Membr Biol 2007; 23:509-20. [PMID: 17127623 DOI: 10.1080/09687860600877292] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Highly dynamic mitochondrial morphology is a prerequisite for fusion and fission. Mitochondrial fusion may represent a rescue mechanism for impaired mitochondria by exchanging constituents (proteins, lipids and mitochondrial DNA) and thus maintaining functionality. Here we followed for the first time the dynamics of a protein complex of the respiratory chain during fusion and fission. HeLa cells with differently labelled respiratory Complex I were fused and the dynamics of Complex I were investigated. The mitochondrial proteins spread throughout the whole mitochondrial population within 3 to 6 h after induction of cell fusion. Mitochondria of fused cells displayed a patchy substructure where the differently labelled proteins occupied separate and distinct spaces. This patchy appearance was already--although less pronounced--observed within single mitochondria before fusion, indicating a specific localization of Complex I with restricted diffusion within the inner membrane. These findings substantiate the view of a homogenous mitochondrial population due to constantly rearranging mitochondria, but also indicate the existence of distinct inner mitochondrial sub-compartments for respiratory chain complexes.
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Affiliation(s)
- Karin B Busch
- Kinematic Cell Research Group, Institute for Cell Biology and Neuroscience, JW Goethe University, Frankfurt/Main, Germany.
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104
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Wiesner RJ, Zsurka G, Kunz WS. Mitochondrial DNA damage and the aging process: facts and imaginations. Free Radic Res 2007; 40:1284-94. [PMID: 17090418 DOI: 10.1080/10715760600913168] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Mitochondrial DNA (mtDNA) is a circular double-stranded molecule organized in nucleoids and covered by the histone-like protein mitochondrial transcription factor A (TFAM). Even though mtDNA repair capacity appears to be adequate the accumulation of mtDNA mutations has been shown to be at least one important molecular mechanism of human aging. Reactive oxygen species (ROS), which are generated at the FMN moiety of mitochondrial respiratory chain (RC) complex I, should be considered to be important at least for the generation of age-dependent mtDNA deletions. However, the accumulation of acquired mutations to functionally relevant levels in aged tissues seems to be a consequence of clonal expansions of single founder molecules and not of ongoing mutational events.
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Affiliation(s)
- Rudolf J Wiesner
- Faculty of Medicine, Institute of Vegetative Physiology, University of Köln, Köln, Germany.
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105
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Sundal S, Sharma S. Ultrastructural Findings for the Mitochondrial Subpopulation of Mice Skeletal Muscle after Adrenergic Stimulation by Clenbuterol. J Physiol Sci 2007; 57:7-14. [PMID: 17169166 DOI: 10.2170/physiolsci.rp007106] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2006] [Accepted: 12/05/2006] [Indexed: 11/05/2022]
Abstract
Clenbuterol, a beta-adrenoceptor agonist, has been reported to induce skeletal muscle hypertrophy. However, it has also been known to reduce aerobic exercise performance and to deleteriously affect endurance and sprint exercise performance in rats. In the present study, the chronic administration of clenbuterol (2 mg/kg body weight; 30 days) resulted in various ultrastructural changes in three different types of muscles, gastrocnemius, a mixed-fiber type; anterior latissimus dorsi (ALD), a predominantly fast-twitch type; and diaphragm, a largely oxidative-type. The most prominent changes included mitochondrial swelling, matricular vesiculation in mitochondria, mitochondrial hyperplasia, sarcoplasmic vesiculation, and intermyofibrillar dilations. An increase in the cross-sectional area of both the subsarcolemmal (170, 167, and 79%) and the intermyofibrillar (129, 134, and 84%) mitochondria is noticed in the gastrocnemius, ALD, and diaphragm, respectively. The ultramicroscopic and morphometric results suggest drug-induced defects in contractile and oxidative activities.
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Affiliation(s)
- Santosh Sundal
- Department of Biosciences, Himachal Pradesh University, Summer Hill, Shimla-171005, India
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106
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Merz S, Hammermeister M, Altmann K, Dürr M, Westermann B. Molecular machinery of mitochondrial dynamics in yeast. Biol Chem 2007; 388:917-26. [PMID: 17696775 DOI: 10.1515/bc.2007.110] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Mitochondria are amazingly dynamic organelles. They continuously move along cytoskeletal tracks and frequently fuse and divide. These processes are important for maintenance of mitochondrial functions, for inheritance of the organelles upon cell division, for cellular differentiation and for apoptosis. As the machinery of mitochondrial behavior has been highly conserved during evolution, it can be studied in simple model organisms, such as yeast. During the past decade, several key components of mitochondrial dynamics have been identified and functionally characterized in Saccharomyces cerevisiae. These include the mitochondrial fusion and fission machineries and proteins required for maintenance of tubular shape and mitochondrial motility. Taken together, these findings reveal a comprehensive picture that shows the cellular processes and molecular components required for mitochondrial inheritance and morphogenesis in a simple eukaryotic cell.
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Affiliation(s)
- Sandra Merz
- Institut für Zellbiologie, Universität Bayreuth, D-95440 Bayreuth, Germany
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107
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De Vos KJ, Sheetz MP. Visualization and quantification of mitochondrial dynamics in living animal cells. Methods Cell Biol 2007; 80:627-82. [PMID: 17445716 DOI: 10.1016/s0091-679x(06)80030-0] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Kurt J De Vos
- Department of Neuroscience, MRC Centre for Neurodegeneration Research, The Institute of Psychiatry, King's College London, De Crespigny Park, Denmark Hill, London, United Kingdom
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108
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Chang DTW, Reynolds IJ. Mitochondrial trafficking and morphology in healthy and injured neurons. Prog Neurobiol 2006; 80:241-68. [PMID: 17188795 DOI: 10.1016/j.pneurobio.2006.09.003] [Citation(s) in RCA: 170] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Revised: 09/14/2006] [Accepted: 09/18/2006] [Indexed: 12/21/2022]
Abstract
Mitochondria are the primary generators of ATP and are important regulators of intracellular calcium homeostasis. These organelles are dynamically transported along lengthy neuronal processes, presumably for appropriate distribution to cellular regions of high metabolic demand and elevated intracellular calcium, such as synapses. The removal of damaged mitochondria that produce harmful reactive oxygen species and promote apoptosis is also thought to be mediated by transport of mitochondria to autophagosomes. Mitochondrial trafficking is therefore important for maintaining neuronal and mitochondrial health while cessation of movement may lead to neuronal and mitochondrial dysfunction. Mitochondrial morphology is also dynamic and is remodeled during neuronal injury and disease. Recent studies reveal different manifestations and mechanisms of impaired mitochondrial movement and altered morphology in injured neurons. These are likely to cause varied courses toward neuronal degeneration and death. The goal of this review is to provide an appreciation of the full range of mitochondrial function, morphology and trafficking, and the critical role these parameters play in neuronal physiology and pathophysiology.
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Affiliation(s)
- Diane T W Chang
- Medical Scientist Training Program, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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109
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Abstract
The characteristic structural organization of mitochondria is the product of synthesis of macromolecules within the mitochondria together with the import of proteins and lipids synthesized outside the organelle. Synthetic and import processes are required for mitochondrial proliferation and might also facilitate the growth of pre-existing mitochondria. Recent evidence indicates that these events are regulated in a complex way by several agonists and environmental conditions, through activation of specific signaling pathways and transcription factors. A newly discovered role of this organelle in retrograde intracellular signaling back to the nucleus has also emerged. This is likely to have far-reaching implications in development, aging, disease and environmental adaptation. Generation of nitric oxide (NO) appears to be an important player in these processes, possibly acting as a unifying molecular switch to trigger the whole mitochondrial biogenesis process. High levels of NO acutely inhibit cell respiration by binding to cytochrome c oxidase. Conversely, chronic, smaller increases in NO levels stimulate mitochondrial biogenesis in diverse cell types. NO-induced mitochondrial biogenesis seems to be linked to proliferation and differentiation of normal and tumor cells, as well as in aging.
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Affiliation(s)
- Enzo Nisoli
- Department of Pharmacology, Chemotherapy and Medical Toxicology, School of Medicine, Milan University, via Vanvitelli 32, 20129 Milan, Italy.
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110
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Buvelot Frei S, Rahl PB, Nussbaum M, Briggs BJ, Calero M, Janeczko S, Regan AD, Chen CZ, Barral Y, Whittaker GR, Collins RN. Bioinformatic and comparative localization of Rab proteins reveals functional insights into the uncharacterized GTPases Ypt10p and Ypt11p. Mol Cell Biol 2006; 26:7299-317. [PMID: 16980630 PMCID: PMC1592887 DOI: 10.1128/mcb.02405-05] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A striking characteristic of a Rab protein is its steady-state localization to the cytosolic surface of a particular subcellular membrane. In this study, we have undertaken a combined bioinformatic and experimental approach to examine the evolutionary conservation of Rab protein localization. A comprehensive primary sequence classification shows that 10 out of the 11 Rab proteins identified in the yeast (Saccharomyces cerevisiae) genome can be grouped within a major subclass, each comprising multiple Rab orthologs from diverse species. We compared the locations of individual yeast Rab proteins with their localizations following ectopic expression in mammalian cells. Our results suggest that green fluorescent protein-tagged Rab proteins maintain localizations across large evolutionary distances and that the major known player in the Rab localization pathway, mammalian Rab-GDI, is able to function in yeast. These findings enable us to provide insight into novel gene functions and classify the uncharacterized Rab proteins Ypt10p (YBR264C) as being involved in endocytic function and Ypt11p (YNL304W) as being localized to the endoplasmic reticulum, where we demonstrate it is required for organelle inheritance.
