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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: 3] [Impact Index Per Article: 3.0] [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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Rombolá-Caldentey B, Mendoza I, Quintero FJ, Pardo JM. Structure-Guided Identification of Critical Residues in the Vacuolar Cation/Proton Antiporter NHX1 from Arabidopsis thaliana. PLANTS (BASEL, SWITZERLAND) 2023; 12:2778. [PMID: 37570932 PMCID: PMC10421325 DOI: 10.3390/plants12152778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 07/24/2023] [Accepted: 07/24/2023] [Indexed: 08/13/2023]
Abstract
Cation/Proton Antiporters (CPA) acting in all biological membranes regulate the volume and pH of cells and of intracellular organelles. A key issue with these proteins is their structure-function relationships since they present intrinsic regulatory features that rely on structural determinants, including pH sensitivity and the stoichiometry of ion exchange. Crystal structures are only available for prokaryotic CPA, whereas the eukaryotic ones have been modeled using the former as templates. Here, we present an updated and improved structural model of the tonoplast-localized K+, Na+/H+ antiporter NHX1 of Arabidopsis as a representative of the vacuolar NHX family that is essential for the accumulation of K+ into plant vacuoles. Conserved residues that were judged as functionally important were mutated, and the resulting protein variants were tested for activity in the yeast Saccharomyces cerevisiae. The results indicate that residue N184 in the ND-motif characteristic of CPA1 could be replaced by the DD-motif of CPA2 family members with minimal consequences for their activity. Attempts to alter the electroneutrality of AtNHX1 by different combinations of amino acid replacements at N184, R353 and R390 residues resulted in inactive or partly active proteins with a differential ability to control the vacuolar pH of the yeast.
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Affiliation(s)
| | | | | | - José M. Pardo
- Instituto de Bioquimica Vegetal y Fotosintesis, cicCartuja, Consejo Superior de Investigaciones Cientificas, Universidad de Sevilla, 41092 Sevilla, Spain; (B.R.-C.); (I.M.); (F.J.Q.)
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3
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Alder A, Sanchez CP, Russell MRG, Collinson LM, Lanzer M, Blackman MJ, Gilberger TW, Matz JM. The role of Plasmodium V-ATPase in vacuolar physiology and antimalarial drug uptake. Proc Natl Acad Sci U S A 2023; 120:e2306420120. [PMID: 37463201 PMCID: PMC10372686 DOI: 10.1073/pnas.2306420120] [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: 04/24/2023] [Accepted: 06/20/2023] [Indexed: 07/20/2023] Open
Abstract
To ensure their survival in the human bloodstream, malaria parasites degrade up to 80% of the host erythrocyte hemoglobin in an acidified digestive vacuole. Here, we combine conditional reverse genetics and quantitative imaging approaches to demonstrate that the human malaria pathogen Plasmodium falciparum employs a heteromultimeric V-ATPase complex to acidify the digestive vacuole matrix, which is essential for intravacuolar hemoglobin release, heme detoxification, and parasite survival. We reveal an additional function of the membrane-embedded V-ATPase subunits in regulating morphogenesis of the digestive vacuole independent of proton translocation. We further show that intravacuolar accumulation of antimalarial chemotherapeutics is surprisingly resilient to severe deacidification of the vacuole and that modulation of V-ATPase activity does not affect parasite sensitivity toward these drugs.
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Affiliation(s)
- Arne Alder
- Cell Biology of Human Parasites Group, Centre for Structural Systems Biology, Hamburg22607, Germany
- Cellular Parasitology Department, Bernhard Nocht Institute for Tropical Medicine, Hamburg20359, Germany
- Department of Biology, University of Hamburg, Hamburg20146, Germany
| | - Cecilia P. Sanchez
- Center of Infectious Diseases, Parasitology, Heidelberg University Hospital, Heidelberg69120, Germany
| | - Matthew R. G. Russell
- Electron Microscopy Science Technology Platform, The Francis Crick Institute, LondonNW1 1AT, United Kingdom
- Centre for Ultrastructural Imaging, King’s College London, LondonSE1 1UL, United Kingdom
| | - Lucy M. Collinson
- Electron Microscopy Science Technology Platform, The Francis Crick Institute, LondonNW1 1AT, United Kingdom
| | - Michael Lanzer
- Center of Infectious Diseases, Parasitology, Heidelberg University Hospital, Heidelberg69120, Germany
| | - Michael J. Blackman
- Malaria Biochemistry Laboratory, The Francis Crick Institute, LondonNW1 1AT, United Kingdom
- Faculty of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, LondonWC1E 7HT, United Kingdom
| | - Tim-Wolf Gilberger
- Cell Biology of Human Parasites Group, Centre for Structural Systems Biology, Hamburg22607, Germany
- Cellular Parasitology Department, Bernhard Nocht Institute for Tropical Medicine, Hamburg20359, Germany
- Department of Biology, University of Hamburg, Hamburg20146, Germany
| | - Joachim M. Matz
- Cell Biology of Human Parasites Group, Centre for Structural Systems Biology, Hamburg22607, Germany
- Cellular Parasitology Department, Bernhard Nocht Institute for Tropical Medicine, Hamburg20359, Germany
- Malaria Biochemistry Laboratory, The Francis Crick Institute, LondonNW1 1AT, United Kingdom
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Tuli F, Kane PM. The cytosolic N-terminal domain of V-ATPase a-subunits is a regulatory hub targeted by multiple signals. Front Mol Biosci 2023; 10:1168680. [PMID: 37398550 PMCID: PMC10313074 DOI: 10.3389/fmolb.2023.1168680] [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: 02/17/2023] [Accepted: 06/05/2023] [Indexed: 07/04/2023] Open
Abstract
Vacuolar H+-ATPases (V-ATPases) acidify several organelles in all eukaryotic cells and export protons across the plasma membrane in a subset of cell types. V-ATPases are multisubunit enzymes consisting of a peripheral subcomplex, V1, that is exposed to the cytosol and an integral membrane subcomplex, Vo, that contains the proton pore. The Vo a-subunit is the largest membrane subunit and consists of two domains. The N-terminal domain of the a-subunit (aNT) interacts with several V1 and Vo subunits and serves to bridge the V1 and Vo subcomplexes, while the C-terminal domain contains eight transmembrane helices, two of which are directly involved in proton transport. Although there can be multiple isoforms of several V-ATPase subunits, the a-subunit is encoded by the largest number of isoforms in most organisms. For example, the human genome encodes four a-subunit isoforms that exhibit a tissue- and organelle-specific distribution. In the yeast S. cerevisiae, the two a-subunit isoforms, Golgi-enriched Stv1 and vacuolar Vph1, are the only V-ATPase subunit isoforms. Current structural information indicates that a-subunit isoforms adopt a similar backbone structure but sequence variations allow for specific interactions during trafficking and in response to cellular signals. V-ATPases are subject to several types of environmental regulation that serve to tune their activity to their cellular location and environmental demands. The position of the aNT domain in the complex makes it an ideal target for modulating V1-Vo interactions and regulating enzyme activity. The yeast a-subunit isoforms have served as a paradigm for dissecting interactions of regulatory inputs with subunit isoforms. Importantly, structures of yeast V-ATPases containing each a-subunit isoform are available. Chimeric a-subunits combining elements of Stv1NT and Vph1NT have provided insights into how regulatory inputs can be integrated to allow V-ATPases to support cell growth under different stress conditions. Although the function and distribution of the four mammalian a-subunit isoforms present additional complexity, it is clear that the aNT domains of these isoforms are also subject to multiple regulatory interactions. Regulatory mechanisms that target mammalian a-subunit isoforms, and specifically the aNT domains, will be described. Altered V-ATPase function is associated with multiple diseases in humans. The possibility of regulating V-ATPase subpopulations via their isoform-specific regulatory interactions are discussed.
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Affiliation(s)
| | - Patricia M. Kane
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, United States
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Du J, Zhao H, Zhu M, Dong Y, Peng L, Li J, Zhao Q, Yu Q, Li M. Atg8 and Ire1 in combination regulate the autophagy-related endoplasmic reticulum stress response in Candida albicans. Res Microbiol 2023; 174:103996. [PMID: 36328097 DOI: 10.1016/j.resmic.2022.103996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 10/24/2022] [Accepted: 10/26/2022] [Indexed: 11/05/2022]
Abstract
The unfolded protein response (UPR) is an important pathway to prevent endoplasmic reticulum (ER) stress in eukaryotic cells. In Saccharomyces cerevisiae, Ire1 is a key regulatory factor required for HAC1 gene splicing for further production of functional Hac1 and activation of UPR gene expression. Autophagy is another mechanism involved in the attenuation of ER stress by ER-phagy, and Atg8 is a core protein in autophagy. Both autophagy and UPR are critical for ER stress response, but whether they act individually or in combination in Candida albicans is unknown. In this study, we explored the interaction between Ire1 and the autophagy protein Atg8 for the ER stress response by constructing the atg8Δ/Δire1Δ/Δ double mutant in the pathogenic fungus C. albicans. Compared to the single mutants atg8Δ/Δ or ire1Δ/Δ, atg8Δ/Δire1Δ/Δ exhibited much higher sensitivity to various ER stress-inducing agents and more severe attenuation of UPR gene expression under ER stress. Further investigations showed that the double mutant had a defect in ER-phagy, which was associated with attenuated vacuolar fusion under ER stress. This study revealed that Ire1 and Atg8 in combination function in the activation of the UPR and ER-phagy to maintain ER homeostasis under ER stress in C. albicans.
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Affiliation(s)
- Jiawen Du
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - He Zhao
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Mengsen Zhu
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Yixuan Dong
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Liping Peng
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Jianrong Li
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Qiang Zhao
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China
| | - Qilin Yu
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China.
| | - Mingchun Li
- Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, College of Life Sciences, Nankai University, Tianjin 300071, China.
