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Rahbani JF, Bunk J, Lagarde D, Samborska B, Roesler A, Xiao H, Shaw A, Kaiser Z, Braun JL, Geromella MS, Fajardo VA, Koza RA, Kazak L. Parallel control of cold-triggered adipocyte thermogenesis by UCP1 and CKB. Cell Metab 2024; 36:526-540.e7. [PMID: 38272036 DOI: 10.1016/j.cmet.2024.01.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2023] [Revised: 11/27/2023] [Accepted: 01/02/2024] [Indexed: 01/27/2024]
Abstract
That uncoupling protein 1 (UCP1) is the sole mediator of adipocyte thermogenesis is a conventional viewpoint that has primarily been inferred from the attenuation of the thermogenic output of mice genetically lacking Ucp1 from birth (germline Ucp1-/-). However, germline Ucp1-/- mice harbor secondary changes within brown adipose tissue. To mitigate these potentially confounding ancillary changes, we constructed mice with inducible adipocyte-selective Ucp1 disruption. We find that, although germline Ucp1-/- mice succumb to cold-induced hypothermia with complete penetrance, most mice with the inducible deletion of Ucp1 maintain homeothermy in the cold. However, inducible adipocyte-selective co-deletion of Ucp1 and creatine kinase b (Ckb, an effector of UCP1-independent thermogenesis) exacerbates cold intolerance. Following UCP1 deletion or UCP1/CKB co-deletion from mature adipocytes, moderate cold exposure triggers the regeneration of mature brown adipocytes that coordinately restore UCP1 and CKB expression. Our findings suggest that thermogenic adipocytes utilize non-paralogous protein redundancy-through UCP1 and CKB-to promote cold-induced energy dissipation.
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Affiliation(s)
- Janane F Rahbani
- Rosalind and Morris Goodman Cancer Institute, McGill University, Montreal, QC H3A 1A3, Canada
| | - Jakub Bunk
- Rosalind and Morris Goodman Cancer Institute, McGill University, Montreal, QC H3A 1A3, Canada; Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada
| | - Damien Lagarde
- Rosalind and Morris Goodman Cancer Institute, McGill University, Montreal, QC H3A 1A3, Canada
| | - Bozena Samborska
- Rosalind and Morris Goodman Cancer Institute, McGill University, Montreal, QC H3A 1A3, Canada
| | - Anna Roesler
- Rosalind and Morris Goodman Cancer Institute, McGill University, Montreal, QC H3A 1A3, Canada; Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada
| | - Haopeng Xiao
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Abhirup Shaw
- Rosalind and Morris Goodman Cancer Institute, McGill University, Montreal, QC H3A 1A3, Canada
| | - Zafir Kaiser
- Rosalind and Morris Goodman Cancer Institute, McGill University, Montreal, QC H3A 1A3, Canada; Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada
| | - Jessica L Braun
- Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Mia S Geromella
- Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Val A Fajardo
- Department of Kinesiology, Brock University, St. Catharines, ON L2S 3A1, Canada
| | - Robert A Koza
- MaineHealth Institute for Research, Scarborough, ME 04074, USA
| | - Lawrence Kazak
- Rosalind and Morris Goodman Cancer Institute, McGill University, Montreal, QC H3A 1A3, Canada; Department of Biochemistry, McGill University, Montreal, QC H3G 1Y6, Canada.
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2
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Urbani A, Prosdocimi E, Carrer A, Checchetto V, Szabò I. Mitochondrial Ion Channels of the Inner Membrane and Their Regulation in Cell Death Signaling. Front Cell Dev Biol 2021; 8:620081. [PMID: 33585458 PMCID: PMC7874202 DOI: 10.3389/fcell.2020.620081] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2020] [Accepted: 12/07/2020] [Indexed: 12/11/2022] Open
Abstract
Mitochondria are bioenergetic organelles with a plethora of fundamental functions ranging from metabolism and ATP production to modulation of signaling events leading to cell survival or cell death. Ion channels located in the outer and inner mitochondrial membranes critically control mitochondrial function and, as a consequence, also cell fate. Opening or closure of mitochondrial ion channels allow the fine-tuning of mitochondrial membrane potential, ROS production, and function of the respiratory chain complexes. In this review, we critically discuss the intracellular regulatory factors that affect channel activity in the inner membrane of mitochondria and, indirectly, contribute to cell death. These factors include various ligands, kinases, second messengers, and lipids. Comprehension of mitochondrial ion channels regulation in cell death pathways might reveal new therapeutic targets in mitochondria-linked pathologies like cancer, ischemia, reperfusion injury, and neurological disorders.
