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Terrar DA. Timing mechanisms to control heart rhythm and initiate arrhythmias: roles for intracellular organelles, signalling pathways and subsarcolemmal Ca 2. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220170. [PMID: 37122228 PMCID: PMC10150226 DOI: 10.1098/rstb.2022.0170] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023] Open
Abstract
Rhythms of electrical activity in all regions of the heart can be influenced by a variety of intracellular membrane bound organelles. This is true both for normal pacemaker activity and for abnormal rhythms including those caused by early and delayed afterdepolarizations under pathological conditions. The influence of the sarcoplasmic reticulum (SR) on cardiac electrical activity is widely recognized, but other intracellular organelles including lysosomes and mitochondria also contribute. Intracellular organelles can provide a timing mechanism (such as an SR clock driven by cyclic uptake and release of Ca2+, with an important influence of intraluminal Ca2+), and/or can act as a Ca2+ store involved in signalling mechanisms. Ca2+ plays many diverse roles including carrying electric current, driving electrogenic sodium-calcium exchange (NCX) particularly when Ca2+ is extruded across the surface membrane causing depolarization, and activation of enzymes which target organelles and surface membrane proteins. Heart function is also influenced by Ca2+ mobilizing agents (cADP-ribose, nicotinic acid adenine dinucleotide phosphate and inositol trisphosphate) acting on intracellular organelles. Lysosomal Ca2+ release exerts its effects via calcium/calmodulin-dependent protein kinase II to promote SR Ca2+ uptake, and contributes to arrhythmias resulting from excessive beta-adrenoceptor stimulation. A separate arrhythmogenic mechanism involves lysosomes, mitochondria and SR. Interacting intracellular organelles, therefore, have profound effects on heart rhythms and NCX plays a central role. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Derek A Terrar
- Department of Pharmacology, University of Oxford, Oxford OX1 3QT, UK
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2
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Yokoi K, Yamaguchi K, Umezawa M, Tsuchiya K, Aoki S. Induction of Paraptosis by Cyclometalated Iridium Complex-Peptide Hybrids and CGP37157 via a Mitochondrial Ca 2+ Overload Triggered by Membrane Fusion between Mitochondria and the Endoplasmic Reticulum. Biochemistry 2022; 61:639-655. [PMID: 35363482 PMCID: PMC9022229 DOI: 10.1021/acs.biochem.2c00061] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
We previously reported that a cyclometalated iridium (Ir) complex-peptide hybrid (IPH) 4 functionalized with a cationic KKKGG peptide unit on the 2-phenylpyridine ligand induces paraptosis, a relatively newly found programmed cell death, in cancer cells (Jurkat cells) via the direct transport of calcium (Ca2+) from the endoplasmic reticulum (ER) to mitochondria. Here, we describe that CGP37157, an inhibitor of a mitochondrial sodium (Na+)/Ca2+ exchanger, induces paraptosis in Jurkat cells via intracellular pathways similar to those induced by 4. The findings allow us to suggest that the induction of paraptosis by 4 and CGP37157 is associated with membrane fusion between mitochondria and the ER, subsequent Ca2+ influx from the ER to mitochondria, and a decrease in the mitochondrial membrane potential (ΔΨm). On the contrary, celastrol, a naturally occurring triterpenoid that had been reported as a paraptosis inducer in cancer cells, negligibly induces mitochondria-ER membrane fusion. Consequently, we conclude that the paraptosis induced by 4 and CGP37157 (termed paraptosis II herein) proceeds via a signaling pathway different from that of the previously known paraptosis induced by celastrol, a process that negligibly involves membrane fusion between mitochondria and the ER (termed paraptosis I herein).
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Affiliation(s)
- Kenta Yokoi
- Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Kohei Yamaguchi
- Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Masakazu Umezawa
- Research Institute for Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Koji Tsuchiya
- Research Institute for Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
| | - Shin Aoki
- Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.,Research Institute for Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.,Research Institute for Biomedical Science (RIBS), Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
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3
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Cyclometalated Iridium(III) Complex-Cationic Peptide Hybrids Trigger Paraptosis in Cancer Cells via an Intracellular Ca 2+ Overload from the Endoplasmic Reticulum and a Decrease in Mitochondrial Membrane Potential. Molecules 2021; 26:molecules26227028. [PMID: 34834120 PMCID: PMC8623854 DOI: 10.3390/molecules26227028] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 11/15/2021] [Accepted: 11/16/2021] [Indexed: 02/05/2023] Open
Abstract
In our previous paper, we reported that amphiphilic Ir complex–peptide hybrids (IPHs) containing basic peptides such as KK(K)GG (K: lysine, G: glycine) (e.g., ASb-2) exhibited potent anticancer activity against Jurkat cells, with the dead cells showing a strong green emission. Our initial mechanistic studies of this cell death suggest that IPHs would bind to the calcium (Ca2+)–calmodulin (CaM) complex and induce an overload of intracellular Ca2+, resulting in the induction of non-apoptotic programmed cell death. In this work, we conduct a detailed mechanistic study of cell death induced by ASb-2, a typical example of IPHs, and describe how ASb-2 induces paraptotic programmed cell death in a manner similar to that of celastrol, a naturally occurring triterpenoid that is known to function as a paraptosis inducer in cancer cells. It is suggested that ASb-2 (50 µM) induces ER stress and decreases the mitochondrial membrane potential (ΔΨm), thus triggering intracellular signaling pathways and resulting in cytoplasmic vacuolization in Jurkat cells (which is a typical phenomenon of paraptosis), while the change in ΔΨm values is negligibly induced by celastrol and curcumin. Other experimental data imply that both ASb-2 and celastrol induce paraptotic cell death in Jurkat cells, but this induction occurs via different signaling pathways.