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The polyHIS Tract of Yeast AMPK Coordinates Carbon Metabolism with Iron Availability. Int J Mol Sci 2023; 24:ijms24021368. [PMID: 36674878 PMCID: PMC9863760 DOI: 10.3390/ijms24021368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 01/06/2023] [Accepted: 01/07/2023] [Indexed: 01/13/2023] Open
Abstract
Energy status in all eukaryotic cells is sensed by AMP-kinases. We have previously found that the poly-histidine tract at the N-terminus of S. cerevisiae AMPK (Snf1) inhibits its function in the presence of glucose via a pH-regulated mechanism. We show here that in the absence of glucose, the poly-histidine tract has a second function, linking together carbon and iron metabolism. Under conditions of iron deprivation, when different iron-intense cellular systems compete for this scarce resource, Snf1 is inhibited. The inhibition is via an interaction of the poly-histidine tract with the low-iron transcription factor Aft1. Aft1 inhibition of Snf1 occurs in the nucleus at the nuclear membrane, and only inhibits nuclear Snf1, without affecting cytosolic Snf1 activities. Thus, the temporal and spatial regulation of Snf1 activity enables a differential response to iron depending upon the type of carbon source. The linkage of nuclear Snf1 activity to iron sufficiency ensures that sufficient clusters are available to support respiratory enzymatic activity and tests mitochondrial competency prior to activation of nuclear Snf1.
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7
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Seidel T. The Plant V-ATPase. FRONTIERS IN PLANT SCIENCE 2022; 13:931777. [PMID: 35845650 PMCID: PMC9280200 DOI: 10.3389/fpls.2022.931777] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 06/03/2022] [Indexed: 05/25/2023]
Abstract
V-ATPase is the dominant proton pump in plant cells. It contributes to cytosolic pH homeostasis and energizes transport processes across endomembranes of the secretory pathway. Its localization in the trans Golgi network/early endosomes is essential for vesicle transport, for instance for the delivery of cell wall components. Furthermore, it is crucial for response to abiotic and biotic stresses. The V-ATPase's rather complex structure and multiple subunit isoforms enable high structural flexibility with respect to requirements for different organs, developmental stages, and organelles. This complexity further demands a sophisticated assembly machinery and transport routes in cells, a process that is still not fully understood. Regulation of V-ATPase is a target of phosphorylation and redox-modifications but also involves interactions with regulatory proteins like 14-3-3 proteins and the lipid environment. Regulation by reversible assembly, as reported for yeast and the mammalian enzyme, has not be proven in plants but seems to be absent in autotrophic cells. Addressing the regulation of V-ATPase is a promising approach to adjust its activity for improved stress resistance or higher crop yield.
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8
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Wilson ZN, Buysse D, West M, Ahrens D, Odorizzi G. Vacuolar H+-ATPase dysfunction rescues intralumenal vesicle cargo sorting in yeast lacking PI(3,5)P2 or Doa4. J Cell Sci 2021; 134:jcs258459. [PMID: 34342352 PMCID: PMC8353521 DOI: 10.1242/jcs.258459] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 06/25/2021] [Indexed: 12/19/2022] Open
Abstract
Endosomes undergo a maturation process highlighted by a reduction in lumenal pH, a conversion of surface markers that prime endosome-lysosome fusion and the sequestration of ubiquitylated transmembrane protein cargos within intralumenal vesicles (ILVs). We investigated ILV cargo sorting in mutant strains of the budding yeast Saccharomyces cerevisiae that are deficient for either the lysosomal/vacuolar signaling lipid PI(3,5)P2 or the Doa4 ubiquitin hydrolase that deubiquitylates ILV cargos. Disruption of PI(3,5)P2 synthesis or Doa4 function causes a defect in sorting of a subset of ILV cargos. We show that these cargo-sorting defects are suppressed by mutations that disrupt Vph1, a subunit of vacuolar H+-ATPase (V-ATPase) complexes that acidify late endosomes and vacuoles. We further show that Vph1 dysfunction increases endosome abundance, and disrupts vacuolar localization of Ypt7 and Vps41, two crucial mediators of endosome-vacuole fusion. Because V-ATPase inhibition attenuates this fusion and rescues the ILV cargo-sorting defects in yeast that lack PI(3,5)P2 or Doa4 activity, our results suggest that the V-ATPase has a role in coordinating ILV cargo sorting with the membrane fusion machinery. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
| | | | | | | | - Greg Odorizzi
- Department of Molecular Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309, USA
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9
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Alexander AJT, Muñoz A, Marcos JF, Read ND. Calcium homeostasis plays important roles in the internalization and activities of the small synthetic antifungal peptide PAF26. Mol Microbiol 2020; 114:521-535. [PMID: 32898933 DOI: 10.1111/mmi.14532] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 05/01/2020] [Accepted: 05/17/2020] [Indexed: 01/22/2023]
Abstract
Fungal diseases are responsible for the deaths of over 1.5 million people worldwide annually. Antifungal peptides represent a useful source of antifungals with novel mechanisms-of-action, and potentially provide new methods of overcoming resistance. Here we investigate the mode-of-action of the small, rationally designed synthetic antifungal peptide PAF26 using the model fungus Neurospora crassa. Here we show that the cell killing activity of PAF26 is dependent on extracellular Ca2+ and the presence of fully functioning fungal Ca2+ homeostatic/signaling machinery. In a screen of mutants with deletions in Ca2+ -signaling machinery, we identified three mutants more tolerant to PAF26. The Ca2+ ATPase NCA-2 was found to be involved in the initial interaction of PAF26 with the cell envelope. The vacuolar Ca2+ channel YVC-1 was shown to be essential for its accumulation and concentration within the vacuolar system. The Ca2+ channel CCH-1 was found to be required to prevent the translocation of PAF26 across the plasma membrane. In the wild type, Ca2+ removal from the medium resulted in the peptide remaining trapped in small vesicles as in the Δyvc-1 mutant. It is, therefore, apparent that cell killing by PAF26 is complex and unusually dependent on extracellular Ca2+ and components of the Ca2+ -regulatory machinery.
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Affiliation(s)
- Akira J T Alexander
- Institute of Infection, Immunity & Inflammation, The University of Glasgow, Glasgow, Scotland
| | - Alberto Muñoz
- MRC Centre for Medical Mycology, University of Exeter, Exeter, UK
| | - Jose F Marcos
- Department of Food Biotechnology, Instituto de Agroquímica y Tecnología de Alimentos (IATA) , Consejo Superior de Investigaciones Científicas (CSIC), Valencia, Spain
| | - Nick D Read
- Manchester Fungal Infection Group, Infection, Immunity & Respiratory Medicine, University of Manchester, Manchester, UK
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Morosin SK, Delforce SJ, Lumbers ER, Pringle KG. The (pro)renin receptor (ATP6AP2) does not play a role in syncytialisation of term human primary trophoblast cells. Placenta 2020; 97:89-94. [PMID: 32792070 DOI: 10.1016/j.placenta.2020.05.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 05/14/2020] [Accepted: 05/25/2020] [Indexed: 12/24/2022]
Abstract
INTRODUCTION In the placenta, the (pro)renin receptor (ATP6AP2) is localised to the syncytiotrophoblast. ATP6AP2 can activate the placental renin-angiotensin system (RAS), producing Angiotensin II (Ang II) which, acting via the angiotensin II type 1 receptor (AGTR1), is important for placental development and function. ATP6AP2 can also independently stimulate intracellular signalling pathways known to regulate trophoblast syncytialisation. We proposed that ATP6AP2 plays a role in trophoblast syncytialisation. METHODS Primary trophoblast cells were isolated from human placentae and transfected with an ATP6AP2 siRNA, a negative control siRNA or vehicle and allowed to spontaneously syncytialise. Syncytialisation was determined by secretion of human chorionic gonadotrophin (hCG) and by decreased CDH1 (E-cadherin) levels. Expression of RAS mRNAs and proteins were measured by qPCR and immunoblotting, respectively. RESULTS Primary trophoblast cells spontaneously syncytialised in culture. Syncytialisation did not affect ATP6AP2 mRNA or protein levels. However, the expression of REN, AGT and AGTR1 mRNAs were increased (P = 0.02, P = 0.01 and P = 0.03, respectively). ATP6AP2 siRNA had no effect on syncytialisation. DISCUSSION In primary trophoblasts, syncytialisation was associated with increased expression of the RAS. hCG was increased during syncytialisation and is known to stimulate REN and possibly AGT, however further experiments are needed to confirm that this was the mechanism via which the RAS was activated. Therefore, syncytialisation of primary trophoblasts may involve hCG-induced RAS activation and downstream activation of signalling pathways and growth factors, which can be stimulated via the interaction of Ang II with AGTR1. Nevertheless, it appears that the (pro)renin receptor is not involved.
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Affiliation(s)
- Saije K Morosin
- School of Biomedical Sciences and Pharmacy, Priority Research Centre for Reproductive Science, Pregnancy and Reproduction Program, Hunter Medical Research Institute, University of Newcastle, Newcastle, 2300, New South Wales, Australia
| | - Sarah J Delforce
- School of Biomedical Sciences and Pharmacy, Priority Research Centre for Reproductive Science, Pregnancy and Reproduction Program, Hunter Medical Research Institute, University of Newcastle, Newcastle, 2300, New South Wales, Australia
| | - Eugenie R Lumbers
- School of Biomedical Sciences and Pharmacy, Priority Research Centre for Reproductive Science, Pregnancy and Reproduction Program, Hunter Medical Research Institute, University of Newcastle, Newcastle, 2300, New South Wales, Australia
| | - Kirsty G Pringle
- School of Biomedical Sciences and Pharmacy, Priority Research Centre for Reproductive Science, Pregnancy and Reproduction Program, Hunter Medical Research Institute, University of Newcastle, Newcastle, 2300, New South Wales, Australia.
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11
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Ahmadpour D, Babazadeh R, Nystrom T. Hitchhiking on vesicles: a way to harness age-related proteopathies? FEBS J 2020; 287:5068-5079. [PMID: 32336030 DOI: 10.1111/febs.15345] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 04/06/2020] [Accepted: 04/23/2020] [Indexed: 12/27/2022]
Abstract
Central to proteopathies and leading to most age-related neurodegenerative disorders is a failure in protein quality control (PQC). To harness the toxicity of misfolded and damaged disease proteins, such proteins are either refolded, degraded by temporal PQC, or sequestered by spatial PQC into specific, organelle-associated, compartments within the cell. Here, we discuss the impact of vesicle trafficking pathways in general, and syntaxin 5 in particular, as key players in spatial PQC directing misfolded proteins to the surface of vacuole and mitochondria, which facilitates their clearance and detoxification. Since boosting vesicle trafficking genetically can positively impact on spatial PQC and make cells less sensitive to misfolded disease proteins, we speculate that regulators of such trafficking might serve as therapeutic targets for age-related neurological disorders.
