201
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5-HTR3 and 5-HTR4 located on the mitochondrial membrane and functionally regulated mitochondrial functions. Sci Rep 2016; 6:37336. [PMID: 27874067 PMCID: PMC5118798 DOI: 10.1038/srep37336] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 10/25/2016] [Indexed: 11/29/2022] Open
Abstract
5-HT has been reported to possess significant effects on cardiac activities, but activation of 5-HTR on the cell membrane failed to illustrate the controversial cardiac reaction. Because 5-HT constantly comes across the cell membrane via 5-HT transporter (5-HTT) into the cytoplasm, whether 5-HTR is functional present on the cellular organelles is unknown. Here we show 5-HTR3 and 5-HTR4 were located in cardiac mitochondria, and regulated mitochondrial activities and cellular functions. Knock down 5-HTR3 and 5-HTR4 in neonatal cardiomyocytes resulted in significant increase of cell damage in response to hypoxia, and also led to alternation in heart beating. Activation of 5-HTR4 attenuated mitochondrial Ca2+ uptake under the both normoxic and hypoxic conditions, whereas 5-HTR3 augmented Ca2+ uptake only under hypoxia. 5-HTR3 and 5-HTR4 exerted the opposite effects on the mitochondrial respiration: 5-HTR3 increased RCR (respiration control ratio), but 5-HTR4 reduced RCR. Moreover, activation of 5-HTR3 and 5-HTR4 both significantly inhibited the opening of mPTP. Our results provided the first evidence that 5-HTR as a GPCR and an ion channel, functionally expressed in mitochondria and participated in the mitochondria function and regulation to maintain homeostasis of mitochondrial [Ca2+], ROS, and ATP generation efficiency in cardiomyocytes in response to stress and O2 tension.
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202
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Prantner D, Perkins DJ, Vogel SN. AMP-activated Kinase (AMPK) Promotes Innate Immunity and Antiviral Defense through Modulation of Stimulator of Interferon Genes (STING) Signaling. J Biol Chem 2016; 292:292-304. [PMID: 27879319 DOI: 10.1074/jbc.m116.763268] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 11/15/2016] [Indexed: 11/06/2022] Open
Abstract
The host protein Stimulator of Interferon Genes (STING) has been shown to be essential for recognition of both viral and intracellular bacterial pathogens, but its regulation remains unclear. Previously, we reported that mitochondrial membrane potential regulates STING-dependent IFN-β induction independently of ATP synthesis. Because mitochondrial membrane potential controls calcium homeostasis, and AMP-activated protein kinase (AMPK) is regulated, in part, by intracellular calcium, we postulated that AMPK participates in STING activation; however, its role has yet to be been defined. Addition of an intracellular calcium chelator or an AMPK inhibitor to either mouse macrophages or mouse embryonic fibroblasts (MEFs) suppressed IFN-β and TNF-α induction following stimulation with the STING-dependent ligand 5,6-dimethyl xanthnone-4-acetic acid (DMXAA). These pharmacological findings were corroborated by showing that MEFs lacking AMPK activity also failed to up-regulate IFN-β and TNF-α after treatment with DMXAA or the natural STING ligand cyclic GMP-AMP (cGAMP). As a result, AMPK-deficient MEFs exhibit impaired control of vesicular stomatitis virus (VSV), a virus sensed by STING that can cause an influenza-like illness in humans. This impairment could be overcome by pretreatment of AMPK-deficient MEFs with type I IFN, illustrating that de novo production of IFN-β in response to VSV plays a key role in antiviral defense during infection. Loss of AMPK also led to dephosphorylation at Ser-555 of the known STING regulator, UNC-51-like kinase 1 (ULK1). However, ULK1-deficient cells responded normally to DMXAA, indicating that AMPK promotes STING-dependent signaling independent of ULK1 in mouse cells.
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Affiliation(s)
- Daniel Prantner
- From the Department of Microbiology and Immunology, University of Maryland, School of Medicine, Baltimore, Maryland 21201
| | - Darren J Perkins
- From the Department of Microbiology and Immunology, University of Maryland, School of Medicine, Baltimore, Maryland 21201
| | - Stefanie N Vogel
- From the Department of Microbiology and Immunology, University of Maryland, School of Medicine, Baltimore, Maryland 21201
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203
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Lucas AM, Caldas FR, da Silva AP, Ventura MM, Leite IM, Filgueiras AB, Silva CGL, Kowaltowski AJ, Facundo HT. Diazoxide prevents reactive oxygen species and mitochondrial damage, leading to anti-hypertrophic effects. Chem Biol Interact 2016; 261:50-55. [PMID: 27867086 DOI: 10.1016/j.cbi.2016.11.012] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Revised: 10/25/2016] [Accepted: 11/16/2016] [Indexed: 11/30/2022]
Abstract
Pathological cardiac hypertrophy is characterized by wall thickening or chamber enlargement of the heart in response to pressure or volume overload, respectively. This condition will, initially, improve the organ contractile function, but if sustained will render dysfunctional mitochondria and oxidative stress. Mitochondrial ATP-sensitive K+ channels (mitoKATP) modulate the redox status of the cell and protect against several cardiac insults. Here, we tested the hypothesis that mitoKATP opening (using diazoxide) will avoid isoproterenol-induced cardiac hypertrophy in vivo by decreasing reactive oxygen species (ROS) production and mitochondrial Ca2+-induced swelling. To induce cardiac hypertrophy, Swiss mice were treated intraperitoneally with isoproterenol (30 mg/kg/day) for 8 days. Diazoxide (5 mg/kg/day) was used to open mitoKATP and 5-hydroxydecanoate (5 mg/kg/day) was administrated as a mitoKATP blocker. Isoproterenol-treated mice had elevated heart weight/tibia length ratios and increased myocyte cross-sectional areas. Additionally, hypertrophic hearts produced higher levels of H2O2 and had lower glutathione peroxidase activity. In contrast, mitoKATP opening with diazoxide blocked all isoproterenol effects in a manner reversed by 5-hydroxydecanoate. Isolated mitochondria from Isoproterenol-induced hypertrophic hearts had increased susceptibility to Ca2+-induced swelling secondary to mitochondrial permeability transition pore opening. MitokATP opening was accompanied by lower Ca2+-induced mitochondrial swelling, an effect blocked by 5-hydroxydecanoate. Our results suggest that mitoKATP opening negatively regulates cardiac hypertrophy by avoiding oxidative impairment and mitochondrial damage.
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Affiliation(s)
- Aline M Lucas
- Faculdade de Medicina, Universidade Federal do Cariri, Barbalha, CE, Brazil
| | - Francisco R Caldas
- Faculdade de Medicina, Universidade Federal do Cariri, Barbalha, CE, Brazil
| | - Amanda P da Silva
- Faculdade de Medicina, Universidade Federal do Cariri, Barbalha, CE, Brazil
| | | | - Iago M Leite
- Faculdade de Medicina, Universidade Federal do Cariri, Barbalha, CE, Brazil
| | - Ana B Filgueiras
- Faculdade de Medicina, Universidade Federal do Cariri, Barbalha, CE, Brazil
| | - Claúdio G L Silva
- Faculdade de Medicina, Universidade Federal do Cariri, Barbalha, CE, Brazil
| | - Alicia J Kowaltowski
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, Brazil
| | - Heberty T Facundo
- Faculdade de Medicina, Universidade Federal do Cariri, Barbalha, CE, Brazil.
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204
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Revealing calcium fluxes by analyzing inhibition dynamics in action potential clamp. J Mol Cell Cardiol 2016; 100:93-108. [DOI: 10.1016/j.yjmcc.2016.08.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 07/19/2016] [Accepted: 08/22/2016] [Indexed: 11/29/2022]
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205
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Coronado LM, Montealegre S, Chaverra Z, Mojica L, Espinosa C, Almanza A, Correa R, Stoute JA, Gittens RA, Spadafora C. Blood Stage Plasmodium falciparum Exhibits Biological Responses to Direct Current Electric Fields. PLoS One 2016; 11:e0161207. [PMID: 27537497 PMCID: PMC4990222 DOI: 10.1371/journal.pone.0161207] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 08/01/2016] [Indexed: 11/18/2022] Open
Abstract
The development of resistance to insecticides by the vector of malaria and the increasingly faster appearance of resistance to antimalarial drugs by the parasite can dangerously hamper efforts to control and eradicate the disease. Alternative ways to treat this disease are urgently needed. Here we evaluate the in vitro effect of direct current (DC) capacitive coupling electrical stimulation on the biology and viability of Plasmodium falciparum. We designed a system that exposes infected erythrocytes to different capacitively coupled electric fields in order to evaluate their effect on P. falciparum. The effect on growth of the parasite, replication of DNA, mitochondrial membrane potential and level of reactive oxygen species after exposure to electric fields demonstrate that the parasite is biologically able to respond to stimuli from DC electric fields involving calcium signaling pathways.
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Affiliation(s)
- Lorena M. Coronado
- Center of Cellular and Molecular Biology of Diseases (CBCMe), Instituto de Investigaciones Científicas y Servicios de Alta Tecnología (INDICASAT AIP), City of Knowledge, Panama, Republic of Panama
- Department of Biotechnology, Acharya Nagarjuna University, Guntur, 522 510, A.P., India
| | - Stephania Montealegre
- School of Biotechnology, Facultad de Ciencias de la Salud “William C. Gorgas”, Universidad Latina, Panama, Republic of Panama
| | - Zumara Chaverra
- School of Biotechnology, Facultad de Ciencias de la Salud “William C. Gorgas”, Universidad Latina, Panama, Republic of Panama
| | - Luis Mojica
- National Center for Metrology of Panama (CENAMEP AIP), City of Knowledge, Panama, Republic of Panama
| | - Carlos Espinosa
- National Center for Metrology of Panama (CENAMEP AIP), City of Knowledge, Panama, Republic of Panama
| | - Alejandro Almanza
- Center of Cellular and Molecular Biology of Diseases (CBCMe), Instituto de Investigaciones Científicas y Servicios de Alta Tecnología (INDICASAT AIP), City of Knowledge, Panama, Republic of Panama
| | - Ricardo Correa
- Center of Cellular and Molecular Biology of Diseases (CBCMe), Instituto de Investigaciones Científicas y Servicios de Alta Tecnología (INDICASAT AIP), City of Knowledge, Panama, Republic of Panama
- Department of Biotechnology, Acharya Nagarjuna University, Guntur, 522 510, A.P., India
| | - José A. Stoute
- Department of Medicine, Division of Infectious Diseases and Epidemiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, United States of America
| | - Rolando A. Gittens
- Center for Biodiversity & Drug Discovery (CBDD), INDICASAT AIP, City of Knowledge, Panama, Republic of Panama
| | - Carmenza Spadafora
- Center of Cellular and Molecular Biology of Diseases (CBCMe), Instituto de Investigaciones Científicas y Servicios de Alta Tecnología (INDICASAT AIP), City of Knowledge, Panama, Republic of Panama
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206
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Macrez R, Stys PK, Vivien D, Lipton SA, Docagne F. Mechanisms of glutamate toxicity in multiple sclerosis: biomarker and therapeutic opportunities. Lancet Neurol 2016; 15:1089-102. [PMID: 27571160 DOI: 10.1016/s1474-4422(16)30165-x] [Citation(s) in RCA: 92] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Revised: 06/21/2016] [Accepted: 06/27/2016] [Indexed: 12/22/2022]
Abstract
Research advances support the idea that excessive activation of the glutamatergic pathway plays an important part in the pathophysiology of multiple sclerosis. Beyond the well established direct toxic effects on neurons, additional sites of glutamate-induced cell damage have been described, including effects in oligodendrocytes, astrocytes, endothelial cells, and immune cells. Such toxic effects could provide a link between various pathological aspects of multiple sclerosis, such as axonal damage, oligodendrocyte cell death, demyelination, autoimmunity, and blood-brain barrier dysfunction. Understanding of the mechanisms underlying glutamate toxicity in multiple sclerosis could help in the development of new approaches for diagnosis, treatment, and follow-up in patients with this debilitating disease. While several clinical trials of glutamatergic modulators have had disappointing results, our growing understanding suggests that there is reason to remain optimistic about the therapeutic potential of these drugs.