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4
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Yokoi K, Balachandran C, Umezawa M, Tsuchiya K, Mitrić A, Aoki S. Amphiphilic Cationic Triscyclometalated Iridium(III) Complex-Peptide Hybrids Induce Paraptosis-like Cell Death of Cancer Cells via an Intracellular Ca 2+-Dependent Pathway. ACS OMEGA 2020; 5:6983-7001. [PMID: 32258934 PMCID: PMC7114882 DOI: 10.1021/acsomega.0c00337] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Accepted: 02/27/2020] [Indexed: 06/11/2023]
Abstract
We report on the design and synthesis of a green-emitting iridium complex-peptide hybrid (IPH) 4, which has an electron-donating hydroxyacetic acid (glycolic acid) moiety between the Ir core and the peptide part. It was found that 4 is selectively cytotoxic against cancer cells, and the dead cells showed a green emission. Mechanistic studies of cell death indicate that 4 induces a paraptosis-like cell death through the increase in mitochondrial Ca2+ concentrations via direct Ca2+ transfer from ER to mitochondria, the loss of mitochondrial membrane potential (ΔΨm), and the vacuolization of cytoplasm and intracellular organelle. Although typical paraptosis and/or autophagy markers were upregulated by 4 through the mitogen-activated protein kinase (MAPK) signaling pathway, as confirmed by Western blot analysis, autophagy is not the main pathway in 4-induced cell death. The degradation of actin, which consists of a cytoskeleton, is also induced by high concentrations of Ca2+, as evidenced by costaining experiments using a specific probe. These results will be presented and discussed.
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Affiliation(s)
- Kenta Yokoi
- Faculty of Pharmaceutical
Sciences, Tokyo University of Science, 2641 Yamazaki,
Noda, Chiba 278-8510, Japan
| | - Chandrasekar Balachandran
- Faculty of Pharmaceutical
Sciences, Tokyo University of Science, 2641 Yamazaki,
Noda, Chiba 278-8510, Japan
| | - Masakazu Umezawa
- Research Institute for Science and Technology (RIST), Tokyo University of Science, 2641 Yamazaki,
Noda, Chiba 278-8510, Japan
| | - Koji Tsuchiya
- Research Institute for Science and Technology (RIST), Tokyo University of Science, 2641 Yamazaki,
Noda, Chiba 278-8510, Japan
| | - Aleksandra Mitrić
- Faculty of Pharmaceutical
Sciences, Tokyo University of Science, 2641 Yamazaki,
Noda, Chiba 278-8510, Japan
- Faculty of Technology and Metallurgy, University of Belgrade, 4 Karnegijeva Street, Belgrade 11000, Serbia
| | - Shin Aoki
- Faculty of Pharmaceutical
Sciences, Tokyo University of Science, 2641 Yamazaki,
Noda, Chiba 278-8510, Japan
- Research Institute for Science and Technology (RIST), Tokyo University of Science, 2641 Yamazaki,
Noda, Chiba 278-8510, Japan
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5
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Boyman L, Karbowski M, Lederer WJ. Regulation of Mitochondrial ATP Production: Ca 2+ Signaling and Quality Control. Trends Mol Med 2019; 26:21-39. [PMID: 31767352 DOI: 10.1016/j.molmed.2019.10.007] [Citation(s) in RCA: 131] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 10/16/2019] [Accepted: 10/23/2019] [Indexed: 02/06/2023]
Abstract
Cardiac ATP production primarily depends on oxidative phosphorylation in mitochondria and is dynamically regulated by Ca2+ levels in the mitochondrial matrix as well as by cytosolic ADP. We discuss mitochondrial Ca2+ signaling and its dysfunction which has recently been linked to cardiac pathologies including arrhythmia and heart failure. Similar dysfunction in other excitable and long-lived cells including neurons is associated with neurodegenerative diseases such as Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and Parkinson's disease (PD). Central to this new understanding is crucial Ca2+ regulation of both mitochondrial quality control and ATP production. Mitochondria-associated membrane (MAM) signaling from the sarcoplasmic reticulum (SR) and the endoplasmic reticulum (ER) to mitochondria is discussed. We propose future research directions that emphasize a need to define quantitatively the physiological roles of MAMs, as well as mitochondrial quality control and ATP production.
