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Hashmi F, Kane PM. V-ATPase Disassembly at the Yeast Lysosome-Like Vacuole Is a Phenotypic Driver of Lysosome Dysfunction in Replicative Aging. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.07.23.604825. [PMID: 39091794 PMCID: PMC11291124 DOI: 10.1101/2024.07.23.604825] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 08/04/2024]
Abstract
Declines in lysosomal acidification and function with aging are observed in organisms ranging from yeast to humans. V-ATPases play a central role in organelle acidification and V-ATPase activity is regulated by reversible disassembly in many different settings. Using the yeast Saccharomyces cerevisiae as a replicative aging model, we demonstrate that V-ATPases disassemble into their V1 and V0 subcomplexes in aging cells, with release of V1 subunit C (Vma5) from the lysosome-like vacuole into the cytosol. Disassembly is observed after ≥5 cell divisions and results in overall vacuole alkalinization. Caloric restriction, an established mechanism for reversing many age-related outcomes, prevents V-ATPase disassembly in older cells and preserves vacuolar pH homeostasis. Reversible disassembly is controlled in part by the activity of two opposing and conserved factors, the RAVE complex and Oxr1. The RAVE complex promotes V-ATPase assembly and a rav1Δ mutant shortens replicative lifespan; Oxr1 promotes disassembly and an oxr1Δ mutation extends lifespan. Importantly, the level of Rav2, a key subunit of the RAVE complex, declines in aged cells. These data indicate that reduced V-ATPase assembly contributes to the loss of lysosome acidification with age, which affects replicative lifespan.
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Affiliation(s)
- Fiza Hashmi
- Department of Biochemistry and Molecular Biology , SUNY Upstate Medical University, Syracuse, NY USA
| | - Patricia M Kane
- Department of Biochemistry and Molecular Biology , SUNY Upstate Medical University, Syracuse, NY USA
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2
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Coupland CE, Karimi R, Bueler SA, Liang Y, Courbon GM, Di Trani JM, Wong CJ, Saghian R, Youn JY, Wang LY, Rubinstein JL. High-resolution electron cryomicroscopy of V-ATPase in native synaptic vesicles. Science 2024; 385:168-174. [PMID: 38900912 DOI: 10.1126/science.adp5577] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2024] [Accepted: 05/16/2024] [Indexed: 06/22/2024]
Abstract
Intercellular communication in the nervous system occurs through the release of neurotransmitters into the synaptic cleft between neurons. In the presynaptic neuron, the proton pumping vesicular- or vacuolar-type ATPase (V-ATPase) powers neurotransmitter loading into synaptic vesicles (SVs), with the V1 complex dissociating from the membrane region of the enzyme before exocytosis. We isolated SVs from rat brain using SidK, a V-ATPase-binding bacterial effector protein. Single-particle electron cryomicroscopy allowed high-resolution structure determination of V-ATPase within the native SV membrane. In the structure, regularly spaced cholesterol molecules decorate the enzyme's rotor and the abundant SV protein synaptophysin binds the complex stoichiometrically. ATP hydrolysis during vesicle loading results in a loss of the V1 region of V-ATPase from the SV membrane, suggesting that loading is sufficient to induce dissociation of the enzyme.
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Affiliation(s)
- Claire E Coupland
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON M5G 1X1, Canada
| | - Ryan Karimi
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON M5G 1X1, Canada
- Department of Medical Biophysics, The University of Toronto, Toronto, ON M5G 1L7, Canada
| | - Stephanie A Bueler
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON M5G 1X1, Canada
| | - Yingke Liang
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON M5G 1X1, Canada
- Department of Biochemistry, The University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Gautier M Courbon
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON M5G 1X1, Canada
- Department of Medical Biophysics, The University of Toronto, Toronto, ON M5G 1L7, Canada
| | - Justin M Di Trani
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON M5G 1X1, Canada
| | - Cassandra J Wong
- Lunenfeld-Tanenbaum Research Institute, Toronto, ON M5G 1X5, Canada
| | - Rayan Saghian
- Neuroscience and Mental Health Program, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
- Department of Physiology, The University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Ji-Young Youn
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON M5G 1X1, Canada
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
- Department of Molecular Genetics, The University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Lu-Yang Wang
- Neuroscience and Mental Health Program, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada
- Department of Physiology, The University of Toronto, Toronto, ON M5S 1A8, Canada
| | - John L Rubinstein
- Molecular Medicine Program, The Hospital for Sick Children, Toronto, ON M5G 1X1, Canada
- Department of Medical Biophysics, The University of Toronto, Toronto, ON M5G 1L7, Canada
- Department of Biochemistry, The University of Toronto, Toronto, ON M5S 1A8, Canada
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3
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Parra KJ. The merger of two major families of proteins that regulate cellular processes. Structure 2024; 32:851-853. [PMID: 38996510 DOI: 10.1016/j.str.2024.06.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2024] [Revised: 06/14/2024] [Accepted: 06/16/2024] [Indexed: 07/14/2024]
Abstract
In this issue of Structure, Oot and Wilkens1 present new mechanistic insights to finally merge the function of V-ATPase and TLDc domain proteins. They show that TLDc proteins directly affect V-ATPase activity and assembly, expanding our understanding of how V-ATPase and TLDc proteins exert a plethora of biological functions.
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Affiliation(s)
- Karlett J Parra
- Department of Biochemistry and Molecular Biology, University of New Mexico School of Medicine, Albuquerque, NM, USA.
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Klössel S, Zhu Y, Amado L, Bisinski DD, Ruta J, Liu F, González Montoro A. Yeast TLDc domain proteins regulate assembly state and subcellular localization of the V-ATPase. EMBO J 2024; 43:1870-1897. [PMID: 38589611 PMCID: PMC11066047 DOI: 10.1038/s44318-024-00097-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2024] [Revised: 03/06/2024] [Accepted: 03/08/2024] [Indexed: 04/10/2024] Open
Abstract
Yeast vacuoles perform crucial cellular functions as acidic degradative organelles, storage compartments, and signaling hubs. These functions are mediated by important protein complexes, including the vacuolar-type H+-ATPase (V-ATPase), responsible for organelle acidification. To gain a more detailed understanding of vacuole function, we performed cross-linking mass spectrometry on isolated vacuoles, detecting many known as well as novel protein-protein interactions. Among these, we identified the uncharacterized TLDc-domain-containing protein Rtc5 as a novel interactor of the V-ATPase. We further analyzed the influence of Rtc5 and of Oxr1, the only other yeast TLDc-domain-containing protein, on V-ATPase function. We find that both Rtc5 and Oxr1 promote the disassembly of the vacuolar V-ATPase in vivo, counteracting the role of the RAVE complex, a V-ATPase assembly chaperone. Furthermore, Oxr1 is necessary for the retention of a Golgi-specific subunit of the V-ATPase in this compartment. Collectively, our results shed light on the in vivo roles of yeast TLDc-domain proteins as regulators of the V-ATPase, highlighting the multifaceted regulation of this crucial protein complex.
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Affiliation(s)
- Samira Klössel
- Osnabrück University, Department of Biology/Chemistry, Cellular Communication Laboratory, Barbarastrasse 13, 49076, Osnabrück, Germany
| | - Ying Zhu
- Department of Structural Biology, Leibniz - Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Roessle-Str. 10, Berlin, 13125, Germany
| | - Lucia Amado
- Osnabrück University, Department of Biology/Chemistry, Cellular Communication Laboratory, Barbarastrasse 13, 49076, Osnabrück, Germany
| | - Daniel D Bisinski
- Osnabrück University, Department of Biology/Chemistry, Cellular Communication Laboratory, Barbarastrasse 13, 49076, Osnabrück, Germany
| | - Julia Ruta
- Department of Structural Biology, Leibniz - Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Roessle-Str. 10, Berlin, 13125, Germany
| | - Fan Liu
- Department of Structural Biology, Leibniz - Forschungsinstitut für Molekulare Pharmakologie (FMP), Robert-Roessle-Str. 10, Berlin, 13125, Germany
- Charité - Universitätsmedizin Berlin, Charitépl. 1, 10117, Berlin, Germany
| | - Ayelén González Montoro
- Osnabrück University, Department of Biology/Chemistry, Cellular Communication Laboratory, Barbarastrasse 13, 49076, Osnabrück, Germany.
- Osnabrück University, Center of Cellular Nanoanalytic Osnabrück (CellNanOs), Barbarastrasse 11, 49076, Osnabrück, Germany.
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Khan MM, Wilkens S. Molecular mechanism of Oxr1p mediated disassembly of yeast V-ATPase. EMBO Rep 2024; 25:2323-2347. [PMID: 38565737 PMCID: PMC11094088 DOI: 10.1038/s44319-024-00126-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Revised: 03/07/2024] [Accepted: 03/09/2024] [Indexed: 04/04/2024] Open
Abstract
The eukaryotic vacuolar H+-ATPase (V-ATPase) is regulated by reversible disassembly into autoinhibited V1-ATPase and Vo proton channel subcomplexes. We recently reported that the TLDc protein Oxr1p induces V-ATPase disassembly in vitro. Whether and how Oxr1p is involved in enzyme disassembly in vivo, however, is not known. Here, using yeast genetics and fluorescence microscopy, we show that Oxr1p is essential for efficient V-ATPase disassembly in the cell. Supporting biochemical and biophysical in vitro experiments show that whereas Oxr1p-driven holoenzyme disassembly can occur in the absence of nucleotides, the presence of ATP greatly accelerates the process. ATP hydrolysis is needed, however, for subsequent release of Oxr1p so that the free V1 can adopt the autoinhibited conformation. Overall, our study unravels the molecular mechanism of Oxr1p-induced disassembly that occurs in vivo as part of the canonical V-ATPase regulation by reversible disassembly.
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Affiliation(s)
- Md Murad Khan
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Stephan Wilkens
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA.
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Sava I, Davis LJ, Gray SR, Bright NA, Luzio JP. Reversible assembly and disassembly of V-ATPase during the lysosome regeneration cycle. Mol Biol Cell 2024; 35:ar63. [PMID: 38446621 PMCID: PMC11151095 DOI: 10.1091/mbc.e23-08-0322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Revised: 02/23/2024] [Accepted: 03/01/2024] [Indexed: 03/08/2024] Open
Abstract
Regulation of the luminal pH of late endocytic compartments in continuously fed mammalian cells is poorly understood. Using normal rat kidney fibroblasts, we investigated the reversible assembly/disassembly of the proton pumping V-ATPase when endolysosomes are formed by kissing and fusion of late endosomes with lysosomes and during the subsequent reformation of lysosomes. We took advantage of previous work showing that sucrosomes formed by the uptake of sucrose are swollen endolysosomes from which lysosomes are reformed after uptake of invertase. Using confocal microscopy and subcellular fractionation of NRK cells stably expressing fluorescently tagged proteins, we found net recruitment of the V1 subcomplex during sucrosome formation and loss during lysosome reformation, with a similar time course to RAB7a loss. Addition of invertase did not alter mTORC1 signalling, suggesting that the regulation of reversible V-ATPase assembly/disassembly in continuously fed cells differs from that in cells subject to amino acid depletion/refeeding. Using live cell microscopy, we demonstrated recruitment of a fluorescently tagged V1 subunit during endolysosome formation and a dynamic equilibrium and rapid exchange between the cytosolic and membrane bound pools of this subunit. We conclude that reversible V-ATPase assembly/disassembly plays a key role in regulating endolysosomal/lysosomal pH in continuously fed cells.
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Affiliation(s)
- Ioana Sava
- Cambridge Institute for Medical Research (CIMR) and Department of Clinical Biochemistry, University of Cambridge School of Clinical Medicine, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY, UK
| | - Luther J. Davis
- Cambridge Institute for Medical Research (CIMR) and Department of Clinical Biochemistry, University of Cambridge School of Clinical Medicine, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY, UK
| | - Sally R. Gray
- Cambridge Institute for Medical Research (CIMR) and Department of Clinical Biochemistry, University of Cambridge School of Clinical Medicine, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY, UK
| | - Nicholas A. Bright
- Cambridge Institute for Medical Research (CIMR) and Department of Clinical Biochemistry, University of Cambridge School of Clinical Medicine, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY, UK
| | - J. Paul Luzio
- Cambridge Institute for Medical Research (CIMR) and Department of Clinical Biochemistry, University of Cambridge School of Clinical Medicine, The Keith Peters Building, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY, UK
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7
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Yanagisawa S, Bukhari ZA, Parra KJ, Frasch WD. Eukaryotic yeast V 1-ATPase rotary mechanism insights revealed by high-resolution single-molecule studies. Front Mol Biosci 2024; 11:1269040. [PMID: 38567099 PMCID: PMC10985318 DOI: 10.3389/fmolb.2024.1269040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Accepted: 02/07/2024] [Indexed: 04/04/2024] Open
Abstract
Vacuolar ATP-dependent proton pumps (V-ATPases) belong to a super-family of rotary ATPases and ATP synthases. The V1 complex consumes ATP to drive rotation of a central rotor that pumps protons across membranes via the Vo complex. Eukaryotic V-ATPases are regulated by reversible disassembly of subunit C, V1 without C, and VO. ATP hydrolysis is thought to generate an unknown rotary state that initiates regulated disassembly. Dissociated V1 is inhibited by subunit H that traps it in a specific rotational position. Here, we report the first single-molecule studies with high resolution of time and rotational position of Saccharomyces cerevisiae V1-ATPase lacking subunits H and C (V1ΔHC), which resolves previously elusive dwells and angular velocity changes. Rotation occurred in 120° power strokes separated by dwells comparable to catalytic dwells observed in other rotary ATPases. However, unique V1ΔHC rotational features included: 1) faltering power stroke rotation during the first 60°; 2) a dwell often occurring ∼45° after the catalytic dwell, which did not increase in duration at limiting MgATP; 3) a second dwell, ∼2-fold longer occurring 112° that increased in duration and occurrence at limiting MgATP; 4) limiting MgATP-dependent decreases in power stroke angular velocity where dwells were not observed. The results presented here are consistent with MgATP binding to the empty catalytic site at 112° and MgADP released at ∼45°, and provide important new insight concerning the molecular basis for the differences in rotary positions of substrate binding and product release between V-type and F-type ATPases.
