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Yu CC, Yang CY, Chang TY, Lan KC, Liu SH. A negative regulatory role of β-cell-derived exosomes in the glucose-stimulated insulin secretion of recipient β-cells. Arch Toxicol 2024; 98:3885-3896. [PMID: 39127846 DOI: 10.1007/s00204-024-03838-8] [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: 06/21/2024] [Accepted: 08/07/2024] [Indexed: 08/12/2024]
Abstract
Exosomes are extracellular vesicles that play a role in intercellular communication through the transportation of their cargo including mRNAs, microRNAs, proteins, and nucleic acids. Exosomes can also regulate glucose homeostasis and insulin secretion under diabetic conditions. However, the role of exosomes in insulin secretion in islet β-cells under physiological conditions remains to be clarified. The aim of this study was to investigate whether exosomes derived from pancreatic islet β-cells could affect insulin secretion in naïve β-cells. We first confirmed that exosomes derived from the RIN-m5f β-cell line interfered with the glucose-stimulated insulin secretion (GSIS) of recipient β-cells without affecting cell viability. The exosomes significantly reduced the protein expression levels of phosphorylated Akt, phosphorylated GSK3α/β, CaMKII, and GLUT2 (insulin-related signaling molecules), and they increased the protein expression levels of phosphorylated NFκB-p65 and Cox-2 (inflammation-related signaling molecules), as determined by a Western blot analysis. A bioinformatics analysis of Next-Generation Sequencing data suggested that exosome-carried microRNAs, such as miR-1224, -122-5p, -133a-3p, -10b-5p, and -423-5p, may affect GSIS in recipient β-cells. Taken together, these findings suggest that β-cell-derived exosomes may upregulate exosomal microRNA-associated signals to dysregulate glucose-stimulated insulin secretion in naïve β-cells.
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Affiliation(s)
- Chia-Ching Yu
- Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Ching-Yao Yang
- Department of Surgery, College of Medicine and Hospital, National Taiwan University, Taipei, Taiwan
| | - Ting-Yu Chang
- Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Kuo-Cheng Lan
- Department of Emergency Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan.
| | - Shing-Hwa Liu
- Institute of Toxicology, College of Medicine, National Taiwan University, Taipei, Taiwan.
- Department of Medical Research, China Medical University Hospital, China Medical University, Taichung, Taiwan.
- Department of Pediatrics, College of Medicine and Hospital, National Taiwan University, Taipei, Taiwan.
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2
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Wang N, Ren L, Danser AHJ. Vacuolar H +-ATPase in Diabetes, Hypertension, and Atherosclerosis. Microcirculation 2024; 31:e12855. [PMID: 38683673 DOI: 10.1111/micc.12855] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 03/29/2024] [Accepted: 04/15/2024] [Indexed: 05/02/2024]
Abstract
Vacuolar H+-ATPase (V-ATPase) is a multisubunit protein complex which, along with its accessory proteins, resides in almost every eukaryotic cell. It acts as a proton pump and as such is responsible for regulating pH in lysosomes, endosomes, and the extracellular space. Moreover, V-ATPase has been implicated in receptor-mediated signaling. Although numerous studies have explored the role of V-ATPase in cancer, osteoporosis, and neurodegenerative diseases, research on its involvement in vascular disease remains limited. Vascular diseases pose significant challenges to human health. This review aimed to shed light on the role of V-ATPase in hypertension and atherosclerosis. Furthermore, given that vascular complications are major complications of diabetes, this review also discusses the pathways through which V-ATPase may contribute to such complications. Beginning with an overview of the structure and function of V-ATPase in hypertension, atherosclerosis, and diabetes, this review ends by exploring the pharmacological potential of targeting V-ATPase.
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Affiliation(s)
- Na Wang
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands
- Clinical Research Center, The First Affiliated Hospital of Shantou University Medical College, Shantou, China
| | - Liwei Ren
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands
- Department of Pharmacy, Shenzhen People's Hospital (The Second Clinical Medical College, Jinan University, The First Affiliated Hospital, Southern University of Science and Technology), Shenzhen, China
| | - A H Jan Danser
- Division of Vascular Medicine and Pharmacology, Department of Internal Medicine, Erasmus MC, Rotterdam, The Netherlands
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3
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Khan MM, Wilkens S. Molecular mechanism of Oxr1p mediated disassembly of yeast V-ATPase. EMBO Rep 2024; 25:2323-2347. [PMID: 38565737 PMCID: PMC11094088 DOI: 10.1038/s44319-024-00126-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2023] [Revised: 03/07/2024] [Accepted: 03/09/2024] [Indexed: 04/04/2024] Open
Abstract
The eukaryotic vacuolar H+-ATPase (V-ATPase) is regulated by reversible disassembly into autoinhibited V1-ATPase and Vo proton channel subcomplexes. We recently reported that the TLDc protein Oxr1p induces V-ATPase disassembly in vitro. Whether and how Oxr1p is involved in enzyme disassembly in vivo, however, is not known. Here, using yeast genetics and fluorescence microscopy, we show that Oxr1p is essential for efficient V-ATPase disassembly in the cell. Supporting biochemical and biophysical in vitro experiments show that whereas Oxr1p-driven holoenzyme disassembly can occur in the absence of nucleotides, the presence of ATP greatly accelerates the process. ATP hydrolysis is needed, however, for subsequent release of Oxr1p so that the free V1 can adopt the autoinhibited conformation. Overall, our study unravels the molecular mechanism of Oxr1p-induced disassembly that occurs in vivo as part of the canonical V-ATPase regulation by reversible disassembly.
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Affiliation(s)
- Md Murad Khan
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA
| | - Stephan Wilkens
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY, 13210, USA.
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4
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Guo B, Li QY, Liu XJ, Luo GH, Wu YJ, Nie J. Diabetes mellitus and Alzheimer's disease: Vacuolar adenosine triphosphatase as a potential link. Eur J Neurosci 2024; 59:2577-2595. [PMID: 38419188 DOI: 10.1111/ejn.16286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 02/01/2024] [Accepted: 02/02/2024] [Indexed: 03/02/2024]
Abstract
Globally, the incidence of diabetes mellitus (DM) and Alzheimer's disease (AD) is increasing year by year, causing a huge economic and social burden, and their pathogenesis and aetiology have been proven to have a certain correlation. In recent years, more and more studies have shown that vacuolar adenosine triphosphatases (v-ATPases) in eukaryotes, which are biomolecules regulating lysosomal acidification and glycolipid metabolism, play a key role in DM and AD. This article describes the role of v-ATPase in DM and AD, including its role in glycolysis, insulin secretion and insulin resistance (IR), as well as its relationship with lysosomal acidification, autophagy and β-amyloid (Aβ). In DM, v-ATPase is involved in the regulation of glucose metabolism and IR. v-ATPase is closely related to glycolysis. On the one hand, v-ATPase affects the rate of glycolysis by affecting the secretion of insulin and changing the activities of key glycolytic enzymes hexokinase (HK) and phosphofructokinase 1 (PFK-1). On the other hand, glucose is the main regulator of this enzyme, and the assembly and activity of v-ATPase depend on glucose, and glucose depletion will lead to its decomposition and inactivation. In addition, v-ATPase can also regulate free fatty acids, thereby improving IR. In AD, v-ATPase can not only improve the abnormal brain energy metabolism by affecting lysosomal acidification and autophagy but also change the deposition of Aβ by affecting the production and degradation of Aβ. Therefore, v-ATPase may be the bridge between DM and AD.
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Affiliation(s)
- Bin Guo
- Key Laboratory of Basic Pharmacology of the Ministry of Education and Joint International Research Laboratory of Ethnomedicine of the Ministry of Education, Zunyi Medical University, Zunyi, Guizhou, China
| | - Qi-Ye Li
- Key Laboratory of Basic Pharmacology of the Ministry of Education and Joint International Research Laboratory of Ethnomedicine of the Ministry of Education, Zunyi Medical University, Zunyi, Guizhou, China
| | - Xue-Jia Liu
- Key Laboratory of Basic Pharmacology of the Ministry of Education and Joint International Research Laboratory of Ethnomedicine of the Ministry of Education, Zunyi Medical University, Zunyi, Guizhou, China
| | - Guo-Hui Luo
- Key Laboratory of Basic Pharmacology of the Ministry of Education and Joint International Research Laboratory of Ethnomedicine of the Ministry of Education, Zunyi Medical University, Zunyi, Guizhou, China
| | - Ya-Juan Wu
- Key Laboratory of Basic Pharmacology of the Ministry of Education and Joint International Research Laboratory of Ethnomedicine of the Ministry of Education, Zunyi Medical University, Zunyi, Guizhou, China
| | - Jing Nie
- Key Laboratory of Basic Pharmacology of the Ministry of Education and Joint International Research Laboratory of Ethnomedicine of the Ministry of Education, Zunyi Medical University, Zunyi, Guizhou, China
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5
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Firdos, Pramanik T, Verma P, Mittal A. (Re-)Viewing Role of Intracellular Glucose Beyond Extracellular Regulation of Glucose-Stimulated Insulin Secretion by Pancreatic Cells. ACS OMEGA 2024; 9:11755-11768. [PMID: 38496986 PMCID: PMC10938456 DOI: 10.1021/acsomega.3c09171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2023] [Revised: 01/31/2024] [Accepted: 02/07/2024] [Indexed: 03/19/2024]
Abstract
For glucose-stimulated insulin secretion (GSIS) by pancreatic β-cells in animals, it is believed that ATP generated from glucose metabolism is primarily responsible. However, this ignores two well-established aspects in literature: (a) intracellular ATP generation from other sources resulting in an overall pool of ATP, regardless of the original source, and (b) that intracellular glucose transport is 10- to 100-fold higher than intracellular glucose phosphorylation in β-cells. The latter especially provides an earlier unaddressed, but highly appealing, observation pertaining to (at least transient) the presence of intracellular glucose molecules. Could these intracellular glucose molecules be responsible for the specificity of GSIS to glucose (instead of the widely believed ATP production from its metabolism)? In this work, we provide a comprehensive compilation of literature on glucose and GSIS using various cellular systems - all studies focus only on the extracellular role of glucose in GSIS. Further, we carried out a comprehensive analysis of differential gene expression in Mouse Insulinoma 6 (MIN6) cells, exposed to low and high extracellular glucose concentrations (EGC), from the existing whole transcriptome data. The expression of other genes involved in glycolysis, Krebs cycle, and electron transport chain was found to be unaffected by EGC, except Gapdh, Atp6v0a4, and Cox20. Remarkably, 3 upregulated genes (Atp6v0a4, Cacnb4, Kif11) in high EGC were identified to have an association with cellular secretion. Using glucose as a possible ligand for the 3 proteins, computational investigations were carried out (that will require future 'wet validation', both in vitro and in vivo, e.g., using primary islets and animal models). The glucose-affinity/binding scores (in kcal/mol) obtained were also compared with glucose binding scores for positive controls (GCK and GLUT2), along with negative controls (RPA1, KU70-80, POLA1, ACAA1A, POLR1A). The binding affinity scores of glucose molecules for the 3 proteins were found to be closer to positive controls. Therefore, we report the glucose binding ability of 3 secretion-related proteins and a possible direct role of intracellular glucose molecules in GSIS.
