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Vanhoutte D, Schips TG, Minerath RA, Huo J, Kavuri NSS, Prasad V, Lin SC, Bround MJ, Sargent MA, Adams CM, Molkentin JD. Thbs1 regulates skeletal muscle mass in a TGFβ-Smad2/3-ATF4-dependent manner. Cell Rep 2024; 43:114149. [PMID: 38678560 DOI: 10.1016/j.celrep.2024.114149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 03/22/2024] [Accepted: 04/09/2024] [Indexed: 05/01/2024] Open
Abstract
Loss of muscle mass is a feature of chronic illness and aging. Here, we report that skeletal muscle-specific thrombospondin-1 transgenic mice (Thbs1 Tg) have profound muscle atrophy with age-dependent decreases in exercise capacity and premature lethality. Mechanistically, Thbs1 activates transforming growth factor β (TGFβ)-Smad2/3 signaling, which also induces activating transcription factor 4 (ATF4) expression that together modulates the autophagy-lysosomal pathway (ALP) and ubiquitin-proteasome system (UPS) to facilitate muscle atrophy. Indeed, myofiber-specific inhibition of TGFβ-receptor signaling represses the induction of ATF4, normalizes ALP and UPS, and partially restores muscle mass in Thbs1 Tg mice. Similarly, myofiber-specific deletion of Smad2 and Smad3 or the Atf4 gene antagonizes Thbs1-induced muscle atrophy. More importantly, Thbs1-/- mice show significantly reduced levels of denervation- and caloric restriction-mediated muscle atrophy, along with blunted TGFβ-Smad3-ATF4 signaling. Thus, Thbs1-mediated TGFβ-Smad3-ATF4 signaling in skeletal muscle regulates tissue rarefaction, suggesting a target for atrophy-based muscle diseases and sarcopenia with aging.
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Affiliation(s)
- Davy Vanhoutte
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Tobias G Schips
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Rachel A Minerath
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Jiuzhou Huo
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Naga Swathi Sree Kavuri
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Vikram Prasad
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Suh-Chin Lin
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Michael J Bround
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Michelle A Sargent
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Christopher M Adams
- Division of Endocrinology, Metabolism and Nutrition, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA
| | - Jeffery D Molkentin
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA.
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2
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Bround MJ, Abay E, Huo J, Havens JR, York AJ, Bers DM, Molkentin JD. MCU-independent Ca 2+ uptake mediates mitochondrial Ca 2+ overload and necrotic cell death in a mouse model of Duchenne muscular dystrophy. Sci Rep 2024; 14:6751. [PMID: 38514795 PMCID: PMC10957967 DOI: 10.1038/s41598-024-57340-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Accepted: 03/18/2024] [Indexed: 03/23/2024] Open
Abstract
Mitochondrial Ca2+ overload can mediate mitochondria-dependent cell death, a major contributor to several human diseases. Indeed, Duchenne muscular dystrophy (MD) is driven by dysfunctional Ca2+ influx across the sarcolemma that causes mitochondrial Ca2+ overload, organelle rupture, and muscle necrosis. The mitochondrial Ca2+ uniporter (MCU) complex is the primary characterized mechanism for acute mitochondrial Ca2+ uptake. One strategy for preventing mitochondrial Ca2+ overload is deletion of the Mcu gene, the pore forming subunit of the MCU-complex. Conversely, enhanced MCU-complex Ca2+ uptake is achieved by deleting the inhibitory Mcub gene. Here we show that myofiber-specific Mcu deletion was not protective in a mouse model of Duchenne MD. Specifically, Mcu gene deletion did not reduce muscle histopathology, did not improve muscle function, and did not prevent mitochondrial Ca2+ overload. Moreover, myofiber specific Mcub gene deletion did not augment Duchenne MD muscle pathology. Interestingly, we observed MCU-independent Ca2+ uptake in dystrophic mitochondria that was sufficient to drive mitochondrial permeability transition pore (MPTP) activation and skeletal muscle necrosis, and this same type of activity was observed in heart, liver, and brain mitochondria. These results demonstrate that mitochondria possess an uncharacterized MCU-independent Ca2+ uptake mechanism that is sufficient to drive MPTP-dependent necrosis in MD in vivo.
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Affiliation(s)
- Michael J Bround
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, 240 Albert Sabin Way, MLC 7020, Cincinnati, OH, 45229-3039, USA
| | - Eaman Abay
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, 240 Albert Sabin Way, MLC 7020, Cincinnati, OH, 45229-3039, USA
| | - Jiuzhou Huo
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, 240 Albert Sabin Way, MLC 7020, Cincinnati, OH, 45229-3039, USA
| | - Julian R Havens
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, 240 Albert Sabin Way, MLC 7020, Cincinnati, OH, 45229-3039, USA
| | - Allen J York
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, 240 Albert Sabin Way, MLC 7020, Cincinnati, OH, 45229-3039, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, CA, 95616, USA
| | - Jeffery D Molkentin
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, 240 Albert Sabin Way, MLC 7020, Cincinnati, OH, 45229-3039, USA.