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Affiliation(s)
- Doryaneh Ahmadpour
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health-AgeCap, University of Gothenburg, Sweden.,Institute of Neuroscience and Physiology, Department of Psychiatry and Neurochemistry, Sahlgrenska Academy at the University of Gothenburg, Sweden
| | - Roja Babazadeh
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health-AgeCap, University of Gothenburg, Sweden.,Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Thomas Nystrom
- Institute for Biomedicine, Sahlgrenska Academy, Centre for Ageing and Health-AgeCap, University of Gothenburg, Sweden
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12
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Translation Inhibition by Rocaglates Activates a Species-Specific Cell Death Program in the Emerging Fungal Pathogen Candida auris. mBio 2020; 11:mBio.03329-19. [PMID: 32156828 PMCID: PMC7064782 DOI: 10.1128/mbio.03329-19] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Emergence of the fungal pathogen Candida auris has ignited intrigue and alarm within the medical community and the public at large. This pathogen is unusually resistant to antifungals, threatening to overwhelm current management options. By screening a library of structurally diverse molecules, we found that C. auris is surprisingly sensitive to translation inhibition by a class of compounds known as rocaglates (also known as flavaglines). Despite the high level of conservation across fungi in their protein synthesis machinery, these compounds inhibited translation initiation and activated a cell death program in C. auris but not in its relative Candida albicans. Our findings highlight a surprising divergence across the cell death programs operating in Candida species and underscore the need to understand the specific biology of a pathogen in attempting to develop more-effective treatments against it. Fungal infections are a major contributor to infectious disease-related deaths worldwide. Recently, global emergence of the fungal pathogen Candida auris has caused considerable concern because most C. auris isolates are resistant to fluconazole, the most commonly administered antifungal, and some isolates are resistant to drugs from all three major antifungal classes. To identify novel agents with bioactivity against C. auris, we screened 2,454 compounds from a diversity-oriented synthesis collection. Of the five hits identified, most shared a common rocaglate core structure and displayed fungicidal activity against C. auris. These rocaglate hits inhibited translation in C. auris but not in its pathogenic relative Candida albicans. Species specificity was contingent on variation at a single amino acid residue in Tif1, a fungal member of the eukaryotic initiation factor 4A (eIF4A) family of translation initiation factors known to be targeted by rocaglates. Rocaglate-mediated inhibition of translation in C. auris activated a cell death program characterized by loss of mitochondrial membrane potential, increased caspase-like activity, and disrupted vacuolar homeostasis. In a rocaglate-sensitized C. albicans mutant engineered to express translation initiation factor 1 (Tif1) with the variant amino acid that we had identified in C. auris, translation was inhibited but no programmed cell death phenotypes were observed. This surprising finding suggests divergence between these related fungal pathogens in their pathways of cellular responses to translation inhibition. From a therapeutic perspective, the chemical biology that we have uncovered reveals species-specific vulnerability in C. auris and identifies a promising target for development of new, mechanistically distinct antifungals in the battle against this emerging pathogen.
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de Araujo MEG, Liebscher G, Hess MW, Huber LA. Lysosomal size matters. Traffic 2019; 21:60-75. [PMID: 31808235 PMCID: PMC6972631 DOI: 10.1111/tra.12714] [Citation(s) in RCA: 105] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 10/30/2019] [Accepted: 10/31/2019] [Indexed: 12/25/2022]
Abstract
Lysosomes are key cellular catabolic centers that also perform fundamental metabolic, signaling and quality control functions. Lysosomes are not static and they respond dynamically to intra‐ and extracellular stimuli triggering changes in organelle numbers, size and position. Such physical changes have a strong impact on lysosomal activity ultimately influencing cellular homeostasis. In this review, we summarize the current knowledge on lysosomal size regulation, on its physiological role(s) and association to several disease conditions.
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Affiliation(s)
- Mariana E G de Araujo
- Institute of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Gudrun Liebscher
- Institute of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria
| | - Michael W Hess
- Institute of Histology and Embryology, Medical University of Innsbruck, Innsbruck, Austria
| | - Lukas A Huber
- Institute of Cell Biology, Biocenter, Medical University of Innsbruck, Innsbruck, Austria.,Austrian Drug Screening Institute, ADSI, Innsbruck, Austria
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14
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Gross AS, Zimmermann A, Pendl T, Schroeder S, Schoenlechner H, Knittelfelder O, Lamplmayr L, Santiso A, Aufschnaiter A, Waltenstorfer D, Ortonobes Lara S, Stryeck S, Kast C, Ruckenstuhl C, Hofer SJ, Michelitsch B, Woelflingseder M, Müller R, Carmona-Gutierrez D, Madl T, Büttner S, Fröhlich KU, Shevchenko A, Eisenberg T. Acetyl-CoA carboxylase 1-dependent lipogenesis promotes autophagy downstream of AMPK. J Biol Chem 2019; 294:12020-12039. [PMID: 31209110 PMCID: PMC6690696 DOI: 10.1074/jbc.ra118.007020] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2018] [Revised: 05/31/2019] [Indexed: 12/16/2022] Open
Abstract
Autophagy, a membrane-dependent catabolic process, ensures survival of aging cells and depends on the cellular energetic status. Acetyl-CoA carboxylase 1 (Acc1) connects central energy metabolism to lipid biosynthesis and is rate-limiting for the de novo synthesis of lipids. However, it is unclear how de novo lipogenesis and its metabolic consequences affect autophagic activity. Here, we show that in aging yeast, autophagy levels highly depend on the activity of Acc1. Constitutively active Acc1 (acc1S/A) or a deletion of the Acc1 negative regulator, Snf1 (yeast AMPK), shows elevated autophagy levels, which can be reversed by the Acc1 inhibitor soraphen A. Vice versa, pharmacological inhibition of Acc1 drastically reduces cell survival and results in the accumulation of Atg8-positive structures at the vacuolar membrane, suggesting late defects in the autophagic cascade. As expected, acc1S/A cells exhibit a reduction in acetate/acetyl-CoA availability along with elevated cellular lipid content. However, concomitant administration of acetate fails to fully revert the increase in autophagy exerted by acc1S/A. Instead, administration of oleate, while mimicking constitutively active Acc1 in WT cells, alleviates the vacuolar fusion defects induced by Acc1 inhibition. Our results argue for a largely lipid-dependent process of autophagy regulation downstream of Acc1. We present a versatile genetic model to investigate the complex relationship between acetate metabolism, lipid homeostasis, and autophagy and propose Acc1-dependent lipogenesis as a fundamental metabolic path downstream of Snf1 to maintain autophagy and survival during cellular aging.
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Affiliation(s)
- Angelina S Gross
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria
| | - Andreas Zimmermann
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria; Central Lab Gracia, NAWI Graz, University of Graz, 8010 Graz, Austria
| | - Tobias Pendl
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria
| | - Sabrina Schroeder
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria; BioTechMed-Graz, 8010 Graz, Austria
| | - Hannes Schoenlechner
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria
| | - Oskar Knittelfelder
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Laura Lamplmayr
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria
| | - Ana Santiso
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria
| | - Andreas Aufschnaiter
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria; Department of Molecular Biosciences, Wenner-Gren Institute, Stockholm University, 114 19 Stockholm, Sweden
| | - Daniel Waltenstorfer
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria
| | - Sandra Ortonobes Lara
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria
| | - Sarah Stryeck
- Gottfried Schatz Research Center for Cell Signaling, Metabolism, and Aging, Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8036 Graz, Austria
| | - Christina Kast
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria
| | - Christoph Ruckenstuhl
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria
| | - Sebastian J Hofer
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria; BioTechMed-Graz, 8010 Graz, Austria
| | - Birgit Michelitsch
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria; Division of Plastic, Aesthetic, and Reconstructive Surgery, Department of Surgery, Medical University of Graz, 8036 Graz, Austria
| | | | - Rolf Müller
- Helmholtz Institute for Pharmaceutical Research Saarland, 66123 Saarbrücken, Germany
| | | | - Tobias Madl
- BioTechMed-Graz, 8010 Graz, Austria; Gottfried Schatz Research Center for Cell Signaling, Metabolism, and Aging, Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8036 Graz, Austria
| | - Sabrina Büttner
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria; Department of Molecular Biosciences, Wenner-Gren Institute, Stockholm University, 114 19 Stockholm, Sweden
| | - Kai-Uwe Fröhlich
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria
| | - Andrej Shevchenko
- Max Planck Institute of Molecular Cell Biology and Genetics, 01307 Dresden, Germany
| | - Tobias Eisenberg
- Institute of Molecular Biosciences, NAWI Graz, University of Graz, 8010 Graz, Austria; Central Lab Gracia, NAWI Graz, University of Graz, 8010 Graz, Austria; BioTechMed-Graz, 8010 Graz, Austria.
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15
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Hirose T, Cabrera-Socorro A, Chitayat D, Lemonnier T, Féraud O, Cifuentes-Diaz C, Gervasi N, Mombereau C, Ghosh T, Stoica L, Bacha JDA, Yamada H, Lauterbach MA, Guillon M, Kaneko K, Norris JW, Siriwardena K, Blasér S, Teillon J, Mendoza-Londono R, Russeau M, Hadoux J, Ito S, Corvol P, Matheus MG, Holden KR, Takei K, Emiliani V, Bennaceur-Griscelli A, Schwartz CE, Nguyen G, Groszer M. ATP6AP2 variant impairs CNS development and neuronal survival to cause fulminant neurodegeneration. J Clin Invest 2019; 129:2145-2162. [PMID: 30985297 DOI: 10.1172/jci79990] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Accepted: 03/05/2019] [Indexed: 12/31/2022] Open
Abstract
Vacuolar H+-ATPase-dependent (V-ATPase-dependent) functions are critical for neural proteostasis and are involved in neurodegeneration and brain tumorigenesis. We identified a patient with fulminant neurodegeneration of the developing brain carrying a de novo splice site variant in ATP6AP2 encoding an accessory protein of the V-ATPase. Functional studies of induced pluripotent stem cell-derived (iPSC-derived) neurons from this patient revealed reduced spontaneous activity and severe deficiency in lysosomal acidification and protein degradation leading to neuronal cell death. These deficiencies could be rescued by expression of full-length ATP6AP2. Conditional deletion of Atp6ap2 in developing mouse brain impaired V-ATPase-dependent functions, causing impaired neural stem cell self-renewal, premature neuronal differentiation, and apoptosis resulting in degeneration of nearly the entire cortex. In vitro studies revealed that ATP6AP2 deficiency decreases V-ATPase membrane assembly and increases endosomal-lysosomal fusion. We conclude that ATP6AP2 is a key mediator of V-ATPase-dependent signaling and protein degradation in the developing human central nervous system.