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Affiliation(s)
- Firdos
- Kusuma
School of Biological Sciences, Indian Institute
of Technology Delhi (IIT Delhi), Hauz Khas, New Delhi 110016, India
| | - Tapabrata Pramanik
- Kusuma
School of Biological Sciences, Indian Institute
of Technology Delhi (IIT Delhi), Hauz Khas, New Delhi 110016, India
| | - Prachi Verma
- Kusuma
School of Biological Sciences, Indian Institute
of Technology Delhi (IIT Delhi), Hauz Khas, New Delhi 110016, India
| | - Aditya Mittal
- Kusuma
School of Biological Sciences, Indian Institute
of Technology Delhi (IIT Delhi), Hauz Khas, New Delhi 110016, India
- Supercomputing
Facility for Bioinformatics and Computational Biology (SCFBio), IIT Delhi, Hauz Khas, New Delhi, 110016, India
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6
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Boyer CK, Blom SE, Machado AE, Rohli KE, Maxson ME, Stephens SB. Loss of the Golgi-localized v-ATPase subunit does not alter insulin granule formation or pancreatic islet β-cell function. Am J Physiol Endocrinol Metab 2024; 326:E245-E257. [PMID: 38265287 PMCID: PMC11193524 DOI: 10.1152/ajpendo.00342.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 01/11/2024] [Accepted: 01/11/2024] [Indexed: 01/25/2024]
Abstract
Delayed Golgi export of proinsulin has recently been identified as an underlying mechanism leading to insulin granule loss and β-cell secretory defects in type 2 diabetes (T2D). Because acidification of the Golgi lumen is critical for proinsulin sorting and delivery into the budding secretory granule, we reasoned that dysregulation of Golgi pH may contribute to proinsulin trafficking defects. In this report, we examined pH regulation of the Golgi and identified a partial alkalinization of the Golgi lumen in a diabetes model. To further explore this, we generated a β-cell specific knockout (KO) of the v0a2 subunit of the v-ATPase pump, which anchors the v-ATPase to the Golgi membrane. Although loss of v0a2 partially neutralized Golgi pH and was accompanied by distension of the Golgi cisternae, proinsulin export from the Golgi and insulin granule formation were not affected. Furthermore, β-cell function was well preserved. β-cell v0a2 KO mice exhibited normal glucose tolerance in both sexes, no genotypic difference to diet-induced obesity, and normal insulin secretory responses. Collectively, our data demonstrate the v0a2 subunit contributes to β-cell Golgi pH regulation but suggest that additional disturbances to Golgi structure and function contribute to proinsulin trafficking defects in diabetes.NEW & NOTEWORTHY Delayed proinsulin export from the Golgi in diabetic β-cells contributes to decreased insulin granule formation, but the underlying mechanisms are not clear. Here, we explored if dysregulation of Golgi pH can alter Golgi function using β-cell specific knockout (KO) of the Golgi-localized subunit of the v-ATPase, v0a2. We show that partial alkalinization of the Golgi dilates the cisternae, but does not affect proinsulin export, insulin granule formation, insulin secretion, or glucose homeostasis.
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Affiliation(s)
- Cierra K Boyer
- Department of Neuroscience and Pharmacology, University of Iowa, Iowa City, Iowa, United States
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, United States
| | - Sandra E Blom
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, United States
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Iowa, Iowa City, Iowa, United States
| | - Ashleigh E Machado
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, United States
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Iowa, Iowa City, Iowa, United States
| | - Kristen E Rohli
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, United States
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Iowa, Iowa City, Iowa, United States
- Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, Iowa, United States
| | - Michelle E Maxson
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Samuel B Stephens
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa, United States
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Iowa, Iowa City, Iowa, United States
- Interdisciplinary Graduate Program in Genetics, University of Iowa, Iowa City, Iowa, United States
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7
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Obradovic M, Zafirovic S, Gluvic Z, Radovanovic J, Isenovic ER. Autophagy and diabetes. EXPLORATION OF MEDICINE 2023:576-588. [DOI: 10.37349/emed.2023.00162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 05/29/2023] [Indexed: 10/13/2023] Open
Abstract
The current literature findings on autophagy’s beneficial and detrimental roles in diabetes mellitus (DM) and diabetes-related comorbidities were reviewed. The effects of oral hypoglycaemic medicines and autophagy in DM. Autophagy plays an important function in cellular homeostasis by promoting cell survival or initiating cell death in physiological settings was also assessed. Although autophagy protects insulin-target tissues, organelle failure caused by autophagy malfunction influences DM and other metabolic diseases. Endoplasmic reticulum and oxidative stress enhance autophagy levels, making it easier to regulate stress-induced intracellular changes. Evidence suggests that autophagy-caused cell death can occur when autophagy is overstimulated and constitutively activated, which might prevent or develop DM. Even though the precise role of autophagy in DM complications is uncertain, deregulation of the autophagic machinery is strongly linked to beta cell destruction and the aetiology of DM. Thus, improving autophagy dysfunction is a possible therapeutic objective in treating DM and other metabolic disorders.
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Affiliation(s)
- Milan Obradovic
- Department of Radiobiology and Molecular Genetics, VINČA Institute of Nuclear Sciences-National Institute of the Republic of Serbia, University of Belgrade, 11000 Belgrade, Serbia
| | - Sonja Zafirovic
- Department of Radiobiology and Molecular Genetics, VINČA Institute of Nuclear Sciences-National Institute of the Republic of Serbia, University of Belgrade, 11000 Belgrade, Serbia
| | - Zoran Gluvic
- Department of Endocrinology and Diabetes, Zemun Clinical Hospital, Faculty of Medicine, University of Belgrade, 11000 Belgrade, Serbia
| | - Jelena Radovanovic
- Department of Radiobiology and Molecular Genetics, VINČA Institute of Nuclear Sciences-National Institute of the Republic of Serbia, University of Belgrade, 11000 Belgrade, Serbia
| | - Esma R. Isenovic
- Department of Radiobiology and Molecular Genetics, VINČA Institute of Nuclear Sciences-National Institute of the Republic of Serbia, University of Belgrade, 11000 Belgrade, Serbia
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8
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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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Taguchi T, Kimura K, Suzuki A, Fujishima R, Shimizu N, Hoshiyama A, Masaki T, Inoue M, Kato Y, Satomi T, Takano K, Imada T, Sasaki S, Miyatsuka T. ATP6AP2 is robustly expressed in pancreatic β cells and neuroendocrine tumors, and plays a role in maintaining cellular viability. Sci Rep 2023; 13:9260. [PMID: 37286698 DOI: 10.1038/s41598-023-36265-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 05/31/2023] [Indexed: 06/09/2023] Open
Abstract
ATP6AP2, also known as (pro)renin receptor, has been shown to be expressed in several tissues including pancreatic β cells. Whereas ATP6AP2 plays an important role in regulating insulin secretion in mouse pancreatic β cells, the expression profiles and roles of ATP6AP2 in human pancreatic endocrine cells and neuroendocrine tumor cells remain unclear. Here in this study, we investigated the expression profiles of ATP6AP2 in pancreatic endocrine cells, and found that ATP6AP2 is robustly expressed in pancreatic insulinoma cells as well as in normal β cells. Although ATP6AP2 was also expressed in low-grade neuroendocrine tumors, it was not or faintly detected in intermediate- and high-grade neuroendocrine tumors. Knockdown experiments of the Atp6ap2 gene in rat insulinoma-derived INS-1 cells demonstrated decreased cell viability accompanied by a significant increase in apoptotic cells. Taken together, these findings suggest that ATP6AP2 plays a role in maintaining cellular homeostasis in insulinoma cells, which could lead to possible therapeutic approaches for endocrine tumors.
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Affiliation(s)
- Tomomi Taguchi
- Department of Endocrinology, Diabetes and Metabolism, Kitasato University School of Medicine, 1-15-1 Kitazato, Minami-Ku, Sagamihara, Kanagawa, 252-0374, Japan.
| | - Kaori Kimura
- Department of Endocrinology, Diabetes and Metabolism, Kitasato University School of Medicine, 1-15-1 Kitazato, Minami-Ku, Sagamihara, Kanagawa, 252-0374, Japan
| | - Agena Suzuki
- Department of Endocrinology, Diabetes and Metabolism, Kitasato University School of Medicine, 1-15-1 Kitazato, Minami-Ku, Sagamihara, Kanagawa, 252-0374, Japan
| | - Rei Fujishima
- Department of Endocrinology, Diabetes and Metabolism, Kitasato University School of Medicine, 1-15-1 Kitazato, Minami-Ku, Sagamihara, Kanagawa, 252-0374, Japan
| | - Naoya Shimizu
- Department of Endocrinology, Diabetes and Metabolism, Kitasato University School of Medicine, 1-15-1 Kitazato, Minami-Ku, Sagamihara, Kanagawa, 252-0374, Japan
| | - Ayako Hoshiyama
- Department of Endocrinology, Diabetes and Metabolism, Kitasato University School of Medicine, 1-15-1 Kitazato, Minami-Ku, Sagamihara, Kanagawa, 252-0374, Japan
| | - Tsuguto Masaki
- Department of Endocrinology, Diabetes and Metabolism, Kitasato University School of Medicine, 1-15-1 Kitazato, Minami-Ku, Sagamihara, Kanagawa, 252-0374, Japan
| | - Mitsuko Inoue
- Department of Endocrinology, Diabetes and Metabolism, Kitasato University School of Medicine, 1-15-1 Kitazato, Minami-Ku, Sagamihara, Kanagawa, 252-0374, Japan
- Health Care Center, Kitasato University, 1-15-1 Kitazato, Minami-Ku, Sagamihara, Kanagawa, 252-0374, Japan
| | - Yukiko Kato
- Department of Endocrinology, Diabetes and Metabolism, Kitasato University School of Medicine, 1-15-1 Kitazato, Minami-Ku, Sagamihara, Kanagawa, 252-0374, Japan
| | - Takebe Satomi
- Department of Endocrinology, Diabetes and Metabolism, Kitasato University School of Medicine, 1-15-1 Kitazato, Minami-Ku, Sagamihara, Kanagawa, 252-0374, Japan
| | - Koji Takano
- Department of Endocrinology, Diabetes and Metabolism, Kitasato University School of Medicine, 1-15-1 Kitazato, Minami-Ku, Sagamihara, Kanagawa, 252-0374, Japan
| | - Tasuku Imada
- Department of Metabolic Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Shugo Sasaki
- Department of Metabolic Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Takeshi Miyatsuka
- Department of Endocrinology, Diabetes and Metabolism, Kitasato University School of Medicine, 1-15-1 Kitazato, Minami-Ku, Sagamihara, Kanagawa, 252-0374, Japan.
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10
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Avari P, Eng PC, Hu M, Chen R, Popovic N, Polychronakos C, Spalding D, Rutter GA, Oliver N, Wernig F. A Novel Somatic Mutation Implicates ATP6V0D1 in Proinsulin Processing. J Endocr Soc 2023; 7:bvac196. [PMID: 36694809 PMCID: PMC9856271 DOI: 10.1210/jendso/bvac196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Indexed: 12/31/2022] Open
Abstract
Context Prohormone convertase 1/3 (PC1/3), encoded by protein convertase subtilisin kexin type 1 (PCSK1), converts inactive prohormones into biologically active peptides. Somatic mutations of insulinomas are associated with genetic defects interfering with control of insulin secretion from pancreatic beta cells. However, somatic mutations in proinsulinomas have not been described. Objective We report a case of a proinsulinoma, with suppressed insulin and C-peptide levels. Methods A 70-year-old woman presented with a 20-year history of "blackouts." During a 72-hour fast, blood glucose level dropped to 1.9 mmol/L with suppressed plasma insulin and C-peptide levels, but proinsulin levels were raised at 37 pmol/L (<10 pmol/L). Results Imaging revealed 3 distinct DOTATATE-avid pancreatic lesions. Laparoscopic spleen-preserving distal pancreatomy was performed. In view of discordant insulin, C-peptide, and proinsulin levels, whole exome sequencing analysis was performed on the tumor. In the somatic exome of the tumor, we found mutations in PCSK expression regulators, as well as a novel truncating somatic mutation in ATP6V0D1, a subunit of the ion pump that acidifies the β-cell compartments where the PCSKs act. Conclusion Appropriately suppressed insulin levels in the context of hypoglycemia do not always indicate the absence of a neuroendocrine islet cell tumor and proinsulin levels may be indicated to solidify the diagnosis. In the context of elevated proinsulin levels, low insulin and C-peptide levels might be explained by somatic mutations that likely implicate proinsulin processing within the tumor. Furthermore, we propose several mechanistic candidates, including ATP6V0D1. Experimental validation using cellular approaches may in future confirm pathomechanisms involved in this rare condition.