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Huo J, Prasad V, Grimes KM, Vanhoutte D, Blair NS, Lin SC, Bround MJ, Bers DM, Molkentin JD. MCUb is an inducible regulator of calcium-dependent mitochondrial metabolism and substrate utilization in muscle. Cell Rep 2023; 42:113465. [PMID: 37976157 PMCID: PMC10842842 DOI: 10.1016/j.celrep.2023.113465] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 09/19/2023] [Accepted: 11/03/2023] [Indexed: 11/19/2023] Open
Abstract
Mitochondria use the electron transport chain to generate high-energy phosphate from oxidative phosphorylation, a process also regulated by the mitochondrial Ca2+ uniporter (MCU) and Ca2+ levels. Here, we show that MCUb, an inhibitor of MCU-mediated Ca2+ influx, is induced by caloric restriction, where it increases mitochondrial fatty acid utilization. To mimic the fasted state with reduced mitochondrial Ca2+ influx, we generated genetically altered mice with skeletal muscle-specific MCUb expression that showed greater fatty acid usage, less fat accumulation, and lower body weight. In contrast, mice lacking Mcub in skeletal muscle showed increased pyruvate dehydrogenase activity, increased muscle malonyl coenzyme A (CoA), reduced fatty acid utilization, glucose intolerance, and increased adiposity. Mechanistically, pyruvate dehydrogenase kinase 4 (PDK4) overexpression in muscle of Mcub-deleted mice abolished altered substrate preference. Thus, MCUb is an inducible control point in regulating skeletal muscle mitochondrial Ca2+ levels and substrate utilization that impacts total metabolic balance.
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Affiliation(s)
- Jiuzhou Huo
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH 45229, USA
| | - Vikram Prasad
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH 45229, USA
| | - Kelly M Grimes
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH 45229, USA
| | - Davy Vanhoutte
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH 45229, USA
| | - N Scott Blair
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH 45229, USA
| | - Suh-Chin Lin
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH 45229, USA
| | - Michael J Bround
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH 45229, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Jeffery D Molkentin
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH 45229, USA.
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4
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Bround MJ, Havens JR, York AJ, Sargent MA, Karch J, Molkentin JD. ANT-dependent MPTP underlies necrotic myofiber death in muscular dystrophy. Sci Adv 2023; 9:eadi2767. [PMID: 37624892 PMCID: PMC10456852 DOI: 10.1126/sciadv.adi2767] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 07/26/2023] [Indexed: 08/27/2023]
Abstract
Mitochondrial permeability transition pore (MPTP) formation contributes to ischemia-reperfusion injury in the heart and several degenerative diseases, including muscular dystrophy (MD). MD is a family of genetic disorders characterized by progressive muscle necrosis and premature death. It has been proposed that the MPTP has two molecular components, the adenine nucleotide translocase (ANT) family of proteins and an unknown component that requires the chaperone cyclophilin D (CypD) to activate. This model was examined in vivo by deleting the gene encoding ANT1 (Slc25a4) or CypD (Ppif) in a δ-sarcoglycan (Sgcd) gene-deleted mouse model of MD, revealing that dystrophic mice lacking Slc25a4 were partially protected from cell death and MD pathology. Dystrophic mice lacking both Slc25a4 and Ppif together were almost completely protected from necrotic cell death and MD disease. This study provides direct evidence that ANT1 and CypD are required MPTP components governing in vivo cell death, suggesting a previously unrecognized therapeutic approach in MD and other necrotic diseases.
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Affiliation(s)
- Michael J. Bround
- Department of Pediatrics, Cincinnati Children's Hospital and the University of Cincinnati, Cincinnati, OH, USA
| | - Julian R. Havens
- Department of Pediatrics, Cincinnati Children's Hospital and the University of Cincinnati, Cincinnati, OH, USA
| | - Allen J. York
- Department of Pediatrics, Cincinnati Children's Hospital and the University of Cincinnati, Cincinnati, OH, USA
| | - Michelle A. Sargent
- Department of Pediatrics, Cincinnati Children's Hospital and the University of Cincinnati, Cincinnati, OH, USA
| | - Jason Karch
- Department of Integrative Physiology, Baylor College of Medicine, Houston, TX, USA
| | - Jeffery D. Molkentin
- Department of Pediatrics, Cincinnati Children's Hospital and the University of Cincinnati, Cincinnati, OH, USA
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5
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Abstract
RATIONALE Mitochondrial Ca2+ loading augments oxidative metabolism to match functional demands during times of increased work or injury. However, mitochondrial Ca2+ overload also directly causes mitochondrial rupture and cardiomyocyte death during ischemia-reperfusion injury by inducing mitochondrial permeability transition pore opening. The MCU (mitochondrial Ca2+ uniporter) mediates mitochondrial Ca2+ influx, and its activity is modulated by partner proteins in its molecular complex, including the MCUb subunit. OBJECTIVE Here, we sought to examine the function of the MCUb subunit of the MCU-complex in regulating mitochondria Ca2+ influx dynamics, acute cardiac injury, and long-term adaptation after ischemic injury. METHODS AND RESULTS Cardiomyocyte-specific MCUb overexpressing transgenic mice and Mcub gene-deleted (Mcub-/-) mice were generated to dissect the molecular function of this protein in the heart. We observed that MCUb protein is undetectable in the adult mouse heart at baseline, but mRNA and protein are induced after ischemia-reperfusion injury. MCUb overexpressing mice demonstrated inhibited mitochondrial Ca2+ uptake in cardiomyocytes and partial protection from ischemia-reperfusion injury by reducing mitochondrial permeability transition pore opening. Antithetically, deletion of the Mcub gene exacerbated pathological cardiac remodeling and infarct expansion after ischemic injury in association with greater mitochondrial Ca2+ uptake. Furthermore, hindlimb remote ischemic preconditioning induced MCUb expression in the heart, which was associated with decreased mitochondrial Ca2+ uptake, collectively suggesting that induction of MCUb protein in the heart is protective. Similarly, mouse embryonic fibroblasts from Mcub-/- mice were more sensitive to Ca2+ overload. CONCLUSIONS Our studies suggest that Mcub is a protective cardiac inducible gene that reduces mitochondrial Ca2+ influx and permeability transition pore opening after ischemic injury to reduce ongoing pathological remodeling.