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Affiliation(s)
- Stéphanie Buvelot Frei
- Institut für Biochemie, Swiss Federal Institute of Technology (ETH), CH-8093 Zürich, Switzerland
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111
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Foster KA, Galeffi F, Gerich FJ, Turner DA, Müller M. Optical and pharmacological tools to investigate the role of mitochondria during oxidative stress and neurodegeneration. Prog Neurobiol 2006; 79:136-71. [PMID: 16920246 PMCID: PMC1994087 DOI: 10.1016/j.pneurobio.2006.07.001] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2006] [Revised: 07/10/2006] [Accepted: 07/11/2006] [Indexed: 02/06/2023]
Abstract
Mitochondria are critical for cellular adenosine triphosphate (ATP) production; however, recent studies suggest that these organelles fulfill a much broader range of tasks. For example, they are involved in the regulation of cytosolic Ca(2+) levels, intracellular pH and apoptosis, and are the major source of reactive oxygen species (ROS). Various reactive molecules that originate from mitochondria, such as ROS, are critical in pathological events, such as ischemia, as well as in physiological events such as long-term potentiation, neuronal-vascular coupling and neuronal-glial interactions. Due to their key roles in the regulation of several cellular functions, the dysfunction of mitochondria may be critical in various brain disorders. There has been increasing interest in the development of tools that modulate mitochondrial function, and the refinement of techniques that allow for real time monitoring of mitochondria, particularly within their intact cellular environment. Innovative imaging techniques are especially powerful since they allow for mitochondrial visualization at high resolution, tracking of mitochondrial structures and optical real time monitoring of parameters of mitochondrial function. The techniques discussed include classic imaging techniques, such as rhodamine-123, the highly advanced semi-conductor nanoparticles (quantum dots), and wide field microscopy as well as high-resolution multiphoton imaging. We have highlighted the use of these techniques to study mitochondrial function in brain tissue and have included studies from our laboratories in which these techniques have been successfully applied.
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Affiliation(s)
- Kelley A. Foster
- Research and Surgery Services Durham Veterans Affairs Medical Center; Neurosurgery and Neurobiology, Duke University Medical Center, Box 3807, Durham, NC 27710, USA
| | - Francesca Galeffi
- Research and Surgery Services Durham Veterans Affairs Medical Center; Neurosurgery and Neurobiology, Duke University Medical Center, Box 3807, Durham, NC 27710, USA
| | - Florian J. Gerich
- Zentrum für Physiologie und Pathophysiologie, Abteilung Neuro- und Sinnesphysiologie, Georg-August-Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany
| | - Dennis A. Turner
- Research and Surgery Services Durham Veterans Affairs Medical Center; Neurosurgery and Neurobiology, Duke University Medical Center, Box 3807, Durham, NC 27710, USA
| | - Michael Müller
- DFG Center Molecular Physiology of the Brain, Georg-August-Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany
- Zentrum für Physiologie und Pathophysiologie, Abteilung Neuro- und Sinnesphysiologie, Georg-August-Universität Göttingen, Humboldtallee 23, D-37073 Göttingen, Germany
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112
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Arakaki N, Nishihama T, Owaki H, Kuramoto Y, Suenaga M, Miyoshi E, Emoto Y, Shibata H, Shono M, Higuti T. Dynamics of mitochondria during the cell cycle. Biol Pharm Bull 2006; 29:1962-5. [PMID: 16946518 DOI: 10.1248/bpb.29.1962] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mitochondria are highly dynamic organelles in eukaryotic cells. Although the role of mitochondria in metabolism, ATP production and apoptosis is more widely recognized, alterations in mitochondrial morphology and abundance are also important for cellular functions. Here we investigated mitochondrial dynamics in synchronized HeLa cells in which the major stages of the cell cycle of the observed cells were resolved by staining phosphorylate histones H1 and H3, and showed that mitochondria exist as filamentous network structures throughout the cell cycle progression, changing their morphology, distribution, and abundance. The current results suggest that mitochondrial condensation occurred at prophase is required for the proper progression of mitochondrial division.
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Affiliation(s)
- Naokatu Arakaki
- Department of Molecular Cell Biology and Medicine, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan.
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113
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González-García JS, Delgado J. Comparison of efficiency of translation between a deformable swimmer versus a rigid body in a bounded fluid domain: consequences for subcellular transport. J Biol Phys 2006; 32:97-115. [PMID: 19669454 DOI: 10.1007/s10867-006-9003-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
In this paper, we compare the translation efficiencies of a deformable circle that swims by means of low amplitude periodic tangential surface waves versus a rigid circle, moving in a bounded fluid domain. The swimmer is found to be much more efficient than the rigid body. We believe that this result gives some support to the active hypothesis of subcellular transport, where it is supposed that the organelle can generate by itself a propulsive flux, (by changes of form or metabolic activities) instead of just being carried by the motion of an external agent, like a molecular motor.
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Affiliation(s)
- José S González-García
- Departamento de Matemáticas, Universidad Autónoma, Metropolitana-Iztapalapa, Vicentina. C.P., 09340, México, D.F., México
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114
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Dürr M, Escobar-Henriques M, Merz S, Geimer S, Langer T, Westermann B. Nonredundant roles of mitochondria-associated F-box proteins Mfb1 and Mdm30 in maintenance of mitochondrial morphology in yeast. Mol Biol Cell 2006; 17:3745-55. [PMID: 16790496 PMCID: PMC1593156 DOI: 10.1091/mbc.e06-01-0053] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2006] [Revised: 06/07/2006] [Accepted: 06/08/2006] [Indexed: 01/24/2023] Open
Abstract
Mitochondria constantly fuse and divide to adapt organellar morphology to the cell's ever-changing physiological conditions. Little is known about the molecular mechanisms regulating mitochondrial dynamics. F-box proteins are subunits of both Skp1-Cullin-F-box (SCF) ubiquitin ligases and non-SCF complexes that regulate a large number of cellular processes. Here, we analyzed the roles of two yeast F-box proteins, Mfb1 and Mdm30, in mitochondrial dynamics. Mfb1 is a novel mitochondria-associated F-box protein. Mitochondria in mutants lacking Mfb1 are fusion competent, but they form aberrant aggregates of interconnected tubules. In contrast, mitochondria in mutants lacking Mdm30 are highly fragmented due to a defect in mitochondrial fusion. Fragmented mitochondria are docked but nonfused in Deltamdm30 cells. Mitochondrial fusion is also blocked during sporulation of homozygous diploid mutants lacking Mdm30, leading to a mitochondrial inheritance defect in ascospores. Mfb1 and Mdm30 exert nonredundant functions and likely have different target proteins. Because defects in F-box protein mutants could not be mimicked by depletion of SCF complex and proteasome core subunits, additional yet unknown factors are likely involved in regulating mitochondrial dynamics. We propose that mitochondria-associated F-box proteins Mfb1 and Mdm30 are key components of a complex machinery that regulates mitochondrial dynamics throughout yeast's entire life cycle.
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Affiliation(s)
| | | | | | - Stefan Geimer
- *Institut für Zellbiologie
- Abteilung für Elektronenmikroskopie, and
| | - Thomas Langer
- Institut für Genetik, Universität zu Köln, 50674 Köln, Germany
| | - Benedikt Westermann
- *Institut für Zellbiologie
- Abteilung für Elektronenmikroskopie, and
- Bayreuther Zentrum für Molekulare Biowissenschaften, Universität Bayreuth, 95440 Bayreuth, Germany; and
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115
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Hackstein JHP, Tjaden J, Huynen M. Mitochondria, hydrogenosomes and mitosomes: products of evolutionary tinkering! Curr Genet 2006; 50:225-45. [PMID: 16897087 DOI: 10.1007/s00294-006-0088-8] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2006] [Revised: 06/29/2006] [Accepted: 07/02/2006] [Indexed: 11/29/2022]
Affiliation(s)
- Johannes H P Hackstein
- Department of Evolutionary Microbiology, Faculty of Science, Radboud University Nijmegen, Toernooiveld 1, 6525, ED Nijmegen, The Netherlands.
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116
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Calamita G, Gena P, Meleleo D, Ferri D, Svelto M. Water permeability of rat liver mitochondria: A biophysical study. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1758:1018-24. [PMID: 16934743 DOI: 10.1016/j.bbamem.2006.07.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2005] [Revised: 07/10/2006] [Accepted: 07/14/2006] [Indexed: 12/01/2022]
Abstract
The movement of water accompanying solutes between the cytoplasm and the mitochondrial spaces is central for mitochondrial volume homeostasis, an important function for mitochondrial activities and for preventing the deleterious effects of excess matrix swelling or contraction. While the discovery of aquaporin water channels in the inner mitochondrial membrane provided valuable insights into the basis of mitochondrial plasticity, questions regarding the identity of mitochondrial water permeability and its regulatory mechanism remain open. Here, we use a stopped flow light scattering approach to define the water permeability and Arrhenius activation energy of the rat liver whole intact mitochondrion and its membrane subcompartments. The water permeabilities of whole brain and testis mitochondria as well as liposome models of the lipid bilayer composing the liver inner mitochondrial membrane are also characterized. Besides finding remarkably high water permeabilities for both mitochondria and their membrane subcompartments, the existence of additional pathways of water movement other than aquaporins are suggested.
