1
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Jenkins BC, Neikirk K, Katti P, Claypool SM, Kirabo A, McReynolds MR, Hinton A. Mitochondria in disease: changes in shapes and dynamics. Trends Biochem Sci 2024; 49:346-360. [PMID: 38402097 PMCID: PMC10997448 DOI: 10.1016/j.tibs.2024.01.011] [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: 09/05/2023] [Revised: 01/14/2024] [Accepted: 01/26/2024] [Indexed: 02/26/2024]
Abstract
Mitochondrial structure often determines the function of these highly dynamic, multifunctional, eukaryotic organelles, which are essential for maintaining cellular health. The dynamic nature of mitochondria is apparent in descriptions of different mitochondrial shapes [e.g., donuts, megamitochondria (MGs), and nanotunnels] and crista dynamics. This review explores the significance of dynamic alterations in mitochondrial morphology and regulators of mitochondrial and cristae shape. We focus on studies across tissue types and also describe new microscopy techniques for detecting mitochondrial morphologies both in vivo and in vitro that can improve understanding of mitochondrial structure. We highlight the potential therapeutic benefits of regulating mitochondrial morphology and discuss prospective avenues to restore mitochondrial bioenergetics to manage diseases related to mitochondrial dysfunction.
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Affiliation(s)
- Brenita C Jenkins
- Department of Biochemistry and Molecular Biology, The Huck Institute of the Life Sciences, Pennsylvania State University, State College, PA 16801, USA
| | - Kit Neikirk
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA
| | - Prasanna Katti
- National Heart, Lung and Blood Institute, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA
| | - Steven M Claypool
- Department of Physiology, Mitochondrial Phospholipid Research Center, Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Annet Kirabo
- Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Vanderbilt Center for Immunobiology, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Vanderbilt Institute for Infection, Immunology and Inflammation, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Vanderbilt Institute for Global Health, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Melanie R McReynolds
- Department of Biochemistry and Molecular Biology, The Huck Institute of the Life Sciences, Pennsylvania State University, State College, PA 16801, USA.
| | - Antentor Hinton
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA.
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2
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Senoo N, Chinthapalli DK, Baile MG, Golla VK, Saha B, Ogunbona OB, Saba JA, Munteanu T, Valdez Y, Whited K, Chorev D, Alder NN, May ER, Robinson CV, Claypool SM. Conserved cardiolipin-mitochondrial ADP/ATP carrier interactions assume distinct structural and functional roles that are clinically relevant. bioRxiv 2023:2023.05.05.539595. [PMID: 37205478 PMCID: PMC10187269 DOI: 10.1101/2023.05.05.539595] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The mitochondrial phospholipid cardiolipin (CL) promotes bioenergetics via oxidative phosphorylation (OXPHOS). Three tightly bound CLs are evolutionarily conserved in the ADP/ATP carrier (AAC in yeast; adenine nucleotide translocator, ANT in mammals) which resides in the inner mitochondrial membrane and exchanges ADP and ATP to enable OXPHOS. Here, we investigated the role of these buried CLs in the carrier using yeast Aac2 as a model. We introduced negatively charged mutations into each CL-binding site of Aac2 to disrupt the CL interactions via electrostatic repulsion. While all mutations disturbing the CL-protein interaction destabilized Aac2 monomeric structure, transport activity was impaired in a pocket-specific manner. Finally, we determined that a disease-associated missense mutation in one CL-binding site in ANT1 compromised its structure and transport activity, resulting in OXPHOS defects. Our findings highlight the conserved significance of CL in AAC/ANT structure and function, directly tied to specific lipid-protein interactions.
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Affiliation(s)
- Nanami Senoo
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Mitochondrial Phospholipid Research Center, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Dinesh K. Chinthapalli
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, OX1 3QU, UK
- Kavli Institute for Nanoscience Discovery, Oxford, OX1 3QU, UK
| | - Matthew G. Baile
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Vinaya K. Golla
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA
| | - Bodhisattwa Saha
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, OX1 3QU, UK
| | - Oluwaseun B. Ogunbona
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - James A. Saba
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Teona Munteanu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Yllka Valdez
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Kevin Whited
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Dror Chorev
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, OX1 3QU, UK
| | - Nathan N. Alder
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA
| | - Eric R. May
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA
| | - Carol V. Robinson
- Physical and Theoretical Chemistry Laboratory, University of Oxford, Oxford, OX1 3QU, UK
- Kavli Institute for Nanoscience Discovery, Oxford, OX1 3QU, UK
| | - Steven M. Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Mitochondrial Phospholipid Research Center, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
- Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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3
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Makena MR, Ko M, Mekile AX, Senoo N, Dang DK, Warrington J, Buckhaults P, Talbot CC, Claypool SM, Rao R. Secretory pathway Ca 2+-ATPase SPCA2 regulates mitochondrial respiration and DNA damage response through store-independent calcium entry. Redox Biol 2022; 50:102240. [PMID: 35063802 PMCID: PMC8783100 DOI: 10.1016/j.redox.2022.102240] [Citation(s) in RCA: 2] [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] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Revised: 01/11/2022] [Accepted: 01/14/2022] [Indexed: 01/04/2023] Open
Abstract
A complex interplay between the extracellular space, cytoplasm and individual organelles modulates Ca2+ signaling to impact all aspects of cell fate and function. In recent years, the molecular machinery linking endoplasmic reticulum stores to plasma membrane Ca2+ entry has been defined. However, the mechanism and pathophysiological relevance of store-independent modes of Ca2+ entry remain poorly understood. Here, we describe how the secretory pathway Ca2+-ATPase SPCA2 promotes cell cycle progression and survival by activating store-independent Ca2+ entry through plasma membrane Orai1 channels in mammary epithelial cells. Silencing SPCA2 expression or briefly removing extracellular Ca2+ increased mitochondrial ROS production, DNA damage and activation of the ATM/ATR-p53 axis leading to G0/G1 phase cell cycle arrest and apoptosis. Consistent with these findings, SPCA2 knockdown confers redox stress and chemosensitivity to DNA damaging agents. Unexpectedly, SPCA2-mediated Ca2+ entry into mitochondria is required for optimal cellular respiration and the generation of mitochondrial membrane potential. In hormone receptor positive (ER+/PR+) breast cancer subtypes, SPCA2 levels are high and correlate with poor survival prognosis. We suggest that elevated SPCA2 expression could drive pro-survival and chemotherapy resistance in cancer cells, and drugs that target store-independent Ca2+ entry pathways may have therapeutic potential in treating cancer.
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Affiliation(s)
- Monish Ram Makena
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Myungjun Ko
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Allatah X Mekile
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Nanami Senoo
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | | | - John Warrington
- Department of Drug Discovery and Biomedical Sciences, College of Pharmacy, University of South Carolina, Columbia, SC, USA
| | - Phillip Buckhaults
- Department of Drug Discovery and Biomedical Sciences, College of Pharmacy, University of South Carolina, Columbia, SC, USA
| | - C Conover Talbot
- Institute for Basic Biomedical Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Rajini Rao
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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4
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Iovine JC, Claypool SM, Alder NN. Characterization of styrene-maleic acid copolymer membrane solubilization using reductionist and mitochondrial systems. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.478] [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: 11/02/2022] Open
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5
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Iovine JC, Claypool SM, Alder NN. Mitochondrial compartmentalization: emerging themes in structure and function. Trends Biochem Sci 2021; 46:902-917. [PMID: 34244035 PMCID: PMC11008732 DOI: 10.1016/j.tibs.2021.06.003] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [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: 03/01/2021] [Revised: 05/26/2021] [Accepted: 06/04/2021] [Indexed: 11/27/2022]
Abstract
Within cellular structures, compartmentalization is the concept of spatial segregation of macromolecules, metabolites, and biochemical pathways. Therefore, this concept bridges organellar structure and function. Mitochondria are morphologically complex, partitioned into several subcompartments by a topologically elaborate two-membrane system. They are also dynamically polymorphic, undergoing morphogenesis events with an extent and frequency that is only now being appreciated. Thus, mitochondrial compartmentalization is something that must be considered both spatially and temporally. Here, we review new developments in how mitochondrial structure is established and regulated, the factors that underpin the distribution of lipids and proteins, and how they spatially demarcate locations of myriad mitochondrial processes. Consistent with its pre-eminence, disturbed mitochondrial compartmentalization contributes to the dysfunction associated with heritable and aging-related diseases.
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Affiliation(s)
- Joseph C Iovine
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA
| | - Steven M Claypool
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Nathan N Alder
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA.
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6
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Elkes M, Andonovski M, Vidal D, Farago M, Modafferi R, Claypool SM, LeBlanc PJ. The Influence of Supplemental Dietary Linoleic Acid on Skeletal Muscle Contractile Function in a Rodent Model of Barth Syndrome. Front Physiol 2021; 12:731961. [PMID: 34489741 PMCID: PMC8416984 DOI: 10.3389/fphys.2021.731961] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 08/02/2021] [Indexed: 11/13/2022] Open
Abstract
Barth syndrome is a rare and incurable X-linked (male-specific) genetic disease that affects the protein tafazzin (Taz). Taz is an important enzyme responsible for synthesizing biologically relevant cardiolipin (for heart and skeletal muscle, cardiolipin rich in linoleic acid), a critical phospholipid of mitochondrial form and function. Mutations to Taz cause dysfunctional mitochondria, resulting in exercise intolerance due to skeletal muscle weakness. To date, there has been limited research on improving skeletal muscle function, with interventions focused on endurance and resistance exercise. Previous cell culture research has shown therapeutic potential for the addition of exogenous linoleic acid in improving Taz-deficient mitochondrial function but has not been examined in vivo. The purpose of this study was to examine the influence of supplemental dietary linoleic acid on skeletal muscle function in a rodent model of Barth syndrome, the inducible Taz knockdown (TazKD) mouse. One of the main findings was that TazKD soleus demonstrated an impaired contractile phenotype (slower force development and rates of relaxation) in vitro compared to their WT littermates. Interestingly, this impaired contractile phenotype seen in vitro did not translate to altered muscle function in vivo at the whole-body level. Also, supplemental linoleic acid attenuated, to some degree, in vitro impaired contractile phenotype in TazKD soleus, and these findings appear to be partially mediated by improvements in cardiolipin content and resulting mitochondrial supercomplex formation. Future research will further examine alternative mechanisms of dietary supplemental LA on improving skeletal muscle contractile dysfunction in TazKD mice.