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Affiliation(s)
- Liron Boyman
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Mariusz Karbowski
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - W Jonathan Lederer
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Department of Physiology, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
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6
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Seidlmayer LK, Mages C, Berbner A, Eder-Negrin P, Arias-Loza PA, Kaspar M, Song M, Dorn GW, Kohlhaas M, Frantz S, Maack C, Gerull B, Dedkova EN. Mitofusin 2 Is Essential for IP 3-Mediated SR/Mitochondria Metabolic Feedback in Ventricular Myocytes. Front Physiol 2019; 10:733. [PMID: 31379586 PMCID: PMC6658196 DOI: 10.3389/fphys.2019.00733] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2018] [Accepted: 05/27/2019] [Indexed: 12/19/2022] Open
Abstract
Aim: Endothelin-1 (ET-1) and angiotensin II (Ang II) are multifunctional peptide hormones that regulate the function of the cardiovascular and renal systems. Both hormones increase the intracellular production of inositol-1,4,5-trisphosphate (IP3) by activating their membrane-bound receptors. We have previously demonstrated that IP3-mediated sarcoplasmic reticulum (SR) Ca2+ release results in mitochondrial Ca2+ uptake and activation of ATP production. In this study, we tested the hypothesis that intact SR/mitochondria microdomains are required for metabolic IP3-mediated SR/mitochondrial feedback in ventricular myocytes. Methods: As a model for disrupted mitochondrial/SR microdomains, cardio-specific tamoxifen-inducible mitofusin 2 (Mfn2) knock out (KO) mice were used. Mitochondrial Ca2+ uptake, membrane potential, redox state, and ATP generation were monitored in freshly isolated ventricular myocytes from Mfn2 KO mice and their control wild-type (WT) littermates. Results: Stimulation of ET-1 receptors in healthy control myocytes increases mitochondrial Ca2+ uptake, maintains mitochondrial membrane potential and redox balance leading to the enhanced ATP generation. Mitochondrial Ca2+ uptake upon ET-1 stimulation was significantly higher in interfibrillar (IFM) and perinuclear (PNM) mitochondria compared to subsarcolemmal mitochondria (SSM) in WT myocytes. Mfn2 KO completely abolished mitochondrial Ca2+ uptake in IFM and PNM mitochondria but not in SSM. However, mitochondrial Ca2+ uptake induced by beta-adrenergic receptors activation with isoproterenol (ISO) was highest in SSM, intermediate in IFM, and smallest in PNM regions. Furthermore, Mfn2 KO did not affect ISO-induced mitochondrial Ca2+ uptake in SSM and IFM mitochondria; however, enhanced mitochondrial Ca2+ uptake in PNM. In contrast to ET-1, ISO induced a decrease in ATP levels in WT myocytes. Mfn2 KO abolished ATP generation upon ET-1 stimulation but increased ATP levels upon ISO application with highest levels observed in PNM regions. Conclusion: When the physical link between SR and mitochondria by Mfn2 was disrupted, the SR/mitochondrial metabolic feedback mechanism was impaired resulting in the inability of the IP3-mediated SR Ca2+ release to induce ATP production in ventricular myocytes from Mfn2 KO mice. Furthermore, we revealed the difference in Mfn2-mediated SR-mitochondrial communication depending on mitochondrial location and type of communication (IP3R-mRyR1 vs. ryanodine receptor type 2-mitochondrial calcium uniporter).
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Affiliation(s)
- Lea K Seidlmayer
- Department of Internal Medicine, Cardiology, University Hospital Würzburg, Würzburg, Germany.,Comprehensive Heart Failure Center, University of Würzburg, Würzburg, Germany
| | - Christine Mages
- Department of Internal Medicine, Cardiology, University Hospital Würzburg, Würzburg, Germany.,Comprehensive Heart Failure Center, University of Würzburg, Würzburg, Germany
| | - Annette Berbner
- Comprehensive Heart Failure Center, University of Würzburg, Würzburg, Germany
| | - Petra Eder-Negrin
- Comprehensive Heart Failure Center, University of Würzburg, Würzburg, Germany
| | | | - Mathias Kaspar
- Comprehensive Heart Failure Center, University of Würzburg, Würzburg, Germany
| | - Moshi Song
- Department of Internal Medicine, Center for Pharmacogenomics, Washington University School of Medicine, St. Louis, MO, United States
| | - Gerald W Dorn
- Department of Internal Medicine, Center for Pharmacogenomics, Washington University School of Medicine, St. Louis, MO, United States
| | - Michael Kohlhaas
- Comprehensive Heart Failure Center, University of Würzburg, Würzburg, Germany
| | - Stefan Frantz
- Department of Internal Medicine, Cardiology, University Hospital Würzburg, Würzburg, Germany.,Comprehensive Heart Failure Center, University of Würzburg, Würzburg, Germany
| | - Christoph Maack
- Comprehensive Heart Failure Center, University of Würzburg, Würzburg, Germany
| | - Brenda Gerull
- Comprehensive Heart Failure Center, University of Würzburg, Würzburg, Germany
| | - Elena N Dedkova
- Department of Pharmacology, School of Medicine, University of California, Davis, Davis, CA, United States.,Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, CA, United States
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7
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Bioenergetic Feedback between Heart Cell Contractile Machinery and Mitochondrial 3D Deformations. Biophys J 2018; 115:1603-1613. [PMID: 30274832 DOI: 10.1016/j.bpj.2018.08.039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 08/12/2018] [Accepted: 08/29/2018] [Indexed: 12/21/2022] Open
Abstract
In the heart, mitochondria are arranged in pairs sandwiched between the contractile machinery, which is the major ATP consumer. Thus, in response to the contraction-relaxation cycle of the cell, the mitochondrial membrane should deform accordingly. Membrane deformations in isolated ATP synthesis or in isolated mitochondria affect ATP production. However, it is unknown whether physiological deformation of the mitochondrial membrane in response to the contraction-relaxation cycle can act as a bioenergetic signaling mechanism between ATP demand to supply. We used both experimental and computational tools to reveal whether bioenergetic feedback exists between heart cell contractile machinery and mitochondrial three-dimensional (3D) deformations. We measured the mitochondrial 3D deformation in contracting rabbit cardiac myocytes and used published data on rat cardiac myocytes. These measurements were an input to a novel biophysics model that includes a description of ionic molecules on the mitochondrial membrane, Ca2+ cycling, and mitochondrial membrane stress. As is the case for rat cardiomyocytes, in rabbit cardiomyocytes, the mitochondrial length contracted and expanded with a similar dynamic as the sarcomere length. In contrast, the mitochondrial width expanded and then contracted with a similar dynamic as the mitochondrial length. Differences in the extent of deformation and fractional deformation between the width- and thick-axes were quantified and interpreted as the degree anisotropy between those respective axes. Finally, the model predicts that significant bioenergetic feedback between heart cell contractile machinery and mitochondrial 3D deformations does exist in unloaded rabbit and rat cells. However, this feedback is not a dominant mechanism in ATP supply to demand matching.