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Affiliation(s)
- Giuseppe Calamita
- Dipartimento di Fisiologia Generale ed Ambientale and Centro di Eccellenza di Genomica in campo Biomedico ed Agrario (CEGBA), Università degli Studi di Bari, Via Amendola 165/A, 70126 Bari, Italy.
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117
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Twig G, Graf SA, Wikstrom JD, Mohamed H, Haigh SE, Elorza A, Deutsch M, Zurgil N, Reynolds N, Shirihai OS. Tagging and tracking individual networks within a complex mitochondrial web with photoactivatable GFP. Am J Physiol Cell Physiol 2006; 291:C176-84. [PMID: 16481372 DOI: 10.1152/ajpcell.00348.2005] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Assembly of mitochondria into networks supports fuel metabolism and calcium transport and is involved in the cellular response to apoptotic stimuli. A mitochondrial network is defined as a continuous matrix lumen whose boundaries limit molecular diffusion. Observation of individual networks has proven challenging in live cells that possess dense populations of mitochondria. Investigation into the electrical and morphological properties of mitochondrial networks has therefore not yielded consistent conclusions. In this study we used matrix-targeted, photoactivatable green fluorescent protein to tag single mitochondrial networks. This approach, coupled with real-time monitoring of mitochondrial membrane potential, permitted the examination of matrix lumen continuity and fusion and fission events over time. We found that adjacent and intertwined mitochondrial structures often represent a collection of distinct networks. We additionally found that all areas of a single network are invariably equipotential, suggesting that a heterogeneous pattern of membrane potential within a cell's mitochondria represents differences between discrete networks. Interestingly, fission events frequently occurred without any gross morphological changes and particularly without fragmentation. These events, which are invisible under standard confocal microscopy, redefine the mitochondrial network boundaries and result in electrically disconnected daughter units.
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Affiliation(s)
- Gilad Twig
- Department of Pharmacology and Experimental Therapeutics, Tufts University, 136 Harrison Ave., Boston, MA 02111, USA
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118
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Dadgar S, Hagens O, Dadgar SR, Haghighi EN, Schimpf S, Wissinger B, Garshasbi M. Structural model of the OPA1 GTPase domain may explain the molecular consequences of a novel mutation in a family with autosomal dominant optic atrophy. Exp Eye Res 2006; 83:702-6. [PMID: 16698014 DOI: 10.1016/j.exer.2006.03.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2005] [Revised: 01/27/2006] [Accepted: 03/07/2006] [Indexed: 11/21/2022]
Abstract
Autosomal dominant optic atrophy (ADOA) is the most frequent hereditary optic neuropathy. Three loci have been reported for ADOA: a major locus, harboring all identified mutations to date, maps to 3q28 (OPA1), a second locus is linked to 18q12.2-q12.3 (OPA4) and a third locus on 22q12.1-q13.1 (OPA5) has been reported recently. We describe a six-generation Iranian family in which optic atrophy runs as an autosomal dominant trait with an age of onset at 14-15years. We performed linkage analysis with markers mapping to 3q28 and 18q12.2-q12.3 and found linkage to 3q28. Subsequent sequencing of OPA1 identified a novel heterozygous missense mutation (c.1313A>G) replacing aspartic acid by glycine (p.D438G) in the GTPase domain of OPA1. Interestingly, another missense mutation at the same position (c.1313A>T, D438V) has been reported before in two unrelated German families, indicating a possible mutation hot spot. Further evidence supporting the importance of D438 is its conservation from human to acoelomata. OPA1 is believed to be the human orthologue of yeast MGM1, a dynamin-related protein required for the integrity of mitochondrial DNA. Homology modeling of the OPA1 GTPase domain revealed extensive structural similarity to the Dictyostelium dynamin A GTPase domain and showed that D438 may interact with residues of the G1 and the G4 motifs, which are crucial in coordinating GTP. Based on this analysis, we propose a mechanism which explains the gradual decline of vision in ADOA patients with OPA1 mutations at position 438.
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119
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Szabadkai G, Simoni AM, Bianchi K, De Stefani D, Leo S, Wieckowski MR, Rizzuto R. Mitochondrial dynamics and Ca2+ signaling. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2006; 1763:442-9. [PMID: 16750865 DOI: 10.1016/j.bbamcr.2006.04.002] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2006] [Revised: 03/28/2006] [Accepted: 04/04/2006] [Indexed: 11/18/2022]
Abstract
Recent data shed light on two novel aspects of the mitochondria-Ca2+ liaison. First, it was extensively investigated how Ca2+ handling is controlled by mitochondrial shape, and positioning; a playground also of cell death and survival regulation. On the other hand, significant progress has been made to explore how intra- and near-mitochondrial Ca2+ signals modify mitochondrial morphology and cellular distribution. Here, we shortly summarize these advances and provide a model of Ca2+-mitochondria interactions.
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Affiliation(s)
- G Szabadkai
- Department of Experimental and Diagnostic Medicine and Interdisciplinary Center for the Study of Inflammation and ER-GenTech, University of Ferrara, Italy
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120
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Banh A, Bantseev V, Choh V, Moran KL, Sivak JG. The lens of the eye as a focusing device and its response to stress. Prog Retin Eye Res 2006; 25:189-206. [PMID: 16330238 DOI: 10.1016/j.preteyeres.2005.10.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The continued peripheral growth of the lens, resulting in the concentration of older tissue toward the center, has the important optical consequence of producing a lens of variable refractive index. An approach consisting of the projection of fine laser beams through excised lenses in physiological solution has been used for in vitro study of lens optical quality. By varying the separation of the incident beams and/or the wavelength characteristics of the laser used, lens refractive properties and relative transparency may be examined. In the review provided, these optical properties are correlated to lens suture anatomy, lens mitochondrial morphology and function and the function of lens heat shock proteins. In addition, lens spherical aberration is evaluated as a function of accommodation. This work can be highlighted as follows: Mammalian lens suture morphology has a direct impact on lens optical function and, while suture structure of mammalian and avian lenses are very different, they both show an age-related deterioration in morphology and focusing ability. The distribution and appearance of mitochondria of the lens epithelium and superficial fiber cells are similar in all vertebrates. Lens mitochondrial integrity is correlated to lens focusing ability, suggesting a correlation between lens optical properties and lens metabolic function. The induction of cold cataract measured optically in cultured mammalian lenses is enhanced by thermal (heat) shock and this effect is prevented by inhibiting heat shock protein production. Finally, lens accommodative function can be studied by measuring lens refractive change using a physiological model involving an intact accommodative apparatus.
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Affiliation(s)
- Alice Banh
- School of Optometry, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
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121
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Aichinger N, Lütz-Meindl U. Organelle interactions and possible degradation pathways visualized in high-pressure frozen algal cells. J Microsc 2005; 219:86-94. [PMID: 16159344 DOI: 10.1111/j.1365-2818.2005.01496.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Summary Organelle interactions, although essential for both anabolic and catabolic pathways in plant cells have not been examined in detail so far. In the present study the structure of different organelle-organelle, organelle-vesicle and organelle-membrane interactions were investigated in growing and nongrowing cells of the green alga Micrasterias denticulata by use of high pressure freeze fixation and energy filtering transmission electron microscopy. It became clear that contacts between mitochondria always occur by formation of a cone-shaped protuberance of one of the mitochondria which penetrates into its fusion partner. In the same way, structural interactions between mitochondria and mucilage vesicles and between microbodies and mucilage vesicles are achieved. Lytic compartments contact mitochondria or mucilage vesicles again by forming protuberances and by extending their contents into the respective compartment. Detached portions of mitochondria are found inside lytic compartments as a consequence of such interactions. Mitochondria found in contact with the plasma membrane reveal structural disintegration. Our study shows that interactions of organelles and vesicles are frequent events in Micrasterias cells of different ages. The interactive contacts between lytic compartments and organelles or vesicles suggest a degradation pathway different from autophagy processes described in the literature. Both the interactions between vesicles and organelles and the degradation pathways occur independently from cytoskeleton function as demonstrated by use of cytochalasin D and the microtubule inhibitor amiprophos-methyl.