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Affiliation(s)
- Mario Elkes
- Faculty of Applied Health Sciences, Center for Bone and Muscle Health, Brock University, St. Catharines, ON, Canada
| | - Martin Andonovski
- Faculty of Applied Health Sciences, Center for Bone and Muscle Health, Brock University, St. Catharines, ON, Canada
| | - Daislyn Vidal
- Faculty of Applied Health Sciences, Center for Bone and Muscle Health, Brock University, St. Catharines, ON, Canada
| | - Madison Farago
- Faculty of Applied Health Sciences, Center for Bone and Muscle Health, Brock University, St. Catharines, ON, Canada
| | - Ryan Modafferi
- Faculty of Applied Health Sciences, Center for Bone and Muscle Health, Brock University, St. Catharines, ON, Canada
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Paul J LeBlanc
- Faculty of Applied Health Sciences, Center for Bone and Muscle Health, Brock University, St. Catharines, ON, Canada
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7
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Maguire ARR, Crozier RWE, Hunter KD, Claypool SM, Fajardo VA, LeBlanc PJ, MacNeil AJ. Tafazzin Modulates Allergen-Induced Mast Cell Inflammatory Mediator Secretion. Immunohorizons 2021; 5:182-192. [PMID: 33895725 DOI: 10.4049/immunohorizons.2000040] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Accepted: 03/26/2021] [Indexed: 11/19/2022] Open
Abstract
Allergic inflammatory diseases are a steadily growing health concern. Mast cells, a driving force behind allergic pathologies, modulate metabolic pathways to carry out various functions following IgE-FcεRI-mediated activation. Tafazzin (TAZ) is a cardiolipin transacylase that functions to remodel, and thereby mature, cardiolipin, which is important for efficient energy production through oxidative phosphorylation. In this study, we aimed to evaluate the contribution of TAZ in IgE-mediated mast cell activation. Fetal liver-derived mast cells (FLMCs) were differentiated from mice with a doxycycline (dox)-inducible TAZ short hairpin RNA (shRNA) cassette (TAZ shRNA+/+) and littermate wild-types (WTs). TAZ knockdown in FLMCs following dox treatment was confirmed by Western blotting (99.1% by day 5), whereas flow cytometry confirmed FLMC phenotype (c-kit+ FcεRI+) and retention of receptor expression post-dox. Five-day dox-treated WT and TAZ shRNA+/+ FLMCs were activated via allergen-bound IgE cross-linking of FcεRI under stem cell factor potentiation. With dox, and in response to allergen, TAZ shRNA+/+ FLMCs displayed a 25% reduction in oxygen consumption and a significant 31% reduction in mast cell degranulation compared with dox-treated WT FLMCs. Secretion of TNF, CCL1, and CCL2 were significantly reduced, with CCL9 also impaired. Notably, gene expression was not impaired for any inflammatory mediator measured. Functionally, this suggests that TAZ is a contributor to mast cell degranulation and inflammatory mediator secretion. Given unimpacted induced gene expression for mediators measured, we propose that TAZ reduction impairs mast cell exocytosis mechanisms. We thus identify a potential new contributor to immunometabolism that enhances our understanding of mast cell signaling metabolic pathway interactions during allergic inflammation.
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Affiliation(s)
- Aindriu R R Maguire
- Department of Health Sciences, Cairns Family Health and Bioscience Research Complex, Brock University, St. Catharines, Niagara Region, St. Catharines, Ontario, Canada
| | - Robert W E Crozier
- Department of Health Sciences, Cairns Family Health and Bioscience Research Complex, Brock University, St. Catharines, Niagara Region, St. Catharines, Ontario, Canada
| | - Katie D Hunter
- Department of Health Sciences, Cairns Family Health and Bioscience Research Complex, Brock University, St. Catharines, Niagara Region, St. Catharines, Ontario, Canada
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD; and
| | - Val A Fajardo
- Department of Kinesiology, Cairns Family Health and Bioscience Research Complex, Brock University, Niagara Region, Ontario, Canada
| | - Paul J LeBlanc
- Department of Health Sciences, Cairns Family Health and Bioscience Research Complex, Brock University, St. Catharines, Niagara Region, St. Catharines, Ontario, Canada
| | - Adam J MacNeil
- Department of Health Sciences, Cairns Family Health and Bioscience Research Complex, Brock University, St. Catharines, Niagara Region, St. Catharines, Ontario, Canada;
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8
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Falabella M, Vernon HJ, Hanna MG, Claypool SM, Pitceathly RDS. Cardiolipin, Mitochondria, and Neurological Disease. Trends Endocrinol Metab 2021; 32:224-237. [PMID: 33640250 PMCID: PMC8277580 DOI: 10.1016/j.tem.2021.01.006] [Citation(s) in RCA: 84] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Revised: 01/26/2021] [Accepted: 01/27/2021] [Indexed: 02/07/2023]
Abstract
Over the past decade, it has become clear that lipid homeostasis is central to cellular metabolism. Lipids are particularly abundant in the central nervous system (CNS) where they modulate membrane fluidity, electric signal transduction, and synaptic stabilization. Abnormal lipid profiles reported in Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and traumatic brain injury (TBI), are further support for the importance of lipid metablism in the nervous system. Cardiolipin (CL), a mitochondria-exclusive phospholipid, has recently emerged as a focus of neurodegenerative disease research. Aberrant CL content, structure, and localization are linked to impaired neurogenesis and neuronal dysfunction, contributing to aging and the pathogenesis of several neurodegenerative diseases, such as AD and PD. Furthermore, the highly tissue-specific acyl chain composition of CL confers it significant potential as a biomarker to diagnose and monitor the progression in several neurological diseases. CL also represents a potential target for pharmacological strategies aimed at treating neurodegeneration. Given the equipoise that currently exists between CL metabolism, mitochondrial function, and neurological disease, we review the role of CL in nervous system physiology and monogenic and neurodegenerative disease pathophysiology, in addition to its potential application as a biomarker and pharmacological target.
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Affiliation(s)
- Micol Falabella
- Department of Neuromuscular Diseases, University College London Queen Square Institute of Neurology, London, UK
| | - Hilary J Vernon
- Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Michael G Hanna
- Department of Neuromuscular Diseases, University College London Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London, UK
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Robert D S Pitceathly
- Department of Neuromuscular Diseases, University College London Queen Square Institute of Neurology and The National Hospital for Neurology and Neurosurgery, London, UK.
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9
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Acoba MG, Senoo N, Claypool SM. Phospholipid ebb and flow makes mitochondria go. J Cell Biol 2021; 219:151918. [PMID: 32614384 PMCID: PMC7401802 DOI: 10.1083/jcb.202003131] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Revised: 05/28/2020] [Accepted: 06/02/2020] [Indexed: 01/19/2023] Open
Abstract
Mitochondria, so much more than just being energy factories, also have the capacity to synthesize macromolecules including phospholipids, particularly cardiolipin (CL) and phosphatidylethanolamine (PE). Phospholipids are vital constituents of mitochondrial membranes, impacting the plethora of functions performed by this organelle. Hence, the orchestrated movement of phospholipids to and from the mitochondrion is essential for cellular integrity. In this review, we capture recent advances in the field of mitochondrial phospholipid biosynthesis and trafficking, highlighting the significance of interorganellar communication, intramitochondrial contact sites, and lipid transfer proteins in maintaining membrane homeostasis. We then discuss the physiological functions of CL and PE, specifically how they associate with protein complexes in mitochondrial membranes to support bioenergetics and maintain mitochondrial architecture.
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Affiliation(s)
- Michelle Grace Acoba
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Nanami Senoo
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD
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10
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Acoba MG, Alpergin ESS, Renuse S, Fernández-Del-Río L, Lu YW, Khalimonchuk O, Clarke CF, Pandey A, Wolfgang MJ, Claypool SM. The mitochondrial carrier SFXN1 is critical for complex III integrity and cellular metabolism. Cell Rep 2021; 34:108869. [PMID: 33730581 PMCID: PMC8048093 DOI: 10.1016/j.celrep.2021.108869] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 01/18/2021] [Accepted: 02/24/2021] [Indexed: 12/13/2022] Open
Abstract
Mitochondrial carriers (MCs) mediate the passage of small molecules across the inner mitochondrial membrane (IMM), enabling regulated crosstalk between compartmentalized reactions. Despite MCs representing the largest family of solute carriers in mammals, most have not been subjected to a comprehensive investigation, limiting our understanding of their metabolic contributions. Here, we functionally characterize SFXN1, a member of the non-canonical, sideroflexin family. We find that SFXN1, an integral IMM protein with an uneven number of transmembrane domains, is a TIM22 complex substrate. SFXN1 deficiency leads to mitochondrial respiratory chain impairments, most detrimental to complex III (CIII) biogenesis, activity, and assembly, compromising coenzyme Q levels. The CIII dysfunction is independent of one-carbon metabolism, the known primary role for SFXN1 as a mitochondrial serine transporter. Instead, SFXN1 supports CIII function by participating in heme and α-ketoglutarate metabolism. Our findings highlight the multiple ways that SFXN1-based amino acid transport impacts mitochondrial and cellular metabolic efficiency.
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Affiliation(s)
- Michelle Grace Acoba
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Ebru S Selen Alpergin
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Santosh Renuse
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; McKusick-Nathans Institute of Genetic Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Lucía Fernández-Del-Río
- Department of Chemistry and Biochemistry and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Ya-Wen Lu
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Oleh Khalimonchuk
- Department of Biochemistry and Nebraska Redox Biology Center, University of Nebraska, Lincoln, NE 68588, USA; Fred & Pamela Buffett Cancer Center, Omaha, NE 68198, USA
| | - Catherine F Clarke
- Department of Chemistry and Biochemistry and Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Akhilesh Pandey
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; McKusick-Nathans Institute of Genetic Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA; Departments of Pathology and Oncology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Michael J Wolfgang
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Steven M Claypool
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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11
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Kliment CR, Nguyen JMK, Kaltreider MJ, Lu Y, Claypool SM, Radder JE, Sciurba FC, Zhang Y, Gregory AD, Iglesias PA, Sidhaye VK, Robinson DN. Adenine nucleotide translocase regulates airway epithelial metabolism, surface hydration and ciliary function. J Cell Sci 2021; 134:jcs.257162. [PMID: 33526710 DOI: 10.1242/jcs.257162] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [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: 11/12/2020] [Accepted: 01/13/2021] [Indexed: 01/10/2023] Open
Abstract
Airway hydration and ciliary function are critical to airway homeostasis and dysregulated in chronic obstructive pulmonary disease (COPD), which is impacted by cigarette smoking and has no therapeutic options. We utilized a high-copy cDNA library genetic selection approach in the amoeba Dictyostelium discoideum to identify genetic protectors to cigarette smoke. Members of the mitochondrial ADP/ATP transporter family adenine nucleotide translocase (ANT) are protective against cigarette smoke in Dictyostelium and human bronchial epithelial cells. Gene expression of ANT2 is reduced in lung tissue from COPD patients and in a mouse smoking model, and overexpression of ANT1 and ANT2 resulted in enhanced oxidative respiration and ATP flux. In addition to the presence of ANT proteins in the mitochondria, they reside at the plasma membrane in airway epithelial cells and regulate airway homeostasis. ANT2 overexpression stimulates airway surface hydration by ATP and maintains ciliary beating after exposure to cigarette smoke, both of which are key functions of the airway. Our study highlights a potential for upregulation of ANT proteins and/or of their agonists in the protection from dysfunctional mitochondrial metabolism, airway hydration and ciliary motility in COPD.This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Corrine R Kliment
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA .,Department of Medicine, Division of Pulmonary and Critical Care, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Department of Medicine, Division of Pulmonary and Critical Care, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Jennifer M K Nguyen
- Department of Medicine, Division of Pulmonary and Critical Care, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Mary Jane Kaltreider
- Department of Medicine, Division of Pulmonary and Critical Care, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - YaWen Lu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Josiah E Radder
- Department of Medicine, Division of Pulmonary and Critical Care, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Frank C Sciurba
- Department of Medicine, Division of Pulmonary and Critical Care, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Yingze Zhang
- Department of Medicine, Division of Pulmonary and Critical Care, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Alyssa D Gregory
- Department of Medicine, Division of Pulmonary and Critical Care, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Pablo A Iglesias
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Venkataramana K Sidhaye
- Department of Medicine, Division of Pulmonary and Critical Care, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Department of Environmental Health Sciences and Engineering, Johns Hopkins University School of Public Health, Baltimore, MD 21205, USA
| | - Douglas N Robinson
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA .,Department of Medicine, Division of Pulmonary and Critical Care, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.,Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD 21218, USA
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12
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Sam PN, Calzada E, Acoba MG, Zhao T, Watanabe Y, Nejatfard A, Trinidad JC, Shutt TE, Neal SE, Claypool SM. Impaired phosphatidylethanolamine metabolism activates a reversible stress response that detects and resolves mutant mitochondrial precursors. iScience 2021; 24:102196. [PMID: 33718843 PMCID: PMC7921845 DOI: 10.1016/j.isci.2021.102196] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 01/27/2021] [Accepted: 02/10/2021] [Indexed: 02/06/2023] Open
Abstract
Phosphatidylethanolamine (PE) made in mitochondria has long been recognized as an important precursor for phosphatidylcholine production that occurs in the endoplasmic reticulum (ER). Recently, the strict mitochondrial localization of the enzyme that makes PE in the mitochondrion, phosphatidylserine decarboxylase 1 (Psd1), was questioned. Since a dual localization of Psd1 to the ER would have far-reaching implications, we initiated our study to independently re-assess the subcellular distribution of Psd1. Our results support the unavoidable conclusion that the vast majority, if not all, of functional Psd1 resides in the mitochondrion. Through our efforts, we discovered that mutant forms of Psd1 that impair a self-processing step needed for it to become functional are dually localized to the ER when expressed in a PE-limiting environment. We conclude that severely impaired cellular PE metabolism provokes an ER-assisted adaptive response that is capable of identifying and resolving nonfunctional mitochondrial precursors. Functional Psd1, the enzyme that makes PE, is mitochondrial localized When cellular PE metabolism is impaired, mutant Psd1 is also targeted to the ER Mutant Psd1 targeted to the ER is ubiquitinated and rapidly degraded Impaired PE metabolism activates a reversible stress response
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Affiliation(s)
- Pingdewinde N. Sam
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Elizabeth Calzada
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Michelle Grace Acoba
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Tian Zhao
- Departments of Medical Genetics and Biochemistry & Molecular Biology, Cumming School of Medicine, Alberta Children's Hospital Research Institute, Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada
| | - Yasunori Watanabe
- Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-machi, Yamagata, Yamagata 990-8560, Japan
| | - Anahita Nejatfard
- Division of Biological Sciences, The Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA, USA
| | | | - Timothy E. Shutt
- Faculty of Science, Yamagata University, 1-4-12 Kojirakawa-machi, Yamagata, Yamagata 990-8560, Japan
| | - Sonya E. Neal
- Division of Biological Sciences, The Section of Cell and Developmental Biology, University of California San Diego, La Jolla, CA, USA
| | - Steven M. Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
- Corresponding author
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13
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Abstract
In this issue of Cell Reports, Oemer et al. (2020) define the acyl chain composition of cardiolipin and other lipid classes in murine tissues. They then employ artificial neural networks to predict mechanisms that govern cardiolipin tissue specificity, with implications for understanding cellular pathogenesis in human disease.