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Affiliation(s)
- Seiga Yanagisawa
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Zain A. Bukhari
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Karlett J. Parra
- Department of Biochemistry and Molecular Biology, University of New Mexico School of Medicine, Albuquerque, NM, United States
| | - Wayne D. Frasch
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
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8
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Hoogstraten CA, Hoenderop JG, de Baaij JHF. Mitochondrial Dysfunction in Kidney Tubulopathies. Annu Rev Physiol 2024; 86:379-403. [PMID: 38012047 DOI: 10.1146/annurev-physiol-042222-025000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Mitochondria play a key role in kidney physiology and pathology. They produce ATP to fuel energy-demanding water and solute reabsorption processes along the nephron. Moreover, mitochondria contribute to cellular health by the regulation of autophagy, (oxidative) stress responses, and apoptosis. Mitochondrial abundance is particularly high in cortical segments, including proximal and distal convoluted tubules. Dysfunction of the mitochondria has been described for tubulopathies such as Fanconi, Gitelman, and Bartter-like syndromes and renal tubular acidosis. In addition, mitochondrial cytopathies often affect renal (tubular) tissues, such as in Kearns-Sayre and Leigh syndromes. Nevertheless, the mechanisms by which mitochondrial dysfunction results in renal tubular diseases are only scarcely being explored. This review provides an overview of mitochondrial dysfunction in the development and progression of kidney tubulopathies. Furthermore, it emphasizes the need for further mechanistic investigations to identify links between mitochondrial function and renal electrolyte reabsorption.
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Affiliation(s)
- Charlotte A Hoogstraten
- Department of Medical Biosciences, Radboud University Medical Center, Nijmegen, The Netherlands;
| | - Joost G Hoenderop
- Department of Medical Biosciences, Radboud University Medical Center, Nijmegen, The Netherlands;
| | - Jeroen H F de Baaij
- Department of Medical Biosciences, Radboud University Medical Center, Nijmegen, The Netherlands;
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9
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Jiang YT, Yang LH, Zheng JX, Geng XC, Bai YX, Wang YC, Xue HW, Lin WH. Vacuolar H +-ATPase and BZR1 form a feedback loop to regulate the homeostasis of BR signaling in Arabidopsis. MOLECULAR PLANT 2023; 16:1976-1989. [PMID: 37837193 DOI: 10.1016/j.molp.2023.10.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 09/29/2023] [Accepted: 10/10/2023] [Indexed: 10/15/2023]
Abstract
Brassinosteroid (BR) is a vital plant hormone that regulates plant growth and development. BRASSINAZOLE RESISTANT 1 (BZR1) is a key transcription factor in BR signaling, and its nucleocytoplasmic localization is crucial for BR signaling. However, the mechanisms that regulate BZR1 nucleocytoplasmic distribution and thus the homeostasis of BR signaling remain largely unclear. The vacuole is the largest organelle in mature plant cells and plays a key role in maintenance of cellular pH, storage of intracellular substances, and transport of ions. In this study, we uncovered a novel mechanism of BR signaling homeostasis regulated by the vacuolar H+-ATPase (V-ATPase) and BZR1 feedback loop. Our results revealed that the vha-a2 vha-a3 mutant (vha2, lacking V-ATPase activity) exhibits enhanced BR signaling with increased total amount of BZR1, nuclear-localized BZR1, and the ratio of BZR1/phosphorylated BZR1 in the nucleus. Further biochemical assays revealed that VHA-a2 and VHA-a3 of V-ATPase interact with the BZR1 protein through a domain that is conserved across multiple species. VHA-a2 and VHA-a3 negatively regulate BR signaling by interacting with BZR1 and promoting its retention in the tonoplast. Interestingly, a series of molecular analyses demonstrated that nuclear-localized BZR1 could bind directly to specific motifs in the promoters of VHA-a2 and VHA-a3 to promote their expression. Taken together, these results suggest that V-ATPase and BZR1 may form a feedback regulatory loop to maintain the homeostasis of BR signaling in Arabidopsis, providing new insights into vacuole-mediated regulation of hormone signaling.
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Affiliation(s)
- Yu-Tong Jiang
- School of Life Sciences and Biotechnology, The Joint International Research Laboratory of Metabolic & Developmental Sciences, Shanghai Jiao Tong University, Shanghai 200240, China; Shanghai Collaborative Innovation Center of Agri-Seeds, Joint Center for Single Cell Biology, Shanghai 200240, China; School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Lu-Han Yang
- School of Life Sciences and Biotechnology, The Joint International Research Laboratory of Metabolic & Developmental Sciences, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Ji-Xuan Zheng
- Zhiyuan College, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Xian-Chen Geng
- School of Life Sciences and Biotechnology, The Joint International Research Laboratory of Metabolic & Developmental Sciences, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yu-Xuan Bai
- Zhiyuan College, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yu-Chen Wang
- Zhiyuan College, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Hong-Wei Xue
- Shanghai Collaborative Innovation Center of Agri-Seeds, Joint Center for Single Cell Biology, Shanghai 200240, China; School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Wen-Hui Lin
- School of Life Sciences and Biotechnology, The Joint International Research Laboratory of Metabolic & Developmental Sciences, Shanghai Jiao Tong University, Shanghai 200240, China; Shanghai Collaborative Innovation Center of Agri-Seeds, Joint Center for Single Cell Biology, Shanghai 200240, China.
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10
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Hwang ES, Song SB. Impaired Autophagic Flux in Glucose-Deprived Cells: An Outcome of Lysosomal Acidification Failure Exacerbated by Mitophagy Dysfunction. Mol Cells 2023; 46:655-663. [PMID: 37867391 PMCID: PMC10654461 DOI: 10.14348/molcells.2023.0121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2023] [Revised: 08/23/2023] [Accepted: 08/29/2023] [Indexed: 10/24/2023] Open
Abstract
Autophagy dysfunction is associated with human diseases and conditions including neurodegenerative diseases, metabolic issues, and chronic infections. Additionally, the decline in autophagic activity contributes to tissue and organ dysfunction and aging-related diseases. Several factors, such as down-regulation of autophagy components and activators, oxidative damage, microinflammation, and impaired autophagy flux, are linked to autophagy decline. An autophagy flux impairment (AFI) has been implicated in neurological disorders and in certain other pathological conditions. Here, to enhance our understanding of AFI, we conducted a comprehensive literature review of findings derived from two well-studied cellular stress models: glucose deprivation and replicative senescence. Glucose deprivation is a condition in which cells heavily rely on oxidative phosphorylation for ATP generation. Autophagy is activated, but its flux is hindered at the autolysis step, primarily due to an impairment of lysosomal acidity. Cells undergoing replicative senescence also experience AFI, which is also known to be caused by lysosomal acidity failure. Both glucose deprivation and replicative senescence elevate levels of reactive oxygen species (ROS), affecting lysosomal acidification. Mitochondrial alterations play a crucial role in elevating ROS generation and reducing lysosomal acidity, highlighting their association with autophagy dysfunction and disease conditions. This paper delves into the underlying molecular and cellular pathways of AFI in glucose-deprived cells, providing insights into potential strategies for managing AFI that is driven by lysosomal acidity failure. Furthermore, the investigation on the roles of mitochondrial dysfunction sheds light on the potential effectiveness of modulating mitochondrial function to overcome AFI, offering new possibilities for therapeutic interventions.
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Affiliation(s)
- Eun Seong Hwang
- Department of Life Science, University of Seoul, Seoul 02504, Korea
| | - Seon Beom Song
- Department of Life Science, University of Seoul, Seoul 02504, Korea
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11
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Mouton SN, Boersma AJ, Veenhoff LM. A physicochemical perspective on cellular ageing. Trends Biochem Sci 2023; 48:949-962. [PMID: 37716870 DOI: 10.1016/j.tibs.2023.08.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 08/17/2023] [Accepted: 08/18/2023] [Indexed: 09/18/2023]
Abstract
Cellular ageing described at the molecular level is a multifactorial process that leads to a spectrum of ageing trajectories. There has been recent discussion about whether a decline in physicochemical homeostasis causes aberrant phase transitions, which are a driver of ageing. Indeed, the function of all biological macromolecules, regardless of their participation in biomolecular condensates, depends on parameters such as pH, crowding, and redox state. We expand on the physicochemical homeostasis hypothesis and summarise recent evidence that the intracellular milieu influences molecular processes involved in ageing.
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Affiliation(s)
- Sara N Mouton
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
| | - Arnold J Boersma
- Cellular Protein Chemistry, Bijvoet Centre for Biomolecular Research, Faculty of Science, Utrecht University, Utrecht, The Netherlands
| | - Liesbeth M Veenhoff
- European Research Institute for the Biology of Ageing, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
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12
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Indrawinata K, Argiropoulos P, Sugita S. Structural and functional understanding of disease-associated mutations in V-ATPase subunit a1 and other isoforms. Front Mol Neurosci 2023; 16:1135015. [PMID: 37465367 PMCID: PMC10352029 DOI: 10.3389/fnmol.2023.1135015] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Accepted: 06/09/2023] [Indexed: 07/20/2023] Open
Abstract
The vacuolar-type ATPase (V-ATPase) is a multisubunit protein composed of the cytosolic adenosine triphosphate (ATP) hydrolysis catalyzing V1 complex, and the integral membrane complex, Vo, responsible for proton translocation. The largest subunit of the Vo complex, subunit a, enables proton translocation upon ATP hydrolysis, mediated by the cytosolic V1 complex. Four known subunit a isoforms (a1-a4) are expressed in different cellular locations. Subunit a1 (also known as Voa1), the neural isoform, is strongly expressed in neurons and is encoded by the ATP6V0A1 gene. Global knockout of this gene in mice causes embryonic lethality, whereas pyramidal neuron-specific knockout resulted in neuronal cell death with impaired spatial and learning memory. Recently reported, de novo and biallelic mutations of the human ATP6V0A1 impair autophagic and lysosomal activities, contributing to neuronal cell death in developmental and epileptic encephalopathies (DEE) and early onset progressive myoclonus epilepsy (PME). The de novo heterozygous R740Q mutation is the most recurrent variant reported in cases of DEE. Homology studies suggest R740 deprotonates protons from specific glutamic acid residues in subunit c, highlighting its importance to the overall V-ATPase function. In this paper, we discuss the structure and mechanism of the V-ATPase, emphasizing how mutations in subunit a1 can lead to lysosomal and autophagic dysfunction in neurodevelopmental disorders, and how mutations to the non-neural isoforms, a2-a4, can also lead to various genetic diseases. Given the growing discovery of disease-causing variants of V-ATPase subunit a and its function as a pump-based regulator of intracellular organelle pH, this multiprotein complex warrants further investigation.
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Affiliation(s)
- Karen Indrawinata
- Division of Translational and Experimental Neuroscience, Krembil Brain Institute, University Health Network, Toronto, ON, Canada
| | - Peter Argiropoulos
- Division of Translational and Experimental Neuroscience, Krembil Brain Institute, University Health Network, Toronto, ON, Canada
| | - Shuzo Sugita
- Division of Translational and Experimental Neuroscience, Krembil Brain Institute, University Health Network, Toronto, ON, Canada
- Department of Physiology, Faculty of Medicine, University of Toronto, Toronto, ON, Canada
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13
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Wilkens S, Khan MM, Knight K, Oot R. Tender love and disassembly: How a TLDc domain protein breaks the V-ATPase. Bioessays 2023; 45:e2200251. [PMID: 37183929 PMCID: PMC10392918 DOI: 10.1002/bies.202200251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 04/13/2023] [Accepted: 05/03/2023] [Indexed: 05/16/2023]
Abstract
Vacuolar ATPases (V-ATPases, V1 Vo -ATPases) are rotary motor proton pumps that acidify intracellular compartments, and, when localized to the plasma membrane, the extracellular space. V-ATPase is regulated by a unique process referred to as reversible disassembly, wherein V1 -ATPase disengages from Vo proton channel in response to diverse environmental signals. Whereas the disassembly step of this process is ATP dependent, the (re)assembly step is not, but requires the action of a heterotrimeric chaperone referred to as the RAVE complex. Recently, an alternative pathway of holoenzyme disassembly was discovered that involves binding of Oxidation Resistance 1 (Oxr1p), a poorly characterized protein implicated in oxidative stress response. Unlike conventional reversible disassembly, which depends on enzyme activity, Oxr1p induced dissociation can occur in absence of ATP. Yeast Oxr1p belongs to the family of TLDc domain containing proteins that are conserved from yeast to mammals, and have been implicated in V-ATPase function in a variety of tissues. This brief perspective summarizes what we know about the molecular mechanisms governing both reversible (ATP dependent) and Oxr1p driven (ATP independent) V-ATPase dissociation into autoinhibited V1 and Vo subcomplexes.