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Affiliation(s)
- N Aichinger
- Plant Physiology, Cell Biology Department, University of Salzburg, Austria
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122
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Banati RB, Egensperger R, Maassen A, Hager G, Kreutzberg GW, Graeber MB. Mitochondria in activated microglia in vitro. ACTA ACUST UNITED AC 2005; 33:535-41. [PMID: 15906160 DOI: 10.1007/s11068-004-0515-7] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2004] [Revised: 11/18/2004] [Accepted: 12/08/2004] [Indexed: 11/26/2022]
Abstract
In the CNS, microglia become activated, i.e. change their functional state and phenotype, in response to a wide variety of pathological stimuli. Since this activation is triggered at a very low threshold and at the same time remains territorially restricted, the spatial distribution of activated microglia can be used as a sensitive, generic measure of the anatomical localisation of ongoing disease processes. One protein complex, undetectable in resting microglia but highly up-regulated upon activation in vivo and in vitro, is the 'peripheral benzodiazepine binding site', as measured by binding of the isoquinoline derivate PK11195. Particularly numerous in the outer membrane of mitochondria, this binding site has also been referred to as the 'mitochondrial benzodiazepine receptor'. The de novo expression of this receptor by activated microglia suggests that the process of activation may be associated with important qualitative changes in the state of mitochondria. Here, we provide confocal light- and electron microscopic evidence that the activation of microglia indeed entails conspicuous mitochondrial alterations. In cultured rat microglia stained with the fluorescent probe, JC-1, a sensitive indicator of mitochondrial membrane potential, we demonstrate that stimulation by bacterial lipopolysaccharide and interferon-gamma increases the number of microglial mitochondrial profiles and leads to marked changes in their morphology. Prominent elongated, "needle-like" mitochondria are a characteristic feature of activated microglia in vitro. Electron microscopically, an abundance of abnormal profiles, including circular cristae or ring- and U-shaped membranes, are found. Our observations support the notion that the previously reported increase in microglial binding of PK11195, that labelled with carbon-11 ([11C] (R)-PK11195) has clinical use for the visualisation of activated microglia in vivo by positron emission tomography, may at least in part relate to an increased number and altered functional state of microglial mitochondria.
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Affiliation(s)
- Richard B Banati
- School of Medical Radiation Sciences, and Ramaciotti Centre for Brain Imaging (Brain-Mind Research Institute), University of Sydney, East Street PO Box 170, Lidcombe NSW 1825, Australia
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123
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Yu T, Fox RJ, Burwell LS, Yoon Y. Regulation of mitochondrial fission and apoptosis by the mitochondrial outer membrane protein hFis1. J Cell Sci 2005; 118:4141-51. [PMID: 16118244 DOI: 10.1242/jcs.02537] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Mitochondrial fission is a highly regulated process mediated by a defined set of protein factors and is involved in the early stage of apoptosis. In mammals, at least two proteins, the dynamin-like protein DLP1/Drp1 and the mitochondrial outer membrane protein hFis1, participate in mitochondrial fission. The cytosolic domain of hFis1 contains six alpha-helices that form two tetratricopeptide repeat (TPR) motifs. Overexpression of hFis1 induces DLP1-mediated fragmentation of mitochondria, suggesting that hFis1 is a limiting factor in mitochondrial fission by recruiting cytosolic DLP1. In the present study, we identified two regions of hFis1 that are necessary for correct fission of mitochondria. We found that the TPR region of hFis1 participates in the interaction with DLP1 or DLP1-containing complex and that the first helix (alpha1) of hFis1 is required for mitochondrial fission presumably by regulating DLP1-hFis1 interaction. Misregulated interaction between DLP1 and hFis1 by alpha1 deletion induced mitochondrial swelling, in part by the mitochondrial permeability transition, but significantly delayed cell death. Our data suggest that hFis1 is a main regulator of mitochondrial fission, controlling the recruitment and assembly of DLP1 during both normal and apoptotic fission processes.
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Affiliation(s)
- Tianzheng Yu
- Department of Anesthesiology, University of Rochester School of Medicine and Dentistry, 601 Elmwood Avenue, Rochester, NY 14642, USA
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124
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Clementi E, Nisoli E. Nitric oxide and mitochondrial biogenesis: a key to long-term regulation of cellular metabolism. Comp Biochem Physiol A Mol Integr Physiol 2005; 142:102-10. [PMID: 16091305 DOI: 10.1016/j.cbpb.2005.04.022] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2005] [Revised: 04/17/2005] [Accepted: 04/19/2005] [Indexed: 11/29/2022]
Abstract
Mitochondria, the site of oxidative energy metabolism in eukariotic cells, are a highly organised structure endowed with different enzymes and reactions localized in discrete membranes and aqueous compartments. Mitochondrial function is regulated in complex ways by several agonists and environmental conditions, through activation of specific transcription factors and signalling pathways. A key player in this scenario is nitric oxide (NO). Its binding to cytochrome c oxidase in the mitochondrial respiratory chain, which is reversible and in competition with oxygen, plays a role in acute oxygen sensing and in the cell response to hypoxia. Evidence of the last two years showed that NO has also long-term effects, leading to biogenesis of functionally active mitochondria, that complement its oxygen sensing function. Mitochondrial biogenesis is triggered by NO through activation of guanylate cyclase and generation of cyclic GMP, and yields formation of functionally active mitochondria. Thus, the combined action of NO at its two known intracellular receptors, cytochrome c oxidase and guanylate cyclase, appears to play a role in coupling energy generation with energy demand. This may explain why dysregulation of the NO signalling pathway is often associated with the pathogenesis of metabolic disorders.
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125
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He XY, Wegiel J, Yang SY. Intracellular oxidation of allopregnanolone by human brain type 10 17beta-hydroxysteroid dehydrogenase. Brain Res 2005; 1040:29-35. [PMID: 15804423 DOI: 10.1016/j.brainres.2005.01.022] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2004] [Revised: 12/30/2004] [Accepted: 01/04/2005] [Indexed: 11/17/2022]
Abstract
Allopregnanolone is a positive allosteric modulator of GABAA receptors, generated by the reduction of 5alpha-dihydroprogesterone (5alpha-DHP) in astrocytes. This neuroactive steroid can be inactivated by its 3alpha-oxidation to yield 5alpha-DHP. It was found that 5alpha-DHP levels in HEK293 cells expressing type 10 17beta-hydroxysteroid dehydrogenase (17beta-HSD10), but not its catalytic inactive mutant, increased significantly as allopregnanolone was added to culture media. The results demonstrate that mitochondrial 17beta-HSD10 effectively catalyzes the intracellular oxidation of allopregnanolone. Moreover, brain astrocytes contain a moderate level of 17beta-HSD10, which is elevated in activated astrocytes of brains with Alzheimer type pathology, including sporadic Alzheimer's disease (AD) and Down's syndrome with AD. The distribution of 17beta-HSD10 was found not to parallel that of 3alpha-HSD3. Cerebral cortex has the lowest level of 17beta-HSD10; whereas the hippocampus, hypothalamus, and amygdala possess relatively higher levels of this enzyme. The catalysis of 17beta-HSD10 appears to be essential for maintaining normal functions of GABAergic neurons. The elevated level of 17beta-HSD10 in activated astrocytes is a new feature found in brains of people with AD, and it may have important impact on AD pathogenesis.
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Affiliation(s)
- Xue-Ying He
- Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, Staten Island, NY 10314, USA
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126
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Xie B, Li H, Wang Q, Xie S, Rahmeh A, Dai W, Lee MYWT. Further Characterization of Human DNA Polymerase δ Interacting Protein 38. J Biol Chem 2005; 280:22375-84. [PMID: 15811854 DOI: 10.1074/jbc.m414597200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polymerase delta interacting protein 38 (PDIP38) was identified as a human DNA polymerase (pol) delta interacting protein through a direct interaction with p50, the small subunit of human pol delta. PDIP38 was also found to interact with proliferating cell nuclear antigen, which suggested that it might play a role in vivo in the processes of DNA replication and DNA repair in the nucleus. In order to characterize further this novel protein, we have examined its subcellular localization by the use of immunochemical and cellular fractionation techniques. These studies show that PDIP38 is a novel mitochondrial protein and is localized mainly to the mitochondria. PDIP38 was shown to possess a functional mitochondrial targeting sequence that is located within the first 35 N-terminal amino acid residues. The mature PDIP38 protein is about 50 amino acid residues smaller than the full-length precursor PDIP38 protein, consistent with it being processed by cleavage of the mitochondrial targeting sequence during entry into the mitochondria. His-tagged mature PDIP38 inhibited pol delta activity in vitro and interacted with human papillomavirus 16 E7 oncoprotein, suggesting that PDIP38 might play a role in the pol delta-mediated viral DNA replication. Although the localization of PDIP38 to the mitochondria suggests that it serves functions within the mitochondria, we cannot eliminate the possibility that it may be involved in pol delta-mediated DNA replication or DNA repair under certain conditions such as viral infection.
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Affiliation(s)
- Bin Xie
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY 10595, USA
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127
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De Vos KJ, Allan VJ, Grierson AJ, Sheetz MP. Mitochondrial function and actin regulate dynamin-related protein 1-dependent mitochondrial fission. Curr Biol 2005; 15:678-83. [PMID: 15823542 DOI: 10.1016/j.cub.2005.02.064] [Citation(s) in RCA: 269] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2004] [Revised: 02/14/2005] [Accepted: 02/16/2005] [Indexed: 12/25/2022]
Abstract
Mitochondria display a variety of shapes, ranging from small and spherical or the classical tubular shape to extended networks. Shape transitions occur frequently and include fusion, fission, and branching. It was reported that some mitochondrial shape transitions are developmentally regulated, whereas others were linked to disease or apoptosis. However, if and how mitochondrial function controls mitochondrial shape through regulation of mitochondrial fission and fusion is unclear. Here, we show that inhibitors of electron transport, ATP synthase, or the permeability transition pore (mtPTP) induced reversible mitochondrial fission. Mitochondrial fission depended on dynamin-related protein 1 (DRP1) and F-actin: Disruption of F-actin attenuated fission and recruitment of DRP1 to mitochondria. In contrast, uncoupling of electron transport and oxidative phosphorylation caused mitochondria to adopt a distinct disk shape. This shape change was independent of the cytoskeleton and DRP1 and was most likely caused by swelling. Thus, disruption of mitochondrial function rapidly and reversibly altered mitochondrial shape either by activation of DRP1-dependent fission or by swelling, indicating a close relationship between mitochondrial fission, shape, and function. Furthermore, our results suggest that the actin cytoskeleton is involved in mitochondrial fission by facilitating mitochondrial recruitment of DRP1.