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Affiliation(s)
- Olivia L Sniezek
- Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Arianna F Anzmann
- Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - Hilary J Vernon
- Department of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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14
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Le CH, Benage LG, Specht KS, Li Puma LC, Mulligan CM, Heuberger AL, Prenni JE, Claypool SM, Chatfield KC, Sparagna GC, Chicco AJ. Tafazzin deficiency impairs CoA-dependent oxidative metabolism in cardiac mitochondria. J Biol Chem 2020; 295:12485-12497. [PMID: 32665401 DOI: 10.1074/jbc.ra119.011229] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 07/07/2020] [Indexed: 12/20/2022] Open
Abstract
Barth syndrome is a mitochondrial myopathy resulting from mutations in the tafazzin (TAZ) gene encoding a phospholipid transacylase required for cardiolipin remodeling. Cardiolipin is a phospholipid of the inner mitochondrial membrane essential for the function of numerous mitochondrial proteins and processes. However, it is unclear how tafazzin deficiency impacts cardiac mitochondrial metabolism. To address this question while avoiding confounding effects of cardiomyopathy on mitochondrial phenotype, we utilized Taz-shRNA knockdown (TazKD ) mice, which exhibit defective cardiolipin remodeling and respiratory supercomplex instability characteristic of human Barth syndrome but normal cardiac function into adulthood. Consistent with previous reports from other models, mitochondrial H2O2 emission and oxidative damage were greater in TazKD than in wild-type (WT) hearts, but there were no differences in oxidative phosphorylation coupling efficiency or membrane potential. Fatty acid and pyruvate oxidation capacities were 40-60% lower in TazKD mitochondria, but an up-regulation of glutamate oxidation supported respiration rates approximating those with pyruvate and palmitoylcarnitine in WT. Deficiencies in mitochondrial CoA and shifts in the cardiac acyl-CoA profile paralleled changes in fatty acid oxidation enzymes and acyl-CoA thioesterases, suggesting limitations of CoA availability or "trapping" in TazKD mitochondrial metabolism. Incubation of TazKD mitochondria with exogenous CoA partially rescued pyruvate and palmitoylcarnitine oxidation capacities, implicating dysregulation of CoA-dependent intermediary metabolism rather than respiratory chain defects in the bioenergetic impacts of tafazzin deficiency. These findings support links among cardiolipin abnormalities, respiratory supercomplex instability, and mitochondrial oxidant production and shed new light on the distinct metabolic consequences of tafazzin deficiency in the mammalian heart.
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Affiliation(s)
- Catherine H Le
- Cell and Molecular Biology Program, Colorado State University, Fort Collins, Colorado, USA
| | - Lindsay G Benage
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, Colorado, USA
| | - Kalyn S Specht
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Lance C Li Puma
- Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA
| | - Christopher M Mulligan
- Department of Food Science and Human Nutrition, Colorado State University, Fort Collins, Colorado, USA
| | - Adam L Heuberger
- Department of Horticulture and Landscape Architecture, Colorado State University, Fort Collins, Colorado, USA
| | - Jessica E Prenni
- Department of Horticulture and Landscape Architecture, Colorado State University, Fort Collins, Colorado, USA
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Kathryn C Chatfield
- Department of Pediatrics, University of Colorado School of Medicine, Children's Hospital Colorado, Aurora, Colorado, USA
| | - Genevieve C Sparagna
- Division of Cardiology, Department of Medicine, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA
| | - Adam J Chicco
- Cell and Molecular Biology Program, Colorado State University, Fort Collins, Colorado, USA .,Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado, USA.,Department of Food Science and Human Nutrition, Colorado State University, Fort Collins, Colorado, USA
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15
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Abstract
Synthesis and regulation of lipid levels and identities is critical for a wide variety of cellular functions, including structural and morphological properties of organelles, energy storage, signaling, and stability and function of membrane proteins. Proteolytic cleavage events regulate and/or influence some of these lipid metabolic processes and as a result help modulate their pleiotropic cellular functions. Proteins involved in lipid regulation are proteolytically cleaved for the purpose of their relocalization, processing, turnover, and quality control, among others. The scope of this review includes proteolytic events governing cellular lipid dynamics. After an initial discussion of the classic example of sterol regulatory element-binding proteins, our focus will shift to the mitochondrion, where a range of proteolytic events are critical for normal mitochondrial phospholipid metabolism and enforcing quality control therein. Recently, mitochondrial phospholipid metabolic pathways have been implicated as important for the proliferative capacity of cancers. Thus, the assorted proteases that regulate, monitor, or influence the activity of proteins that are important for phospholipid metabolism represent attractive targets to be manipulated for research purposes and clinical applications.
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Affiliation(s)
- Pingdewinde N. Sam
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
| | - Erica Avery
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
| | - Steven M. Claypool
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, United States
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16
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Suresh K, Servinsky L, Jiang H, Bigham Z, Zaldumbide J, Huetsch JC, Kliment C, Acoba MG, Kirsch BJ, Claypool SM, Le A, Damarla M, Shimoda LA. Regulation of mitochondrial fragmentation in microvascular endothelial cells isolated from the SU5416/hypoxia model of pulmonary arterial hypertension. Am J Physiol Lung Cell Mol Physiol 2019; 317:L639-L652. [PMID: 31461316 PMCID: PMC6879901 DOI: 10.1152/ajplung.00396.2018] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [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: 08/24/2018] [Revised: 08/16/2019] [Accepted: 08/17/2019] [Indexed: 01/10/2023] Open
Abstract
Pulmonary arterial hypertension (PAH) is a morbid disease characterized by progressive right ventricle (RV) failure due to elevated pulmonary artery pressures (PAP). In PAH, histologically complex vaso-occlusive lesions in the pulmonary vasculature contribute to elevated PAP. However, the mechanisms underlying dysfunction of the microvascular endothelial cells (MVECs) that comprise a significant portion of these lesions are not well understood. We recently showed that MVECs isolated from the Sugen/hypoxia (SuHx) rat experimental model of PAH (SuHx-MVECs) exhibit increases in migration/proliferation, mitochondrial reactive oxygen species (ROS; mtROS) production, intracellular calcium levels ([Ca2+]i), and mitochondrial fragmentation. Furthermore, quenching mtROS with the targeted antioxidant MitoQ attenuated basal [Ca2+]i, migration and proliferation; however, whether increased mtROS-induced [Ca2+]i entry affected mitochondrial morphology was not clear. In this study, we sought to better understand the relationship between increased ROS, [Ca2+]i, and mitochondrial morphology in SuHx-MVECs. We measured changes in mitochondrial morphology at baseline and following inhibition of mtROS, with the targeted antioxidant MitoQ, or transient receptor potential vanilloid-4 (TRPV4) channels, which we previously showed were responsible for mtROS-induced increases in [Ca2+]i in SuHx-MVECs. Quenching mtROS or inhibiting TRPV4 attenuated fragmentation in SuHx-MVECs. Conversely, inducing mtROS production in MVECs from normoxic rats (N-MVECs) increased fragmentation. Ca2+ entry induced by the TRPV4 agonist GSK1017920A was significantly increased in SuHx-MVECs and was attenuated with MitoQ treatment, indicating that mtROS contributes to increased TRPV4 activity in SuHx-MVECs. Basal and maximal respiration were depressed in SuHx-MVECs, and inhibiting mtROS, but not TRPV4, improved respiration in these cells. Collectively, our data show that, in SuHx-MVECs, mtROS production promotes TRPV4-mediated increases in [Ca2+]i, mitochondrial fission, and decreased mitochondrial respiration. These results suggest an important role for mtROS in driving MVEC dysfunction in PAH.