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Affiliation(s)
- Andrea Urbani
- Department of Biomedical Sciences, University of Padova, Padua, Italy
- Department of Biology, University of Padova, Padua, Italy
| | | | - Andrea Carrer
- Department of Biomedical Sciences, University of Padova, Padua, Italy
- Department of Biology, University of Padova, Padua, Italy
| | | | - Ildikò Szabò
- Department of Biology, University of Padova, Padua, Italy
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3
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Mitochondrial Uncoupling: A Key Controller of Biological Processes in Physiology and Diseases. Cells 2019; 8:cells8080795. [PMID: 31366145 PMCID: PMC6721602 DOI: 10.3390/cells8080795] [Citation(s) in RCA: 224] [Impact Index Per Article: 44.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 07/26/2019] [Accepted: 07/28/2019] [Indexed: 12/27/2022] Open
Abstract
Mitochondrial uncoupling can be defined as a dissociation between mitochondrial membrane potential generation and its use for mitochondria-dependent ATP synthesis. Although this process was originally considered a mitochondrial dysfunction, the identification of UCP-1 as an endogenous physiological uncoupling protein suggests that the process could be involved in many other biological processes. In this review, we first compare the mitochondrial uncoupling agents available in term of mechanistic and non-specific effects. Proteins regulating mitochondrial uncoupling, as well as chemical compounds with uncoupling properties are discussed. Second, we summarize the most recent findings linking mitochondrial uncoupling and other cellular or biological processes, such as bulk and specific autophagy, reactive oxygen species production, protein secretion, cell death, physical exercise, metabolic adaptations in adipose tissue, and cell signaling. Finally, we show how mitochondrial uncoupling could be used to treat several human diseases, such as obesity, cardiovascular diseases, or neurological disorders.
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Zhao RZ, Jiang S, Zhang L, Yu ZB. Mitochondrial electron transport chain, ROS generation and uncoupling (Review). Int J Mol Med 2019; 44:3-15. [PMID: 31115493 PMCID: PMC6559295 DOI: 10.3892/ijmm.2019.4188] [Citation(s) in RCA: 420] [Impact Index Per Article: 84.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2019] [Accepted: 04/19/2019] [Indexed: 12/18/2022] Open
Abstract
The mammalian mitochondrial electron transport chain (ETC) includes complexes I-IV, as well as the electron transporters ubiquinone and cytochrome c. There are two electron transport pathways in the ETC: Complex I/III/IV, with NADH as the substrate and complex II/III/IV, with succinic acid as the substrate. The electron flow is coupled with the generation of a proton gradient across the inner membrane and the energy accumulated in the proton gradient is used by complex V (ATP synthase) to produce ATP. The first part of this review briefly introduces the structure and function of complexes I-IV and ATP synthase, including the specific electron transfer process in each complex. Some electrons are directly transferred to O2 to generate reactive oxygen species (ROS) in the ETC. The second part of this review discusses the sites of ROS generation in each ETC complex, including sites IF and IQ in complex I, site IIF in complex II and site IIIQo in complex III, and the physiological and pathological regulation of ROS. As signaling molecules, ROS play an important role in cell proliferation, hypoxia adaptation and cell fate determination, but excessive ROS can cause irreversible cell damage and even cell death. The occurrence and development of a number of diseases are closely related to ROS overproduction. Finally, proton leak and uncoupling proteins (UCPS) are discussed. Proton leak consists of basal proton leak and induced proton leak. Induced proton leak is precisely regulated and induced by UCPs. A total of five UCPs (UCP1-5) have been identified in mammalian cells. UCP1 mainly plays a role in the maintenance of body temperature in a cold environment through non-shivering thermogenesis. The core role of UCP2-5 is to reduce oxidative stress under certain conditions, therefore exerting cytoprotective effects. All diseases involving oxidative stress are associated with UCPs.