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Affiliation(s)
- Parizad Avari
- Correspondence: Parizad Avari, PhD, Department of Endocrinology, Hammersmith Hospital, Du Cane Road, London W12 ONN, UK.
| | | | - Ming Hu
- Section of Cell Biology and Functional Genomics, Department of Metabolism, Diabetes and Reproduction, Imperial College London, London W120NN, UK
| | - Runzhi Chen
- Section of Endocrinology, Hammersmith Hospital, Imperial College Healthcare NHS Trust London, London W120HS, UK
| | - Natalija Popovic
- The Endocrine Genetics Laboratory, Research Institute of the McGill University Health Centre and the Montreal Children's Hospital, Montréal, QC H4A3J1, Canada
| | - Constantin Polychronakos
- The Endocrine Genetics Laboratory, Research Institute of the McGill University Health Centre and the Montreal Children's Hospital, Montréal, QC H4A3J1, Canada
- Department of Endocrinology, Zhejiang University Children's Hospital, Hangzhou 310006, People's Republic of China
| | - Duncan Spalding
- Department of Hepatobiliary Surgery, Hammersmith Hospital, Imperial College London Healthcare NHS Trust London, London H2X049, UK
| | - Guy A Rutter
- Section of Cell Biology and Functional Genomics, Department of Metabolism, Diabetes and Reproduction, Imperial College London, London W120NN, UK
- Faculty of Medicine, CHUM Research Center and University of Montreal, Montreal, QC 639798, Canada
- Lee Kong Chian School of Medicine, Nan Yang Technological University, Singapore 308232, Singapore
| | - Nick Oliver
- Section of Endocrinology, Hammersmith Hospital, Imperial College Healthcare NHS Trust London, London W120HS, UK
- Department of Metabolism, Digestion and Reproduction, Imperial College London, London W120NN, UK
- Section of Cell Biology and Functional Genomics, Department of Metabolism, Diabetes and Reproduction, Imperial College London, London W120NN, UK
| | - Florian Wernig
- Section of Endocrinology, Hammersmith Hospital, Imperial College Healthcare NHS Trust London, London W120HS, UK
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11
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Capo V, Abinun M, Villa A. Osteoclast rich osteopetrosis due to defects in the TCIRG1 gene. Bone 2022; 165:116519. [PMID: 35981697 DOI: 10.1016/j.bone.2022.116519] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 08/10/2022] [Accepted: 08/11/2022] [Indexed: 11/28/2022]
Abstract
Discovery that mutations in TCIRG1 (also known as Atp6i) gene are responsible for most instances of autosomal recessive osteopetrosis (ARO) heralded a new era for comprehension and treatment of this phenotypically heterogeneous rare bone disease. TCIRG1 encodes the a3 subunit, an essential isoform of the vacuolar ATPase proton pump involved in acidification of the osteoclast resorption lacuna and in secretory lysosome trafficking. TCIRG1 defects lead to inefficient bone resorption by nonfunctional osteoclasts seen in abundance on bone marrow biopsy, delineating this ARO as 'osteoclast-rich'. Presentation is usually in early childhood and features of extramedullary haematopoiesis (hepatosplenomegaly, anaemia, thrombocytopenia) due to bone marrow fibrosis, and cranial nerve impingement (blindness in particular). Impaired dietary calcium uptake due to high pH causes the co-occurrence of rickets, described as "osteopetrorickets". Osteoclast dysfunction leads to early death if untreated, and allogeneic haematopoietic stem cell transplantation is currently the treatment of choice. Studies of patients as well as of mouse models carrying spontaneous (the oc/oc mouse) or targeted disruption of Atp6i (TCIRG1) gene have been instrumental providing insight into disease pathogenesis and development of novel cellular therapies that exploit gene correction.
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Affiliation(s)
- Valentina Capo
- San Raffaele Telethon Institute for Gene Therapy (SR-Tiget), IRCCS San Raffaele Scientific Institute, Milan, Italy; Institute of Genetic and Biomedical Research, Milan Unit, National Research Council, Milan, Italy
| | - Mario Abinun
- Children's Haematopoietic Stem Cell Transplantation Unit, Great North Children's Hospital, Newcastle upon Tyne Hospitals NHS Foundation Trust, Newcastle upon Tyne, UK; Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Anna Villa
- San Raffaele Telethon Institute for Gene Therapy (SR-Tiget), IRCCS San Raffaele Scientific Institute, Milan, Italy; Institute of Genetic and Biomedical Research, Milan Unit, National Research Council, Milan, Italy.
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12
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Nakanishi-Matsui M, Matsumoto N. V-ATPase a3 Subunit in Secretory Lysosome Trafficking in Osteoclasts. Biol Pharm Bull 2022; 45:1426-1431. [PMID: 36184499 DOI: 10.1248/bpb.b22-00371] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Vacuolar-type ATPase (V-ATPase) shares its structure and rotational catalysis with F-type ATPase (F-ATPase, ATP synthase). However, unlike subunits of F-ATPase, those of V-ATPase have tissue- and/or organelle-specific isoforms. Structural diversity of V-ATPase generated by different combinations of subunit isoforms enables it to play diverse physiological roles in mammalian cells. Among these various roles, this review focuses on the functions of lysosome-specific V-ATPase in bone resorption by osteoclasts. Lysosomes remain in the cytoplasm in most cell types, but in osteoclasts, secretory lysosomes move toward and fuse with the plasma membrane to secrete lysosomal enzymes, which is essential for bone resorption. Through this process, lysosomal V-ATPase harboring the a3 isoform of the a subunit is relocated to the plasma membrane, where it transports protons from the cytosol to the cell exterior to generate the acidic extracellular conditions required for secreted lysosomal enzymes. In addition to this role as a proton pump, we recently found that the lysosomal a3 subunit of V-ATPase is essential for anterograde trafficking of secretory lysosomes. Specifically, a3 interacts with Rab7, a member of the Rab guanosine 5'-triphosphatase (GTPase) family that regulates organelle trafficking, and recruits it to the lysosomal membrane. These findings revealed the multifunctionality of lysosomal V-ATPase in osteoclasts; V-ATPase is responsible not only for the formation of the acidic environment by transporting protons, but also for intracellular trafficking of secretory lysosomes by recruiting organelle trafficking factors. Herein, we summarize the molecular mechanism underlying secretory lysosome trafficking in osteoclasts, and discuss the possible regulatory role of V-ATPase in organelle trafficking.
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Affiliation(s)
| | - Naomi Matsumoto
- Division of Biochemistry, School of Pharmacy, Iwate Medical University
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13
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The a subunit isoforms of vacuolar-type proton ATPase exhibit differential distribution in mouse perigastrulation embryos. Sci Rep 2022; 12:13590. [PMID: 35948619 PMCID: PMC9365772 DOI: 10.1038/s41598-022-18002-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 08/03/2022] [Indexed: 11/25/2022] Open
Abstract
Vacuolar-type H+-ATPases (V-ATPases) are large multi-subunit complexes that play critical roles in the acidification of a variety of intracellular or extracellular compartments. Mammalian cells contain four isoforms of the membrane integral subunit a (a1–a4); these isoforms contain the information necessary to target the enzyme to different cellular destinations. They are also involved in regulating the efficiency of ATP hydrolysis and proton transport. Previously, we showed that early embryogenesis requires V-ATPase function, and the luminal acidic endocytic and lysosomal compartments in the visceral endoderm of mouse embryos at the pre-gastrulation stage (E6.5) are essential for both nutrition and signal transduction during early embryogenesis. In this study, we examined the expression and distribution of a subunit isoforms in mouse embryos at E6.5. We found that all four isoforms expressed and exhibited differential distribution in the E6.5 embryo. At this developmental stage, the embryos establish highly elaborate endocytic compartments called apical vacuoles, on which the a3 isoform specifically accumulated.
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14
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Integrating genome-wide association study and pathway analysis reveals physiological aspects affecting heifer early calving defined at different ages in Nelore cattle. Genomics 2022; 114:110395. [DOI: 10.1016/j.ygeno.2022.110395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 05/23/2022] [Accepted: 06/01/2022] [Indexed: 11/22/2022]
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15
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Endosomal v-ATPase as a Sensor Determining Myocardial Substrate Preference. Metabolites 2022; 12:metabo12070579. [PMID: 35888703 PMCID: PMC9316095 DOI: 10.3390/metabo12070579] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 06/16/2022] [Accepted: 06/20/2022] [Indexed: 11/17/2022] Open
Abstract
The heart is a metabolically flexible omnivore that can utilize a variety of substrates for energy provision. To fulfill cardiac energy requirements, the healthy adult heart mainly uses long-chain fatty acids and glucose in a balanced manner, but when exposed to physiological or pathological stimuli, it can switch its substrate preference to alternative substrates such as amino acids (AAs) and ketone bodies. Using the failing heart as an example, upon stress, the fatty acid/glucose substrate balance is upset, resulting in an over-reliance on either fatty acids or glucose. A chronic fuel shift towards a single type of substrate is linked with cardiac dysfunction. Re-balancing myocardial substrate preference is suggested as an effective strategy to rescue the failing heart. In the last decade, we revealed that vacuolar-type H+-ATPase (v-ATPase) functions as a key regulator of myocardial substrate preference and, therefore, as a novel potential treatment approach for the failing heart. Fatty acids, glucose, and AAs selectively influence the assembly state of v-ATPase resulting in modulation of its proton-pumping activity. In this review, we summarize these novel insights on v-ATPase as an integrator of nutritional information. We also describe its exploitation as a therapeutic target with focus on supplementation of AA as a nutraceutical approach to fight lipid-induced insulin resistance and contractile dysfunction of the heart.
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16
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Maxson ME, Abbas YM, Wu JZ, Plumb JD, Grinstein S, Rubinstein JL. Detection and quantification of the vacuolar H+ATPase using the Legionella effector protein SidK. J Biophys Biochem Cytol 2022; 221:212963. [PMID: 35024770 PMCID: PMC8763849 DOI: 10.1083/jcb.202107174] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 12/14/2021] [Accepted: 12/21/2021] [Indexed: 12/11/2022] Open
Abstract
Acidification of secretory and endocytic organelles is required for proper receptor recycling, membrane traffic, protein degradation, and solute transport. Proton-pumping vacuolar H+ ATPases (V-ATPases) are responsible for this luminal acidification, which increases progressively as secretory and endocytic vesicles mature. An increasing density of V-ATPase complexes is thought to account for the gradual decrease in pH, but available reagents have not been sufficiently sensitive or specific to test this hypothesis. We introduce a new probe to localize and quantify V-ATPases. The probe is derived from SidK, a Legionella pneumophila effector protein that binds to the V-ATPase A subunit. We generated plasmids encoding fluorescent chimeras of SidK1-278, and labeled recombinant SidK1-278 with Alexa Fluor 568 to visualize and quantify V-ATPases with high specificity in live and fixed cells, respectively. We show that V-ATPases are acquired progressively during phagosome maturation, that they distribute in discrete membrane subdomains, and that their density in lysosomes depends on their subcellular localization.
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Affiliation(s)
- Michelle E Maxson
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada
| | - Yazan M Abbas
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, Canada
| | - Jing Ze Wu
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada.,Department of Biochemistry, University of Toronto, Toronto, Canada
| | - Jonathan D Plumb
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada
| | - Sergio Grinstein
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada.,Department of Biochemistry, University of Toronto, Toronto, Canada
| | - John L Rubinstein
- Program in Molecular Medicine, The Hospital for Sick Children Research Institute, Toronto, Canada.,Department of Medical Biophysics, University of Toronto, Toronto, Canada.,Department of Biochemistry, University of Toronto, Toronto, Canada
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17
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Khan MM, Lee S, Couoh‐Cardel S, Oot RA, Kim H, Wilkens S, Roh S. Oxidative stress protein Oxr1 promotes V-ATPase holoenzyme disassembly in catalytic activity-independent manner. EMBO J 2022; 41:e109360. [PMID: 34918374 PMCID: PMC8804929 DOI: 10.15252/embj.2021109360] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 10/30/2021] [Accepted: 11/15/2021] [Indexed: 11/09/2022] Open
Abstract
The vacuolar ATPase (V-ATPase) is a rotary motor proton pump that is regulated by an assembly equilibrium between active holoenzyme and autoinhibited V1 -ATPase and Vo proton channel subcomplexes. Here, we report cryo-EM structures of yeast V-ATPase assembled in vitro from lipid nanodisc reconstituted Vo and mutant V1 . Our analysis identified holoenzymes in three active rotary states, indicating that binding of V1 to Vo provides sufficient free energy to overcome Vo autoinhibition. Moreover, the structures suggest that the unequal spacing of Vo 's proton-carrying glutamic acid residues serves to alleviate the symmetry mismatch between V1 and Vo motors, a notion that is supported by mutagenesis experiments. We also uncover a structure of free V1 bound to Oxr1, a conserved but poorly characterized factor involved in the oxidative stress response. Biochemical experiments show that Oxr1 inhibits V1 -ATPase and causes disassembly of the holoenzyme, suggesting that Oxr1 plays a direct role in V-ATPase regulation.