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Affiliation(s)
- Karthik Suresh
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Laura Servinsky
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Haiyang Jiang
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Zahna Bigham
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Joel Zaldumbide
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - John C Huetsch
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Corrine Kliment
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Michelle G Acoba
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Brian J Kirsch
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Anne Le
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Mahendra Damarla
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - Larissa A Shimoda
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland
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17
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Seneviratne AK, Xu M, Aristizabal Henao JJ, Fajardo VA, Hao Z, Voisin V, Xu GW, Hurren R, Kim S, MacLean N, Wang X, Gronda M, Jeyaraju D, Jitkova Y, Ketela T, Mullokandov M, Sharon D, Thomas G, Chouinard-Watkins R, Hawley JR, Schafer C, Yau HL, Khuchua Z, Aman A, Al-awar R, Gross A, Claypool SM, Bazinet RP, Lupien M, Chan S, De Carvalho DD, Minden MD, Bader GD, Stark KD, LeBlanc P, Schimmer AD. The Mitochondrial Transacylase, Tafazzin, Regulates AML Stemness by Modulating Intracellular Levels of Phospholipids. Cell Stem Cell 2019; 24:1007. [DOI: 10.1016/j.stem.2019.04.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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18
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Gokhale A, Hartwig C, Freeman AAH, Bassell JL, Zlatic SA, Sapp Savas C, Vadlamudi T, Abudulai F, Pham TT, Crocker A, Werner E, Wen Z, Repetto GM, Gogos JA, Claypool SM, Forsyth JK, Bearden CE, Glausier J, Lewis DA, Seyfried NT, Kwong JQ, Faundez V. Systems Analysis of the 22q11.2 Microdeletion Syndrome Converges on a Mitochondrial Interactome Necessary for Synapse Function and Behavior. J Neurosci 2019; 39:3561-3581. [PMID: 30833507 PMCID: PMC6495129 DOI: 10.1523/jneurosci.1983-18.2019] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [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: 08/02/2018] [Revised: 01/18/2019] [Accepted: 02/15/2019] [Indexed: 11/21/2022] Open
Abstract
Neurodevelopmental disorders offer insight into synaptic mechanisms. To unbiasedly uncover these mechanisms, we studied the 22q11.2 syndrome, a recurrent copy number variant, which is the highest schizophrenia genetic risk factor. We quantified the proteomes of 22q11.2 mutant human fibroblasts from both sexes and mouse brains carrying a 22q11.2-like defect, Df(16)A+/- Molecular ontologies defined mitochondrial compartments and pathways as some of top ranked categories. In particular, we identified perturbations in the SLC25A1-SLC25A4 mitochondrial transporter interactome as associated with the 22q11.2 genetic defect. Expression of SLC25A1-SLC25A4 interactome components was affected in neuronal cells from schizophrenia patients. Furthermore, hemideficiency of the Drosophila SLC25A1 or SLC25A4 orthologues, dSLC25A1-sea and dSLC25A4-sesB, affected synapse morphology, neurotransmission, plasticity, and sleep patterns. Our findings indicate that synapses are sensitive to partial loss of function of mitochondrial solute transporters. We propose that mitoproteomes regulate synapse development and function in normal and pathological conditions in a cell-specific manner.SIGNIFICANCE STATEMENT We address the central question of how to comprehensively define molecular mechanisms of the most prevalent and penetrant microdeletion associated with neurodevelopmental disorders, the 22q11.2 microdeletion syndrome. This complex mutation reduces gene dosage of ∼63 genes in humans. We describe a disruption of the mitoproteome in 22q11.2 patients and brains of a 22q11.2 mouse model. In particular, we identify a network of inner mitochondrial membrane transporters as a hub required for synapse function. Our findings suggest that mitochondrial composition and function modulate the risk of neurodevelopmental disorders, such as schizophrenia.
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Affiliation(s)
| | | | | | | | | | | | - Trishna Vadlamudi
- Department of Chemistry, Agnes Scott College, Decatur, Georgia 30030
| | - Farida Abudulai
- Department of Chemistry, Agnes Scott College, Decatur, Georgia 30030
| | | | - Amanda Crocker
- Program in Neuroscience, Middlebury College, Middlebury, Vermont 05753
| | | | | | - Gabriela M Repetto
- Centro de Genética y Genómica, Facultad de Medicina, Clínica Alemana Universidad del Desarrollo, Santiago, Chile
| | - Joseph A Gogos
- Departments of Neuroscience and Physiology, Columbia University, New York, New York 10032
| | - Steven M Claypool
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Jennifer K Forsyth
- Semel Institute for Neuroscience and Human Behavior and Department of Psychology, UCLA, Los Angeles, California, 90095, and
| | - Carrie E Bearden
- Semel Institute for Neuroscience and Human Behavior and Department of Psychology, UCLA, Los Angeles, California, 90095, and
| | - Jill Glausier
- Departments of Psychiatry and Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, 15213
| | - David A Lewis
- Departments of Psychiatry and Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, 15213
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19
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Calzada E, Avery E, Sam PN, Modak A, Wang C, McCaffery JM, Han X, Alder NN, Claypool SM. Phosphatidylethanolamine made in the inner mitochondrial membrane is essential for yeast cytochrome bc 1 complex function. Nat Commun 2019; 10:1432. [PMID: 30926815 PMCID: PMC6441012 DOI: 10.1038/s41467-019-09425-1] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 03/11/2019] [Indexed: 12/18/2022] Open
Abstract
Of the four separate PE biosynthetic pathways in eukaryotes, one occurs in the mitochondrial inner membrane (IM) and is executed by phosphatidylserine decarboxylase (Psd1). Deletion of Psd1 is lethal in mice and compromises mitochondrial function. We hypothesize that this reflects inefficient import of non-mitochondrial PE into the IM. Here, we test this by re-wiring PE metabolism in yeast by re-directing Psd1 to the outer mitochondrial membrane or the endomembrane system and show that PE can cross the IMS in both directions. Nonetheless, PE synthesis in the IM is critical for cytochrome bc1 complex (III) function and mutations predicted to disrupt a conserved PE-binding site in the complex III subunit, Qcr7, impair complex III activity similar to PSD1 deletion. Collectively, these data challenge the current dogma of PE trafficking and demonstrate that PE made in the IM by Psd1 support the intrinsic functionality of complex III. Phosphatidylethanolamine (PE) is synthesized by four separate pathways, although surprisingly, perturbing mitochondrial PE synthesis compromises mitochondrial function. Here, the authors show that mitochondrial PE synthesis is required for Complex III function and challenge PE trafficking dogma.
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Affiliation(s)
- Elizabeth Calzada
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Erica Avery
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Pingdewinde N Sam
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Arnab Modak
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, USA
| | - Chunyan Wang
- Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - J Michael McCaffery
- Integrated Imaging Center, Department of Biology, Johns Hopkins University, Baltimore, MD, USA
| | - Xianlin Han
- Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - Nathan N Alder
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT, USA
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
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20
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Seneviratne AK, Xu M, Henao JJA, Fajardo VA, Hao Z, Voisin V, Xu GW, Hurren R, Kim S, MacLean N, Wang X, Gronda M, Jeyaraju D, Jitkova Y, Ketela T, Mullokandov M, Sharon D, Thomas G, Chouinard-Watkins R, Hawley JR, Schafer C, Yau HL, Khuchua Z, Aman A, Al-Awar R, Gross A, Claypool SM, Bazinet RP, Lupien M, Chan S, De Carvalho DD, Minden MD, Bader GD, Stark KD, LeBlanc P, Schimmer AD. The Mitochondrial Transacylase, Tafazzin, Regulates for AML Stemness by Modulating Intracellular Levels of Phospholipids. Cell Stem Cell 2019; 24:621-636.e16. [PMID: 30930145 DOI: 10.1016/j.stem.2019.02.020] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [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: 06/12/2018] [Revised: 12/19/2018] [Accepted: 02/27/2019] [Indexed: 12/17/2022]
Abstract
Tafazzin (TAZ) is a mitochondrial transacylase that remodels the mitochondrial cardiolipin into its mature form. Through a CRISPR screen, we identified TAZ as necessary for the growth and viability of acute myeloid leukemia (AML) cells. Genetic inhibition of TAZ reduced stemness and increased differentiation of AML cells both in vitro and in vivo. In contrast, knockdown of TAZ did not impair normal hematopoiesis under basal conditions. Mechanistically, inhibition of TAZ decreased levels of cardiolipin but also altered global levels of intracellular phospholipids, including phosphatidylserine, which controlled AML stemness and differentiation by modulating toll-like receptor (TLR) signaling.
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Affiliation(s)
- Ayesh K Seneviratne
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada; Institute of Medical Sciences, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Mingjing Xu
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
| | - Juan J Aristizabal Henao
- Laboratory of Nutritional Lipidomics, Department of Kinesiology, University of Waterloo, Waterloo, ON, Canada
| | - Val A Fajardo
- Department of Health Sciences, Faculty of Applied Health Sciences, Brock University, St. Catharines, ON, Canada
| | - Zhenyue Hao
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
| | - Veronique Voisin
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - G Wei Xu
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
| | - Rose Hurren
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
| | - S Kim
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
| | - Neil MacLean
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
| | - Xiaoming Wang
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
| | - Marcela Gronda
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
| | - Danny Jeyaraju
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
| | - Yulia Jitkova
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
| | - Troy Ketela
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
| | | | - David Sharon
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
| | - Geethu Thomas
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada
| | | | - James R Hawley
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - Caitlin Schafer
- Department of Pediatrics, College of Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Helen Loo Yau
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - Zaza Khuchua
- Department of Biochemistry, Sechenov Medical University, Moscow, Russian Federation; Institute of Medical Research Ilia State University, Tbilisi, Georgia
| | - Ahmed Aman
- Drug Discovery Program, Ontario Institute for Cancer Research, Toronto, ON, Canada; Department of Pharmacology and Toxicology, University of Toronto, ON, Canada
| | - Rima Al-Awar
- Drug Discovery Program, Ontario Institute for Cancer Research, Toronto, ON, Canada; Department of Pharmacology and Toxicology, University of Toronto, ON, Canada
| | - Atan Gross
- Department of Biological Regulation, Weizmann Institute, Rehovot, Israel
| | - Steven M Claypool
- Department of Physiology, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Richard P Bazinet
- Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
| | - Mathieu Lupien
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - Steven Chan
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - Daniel D De Carvalho
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - Mark D Minden
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada
| | - Gary D Bader
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
| | - Ken D Stark
- Laboratory of Nutritional Lipidomics, Department of Kinesiology, University of Waterloo, Waterloo, ON, Canada
| | - Paul LeBlanc
- Department of Health Sciences, Faculty of Applied Health Sciences, Brock University, St. Catharines, ON, Canada
| | - Aaron D Schimmer
- Princess Margaret Cancer Centre, University Health Network, Toronto, ON, Canada; Institute of Medical Sciences, Faculty of Medicine, University of Toronto, Toronto, ON, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON, Canada.
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21
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Zhao T, Goedhart CM, Sam PN, Sabouny R, Lingrell S, Cornish AJ, Lamont RE, Bernier FP, Sinasac D, Parboosingh JS, Vance JE, Claypool SM, Innes AM, Shutt TE. PISD is a mitochondrial disease gene causing skeletal dysplasia, cataracts, and white matter changes. Life Sci Alliance 2019; 2:2/2/e201900353. [PMID: 30858161 PMCID: PMC6412922 DOI: 10.26508/lsa.201900353] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 02/25/2019] [Accepted: 02/26/2019] [Indexed: 12/18/2022] Open
Abstract
This work demonstrates that pathogenic variants in PISD cause mitochondrial disease and suggests a novel mechanistic link whereby impaired lipid content in the inner mitochondrial membrane alters the activity of inner mitochondrial membrane proteases. Exome sequencing of two sisters with congenital cataracts, short stature, and white matter changes identified compound heterozygous variants in the PISD gene, encoding the phosphatidylserine decarboxylase enzyme that converts phosphatidylserine to phosphatidylethanolamine (PE) in the inner mitochondrial membrane (IMM). Decreased conversion of phosphatidylserine to PE in patient fibroblasts is consistent with impaired phosphatidylserine decarboxylase (PISD) enzyme activity. Meanwhile, as evidence for mitochondrial dysfunction, patient fibroblasts exhibited more fragmented mitochondrial networks, enlarged lysosomes, decreased maximal oxygen consumption rates, and increased sensitivity to 2-deoxyglucose. Moreover, treatment with lyso-PE, which can replenish the mitochondrial pool of PE, and genetic complementation restored mitochondrial and lysosome morphology in patient fibroblasts. Functional characterization of the PISD variants demonstrates that the maternal variant causes an alternative splice product. Meanwhile, the paternal variant impairs autocatalytic self-processing of the PISD protein required for its activity. Finally, evidence for impaired activity of mitochondrial IMM proteases suggests an explanation as to why the phenotypes of these PISD patients resemble recently described “mitochondrial chaperonopathies.” Collectively, these findings demonstrate that PISD is a novel mitochondrial disease gene.