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Affiliation(s)
| | - Peter K Stys
- Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada
| | - Denis Vivien
- INSERM U919, University of Caen Normandy, Caen, France
| | - Stuart A Lipton
- Scintillon Institute San Diego, CA, USA; Scripps Research Institute, La Jolla, CA, USA; School of Mecicine, University of California, San Diego, CA, USA
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207
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Tse G, Yan BP, Chan YWF, Tian XY, Huang Y. Reactive Oxygen Species, Endoplasmic Reticulum Stress and Mitochondrial Dysfunction: The Link with Cardiac Arrhythmogenesis. Front Physiol 2016; 7:313. [PMID: 27536244 PMCID: PMC4971160 DOI: 10.3389/fphys.2016.00313] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 07/11/2016] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Cardiac arrhythmias represent a significant problem globally, leading to cerebrovascular accidents, myocardial infarction, and sudden cardiac death. There is increasing evidence to suggest that increased oxidative stress from reactive oxygen species (ROS), which is elevated in conditions such as diabetes and hypertension, can lead to arrhythmogenesis. METHOD A literature review was undertaken to screen for articles that investigated the effects of ROS on cardiac ion channel function, remodeling and arrhythmogenesis. RESULTS Prolonged endoplasmic reticulum stress is observed in heart failure, leading to increased production of ROS. Mitochondrial ROS, which is elevated in diabetes and hypertension, can stimulate its own production in a positive feedback loop, termed ROS-induced ROS release. Together with activation of mitochondrial inner membrane anion channels, it leads to mitochondrial depolarization. Abnormal function of these organelles can then activate downstream signaling pathways, ultimately culminating in altered function or expression of cardiac ion channels responsible for generating the cardiac action potential (AP). Vascular and cardiac endothelial cells become dysfunctional, leading to altered paracrine signaling to influence the electrophysiology of adjacent cardiomyocytes. All of these changes can in turn produce abnormalities in AP repolarization or conduction, thereby increasing likelihood of triggered activity and reentry. CONCLUSION ROS plays a significant role in producing arrhythmic substrate. Therapeutic strategies targeting upstream events include production of a strong reducing environment or the use of pharmacological agents that target organelle-specific proteins and ion channels. These may relieve oxidative stress and in turn prevent arrhythmic complications in patients with diabetes, hypertension, and heart failure.
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Affiliation(s)
- Gary Tse
- Li Ka Shing Faculty of Medicine, School of Biomedical Sciences, University of Hong KongHong Kong, China
- Department of Medicine and Therapeutics, Faculty of Medicine, Chinese University of Hong KongHong Kong, China
| | - Bryan P. Yan
- Department of Medicine and Therapeutics, Faculty of Medicine, Chinese University of Hong KongHong Kong, China
- Department of Epidemiology and Preventive Medicine, Monash UniversityMelbourne, VIC, Australia
| | - Yin W. F. Chan
- Department of Psychology, School of Biological Sciences, University of CambridgeCambridge, UK
| | - Xiao Yu Tian
- Faculty of Medicine, School of Biomedical Sciences, Chinese University of Hong KongHong Kong, China
| | - Yu Huang
- Faculty of Medicine, School of Biomedical Sciences, Chinese University of Hong KongHong Kong, China
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208
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Filippi-Chiela EC, Viegas MS, Thomé MP, Buffon A, Wink MR, Lenz G. Modulation of Autophagy by Calcium Signalosome in Human Disease. Mol Pharmacol 2016; 90:371-84. [DOI: 10.1124/mol.116.105171] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 07/18/2016] [Indexed: 12/30/2022] Open
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209
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Murphy E, Ardehali H, Balaban RS, DiLisa F, Dorn GW, Kitsis RN, Otsu K, Ping P, Rizzuto R, Sack MN, Wallace D, Youle RJ. Mitochondrial Function, Biology, and Role in Disease: A Scientific Statement From the American Heart Association. Circ Res 2016; 118:1960-91. [PMID: 27126807 PMCID: PMC6398603 DOI: 10.1161/res.0000000000000104] [Citation(s) in RCA: 290] [Impact Index Per Article: 36.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Cardiovascular disease is a major leading cause of morbidity and mortality in the United States and elsewhere. Alterations in mitochondrial function are increasingly being recognized as a contributing factor in myocardial infarction and in patients presenting with cardiomyopathy. Recent understanding of the complex interaction of the mitochondria in regulating metabolism and cell death can provide novel insight and therapeutic targets. The purpose of this statement is to better define the potential role of mitochondria in the genesis of cardiovascular disease such as ischemia and heart failure. To accomplish this, we will define the key mitochondrial processes that play a role in cardiovascular disease that are potential targets for novel therapeutic interventions. This is an exciting time in mitochondrial research. The past decade has provided novel insight into the role of mitochondria function and their importance in complex diseases. This statement will define the key roles that mitochondria play in cardiovascular physiology and disease and provide insight into how mitochondrial defects can contribute to cardiovascular disease; it will also discuss potential biomarkers of mitochondrial disease and suggest potential novel therapeutic approaches.
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210
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MCUR1 Is a Scaffold Factor for the MCU Complex Function and Promotes Mitochondrial Bioenergetics. Cell Rep 2016; 15:1673-85. [PMID: 27184846 DOI: 10.1016/j.celrep.2016.04.050] [Citation(s) in RCA: 165] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 03/05/2016] [Accepted: 04/12/2016] [Indexed: 11/21/2022] Open
Abstract
Mitochondrial Ca(2+) Uniporter (MCU)-dependent mitochondrial Ca(2+) uptake is the primary mechanism for increasing matrix Ca(2+) in most cell types. However, a limited understanding of the MCU complex assembly impedes the comprehension of the precise mechanisms underlying MCU activity. Here, we report that mouse cardiomyocytes and endothelial cells lacking MCU regulator 1 (MCUR1) have severely impaired [Ca(2+)]m uptake and IMCU current. MCUR1 binds to MCU and EMRE and function as a scaffold factor. Our protein binding analyses identified the minimal, highly conserved regions of coiled-coil domain of both MCU and MCUR1 that are necessary for heterooligomeric complex formation. Loss of MCUR1 perturbed MCU heterooligomeric complex and functions as a scaffold factor for the assembly of MCU complex. Vascular endothelial deletion of MCU and MCUR1 impaired mitochondrial bioenergetics, cell proliferation, and migration but elicited autophagy. These studies establish the existence of a MCU complex that assembles at the mitochondrial integral membrane and regulates Ca(2+)-dependent mitochondrial metabolism.
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211
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Toglia P, Ullah G. The gain-of-function enhancement of IP3-receptor channel gating by familial Alzheimer's disease-linked presenilin mutants increases the open probability of mitochondrial permeability transition pore. Cell Calcium 2016; 60:13-24. [PMID: 27184076 DOI: 10.1016/j.ceca.2016.05.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2016] [Revised: 04/19/2016] [Accepted: 05/05/2016] [Indexed: 12/13/2022]
Abstract
Mutants in presenilins (PS1 or PS2) are the major cause of familial Alzheimer's disease (FAD). They affect intracellular Ca(2+) homeostasis by increasing the open probability (Po) of inositol 1,4,5-trisposphate (IP3) receptor (IP3R) Ca(2+) release channel located on the endoplasmic reticulum (ER) leading to exaggerated Ca(2+) release into a cytoplasmic microdomain formed by neighboring cluster of a few IP3R channels and mitochondrial Ca(2+) uniporter (MCU). Ca(2+) concentration in the microdomain ( [Formula: see text] ) depends on the distance between the cluster and MCU (r); the number of IP3R in the cluster releasing Ca(2+) to the cytoplasm ( [Formula: see text] ), and Po of IP3R. Using experimental whole-cell IP3R-mediated cytosolic Ca(2+) data, in conjunction with a computational model of cell bioenergetics, a data-driven Markov chain model for IP3R gating, and a model for the dynamics of the mitochondrial permeability transition pore (PTP), we explore differences in mitochondrial Ca(2+) uptake in cells expressing wild type (PS1-WT) and FAD-causing mutant (PS1-M146L) PS. We find that increased mitochondrial [Formula: see text] due to the gain-of-function enhancement of IP3R channels in the cells expressing PS1-M146L leads to the opening of PTP in high conductance state (PTPh), where the latency of opening is inversely correlated with r and proportional to [Formula: see text] . Furthermore, we observe diminished inner mitochondrial membrane potential (ΔΨm), [NADH], [Formula: see text] , and [ATP] when PTP opens. Additionally, we explore how parameters such as the pH gradient, inorganic phosphate concentration, and the rate of the Na(+)/Ca(2+)-exchanger affect the latency of PTP to open in PTPh.
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Affiliation(s)
- Patrick Toglia
- Department of Physics, University of South Florida, Tampa, FL 33620, USA
| | - Ghanim Ullah
- Department of Physics, University of South Florida, Tampa, FL 33620, USA.
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212
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Wescott AP, Jafri MS, Lederer WJ, Williams GSB. Ryanodine receptor sensitivity governs the stability and synchrony of local calcium release during cardiac excitation-contraction coupling. J Mol Cell Cardiol 2016; 92:82-92. [PMID: 26827896 PMCID: PMC4807626 DOI: 10.1016/j.yjmcc.2016.01.024] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 01/13/2016] [Accepted: 01/27/2016] [Indexed: 11/27/2022]
Abstract
Calcium-induced calcium release is the principal mechanism that triggers the cell-wide [Ca(2+)]i transient that activates muscle contraction during cardiac excitation-contraction coupling (ECC). Here, we characterize this process in mouse cardiac myocytes with a novel mathematical action potential (AP) model that incorporates realistic stochastic gating of voltage-dependent L-type calcium (Ca(2+)) channels (LCCs) and sarcoplasmic reticulum (SR) Ca(2+) release channels (the ryanodine receptors, RyR2s). Depolarization of the sarcolemma during an AP stochastically activates the LCCs elevating subspace [Ca(2+)] within each of the cell's 20,000 independent calcium release units (CRUs) to trigger local RyR2 opening and initiate Ca(2+) sparks, the fundamental unit of triggered Ca(2+) release. Synchronization of Ca(2+) sparks during systole depends on the nearly uniform cellular activation of LCCs and the likelihood of local LCC openings triggering local Ca(2+) sparks (ECC fidelity). The detailed design and true SR Ca(2+) pump/leak balance displayed by our model permits investigation of ECC fidelity and Ca(2+) spark fidelity, the balance between visible (Ca(2+) spark) and invisible (Ca(2+) quark/sub-spark) SR Ca(2+) release events. Excess SR Ca(2+) leak is examined as a disease mechanism in the context of "catecholaminergic polymorphic ventricular tachycardia (CPVT)", a Ca(2+)-dependent arrhythmia. We find that that RyR2s (and therefore Ca(2+) sparks) are relatively insensitive to LCC openings across a wide range of membrane potentials; and that key differences exist between Ca(2+) sparks evoked during quiescence, diastole, and systole. The enhanced RyR2 [Ca(2+)]i sensitivity during CPVT leads to increased Ca(2+) spark fidelity resulting in asynchronous systolic Ca(2+) spark activity. It also produces increased diastolic SR Ca(2+) leak with some prolonged Ca(2+) sparks that at times become "metastable" and fail to efficiently terminate. There is a huge margin of safety for stable Ca(2+) handling within the cell and this novel mechanistic model provides insight into the molecular signaling characteristics that help maintain overall Ca(2+) stability even under the conditions of high SR Ca(2+) leak during CPVT. Finally, this model should provide tools for investigators to examine normal and pathological Ca(2+) signaling characteristics in the heart.
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Affiliation(s)
- Andrew P Wescott
- Center for Biomedical Engineering and Technology & Department of Physiology, University of Maryland, Baltimore, Baltimore, MD, United States
| | - M Saleet Jafri
- Center for Biomedical Engineering and Technology & Department of Physiology, University of Maryland, Baltimore, Baltimore, MD, United States; Molecular Neuroscience Department, George Mason University, Fairfax, VA, United States
| | - W J Lederer
- Center for Biomedical Engineering and Technology & Department of Physiology, University of Maryland, Baltimore, Baltimore, MD, United States
| | - George S B Williams
- Center for Biomedical Engineering and Technology & Department of Physiology, University of Maryland, Baltimore, Baltimore, MD, United States.