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Affiliation(s)
- Ru-Zhou Zhao
- Department of Aerospace Physiology, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Shuai Jiang
- Department of Aerospace Physiology, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Lin Zhang
- Department of Aerospace Physiology, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Zhi-Bin Yu
- Department of Aerospace Physiology, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
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5
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Ježek P, Jabůrek M, Porter RK. Uncoupling mechanism and redox regulation of mitochondrial uncoupling protein 1 (UCP1). BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2019; 1860:259-269. [DOI: 10.1016/j.bbabio.2018.11.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Revised: 10/15/2018] [Accepted: 11/07/2018] [Indexed: 01/11/2023]
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Tarry-Adkins JL, Aiken CE, Ashmore TJ, Fernandez-Twinn DS, Chen JH, Ozanne SE. A suboptimal maternal diet combined with accelerated postnatal growth results in an altered aging profile in the thymus of male rats. FASEB J 2019; 33:239-253. [PMID: 29975569 PMCID: PMC6314471 DOI: 10.1096/fj.201701350rr] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Reduced fetal nutrition and rapid postnatal growth accelerates the aging phenotype in many organ systems; however, effects on the immune system are unclear. We addressed this by studying the thymus from a rat model of developmental programming. The recuperated group was generated by in utero protein restriction, followed by cross-fostering to control-fed mothers, and were then compared with controls. Fat infiltration and adipocyte size increased with age ( P < 0.001) and in recuperated thymi ( P < 0.05). Cortex/medulla ratio decreased with age ( P < 0.001) and decreased ( P < 0.05) in 12-mo recuperated thymi. Age-associated decreases in thymic-epithelial cell ( P < 0.01) and thymocyte markers ( P < 0.01) were observed in both groups and was decreased ( P < 0.05) in recuperated thymi. These data demonstrate effects of developmental programming upon thymic involution. The recuperated group had longer thymic telomeres than controls ( P < 0.001) at 22 d and at 3 mo, which was associated with increased expression of telomere-length maintenance molecules [telomerase RNA component ( Terc; P < 0.01), P23 ( P = 0.02), and Ku70 and Ku80 ( P < 0.01)]. By 12 mo, recuperated offspring had shorter thymic telomeres than controls had ( P < 0.001) and reduced DNA damage-response markers [( DNA-PKcs, Mre11 ( P < 0.01), Xrcc4 ( P = 0.02), and γ-H2ax ( P < 0.001], suggesting failure of earlier compensatory responses. Our results suggest that low birth weight with rapid postnatal growth results in premature thymic maturation, resulting in accelerated thymic aging. This could lead to increased age-associated vulnerability to infection.-Tarry-Adkins, J. L., Aiken, C. E., Ashmore, T. J., Fernandez-Twinn, D. S., Chen, J.-H., Ozanne, S. E. A suboptimal maternal diet combined with accelerated postnatal growth results in an altered aging profile in the thymus of male rats.
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Affiliation(s)
- Jane L. Tarry-Adkins
- University of Cambridge Metabolic Research Laboratories and Medical Research Council (MRC) Metabolic Diseases Unit, Wellcome Trust–MRC Institute of Metabolic Science, Addenbrooke’s Treatment Centre, Addenbrooke’s Hospital, Cambridge, United Kingdom,Correspondence: University of Cambridge Metabolic Research Laboratories and Medical Research Council (MRC) Metabolic Diseases Unit, Wellcome Trust–MRC Institute of Metabolic Science, Level 4, Box 289, Addenbrooke’s Treatment Centre, Addenbrooke’s Hospital, Hills Rd., Cambridge CB2 OQQ, United Kingdom. E-mail:
| | - Catherine E. Aiken
- University of Cambridge Metabolic Research Laboratories and Medical Research Council (MRC) Metabolic Diseases Unit, Wellcome Trust–MRC Institute of Metabolic Science, Addenbrooke’s Treatment Centre, Addenbrooke’s Hospital, Cambridge, United Kingdom
| | - Thomas J. Ashmore
- University of Cambridge Metabolic Research Laboratories and Medical Research Council (MRC) Metabolic Diseases Unit, Wellcome Trust–MRC Institute of Metabolic Science, Addenbrooke’s Treatment Centre, Addenbrooke’s Hospital, Cambridge, United Kingdom
| | - Denise S. Fernandez-Twinn
- University of Cambridge Metabolic Research Laboratories and Medical Research Council (MRC) Metabolic Diseases Unit, Wellcome Trust–MRC Institute of Metabolic Science, Addenbrooke’s Treatment Centre, Addenbrooke’s Hospital, Cambridge, United Kingdom
| | - Jian-Hua Chen
- University of Cambridge Metabolic Research Laboratories and Medical Research Council (MRC) Metabolic Diseases Unit, Wellcome Trust–MRC Institute of Metabolic Science, Addenbrooke’s Treatment Centre, Addenbrooke’s Hospital, Cambridge, United Kingdom