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Affiliation(s)
- Stephan Wilkens
- Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY
| | - Md. Murad Khan
- Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY
| | - Kassidy Knight
- Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY
| | - Rebecca Oot
- Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, NY
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14
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Tuli F, Kane PM. Chimeric a-subunit isoforms generate functional yeast V-ATPases with altered regulatory properties in vitro and in vivo. Mol Biol Cell 2023; 34:ar14. [PMID: 36598799 PMCID: PMC10011726 DOI: 10.1091/mbc.e22-07-0265] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
V-ATPases are highly regulated proton pumps that acidify organelles. The V-ATPase a-subunit is a two-domain protein containing a C-terminal transmembrane domain responsible for proton transport and an N-terminal cytosolic domain (aNT) that is a regulatory hub, integrating environmental inputs to regulate assembly, localization, and V-ATPase activity. The yeast Saccharomyces cerevisiae encodes only two organelle-specific a-isoforms, Stv1 in the Golgi and Vph1 in the vacuole. On the basis of recent structures, we designed chimeric yeast aNTs in which the globular proximal and distal ends are exchanged. The Vph1 proximal-Stv1 distal (VPSD) aNT chimera binds to the glucose-responsive RAVE assembly factor in vitro but exhibits little binding to PI(3,5)P2. The Stv1 proximal-Vph1 distal (SPVD) aNT lacks RAVE binding but binds more tightly to phosphoinositides than Vph1 or Stv1. When attached to the Vph1 C-terminal domain in vivo, both chimeras complement growth defects of a vph1∆ mutant, but only the SPVD chimera exhibits wild-type V-ATPase activity. Cells containing the SPVD chimera adapt more slowly to a poor carbon source than wild-type cells but grow more rapidly than wild-type cells after a shift to alkaline pH. This is the first example of a "redesigned" V-ATPase with altered regulatory properties and adaptation to specific stresses.
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Affiliation(s)
- Farzana Tuli
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210
| | - Patricia M Kane
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210
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15
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Jin X, Zhou M, Chen S, Li D, Cao X, Liu B. Effects of pH alterations on stress- and aging-induced protein phase separation. Cell Mol Life Sci 2022; 79:380. [PMID: 35750966 PMCID: PMC9232405 DOI: 10.1007/s00018-022-04393-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 04/26/2022] [Accepted: 05/21/2022] [Indexed: 01/18/2023]
Abstract
Upon stress challenges, proteins/RNAs undergo liquid–liquid phase separation (LLPS) to fine-tune cell physiology and metabolism to help cells adapt to adverse environments. The formation of LLPS has been recently linked with intracellular pH, and maintaining proper intracellular pH homeostasis is known to be essential for the survival of organisms. However, organisms are constantly exposed to diverse stresses, which are accompanied by alterations in the intracellular pH. Aging processes and human diseases are also intimately linked with intracellular pH alterations. In this review, we summarize stress-, aging-, and cancer-associated pH changes together with the mechanisms by which cells regulate cytosolic pH homeostasis. How critical cell components undergo LLPS in response to pH alterations is also discussed, along with the functional roles of intracellular pH fluctuation in the regulation of LLPS. Further studies investigating the interplay of pH with other stressors in LLPS regulation and identifying protein responses to different pH levels will provide an in-depth understanding of the mechanisms underlying pH-driven LLPS in cell adaptation. Moreover, deciphering aging and disease-associated pH changes that influence LLPS condensate formation could lead to a deeper understanding of the functional roles of biomolecular condensates in aging and aging-related diseases.
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Affiliation(s)
- Xuejiao Jin
- State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A&F University, Lin'an, Hangzhou, 311300, China
| | - Min Zhou
- State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A&F University, Lin'an, Hangzhou, 311300, China
| | - Shuxin Chen
- State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A&F University, Lin'an, Hangzhou, 311300, China
| | - Danqi Li
- State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A&F University, Lin'an, Hangzhou, 311300, China
| | - Xiuling Cao
- State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A&F University, Lin'an, Hangzhou, 311300, China.
| | - Beidong Liu
- State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A&F University, Lin'an, Hangzhou, 311300, China. .,Department of Chemistry and Molecular Biology, University of Gothenburg, Medicinaregatan 9C, 413 90, Goteborg, Sweden. .,Center for Large-Scale Cell-Based Screening, Faculty of Science, University of Gothenburg, Medicinaregatan 9C, 413 90, Goteborg, Sweden.
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16
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Endosomal v-ATPase as a Sensor Determining Myocardial Substrate Preference. Metabolites 2022; 12:metabo12070579. [PMID: 35888703 PMCID: PMC9316095 DOI: 10.3390/metabo12070579] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 06/16/2022] [Accepted: 06/20/2022] [Indexed: 11/17/2022] Open
Abstract
The heart is a metabolically flexible omnivore that can utilize a variety of substrates for energy provision. To fulfill cardiac energy requirements, the healthy adult heart mainly uses long-chain fatty acids and glucose in a balanced manner, but when exposed to physiological or pathological stimuli, it can switch its substrate preference to alternative substrates such as amino acids (AAs) and ketone bodies. Using the failing heart as an example, upon stress, the fatty acid/glucose substrate balance is upset, resulting in an over-reliance on either fatty acids or glucose. A chronic fuel shift towards a single type of substrate is linked with cardiac dysfunction. Re-balancing myocardial substrate preference is suggested as an effective strategy to rescue the failing heart. In the last decade, we revealed that vacuolar-type H+-ATPase (v-ATPase) functions as a key regulator of myocardial substrate preference and, therefore, as a novel potential treatment approach for the failing heart. Fatty acids, glucose, and AAs selectively influence the assembly state of v-ATPase resulting in modulation of its proton-pumping activity. In this review, we summarize these novel insights on v-ATPase as an integrator of nutritional information. We also describe its exploitation as a therapeutic target with focus on supplementation of AA as a nutraceutical approach to fight lipid-induced insulin resistance and contractile dysfunction of the heart.
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17
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Stress- and metabolic responses of Candida albicans require Tor1 kinase N-terminal HEAT repeats. PLoS Pathog 2022; 18:e1010089. [PMID: 35687592 PMCID: PMC9223334 DOI: 10.1371/journal.ppat.1010089] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 06/23/2022] [Accepted: 05/12/2022] [Indexed: 11/19/2022] Open
Abstract
Whether to commit limited cellular resources toward growth and proliferation, or toward survival and stress responses, is an essential determination made by Target of Rapamycin Complex 1 (TORC1) for a eukaryotic cell in response to favorable or adverse conditions. Loss of TORC1 function is lethal. The TORC1 inhibitor rapamycin that targets the highly conserved Tor kinase domain kills fungal pathogens like Candida albicans, but is also severely toxic to human cells. The least conserved region of fungal and human Tor kinases are the N-terminal HEAT domains. We examined the role of the 8 most N-terminal HEAT repeats of C. albicans Tor1. We compared nutritional- and stress responses of cells that express a message for N-terminally truncated Tor1 from repressible tetO, with cells expressing wild type TOR1 from tetO or from the native promoter. Some but not all stress responses were significantly impaired by loss of Tor1 N-terminal HEAT repeats, including those to oxidative-, cell wall-, and heat stress; in contrast, plasma membrane stress and antifungal agents that disrupt plasma membrane function were tolerated by cells lacking this Tor1 region. Translation was inappropriately upregulated during oxidative stress in cells lacking N-terminal Tor1 HEAT repeats despite simultaneously elevated Gcn2 activity, while activation of the oxidative stress response MAP kinase Hog1 was weak. Conversely, these cells were unable to take advantage of favorable nutritional conditions by accelerating their growth. Consuming oxygen more slowly than cells containing wild type TOR1 alleles during growth in glucose, cells lacking N-terminal Tor1 HEAT repeats additionally were incapable of utilizing non-fermentable carbon sources. They were also hypersensitive to inhibitors of specific complexes within the respiratory electron transport chain, suggesting that inefficient ATP generation and a resulting dearth of nucleotide sugar building blocks for cell wall polysaccharides causes cell wall integrity defects in these mutants. Genome-wide expression analysis of cells lacking N-terminal HEAT repeats showed dysregulation of carbon metabolism, cell wall biosynthetic enzymes, translational machinery biosynthesis, oxidative stress responses, and hyphal- as well as white-opaque cell type-associated genes. Targeting fungal-specific Tor1 N-terminal HEAT repeats with small molecules might selectively abrogate fungal viability, especially when during infection multiple stresses are imposed by the host immune system. Whether growing harmlessly on our mucous membranes in competition with bacterial multitudes, or invading our tissues and bloodstream, the fungus Candida albicans must be capable of rapid growth when it finds abundant nutrients and favorable conditions. It must also be able to switch to stress- and survival mode when encountering host immune cells and when starving for nutrients. Tor1 kinase is the central regulator at the heart of these cellular decisions. As an essential protein, it is an attractive drug target. But the Tor1 kinase domain is very similar to its human counterpart, rendering its inhibitors like rapamycin toxic for humans. We identified a region of helical protein-protein interaction domains, the N-terminal HEAT repeats, as the least conserved part of C. albicans Tor1. Using genetic- and genome-wide expression analysis, we found that 8 N-terminal HEAT repeats are required for growth acceleration in nutrient-rich environments and for decreased translation in starvation- and stress conditions. This Tor1 region contributes to oxidative-, cell wall- and heat stress reponses, to hyphal growth and to respiration, but apparently not to plasma membrane stress endurance or fermentation. Small molecules that disrupt the protein-protein interactions mediated by this region could become fungal-selective inhibitors of Tor kinase.
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18
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Maxson ME, Abbas YM, Wu JZ, Plumb JD, Grinstein S, Rubinstein JL. Detection and quantification of the vacuolar H+ATPase using the Legionella effector protein SidK. J Biophys Biochem Cytol 2022; 221:212963. [PMID: 35024770 PMCID: PMC8763849 DOI: 10.1083/jcb.202107174] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 12/14/2021] [Accepted: 12/21/2021] [Indexed: 12/11/2022] Open
Abstract
Acidification of secretory and endocytic organelles is required for proper receptor recycling, membrane traffic, protein degradation, and solute transport. Proton-pumping vacuolar H+ ATPases (V-ATPases) are responsible for this luminal acidification, which increases progressively as secretory and endocytic vesicles mature. An increasing density of V-ATPase complexes is thought to account for the gradual decrease in pH, but available reagents have not been sufficiently sensitive or specific to test this hypothesis. We introduce a new probe to localize and quantify V-ATPases. The probe is derived from SidK, a Legionella pneumophila effector protein that binds to the V-ATPase A subunit. We generated plasmids encoding fluorescent chimeras of SidK1-278, and labeled recombinant SidK1-278 with Alexa Fluor 568 to visualize and quantify V-ATPases with high specificity in live and fixed cells, respectively. We show that V-ATPases are acquired progressively during phagosome maturation, that they distribute in discrete membrane subdomains, and that their density in lysosomes depends on their subcellular localization.
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Affiliation(s)
- Michelle E Maxson
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada
| | - Yazan M Abbas
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, Canada
| | - Jing Ze Wu
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada.,Department of Biochemistry, University of Toronto, Toronto, Canada
| | - Jonathan D Plumb
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada
| | - Sergio Grinstein
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada.,Department of Biochemistry, University of Toronto, Toronto, Canada
| | - John L Rubinstein
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, Canada.,Department of Biochemistry, University of Toronto, Toronto, Canada
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19
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Nowosad A, Besson A. Lysosomes at the Crossroads of Cell Metabolism, Cell Cycle, and Stemness. Int J Mol Sci 2022; 23:ijms23042290. [PMID: 35216401 PMCID: PMC8879101 DOI: 10.3390/ijms23042290] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 02/11/2022] [Accepted: 02/16/2022] [Indexed: 02/07/2023] Open
Abstract
Initially described as lytic bodies due to their degradative and recycling functions, lysosomes play a critical role in metabolic adaptation to nutrient availability. More recently, the contribution of lysosomal proteins to cell signaling has been established, and lysosomes have emerged as signaling hubs that regulate diverse cellular processes, including cell proliferation and cell fate. Deciphering these signaling pathways has revealed an extensive crosstalk between the lysosomal and cell cycle machineries that is only beginning to be understood. Recent studies also indicate that a number of lysosomal proteins are involved in the regulation of embryonic and adult stem cell fate and identity. In this review, we will focus on the role of the lysosome as a signaling platform with an emphasis on its function in integrating nutrient sensing with proliferation and cell cycle progression, as well as in stemness-related features, such as self-renewal and quiescence.