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213
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Reciprocal Regulation of Mitochondrial Dynamics and Calcium Signaling in Astrocyte Processes. J Neurosci 2016; 35:15199-213. [PMID: 26558789 DOI: 10.1523/jneurosci.2049-15.2015] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED We recently showed that inhibition of neuronal activity, glutamate uptake, or reversed-Na(+)/Ca(2+)-exchange with TTX, TFB-TBOA, or YM-244769, respectively, increases mitochondrial mobility in astrocytic processes. In the present study, we examined the interrelationships between mitochondrial mobility and Ca(2+) signaling in astrocyte processes in organotypic cultures of rat hippocampus. All of the treatments that increase mitochondrial mobility decreased basal Ca(2+). As recently reported, we observed spontaneous Ca(2+) spikes with half-lives of ∼1 s that spread ∼6 μm and are almost abolished by a TRPA1 channel antagonist. Virtually all of these Ca(2+) spikes overlap mitochondria (98%), and 62% of mitochondria are overlapped by these spikes. Although tetrodotoxin, TFB-TBOA, or YM-244769 increased Ca(2+) signaling, the specific effects on peak, decay time, and/or frequency were different. To more specifically manipulate mitochondrial mobility, we explored the effects of Miro motor adaptor proteins. We show that Miro1 and Miro2 are both expressed in astrocytes and that exogenous expression of Ca(2+)-insensitive Miro mutants (KK) nearly doubles the percentage of mobile mitochondria. Expression of Miro1(KK) had a modest effect on the frequency of these Ca(2+) spikes but nearly doubled the decay half-life. The mitochondrial proton ionophore, FCCP, caused a large, prolonged increase in cytosolic Ca(2+) followed by an increase in the decay time and the spread of the spontaneous Ca(2+) spikes. Photo-ablation of mitochondria in individual astrocyte processes has similar effects on Ca(2+). Together, these studies show that Ca(2+) regulates mitochondrial mobility, and mitochondria in turn regulate Ca(2+) signals in astrocyte processes. SIGNIFICANCE STATEMENT In neurons, the movement and positioning of mitochondria at sites of elevated activity are important for matching local energy and Ca(2+) buffering capacity. Previously, we demonstrated that mitochondria are immobilized in astrocytes in response to neuronal activity and glutamate uptake. Here, we demonstrate a mechanism by which mitochondria are immobilized in astrocytes subsequent to increases in intracellular [Ca(2+)] and provide evidence that mitochondria contribute to the compartmentalization of spontaneous Ca(2+) signals in astrocyte processes. Immobilization of mitochondria at sites of glutamate uptake in astrocyte processes provides a mechanism to coordinate increases in activity with increases in mitochondrial metabolism.
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214
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Abstract
In the heart, Ca(2+) signals regulate a variety of biological functions ranging from contractility to gene expression, cellular hypertrophy and death. In this review, we summarize the role of local Ca(2+) homeostasis in these processes in healthy cardiac muscle cells, and highlight how mismanaged Ca(2+) handling contributes to the pathophysiology of conditions such as cardiac arrhythmia, ischemic heart disease, cardiac hypertrophy and heart failure. Aiming to provide an introduction to the field with a clinical perspective, we also indicate how current and future therapies may modulate cardiomyocytes Ca(2+) handling for the treatment of patients.
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Affiliation(s)
| | - William E Louch
- b Institute for Experimental Medical Research, Oslo University Hospital Ullevål and University of Oslo , Oslo , Norway
| | - Ivar Sjaastad
- b Institute for Experimental Medical Research, Oslo University Hospital Ullevål and University of Oslo , Oslo , Norway
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215
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Motloch LJ, Larbig R, Gebing T, Reda S, Schwaiger A, Leitner J, Wolny M, Eckardt L, Hoppe UC. By Regulating Mitochondrial Ca2+-Uptake UCP2 Modulates Intracellular Ca2+. PLoS One 2016; 11:e0148359. [PMID: 26849136 PMCID: PMC4746117 DOI: 10.1371/journal.pone.0148359] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 01/19/2016] [Indexed: 12/31/2022] Open
Abstract
Introduction The possible role of UCP2 in modulating mitochondrial Ca2+-uptake (mCa2+-uptake) via the mitochondrial calcium uniporter (MCU) is highly controversial. Methods Thus, we analyzed mCa2+-uptake in isolated cardiac mitochondria, MCU single-channel activity in cardiac mitoplasts, dual Ca2+-transients from mitochondrial ((Ca2+)m) and intracellular compartment ((Ca2+)c) in the whole-cell configuration in cardiomyocytes of wild-type (WT) and UCP2-/- mice. Results Isolated mitochondria showed a Ru360 sensitive mCa2+-uptake, which was significantly decreased in UCP2-/- (229.4±30.8 FU vs. 146.3±23.4 FU, P<0.05). Single-channel registrations confirmed a Ru360 sensitive voltage-gated Ca2+-channel in mitoplasts, i.e. mCa1, showing a reduced single-channel activity in UCP2-/- (Po,total: 0.34±0.05% vs. 0.07±0.01%, P<0.05). In UCP2-/- cardiomyocytes (Ca2+)m was decreased (0.050±0.009 FU vs. 0.021±0.005 FU, P<0.05) while (Ca2+)c was unchanged (0.032±0.002 FU vs. 0.028±0.004 FU, P>0.05) and transsarcolemmal Ca2+-influx was inhibited suggesting a possible compensatory mechanism. Additionally, we observed an inhibitory effect of ATP on mCa2+-uptake in WT mitoplasts and (Ca2+)m of cardiomyocytes leading to an increase of (Ca2+)c while no ATP dependent effect was observed in UCP2-/-. Conclusion Our results indicate regulatory effects of UCP2 on mCa2+-uptake. Furthermore, we propose, that previously described inhibitory effects on MCU by ATP may be mediated via UCP2 resulting in changes of excitation contraction coupling.
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Affiliation(s)
- Lukas Jaroslaw Motloch
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
- * E-mail:
| | - Robert Larbig
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
- Division of Electrophysiology, Department of Cardiovascular Medicine, University Hospital Muenster, Muenster, Germany
| | - Tina Gebing
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - Sara Reda
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - Astrid Schwaiger
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - Johannes Leitner
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - Martin Wolny
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
| | - Lars Eckardt
- Division of Electrophysiology, Department of Cardiovascular Medicine, University Hospital Muenster, Muenster, Germany
| | - Uta C. Hoppe
- Department of Internal Medicine II, Paracelsus Medical University, Salzburg, Austria
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Roles of calcium and Mitochondria-Associated Membranes in the development of obesity and diabetes. MEDICINA UNIVERSITARIA 2016. [DOI: 10.1016/j.rmu.2015.10.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
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217
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Cytotoxic Effects of Tropodithietic Acid on Mammalian Clonal Cell Lines of Neuronal and Glial Origin. Mar Drugs 2015; 13:7113-23. [PMID: 26633426 PMCID: PMC4699232 DOI: 10.3390/md13127058] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 11/07/2015] [Accepted: 11/18/2015] [Indexed: 01/08/2023] Open
Abstract
The marine metabolite tropodithietic acid (TDA), produced by several Roseobacter clade bacteria, is known for its broad antimicrobial activity. TDA is of interest not only as a probiotic in aquaculture, but also because it might be of use as an antibacterial agent in non-marine or non-aquatic environments, and thus the potentially cytotoxic influences on eukaryotic cells need to be evaluated. The present study was undertaken to investigate its effects on cells of the mammalian nervous system, i.e., neuronal N2a cells and OLN-93 cells as model systems for nerve cells and glia. The data show that in both cell lines TDA exerted morphological changes and cytotoxic effects at a concentration of 0.3–0.5 µg/mL (1.4–2.4 µM). Furthermore, TDA caused a breakdown of the mitochondrial membrane potential, the activation of extracellular signal-regulated kinases ERK1/2, and the induction of the small heat shock protein HSP32/HO-1, which is considered as a sensor of oxidative stress. The cytotoxic effects were accompanied by an increase in intracellular Ca2+-levels, the disturbance of the microtubule network, and the reorganization of the microfilament system. Hence, mammalian cells are a sensitive target for the action of TDA and react by the activation of a stress response resulting in cell death.
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218
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Winslow RL, Walker MA, Greenstein JL. Modeling calcium regulation of contraction, energetics, signaling, and transcription in the cardiac myocyte. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2015; 8:37-67. [PMID: 26562359 DOI: 10.1002/wsbm.1322] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2015] [Revised: 09/29/2015] [Accepted: 09/30/2015] [Indexed: 12/11/2022]
Abstract
Calcium (Ca(2+)) plays many important regulatory roles in cardiac muscle cells. In the initial phase of the action potential, influx of Ca(2+) through sarcolemmal voltage-gated L-type Ca(2+) channels (LCCs) acts as a feed-forward signal that triggers a large release of Ca(2+) from the junctional sarcoplasmic reticulum (SR). This Ca(2+) drives heart muscle contraction and pumping of blood in a process known as excitation-contraction coupling (ECC). Triggered and released Ca(2+) also feed back to inactivate LCCs, attenuating the triggered Ca(2+) signal once release has been achieved. The process of ECC consumes large amounts of ATP. It is now clear that in a process known as excitation-energetics coupling, Ca(2+) signals exert beat-to-beat regulation of mitochondrial ATP production that closely couples energy production with demand. This occurs through transport of Ca(2+) into mitochondria, where it regulates enzymes of the tricarboxylic acid cycle. In excitation-signaling coupling, Ca(2+) activates a number of signaling pathways in a feed-forward manner. Through effects on their target proteins, these interconnected pathways regulate Ca(2+) signals in complex ways to control electrical excitability and contractility of heart muscle. In a process known as excitation-transcription coupling, Ca(2+) acting primarily through signal transduction pathways also regulates the process of gene transcription. Because of these diverse and complex roles, experimentally based mechanistic computational models are proving to be very useful for understanding Ca(2+) signaling in the cardiac myocyte.
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Affiliation(s)
- Raimond L Winslow
- Institute for Computational Medicine and Department of Biomedical Engineering, The Johns Hopkins University School of Medicine and Whiting School of Engineering, Baltimore, MD, USA
| | - Mark A Walker
- Institute for Computational Medicine and Department of Biomedical Engineering, The Johns Hopkins University School of Medicine and Whiting School of Engineering, Baltimore, MD, USA
| | - Joseph L Greenstein
- Institute for Computational Medicine and Department of Biomedical Engineering, The Johns Hopkins University School of Medicine and Whiting School of Engineering, Baltimore, MD, USA
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219
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Riojas-Hernández A, Bernal-Ramírez J, Rodríguez-Mier D, Morales-Marroquín FE, Domínguez-Barragán EM, Borja-Villa C, Rivera-Álvarez I, García-Rivas G, Altamirano J, García N. Enhanced oxidative stress sensitizes the mitochondrial permeability transition pore to opening in heart from Zucker Fa/fa rats with type 2 diabetes. Life Sci 2015; 141:32-43. [DOI: 10.1016/j.lfs.2015.09.018] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Revised: 08/18/2015] [Accepted: 09/22/2015] [Indexed: 12/13/2022]
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220
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Grinstead K, Joel S, Zingg JM, Dikici E, Daunert S. Enabling Aequorin for Biotechnology Applications Through Genetic Engineering. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2015:149-179. [PMID: 26475468 DOI: 10.1007/10_2015_336] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In recent years, luminescent proteins have been studied for their potential application in a variety of detection systems. Bioluminescent proteins, which do not require an external excitation source, are especially well-suited as reporters in analytical detection. The photoprotein aequorin is a bioluminescent protein that can be engineered for use as a molecular reporter under a wide range of conditions while maintaining its sensitivity. Herein, the characteristics of aequorin as well as the engineering and production of aequorin variants and their impact on signal detection in biological systems are presented. The structural features and activity of aequorin, its benefits as a label for sensing and applications in highly sensitive detection, as well as in gaining insight into biological processes are discussed. Among those, focus has been placed on the highly sensitive calcium detection in vivo, in vitro DNA and small molecule sensing, and development of in vivo imaging technologies. Graphical Abstract.
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Affiliation(s)
- Kristen Grinstead
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA
| | - Smita Joel
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA
| | - Jean-Marc Zingg
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA
| | - Emre Dikici
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA
| | - Sylvia Daunert
- Department of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, FL, 33136, USA.