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Affiliation(s)
- Takuo Hirose
- Collège de France, Center for Interdisciplinary Research in Biology, Paris, France
| | - Alfredo Cabrera-Socorro
- INSERM, UMR-S 1270, Paris, France.,Sorbonne Université, Paris, France.,Institut du Fer à Moulin, Paris, France
| | - David Chitayat
- Prenatal Diagnosis and Medical Genetics Program, Department of Obstetrics and Gynecology, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada.,Division of Clinical and Metabolic Genetics and.,Department of Diagnostic Imaging, Division of Pediatric Neuroradiology, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Thomas Lemonnier
- INSERM, UMR-S 1270, Paris, France.,Sorbonne Université, Paris, France.,Institut du Fer à Moulin, Paris, France
| | - Olivier Féraud
- INSERM, UMR 935, ESTeam Paris Sud, SFR André Lwoff, Université Paris Sud, Villejuif, France.,Infrastructure Nationale INGESTEM, Université Paris Sud, INSERM, Paris, France
| | - Carmen Cifuentes-Diaz
- INSERM, UMR-S 1270, Paris, France.,Sorbonne Université, Paris, France.,Institut du Fer à Moulin, Paris, France
| | - Nicolas Gervasi
- INSERM, UMR-S 1270, Paris, France.,Sorbonne Université, Paris, France.,Institut du Fer à Moulin, Paris, France
| | - Cedric Mombereau
- INSERM, UMR-S 1270, Paris, France.,Sorbonne Université, Paris, France.,Institut du Fer à Moulin, Paris, France
| | - Tanay Ghosh
- INSERM, UMR-S 1270, Paris, France.,Sorbonne Université, Paris, France.,Institut du Fer à Moulin, Paris, France
| | - Loredana Stoica
- INSERM, UMR-S 1270, Paris, France.,Sorbonne Université, Paris, France.,Institut du Fer à Moulin, Paris, France
| | - Jeanne d'Arc Al Bacha
- Collège de France, Center for Interdisciplinary Research in Biology, Paris, France.,Sorbonne Université, Paris, France.,Institut du Fer à Moulin, Paris, France.,Laboratory of Applied Biotechnology, Azm Center for the Research in Biotechnology and Its Applications, Doctoral School for Sciences and Technology, Lebanese University, Tripoli, Lebanon.,Reviva Regenerative Medicine Center, Human Genetic Center, Middle East Institute of Health Hospital, Bsalim, Lebanon
| | - Hiroshi Yamada
- Department of Neuroscience, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Marcel A Lauterbach
- Wavefront-Engineering Microscopy Group, Neurophotonics Laboratory, CNRS, UMR 8250, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Marc Guillon
- Wavefront-Engineering Microscopy Group, Neurophotonics Laboratory, CNRS, UMR 8250, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Kiriko Kaneko
- Department of Endocrinology and Applied Medical Science, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Joy W Norris
- Greenwood Genetic Center, Greenwood, South Carolina, USA
| | | | | | - Jérémie Teillon
- Collège de France, Center for Interdisciplinary Research in Biology, Paris, France.,INSERM, U1050, Paris, France.,CNRS, UMR 7241, Paris, France
| | | | - Marion Russeau
- INSERM, UMR-S 1270, Paris, France.,Sorbonne Université, Paris, France.,Institut du Fer à Moulin, Paris, France
| | - Julien Hadoux
- INSERM, UMR 935, ESTeam Paris Sud, SFR André Lwoff, Université Paris Sud, Villejuif, France.,Infrastructure Nationale INGESTEM, Université Paris Sud, INSERM, Paris, France
| | - Sadayoshi Ito
- Division of Nephrology, Endocrinology and Vascular Medicine, Department of Medicine, Tohoku University Graduate School of Medicine, Sendai, Japan
| | - Pierre Corvol
- Collège de France, Center for Interdisciplinary Research in Biology, Paris, France.,INSERM, U1050, Paris, France.,CNRS, UMR 7241, Paris, France
| | | | - Kenton R Holden
- Department of Radiology, Medical University of South Carolina, Charleston, South Carolina, USA
| | - Kohji Takei
- Department of Neuroscience, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Valentina Emiliani
- Wavefront-Engineering Microscopy Group, Neurophotonics Laboratory, CNRS, UMR 8250, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Annelise Bennaceur-Griscelli
- INSERM, UMR 935, ESTeam Paris Sud, SFR André Lwoff, Université Paris Sud, Villejuif, France.,Infrastructure Nationale INGESTEM, Université Paris Sud, INSERM, Paris, France.,Faculté de Médecine, Kremlin-Bicêtre, Université Paris Sud, Paris Saclay, France.,AP-HP, Service d'Hématologie, Hôpitaux Universitaires Paris Sud, Hôpital Paul Brousse, Villejuif, France
| | | | - Genevieve Nguyen
- Collège de France, Center for Interdisciplinary Research in Biology, Paris, France.,INSERM, U1050, Paris, France.,CNRS, UMR 7241, Paris, France
| | - Matthias Groszer
- INSERM, UMR-S 1270, Paris, France.,Sorbonne Université, Paris, France.,Institut du Fer à Moulin, Paris, France
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16
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Aufschnaiter A, Büttner S. The vacuolar shapes of ageing: From function to morphology. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2019; 1866:957-970. [PMID: 30796938 DOI: 10.1016/j.bbamcr.2019.02.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2018] [Revised: 02/13/2019] [Accepted: 02/15/2019] [Indexed: 12/21/2022]
Abstract
Cellular ageing results in accumulating damage to various macromolecules and the progressive decline of organelle function. Yeast vacuoles as well as their counterpart in higher eukaryotes, the lysosomes, emerge as central organelles in lifespan determination. These acidic organelles integrate enzymatic breakdown and recycling of cellular waste with nutrient sensing, storage, signalling and mobilization. Establishing physical contact with virtually all other organelles, vacuoles serve as hubs of cellular homeostasis. Studies in Saccharomyces cerevisiae contributed substantially to our understanding of the ageing process per se and the multifaceted roles of vacuoles/lysosomes in the maintenance of cellular fitness with progressing age. Here, we discuss the multiple roles of the vacuole during ageing, ranging from vacuolar dynamics and acidification as determinants of lifespan to the function of this organelle as waste bin, recycling facility, nutrient reservoir and integrator of nutrient signalling.
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Affiliation(s)
- Andreas Aufschnaiter
- Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, 8010 Graz, Austria
| | - Sabrina Büttner
- Institute of Molecular Biosciences, University of Graz, Humboldtstraße 50, 8010 Graz, Austria; Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Svante Arrhenius väg 20C, 106 91 Stockholm, Sweden.
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17
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Sun G, Elowsky C, Li G, Wilson RA. TOR-autophagy branch signaling via Imp1 dictates plant-microbe biotrophic interface longevity. PLoS Genet 2018; 14:e1007814. [PMID: 30462633 PMCID: PMC6281275 DOI: 10.1371/journal.pgen.1007814] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 12/05/2018] [Accepted: 11/06/2018] [Indexed: 01/07/2023] Open
Abstract
Like other intracellular eukaryotic phytopathogens, the devastating rice blast fungus Magnaporthe (Pyricularia) oryzae first infects living host cells by elaborating invasive hyphae (IH) surrounded by a plant-derived membrane. This forms an extended biotrophic interface enclosing an apoplastic compartment into which fungal effectors can be deployed to evade host detection. M. oryzae also forms a focal, plant membrane-rich structure, the biotrophic interfacial complex (BIC), that accumulates cytoplasmic effectors for translocation into host cells. Molecular decision-making processes integrating fungal growth and metabolism in host cells with interface function and dynamics are unknown. Here, we report unanticipated roles for the M. oryzae Target-of-Rapamycin (TOR) nutrient-signaling pathway in mediating plant-fungal biotrophic interface membrane integrity. Through a forward genetics screen for M. oryzae mutant strains resistant to the specific TOR kinase inhibitor rapamycin, we discovered IMP1 encoding a novel vacuolar protein required for membrane trafficking, V-ATPase assembly, organelle acidification and autophagy induction. During infection, Δimp1 deletants developed intracellular IH in the first infected rice cell following cuticle penetration. However, fluorescently labeled effector probes revealed that interface membrane integrity became compromised as biotrophy progressed, abolishing the BIC and releasing apoplastic effectors into host cytoplasm. Growth between rice cells was restricted. TOR-independent autophagy activation in Δimp1 deletants (following infection) remediated interface function and cell-to-cell growth. Autophagy inhibition in wild type (following infection) recapitulated Δimp1. In addition to vacuoles, Imp1GFP localized to IH membranes in an autophagy-dependent manner. Collectively, our results suggest TOR-Imp1-autophagy branch signaling mediates membrane homeostasis to prevent catastrophic erosion of the biotrophic interface, thus facilitating fungal growth in living rice cells. The significance of this work lays in elaborating a novel molecular mechanism of infection stressing the dominance of fungal metabolism and metabolic control in sustaining long-term plant-microbe interactions. This work also has implications for understanding the enigmatic biotrophy to necrotrophy transition. Plant-associated fungi can form intimate connections with living host cells. Clarifying the molecular drivers of these interactions, and which partner is dominant, might be important in understanding how beneficial plant-fungal relationships can be enhanced to improve crop yields while pathogenic interactions that threaten crop health are disrupted. In common with other symbionts and phytopathogens, the devastating rice blast fungus Magnaporthe oryzae elaborates invasive hyphae in living host cells surrounded by plant-derived membranes. Nothing is known at the molecular signaling level about how such plant-microbe biotrophic interfacial zones are maintained as the fungus grows in and between host cells. Here, we report that fungal membrane trafficking processes controlled by nutrient signaling pathways are critical for maintaining biotrophic interface integrity during M. oryzae growth in rice cells. Impairing these processes resulted in erosion of the plant-microbe interface and failure of the fungus to thrive. To our knowledge, this work presents the first evidence indicating that the fungal partner is dominant in propagating the plant-microbe boundary. This suggests that the biotrophic interface is a fungal construct and provides clues on how such interfaces might be modulated to benefit the host plant.