| | - Susan E. Ozanne
- University of Cambridge Metabolic Research Laboratories and Medical Research Council (MRC) Metabolic Diseases Unit, Wellcome Trust–MRC Institute of Metabolic Science, Addenbrooke’s Treatment Centre, Addenbrooke’s Hospital, Cambridge, United Kingdom
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7
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Previte DM, Piganelli JD. Reactive Oxygen Species and Their Implications on CD4 + T Cells in Type 1 Diabetes. Antioxid Redox Signal 2018; 29:1399-1414. [PMID: 28990401 DOI: 10.1089/ars.2017.7357] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Previous work has indicated that type 1 diabetes (T1D) pathology is highly driven by reactive oxygen species (ROS). One way in which ROS shape the autoimmune response demonstrated in T1D is by promoting CD4+ T cell activation and differentiation. As CD4+ T cells are a significant contributor to pancreatic β cell destruction in T1D, understanding how ROS impact their development, activation, and differentiation is critical. Recent Advances: CD4+ T cells themselves generate ROS via nicotinamide adenine dinucleotide phosphate (NADPH) oxidase expression and electron transport chain activity. Moreover, T cells can also be exposed to exogenous ROS generated by other immune cells (e.g., macrophages and dendritic cells) and β cells. Genetically modified animals and ROS inhibitors have demonstrated that ROS blockade during activation results in CD4+ T cell hyporesponsiveness and reduced diabetes incidence. Critical Issues and Future Directions: Although the majority of studies with regard to T1D and CD4+ T cells have been done to examine the influence of redox on CD4+ T cell activation, this is not the only circumstance in which a T cell can be impacted by redox. ROS and redox have also been shown to play roles in CD4+ T cell-related tolerogenic mechanisms, including thymic selection and regulatory T cell-mediated suppression. However, the effect of these mechanisms with respect to T1D pathogenesis remains elusive. Therefore, pursuing these avenues may provide valuable insight into the global role of ROS and redox in autoreactive CD4+ T cell formation and function.
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Affiliation(s)
- Dana M Previte
- Department of Surgery, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center , Pittsburgh, Pennsylvania
| | - Jon D Piganelli
- Department of Surgery, Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center , Pittsburgh, Pennsylvania
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8
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Ježek P, Holendová B, Garlid KD, Jabůrek M. Mitochondrial Uncoupling Proteins: Subtle Regulators of Cellular Redox Signaling. Antioxid Redox Signal 2018; 29:667-714. [PMID: 29351723 PMCID: PMC6071544 DOI: 10.1089/ars.2017.7225] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
SIGNIFICANCE Mitochondria are the energetic, metabolic, redox, and information signaling centers of the cell. Substrate pressure, mitochondrial network dynamics, and cristae morphology state are integrated by the protonmotive force Δp or its potential component, ΔΨ, which are attenuated by proton backflux into the matrix, termed uncoupling. The mitochondrial uncoupling proteins (UCP1-5) play an eminent role in the regulation of each of the mentioned aspects, being involved in numerous physiological events including redox signaling. Recent Advances: UCP2 structure, including purine nucleotide and fatty acid (FA) binding sites, strongly support the FA cycling mechanism: UCP2 expels FA anions, whereas uncoupling is achieved by the membrane backflux of protonated FA. Nascent FAs, cleaved by phospholipases, are preferential. The resulting Δp dissipation decreases superoxide formation dependent on Δp. UCP-mediated antioxidant protection and its impairment are expected to play a major role in cell physiology and pathology. Moreover, UCP2-mediated aspartate, oxaloacetate, and malate antiport with phosphate is expected to alter metabolism of cancer cells. CRITICAL ISSUES A wide range of UCP antioxidant effects and participations in redox signaling have been reported; however, mechanisms of UCP activation are still debated. Switching off/on the UCP2 protonophoretic function might serve as redox signaling either by employing/releasing the extra capacity of cell antioxidant systems or by directly increasing/decreasing mitochondrial superoxide sources. Rapid UCP2 degradation, FA levels, elevation of purine nucleotides, decreased Mg2+, or increased pyruvate accumulation may initiate UCP-mediated redox signaling. FUTURE DIRECTIONS Issues such as UCP2 participation in glucose sensing, neuronal (synaptic) function, and immune cell activation should be elucidated. Antioxid. Redox Signal. 29, 667-714.