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8
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Smolina N, Bruton J, Sjoberg G, Kostareva A, Sejersen T. Aggregate-prone desmin mutations impair mitochondrial calcium uptake in primary myotubes. Cell Calcium 2014; 56:269-75. [PMID: 25171807 DOI: 10.1016/j.ceca.2014.08.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 07/10/2014] [Accepted: 08/01/2014] [Indexed: 01/25/2023]
Abstract
Desmin, being a major intermediate filament of mature muscle cell, interacts with mitochondria within the cell and participates in mitochondria proper localization. The goal of the present study was to assess the effect of aggregate-prone and non-aggregate-prone desmin mutations on mitochondrial calcium uptake. Primary murine satellite cells were transduced with lentiviruses carrying desmin in wild type or mutant form, and were induced to differentiate into myotubes. Four mutations resulting in different degree of desmin aggregates formation were analyzed. Tail domain mutation Asp399Tyr has the mildest impact on desmin filament polymerization, rod domain mutation Ala357Pro causes formation of large aggregates composed of filamentous material, and Leu345Pro and Leu370Pro are considered to be the most severest in their impact on desmin polymerization and structure. For mitochondrial calcium measurement cells were loaded with rhod 2-AM. We found that aggregate-prone mutations significantly decreased [Ca(2+)]mit, whereas non-aggregate-prone mutations did not decrease [Ca(2+)]mit. Moreover aggregate-prone desmin mutations resulted in increased resting cytosolic [Ca(2+)]. However this increase was not accompanied by any alterations in sarcoplasmic reticulum calcium release. We suggest that the observed decline in [Ca(2+)]mit was due to desmin aggregate accumulation resulting in the loss of desmin mitochondria interactions.
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Affiliation(s)
- Natalia Smolina
- Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden; Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden; Federal Almazov Medical Research Centre, St-Petersburg, Russia.
| | - Joseph Bruton
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - Gunnar Sjoberg
- Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden; Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Anna Kostareva
- Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden; Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden; Federal Almazov Medical Research Centre, St-Petersburg, Russia
| | - Thomas Sejersen
- Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden; Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
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9
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Villanueva J, Viniegra S, Gimenez-Molina Y, García-Martinez V, Expósito-Romero G, del Mar Frances M, García-Sancho J, Gutiérrez LM. The distribution of mitochondria and endoplasmic reticulum in relation with secretory sites in chromaffin cells. J Cell Sci 2014; 127:5105-14. [DOI: 10.1242/jcs.160242] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The distribution of mitochondria and ER in relation to exocytotic sites is relevant to understand the influence of these organelles in tuning calcium signals and secretion. Confocal images of probes tagged to mitochondria and F-actin cytoskeleton revealed the existence of two populations of mitochondria, one cortical and the other perinuclear. This mitochondrial distribution was also confirmed by using electron microscopy. In contrast, ER was sparse in the cortex and more abundant in deep cytoplasmic regions. The mitochondrial distribution may be due to organellar transport, which experiences increasing restrictions in the cell cortex. Further study of organelle distribution in relation to SNARE microdomains or the granule fusion sites revealed that 1/3 of the cortical mitochondria co-localized with exocytotic sites whereas another 1/3 located at a distance smaller than 2 vesicle diameters. ER structures were also present in the vicinity of secretory sites but at a lower density. Therefore, mitochondria and ER have a spatial distribution that suggests a specialized role in modulation of exocytosis and fits with cytosolic Ca2+ microdomains described before.