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221
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Henderson MJ, Baldwin HA, Werley CA, Boccardo S, Whitaker LR, Yan X, Holt GT, Schreiter ER, Looger LL, Cohen AE, Kim DS, Harvey BK. A Low Affinity GCaMP3 Variant (GCaMPer) for Imaging the Endoplasmic Reticulum Calcium Store. PLoS One 2015; 10:e0139273. [PMID: 26451944 PMCID: PMC4599735 DOI: 10.1371/journal.pone.0139273] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 09/09/2015] [Indexed: 12/22/2022] Open
Abstract
Endoplasmic reticulum calcium homeostasis is critical for cellular functions and is disrupted in diverse pathologies including neurodegeneration and cardiovascular disease. Owing to the high concentration of calcium within the ER, studying this subcellular compartment requires tools that are optimized for these conditions. To develop a single-fluorophore genetically encoded calcium indicator for this organelle, we targeted a low affinity variant of GCaMP3 to the ER lumen (GCaMPer (10.19)). A set of viral vectors was constructed to express GCaMPer in human neuroblastoma cells, rat primary cortical neurons, and human induced pluripotent stem cell-derived cardiomyocytes. We observed dynamic changes in GCaMPer (10.19) fluorescence in response to pharmacologic manipulations of the ER calcium store. Additionally, periodic calcium efflux from the ER was observed during spontaneous beating of cardiomyocytes. GCaMPer (10.19) has utility in imaging ER calcium in living cells and providing insight into luminal calcium dynamics under physiologic and pathologic states.
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Affiliation(s)
- Mark J. Henderson
- National Institute on Drug Abuse, National Institutes of Health, 251 Bayview Blvd, Baltimore, Maryland, 21224, United States of America
- * E-mail: (MJH); (BKH)
| | - Heather A. Baldwin
- National Institute on Drug Abuse, National Institutes of Health, 251 Bayview Blvd, Baltimore, Maryland, 21224, United States of America
| | - Christopher A. Werley
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, 02138, United States of America
| | - Stefano Boccardo
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, 02138, United States of America
| | - Leslie R. Whitaker
- National Institute on Drug Abuse, National Institutes of Health, 251 Bayview Blvd, Baltimore, Maryland, 21224, United States of America
| | - Xiaokang Yan
- National Institute on Drug Abuse, National Institutes of Health, 251 Bayview Blvd, Baltimore, Maryland, 21224, United States of America
| | - Graham T. Holt
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, Virginia, 20147, United States of America
| | - Eric R. Schreiter
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, Virginia, 20147, United States of America
| | - Loren L. Looger
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, Virginia, 20147, United States of America
| | - Adam E. Cohen
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts, 02138, United States of America
- Department of Physics, Harvard University, Cambridge, Massachusetts, 02138, United States of America
- Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts, 02138, United States of America
- Howard Hughes Medical Institute, Harvard University, Cambridge, Massachusetts, 02138, United States of America
| | - Douglas S. Kim
- Janelia Research Campus, Howard Hughes Medical Institute, 19700 Helix Drive, Ashburn, Virginia, 20147, United States of America
| | - Brandon K. Harvey
- National Institute on Drug Abuse, National Institutes of Health, 251 Bayview Blvd, Baltimore, Maryland, 21224, United States of America
- * E-mail: (MJH); (BKH)
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222
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Thai TL, Yu L, Galarza-Paez L, Wu MM, Lam HYC, Bao HF, Duke BJ, Al-Khalili O, Ma HP, Liu B, Eaton DC. The Polarized Effect of Intracellular Calcium on the Renal Epithelial Sodium Channel Occurs as a Result of Subcellular Calcium Signaling Domains Maintained by Mitochondria. J Biol Chem 2015; 290:28805-11. [PMID: 26451045 DOI: 10.1074/jbc.m115.668293] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Indexed: 12/27/2022] Open
Abstract
The renal epithelial sodium channel (ENaC) provides regulated sodium transport in the distal nephron. The effects of intracellular calcium ([Ca(2+)]i) on this channel are only beginning to be elucidated. It appears from previous studies that the [Ca(2+)]i increases downstream of ATP administration may have a polarized effect on ENaC, where apical application of ATP and the subsequent [Ca(2+)]i increase have an inhibitory effect on the channel, whereas basolateral ATP and [Ca(2+)]i have a stimulatory effect. We asked whether this polarized effect of ATP is, in fact, reflective of a polarized effect of increased [Ca(2+)]i on ENaC and what underlying mechanism is responsible. We began by performing patch clamp experiments in which ENaC activity was measured during apical or basolateral application of ionomycin to increase [Ca(2+)]i near the apical or basolateral membrane, respectively. We found that ENaC does indeed respond to increased [Ca(2+)]i in a polarized fashion, with apical increases being inhibitory and basolateral increases stimulating channel activity. In other epithelial cell types, mitochondria sequester [Ca(2+)]i, creating [Ca(2+)]i signaling microdomains within the cell that are dependent on mitochondrial localization. We found that mitochondria localize in bands just beneath the apical and basolateral membranes in two different cortical collecting duct principal cell lines and in cortical collecting duct principal cells in mouse kidney tissue. We found that inhibiting mitochondrial [Ca(2+)]i uptake destroyed the polarized response of ENaC to [Ca(2+)]i. Overall, our data suggest that ENaC is regulated by [Ca(2+)]i in a polarized fashion and that this polarization is maintained by mitochondrial [Ca(2+)]i sequestration.
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Affiliation(s)
- Tiffany L Thai
- From the Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Ling Yu
- From the Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Laura Galarza-Paez
- From the Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Ming Ming Wu
- From the Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Ho Yin Colin Lam
- From the Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Hui Fang Bao
- From the Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Billie Jeanne Duke
- From the Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Otor Al-Khalili
- From the Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - He-Ping Ma
- From the Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Bingchen Liu
- From the Department of Physiology, Emory University, Atlanta, Georgia 30322
| | - Douglas C Eaton
- From the Department of Physiology, Emory University, Atlanta, Georgia 30322
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223
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Shanmughapriya S, Rajan S, Hoffman NE, Higgins AM, Tomar D, Nemani N, Hines KJ, Smith DJ, Eguchi A, Vallem S, Shaikh F, Cheung M, Leonard NJ, Stolakis RS, Wolfers MP, Ibetti J, Chuprun JK, Jog NR, Houser SR, Koch WJ, Elrod JW, Madesh M. SPG7 Is an Essential and Conserved Component of the Mitochondrial Permeability Transition Pore. Mol Cell 2015; 60:47-62. [PMID: 26387735 DOI: 10.1016/j.molcel.2015.08.009] [Citation(s) in RCA: 118] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 06/05/2015] [Accepted: 08/14/2015] [Indexed: 12/31/2022]
Abstract
Mitochondrial permeability transition is a phenomenon in which the mitochondrial permeability transition pore (PTP) abruptly opens, resulting in mitochondrial membrane potential (ΔΨm) dissipation, loss of ATP production, and cell death. Several genetic candidates have been proposed to form the PTP complex, however, the core component is unknown. We identified a necessary and conserved role for spastic paraplegia 7 (SPG7) in Ca(2+)- and ROS-induced PTP opening using RNAi-based screening. Loss of SPG7 resulted in higher mitochondrial Ca(2+) retention, similar to cyclophilin D (CypD, PPIF) knockdown with sustained ΔΨm during both Ca(2+) and ROS stress. Biochemical analyses revealed that the PTP is a heterooligomeric complex composed of VDAC, SPG7, and CypD. Silencing or disruption of SPG7-CypD binding prevented Ca(2+)- and ROS-induced ΔΨm depolarization and cell death. This study identifies an ubiquitously expressed IMM integral protein, SPG7, as a core component of the PTP at the OMM and IMM contact site.
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Affiliation(s)
- Santhanam Shanmughapriya
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Sudarsan Rajan
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Nicholas E Hoffman
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Andrew M Higgins
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Dhanendra Tomar
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Neeharika Nemani
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Kevin J Hines
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Dylan J Smith
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Akito Eguchi
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Sandhya Vallem
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Farah Shaikh
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Maggie Cheung
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Nicole J Leonard
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Ryan S Stolakis
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Matthew P Wolfers
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Jessica Ibetti
- Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA; Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - J Kurt Chuprun
- Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA; Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Neelakshi R Jog
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Steven R Houser
- Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Walter J Koch
- Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA; Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - John W Elrod
- Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA; Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Muniswamy Madesh
- Department of Biochemistry, Temple University School of Medicine, Philadelphia, PA 19140, USA; Center for Translational Medicine, Temple University School of Medicine, Philadelphia, PA 19140, USA; Cardiovascular Research Center, Temple University School of Medicine, Philadelphia, PA 19140, USA.
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224
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Furuno T, Shinkai N, Inoh Y, Nakanishi M. Impaired expression of the mitochondrial calcium uniporter suppresses mast cell degranulation. Mol Cell Biochem 2015; 410:215-21. [PMID: 26350567 DOI: 10.1007/s11010-015-2554-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Accepted: 09/02/2015] [Indexed: 01/28/2023]
Abstract
Calcium ion (Ca(2+)) uptake into the mitochondrial matrix influences ATP production, Ca(2+) homeostasis, and apoptosis regulation. Ca(2+) uptake across the ion-impermeable inner mitochondrial membrane is mediated by the mitochondrial Ca(2+) uniporter (MCU) complex. The MCU complex forms a pore structure composed of several proteins. MCU is a Ca(2+)-selective channel in the inner-mitochondrial membrane that allows electrophoretic Ca(2+) entry into the matrix. Mitochondrial Ca(2+) uptake 1 (MICU1) functions as a Ca(2+)-sensing regulator of the MCU complex. Previously, by microscopic analysis at the single-cell level, we found that during mast cell activation, mitochondria capture cytosolic Ca(2+) in two steps. Consequently, mitochondrial Ca(2+) uptake likely plays a role in cellular function through cytosolic Ca(2+) buffering. Here, we investigate the role of MCU and MICU1 in mitochondrial Ca(2+) uptake and mast cell degranulation using MCU- and MICU1-knockdown (KD) mast cells. Whereas MCU- and MICU1-KD mast cells show normal proliferation rates and mitochondrial membrane potential, they exhibit slow and reduced cytosolic and mitochondrial Ca(2+) elevation after antigen stimulation. Moreover, β-hexosaminidase release induced by antigen was significantly suppressed in MCU-KD cells but not MICU1-KD cells. This suggests that both MCU and MICU1 are involved in mitochondrial Ca(2+) uptake in mast cells, while MCU plays a role in mast cell degranulation.