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Affiliation(s)
- Petr Ježek
- 1 Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences , Prague, Czech Republic
| | - Blanka Holendová
- 1 Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences , Prague, Czech Republic
| | - Keith D Garlid
- 2 UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA , Los Angeles, California
| | - Martin Jabůrek
- 1 Department of Mitochondrial Physiology, Institute of Physiology of the Czech Academy of Sciences , Prague, Czech Republic
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9
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The conserved regulation of mitochondrial uncoupling proteins: From unicellular eukaryotes to mammals. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2016; 1858:21-33. [PMID: 27751905 DOI: 10.1016/j.bbabio.2016.10.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 09/29/2016] [Accepted: 10/13/2016] [Indexed: 12/19/2022]
Abstract
Uncoupling proteins (UCPs) belong to the mitochondrial anion carrier protein family and mediate regulated proton leak across the inner mitochondrial membrane. Free fatty acids, aldehydes such as hydroxynonenal, and retinoids activate UCPs. However, there are some controversies about the effective action of retinoids and aldehydes alone; thus, only free fatty acids are commonly accepted positive effectors of UCPs. Purine nucleotides such as GTP inhibit UCP-mediated mitochondrial proton leak. In turn, membranous coenzyme Q may play a role as a redox state-dependent metabolic sensor that modulates the complete activation/inhibition of UCPs. Such regulation has been observed for UCPs in microorganisms, plant and animal UCP1 homologues, and UCP1 in mammalian brown adipose tissue. The origin of UCPs is still under debate, but UCP homologues have been identified in all systematic groups of eukaryotes. Despite the differing levels of amino acid/DNA sequence similarities, functional studies in unicellular and multicellular organisms, from amoebae to mammals, suggest that the mechanistic regulation of UCP activity is evolutionarily well conserved. This review focuses on the regulatory feedback loops of UCPs involving free fatty acids, aldehydes, retinoids, purine nucleotides, and coenzyme Q (particularly its reduction level), which may derive from the early stages of evolution as UCP first emerged.
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10
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Clarke KJ, Carroll AM, O'Brien G, Porter RK. Detection of UCP1 protein and measurements of dependent GDP-sensitive proton leak in non-phosphorylating thymus mitochondria. Methods Mol Biol 2015; 1241:123-35. [PMID: 25308493 DOI: 10.1007/978-1-4939-1875-1_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Over several years we have provided evidence that uncoupling protein 1 (UCP1) is present in thymus mitochondria. We have demonstrated the conclusive evidence for the presence of UCP1 in thymus mitochondria and we have been able to demonstrate a GDP-sensitive UCP1-dependent proton leak in non-phosphorylating thymus mitochondria. In this chapter, we show how to detect UCP1 in mitochondria isolated from whole thymus using immunoblotting. We show how to measure GDP-sensitive UCP1-dependent oxygen consumption in non-phosphorylating thymus mitochondria and we show that increased reactive oxygen species production occurs on addition of GDP to non-phosphorylating thymus mitochondria. We conclude that reactive oxygen species production rate can be used as a surrogate for detecting UCP1 catalyzed proton leak activity in thymus mitochondria.