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Affiliation(s)
- Ada Nowosad
- Molecular, Cellular and Developmental Biology Department (MCD), Centre de Biologie Intégrative (CBI), University of Toulouse, CNRS, UPS, 31062 Toulouse, France;
- Department of Oncology, KULeuven, Laboratory for Molecular Cancer Biology, Center for Cancer Biology, VIB, 3000 Leuven, Belgium
| | - Arnaud Besson
- Molecular, Cellular and Developmental Biology Department (MCD), Centre de Biologie Intégrative (CBI), University of Toulouse, CNRS, UPS, 31062 Toulouse, France;
- Correspondence: ; Tel.: +33-561558486
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20
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Khan MM, Lee S, Couoh‐Cardel S, Oot RA, Kim H, Wilkens S, Roh S. Oxidative stress protein Oxr1 promotes V-ATPase holoenzyme disassembly in catalytic activity-independent manner. EMBO J 2022; 41:e109360. [PMID: 34918374 PMCID: PMC8804929 DOI: 10.15252/embj.2021109360] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 10/30/2021] [Accepted: 11/15/2021] [Indexed: 11/09/2022] Open
Abstract
The vacuolar ATPase (V-ATPase) is a rotary motor proton pump that is regulated by an assembly equilibrium between active holoenzyme and autoinhibited V1 -ATPase and Vo proton channel subcomplexes. Here, we report cryo-EM structures of yeast V-ATPase assembled in vitro from lipid nanodisc reconstituted Vo and mutant V1 . Our analysis identified holoenzymes in three active rotary states, indicating that binding of V1 to Vo provides sufficient free energy to overcome Vo autoinhibition. Moreover, the structures suggest that the unequal spacing of Vo 's proton-carrying glutamic acid residues serves to alleviate the symmetry mismatch between V1 and Vo motors, a notion that is supported by mutagenesis experiments. We also uncover a structure of free V1 bound to Oxr1, a conserved but poorly characterized factor involved in the oxidative stress response. Biochemical experiments show that Oxr1 inhibits V1 -ATPase and causes disassembly of the holoenzyme, suggesting that Oxr1 plays a direct role in V-ATPase regulation.
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Affiliation(s)
- Md. Murad Khan
- Department of Biochemistry and Molecular BiologySUNY Upstate Medical UniversitySyracuseNYUSA
| | - Seowon Lee
- School of Biological ScienceInstitute of Molecular Biology and GeneticsSeoul National UniversitySeoulSouth Korea
| | - Sergio Couoh‐Cardel
- Department of Biochemistry and Molecular BiologySUNY Upstate Medical UniversitySyracuseNYUSA
- Present address:
Department of Molecular and Cellular PhysiologyStanford UniversityStanfordCAUSA
| | - Rebecca A Oot
- Department of Biochemistry and Molecular BiologySUNY Upstate Medical UniversitySyracuseNYUSA
| | - Hyunmin Kim
- School of Biological ScienceInstitute of Molecular Biology and GeneticsSeoul National UniversitySeoulSouth Korea
| | - Stephan Wilkens
- Department of Biochemistry and Molecular BiologySUNY Upstate Medical UniversitySyracuseNYUSA
| | - Soung‐Hun Roh
- School of Biological ScienceInstitute of Molecular Biology and GeneticsSeoul National UniversitySeoulSouth Korea
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21
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Oot RA, Yao Y, Manolson MF, Wilkens S. Purification of active human vacuolar H +-ATPase in native lipid-containing nanodiscs. J Biol Chem 2021; 297:100964. [PMID: 34270960 PMCID: PMC8353480 DOI: 10.1016/j.jbc.2021.100964] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 07/07/2021] [Accepted: 07/12/2021] [Indexed: 12/26/2022] Open
Abstract
Vacuolar H+-ATPases (V-ATPases) are large, multisubunit proton pumps that acidify the lumen of organelles in virtually every eukaryotic cell and in specialized acid-secreting animal cells, the enzyme pumps protons into the extracellular space. In higher organisms, most of the subunits are expressed as multiple isoforms, with some enriched in specific compartments or tissues and others expressed ubiquitously. In mammals, subunit a is expressed as four isoforms (a1-4) that target the enzyme to distinct biological membranes. Mutations in a isoforms are known to give rise to tissue-specific disease, and some a isoforms are upregulated and mislocalized to the plasma membrane in invasive cancers. However, isoform complexity and low abundance greatly complicate purification of active human V-ATPase, a prerequisite for developing isoform-specific therapeutics. Here, we report the purification of an active human V-ATPase in native lipid nanodiscs from a cell line stably expressing affinity-tagged a isoform 4 (a4). We find that exogenous expression of this single subunit in HEK293F cells permits assembly of a functional V-ATPase by incorporation of endogenous subunits. The ATPase activity of the preparation is >95% sensitive to concanamycin A, indicating that the lipid nanodisc-reconstituted enzyme is functionally coupled. Moreover, this strategy permits purification of the enzyme's isolated membrane subcomplex together with biosynthetic assembly factors coiled-coil domain-containing protein 115, transmembrane protein 199, and vacuolar H+-ATPase assembly integral membrane protein 21. Our work thus lays the groundwork for biochemical characterization of active human V-ATPase in an a subunit isoform-specific manner and establishes a platform for the study of the assembly and regulation of the human holoenzyme.
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Affiliation(s)
- Rebecca A Oot
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Yeqi Yao
- Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada
| | - Morris F Manolson
- Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada
| | - Stephan Wilkens
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA.
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22
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Jaskolka MC, Winkley SR, Kane PM. RAVE and Rabconnectin-3 Complexes as Signal Dependent Regulators of Organelle Acidification. Front Cell Dev Biol 2021; 9:698190. [PMID: 34249946 PMCID: PMC8264551 DOI: 10.3389/fcell.2021.698190] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 05/28/2021] [Indexed: 12/12/2022] Open
Abstract
The yeast RAVE (Regulator of H+-ATPase of Vacuolar and Endosomal membranes) complex and Rabconnectin-3 complexes of higher eukaryotes regulate acidification of organelles such as lysosomes and endosomes by catalyzing V-ATPase assembly. V-ATPases are highly conserved proton pumps consisting of a peripheral V1 subcomplex that contains the sites of ATP hydrolysis, attached to an integral membrane Vo subcomplex that forms the transmembrane proton pore. Reversible disassembly of the V-ATPase is a conserved regulatory mechanism that occurs in response to multiple signals, serving to tune ATPase activity and compartment acidification to changing extracellular conditions. Signals such as glucose deprivation can induce release of V1 from Vo, which inhibits both ATPase activity and proton transport. Reassembly of V1 with Vo restores ATP-driven proton transport, but requires assistance of the RAVE or Rabconnectin-3 complexes. Glucose deprivation triggers V-ATPase disassembly in yeast and is accompanied by binding of RAVE to V1 subcomplexes. Upon glucose readdition, RAVE catalyzes both recruitment of V1 to the vacuolar membrane and its reassembly with Vo. The RAVE complex can be recruited to the vacuolar membrane by glucose in the absence of V1 subunits, indicating that the interaction between RAVE and the Vo membrane domain is glucose-sensitive. Yeast RAVE complexes also distinguish between organelle-specific isoforms of the Vo a-subunit and thus regulate distinct V-ATPase subpopulations. Rabconnectin-3 complexes in higher eukaryotes appear to be functionally equivalent to yeast RAVE. Originally isolated as a two-subunit complex from rat brain, the Rabconnectin-3 complex has regions of homology with yeast RAVE and was shown to interact with V-ATPase subunits and promote endosomal acidification. Current understanding of the structure and function of RAVE and Rabconnectin-3 complexes, their interactions with the V-ATPase, their role in signal-dependent modulation of organelle acidification, and their impact on downstream pathways will be discussed.
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Affiliation(s)
- Michael C Jaskolka
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
| | - Samuel R Winkley
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
| | - Patricia M Kane
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
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23
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Jaskolka MC, Tarsio M, Smardon AM, Khan MM, Kane PM. Defining steps in RAVE-catalyzed V-ATPase assembly using purified RAVE and V-ATPase subcomplexes. J Biol Chem 2021; 296:100703. [PMID: 33895134 PMCID: PMC8138766 DOI: 10.1016/j.jbc.2021.100703] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 04/20/2021] [Accepted: 04/21/2021] [Indexed: 12/30/2022] Open
Abstract
The vacuolar H+-ATPase (V-ATPase) is a highly conserved proton pump responsible for the acidification of intracellular organelles in virtually all eukaryotic cells. V-ATPases are regulated by the rapid and reversible disassembly of the peripheral V1 domain from the integral membrane Vo domain, accompanied by release of the V1 C subunit from both domains. Efficient reassembly of V-ATPases requires the Regulator of the H+-ATPase of Vacuoles and Endosomes (RAVE) complex in yeast. Although a number of pairwise interactions between RAVE and V-ATPase subunits have been mapped, the low endogenous levels of the RAVE complex and lethality of constitutive RAV1 overexpression have hindered biochemical characterization of the intact RAVE complex. We describe a novel inducible overexpression system that allows purification of native RAVE and RAVE–V1 complexes. Both purified RAVE and RAVE–V1 contain substoichiometric levels of subunit C. RAVE–V1 binds tightly to expressed subunit C in vitro, but binding of subunit C to RAVE alone is weak. Neither RAVE nor RAVE–V1 interacts with the N-terminal domain of Vo subunit Vph1 in vitro. RAVE–V1 complexes, like isolated V1, have no MgATPase activity, suggesting that RAVE cannot reverse V1 inhibition generated by rotation of subunit H and entrapment of MgADP that occur upon disassembly. However, purified RAVE can accelerate reassembly of V1 carrying a mutant subunit H incapable of inhibition with Vo complexes reconstituted into lipid nanodiscs, consistent with its catalytic activity in vivo. These results provide new insights into the possible order of events in V-ATPase reassembly and the roles of the RAVE complex in each event.
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Affiliation(s)
- Michael C Jaskolka
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Maureen Tarsio
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Anne M Smardon
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Md Murad Khan
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Patricia M Kane
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA.
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24
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Breyer F, Härtlova A, Thurston T, Flynn HR, Chakravarty P, Janzen J, Peltier J, Heunis T, Snijders AP, Trost M, Ley SC. TPL-2 kinase induces phagosome acidification to promote macrophage killing of bacteria. EMBO J 2021; 40:e106188. [PMID: 33881780 PMCID: PMC8126920 DOI: 10.15252/embj.2020106188] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 03/11/2021] [Accepted: 03/15/2021] [Indexed: 02/05/2023] Open
Abstract
Tumour progression locus 2 (TPL‐2) kinase mediates Toll‐like receptor (TLR) activation of ERK1/2 and p38α MAP kinases in myeloid cells to modulate expression of key cytokines in innate immunity. This study identified a novel MAP kinase‐independent regulatory function for TPL‐2 in phagosome maturation, an essential process for killing of phagocytosed microbes. TPL‐2 catalytic activity was demonstrated to induce phagosome acidification and proteolysis in primary mouse and human macrophages following uptake of latex beads. Quantitative proteomics revealed that blocking TPL‐2 catalytic activity significantly altered the protein composition of phagosomes, particularly reducing the abundance of V‐ATPase proton pump subunits. Furthermore, TPL‐2 stimulated the phosphorylation of DMXL1, a regulator of V‐ATPases, to induce V‐ATPase assembly and phagosome acidification. Consistent with these results, TPL‐2 catalytic activity was required for phagosome acidification and the efficient killing of Staphylococcus aureus and Citrobacter rodentium following phagocytic uptake by macrophages. TPL‐2 therefore controls innate immune responses of macrophages to bacteria via V‐ATPase induction of phagosome maturation.