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Affiliation(s)
- Tadahide Furuno
- School of Pharmacy, Aichi Gakuin University, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya, 464-8650, Japan.
| | - Narumi Shinkai
- School of Pharmacy, Aichi Gakuin University, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya, 464-8650, Japan
| | - Yoshikazu Inoh
- School of Pharmacy, Aichi Gakuin University, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya, 464-8650, Japan
| | - Mamoru Nakanishi
- School of Pharmacy, Aichi Gakuin University, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya, 464-8650, Japan
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225
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Rajagopal V, Bass G, Walker CG, Crossman DJ, Petzer A, Hickey A, Siekmann I, Hoshijima M, Ellisman MH, Crampin EJ, Soeller C. Examination of the Effects of Heterogeneous Organization of RyR Clusters, Myofibrils and Mitochondria on Ca2+ Release Patterns in Cardiomyocytes. PLoS Comput Biol 2015; 11:e1004417. [PMID: 26335304 PMCID: PMC4559435 DOI: 10.1371/journal.pcbi.1004417] [Citation(s) in RCA: 30] [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: 11/07/2014] [Accepted: 06/26/2015] [Indexed: 11/18/2022] Open
Abstract
Spatio-temporal dynamics of intracellular calcium, [Ca2+]i, regulate the contractile function of cardiac muscle cells. Measuring [Ca2+]i flux is central to the study of mechanisms that underlie both normal cardiac function and calcium-dependent etiologies in heart disease. However, current imaging techniques are limited in the spatial resolution to which changes in [Ca2+]i can be detected. Using spatial point process statistics techniques we developed a novel method to simulate the spatial distribution of RyR clusters, which act as the major mediators of contractile Ca2+ release, upon a physiologically-realistic cellular landscape composed of tightly-packed mitochondria and myofibrils. We applied this method to computationally combine confocal-scale (~ 200 nm) data of RyR clusters with 3D electron microscopy data (~ 30 nm) of myofibrils and mitochondria, both collected from adult rat left ventricular myocytes. Using this hybrid-scale spatial model, we simulated reaction-diffusion of [Ca2+]i during the rising phase of the transient (first 30 ms after initiation). At 30 ms, the average peak of the simulated [Ca2+]i transient and of the simulated fluorescence intensity signal, F/F0, reached values similar to that found in the literature ([Ca2+]i ≈1 μM; F/F0≈5.5). However, our model predicted the variation in [Ca2+]i to be between 0.3 and 12.7 μM (~3 to 100 fold from resting value of 0.1 μM) and the corresponding F/F0 signal ranging from 3 to 9.5. We demonstrate in this study that: (i) heterogeneities in the [Ca2+]i transient are due not only to heterogeneous distribution and clustering of mitochondria; (ii) but also to heterogeneous local densities of RyR clusters. Further, we show that: (iii) these structure-induced heterogeneities in [Ca2+]i can appear in line scan data. Finally, using our unique method for generating RyR cluster distributions, we demonstrate the robustness in the [Ca2+]i transient to differences in RyR cluster distributions measured between rat and human cardiomyocytes. Calcium (Ca2+) acts as a signal for many functions in the heart cell, from its primary role in triggering contractions during the heartbeat to acting as a signal for cell growth. Cellular function is tightly coupled to its ultra-structural organization. Spatially-realistic and biophysics-based computational models can provide quantitative insights into structure-function relationships in Ca2+ signaling. We developed a novel computational model of a rat ventricular myocyte that integrates structural information from confocal and electron microscopy datasets that were independently acquired and includes: myofibrils (protein complexes that contract during the heartbeat), mitochondria (organelles that provide energy for contraction), and ryanodine receptors (RyR, ion channels that release the Ca2+ required to trigger myofibril contraction from intracellular stores). Using this model, we examined [Ca2+]i dynamics throughout the cell cross-section at a much higher resolution than previously possible. We estimated the size of structural maladaptation that would cause disease-related alterations in [Ca2+]i dynamics. Using our methods for data integration, we also tested whether reducing the density of RyRs in human cardiomyocytes (~40% relative to rat) would have a significant effect on [Ca2+]i. We found that Ca2+ release patterns between the two species are similar, suggesting Ca2+ dynamics are robust to variations in cell ultrastructure.
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Affiliation(s)
- Vijay Rajagopal
- Department of Mechanical Engineering, University of Melbourne, Melbourne, Australia
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
- Systems Biology Laboratory, Melbourne School of Engineering, University of Melbourne, Melbourne, Australia
- * E-mail:
| | - Gregory Bass
- Systems Biology Laboratory, Melbourne School of Engineering, University of Melbourne, Melbourne, Australia
| | - Cameron G. Walker
- Department of Engineering Science, University of Auckland, Auckland, New Zealand
| | - David J. Crossman
- Department of Physiology, University of Auckland, Auckland, New Zealand
| | - Amorita Petzer
- School of Biological Sciences, University of Auckland, Auckland. New Zealand
| | - Anthony Hickey
- School of Biological Sciences, University of Auckland, Auckland. New Zealand
| | - Ivo Siekmann
- Department of Mechanical Engineering, University of Melbourne, Melbourne, Australia
| | - Masahiko Hoshijima
- Department of Medicine, University of California San Diego, San Diego, United States of America
- National Center for Microscopy and Imaging Research, University of California San Diego, San Diego, United States of America
| | - Mark H. Ellisman
- National Center for Microscopy and Imaging Research, University of California San Diego, San Diego, United States of America
| | - Edmund J. Crampin
- Systems Biology Laboratory, Melbourne School of Engineering, University of Melbourne, Melbourne, Australia
- School of Mathematics and Statistics, Faculty of Science, University of Melbourne, Melbourne, Australia
- School of Medicine, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Melbourne, Australia
- ARC Centre of Excellence in Convergent Bio-Nano Science and Technology, University of Melbourne, Melbourne, Australia
| | - Christian Soeller
- Department of Physiology, University of Auckland, Auckland, New Zealand
- Biomedical Physics, University of Exeter, Exeter, United Kingdom
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226
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The growing importance of mitochondrial calcium in health and disease. Proc Natl Acad Sci U S A 2015; 112:11150-1. [PMID: 26311848 DOI: 10.1073/pnas.1514284112] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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227
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Chweih H, Castilho RF, Figueira TR. Tissue and sex specificities in Ca2+handling by isolated mitochondria in conditions avoiding the permeability transition. Exp Physiol 2015; 100:1073-92. [DOI: 10.1113/ep085248] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 06/05/2015] [Indexed: 12/12/2022]
Affiliation(s)
- Hanan Chweih
- Department of Clinical Pathology; Faculty of Medical Sciences; State University of Campinas; Campinas Brazil
| | - Roger F. Castilho
- Department of Clinical Pathology; Faculty of Medical Sciences; State University of Campinas; Campinas Brazil
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228
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Chen Q, Lesnefsky EJ. Heart mitochondria and calpain 1: Location, function, and targets. Biochim Biophys Acta Mol Basis Dis 2015; 1852:2372-8. [PMID: 26259540 DOI: 10.1016/j.bbadis.2015.08.004] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Revised: 07/17/2015] [Accepted: 08/06/2015] [Indexed: 12/22/2022]
Abstract
Calpain 1 is an ubiquitous Ca(2+)-dependent cysteine protease. Although calpain 1 has been found in cardiac mitochondria, the exact location within mitochondrial compartments and its function remain unclear. The aim of the current review is to discuss the localization of calpain 1 in different mitochondrial compartments in relationship to its function, especially in pathophysiological conditions. Briefly, mitochondrial calpain 1 (mit-CPN1) is located within the intermembrane space and mitochondrial matrix. Activation of the mit-CPN1 within intermembrane space cleaves apoptosis inducing factor (AIF), whereas the activated mit-CPN1 within matrix cleaves complex I subunits and metabolic enzymes. Inhibition of the mit-CPN1 could be a potential strategy to decrease cardiac injury during ischemia-reperfusion.
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Affiliation(s)
- Qun Chen
- Department of Medicine (Division of Cardiology, Pauley Heart Center), Virginia Commonwealth University, Richmond, VA 23298, United States.
| | - Edward J Lesnefsky
- Department of Medicine (Division of Cardiology, Pauley Heart Center), Virginia Commonwealth University, Richmond, VA 23298, United States; Department of Biochemistry, Virginia Commonwealth University, Richmond, VA 23298, United States; Department of Physiology, Virginia Commonwealth University, Richmond, VA 23298, United States; McGuire VA Medical Center, Richmond, VA 23249, United States
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229
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Bernardi P, Di Lisa F, Fogolari F, Lippe G. From ATP to PTP and Back: A Dual Function for the Mitochondrial ATP Synthase. Circ Res 2015; 116:1850-62. [PMID: 25999424 DOI: 10.1161/circresaha.115.306557] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Mitochondria not only play a fundamental role in heart physiology but are also key effectors of dysfunction and death. This dual role assumes a new meaning after recent advances on the nature and regulation of the permeability transition pore, an inner membrane channel whose opening requires matrix Ca(2+) and is modulated by many effectors including reactive oxygen species, matrix cyclophilin D, Pi (inorganic phosphate), and matrix pH. The recent demonstration that the F-ATP synthase can reversibly undergo a Ca(2+)-dependent transition to form a channel that mediates the permeability transition opens new perspectives to the field. These findings demand a reassessment of the modifications of F-ATP synthase that take place in the heart under pathological conditions and of their potential role in determining the transition of F-ATP synthase from and energy-conserving into an energy-dissipating device.
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Affiliation(s)
- Paolo Bernardi
- From the Department of Biomedical Sciences, University of Padova, Italy (P.B., F.D.L.); and Department of Medical and Biological Sciences (F.F) and Department of Food Science (G.L.), University of Udine, Udine, Italy.
| | - Fabio Di Lisa
- From the Department of Biomedical Sciences, University of Padova, Italy (P.B., F.D.L.); and Department of Medical and Biological Sciences (F.F) and Department of Food Science (G.L.), University of Udine, Udine, Italy
| | - Federico Fogolari
- From the Department of Biomedical Sciences, University of Padova, Italy (P.B., F.D.L.); and Department of Medical and Biological Sciences (F.F) and Department of Food Science (G.L.), University of Udine, Udine, Italy
| | - Giovanna Lippe
- From the Department of Biomedical Sciences, University of Padova, Italy (P.B., F.D.L.); and Department of Medical and Biological Sciences (F.F) and Department of Food Science (G.L.), University of Udine, Udine, Italy
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230
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Mitochondrial DNA Haplogroup A Decreases the Risk of Drug Addiction but Conversely Increases the Risk of HIV-1 Infection in Chinese Addicts. Mol Neurobiol 2015; 53:3873-3881. [PMID: 26162319 DOI: 10.1007/s12035-015-9323-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 06/24/2015] [Indexed: 01/19/2023]
Abstract
Drug addiction is one of the most serious social problems in the world today and addicts are always at a high risk of acquiring HIV infection. Mitochondrial impairment has been reported in both drug addicts and in HIV patients undergoing treatment. In this study, we aimed to investigate whether mitochondrial DNA (mtDNA) haplogroup could affect the risk of drug addiction and HIV-1 infection in Chinese. We analyzed mtDNA sequence variations of 577 Chinese intravenous drug addicts (289 with HIV-1 infection and 288 without) and compared with 2 control populations (n = 362 and n = 850). We quantified the viral load in HIV-1-infected patients with and without haplogroup A status and investigated the potential effect of haplogroup A defining variants m.4824A > G and m.8794C > T on the cellular reactive oxygen species (ROS) levels by using an allotopic expression assay. mtDNA haplogroup A had a protective effect against drug addiction but appeared to confer an increased risk of HIV infection in addicts. HIV-1-infected addicts with haplogroup A had a trend for a higher viral load, although the mean viral load was similar between carriers of haplogroup A and those with other haplogroup. Hela cells overexpressing allele m.8794 T showed significantly decreased ROS levels as compared to cells with the allele m.8794C (P = 0.03). Our results suggested that mtDNA haplogroup A might protect against drug addiction but increase the risk of HIV-1 infection. The contradictory role of haplogroup A might be caused by an alteration in mitochondrial function due to a particular mtDNA ancestral variant.
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231
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Inhibition of MCU forces extramitochondrial adaptations governing physiological and pathological stress responses in heart. Proc Natl Acad Sci U S A 2015; 112:9129-34. [PMID: 26153425 DOI: 10.1073/pnas.1504705112] [Citation(s) in RCA: 127] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Myocardial mitochondrial Ca(2+) entry enables physiological stress responses but in excess promotes injury and death. However, tissue-specific in vivo systems for testing the role of mitochondrial Ca(2+) are lacking. We developed a mouse model with myocardial delimited transgenic expression of a dominant negative (DN) form of the mitochondrial Ca(2+) uniporter (MCU). DN-MCU mice lack MCU-mediated mitochondrial Ca(2+) entry in myocardium, but, surprisingly, isolated perfused hearts exhibited higher O2 consumption rates (OCR) and impaired pacing induced mechanical performance compared with wild-type (WT) littermate controls. In contrast, OCR in DN-MCU-permeabilized myocardial fibers or isolated mitochondria in low Ca(2+) were not increased compared with WT, suggesting that DN-MCU expression increased OCR by enhanced energetic demands related to extramitochondrial Ca(2+) homeostasis. Consistent with this, we found that DN-MCU ventricular cardiomyocytes exhibited elevated cytoplasmic [Ca(2+)] that was partially reversed by ATP dialysis, suggesting that metabolic defects arising from loss of MCU function impaired physiological intracellular Ca(2+) homeostasis. Mitochondrial Ca(2+) overload is thought to dissipate the inner mitochondrial membrane potential (ΔΨm) and enhance formation of reactive oxygen species (ROS) as a consequence of ischemia-reperfusion injury. Our data show that DN-MCU hearts had preserved ΔΨm and reduced ROS during ischemia reperfusion but were not protected from myocardial death compared with WT. Taken together, our findings show that chronic myocardial MCU inhibition leads to previously unanticipated compensatory changes that affect cytoplasmic Ca(2+) homeostasis, reprogram transcription, increase OCR, reduce performance, and prevent anticipated therapeutic responses to ischemia-reperfusion injury.