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10
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Scorzeto M, Giacomello M, Toniolo L, Canato M, Blaauw B, Paolini C, Protasi F, Reggiani C, Stienen GJM. Mitochondrial Ca2+-handling in fast skeletal muscle fibers from wild type and calsequestrin-null mice. PLoS One 2013; 8:e74919. [PMID: 24098358 PMCID: PMC3789688 DOI: 10.1371/journal.pone.0074919] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 08/07/2013] [Indexed: 11/19/2022] Open
Abstract
Mitochondrial calcium handling and its relation with calcium released from sarcoplasmic reticulum (SR) in muscle tissue are subject of lively debate. In this study we aimed to clarify how the SR determines mitochondrial calcium handling using dCASQ-null mice which lack both isoforms of the major Ca2+-binding protein inside SR, calsequestrin. Mitochondrial free Ca2+-concentration ([Ca2+]mito) was determined by means of a genetically targeted ratiometric FRET-based probe. Electron microscopy revealed a highly significant increase in intermyofibrillar mitochondria (+55%) and augmented coupling (+12%) between Ca2+ release units of the SR and mitochondria in dCASQ-null vs. WT fibers. Significant differences in the baseline [Ca2+]mito were observed between quiescent WT and dCASQ-null fibers, but not in the resting cytosolic Ca2+ concentration. The rise in [Ca2+]mito during electrical stimulation occurred in 20−30 ms, while the decline during and after stimulation was governed by 4 rate constants of approximately 40, 1.6, 0.2 and 0.03 s−1. Accordingly, frequency-dependent increase in [Ca2+]mito occurred during sustained contractions. In dCASQ-null fibers the increases in [Ca2+]mito were less pronounced than in WT fibers and even lower when extracellular calcium was removed. The amplitude and duration of [Ca2+]mito transients were increased by inhibition of mitochondrial Na+/Ca2+ exchanger (mNCX). These results provide direct evidence for fast Ca2+ accumulation inside the mitochondria, involvement of the mNCX in mitochondrial Ca2+-handling and a dependence of mitochondrial Ca2+-handling on intracellular (SR) and external Ca2+ stores in fast skeletal muscle fibers. dCASQ-null mice represent a model for malignant hyperthermia. The differences in structure and in mitochondrial function observed relative to WT may represent compensatory mechanisms for the disease-related reduction of calcium storage capacity of the SR and/or SR Ca2+-leakage.
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Affiliation(s)
- Michele Scorzeto
- Department of Biomedical Sciences and Interuniversity Institute of Myology (IIM), University of Padova, Padua, Italy
| | | | - Luana Toniolo
- Department of Biomedical Sciences and Interuniversity Institute of Myology (IIM), University of Padova, Padua, Italy
| | - Marta Canato
- Department of Biomedical Sciences and Interuniversity Institute of Myology (IIM), University of Padova, Padua, Italy
| | - Bert Blaauw
- Department of Biomedical Sciences and Interuniversity Institute of Myology (IIM), University of Padova, Padua, Italy
- Venetian Institute of Molecular Medicine, Padua, Italy
| | - Cecilia Paolini
- Department of Neuroscience and Imaging (DNI) and Center for Research on Ageing (CeSI), and Interuniversity Institute of Myology (IIM), University G. d' Annunzio, Chieti, Italy
| | - Feliciano Protasi
- Department of Neuroscience and Imaging (DNI) and Center for Research on Ageing (CeSI), and Interuniversity Institute of Myology (IIM), University G. d' Annunzio, Chieti, Italy
| | - Carlo Reggiani
- Department of Biomedical Sciences and Interuniversity Institute of Myology (IIM), University of Padova, Padua, Italy
| | - Ger J. M. Stienen
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands
- Department of Physics and Astronomy, VU University Amsterdam, Amsterdam, The Netherlands
- * E-mail:
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11
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Myocardial energetics in heart failure. Basic Res Cardiol 2013; 108:358. [PMID: 23740216 DOI: 10.1007/s00395-013-0358-9] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/24/2013] [Accepted: 05/09/2013] [Indexed: 12/12/2022]
Abstract
It has become common sense that the failing heart is an "engine out of fuel". However, undisputable evidence that, indeed, the failing heart is limited by insufficient ATP supply is currently lacking. Over the last couple of years, an increasingly complex picture of mechanisms evolved that suggests that potentially metabolic intermediates and redox state could play the more dominant roles for signaling that eventually results in left ventricular remodeling and contractile dysfunction. In the pathophysiology of heart failure, mitochondria emerge in the crossfire of defective excitation-contraction coupling and increased energetic demand, which may provoke oxidative stress as an important upstream mediator of cardiac remodeling and cell death. Thus, future therapies may be guided towards restoring defective ion homeostasis and mitochondrial redox shifts rather than aiming solely at improving the generation of ATP.
