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Fang Y, Feng H, Zhang B, Zhang S, Zhou Y, Hao P, Zhou Z, Zhou S, Li N, Hui Y, Ma L, Xiong J, Wu J, Liu L, Zhang X. Cytosolic pH is a direct nexus in linking environmental cues with insulin processing and secretion in pancreatic β cells. Cell Metab 2024; 36:1237-1251.e4. [PMID: 38513648 DOI: 10.1016/j.cmet.2024.02.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 09/01/2023] [Accepted: 02/22/2024] [Indexed: 03/23/2024]
Abstract
Pancreatic β cells actively respond to glucose fluctuations through regulating insulin processing and secretion. However, how this process is elaborately tuned in circumstance of variable microenvironments as well as β cell-intrinsic states and whether its dysfunction links to metabolic diseases remain largely elusive. Here, we show that the cytosolic pH (pHc) in β cells is increased upon glucose challenge, which can be sensed by Smad5 via its nucleocytoplasmic shuttling. Lesion of Smad5 in β cells results in hyperglycemia and glucose intolerance due to insulin processing and secretion deficiency. The role of Smad5 in regulating insulin processing and secretion attributes to its non-canonical function by regulating V-ATPase activity for granule acidification. Genetic mutation of Smad5 or administration of alkaline water to mirror cytosolic alkalization ameliorated glucose intolerance in high-fat diet (HFD)-treated mice. Collectively, our findings suggest that pHc is a direct nexus in linking environmental cues with insulin processing and secretion in β cells.
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Affiliation(s)
- Yujiang Fang
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China.
| | - Hexi Feng
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Bowen Zhang
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Shuwei Zhang
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Yanjie Zhou
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Pengcheng Hao
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Zhongshu Zhou
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Shanshan Zhou
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Nan Li
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Yi Hui
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Lin Ma
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Jie Xiong
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China
| | - Jinjin Wu
- Shanghai Children's Medical Center, Shanghai Jiaotong University, Shanghai, China
| | - Ling Liu
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China.
| | - Xiaoqing Zhang
- Translational Medical Center for Stem Cell Therapy, Shanghai East Hospital, School of Medicine, Tongji University, Shanghai, China; Translational Research Institute of Brain and Brain-Like Intelligence, Shanghai Fourth People's Hospital, School of Medicine, Tongji University, Shanghai, China; Key Laboratory of Spine and Spinal Cord Injury Repair and Regeneration of Ministry of Education, Orthopaedic Department of Tongji Hospital, Shanghai, China; Shanghai Institute of Stem Cell Research and Clinical Translation, Shanghai, China; Key Laboratory of Neuroregeneration of Shanghai Universities, School of Medicine, Tongji University, Shanghai, China; Clinical Center for Brain and Spinal Cord Research, Tongji University, Shanghai, China.
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Zapata RC, Carretero M, Reis FCG, Chaudry BS, Ofrecio J, Zhang D, Sasik R, Ciaraldi T, Petrascheck M, Osborn O. Adipocytes control food intake and weight regain via Vacuolar-type H + ATPase. Nat Commun 2022; 13:5092. [PMID: 36042358 PMCID: PMC9427743 DOI: 10.1038/s41467-022-32764-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Accepted: 08/12/2022] [Indexed: 11/10/2022] Open
Abstract
Energy metabolism becomes dysregulated in individuals with obesity and many of these changes persist after weight loss and likely play a role in weight regain. In these studies, we use a mouse model of diet-induced obesity and weight loss to study the transcriptional memory of obesity. We found that the 'metabolic memory' of obesity is predominantly localized in adipocytes. Utilizing a C. elegans-based food intake assay, we identify 'metabolic memory' genes that play a role in food intake regulation. We show that expression of ATP6v0a1, a subunit of V-ATPase, is significantly induced in both obese mouse and human adipocytes that persists after weight loss. C. elegans mutants deficient in Atp6v0A1/unc32 eat less than WT controls. Adipocyte-specific Atp6v0a1 knockout mice have reduced food intake and gain less weight in response to HFD. Pharmacological disruption of V-ATPase assembly leads to decreased food intake and less weight re-gain. In summary, using a series of genetic tools from invertebrates to vertebrates, we identify ATP6v0a1 as a regulator of peripheral metabolic memory, providing a potential target for regulation of food intake, weight loss maintenance and the treatment of obesity.
