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Sabbir MG, Swanson M, Speth RC, Albensi BC. Hippocampal versus cortical deletion of cholinergic receptor muscarinic 1 in mice differentially affects post-translational modifications and supramolecular assembly of respiratory chain-associated proteins, mitochondrial ultrastructure, and respiration: implications in Alzheimer's disease. Front Cell Dev Biol 2023; 11:1179252. [PMID: 37293125 PMCID: PMC10246746 DOI: 10.3389/fcell.2023.1179252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 05/02/2023] [Indexed: 06/10/2023] Open
Abstract
Introduction: In a previous retrospective study using postmortem human brain tissues, we demonstrated that loss of Cholinergic Receptor Muscarinic 1 (CHRM1) in the temporal cortex of a subset of Alzheimer's patients was associated with poor survival, whereas similar loss in the hippocampus showed no such association. Mitochondrial dysfunction underlies Alzheimer's pathogenesis. Therefore, to investigate the mechanistic basis of our findings, we evaluated cortical mitochondrial phenotypes in Chrm1 knockout (Chrm1-/-) mice. Cortical Chrm1 loss resulted in reduced respiration, reduced supramolecular assembly of respiratory protein complexes, and caused mitochondrial ultrastructural abnormalities. These mouse-based findings mechanistically linked cortical CHRM1 loss with poor survival of Alzheimer's patients. However, evaluation of the effect of Chrm1 loss on mouse hippocampal mitochondrial characteristics is necessary to fully understand our retrospective human tissue-based observations. This is the objective of this study. Methods: Enriched hippocampal and cortical mitochondrial fractions (EHMFs/ECMFs, respectively) derived from wild-type and Chrm1-/- mice were used to measure respiration by quantifying real-time oxygen consumption, supramolecular assembly of oxidative phosphorylation (OXPHOS)-associated proteins by blue native polyacrylamide gel electrophoresis, post-translational modifications (PTMs) by isoelectric focusing (IEF), and mitochondrial ultrastructure by electron microscopy. Results: In contrast to our previous observations in Chrm1-/- ECMFs, EHMFs of Chrm1-/- mice significantly increased respiration with a concomitant increase in the supramolecular assembly of OXPHOS-associated proteins, specifically Atp5a and Uqcrc2, with no mitochondrial ultrastructural alterations. IEF of ECMFs and EHMFs from Chrm1-/- mice showed a decrease and an increase, respectively in a negatively charged (pH∼3) fraction of Atp5a relative to the wild-type mice, with a corresponding decrease or increase in the supramolecular assembly of Atp5a and respiration indicating a tissue-specific signaling effect. Discussion: Our findings indicate that loss of Chrm1 in the cortex causes structural, and physiological alterations to mitochondria that compromise neuronal function, whereas Chrm1 loss in the hippocampus may benefit neuronal function by enhancing mitochondrial function. This brain region-specific differential effect of Chrm1 deletion on mitochondrial function supports our human brain region-based findings and Chrm1-/- mouse behavioral phenotypes. Furthermore, our study indicates that Chrm1-mediated brain region-specific differential PTMs of Atp5a may alter complex-V supramolecular assembly which in turn regulates mitochondrial structure-function.