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Affiliation(s)
- Md. Murad Khan
- Department of Biochemistry and Molecular BiologySUNY Upstate Medical UniversitySyracuseNYUSA
| | - Seowon Lee
- School of Biological ScienceInstitute of Molecular Biology and GeneticsSeoul National UniversitySeoulSouth Korea
| | - Sergio Couoh‐Cardel
- Department of Biochemistry and Molecular BiologySUNY Upstate Medical UniversitySyracuseNYUSA
- Present address:
Department of Molecular and Cellular PhysiologyStanford UniversityStanfordCAUSA
| | - Rebecca A Oot
- Department of Biochemistry and Molecular BiologySUNY Upstate Medical UniversitySyracuseNYUSA
| | - Hyunmin Kim
- School of Biological ScienceInstitute of Molecular Biology and GeneticsSeoul National UniversitySeoulSouth Korea
| | - Stephan Wilkens
- Department of Biochemistry and Molecular BiologySUNY Upstate Medical UniversitySyracuseNYUSA
| | - Soung‐Hun Roh
- School of Biological ScienceInstitute of Molecular Biology and GeneticsSeoul National UniversitySeoulSouth Korea
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18
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Yang S, Hou Y, Zhang H, Hao Y, Zhang Y, Zhao Z, Ruan W, Duan X. ATP6V1H deficiency impairs glucose tolerance by augmenting endoplasmic reticulum stress in high fat diet fed mice. Arch Biochem Biophys 2022; 716:109116. [PMID: 34990584 DOI: 10.1016/j.abb.2022.109116] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 12/19/2021] [Accepted: 12/31/2021] [Indexed: 11/18/2022]
Abstract
Vacuolar H+-ATPase (V-ATPase) is a ubiquitous proton pump that mediates the proton transmembrane transportation in various cells. Previously, H subunit of V-ATPase (ATP6V1H) was found to be related with insulin secretion and diabetes. However, the mechanism by which ATP6V1H regulates insulin secretion and glucose metabolism remains unclear. Herein, we established a high-fat-diet (HFD) fed model with Atp6v1h+/- mice and detected the expression and secretion of insulin and some biochemical indices of glucose metabolism, in order to explore the related mechanisms in β-cells. Transcriptome sequencing, qPCR and western blot analysis showed that ATP6V1H deficiency worsened fatty acid-induced glucose tolerance impairment by augmenting endoplasmic reticulum stress in β-cells, and alternative splicing of ATP6V1H might be involved in this process. These results indicated that ATP6V1H deficiency increased the susceptibility to T2DM.
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Affiliation(s)
- Shaoqing Yang
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Oral Biology, School of Stomatology, The Fourth Military Medical University. Xi'an, 710032, China
| | - Yuzhuan Hou
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Oral Biology, School of Stomatology, The Fourth Military Medical University. Xi'an, 710032, China; College of Stomatology, Ningxia Medical University, Yinchuan, 750004, China
| | - Hengwei Zhang
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Oral Biology, School of Stomatology, The Fourth Military Medical University. Xi'an, 710032, China
| | - Ying Hao
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Oral Biology, School of Stomatology, The Fourth Military Medical University. Xi'an, 710032, China
| | - Yanli Zhang
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Oral Biology, School of Stomatology, The Fourth Military Medical University. Xi'an, 710032, China
| | - Zanyan Zhao
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Oral Biology, School of Stomatology, The Fourth Military Medical University. Xi'an, 710032, China; School of Life Sciences, Yan'an University, Yan'an, 716000, China
| | - Wenyan Ruan
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Oral Biology, School of Stomatology, The Fourth Military Medical University. Xi'an, 710032, China; College of Stomatology, Ningxia Medical University, Yinchuan, 750004, China
| | - Xiaohong Duan
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Key Laboratory of Stomatology, Department of Oral Biology, School of Stomatology, The Fourth Military Medical University. Xi'an, 710032, China.
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19
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Integrative structural modelling and visualisation of a cellular organelle. QRB DISCOVERY 2022. [PMID: 37529283 PMCID: PMC10392685 DOI: 10.1017/qrd.2022.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
Abstract
Models of insulin secretory vesicles from pancreatic beta cells have been created using the cellPACK suite of tools to research, curate, construct and visualise the current state of knowledge. The model integrates experimental information from proteomics, structural biology, cryoelectron microscopy and X-ray tomography, and is used to generate models of mature and immature vesicles. A new method was developed to generate a confidence score that reconciles inconsistencies between three available proteomes using expert annotations of cellular localisation. The models are used to simulate soft X-ray tomograms, allowing quantification of features that are observed in experimental tomograms, and in turn, allowing interpretation of X-ray tomograms at the molecular level.
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20
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An inhibitor-mediated beta-cell dedifferentiation model reveals distinct roles for FoxO1 in glucagon repression and insulin maturation. Mol Metab 2021; 54:101329. [PMID: 34454092 PMCID: PMC8476777 DOI: 10.1016/j.molmet.2021.101329] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Revised: 08/20/2021] [Accepted: 08/20/2021] [Indexed: 11/21/2022] Open
Abstract
OBJECTIVE The loss of forkhead box protein O1 (FoxO1) signaling in response to metabolic stress contributes to the etiology of type II diabetes, causing the dedifferentiation of pancreatic beta cells to a cell type reminiscent of endocrine progenitors. Lack of methods to easily model this process in vitro, however, have hindered progress into the identification of key downstream targets and potential inhibitors. We therefore aimed to establish such an in vitro cellular dedifferentiation model and apply it to identify novel agents involved in the maintenance of beta-cell identity. METHODS The murine beta-cell line, Min6, was used for primary experiments and high-content screening. Screens encompassed a library of small-molecule drugs representing the chemical and target space of all FDA-approved small molecules with an automated immunofluorescence readout. Validation experiments were performed in a murine alpha-cell line as well as in primary murine and human diabetic islets. Developmental effects were studied in zebrafish and C. elegans models, while diabetic db/db mouse models were used to elucidate global glucose metabolism outcomes. RESULTS We show that short-term pharmacological FoxO1 inhibition can model beta-cell dedifferentiation by downregulating beta-cell-specific transcription factors, resulting in the aberrant expression of progenitor genes and the alpha-cell marker glucagon. From a high-content screen, we identified loperamide as a small molecule that can prevent FoxO inhibitor-induced glucagon expression and further stimulate insulin protein processing and secretion by altering calcium levels, intracellular pH, and FoxO1 localization. CONCLUSIONS Our study provides novel models, molecular targets, and drug candidates for studying and preventing beta-cell dedifferentiation.
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21
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Germanos M, Gao A, Taper M, Yau B, Kebede MA. Inside the Insulin Secretory Granule. Metabolites 2021; 11:metabo11080515. [PMID: 34436456 PMCID: PMC8401130 DOI: 10.3390/metabo11080515] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Revised: 08/03/2021] [Accepted: 08/03/2021] [Indexed: 12/19/2022] Open
Abstract
The pancreatic β-cell is purpose-built for the production and secretion of insulin, the only hormone that can remove glucose from the bloodstream. Insulin is kept inside miniature membrane-bound storage compartments known as secretory granules (SGs), and these specialized organelles can readily fuse with the plasma membrane upon cellular stimulation to release insulin. Insulin is synthesized in the endoplasmic reticulum (ER) as a biologically inactive precursor, proinsulin, along with several other proteins that will also become members of the insulin SG. Their coordinated synthesis enables synchronized transit through the ER and Golgi apparatus for congregation at the trans-Golgi network, the initiating site of SG biogenesis. Here, proinsulin and its constituents enter the SG where conditions are optimized for proinsulin processing into insulin and subsequent insulin storage. A healthy β-cell is continually generating SGs to supply insulin in vast excess to what is secreted. Conversely, in type 2 diabetes (T2D), the inability of failing β-cells to secrete may be due to the limited biosynthesis of new insulin. Factors that drive the formation and maturation of SGs and thus the production of insulin are therefore critical for systemic glucose control. Here, we detail the formative hours of the insulin SG from the luminal perspective. We do this by mapping the journey of individual members of the SG as they contribute to its genesis.
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22
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Oot RA, Yao Y, Manolson MF, Wilkens S. Purification of active human vacuolar H +-ATPase in native lipid-containing nanodiscs. J Biol Chem 2021; 297:100964. [PMID: 34270960 PMCID: PMC8353480 DOI: 10.1016/j.jbc.2021.100964] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Revised: 07/07/2021] [Accepted: 07/12/2021] [Indexed: 12/26/2022] Open
Abstract
Vacuolar H+-ATPases (V-ATPases) are large, multisubunit proton pumps that acidify the lumen of organelles in virtually every eukaryotic cell and in specialized acid-secreting animal cells, the enzyme pumps protons into the extracellular space. In higher organisms, most of the subunits are expressed as multiple isoforms, with some enriched in specific compartments or tissues and others expressed ubiquitously. In mammals, subunit a is expressed as four isoforms (a1-4) that target the enzyme to distinct biological membranes. Mutations in a isoforms are known to give rise to tissue-specific disease, and some a isoforms are upregulated and mislocalized to the plasma membrane in invasive cancers. However, isoform complexity and low abundance greatly complicate purification of active human V-ATPase, a prerequisite for developing isoform-specific therapeutics. Here, we report the purification of an active human V-ATPase in native lipid nanodiscs from a cell line stably expressing affinity-tagged a isoform 4 (a4). We find that exogenous expression of this single subunit in HEK293F cells permits assembly of a functional V-ATPase by incorporation of endogenous subunits. The ATPase activity of the preparation is >95% sensitive to concanamycin A, indicating that the lipid nanodisc-reconstituted enzyme is functionally coupled. Moreover, this strategy permits purification of the enzyme's isolated membrane subcomplex together with biosynthetic assembly factors coiled-coil domain-containing protein 115, transmembrane protein 199, and vacuolar H+-ATPase assembly integral membrane protein 21. Our work thus lays the groundwork for biochemical characterization of active human V-ATPase in an a subunit isoform-specific manner and establishes a platform for the study of the assembly and regulation of the human holoenzyme.
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Affiliation(s)
- Rebecca A Oot
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA
| | - Yeqi Yao
- Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada
| | - Morris F Manolson
- Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada
| | - Stephan Wilkens
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, New York, USA.
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23
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Chu A, Zirngibl RA, Manolson MF. The V-ATPase a3 Subunit: Structure, Function and Therapeutic Potential of an Essential Biomolecule in Osteoclastic Bone Resorption. Int J Mol Sci 2021; 22:ijms22136934. [PMID: 34203247 PMCID: PMC8269383 DOI: 10.3390/ijms22136934] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 06/18/2021] [Accepted: 06/21/2021] [Indexed: 12/29/2022] Open
Abstract
This review focuses on one of the 16 proteins composing the V-ATPase complex responsible for resorbing bone: the a3 subunit. The rationale for focusing on this biomolecule is that mutations in this one protein account for over 50% of osteopetrosis cases, highlighting its critical role in bone physiology. Despite its essential role in bone remodeling and its involvement in bone diseases, little is known about the way in which this subunit is targeted and regulated within osteoclasts. To this end, this review is broadened to include the three other mammalian paralogues (a1, a2 and a4) and the two yeast orthologs (Vph1p and Stv1p). By examining the literature on all of the paralogues/orthologs of the V-ATPase a subunit, we hope to provide insight into the molecular mechanisms and future research directions specific to a3. This review starts with an overview on bone, highlighting the role of V-ATPases in osteoclastic bone resorption. We then cover V-ATPases in other location/functions, highlighting the roles which the four mammalian a subunit paralogues might play in differential targeting and/or regulation. We review the ways in which the energy of ATP hydrolysis is converted into proton translocation, and go in depth into the diverse role of the a subunit, not only in proton translocation but also in lipid binding, cell signaling and human diseases. Finally, the therapeutic implication of targeting a3 specifically for bone diseases and cancer is discussed, with concluding remarks on future directions.