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Affiliation(s)
- Tian Zhao
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Caitlin M Goedhart
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Pingdewinde N Sam
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Rasha Sabouny
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Susanne Lingrell
- Department of Medicine and Group on Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Alberta, Canada
| | - Adam J Cornish
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Ryan E Lamont
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Francois P Bernier
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - David Sinasac
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Jillian S Parboosingh
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | | | - Jean E Vance
- Department of Medicine and Group on Molecular and Cell Biology of Lipids, University of Alberta, Edmonton, Alberta, Canada
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - A Micheil Innes
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada .,Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Department of Pediatrics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Timothy E Shutt
- Alberta Children's Hospital Research Institute, Department of Medical Genetics, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada .,Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.,Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
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22
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Ogunbona OB, Claypool SM. Emerging Roles in the Biogenesis of Cytochrome c Oxidase for Members of the Mitochondrial Carrier Family. Front Cell Dev Biol 2019; 7:3. [PMID: 30766870 PMCID: PMC6365663 DOI: 10.3389/fcell.2019.00003] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2018] [Accepted: 01/10/2019] [Indexed: 12/11/2022] Open
Abstract
The mitochondrial carrier family (MCF) is a group of transport proteins that are mostly localized to the inner mitochondrial membrane where they facilitate the movement of various solutes across the membrane. Although these carriers represent potential targets for therapeutic application and are repeatedly associated with human disease, research on the MCF has not progressed commensurate to their physiologic and pathophysiologic importance. Many of the 53 MCF members in humans are orphans and lack known transport substrates. Even for the relatively well-studied members of this family, such as the ADP/ATP carrier and the uncoupling protein, there exist fundamental gaps in our understanding of their biological roles including a clear rationale for the existence of multiple isoforms. Here, we briefly review this important family of mitochondrial carriers, provide a few salient examples of their diverse metabolic roles and disease associations, and then focus on an emerging link between several distinct MCF members, including the ADP/ATP carrier, and cytochrome c oxidase biogenesis. As the ADP/ATP carrier is regarded as the paradigm of the entire MCF, its newly established role in regulating translation of the mitochondrial genome highlights that we still have a lot to learn about these metabolite transporters.
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Affiliation(s)
- Oluwaseun B. Ogunbona
- Department of Physiology, School of Medicine, Johns Hopkins University, Baltimore, MD, United States
- Department of Pathology & Laboratory Medicine, School of Medicine, Emory University, Atlanta, GA, United States
| | - Steven M. Claypool
- Department of Physiology, School of Medicine, Johns Hopkins University, Baltimore, MD, United States
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23
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Ogunbona OB, Baile MG, Claypool SM. Cardiomyopathy-associated mutation in the ADP/ATP carrier reveals translation-dependent regulation of cytochrome c oxidase activity. Mol Biol Cell 2018; 29:1449-1464. [PMID: 29688796 PMCID: PMC6014099 DOI: 10.1091/mbc.e17-12-0700] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Revised: 03/16/2018] [Accepted: 04/18/2018] [Indexed: 01/07/2023] Open
Abstract
How the absence of the major mitochondrial ADP/ATP carrier in yeast, Aac2p, results in a specific defect in cytochrome c oxidase (COX; complex IV) activity is a long-standing mystery. Aac2p physically associates with respiratory supercomplexes, which include complex IV, raising the possibility that its activity is dependent on its association with Aac2p. Here, we have leveraged a transport-dead pathogenic AAC2 point mutant to determine the basis for the reduced COX activity in the absence of Aac2p. The steady-state levels of complex IV subunits encoded by the mitochondrial genome are significantly reduced in the absence of Aac2p function, whether its association with respiratory supercomplexes is preserved or not. This diminution in COX amounts is not caused by a reduction in the mitochondrial genome copy number or the steady-state level of its transcripts, and does not reflect a defect in complex IV assembly. Instead, the absence of Aac2p activity, genetically or pharmacologically, results in an aberrant pattern of mitochondrial translation. Interestingly, compared with the complete absence of Aac2p, the complex IV-related defects are greater in mitochondria expressing the transport-inactive Aac2p mutant. Our results highlight a critical role for Aac2p transport in mitochondrial translation whose disturbance uniquely impacts cytochrome c oxidase.
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Affiliation(s)
- Oluwaseun B. Ogunbona
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2185
| | | | - Steven M. Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2185
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24
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Ogunbona OB, Baile MG, Claypool SM. Abstract 434: Cardiomyopathy-associated Point Mutation in the ADP-ATP Carrier Reveals Translation-dependent Regulation of Cytochrome
c o
xidase Activity in Yeast. Circ Res 2017. [DOI: 10.1161/res.121.suppl_1.434] [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
The interaction between the ADP/ATP carrier and the respiratory supercomplexes is evolutionarily-conserved, is dependent on cardiolipin, and is functionally significant as yeast lacking Aac2p have reduced activity of respiratory complex IV (
cytochrome c oxidase
or COX). We have leveraged a transport-dead pathogenic
AAC2
point mutant discovered in a patient with hypertrophic cardiomyopathy and mild myopathy to determine whether the reduction in complex IV activity in the absence of Aac2p reflects the absence of the interaction between Aac2p and components of the electron transport chain and/or the absence of nucleotide transport (i.e. Aac2p function). Importantly, the pathogenic A137D allele of
AAC2
is expressed normally and still interacts with components of the yeast respiratory supercomplex but is unable to support growth on respiratory media due to its inability to transport ADP/ATP. Amazingly, in the absence of Aac2p function, the expression levels of complex IV subunits that are encoded by the mitochondrial genome (and which form the catalytic core of the complex IV holoenzyme) are specifically reduced, even though assembly and interaction with the respiratory supercomplexes are preserved in the mutant Aac2p. This reduction in the levels of complex IV subunits is not caused by a reduction in either the mitochondrial genome copy number or the steady state level of mitochondrial DNA transcripts. Instead, there is a noticeable alteration in the pattern of the mitochondrial translation in the absence of Aac2p activity. Our results suggest that Aac2p function is important for normal translation of the mitochondrial encoded complex IV subunits and that Aac2p activity plays a significant role in regulating oxidative phosphorylation.
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25
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Lu YW, Acoba MG, Selvaraju K, Huang TC, Nirujogi RS, Sathe G, Pandey A, Claypool SM. Human adenine nucleotide translocases physically and functionally interact with respirasomes. Mol Biol Cell 2017; 28:1489-1506. [PMID: 28404750 PMCID: PMC5449148 DOI: 10.1091/mbc.e17-03-0195] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 03/30/2017] [Accepted: 04/04/2017] [Indexed: 11/11/2022] Open
Abstract
A network of interactions for human adenine nucleotide translocases, required for oxidative phosphorylation, is reported. Of particular interest is an evolutionarily conserved and functionally important association with respiratory supercomplexes, which is surprising because the respirasomes of yeast and mammals are different. Members of the adenine nucleotide translocase (ANT) family exchange ADP for ATP across the mitochondrial inner membrane, an activity that is essential for oxidative phosphorylation (OXPHOS). Mutations in or dysregulation of ANTs is associated with progressive external ophthalmoplegia, cardiomyopathy, nonsyndromic intellectual disability, apoptosis, and the Warburg effect. Binding partners of human ANTs have not been systematically identified. The absence of such information has prevented a detailed molecular understanding of the assorted ANT-associated diseases, including insight into their disparate phenotypic manifestations. To fill this void, in this study, we define the interactomes of two human ANT isoforms. Analogous to its yeast counterpart, human ANTs associate with heterologous partner proteins, including the respiratory supercomplex (RSC) and other solute carriers. The evolutionarily conserved ANT–RSC association is particularly noteworthy because the composition, and thereby organization, of RSCs in yeast and human is different. Surprisingly, absence of the major ANT isoform only modestly impairs OXPHOS in HEK293 cells, indicating that the low levels of other isoforms provide functional redundancy. In contrast, pharmacological inhibition of OXPHOS expression and function inhibits ANT-dependent ADP/ATP exchange. Thus ANTs and the OXPHOS machinery physically interact and functionally cooperate to enhance ANT transport capacity and mitochondrial respiration.
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Affiliation(s)
- Ya-Wen Lu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2185
| | - Michelle Grace Acoba
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2185
| | - Kandasamy Selvaraju
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2185
| | - Tai-Chung Huang
- McKusick-Nathans Institute of Genetic Medicine, Departments of Biological Chemistry, Pathology and Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2185.,Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University Cancer Center, Taipei 10051, Taiwan
| | - Raja S Nirujogi
- McKusick-Nathans Institute of Genetic Medicine, Departments of Biological Chemistry, Pathology and Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2185
| | - Gajanan Sathe
- McKusick-Nathans Institute of Genetic Medicine, Departments of Biological Chemistry, Pathology and Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2185
| | - Akhilesh Pandey
- McKusick-Nathans Institute of Genetic Medicine, Departments of Biological Chemistry, Pathology and Oncology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2185
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2185
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26
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Steffen J, Vashisht AA, Wan J, Jen JC, Claypool SM, Wohlschlegel JA, Koehler CM. Rapid degradation of mutant SLC25A46 by the ubiquitin-proteasome system results in MFN1/2-mediated hyperfusion of mitochondria. Mol Biol Cell 2017; 28:600-612. [PMID: 28057766 PMCID: PMC5328619 DOI: 10.1091/mbc.e16-07-0545] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 12/12/2016] [Accepted: 12/30/2016] [Indexed: 11/29/2022] Open
Abstract
SCL25A46 is a mitochondrial carrier protein that localizes to the outer membrane. Mutation L341P causes rapid degradation of SLC25A46 by the ubiquitin-proteasome system, independent of activated stress pathways, including mitophagy and apoptosis. SLC25A46 regulates oligomerization of MFN1/2 and mitochondrial dynamics. SCL25A46 is a mitochondrial carrier protein that surprisingly localizes to the outer membrane and is distantly related to Ugo1. Here we show that a subset of SLC25A46 interacts with mitochondrial dynamics components and the MICOS complex. Decreased expression of SLC25A46 results in increased stability and oligomerization of MFN1 and MFN2 on mitochondria, promoting mitochondrial hyperfusion. A mutation at L341P causes rapid degradation of SLC25A46, which manifests as a rare disease, pontocerebellar hypoplasia. The E3 ubiquitin ligases MULAN and MARCH5 coordinate ubiquitylation of SLC25A46 L341P, leading to degradation by organized activities of P97 and the proteasome. Whereas outer mitochondrial membrane–associated degradation is typically associated with apoptosis or a specialized type of autophagy termed mitophagy, SLC25A46 degradation operates independently of activation of outer membrane stress pathways. Thus SLC25A46 is a new component in mitochondrial dynamics that serves as a regulator for MFN1/2 oligomerization. Moreover, SLC25A46 is selectively degraded from the outer membrane independently of mitophagy and apoptosis, providing a framework for mechanistic studies in the proteolysis of outer membrane proteins.