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Affiliation(s)
- Kurt J De Vos
- Academic Unit of Neurology, Division of Genomic Medicine, School of Medicine and Biomedical Science, University of Sheffield, Sheffield S10 2RX, United Kingdom.
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128
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Dimmer KS, Jakobs S, Vogel F, Altmann K, Westermann B. Mdm31 and Mdm32 are inner membrane proteins required for maintenance of mitochondrial shape and stability of mitochondrial DNA nucleoids in yeast. ACTA ACUST UNITED AC 2005; 168:103-15. [PMID: 15631992 PMCID: PMC2171677 DOI: 10.1083/jcb.200410030] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The MDM31 and MDM32 genes are required for normal distribution and morphology of mitochondria in the yeast Saccharomyces cerevisiae. They encode two related proteins located in distinct protein complexes in the mitochondrial inner membrane. Cells lacking Mdm31 and Mdm32 harbor giant spherical mitochondria with highly aberrant internal structure. Mitochondrial DNA (mtDNA) is instable in the mutants, mtDNA nucleoids are disorganized, and their association with Mmm1-containing complexes in the outer membrane is abolished. Mutant mitochondria are largely immotile, resulting in a mitochondrial inheritance defect. Deletion of either one of the MDM31 and MDM32 genes is synthetically lethal with deletion of either one of the MMM1, MMM2, MDM10, and MDM12 genes, which encode outer membrane proteins involved in mitochondrial morphogenesis and mtDNA inheritance. We propose that Mdm31 and Mdm32 cooperate with Mmm1, Mmm2, Mdm10, and Mdm12 in maintenance of mitochondrial morphology and mtDNA.
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Affiliation(s)
- Kai Stefan Dimmer
- Institut für Physiologische Chemie, Universität München, 81377 München, Germany
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129
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Calamita G, Ferri D, Gena P, Liquori GE, Cavalier A, Thomas D, Svelto M. The inner mitochondrial membrane has aquaporin-8 water channels and is highly permeable to water. J Biol Chem 2005; 280:17149-53. [PMID: 15749715 DOI: 10.1074/jbc.c400595200] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondria are remarkably plastic organelles constantly changing their shape to fulfil their various functional activities. Although the osmotic movement of water into and out of the mitochondrion is central for its morphology and activity, the molecular mechanisms and the pathways for water transport across the inner mitochondrial membrane (IMM), the main barrier for molecules moving into and out of the organelle, are completely unknown. Here, we show the presence of a member of the aquaporin family of water channels, AQP8, and demonstrate the strikingly high water permeability (Pf) characterizing the rat liver IMM. Immunoblotting, electron microscopy, and biophysical studies show that the largest mitochondria feature the highest AQP8 expression and IMM Pf. AQP8 was also found in the mitochondria of other organs, whereas no other known aquaporins were seen. The osmotic water transport of liver IMM was partially inhibited by the aquaporin blocker Hg2+, while the related activation energy remained low, suggesting the presence of a Hg2+-insensitive facilitated pathway in addition to AQP8. It is suggested that AQP8-mediated water transport may be particularly important for rapid expansions of mitochondrial volume such as those occurring during active oxidative phosphorylation and those following apoptotic signals.
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Affiliation(s)
- Giuseppe Calamita
- Dipartimento di Fisiologia Generale ed Ambientale and Dipartimento di Zoologia, Laboratorio di Istologia e di Anatomia Comparata, Università degli Studi di Bari, 70126 Bari, Italy.
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130
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Popov V, Medvedev NI, Davies HA, Stewart MG. Mitochondria form a filamentous reticular network in hippocampal dendrites but are present as discrete bodies in axons: A three-dimensional ultrastructural study. J Comp Neurol 2005; 492:50-65. [PMID: 16175555 DOI: 10.1002/cne.20682] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The fine structure of mitochondria and smooth endoplasmic reticulum (SER) was studied via electron microscopy in dendritic and axonal neuronal segments of hippocampal areas CA1, CA3, and dentate gyrus (DG) of both ground squirrels in normothermic and hibernating conditions, and rats. Ultrathin serial sections of approximately 60 nm (up to 150 per series) were taken and three-dimensional (3D) reconstructions made of dendritic segments, up to 36 microm in length. Mitochondria were demonstrated to be present in filamentous form in every dendrite examined, in each of the hippocampal regions studied, whether in rat or ground squirrel. In addition, apparent continuity between the outer mitochondrial membrane and that of SER was observed by 3D reconstructions of very ultrathin (20 nm) serial sections prepared from dendritic segments. It is believed that SER penetrate into the heads of thin and mushroom spines but mitochondria do not enter the heads of these types of spines in dentate gyrus or CA1 of either rat or ground squirrel. However, in CA3 we have shown here that mitochondria penetrate into the base of the large thorny excrescences. Mushroom dendritic spines (but not thin spines) contained puncta adherentia, formed between pre- and postsynaptic membranes. In contrast to dendrites, the mitochondrial population of axonal processes in the same hippocampal regions were found only in the form of discrete bodies no more than 3 microm in length. The issue of the likely function of this network in dendrites and its potential role in calcium movement is discussed.
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Affiliation(s)
- Victor Popov
- The Open University, Department of Biological Sciences, Milton Keynes MK7 6AA, United Kingdom
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131
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Bertoni-Freddari C, Fattoretti P, Giorgetti B, Spazzafumo L, Solazzi M, Balietti M. Age-related decline in metabolic competence of small and medium-sized synaptic mitochondria. Naturwissenschaften 2004; 92:82-5. [PMID: 15619093 DOI: 10.1007/s00114-004-0591-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2004] [Accepted: 11/03/2004] [Indexed: 10/26/2022]
Abstract
A computer-assisted morphometric investigation of cytochrome oxidase (COX) activity, selectively evidenced by preferential diaminobenzidine cytochemistry, has been carried out on synaptic mitochondria in the cerebellar cortex of adult and old rats. The ratio (R) of the area of the cytochemical precipitate (CPA) to the overall area of each mitochondrion (MA) was calculated. R refers to the fraction of the inner mitochondrial membrane actively involved in cellular respiration, thus its quantitative estimation constitutes a reliable index of the mitochondrial metabolic competence (MMC). In adult rats a significant negative correlation between MA and R values was found, while in old animals there was just a positive trend. Paired-quartile comparisons of R values showed a significant age-related decrease in small and medium-sized mitochondria, whereas the lowest and not significant age-related reduction was found in oversized organelles. A paired decrease in number and increase in size is reported to be a general trend for mitochondria during aging, but oversized organelles, according to their low R value, constitute a scanty, though functional, compensating reaction. Thus, the present findings support the argument that the currently reported age-related cellular metabolic decay appears to rely both on the decline in MMC of the small and medium-sized mitochondria, and on their specific reduction in number. This novel result is of biological relevance since it is largely the small and medium-sized mitochondria that are required for the provision of adequate amounts of ATP for actual cellular performance, while the significantly enlarged organelles are thought to represent an intermediate ultrastructural feature in mitochondrial genesis and/or remodelling.
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Affiliation(s)
- Carlo Bertoni-Freddari
- Neurobiology of Aging Laboratory, INRCA Research Department, Via Birarelli 8, 60121 Ancona, Italy.
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132
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Thar R, Kühl M. Propagation of electromagnetic radiation in mitochondria? J Theor Biol 2004; 230:261-70. [PMID: 15302557 DOI: 10.1016/j.jtbi.2004.05.021] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2004] [Revised: 05/12/2004] [Accepted: 05/13/2004] [Indexed: 11/20/2022]
Abstract
Mitochondria are the main source of ultra-weak chemiluminescence generated by reactive oxygen species, which are continuously formed during the mitochondrial oxidative metabolism. Vertebrate cells show typically filamentous mitochondria associated with the microtubules of the cytoskeleton, forming together a continuous network (mitochondrial reticulum). The refractive index of both mitochondria and microtubules is higher than the surrounding cytoplasm, which results that the mitochondrial reticulum can act as an optical waveguide, i.e. electromagnetic radiation can propagate within the network. A detailed analysis of the inner structure of mitochondria shows, that they can be optically modelled as a multi-layer system with alternating indices of refraction. The parameters of this multi-layer system are dependent on the physiologic state of the mitochondria. The effect of the multi-layer system on electromagnetic radiation propagating along the mitochondrial reticulum is analysed by the transfer-matrix method. If induced light emission could take place in mitochondria, the multi-layer system could lead to lasing action like it has been realized in technical distributed feedback laser. Based on former reports about the influence of external illumination on the physiology of mitochondria it is speculated whether there exists some kind of long-range interaction between individual mitochondria mediated by electromagnetic radiation.