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24
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Kawamura N, Takaoka K, Hamada H, Hadjantonakis AK, Sun-Wada GH, Wada Y. Rab7-Mediated Endocytosis Establishes Patterning of Wnt Activity through Inactivation of Dkk Antagonism. Cell Rep 2021; 31:107733. [PMID: 32521258 PMCID: PMC8171381 DOI: 10.1016/j.celrep.2020.107733] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Revised: 03/16/2020] [Accepted: 05/13/2020] [Indexed: 12/12/2022] Open
Abstract
Endocytosis has been proposed to modulate cell signaling activities. However, the role of endocytosis in embryogenesis, which requires coordination of multiple signaling inputs, has remained less understood. We previously showed that mouse embryos lacking a small guanosine triphosphate (GTP)-binding protein Rab7 implicated in endocytic flow are defective in gastrulation. Here, we investigate how subcellular defects associated with Rab7 deficiency are related to the observed developmental defects. Rab7-deficient embryos fail to organize mesodermal tissues due to defects in Wnt-β-catenin signaling. Visceral endoderm (VE)-specific ablation of Rab7 results in patterning defects similar to systemic Rab7 deletion. Rab7 mutants accumulate the Wnt antagonist Dkk1 in the extracellular space and in intracellular compartments throughout the VE epithelium. These data indicate that Rab7-dependent endocytosis regulates the concentration and availability of extracellular Dkk1, thereby relieving the epiblast of antagonism. This intercellular mechanism therefore organizes distinct spatiotemporal patterns of canonical Wnt activity during the peri-gastrulation stages of embryonic development.
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Affiliation(s)
- Nobuyuki Kawamura
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Doshisha Women's College of Liberal Arts, Kohdo, Kyotanabe, Kyoto 610-0395, Japan
| | - Katsuyoshi Takaoka
- Institute of Advanced Medical Sciences, Tokushima University, 3-18-15 Kuramoto, Tokushima 770-8503, Japan
| | - Hiroshi Hamada
- RIKEN Center for Biosystems Dynamics Research, 2-2-3 Minatojima-minamimachi, Chuo-ku, Kobe 650-0047, Japan; Developmental Genetics Group, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamada-oka, Suita, Osaka 565-0871, Japan
| | - Anna-Katerina Hadjantonakis
- Developmental Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center, New York, NY 10065, USA
| | - Ge-Hong Sun-Wada
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Doshisha Women's College of Liberal Arts, Kohdo, Kyotanabe, Kyoto 610-0395, Japan.
| | - Yoh Wada
- Division of Biological Sciences, Institute of Scientific and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
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Morosin SK, Lochrin AJ, Delforce SJ, Lumbers ER, Pringle KG. The (pro)renin receptor ((P)RR) and soluble (pro)renin receptor (s(P)RR) in pregnancy. Placenta 2021; 116:43-50. [PMID: 34020806 DOI: 10.1016/j.placenta.2021.04.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 03/31/2021] [Accepted: 04/27/2021] [Indexed: 11/25/2022]
Abstract
The (pro)renin receptor ((P)RR) is a multi-functional protein that can be proteolytically cleaved and released in a soluble form (s(P)RR). Recently, the (P)RR and s(P)RR have become of interest in pregnancy and its associated pathologies. This is because the (P)RR not only activates tissue renin angiotensin systems, but it is also an integral component of vacuolar-ATPase, activates the wingless/integrated (Wnt)/β-catenin and extracellular signal regulated kinases 1 and 2/mitogen-activated protein kinase signalling pathways, and stabilises the β subunit of pyruvate dehydrogenase. Additionally, s(P)RR is detected in plasma and urine, and maternal plasma levels are elevated in pregnancy complications including fetal growth restriction, preeclampsia and gestational diabetes mellitus. Therefore, s(P)RR has potential as a biomarker for these pregnancy pathologies. Preliminary functional findings suggest that s(P)RR may be important for regulating fluid balance, inflammation and blood pressure, all of which contribute to a successful pregnancy. The (P)RR and s(P)RR regulate pathways that are known to be important in maintaining pregnancy, however their role in the physiological context of pregnancy is poorly characterised. This review summarises the known and potential functions of the (P)RR and s(P)RR in pregnancy, and how their dysregulation may contribute to pregnancy complications. It also highlights the need for further research into the source and function of s(P)RR in pregnancy. Soluble (P)RR levels could be indicative of placental, kidney or liver dysfunction and therefore be a novel clinical biomarker, or therapeutic target, to improve the detection and treatment of pregnancy pathologies.
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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, New Lambton Heights, 2305, New South Wales, Australia
| | - Alyssa J Lochrin
- School of Biomedical Sciences and Pharmacy, Priority Research Centre for Reproductive Science, Pregnancy and Reproduction Program, Hunter Medical Research Institute, University of Newcastle, New Lambton Heights, 2305, 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, New Lambton Heights, 2305, 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, New Lambton Heights, 2305, 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, New Lambton Heights, 2305, New South Wales, Australia.
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26
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Muralidharan C, Conteh AM, Marasco MR, Crowder JJ, Kuipers J, de Boer P, Linnemann AK. Pancreatic beta cell autophagy is impaired in type 1 diabetes. Diabetologia 2021; 64:865-877. [PMID: 33515072 PMCID: PMC7940272 DOI: 10.1007/s00125-021-05387-6] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 12/01/2020] [Indexed: 12/19/2022]
Abstract
AIMS/HYPOTHESIS Pancreatic beta cells are subjected to exogenous damaging factors such as proinflammatory cytokines or excess glucose that can cause accumulation of damage-inducing reactive oxygen species during the pathogenesis of diabetes. We and others have shown that beta cell autophagy can reduce reactive oxygen species to protect against apoptosis. While impaired islet autophagy has been demonstrated in human type 2 diabetes, it is unknown if islet autophagy is perturbed in the pathogenesis of type 1 diabetes. We hypothesised that beta cell autophagy is dysfunctional in type 1 diabetes, and that there is a progressive loss during early diabetes development. METHODS Pancreases were collected from chloroquine-injected and non-injected non-obese diabetes-resistant (NOR) and non-obese diabetic (NOD) mice. Age- and BMI-matched pancreas tissue sections from human organ donors (N = 34) were obtained from the Network for Pancreatic Organ Donors with Diabetes (nPOD). Tissue sections were stained with antibodies against proinsulin or insulin (beta cell markers), microtubule-associated protein 1 light chain 3 A/B (LC3A/B; autophagosome marker), lysosomal-associated membrane protein 1 (LAMP1; lysosome marker) and p62 (autophagy adaptor). Images collected on a scanning laser confocal microscope were analysed with CellProfiler and ImageJ. Secondary lysosomes and telolysosomes were assessed in electron micrographs of human pancreatic tissue sections (n = 12), and energy dispersive x-ray analysis was performed to assess distribution of elements (n = 5). RESULTS We observed increased autophagosome numbers in islets of diabetic NOD mice (p = 0.008) and increased p62 in islets of both non-diabetic and diabetic NOD mice (p < 0.001) vs NOR mice. There was also a reduction in LC3-LAMP1 colocalisation in islets of diabetic NOD mice compared with both non-diabetic NOD (p < 0.001) and NOR mice (p < 0.001). Chloroquine elicited accumulation of autophagosomes in the islets of NOR (p = 0.003) and non-diabetic NOD mice (p < 0.001), but not in islets of diabetic NOD mice; and stimulated accumulation of p62 in NOR (p < 0.001), but not in NOD mice. We observed reduced LC3-LAMP1 colocalisation (p < 0.001) in residual beta cells of human donors with type 1 diabetes vs non-diabetic participants. We also observed reduced colocalisation of proinsulin with LAMP1 in donors with type 1 diabetes (p < 0.001). Electron microscopy also revealed accumulation of telolysosomes with nitrogen-dense rings in beta cells of autoantibody-positive donors (p = 0.002). CONCLUSIONS/INTERPRETATION We provide evidence of islet macroautophagy/crinophagy impairment in human type 1 diabetes. We also document accumulation of telolysosomes with peripheral nitrogen in beta cells of autoantibody-positive donors, demonstrating altered lysosome content that may be associated with lysosome dysfunction before clinical hyperglycaemia. Similar macroautophagy impairments are present in the NOD mouse model of type 1 diabetes.
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Affiliation(s)
- Charanya Muralidharan
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Abass M Conteh
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Michelle R Marasco
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Justin J Crowder
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Jeroen Kuipers
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Pascal de Boer
- Department of Biomedical Sciences of Cells and Systems, University of Groningen, University Medical Center Groningen, Groningen, the Netherlands
| | - Amelia K Linnemann
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, USA.
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN, USA.
- Center for Diabetes and Metabolic Diseases, Indiana University School of Medicine, Indianapolis, IN, USA.
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27
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Santos-Pereira C, Rodrigues LR, Côrte-Real M. Emerging insights on the role of V-ATPase in human diseases: Therapeutic challenges and opportunities. Med Res Rev 2021; 41:1927-1964. [PMID: 33483985 DOI: 10.1002/med.21782] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 12/05/2020] [Accepted: 01/05/2021] [Indexed: 12/13/2022]
Abstract
The control of the intracellular pH is vital for the survival of all organisms. Membrane transporters, both at the plasma and intracellular membranes, are key players in maintaining a finely tuned pH balance between intra- and extracellular spaces, and therefore in cellular homeostasis. V-ATPase is a housekeeping ATP-driven proton pump highly conserved among prokaryotes and eukaryotes. This proton pump, which exhibits a complex multisubunit structure based on cell type-specific isoforms, is essential for pH regulation and for a multitude of ubiquitous and specialized functions. Thus, it is not surprising that V-ATPase aberrant overexpression, mislocalization, and mutations in V-ATPase subunit-encoding genes have been associated with several human diseases. However, the ubiquitous expression of this transporter and the high toxicity driven by its off-target inhibition, renders V-ATPase-directed therapies very challenging and increases the need for selective strategies. Here we review emerging evidence linking V-ATPase and both inherited and acquired human diseases, explore the therapeutic challenges and opportunities envisaged from recent data, and advance future research avenues. We highlight the importance of V-ATPases with unique subunit isoform molecular signatures and disease-associated isoforms to design selective V-ATPase-directed therapies. We also discuss the rational design of drug development pipelines and cutting-edge methodological approaches toward V-ATPase-centered drug discovery. Diseases like cancer, osteoporosis, and even fungal infections can benefit from V-ATPase-directed therapies.
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Affiliation(s)
- Cátia Santos-Pereira
- Department of Biology, Centre of Molecular and Environmental Biology (CBMA), University of Minho, Braga, Portugal.,Department of Biological Engineering, Centre of Biological Engineering (CEB), University of Minho, Braga, Portugal
| | - Lígia R Rodrigues
- Department of Biological Engineering, Centre of Biological Engineering (CEB), University of Minho, Braga, Portugal
| | - Manuela Côrte-Real
- Department of Biology, Centre of Molecular and Environmental Biology (CBMA), University of Minho, Braga, Portugal
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28
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Morimoto S, Morishima N, Watanabe D, Kato Y, Shibata N, Ichihara A. Immunohistochemistry for (Pro)renin Receptor in Humans. Int J Endocrinol 2021; 2021:8828610. [PMID: 34367278 PMCID: PMC8337151 DOI: 10.1155/2021/8828610] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 07/16/2021] [Indexed: 12/27/2022] Open
Abstract
The (pro)renin receptor is a multifunctional protein with roles in angiotensin-II-dependent and -independent intracellular cell signaling and roles as an intracellular accessory protein for the vacuolar H+-ATPase, including hormone secretion. While (pro)renin receptor mRNA is widely expressed in various human tissues, localization of (pro)renin receptor protein expression has not yet been systemically determined. Therefore, this study localized (pro)renin receptor protein expression in human organs. Systemic immunohistochemical examination of (pro)renin receptor expression was performed in whole body organs of autopsy cases. (Pro)renin receptor immunostaining was observed in the cytoplasm of cells in almost all human organs. It was observed in thyroid follicular epithelial cells, hepatic cells, pancreatic duct epithelial cells, zona glomerulosa and zona reticularis of the cortex and medulla of the adrenal gland, proximal and distal tubules and collecting ducts of the kidney, cardiomyocytes, and skeletal muscle cells. In the brain, (pro)renin receptor staining was detected in neurons throughout all areas, especially in the medulla oblongata, paraventricular nucleus and supraoptic nucleus of the hypothalamus, cerebrum, granular layer of the hippocampus, Purkinje cell layer of the cerebellum, and the pituitary anterior and posterior lobes. In the anterior lobe of the pituitary gland, all types of anterior pituitary hormone-positive cells showed double staining with (pro)renin receptor. These data showed that (pro)renin receptor protein was expressed in almost all organs of the human body. Its expression pattern was not uniform, and cell-specific expression pattern was observed, supporting the notion that (pro)renin receptor plays numerous physiological roles in each human organ.