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Affiliation(s)
- Janos Steffen
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095
| | - Ajay A Vashisht
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| | - Jijun Wan
- Department of Neurology, University of California, Los Angeles, Los Angeles, CA 90095
| | - Joanna C Jen
- Department of Neurology, University of California, Los Angeles, Los Angeles, CA 90095
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - James A Wohlschlegel
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095.,Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095
| | - Carla M Koehler
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, CA 90095 .,Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095.,Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, CA 90095
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27
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Cole LK, Mejia EM, Vandel M, Sparagna GC, Claypool SM, Dyck-Chan L, Klein J, Hatch GM. Erratum. Impaired Cardiolipin Biosynthesis Prevents Hepatic Steatosis and Diet-Induced Obesity. Diabetes 2016;65:3289-3300. Diabetes 2017; 66:231. [PMID: 27856607 PMCID: PMC5379051 DOI: 10.2337/db17-er01a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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28
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Cole LK, Mejia EM, Vandel M, Sparagna GC, Claypool SM, Dyck-Chan L, Klein J, Hatch GM. Impaired Cardiolipin Biosynthesis Prevents Hepatic Steatosis and Diet-Induced Obesity. Diabetes 2016; 65:3289-3300. [PMID: 27495222 PMCID: PMC5079636 DOI: 10.2337/db16-0114] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 07/26/2016] [Indexed: 12/16/2022]
Abstract
Mitochondria are the nexus of energy metabolism, and consequently their dysfunction has been implicated in the development of metabolic complications and progression to insulin resistance and type 2 diabetes. The unique tetra-acyl phospholipid cardiolipin (CL) is located in the inner mitochondrial membrane, where it maintains mitochondrial integrity. Here we show that knockdown of Tafazzin (TAZ kd), a CL transacylase, in mice results in protection against the development of obesity, insulin resistance, and hepatic steatosis. We determined that hypermetabolism protected TAZ kd mice from weight gain. Unexpectedly, the large reduction of CL in the heart and skeletal muscle of TAZ kd mice was not mirrored in the liver. As a result, TAZ kd mice exhibited normal hepatic mitochondrial supercomplex formation and elevated hepatic fatty acid oxidation. Collectively, these studies identify a key role for hepatic CL remodeling in regulating susceptibility to insulin resistance and as a novel therapeutic target for diet-induced obesity.
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Affiliation(s)
- Laura K Cole
- Children's Hospital Research Institute of Manitoba, Department of Pharmacology & Therapeutics, Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada
| | - Edgard M Mejia
- Children's Hospital Research Institute of Manitoba, Department of Pharmacology & Therapeutics, Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada
| | - Marilyne Vandel
- Children's Hospital Research Institute of Manitoba, Department of Pharmacology & Therapeutics, Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada
| | - Genevieve C Sparagna
- Department of Medicine, University of Colorado Denver, Anschutz Medical Campus, Aurora, CO
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD
| | - Laura Dyck-Chan
- Children's Hospital Research Institute of Manitoba, Department of Pharmacology & Therapeutics, Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada
| | | | - Grant M Hatch
- Children's Hospital Research Institute of Manitoba, Department of Pharmacology & Therapeutics, Faculty of Health Sciences, University of Manitoba, Winnipeg, Canada
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29
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Seifert EL, Gál A, Acoba MG, Li Q, Anderson-Pullinger L, Golenár T, Moffat C, Sondheimer N, Claypool SM, Hajnóczky G. Natural and Induced Mitochondrial Phosphate Carrier Loss: DIFFERENTIAL DEPENDENCE OF MITOCHONDRIAL METABOLISM AND DYNAMICS AND CELL SURVIVAL ON THE EXTENT OF DEPLETION. J Biol Chem 2016; 291:26126-26137. [PMID: 27780865 DOI: 10.1074/jbc.m116.744714] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [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: 06/22/2016] [Revised: 10/06/2016] [Indexed: 12/22/2022] Open
Abstract
The relevance of mitochondrial phosphate carrier (PiC), encoded by SLC25A3, in bioenergetics is well accepted. However, little is known about the mechanisms mediating the cellular impairments induced by pathological SLC25A3 variants. To this end, we investigated the pathogenicity of a novel compound heterozygous mutation in SLC25A3 First, each variant was modeled in yeast, revealing that substituting GSSAS for QIP within the fifth matrix loop is incompatible with survival on non-fermentable substrate, whereas the L200W variant is functionally neutral. Next, using skin fibroblasts from an individual expressing these variants and HeLa cells with varying degrees of PiC depletion, PiC loss of ∼60% was still compatible with uncompromised maximal oxidative phosphorylation (oxphos), whereas lower maximal oxphos was evident at ∼85% PiC depletion. Furthermore, intact mutant fibroblasts displayed suppressed mitochondrial bioenergetics consistent with a lower substrate availability rather than phosphate limitation. This was accompanied by slowed proliferation in glucose-replete medium; however, proliferation ceased when only mitochondrial substrate was provided. Both mutant fibroblasts and HeLa cells with 60% PiC loss showed a less interconnected mitochondrial network and a mitochondrial fusion defect that is not explained by altered abundance of OPA1 or MFN1/2 or relative amount of different OPA1 forms. Altogether these results indicate that PiC depletion may need to be profound (>85%) to substantially affect maximal oxphos and that pathogenesis associated with PiC depletion or loss of function may be independent of phosphate limitation when ATP requirements are not high.
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Affiliation(s)
- Erin L Seifert
- From the MitoCare Center for Imaging Research and Diagnostics, Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107,
| | - Aniko Gál
- From the MitoCare Center for Imaging Research and Diagnostics, Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Michelle G Acoba
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, and
| | - Qipei Li
- From the MitoCare Center for Imaging Research and Diagnostics, Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Lauren Anderson-Pullinger
- From the MitoCare Center for Imaging Research and Diagnostics, Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Tunde Golenár
- From the MitoCare Center for Imaging Research and Diagnostics, Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Cynthia Moffat
- From the MitoCare Center for Imaging Research and Diagnostics, Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107
| | - Neal Sondheimer
- Division of Clinical and Metabolic Genetics, Hospital for Sick Children and Department of Paediatrics, University of Toronto, Toronto, Ontario M5G 1X8, Canada
| | - Steven M Claypool
- Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, and
| | - György Hajnóczky
- From the MitoCare Center for Imaging Research and Diagnostics, Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107,
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30
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Lu YW, Galbraith L, Herndon JD, Lu YL, Pras-Raves M, Vervaart M, Van Kampen A, Luyf A, Koehler CM, McCaffery JM, Gottlieb E, Vaz FM, Claypool SM. Defining functional classes of Barth syndrome mutation in humans. Hum Mol Genet 2016; 25:1754-70. [PMID: 26908608 PMCID: PMC4986330 DOI: 10.1093/hmg/ddw046] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 02/08/2016] [Accepted: 02/15/2016] [Indexed: 11/13/2022] Open
Abstract
The X-linked disease Barth syndrome (BTHS) is caused by mutations in TAZ; TAZ is the main determinant of the final acyl chain composition of the mitochondrial-specific phospholipid, cardiolipin. To date, a detailed characterization of endogenous TAZ has only been performed in yeast. Further, why a given BTHS-associated missense mutation impairs TAZ function has only been determined in a yeast model of this human disease. Presently, the detailed characterization of yeast tafazzin harboring individual BTHS mutations at evolutionarily conserved residues has identified seven distinct loss-of-function mechanisms caused by patient-associated missense alleles. However, whether the biochemical consequences associated with individual mutations also occur in the context of human TAZ in a validated mammalian model has not been demonstrated. Here, utilizing newly established monoclonal antibodies capable of detecting endogenous TAZ, we demonstrate that mammalian TAZ, like its yeast counterpart, is localized to the mitochondrion where it adopts an extremely protease-resistant fold, associates non-integrally with intermembrane space-facing membranes and assembles in a range of complexes. Even though multiple isoforms are expressed at the mRNA level, only a single polypeptide that co-migrates with the human isoform lacking exon 5 is expressed in human skin fibroblasts, HEK293 cells, and murine heart and liver mitochondria. Finally, using a new genome-edited mammalian BTHS cell culture model, we demonstrate that the loss-of-function mechanisms for two BTHS alleles that represent two of the seven functional classes of BTHS mutation as originally defined in yeast, are the same when modeled in human TAZ.
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Affiliation(s)
- Ya-Wen Lu
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2185, USA
| | - Laura Galbraith
- Cancer Research UK, The Beatson Institute for Cancer Research, Glasgow G61 1BD, UK
| | - Jenny D Herndon
- Department of Chemistry and Biochemistry, Molecular Biology Institute, and Jonsson Comprehensive Cancer Center, University of California, Los Angeles, CA 90095-1569, USA
| | - Ya-Lin Lu
- Division of Biology and Biomedical Sciences, Graduate School of Arts and Sciences, Washington University, St. Louis, MO 63130-4899, USA
| | - Mia Pras-Raves
- Departments of Clinical Chemistry and Pediatrics, Laboratory Genetic Metabolic Diseases and
| | - Martin Vervaart
- Departments of Clinical Chemistry and Pediatrics, Laboratory Genetic Metabolic Diseases and
| | - Antoine Van Kampen
- Bioinformatics Laboratory, Department of Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Center, Amsterdam, The Netherlands and
| | - Angela Luyf
- Bioinformatics Laboratory, Department of Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Center, Amsterdam, The Netherlands and
| | - Carla M Koehler
- Department of Chemistry and Biochemistry, Molecular Biology Institute, and Jonsson Comprehensive Cancer Center, University of California, Los Angeles, CA 90095-1569, USA
| | - J Michael McCaffery
- Integrated Imaging Center, Department of Biology, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Eyal Gottlieb
- Cancer Research UK, The Beatson Institute for Cancer Research, Glasgow G61 1BD, UK
| | - Frederic M Vaz
- Departments of Clinical Chemistry and Pediatrics, Laboratory Genetic Metabolic Diseases and
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205-2185, USA,
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31
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Seifert E, Gal A, Acoba MG, Claypool SM, Anderson-Pullinger L, Varnai P, Moffat C, Weaver D, Sondheimer N, Hajnoczky G. Novel Mutations in SLC25A3 Encoding the Mitochondrial Phosphate Carrier. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.2536] [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: 11/28/2022] Open
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32
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Abstract
Phosphatidylethanolamine (PE) is the second most abundant glycerophospholipid in eukaryotic cells. The existence of four only partially redundant biochemical pathways that produce PE, highlights the importance of this essential phospholipid. The CDP-ethanolamine and phosphatidylserine decarboxylase pathways occur in different subcellular compartments and are the main sources of PE in cells. Mammalian development fails upon ablation of either pathway. Once made, PE has diverse cellular functions that include serving as a precursor for phosphatidylcholine and a substrate for important posttranslational modifications, influencing membrane topology, and promoting cell and organelle membrane fusion, oxidative phosphorylation, mitochondrial biogenesis, and autophagy. The importance of PE metabolism in mammalian health has recently emerged following its association with Alzheimer's disease, Parkinson's disease, nonalcoholic liver disease, and the virulence of certain pathogenic organisms.