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Affiliation(s)
- Kieran J Clarke
- School of Biochemistry & Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, Pearse Street, Dublin 2, Ireland
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11
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Leamy LJ, Elo K, Nielsen MK, Thorn SR, Valdar W, Pomp D. Quantitative trait loci for energy balance traits in an advanced intercross line derived from mice divergently selected for heat loss. PeerJ 2014; 2:e392. [PMID: 24918027 PMCID: PMC4045330 DOI: 10.7717/peerj.392] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 05/01/2014] [Indexed: 11/28/2022] Open
Abstract
Obesity in human populations, currently a serious health concern, is considered to be the consequence of an energy imbalance in which more energy in calories is consumed than is expended. We used interval mapping techniques to investigate the genetic basis of a number of energy balance traits in an F11 advanced intercross population of mice created from an original intercross of lines selected for increased and decreased heat loss. We uncovered a total of 137 quantitative trait loci (QTLs) for these traits at 41 unique sites on 18 of the 20 chromosomes in the mouse genome, with X-linked QTLs being most prevalent. Two QTLs were found for the selection target of heat loss, one on distal chromosome 1 and another on proximal chromosome 2. The number of QTLs affecting the various traits generally was consistent with previous estimates of heritabilities in the same population, with the most found for two bone mineral traits and the least for feed intake and several body composition traits. QTLs were generally additive in their effects, and some, especially those affecting the body weight traits, were sex-specific. Pleiotropy was extensive within trait groups (body weights, adiposity and organ weight traits, bone traits) and especially between body composition traits adjusted and not adjusted for body weight at sacrifice. Nine QTLs were found for one or more of the adiposity traits, five of which appeared to be unique. The confidence intervals among all QTLs averaged 13.3 Mb, much smaller than usually observed in an F2 cross, and in some cases this allowed us to make reasonable inferences about candidate genes underlying these QTLs. This study combined QTL mapping with genetic parameter analysis in a large segregating population, and has advanced our understanding of the genetic architecture of complex traits related to obesity.
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Affiliation(s)
- Larry J Leamy
- Department of Biological Sciences, University of North Carolina at Charlotte, Charlotte, NC, USA
| | - Kari Elo
- Department of Animal Science, University of Nebraska, Lincoln, NE, USA
| | - Merlyn K Nielsen
- Department of Animal Science, University of Nebraska, Lincoln, NE, USA
| | - Stephanie R Thorn
- Department of Animal Science, University of Nebraska, Lincoln, NE, USA
| | - William Valdar
- Department of Genetics, University of North Carolina, Chapel Hill, NC, USA
| | - Daniel Pomp
- Department of Genetics, University of North Carolina, Chapel Hill, NC, USA
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Lack of activation of UCP1 in isolated brown adipose tissue mitochondria by glucose-O-ω-modified saturated fatty acids of various chain lengths. J Chem Biol 2013; 6:121-33. [PMID: 24432128 DOI: 10.1007/s12154-013-0093-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Accepted: 03/04/2013] [Indexed: 01/28/2023] Open
Abstract
We previously demonstrated that uncoupling protein 1 activity, as measured in isolated brown adipose tissue mitochondria (and as a native protein reconstituted into liposome membranes), was not activated by the non-flippable modified saturated fatty acid, glucose-O-ω-palmitate, whereas activity was stimulated by palmitate alone (40 nM free final concentration). In this study, we investigated whether fatty acid chain length had any bearing on the ability of glucose-O-ω-fatty acids to activate uncoupling protein 1. Glucose-O-ω-saturated fatty acids of various chain lengths were synthesized and tested for their potential to activate GDP-inhibited uncoupling protein 1-dependent oxygen consumption in brown adipose tissue mitochondria, and the results were compared with equivalent non-modified fatty acid controls. Here we demonstrate that laurate (12C), palmitate (16C) and stearate (18C) could activate GDP-inhibited uncoupling protein 1-dependent oxygen consumption in brown adipose tissue mitochondria, whereas there was no activation with glucose-O-ω-laurate (12C), glucose-O-ω-palmitate (16C), glucose-O-ω-stearate (18C), glucose-O-ω-arachidate (20C) or arachidate alone. We conclude that non-flippable fatty acids cannot activate uncoupling protein 1 irrespective of chain length. Our data further undermine the cofactor activation model of uncoupling protein 1 function but are compatible with the model that uncoupling protein 1 functions by flipping long-chain fatty acid anions.
