1351
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Abstract
Contrary to conventional wisdom, functional mitochondria are essential for the cancer cell. Although mutations in mitochondrial genes are common in cancer cells, they do not inactivate mitochondrial energy metabolism but rather alter the mitochondrial bioenergetic and biosynthetic state. These states communicate with the nucleus through mitochondrial 'retrograde signalling' to modulate signal transduction pathways, transcriptional circuits and chromatin structure to meet the perceived mitochondrial and nuclear requirements of the cancer cell. Cancer cells then reprogramme adjacent stromal cells to optimize the cancer cell environment. These alterations activate out-of-context programmes that are important in development, stress response, wound healing and nutritional status.
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Affiliation(s)
- Douglas C Wallace
- Children's Hospital of Philadelphia, Center for Mitochondrial and Epigenomic Medicine, Philadelphia, Pennsylvania 19104, USA.
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1352
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Mitochondrial free [Ca(2+)] dynamics measured with a novel low-Ca(2+) affinity aequorin probe. Biochem J 2012; 445:371-6. [PMID: 22671130 DOI: 10.1042/bj20120423] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Mitochondria have a very large capacity to accumulate Ca(2+) during cell stimulation driven by the mitochondrial membrane potential. Under these conditions, [Ca(2+)](M) (mitochondrial [Ca(2+)]) may well reach millimolar levels in a few seconds. Measuring the dynamics of [Ca(2+)](M) during prolonged stimulation has been previously precluded by the high Ca(2+) affinity of the probes available. We have now developed a mitochondrially targeted double-mutated form of the photoprotein aequorin which is able to measure [Ca(2+)] in the millimolar range for long periods of time without problems derived from aequorin consumption. We show in the present study that addition of Ca(2+) to permeabilized HeLa cells triggers an increase in [Ca(2+)](M) up to an steady state of approximately 2-3 mM in the absence of phosphate and 0.5-1 mM in the presence of phosphate, suggesting buffering or precipitation of calcium phosphate when the free [Ca(2+)] reaches 0.5-1 mM. Mitochondrial pH acidification partially re-dissolved these complexes. These millimolar [Ca(2+)](M) levels were stable for long periods of time provided the mitochondrial membrane potential was not collapsed. Silencing of the mitochondrial Ca(2+) uniporter largely reduced the rate of [Ca(2+)](M) increase, but the final steady-state [Ca(2+)](M) reached was similar. In intact cells, the new probe allows monitoring of agonist-induced increases of [Ca(2+)](M) without problems derived from aequorin consumption.
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1353
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Kohlhaas M, Maack C. Interplay of defective excitation-contraction coupling, energy starvation, and oxidative stress in heart failure. Trends Cardiovasc Med 2012; 21:69-73. [PMID: 22626245 DOI: 10.1016/j.tcm.2012.03.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
In chronic heart failure, maladaptive remodeling of the left ventricle (LV) with systolic and diastolic dysfunction underlies the inability of the heart to pump sufficient blood to supply the body with blood and oxygen. Three integral aspects of this maladaptive LV remodeling are (1) defects in excitation-contraction (EC) coupling, particularly of cellular Ca(2+) and Na(+) homeostasis; (2) an energetic deficit; and (3) oxidative stress. Although these three aspects are often investigated separately from each other, their close and dynamic interplay are increasingly recognized. Central to this novel approach are mitochondria, which are the main source for cellular ATP, but also for reactive oxygen species, and their function is critically regulated by Ca(2+) and Na(+). Here, we review recent advances in our understanding of how maladaptive changes of EC coupling can contribute to the energetic deficit and oxidative stress, which may initiate a vicious cycle leading to progressive cardiac dysfunction.
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Affiliation(s)
- Michael Kohlhaas
- Medizinische Klinik und Poliklinik, Innere Medizin III, Universitätsklinikum des Saarlandes, 66421 Homburg/Saar, Germany
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1354
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Waldeck-Weiermair M, Alam MR, Khan MJ, Deak AT, Vishnu N, Karsten F, Imamura H, Graier WF, Malli R. Spatiotemporal correlations between cytosolic and mitochondrial Ca(2+) signals using a novel red-shifted mitochondrial targeted cameleon. PLoS One 2012; 7:e45917. [PMID: 23029314 PMCID: PMC3448721 DOI: 10.1371/journal.pone.0045917] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Accepted: 08/23/2012] [Indexed: 01/11/2023] Open
Abstract
The transfer of Ca2+ from the cytosol into the lumen of mitochondria is a crucial process that impacts cell signaling in multiple ways. Cytosolic Ca2+ ([Ca2+]cyto) can be excellently quantified with the ratiometric Ca2+ probe fura-2, while genetically encoded Förster resonance energy transfer (FRET)-based fluorescent Ca2+ sensors, the cameleons, are efficiently used to specifically measure Ca2+ within organelles. However, because of a significant overlap of the fura-2 emission with the spectra of the cyan and yellow fluorescent protein of most of the existing cameleons, the measurement of fura-2 and cameleons within one given cell is a complex task. In this study, we introduce a novel approach to simultaneously assess [Ca2+]cyto and mitochondrial Ca2+ ([Ca2+]mito) signals at the single cell level. In order to eliminate the spectral overlap we developed a novel red-shifted cameleon, D1GO-Cam, in which the green and orange fluorescent proteins were used as the FRET pair. This ratiometric Ca2+ probe could be successfully targeted to mitochondria and was suitable to be used simultaneously with fura-2 to correlate [Ca2+]cyto and [Ca2+]mito within same individual cells. Our data indicate that depending on the kinetics of [Ca2+]cyto rises there is a significant lag between onset of [Ca2+]cyto and [Ca2+]mito signals, pointing to a certain threshold of [Ca2+]cyto necessary to activate mitochondrial Ca2+ uptake. The temporal correlation between [Ca2+]mito and [Ca2+]cyto as well as the efficiency of the transfer of Ca2+ from the cytosol into mitochondria varies between different cell types. Moreover, slow mitochondrial Ca2+ extrusion and a desensitization of mitochondrial Ca2+ uptake cause a clear difference in patterns of mitochondrial and cytosolic Ca2+ oscillations of pancreatic beta-cells in response to D-glucose.
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Affiliation(s)
- Markus Waldeck-Weiermair
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Muhammad Rizwan Alam
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Muhammad Jadoon Khan
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Andras T. Deak
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Neelanjan Vishnu
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Felix Karsten
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Hiromi Imamura
- Precursory Research for Embryonic Science, Japan Science and Technology Agency, Tokyo, Japan
| | - Wolfgang F. Graier
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
| | - Roland Malli
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Graz, Austria
- * E-mail:
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1355
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Abstract
The most well-characterized organelle contact sites are those between the endoplasmic reticulum (ER) and mitochondria. Increased understanding is being gained of how ER-mitochondria contact sites are organized and which factors converge at this interface, some of which may provide a tethering function. The role of the ER-mitochondria junction in coordinating the functions of these two organelles is also becoming clearer, and it has been shown to be involved in the regulation of lipid synthesis, Ca(2+) signalling and the control of mitochondrial biogenesis and intracellular trafficking.