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Affiliation(s)
- Guangchao Sun
- Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Christian Elowsky
- Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Gang Li
- Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
| | - Richard A. Wilson
- Department of Plant Pathology, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America
- * E-mail:
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18
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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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19
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Wilson ZN, Scott AL, Dowell RD, Odorizzi G. PI(3,5)P 2 controls vacuole potassium transport to support cellular osmoregulation. Mol Biol Cell 2018; 29:1718-1731. [PMID: 29791245 PMCID: PMC6080712 DOI: 10.1091/mbc.e18-01-0015] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Lysosomes are dynamic organelles with critical roles in cellular physiology. The lysosomal signaling lipid phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) is a key regulator that has been implicated to control lysosome ion homeostasis, but the scope of ion transporters targeted by PI(3,5)P2 and the purpose of this regulation is not well understood. Through an unbiased screen in Saccharomyces cerevisiae, we identified loss-of-function mutations in the vacuolar H+-ATPase (V-ATPase) and in Vnx1, a vacuolar monovalent cation/proton antiporter, as suppressor mutations that relieve the growth defects and osmotic swelling of vacuoles (lysosomes) in yeast lacking PI(3,5)P2. We observed that depletion of PI(3,5)P2 synthesis in yeast causes a robust accumulation of multiple cations, most notably an ∼85 mM increase in the cellular concentration of potassium, a critical ion used by cells to regulate osmolarity. The accumulation of potassium and other cations in PI(3,5)P2-deficient yeast is relieved by mutations that inactivate Vnx1 or inactivate the V-ATPase and by mutations that increase the activity of a vacuolar cation export channel, Yvc1. Collectively, our data demonstrate that PI(3,5)P2 signaling orchestrates vacuole/lysosome cation transport to aid cellular osmoregulation.
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Affiliation(s)
- Zachary N Wilson
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309-0347
| | - Amber L Scott
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309-0347
| | - Robin D Dowell
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309-0347
| | - Greg Odorizzi
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309-0347
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20
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Zhao H, Wang J, Wang T. The V-ATPase V1 subunit A1 is required for rhodopsin anterograde trafficking in Drosophila. Mol Biol Cell 2018; 29:1640-1651. [PMID: 29742016 PMCID: PMC6080656 DOI: 10.1091/mbc.e17-09-0546] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Synthesis and maturation of the light sensor, rhodopsin, are critical for the maintenance of light sensitivity and for photoreceptor homeostasis. In Drosophila, the main rhodopsin, Rh1, is synthesized in the endoplasmic reticulum and transported to the rhabdomere through the secretory pathway. In an unbiased genetic screen for factors involved in rhodopsin homeostasis, we identified mutations in vha68-1, which encodes the vacuolar proton-translocating ATPase (V-ATPase) catalytic subunit A isoform 1 of the V1 component. Loss of vha68-1 in photoreceptor cells disrupted post-Golgi anterograde trafficking of Rh1, reduced light sensitivity, increased secretory vesicle pH, and resulted in incomplete Rh1 deglycosylation. In addition, vha68-1 was required for activity-independent photoreceptor cell survival. Importantly, vha68-1 mutants exhibited phenotypes similar to those exhibited by mutations in the V0 component of V-ATPase, vha100-1. These data demonstrate that the V1 and V0 components of V-ATPase play key roles in post-Golgi trafficking of Rh1 and that Drosophila may represent an important animal model system for studying diseases associated with V-ATPase dysfunction.
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Affiliation(s)
- Haifang Zhao
- School of Life Sciences, Tsinghua University, Beijing 100084, China.,National Institute of Biological Sciences, Beijing 102206, China
| | - Jing Wang
- National Institute of Biological Sciences, Beijing 102206, China
| | - Tao Wang
- National Institute of Biological Sciences, Beijing 102206, China
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21
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Karim MA, Brett CL. The Na +(K +)/H + exchanger Nhx1 controls multivesicular body-vacuolar lysosome fusion. Mol Biol Cell 2018; 29:317-325. [PMID: 29212874 PMCID: PMC5996954 DOI: 10.1091/mbc.e17-08-0496] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 11/07/2017] [Accepted: 11/28/2017] [Indexed: 01/12/2023] Open
Abstract
Loss-of-function mutations in human endosomal Na+(K+)/H+ exchangers (NHEs) NHE6 and NHE9 are implicated in neurological disorders including Christianson syndrome, autism, and attention deficit and hyperactivity disorder. These mutations disrupt retention of surface receptors within neurons and glial cells by affecting their delivery to lysosomes for degradation. However, the molecular basis of how these endosomal NHEs control endocytic trafficking is unclear. Using Saccharomyces cerevisiae as a model, we conducted cell-free organelle fusion assays to show that transport activity of the orthologous endosomal NHE Nhx1 is important for multivesicular body (MVB)-vacuolar lysosome fusion, the last step of endocytosis required for surface protein degradation. We find that deleting Nhx1 disrupts the fusogenicity of the MVB, not the vacuole, by targeting pH-sensitive machinery downstream of the Rab-GTPase Ypt7 needed for SNARE-mediated lipid bilayer merger. All contributing mechanisms are evolutionarily conserved offering new insight into the etiology of human disorders linked to loss of endosomal NHE function.
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22
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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: 25] [Impact Index Per Article: 4.2] [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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23
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Xu Y, Quan H, Wang Y, Zhong H, Sun J, Xu J, Jia N, Jiang Y. Requirement for Ergosterol in Berberine Tolerance Underlies Synergism of Fluconazole and Berberine against Fluconazole-Resistant Candida albicans Isolates. Front Cell Infect Microbiol 2017; 7:491. [PMID: 29238700 PMCID: PMC5712545 DOI: 10.3389/fcimb.2017.00491] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Accepted: 11/15/2017] [Indexed: 12/19/2022] Open
Abstract
Candida albicans is one of the most common fungal pathogens. Our previous study demonstrated that concomitant use of berberine (BBR) and fluconazole (FLC) showed a synergistic action against FLC-resistant C. albicans in vitro and BBR had a major antifungal effect in the synergism, while FLC played a role of increasing the intracellular BBR concentration. Since the antifungal activity of BBR alone is very weak (MIC > 128 μg/mL), it was assumed that FLC-resistant C. albicans was naturally tolerant to BBR, and this tolerance could be reversed by FLC. The present study aimed to elucidate the mechanism underlying BBR tolerance in FLC-resistant C. albicans and its disruption by FLC. The ergosterol quantitative analysis showed that the BBR monotreatment could increase the content of cellular ergosterol. Real-time RT-PCR revealed a global upregulation of ergosterol synthesis genes in response to BBR exposure. In addition, exogenous ergosterol could decrease intracellular BBR concentration and increase the expression of drug efflux pump genes, further reducing the susceptibility of C. albicans to BBR. Similar to FLC, other antifungal agents acting on ergosterol were able to synergize with BBR against FLC-resistant C. albicans. However, the antifungal agents not acting on ergosterol were not synergistic with BBR. These results suggested that ergosterol was required for BBR tolerance, and FLC could enhance the susceptibility of FLC-resistant C. albicans to BBR by inhibiting ergosterol synthesis.
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Affiliation(s)
- Yi Xu
- Department of Pharmacy, Jinan Military General Hospital, Jinan, China
| | - Hua Quan
- New Drug Research and Development Center, School of Pharmacy, Second Military Medical University, Shanghai, China.,Shanghai Pudong Institute for Food and Drug Control, Shanghai, China
| | - Yan Wang
- New Drug Research and Development Center, School of Pharmacy, Second Military Medical University, Shanghai, China
| | - Hua Zhong
- New Drug Research and Development Center, School of Pharmacy, Second Military Medical University, Shanghai, China
| | - Jun Sun
- Department of Pharmacy, Jinan Military General Hospital, Jinan, China
| | - Jianjiang Xu
- Department of Pharmacy, Jinan Military General Hospital, Jinan, China
| | - Nuan Jia
- Department of Pharmacy, Jinan Military General Hospital, Jinan, China
| | - Yuanying Jiang
- New Drug Research and Development Center, School of Pharmacy, Second Military Medical University, Shanghai, China
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24
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Asymmetric Inheritance of Aggregated Proteins and Age Reset in Yeast Are Regulated by Vac17-Dependent Vacuolar Functions. Cell Rep 2017; 16:826-38. [PMID: 27373154 PMCID: PMC4963537 DOI: 10.1016/j.celrep.2016.06.016] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 01/29/2016] [Accepted: 05/31/2016] [Indexed: 11/24/2022] Open
Abstract
Age can be reset during mitosis in both yeast and stem cells to generate a young daughter cell from an aged and deteriorated one. This phenomenon requires asymmetry-generating genes (AGGs) that govern the asymmetrical inheritance of aggregated proteins. Using a genome-wide imaging screen to identify AGGs in Saccharomyces cerevisiae, we discovered a previously unknown role for endocytosis, vacuole fusion, and the myosin-dependent adaptor protein Vac17 in asymmetrical inheritance of misfolded proteins. Overproduction of Vac17 increases deposition of aggregates into cytoprotective vacuole-associated sites, counteracts age-related breakdown of endocytosis and vacuole integrity, and extends replicative lifespan. The link between damage asymmetry and vesicle trafficking can be explained by a direct interaction between aggregates and vesicles. We also show that the protein disaggregase Hsp104 interacts physically with endocytic vesicle-associated proteins, such as the dynamin-like protein, Vps1, which was also shown to be required for Vac17-dependent sequestration of protein aggregates. These data demonstrate that two physiognomies of aging-reduced endocytosis and protein aggregation-are interconnected and regulated by Vac17.