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Affiliation(s)
| | - Anetta Härtlova
- Biosciences Institute, Newcastle University, Newcastle-upon-Tyne, UK.,Wallenberg Centre for Molecular and Translational Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Teresa Thurston
- Department of Infectious Diseases, MRC Centre for Molecular Bacteriology & Infection, Imperial College London, London, UK
| | | | | | | | - Julien Peltier
- Biosciences Institute, Newcastle University, Newcastle-upon-Tyne, UK
| | - Tiaan Heunis
- Biosciences Institute, Newcastle University, Newcastle-upon-Tyne, UK
| | | | - Matthias Trost
- Biosciences Institute, Newcastle University, Newcastle-upon-Tyne, UK
| | - Steven C Ley
- The Francis Crick Institute, London, UK.,Department of Immunology & Inflammation, Centre for Molecular Immunology & Inflammation, Imperial College London, London, UK
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25
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Santos-Pereira C, Rodrigues LR, Côrte-Real M. Emerging insights on the role of V-ATPase in human diseases: Therapeutic challenges and opportunities. Med Res Rev 2021; 41:1927-1964. [PMID: 33483985 DOI: 10.1002/med.21782] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 12/05/2020] [Accepted: 01/05/2021] [Indexed: 12/13/2022]
Abstract
The control of the intracellular pH is vital for the survival of all organisms. Membrane transporters, both at the plasma and intracellular membranes, are key players in maintaining a finely tuned pH balance between intra- and extracellular spaces, and therefore in cellular homeostasis. V-ATPase is a housekeeping ATP-driven proton pump highly conserved among prokaryotes and eukaryotes. This proton pump, which exhibits a complex multisubunit structure based on cell type-specific isoforms, is essential for pH regulation and for a multitude of ubiquitous and specialized functions. Thus, it is not surprising that V-ATPase aberrant overexpression, mislocalization, and mutations in V-ATPase subunit-encoding genes have been associated with several human diseases. However, the ubiquitous expression of this transporter and the high toxicity driven by its off-target inhibition, renders V-ATPase-directed therapies very challenging and increases the need for selective strategies. Here we review emerging evidence linking V-ATPase and both inherited and acquired human diseases, explore the therapeutic challenges and opportunities envisaged from recent data, and advance future research avenues. We highlight the importance of V-ATPases with unique subunit isoform molecular signatures and disease-associated isoforms to design selective V-ATPase-directed therapies. We also discuss the rational design of drug development pipelines and cutting-edge methodological approaches toward V-ATPase-centered drug discovery. Diseases like cancer, osteoporosis, and even fungal infections can benefit from V-ATPase-directed therapies.
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Affiliation(s)
- Cátia Santos-Pereira
- Department of Biology, Centre of Molecular and Environmental Biology (CBMA), University of Minho, Braga, Portugal.,Department of Biological Engineering, Centre of Biological Engineering (CEB), University of Minho, Braga, Portugal
| | - Lígia R Rodrigues
- Department of Biological Engineering, Centre of Biological Engineering (CEB), University of Minho, Braga, Portugal
| | - Manuela Côrte-Real
- Department of Biology, Centre of Molecular and Environmental Biology (CBMA), University of Minho, Braga, Portugal
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26
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Eaton AF, Merkulova M, Brown D. The H +-ATPase (V-ATPase): from proton pump to signaling complex in health and disease. Am J Physiol Cell Physiol 2020; 320:C392-C414. [PMID: 33326313 PMCID: PMC8294626 DOI: 10.1152/ajpcell.00442.2020] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A primary function of the H+-ATPase (or V-ATPase) is to create an electrochemical proton gradient across eukaryotic cell membranes, which energizes fundamental cellular processes. Its activity allows for the acidification of intracellular vesicles and organelles, which is necessary for many essential cell biological events to occur. In addition, many specialized cell types in various organ systems such as the kidney, bone, male reproductive tract, inner ear, olfactory mucosa, and more, use plasma membrane V-ATPases to perform specific activities that depend on extracellular acidification. It is, however, increasingly apparent that V-ATPases are central players in many normal and pathophysiological processes that directly influence human health in many different and sometimes unexpected ways. These include cancer, neurodegenerative diseases, diabetes, and sensory perception, as well as energy and nutrient-sensing functions within cells. This review first covers the well-established role of the V-ATPase as a transmembrane proton pump in the plasma membrane and intracellular vesicles and outlines factors contributing to its physiological regulation in different cell types. This is followed by a discussion of the more recently emerging unconventional roles for the V-ATPase, such as its role as a protein interaction hub involved in cell signaling, and the (patho)physiological implications of these interactions. Finally, the central importance of endosomal acidification and V-ATPase activity on viral infection will be discussed in the context of the current COVID-19 pandemic.
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Affiliation(s)
- Amity F Eaton
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Maria Merkulova
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Dennis Brown
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
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27
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Collins MP, Forgac M. Regulation and function of V-ATPases in physiology and disease. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183341. [PMID: 32422136 DOI: 10.1016/j.bbamem.2020.183341] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 04/30/2020] [Accepted: 05/03/2020] [Indexed: 02/07/2023]
Abstract
The vacuolar H+-ATPases (V-ATPases) are essential, ATP-dependent proton pumps present in a variety of eukaryotic cellular membranes. Intracellularly, V-ATPase-dependent acidification functions in such processes as membrane traffic, protein degradation, autophagy and the coupled transport of small molecules. V-ATPases at the plasma membrane of certain specialized cells function in such processes as bone resorption, sperm maturation and urinary acidification. V-ATPases also function in disease processes such as pathogen entry and cancer cell invasiveness, while defects in V-ATPase genes are associated with disorders such as osteopetrosis, renal tubular acidosis and neurodegenerative diseases. This review highlights recent advances in our understanding of V-ATPase structure, mechanism, function and regulation, with an emphasis on the signaling pathways controlling V-ATPase assembly in mammalian cells. The role of V-ATPases in cancer and other human pathologies, and the prospects for therapeutic intervention, are also discussed.
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Affiliation(s)
- Michael P Collins
- Cell, Molecular and Developmental Biology, Tufts University Graduate School of Biomedical Sciences, United States of America
| | - Michael Forgac
- Cell, Molecular and Developmental Biology, Tufts University Graduate School of Biomedical Sciences, United States of America; Dept. of Developmental, Molecular and Chemical Biology, Tufts University School of Medicine, Boston, MA 02111, United States of America.
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28
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Ghazi S, Bourgeois S, Gomariz A, Bugarski M, Haenni D, Martins JR, Nombela-Arrieta C, Unwin RJ, Wagner CA, Hall AM, Craigie E. Multiparametric imaging reveals that mitochondria-rich intercalated cells in the kidney collecting duct have a very high glycolytic capacity. FASEB J 2020; 34:8510-8525. [PMID: 32367531 DOI: 10.1096/fj.202000273r] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 03/30/2020] [Accepted: 04/16/2020] [Indexed: 02/06/2023]
Abstract
Alpha intercalated cells (αICs) in the kidney collecting duct (CD) belong to a family of mitochondria rich cells (MRCs) and have a crucial role in acidifying the urine via apical V-ATPase pumps. The nature of metabolism in αICs and its relationship to transport was not well-understood. Here, using multiphoton live cell imaging in mouse kidney tissue, FIB-SEM, and other complementary techniques, we provide new insights into mitochondrial structure and function in αICs. We show that αIC mitochondria have a rounded structure and are not located in close proximity to V-ATPase containing vesicles. They display a bright NAD(P)H fluorescence signal and low uptake of voltage-dependent dyes, but are energized by a pH gradient. However, expression of complex V (ATP synthase) is relatively low in αICs, even when stimulated by metabolic acidosis. In contrast, anaerobic glycolytic capacity is surprisingly high, and sufficient to maintain intracellular calcium homeostasis in the presence of complete aerobic inhibition. Moreover, glycolysis is essential for V-ATPase-mediated proton pumping. Key findings were replicated in narrow/clear cells in the epididymis, also part of the MRC family. In summary, using a range of cutting-edge techniques to investigate αIC metabolism in situ, we have discovered that these mitochondria dense cells have a high glycolytic capacity.
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Affiliation(s)
- Susan Ghazi
- Institute of Anatomy, University of Zurich, Zurich, Switzerland
| | - Soline Bourgeois
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Alvaro Gomariz
- Department of Medical Oncology and Hematology, University of Zurich, Zurich, Switzerland.,Computer Vision Laboratory, ETH Zurich, Zurich, Switzerland
| | - Milica Bugarski
- Institute of Anatomy, University of Zurich, Zurich, Switzerland
| | - Dominik Haenni
- Institute of Anatomy, University of Zurich, Zurich, Switzerland.,Center for Microscopy and Image Analysis, University of Zurich, Zurich, Switzerland
| | - Joana R Martins
- Center for Microscopy and Image Analysis, University of Zurich, Zurich, Switzerland
| | - César Nombela-Arrieta
- Department of Medical Oncology and Hematology, University of Zurich, Zurich, Switzerland
| | - Robert J Unwin
- Department of Renal Medicine, University College London, UK.,AstraZeneca Biopharmaceuticals R&D, Gothenburg, Sweden
| | - Carsten A Wagner
- Institute of Physiology, University of Zurich, Zurich, Switzerland
| | - Andrew M Hall
- Institute of Anatomy, University of Zurich, Zurich, Switzerland.,Department of Nephrology, University Hospital Zurich, Switzerland
| | - Eilidh Craigie
- Institute of Anatomy, University of Zurich, Zurich, Switzerland
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29
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Vasanthakumar T, Rubinstein JL. Structure and Roles of V-type ATPases. Trends Biochem Sci 2020; 45:295-307. [PMID: 32001091 DOI: 10.1016/j.tibs.2019.12.007] [Citation(s) in RCA: 95] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 12/05/2019] [Accepted: 12/31/2019] [Indexed: 12/19/2022]
Abstract
V-ATPases are membrane-embedded protein complexes that function as ATP hydrolysis-driven proton pumps. V-ATPases are the primary source of organellar acidification in all eukaryotes, making them essential for many fundamental cellular processes. Enzymatic activity can be modulated by regulated and reversible disassembly of the complex, and several subunits of mammalian V-ATPase have multiple isoforms that are differentially localized. Although the biochemical properties of the different isoforms are currently unknown, mutations in specific subunit isoforms have been associated with various diseases, making V-ATPases potential drug targets. V-ATPase structure and activity have been best characterized in Saccharomyces cerevisiae, where recent structures have revealed details about the dynamics of the enzyme, the proton translocation pathway, and conformational changes associated with regulated disassembly and autoinhibition.
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Affiliation(s)
- Thamiya Vasanthakumar
- The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, The University of Toronto, Toronto, ON M5S 1A8, Canada.
| | - John L Rubinstein
- The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, The University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Medical Biophysics, The University of Toronto, Toronto, ON M5G 1L7, Canada.
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30
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Galkina SI, Fedorova NV, Golenkina EA, Stadnichuk VI, Sud’ina GF. Cytonemes Versus Neutrophil Extracellular Traps in the Fight of Neutrophils with Microbes. Int J Mol Sci 2020; 21:ijms21020586. [PMID: 31963289 PMCID: PMC7014225 DOI: 10.3390/ijms21020586] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 01/09/2020] [Accepted: 01/10/2020] [Indexed: 12/11/2022] Open
Abstract
Neutrophils can phagocytose microorganisms and destroy them intracellularly using special bactericides located in intracellular granules. Recent evidence suggests that neutrophils can catch and kill pathogens extracellularly using the same bactericidal agents. For this, live neutrophils create a cytoneme network, and dead neutrophils provide chromatin and proteins to form neutrophil extracellular traps (NETs). Cytonemes are filamentous tubulovesicular secretory protrusions of living neutrophils with intact nuclei. Granular bactericides are localized in membrane vesicles and tubules of which cytonemes are composed. NETs are strands of decondensed DNA associated with histones released by died neutrophils. In NETs, bactericidal neutrophilic agents are adsorbed onto DNA strands and are not covered with a membrane. Cytonemes and NETs occupy different places in protecting the body against infections. Cytonemes can develop within a few minutes at the site of infection through the action of nitric oxide or actin-depolymerizing alkaloids of invading microbes. The formation of NET in vitro occurs due to chromatin decondensation resulting from prolonged activation of neutrophils with PMA (phorbol 12-myristate 13-acetate) or other stimuli, or in vivo due to citrullination of histones with peptidylarginine deiminase 4. In addition to antibacterial activity, cytonemes are involved in cell adhesion and communications. NETs play a role in autoimmunity and thrombosis.
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Affiliation(s)
- Svetlana I. Galkina
- Lomonosov Moscow State University, A. N. Belozersky Institute of Physico-Chemical Biology, 119991 Moscow, Russia; (N.V.F.); (E.A.G.)
- Correspondence: (S.I.G.); (G.F.S.); Tel.: +7-495-939-5408 (S.I.G.)
| | - Natalia V. Fedorova
- Lomonosov Moscow State University, A. N. Belozersky Institute of Physico-Chemical Biology, 119991 Moscow, Russia; (N.V.F.); (E.A.G.)
| | - Ekaterina A. Golenkina
- Lomonosov Moscow State University, A. N. Belozersky Institute of Physico-Chemical Biology, 119991 Moscow, Russia; (N.V.F.); (E.A.G.)
| | | | - Galina F. Sud’ina
- Lomonosov Moscow State University, A. N. Belozersky Institute of Physico-Chemical Biology, 119991 Moscow, Russia; (N.V.F.); (E.A.G.)
- Correspondence: (S.I.G.); (G.F.S.); Tel.: +7-495-939-5408 (S.I.G.)