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Affiliation(s)
- Roland Thar
- Marine Biological Laboratory Helsingør, University of Copenhagen, Strandpromenaden 5, Helsingør 3600, Denmark.
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133
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Freitag M, Hickey PC, Raju NB, Selker EU, Read ND. GFP as a tool to analyze the organization, dynamics and function of nuclei and microtubules in Neurospora crassa. Fungal Genet Biol 2004; 41:897-910. [PMID: 15341912 DOI: 10.1016/j.fgb.2004.06.008] [Citation(s) in RCA: 254] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2004] [Accepted: 06/28/2004] [Indexed: 11/21/2022]
Abstract
We report the construction of a versatile GFP expression plasmid and demonstrate its utility in Neurospora crassa. To visualize nuclei and microtubules, we generated carboxy-terminal fusions of sgfp to Neurospora histone H1 (hH1) and beta-tubulin (Bml). Strong expression of GFP fusion proteins was achieved with the inducible Neurospora ccg-1 promoter. Nuclear and microtubule organization and dynamics were observed in live vegetative hyphae, developing asci, and ascospores by conventional and confocal laser scanning fluorescence microscopy. Observations of GFP fusion proteins in live cells largely confirmed previous results obtained by examination of fixed cells with various microscopic techniques. H1-GFP revealed dynamic nuclear shapes. Microtubules were mostly aligned parallel to the growth axis in apical compartments but more randomly arranged in sub-apical compartments. Time-lapse imaging of beta-tubulin-GFP in germinating macroconidia revealed polymerization and depolymerization of microtubules. In heterozygous crosses, H1-GFP and beta-tubulin-GFP expression was silenced, presumably by meiotic silencing. H1-GFP was translated in the vicinity of hH1+-sgfp+ nuclei in the common cytoplasm of giant Banana ascospores, but it diffused into all nuclei, another illustration of the utility of GFP fusion proteins.
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Affiliation(s)
- Michael Freitag
- Institute of Molecular Biology and Department of Biology, University of Oregon, Eugene, OR 97403, USA.
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134
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Fuchs F, Westermann B. Role of Unc104/KIF1-related motor proteins in mitochondrial transport in Neurospora crassa. Mol Biol Cell 2004; 16:153-61. [PMID: 15483054 PMCID: PMC539160 DOI: 10.1091/mbc.e04-05-0413] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Eukaryotic cells use diverse cytoskeleton-dependent machineries to control inheritance and intracellular positioning of mitochondria. In particular, microtubules play a major role in mitochondrial motility in the filamentous fungus Neurospora crassa and in mammalian cells. We examined the role of two novel Unc104/KIF1-related members of the kinesin family, Nkin2 and Nkin3, in mitochondrial motility in Neurospora. The Nkin2 protein is required for mitochondrial interactions with microtubules in vitro. Mutant hyphae lacking Nkin2 show mitochondrial motility defects in vivo early after germination of conidiospores. Nkin3, a member of a unique fungal-specific subgroup of small Unc104/KIF1-related proteins, is not associated with mitochondria in wild-type cells. However, it is highly expressed and recruited to mitochondria in Deltankin-2 mutants. Mitochondria lacking Nkin2 require Nkin3 for binding to microtubules in vitro, and mitochondrial motility defects in Deltankin-2 mutants disappear with up-regulation of Nkin3 in vivo. We propose that mitochondrial transport is mediated by Nkin2 in Neurospora, and organelle motility defects in Deltankin-2 mutants are rescued by Nkin3. Apparently, a highly versatile complement of organelle motors allows the cell to efficiently respond to exogenous challenges, a process that might also account for the great variety of different mitochondrial transport systems that have evolved in eukaryotic cells.
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Affiliation(s)
- Florian Fuchs
- Institut für Physiologische Chemie, Universität München, 81377 München, Germany
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135
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Brookes PS, Yoon Y, Robotham JL, Anders MW, Sheu SS. Calcium, ATP, and ROS: a mitochondrial love-hate triangle. Am J Physiol Cell Physiol 2004; 287:C817-33. [PMID: 15355853 DOI: 10.1152/ajpcell.00139.2004] [Citation(s) in RCA: 1854] [Impact Index Per Article: 92.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The mitochondrion is at the core of cellular energy metabolism, being the site of most ATP generation. Calcium is a key regulator of mitochondrial function and acts at several levels within the organelle to stimulate ATP synthesis. However, the dysregulation of mitochondrial Ca2+homeostasis is now recognized to play a key role in several pathologies. For example, mitochondrial matrix Ca2+overload can lead to enhanced generation of reactive oxygen species, triggering of the permeability transition pore, and cytochrome c release, leading to apoptosis. Despite progress regarding the independent roles of both Ca2+and mitochondrial dysfunction in disease, the molecular mechanisms by which Ca2+can elicit mitochondrial dysfunction remain elusive. This review highlights the delicate balance between the positive and negative effects of Ca2+and the signaling events that perturb this balance. Overall, a “two-hit” hypothesis is developed, in which Ca2+plus another pathological stimulus can bring about mitochondrial dysfunction.
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Affiliation(s)
- Paul S Brookes
- University of Rochester Medical Center, 601 Elmwood Ave., Box 711, Rochester, NY 14642, USA
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136
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Lee YJ, Jeong SY, Karbowski M, Smith CL, Youle RJ. Roles of the mammalian mitochondrial fission and fusion mediators Fis1, Drp1, and Opa1 in apoptosis. Mol Biol Cell 2004; 15:5001-11. [PMID: 15356267 PMCID: PMC524759 DOI: 10.1091/mbc.e04-04-0294] [Citation(s) in RCA: 835] [Impact Index Per Article: 41.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
During apoptosis, the mitochondrial network fragments. Using short hairpin RNAs for RNA interference, we manipulated the expression levels of the proteins hFis1, Drp1, and Opa1 that are involved in mitochondrial fission and fusion in mammalian cells, and we characterized their functions in mitochondrial morphology and apoptosis. Down-regulation of hFis1 powerfully inhibits cell death to an extent significantly greater than down-regulation of Drp1 and at a stage of apoptosis distinct from that induced by Drp1 inhibition. Cells depleted of Opa1 are extremely sensitive to exogenous apoptosis induction, and some die spontaneously by a process that requires hFis1 expression. Wild-type Opa1 may function normally as an antiapoptotic protein, keeping spontaneous apoptosis in check. However, if hFis1 is down-regulated, cells do not require Opa1 to prevent apoptosis, suggesting that Opa1 may be normally counteracting the proapoptotic action of hFis1. We also demonstrate in this study that mitochondrial fragmentation per se does not result in apoptosis. However, we provide further evidence that multiple components of the mitochondrial morphogenesis machinery can positively and negatively regulate apoptosis.
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Affiliation(s)
- Yang-ja Lee
- Biochemistry Section, Surgical Neurology Branch, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892, USA
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137
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James R, Adams RR, Christie S, Buchanan SR, Porteous DJ, Millar JK. Disrupted in Schizophrenia 1 (DISC1) is a multicompartmentalized protein that predominantly localizes to mitochondria. Mol Cell Neurosci 2004; 26:112-22. [PMID: 15121183 DOI: 10.1016/j.mcn.2004.01.013] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2003] [Revised: 01/19/2004] [Accepted: 01/21/2004] [Indexed: 02/08/2023] Open
Abstract
DISC1 is disrupted by a chromosomal translocation cosegregating with schizophrenia and recurrent major depression in a large Scottish family and has also been reported as a potential susceptibility locus in independent populations. We reveal a widespread and complex pattern of DISC1 expression, with at least five forms of Disrupted in Schizophrenia 1 DISC1 detectable. Mitochondria are the predominant site of DISC1 expression with additional nuclear, cytoplasmic, and actin-associated locations evident. Although the subcellular targeting of DISC1 is clearly complex, the association with mitochondria is of interest as many mitochondrial deficits have been reported in schizophrenia and other neuropsychiatric illnesses. Moreover, of the many cellular functions performed by mitochondria, their role in oxidative phosphorylation, calcium homeostasis, and apoptosis may hold particular relevance for the neuronal disturbances believed to be involved in the pathogenesis of schizophrenia.
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Affiliation(s)
- R James
- Medical Genetics Section, Department of Medical Sciences, University of Edinburgh, Molecular Medicine Centre, Western General Hospital, Edinburgh EH4 2XU, UK.
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138
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Abstract
Mitochondria are essential organelles that are involved in numerous metabolic pathways and produce the major part of intracellular ATP by oxidative phosphorylation. Their ultrastructure was solved in the 1950s by electron microscopic analysis of ultrathin sections. Based on these pioneering studies and on the endosymbiotic origin of mitochondria, cells are often assumed to contain numerous independent mitochondria with a size similar to that of bacteria. However, electron microscopy of thick sections reveals that mitochondria form elongated and branched filaments. Optical microscopy of living cells demonstrates that mitochondrial filaments continuously modify their position and morphology and that they undergo frequent fission and fusion reactions. In this review, we revise the actual knowledge on the ultrastructure, the organization and the dynamics of the mitochondrial compartment. We review recent findings showing that mitochondria exchange molecules by fusion and we present the main proteins involved in mitochondrial fusion and fission reactions. Finally, we discuss the functional and physiological relevance of mitochondrial dynamics.