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Affiliation(s)
- Jiuzhou Huo
- From the Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, OH (J.H., M.J.B., K.M.G., M.A.S., J.D.M.)
| | - Shan Lu
- Department of Pharmacology, University of California, Davis (S.L., D.M.B.)
| | - Jennifer Q Kwong
- Division of Pediatric Cardiology, Department of Pediatrics, Emory University School of Medicine, Atlanta, GA (J.Q.K.)
| | - Michael J Bround
- From the Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, OH (J.H., M.J.B., K.M.G., M.A.S., J.D.M.)
| | - Kelly M Grimes
- From the Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, OH (J.H., M.J.B., K.M.G., M.A.S., J.D.M.)
| | - Michelle A Sargent
- From the Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, OH (J.H., M.J.B., K.M.G., M.A.S., J.D.M.)
| | - Milton E Brown
- Wallace H. Coulter Department of Biomedical Engineering, Emory University School of Medicine, Atlanta, GA (M.E.B., M.E.D.)
| | - Michael E Davis
- Wallace H. Coulter Department of Biomedical Engineering, Emory University School of Medicine, Atlanta, GA (M.E.B., M.E.D.)
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis (S.L., D.M.B.)
| | - Jeffery D Molkentin
- From the Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, OH (J.H., M.J.B., K.M.G., M.A.S., J.D.M.)
- Howard Hughes Medical Institute, Cincinnati Children's Hospital Medical Center, OH (J.D.M.)
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6
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Bround MJ, Bers DM, Molkentin JD. A 20/20 view of ANT function in mitochondrial biology and necrotic cell death. J Mol Cell Cardiol 2020; 144:A3-A13. [PMID: 32454061 DOI: 10.1016/j.yjmcc.2020.05.012] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Revised: 04/16/2020] [Accepted: 05/20/2020] [Indexed: 12/25/2022]
Abstract
The adenosine nucleotide translocase (ANT) family of proteins are inner mitochondrial membrane proteins involved in energy homeostasis and cell death. The primary function of ANT proteins is to exchange cytosolic ADP with matrix ATP, facilitating the export of newly synthesized ATP to the cell while providing new ADP substrate to the mitochondria. As such, the ANT proteins are central to maintaining energy homeostasis in all eukaryotic cells. Evidence also suggests that the ANTs constitute a pore-forming component of the mitochondrial permeability transition pore (MPTP), a structure that forms in the inner mitochondrial membrane that is thought to underlie regulated necrotic cell death. Additionally, emerging studies suggest that ANT proteins are also critical for mitochondrial uncoupling and for promoting mitophagy. Thus, the ANTs are multifunctional proteins that are poised to participate in several aspects of mitochondrial biology and the greater regulation of cell death, which will be discussed here.
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Affiliation(s)
- Michael J Bround
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH 45229, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, Davis, CA 95616, USA
| | - Jeffery D Molkentin
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH 45229, USA; Howard Hughes Medical Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH 45229, USA.
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7
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Antonucci S, Di Sante M, Sileikyte J, Deveraux J, Bauer T, Bround MJ, Menabò R, Paillard M, Alanova P, Carraro M, Ovize M, Molkentin JD, Cohen M, Forte MA, Bernardi P, Di Lisa F, Murphy E. A novel class of cardioprotective small-molecule PTP inhibitors. Pharmacol Res 2019; 151:104548. [PMID: 31759087 DOI: 10.1016/j.phrs.2019.104548] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2019] [Revised: 11/12/2019] [Accepted: 11/14/2019] [Indexed: 01/03/2023]
Abstract
Ischemia/reperfusion (I/R) injury is mediated in large part by opening of the mitochondrial permeability transition pore (PTP). Consequently, inhibitors of the PTP hold great promise for the treatment of a variety of cardiovascular disorders. At present, PTP inhibition is obtained only through the use of drugs (e.g. cyclosporine A, CsA) targeting cyclophilin D (CyPD) which is a key modulator, but not a structural component of the PTP. This limitation might explain controversial findings in clinical studies. Therefore, we investigated the protective effects against I/R injury of small-molecule inhibitors of the PTP (63 and TR002) that do not target CyPD. Both compounds exhibited a dose-dependent inhibition of PTP opening in isolated mitochondria and were more potent than CsA. Notably, PTP inhibition was observed also in mitochondria devoid of CyPD. Compounds 63 and TR002 prevented PTP opening and mitochondrial depolarization induced by Ca2+ overload and by reactive oxygen species in neonatal rat ventricular myocytes (NRVMs). Remarkably, both compounds prevented cell death, contractile dysfunction and sarcomeric derangement induced by anoxia/reoxygenation injury in NRVMs at sub-micromolar concentrations, and were more potent than CsA. Cardioprotection was observed also in adult mouse ventricular myocytes and human iPSc-derived cardiomyocytes, as well as ex vivo in perfused hearts. Thus, this study demonstrates that 63 and TR002 represent novel cardioprotective agents that inhibit PTP opening independent of CyPD targeting.