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Affiliation(s)
- Satoshi Morimoto
- Department of Endocrinology and Hypertension, Tokyo Women's Medical University, Tokyo, Japan
| | - Noriko Morishima
- Department of Endocrinology and Hypertension, Tokyo Women's Medical University, Tokyo, Japan
| | - Daisuke Watanabe
- Department of Endocrinology and Hypertension, Tokyo Women's Medical University, Tokyo, Japan
| | - Yoichiro Kato
- Department of Pathology, Tokyo Women's Medical University, Tokyo, Japan
| | - Noriyuki Shibata
- Department of Pathology, Tokyo Women's Medical University, Tokyo, Japan
| | - Atsuhiro Ichihara
- Department of Endocrinology and Hypertension, Tokyo Women's Medical University, Tokyo, Japan
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29
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Eaton AF, Merkulova M, Brown D. The H +-ATPase (V-ATPase): from proton pump to signaling complex in health and disease. Am J Physiol Cell Physiol 2020; 320:C392-C414. [PMID: 33326313 PMCID: PMC8294626 DOI: 10.1152/ajpcell.00442.2020] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A primary function of the H+-ATPase (or V-ATPase) is to create an electrochemical proton gradient across eukaryotic cell membranes, which energizes fundamental cellular processes. Its activity allows for the acidification of intracellular vesicles and organelles, which is necessary for many essential cell biological events to occur. In addition, many specialized cell types in various organ systems such as the kidney, bone, male reproductive tract, inner ear, olfactory mucosa, and more, use plasma membrane V-ATPases to perform specific activities that depend on extracellular acidification. It is, however, increasingly apparent that V-ATPases are central players in many normal and pathophysiological processes that directly influence human health in many different and sometimes unexpected ways. These include cancer, neurodegenerative diseases, diabetes, and sensory perception, as well as energy and nutrient-sensing functions within cells. This review first covers the well-established role of the V-ATPase as a transmembrane proton pump in the plasma membrane and intracellular vesicles and outlines factors contributing to its physiological regulation in different cell types. This is followed by a discussion of the more recently emerging unconventional roles for the V-ATPase, such as its role as a protein interaction hub involved in cell signaling, and the (patho)physiological implications of these interactions. Finally, the central importance of endosomal acidification and V-ATPase activity on viral infection will be discussed in the context of the current COVID-19 pandemic.
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Affiliation(s)
- Amity F Eaton
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Maria Merkulova
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Dennis Brown
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
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30
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Bertolini I, Storaci AM, Terrasi A, Cristofori AD, Locatelli M, Caroli M, Ferrero S, Altieri DC, Vaira V. Interplay Between V-ATPase G1 and Small EV-miRNAs Modulates ERK1/2 Activation in GBM Stem Cells and Nonneoplastic Milieu. Mol Cancer Res 2020; 18:1744-1754. [PMID: 32753475 DOI: 10.1158/1541-7786.mcr-20-0078] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 04/17/2020] [Accepted: 07/24/2020] [Indexed: 12/15/2022]
Abstract
The ATP6V1G1 subunit (V1G1) of the vacuolar proton ATPase (V-ATPase) pump is crucial for glioma stem cells (GSC) maintenance and in vivo tumorigenicity. Moreover, V-ATPase reprograms the tumor microenvironment through acidification and release of extracellular vesicles (EV). Therefore, we investigated the role of V1G1 in GSC small EVs and their effects on primary brain cultures. To this end, small EVs were isolated from patients-derived GSCs grown as neurospheres (NS) with high (V1G1HIGH-NS) or low (V1G1LOW-NS) V1G1 expression and analyzed for V-ATPase subunits presence, miRNA contents, and cellular responses in recipient cultures. Our results show that NS-derived small EVs stimulate proliferation and motility of recipient cells, with small EV derived from V1G1HIGH-NS showing the most pronounced activity. This involved activation of ERK1/2 signaling, in a response reversed by V-ATPase inhibition in NS-producing small EV. The miRNA profile of V1G1HIGH-NS-derived small EVs differed significantly from that of V1G1LOW-NS, which included miRNAs predicted to target MAPK/ERK signaling. Mechanistically, forced expression of a MAPK-targeting pool of miRNAs in recipient cells suppressed MAPK/ERK pathway activation and blunted the prooncogenic effects of V1G1HIGH small EV. These findings propose that the GSC influences the brain milieu through a V1G1-coordinated EVs release of MAPK/ERK-targeting miRNAs. Interfering with V-ATPase activity could prevent ERK-dependent oncogenic reprogramming of the microenvironment, potentially hampering local GBM infiltration. IMPLICATIONS: Our data identify a novel molecular mechanism of gliomagenesis specific of the GBM stem cell niche, which coordinates a V-ATPase-dependent reprogramming of the brain microenvironment through the release of specialized EVs.
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Affiliation(s)
- Irene Bertolini
- Division of Pathology, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Alessandra Maria Storaci
- Division of Pathology, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.,Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
| | - Andrea Terrasi
- Division of Pathology, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Andrea Di Cristofori
- Division of Neurosurgery, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Marco Locatelli
- Division of Neurosurgery, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Manuela Caroli
- Division of Neurosurgery, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy
| | - Stefano Ferrero
- Division of Pathology, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.,Department of Biomedical, Surgical and Dental Sciences University of Milan, Milan, Italy
| | - Dario C Altieri
- Immunology, Microenvironment and Metastasis Program, The Wistar Institute, Philadelphia, Pennsylvania
| | - Valentina Vaira
- Division of Pathology, Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy.
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31
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Song Q, Meng B, Xu H, Mao Z. The emerging roles of vacuolar-type ATPase-dependent Lysosomal acidification in neurodegenerative diseases. Transl Neurodegener 2020; 9:17. [PMID: 32393395 PMCID: PMC7212675 DOI: 10.1186/s40035-020-00196-0] [Citation(s) in RCA: 96] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 04/23/2020] [Indexed: 12/15/2022] Open
Abstract
Background Lysosomes digest extracellular material from the endocytic pathway and intracellular material from the autophagic pathway. This process is performed by the resident hydrolytic enzymes activated by the highly acidic pH within the lysosomal lumen. Lysosome pH gradients are mainly maintained by the vacuolar (H+) ATPase (or V-ATPase), which pumps protons into lysosomal lumen by consuming ATP. Dysfunction of V-ATPase affects lysosomal acidification, which disrupts the clearance of substrates and leads to many disorders, including neurodegenerative diseases. Main body As a large multi-subunit complex, the V-ATPase is composed of an integral membrane V0 domain involved in proton translocation and a peripheral V1 domain catalyzing ATP hydrolysis. The canonical functions of V-ATPase rely on its H+-pumping ability in multiple vesicle organelles to regulate endocytic traffic, protein processing and degradation, synaptic vesicle loading, and coupled transport. The other non-canonical effects of the V-ATPase that are not readily attributable to its proton-pumping activity include membrane fusion, pH sensing, amino-acid-induced activation of mTORC1, and scaffolding for protein-protein interaction. In response to various stimuli, V-ATPase complex can reversibly dissociate into V1 and V0 domains and thus close ATP-dependent proton transport. Dysregulation of pH and lysosomal dysfunction have been linked to many human diseases, including neurodegenerative disorders such as Alzheimer disease, Parkinson’s disease, amyotrophic lateral sclerosis as well as neurodegenerative lysosomal storage disorders. Conclusion V-ATPase complex is a universal proton pump and plays an important role in lysosome acidification in all types of cells. Since V-ATPase dysfunction contributes to the pathogenesis of multiple neurodegenerative diseases, further understanding the mechanisms that regulate the canonical and non-canonical functions of V-ATPase will reveal molecular details of disease process and help assess V-ATPase or molecules related to its regulation as therapeutic targets.
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Affiliation(s)
- Qiaoyun Song
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA.,Department of Reproductive Genetics, Hebei General Hospital, Shijiazhuang, Hebei Province, 050051, People's Republic of China.,Department of Neurology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Bo Meng
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA.,Department of Neurology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Haidong Xu
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA.,Department of Neurology, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Zixu Mao
- Department of Pharmacology and Chemical Biology, Emory University School of Medicine, Atlanta, GA, 30322, USA. .,Department of Neurology, Emory University School of Medicine, Atlanta, GA, 30322, USA.
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32
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Hirao J, Tojo A, Hatakeyama S, Satonaka H, Ishimitsu T. V-ATPase blockade reduces renal gluconeogenesis and improves insulin secretion in type 2 diabetic rats. Hypertens Res 2020; 43:1079-1088. [PMID: 32382157 DOI: 10.1038/s41440-020-0450-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2020] [Revised: 03/28/2020] [Accepted: 03/30/2020] [Indexed: 12/16/2022]
Abstract
Vacuolar H+-adenosine triphosphatase (V-ATPase) stimulates vesicular acidification that may activate cytoplasmic enzymes, hormone secretion and membrane recycling of transporters. We investigated the effect of blockade of V-ATPase by bafilomycin B1 on renal gluconeogenesis, mitochondrial enzymes, and insulin secretion in type 2 diabetic rats. Spontaneous type 2 diabetic Torii rats were treated with intraperitoneal injection of bafilomycin B1 for 1 week, and the kidneys were examined after 24 h of starvation in metabolic cages. The renal expression and activity of V-ATPase were increased in the brush border membrane of the proximal tubules in diabetic rats. The blockade of V-ATPase by bafilomycin B1 reduced renal V-ATPase activity and urinary ammonium in diabetic rats. Treatment with bafilomycin suppressed the enhanced renal gluconeogenesis enzymes and mitochondrial electron transport enzymes in type 2 diabetic rats and reduced the renal cytoplasmic glucose levels. The insulin index and pancreatic insulin granules were decreased in diabetic rats with increased V-ATPase expression in islet cells, and treatment with bafilomycin B1 reversed these changes and increased the insulin secretion index. Hepatosteatosis in type 2 diabetic rats was ameliorated by bafilomycin treatment. As a consequence, treatment with bafilomycin B1 significantly decreased the plasma glucose level after 24 h of starvation in diabetic rats. In conclusion, a V-ATPase inhibitor improved plasma glucose levels in type 2 diabetes by inhibiting renal mitochondrial gluconeogenesis and improving insulin secretion.
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Affiliation(s)
- Jun Hirao
- Department of Nephrology and Hypertension, Dokkyo Medical University, Mibu, Tochigi, Japan
| | - Akihiro Tojo
- Department of Nephrology and Hypertension, Dokkyo Medical University, Mibu, Tochigi, Japan.
| | - Saaya Hatakeyama
- Department of Nephrology and Hypertension, Dokkyo Medical University, Mibu, Tochigi, Japan
| | - Hiroshi Satonaka
- Department of Nephrology and Hypertension, Dokkyo Medical University, Mibu, Tochigi, Japan
| | - Toshihiko Ishimitsu
- Department of Nephrology and Hypertension, Dokkyo Medical University, Mibu, Tochigi, Japan
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Haddadi MH, Hajizadeh-Saffar E, Khosravi-Maharlooei M, Basiri M, Negahdari B, Baharvand H. Autoimmunity as a target for chimeric immune receptor therapy: A new vision to therapeutic potential. Blood Rev 2020; 41:100645. [DOI: 10.1016/j.blre.2019.100645] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 11/12/2019] [Accepted: 11/22/2019] [Indexed: 12/25/2022]
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34
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Chitirala P, Ravichandran K, Schirra C, Chang HF, Krause E, Kazmaier U, Lauterbach MA, Rettig J. Role of V-ATPase a3-Subunit in Mouse CTL Function. THE JOURNAL OF IMMUNOLOGY 2020; 204:2818-2828. [PMID: 32269094 DOI: 10.4049/jimmunol.1901536] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Accepted: 02/26/2020] [Indexed: 12/17/2022]
Abstract
CTLs release cytotoxic proteins such as granzymes and perforin through fusion of cytotoxic granules (CG) at the target cell interface, the immune synapse, to kill virus-infected and tumorigenic target cells. A characteristic feature of these granules is their acidic pH inside the granule lumen, which is required to process precursors of granzymes and perforin to their mature form. However, the role of acidic pH in CG maturation, transport, and fusion is not understood. We demonstrate in primary murine CTLs that the a3-subunit of the vacuolar-type (H+)-adenosine triphosphatase is required for establishing a luminal pH of 6.1 inside CG using ClopHensorN(Q69M), a newly generated CG-specific pH indicator. Knockdown of the a3-subunit resulted in a significantly reduced killing of target cells and a >50% reduction in CG fusion in total internal reflection fluorescence microscopy, which was caused by a reduced number of CG at the immune synapse. Superresolution microscopy revealed a reduced interaction of CG with the microtubule network upon a3-subunit knockdown. Finally, we find by electron and structured illumination microscopy that knockdown of the a3-subunit altered the diameter and density of individual CG, whereas the number of CG per CTL was unaffected. We conclude that the a3-subunit of the vacuolar adenosine triphosphatase is not only responsible for the acidification of CG, but also contributes to the maturation and efficient transport of the CG to the immune synapse.