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Affiliation(s)
- Rizaldy C Zapata
- Division of Endocrinology and Metabolism, School of Medicine, University of California San Diego, La Jolla, CA, 92093, USA
| | - Maria Carretero
- Department of Molecular Medicine and Department of Neuroscience, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Felipe Castellani Gomes Reis
- Division of Endocrinology and Metabolism, School of Medicine, University of California San Diego, La Jolla, CA, 92093, USA
| | - Besma S Chaudry
- Division of Endocrinology and Metabolism, School of Medicine, University of California San Diego, La Jolla, CA, 92093, USA
| | - Jachelle Ofrecio
- Division of Endocrinology and Metabolism, School of Medicine, University of California San Diego, La Jolla, CA, 92093, USA
| | - Dinghong Zhang
- Division of Endocrinology and Metabolism, School of Medicine, University of California San Diego, La Jolla, CA, 92093, USA
| | - Roman Sasik
- Center for Computational Biology & Bioinformatics, School of Medicine, University of California San Diego, La Jolla, CA, 92093, USA
| | - Theodore Ciaraldi
- Division of Endocrinology and Metabolism, School of Medicine, University of California San Diego, La Jolla, CA, 92093, USA
- VA San Diego Healthcare System, La Jolla, CA, 92037, USA
| | - Michael Petrascheck
- Department of Molecular Medicine and Department of Neuroscience, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Olivia Osborn
- Division of Endocrinology and Metabolism, School of Medicine, University of California San Diego, La Jolla, CA, 92093, USA.
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Coordinated glucose-induced Ca 2+ and pH responses in yeast Saccharomyces cerevisiae. Cell Calcium 2021; 100:102479. [PMID: 34610487 DOI: 10.1016/j.ceca.2021.102479] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 09/23/2021] [Accepted: 09/24/2021] [Indexed: 12/13/2022]
Abstract
Ca2+ and pH homeostasis are closely intertwined and this interrelationship is crucial in the cells' ability to adapt to varying environmental conditions. To further understand this Ca2+-pH link, cytosolic Ca2+ was monitored using the aequorin-based bioluminescent assay in parallel with fluorescence reporter-based assays to monitor plasma membrane potentials and intracellular (cytosolic and vacuolar) pH in yeast Saccharomyces cerevisiae. At external pH 5, starved yeast cells displayed depolarized membrane potentials and responded to glucose re-addition with small Ca2+ transients accompanied by cytosolic alkalinization and profound vacuolar acidification. In contrast, starved cells at external pH 7 were hyperpolarized and glucose re-addition induced large Ca2+ transients and vacuolar alkalinization. In external Ca2+-free medium, glucose-induced pH responses were not affected but Ca2+ transients were abolished, indicating that the intracellular [Ca2+] increase was not prerequisite for activation of the two primary proton pumps, being Pma1 at the plasma membrane and the vacuolar and Golgi localized V-ATPases. A reduction in Pma1 expression resulted in membrane depolarization and reduced Ca2+ transients, indicating that the membrane hyperpolarization generated by Pma1 activation governed the Ca2+ influx that is associated with glucose-induced Ca2+ transients. Loss of V-ATPase activity through concanamycin A inhibition did not alter glucose-induced cytosolic pH responses but affected vacuolar pH changes and Ca2+ transients, indicating that the V-ATPase established vacuolar proton gradient is substantial for organelle H+/Ca2+ exchange. Finally, a systematic analysis of yeast deletion strains allowed us to reveal an essential role for both the vacuolar H+/Ca2+ exchanger Vcx1 and the Golgi exchanger Gdt1 in the dissipation of intracellular Ca2+.
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Tang Q, Liu M, Liu Y, Hwang RD, Zhang T, Wang J. NDST3 deacetylates α-tubulin and suppresses V-ATPase assembly and lysosomal acidification. EMBO J 2021; 40:e107204. [PMID: 34435379 PMCID: PMC8488563 DOI: 10.15252/embj.2020107204] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2020] [Revised: 07/18/2021] [Accepted: 07/20/2021] [Indexed: 12/18/2022] Open
Abstract
Lysosomes are key organelles maintaining cellular homeostasis in health and disease. Here, we report the identification of N‐deacetylase and N‐sulfotransferase 3 (NDST3) as a potent regulator of lysosomal functions through an unbiased genetic screen. NDST3 constitutes a new member of the histone deacetylase (HDAC) family and catalyzes the deacetylation of α‐tubulin. Loss of NDST3 promotes assembly of the V‐ATPase holoenzyme on the lysosomal membrane and thereby increases the acidification of the organelle. NDST3 is downregulated in tissues and cells from patients carrying the C9orf72 hexanucleotide repeat expansion linked to the neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Deficiency in C9orf72 decreases the level of NDST3, and downregulation of NDST3 exacerbates the proteotoxicity of poly‐dipeptides generated from the C9orf72 hexanucleotide repeats. These results demonstrate a previously unknown regulatory mechanism through which microtubule acetylation regulates lysosomal activities and suggest that NDST3 could be targeted to modulate microtubule and lysosomal functions in relevant diseases.