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Affiliation(s)
- Mohammad Golam Sabbir
- Division of Neurodegenerative Disorders, St. Boniface Hospital Albrechtsen Research Centre, Winnipeg, MB, Canada
- Alzo Biosciences Inc., San Diego, CA, United States
- Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Albrechtsen Research Centre, Winnipeg, MB, Canada
- Barry & Judy Silverman College of Pharmacy, Nova Southeastern University, Fort Lauderdale, FL, United States
| | - Mamiko Swanson
- Alzo Biosciences Inc., San Diego, CA, United States
- Barry & Judy Silverman College of Pharmacy, Nova Southeastern University, Fort Lauderdale, FL, United States
| | - Robert C. Speth
- Barry & Judy Silverman College of Pharmacy, Nova Southeastern University, Fort Lauderdale, FL, United States
- Department of Pharmacology and Physiology, School of Medicine, Georgetown University, Washington, DC, United States
| | - Benedict C. Albensi
- Division of Neurodegenerative Disorders, St. Boniface Hospital Albrechtsen Research Centre, Winnipeg, MB, Canada
- Barry & Judy Silverman College of Pharmacy, Nova Southeastern University, Fort Lauderdale, FL, United States
- Department of Pharmacology and Therapeutics, University of Manitoba, Winnipeg, MB, Canada
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Hutchinson AJ, Duffy BM, Staples JF. Hibernation is super complex: distribution, dynamics, and stability of electron transport system supercomplexes in Ictidomys tridecemlineatus. Am J Physiol Regul Integr Comp Physiol 2022; 323:R28-R42. [PMID: 35470710 DOI: 10.1152/ajpregu.00008.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Complexes of the electron transport system can associate with each other to form supercomplexes (SCs) within mitochondrial membranes, perhaps increasing respiratory capacity or reducing reactive oxygen species production. In this study, we determined the abundance, composition, and stability of SCs in a mammalian hibernator, in which both whole-animal and mitochondria metabolism change greatly throughout winter. We isolated mitochondria from thirteen-lined ground squirrels (Ictidomys tridecemlineatus) in different hibernation states, as well as from rats (Rattus norvegicus). We extracted mitochondrial proteins using two non-ionic detergents of different strengths, and quantified SC abundance using two-dimensional gel electrophoresis and immunoblotting. Rat heart and liver had fewer SCs than ground squirrels. Within ground squirrels, SCs are dynamic, changing among hibernation states within a matter of hours. In brown adipose tissue, Complex III composition in different SCs differed between the torpid and interbout euthermic phase of a hibernation bout. In heart and liver, complex III composition changed between winter and summer. We also evaluated the stability of liver SCs using a stronger detergent and found that the stability of SCs differed: torpor SCs were more stable than the SCs of ground squirrels in other states and rats. This study is the first report of SC changes during hibernation, and the first to demonstrate their dynamics on a short timescale.
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Affiliation(s)
| | - Brynne Morgan Duffy
- Department of biology, the University of Western Ontario, London, Ontario, Canada
| | - James F Staples
- Department of biology, the University of Western Ontario, London, Ontario, Canada
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3
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Ordered Clusters of the Complete Oxidative Phosphorylation System in Cardiac Mitochondria. Int J Mol Sci 2021; 22:ijms22031462. [PMID: 33540542 PMCID: PMC7867189 DOI: 10.3390/ijms22031462] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 01/26/2021] [Accepted: 01/30/2021] [Indexed: 01/10/2023] Open
Abstract
The existence of a complete oxidative phosphorylation system (OXPHOS) supercomplex including both electron transport system and ATP synthases has long been assumed based on functional evidence. However, no structural confirmation of the docking between ATP synthase and proton pumps has been obtained. In this study, cryo-electron tomography was used to reveal the supramolecular architecture of the rat heart mitochondria cristae during ATP synthesis. Respirasome and ATP synthase structure in situ were determined using subtomogram averaging. The obtained reconstructions of the inner mitochondrial membrane demonstrated that rows of respiratory chain supercomplexes can dock with rows of ATP synthases forming oligomeric ordered clusters. These ordered clusters indicate a new type of OXPHOS structural organization. It should ensure the quickness, efficiency, and damage resistance of OXPHOS, providing a direct proton transfer from pumps to ATP synthase along the lateral pH gradient without energy dissipation.
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Alternative assembly of respiratory complex II connects energy stress to metabolic checkpoints. Nat Commun 2018; 9:2221. [PMID: 29880867 PMCID: PMC5992162 DOI: 10.1038/s41467-018-04603-z] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2017] [Accepted: 05/07/2018] [Indexed: 01/07/2023] Open
Abstract
Cell growth and survival depend on a delicate balance between energy production and synthesis of metabolites. Here, we provide evidence that an alternative mitochondrial complex II (CII) assembly, designated as CIIlow, serves as a checkpoint for metabolite biosynthesis under bioenergetic stress, with cells suppressing their energy utilization by modulating DNA synthesis and cell cycle progression. Depletion of CIIlow leads to an imbalance in energy utilization and metabolite synthesis, as evidenced by recovery of the de novo pyrimidine pathway and unlocking cell cycle arrest from the S-phase. In vitro experiments are further corroborated by analysis of paraganglioma tissues from patients with sporadic, SDHA and SDHB mutations. These findings suggest that CIIlow is a core complex inside mitochondria that provides homeostatic control of cellular metabolism depending on the availability of energy. Mitochondrial complex II is normally composed of four subunits. Here the authors show that bioenergetic stress conditions give rise to a partially assembled variant of complex II, which shifts the anabolic pathways to less energy demanding processes.