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Affiliation(s)
- Praneeth Chitirala
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany
| | - Keerthana Ravichandran
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany
| | - Claudia Schirra
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany
| | - Hsin-Fang Chang
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany
| | - Elmar Krause
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany
| | - Uli Kazmaier
- Organic Chemistry, Saarland University, 66123 Saarbrücken, Germany; and
| | - Marcel A Lauterbach
- Molecular Imaging, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany
| | - Jens Rettig
- Cellular Neurophysiology, Center for Integrative Physiology and Molecular Medicine, Saarland University, 66421 Homburg, Germany;
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Abstract
The (pro)renin receptor ((P)RR) was first identified as a single-transmembrane receptor in human kidneys and initially attracted attention owing to its potential role as a regulator of the tissue renin-angiotensin system (RAS). Subsequent studies found that the (P)RR is widely distributed in organs throughout the body, including the kidneys, heart, brain, eyes, placenta and the immune system, and has multifaceted functions in vivo. The (P)RR has roles in various physiological processes, such as the cell cycle, autophagy, acid-base balance, energy metabolism, embryonic development, T cell homeostasis, water balance, blood pressure regulation, cardiac remodelling and maintenance of podocyte structure. These roles of the (P)RR are mediated by its effects on important biological systems and pathways including the tissue RAS, vacuolar H+-ATPase, Wnt, partitioning defective homologue (Par) and tyrosine phosphorylation. In addition, the (P)RR has been reported to contribute to the pathogenesis of diseases such as fibrosis, hypertension, pre-eclampsia, diabetic microangiopathy, acute kidney injury, cardiovascular disease, cancer and obesity. Current evidence suggests that the (P)RR has key roles in the normal development and maintenance of vital organs and that dysfunction of the (P)RR is associated with diseases that are characterized by a disruption of the homeostasis of physiological functions.
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36
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Flinck M, Hagelund S, Gorbatenko A, Severin M, Pedraz-Cuesta E, Novak I, Stock C, Pedersen SF. The Vacuolar H + ATPase α3 Subunit Negatively Regulates Migration and Invasion of Human Pancreatic Ductal Adenocarcinoma Cells. Cells 2020; 9:E465. [PMID: 32085585 PMCID: PMC7072798 DOI: 10.3390/cells9020465] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 02/10/2020] [Accepted: 02/13/2020] [Indexed: 12/12/2022] Open
Abstract
Increased metabolic acid production and upregulation of net acid extrusion render pH homeostasis profoundly dysregulated in many cancers. Plasma membrane activity of vacuolar H+ ATPases (V-ATPases) has been implicated in acid extrusion and invasiveness of some cancers, yet often on the basis of unspecific inhibitors. Serving as a membrane anchor directing V-ATPase localization, the a subunit of the V0 domain of the V-ATPase (ATP6V0a1-4) is particularly interesting in this regard. Here, we map the regulation and roles of ATP6V0a3 in migration, invasion, and growth in pancreatic ductal adenocarcinoma (PDAC) cells. a3 mRNA and protein levels were upregulated in PDAC cell lines compared to non-cancer pancreatic epithelial cells. Under control conditions, a3 localization was mainly endo-/lysosomal, and its knockdown had no detectable effect on pHi regulation after acid loading. V-ATPase inhibition, but not a3 knockdown, increased HIF-1 expression and decreased proliferation and autophagic flux under both starved and non-starved conditions, and spheroid growth of PDAC cells was also unaffected by a3 knockdown. Strikingly, a3 knockdown increased migration and transwell invasion of Panc-1 and BxPC-3 PDAC cells, and increased gelatin degradation in BxPC-3 cells yet decreased it in Panc-1 cells. We conclude that in these PDAC cells, a3 is upregulated and negatively regulates migration and invasion, likely in part via effects on extracellular matrix degradation.
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Affiliation(s)
- Mette Flinck
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, DK-2100 Copenhagen, Denmark; (M.F.); (S.H.); (M.S.); (E.P.-C.); (I.N.)
| | - Sofie Hagelund
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, DK-2100 Copenhagen, Denmark; (M.F.); (S.H.); (M.S.); (E.P.-C.); (I.N.)
| | - Andrej Gorbatenko
- Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA;
| | - Marc Severin
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, DK-2100 Copenhagen, Denmark; (M.F.); (S.H.); (M.S.); (E.P.-C.); (I.N.)
| | - Elena Pedraz-Cuesta
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, DK-2100 Copenhagen, Denmark; (M.F.); (S.H.); (M.S.); (E.P.-C.); (I.N.)
| | - Ivana Novak
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, DK-2100 Copenhagen, Denmark; (M.F.); (S.H.); (M.S.); (E.P.-C.); (I.N.)
| | - Christian Stock
- Department of Gastroentero-, Hepato- and Endocrinology, Hannover Medical School, D-30625 Hannover, Germany;
| | - Stine Falsig Pedersen
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, DK-2100 Copenhagen, Denmark; (M.F.); (S.H.); (M.S.); (E.P.-C.); (I.N.)
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37
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Vasanthakumar T, Rubinstein JL. Structure and Roles of V-type ATPases. Trends Biochem Sci 2020; 45:295-307. [PMID: 32001091 DOI: 10.1016/j.tibs.2019.12.007] [Citation(s) in RCA: 116] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 12/05/2019] [Accepted: 12/31/2019] [Indexed: 12/19/2022]
Abstract
V-ATPases are membrane-embedded protein complexes that function as ATP hydrolysis-driven proton pumps. V-ATPases are the primary source of organellar acidification in all eukaryotes, making them essential for many fundamental cellular processes. Enzymatic activity can be modulated by regulated and reversible disassembly of the complex, and several subunits of mammalian V-ATPase have multiple isoforms that are differentially localized. Although the biochemical properties of the different isoforms are currently unknown, mutations in specific subunit isoforms have been associated with various diseases, making V-ATPases potential drug targets. V-ATPase structure and activity have been best characterized in Saccharomyces cerevisiae, where recent structures have revealed details about the dynamics of the enzyme, the proton translocation pathway, and conformational changes associated with regulated disassembly and autoinhibition.
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Affiliation(s)
- Thamiya Vasanthakumar
- The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, The University of Toronto, Toronto, ON M5S 1A8, Canada.
| | - John L Rubinstein
- The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada; Department of Biochemistry, The University of Toronto, Toronto, ON M5S 1A8, Canada; Department of Medical Biophysics, The University of Toronto, Toronto, ON M5G 1L7, Canada.
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38
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Atp6ap2 deletion causes extensive vacuolation that consumes the insulin content of pancreatic β cells. Proc Natl Acad Sci U S A 2019; 116:19983-19988. [PMID: 31527264 DOI: 10.1073/pnas.1903678116] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Pancreatic β cells store insulin within secretory granules which undergo exocytosis upon elevation of blood glucose levels. Crinophagy and autophagy are instead responsible to deliver damaged or old granules to acidic lysosomes for intracellular degradation. However, excessive consumption of insulin granules can impair β cell function and cause diabetes. Atp6ap2 is an essential accessory component of the vacuolar ATPase required for lysosomal degradative functions and autophagy. Here, we show that Cre recombinase-mediated conditional deletion of Atp6ap2 in mouse β cells causes a dramatic accumulation of large, multigranular vacuoles in the cytoplasm, with reduction of insulin content and compromised glucose homeostasis. Loss of insulin stores and gigantic vacuoles were also observed in cultured insulinoma INS-1 cells upon CRISPR/Cas9-mediated removal of Atp6ap2. Remarkably, these phenotypic alterations could not be attributed to a deficiency in autophagy or acidification of lysosomes. Together, these data indicate that Atp6ap2 is critical for regulating the stored insulin pool and that a balanced regulation of granule turnover is key to maintaining β cell function and diabetes prevention.
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39
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Peterson TV, Jaiswal MK, Beaman KD, Reynolds JM. Conditional Deletion of the V-ATPase a2-Subunit Disrupts Intrathymic T Cell Development. Front Immunol 2019; 10:1911. [PMID: 31456807 PMCID: PMC6700305 DOI: 10.3389/fimmu.2019.01911] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 07/29/2019] [Indexed: 11/13/2022] Open
Abstract
Proper orchestration of T lymphocyte development is critical, as T cells underlie nearly all responses of the adaptive immune system. Developing thymocytes differentiate in response to environmental cues carried from cell surface receptors to the nucleus, shaping a distinct transcriptional program that defines their developmental outcome. Our recent work has identified a previously undescribed role for the vacuolar ATPase (V-ATPase) in facilitating the development of murine thymocytes progressing toward the CD4+ and CD8+ αβ T cell lineages. Vav1Cre recombinase-mediated deletion of the a2 isoform of the V-ATPase (a2V) in mouse hematopoietic cells leads to a specific and profound loss of peripheral CD4+ and CD8+ αβ T cells. Utilizing T cell-restricted LckCre and CD4Cre strains, we further traced this deficiency to the thymus and found that a2V plays a cell-intrinsic role throughout intrathymic development. Loss of a2V manifests as a partial obstruction in the double negative stage of T cell development, and later, a near complete failure of positive selection. These data deepen our understanding of the biological mechanisms that orchestrate T cell development and lend credence to the recent focus on V-ATPase as a potential chemotherapeutic target to combat proliferative potential in T cell lymphoblastic leukemias and autoimmune disease.
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Affiliation(s)
- Theodore V Peterson
- Center for Cancer Cell Biology, Immunology and Infection, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
| | - Mukesh K Jaiswal
- Center for Cancer Cell Biology, Immunology and Infection, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
| | - Kenneth D Beaman
- Center for Cancer Cell Biology, Immunology and Infection, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States
| | - Joseph M Reynolds
- Center for Cancer Cell Biology, Immunology and Infection, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, IL, United States.,Edward Hines, Jr. VA Hospital, Hines, IL, United States
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40
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Abe M, Saito M, Tsukahara A, Shiokawa S, Ueno K, Shimamura H, Nagano M, Toshima JY, Toshima J. Functional complementation reveals that 9 of the 13 human V-ATPase subunits can functionally substitute for their yeast orthologs. J Biol Chem 2019; 294:8273-8285. [PMID: 30952699 DOI: 10.1074/jbc.ra118.006192] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 03/27/2019] [Indexed: 11/06/2022] Open
Abstract
Vacuolar-type H+-ATPase (V-ATPase) is a highly conserved proton pump responsible for acidification of intracellular organelles and potential drug target. It is a multisubunit complex comprising a cytoplasmic V1 domain responsible for ATP hydrolysis and a membrane-embedded Vo domain that contributes to proton translocation across the membrane. Saccharomyces cerevisiae V-ATPase is composed of 14 subunits, deletion of any one of which results in well-defined growth defects. As the structure of V-ATPase and the function of each subunit have been well-characterized in yeast, this organism has been recognized as a preferred model for studies of V-ATPases. In this study, to assess the functional relatedness of the yeast and human V-ATPase subunits, we investigated whether human V-ATPase subunits can complement calcium- or pH-sensitive growth, acidification of the vacuolar lumen, assembly of the V-ATPase complex, and protein sorting in yeast mutants lacking the equivalent yeast genes. These assessments revealed that 9 of the 13 human V-ATPase subunits can partially or fully complement the function of the corresponding yeast subunits. Importantly, sequence similarity was not necessarily correlated with functional complementation. We also found that besides all Vo domain subunits, the V1 F subunit is required for proper assembly of the Vo domain at the endoplasmic reticulum. Furthermore, the human H subunit fully restored the level of vacuolar acidification, but only partially rescued calcium-sensitive growth, suggesting a specific role of the H subunit in V-ATPase activity. These findings provide important insights into functional homologies between yeast and human V-ATPases.