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31
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Singh A, Marcoline FV, Veshaguri S, Kao AW, Bruchez M, Mindell JA, Stamou D, Grabe M. Protons in small spaces: Discrete simulations of vesicle acidification. PLoS Comput Biol 2019; 15:e1007539. [PMID: 31869334 PMCID: PMC6946529 DOI: 10.1371/journal.pcbi.1007539] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 01/07/2020] [Accepted: 11/11/2019] [Indexed: 12/23/2022] Open
Abstract
The lumenal pH of an organelle is one of its defining characteristics and central to its biological function. Experiments have elucidated many of the key pH regulatory elements and how they vary from compartment-to-compartment, and continuum mathematical models have played an important role in understanding how these elements (proton pumps, counter-ion fluxes, membrane potential, buffering capacity, etc.) work together to achieve specific pH setpoints. While continuum models have proven successful in describing ion regulation at the cellular length scale, it is unknown if they are valid at the subcellular level where volumes are small, ion numbers may fluctuate wildly, and biochemical heterogeneity is large. Here, we create a discrete, stochastic (DS) model of vesicular acidification to answer this question. We used this simplified model to analyze pH measurements of isolated vesicles containing single proton pumps and compared these results to solutions from a continuum, ordinary differential equations (ODE)-based model. Both models predict similar parameter estimates for the mean proton pumping rate, membrane permeability, etc., but, as expected, the ODE model fails to report on the fluctuations in the system. The stochastic model predicts that pH fluctuations decrease during acidification, but noise analysis of single-vesicle data confirms our finding that the experimental noise is dominated by the fluorescent dye, and it reveals no insight into the true noise in the proton fluctuations. Finally, we again use the reduced DS model explore the acidification of large, lysosome-like vesicles to determine how stochastic elements, such as variations in proton-pump copy number and cycling between on and off states, impact the pH setpoint and fluctuations around this setpoint. Organelles harbor specific ion channels, transporters, and other molecular components that allow them to achieve specific intracellular ionic conditions required for their proper function. How all of these components work together to regulate these concentrations, such as maintaining a specific pH value, is complex, and continuum mathematical models have been helpful for evaluating different mechanisms and making quantitative predictions that can be tested experimentally. Nonetheless, organelles can be quite small and some contain only a handful of free protons—can continuum models accurately describe systems with so few molecules? We tested this by creating a discrete, stochastic (DS) model of vesicle acidification that tracks how all of these individual molecules in the vesicle change their state in time. When fitting experimental data, the DS model provides the same parameter estimates as a corresponding continuum model, indicating that both models are equally valid. However, the DS model additionally informs on the noise in the vesicle. When compared to the experimental noise in pH, we show that there is no agreement, because experimental fluctuations do not report on the true pH fluctuations, but rather they report on the fluctuations in reporter molecule protonation. Given experimental limitations, our result highlights the importance of DS models in predicting noise in organelles.
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Affiliation(s)
- Apeksha Singh
- College of Letters and Science, University of California Berkeley, Berkeley, California, United States of America
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
| | - Frank V. Marcoline
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
- * E-mail: (FVM); (MG)
| | - Salome Veshaguri
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark
- Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
- Nano-Science Center, University of Copenhagen, Copenhagen, Denmark
- Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Aimee W. Kao
- Memory and Aging Center, Department of Neurology, University of California San Francisco, San Francisco, California, United States of America
| | - Marcel Bruchez
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America
- Molecular Biosensor and Imaging Center, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America
| | - Joseph A. Mindell
- Membrane Transport Biophysics Unit, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Dimitrios Stamou
- Bionanotecnology and Nanomedicine Laboratory, University of Copenhagen, Copenhagen, Denmark
- Department of Chemistry, University of Copenhagen, Copenhagen, Denmark
- Nano-Science Center, University of Copenhagen, Copenhagen, Denmark
- Lundbeck Foundation Center Biomembranes in Nanomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Michael Grabe
- Cardiovascular Research Institute, Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, United States of America
- * E-mail: (FVM); (MG)
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32
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Sharma S, Oot RA, Khan MM, Wilkens S. Functional reconstitution of vacuolar H +-ATPase from V o proton channel and mutant V 1-ATPase provides insight into the mechanism of reversible disassembly. J Biol Chem 2019; 294:6439-6449. [PMID: 30792311 DOI: 10.1074/jbc.ra119.007577] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 02/10/2019] [Indexed: 12/12/2022] Open
Abstract
The vacuolar H+-ATPase (V-ATPase; V1Vo-ATPase) is an ATP-dependent proton pump that acidifies subcellular compartments in all eukaryotic organisms. V-ATPase activity is regulated by reversible disassembly into autoinhibited V1-ATPase and Vo proton channel subcomplexes, a process that is poorly understood on the molecular level. V-ATPase is a rotary motor, and recent structural analyses have revealed different rotary states for disassembled V1 and Vo, a mismatch that is likely responsible for their inability to reconstitute into holo V-ATPase in vitro Here, using the model organism Saccharomyces cerevisiae, we show that a key impediment for binding of V1 to Vo is the conformation of the inhibitory C-terminal domain of subunit H (HCT). Using biolayer interferometry and biochemical analyses of purified mutant V1-ATPase and Vo proton channel reconstituted into vacuolar lipid-containing nanodiscs, we further demonstrate that disruption of HCT's V1-binding site facilitates assembly of a functionally coupled and stable V1Vo-ATPase. Unlike WT, this mutant enzyme was resistant to MgATP hydrolysis-induced dissociation, further highlighting HCT's role in the mechanism of V-ATPase regulation. Our findings provide key insight into the molecular events underlying regulation of V-ATPase activity by reversible disassembly.
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Affiliation(s)
- Stuti Sharma
- From the Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Rebecca A Oot
- From the Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Md Murad Khan
- From the Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Stephan Wilkens
- From the Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
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33
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Hayek SR, Rane HS, Parra KJ. Reciprocal Regulation of V-ATPase and Glycolytic Pathway Elements in Health and Disease. Front Physiol 2019; 10:127. [PMID: 30828305 PMCID: PMC6384264 DOI: 10.3389/fphys.2019.00127] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 01/31/2019] [Indexed: 12/24/2022] Open
Abstract
The ability of cells to adapt to fluctuations in glucose availability is crucial for their survival and involves the vacuolar proton-translocating ATPase (V-ATPase), a proton pump found in all eukaryotes. V-ATPase hydrolyzes ATP via its V1 domain and uses the energy released to transport protons across membranes via its Vo domain. This activity is critical for pH homeostasis and generation of a membrane potential that drives cellular metabolism. A number of stimuli have been reported to alter V-ATPase assembly in yeast and higher eukaryotes. Glucose flux is one of the strongest and best-characterized regulators of V-ATPase; this review highlights current models explaining how glycolysis and V-ATPase are coordinated in both the Saccharomyces cerevisiae model fungus and in mammalian systems. Glucose-dependent assembly and trafficking of V-ATPase, V-ATPase-dependent modulations in glycolysis, and the recent discovery that glucose signaling through V-ATPase acts as a molecular switch to dictate anabolic versus catabolic metabolism are discussed. Notably, metabolic plasticity and altered glycolytic flux are critical drivers of numerous human pathologies, and the expression and activity of V-ATPase is often altered in disease states or can be pharmacologically manipulated as treatment. This overview will specifically discuss connections between V-ATPase and glycolysis in cancer.
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Affiliation(s)
- Summer R Hayek
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
| | - Hallie S Rane
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
| | - Karlett J Parra
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
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34
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Harrison MA, Muench SP. The Vacuolar ATPase - A Nano-scale Motor That Drives Cell Biology. Subcell Biochem 2018; 87:409-459. [PMID: 29464568 DOI: 10.1007/978-981-10-7757-9_14] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The vacuolar H+-ATPase (V-ATPase) is a ~1 MDa membrane protein complex that couples the hydrolysis of cytosolic ATP to the transmembrane movement of protons. In essentially all eukaryotic cells, this acid pumping function plays critical roles in the acidification of endosomal/lysosomal compartments and hence in transport, recycling and degradative pathways. It is also important in acid extrusion across the plasma membrane of some cells, contributing to homeostatic control of cytoplasmic pH and maintenance of appropriate extracellular acidity. The complex, assembled from up to 30 individual polypeptides, operates as a molecular motor with rotary mechanics. Historically, structural inferences about the eukaryotic V-ATPase and its subunits have been made by comparison to the structures of bacterial homologues. However, more recently, we have developed a much better understanding of the complete structure of the eukaryotic complex, in particular through advances in cryo-electron microscopy. This chapter explores these recent developments, and examines what they now reveal about the catalytic mechanism of this essential proton pump and how its activity might be regulated in response to cellular signals.
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Affiliation(s)
- Michael A Harrison
- School of Biomedical Sciences, Faculty of Biological Sciences, The University of Leeds, Leeds, UK.
| | - Steven P Muench
- School of Biomedical Sciences, Faculty of Biological Sciences, The University of Leeds, Leeds, UK
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35
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Collins MP, Forgac M. Regulation of V-ATPase Assembly in Nutrient Sensing and Function of V-ATPases in Breast Cancer Metastasis. Front Physiol 2018; 9:902. [PMID: 30057555 PMCID: PMC6053528 DOI: 10.3389/fphys.2018.00902] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Accepted: 06/21/2018] [Indexed: 12/20/2022] Open
Abstract
V-ATPases are proton pumps that function to acidify intracellular compartments in all eukaryotic cells, and to transport protons across the plasma membrane of certain specialized cells. V-ATPases function in many normal and disease processes, including membrane traffic, protein degradation, pathogen entry, and cancer cell invasion. An important mechanism of regulating V-ATPase activity in vivo is regulated assembly, which is the reversible dissociation of the ATP-hydrolytic V1 domain from the proton-conducting V0 domain. Regulated assembly is highly conserved and occurs in response to various nutrient cues, suggesting that it plays an important role in cellular homeostasis. We have recently found that starvation of mammalian cells for either amino acids or glucose increases V-ATPase assembly on lysosomes, possibly to increase protein degradation (for amino acid homeostasis) or for the utilization of alternative energy sources (during glucose starvation). While regulation of assembly in response to amino acid starvation does not involve PI3K or mTORC1, glucose-regulated assembly involves both PI3K and AMPK. Another important form of V-ATPase regulation is the targeting of the enzyme to different cellular membranes, which is controlled by isoforms of subunit a. We have shown that V-ATPases are localized to the plasma membrane of highly invasive breast cancer cells, where they promote cell migration and invasion. Furthermore, overexpression of the a3 isoform is responsible for plasma membrane targeting of V-ATPases in breast tumor cells leading to their increased invasiveness.
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Affiliation(s)
- Michael P Collins
- Program in Cell, Molecular and Developmental Biology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, United States
| | - Michael Forgac
- Program in Cell, Molecular and Developmental Biology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, United States.,Department of Developmental, Molecular and Chemical Biology, School of Medicine, Tufts University, Boston, MA, United States
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36
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Sharma S, Oot RA, Wilkens S. MgATP hydrolysis destabilizes the interaction between subunit H and yeast V 1-ATPase, highlighting H's role in V-ATPase regulation by reversible disassembly. J Biol Chem 2018; 293:10718-10730. [PMID: 29754144 DOI: 10.1074/jbc.ra118.002951] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 04/22/2018] [Indexed: 01/01/2023] Open
Abstract
Vacuolar H+-ATPases (V-ATPases; V1Vo-ATPases) are rotary-motor proton pumps that acidify intracellular compartments and, in some tissues, the extracellular space. V-ATPase is regulated by reversible disassembly into autoinhibited V1-ATPase and Vo proton channel sectors. An important player in V-ATPase regulation is subunit H, which binds at the interface of V1 and Vo H is required for MgATPase activity in holo-V-ATPase but also for stabilizing the MgADP-inhibited state in membrane-detached V1 However, how H fulfills these two functions is poorly understood. To characterize the H-V1 interaction and its role in reversible disassembly, we determined binding affinities of full-length H and its N-terminal domain (HNT) for an isolated heterodimer of subunits E and G (EG), the N-terminal domain of subunit a (aNT), and V1 lacking subunit H (V1ΔH). Using isothermal titration calorimetry (ITC) and biolayer interferometry (BLI), we show that HNT binds EG with moderate affinity, that full-length H binds aNT weakly, and that both H and HNT bind V1ΔH with high affinity. We also found that only one molecule of HNT binds V1ΔH with high affinity, suggesting conformational asymmetry of the three EG heterodimers in V1ΔH. Moreover, MgATP hydrolysis-driven conformational changes in V1 destabilized the interaction of H or HNT with V1ΔH, suggesting an interplay between MgADP inhibition and subunit H. Our observation that H binding is affected by MgATP hydrolysis in V1 points to H's role in the mechanism of reversible disassembly.