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1356
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Konstantinidis K, Lederer WJ, Rizzuto R, Kitsis RN. Mitofusin 2 joins the sarcoplasmic reticulum and mitochondria at the hip to sustain cardiac energetics. Circ Res 2012; 111:821-3. [PMID: 22982869 PMCID: PMC3904362 DOI: 10.1161/circresaha.112.277269] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Klitos Konstantinidis
- Departments of Medicine and Cell Biology, Wilf Family Cardiovascular
Research Institute, Albert Einstein Cancer Center, and Diabetes Research Center,
Albert Einstein College of Medicine, Bronx, NY
- Department of Medicine, University of Pittsburg Medical Center,
Pittsburgh, PA
| | - W. Jonathan Lederer
- Center for Biomedical Engineering and Technology and Department of
Physiology, University of Maryland School of Medicine, Baltimore, MD
| | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padua and CNR
Neuroscience Institute, Padua, Italy
| | - Richard N. Kitsis
- Departments of Medicine and Cell Biology, Wilf Family Cardiovascular
Research Institute, Albert Einstein Cancer Center, and Diabetes Research Center,
Albert Einstein College of Medicine, Bronx, NY
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1357
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Ben-Hail D, Lemelson D, Israelson A, Shoshan-Barmatz V. New fluorescent reagents specific for Ca2+-binding proteins. Biochem Biophys Res Commun 2012; 426:158-64. [DOI: 10.1016/j.bbrc.2012.08.060] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Accepted: 08/11/2012] [Indexed: 10/28/2022]
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1358
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Possible involvement of mitochondrial uncoupling protein-2 in cytotoxicity mediated by acquired N-methyl-d-aspartate receptor channels. Neurochem Int 2012; 61:498-505. [DOI: 10.1016/j.neuint.2012.03.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Revised: 03/22/2012] [Accepted: 03/24/2012] [Indexed: 01/08/2023]
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1359
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Alam MR, Groschner LN, Parichatikanond W, Kuo L, Bondarenko AI, Rost R, Waldeck-Weiermair M, Malli R, Graier WF. Mitochondrial Ca2+ uptake 1 (MICU1) and mitochondrial ca2+ uniporter (MCU) contribute to metabolism-secretion coupling in clonal pancreatic β-cells. J Biol Chem 2012; 287:34445-54. [PMID: 22904319 PMCID: PMC3464549 DOI: 10.1074/jbc.m112.392084] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
In pancreatic β-cells, uptake of Ca2+ into mitochondria facilitates metabolism-secretion coupling by activation of various matrix enzymes, thus facilitating ATP generation by oxidative phosphorylation and, in turn, augmenting insulin release. We employed an siRNA-based approach to evaluate the individual contribution of four proteins that were recently described to be engaged in mitochondrial Ca2+ sequestration in clonal INS-1 832/13 pancreatic β-cells: the mitochondrial Ca2+ uptake 1 (MICU1), mitochondrial Ca2+ uniporter (MCU), uncoupling protein 2 (UCP2), and leucine zipper EF-hand-containing transmembrane protein 1 (LETM1). Using a FRET-based genetically encoded Ca2+ sensor targeted to mitochondria, we show that a transient knockdown of MICU1 or MCU diminished mitochondrial Ca2+ uptake upon both intracellular Ca2+ release and Ca2+ entry via L-type channels. In contrast, knockdown of UCP2 and LETM1 exclusively reduced mitochondrial Ca2+ uptake in response to either intracellular Ca2+ release or Ca2+ entry, respectively. Therefore, we further investigated the role of MICU1 and MCU in metabolism-secretion coupling. Diminution of MICU1 or MCU reduced mitochondrial Ca2+ uptake in response to d-glucose, whereas d-glucose-triggered cytosolic Ca2+ oscillations remained unaffected. Moreover, d-glucose-evoked increases in cytosolic ATP and d-glucose-stimulated insulin secretion were diminished in MICU1- or MCU-silenced cells. Our data highlight the crucial role of MICU1 and MCU in mitochondrial Ca2+ uptake in pancreatic β-cells and their involvement in the positive feedback required for sustained insulin secretion.
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Affiliation(s)
- Muhammad Rizwan Alam
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, 8010 Graz, Austria
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1360
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Prole DL, Taylor CW. Identification and analysis of cation channel homologues in human pathogenic fungi. PLoS One 2012; 7:e42404. [PMID: 22876320 PMCID: PMC3410928 DOI: 10.1371/journal.pone.0042404] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 07/05/2012] [Indexed: 01/08/2023] Open
Abstract
Fungi are major causes of human, animal and plant disease. Human fungal infections can be fatal, but there are limited options for therapy, and resistance to commonly used anti-fungal drugs is widespread. The genomes of many fungi have recently been sequenced, allowing identification of proteins that may become targets for novel therapies. We examined the genomes of human fungal pathogens for genes encoding homologues of cation channels, which are prominent drug targets. Many of the fungal genomes examined contain genes encoding homologues of potassium (K+), calcium (Ca2+) and transient receptor potential (Trp) channels, but not sodium (Na+) channels or ligand-gated channels. Some fungal genomes contain multiple genes encoding homologues of K+ and Trp channel subunits, and genes encoding novel homologues of voltage-gated Kv channel subunits are found in Cryptococcus spp. Only a single gene encoding a homologue of a plasma membrane Ca2+ channel was identified in the genome of each pathogenic fungus examined. These homologues are similar to the Cch1 Ca2+ channel of Saccharomyces cerevisiae. The genomes of Aspergillus spp. and Cryptococcus spp., but not those of S. cerevisiae or the other pathogenic fungi examined, also encode homologues of the mitochondrial Ca2+ uniporter (MCU). In contrast to humans, which express many K+, Ca2+ and Trp channels, the genomes of pathogenic fungi encode only very small numbers of K+, Ca2+ and Trp channel homologues. Furthermore, the sequences of fungal K+, Ca2+, Trp and MCU channels differ from those of human channels in regions that suggest differences in regulation and susceptibility to drugs.
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Affiliation(s)
- David L Prole
- Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge, United Kingdom.
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1361
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Abstract
During the past two decades calcium (Ca(2+)) accumulation in energized mitochondria has emerged as a biological process of utmost physiological relevance. Mitochondrial Ca(2+) uptake was shown to control intracellular Ca(2+) signalling, cell metabolism, cell survival and other cell-type specific functions by buffering cytosolic Ca(2+) levels and regulating mitochondrial effectors. Recently, the identity of mitochondrial Ca(2+) transporters has been revealed, opening new perspectives for investigation and molecular intervention.
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1362
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Mitochondrial Ca2+ uptake contributes to buffering cytoplasmic Ca2+ peaks in cardiomyocytes. Proc Natl Acad Sci U S A 2012; 109:12986-91. [PMID: 22822213 DOI: 10.1073/pnas.1210718109] [Citation(s) in RCA: 170] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Mitochondrial ability of shaping Ca(2+) signals has been demonstrated in a large number of cell types, but it is still debated in heart cells. Here, we take advantage of the molecular identification of the mitochondrial Ca(2+) uniporter (MCU) and of unique targeted Ca(2+) probes to directly address this issue. We demonstrate that, during spontaneous Ca(2+) pacing, Ca(2+) peaks on the outer mitochondrial membrane (OMM) are much greater than in the cytoplasm because of a large number of Ca(2+) hot spots generated on the OMM surface. Cytoplasmic Ca(2+) peaks are reduced or enhanced by MCU overexpression and siRNA silencing, respectively; the opposite occurs within the mitochondrial matrix. Accordingly, the extent of contraction is reduced by overexpression of MCU and augmented by its down-regulation. Modulation of MCU levels does not affect the ATP content of the cardiomyocytes. Thus, in neonatal cardiac myocytes, mitochondria significantly contribute to buffering the amplitude of systolic Ca(2+) rises.
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1363
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Palty R, Hershfinkel M, Sekler I. Molecular identity and functional properties of the mitochondrial Na+/Ca2+ exchanger. J Biol Chem 2012; 287:31650-7. [PMID: 22822063 DOI: 10.1074/jbc.r112.355867] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mitochondrial membrane potential that powers the generation of ATP also facilitates mitochondrial Ca(2+) shuttling. This process is fundamental to a wide range of cellular activities, as it regulates ATP production, shapes cytosolic and endoplasmic recticulum Ca(2+) signaling, and determines cell fate. Mitochondrial Ca(2+) transport is mediated primarily by two major transporters: a Ca(2+) uniporter that mediates Ca(2+) uptake and a Na(+)/Ca(2+) exchanger that subsequently extrudes mitochondrial Ca(2+). In this minireview, we focus on the specific role of the mitochondrial Na(+)/Ca(2+) exchanger and describe its ion exchange mechanism, regulation by ions, and putative partner proteins. We discuss the recent molecular identification of the mitochondrial exchanger and how its activity is linked to physiological and pathophysiological processes.
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Affiliation(s)
- Raz Palty
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA. palty35@berkeley
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1364
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Tarasov AI, Semplici F, Ravier MA, Bellomo EA, Pullen TJ, Gilon P, Sekler I, Rizzuto R, Rutter GA. The mitochondrial Ca2+ uniporter MCU is essential for glucose-induced ATP increases in pancreatic β-cells. PLoS One 2012; 7:e39722. [PMID: 22829870 PMCID: PMC3400633 DOI: 10.1371/journal.pone.0039722] [Citation(s) in RCA: 138] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2012] [Accepted: 05/25/2012] [Indexed: 01/09/2023] Open
Abstract
Glucose induces insulin release from pancreatic β-cells by stimulating ATP synthesis, membrane depolarisation and Ca2+ influx. As well as activating ATP-consuming processes, cytosolic Ca2+ increases may also potentiate mitochondrial ATP synthesis. Until recently, the ability to study the role of mitochondrial Ca2+ transport in glucose-stimulated insulin secretion has been hindered by the absence of suitable approaches either to suppress Ca2+ uptake into these organelles, or to examine the impact on β-cell excitability. Here, we have combined patch-clamp electrophysiology with simultaneous real-time imaging of compartmentalised changes in Ca2+ and ATP/ADP ratio in single primary mouse β-cells, using recombinant targeted (Pericam or Perceval, respectively) as well as entrapped intracellular (Fura-Red), probes. Through shRNA-mediated silencing we show that the recently-identified mitochondrial Ca2+ uniporter, MCU, is required for depolarisation-induced mitochondrial Ca2+ increases, and for a sustained increase in cytosolic ATP/ADP ratio. By contrast, silencing of the mitochondrial Na+-Ca2+ exchanger NCLX affected the kinetics of glucose-induced changes in, but not steady state values of, cytosolic ATP/ADP. Exposure to gluco-lipotoxic conditions delayed both mitochondrial Ca2+ uptake and cytosolic ATP/ADP ratio increases without affecting the expression of either gene. Mitochondrial Ca2+ accumulation, mediated by MCU and modulated by NCLX, is thus required for normal glucose sensing by pancreatic β-cells, and becomes defective in conditions mimicking the diabetic milieu.