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Affiliation(s)
- Elizabeth Calzada
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Ouma Onguka
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Pokorná L, Čermáková P, Horváth A, Baile MG, Claypool SM, Griač P, Malínský J, Balážová M. Specific degradation of phosphatidylglycerol is necessary for proper mitochondrial morphology and function. Biochim Biophys Acta 2015; 1857:34-45. [PMID: 26482708 DOI: 10.1016/j.bbabio.2015.10.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Revised: 09/22/2015] [Accepted: 10/15/2015] [Indexed: 02/01/2023]
Abstract
In yeast, phosphatidylglycerol (PG) is a minor phospholipid under standard conditions; it can be utilized for cardiolipin (CL) biosynthesis by CL synthase, Crd1p, or alternatively degraded by the phospholipase Pgc1p. The Saccharomyces cerevisiae deletion mutants crd1Δ and pgc1Δ both accumulate PG. Based on analyses of the phospholipid content of pgc1Δ and crd1Δ yeast, we revealed that in yeast mitochondria, two separate pools of PG are present, which differ in their fatty acid composition and accessibility for Pgc1p-catalyzed degradation. In contrast to CL-deficient crd1Δ yeast, the pgc1Δ mutant contains normal levels of CL. This makes the pgc1Δ strain a suitable model to study the effect of accumulation of PG per se. Using fluorescence microscopy, we show that accumulation of PG with normal levels of CL resulted in increased fragmentation of mitochondria, while in the absence of CL, accumulation of PG led to the formation of large mitochondrial sheets. We also show that pgc1Δ mitochondria exhibited increased respiration rates due to increased activity of cytochrome c oxidase. Taken together, our results indicate that not only a lack of anionic phospholipids, but also excess PG, or unbalanced ratios of anionic phospholipids in mitochondrial membranes, have harmful consequences on mitochondrial morphology and function.
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Affiliation(s)
- Lucia Pokorná
- Department of Membrane Biochemistry, Institute of Animal Biochemistry and Genetics, Slovak Academy of Sciences, Ivanka pri Dunaji, Slovakia
| | - Petra Čermáková
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia
| | - Anton Horváth
- Department of Biochemistry, Faculty of Natural Sciences, Comenius University, Bratislava, Slovakia
| | - Matthew G Baile
- Department of Physiology, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Steven M Claypool
- Department of Physiology, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Peter Griač
- Department of Membrane Biochemistry, Institute of Animal Biochemistry and Genetics, Slovak Academy of Sciences, Ivanka pri Dunaji, Slovakia
| | - Jan Malínský
- Microscopy Unit, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Mária Balážová
- Department of Membrane Biochemistry, Institute of Animal Biochemistry and Genetics, Slovak Academy of Sciences, Ivanka pri Dunaji, Slovakia.
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34
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Lu YW, Galbraith L, Herndon JD, Lu YL, Pras-Raves M, Vervaart M, van Kampen A, Luyf A, Koehler CM, Gottlieb E, Vaz FM, Claypool SM. Topological differences but dysfunctional conservation of cardiolipin remodeling in mammals and yeast. Mitochondrion 2015. [DOI: 10.1016/j.mito.2015.07.019] [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: 11/16/2022]
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35
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Onguka O, Calzada E, Ogunbona OB, Claypool SM. Phosphatidylserine decarboxylase 1 autocatalysis and function does not require a mitochondrial-specific factor. J Biol Chem 2015; 290:12744-52. [PMID: 25829489 DOI: 10.1074/jbc.m115.641118] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [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: 01/26/2015] [Indexed: 11/06/2022] Open
Abstract
Phosphatidylethanolamine (PE) is a major cellular phospholipid that can be made by four separate pathways, one of which resides in the mitochondrion. The mitochondrial enzyme that generates PE is phosphatidylserine decarboxylase 1 (Psd1p). The pool of PE produced by Psd1p, which cannot be compensated for by the other cellular PE metabolic pathways, is important for numerous mitochondrial functions, including oxidative phosphorylation and mitochondrial dynamics and morphology, and is essential for murine development. To become catalytically active, Psd1p undergoes an autocatalytic processing step involving a conserved LGST motif that separates the enzyme into α and β subunits that remain non-covalently attached and are anchored to the inner membrane by virtue of the membrane-embedded β subunit. It was speculated that Psd1p autocatalysis requires a mitochondrial-specific factor and that for Psd1p to function in vivo, it had to be embedded with the correct topology in the mitochondrial inner membrane. However, the identity of the mitochondrial factor required for Psd1p autocatalysis has not been identified. With the goal of defining molecular requirements for Psd1p autocatalysis, we demonstrate that: 1) despite the conservation of the LGST motif from bacteria to humans, only the serine residue is absolutely required for Psd1p autocatalysis and function; 2) yeast Psd1p does not require its substrate phosphatidylserine for autocatalysis; and 3) contrary to a prior report, yeast Psd1p autocatalysis does not require mitochondrial-specific phospholipids, proteins, or co-factors, because Psd1p re-directed to the secretory pathway undergoes autocatalysis normally and is fully functional in vivo.
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Affiliation(s)
- Ouma Onguka
- From the Department of Physiology, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
| | - Elizabeth Calzada
- From the Department of Physiology, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
| | - Oluwaseun B Ogunbona
- From the Department of Physiology, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
| | - Steven M Claypool
- From the Department of Physiology, Johns Hopkins School of Medicine, Baltimore, Maryland 21205
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36
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Lu YW, Claypool SM. Disorders of phospholipid metabolism: an emerging class of mitochondrial disease due to defects in nuclear genes. Front Genet 2015; 6:3. [PMID: 25691889 PMCID: PMC4315098 DOI: 10.3389/fgene.2015.00003] [Citation(s) in RCA: 103] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 01/06/2015] [Indexed: 01/14/2023] Open
Abstract
The human nuclear and mitochondrial genomes co-exist within each cell. While the mitochondrial genome encodes for a limited number of proteins, transfer RNAs, and ribosomal RNAs, the vast majority of mitochondrial proteins are encoded in the nuclear genome. Of the multitude of mitochondrial disorders known to date, only a fifth are maternally inherited. The recent characterization of the mitochondrial proteome therefore serves as an important step toward delineating the nosology of a large spectrum of phenotypically heterogeneous diseases. Following the identification of the first nuclear gene defect to underlie a mitochondrial disorder, a plenitude of genetic variants that provoke mitochondrial pathophysiology have been molecularly elucidated and classified into six categories that impact: (1) oxidative phosphorylation (subunits and assembly factors); (2) mitochondrial DNA maintenance and expression; (3) mitochondrial protein import and assembly; (4) mitochondrial quality control (chaperones and proteases); (5) iron–sulfur cluster homeostasis; and (6) mitochondrial dynamics (fission and fusion). Here, we propose that an additional class of genetic variant be included in the classification schema to acknowledge the role of genetic defects in phospholipid biosynthesis, remodeling, and metabolism in mitochondrial pathophysiology. This seventh class includes a small but notable group of nuclear-encoded proteins whose dysfunction impacts normal mitochondrial phospholipid metabolism. The resulting human disorders present with a diverse array of pathologic consequences that reflect the variety of functions that phospholipids have in mitochondria and highlight the important role of proper membrane homeostasis in mitochondrial biology.
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Affiliation(s)
- Ya-Wen Lu
- Department of Physiology, School of Medicine, Johns Hopkins University Baltimore, MD, USA
| | - Steven M Claypool
- Department of Physiology, School of Medicine, Johns Hopkins University Baltimore, MD, USA
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37
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Moffat C, Bhatia L, Nguyen T, Lynch P, Wang M, Wang D, Ilkayeva OR, Han X, Hirschey MD, Claypool SM, Seifert EL. Acyl-CoA thioesterase-2 facilitates mitochondrial fatty acid oxidation in the liver. J Lipid Res 2014; 55:2458-70. [PMID: 25114170 DOI: 10.1194/jlr.m046961] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Acyl-CoA thioesterase (Acot)2 localizes to the mitochondrial matrix and hydrolyses long-chain fatty acyl-CoA into free FA and CoASH. Acot2 is expressed in highly oxi-dative tissues and is poised to modulate mitochondrial FA oxidation (FAO), yet its biological role is unknown. Using a model of adenoviral Acot2 overexpression in mouse liver (Ad-Acot2), we show that Acot2 increases the utilization of FA substrate during the daytime in ad libitum-fed mice, but the nighttime switch to carbohydrate oxidation is similar to control mice. In further support of elevated FAO in Acot2 liver, daytime serum ketones were higher in Ad-Acot2 mice, and overnight fasting led to minimal hepatic steatosis as compared with control mice. In liver mitochondria from Ad-Acot2 mice, phosphorylating O₂ consumption was higher with lipid substrate, but not with nonlipid substrate. This increase depended on whether FA could be activated on the outer mitochondrial membrane, suggesting that the FA released by Acot2 could be effluxed from mitochondria then taken back up again for oxidation. This circuit would prevent the build-up of inhibitory long-chain fatty acyl-CoA esters. Altogether, our findings indicate that Acot2 can enhance FAO, possibly by mitigating the accumulation of FAO intermediates within the mitochondrial matrix.
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Affiliation(s)
- Cynthia Moffat
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107
| | - Lavesh Bhatia
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107
| | - Teresa Nguyen
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107
| | - Peter Lynch
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107
| | - Miao Wang
- Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL 32827
| | - Dongning Wang
- Sarah W. Stedman Nutrition and Metabolism Center, Duke University Medical Center, Durham, NC 27710
| | - Olga R Ilkayeva
- Sarah W. Stedman Nutrition and Metabolism Center, Duke University Medical Center, Durham, NC 27710
| | - Xianlin Han
- Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL 32827
| | - Matthew D Hirschey
- Sarah W. Stedman Nutrition and Metabolism Center, Duke University Medical Center, Durham, NC 27710
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins School of Medicine, Baltimore, MD 21205
| | - Erin L Seifert
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107
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38
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Baile MG, Sathappa M, Lu YW, Pryce E, Whited K, McCaffery JM, Han X, Alder NN, Claypool SM. Unremodeled and remodeled cardiolipin are functionally indistinguishable in yeast. J Biol Chem 2013; 289:1768-78. [PMID: 24285538 DOI: 10.1074/jbc.m113.525733] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [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: 11/06/2022] Open
Abstract
After biosynthesis, an evolutionarily conserved acyl chain remodeling process generates a final highly homogeneous and yet tissue-specific molecular form of the mitochondrial lipid cardiolipin. Hence, cardiolipin molecules in different organisms, and even different tissues within the same organism, contain a distinct collection of attached acyl chains. This observation is the basis for the widely accepted paradigm that the acyl chain composition of cardiolipin is matched to the unique mitochondrial demands of a tissue. For this hypothesis to be correct, cardiolipin molecules with different acyl chain compositions should have distinct functional capacities, and cardiolipin that has been remodeled should promote cardiolipin-dependent mitochondrial processes better than its unremodeled form. However, functional disparities between different molecular forms of cardiolipin have never been established. Here, we interrogate this simple but crucial prediction utilizing the best available model to do so, Saccharomyces cerevisiae. Specifically, we compare the ability of unremodeled and remodeled cardiolipin, which differ markedly in their acyl chain composition, to support mitochondrial activities known to require cardiolipin. Surprisingly, defined changes in the acyl chain composition of cardiolipin do not alter either mitochondrial morphology or oxidative phosphorylation. Importantly, preventing cardiolipin remodeling initiation in yeast lacking TAZ1, an ortholog of the causative gene in Barth syndrome, ameliorates mitochondrial dysfunction. Thus, our data do not support the prevailing hypothesis that unremodeled cardiolipin is functionally distinct from remodeled cardiolipin, at least for the functions examined, suggesting alternative physiological roles for this conserved pathway.