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232
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Activation of large-conductance Ca(2+)-activated K(+) channels inhibits glutamate-induced oxidative stress through attenuating ER stress and mitochondrial dysfunction. Neurochem Int 2015; 90:28-35. [PMID: 26163046 DOI: 10.1016/j.neuint.2015.07.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2015] [Revised: 06/22/2015] [Accepted: 07/02/2015] [Indexed: 12/17/2022]
Abstract
Large-conductance Ca(2+)-activated K(+) channels (BK channels) are widely expressed throughout the vertebrate nervous system, and are involved in the regulation of neurotransmitter release and neuronal excitability. Here, the neuroprotective effects of NS11021, a selective and chemically unrelated BK channel activator, and potential molecular mechanism involved have been studied in rat cortical neurons exposed to glutamate in vitro. Pretreatment with NS11021 significantly inhibited the loss of neuronal viability, LDH release and neuronal apoptosis in a dose-dependent manner. All these protective effects were fully antagonized by the BK-channel inhibitor paxilline. NS11021-induced neuroprotection was associated with reduced oxidative stress, as evidenced by decreased reactive oxygen species (ROS) generation, lipid peroxidation and preserved activity of antioxidant enzymes. Moreover, NS11021 significantly attenuated the glutamate-induced endoplasmic reticulum (ER) calcium release and activation of ER stress markers, including glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP) and caspase-12. Pretreatment with NS11021 also mitigated the mitochondrial membrane potential (MMP) collapse, cytochrome c release, and preserved mitochondrial Ca(2+) buffering capacity and ATP synthesis after glutamate exposure. Taken together, these results suggest that activation of BK channels via NS11021 protects cortical neurons against glutamate-induced excitatory damage, which may be dependent on the inhibition of ER stress and preservation of mitochondrial dysfunction.
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233
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Luongo TS, Lambert JP, Yuan A, Zhang X, Gross P, Song J, Shanmughapriya S, Gao E, Jain M, Houser SR, Koch WJ, Cheung JY, Madesh M, Elrod JW. The Mitochondrial Calcium Uniporter Matches Energetic Supply with Cardiac Workload during Stress and Modulates Permeability Transition. Cell Rep 2015; 12:23-34. [PMID: 26119731 DOI: 10.1016/j.celrep.2015.06.017] [Citation(s) in RCA: 279] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 05/08/2015] [Accepted: 06/04/2015] [Indexed: 12/13/2022] Open
Abstract
Cardiac contractility is mediated by a variable flux in intracellular calcium (Ca(2+)), thought to be integrated into mitochondria via the mitochondrial calcium uniporter (MCU) channel to match energetic demand. Here, we examine a conditional, cardiomyocyte-specific, mutant mouse lacking Mcu, the pore-forming subunit of the MCU channel, in adulthood. Mcu(-/-) mice display no overt baseline phenotype and are protected against mCa(2+) overload in an in vivo myocardial ischemia-reperfusion injury model by preventing the activation of the mitochondrial permeability transition pore, decreasing infarct size, and preserving cardiac function. In addition, we find that Mcu(-/-) mice lack contractile responsiveness to acute β-adrenergic receptor stimulation and in parallel are unable to activate mitochondrial dehydrogenases and display reduced bioenergetic reserve capacity. These results support the hypothesis that MCU may be dispensable for homeostatic cardiac function but required to modulate Ca(2+)-dependent metabolism during acute stress.
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Affiliation(s)
- Timothy S Luongo
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Jonathan P Lambert
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Ancai Yuan
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Xueqian Zhang
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Polina Gross
- Center for Cardiovascular Research, Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Jianliang Song
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Santhanam Shanmughapriya
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Erhe Gao
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Mohit Jain
- Department of Pharmacology, University of California San Diego, La Jolla, CA 92093, USA
| | - Steven R Houser
- Center for Cardiovascular Research, Department of Physiology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Walter J Koch
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Joseph Y Cheung
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - Muniswamy Madesh
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA
| | - John W Elrod
- Center for Translational Medicine, Department of Pharmacology, Temple University School of Medicine, Philadelphia, PA 19140, USA.
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234
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MacVicar TDB, Mannack LVJC, Lees RM, Lane JD. Targeted siRNA Screens Identify ER-to-Mitochondrial Calcium Exchange in Autophagy and Mitophagy Responses in RPE1 Cells. Int J Mol Sci 2015; 16:13356-80. [PMID: 26110381 PMCID: PMC4490499 DOI: 10.3390/ijms160613356] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2015] [Revised: 06/04/2015] [Accepted: 06/05/2015] [Indexed: 12/25/2022] Open
Abstract
Autophagy is an important stress response pathway responsible for the removal and recycling of damaged or redundant cytosolic constituents. Mitochondrial damage triggers selective mitochondrial autophagy (mitophagy), mediated by a variety of response factors including the Pink1/Parkin system. Using human retinal pigment epithelial cells stably expressing autophagy and mitophagy reporters, we have conducted parallel screens of regulators of endoplasmic reticulum (ER) and mitochondrial morphology and function contributing to starvation-induced autophagy and damage-induced mitophagy. These screens identified the ER chaperone and Ca2+ flux modulator, sigma non-opioid intracellular receptor 1 (SIGMAR1), as a regulator of autophagosome expansion during starvation. Screens also identified phosphatidyl ethanolamine methyl transferase (PEMT) and the IP3-receptors (IP3Rs) as mediators of Parkin-induced mitophagy. Further experiments suggested that IP3R-mediated transfer of Ca2+ from the ER lumen to the mitochondrial matrix via the mitochondrial Ca2+ uniporter (MCU) primes mitochondria for mitophagy. Importantly, recruitment of Parkin to damaged mitochondria did not require IP3R-mediated ER-to-mitochondrial Ca2+ transfer, but mitochondrial clustering downstream of Parkin recruitment was impaired, suggesting involvement of regulators of mitochondrial dynamics and/or transport. Our data suggest that Ca2+ flux between ER and mitochondria at presumed ER/mitochondrial contact sites is needed both for starvation-induced autophagy and for Parkin-mediated mitophagy, further highlighting the importance of inter-organellar communication for effective cellular homeostasis.
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Affiliation(s)
- Thomas D B MacVicar
- Cell Biology Laboratories, School of Biochemistry, University of Bristol, Bristol BS81TD, UK.
| | - Lilith V J C Mannack
- Cell Biology Laboratories, School of Biochemistry, University of Bristol, Bristol BS81TD, UK.
| | - Robert M Lees
- Cell Biology Laboratories, School of Biochemistry, University of Bristol, Bristol BS81TD, UK.
| | - Jon D Lane
- Cell Biology Laboratories, School of Biochemistry, University of Bristol, Bristol BS81TD, UK.
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235
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Yang KC, Kyle JW, Makielski JC, Dudley SC. Mechanisms of sudden cardiac death: oxidants and metabolism. Circ Res 2015; 116:1937-55. [PMID: 26044249 PMCID: PMC4458707 DOI: 10.1161/circresaha.116.304691] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2014] [Accepted: 02/09/2015] [Indexed: 02/07/2023]
Abstract
Ventricular arrhythmia is the leading cause of sudden cardiac death (SCD). Deranged cardiac metabolism and abnormal redox state during cardiac diseases foment arrhythmogenic substrates through direct or indirect modulation of cardiac ion channel/transporter function. This review presents current evidence on the mechanisms linking metabolic derangement and excessive oxidative stress to ion channel/transporter dysfunction that predisposes to ventricular arrhythmias and SCD. Because conventional antiarrhythmic agents aiming at ion channels have proven challenging to use, targeting arrhythmogenic metabolic changes and redox imbalance may provide novel therapeutics to treat or prevent life-threatening arrhythmias and SCD.
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Affiliation(s)
- Kai-Chien Yang
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.)
| | - John W Kyle
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.)
| | - Jonathan C Makielski
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.).
| | - Samuel C Dudley
- From the Department of Pharmacology (K.-C.Y.) and Division of Cardiology, Department of Internal Medicine (K.-C.Y.), National Taiwan University Hospital, Taipei, Taiwan; Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin, Madison (J.W.K., J.C.M.); and Lifespan Cardiovascular Institute, the Providence VA Medical Center, and Brown University, RI (S.C.D.).
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236
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Synaptic dysfunction, memory deficits and hippocampal atrophy due to ablation of mitochondrial fission in adult forebrain neurons. Cell Death Differ 2015; 23:18-28. [PMID: 25909888 PMCID: PMC4815974 DOI: 10.1038/cdd.2015.39] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 02/27/2015] [Accepted: 03/03/2015] [Indexed: 12/22/2022] Open
Abstract
Well-balanced mitochondrial fission and fusion processes are essential for nervous system development. Loss of function of the main mitochondrial fission mediator, dynamin-related protein 1 (Drp1), is lethal early during embryonic development or around birth, but the role of mitochondrial fission in adult neurons remains unclear. Here we show that inducible Drp1 ablation in neurons of the adult mouse forebrain results in progressive, neuronal subtype-specific alterations of mitochondrial morphology in the hippocampus that are marginally responsive to antioxidant treatment. Furthermore, DRP1 loss affects synaptic transmission and memory function. Although these changes culminate in hippocampal atrophy, they are not sufficient to cause neuronal cell death within 10 weeks of genetic Drp1 ablation. Collectively, our in vivo observations clarify the role of mitochondrial fission in neurons, demonstrating that Drp1 ablation in adult forebrain neurons compromises critical neuronal functions without causing overt neurodegeneration.
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237
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Rattanasopa C, Phungphong S, Wattanapermpool J, Bupha-Intr T. Significant role of estrogen in maintaining cardiac mitochondrial functions. J Steroid Biochem Mol Biol 2015; 147:1-9. [PMID: 25448746 DOI: 10.1016/j.jsbmb.2014.11.009] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2014] [Revised: 11/06/2014] [Accepted: 11/08/2014] [Indexed: 01/16/2023]
Abstract
Increased susceptibility to stress-induced myocardial damage is a significant concern in addition to decreased cardiac performance in postmenopausal females. To determine the potential mechanisms underlying myocardial vulnerability after deprivation of female sex hormones, cardiac mitochondrial function is determined in 10-week ovariectomized rats (OVX). Significant mitochondrial swelling in the heart of OVX rats is observed. This structural alteration can be prevented with either estrogen or progesterone supplementation. Using an isolated mitochondrial preparation, a decrease in ATP synthesis by complex I activation in an OVX rat is completely restored by estrogen, but not progesterone. At basal activation, reactive oxygen species (ROS) production from the mitochondria is not affected by the ovariectomy. However, after incubated in the presence of either high Ca(2+) or antimycin-A, there is a significantly higher mitochondrial ROS production in the OVX sample compared to the control. This increased stress-induced ROS production is not observed in the preparation isolated from the hearts of OVX rats with estrogen or progesterone supplementation. However, deprivation of female sex hormones has no effect on the protein expression of electron transport chain complexes, mitofusin 2, or superoxide dismutase 2. Taken together, these findings suggest that female sex hormones, estrogen and progesterone, play significant regulatory roles in maintaining normal mitochondrial properties by stabilizing the structural assembly of mitochondria as well as attenuating mitochondrial ROS production. Estrogen, but not progesterone, also plays an important role in modulating mitochondrial ATP synthesis.
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Affiliation(s)
- Chutima Rattanasopa
- Department of Physiology, Faculty of Science, Mahidol University, 272 Rama 6 Road, Bangkok, 10400 Thailand
| | - Sukanya Phungphong
- Department of Physiology, Faculty of Science, Mahidol University, 272 Rama 6 Road, Bangkok, 10400 Thailand
| | - Jonggonnee Wattanapermpool
- Department of Physiology, Faculty of Science, Mahidol University, 272 Rama 6 Road, Bangkok, 10400 Thailand
| | - Tepmanas Bupha-Intr
- Department of Physiology, Faculty of Science, Mahidol University, 272 Rama 6 Road, Bangkok, 10400 Thailand.