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Affiliation(s)
- Qing Tang
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA.,Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Mingming Liu
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA.,Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Yang Liu
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA.,Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Ran-Der Hwang
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA.,Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Tao Zhang
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA.,Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Jiou Wang
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD, USA.,Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, MD, USA
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Karanth DS, Martin ML, Holliday LS. Plasma Membrane Receptors Involved in the Binding and Response of Osteoclasts to Noncellular Components of the Bone. Int J Mol Sci 2021; 22:ijms221810097. [PMID: 34576260 PMCID: PMC8466431 DOI: 10.3390/ijms221810097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 09/13/2021] [Accepted: 09/16/2021] [Indexed: 12/21/2022] Open
Abstract
Osteoclasts differentiate from hematopoietic cells and resorb the bone in response to various signals, some of which are received directly from noncellular elements of the bone. In vitro, adherence to the bone triggers the reduction of cell–cell fusion events between osteoclasts and the activation of osteoclasts to form unusual dynamic cytoskeletal and membrane structures that are required for degrading the bone. Integrins on the surface of osteoclasts are known to receive regulatory signals from the bone matrix. Regulation of the availability of these signals is accomplished by enzymatic alterations of the bone matrix by protease activity and phosphorylation/dephosphorylation events. Other membrane receptors are present in osteoclasts and may interact with as yet unidentified signals in the bone. Bone mineral has been shown to have regulatory effects on osteoclasts, and osteoclast activity is also directly modulated by mechanical stress. As understanding of how osteoclasts and other bone cells interact with the bone has emerged, increasingly sophisticated efforts have been made to create bone biomimetics that reproduce both the structural properties of the bone and the bone’s ability to regulate osteoclasts and other bone cells. A more complete understanding of the interactions between osteoclasts and the bone may lead to new strategies for the treatment of bone diseases and the production of bone biomimetics to repair defects.
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Affiliation(s)
- Divakar S. Karanth
- Department of Orthodontics, College of Dentistry, University of Florida, Gainesville, FL 32610, USA; (D.S.K.); (M.L.M.)
| | - Macey L. Martin
- Department of Orthodontics, College of Dentistry, University of Florida, Gainesville, FL 32610, USA; (D.S.K.); (M.L.M.)
| | - Lexie S. Holliday
- Department of Orthodontics, College of Dentistry, University of Florida, Gainesville, FL 32610, USA; (D.S.K.); (M.L.M.)
- Department of Anatomy & Cell Biology, College of Medicine, University of Florida, Gainesville, FL 32610, USA
- Correspondence:
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6
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Eaton AF, Merkulova M, Brown D. The H +-ATPase (V-ATPase): from proton pump to signaling complex in health and disease. Am J Physiol Cell Physiol 2020; 320:C392-C414. [PMID: 33326313 PMCID: PMC8294626 DOI: 10.1152/ajpcell.00442.2020] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
A primary function of the H+-ATPase (or V-ATPase) is to create an electrochemical proton gradient across eukaryotic cell membranes, which energizes fundamental cellular processes. Its activity allows for the acidification of intracellular vesicles and organelles, which is necessary for many essential cell biological events to occur. In addition, many specialized cell types in various organ systems such as the kidney, bone, male reproductive tract, inner ear, olfactory mucosa, and more, use plasma membrane V-ATPases to perform specific activities that depend on extracellular acidification. It is, however, increasingly apparent that V-ATPases are central players in many normal and pathophysiological processes that directly influence human health in many different and sometimes unexpected ways. These include cancer, neurodegenerative diseases, diabetes, and sensory perception, as well as energy and nutrient-sensing functions within cells. This review first covers the well-established role of the V-ATPase as a transmembrane proton pump in the plasma membrane and intracellular vesicles and outlines factors contributing to its physiological regulation in different cell types. This is followed by a discussion of the more recently emerging unconventional roles for the V-ATPase, such as its role as a protein interaction hub involved in cell signaling, and the (patho)physiological implications of these interactions. Finally, the central importance of endosomal acidification and V-ATPase activity on viral infection will be discussed in the context of the current COVID-19 pandemic.