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12
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Boyman L, Williams GSB, Khananshvili D, Sekler I, Lederer WJ. NCLX: the mitochondrial sodium calcium exchanger. J Mol Cell Cardiol 2013; 59:205-13. [PMID: 23538132 PMCID: PMC3951392 DOI: 10.1016/j.yjmcc.2013.03.012] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Accepted: 03/15/2013] [Indexed: 11/18/2022]
Abstract
The free Ca(2+) concentration within the mitochondrial matrix ([Ca(2+)]m) regulates the rate of ATP production and other [Ca(2+)]m sensitive processes. It is set by the balance between total Ca(2+) influx (through the mitochondrial Ca(2+) uniporter (MCU) and any other influx pathways) and the total Ca(2+) efflux (by the mitochondrial Na(+)/Ca(2+) exchanger and any other efflux pathways). Here we review and analyze the experimental evidence reported over the past 40years which suggest that in the heart and many other mammalian tissues a putative Na(+)/Ca(2+) exchanger is the major pathway for Ca(2+) efflux from the mitochondrial matrix. We discuss those reports with respect to a recent discovery that the protein product of the human FLJ22233 gene mediates such Na(+)/Ca(2+) exchange across the mitochondrial inner membrane. Among its many functional similarities to other Na(+)/Ca(2+) exchanger proteins is a unique feature: it efficiently mediates Li(+)/Ca(2+) exchange (as well as Na(+)/Ca(2+) exchange) and was therefore named NCLX. The discovery of NCLX provides both the identity of a novel protein and new molecular means of studying various unresolved quantitative aspects of mitochondrial Ca(2+) movement out of the matrix. Quantitative and qualitative features of NCLX are discussed as is the controversy regarding the stoichiometry of the NCLX Na(+)/Ca(2+) exchange, the electrogenicity of NCLX, the [Na(+)]i dependency of NCLX and the magnitude of NCLX Ca(2+) efflux. Metabolic features attributable to NCLX and the physiological implication of the Ca(2+) efflux rate via NCLX during systole and diastole are also briefly discussed.
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Affiliation(s)
- Liron Boyman
- Center for Biomedical Engineering and Technology and Dept. Physiology, University of Maryland School of Medicine, Baltimore, MD 21201
| | - George S. B. Williams
- Center for Biomedical Engineering and Technology and Dept. Physiology, University of Maryland School of Medicine, Baltimore, MD 21201
- School of Systems Biology, College of Science, George Mason University, Manassas, VA 20110
| | - Daniel Khananshvili
- Sackler School of Medicine, Department of Physiology and Pharmacology, Tel-Aviv University, Ramat-Aviv 69978, Israel
| | - Israel Sekler
- Goldman Medical School, Dept. Biology & Neurobiology, Ben Gurion University of the Negev, P.O.B. 653, Beer-Sheva 84105, Israel
| | - W. J. Lederer
- Center for Biomedical Engineering and Technology and Dept. Physiology, University of Maryland School of Medicine, Baltimore, MD 21201
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13
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Bay J, Kohlhaas M, Maack C. Intracellular Na⁺ and cardiac metabolism. J Mol Cell Cardiol 2013; 61:20-7. [PMID: 23727097 DOI: 10.1016/j.yjmcc.2013.05.010] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Revised: 05/08/2013] [Accepted: 05/20/2013] [Indexed: 12/13/2022]
Abstract
In heart failure, alterations of excitation-contraction underlie contractile dysfunction. One important defect is an elevation of the intracellular Na(+) concentration in cardiac myocytes ([Na(+)]i), which has an important impact on cytosolic and mitochondrial Ca(2+) homeostasis. While elevated [Na(+)]i is thought to compensate for decreased Ca(2+) load of the sarcoplasmic reticulum (SR), it yet negatively affects energy supply-and-demand matching and can even induce mitochondrial oxidative stress. Here, we review the mechanisms underlying these pathophysiological changes. The chain of events may constitute a vicious cycle of ion dysregulation, oxidative stress and energetic deficit, resembling characteristic cellular deficits that are considered key hallmarks of the failing heart. This article is part of a Special Issue entitled "Na(+) Regulation in Cardiac Myocytes".
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Affiliation(s)
- Johannes Bay
- Klinik für Innere Medizin III, Universitätsklinikum des Saarlandes, Homburg, Germany
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14
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Mannella CA, Lederer WJ, Jafri MS. The connection between inner membrane topology and mitochondrial function. J Mol Cell Cardiol 2013; 62:51-7. [PMID: 23672826 DOI: 10.1016/j.yjmcc.2013.05.001] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 03/27/2013] [Accepted: 05/03/2013] [Indexed: 12/23/2022]
Abstract
The mitochondrial inner membrane has a complex and dynamic structure that plays an important role in the function of this organelle. The internal compartments called cristae are created by processes that are just beginning to be understood. Crista size and morphology influence the internal diffusion of solutes and the surface area of the inner membrane, which is home to critical membrane proteins including ATP synthase and electron transport chain complexes; metabolite and ion transporters including the adenine nucleotide translocase, the calcium uniporter (MCU), and the sodium/calcium exchanger (NCLX); and many more. Here we provide a brief overview of what is known about crista structure and formation, and discuss mitochondrial function in the context of that structure. We also suggest that mathematical modeling of mitochondria that incorporates accurate information about the organelle's internal architecture can lead to a better understanding of its diverse functions. This article is part of a Special Issue entitled 'Calcium Signalling in Heart'.
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Affiliation(s)
- Carmen A Mannella
- Wadsworth Center, New York State Department of Health, Empire State Plaza, Box 509, Albany, NY 12201-0509, USA.
