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Miragoli M, Cabassi A. Mitochondrial Mechanosensor Microdomains in Cardiovascular Disorders. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 982:247-264. [PMID: 28551791 DOI: 10.1007/978-3-319-55330-6_13] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The cardiomyocytes populating the 'working myocardium' are highly organized and such organization ranges from macroscale (e.g. the geometrical rod shape) to microscale (dyad/t-tubules) domains. This meticulous level of organization is imperative for assuring the normal and physiological pump-function of the heart. In the pathological cardiac tissue, the domains-related architecture is partially lost, resulting in morphological, electrical and metabolic remodeling and promoting cardiovascular diseases including heart failure and arrhythmias. Indeed, arrhythmogenesis during heart failure is a major clinical problem. Arrhythmias have been extensively studied from an electrical etiology, but only recently, physiologists and scientists have focused their attention on cellular and subcellular mechanosensors. We and others have investigated whether the nanoscale mechanosensitive properties of cardiomyocytes from failing hearts have a bearing upon the initiation of abnormal electrical activity. This chapter highlights the recent findings in the field, especially the role of mitochondria function and alignment in failing cardiomyocytes interrogated via nanomechanical stimuli.
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Affiliation(s)
- Michele Miragoli
- Department of Medicine and Surgery, University of Parma, Parma, 43124, Italy. .,Humanitas Clinical and Research Center, Rozzano, MI, Italy.
| | - Aderville Cabassi
- Department of Medicine and Surgery, University of Parma, Parma, 43124, Italy
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2
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Spät A, Szanda G. The Role of Mitochondria in the Activation/Maintenance of SOCE: Store-Operated Ca 2+ Entry and Mitochondria. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 993:257-275. [PMID: 28900919 DOI: 10.1007/978-3-319-57732-6_14] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mitochondria extensively modify virtually all cellular Ca2+ transport processes, and store-operated Ca2+ entry (SOCE) is no exception to this rule. The interaction between SOCE and mitochondria is complex and reciprocal, substantially altering and, ultimately, fine-tuning both capacitative Ca2+ influx and mitochondrial function. Mitochondria, owing to their considerable Ca2+ accumulation ability, extensively buffer the cytosolic Ca2+ in their vicinity. In turn, the accumulated ion is released back into the neighboring cytosol during net Ca2+ efflux. Since store depletion itself and the successive SOCE are both Ca2+-regulated phenomena, mitochondrial Ca2+ handling may have wide-ranging effects on capacitative Ca2+ influx at any given time. In addition, mitochondria may also produce or consume soluble factors known to affect store-operated channels. On the other hand, Ca2+ entering the cell during SOCE is sensed by mitochondria, and the ensuing mitochondrial Ca2+ uptake boosts mitochondrial energy metabolism and, if Ca2+ overload occurs, may even lead to apoptosis or cell death. In several cell types, mitochondria seem to be sterically excluded from the confined space that forms between the plasma membrane (PM) and endoplasmic reticulum (ER) during SOCE. This implies that high-Ca2+ microdomains comparable to those observed between the ER and mitochondria do not form here. In the following chapter, the above aspects of the many-sided SOCE-mitochondrion interplay will be discussed in greater detail.
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Affiliation(s)
- András Spät
- Department of Physiology, Semmelweis University Medical School, POB 2, 1428, Budapest, Hungary.
- Laboratory of Molecular Physiology, Hungarian Academy of Sciences, Budapest, Hungary.