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Affiliation(s)
- Stuti Sharma
- From the Department of Biochemistry and Molecular Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, New York 13210
| | - Rebecca A Oot
- From the Department of Biochemistry and Molecular Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, New York 13210
| | - Stephan Wilkens
- From the Department of Biochemistry and Molecular Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, New York 13210
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McGuire CM, Forgac M. Glucose starvation increases V-ATPase assembly and activity in mammalian cells through AMP kinase and phosphatidylinositide 3-kinase/Akt signaling. J Biol Chem 2018. [PMID: 29540478 DOI: 10.1074/jbc.ra117.001327] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The vacuolar H+-ATPase (V-ATPase) is an ATP-driven proton pump involved in many cellular processes. An important mechanism by which V-ATPase activity is controlled is the reversible assembly of its two domains, namely the peripheral V1 domain and the integral V0 domain. Although reversible assembly is conserved across all eukaryotic organisms, the signaling pathways controlling it have not been fully characterized. Here, we identify glucose starvation as a novel regulator of V-ATPase assembly in mammalian cells. During acute glucose starvation, the V-ATPase undergoes a rapid and reversible increase in assembly and activity as measured by lysosomal acidification. Because the V-ATPase has recently been implicated in the activation of AMP kinase (AMPK), a critical cellular energy sensor that is also activated upon glucose starvation, we compared the time course of AMPK activation and V-ATPase assembly upon glucose starvation. We observe that AMPK activation precedes increased V-ATPase activity. Moreover, the starvation-induced increase in V-ATPase activity and assembly are prevented by the AMPK inhibitor dorsomorphin. These results suggest that increased assembly and activity of the V-ATPase upon glucose starvation are dependent upon AMPK. We also find that the PI3K/Akt pathway, which has previously been implicated in controlling V-ATPase assembly in mammalian cells, also plays a role in the starvation-induced increase in V-ATPase assembly and activity. These studies thus identify a novel stimulus of V-ATPase assembly and a novel signaling pathway involved in regulating this process. The possible function of starvation-induced increase in lysosomal V-ATPase activity is discussed.
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Affiliation(s)
- Christina M McGuire
- From the Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine and the Program in Biochemistry, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, Massachusetts 02111
| | - Michael Forgac
- From the Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine and the Program in Biochemistry, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, Massachusetts 02111
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38
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Roh SH, Stam NJ, Hryc CF, Couoh-Cardel S, Pintilie G, Chiu W, Wilkens S. The 3.5-Å CryoEM Structure of Nanodisc-Reconstituted Yeast Vacuolar ATPase V o Proton Channel. Mol Cell 2018. [PMID: 29526695 DOI: 10.1016/j.molcel.2018.02.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The molecular mechanism of transmembrane proton translocation in rotary motor ATPases is not fully understood. Here, we report the 3.5-Å resolution cryoEM structure of the lipid nanodisc-reconstituted Vo proton channel of the yeast vacuolar H+-ATPase, captured in a physiologically relevant, autoinhibited state. The resulting atomic model provides structural detail for the amino acids that constitute the proton pathway at the interface of the proteolipid ring and subunit a. Based on the structure and previous mutagenesis studies, we propose the chemical basis of transmembrane proton transport. Moreover, we discovered that the C terminus of the assembly factor Voa1 is an integral component of mature Vo. Voa1's C-terminal transmembrane α helix is bound inside the proteolipid ring, where it contributes to the stability of the complex. Our structure rationalizes possible mechanisms by which mutations in human Vo can result in disease phenotypes and may thus provide new avenues for therapeutic interventions.
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Affiliation(s)
- Soung-Hun Roh
- Department of Bioengineering and James H. Clark Center, Stanford University, Stanford, CA 94305, USA; Biosciences Division, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - Nicholas J Stam
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Corey F Hryc
- Graduate Program in Quantitative and Computational Biosciences, Baylor College of Medicine, Houston, TX 77030, USA; Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Sergio Couoh-Cardel
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA
| | - Grigore Pintilie
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Wah Chiu
- Department of Bioengineering and James H. Clark Center, Stanford University, Stanford, CA 94305, USA; Biosciences Division, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA; Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, TX 77030, USA.
| | - Stephan Wilkens
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA.
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Deprez MA, Eskes E, Wilms T, Ludovico P, Winderickx J. pH homeostasis links the nutrient sensing PKA/TORC1/Sch9 ménage-à-trois to stress tolerance and longevity. MICROBIAL CELL 2018; 5:119-136. [PMID: 29487859 PMCID: PMC5826700 DOI: 10.15698/mic2018.03.618] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The plasma membrane H+-ATPase Pma1 and the vacuolar V-ATPase act in close harmony to tightly control pH homeostasis, which is essential for a vast number of physiological processes. As these main two regulators of pH are responsive to the nutritional status of the cell, it seems evident that pH homeostasis acts in conjunction with nutrient-induced signalling pathways. Indeed, both PKA and the TORC1-Sch9 axis influence the proton pumping activity of the V-ATPase and possibly also of Pma1. In addition, it recently became clear that the proton acts as a second messenger to signal glucose availability via the V-ATPase to PKA and TORC1-Sch9. Given the prominent role of nutrient signalling in longevity, it is not surprising that pH homeostasis has been linked to ageing and longevity as well. A first indication is provided by acetic acid, whose uptake by the cell induces toxicity and affects longevity. Secondly, vacuolar acidity has been linked to autophagic processes, including mitophagy. In agreement with this, a decline in vacuolar acidity was shown to induce mitochondrial dysfunction and shorten lifespan. In addition, the asymmetric inheritance of Pma1 has been associated with replicative ageing and this again links to repercussions on vacuolar pH. Taken together, accumulating evidence indicates that pH homeostasis plays a prominent role in the determination of ageing and longevity, thereby providing new perspectives and avenues to explore the underlying molecular mechanisms.
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Affiliation(s)
| | - Elja Eskes
- Functional Biology, KU Leuven, Leuven, Belgium
| | | | - Paula Ludovico
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Braga, Portugal; ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
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40
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Hesketh GG, Wartosch L, Davis LJ, Bright NA, Luzio JP. The Lysosome and Intracellular Signalling. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2018; 57:151-180. [PMID: 30097775 DOI: 10.1007/978-3-319-96704-2_6] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In addition to being the terminal degradative compartment of the cell's endocytic and autophagic pathways, the lysosome is a multifunctional signalling hub integrating the cell's response to nutrient status and growth factor/hormone signalling. The cytosolic surface of the limiting membrane of the lysosome is the site of activation of the multiprotein complex mammalian target of rapamycin complex 1 (mTORC1), which phosphorylates numerous cell growth-related substrates, including transcription factor EB (TFEB). Under conditions in which mTORC1 is inhibited including starvation, TFEB becomes dephosphorylated and translocates to the nucleus where it functions as a master regulator of lysosome biogenesis. The signalling role of lysosomes is not limited to this pathway. They act as an intracellular Ca2+ store, which can release Ca2+ into the cytosol for both local effects on membrane fusion and pleiotropic effects within the cell. The relationship and crosstalk between the lysosomal and endoplasmic reticulum (ER) Ca2+ stores play a role in shaping intracellular Ca2+ signalling. Lysosomes also perform other signalling functions, which are discussed. Current views of the lysosomal compartment recognize its dynamic nature. It includes endolysosomes, autolysosome and storage lysosomes that are constantly engaged in fusion/fission events and lysosome regeneration. How signalling is affected by individual lysosomal organelles being at different stages of these processes and/or at different sites within the cell is poorly understood, but is discussed.
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Affiliation(s)
- Geoffrey G Hesketh
- Lunenfeld-Tanenbaum Research Institute, Sinai Health System, Toronto, ON, M5G 1X5, Canada
| | - Lena Wartosch
- Department of Clinical Biochemistry and Cambridge Institute for Medical Research, School of Clinical Medicine, Wellcome Trust/MRC Building, University of Cambridge, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY, UK
| | - Luther J Davis
- Department of Clinical Biochemistry and Cambridge Institute for Medical Research, School of Clinical Medicine, Wellcome Trust/MRC Building, University of Cambridge, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY, UK
| | - Nicholas A Bright
- Department of Clinical Biochemistry and Cambridge Institute for Medical Research, School of Clinical Medicine, Wellcome Trust/MRC Building, University of Cambridge, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY, UK
| | - J Paul Luzio
- Department of Clinical Biochemistry and Cambridge Institute for Medical Research, School of Clinical Medicine, Wellcome Trust/MRC Building, University of Cambridge, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY, UK.
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41
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Fu S. From glucose sensing to a unified model of AMPK and mTOR regulation. Sci Bull (Beijing) 2017; 62:1233-1234. [PMID: 36659449 DOI: 10.1016/j.scib.2017.08.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Suneng Fu
- Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China.
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42
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Konarzewska P, Sherr GL, Ahmed S, Ursomanno B, Shen CH. Vma3p protects cells from programmed cell death through the regulation of Hxk2p expression. Biochem Biophys Res Commun 2017; 493:233-239. [PMID: 28899778 DOI: 10.1016/j.bbrc.2017.09.041] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 09/08/2017] [Indexed: 10/18/2022]
Abstract
In yeast, the vacuolar proton-pumping ATPase (V-ATPase) acidifies vacuoles to maintain pH of cytoplasm. Yeast cells lacking V-ATPase activity, due to a disruption of any VMA (vacuolar membrane ATPase) gene, remain viable but demonstrate growth defects. Although it has been suggested that VMA genes are critical for phospholipid biosynthesis, the link between VMA genes and phospholipid biosynthesis is still uncertain. Here, we found that cells lacking Vma3p, one of the major V-ATPase assembly genes, had a growth defect in the absence of inositol, suggesting that Vma3p is important in phospholipid biosynthesis. Through real-time PCR, we found that cells lacking Vma3p down-regulated HXK2 expression. Furthermore, acetic acid sensitivity assay showed that cells lacking Vma3p were more sensitive to acetic acid than WT cells. HXK2 encodes hexokinase 2 which can phosphorylate glucose during phospholipid biosynthesis. Since cells lacking HXK2 are sensitive to acetic acid and this is an indicator of programmed cell death, our observations suggest that Vma3p plays an important role in programmed cell death. Taken together, we have proposed a working model to describe how Vma3p protects cells against apoptosis through the regulation of HXK2 expression.
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Affiliation(s)
- Paulina Konarzewska
- Department of Biology, College of Staten Island, City University of New York, 2800 Victory Blvd, Staten Island, NY 10314, USA; PhD Program in Biology, The Graduate Center, City University of New York, 365 Fifth Avenue, New York 10016, USA
| | - Goldie Libby Sherr
- Department of Biology, College of Staten Island, City University of New York, 2800 Victory Blvd, Staten Island, NY 10314, USA; PhD Program in Biology, The Graduate Center, City University of New York, 365 Fifth Avenue, New York 10016, USA
| | - Suzanne Ahmed
- Department of Biology, College of Staten Island, City University of New York, 2800 Victory Blvd, Staten Island, NY 10314, USA
| | - Brendon Ursomanno
- Department of Biology, College of Staten Island, City University of New York, 2800 Victory Blvd, Staten Island, NY 10314, USA
| | - Chang-Hui Shen
- Department of Biology, College of Staten Island, City University of New York, 2800 Victory Blvd, Staten Island, NY 10314, USA; PhD Program in Biology, The Graduate Center, City University of New York, 365 Fifth Avenue, New York 10016, USA; Institute for Macromolecular Assemblies, City University of New York, 160 Convent Avenue, New York, NY 10031, USA.
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43
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Kissing S, Saftig P, Haas A. Vacuolar ATPase in phago(lyso)some biology. Int J Med Microbiol 2017; 308:58-67. [PMID: 28867521 DOI: 10.1016/j.ijmm.2017.08.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2017] [Revised: 07/28/2017] [Accepted: 08/23/2017] [Indexed: 12/23/2022] Open
Abstract
Many eukaryotic cells ingest extracellular particles in a process termed phagocytosis which entails the generation of a new intracellular compartment, the phagosome. Phagosomes change their composition over time and this maturation process culminates in their fusion with acidic, hydrolase-rich lysosomes. During the maturation process, degradation and, when applicable, killing of the cargo may ensue. Many of the events that are pathologically relevant depend on strong acidification of phagosomes by the 'vacuolar' ATPase (V-ATPase). This protein complex acidifies the lumen of some intracellular compartments at the expense of ATP hydrolysis. We discuss here the roles and importance of V-ATPase in intracellular trafficking, its distribution, inhibition and activities, its role in the defense against microorganisms and the counteractivities of pathogens.
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Affiliation(s)
- Sandra Kissing
- Institut für Biochemie, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany
| | - Paul Saftig
- Institut für Biochemie, Christian-Albrechts-Universität zu Kiel, Olshausenstrasse 40, D-24098 Kiel, Germany.
| | - Albert Haas
- Institut für Zellbiologie, Friedrich-Wilhelms-Universität Bonn, Ulrich-Haberland-Str. 61A, D-53121 Bonn, Germany.