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Affiliation(s)
| | - Moises Di Sante
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Justina Sileikyte
- Vollum Institute, and Department of Physiology and Pharmacology, Portland, OR, USA
| | - Jordan Deveraux
- Vollum Institute, and Department of Physiology and Pharmacology, Portland, OR, USA
| | - Tyler Bauer
- Systems Biology Center, NHLBI, NIH, Bethesda, MD, USA
| | - Michael J Bround
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH, USA
| | - Roberta Menabò
- Department of Biomedical Sciences, University of Padova, Padova, Italy; National Research Council of Italy (CNR), Padova, Italy
| | - Melanie Paillard
- CarMeN Laboratory, University Claude Bernard Lyon 1, INSA Lyon, Oullins, France
| | - Petra Alanova
- Department of Biomedical Sciences, University of Padova, Padova, Italy; Department of Developmental Cardiology, Institute of Physiology CAS, Prague, Czech Republic
| | - Michela Carraro
- Department of Biomedical Sciences, University of Padova, Padova, Italy
| | - Michel Ovize
- CarMeN Laboratory, University Claude Bernard Lyon 1, INSA Lyon, Oullins, France
| | - Jeffery D Molkentin
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, OH, USA; Howard Hughes Medical Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Michael Cohen
- Vollum Institute, and Department of Physiology and Pharmacology, Portland, OR, USA
| | - Michael A Forte
- Vollum Institute, and Department of Physiology and Pharmacology, Portland, OR, USA
| | - Paolo Bernardi
- Department of Biomedical Sciences, University of Padova, Padova, Italy; National Research Council of Italy (CNR), Padova, Italy
| | - Fabio Di Lisa
- Department of Biomedical Sciences, University of Padova, Padova, Italy; National Research Council of Italy (CNR), Padova, Italy.
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8
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Karch J, Bround MJ, Khalil H, Sargent MA, Latchman N, Terada N, Peixoto PM, Molkentin JD. Inhibition of mitochondrial permeability transition by deletion of the ANT family and CypD. Sci Adv 2019; 5:eaaw4597. [PMID: 31489369 PMCID: PMC6713508 DOI: 10.1126/sciadv.aaw4597] [Citation(s) in RCA: 148] [Impact Index Per Article: 29.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 07/25/2019] [Indexed: 05/19/2023]
Abstract
The mitochondrial permeability transition pore (MPTP) has resisted molecular identification. The original model of the MPTP that proposed the adenine nucleotide translocator (ANT) as the inner membrane pore-forming component was challenged when mitochondria from Ant1/2 double null mouse liver still had MPTP activity. Because mice express three Ant genes, we reinvestigated whether the ANTs comprise the MPTP. Liver mitochondria from Ant1, Ant2, and Ant4 deficient mice were highly refractory to Ca2+-induced MPTP formation, and when also given cyclosporine A (CsA), the MPTP was completely inhibited. Moreover, liver mitochondria from mice with quadruple deletion of Ant1, Ant2, Ant4, and Ppif (cyclophilin D, target of CsA) lacked Ca2+-induced MPTP formation. Inner-membrane patch clamping in mitochondria from Ant1, Ant2, and Ant4 triple null mouse embryonic fibroblasts showed a loss of MPTP activity. Our findings suggest a model for the MPTP consisting of two distinct molecular components: The ANTs and an unknown species requiring CypD.
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Affiliation(s)
- Jason Karch
- Department of Pediatrics, Cincinnati Children's Hospital and University of Cincinnati, Cincinnati, OH, USA
- Department of Molecular Physiology and Biophysics, Cardiovascular Research Institute, Baylor College of Medicine, Houston TX, USA
| | - Michael J. Bround
- Department of Pediatrics, Cincinnati Children's Hospital and University of Cincinnati, Cincinnati, OH, USA
| | - Hadi Khalil
- Department of Pediatrics, Cincinnati Children's Hospital and University of Cincinnati, Cincinnati, OH, USA
| | - Michelle A. Sargent
- Department of Pediatrics, Cincinnati Children's Hospital and University of Cincinnati, Cincinnati, OH, USA
| | - Nadina Latchman
- Baruch College and Graduate Center of City University of New York, NY, USA
| | - Naohiro Terada
- Department of Pathology, University of Florida College of Medicine, Gainesville, FL, USA
| | - Pablo M. Peixoto
- Baruch College and Graduate Center of City University of New York, NY, USA
| | - Jeffery D. Molkentin
- Department of Pediatrics, Cincinnati Children's Hospital and University of Cincinnati, Cincinnati, OH, USA
- Howard Hughes Medical Institute, Chevy Chase, MD, USA
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9
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Kwong JQ, Huo J, Bround MJ, Boyer JG, Schwanekamp JA, Ghazal N, Maxwell JT, Jang YC, Khuchua Z, Shi K, Bers DM, Davis J, Molkentin JD. The mitochondrial calcium uniporter underlies metabolic fuel preference in skeletal muscle. JCI Insight 2018; 3:121689. [PMID: 30429366 DOI: 10.1172/jci.insight.121689] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 10/04/2018] [Indexed: 01/17/2023] Open
Abstract
The mitochondrial Ca2+ uniporter (MCU) complex mediates acute mitochondrial Ca2+ influx. In skeletal muscle, MCU links Ca2+ signaling to energy production by directly enhancing the activity of key metabolic enzymes in the mitochondria. Here, we examined the role of MCU in skeletal muscle development and metabolic function by generating mouse models for the targeted deletion of Mcu in embryonic, postnatal, and adult skeletal muscle. Loss of Mcu did not affect muscle growth and maturation or otherwise cause pathology. Skeletal muscle-specific deletion of Mcu in mice also did not affect myofiber intracellular Ca2+ handling, but it did inhibit acute mitochondrial Ca2+ influx and mitochondrial respiration stimulated by Ca2+, resulting in reduced acute exercise performance in mice. However, loss of Mcu also resulted in enhanced muscle performance under conditions of fatigue, with a preferential shift toward fatty acid metabolism, resulting in reduced body fat with aging. Together, these results demonstrate that MCU-mediated mitochondrial Ca2+ regulation underlies skeletal muscle fuel selection at baseline and under enhanced physiological demands, which affects total homeostatic metabolism.