| | - Gergö Szanda
- Department of Physiology, Semmelweis University Medical School, POB 2, 1428, Budapest, Hungary
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Roberts RC, Roche JK, McCullumsmith RE. Localization of excitatory amino acid transporters EAAT1 and EAAT2 in human postmortem cortex: a light and electron microscopic study. Neuroscience 2014; 277:522-40. [PMID: 25064059 PMCID: PMC4164610 DOI: 10.1016/j.neuroscience.2014.07.019] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Accepted: 07/14/2014] [Indexed: 01/03/2023]
Abstract
The process of glutamate release, activity, and reuptake involves the astrocyte, the presynaptic and postsynaptic neurons. Glutamate is released into the synapse and may occupy and activate receptors on both neurons and astrocytes. Glutamate is rapidly removed from the synapse by a family of plasma membrane excitatory amino acid transporters (EAATs), also localized to neurons and astrocytes. The purpose of the present study was to examine EAAT labeling in the postmortem human cortex at the light and electron microscopic (EM) levels. The postmortem prefrontal cortex was processed for EAAT1 and EAAT2 immunohistochemistry. At the light microscopic level, EAAT1 and EAAT2 labeling was found in both gray and white matter. Most cellular labeling was in small cells which were morphologically similar to glia. In addition, EAAT1-labeled neurons were scattered throughout, some of which were pyramidal in shape. At the EM level, EAAT1 and EAAT2 labeling was found in astrocytic soma and processes surrounding capillaries. EAAT labeling was also found in small astrocytic processes adjacent to axon terminals forming asymmetric (glutamatergic) synapses. While EAAT2 labeling was most prevalent in astrocytic processes, EAAT1 labeling was also present in neuronal processes including the soma, axons, and dendritic spines. Expression of EAAT1 protein on neurons may be due to the hypoxia associated with the postmortem interval, and requires further confirmation. The localization of EAATs on the astrocytic plasma membrane and adjacent to excitatory synapses is consistent with the function of facilitating glutamate reuptake and limiting glutamate spillover. Establishment that EAAT1 and EAAT2 can be measured at the EM level in human postmortem tissues will permit testing of hypotheses related to these molecules in diseases lacking analogous animal models.
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Affiliation(s)
- R C Roberts
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, USA.
| | - J K Roche
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, Birmingham, AL, USA
| | - R E McCullumsmith
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati College of Medicine, Cincinnati, OH, USA.
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Waldeck-Weiermair M, Deak AT, Groschner LN, Alam MR, Jean-Quartier C, Malli R, Graier WF. Molecularly distinct routes of mitochondrial Ca2+ uptake are activated depending on the activity of the sarco/endoplasmic reticulum Ca2+ ATPase (SERCA). J Biol Chem 2013; 288:15367-79. [PMID: 23592775 PMCID: PMC3663555 DOI: 10.1074/jbc.m113.462259] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The transfer of Ca2+ across the inner mitochondrial membrane is an important physiological process linked to the regulation of metabolism, signal transduction, and cell death. While the definite molecular composition of mitochondrial Ca2+ uptake sites remains unknown, several proteins of the inner mitochondrial membrane, that are likely to accomplish mitochondrial Ca2+ fluxes, have been described: the novel uncoupling proteins 2 and 3, the leucine zipper-EF-hand containing transmembrane protein 1 and the mitochondrial calcium uniporter. It is unclear whether these proteins contribute to one unique mitochondrial Ca2+ uptake pathway or establish distinct routes for mitochondrial Ca2+ sequestration. In this study, we show that a modulation of Ca2+ release from the endoplasmic reticulum by inhibition of the sarco/endoplasmatic reticulum ATPase modifies cytosolic Ca2+ signals and consequently switches mitochondrial Ca2+ uptake from an uncoupling protein 3- and mitochondrial calcium uniporter-dependent, but leucine zipper-EF-hand containing transmembrane protein 1-independent to a leucine zipper-EF-hand containing transmembrane protein 1- and mitochondrial calcium uniporter-mediated, but uncoupling protein 3-independent pathway. Thus, the activity of sarco/endoplasmatic reticulum ATPase is significant for the mode of mitochondrial Ca2+ sequestration and determines which mitochondrial proteins might actually accomplish the transfer of Ca2+ across the inner mitochondrial membrane. Moreover, our findings herein support the existence of distinct mitochondrial Ca2+ uptake routes that might be essential to ensure an efficient ion transfer into mitochondria despite heterogeneous cytosolic Ca2+ rises.