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Affiliation(s)
- Andrei I. Tarasov
- Section of Cell Biology, Division of Diabetes Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, United Kingdom
| | - Francesca Semplici
- Section of Cell Biology, Division of Diabetes Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, United Kingdom
| | - Magalie A. Ravier
- Section of Cell Biology, Division of Diabetes Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, United Kingdom
- Institut de Génomique Fonctionnelle, INSERM U661, CNRS UMR5203, Université Montpellier I et II, Montpellier, France
| | - Elisa A. Bellomo
- Section of Cell Biology, Division of Diabetes Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, United Kingdom
| | - Timothy J. Pullen
- Section of Cell Biology, Division of Diabetes Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, United Kingdom
| | - Patrick Gilon
- Pole of Endocrinology, Diabetes and Nutrition, Faculty of Medicine, Université Catholique de Louvain, Brussels, Belgium
| | - Israel Sekler
- Department of Physiology, Faculty of Health Sciences, Ben Gurion University, Beer-Sheva, Israel
| | - Rosario Rizzuto
- Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Guy A. Rutter
- Section of Cell Biology, Division of Diabetes Endocrinology and Metabolism, Department of Medicine, Imperial College London, London, United Kingdom
- * E-mail:
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1365
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Abstract
A wide range of Ca2+ signalling systems deliver the spatial and temporal Ca2+ signals necessary to control the specific functions of different cell types. Release of Ca2+ by InsP3 (inositol 1,4,5-trisphosphate) plays a central role in many of these signalling systems. Ongoing transcriptional processes maintain the integrity and stability of these cell-specific signalling systems. However, these homoeostatic systems are highly plastic and can undergo a process of phenotypic remodelling, resulting in the Ca2+ signals being set either too high or too low. Such subtle dysregulation of Ca2+ signals have been linked to some of the major diseases in humans such as cardiac disease, schizophrenia, bipolar disorder and Alzheimer's disease.
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1366
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Groschner LN, Waldeck-Weiermair M, Malli R, Graier WF. Endothelial mitochondria--less respiration, more integration. Pflugers Arch 2012; 464:63-76. [PMID: 22382745 PMCID: PMC3387498 DOI: 10.1007/s00424-012-1085-z] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 02/11/2012] [Indexed: 12/21/2022]
Abstract
Lining the inner surface of the circulatory system, the vascular endothelium accomplishes a vast variety of specialized functions. Even slight alterations of these functions are implicated in the development of certain cardiovascular diseases that represent major causes of morbidity and mortality in developed countries. Endothelial mitochondria are essential to the functional integrity of the endothelial cell as they integrate a wide range of cellular processes including Ca²⁺ handling, redox signaling and apoptosis, all of which are closely interrelated. Growing evidence supports the notion that impairment of mitochondrial signaling in the endothelium is an early event and a causative factor in the development of diseases such as atherosclerosis or diabetic complications. In this review, we want to outline the significance of mitochondria in both physiology and pathology of the vascular endothelium.
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Affiliation(s)
- Lukas N. Groschner
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria
| | - Markus Waldeck-Weiermair
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria
| | - Roland Malli
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria
| | - Wolfgang F. Graier
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria
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1367
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Mitochondrial regulation of CRAC channel-driven cellular responses. Cell Calcium 2012; 52:52-6. [DOI: 10.1016/j.ceca.2012.02.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Revised: 02/08/2012] [Accepted: 02/09/2012] [Indexed: 11/15/2022]
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1368
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Loro G, Drago I, Pozzan T, Schiavo FL, Zottini M, Costa A. Targeting of Cameleons to various subcellular compartments reveals a strict cytoplasmic/mitochondrial Ca²⁺ handling relationship in plant cells. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 71:1-13. [PMID: 22372377 DOI: 10.1111/j.1365-313x.2012.04968.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Here we describe use of a mitochondrial targeted Cameleon to produce stably transformed Arabidopsis plants that enable analyses of mitochondrial Ca²⁺ dynamics in planta and allow monitoring of the intra-mitochondrial Ca²⁺ concentration in response to physiological or environmental stimuli. Transgenic plants co-expressing nuclear and mitochondrial targeted Cameleons were also generated and analyzed. Here we show that mitochondrial Ca²⁺ accumulation is strictly related to the intensity of the cytoplasmic Ca²⁺ increase, demonstrating a tight association between mitochondrial and cytoplasmic Ca²⁺ dynamics. However, under all experimental conditions, mitochondrial Ca²⁺ dynamics were substantially different from those monitored in the cytoplasm, demonstrating that mitochondria do not passively sense cytosolic Ca²⁺, but actively modulate the intra-mitochondrial level of the cation. In particular, our analyses show that the kinetics of Ca²⁺ release from mitochondria are much slower than in the cytoplasm and nucleus. The mechanisms and functional implications of these differences are discussed.
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Affiliation(s)
- Giovanna Loro
- Dipartimento di Biologia, Università degli Studi di Padova, Via U. Bassi 58/B, 35131 Padova, Italy
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1369
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Macroautophagy and cell responses related to mitochondrial dysfunction, lipid metabolism and unconventional secretion of proteins. Cells 2012; 1:168-203. [PMID: 24710422 PMCID: PMC3901093 DOI: 10.3390/cells1020168] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Revised: 06/03/2012] [Accepted: 06/12/2012] [Indexed: 12/28/2022] Open
Abstract
Macroautophagy has important physiological roles and its cytoprotective or detrimental function is compromised in various diseases such as many cancers and metabolic diseases. However, the importance of autophagy for cell responses has also been demonstrated in many other physiological and pathological situations. In this review, we discuss some of the recently discovered mechanisms involved in specific and unspecific autophagy related to mitochondrial dysfunction and organelle degradation, lipid metabolism and lipophagy as well as recent findings and evidence that link autophagy to unconventional protein secretion.
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1370
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Pizzo P, Drago I, Filadi R, Pozzan T. Mitochondrial Ca²⁺ homeostasis: mechanism, role, and tissue specificities. Pflugers Arch 2012; 464:3-17. [PMID: 22706634 DOI: 10.1007/s00424-012-1122-y] [Citation(s) in RCA: 116] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 05/29/2012] [Indexed: 12/18/2022]
Abstract
Mitochondria from every tissue are quite similar in their capability to accumulate Ca²⁺ in a process that depends on the electrical potential across the inner membrane; it is catalyzed by a gated channel (named mitochondrial Ca²⁺ uniporter), the molecular identity of which has only recently been unraveled. The release of accumulated Ca²⁺ in mitochondria from different tissues is, on the contrary, quite variable, both in terms of speed and mechanism: a Na⁺-dependent efflux in excitable cells (catalyzed by NCLX) and a H⁺/Ca²⁺ exchanger in other cells. The efficacy of mitochondrial Ca²⁺ uptake in living cells is strictly dependent on the topological arrangement of the organelles with respect to the source of Ca²⁺ flowing into the cytoplasm, i.e., plasma membrane or intracellular channels. In turn, the structural and functional relationships between mitochondria and other cellular membranes are dictated by the specific architecture of different cells. Mitochondria not only modulate the amplitude and the kinetics of local and bulk cytoplasmic Ca²⁺ changes but also depend on the Ca²⁺ signal for their own functionality, in particular for their capacity to produce ATP. In this review, we summarize the processes involved in mitochondrial Ca²⁺ handling and its integration in cell physiology, highlighting the main common characteristics as well as key differences, in different tissues.
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Affiliation(s)
- Paola Pizzo
- Department of Biomedical Sciences, University of Padua, Padua, Italy
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1371
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Sheu SS, Dirksen RT, Pugh EN. The 65th Symposium of the Society for General Physiologists: energizing research in mitochondrial physiology and medicine. ACTA ACUST UNITED AC 2012; 138:563-7. [PMID: 22124113 PMCID: PMC3226972 DOI: 10.1085/jgp.201110739] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Shey-Shing Sheu
- Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA 19010, USA
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1372
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Feske S, Skolnik EY, Prakriya M. Ion channels and transporters in lymphocyte function and immunity. Nat Rev Immunol 2012; 12:532-47. [PMID: 22699833 DOI: 10.1038/nri3233] [Citation(s) in RCA: 334] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Lymphocyte function is regulated by a network of ion channels and transporters in the plasma membrane of B and T cells. These proteins modulate the cytoplasmic concentrations of diverse cations, such as calcium, magnesium and zinc ions, which function as second messengers to regulate crucial lymphocyte effector functions, including cytokine production, differentiation and cytotoxicity. The repertoire of ion-conducting proteins includes calcium release-activated calcium (CRAC) channels, P2X receptors, transient receptor potential (TRP) channels, potassium channels, chloride channels and magnesium and zinc transporters. This Review discusses the roles of ion conduction pathways in lymphocyte function and immunity.