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Clarke KJ, Porter RK. Uncoupling protein 1 dependent reactive oxygen species production by thymus mitochondria. Int J Biochem Cell Biol 2012; 45:81-9. [PMID: 23036787 DOI: 10.1016/j.biocel.2012.09.023] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Revised: 09/03/2012] [Accepted: 09/25/2012] [Indexed: 11/29/2022]
Abstract
We have previously shown that uncoupling protein 1 is present in thymus and has a role in T-cell development. As reactive oxygen species have been implicated in T-cell development, we set out to determine whether uncoupling protein 1 had the potential to regulate reactive oxygen species production in mitochondria isolated from thymus. This was achieved by inhibiting proton leak through uncoupling protein 1 using the purine nucleotide GDP and through ablation of uncoupling protein 1, measuring the amplex red sensitive reactive oxygen species production by mitochondria. In this work we demonstrate, for the first time, that uncoupling protein 1 has the potential to regulate reactive oxygen species production in thymus mitochondria. We also show that reverse electron transport is possible in thymus mitochondria respiring on succinate and glycerol-3-phosphate. The implications of this regulatory role for uncoupling protein 1 are discussed in the context of thymus function. This article is part of a Directed Issue entitled: Bioenergetic dysfunction, adaptation and therapy.
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Affiliation(s)
- Kieran J Clarke
- School of Biochemistry and Immunology, Trinity Institute of Biomedical Science, Trinity College Dublin, Ireland.
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14
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Porter RK. Studies on the function and regulation of mitochondrial uncoupling proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 748:171-84. [PMID: 22729858 DOI: 10.1007/978-1-4614-3573-0_7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
Mitochondrial uncoupling proteins are members of the SLC25 family of solute carriers. Models of mitochondrial transporter function predict that uncoupling proteins are solute carriers. Evidence in the literature suggests that uncoupling proteins can transport protons, fatty acid anions, chloride anions, and recently the dicarboxylate succinate. Studies have also demonstrated that UCPs can be covalently modified and in some instances this covalent modification is needed to affect uncoupling function. The current evidence from functional analyses of mammalian uncoupling proteins is summarized in this chapter.
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Affiliation(s)
- Richard K Porter
- School of Biochemistry and Immunology, Trinity College Dublin, Dublin 2, Ireland.
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Jastroch M, Hirschberg V, Klingenspor M. Functional characterization of UCP1 in mammalian HEK293 cells excludes mitochondrial uncoupling artefacts and reveals no contribution to basal proton leak. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:1660-70. [PMID: 22676960 DOI: 10.1016/j.bbabio.2012.05.014] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Revised: 05/22/2012] [Accepted: 05/28/2012] [Indexed: 02/02/2023]
Abstract
Mechanistic studies on uncoupling proteins (UCPs) not only are important to identify their cellular function but also are pivotal to identify potential drug targets to manipulate mitochondrial energy transduction. So far, functional and comparative studies of uncoupling proteins in their native environment are hampered by different mitochondrial, cellular and genetic backgrounds. Artificial systems such as yeast ectopically expressing UCPs or liposomes with reconstituted UCPs were employed to address crucial mechanistic questions but these systems also produced inconsistencies with results from native mitochondria. We here introduce a novel mammalian cell culture system (Human Embryonic Kidney 293 - HEK293) to study UCP1 function. Stably transfected HEK293 cell lines were derived that contain mouse UCP1 at concentrations comparable to tissue mitochondria. In this cell-based test system UCP1 displays native functional behaviour as it can be activated with fatty acids (palmitate) and inhibited with purine nucleotides guanosine-diphosphate (GDP). The catalytic centre activity of the UCP1 homodimer in HEK293 is comparable to activities in brown adipose tissue supporting functionality of UCP1. Importantly, at higher protein levels than in yeast mitochondria, UCP1 in HEK293 cell mitochondria is fully inhibitable and does not contribute to basal proton conductance, thereby emphasizing the requirement of UCP1 activation for therapeutic purposes. These findings and resulting analysis on UCP1 characteristics demonstrate that the mammalian HEK293 cell system is suitable for mechanistic and comparative functional studies on UCPs and provides a non-confounding mitochondrial, cellular and genetic background.
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Affiliation(s)
- Martin Jastroch
- Institute for Diabetes and Obesity, Helmholtz Zentrum Munich, Neuherberg, Germany.