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Affiliation(s)
- Markus Waldeck-Weiermair
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, 8010 Graz, Austria
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Clementi EA, Marks LR, Duffey ME, Hakansson AP. A novel initiation mechanism of death in Streptococcus pneumoniae induced by the human milk protein-lipid complex HAMLET and activated during physiological death. J Biol Chem 2012; 287:27168-82. [PMID: 22700972 DOI: 10.1074/jbc.m112.371070] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
To cause colonization or infection, most bacteria grow in biofilms where differentiation and death of subpopulations is critical for optimal survival of the whole population. However, little is known about initiation of bacterial death under physiological conditions. Membrane depolarization has been suggested, but never shown to be involved, due to the difficulty of performing such studies in bacteria and the paucity of information that exists regarding ion transport mechanisms in prokaryotes. In this study, we performed the first extensive investigation of ion transport and membrane depolarization in a bacterial system. We found that HAMLET, a human milk protein-lipid complex, kills Streptococcus pneumoniae (the pneumococcus) in a manner that shares features with activation of physiological death from starvation. Addition of HAMLET to pneumococci dissipated membrane polarity, but depolarization per se was not enough to trigger death. Rather, both HAMLET- and starvation-induced death of pneumococci specifically required a sodium-dependent calcium influx, as shown using calcium and sodium transport inhibitors. This mechanism was verified under low sodium conditions, and in the presence of ionomycin or monensin, which enhanced pneumococcal sensitivity to HAMLET- and starvation-induced death. Pneumococcal death was also inhibited by kinase inhibitors, and indicated the involvement of Ser/Thr kinases in these processes. The importance of this activation mechanism was made evident, as dysregulation and manipulation of physiological death was detrimental to biofilm formation, a hallmark of bacterial colonization. Overall, our findings provide novel information on the role of ion transport during bacterial death, with the potential to uncover future antimicrobial targets.
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Affiliation(s)
- Emily A Clementi
- Department of Microbiology and Immunology, University at Buffalo, State University of New York, Buffalo, New York 14214, USA
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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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7
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Petersen OH. Specific mitochondrial functions in separate sub-cellular domains of pancreatic acinar cells. Pflugers Arch 2012; 464:77-87. [PMID: 22491894 DOI: 10.1007/s00424-012-1099-6] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Accepted: 03/14/2012] [Indexed: 01/06/2023]
Abstract
The pancreatic acinar cell synthesizes many digestive proenzymes, which are packaged into secretory (zymogen) granules and secreted by exocytosis upon the action of the neurotransmitter acetylcholine, released from vagal nerve endings, or the hormone cholecystokinin. These secretagogues mobilize Ca(2+) from internal stores and thereby create the cytosolic Ca(2+) signals that control exocytosis. Exocytosis requires Ca(2+), Mg(2+) and ATP. Mg(2+) is present in millimolars concentration throughout the cytosol, but high cytosolic Ca(2+) concentrations need to be created in the local domains near the apical plasma membrane. A special group of mitochondria surrounding the apical granular area play a crucial role in confining cytosolic Ca(2+) elevations to this part of the cell by acting as a Ca(2+) buffer barrier. The Ca(2+) uptake into these mitochondria during apical Ca(2+) spiking stimulates mitochondrial ATP synthesis. ATP is also required for Ca(2+) extrusion via the plasma membrane Ca(2+) pumps, mainly located in the apical area, as well as for Ca(2+) reuptake into the endoplasmic reticulum. Because Ca(2+) extrusion occurs during Ca(2+) spiking, there is a need for compensatory Ca(2+) entry via store-operated Ca(2+) channels. Sub-plasmalemmal (peripheral) mitochondria play an important role in supporting both store-operated Ca(2+) entry at the base as well as the subsequent Ca(2+) pumping into the endoplasmic reticulum. A third group of mitochondria surround the nucleus. They protect the nucleus against unwarranted Ca(2+) signals generated elsewhere and are capable of confining Ca(2+) signals primarily generated inside the nucleus to this part of the cell.
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Affiliation(s)
- Ole H Petersen
- MRC Group, School of Biosciences, Cardiff University, Biomedical Sciences Building, Museum Avenue, Cardiff, CF10 3AX, Wales, UK.