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238
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Boyman L, Chikando AC, Williams GSB, Khairallah RJ, Kettlewell S, Ward CW, Smith GL, Kao JPY, Lederer WJ. Calcium movement in cardiac mitochondria. Biophys J 2015; 107:1289-301. [PMID: 25229137 DOI: 10.1016/j.bpj.2014.07.045] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 07/08/2014] [Accepted: 07/22/2014] [Indexed: 10/24/2022] Open
Abstract
Existing theory suggests that mitochondria act as significant, dynamic buffers of cytosolic calcium ([Ca(2+)]i) in heart. These buffers can remove up to one-third of the Ca(2+) that enters the cytosol during the [Ca(2+)]i transients that underlie contractions. However, few quantitative experiments have been presented to test this hypothesis. Here, we investigate the influence of Ca(2+) movement across the inner mitochondrial membrane during both subcellular and global cellular cytosolic Ca(2+) signals (i.e., Ca(2+) sparks and [Ca(2+)]i transients, respectively) in isolated rat cardiomyocytes. By rapidly turning off the mitochondria using depolarization of the inner mitochondrial membrane potential (ΔΨm), the role of the mitochondria in buffering cytosolic Ca(2+) signals was investigated. We show here that rapid loss of ΔΨm leads to no significant changes in cytosolic Ca(2+) signals. Second, we make direct measurements of mitochondrial [Ca(2+)] ([Ca(2+)]m) using a mitochondrially targeted Ca(2+) probe (MityCam) and these data suggest that [Ca(2+)]m is near the [Ca(2+)]i level (∼100 nM) under quiescent conditions. These two findings indicate that although the mitochondrial matrix is fully buffer-capable under quiescent conditions, it does not function as a significant dynamic buffer during physiological Ca(2+) signaling. Finally, quantitative analysis using a computational model of mitochondrial Ca(2+) cycling suggests that mitochondrial Ca(2+) uptake would need to be at least ∼100-fold greater than the current estimates of Ca(2+) influx for mitochondria to influence measurably cytosolic [Ca(2+)] signals under physiological conditions. Combined, these experiments and computational investigations show that mitochondrial Ca(2+) uptake does not significantly alter cytosolic Ca(2+) signals under normal conditions and indicates that mitochondria do not act as important dynamic buffers of [Ca(2+)]i under physiological conditions in heart.
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Affiliation(s)
- Liron Boyman
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland; Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - Aristide C Chikando
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland; Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - George S B Williams
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland; Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland; School of Systems Biology, George Mason University, Fairfax, Virginia
| | - Ramzi J Khairallah
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland; University of Maryland School of Nursing, Baltimore, Maryland; Department of Cell and Molecular Physiology, Loyola University Chicago, Maywood, Illinois
| | - Sarah Kettlewell
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, G12 8QQ Glasgow, United Kingdom
| | - Christopher W Ward
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland; University of Maryland School of Nursing, Baltimore, Maryland
| | - Godfrey L Smith
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, G12 8QQ Glasgow, United Kingdom
| | - Joseph P Y Kao
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland; Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland
| | - W Jonathan Lederer
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland; Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland.
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239
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Zhang XH, Wei H, Šarić T, Hescheler J, Cleemann L, Morad M. Regionally diverse mitochondrial calcium signaling regulates spontaneous pacing in developing cardiomyocytes. Cell Calcium 2015; 57:321-36. [PMID: 25746147 DOI: 10.1016/j.ceca.2015.02.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 01/28/2015] [Accepted: 02/10/2015] [Indexed: 12/16/2022]
Abstract
The quintessential property of developing cardiomyocytes is their ability to beat spontaneously. The mechanisms underlying spontaneous beating in developing cardiomyocytes are thought to resemble those of adult heart, but have not been directly tested. Contributions of sarcoplasmic and mitochondrial Ca(2+)-signaling vs. If-channel in initiating spontaneous beating were tested in human induced Pluripotent Stem cell-derived cardiomyocytes (hiPS-CM) and rat Neonatal cardiomyocytes (rN-CM). Whole-cell and perforated-patch voltage-clamping and 2-D confocal imaging showed: (1) both cell types beat spontaneously (60-140/min, at 24°C); (2) holding potentials between -70 and 0mV had no significant effects on spontaneous pacing, but suppressed action potential formation; (3) spontaneous pacing at -50mV activated cytosolic Ca(2+)-transients, accompanied by in-phase inward current oscillations that were suppressed by Na(+)-Ca(2+)-exchanger (NCX)- and ryanodine receptor (RyR2)-blockers, but not by Ca(2+)- and If-channels blockers; (4) spreading fluorescence images of cytosolic Ca(2+)-transients emanated repeatedly from preferred central cellular locations during spontaneous beating; (5) mitochondrial un-coupler, FCCP at non-depolarizing concentrations (∼50nM), reversibly suppressed spontaneous pacing; (6) genetically encoded mitochondrial Ca(2+)-biosensor (mitycam-E31Q) detected regionally diverse, and FCCP-sensitive mitochondrial Ca(2+)-uptake and release signals activating during INCX oscillations; (7) If-channel was absent in rN-CM, but activated only negative to -80mV in hiPS-CM; nevertheless blockers of If-channel failed to alter spontaneous pacing.
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Affiliation(s)
- Xiao-Hua Zhang
- Cardiac Signaling Center of USC, MUSC, & Clemson University, Charleston, SC, USA
| | - Hua Wei
- Cardiac Signaling Center of USC, MUSC, & Clemson University, Charleston, SC, USA
| | - Tomo Šarić
- Institute for Neurophysiology, Medical Faculty, University of Cologne, Cologne, Germany
| | - Jürgen Hescheler
- Institute for Neurophysiology, Medical Faculty, University of Cologne, Cologne, Germany
| | - Lars Cleemann
- Cardiac Signaling Center of USC, MUSC, & Clemson University, Charleston, SC, USA
| | - Martin Morad
- Cardiac Signaling Center of USC, MUSC, & Clemson University, Charleston, SC, USA.
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240
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Optimal microdomain crosstalk between endoplasmic reticulum and mitochondria for Ca2+ oscillations. Sci Rep 2015; 5:7984. [PMID: 25614067 PMCID: PMC4303883 DOI: 10.1038/srep07984] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 12/24/2014] [Indexed: 12/11/2022] Open
Abstract
A Ca2+ signaling model is proposed to consider the crosstalk of Ca2+ ions between endoplasmic reticulum (ER) and mitochondria within microdomains around inositol 1, 4, 5-trisphosphate receptors (IP3R) and the mitochondrial Ca2+ uniporter (MCU). Our model predicts that there is a critical IP3R-MCU distance at which 50% of the ER-released Ca2+ is taken up by mitochondria and that mitochondria modulate Ca2+ signals differently when outside of this critical distance. This study highlights the importance of the IP3R-MCU distance on Ca2+ signaling dynamics. The model predicts that when MCU are too closely associated with IP3Rs, the enhanced mitochondrial Ca2+ uptake will produce an increase of cytosolic Ca2+ spike amplitude. Notably, the model demonstrates the existence of an optimal IP3R-MCU distance (30–85 nm) for effective Ca2+ transfer and the successful generation of Ca2+ signals in healthy cells. We suggest that the space between the inner and outer mitochondria membranes provides a defense mechanism against occurrences of high [Ca2+]Cyt. Our results also hint at a possible pathological mechanism in which abnormally high [Ca2+]Cyt arises when the IP3R-MCU distance is in excess of the optimal range.
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241
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Biesiadecki BJ, Davis JP, Ziolo MT, Janssen PML. Tri-modal regulation of cardiac muscle relaxation; intracellular calcium decline, thin filament deactivation, and cross-bridge cycling kinetics. Biophys Rev 2014; 6:273-289. [PMID: 28510030 PMCID: PMC4255972 DOI: 10.1007/s12551-014-0143-5] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 06/27/2014] [Indexed: 01/09/2023] Open
Abstract
Cardiac muscle relaxation is an essential step in the cardiac cycle. Even when the contraction of the heart is normal and forceful, a relaxation phase that is too slow will limit proper filling of the ventricles. Relaxation is too often thought of as a mere passive process that follows contraction. However, many decades of advancements in our understanding of cardiac muscle relaxation have shown it is a highly complex and well-regulated process. In this review, we will discuss three distinct events that can limit the rate of cardiac muscle relaxation: the rate of intracellular calcium decline, the rate of thin-filament de-activation, and the rate of cross-bridge cycling. Each of these processes are directly impacted by a plethora of molecular events. In addition, these three processes interact with each other, further complicating our understanding of relaxation. Each of these processes is continuously modulated by the need to couple bodily oxygen demand to cardiac output by the major cardiac physiological regulators. Length-dependent activation, frequency-dependent activation, and beta-adrenergic regulation all directly and indirectly modulate calcium decline, thin-filament deactivation, and cross-bridge kinetics. We hope to convey our conclusion that cardiac muscle relaxation is a process of intricate checks and balances, and should not be thought of as a single rate-limiting step that is regulated at a single protein level. Cardiac muscle relaxation is a system level property that requires fundamental integration of three governing systems: intracellular calcium decline, thin filament deactivation, and cross-bridge cycling kinetics.
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Affiliation(s)
- Brandon J Biesiadecki
- Department of Physiology and Cell Biology and Dorothy M. Davis Heart Lung Institute, College of Medicine, The Ohio State University, 304 Hamilton Hall, 1645 Neil Avenue, Columbus, OH, 43210-1218, USA
| | - Jonathan P Davis
- Department of Physiology and Cell Biology and Dorothy M. Davis Heart Lung Institute, College of Medicine, The Ohio State University, 304 Hamilton Hall, 1645 Neil Avenue, Columbus, OH, 43210-1218, USA
| | - Mark T Ziolo
- Department of Physiology and Cell Biology and Dorothy M. Davis Heart Lung Institute, College of Medicine, The Ohio State University, 304 Hamilton Hall, 1645 Neil Avenue, Columbus, OH, 43210-1218, USA
| | - Paul M L Janssen
- Department of Physiology and Cell Biology and Dorothy M. Davis Heart Lung Institute, College of Medicine, The Ohio State University, 304 Hamilton Hall, 1645 Neil Avenue, Columbus, OH, 43210-1218, USA.
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242
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The mitochondrial Ca(2+) uniporter complex. J Mol Cell Cardiol 2014; 78:3-8. [PMID: 25463276 DOI: 10.1016/j.yjmcc.2014.11.015] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2014] [Revised: 11/13/2014] [Accepted: 11/14/2014] [Indexed: 01/09/2023]
Abstract
Calcium influx into the mitochondrial matrix plays important roles in the regulation of cell death pathways, bioenergetics and cytoplasmic Ca(2+) signals. During the last few years, several molecular components of the inner membrane mitochondrial Ca(2+) uniporter, the dominant pathway for Ca(2+) influx into the mitochondrial matrix, have been identified. The uniporter is now recognized as a complex of proteins that include a Ca(2+) pore forming component and accessory proteins that are either required for its channel activity or regulate it under various conditions. This review summarizes recent discoveries about the molecular basis of the uniporter complex. This article is part of a Special Issue entitled "Mitochondria: From Basic Mitochondrial Biology to Cardiovascular Disease."
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243
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Murgia M, Rizzuto R. Molecular diversity and pleiotropic role of the mitochondrial calcium uniporter. Cell Calcium 2014; 58:11-7. [PMID: 26048007 DOI: 10.1016/j.ceca.2014.11.001] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2014] [Revised: 10/31/2014] [Accepted: 11/04/2014] [Indexed: 11/28/2022]
Abstract
The long awaited molecular identification of the mitochondrial calcium uniporter (MCU) in 2011 has opened an exciting phase in the study of mitochondrial calcium homeostasis. On the one hand, MCU proved to be the core of a complex signaling system, composed of a channel moiety (MCU itself and the related MCUb protein) and a family of essential regulators (the MICUs, MCUR, EMRE). On the other hand, the availability of molecular information and tools opened the possibility of directly altering mitochondrial calcium homeostasis in cell cultures or intact organisms, thus obtaining new insight into its role in physiological and pathological events. We will review here these exciting advancements, summarizing the current knowledge of the molecular composition of the MCU complex and of its role in shaping mitochondrial and cytosolic [Ca(2+)] signals.