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25
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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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26
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Aufschnaiter A, Habernig L, Kohler V, Diessl J, Carmona-Gutierrez D, Eisenberg T, Keller W, Büttner S. The Coordinated Action of Calcineurin and Cathepsin D Protects Against α-Synuclein Toxicity. Front Mol Neurosci 2017; 10:207. [PMID: 28713240 PMCID: PMC5491553 DOI: 10.3389/fnmol.2017.00207] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 06/12/2017] [Indexed: 11/24/2022] Open
Abstract
The degeneration of dopaminergic neurons during Parkinson’s disease (PD) is intimately linked to malfunction of α-synuclein (αSyn), the main component of the proteinaceous intracellular inclusions characteristic for this pathology. The cytotoxicity of αSyn has been attributed to disturbances in several biological processes conserved from yeast to humans, including Ca2+ homeostasis, general lysosomal function and autophagy. However, the precise sequence of events that eventually results in cell death remains unclear. Here, we establish a connection between the major lysosomal protease cathepsin D (CatD) and the Ca2+/calmodulin-dependent phosphatase calcineurin. In a yeast model for PD, high levels of human αSyn triggered cytosolic acidification and reduced vacuolar hydrolytic capacity, finally leading to cell death. This could be counteracted by overexpression of yeast CatD (Pep4), which re-installed pH homeostasis and vacuolar proteolytic function, decreased αSyn oligomers and aggregates, and provided cytoprotection. Interestingly, these beneficial effects of Pep4 were independent of autophagy. Instead, they required functional calcineurin signaling, since deletion of calcineurin strongly reduced both the proteolytic activity of endogenous Pep4 and the cytoprotective capacity of overexpressed Pep4. Calcineurin contributed to proper endosomal targeting of Pep4 to the vacuole and the recycling of the Pep4 sorting receptor Pep1 from prevacuolar compartments back to the trans-Golgi network. Altogether, we demonstrate that stimulation of this novel calcineurin-Pep4 axis reduces αSyn cytotoxicity.
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Affiliation(s)
| | - Lukas Habernig
- Institute of Molecular Biosciences, University of GrazGraz, Austria.,Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm UniversityStockholm, Sweden
| | - Verena Kohler
- Institute of Molecular Biosciences, University of GrazGraz, Austria
| | - Jutta Diessl
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm UniversityStockholm, Sweden
| | | | - Tobias Eisenberg
- Institute of Molecular Biosciences, University of GrazGraz, Austria
| | - Walter Keller
- Institute of Molecular Biosciences, University of GrazGraz, Austria
| | - Sabrina Büttner
- Institute of Molecular Biosciences, University of GrazGraz, Austria.,Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm UniversityStockholm, Sweden
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27
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Gottschling DE, Nyström T. The Upsides and Downsides of Organelle Interconnectivity. Cell 2017; 169:24-34. [PMID: 28340346 DOI: 10.1016/j.cell.2017.02.030] [Citation(s) in RCA: 66] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 02/13/2017] [Accepted: 02/21/2017] [Indexed: 12/31/2022]
Abstract
Interconnectivity and feedback control are hallmarks of biological systems. This includes communication between organelles, which allows them to function and adapt to changing cellular environments. While the specific mechanisms for all communications remain opaque, unraveling the wiring of organelle networks is critical to understand how biological systems are built and why they might collapse, as occurs in aging. A comprehensive understanding of all the routes involved in inter-organelle communication is still lacking, but important themes are beginning to emerge, primarily in budding yeast. These routes are reviewed here in the context of sub-system proteostasis and complex adaptive systems theory.
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Affiliation(s)
| | - Thomas Nyström
- Institute for Biomedicine, Sahlgrenska Academy, University of Gothenburg, 405 30 Gothenburg, Sweden.
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28
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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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29
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Stauffer B, Powers T. Target of rapamycin signaling mediates vacuolar fragmentation. Curr Genet 2016; 63:35-42. [PMID: 27233284 DOI: 10.1007/s00294-016-0616-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 05/13/2016] [Accepted: 05/17/2016] [Indexed: 11/26/2022]
Abstract
In eukaryotic cells, cellular homeostasis requires that different organelles respond to intracellular as well as environmental signals and modulate their behavior as conditions demand. Understanding the molecular mechanisms required for these changes remains an outstanding goal. One such organelle is the lysosome/vacuole, which undergoes alterations in size and number in response to environmental and physiological stimuli. Changes in the morphology of this organelle are mediated in part by the equilibrium between fusion and fission processes. While the fusion of the yeast vacuole has been studied intensively, the regulation of vacuolar fission remains poorly characterized by comparison. In recent years, a number of studies have incorporated genome-wide visual screens and high-throughput microscopy to identify factors required for vacuolar fission in response to diverse cellular insults, including hyperosmotic and endoplasmic reticulum stress. Available evidence now demonstrates that the rapamycin-sensitive TOR network, a master regulator of cell growth, is required for vacuolar fragmentation in response to stress. Importantly, many of the genes identified in these studies provide new insights into potential links between the vacuolar fission machinery and TOR signaling. Together these advances both extend our understanding of the regulation of vacuolar fragmentation in yeast as well as underscore the role of analogous events in mammalian cells.
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Affiliation(s)
- Bobbiejane Stauffer
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, One Shields Ave., Davis, CA, 95616, USA
| | - Ted Powers
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, One Shields Ave., Davis, CA, 95616, USA.
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30
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Couoh-Cardel S, Hsueh YC, Wilkens S, Movileanu L. Yeast V-ATPase Proteolipid Ring Acts as a Large-conductance Transmembrane Protein Pore. Sci Rep 2016; 6:24774. [PMID: 27098228 PMCID: PMC4838861 DOI: 10.1038/srep24774] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Accepted: 04/04/2016] [Indexed: 12/12/2022] Open
Abstract
The vacuolar H+ -ATPase (V-ATPase) is a rotary motor enzyme that acidifies intracellular organelles and the extracellular milieu in some tissues. Besides its canonical proton-pumping function, V-ATPase’s membrane sector, Vo, has been implicated in non-canonical functions including membrane fusion and neurotransmitter release. Here, we report purification and biophysical characterization of yeast V-ATPase c subunit ring (c-ring) using electron microscopy and single-molecule electrophysiology. We find that yeast c-ring forms dimers mediated by the c subunits’ cytoplasmic loops. Electrophysiology measurements of the c-ring reconstituted into a planar lipid bilayer revealed a large unitary conductance of ~8.3 nS. Thus, the data support a role of V-ATPase c-ring in membrane fusion and neuronal communication.
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Affiliation(s)
- Sergio Couoh-Cardel
- Department of Biochemistry &Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, USA
| | - Yi-Ching Hsueh
- Department of Physics, Syracuse University, 201 Physics Bldg., Syracuse, New York 13244-1130, USA
| | - Stephan Wilkens
- Department of Biochemistry &Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210, USA
| | - Liviu Movileanu
- Department of Physics, Syracuse University, 201 Physics Bldg., Syracuse, New York 13244-1130, USA.,Structural Biology, Biochemistry, and Biophysics Program, Syracuse University, 111 College Place, Syracuse, New York 13244-4100, USA.,The Syracuse Biomaterials Institute, Syracuse University, 318 Bowne Hall, Syracuse, New York 13244-1200, USA
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31
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Cotter K, Stransky L, McGuire C, Forgac M. Recent Insights into the Structure, Regulation, and Function of the V-ATPases. Trends Biochem Sci 2016; 40:611-622. [PMID: 26410601 DOI: 10.1016/j.tibs.2015.08.005] [Citation(s) in RCA: 174] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Revised: 08/06/2015] [Accepted: 08/07/2015] [Indexed: 10/23/2022]
Abstract
The vacuolar (H(+))-ATPases (V-ATPases) are ATP-dependent proton pumps that acidify intracellular compartments and are also present at the plasma membrane. They function in such processes as membrane traffic, protein degradation, virus and toxin entry, bone resorption, pH homeostasis, and tumor cell invasion. V-ATPases are large multisubunit complexes, composed of an ATP-hydrolytic domain (V1) and a proton translocation domain (V0), and operate by a rotary mechanism. This review focuses on recent insights into their structure and mechanism, the mechanisms that regulate V-ATPase activity (particularly regulated assembly and trafficking), and the role of V-ATPases in processes such as cell signaling and cancer. These developments have highlighted the potential of V-ATPases as a therapeutic target in a variety of human diseases.
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Affiliation(s)
- Kristina Cotter
- Program in Cellular and Molecular Physiology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
| | - Laura Stransky
- Program in Cellular and Molecular Physiology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
| | - Christina McGuire
- Program in Biochemistry, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
| | - Michael Forgac
- Program in Cellular and Molecular Physiology, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA; Program in Biochemistry, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA; Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA.
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32
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Bioengineered yeast-derived vacuoles with enhanced tissue-penetrating ability for targeted cancer therapy. Proc Natl Acad Sci U S A 2015; 113:710-5. [PMID: 26715758 DOI: 10.1073/pnas.1509371113] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Despite the appreciable success of synthetic nanomaterials for targeted cancer therapy in preclinical studies, technical challenges involving their large-scale, cost-effective production and intrinsic toxicity associated with the materials, as well as their inability to penetrate tumor tissues deeply, limit their clinical translation. Here, we describe biologically derived nanocarriers developed from a bioengineered yeast strain that may overcome such impediments. The budding yeast Saccharomyces cerevisiae was genetically engineered to produce nanosized vacuoles displaying human epidermal growth factor receptor 2 (HER2)-specific affibody for active targeting. These nanosized vacuoles efficiently loaded the anticancer drug doxorubicin (Dox) and were effectively endocytosed by cultured cancer cells. Their cancer-targeting ability, along with their unique endomembrane compositions, significantly enhanced drug penetration in multicellular cultures and improved drug distribution in a tumor xenograft. Furthermore, Dox-loaded vacuoles successfully prevented tumor growth without eliciting any prolonged immune responses. The current study provides a platform technology for generating cancer-specific, tissue-penetrating, safe, and scalable biological nanoparticles for targeted cancer therapy.
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33
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Kriegel A, Andrés Z, Medzihradszky A, Krüger F, Scholl S, Delang S, Patir-Nebioglu MG, Gute G, Yang H, Murphy AS, Peer WA, Pfeiffer A, Krebs M, Lohmann JU, Schumacher K. Job Sharing in the Endomembrane System: Vacuolar Acidification Requires the Combined Activity of V-ATPase and V-PPase. THE PLANT CELL 2015; 27:3383-96. [PMID: 26589552 PMCID: PMC4707456 DOI: 10.1105/tpc.15.00733] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 10/21/2015] [Accepted: 11/05/2015] [Indexed: 05/19/2023]
Abstract
The presence of a large central vacuole is one of the hallmarks of a prototypical plant cell, and the multiple functions of this compartment require massive fluxes of molecules across its limiting membrane, the tonoplast. Transport is assumed to be energized by the membrane potential and the proton gradient established by the combined activity of two proton pumps, the vacuolar H(+)-pyrophosphatase (V-PPase) and the vacuolar H(+)-ATPase (V-ATPase). Exactly how labor is divided between these two enzymes has remained elusive. Here, we provide evidence using gain- and loss-of-function approaches that lack of the V-ATPase cannot be compensated for by increased V-PPase activity. Moreover, we show that increased V-ATPase activity during cold acclimation requires the presence of the V-PPase. Most importantly, we demonstrate that a mutant lacking both of these proton pumps is conditionally viable and retains significant vacuolar acidification, pointing to a so far undetected contribution of the trans-Golgi network/early endosome-localized V-ATPase to vacuolar pH.