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Spät A, Szanda G. Special features of mitochondrial Ca²⁺ signalling in adrenal glomerulosa cells. Pflugers Arch 2012; 464:43-50. [PMID: 22395411 DOI: 10.1007/s00424-012-1086-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2012] [Revised: 02/10/2012] [Accepted: 02/14/2012] [Indexed: 11/30/2022]
Abstract
Aldosterone, secreted by adrenal glomerulosa cells, allows the adaptation of the vertebrate organism to a wide range of physiological and pathological stimuli including acute haemodynamic challenges and long-term changes in dietary sodium and potassium intake. Most of the extracellular signals are mediated by cytosolic Ca²⁺ signal deriving from Ca²⁺ release, store-operated and/or voltage-gated Ca²⁺ influx. Mitochondria in glomerulosa cells play a fundamental role in generating and modulating the final biological response. These organelles not only house several enzymes of aldosterone biosynthesis but also-in a Ca²⁺-dependent manner-provide NADPH for the function of these enzymes. Moreover, mitochondria, constituting a high portion of cytoplasmic volume and displaying a uniquely low-threshold Ca²⁺ sequestering ability, shape and thus modulate the decoding of the complex cytosolic Ca²⁺ response. The unusual features of mitochondrial Ca²⁺ signalling that permit such an integrative function in adrenal glomerulosa cells are hereby described.
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Affiliation(s)
- András Spät
- Department of Physiology, Semmelweis University, Budapest, Hungary.
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9
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Bose J, Pottosin II, Shabala SS, Palmgren MG, Shabala S. Calcium efflux systems in stress signaling and adaptation in plants. FRONTIERS IN PLANT SCIENCE 2011; 2:85. [PMID: 22639615 PMCID: PMC3355617 DOI: 10.3389/fpls.2011.00085] [Citation(s) in RCA: 140] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Accepted: 11/04/2011] [Indexed: 05/18/2023]
Abstract
Transient cytosolic calcium ([Ca(2+)](cyt)) elevation is an ubiquitous denominator of the signaling network when plants are exposed to literally every known abiotic and biotic stress. These stress-induced [Ca(2+)](cyt) elevations vary in magnitude, frequency, and shape, depending on the severity of the stress as well the type of stress experienced. This creates a unique stress-specific calcium "signature" that is then decoded by signal transduction networks. While most published papers have been focused predominantly on the role of Ca(2+) influx mechanisms to shaping [Ca(2+)](cyt) signatures, restoration of the basal [Ca(2+)](cyt) levels is impossible without both cytosolic Ca(2+) buffering and efficient Ca(2+) efflux mechanisms removing excess Ca(2+) from cytosol, to reload Ca(2+) stores and to terminate Ca(2+) signaling. This is the topic of the current review. The molecular identity of two major types of Ca(2+) efflux systems, Ca(2+)-ATPase pumps and Ca(2+)/H(+) exchangers, is described, and their regulatory modes are analyzed in detail. The spatial and temporal organization of calcium signaling networks is described, and the importance of existence of intracellular calcium microdomains is discussed. Experimental evidence for the role of Ca(2+) efflux systems in plant responses to a range of abiotic and biotic factors is summarized. Contribution of Ca(2+)-ATPase pumps and Ca(2+)/H(+) exchangers in shaping [Ca(2+)](cyt) signatures is then modeled by using a four-component model (plasma- and endo-membrane-based Ca(2+)-permeable channels and efflux systems) taking into account the cytosolic Ca(2+) buffering. It is concluded that physiologically relevant variations in the activity of Ca(2+)-ATPase pumps and Ca(2+)/H(+) exchangers are sufficient to fully describe all the reported experimental evidence and determine the shape of [Ca(2+)](cyt) signatures in response to environmental stimuli, emphasizing the crucial role these active efflux systems play in plant adaptive responses to environment.