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Affiliation(s)
- F Malka
- INSERM U582 (IFR 14 UPMC)-Institut de Myologie, Groupe Hospitalier Pitié-Salpêtrière, 47, boulevard de l'Hôpital, 75651 Paris, France
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139
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Pham NA, Richardson T, Cameron J, Chue B, Robinson BH. Altered mitochondrial structure and motion dynamics in living cells with energy metabolism defects revealed by real time microscope imaging. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2004; 10:247-260. [PMID: 15306050 DOI: 10.1017/s143192760404005x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2002] [Indexed: 05/24/2023]
Abstract
Using the real time microscope (RTM), a system applying new developments in light microscopy, we documented the spatial and temporal dynamics of mitochondrial behavior in human cultured skin fibroblasts. Without the use of stains or probes, we resolved fibroblast mitochondria as dark slender filaments of approximately 0.2 m wide and up to 10 m long, as well as a few smaller ovoid forms. In the living cell, the three most common mitochondrial movements were: (1) small oscillatory movements; (2) larger movements including filament extension, retraction, and branching as well as combinations of these actions; and (3) whole transit movements of single mitochondrial filaments. Skin fibroblasts from patients with mitochondrial complex I deficiency and normal fibroblasts during incubation with rotenone, or antimycin A, contained higher proportions of mitochondria in the swollen filamentous forms, nodal filaments, and ovoid forms rather than the slender filamentous forms in normal cells. Interestingly, decreased motility was observed with the more ovoid mitochondrial forms compared to the filamentous forms. We conclude that mitochondrial morphology and dynamic motion are strongly associated with changes in mitochondrial energy metabolism. Images documenting our observations are presented both at single time points and as QuickTime videos.
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Affiliation(s)
- Nhu-An Pham
- Richardson Technologies Inc. at The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada
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140
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Villa AM, Doglia SM. Mitochondria in tumor cells studied by laser scanning confocal microscopy. JOURNAL OF BIOMEDICAL OPTICS 2004; 9:385-394. [PMID: 15065906 DOI: 10.1117/1.1646414] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We present here a confocal fluorescence microscopy study of mitochondria in sensitive and resistant carcinoma cells by using two potentiometric probes of mitochondria, rhodamine 123 (R123) and dimethylaminostyryl-methylpyridiniumiodine. We have found that active mitochondria in sensitive MCF-7 and multidrug resistant MCF-7/DX carcinoma cells are very different in localization and morphology. In sensitive cells active mitochondria are found in the perinuclear region, whereas in the multidrug resistance (MDR) subline they are confined to the cell periphery. Interestingly, the MDR revertant verapamil has been found to restore in MCF-7/DX cells the same pattern of active mitochondria seen in sensitive cells. We have also studied R123 in human lung carcinoma A549 cells, which display a low responsivity to doxorubicin, and overexpress the lung resistance-related protein. In addition to perinuclear mitochondria, peripheral mitochondria with weaker fluorescence can be seen in this cell line. Interestingly, in the two examined carcinoma lines we have been able to recognize by image analysis a common new star-lobed morphology. Our results indicate that in resistant carcinoma cells two populations of mitochondria coexist with different localization, morphology, and activity.
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Affiliation(s)
- Anna Maria Villa
- INFM-UdR Milano Bicocca and Dipartimento di Biotecnologie e Bioscienze, Universita degli Studi di Milano Bicocca, Piazza della Scienza 2, 20126 Milano, Italy
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141
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Nisoli E, Clementi E, Moncada S, Carruba MO. Mitochondrial biogenesis as a cellular signaling framework. Biochem Pharmacol 2004; 67:1-15. [PMID: 14667924 DOI: 10.1016/j.bcp.2003.10.015] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The identification, more than 50 years ago, of mitochondria as the site of oxidative energy metabolism has prompted studies that have unraveled the complexity of the numerous biosynthetic and degradative reactions, fundamental to cell function, carried out by these organelles. These activities depend on a distinctive mitochondrial structure, with different enzymes and reactions localized in discrete membranes and aqueous compartments. The characteristic mitochondrial structural organization is the product of both synthesis of macromolecules within the mitochondria and the import of proteins and lipids synthesized outside the organelle. Synthesis and import of mitochondrial components are required for mitochondrial proliferation, but rather than producing new organelles, these processes may facilitate the growth of pre-existing mitochondria. Recent evidence indicates that these events are regulated in a complex way by several agonists and environmental conditions, through activation of specific transcription factors and signaling pathways. Some of these are now being elucidated. Generation of nitric oxide (NO) appears to be a novel player in this scenario, possibly acting as a unifying molecular switch to trigger the whole mitochondriogenic process.
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Affiliation(s)
- Enzo Nisoli
- Center for Study and Research on Obesity, Department of Preclinical Sciences, LITA Vialba, Luigi Sacco Hospital, University of Milan, via G.B. Grassi 74, 20157, Milan, Italy.
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142
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143
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Nisoli E, Clementi E, Tonello C, Moncada S, Carruba MO. Can endogenous gaseous messengers control mitochondrial biogenesis in mammalian cells? Prostaglandins Other Lipid Mediat 2004; 73:9-27. [PMID: 15165028 DOI: 10.1016/j.prostaglandins.2004.01.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mitochondria have been identified as the site of oxidative energy metabolism and of numerous biosynthetic and degradative reactions, which depend on a distinctive mitochondrial structure, with different enzymes and reactions localised in discrete membranes and aqueous compartments. Synthesis and import of mitochondrial components are required for mitochondrial proliferation, but rather than producing new organelles, these processes may facilitate the growth of preexisting mitochondria. Recent evidence indicates that these events are regulated in a complex way by several agonists and environmental conditions, through activation of specific transcription factors and signaling pathways. Some of these are now being elucidated. Generation of nitric oxide (NO) appears to be a novel player in this scenario, possibly acting as a unifying molecular switch to trigger the whole process of the mitochondrial biogenesis.
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Affiliation(s)
- Enzo Nisoli
- Department of Preclinical Sciences, Center for Study and Research on Obesity, LITA Vialba, Luigi Sacco Hospital, University of Milan, via G.B. Grassi 74, 20157 Milan, Italy.
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144
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Bezaire V, Heigenhauser GJF, Spriet LL. Regulation of CPT I activity in intermyofibrillar and subsarcolemmal mitochondria from human and rat skeletal muscle. Am J Physiol Endocrinol Metab 2004; 286:E85-91. [PMID: 12954596 DOI: 10.1152/ajpendo.00237.2003] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Carnitine palmitoyltransferase I (CPT I) is considered the rate-limiting enzyme in the transfer of long-chain fatty acids (LCFA) into the mitochondria and is reversibly inhibited by malonyl-CoA (M-CoA) in vitro. In rat skeletal muscle, M-CoA levels decrease during exercise, releasing the inhibition of CPT I and increasing LCFA oxidation. However, in human skeletal muscle, M-CoA levels do not change during moderate-intensity exercise despite large increases in fat oxidation, suggesting that M-CoA is not the sole regulator of increased CPT I activity during exercise. In the present study, we measured CPT I activity in intermyofibrillar (IMF) and subsarcolemmal (SS) mitochondria isolated from human vastus lateralis (VL), rat soleus (Sol), and red gastrocnemius (RG) muscles. We tested whether exercise-related levels ( approximately 65% maximal O2 uptake) of calcium and adenylate charge metabolites (free AMP, ADP, and Pi) could override the M-CoA-induced inhibition of CPT I activity and explain the increased CPT I flux during exercise. Protein content was approximately 25-40% higher in IMF than in SS mitochondria in all muscles. Maximal CPT I activity was similar in IMF and SS mitochondria in all muscles (VL: 282 +/- 46 vs. 280 +/- 51; Sol: 390 +/- 81 vs. 368 +/- 82; RG: 252 +/- 71 vs. 278 +/- 44 nmol.min-1.mg protein-1). Sensitivity to M-CoA did not differ between IMF and SS mitochondria in all muscles (25-31% inhibition in VL, 52-70% in Sol and RG). Calcium and adenylate charge metabolites did not override the M-CoA-induced inhibition of CPT I activity in mitochondria isolated from VL, Sol, and RG muscles. Decreasing pH from 7.1 to 6.8 reduced CPT I activity by approximately 34-40% in both VL mitochondrial fractions. In summary, this study reports no differences in CPT I activity or sensitivity to M-CoA between IMF and SS mitochondria isolated from human and rat skeletal muscles. Exercise-induced increases in calcium and adenylate charge metabolites do not appear responsible for upregulating CPT I activity in human or rat skeletal muscle during moderate aerobic exercise.