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Affiliation(s)
- Michiko Abe
- Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585
| | - Mayu Saito
- Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585
| | - Ayana Tsukahara
- Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585
| | - Shuka Shiokawa
- Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585
| | - Kazuma Ueno
- Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585
| | - Hiroki Shimamura
- Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585
| | - Makoto Nagano
- Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585
| | - Junko Y Toshima
- School of Health Science, Tokyo University of Technology, Ota-ku, Tokyo 144-8535, Japan.
| | - Jiro Toshima
- Department of Biological Science and Technology, Tokyo University of Science, 6-3-1 Niijyuku, Katsushika-ku, Tokyo 125-8585.
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41
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Krah A, Marzinek JK, Bond PJ. Insights into water accessible pathways and the inactivation mechanism of proton translocation by the membrane-embedded domain of V-type ATPases. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:1004-1010. [DOI: 10.1016/j.bbamem.2019.02.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 01/29/2019] [Accepted: 02/27/2019] [Indexed: 01/25/2023]
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42
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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: 36] [Impact Index Per Article: 6.0] [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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43
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Proton pumping V-ATPase inhibitor bafilomycin A1 affects Rab7 lysosomal localization and abolishes anterograde trafficking of osteoclast secretory lysosomes. Biochem Biophys Res Commun 2019; 510:421-426. [DOI: 10.1016/j.bbrc.2019.01.118] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Accepted: 01/26/2019] [Indexed: 01/03/2023]
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44
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Sharma S, Oot RA, Khan MM, Wilkens S. Functional reconstitution of vacuolar H +-ATPase from V o proton channel and mutant V 1-ATPase provides insight into the mechanism of reversible disassembly. J Biol Chem 2019; 294:6439-6449. [PMID: 30792311 DOI: 10.1074/jbc.ra119.007577] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Revised: 02/10/2019] [Indexed: 12/12/2022] Open
Abstract
The vacuolar H+-ATPase (V-ATPase; V1Vo-ATPase) is an ATP-dependent proton pump that acidifies subcellular compartments in all eukaryotic organisms. V-ATPase activity is regulated by reversible disassembly into autoinhibited V1-ATPase and Vo proton channel subcomplexes, a process that is poorly understood on the molecular level. V-ATPase is a rotary motor, and recent structural analyses have revealed different rotary states for disassembled V1 and Vo, a mismatch that is likely responsible for their inability to reconstitute into holo V-ATPase in vitro Here, using the model organism Saccharomyces cerevisiae, we show that a key impediment for binding of V1 to Vo is the conformation of the inhibitory C-terminal domain of subunit H (HCT). Using biolayer interferometry and biochemical analyses of purified mutant V1-ATPase and Vo proton channel reconstituted into vacuolar lipid-containing nanodiscs, we further demonstrate that disruption of HCT's V1-binding site facilitates assembly of a functionally coupled and stable V1Vo-ATPase. Unlike WT, this mutant enzyme was resistant to MgATP hydrolysis-induced dissociation, further highlighting HCT's role in the mechanism of V-ATPase regulation. Our findings provide key insight into the molecular events underlying regulation of V-ATPase activity by reversible disassembly.
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Affiliation(s)
- Stuti Sharma
- From the Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Rebecca A Oot
- From the Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Md Murad Khan
- From the Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
| | - Stephan Wilkens
- From the Department of Biochemistry & Molecular Biology, SUNY Upstate Medical University, Syracuse, New York 13210
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45
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FUTAI M, SUN-WADA GH, WADA Y, MATSUMOTO N, NAKANISHI-MATSUI M. Vacuolar-type ATPase: A proton pump to lysosomal trafficking. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2019; 95:261-277. [PMID: 31189779 PMCID: PMC6751294 DOI: 10.2183/pjab.95.018] [Citation(s) in RCA: 66] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Vacuolar-type ATPase (V-ATPase), initially identified in yeast and plant vacuoles, pumps protons into the lumen of organelles coupled with ATP hydrolysis. The mammalian counterpart is found ubiquitously in endomembrane organelles and the plasma membrane of specialized cells such as osteoclasts. V-ATPase is also present in unique organelles such as insulin secretory granules, neural synaptic vesicles, and acrosomes of spermatozoa. Consistent with its diverse physiological roles and unique localization, the seven subunits of V-ATPase have 2-4 isoforms that are organelle- or cell-specific. Subunits of the enzyme function in trafficking organelles and vesicles by interacting with small molecule GTPases. During osteoclast differentiation, one of the four isoforms of subunit a, a3, is indispensable for secretory lysosome trafficking to the plasma membrane. Diseases such as osteopetrosis, renal acidosis, and hearing loss are related to V-ATPase isoforms. In addition to its role as an enzyme, V-ATPase has versatile physiological roles in eukaryotic cells.
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Affiliation(s)
- Masamitsu FUTAI
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Morioka, Iwate, Japan
- Department of Biological Sciences, Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, Japan
- Emeritus Professor, Osaka University, Osaka, Japan
- Correspondence should be addressed: M. Futai, Emeritus Professor, Iwate Medical University, 19-1 Uchimaru, Morioka, Iwate 020-8505, Japan (e-mail: )
| | - Ge-Hong SUN-WADA
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Doshisha Women’s College, Kyoto, Kyotanabe, Japan
| | - Yoh WADA
- Department of Biological Sciences, Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, Japan
| | - Naomi MATSUMOTO
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Morioka, Iwate, Japan
| | - Mayumi NAKANISHI-MATSUI
- Department of Biochemistry, Faculty of Pharmaceutical Sciences, Iwate Medical University, Morioka, Iwate, Japan
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46
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Miner GE, Sullivan KD, Guo A, Jones BC, Hurst LR, Ellis EC, Starr ML, Fratti RA. Phosphatidylinositol 3,5-bisphosphate regulates the transition between trans-SNARE complex formation and vacuole membrane fusion. Mol Biol Cell 2018; 30:201-208. [PMID: 30427760 PMCID: PMC6589561 DOI: 10.1091/mbc.e18-08-0505] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Phosphoinositides (PIs) regulate a myriad of cellular functions including membrane fusion, as exemplified by the yeast vacuole, which uses various PIs at different stages of fusion. In light of this, the effect of phosphatidylinositol 3,5-bisphosphate (PI(3,5)P2) on vacuole fusion remains unknown. PI(3,5)P2 is made by the PI3P 5-kinase Fab1 and has been characterized as a regulator of vacuole fission during hyperosmotic shock, where it interacts with the TRP Ca2+ channel Yvc1. Here we demonstrate that exogenously added dioctanoyl (C8) PI(3,5)P2 abolishes homotypic vacuole fusion. This effect was not linked to Yvc1, as fusion was equally affected using yvc1Δ vacuoles. Thus, the effects of C8-PI(3,5)P2 on fusion and fission operate through distinct mechanisms. Further testing showed that C8-PI(3,5)P2 inhibited vacuole fusion after trans-SNARE pairing. Although SNARE complex formation was unaffected, we found that C8-PI(3,5)P2 blocked outer leaflet lipid mixing. Overproduction of endogenous PI(3,5)P2 by the fab1T2250A hyperactive kinase mutant also inhibited the lipid mixing stage, bolstering the model in which PI(3,5)P2 inhibits fusion when present at elevated levels. Taken together, this work identifies a novel function for PI(3,5)P2 as a regulator of vacuolar fusion. Moreover, it suggests that this lipid acts as a molecular switch between fission and fusion.
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Affiliation(s)
- Gregory E Miner
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Katherine D Sullivan
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Annie Guo
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Brandon C Jones
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Logan R Hurst
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Ez C Ellis
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Matthew L Starr
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801
| | - Rutilio A Fratti
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.,Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801
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47
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Chromophore-Assisted Light Inactivation of the V-ATPase V0c Subunit Inhibits Neurotransmitter Release Downstream of Synaptic Vesicle Acidification. Mol Neurobiol 2018; 56:3591-3602. [PMID: 30155790 DOI: 10.1007/s12035-018-1324-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 08/17/2018] [Indexed: 10/28/2022]
Abstract
Synaptic vesicle proton V-ATPase is an essential component in synaptic vesicle function. Active acidification of synaptic vesicles, triggered by the V-ATPase, is necessary for neurotransmitter storage. Independently from its proton transport activity, an additional important function of the membrane-embedded sector of the V-ATPase has been uncovered over recent years. Subunits a and c of the membrane sector of this multi-molecular complex have been shown to interact with SNARE proteins and to be involved in modulating neurotransmitter release. The c-subunit interacts with the v-SNARE VAMP2 and facilitates neurotransmission. In this study, we used chromophore-assisted light inactivation and monitored the consequences on neurotransmission on line in CA3 pyramidal neurons. We show that V-ATPase c-subunit V0c is a key element in modulating neurotransmission and that its specific inactivation rapidly inhibited neurotransmission.
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48
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Valproate inhibits glucose-stimulated insulin secretion in beta cells. Histochem Cell Biol 2018; 150:395-401. [PMID: 30145684 DOI: 10.1007/s00418-018-1713-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/20/2018] [Indexed: 10/28/2022]
Abstract
Valproate (VPA), an FDA approved anti-epileptic drug with a half-life of 12-18 h in humans, has been shown to perturb the vacuolar proton pump (vH+-ATPase) function in yeasts by inhibiting myo-inositol phosphate synthase, the first and rate-limiting enzyme in inositol biosynthesis, thereby resulting in inositol depletion. vH+-ATPase transfers protons (H+) across cell membranes, which help maintain pH gradients within cells necessary for various cellular functions including secretion. This proton pump has a membrane (V0) and a soluble cytosolic (V1) domain, with C-subunit associated with V1. In secretory cells such as neurons and insulin-secreting beta cells, vH+-ATPase acidifies vesicles essential for secretion. In this study, we demonstrate that exposure of insulin-secreting Min6 cells to a clinical dose of VPA results in inositol depletion and loss of co-localization of subunit C of vH+-ATPase with insulin-secreting granules. Consequently, a reduction of glucose-stimulated insulin secretion is observed following VPA exposure. These results merit caution and the reassessment of the clinical use of VPA.
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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: 1.9] [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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50
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Schuchman RM, Vancini R, Piper A, Breuer D, Ribeiro M, Ferreira D, Magliocca J, Emmerich V, Hernandez R, Brown DT. Role of the vacuolar ATPase in the Alphavirus replication cycle. Heliyon 2018; 4:e00701. [PMID: 30094371 PMCID: PMC6074608 DOI: 10.1016/j.heliyon.2018.e00701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 06/07/2018] [Accepted: 07/18/2018] [Indexed: 02/06/2023] Open
Abstract
We have shown that Alphaviruses can enter cells by direct penetration at the plasma membrane (R. Vancini, G. Wang, D. Ferreira, R. Hernandez, and D. Brown, J Virol, 87:4352–4359, 2013). Direct penetration removes the requirement for receptor-mediated endocytosis exposure to low pH and membrane fusion in the process of RNA entry. Endosomal pH as well as the pH of the cell cytoplasm is maintained by the activity of the vacuolar ATPase (V-ATPase). Bafilomycin is a specific inhibitor of V-ATPase. To characterize the roll of the V-ATPase in viral replication we generated a Bafilomycin A1(BAF) resistant mutant of Sindbis virus (BRSV). BRSV produced mature virus and virus RNA in greater amounts than parent virus in BAF-treated cells. Sequence analysis revealed mutations in the E2 glycoprotein, T15I/Y18H, were responsible for the phenotype. These results show that a functional V-ATPase is required for efficient virus RNA synthesis and virus maturation in Alphavirus infection.
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Affiliation(s)
- Ryan M Schuchman
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC, USA
| | - Ricardo Vancini
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC, USA
| | - Amanda Piper
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC, USA
| | - Denitra Breuer
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC, USA
| | - Mariana Ribeiro
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC, USA
| | - Davis Ferreira
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC, USA.,Institute of Microbiology, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Joseph Magliocca
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC, USA
| | - Veronica Emmerich
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC, USA
| | - Raquel Hernandez
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC, USA
| | - Dennis T Brown
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC, USA
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