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Affiliation(s)
- Marta Murgia
- Department of Biomedical Sciences and CNR Neuroscience Institute, University of Padua, Padua, Italy
| | - Rosario Rizzuto
- Department of Biomedical Sciences and CNR Neuroscience Institute, University of Padua, Padua, Italy.
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244
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Fieni F, Johnson DE, Hudmon A, Kirichok Y. Mitochondrial Ca2+ uniporter and CaMKII in heart. Nature 2014; 513:E1-2. [PMID: 25254480 DOI: 10.1038/nature13626] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 06/17/2014] [Indexed: 01/12/2023]
Affiliation(s)
- Francesca Fieni
- Department of Physiology, University of California San Francisco, San Francisco, California 94158, USA
| | - Derrick E Johnson
- Department of Biochemistry and Molecular Biology, Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
| | - Andy Hudmon
- Department of Biochemistry and Molecular Biology, Stark Neuroscience Research Institute, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
| | - Yuriy Kirichok
- Department of Physiology, University of California San Francisco, San Francisco, California 94158, USA
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245
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Williams GSB, Boyman L, Lederer WJ. Mitochondrial calcium and the regulation of metabolism in the heart. J Mol Cell Cardiol 2014; 78:35-45. [PMID: 25450609 DOI: 10.1016/j.yjmcc.2014.10.019] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Revised: 10/28/2014] [Accepted: 10/30/2014] [Indexed: 01/28/2023]
Abstract
Consumption of adenosine triphosphate (ATP) by the heart can change dramatically as the energetic demands increase from a period of rest to strenuous activity. Mitochondrial ATP production is central to this metabolic response since the heart relies largely on oxidative phosphorylation as its source of intracellular ATP. Significant evidence has been acquired indicating that Ca(2+) plays a critical role in regulating ATP production by the mitochondria. Here the evidence that the Ca(2+) concentration in the mitochondrial matrix ([Ca(2+)]m) plays a pivotal role in regulating ATP production by the mitochondria is critically reviewed and aspects of this process that are under current active investigation are highlighted. Importantly, current quantitative information on the bidirectional Ca(2+) movement across the inner mitochondrial membrane (IMM) is examined in two parts. First, we review how Ca(2+) influx into the mitochondrial matrix depends on the mitochondrial Ca(2+) channel (i.e., the mitochondrial calcium uniporter or MCU). This discussion includes how the MCU open probability (PO) depends on the cytosolic Ca(2+) concentration ([Ca(2+)]i) and on the mitochondrial membrane potential (ΔΨm). Second, we discuss how steady-state [Ca(2+)]m is determined by the dynamic balance between this MCU-based Ca(2+) influx and mitochondrial Na(+)/Ca(2+) exchanger (NCLX) based Ca(2+) efflux. These steady-state [Ca(2+)]m levels are suggested to regulate the metabolic energy supply due to Ca(2+)-dependent regulation of mitochondrial enzymes of the tricarboxylic acid cycle (TCA), the proteins of the electron transport chain (ETC), and the F1F0 ATP synthase itself. We conclude by discussing the roles played by [Ca(2+)]m in influencing mitochondrial responses under pathological conditions. This article is part of a Special Issue entitled "Mitochondria: From BasicMitochondrial Biology to Cardiovascular Disease."
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Affiliation(s)
- George S B Williams
- 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
| | - 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
| | - 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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246
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Lee WK, Dittmar T. Cytosolic calcium measurements in renal epithelial cells by flow cytometry. J Vis Exp 2014:e51857. [PMID: 25407650 DOI: 10.3791/51857] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
A variety of cellular processes, both physiological and pathophysiological, require or are governed by calcium, including exocytosis, mitochondrial function, cell death, cell metabolism and cell migration to name but a few. Cytosolic calcium is normally maintained at low nanomolar concentrations; rather it is found in high micromolar to millimolar concentrations in the endoplasmic reticulum, mitochondrial matrix and the extracellular compartment. Upon stimulation, a transient increase in cytosolic calcium serves to signal downstream events. Detecting changes in cytosolic calcium is normally performed using a live cell imaging set up with calcium binding dyes that exhibit either an increase in fluorescence intensity or a shift in the emission wavelength upon calcium binding. However, a live cell imaging set up is not freely accessible to all researchers. Alternative detection methods have been optimized for immunological cells with flow cytometry and for non-immunological adherent cells with a fluorescence microplate reader. Here, we describe an optimized, simple method for detecting changes in epithelial cells with flow cytometry using a single wavelength calcium binding dye. Adherent renal proximal tubule epithelial cells, which are normally difficult to load with dyes, were loaded with a fluorescent cell permeable calcium binding dye in the presence of probenecid, brought into suspension and calcium signals were monitored before and after addition of thapsigargin, tunicamycin and ionomycin.
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Affiliation(s)
- Wing-Kee Lee
- Institute for Physiology, Pathophysiology, & Toxicology, Centre for Biomedical Research and Training (ZBAF), University of Witten/Herdecke;
| | - Thomas Dittmar
- Institute for Immunology & Experimental Oncology, Centre for Biomedical Research and Training (ZBAF), University of Witten/Herdecke
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247
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Demine S, Reddy N, Renard P, Raes M, Arnould T. Unraveling biochemical pathways affected by mitochondrial dysfunctions using metabolomic approaches. Metabolites 2014; 4:831-78. [PMID: 25257998 PMCID: PMC4192695 DOI: 10.3390/metabo4030831] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2014] [Revised: 09/02/2014] [Accepted: 09/18/2014] [Indexed: 02/06/2023] Open
Abstract
Mitochondrial dysfunction(s) (MDs) can be defined as alterations in the mitochondria, including mitochondrial uncoupling, mitochondrial depolarization, inhibition of the mitochondrial respiratory chain, mitochondrial network fragmentation, mitochondrial or nuclear DNA mutations and the mitochondrial accumulation of protein aggregates. All these MDs are known to alter the capacity of ATP production and are observed in several pathological states/diseases, including cancer, obesity, muscle and neurological disorders. The induction of MDs can also alter the secretion of several metabolites, reactive oxygen species production and modify several cell-signalling pathways to resolve the mitochondrial dysfunction or ultimately trigger cell death. Many metabolites, such as fatty acids and derived compounds, could be secreted into the blood stream by cells suffering from mitochondrial alterations. In this review, we summarize how a mitochondrial uncoupling can modify metabolites, the signalling pathways and transcription factors involved in this process. We describe how to identify the causes or consequences of mitochondrial dysfunction using metabolomics (liquid and gas chromatography associated with mass spectrometry analysis, NMR spectroscopy) in the obesity and insulin resistance thematic.
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Affiliation(s)
- Stéphane Demine
- Laboratory of Biochemistry and Cell Biology (URBC), NARILIS (Namur Research Institute for Life Sciences), University of Namur (UNamur), 61 rue de Bruxelles, Namur 5000, Belgium.
| | - Nagabushana Reddy
- Laboratory of Biochemistry and Cell Biology (URBC), NARILIS (Namur Research Institute for Life Sciences), University of Namur (UNamur), 61 rue de Bruxelles, Namur 5000, Belgium.
| | - Patricia Renard
- Laboratory of Biochemistry and Cell Biology (URBC), NARILIS (Namur Research Institute for Life Sciences), University of Namur (UNamur), 61 rue de Bruxelles, Namur 5000, Belgium.
| | - Martine Raes
- Laboratory of Biochemistry and Cell Biology (URBC), NARILIS (Namur Research Institute for Life Sciences), University of Namur (UNamur), 61 rue de Bruxelles, Namur 5000, Belgium.
| | - Thierry Arnould
- Laboratory of Biochemistry and Cell Biology (URBC), NARILIS (Namur Research Institute for Life Sciences), University of Namur (UNamur), 61 rue de Bruxelles, Namur 5000, Belgium.
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248
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Functional implications of mitofusin 2-mediated mitochondrial-SR tethering. J Mol Cell Cardiol 2014; 78:123-8. [PMID: 25252175 DOI: 10.1016/j.yjmcc.2014.09.015] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Revised: 09/09/2014] [Accepted: 09/13/2014] [Indexed: 11/23/2022]
Abstract
Cardiomyocyte mitochondria have an intimate physical and functional relationship with sarcoplasmic reticulum (SR). Under normal conditions mitochondrial ATP is essential to power SR calcium cycling that drives phasic contraction/relaxation, and changes in SR calcium release are sensed by mitochondria and used to modulate oxidative phosphorylation according to metabolic need. When perturbed, mitochondrial-SR calcium crosstalk can evoke programmed cell death. Physical proximity and functional interplay between mitochondria and SR are maintained in part through tethering of these two organelles by the membrane protein mitofusin 2 (Mfn2). Here we review and discuss findings from our two laboratories that derive from genetic manipulation of Mfn2 and closely related Mfn1 in mouse hearts and other experimental systems. By comparing the findings of our two independent research efforts we arrive at several conclusions that appear to be strongly supported, and describe a few areas of incomplete understanding that will require further study. In so doing we hope to clarify some misconceptions regarding the many varied roles of Mfn2 as both physical trans-organelle tether and mitochondrial fusion protein. This article is part of a Special Issue entitled "Mitochondria: From Basic Mitochondrial Biology to Cardiovascular Disease."
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249
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Gong G, Liu X, Wang W. Regulation of metabolism in individual mitochondria during excitation-contraction coupling. J Mol Cell Cardiol 2014; 76:235-46. [PMID: 25252178 DOI: 10.1016/j.yjmcc.2014.09.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/09/2014] [Accepted: 09/11/2014] [Indexed: 01/03/2023]
Abstract
The heart is an excitable organ that undergoes spontaneous force generation and relaxation cycles driven by excitation-contraction (EC) coupling. A fraction of the oscillating cytosolic Ca(2+) during each heartbeat is taken up by mitochondria to stimulate mitochondrial metabolism, the major source of energy in the heart. Whether the mitochondrial metabolism is regulated individually during EC coupling and whether this heterogeneous regulation bears any physiological or pathological relevance have not been studied. Here, we developed a novel approach to determine the regulation of individual mitochondrial metabolism during cardiac EC coupling. Through monitoring superoxide flashes, which are stochastic and bursting superoxide production events arising from increased metabolism in individual mitochondria, we found that EC coupling stimulated the metabolism in individual mitochondria as indicated by significantly increased superoxide flash activity during electrical stimulation of the cultured intact myocytes or perfused heart. Mechanistically, cytosolic calcium transients promoted individual mitochondria to take up calcium via mitochondrial calcium uniporter, which subsequently triggered transient opening of the permeability transition pore and stimulated metabolism and bursting superoxide flash in that mitochondrion. The bursting superoxide, in turn, promoted local calcium release. In the early stage of heart failure, EC coupling regulation of superoxide flashes was compromised. This study highlights the heterogeneity in the regulation of cardiac mitochondrial metabolism, which may contribute to local redox signaling.
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Affiliation(s)
- Guohua Gong
- Mitochondria and Metabolism Center, Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA 98109, USA
| | - Xiaoyun Liu
- Mitochondria and Metabolism Center, Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA 98109, USA; Department of Neurology, Second Hospital of Hebei Medical University, Shijiazhuang, Hebei 050000, China
| | - Wang Wang
- Mitochondria and Metabolism Center, Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA 98109, USA.
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250
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Abstract
The role of mitochondria in white adipocytes has long been neglected due in part to their lower abundance in these cells. However, accumulating evidence suggests that mitochondria are vital for maintaining metabolic homeostasis in white adipocytes because of their involvement in adipogenesis, fatty acid synthesis and esterification, branched-chain amino acid catabolism and lipolysis. It is therefore not surprising that white adipose tissue function can be perturbed by altering mitochondrial components or oxidative capacity. Moreover, studies in humans and animals with significantly altered fat mass, such as in obesity or lipoatrophy, indicate that impaired mitochondrial function in adipocytes may be linked directly to the development of metabolic diseases such as diabetes and insulin resistance. However, recent studies that specifically targeted mitochondrial function in adipocytes indicated dissociation between impaired mitochondrial oxidative capacity and systemic insulin sensitivity.
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Affiliation(s)
- Sihem Boudina
- Division of Endocrinology, Metabolism and Diabetes and Program in Molecular Medicine, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Timothy E Graham
- Division of Endocrinology, Metabolism and Diabetes and Program in Molecular Medicine, University of Utah School of Medicine, Salt Lake City, UT, USA
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