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Affiliation(s)
- Anne Kriegel
- Department of Plant Developmental Biology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
| | - Zaida Andrés
- Department of Plant Developmental Biology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
| | - Anna Medzihradszky
- Department of Stem Cell Biology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
| | - Falco Krüger
- Department of Plant Developmental Biology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
| | - Stefan Scholl
- Department of Plant Developmental Biology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
| | - Simon Delang
- Department of Plant Developmental Biology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
| | - M Görkem Patir-Nebioglu
- Department of Plant Developmental Biology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
| | - Gezahegn Gute
- Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20742
| | - Haibing Yang
- Horticulture and Landscape Architecture, Purdue University, West Lafayette, Indiana 47907
| | - Angus S Murphy
- Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20742
| | - Wendy Ann Peer
- Plant Science and Landscape Architecture, University of Maryland, College Park, Maryland 20742 Environmental Science and Technology, University of Maryland, College Park, Maryland 20742
| | - Anne Pfeiffer
- Department of Stem Cell Biology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
| | - Melanie Krebs
- Department of Plant Developmental Biology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
| | - Jan U Lohmann
- Department of Plant Developmental Biology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
| | - Karin Schumacher
- Department of Plant Developmental Biology, Centre for Organismal Studies, Heidelberg University, 69120 Heidelberg, Germany
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34
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Stauffer B, Powers T. Target of rapamycin signaling mediates vacuolar fission caused by endoplasmic reticulum stress in Saccharomyces cerevisiae. Mol Biol Cell 2015; 26:4618-30. [PMID: 26466677 PMCID: PMC4678019 DOI: 10.1091/mbc.e15-06-0344] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 10/07/2015] [Indexed: 01/15/2023] Open
Abstract
The yeast vacuole is equivalent to the mammalian lysosome and, in response to diverse physiological and environmental stimuli, undergoes alterations both in size and number. Here we demonstrate that vacuoles fragment in response to stress within the endoplasmic reticulum (ER) caused by chemical or genetic perturbations. We establish that this response does not involve known signaling pathways linked previously to ER stress but instead requires the rapamycin-sensitive TOR Complex 1 (TORC1), a master regulator of cell growth, together with its downstream effectors, Tap42/Sit4 and Sch9. To identify additional factors required for ER stress-induced vacuolar fragmentation, we conducted a high-throughput, genome-wide visual screen for yeast mutants that are refractory to ER stress-induced changes in vacuolar morphology. We identified several genes shown previously to be required for vacuolar fusion and/or fission, validating the utility of this approach. We also identified a number of new components important for fragmentation, including a set of proteins involved in assembly of the V-ATPase. Remarkably, we find that one of these, Vph2, undergoes a change in intracellular localization in response to ER stress and, moreover, in a manner that requires TORC1 activity. Together these results reveal a new role for TORC1 in the regulation of vacuolar behavior.
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Affiliation(s)
- Bobbiejane Stauffer
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, Davis, CA 95616
| | - Ted Powers
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, Davis, CA 95616 )
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35
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Hernández A, Serrano-Bueno G, Perez-Castiñeira JR, Serrano A. 8-Dehydrosterols induce membrane traffic and autophagy defects through V-ATPase dysfunction in Saccharomyces cerevisae. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:2945-56. [PMID: 26344037 DOI: 10.1016/j.bbamcr.2015.09.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 09/01/2015] [Indexed: 12/11/2022]
Abstract
8-Dehydrosterols are present in a wide range of biologically relevant situations, from human rare diseases to amine fungicide-treated fungi and crops. However, the molecular bases of their toxicity are still obscure. We show here that 8-dehydrosterols, but not other sterols, affect yeast vacuole acidification through V-ATPases. Moreover, erg2Δ cells display reductions in proton pumping rates consistent with ion-transport uncoupling in vitro. Concomitantly, subunit Vph1p shows conformational changes in the presence of 8-dehydrosterols. Expression of a plant vacuolar H(+)-pumping pyrophosphatase as an alternative H(+)-pump relieves Vma(-)-like phenotypes in erg2Δ-derived mutant cells. As a consequence of these acidification defects, endo- and exo-cytic traffic deficiencies that can be alleviated with a H(+)-pumping pyrophosphatase are also observed. Despite their effect on membrane traffic, 8-dehydrosterols do not induce endoplasmic reticulum stress or assembly defects on the V-ATPase. Autophagy is a V-ATPase dependent process and erg2Δ mutants accumulate autophagic bodies under nitrogen starvation similar to Vma(-) mutants. In contrast to classical Atg(-) mutants, this defect is not accompanied by impairment of traffic through the CVT pathway, processing of Pho8Δ60p, GFP-Atg8p localisation or difficulties to survive under nitrogen starvation conditions, but it is concomitant to reduced vacuolar protease activity. All in all, erg2Δ cells are autophagy mutants albeit some of their phenotypic features differ from classical Atg(-) defective cells. These results may pave the way to understand the aetiology of sterol-related diseases, the cytotoxic effect of amine fungicides, and may explain the tolerance to these compounds observed in plants.
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Affiliation(s)
- Agustín Hernández
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Avda Américo Vespucio 48, 41092 Sevilla, Spain.
| | - Gloria Serrano-Bueno
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Avda Américo Vespucio 48, 41092 Sevilla, Spain
| | - José Román Perez-Castiñeira
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Avda Américo Vespucio 48, 41092 Sevilla, Spain
| | - Aurelio Serrano
- Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla-CSIC, Avda Américo Vespucio 48, 41092 Sevilla, Spain.
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36
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Maxson ME, Grinstein S. The vacuolar-type H⁺-ATPase at a glance - more than a proton pump. J Cell Sci 2015; 127:4987-93. [PMID: 25453113 DOI: 10.1242/jcs.158550] [Citation(s) in RCA: 171] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The vacuolar H(+)-ATPase (V-ATPase) has long been appreciated to function as an electrogenic H(+) pump. By altering the pH of intracellular compartments, the V-ATPase dictates enzyme activity, governs the dissociation of ligands from receptors and promotes the coupled transport of substrates across membranes, a role often aided by the generation of a transmembrane electrical potential. In tissues where the V-ATPase is expressed at the plasma membrane, it can serve to acidify the extracellular microenvironment. More recently, however, the V-ATPase has been implicated in a bewildering variety of additional roles that seem independent of its ability to translocate H(+). These non-canonical functions, which include fusogenicity, cytoskeletal tethering and metabolic sensing, are described in this Cell Science at a Glance article and accompanying poster, together with a brief overview of the conventional functions of the V-ATPase.
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Affiliation(s)
- Michelle E Maxson
- Program in Cell Biology, Hospital for Sick Children, 686 Bay Street, Toronto, ON, M5G 0A4, Canada
| | - Sergio Grinstein
- Program in Cell Biology, Hospital for Sick Children, 686 Bay Street, Toronto, ON, M5G 0A4, Canada Keenan Research Centre of the Li Ka Shing Knowledge Institute, St. Michael's Hospital, 290 Victoria Street, Toronto, ON, M5C 1N8, Canada
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37
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Morel N, Poëa-Guyon S. The membrane domain of vacuolar H(+)ATPase: a crucial player in neurotransmitter exocytotic release. Cell Mol Life Sci 2015; 72:2561-73. [PMID: 25795337 PMCID: PMC11113229 DOI: 10.1007/s00018-015-1886-2] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 03/10/2015] [Accepted: 03/12/2015] [Indexed: 12/31/2022]
Abstract
V-ATPases are multimeric enzymes made of two sectors, a V1 catalytic domain and a V0 membrane domain. They accumulate protons in various intracellular organelles. Acidification of synaptic vesicles by V-ATPase energizes the accumulation of neurotransmitters in these storage organelles and is therefore required for efficient synaptic transmission. In addition to this well-accepted role, functional studies have unraveled additional hidden roles of V0 in neurotransmitter exocytosis that are independent of the transport of protons. V0 interacts with SNAREs and calmodulin, and perturbing these interactions affects neurotransmitter release. Here, we discuss these data in relation with previous results obtained in reconstituted membranes and on yeast vacuole fusion. We propose that V0 could be a sensor of intra-vesicular pH that controls the exocytotic machinery, probably regulating SNARE complex assembly during the synaptic vesicle priming step, and that, during the membrane fusion step, V0 might favor lipid mixing and fusion pore stability.
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Affiliation(s)
- Nicolas Morel
- Centre de Neurosciences Paris-Sud, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8195 and Université Paris-Sud, 91405, Orsay, France,
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Sun-Wada GH, Wada Y. Role of vacuolar-type proton ATPase in signal transduction. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1847:1166-72. [PMID: 26072192 DOI: 10.1016/j.bbabio.2015.06.010] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 06/01/2015] [Accepted: 06/03/2015] [Indexed: 12/21/2022]
Abstract
The vacuolar H(+)-ATPase (V-ATPase) was first identified as an electrogenic proton pump that acidifies the lumen of intra- and extracellular compartments. The acidic pH generated by V-ATPase is important for a wide range of cellular processes as well as acidification-independent processes such as secretion and membrane fusion. In addition to these housekeeping functions, recent studies implicate V-ATPase in the direct regulation and function of signaling pathways. In this review, we describe recent findings on the functions of V-ATPase in growth regulation and tissue physiology.
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Affiliation(s)
- Ge-Hong Sun-Wada
- Faculty of Pharmaceutical Sciences, Doshisha Women's College of Liberal Arts, Kohdo, Kyotanabe, Kyoto 610-0395, Japan.
| | - Yoh Wada
- Division of Biological Science, Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.