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44
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Wang A, Carraro-Lacroix LR, Owen C, Gao B, Corey PN, Tyrrell P, Brumell JH, Voronov I. Activity-independent targeting of mTOR to lysosomes in primary osteoclasts. Sci Rep 2017; 7:3005. [PMID: 28592812 PMCID: PMC5462732 DOI: 10.1038/s41598-017-03494-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 04/28/2017] [Indexed: 12/14/2022] Open
Abstract
Mammalian target of rapamycin (mTOR) is activated by numerous stimuli, including amino acids and growth factors. This kinase is part of the mTOR complex 1 (mTORC1) which regulates cell proliferation, differentiation, and autophagy. Active mTORC1 is located on lysosomes and has been reported to disassociate from the lysosomal surface in the absence of amino acids. Furthermore, mTORC1 activity has been linked to the vacuolar H+-ATPases (V-ATPases), the proton pumps responsible for lysosomal acidification; however, the exact role of the V-ATPases in mTORC1 signaling is not known. To elucidate the mechanisms involved in mTORC1 regulation by the V-ATPases, we used primary osteoclasts derived from mice carrying a point (R740S) mutation in the a3 subunit of the V-ATPase. In these cells, the mutant protein is expressed but the pump is not functional, resulting in higher lysosomal pH. By analyzing mTOR activation, mTOR/lysosome co-localization, and lysosomal positioning using confocal microscopy, fractionation, and ultrapure lysosomal purification methods, we demonstrate that in primary osteoclasts, mTOR is localized on the lysosomal surface even when mTOR activity is inhibited. Our findings reveal that mTOR targeting to the lysosome in osteoclasts is activity-independent, and that its disassociation from the lysosome during starvation is not universal.
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Affiliation(s)
- Andrew Wang
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada
| | | | - Celeste Owen
- Centre for Modeling Human Disease, Samuel Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada
| | - Bowen Gao
- Department of Statistical Sciences, University of Toronto, Toronto, ON, Canada
| | - Paul N Corey
- Department of Statistical Sciences, University of Toronto, Toronto, ON, Canada
| | - Pascal Tyrrell
- Department of Statistical Sciences, University of Toronto, Toronto, ON, Canada.,Department of Medical Imaging, University of Toronto, Toronto, ON, Canada
| | - John H Brumell
- Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada.,Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada.,Institute of Medical Science, University of Toronto, Toronto, ON, Canada
| | - Irina Voronov
- Faculty of Dentistry, University of Toronto, Toronto, ON, Canada.
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45
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Zhao J, Beyrakhova K, Liu Y, Alvarez CP, Bueler SA, Xu L, Xu C, Boniecki MT, Kanelis V, Luo ZQ, Cygler M, Rubinstein JL. Molecular basis for the binding and modulation of V-ATPase by a bacterial effector protein. PLoS Pathog 2017; 13:e1006394. [PMID: 28570695 PMCID: PMC5469503 DOI: 10.1371/journal.ppat.1006394] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2017] [Revised: 06/13/2017] [Accepted: 05/01/2017] [Indexed: 12/16/2022] Open
Abstract
Intracellular pathogenic bacteria evade the immune response by replicating within host cells. Legionella pneumophila, the causative agent of Legionnaires’ Disease, makes use of numerous effector proteins to construct a niche supportive of its replication within phagocytic cells. The L. pneumophila effector SidK was identified in a screen for proteins that reduce the activity of the proton pumping vacuolar-type ATPases (V-ATPases) when expressed in the yeast Saccharomyces cerevisae. SidK is secreted by L. pneumophila in the early stages of infection and by binding to and inhibiting the V-ATPase, SidK reduces phagosomal acidification and promotes survival of the bacterium inside macrophages. We determined crystal structures of the N-terminal region of SidK at 2.3 Å resolution and used single particle electron cryomicroscopy (cryo-EM) to determine structures of V-ATPase:SidK complexes at ~6.8 Å resolution. SidK is a flexible and elongated protein composed of an α-helical region that interacts with subunit A of the V-ATPase and a second region of unknown function that is flexibly-tethered to the first. SidK binds V-ATPase strongly by interacting via two α-helical bundles at its N terminus with subunit A. In vitro activity assays show that SidK does not inhibit the V-ATPase completely, but reduces its activity by ~40%, consistent with the partial V-ATPase deficiency phenotype its expression causes in yeast. The cryo-EM analysis shows that SidK reduces the flexibility of the A-subunit that is in the ‘open’ conformation. Fluorescence experiments indicate that SidK binding decreases the affinity of V-ATPase for a fluorescent analogue of ATP. Together, these results reveal the structural basis for the fine-tuning of V-ATPase activity by SidK. V-ATPase-driven acidification of lysosomes in phagocytic cells activates enzymes important for killing of phagocytized pathogens. Successful pathogens can subvert host defenses by secreting effectors that target V-ATPases to inhibit lysosomal acidification or lysosomal fusion with other cell compartments. This study reveals the structure of the V-ATPase:SidK complex, an assembly formed from the interaction of host and pathogen proteins involved in the infection of phagocytic white blood cells by Legionella pneumophila. The structure and activity of the V-ATPase is altered upon SidK binding, providing insight into the infection strategy used by L. pneumophila and possibly other intravacuolar pathogens.
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Affiliation(s)
- Jianhua Zhao
- The Hospital for Sick Children Research Institute, Toronto, Ontario, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - Ksenia Beyrakhova
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Yao Liu
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Claudia P. Alvarez
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario, Canada
| | | | - Li Xu
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Caishuang Xu
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Michal T. Boniecki
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Voula Kanelis
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, Mississauga, Ontario, Canada
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Zhao-Qing Luo
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana, United States of America
| | - Miroslaw Cygler
- Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
- * E-mail: (JLR); (MC)
| | - John L. Rubinstein
- The Hospital for Sick Children Research Institute, Toronto, Ontario, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
- * E-mail: (JLR); (MC)
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46
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Oot RA, Couoh-Cardel S, Sharma S, Stam NJ, Wilkens S. Breaking up and making up: The secret life of the vacuolar H + -ATPase. Protein Sci 2017; 26:896-909. [PMID: 28247968 DOI: 10.1002/pro.3147] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2017] [Accepted: 02/21/2017] [Indexed: 01/24/2023]
Abstract
The vacuolar ATPase (V-ATPase; V1 Vo -ATPase) is a large multisubunit proton pump found in the endomembrane system of all eukaryotic cells where it acidifies the lumen of subcellular organelles including lysosomes, endosomes, the Golgi apparatus, and clathrin-coated vesicles. V-ATPase function is essential for pH and ion homeostasis, protein trafficking, endocytosis, mechanistic target of rapamycin (mTOR), and Notch signaling, as well as hormone secretion and neurotransmitter release. V-ATPase can also be found in the plasma membrane of polarized animal cells where its proton pumping function is involved in bone remodeling, urine acidification, and sperm maturation. Aberrant (hypo or hyper) activity has been associated with numerous human diseases and the V-ATPase has therefore been recognized as a potential drug target. Recent progress with moderate to high-resolution structure determination by cryo electron microscopy and X-ray crystallography together with sophisticated single-molecule and biochemical experiments have provided a detailed picture of the structure and unique mode of regulation of the V-ATPase. This review summarizes the recent advances, focusing on the structural and biophysical aspects of the field.
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Affiliation(s)
- Rebecca A Oot
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, 13210
| | - Sergio Couoh-Cardel
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, 13210
| | - Stuti Sharma
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, 13210
| | - Nicholas J Stam
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, 13210
| | - Stephan Wilkens
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, 13210
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47
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Sharma S, Wilkens S. Biolayer interferometry of lipid nanodisc-reconstituted yeast vacuolar H + -ATPase. Protein Sci 2017; 26:1070-1079. [PMID: 28241399 DOI: 10.1002/pro.3143] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 02/15/2017] [Accepted: 02/17/2017] [Indexed: 01/24/2023]
Abstract
Vacuolar H+ -ATPase (V-ATPase) is a large, multisubunit membrane protein complex responsible for the acidification of subcellular compartments and the extracellular space. V-ATPase activity is regulated by reversible disassembly, resulting in cytosolic V1 -ATPase and membrane-integral V0 proton channel sectors. Reversible disassembly is accompanied by transient interaction with cellular factors and assembly chaperones. Quantifying protein-protein interactions involving membrane proteins, however, is challenging. Here we present a novel method to determine kinetic constants of membrane protein-protein interactions using biolayer interferometry (BLI). Yeast vacuoles are solubilized, vacuolar proteins are reconstituted into lipid nanodiscs with native vacuolar lipids and biotinylated membrane scaffold protein (MSP) followed by affinity purification of nanodisc-reconstituted V-ATPase (V1 V0 ND). We show that V1 V0 ND can be immobilized on streptavidin-coated BLI sensors to quantitate binding of a pathogen derived inhibitor and to measure the kinetics of nucleotide dependent enzyme dissociation.
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Affiliation(s)
- Stuti Sharma
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University 750 East Adams Street, Syracuse, New York, 13210
| | - Stephan Wilkens
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University 750 East Adams Street, Syracuse, New York, 13210
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48
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Stam NJ, Wilkens S. Structure of the Lipid Nanodisc-reconstituted Vacuolar ATPase Proton Channel: DEFINITION OF THE INTERACTION OF ROTOR AND STATOR AND IMPLICATIONS FOR ENZYME REGULATION BY REVERSIBLE DISSOCIATION. J Biol Chem 2016; 292:1749-1761. [PMID: 27965356 DOI: 10.1074/jbc.m116.766790] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 12/11/2016] [Indexed: 12/14/2022] Open
Abstract
Eukaryotic vacuolar H+-ATPase (V-ATPase) is a multisubunit enzyme complex that acidifies subcellular organelles and the extracellular space. V-ATPase consists of soluble V1-ATPase and membrane-integral Vo proton channel sectors. To investigate the mechanism of V-ATPase regulation by reversible disassembly, we recently determined a cryo-EM reconstruction of yeast Vo The structure indicated that, when V1 is released from Vo, the N-terminal cytoplasmic domain of subunit a (aNT) changes conformation to bind rotor subunit d However, insufficient resolution precluded a precise definition of the aNT-d interface. Here we reconstituted Vo into lipid nanodiscs for single-particle EM. 3D reconstructions calculated at ∼15-Å resolution revealed two sites of contact between aNT and d that are mediated by highly conserved charged residues. Alanine mutagenesis of some of these residues disrupted the aNT-d interaction, as shown by isothermal titration calorimetry and gel filtration of recombinant subunits. A recent cryo-EM study of holo V-ATPase revealed three major conformations corresponding to three rotational states of the central rotor of the enzyme. Comparison of the three V-ATPase conformations with the structure of nanodisc-bound Vo revealed that Vo is halted in rotational state 3. Combined with our prior work that showed autoinhibited V1-ATPase to be arrested in state 2, we propose a model in which the conformational mismatch between free V1 and Vo functions to prevent unintended reassembly of holo V-ATPase when activity is not needed.
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Affiliation(s)
- Nicholas J Stam
- From the Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, New York 13210
| | - Stephan Wilkens
- From the Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, New York 13210.
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49
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Organelle acidification negatively regulates vacuole membrane fusion in vivo. Sci Rep 2016; 6:29045. [PMID: 27363625 PMCID: PMC4929563 DOI: 10.1038/srep29045] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 06/10/2016] [Indexed: 12/13/2022] Open
Abstract
The V-ATPase is a proton pump consisting of a membrane-integral V0 sector and a peripheral V1 sector, which carries the ATPase activity. In vitro studies of yeast vacuole fusion and evidence from worms, flies, zebrafish and mice suggested that V0 interacts with the SNARE machinery for membrane fusion, that it promotes the induction of hemifusion and that this activity requires physical presence of V0 rather than its proton pump activity. A recent in vivo study in yeast has challenged these interpretations, concluding that fusion required solely lumenal acidification but not the V0 sector itself. Here, we identify the reasons for this discrepancy and reconcile it. We find that acute pharmacological or physiological inhibition of V-ATPase pump activity de-acidifies the vacuole lumen in living yeast cells within minutes. Time-lapse microscopy revealed that de-acidification induces vacuole fusion rather than inhibiting it. Cells expressing mutated V0 subunits that maintain vacuolar acidity were blocked in this fusion. Thus, proton pump activity of the V-ATPase negatively regulates vacuole fusion in vivo. Vacuole fusion in vivo does, however, require physical presence of a fusion-competent V0 sector.
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Oot RA, Kane PM, Berry EA, Wilkens S. Crystal structure of yeast V1-ATPase in the autoinhibited state. EMBO J 2016; 35:1694-706. [PMID: 27295975 DOI: 10.15252/embj.201593447] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 05/12/2016] [Indexed: 01/23/2023] Open
Abstract
Vacuolar ATPases (V-ATPases) are essential proton pumps that acidify the lumen of subcellular organelles in all eukaryotic cells and the extracellular space in some tissues. V-ATPase activity is regulated by a unique mechanism referred to as reversible disassembly, wherein the soluble catalytic sector, V1, is released from the membrane and its MgATPase activity silenced. The crystal structure of yeast V1 presented here shows that activity silencing involves a large conformational change of subunit H, with its C-terminal domain rotating ~150° from a position near the membrane in holo V-ATPase to a position at the bottom of V1 near an open catalytic site. Together with biochemical data, the structure supports a mechanistic model wherein subunit H inhibits ATPase activity by stabilizing an open catalytic site that results in tight binding of inhibitory ADP at another site.
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Affiliation(s)
- Rebecca A Oot
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Patricia M Kane
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Edward A Berry
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Stephan Wilkens
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, USA
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