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Affiliation(s)
- Jayakumar Bose
- School of Agricultural Science, University of TasmaniaHobart, TAS, Australia
| | - Igor I. Pottosin
- Centro Universitario de Investigaciones Biomédicas, Universidad de ColimaColima, México
| | | | | | - Sergey Shabala
- School of Agricultural Science, University of TasmaniaHobart, TAS, Australia
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Waldeck-Weiermair M, Jean-Quartier C, Rost R, Khan MJ, Vishnu N, Bondarenko AI, Imamura H, Malli R, Graier WF. Leucine zipper EF hand-containing transmembrane protein 1 (Letm1) and uncoupling proteins 2 and 3 (UCP2/3) contribute to two distinct mitochondrial Ca2+ uptake pathways. J Biol Chem 2011; 286:28444-55. [PMID: 21613221 PMCID: PMC3151087 DOI: 10.1074/jbc.m111.244517] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Cytosolic Ca2+ signals are transferred into mitochondria over a huge concentration range. In our recent work we described uncoupling proteins 2 and 3 (UCP2/3) to be fundamental for mitochondrial uptake of high Ca2+ domains in mitochondria-ER junctions. On the other hand, the leucine zipper EF hand-containing transmembrane protein 1 (Letm1) was identified as a mitochondrial Ca2+/H+ antiporter that achieved mitochondrial Ca2+ sequestration at small Ca2+ increases. Thus, the contributions of Letm1 and UCP2/3 to mitochondrial Ca2+ uptake were compared in endothelial cells. Knock-down of Letm1 did not affect the UCP2/3-dependent mitochondrial uptake of intracellularly released Ca2+ but strongly diminished the transfer of entering Ca2+ into mitochondria, subsequently, resulting in a reduction of store-operated Ca2+ entry (SOCE). Knock-down of Letm1 and UCP2/3 did neither impact on cellular ATP levels nor the membrane potential. The enhanced mitochondrial Ca2+ signals in cells overexpressing UCP2/3 rescued SOCE upon Letm1 knock-down. In digitonin-permeabilized cells, Letm1 exclusively contributed to mitochondrial Ca2+ uptake at low Ca2+ conditions. Neither the Letm1- nor the UCP2/3-dependent mitochondrial Ca2+ uptake was affected by a knock-down of mRNA levels of mitochondrial calcium uptake 1 (MICU1), a protein that triggers mitochondrial Ca2+ uptake in HeLa cells. Our data indicate that Letm1 and UCP2/3 independently contribute to two distinct, mitochondrial Ca2+ uptake pathways in intact endothelial cells.
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Affiliation(s)
- Markus Waldeck-Weiermair
- Institute of Molecular Biology and Biochemistry, Molecular and Cellular Physiology Research Unit, Center of Molecular Medicine, Medical University Graz, Harrachgasse 21/III, 8010 Graz, Austria
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Waldeck-Weiermair M, Duan X, Naghdi S, Khan MJ, Trenker M, Malli R, Graier WF. Uncoupling protein 3 adjusts mitochondrial Ca(2+) uptake to high and low Ca(2+) signals. Cell Calcium 2010; 48:288-301. [PMID: 21047682 PMCID: PMC2998676 DOI: 10.1016/j.ceca.2010.10.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Accepted: 10/07/2010] [Indexed: 12/12/2022]
Abstract
Uncoupling proteins 2 and 3 (UCP2/3) are essential for mitochondrial Ca2+ uptake but both proteins exhibit distinct activities in regard to the source and mode of Ca2+ mobilization. In the present work, structural determinants of their contribution to mitochondrial Ca2+ uptake were explored. Previous findings indicate the importance of the intermembrane loop 2 (IML2) for the contribution of UCP2/3. Thus, the IML2 of UCP2/3 was substituted by that of UCP1. These chimeras had no activity in mitochondrial uptake of intracellularly released Ca2+, while they mimicked the wild-type proteins by potentiating mitochondrial sequestration of entering Ca2+. Alignment of the IML2 sequences revealed that UCP1, UCP2 and UCP3 share a basic amino acid in positions 163, 164 and 167, while only UCP2 and UCP3 contain a second basic residue in positions 168 and 171, respectively. Accordingly, mutants of UCP3 in positions 167 and 171/172 were made. In permeabilized cells, these mutants exhibited distinct Ca2+ sensitivities in regard to mitochondrial Ca2+ sequestration. In intact cells, these mutants established different activities in mitochondrial uptake of either intracellularly released (UCP3R171,E172) or entering (UCP3R167) Ca2+. Our data demonstrate that distinct sites in the IML2 of UCP3 effect mitochondrial uptake of high and low Ca2+ signals.