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Affiliation(s)
- Jennifer Q Kwong
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, Ohio, USA.,Department of Pediatrics, Division of Cardiovascular Biology, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Jiuzhou Huo
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, Ohio, USA
| | - Michael J Bround
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, Ohio, USA
| | - Justin G Boyer
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, Ohio, USA
| | - Jennifer A Schwanekamp
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, Ohio, USA
| | - Nasab Ghazal
- Department of Pediatrics, Division of Cardiovascular Biology, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Joshua T Maxwell
- Department of Pediatrics, Division of Cardiovascular Biology, Emory University School of Medicine, Atlanta, Georgia, USA
| | - Young C Jang
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Zaza Khuchua
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, Ohio, USA.,Sechenov University, Moscow, Russia
| | - Kevin Shi
- Department of Bioengineering, University of Washington, Seattle, Washington, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, California, USA
| | - Jennifer Davis
- Department of Bioengineering, University of Washington, Seattle, Washington, USA
| | - Jeffery D Molkentin
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati, Cincinnati, Ohio, USA.,Howard Hughes Medical Institute, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
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10
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Karch J, Bround MJ, Parks RJ, Terada N, Wallace DC, Murphy E, Molkentin JD. Abstract 486: Role of the Adenine Nucleotide Translocator Family in the Mitochondrial Permeability Transition Pore. Circ Res 2018. [DOI: 10.1161/res.123.suppl_1.486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cardiomyocyte necrosis is dependent on the prolonged opening of the mitochondrial permeability transition pore (MPTP) which has escaped molecular identification for decades. Once thought to be comprised of the adenine nucleotide translocator (ANT) family, this hypothesis has fell by the way side when it was shown that liver mitochondria devoid of ANT 1 and 2 still display MPTP opening, even though these mitochondria were desensitized to MPTP opening and required a greater calcium bolus for it to engage. Thus, the ANT family has been labeled as a critical regulator of the MPTP and not the pore forming component. However, mice express three isoforms of ANT and only two of the three isoforms where deleted when ANTs were deemed to be non-essential. We hypothesize that the third ANT isoform may have compensated for the loss of the other two ANT family members during this analysis. Here, we have generated mice lacking all isoforms of ANT in a heart-, liver-, or cell-specific manner. Surprisingly, mice lacking all isoforms of ANT specifically in the liver are viable and are highly resistant to MPTP opening. Indeed, the amount of calcium required to engage the MPTP in mitochondria lacking all ANTs is 11 fold higher than wild type mitochondria and greater than 2 fold higher than wild type mitochondria treated with the MPTP inhibitor cyclosporine A (CsA). Furthermore, the treatment of CsA on ANT null liver mitochondria completely blocks MPTP opening suggesting that the ANT family is the primary pore in the liver. However, when subjected to extreme levels of calcium, a cyclophilin D (CypD) dependent pore engages. CypD is the MPTP trigger located in the matrix of the mitochondria which is inhibited by CsA and in wild type mitochondria high levels of calcium are enough to overcome the inhibition of CypD to open the pore. But, in ANT depleted liver mitochondria, extremely high levels of calcium do not override CypD inhibition which is suggestive of the presence of an additional pore. Further experimentation is underway to determine if MPTP-conductance is detectable by patch clamping mitoplasts lacking all isoforms of ANT.
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Affiliation(s)
- Jason Karch
- Cincinnati Children’s Hosp Med Cntr, Cincinnati, OH
| | | | - Randi J Parks
- Systems Biology Cntr, National Heart Lung and Blood Institute,, Bethesda, MD
| | | | | | - Elizabeth Murphy
- Systems Biology Cntr, National Heart, Lung and Blood Institute, Bethesda, MD
| | - Jeffery D Molkentin
- Cincinnati Children’s Hosp Med Cntr, Cincinnati, OH
- Howard Hughes Med Institute, Cincinnati, OH
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11
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Bround MJ, Wambolt R, Cen H, Asghari P, Albu RF, Han J, McAfee D, Pourrier M, Scott NE, Bohunek L, Kulpa JE, Chen SRW, Fedida D, Brownsey RW, Borchers CH, Foster LJ, Mayor T, Moore EDW, Allard MF, Johnson JD. Cardiac Ryanodine Receptor (Ryr2)-mediated Calcium Signals Specifically Promote Glucose Oxidation via Pyruvate Dehydrogenase. J Biol Chem 2016; 291:23490-23505. [PMID: 27621312 DOI: 10.1074/jbc.m116.756973] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Indexed: 11/06/2022] Open
Abstract
Cardiac ryanodine receptor (Ryr2) Ca2+ release channels and cellular metabolism are both disrupted in heart disease. Recently, we demonstrated that total loss of Ryr2 leads to cardiomyocyte contractile dysfunction, arrhythmia, and reduced heart rate. Acute total Ryr2 ablation also impaired metabolism, but it was not clear whether this was a cause or consequence of heart failure. Previous in vitro studies revealed that Ca2+ flux into the mitochondria helps pace oxidative metabolism, but there is limited in vivo evidence supporting this concept. Here, we studied heart-specific, inducible Ryr2 haploinsufficient (cRyr2Δ50) mice with a stable 50% reduction in Ryr2 protein. This manipulation decreased the amplitude and frequency of cytosolic and mitochondrial Ca2+ signals in isolated cardiomyocytes, without changes in cardiomyocyte contraction. Remarkably, in the context of well preserved contractile function in perfused hearts, we observed decreased glucose oxidation, but not fat oxidation, with increased glycolysis. cRyr2Δ50 hearts exhibited hyperphosphorylation and inhibition of pyruvate dehydrogenase, the key Ca2+-sensitive gatekeeper to glucose oxidation. Metabolomic, proteomic, and transcriptomic analyses revealed additional functional networks associated with altered metabolism in this model. These results demonstrate that Ryr2 controls mitochondrial Ca2+ dynamics and plays a specific, critical role in promoting glucose oxidation in cardiomyocytes. Our findings indicate that partial RYR2 loss is sufficient to cause metabolic abnormalities seen in heart disease.