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Affiliation(s)
- Amity F Eaton
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Maria Merkulova
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
| | - Dennis Brown
- Program in Membrane Biology and Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts
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Laiouar S, Berns N, Brech A, Riechmann V. RabX1 Organizes a Late Endosomal Compartment that Forms Tubular Connections to Lysosomes Consistent with a “Kiss and Run” Mechanism. Curr Biol 2020; 30:1177-1188.e5. [DOI: 10.1016/j.cub.2020.01.048] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 12/17/2019] [Accepted: 01/14/2020] [Indexed: 01/26/2023]
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8
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Jung YS, Park JI. Wnt signaling in cancer: therapeutic targeting of Wnt signaling beyond β-catenin and the destruction complex. Exp Mol Med 2020; 52:183-191. [PMID: 32037398 PMCID: PMC7062731 DOI: 10.1038/s12276-020-0380-6] [Citation(s) in RCA: 281] [Impact Index Per Article: 70.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 12/20/2019] [Accepted: 12/26/2019] [Indexed: 02/07/2023] Open
Abstract
Wnt/β-catenin signaling is implicated in many physiological processes, including development, tissue homeostasis, and tissue regeneration. In human cancers, Wnt/β-catenin signaling is highly activated, which has led to the development of various Wnt signaling inhibitors for cancer therapies. Nonetheless, the blockade of Wnt signaling causes side effects such as impairment of tissue homeostasis and regeneration. Recently, several studies have identified cancer-specific Wnt signaling regulators. In this review, we discuss the Wnt inhibitors currently being used in clinical trials and suggest how additional cancer-specific regulators could be utilized to treat Wnt signaling-associated cancer.
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Affiliation(s)
- Youn-Sang Jung
- 0000 0001 2291 4776grid.240145.6Department of Experimental Radiation Oncology, Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030 USA
| | - Jae-Il Park
- 0000 0001 2291 4776grid.240145.6Department of Experimental Radiation Oncology, Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030 USA ,0000 0001 2291 4776grid.240145.6Graduate School of Biomedical Sciences, The University of Texas MD Anderson Cancer Center, Houston, TX 77030 USA ,0000 0001 2291 4776grid.240145.6Program in Genetics and Epigenetics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030 USA
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9
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D'Souza Z, Blackburn JB, Kudlyk T, Pokrovskaya ID, Lupashin VV. Defects in COG-Mediated Golgi Trafficking Alter Endo-Lysosomal System in Human Cells. Front Cell Dev Biol 2019; 7:118. [PMID: 31334232 PMCID: PMC6616090 DOI: 10.3389/fcell.2019.00118] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Accepted: 06/11/2019] [Indexed: 12/27/2022] Open
Abstract
The conserved oligomeric complex (COG) is a multi-subunit vesicle tethering complex that functions in retrograde trafficking at the Golgi. We have previously demonstrated that the formation of enlarged endo-lysosomal structures (EELSs) is one of the major glycosylation-independent phenotypes of cells depleted for individual COG complex subunits. Here, we characterize the EELSs in HEK293T cells using microscopy and biochemical approaches. Our analysis revealed that the EELSs are highly acidic and that vATPase-dependent acidification is essential for the maintenance of this enlarged compartment. The EELSs are accessible to both trans-Golgi enzymes and endocytic cargo. Moreover, the EELSs specifically accumulate endolysosomal proteins Lamp2, CD63, Rab7, Rab9, Rab39, Vamp7, and STX8 on their surface. The EELSs are distinct from lysosomes and do not accumulate active Cathepsin B. Retention using selective hooks (RUSH) experiments revealed that biosynthetic cargo mCherry-Lamp1 reaches the EELSs much faster as compared to both receptor-mediated and soluble endocytic cargo, indicating TGN origin of the EELSs. In support to this hypothesis, EELSs are enriched with TGN specific lipid PI4P. Additionally, analysis of COG4/VPS54 double KO cells revealed that the activity of the GARP tethering complex is necessary for EELSs’ accumulation, indicating that protein mistargeting and the imbalance of Golgi-endosome membrane flow leads to the formation of EELSs in COG-deficient cells. The EELSs are likely to serve as a degradative storage hybrid organelle for mistargeted Golgi enzymes and underglycosylated glycoconjugates. To our knowledge this is the first report of the formation of an enlarged hybrid endosomal compartment in a response to malfunction of the intra-Golgi trafficking machinery.