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Szanda G, Halász E, Spät A. Protein kinases reduce mitochondrial Ca2+ uptake through an action on the outer mitochondrial membrane. Cell Calcium 2010; 48:168-75. [DOI: 10.1016/j.ceca.2010.08.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2010] [Revised: 08/10/2010] [Accepted: 08/12/2010] [Indexed: 12/30/2022]
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The contribution of UCP2 and UCP3 to mitochondrial Ca(2+) uptake is differentially determined by the source of supplied Ca(2+). Cell Calcium 2010; 47:433-40. [PMID: 20403634 DOI: 10.1016/j.ceca.2010.03.004] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2009] [Revised: 03/08/2010] [Accepted: 03/15/2010] [Indexed: 11/21/2022]
Abstract
The transmission of Ca(2+) signals to mitochondria is an important phenomenon in cell signaling. We have recently reported that the novel uncoupling proteins UCP2 and UCP3 (UCP2/3) are fundamental for mitochondrial Ca(2+) uniport (MCU). In the present study we investigate the contribution of UCP2/3 to mitochondrial accumulation of Ca(2+) either exclusively released from the ER or entering the cell via the store-operated Ca(2+) entry (SOCE) pathway. Using siRNA we demonstrate that constitutively expressed UCP2/3 are essentially involved in mitochondrial sequestration of intracellularly released Ca(2+) but not of that entering the cells via SOCE. However, overexpression of UCP2/3 yielded elevated mitochondrial Ca(2+) uptake from both sources, though it was more pronounced in case of entering Ca(2+), indicating that the expression levels of UCP2/3 are crucial for the capacity of mitochondria to sequester entering Ca(2+). Our data point to distinct UCP2/3-dependent and UCP2/3-independent modes of mitochondrial Ca(2+) sequestration, which may meet the various demands necessary for an adequate organelle Ca(2+) loading from different Ca(2+) sources in intact cells.
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Mitochondrial Ca2+ channels: Great unknowns with important functions. FEBS Lett 2010; 584:1942-7. [PMID: 20074570 DOI: 10.1016/j.febslet.2010.01.010] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2009] [Revised: 12/30/2009] [Accepted: 01/05/2010] [Indexed: 01/31/2023]
Abstract
Mitochondria process local and global Ca(2+) signals. Thereby the spatiotemporal patterns of mitochondrial Ca(2+) signals determine whether the metabolism of these organelles is adjusted or cell death is executed. Mitochondrial Ca(2+) channels of the inner mitochondrial membrane (IMM) actually implement mitochondrial uptake from cytosolic Ca(2+) rises. Despite great efforts in the past, the identity of mitochondrial Ca(2+) channels is still elusive. Numerous studies aimed to characterize mitochondrial Ca(2+) uniport channels and provided a detailed profile of these great unknowns with important functions. This mini-review revisits previous research on the mechanisms of mitochondrial Ca(2+) uptake and aligns them with most recent findings.
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Santo-Domingo J, Demaurex N. Calcium uptake mechanisms of mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:907-12. [PMID: 20079335 DOI: 10.1016/j.bbabio.2010.01.005] [Citation(s) in RCA: 227] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Revised: 01/06/2010] [Accepted: 01/08/2010] [Indexed: 12/16/2022]
Abstract
The ability of mitochondria to capture Ca2+ ions has important functional implications for cells, because mitochondria shape cellular Ca2+ signals by acting as a Ca2+ buffer and respond to Ca2+ elevations either by increasing the cell energy supply or by triggering the cell death program of apoptosis. A mitochondrial Ca2+ channel known as the uniporter drives the rapid and massive entry of Ca2+ ions into mitochondria. The uniporter operates at high, micromolar cytosolic Ca2+ concentrations that are only reached transiently in cells, near Ca2+ release channels. Mitochondria can also take up Ca2+ at low, nanomolar concentrations, but this high affinity mode of Ca2+ uptake is not well characterized. Recently, leucine-zipper-EF hand-containing transmembrane region (Letm1) was proposed to be an electrogenic 1:1 mitochondrial Ca2+/H+ antiporter that drives the uptake of Ca2+ into mitochondria at nanomolar cytosolic Ca2+ concentrations. In this article, we will review the properties of the Ca2+ import systems of mitochondria and discuss how Ca2+ uptake via an electrogenic 1:1 Ca2+/H+ antiport challenges our current thinking of the mitochondrial Ca2+ uptake mechanism.