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Affiliation(s)
- Michael J Bround
- From the Cardiovascular Research Group, Life Sciences Institute and.,Departments of Cellular and Physiological Sciences
| | - Rich Wambolt
- From the Cardiovascular Research Group, Life Sciences Institute and.,the Department of Pathology and Laboratory Medicine, University of British Columbia and the Centre for Heart and Lung Innovation, St. Paul's Hospital, Vancouver, British Columbia V6Z 1Y6
| | - Haoning Cen
- From the Cardiovascular Research Group, Life Sciences Institute and.,Departments of Cellular and Physiological Sciences
| | - Parisa Asghari
- From the Cardiovascular Research Group, Life Sciences Institute and.,Departments of Cellular and Physiological Sciences
| | - Razvan F Albu
- Biochemistry and Molecular Biology, and.,the Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T 1Z4
| | - Jun Han
- the University of Victoria-Genome British Columbia Proteomics Centre, Victoria, British Columbia V8Z 7X8, and
| | - Donald McAfee
- From the Cardiovascular Research Group, Life Sciences Institute and.,Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3
| | - Marc Pourrier
- From the Cardiovascular Research Group, Life Sciences Institute and.,Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3
| | - Nichollas E Scott
- Biochemistry and Molecular Biology, and.,the Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T 1Z4
| | - Lubos Bohunek
- the Department of Pathology and Laboratory Medicine, University of British Columbia and the Centre for Heart and Lung Innovation, St. Paul's Hospital, Vancouver, British Columbia V6Z 1Y6
| | | | - S R Wayne Chen
- the Libin Cardiovascular Institute of Alberta, Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 2T9, Canada
| | - David Fedida
- From the Cardiovascular Research Group, Life Sciences Institute and.,Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3
| | | | - Christoph H Borchers
- the University of Victoria-Genome British Columbia Proteomics Centre, Victoria, British Columbia V8Z 7X8, and
| | - Leonard J Foster
- Biochemistry and Molecular Biology, and.,the Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T 1Z4
| | - Thibault Mayor
- Biochemistry and Molecular Biology, and.,the Michael Smith Laboratories, University of British Columbia, Vancouver, British Columbia V6T 1Z4
| | - Edwin D W Moore
- From the Cardiovascular Research Group, Life Sciences Institute and.,Departments of Cellular and Physiological Sciences
| | - Michael F Allard
- From the Cardiovascular Research Group, Life Sciences Institute and.,the Department of Pathology and Laboratory Medicine, University of British Columbia and the Centre for Heart and Lung Innovation, St. Paul's Hospital, Vancouver, British Columbia V6Z 1Y6
| | - James D Johnson
- From the Cardiovascular Research Group, Life Sciences Institute and .,Departments of Cellular and Physiological Sciences
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12
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Szabat M, Page MM, Panzhinskiy E, Skovsø S, Mojibian M, Fernandez-Tajes J, Bruin JE, Bround MJ, Lee JTC, Xu EE, Taghizadeh F, O'Dwyer S, van de Bunt M, Moon KM, Sinha S, Han J, Fan Y, Lynn FC, Trucco M, Borchers CH, Foster LJ, Nislow C, Kieffer TJ, Johnson JD. Reduced Insulin Production Relieves Endoplasmic Reticulum Stress and Induces β Cell Proliferation. Cell Metab 2016; 23:179-93. [PMID: 26626461 DOI: 10.1016/j.cmet.2015.10.016] [Citation(s) in RCA: 132] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 09/13/2015] [Accepted: 10/25/2015] [Indexed: 11/25/2022]
Abstract
Pancreatic β cells are mostly post-mitotic, but it is unclear what locks them in this state. Perturbations including uncontrolled hyperglycemia can drive β cells into more pliable states with reduced cellular insulin levels, increased β cell proliferation, and hormone mis-expression, but it is unknown whether reduced insulin production itself plays a role. Here, we define the effects of ∼50% reduced insulin production in Ins1(-/-):Ins2(f/f):Pdx1Cre(ERT):mTmG mice prior to robust hyperglycemia. Transcriptome, proteome, and network analysis revealed alleviation of chronic endoplasmic reticulum (ER) stress, indicated by reduced Ddit3, Trib3, and Atf4 expression; reduced Xbp1 splicing; and reduced phospho-eIF2α. This state was associated with hyper-phosphorylation of Akt, which is negatively regulated by Trib3, and with cyclinD1 upregulation. Remarkably, β cell proliferation was increased 2-fold after reduced insulin production independently of hyperglycemia. Eventually, recombined cells mis-expressed glucagon in the hyperglycemic state. We conclude that the normally high rate of insulin production suppresses β cell proliferation in a cell-autonomous manner.