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Arachchige D, Margaret Harris M, Coon Z, Carlsen J, Holub JM. Role of single disulfide linkages in the folding and activity of scyllatoxin-based BH3 domain mimetics. J Pept Sci 2017; 23:367-373. [PMID: 28326661 DOI: 10.1002/psc.2999] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 03/06/2017] [Accepted: 03/07/2017] [Indexed: 12/18/2022]
Abstract
Anti-apoptotic Bcl-2 proteins are implicated in pathogenic cell survival and have attracted considerable interest as therapeutic targets. We recently developed a class of synthetic peptide based on scyllatoxin (ScTx) designed to mimic the helical BH3 interaction domain of the pro-apoptotic Bcl-2 protein Bax. In this communication, the contribution of single disulfides in the folding and function of ScTx-Bax peptides was investigated. We synthesized five ScTx-Bax variants, each presenting a different combination of native disulfide linkage and evaluated their ability to directly bind Bcl-2 in vitro. It was determined that the position of the disulfide linkage had significant implications on the structure and function of ScTx-Bax peptides. This study underscores the importance of structural dynamics in BH3:Bcl-2 interactions and further validates ScTx-based ligands as potential modulators of anti-apoptotic Bcl-2 function. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.
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Affiliation(s)
- Danushka Arachchige
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH, 45701, USA
| | - M Margaret Harris
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH, 45701, USA
| | - Zachary Coon
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH, 45701, USA
| | - Jacob Carlsen
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH, 45701, USA
| | - Justin M Holub
- Department of Chemistry and Biochemistry, Ohio University, Athens, OH, 45701, USA.,Edison Biotechnology Institute, Ohio University, Athens, OH, 45701, USA.,Molecular and Cellular Biology Program, Ohio University, Athens, OH, 45701, USA
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Alkhaldi AAM, Martinek J, Panicucci B, Dardonville C, Zíková A, de Koning HP. Trypanocidal action of bisphosphonium salts through a mitochondrial target in bloodstream form Trypanosoma brucei. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2015; 6:23-34. [PMID: 27054061 PMCID: PMC4805778 DOI: 10.1016/j.ijpddr.2015.12.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Revised: 12/03/2015] [Accepted: 12/07/2015] [Indexed: 12/21/2022]
Abstract
Lipophilic bisphosphonium salts are among the most promising antiprotozoal leads currently under investigation. As part of their preclinical evaluation we here report on their mode of action against African trypanosomes, the etiological agents of sleeping sickness. The bisphosphonium compounds CD38 and AHI-9 exhibited rapid inhibition of Trypanosoma brucei growth, apparently the result of cell cycle arrest that blocked the replication of mitochondrial DNA, contained in the kinetoplast, thereby preventing the initiation of S-phase. Incubation with either compound led to a rapid reduction in mitochondrial membrane potential, and ATP levels decreased by approximately 50% within 1 h. Between 4 and 8 h, cellular calcium levels increased, consistent with release from the depolarized mitochondria. Within the mitochondria, the Succinate Dehydrogenase complex (SDH) was investigated as a target for bisphosphonium salts, but while its subunit 1 (SDH1) was present at low levels in the bloodstream form trypanosomes, the assembled complex was hardly detectable. RNAi knockdown of the SDH1 subunit produced no growth phenotype, either in bloodstream or in the procyclic (insect) forms and we conclude that in trypanosomes SDH is not the target for bisphosphonium salts. Instead, the compounds inhibited ATP production in intact mitochondria, as well as the purified F1 ATPase, to a level that was similar to 1 mM azide. Co-incubation with azide and bisphosphonium compounds did not inhibit ATPase activity more than either product alone. The results show that, in T. brucei, bisphosphonium compounds do not principally act on succinate dehydrogenase but on the mitochondrial FoF1 ATPase. Bisphosphonium salts display highly promising antiprotozoal activity. It has been reported that, in Leishmania, they act on the mitochondrial SDH complex. We show that in Trypanosoma brucei SDH is not essential and not the drug target. Instead, we present strong evidence that the F1F0 ATPase is the target.