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Affiliation(s)
- Stefan Feske
- Department of Pathology, New York University Langone Medical Center, New York, New York 10016, USA.
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1373
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COLAÇO R, MORENO N, FEIJÓ J. On the fast lane: mitochondria structure, dynamics and function in growing pollen tubes. J Microsc 2012; 247:106-18. [DOI: 10.1111/j.1365-2818.2012.03628.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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1374
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Delmotte P, Yang B, Thompson MA, Pabelick CM, Prakash YS, Sieck GC. Inflammation alters regional mitochondrial Ca²+ in human airway smooth muscle cells. Am J Physiol Cell Physiol 2012; 303:C244-56. [PMID: 22673614 DOI: 10.1152/ajpcell.00414.2011] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Regulation of cytosolic Ca(2+) concentration ([Ca(2+)](cyt)) in airway smooth muscle (ASM) is a key aspect of airway contractility and can be modulated by inflammation. Mitochondria have tremendous potential for buffering [Ca(2+)](cyt), helping prevent Ca(2+) overload, and modulating other intracellular events. Here, compartmentalization of mitochondria to different cellular regions may subserve different roles. In the present study, we examined the role of Ca(2+) buffering by mitochondria and mitochondrial Ca(2+) transport mechanisms in the regulation of [Ca(2+)](cyt) in enzymatically dissociated human ASM cells upon exposure to the proinflammatory cytokines TNF-α and IL-13. Cells were loaded simultaneously with fluo-3 AM and rhod-2 AM, and [Ca(2+)](cyt) and mitochondrial Ca(2+) concentration ([Ca(2+)](mito)) were measured, respectively, using real-time two-color fluorescence microscopy in both the perinuclear and distal, perimembranous regions of cells. Histamine induced a rapid increase in both [Ca(2+)](cyt) and [Ca(2+)](mito), with a significant delay in the mitochondrial response. Inhibition of the mitochondrial Na(+)/Ca(2+) exchanger (1 μM CGP-37157) increased [Ca(2+)](mito) responses in perinuclear mitochondria but not distal mitochondria. Inhibition of the mitochondrial uniporter (1 μM Ru360) decreased [Ca(2+)](mito) responses in perinuclear and distal mitochondria. CGP-37157 and Ru360 significantly enhanced histamine-induced [Ca(2+)](cyt). TNF-α and IL-13 both increased [Ca(2+)](cyt), which was associated with decreased [Ca(2+)](mito) in the case of TNF-α but not IL-13. The effects of TNF-α on both [Ca(2+)](cyt) and [Ca(2+)](mito) were affected by CGP-37157 but not by Ru360. Overall, these data demonstrate that in human ASM cells, mitochondria buffer [Ca(2+)](cyt) after agonist stimulation and its enhancement by inflammation. The differential regulation of [Ca(2+)](mito) in different parts of ASM cells may serve to locally regulate Ca(2+) fluxes from intracellular sources versus the plasma membrane as well as respond to differential energy demands at these sites. We propose that such differential mitochondrial regulation, and its disruption, may play a role in airway hyperreactivity in diseases such as asthma, where [Ca(2+)](cyt) is increased.
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Affiliation(s)
- Philippe Delmotte
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905, USA
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1375
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Raffaello A, De Stefani D, Rizzuto R. The mitochondrial Ca(2+) uniporter. Cell Calcium 2012; 52:16-21. [PMID: 22672876 DOI: 10.1016/j.ceca.2012.04.006] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 04/08/2012] [Accepted: 04/11/2012] [Indexed: 11/19/2022]
Abstract
Mitochondrial Ca(2+) uptake plays a fundamental role in the regulation of energy production and cell survival. Under physiological conditions, mitochondrial Ca(2+) uptake occurs by a uniport mechanism driven electrophoretically by the membrane potential created by the respiratory chain. The activity and the biochemical properties of the mitochondrial calcium uniporter (MCU) were extensively characterized for decades but the molecular identity of the channel has remained elusive. Here, we review the recent discovery of the mitochondria Ca(2+) uniporter that represents a groundbreaking result for the molecular understanding of mitochondrial Ca(2+) homeostasis and will provide insight into the role of mitochondrial Ca(2+) deregulation in the pathogenesis of human disorders.
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Affiliation(s)
- Anna Raffaello
- Department of Biomedical Sciences, University of Padua and CNR Neuroscience Institute, Via G. Colombo 3, 35131 Padua, Italy
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1376
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Abstract
Calcium uptake into mitochondria occurs via a recently identified ion channel called the uniporter. Here, we characterize the phylogenomic distribution of the uniporter's membrane-spanning pore subunit (MCU) and regulatory partner (MICU1). Homologs of both components tend to co-occur in all major branches of eukaryotic life, but both have been lost along certain protozoan and fungal lineages. Several bacterial genomes also contain putative MCU homologs that may represent prokaryotic calcium channels. The analyses indicate that the uniporter may have been an early feature of mitochondria.
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Affiliation(s)
- Alexander G Bick
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA
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1377
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Abstract
Mitochondria may function as multiple separate organelles or as a single electrically coupled continuum to modulate changes in [Ca2+]c (cytoplasmic Ca2+ concentration) in various cell types. Mitochondria may also be tethered to the internal Ca2+ store or plasma membrane in particular parts of cells to facilitate the organelles modulation of local and global [Ca2+]c increases. Differences in the organization and positioning contributes significantly to the at times apparently contradictory reports on the way mitochondria modulate [Ca2+]c signals. In the present paper, we review the organization of mitochondria and the organelles role in Ca2+ signalling.
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1378
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Calì T, Ottolini D, Brini M. Mitochondrial Ca(2+) and neurodegeneration. Cell Calcium 2012; 52:73-85. [PMID: 22608276 PMCID: PMC3396847 DOI: 10.1016/j.ceca.2012.04.015] [Citation(s) in RCA: 95] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2012] [Revised: 04/18/2012] [Accepted: 04/20/2012] [Indexed: 12/16/2022]
Abstract
Mitochondria are essential for ensuring numerous fundamental physiological processes such as cellular energy, redox balance, modulation of Ca2+ signaling and important biosynthetic pathways. They also govern the cell fate by participating in the apoptosis pathway. The mitochondrial shape, volume, number and distribution within the cells are strictly controlled. The regulation of these parameters has an impact on mitochondrial function, especially in the central nervous system, where trafficking of mitochondria is critical to their strategic intracellular distribution, presumably according to local energy demands. Thus, the maintenance of a healthy mitochondrial population is essential to avoid the impairment of the processes they regulate: for this purpose, cells have developed mechanisms involving a complex system of quality control to remove damaged mitochondria, or to renew them. Defects of these processes impair mitochondrial function and lead to disordered cell function, i.e., to a disease condition. Given the standard role of mitochondria in all cells, it might be expected that their dysfunction would give rise to similar defects in all tissues. However, damaged mitochondrial function has pleiotropic effects in multicellular organisms, resulting in diverse pathological conditions, ranging from cardiac and brain ischemia, to skeletal muscle myopathies to neurodegenerative diseases. In this review, we will focus on the relationship between mitochondrial (and cellular) derangements and Ca2+ dysregulation in neurodegenerative diseases, emphasizing the evidence obtained in genetic models. Common patterns, that recognize the derangement of Ca2+ and energy control as a causative factor, have been identified: advances in the understanding of the molecular regulation of Ca2+ homeostasis, and on the ways in which it could become perturbed in neurological disorders, may lead to the development of therapeutic strategies that modulate neuronal Ca2+ signaling.
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Affiliation(s)
- Tito Calì
- Department of Comparative Biomedicine and Food Science, University of Padova, Padova, Italy
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1379
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Carafoli E. The interplay of mitochondria with calcium: an historical appraisal. Cell Calcium 2012; 52:1-8. [PMID: 22591641 DOI: 10.1016/j.ceca.2012.02.007] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 02/23/2012] [Indexed: 11/26/2022]
Abstract
Indirect findings in the 1950s had indicated that mitochondria could accumulate Ca(2+), but only in 1961 isolated mitochondria were directly shown to take it up in a process driven by the activity of the respiratory chain or by the hydrolysis of added ATP. The uptake of Ca(2+) could be accompanied by the simultaneous uptake of inorganic phosphate, leading to the precipitation of hydroxyapatite in the matrix and to the effective buffering of the free Ca(2+) concentration in it. The uptake of Ca(2+) occurred via an electrophoretic uniporter that has been molecularly identified only recently. Ca(2+) was then released through a Na(+)/Ca(2+) exchanger that has also been identified very recently (a H(+)/Ca(2+) antiporter has also been described in some mitochondrial types). In the matrix two TCA cycle dehydrogenases and pyruvate dehydrogenase phosphate phosphatase were found to be regulated by Ca(2+), providing a rationale for the Ca(2+) cycling process. The affinity of the uptake uniporter was found to be too low to efficiently regulate Ca(2+) in the low to mid nM concentration in the cytosol. However, a number of findings showed that energy linked transport of Ca(2+) did nevertheless occur in mitochondria in situ. The enigma was solved in the 1990s, when it was found that perimitochondrial Ca(2+) pools are created by the discharge of Ca(2+) from vicinal endoplasmic reticulum stores in which the concentration of Ca(2+) is high enough to satisfy the poor affinity of the uniporter. Thus, mitochondria have now regained a key role in the regulation of cytosolic Ca(2+) (not only of their own internal Ca(2+)).