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Affiliation(s)
- Marta Szabat
- Department of Cellular and Physiological Sciences, Diabetes Research Group, Life Sciences Institute, University of British Columbia, BC V6T1Z3, Canada
| | - Melissa M Page
- Department of Cellular and Physiological Sciences, Diabetes Research Group, Life Sciences Institute, University of British Columbia, BC V6T1Z3, Canada
| | - Evgeniy Panzhinskiy
- Department of Cellular and Physiological Sciences, Diabetes Research Group, Life Sciences Institute, University of British Columbia, BC V6T1Z3, Canada
| | - Søs Skovsø
- Department of Cellular and Physiological Sciences, Diabetes Research Group, Life Sciences Institute, University of British Columbia, BC V6T1Z3, Canada
| | - Majid Mojibian
- Department of Cellular and Physiological Sciences, Diabetes Research Group, Life Sciences Institute, University of British Columbia, BC V6T1Z3, Canada
| | - Juan Fernandez-Tajes
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Jennifer E Bruin
- Department of Cellular and Physiological Sciences, Diabetes Research Group, Life Sciences Institute, University of British Columbia, BC V6T1Z3, Canada
| | - Michael J Bround
- Department of Cellular and Physiological Sciences, Diabetes Research Group, Life Sciences Institute, University of British Columbia, BC V6T1Z3, Canada
| | - Jason T C Lee
- Department of Cellular and Physiological Sciences, Diabetes Research Group, Life Sciences Institute, University of British Columbia, BC V6T1Z3, Canada
| | - Eric E Xu
- Child and Family Research Institute, University of British Columbia, BC V5Z 4H4, Canada
| | - Farnaz Taghizadeh
- Department of Cellular and Physiological Sciences, Diabetes Research Group, Life Sciences Institute, University of British Columbia, BC V6T1Z3, Canada
| | - Shannon O'Dwyer
- Department of Cellular and Physiological Sciences, Diabetes Research Group, Life Sciences Institute, University of British Columbia, BC V6T1Z3, Canada
| | - Martijn van de Bunt
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Kyung-Mee Moon
- Centre for High-Throughput Biology, University of British Columbia, BC V6T 1Z3, Canada
| | - Sunita Sinha
- Faculty of Pharmaceutical Sciences, University of British Columbia, BC V6T 1Z3, Canada
| | - Jun Han
- UVic-Genome BC Proteomics Centre, University of Victoria, BC V8Z 7X8, Canada
| | - Yong Fan
- Institute of Cellular Therapeutics, Allegheny Health Network, Pittsburgh, PA 15212-4772, USA
| | - Francis C Lynn
- Child and Family Research Institute, University of British Columbia, BC V5Z 4H4, Canada
| | - Massimo Trucco
- Institute of Cellular Therapeutics, Allegheny Health Network, Pittsburgh, PA 15212-4772, USA
| | | | - Leonard J Foster
- Centre for High-Throughput Biology, University of British Columbia, BC V6T 1Z3, Canada
| | - Corey Nislow
- Faculty of Pharmaceutical Sciences, University of British Columbia, BC V6T 1Z3, Canada
| | - Timothy J Kieffer
- Department of Cellular and Physiological Sciences, Diabetes Research Group, Life Sciences Institute, University of British Columbia, BC V6T1Z3, Canada
| | - James D Johnson
- Department of Cellular and Physiological Sciences, Diabetes Research Group, Life Sciences Institute, University of British Columbia, BC V6T1Z3, Canada.
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13
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Zhang D, Wan A, Chiu APL, Wang Y, Wang F, Neumaier K, Lal N, Bround MJ, Johnson JD, Vlodavsky I, Rodrigues B. Hyperglycemia-induced secretion of endothelial heparanase stimulates a vascular endothelial growth factor autocrine network in cardiomyocytes that promotes recruitment of lipoprotein lipase. Arterioscler Thromb Vasc Biol 2013; 33:2830-8. [PMID: 24115032 DOI: 10.1161/atvbaha.113.302222] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
OBJECTIVE During diabetes mellitus, coronary lipoprotein lipase increases to promote the predominant use of fatty acids. We have reported that high glucose stimulates active heparanase secretion from endothelial cells to cleave cardiomyocyte heparan sulfate and release bound lipoprotein lipase for transfer to the vascular lumen. In the current study, we examined whether heparanase also has a function to release cardiomyocyte vascular endothelial growth factor (VEGF), and whether this growth factor influences cardiomyocyte fatty acid delivery in an autocrine manner. APPROACH AND RESULTS Acute, reversible hyperglycemia was induced in rats, and a modified Langendorff heart perfusion was used to separate the coronary perfusate from the interstitial effluent. Coronary artery endothelial cells were exposed to high glucose to generate conditioned medium, and VEGF release from isolated cardiomyocytes was tested using endothelial cell conditioned medium or purified active and latent heparanase. Autocrine signaling of myocyte-derived VEGF on cardiac metabolism was studied. High glucose promoted latent and active heparanase secretion into endothelial cell conditioned medium, an effective stimulus for releasing cardiomyocyte VEGF. Intriguingly, latent heparanase was more efficient than active heparanase in releasing VEGF from a unique cell surface pool. VEGF augmented cardiomyocyte intracellular calcium and AMP-activated protein kinase phosphorylation and increased heparin-releasable lipoprotein lipase. CONCLUSIONS Our data suggest that the heparanase-lipoprotein lipase-VEGF axis amplifies fatty acid delivery, a rapid and adaptive mechanism that is geared to overcome the loss of glucose consumption by the diabetic heart. If prolonged, the resultant lipotoxicity could lead to cardiovascular disease in humans.
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Affiliation(s)
- Dahai Zhang
- From the Faculty of Pharmaceutical Sciences (D.Z., A.W., A.P.-L.C., Y.W., F.W., K.N., N.L., B.R.), and Department of Cellular and Physiological Sciences (M.J.B., J.D.J.), University of British Columbia, Canada; and Rappaport Faculty of Medicine, Technion Israel Institute of Technology, Israel (I.V.)