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Affiliation(s)
- Abdulsalam A M Alkhaldi
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Jan Martinek
- Institute of Parasitology, Biology Centre & Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Brian Panicucci
- Institute of Parasitology, Biology Centre & Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | | | - Alena Zíková
- Institute of Parasitology, Biology Centre & Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic.
| | - Harry P de Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
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Mitochondrial ATP synthasome: Expression and structural interaction of its components. Biochem Biophys Res Commun 2015; 464:787-93. [PMID: 26168732 DOI: 10.1016/j.bbrc.2015.07.034] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2015] [Accepted: 07/07/2015] [Indexed: 11/20/2022]
Abstract
Mitochondrial ATP synthase, ADP/ATP translocase (ANT), and inorganic phosphate carrier (PiC) are supposed to form a supercomplex called ATP synthasome. Our protein and transcript analysis of rat tissues indicates that the expression of ANT and PiC is transcriptionally controlled in accordance with the biogenesis of ATP synthase. In contrast, the content of ANT and PiC is increased in ATP synthase deficient patients' fibroblasts, likely due to a post-transcriptional adaptive mechanism. A structural analysis of rat heart mitochondria by immunoprecipitation, blue native/SDS electrophoresis, immunodetection and MS analysis revealed the presence of ATP synthasome. However, the majority of PiC and especially ANT did not associate with ATP synthase, suggesting that most of PiC, ANT and ATP synthase exist as separate entities.
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Nesti C, Meschini MC, Meunier B, Sacchini M, Doccini S, Romano A, Petrillo S, Pezzini I, Seddiki N, Rubegni A, Piemonte F, Donati MA, Brasseur G, Santorelli FM. Additive effect of nuclear and mitochondrial mutations in a patient with mitochondrial encephalomyopathy. Hum Mol Genet 2015; 24:3248-56. [PMID: 25736212 DOI: 10.1093/hmg/ddv078] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 02/26/2015] [Indexed: 12/12/2022] Open
Abstract
We describe the case of a woman in whom combination of a mitochondrial (MT-CYB) and a nuclear (SDHB) mutation was associated with clinical and metabolic features suggestive of a mitochondrial disorder. The mutations impaired overall energy metabolism in the patient's muscle and fibroblasts and increased cellular susceptibility to oxidative stress. To clarify the contribution of each mutation to the phenotype, mutant yeast strains were generated. A significant defect in strains carrying the Sdh2 mutation, either alone or in combination with the cytb variant, was observed. Our data suggest that the SDHB mutation was causative of the mitochondrial disorder in our patient with a possible cumulative contribution of the MT-CYB variant. To our knowledge, this is the first association of bi-genomic variants in the mtDNA and in a nuclear gene encoding a subunit of complex II.
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Affiliation(s)
| | | | - Brigitte Meunier
- Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, Université Paris-Sud, 1 Avenue de la Terrasse, 91198 Gif-sur-Yvette, France
| | - Michele Sacchini
- Metabolic and Neuromuscular Unit, AOU Meyer Hospital, Florence, Italy
| | | | - Alessandro Romano
- Neuropathology Unit, Institute of Experimental Neurology and Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Sara Petrillo
- Unit for Neuromuscular and Neurodegenerative Diseases, "Bambino Gesù" Children's Hospital, Rome, Italy and
| | | | - Nadir Seddiki
- Laboratoire de Chimie Bactérienne, CNRS, 31 ch. J. Aiguier, 13402 Marseilles, France
| | - Anna Rubegni
- Molecular Medicine, IRCCS Stella Maris, Pisa, Italy
| | - Fiorella Piemonte
- Unit for Neuromuscular and Neurodegenerative Diseases, "Bambino Gesù" Children's Hospital, Rome, Italy and
| | - M Alice Donati
- Metabolic and Neuromuscular Unit, AOU Meyer Hospital, Florence, Italy
| | - Gael Brasseur
- Laboratoire de Chimie Bactérienne, CNRS, 31 ch. J. Aiguier, 13402 Marseilles, France
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