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Affiliation(s)
- Ernesto Carafoli
- Venetian Institute of Molecular Medicine, University of Padova, Italy.
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1380
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Voronina S, Tepikin A. Mitochondrial calcium in the life and death of exocrine secretory cells. Cell Calcium 2012; 52:86-92. [PMID: 22571865 DOI: 10.1016/j.ceca.2012.03.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Revised: 03/26/2012] [Accepted: 03/27/2012] [Indexed: 01/11/2023]
Abstract
The remarkable recent discoveries of the proteins mediating mitochondrial Ca(2+) transport (reviewed in this issue) provide an exciting opportunity to utilise this new knowledge to improve our fundamental understanding of relationships between Ca(2+) signalling and bioenergetics and, importantly, to improve the understanding of diseases in which Ca(2+) toxicity and mitochondrial malfunction play a crucial role. Ca(2+) is an important activator of exocrine secretion, a regulator of the bioenergetics of exocrine cells and a contributor to exocrine cell damage. Exocrine secretory cells, exocrine tissues and diseases affecting exocrine glands (like Sjögren's syndrome and acute pancreatitis) will, therefore, provide worthy research areas for the application of this new knowledge of the Ca(2+) transport mechanisms in mitochondria.
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Affiliation(s)
- Svetlana Voronina
- Department of Cellular and Molecular Physiology, The Physiological Laboratory, Institute of Translational Medicine, The University of Liverpool, Crown Street, Liverpool L69 3BX, UK
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1381
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Abstract
Mitochondria perform diverse yet interconnected functions, producing ATP and many biosynthetic intermediates while also contributing to cellular stress responses such as autophagy and apoptosis. Mitochondria form a dynamic, interconnected network that is intimately integrated with other cellular compartments. In addition, mitochondrial functions extend beyond the boundaries of the cell and influence an organism's physiology by regulating communication between cells and tissues. It is therefore not surprising that mitochondrial dysfunction has emerged as a key factor in a myriad of diseases, including neurodegenerative and metabolic disorders. We provide a current view of how mitochondrial functions impinge on health and disease.
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Affiliation(s)
- Jodi Nunnari
- Department of Molecular and Cellular Biology, University of California, Davis, Davis, CA 95616, USA.
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1382
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Raturi A, Simmen T. Where the endoplasmic reticulum and the mitochondrion tie the knot: the mitochondria-associated membrane (MAM). BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:213-24. [PMID: 22575682 DOI: 10.1016/j.bbamcr.2012.04.013] [Citation(s) in RCA: 343] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 04/12/2012] [Accepted: 04/25/2012] [Indexed: 01/01/2023]
Abstract
More than a billion years ago, bacterial precursors of mitochondria became endosymbionts in what we call eukaryotic cells today. The true significance of the word "endosymbiont" has only become clear to cell biologists with the discovery that the endoplasmic reticulum (ER) superorganelle dedicates a special domain for the metabolic interaction with mitochondria. This domain, identified in all eukaryotic cell systems from yeast to man and called the mitochondria-associated membrane (MAM), has a distinct proteome, specific tethers on the cytosolic face and regulatory proteins in the ER lumen of the ER. The MAM has distinct biochemical properties and appears as ER tubules closely apposed to mitochondria on electron micrographs. The functions of the MAM range from lipid metabolism and calcium signaling to inflammasome formation. Consistent with these functions, the MAM is enriched in lipid metabolism enzymes and calcium handling proteins. During cellular stress situations, like an altered cellular redox state, the MAM alters its set of regulatory proteins and thus alters MAM functions. Notably, this set prominently comprises ER chaperones and oxidoreductases that connect protein synthesis and folding inside the ER to mitochondrial metabolism. Moreover, ER membranes associated with mitochondria also accommodate parts of the machinery that determines mitochondrial membrane dynamics and connect mitochondria to the cytoskeleton. Together, these exciting findings demonstrate that the physiological interactions between the ER and mitochondria are so bilateral that we are tempted to compare their relationship to the one of a married couple: distinct, but inseparable and certainly dependent on each other. In this paradigm, the MAM stands for the intracellular location where the two organelles tie the knot. Resembling "real life", the happy marriage between the two organelles prevents the onset of diseases that are characterized by disrupted metabolism and decreased lifespan, including neurodegeneration and cancer. This article is part of a Special Issue entitled: Mitochondrial dynamics and physiology.
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Affiliation(s)
- Arun Raturi
- Department of Cell Biology, University of Alberta, Edmonton, Alberta, Canada
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1383
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Wiederkehr A, Wollheim CB. Mitochondrial signals drive insulin secretion in the pancreatic β-cell. Mol Cell Endocrinol 2012; 353:128-37. [PMID: 21784130 DOI: 10.1016/j.mce.2011.07.016] [Citation(s) in RCA: 114] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Accepted: 07/07/2011] [Indexed: 12/31/2022]
Abstract
β-Cell nutrient sensing depends on mitochondrial function. Oxidation of nutrient-derived metabolites in the mitochondria leads to plasma membrane depolarization, Ca(2+) influx and insulin granule exocytosis. Subsequent mitochondrial Ca(2+) uptake further accelerates metabolism and oxidative phosphorylation. Nutrient activation also increases the mitochondrial matrix pH. This alkalinization is required to maintain elevated insulin secretion during prolonged nutrient stimulation. Together the mitochondrial Ca(2+) rise and matrix alkalinization assure optimal ATP synthesis necessary for efficient activation of the triggering pathway of insulin secretion. The sustained, amplifying pathway of insulin release also depends on mitochondrial Ca(2+) signals, which likely influence the generation of glucose-derived metabolites serving as coupling factors. Therefore, mitochondria are both recipients and generators of signals essential for metabolism-secretion coupling. Activation of these signaling pathways would be an attractive target for the improvement of β-cell function and the treatment of type 2 diabetes.
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1384
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Szanda G, Rajki A, Spät A. Control mechanisms of mitochondrial Ca(2+) uptake - feed-forward modulation of aldosterone secretion. Mol Cell Endocrinol 2012; 353:101-8. [PMID: 21924321 DOI: 10.1016/j.mce.2011.08.042] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 08/31/2011] [Accepted: 08/31/2011] [Indexed: 12/23/2022]
Abstract
Mitochondrial Ca(2+) signal activates metabolism by boosting pyridine nucleotide reduction and ATP synthesis or, if Ca(2+) sequestration is supraphysiological, may even lead to apoptosis. Although the molecular background of mitochondrial Ca(2+) uptake has recently been elucidated, the regulation of Ca(2+) handling is still not properly clarified. In human adrenocortical H295R cells we found a regulatory mechanism involving p38 MAPK and novel-type PKC isoforms. Upon stimulation with angiotensin II (AII) these kinases are activated typically prior to the release of Ca(2+) and - most probably by reducing the Ca(2+) permeation through the outer mitochondrial membrane - attenuate mitochondrial Ca(2+) uptake in a feed-forward manner. The biologic significance of the kinase-mediated reduction of mitochondrial Ca(2+) signal is also reflected by the attenuation of AII-mediated aldosterone secretion. As another feed-forward mechanism, we found in HEK-293T and H295R cells that Ca(2+) signal evoked either by IP(3) or by voltage-gated influx is accompanied by a concomitant cytosolic Mg(2+) signal. In permeabilized HEK-293T cells Mg(2+) was found to be a potent inhibitor of mitochondrial Ca(2+) uptake in the physiologic [Mg(2+)] and [Ca(2+)] range. Thus, these inhibitory mechanisms may serve not only as protection against mitochondrial Ca(2+) overload and subsequent apoptosis but also have the potential to substantially alter physiological responses.