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39
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PEP3 overexpression shortens lag phase but does not alter growth rate in Saccharomyces cerevisiae exposed to acetic acid stress. Appl Microbiol Biotechnol 2015; 99:8667-80. [PMID: 26051671 DOI: 10.1007/s00253-015-6708-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Revised: 04/22/2015] [Accepted: 05/19/2015] [Indexed: 12/12/2022]
Abstract
In fungi, two recognized mechanisms contribute to pH homeostasis: the plasma membrane proton-pumping ATPase that exports excess protons and the vacuolar proton-pumping ATPase (V-ATPase) that mediates vacuolar proton uptake. Here, we report that overexpression of PEP3 which encodes a component of the HOPS and CORVET complexes involved in vacuolar biogenesis, shortened lag phase in Saccharomyces cerevisiae exposed to acetic acid stress. By confocal microscopy, PEP3-overexpressing cells stained with the vacuolar membrane-specific dye, FM4-64 had more fragmented vacuoles than the wild-type control. The stained overexpression mutant was also found to exhibit about 3.6-fold more FM4-64 fluorescence than the wild-type control as determined by flow cytometry. While the vacuolar pH of the wild-type strain grown in the presence of 80 mM acetic acid was significantly higher than in the absence of added acid, no significant difference was observed in vacuolar pH of the overexpression strain grown either in the presence or absence of 80 mM acetic acid. Based on an indirect growth assay, the PEP3-overexpression strain exhibited higher V-ATPase activity. We hypothesize that PEP3 overexpression provides protection from acid stress by increasing vacuolar surface area and V-ATPase activity and, hence, proton-sequestering capacity.
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40
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Mauvezin C, Nagy P, Juhász G, Neufeld TP. Autophagosome-lysosome fusion is independent of V-ATPase-mediated acidification. Nat Commun 2015; 6:7007. [PMID: 25959678 PMCID: PMC4428688 DOI: 10.1038/ncomms8007] [Citation(s) in RCA: 281] [Impact Index Per Article: 31.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 03/23/2015] [Indexed: 12/20/2022] Open
Abstract
The ATP-dependent proton pump V-ATPase ensures low intralysosomal pH, which is essential for lysosomal hydrolase activity. Based on studies with the V-ATPase inhibitor BafilomycinA1, lysosomal acidification is also thought to be required for fusion with incoming vesicles from the autophagic and endocytic pathways. Here we show that loss of V-ATPase subunits in the Drosophila fat body causes an accumulation of non-functional lysosomes, leading to a block in autophagic flux. However, V-ATPase-deficient lysosomes remain competent to fuse with autophagosomes and endosomes, resulting in a time-dependent formation of giant autolysosomes. In contrast, BafilomycinA1 prevents autophagosome–lysosome fusion in these cells, and this defect is phenocopied by depletion of the Ca2+ pump SERCA, a secondary target of this drug. Moreover, activation of SERCA promotes fusion in a BafilomycinA1-sensitive manner. Collectively, our results indicate that lysosomal acidification is not a prerequisite for fusion, and that BafilomycinA1 inhibits fusion independent of its effect on lysosomal pH. BafilomycinA1 is an autophagy inhibitor, presumably owing to its blocking effect on the lysosomal proton pump V-ATPase. Here the authors show that V-ATPase-deficient lysosomes can still fuse with autophagosomes, showing that lysosomal acidification and fusion are two separable, independent events.
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Affiliation(s)
- Caroline Mauvezin
- Department of Genetics, Cell Biology and Development, University of Minnesota, 6-160 Jackson Hall, 321 Church Street SE, Minneapolis, Minnesota 55455, USA
| | - Péter Nagy
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Pazmany s. 1/C. 6.520, Budapest H-1117, Hungary
| | - Gábor Juhász
- Department of Anatomy, Cell and Developmental Biology, Eötvös Loránd University, Pazmany s. 1/C. 6.520, Budapest H-1117, Hungary
| | - Thomas P Neufeld
- Department of Genetics, Cell Biology and Development, University of Minnesota, 6-160 Jackson Hall, 321 Church Street SE, Minneapolis, Minnesota 55455, USA
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Kissing S, Hermsen C, Repnik U, Nesset CK, von Bargen K, Griffiths G, Ichihara A, Lee BS, Schwake M, De Brabander J, Haas A, Saftig P. Vacuolar ATPase in phagosome-lysosome fusion. J Biol Chem 2015; 290:14166-80. [PMID: 25903133 DOI: 10.1074/jbc.m114.628891] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2014] [Indexed: 01/11/2023] Open
Abstract
The vacuolar H(+)-ATPase (v-ATPase) complex is instrumental in establishing and maintaining acidification of some cellular compartments, thereby ensuring their functionality. Recently it has been proposed that the transmembrane V0 sector of v-ATPase and its a-subunits promote membrane fusion in the endocytic and exocytic pathways independent of their acidification functions. Here, we tested if such a proton-pumping independent role of v-ATPase also applies to phagosome-lysosome fusion. Surprisingly, endo(lyso)somes in mouse embryonic fibroblasts lacking the V0 a3 subunit of the v-ATPase acidified normally, and endosome and lysosome marker proteins were recruited to phagosomes with similar kinetics in the presence or absence of the a3 subunit. Further experiments used macrophages with a knockdown of v-ATPase accessory protein 2 (ATP6AP2) expression, resulting in a strongly reduced level of the V0 sector of the v-ATPase. However, acidification appeared undisturbed, and fusion between latex bead-containing phagosomes and lysosomes, as analyzed by electron microscopy, was even slightly enhanced, as was killing of non-pathogenic bacteria by V0 mutant macrophages. Pharmacologically neutralized lysosome pH did not affect maturation of phagosomes in mouse embryonic cells or macrophages. Finally, locking the two large parts of the v-ATPase complex together by the drug saliphenylhalamide A did not inhibit in vitro and in cellulo fusion of phagosomes with lysosomes. Hence, our data do not suggest a fusion-promoting role of the v-ATPase in the formation of phagolysosomes.
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Affiliation(s)
- Sandra Kissing
- From the Institute of Biochemistry, Christian-Albrechts-University of Kiel, D-24098 Kiel, Germany
| | - Christina Hermsen
- Institute for Cell Biology, Friedrich-Wilhelms University, D-53121 Bonn, Germany
| | - Urska Repnik
- Department of Biosciences, University of Oslo, 0316 Oslo, Norway
| | | | - Kristine von Bargen
- Institute for Cell Biology, Friedrich-Wilhelms University, D-53121 Bonn, Germany
| | - Gareth Griffiths
- Department of Biosciences, University of Oslo, 0316 Oslo, Norway
| | - Atsuhiro Ichihara
- Department of Medicine II, Tokyo Women's Medical University, Tokyo 162-866, Japan
| | - Beth S Lee
- Department of Physiology and Cell Biology, The Ohio State University College of Medicine, Columbus, Ohio 42210
| | - Michael Schwake
- Department of Chemistry, Biochemistry III, University of Bielefeld, D-33615 Bielefeld, Germany, and
| | - Jef De Brabander
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Albert Haas
- Institute for Cell Biology, Friedrich-Wilhelms University, D-53121 Bonn, Germany,
| | - Paul Saftig
- From the Institute of Biochemistry, Christian-Albrechts-University of Kiel, D-24098 Kiel, Germany,
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43
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Vibrio effector protein VopQ inhibits fusion of V-ATPase-containing membranes. Proc Natl Acad Sci U S A 2014; 112:100-5. [PMID: 25453092 DOI: 10.1073/pnas.1413764111] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Vesicle fusion governs many important biological processes, and imbalances in the regulation of membrane fusion can lead to a variety of diseases such as diabetes and neurological disorders. Here we show that the Vibrio parahaemolyticus effector protein VopQ is a potent inhibitor of membrane fusion based on an in vitro yeast vacuole fusion model. Previously, we demonstrated that VopQ binds to the V(o) domain of the conserved V-type H(+)-ATPase (V-ATPase) found on acidic compartments such as the yeast vacuole. VopQ forms a nonspecific, voltage-gated membrane channel of 18 Å resulting in neutralization of these compartments. We now present data showing that VopQ inhibits yeast vacuole fusion. Furthermore, we identified a unique mutation in VopQ that delineates its two functions, deacidification and inhibition of membrane fusion. The use of VopQ as a membrane fusion inhibitor in this manner now provides convincing evidence that vacuole fusion occurs independently of luminal acidification in vitro.
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Abstract
Neurons fire by releasing neurotransmitters via fusion of synaptic vesicles with the plasma membrane. Fusion can be evoked by an incoming signal from a preceding neuron or can occur spontaneously. Synaptic vesicle fusion requires the formation of trans complexes between SNAREs as well as Ca(2+) ions. Wang et al. (2014. J. Cell Biol. http://dx.doi.org/jcb.201312109) now find that the Ca(2+)-binding protein Calmodulin promotes spontaneous release and SNARE complex formation via its interaction with the V0 sector of the V-ATPase.
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Affiliation(s)
- Stefano Vavassori
- Département de Biochimie, Université de Lausanne, 1066 Epalinges, Switzerland
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45
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Wang D, Epstein D, Khalaf O, Srinivasan S, Williamson WR, Fayyazuddin A, Quiocho FA, Hiesinger PR. Ca2+-Calmodulin regulates SNARE assembly and spontaneous neurotransmitter release via v-ATPase subunit V0a1. ACTA ACUST UNITED AC 2014; 205:21-31. [PMID: 24733584 PMCID: PMC3987144 DOI: 10.1083/jcb.201312109] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Ca2+–Calmodulin binding to neuronal v-ATPase V0 subunit a1 (V100) regulates SNARE complex assembly for a putative subset of synaptic vesicles that sustain spontaneous release in Drosophila. Most chemical neurotransmission occurs through Ca2+-dependent evoked or spontaneous vesicle exocytosis. In both cases, Ca2+ sensing is thought to occur shortly before exocytosis. In this paper, we provide evidence that the Ca2+ dependence of spontaneous vesicle release may partly result from an earlier requirement of Ca2+ for the assembly of soluble N-ethylmaleimide–sensitive fusion attachment protein receptor (SNARE) complexes. We show that the neuronal vacuolar-type H+-adenosine triphosphatase V0 subunit a1 (V100) can regulate the formation of SNARE complexes in a Ca2+–Calmodulin (CaM)-dependent manner. Ca2+–CaM regulation of V100 is not required for vesicle acidification. Specific disruption of the Ca2+-dependent regulation of V100 by CaM led to a >90% loss of spontaneous release but only had a mild effect on evoked release at Drosophila melanogaster embryo neuromuscular junctions. Our data suggest that Ca2+–CaM regulation of V100 may control SNARE complex assembly for a subset of synaptic vesicles that sustain spontaneous release.
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Affiliation(s)
- Dong Wang
- Department of Physiology and 2 Green Center Division for Systems Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390
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