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Affiliation(s)
- Matthew G Baile
- From the Department of Physiology, The Johns Hopkins School of Medicine, Baltimore, Maryland 21205
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39
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Baile MG, Lu YW, Claypool SM. The topology and regulation of cardiolipin biosynthesis and remodeling in yeast. Chem Phys Lipids 2013; 179:25-31. [PMID: 24184646 DOI: 10.1016/j.chemphyslip.2013.10.008] [Citation(s) in RCA: 44] [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] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Revised: 10/16/2013] [Accepted: 10/19/2013] [Indexed: 01/06/2023]
Abstract
The signature mitochondrial phospholipid cardiolipin plays an important role in mitochondrial function, and alterations in cardiolipin metabolism are associated with human disease. Topologically, cardiolipin biosynthesis and remodeling are complex. Precursor phospholipids must be transported from the ER, across the mitochondrial outer membrane to the matrix-facing leaflet of the inner membrane, where cardiolipin biosynthesis commences. Post-synthesis, cardiolipin undergoes acyl chain remodeling, requiring additional trafficking steps, before it achieves its final distribution within both mitochondrial membranes. This process is regulated at several points via multiple independent mechanisms. Here, we review the regulation and topology of cardiolipin biosynthesis and remodeling in the yeast Saccharomyces cerevisiae. Although cardiolipin metabolism is more complicated in mammals, yeast have been an invaluable model for dissecting the steps required for this process.
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Affiliation(s)
- Matthew G Baile
- Department of Physiology, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
| | - Ya-Wen Lu
- Department of Physiology, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
| | - Steven M Claypool
- Department of Physiology, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA.
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40
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Abstract
Our understanding of the clinically relevant tafazzin-mediated cardiolipin (CL) remodeling pathway is incomplete. In this study, a new trafficking step required for CL remodeling has been identified. Further, it is demonstrated that flux through this CL remodeling pathway is controlled by the strength of the mitochondrial electrochemical gradient. The mitochondrial-specific lipid cardiolipin (CL) is required for numerous processes therein. After its synthesis on the matrix-facing leaflet of the inner membrane (IM), CL undergoes acyl chain remodeling to achieve its final form. In yeast, this process is completed by the transacylase tafazzin, which associates with intermembrane space (IMS)-facing membrane leaflets. Mutations in TAZ1 result in the X-linked cardiomyopathy Barth syndrome. Amazingly, despite this clear pathophysiological association, the physiological importance of CL remodeling is unresolved. In this paper, we show that the lipase initiating CL remodeling, Cld1p, is associated with the matrix-facing leaflet of the mitochondrial IM. Thus monolysocardiolipin generated by Cld1p must be transported to IMS-facing membrane leaflets to gain access to tafazzin, identifying a previously unknown step required for CL remodeling. Additionally, we show that Cld1p is the major site of regulation in CL remodeling; and that, like CL biosynthesis, CL remodeling is augmented in growth conditions requiring mitochondrially produced energy. However, unlike CL biosynthesis, dissipation of the mitochondrial membrane potential stimulates CL remodeling, identifying a novel feedback mechanism linking CL remodeling to oxidative phosphorylation capacity.
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Affiliation(s)
- Matthew G Baile
- Department of Physiology, Johns Hopkins School of Medicine, Baltimore, MD 21205-2185, USA
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41
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Baile MG, Whited K, Claypool SM. Defining Trafficking Steps Required for Cardiolipin Remodeling. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.585.14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Kevin Whited
- PhysiologyJohns Hopkins School of MedicineBaltimoreMD
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42
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Onguka O, Claypool SM. Characterizing Mitochondrial Phostidylserine Decarboxylase 1. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.585.17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Ouma Onguka
- PhysiologyJohns Hopkins School of MedicineBaltimoreMD
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43
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Abstract
Mitochondria participate in a variety of cellular functions. As such, mitochondrial diseases exhibit numerous clinical phenotypes. Because mitochondrial functions are highly conserved between humans and Saccharomyces cerevisiae, yeast are an excellent model to study mitochondrial disease, providing insight into both physiological and pathophysiological processes.
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Affiliation(s)
- Matthew G Baile
- Dept. of Physiology, Johns Hopkins School of Medicine, 725 N. Wolfe St., Baltimore, MD 21205-2185, USA
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44
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Tamura Y, Onguka O, Itoh K, Endo T, Iijima M, Claypool SM, Sesaki H. Phosphatidylethanolamine biosynthesis in mitochondria: phosphatidylserine (PS) trafficking is independent of a PS decarboxylase and intermembrane space proteins UPS1P and UPS2P. J Biol Chem 2012; 287:43961-71. [PMID: 23124206 DOI: 10.1074/jbc.m112.390997] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphatidylethanolamine (PE) plays important roles for the structure and function of mitochondria and other intracellular organelles. In yeast, the majority of PE is produced from phosphatidylserine (PS) by a mitochondrion-located PS decarboxylase, Psd1p. Because PS is synthesized in the endoplasmic reticulum (ER), PS is transported from the ER to mitochondria and converted to PE. After its synthesis, a portion of PE moves back to the ER. Two mitochondrial proteins located in the intermembrane space, Ups1p and Ups2p, have been shown to regulate PE metabolism by controlling the export of PE. It remains to be determined where PS is decarboxylated in mitochondria and whether decarboxylation is coupled to trafficking of PS. Here, using fluorescent PS as a substrate in an in vitro assay for Psd1p-dependent PE production in isolated mitochondria, we show that PS is transferred from the mitochondrial outer membrane to the inner membrane independently of Psd1p, Ups1p, and Ups2p and decarboxylated to PE by Psd1p in the inner membrane. Interestingly, Ups1p is required for the maintenance of Psd1p and therefore PE production. Restoration of Psd1p levels rescued PE production defects in ups1Δ mitochondria. Our data provide novel mechanistic insight into PE biogenesis in mitochondria.
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Affiliation(s)
- Yasushi Tamura
- Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
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45
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Abstract
Patients with Barth syndrome (BTHS), a rare X-linked disease, suffer from skeletal and cardiomyopathy and bouts of cyclic neutropenia. The causative gene encodes tafazzin, a transacylase, which is the major determinant of the final acyl chain composition of the mitochondrial-specific phospholipid, CL. In addition to numerous frame shift and splice-site mutations, 36 missense mutations have been associated with BTHS. Previously, we established a BTHS-mutant panel in the yeast Saccharomyces cerevisiae that successfully models 18/21 conserved pathogenic missense mutations and defined the loss-of-function mechanism associated with a subset of the mutant tafazzins. Here, we report the biochemical and cell biological characterization of the rest of the yeast BTHS-mutant panel and in so doing identify three additional modes of tafazzin dysfunction. The largest group of mutant tafazzins is catalytically null, two mutants encode hypomorphic alleles, and another two mutants are temperature sensitive. Additionally, we have expanded the defects associated with previously characterized matrix-mislocalized-mutant tafazzins to include the rapid degradation of aggregation-prone polypeptides that correctly localize to the mitochondrial IMS. In sum, our in-depth characterization of the yeast BTHS-mutant panel has identified seven functional classes of BTHS mutation.
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Affiliation(s)
- Kevin Whited
- Department of Physiology, Johns Hopkins School of Medicine, Baltimore, MD 21205-2185, USA
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46
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Tamura Y, Onguka O, Aiken Hobbs AE, Jensen RE, Iijima M, Claypool SM, Sesaki H. Role for two conserved intermembrane space proteins, Ups1p and Ups2p, in intra-mitochondrial phospholipid trafficking. J Biol Chem 2012. [DOI: 10.1074/jbc.a111.338665] [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: 11/06/2022] Open
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47
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Claypool SM, Oktay Y, Boontheung P, Loo JA, Koehler CM. Cardiolipin defines the interactome of the major ADP/ATP carrier protein of the mitochondrial inner membrane. J Biophys Biochem Cytol 2012. [PMCID: PMC3384408 DOI: 10.1083/jcb.2008011521977c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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48
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Tamura Y, Onguka O, Hobbs AEA, Jensen RE, Iijima M, Claypool SM, Sesaki H. Role for two conserved intermembrane space proteins, Ups1p and Ups2p, [corrected] in intra-mitochondrial phospholipid trafficking. J Biol Chem 2012; 287:15205-18. [PMID: 22403410 DOI: 10.1074/jbc.m111.338665] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mitochondrial membranes maintain a specific phospholipid composition. Most phospholipids are synthesized in the endoplasmic reticulum (ER) and transported to mitochondria, but cardiolipin and phosphatidylethanolamine are produced in mitochondria. In the yeast Saccharomyces cerevisiae, phospholipid exchange between the ER and mitochondria relies on the ER-mitochondria encounter structure (ERMES) complex, which physically connects the ER and mitochondrial outer membrane. However, the proteins and mechanisms involved in phospholipid transport within mitochondria remain elusive. Here, we investigated the role of the conserved intermembrane space proteins, Ups1p and Ups2p, and an inner membrane protein, Mdm31p, in phospholipid metabolism. Our data show that loss of the ERMES complex, Ups1p, and Mdm31p causes similar defects in mitochondrial phospholipid metabolism, mitochondrial morphology, and cell growth. Defects in cells lacking the ERMES complex or Ups1p are suppressed by Mdm31p overexpression as well as additional loss of Ups2p, which antagonizes Ups1p. Combined loss of the ERMES complex and Ups1p exacerbates phospholipid defects. Finally, pulse-chase experiments using [(14)C]serine revealed that Ups1p and Ups2p antagonistically regulate conversion of phosphatidylethanolamine to phosphatidylcholine. Our results suggest that Ups proteins and Mdm31p play important roles in phospholipid biosynthesis in mitochondria. Ups proteins may function in phospholipid trafficking between the outer and inner mitochondrial membranes.
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Affiliation(s)
- Yasushi Tamura
- Department of Cell Biology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
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49
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Claypool SM, Koehler CM. The complexity of cardiolipin in health and disease. Trends Biochem Sci 2011; 37:32-41. [PMID: 22014644 DOI: 10.1016/j.tibs.2011.09.003] [Citation(s) in RCA: 250] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Revised: 09/12/2011] [Accepted: 09/19/2011] [Indexed: 11/29/2022]
Abstract
Cardiolipin, the signature phospholipid of mitochondria, is a lipid dimer that is important for a diverse range of mitochondrial activities beyond the process of ATP production. Thus not surprisingly, derangements in cardiolipin metabolism are now appreciated to contribute to an assortment of pathological conditions. A comprehensive inventory of enzymes involved in cardiolipin biosynthesis and remodeling was just recently obtained. Post-biosynthesis, the acyl chain composition of cardiolipin is modified by up to three distinct remodeling enzymes that produce either a homogeneous tissue-specific mature form of cardiolipin or alternatively 'bad' cardiolipin that has been linked to mitochondrial dysfunction. In this review, we initially focus on the newly identified players in cardiolipin metabolism and then shift our attention to how changes in cardiolipin metabolism contribute to human disease.
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Affiliation(s)
- Steven M Claypool
- Department of Physiology, Johns Hopkins School of Medicine, Baltimore, MD 21205-2185, USA.
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50
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Abstract
Deficits in mitochondrial function result in many human diseases. The X-linked disease Barth syndrome (BTHS) is caused by mutations in the tafazzin gene TAZ1. Its product, Taz1p, participates in the metabolism of cardiolipin, the signature phospholipid of mitochondria. In this paper, a yeast BTHS mutant tafazzin panel is established, and 18 of the 21 tested BTHS missense mutations cannot functionally replace endogenous tafazzin. Four BTHS mutant tafazzins expressed at low levels are degraded by the intermembrane space AAA (i-AAA) protease, suggesting misfolding of the mutant polypeptides. Paradoxically, each of these mutant tafazzins assembles in normal protein complexes. Furthermore, in the absence of the i-AAA protease, increased expression and assembly of two of the BTHS mutants improve their function. However, the BTHS mutant complexes are extremely unstable and accumulate as insoluble aggregates when disassembled in the absence of the i-AAA protease. Thus, the loss of function for these BTHS mutants results from the inherent instability of the mutant tafazzin complexes.
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Affiliation(s)
- Steven M Claypool
- Department of Physiology, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA.
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