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14
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Bround MJ, Wambolt R, Bohunek L, Allard MF, Johnson JD. Inducible, Heterozygous Ryr2 Knockout Mice Reveal a Key Role for Sr Ca2+ Release in Cardiac Metabolism. Can J Cardiol 2013. [DOI: 10.1016/j.cjca.2013.07.156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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15
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Bround MJ, Wambolt R, Luciani DS, Kulpa JE, Rodrigues B, Brownsey RW, Allard MF, Johnson JD. Cardiomyocyte ATP production, metabolic flexibility, and survival require calcium flux through cardiac ryanodine receptors in vivo. J Biol Chem 2013; 288:18975-86. [PMID: 23678000 DOI: 10.1074/jbc.m112.427062] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Ca(2+) fluxes between adjacent organelles are thought to control many cellular processes, including metabolism and cell survival. In vitro evidence has been presented that constitutive Ca(2+) flux from intracellular stores into mitochondria is required for basal cellular metabolism, but these observations have not been made in vivo. We report that controlled in vivo depletion of cardiac RYR2, using a conditional gene knock-out strategy (cRyr2KO mice), is sufficient to reduce mitochondrial Ca(2+) and oxidative metabolism, and to establish a pseudohypoxic state with increased autophagy. Dramatic metabolic reprogramming was evident at the transcriptional level via Sirt1/Foxo1/Pgc1α, Atf3, and Klf15 gene networks. Ryr2 loss also induced a non-apoptotic form of programmed cell death associated with increased calpain-10 but not caspase-3 activation or endoplasmic reticulum stress. Remarkably, cRyr2KO mice rapidly exhibited many of the structural, metabolic, and molecular characteristics of heart failure at a time when RYR2 protein was reduced 50%, a similar degree to that which has been reported in heart failure. RYR2-mediated Ca(2+) fluxes are therefore proximal controllers of mitochondrial Ca(2+), ATP levels, and a cascade of transcription factors controlling metabolism and survival.
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Affiliation(s)
- Michael J Bround
- Cardiovascular Research Group, Life Sciences Institute, University of British Columbia, Vancouver V6T 1Z3, Canada
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16
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Bround MJ, Asghari P, Wambolt R, Bohunek L, Luciani DS, Taghizadeh F, Kulpa JE, Boheler KR, Rodrigues B, Brownsey RW, Moore ED, Allard MF, Johnson JD. Acute Cardiac Ryanodine Receptor Loss-of-Function Leads to Cardiomyopathy and Metabolic Dysfunction: Implications for Diabetes Complications. Can J Diabetes 2012. [DOI: 10.1016/j.jcjd.2012.07.379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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17
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Bround MJ, Asghari P, Wambolt RB, Bohunek L, Smits C, Philit M, Kieffer TJ, Lakatta EG, Boheler KR, Moore EDW, Allard MF, Johnson JD. Cardiac ryanodine receptors control heart rate and rhythmicity in adult mice. Cardiovasc Res 2012; 96:372-80. [PMID: 22869620 DOI: 10.1093/cvr/cvs260] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
AIMS The molecular mechanisms controlling heart function and rhythmicity are incompletely understood. While it is widely accepted that the type 2 ryanodine receptor (Ryr2) is the major Ca(2+) release channel in excitation-contraction coupling, the role of these channels in setting a consistent beating rate remains controversial. Gain-of-function RYR2 mutations in humans and genetically engineered mouse models are known to cause Ca(2+) leak, arrhythmias, and sudden cardiac death. Embryonic stem-cell derived cardiomyocytes lacking Ryr2 display slower beating rates, but no supporting in vivo evidence has been presented. The aim of the present study was to test the hypothesis that RYR2 loss-of-function would reduce heart rate and rhythmicity in vivo. METHODS AND RESULTS We generated inducible, tissue-specific Ryr2 knockout mice with acute ∼50% loss of RYR2 protein in the heart but not in other tissues. Echocardiography, working heart perfusion, and in vivo ECG telemetry demonstrated that deletion of Ryr2 was sufficient to cause bradycardia and arrhythmia. Our results also show that cardiac Ryr2 knockout mice exhibit functional and structural hallmarks of heart failure, including sudden cardiac death. CONCLUSION These results illustrate that the RYR2 channel plays an essential role in pacing heart rate. Moreover, we find that RYR2 loss-of-function can lead to fatal arrhythmias typically associated with gain-of-function mutations. Given that RYR2 levels can be reduced in pathological conditions, including heart failure and diabetic cardiomyopathy, we predict that RYR2 loss contributes to disease-associated bradycardia, arrhythmia, and sudden death.
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Affiliation(s)
- Michael J Bround
- Cardiovascular Research Group, Life Sciences Institute, University of British Columbia, 5358 Life Sciences Building, 2350 Health Sciences Mall, Vancouver, BC, Canada V6T 1Z3
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18
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Johnson JD, Bround MJ, White SA, Luciani DS. Nanospaces between endoplasmic reticulum and mitochondria as control centres of pancreatic β-cell metabolism and survival. Protoplasma 2012; 249 Suppl 1:S49-S58. [PMID: 22105567 DOI: 10.1007/s00709-011-0349-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 11/07/2011] [Indexed: 05/31/2023]
Abstract
Nanometre-scale spaces between organelles represent focused nodes for signal transduction and the control of cellular decisions. The endoplasmic reticulum (ER) and the mitochondria form dynamic quasi-synaptic interaction nanodomains in all cell types examined, but the functional role of these junctions in cellular metabolism and cell survival remains to be fully understood. In this paper, we review recent evidence that ER Ca(2+) channels, such as the RyR and IP(3)R, can signal specifically across this nanodomain to the adjacent mitochondria to pace basal metabolism, with focus on the pancreatic β-cell. Blocking these signals in the basal state leads to a form of programmed cell death associated with reduced ATP and the induction of calpain-10 and hypoxia-inducible factors. On the other hand, the hyperactivity of this signalling domain plays a deleterious role during classical forms of apoptosis. Thus, the nanospace between ER and mitochondria represents a critical rheostat controlling both metabolism and programmed cell death. Many aspects of the mechanisms underlying this control system remain to be uncovered, and new nanotechnologies are required understand these domains at a molecular level.
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Affiliation(s)
- James D Johnson
- Department of Cellular and Physiological Sciences, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, Canada.
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