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15
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16
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Kohl T, Westphal V, Hell SW, Lehnart SE. Superresolution microscopy in heart - cardiac nanoscopy. J Mol Cell Cardiol 2012; 58:13-21. [PMID: 23219451 DOI: 10.1016/j.yjmcc.2012.11.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 11/03/2012] [Accepted: 11/24/2012] [Indexed: 12/23/2022]
Abstract
Detailed understanding of the adaptive nature of cardiac cells in health and disease requires investigation of proteins and membranes in their native physiological environment, ideally by noninvasive optical methods. However, conventional light microscopy does not resolve the spatial characteristics of small fluorescently labeled protein or membrane structures in cells. Due to diffraction limiting resolution to half the wavelength of light, adjacent fluorescent molecules spaced at less than ~250 nm are not separately visualized. This fundamental problem has lead to a rapidly growing area of research, superresolution fluorescence microscopy, also called nanoscopy. We discuss pioneering applications of superresolution microscopy relevant to the heart, emphasizing different nanoscopy strategies toward new insight in cardiac cell biology. Here, we focus on molecular and structural readouts from subcellular nanodomains and organelles related to Ca(2+) signaling during excitation-contraction (EC) coupling, including live cell imaging strategies. Based on existing data and superresolution techniques, we suggest that an important future aim will be subcellular in situ structure-function analysis with nanometric resolving power in organotypic cells.
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Affiliation(s)
- Tobias Kohl
- Heart Research Center Goettingen, University Medicine Goettingen, Germany
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17
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Bazil JN, Blomeyer CA, Pradhan RK, Camara AKS, Dash RK. Modeling the calcium sequestration system in isolated guinea pig cardiac mitochondria. J Bioenerg Biomembr 2012. [PMID: 23180139 DOI: 10.1007/s10863-012-9488-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Under high Ca(2+) load conditions, Ca(2+) concentrations in the extra-mitochondrial and mitochondrial compartments do not display reciprocal dynamics. This is due to a paradoxical increase in the mitochondrial Ca(2+) buffering power as the Ca(2+) load increases. Here we develop and characterize a mechanism of the mitochondrial Ca(2+) sequestration system using an experimental data set from isolated guinea pig cardiac mitochondria. The proposed mechanism elucidates this phenomenon and others in a mathematical framework and is integrated into a previously corroborated model of oxidative phosphorylation including the Na(+)/Ca(2+) cycle. The integrated model reproduces the Ca(2+) dynamics observed in both compartments of the isolated mitochondria respiring on pyruvate after a bolus of CaCl2 followed by ruthenium red and a bolus of NaCl. The model reveals why changes in mitochondrial Ca(2+) concentration of Ca(2+) loaded mitochondria appear significantly mitigated relative to the corresponding extra-mitochondrial Ca(2+) concentration changes after Ca(2+) efflux is initiated. The integrated model was corroborated by simulating the set-point phenomenon. The computational results support the conclusion that the Ca(2+) sequestration system is composed of at least two classes of Ca(2+) buffers. The first class represents prototypical Ca(2+) buffering, and the second class encompasses the complex binding events associated with the formation of amorphous calcium phosphate. With the Ca(2+) sequestration system in mitochondria more precisely defined, computer simulations can aid in the development of innovative therapeutics aimed at addressing the myriad of complications that arise due to mitochondrial Ca(2+) overload.
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Affiliation(s)
- Jason N Bazil
- Biotechnology and Bioengineering Center and Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA
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18
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Lee YS, Liu OZ, Sobie EA. Decoding myocardial Ca²⁺ signals across multiple spatial scales: a role for sensitivity analysis. J Mol Cell Cardiol 2012; 58:92-9. [PMID: 23026728 DOI: 10.1016/j.yjmcc.2012.09.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 09/20/2012] [Indexed: 11/28/2022]
Abstract
Numerous studies have employed mathematical modeling to quantitatively understand release of Ca(2+) from the sarcoplasmic reticulum (SR) in the heart. Models have been used to investigate physiologically important phenomena such as triggering of SR Ca(2+) release by Ca(2+) entry across the cell membrane and spontaneous leak of Ca(2+) from the SR in quiescent heart cells. In this review we summarize studies that have modeled myocardial Ca(2+) at different spatial scales: the sub-cellular level, the cellular level, and the multicellular level. We discuss each category of models from the standpoint of parameter sensitivity analysis, a common simulation procedure that can generate quantitative, comprehensive predictions about how changes in conditions influence model output. We propose that this is a useful perspective for conceptualizing models, in part because a sensitivity analysis requires the investigator to define the relevant parameters and model outputs. This procedure therefore helps to illustrate the capabilities and limitations of each model. We further suggest that in future studies, sensitivity analyses will aid in simplifying complex models and in suggesting experiments to differentiate between competing models built with different assumptions. We conclude with a discussion of unresolved questions that are likely to be addressed over the next several years.