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Clarke KJ, Adams AE, Manzke LH, Pearson TW, Borchers CH, Porter RK. A role for ubiquitinylation and the cytosolic proteasome in turnover of mitochondrial uncoupling protein 1 (UCP1). BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:1759-67. [PMID: 22531154 DOI: 10.1016/j.bbabio.2012.03.035] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/08/2012] [Revised: 03/23/2012] [Accepted: 03/29/2012] [Indexed: 11/19/2022]
Abstract
In this study we show that mitochondrial uncoupling protein 1 (UCP1) in brown adipose tissue (BAT) and thymus mitochondria can be ubiquitinylated and degraded by the cytosolic proteasome. Using a ubiquitin conjugating system, we show that UCP1 can be ubiquitinylated in vitro. We demonstrate that UCP1 is ubiquitinylated in vivo using isolated mitochondria from brown adipose tissue, thymus and whole brown adipocytes. Using an in vitro ubiquitin conjugating-proteasome degradation system, we show that the cytosolic proteasome can degrade UCP1 at a rate commensurate with the half-life of UCP1 (i.e. 30-72h in brown adipocytes and ~3h, in thymocytes). In addition, we demonstrate that the cytoplasmic proteasome is required for UCP1 degradation from mitochondria that the process is inhibited by the proteasome inhibitor MG132 and that dissipation of the mitochondrial membrane potential inhibits degradation of UCP1. There also appears to be a greater amount of ubiquitinylated UCP1 associated with BAT mitochondria from cold-acclimated animals. We have also identified (using immunoprecipitation coupled with mass spectrometry) ubiquitinylated proteins with molecular masses greater than 32kDa, as being UCP1. We conclude that there is a role for ubiquitinylation and the cytosolic proteasome in turnover of mitochondrial UCP1. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).
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Affiliation(s)
- Kieran J Clarke
- School of Biochemistry and Immunology, Trinity College Dublin, Dublin 2, Ireland
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Divakaruni AS, Brand MD. The regulation and physiology of mitochondrial proton leak. Physiology (Bethesda) 2011; 26:192-205. [PMID: 21670165 DOI: 10.1152/physiol.00046.2010] [Citation(s) in RCA: 279] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Mitochondria couple respiration to ATP synthesis through an electrochemical proton gradient. Proton leak across the inner membrane allows adjustment of the coupling efficiency. The aim of this review is threefold: 1) introduce the unfamiliar reader to proton leak and its physiological significance, 2) review the role and regulation of uncoupling proteins, and 3) outline the prospects of proton leak as an avenue to treat obesity, diabetes, and age-related disease.
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Affiliation(s)
- Ajit S Divakaruni
- Medical Research Council Mitochondrial Biology Unit, Wellcome Trust/MRC Building, Cambridge, United Kingdom
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Absence of mitochondrial uncoupling protein 3: effect on thymus and spleen in the fed and fasted mice. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1064-74. [PMID: 21689632 DOI: 10.1016/j.bbabio.2011.06.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Revised: 06/04/2011] [Accepted: 06/06/2011] [Indexed: 11/21/2022]
Abstract
Mitochondrial uncoupling protein 3 (UCP3) is constitutively expressed in mitochondria from thymus and spleen of mice, and confocal microscopy has been used to visualize UCP3 in situ in mouse thymocytes. UCP3 is present in mitochondria of thymus and spleen up to at least 16 weeks after birth, but levels decrease by a half in thymus and a fifth in spleen after three weeks, probably reflecting the suckling to weaning transition. UCP3 protein levels increase approximately 3-fold in thymus on starvation, but expression levels in spleen were unaffected by starvation. Lack of UCP3 had little effect on thymus mass or thymocyte number. However, lack of UCP3 affected spleen mass and splenocyte number (in the fasted state) and results in reduced CD4+ single positive cell numbers and reduced double negative cells in the thymus, but as a 2-fold increase in the proportion of CD4(+), CD8(+) and DP cells in spleen. Starvation attenuates these proportionate differences in the spleen. A lack of UCP3 had no apparent effect on basal oxygen consumption of thymocytes or splenocytes or on oxygen consumption due to mitochondrial proton leak. Splenocytes from UCP3 knock-out mice are also more resistant to apoptosis than those from wild-type mice. Overall we can conclude that UCP3 affects thymocyte and spleen cell profiles in the fed and fasted states.
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