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Affiliation(s)
- Gergö Szanda
- Department of Physiology, Semmelweis University, POB 259, H-1444 Budapest, Hungary
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1385
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Jean-Quartier C, Bondarenko AI, Alam MR, Trenker M, Waldeck-Weiermair M, Malli R, Graier WF. Studying mitochondrial Ca(2+) uptake - a revisit. Mol Cell Endocrinol 2012; 353:114-27. [PMID: 22100614 PMCID: PMC3334272 DOI: 10.1016/j.mce.2011.10.033] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 09/29/2011] [Accepted: 10/29/2011] [Indexed: 01/28/2023]
Abstract
Mitochondrial Ca(2+) sequestration is a well-known process that is involved in various physiological and pathological mechanisms. Using isolated suspended mitochondria one unique mitochondrial Ca(2+) uniporter was considered to account ubiquitously for the transfer of Ca(2+) into these organelles. However, by applying alternative techniques for measuring mitochondrial Ca(2+) uptake evidences for molecularly distinct mitochondrial Ca(2+) carriers accumulated recently. Herein we compared different methodical approaches of studying mitochondrial Ca(2+) uptake. Patch clamp technique on mitoplasts from endothelial and HeLa cells revealed the existence of three and two mitoplast Ca(2+) currents (I(CaMito)), respectively. According to their conductance, these channels were named small (s-), intermediate (i-), large (l-) and extra-large (xl-) mitoplast Ca(2+) currents (MCC). i-MCC was found in mitoplasts of both cell types whereas s-MCC and l-MCC or xl-MCC were/was exclusively found in mitoplasts from endothelial cells or HeLa cells. The comparison of mitochondrial Ca(2+) signals, measured either indirectly by sensing extra-mitochondrial Ca(2+) or directly by recording changes of the matrix Ca(2+), showed different Ca(2+) sensitivities of the distinct mitochondrial Ca(2+) uptake routes. Subpopulations of mitochondria with different Ca(2+) uptake capacities in intact endothelial cells could be identified using Rhod-2/AM. In contrast, cells expressing mitochondrial targeted pericam or cameleon (4mtD3cpv) showed homogeneous mitochondrial Ca(2+) signals in response to cell stimulation. The comparison of different experimental approaches and protocols using isolated organelles, permeabilized and intact cells, pointed to cell-type specific and versatile pathways for mitochondrial Ca(2+) uptake. Moreover, this work highlights the necessity of the utilization of multiple technical approaches to study the complexity of mitochondrial Ca(2+) homeostasis.
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Affiliation(s)
| | | | | | | | | | | | - Wolfgang F. Graier
- Corresponding author. Address: Molecular and Cellular Physiology Research Unit, Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, A-8010 Graz, Austria. Tel.: +43 316 380 7560; fax: +43 316 380 9615.
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1386
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Csordás G, Várnai P, Golenár T, Sheu SS, Hajnóczky G. Calcium transport across the inner mitochondrial membrane: molecular mechanisms and pharmacology. Mol Cell Endocrinol 2012; 353:109-13. [PMID: 22123069 PMCID: PMC3295916 DOI: 10.1016/j.mce.2011.11.011] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Revised: 11/10/2011] [Accepted: 11/10/2011] [Indexed: 01/21/2023]
Abstract
Growing evidence supports that mitochondrial calcium uptake is important for cell metabolism, signaling and survival. However, both the molecular nature of the mitochondrial Ca(2+) transport sites and the calcium signals they respond to remained elusive. Recent RNA interference studies have identified new candidate proteins for Ca(2+) transport across the inner mitochondrial membrane, including LETM1, MCU, MICU1 and NCLX. The sensitivity of these factors to several drugs has been tested and in parallel, some new inhibitors of mitochondrial Ca(2+) uptake have been described. This paper provides an update on the pharmacological aspects of the molecular mechanisms of the inner mitochondrial membrane Ca(2+) transport.
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Affiliation(s)
- György Csordás
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107
| | - Peter Várnai
- Department of Physiology, Semmelweis University Budapest, Hungary
| | - Tünde Golenár
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107
| | - Shey-Shing Sheu
- Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA 19107
| | - György Hajnóczky
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107
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1387
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Taylor CW, Dale P. Intracellular Ca(2+) channels - a growing community. Mol Cell Endocrinol 2012; 353:21-8. [PMID: 21889573 DOI: 10.1016/j.mce.2011.08.028] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Revised: 08/16/2011] [Accepted: 08/18/2011] [Indexed: 12/24/2022]
Abstract
The Ca(2+) signals that control almost every cellular activity are generated by regulating Ca(2+) transport, usually via Ca(2+)-permeable channels, across the plasma membrane or the membranes of intracellular organelles. The most widespread and best understood of the intracellular Ca(2+) channels are inositol trisphosphate receptors (IP(3)R) and ryanodine receptors, most of which are expressed in the endoplasmic or sarcoplasmic reticulum. However, accumulating evidence suggests physiological roles for many additional Ca(2+) channels in both ER and other intracellular organelles. Interactions between these channels, whether mediated by Ca(2+) itself or interactions between proteins, is a recurrent feature of the Ca(2+) signals evoked by physiological stimuli. We focus on two specific examples, clustering of IP(3)Rs and NAADP (nicotinic acid dinucleotide phosphate)-evoked Ca(2+) release from endo-lysosomes, to illustrate the diversity of Ca(2+) channels and the interplay between them.
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1388
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Ren W, Sain NM, Beebe SJ. Nanosecond pulsed electric fields (nsPEFs) activate intrinsic caspase-dependent and caspase-independent cell death in Jurkat cells. Biochem Biophys Res Commun 2012; 421:808-12. [PMID: 22554515 DOI: 10.1016/j.bbrc.2012.04.094] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 04/18/2012] [Indexed: 10/28/2022]
Abstract
NsPEF ablation induces apoptosis markers, but specific cell death pathways have not been fully defined. To identify nsPEF-activated cell death pathways, wildtype human Jurkat cells and clones with deficiencies in extrinsic and intrinsic apoptosis pathways were investigated. NsPEFs activated caspase isozymes and induced identical electric field-dependent cell death in clones deficient in FADD or caspase-8, indicating that extrinsic apoptosis pathways were not activated. This was confirmed when cytochrome c release was shown to be unaffected by the pan caspase inhibitor, z-VAD-fmk. NsPEF-treated APAF-1-silenced cells did not exhibit caspase-3/7 and -9 activities and corresponding electric field-dependent cell death in this clone was attenuated compared to its vector control at low, but not at high electric fields. These data demonstrate that nsPEFs induce intrinsic apoptosis activate by cytochrome c release from mitochondria through an APAF-1- and caspase-dependent pathway as well as through caspase-independent mechanisms that remain to be defined. Furthermore, the results establish that nsPEFs can overcome natural and oncogenic mechanisms that promote cell survival through inhibition of apoptosis and other cell death mechanisms.
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Affiliation(s)
- Wei Ren
- Frank Reidy Research Center for Bioelectric, Old Dominion University, Norfolk, VA 23508, United States
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1389
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Poburko D, Demaurex N. Regulation of the mitochondrial proton gradient by cytosolic Ca²⁺ signals. Pflugers Arch 2012; 464:19-26. [PMID: 22526460 DOI: 10.1007/s00424-012-1106-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 04/02/2012] [Indexed: 12/16/2022]
Abstract
Mitochondria convert the energy stored in carbohydrate and fat into ATP molecules that power enzymatic reactions within cells, and this process influences cellular calcium signals in several ways. By providing ATP to calcium pumps at the plasma and intracellular membranes, mitochondria power the calcium gradients that drive the release of Ca²⁺ from stores and the entry of Ca²⁺ across plasma membrane channels. By taking up and subsequently releasing calcium ions, mitochondria determine the spatiotemporal profile of cellular Ca²⁺ signals and the activity of Ca²⁺-regulated proteins, including Ca²⁺ entry channels that are themselves part of the Ca²⁺ circuitry. Ca²⁺ elevations in the mitochondrial matrix, in turn, activate Ca²⁺-dependent enzymes that boost the respiratory chain, increasing the ability of mitochondria to buffer calcium ions. Mitochondria are able to encode and decode Ca²⁺ signals because the respiratory chain generates an electrochemical gradient for protons across the inner mitochondrial membrane. This proton motive force (Δp) drives the activity of the ATP synthase and has both an electrical component, the mitochondrial membrane potential (ΔΨ(m)), and a chemical component, the mitochondrial proton gradient (ΔpH(m)). ΔΨ(m) contributes about 190 mV to Δp and drives the entry of Ca²⁺ across a recently identified Ca²⁺-selective channel known as the mitochondrial Ca²⁺ uniporter. ΔpH(m) contributes ~30 mV to Δp and is usually ignored or considered a minor component of mitochondria respiratory state. However, the mitochondrial proton gradient is an essential component of the chemiosmotic theory formulated by Peter Mitchell in 1961 as ΔpH(m) sustains the entry of substrates and metabolites required for the activity of the respiratory chain and drives the activity of electroneutral ion exchangers that allow mitochondria to maintain their osmolarity and volume. In this review, we summarize the mechanisms that regulate the mitochondrial proton gradient and discuss how thermodynamic concepts derived from measurements in purified mitochondria can be reconciled with our recent findings that mitochondria have high proton permeability in situ and that ΔpH(m) decreases during mitochondrial Ca²⁺ elevations.