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Affiliation(s)
- Young-Seon Lee
- Pharmacology and Systems Therapeutics, Mount Sinai School of Medicine, New York, NY, USA
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19
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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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20
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Chen Y, Csordás G, Jowdy C, Schneider TG, Csordás N, Wang W, Liu Y, Kohlhaas M, Meiser M, Bergem S, Nerbonne JM, Dorn GW, Maack C. Mitofusin 2-containing mitochondrial-reticular microdomains direct rapid cardiomyocyte bioenergetic responses via interorganelle Ca(2+) crosstalk. Circ Res 2012; 111:863-75. [PMID: 22777004 DOI: 10.1161/circresaha.112.266585] [Citation(s) in RCA: 271] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
RATIONALE Mitochondrial Ca(2+) uptake is essential for the bioenergetic feedback response through stimulation of Krebs cycle dehydrogenases. Close association of mitochondria to the sarcoplasmic reticulum (SR) may explain efficient mitochondrial Ca(2+) uptake despite low Ca(2+) affinity of the mitochondrial Ca(2+) uniporter. However, the existence of such mitochondrial Ca(2+) microdomains and their functional role are presently unresolved. Mitofusin (Mfn) 1 and 2 mediate mitochondrial outer membrane fusion, whereas Mfn2 but not Mfn1 tethers endoplasmic reticulum to mitochondria in noncardiac cells. OBJECTIVE To elucidate roles for Mfn1 and 2 in SR-mitochondrial tethering, Ca(2+) signaling, and bioenergetic regulation in cardiac myocytes. METHODS AND RESULTS Fruit fly heart tubes deficient of the Drosophila Mfn ortholog MARF had increased contraction-associated and caffeine-sensitive Ca(2+) release, suggesting a role for Mfn in SR Ca(2+) handling. Whereas cardiac-specific Mfn1 ablation had no effects on murine heart function or Ca(2+) cycling, Mfn2 deficiency decreased cardiomyocyte SR-mitochondrial contact length by 30% and reduced the content of SR-associated proteins in mitochondria-associated membranes. This was associated with decreased mitochondrial Ca(2+) uptake (despite unchanged mitochondrial membrane potential) but increased steady-state and caffeine-induced SR Ca(2+) release. Accordingly, Ca(2+)-induced stimulation of Krebs cycle dehydrogenases during β-adrenergic stimulation was hampered in Mfn2-KO but not Mfn1-KO myocytes, evidenced by oxidation of the redox states of NAD(P)H/NAD(P)(+) and FADH(2)/FAD. CONCLUSIONS Physical tethering of SR and mitochondria via Mfn2 is essential for normal interorganelle Ca(2+) signaling in the myocardium, consistent with a requirement for SR-mitochondrial Ca(2+) signaling through microdomains in the cardiomyocyte bioenergetic feedback response to physiological stress.
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Affiliation(s)
- Yun Chen
- Center for Pharmacogenomics, Department of Internal Medicine, Washington University School of Medicine, St Louis, MO 63110, USA
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21
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Yaniv Y, Spurgeon HA, Lyashkov AE, Yang D, Ziman BD, Maltsev VA, Lakatta EG. Crosstalk between mitochondrial and sarcoplasmic reticulum Ca2+ cycling modulates cardiac pacemaker cell automaticity. PLoS One 2012; 7:e37582. [PMID: 22666369 PMCID: PMC3362629 DOI: 10.1371/journal.pone.0037582] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 04/22/2012] [Indexed: 01/02/2023] Open
Abstract
Background Mitochondria dynamically buffer cytosolic Ca2+ in cardiac ventricular cells and this affects the Ca2+ load of the sarcoplasmic reticulum (SR). In sinoatrial-node cells (SANC) the SR generates periodic local, subsarcolemmal Ca2+ releases (LCRs) that depend upon the SR load and are involved in SANC automaticity: LCRs activate an inward Na+-Ca2+ exchange current to accelerate the diastolic depolarization, prompting the ensemble of surface membrane ion channels to generate the next action potential (AP). Objective To determine if mitochondrial Ca2+ (Ca2+m), cytosolic Ca2+ (Ca2+c)-SR-Ca2+ crosstalk occurs in single rabbit SANC, and how this may relate to SANC normal automaticity. Results Inhibition of mitochondrial Ca2+ influx into (Ru360) or Ca2+ efflux from (CGP-37157) decreased [Ca2+]m to 80±8% control or increased [Ca2+]m to 119±7% control, respectively. Concurrent with inhibition of mitochondrial Ca2+ influx or efflux, the SR Ca2+ load, and LCR size, duration, amplitude and period (imaged via confocal linescan) significantly increased or decreased, respectively. Changes in total ensemble LCR Ca2+ signal were highly correlated with the change in the SR Ca2+ load (r2 = 0.97). Changes in the spontaneous AP cycle length (Ru360, 111±1% control; CGP-37157, 89±2% control) in response to changes in [Ca2+]m were predicted by concurrent changes in LCR period (r2 = 0.84). Conclusion A change in SANC Ca2+m flux translates into a change in the AP firing rate by effecting changes in Ca2+c and SR Ca2+ loading, which affects the characteristics of spontaneous SR Ca2+ release.
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Affiliation(s)
- Yael Yaniv
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Harold A. Spurgeon
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Alexey E. Lyashkov
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Dongmei Yang
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Bruce D. Ziman
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Victor A. Maltsev
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
| | - Edward G. Lakatta
- Laboratory of Cardiovascular Science, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America
- * E-mail:
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