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Affiliation(s)
- Veronic Bezaire
- Department of Human Biology and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
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145
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Kooijman SALM, Auger P, Poggiale JC, Kooi BW. Quantitative steps in symbiogenesis and the evolution of homeostasis. Biol Rev Camb Philos Soc 2003; 78:435-63. [PMID: 14558592 DOI: 10.1017/s1464793102006127] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The merging of two independent populations of heterotrophs and autotrophs into a single population of mixotrophs has occurred frequently in evolutionary history. It is an example of a wide class of related phenomena, known as symbiogenesis. The physiological basis is almost always (reciprocal) syntrophy, where each species uses the products of the other species. Symbiogenesis can repeat itself after specialization on particular assimilatory substrates. We discuss quantitative aspects and delineate eight steps from two free-living interacting populations to a single fully integrated endosymbiotic one. The whole process of gradual interlocking of the two populations could be mimicked by incremental changes of particular parameter values. The role of products gradually changes from an ecological to a physiological one. We found conditions where the free-living, epibiotic and endobiotic populations of symbionts can co-exist, as well as conditions where the endobiotic symbionts outcompete other symbionts. Our population dynamical analyses give new insights into the evolution of cellular homeostasis. We show how structural biomass with a constant chemical composition can evolve in a chemically varying environment if the parameters for the formation of products satisfy simple constraints. No additional regulation mechanisms are required for homeostasis within the context of the dynamic energy budget (DEB) theory for the uptake and use of substrates by organisms. The DEB model appears to be dosed under endosymbiosis. This means that when each free-living partner follows DEB rules for substrate uptake and use, and they become engaged in an endosymbiotic relationship, a gradual transition to a single fully integrated system is possible that again follows DEB rules for substrate uptake and use.
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Affiliation(s)
- S A L M Kooijman
- Department of Theoretical Biology, Institute of Ecological Science, Vrije Universiteit, de Boelelaan 1087, 1081 HV Amsterdam, The Netherlands.
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146
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Filippin L, Magalhães PJ, Di Benedetto G, Colella M, Pozzan T. Stable interactions between mitochondria and endoplasmic reticulum allow rapid accumulation of calcium in a subpopulation of mitochondria. J Biol Chem 2003; 278:39224-34. [PMID: 12874292 DOI: 10.1074/jbc.m302301200] [Citation(s) in RCA: 199] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To better understand the functional role of the mitochondrial network in shaping the Ca2+ signals in living cells, we took advantage both of the newest genetically engineered green fluorescent protein-based Ca2+ sensors ("Cameleons," "Camgaroos," and "Pericams") and of the classical Ca(2+)-sensitive photoprotein aequorin, all targeted to the mitochondrial matrix. The properties of the green fluorescent protein-based probes in terms of subcellular localization, photosensitivity, and Ca2+ affinity have been analyzed in detail. It is concluded that the ratiometric pericam is, at present, the most reliable mitochondrial Ca2+ probe for single cell studies, although this probe too is not devoid of problems. The results obtained with ratiometric pericam in single cells, combined with those obtained at the population level with aequorin, provide strong evidence demonstrating that the close vicinity of mitochondria to the Ca2+ release channels (and thus responsible for the fast uptake of Ca2+ by mitochondria upon receptor activation) are highly stable in time, suggesting the existence of specific interactions between mitochondria and the endoplasmic reticulum.
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Affiliation(s)
- Luisa Filippin
- Department of Biomedical Sciences and CNR Institute of Neuroscience, University of Padua, Viale G. Colombo 3, 35121 Padua, Italy.
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147
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Abstract
Mitochondrial fusion has been observed in a great variety of organisms from yeast to man. It serves to mix and unify the mitochondrial compartment and plays roles in cellular aging, cell development, energy dissipation and mitochondrial DNA inheritance. Large GTPases in the mitochondrial outer membrane, termed Fzo or mitofusins, have been identified as key components of the mitochondrial fusion machinery in yeast, flies and mammalian cells. Recent studies in yeast suggest an involvement of a dynamin-related protein in the intermembrane space. Additional components have been identified by genetic screens. These findings suggest a unique and evolutionarily conserved mechanism for mitochondrial membrane fusion.
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Affiliation(s)
- Benedikt Westermann
- Institut für Physiologische Chemie der Universität München, Butenandtstr. 5, 81377, München, Germany.
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148
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Kerkweg U, Jacob M, De Groot H, Mannherz HG, Rauen U. Cold-induced apoptosis of rat liver endothelial cells: contribution of mitochondrial alterations. Transplantation 2003; 76:501-8. [PMID: 12923435 DOI: 10.1097/01.tp.0000069830.78758.1c] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
BACKGROUND Maintenance of the integrity of the vascular endothelium is a critical issue in liver preservation, but hypothermia, applied for cellular protection, induces apoptotic cell death in liver endothelial cells. This cold-induced apoptosis is mediated by an iron-dependent formation of reactive oxygen species. Here, we study the involvement of mitochondria in this process. METHODS Cultured rat liver endothelial cells were incubated in cold University of Wisconsin solution for 18 hr and subsequently rewarmed in cell culture medium. Mitochondrial morphology and membrane potential were evaluated using laser scanning microscopy. RESULTS During cold incubation in University of Wisconsin solution, a marked, progressive mitochondrial shortening and a reduction in mitochondrial membrane potential occurred. Rewarming of the cells led to mitochondrial ultracondensation, complete loss of the mitochondrial membrane potential, and subsequent apoptotic cell death. The inhibitors of mitochondrial permeability transition, trifluoperazine and fructose, or iron chelation with deferoxamine did not affect mitochondrial shortening during cold incubation but inhibited ultracondensation, loss of mitochondrial membrane potential, and loss of viability during rewarming. Moreover, in these protected cells, an almost complete reestablishment of the mitochondrial membrane potential and morphology could be observed; the few mitochondria that were irreversibly damaged were incorporated into autophagosomes during cellular recovery. CONCLUSION Two apparently independent mitochondrial alterations take place during cold incubation and subsequent rewarming of liver endothelial cells. Cold-induced mitochondrial shortening represents a reversible process, whereas iron-mediated mitochondrial permeability transition and ultracondensation during rewarming are irreversible and constitute an important mediator of cold-induced apoptosis.
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Affiliation(s)
- Uta Kerkweg
- Institut für Physiologische Chemie, Universitätsklinikum, Essen, Germany
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149
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Tsang WY, Lemire BD. The role of mitochondria in the life of the nematode, Caenorhabditis elegans. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1638:91-105. [PMID: 12853115 DOI: 10.1016/s0925-4439(03)00079-6] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mitochondria are essential organelles involved in energy metabolism via oxidative phosphorylation. They play a vital role in diverse biological processes such as aging and apoptosis. In humans, defects in the mitochondrial respiratory chain (MRC) are responsible for or associated with a bewildering variety of diseases. The nematode Caenorhabditis elegans is a simple animal and a powerful genetic and developmental model system. In this review, we discuss how the nematode model system has contributed to our understanding of mitochondrial dynamics, of the genetics and inheritance of the mitochondrial genome, and of the consequences of nuclear and mitochondrial DNA (mtDNA) mutations. Mitochondrial respiration is vital to energy metabolism but also to other aspects of multicellular life such as aging and development. We anticipate that further significant contributions to our understanding of mitochondrial function in animal biology are forthcoming with the C. elegans model system.
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Affiliation(s)
- William Y Tsang
- Canadian Institutes of Health Research Group in Membrane Protein Research, Department of Biochemistry, University of Alberta, 474 Medical Sciences Bldg., Edmonton, Alberta, Canada T6G 2H7
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150
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Lluch S, López-Fuster MJ, Ventura J. Giant mitochondria in the retina cone inner segments of shrews of genus Sorex (Insectivora, Soricidae). THE ANATOMICAL RECORD. PART A, DISCOVERIES IN MOLECULAR, CELLULAR, AND EVOLUTIONARY BIOLOGY 2003; 272:484-90. [PMID: 12740941 DOI: 10.1002/ar.a.10066] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The retinas of three species of shrews (Sorex araneus, S. coronatus, and S. minutus) were analyzed. Two kinds of photoreceptors were identified according to (among other characteristics) the traits of the mitochondria of their inner segments. The rod inner segments contained several round or oval mitochondria distributed longitudinally inside the ellipsoid. The cone inner segment showed a few mitochondria, which we classified as megamitochondria (maximum length = 4.22 microm in S. araneus, 5.68 microm in S. coronatus, and 2.42 microm in S. minutus). An analysis of serial thin sections in S. coronatus showed that these large organelles occurred in the apical and central portions of the ellipsoid. In the peripheral and basal regions of the ellipsoid, megamitochondria were frequently accompanied by smaller mitochondria. The giant mitochondria were irregular in form and densely packed, and a reduced cytosol was observed between each mitochondria. In general, they exhibited an electron-dense matrix and a complex system of cristae, which varied in length and array. In mammalian retina, megamitochondria have only been described in the ellipsoid of the tree shrews Tupaia glis and T. belangeri, two diurnal Scandentia with a rich-cone retina. In general terms, Sorex megamitochondria are morphologically very similar to those reported for Tupaia, especially in their arrangement in the cone ellipsoid. However, they differ in the orientation of the cristae. We propose that the ellipsoid of Sorex may serve two functions: as a source of energy for receptor cells, and as a device for improving the cone outer segment optics.
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Affiliation(s)
- Sara Lluch
- Departament d'Optica i Optometria, Universitat Politècnica de Catalunya, Barcelona, Spain.
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