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Affiliation(s)
- Damon Poburko
- Department of Biomedical Physiology & Kinesiology, Simon Fraser University, Vancouver, BC, Canada
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1390
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Bernardi P, von Stockum S. The permeability transition pore as a Ca(2+) release channel: new answers to an old question. Cell Calcium 2012; 52:22-7. [PMID: 22513364 PMCID: PMC3396848 DOI: 10.1016/j.ceca.2012.03.004] [Citation(s) in RCA: 134] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 03/21/2012] [Accepted: 03/21/2012] [Indexed: 01/08/2023]
Abstract
Mitochondria possess a sophisticated array of Ca2+ transport systems reflecting their key role in physiological Ca2+ homeostasis. With the exception of most yeast strains, energized organelles are endowed with a very fast and efficient mechanism for Ca2+ uptake, the ruthenium red (RR)-sensitive mitochondrial Ca2+ uniporter (MCU); and one main mechanism for Ca2+ release, the RR-insensitive 3Na+–Ca2+ antiporter. An additional mechanism for Ca2+ release is provided by a Na+ and RR-insensitive release mechanism, the putative 3H+–Ca2+ antiporter. A potential kinetic imbalance is present, however, because the Vmax of the MCU is of the order of 1400 nmol Ca2+ mg−1 protein min−1 while the combined Vmax of the efflux pathways is about 20 nmol Ca2+ mg−1 protein min−1. This arrangement exposes mitochondria to the hazards of Ca2+ overload when the rate of Ca2+ uptake exceeds that of the combined efflux pathways, e.g. for sharp increases of cytosolic [Ca2+]. In this short review we discuss the hypothesis that transient opening of the Ca2+-dependent permeability transition pore may provide mitocondria with a fast Ca2+ release channel preventing Ca2+ overload. We also address the relevance of a mitochondrial Ca2+ release channel recently discovered in Drosophila melanogaster, which possesses intermediate features between the permeability transition pore of yeast and mammals.
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Affiliation(s)
- Paolo Bernardi
- Department of Biomedical Sciences and CNR Institute of Neuroscience, University of Padova, Padova, Italy.
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1391
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Smith M, Flodman PL, Gargus JJ, Simon MT, Verrell K, Haas R, Reiner GE, Naviaux R, Osann K, Spence MA, Wallace DC. Mitochondrial and ion channel gene alterations in autism. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:1796-802. [PMID: 22538295 DOI: 10.1016/j.bbabio.2012.04.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Revised: 04/09/2012] [Accepted: 04/10/2012] [Indexed: 10/28/2022]
Abstract
To evaluate the potential importance in autistic subjects of copy number variants (CNVs) that alter genes of relevance to bioenergetics, ionic metabolism, and synaptic function, we conducted a detailed microarray analysis of 69 autism probands and 35 parents, compared to 89 CEU HapMap controls. This revealed that the frequency CNVs of≥100kb and CNVs of≥10 Kb were markedly increased in probands over parents and in probands and parents over controls. Evaluation of CNVs≥1Mb by chromosomal FISH confirmed the molecular identity of a subset of the CNVs, some of which were associated with chromosomal rearrangements. In a number of the cases, CNVs were found to alter the copy number of genes that are important in mitochondrial oxidative phosphorylation (OXPHOS), ion and especially calcium transport, and synaptic structure. Hence, autism might result from alterations in multiple bioenergetic and metabolic genes required for mental function. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).
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Affiliation(s)
- Moyra Smith
- Department of Pediatrics University of California, Irvine, CA, USA.
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1392
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Kawamoto EM, Vivar C, Camandola S. Physiology and pathology of calcium signaling in the brain. Front Pharmacol 2012; 3:61. [PMID: 22518105 PMCID: PMC3325487 DOI: 10.3389/fphar.2012.00061] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Accepted: 03/26/2012] [Indexed: 12/31/2022] Open
Abstract
Calcium (Ca(2+)) plays fundamental and diversified roles in neuronal plasticity. As second messenger of many signaling pathways, Ca(2+) as been shown to regulate neuronal gene expression, energy production, membrane excitability, synaptogenesis, synaptic transmission, and other processes underlying learning and memory and cell survival. The flexibility of Ca(2+) signaling is achieved by modifying cytosolic Ca(2+) concentrations via regulated opening of plasma membrane and subcellular Ca(2+) sensitive channels. The spatiotemporal patterns of intracellular Ca(2+) signals, and the ultimate cellular biological outcome, are also dependent upon termination mechanism, such as Ca(2+) buffering, extracellular extrusion, and intra-organelle sequestration. Because of the central role played by Ca(2+) in neuronal physiology, it is not surprising that even modest impairments of Ca(2+) homeostasis result in profound functional alterations. Despite their heterogeneous etiology neurodegenerative disorders, as well as the healthy aging process, are all characterized by disruption of Ca(2+) homeostasis and signaling. In this review we provide an overview of the main types of neuronal Ca(2+) channels and their role in neuronal plasticity. We will also discuss the participation of Ca(2+) signaling in neuronal aging and degeneration.
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Affiliation(s)
- Elisa Mitiko Kawamoto
- Laboratory of Neurosciences, National Institute on Aging, Intramural Research ProgramBaltimore, MD, USA
| | - Carmen Vivar
- Laboratory of Neurosciences, National Institute on Aging, Intramural Research ProgramBaltimore, MD, USA
| | - Simonetta Camandola
- Laboratory of Neurosciences, National Institute on Aging, Intramural Research ProgramBaltimore, MD, USA
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1393
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Tarasov AI, Griffiths EJ, Rutter GA. Regulation of ATP production by mitochondrial Ca(2+). Cell Calcium 2012; 52:28-35. [PMID: 22502861 PMCID: PMC3396849 DOI: 10.1016/j.ceca.2012.03.003] [Citation(s) in RCA: 187] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2012] [Revised: 03/10/2012] [Accepted: 03/14/2012] [Indexed: 01/09/2023]
Abstract
Stimulation of mitochondrial oxidative metabolism by Ca(2+) is now generally recognised as important for the control of cellular ATP homeostasis. Here, we review the mechanisms through which Ca(2+) regulates mitochondrial ATP synthesis. We focus on cardiac myocytes and pancreatic β-cells, where tight control of this process is likely to play an important role in the response to rapid changes in workload and to nutrient stimulation, respectively. We also describe a novel approach for imaging the Ca(2+)-dependent regulation of ATP levels dynamically in single cells.
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Affiliation(s)
- Andrei I Tarasov
- Section of Cell Biology, Division of Diabetes Endocrinology and Metabolism, Department of Medicine, Imperial College London, SW7 2AZ, London, UK
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1394
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Abstract
Calcium is an important signaling molecule involved in the regulation of many cellular functions. The large free energy in the Ca(2+) ion membrane gradients makes Ca(2+) signaling inherently sensitive to the available cellular free energy, primarily in the form of ATP. In addition, Ca(2+) regulates many cellular ATP-consuming reactions such as muscle contraction, exocytosis, biosynthesis, and neuronal signaling. Thus, Ca(2+) becomes a logical candidate as a signaling molecule for modulating ATP hydrolysis and synthesis during changes in numerous forms of cellular work. Mitochondria are the primary source of aerobic energy production in mammalian cells and also maintain a large Ca(2+) gradient across their inner membrane, providing a signaling potential for this molecule. The demonstrated link between cytosolic and mitochondrial Ca(2+) concentrations, identification of transport mechanisms, and the proximity of mitochondria to Ca(2+) release sites further supports the notion that Ca(2+) can be an important signaling molecule in the energy metabolism interplay of the cytosol with the mitochondria. Here we review sites within the mitochondria where Ca(2+) plays a role in the regulation of ATP generation and potentially contributes to the orchestration of cellular metabolic homeostasis. Early work on isolated enzymes pointed to several matrix dehydrogenases that are stimulated by Ca(2+), which were confirmed in the intact mitochondrion as well as cellular and in vivo systems. However, studies in these intact systems suggested a more expansive influence of Ca(2+) on mitochondrial energy conversion. Numerous noninvasive approaches monitoring NADH, mitochondrial membrane potential, oxygen consumption, and workloads suggest significant effects of Ca(2+) on other elements of NADH generation as well as downstream elements of oxidative phosphorylation, including the F(1)F(O)-ATPase and the cytochrome chain. These other potential elements of Ca(2+) modification of mitochondrial energy conversion will be the focus of this review. Though most specific molecular mechanisms have yet to be elucidated, it is clear that Ca(2+) provides a balanced activation of mitochondrial energy metabolism that exceeds the alteration of dehydrogenases alone.
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Affiliation(s)
- Brian Glancy
- Laboratory of Cardiac Energetics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20817, USA
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1395
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ER-Mitochondria Crosstalk during Cerebral Ischemia: Molecular Chaperones and ER-Mitochondrial Calcium Transfer. Int J Cell Biol 2012; 2012:493934. [PMID: 22577383 PMCID: PMC3335182 DOI: 10.1155/2012/493934] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 01/12/2012] [Indexed: 11/24/2022] Open
Abstract
It is commonly believed that sustained elevations in the mitochondrial matrix Ca2+ concentration are a major feature of the intracellular cascade of lethal events during cerebral ischemia. The physical association between the endoplasmic reticulum (ER) and mitochondria, known as the mitochondria-associated ER membrane (MAM), enables highly efficient transmission of Ca2+ from the ER to mitochondria under both physiological and pathological conditions. Molecular chaperones are well known for their protective effects during cerebral ischemia. It has been demonstrated recently that many molecular chaperones coexist with MAM and regulate the MAM and thus Ca2+ concentration inside mitochondria. Here, we review recent research on cerebral ischemia and MAM, with a focus on molecular chaperones and ER-mitochondrial calcium transfer.