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Affiliation(s)
- Jaime Santo-Domingo
- Department of Cell Physiology and Metabolism, University of Geneva, 1, rue Michel-Servet, CH-1211 Geneva 4, Switzerland
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16
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Koncz P, Szanda G, Fülöp L, Rajki A, Spät A. Mitochondrial Ca2+ uptake is inhibited by a concerted action of p38 MAPK and protein kinase D. Cell Calcium 2009; 46:122-9. [DOI: 10.1016/j.ceca.2009.06.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2009] [Revised: 06/05/2009] [Accepted: 06/20/2009] [Indexed: 10/20/2022]
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17
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Petersen OH, Tepikin AV, Gerasimenko JV, Gerasimenko OV, Sutton R, Criddle DN. Fatty acids, alcohol and fatty acid ethyl esters: toxic Ca2+ signal generation and pancreatitis. Cell Calcium 2009; 45:634-42. [PMID: 19327825 DOI: 10.1016/j.ceca.2009.02.005] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Revised: 02/17/2009] [Accepted: 02/19/2009] [Indexed: 01/11/2023]
Abstract
Pancreatitis, a potentially fatal disease in which the pancreas digests itself as well as its surroundings, is a well recognized complication of hyperlipidemia. Fatty acids have toxic effects on pancreatic acinar cells and these are mediated by large sustained elevations of the cytosolic Ca(2+) concentration. An important component of the effect of fatty acids is due to inhibition of mitochondrial function and subsequent ATP depletion, which reduces the operation of Ca(2+)-activated ATPases in both the endoplasmic reticulum and the plasma membrane. One of the main causes of pancreatitis is alcohol abuse. Whereas the effects of even high alcohol concentrations on isolated pancreatic acinar cells are variable and often small, fatty acid ethyl esters--synthesized by combination of alcohol and fatty acids--consistently evoke major Ca(2+) release from intracellular stores, subsequently opening Ca(2+) entry channels in the plasma membrane. The crucial trigger for pancreatic autodigestion is intracellular trypsin activation. Although there is still uncertainty about the exact molecular mechanism by which this Ca(2+)-dependent process occurs, progress has been made in identifying a subcellular compartment--namely acid post-exocytotic endocytic vacuoles--in which this activation takes place.
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Affiliation(s)
- O H Petersen
- MRC Secretory Control Research Group, Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Liverpool, UK.
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Walsh C, Barrow S, Voronina S, Chvanov M, Petersen OH, Tepikin A. Modulation of calcium signalling by mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2009; 1787:1374-82. [PMID: 19344663 DOI: 10.1016/j.bbabio.2009.01.007] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2008] [Revised: 01/12/2009] [Accepted: 01/13/2009] [Indexed: 02/07/2023]
Abstract
In this review we will attempt to summarise the complex and sometimes contradictory effects that mitochondria have on different forms of calcium signalling. Mitochondria can influence Ca(2+) signalling indirectly by changing the concentration of ATP, NAD(P)H, pyruvate and reactive oxygen species - which in turn modulate components of the Ca(2+) signalling machinery i.e. buffering, release from internal stores, influx from the extracellular solution, uptake into cellular organelles and extrusion by plasma membrane Ca(2+) pumps. Mitochondria can directly influence the calcium concentration in the cytosol of the cell by importing Ca(2+) via the mitochondrial Ca(2+) uniporter or transporting Ca(2+) from the interior of the organelle into the cytosol by means of Na+/Ca(2+) or H+/Ca(2+) exchangers. Considerable progress in understanding the relationship between Ca(2+) signalling cascades and mitochondrial physiology has been accumulated over the last few years due to the development of more advanced optical techniques and electrophysiological approaches.
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Affiliation(s)
- Ciara Walsh
- Department of Physiology, School of Biomedical Sciences, The University of Liverpool, Crown Street, Liverpool L69 3BX, UK
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