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1396
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Nurbaeva MK, Schmid E, Szteyn K, Yang W, Viollet B, Shumilina E, Lang F. Enhanced Ca²⁺ entry and Na+/Ca²⁺ exchanger activity in dendritic cells from AMP-activated protein kinase-deficient mice. FASEB J 2012; 26:3049-58. [PMID: 22474243 DOI: 10.1096/fj.12-204024] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In dendritic cells (DCs), chemotactic chemokines, such as CXCL12, rapidly increase cytosolic Ca(2+)concentrations ([Ca(2+)](i)) by triggering Ca(2+) release from intracellular stores followed by store-operated Ca(2+) (SOC) entry. Increase of [Ca(2+)](i) is blunted and terminated by Ca(2+) extrusion, accomplished by K(+)-independent Na(+)/Ca(2+) exchangers (NCXs) and K(+)-dependent Na(+)/Ca(2+) exchangers (NCKXs). Increased [Ca(2+)](i) activates energy-sensing AMP-activated protein kinase (AMPK), which suppresses proinflammatory responses of DCs and macrophages. The present study explored whether AMPK participates in the regulation of DC [Ca(2+)](i) and migration. DCs were isolated from AMPKα1-deficient (ampk(-/-)) mice and, as control, from their wild-type (ampk(+/+)) littermates. AMPKα1, Orai1-2, STIM1-2, and mitochondrial calcium uniporter protein expression was determined by Western blotting, [Ca(2+)](i) by Fura-2 fluorescence, SOC entry by inhibition of endosomal Ca(2+) ATPase with thapsigargin (1 μM), Na(+)/Ca(2+) exchanger activity from increase of [Ca(2+)](i), and respective whole-cell current in patch clamp following removal of extracellular Na(+). Migration was quantified utilizing transwell chambers. AMPKα1 protein is expressed in ampk(+/+) DCs but not in ampk(-/-) DCs. CXCL12 (300 ng/ml)-induced increase of [Ca(2+)](i), SOC entry, Orai 1 protein abundance, NCX, and NCKX were all significantly higher in ampk(-/-) DCs than in ampk(+/+) DCs. NCX and NCKX currents were similarly increased in ampk(-/-) DCs. Moreover, CXCL12 (50 ng/ml)-induced DC migration was enhanced in ampk(-/-) DCs. AMPK thus inhibits SOC entry, Na(+)/Ca(2+) exchangers, and migration of DCs.
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1397
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Zampese E, Pizzo P. Intracellular organelles in the saga of Ca2+ homeostasis: different molecules for different purposes? Cell Mol Life Sci 2012; 69:1077-104. [PMID: 21968921 PMCID: PMC11114864 DOI: 10.1007/s00018-011-0845-9] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Revised: 09/15/2011] [Accepted: 09/19/2011] [Indexed: 11/28/2022]
Abstract
An increase in the concentration of cytosolic free Ca(2+) is a key component regulating different cellular processes ranging from egg fertilization, active secretion and movement, to cell differentiation and death. The multitude of phenomena modulated by Ca(2+), however, do not simply rely on increases/decreases in its concentration, but also on specific timing, shape and sub-cellular localization of its signals that, combined together, provide a huge versatility in Ca(2+) signaling. Intracellular organelles and their Ca(2+) handling machineries exert key roles in this complex and precise mechanism, and this review will try to depict a map of Ca(2+) routes inside cells, highlighting the uniqueness of the different Ca(2+) toolkit components and the complexity of the interactions between them.
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Affiliation(s)
- Enrico Zampese
- Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy
| | - Paola Pizzo
- Department of Biomedical Sciences, University of Padova, Viale G. Colombo 3, 35121 Padova, Italy
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1398
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Mitochondrial Ca(2+) signals in autophagy. Cell Calcium 2012; 52:44-51. [PMID: 22459281 DOI: 10.1016/j.ceca.2012.03.001] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Revised: 02/29/2012] [Accepted: 03/01/2012] [Indexed: 01/05/2023]
Abstract
Macroautophagy (autophagy) is a lysosomal degradation pathway that is conserved from yeast to humans that plays an important role in recycling cellular constituents in all cells. A number of protein complexes and signaling pathways impinge on the regulation of autophagy, with the mammalian target of rapamycin (mTOR) as the central player in the canonical pathway. Cytoplasmic Ca(2+) signaling also regulates autophagy, with both activating and inhibitory effects, mediated by the canonical as well as non-canonical pathways. Here we review this regulation, with a focus on the role of an mTOR-independent pathway that involves the inositol trisphosphate receptor (InsP(3)R) Ca(2+) release channel and Ca(2+) signaling to mitochondria. Constitutive InsP(3)R Ca(2+) transfer to mitochondria is required for autophagy suppression in cells in nutrient-replete media. In its absence, cells become metabolically compromised due to insufficient production of reducing equivalents to support oxidative phosphorylation. Absence of this Ca(2+) transfer to mitochondria results in activation of AMPK, which activates mTOR-independent pro-survival autophagy. Constitutive InsP(3)R Ca(2+) release to mitochondria is an essential cellular process that is required for efficient mitochondrial respiration, maintenance of normal cell bioenergetics and suppression of autophagy.
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1399
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Mitochondrial Ca(2+) mobilization is a key element in olfactory signaling. Nat Neurosci 2012; 15:754-62. [PMID: 22446879 DOI: 10.1038/nn.3074] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Accepted: 02/21/2012] [Indexed: 12/13/2022]
Abstract
In olfactory sensory neurons (OSNs), cytosolic Ca(2+) controls the gain and sensitivity of olfactory signaling. Important components of the molecular machinery that orchestrates OSN Ca(2+) dynamics have been described, but key details are still missing. Here, we demonstrate a critical physiological role of mitochondrial Ca(2+) mobilization in mouse OSNs. Combining a new mitochondrial Ca(2+) imaging approach with patch-clamp recordings, organelle mobility assays and ultrastructural analyses, our study identifies mitochondria as key determinants of olfactory signaling. We show that mitochondrial Ca(2+) mobilization during sensory stimulation shapes the cytosolic Ca(2+) response profile in OSNs, ensures a broad dynamic response range and maintains sensitivity of the spike generation machinery. When mitochondrial function is impaired, olfactory neurons function as simple stimulus detectors rather than as intensity encoders. Moreover, we describe activity-dependent recruitment of mitochondria to olfactory knobs, a mechanism that provides a context-dependent tool for OSNs to maintain cellular homeostasis and signaling integrity.
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1400
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Palty R, Sekler I. The mitochondrial Na(+)/Ca(2+) exchanger. Cell Calcium 2012; 52:9-15. [PMID: 22430014 DOI: 10.1016/j.ceca.2012.02.010] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2012] [Revised: 02/24/2012] [Accepted: 02/27/2012] [Indexed: 01/20/2023]
Abstract
Powered by the steep mitochondrial membrane potential Ca(2+) permeates into the mitochondria via the Ca(2+) uniporter and is then extruded by a mitochondrial Na(+)/Ca(2+) exchanger. This mitochondrial Ca(2+) shuttling regulates the rate of ATP production and participates in cellular Ca(2+) signaling. Despite the fact that the exchanger was functionally identified 40 years ago its molecular identity remained a mystery. Early studies on isolated mitochondria and intact cells characterized the functional properties of a mitochondrial Na(+)/Ca(2+) exchanger, and showed that it possess unique functional fingerprints such as Li(+)/Ca(2+) exchange and that it is displaying selective sensitivity to inhibitors. Purification of mitochondria proteins combined with functional reconstitution led to the isolation of a polypeptide candidate of the exchanger but failed to molecularly identify it. A turning point in the search for the exchanger molecule came with the recent cloning of the last member of the Na(+)/Ca(2+) exchanger superfamily termed NCLX (Na(+)/Ca(2+)/Li(+) exchanger). NCLX is localized in the inner mitochondria membrane and its expression is linked to mitochondria Na(+)/Ca(2+) exchange matching the functional fingerprints of the putative mitochondrial Na(+)/Ca(2+) exchanger. Thus NCLX emerges as the long sought mitochondria Na(+)/Ca(2+) exchanger and provide a critical molecular handle to study mitochondrial Ca(2+) signaling and transport. Here we summarize some of the main topics related to the molecular properties of the Na(+)/Ca(2+) exchanger, beginning with the early days of its functional identification, its kinetic properties and regulation, and culminating in its molecular identification.
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Affiliation(s)
- Raz Palty
- Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA 94720, USA.
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