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Affiliation(s)
- Zinia D'Souza
- Department of Physiology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Jessica Bailey Blackburn
- Department of Physiology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Tetyana Kudlyk
- Department of Physiology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Irina D Pokrovskaya
- Department of Physiology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
| | - Vladimir V Lupashin
- Department of Physiology, University of Arkansas for Medical Sciences, Little Rock, AR, United States
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10
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Lipids and lipid domains of the yeast vacuole. Biochem Soc Trans 2018; 46:1047-1054. [PMID: 30242116 DOI: 10.1042/bst20180120] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2018] [Revised: 07/30/2018] [Accepted: 08/01/2018] [Indexed: 11/17/2022]
Abstract
The membrane raft has been a focus of intensive research for the past two decades. Liquid-ordered domains form in artificial liposomes containing sterol and saturated lipids, but their presence in living cell membranes has been controversial. The yeast vacuole is exceptional in that micron-sized raft-like domains form in the stationary phase and under several other conditions. The sterol content of the vacuole in the log phase is much lower than that of liposomes showing liquid-ordered domains, suggesting that sterols may need to be supplied to the vacuole for the raft-like domain formation. We will discuss how lipids and lipid domains are organized in the vacuolar membrane and examine whether evidence is strong enough to conclude that the observed micron-sized domains are rafts.
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11
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Marshansky V, Rubinstein JL, Grüber G. Eukaryotic V-ATPase: novel structural findings and functional insights. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:857-79. [PMID: 24508215 DOI: 10.1016/j.bbabio.2014.01.018] [Citation(s) in RCA: 127] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2013] [Revised: 12/25/2013] [Accepted: 01/27/2014] [Indexed: 02/06/2023]
Abstract
The eukaryotic V-type adenosine triphosphatase (V-ATPase) is a multi-subunit membrane protein complex that is evolutionarily related to F-type adenosine triphosphate (ATP) synthases and A-ATP synthases. These ATPases/ATP synthases are functionally conserved and operate as rotary proton-pumping nano-motors, invented by Nature billions of years ago. In the first part of this review we will focus on recent structural findings of eukaryotic V-ATPases and discuss the role of different subunits in the function of the V-ATPase holocomplex. Despite structural and functional similarities between rotary ATPases, the eukaryotic V-ATPases are the most complex enzymes that have acquired some unconventional cellular functions during evolution. In particular, the novel roles of V-ATPases in the regulation of cellular receptors and their trafficking via endocytotic and exocytotic pathways were recently uncovered. In the second part of this review we will discuss these unique roles of V-ATPases in modulation of function of cellular receptors, involved in the development and progression of diseases such as cancer and diabetes as well as neurodegenerative and kidney disorders. Moreover, it was recently revealed that the V-ATPase itself functions as an evolutionarily conserved pH sensor and receptor for cytohesin-2/Arf-family GTP-binding proteins. Thus, in the third part of the review we will evaluate the structural basis for and functional insights into this novel concept, followed by the analysis of the potentially essential role of V-ATPase in the regulation of this signaling pathway in health and disease. Finally, future prospects for structural and functional studies of the eukaryotic V-ATPase will be discussed.
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Affiliation(s)
- Vladimir Marshansky
- Center for Systems Biology, Program in Membrane Biology, Division of Nephrology, Simches Research Center, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA; Department of Medicine, Harvard Medical School, Boston, MA 02114, USA; Kadmon Pharmaceuticals Corporation, Alexandria Center for Life Science, 450 East 29th Street, New York, NY 10016, USA.
| | - John L Rubinstein
- Molecular Structure and Function Program, The Hospital for Sick Children Research Institute, University of Toronto, Toronto, ON M5G 1X8, Canada; Department of Biochemistry, University of Toronto, Toronto, ON M5G 1X8, Canada; Department of Medical Biophysics, University of Toronto, Toronto, ON M5G 1X8, Canada
| | - Gerhard Grüber
- Nanyang Technological University, Division of Structural Biology and Biochemistry, School of Biological Sciences, Singapore 637551, Republic of Singapore; Bioinformatics Institute, A(⁎)STAR, 60 Nanyang Drive, Singapore 637551, Republic of Singapore
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12
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Smardon AM, Diab HI, Tarsio M, Diakov TT, Nasab ND, West RW, Kane PM. The RAVE complex is an isoform-specific V-ATPase assembly factor in yeast. Mol Biol Cell 2013; 25:356-67. [PMID: 24307682 PMCID: PMC3907276 DOI: 10.1091/mbc.e13-05-0231] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Vacuolar H+-ATPases (V-ATPases) acidify multiple organelles, and subunit isoforms help impart organelle-specific regulation of acidification. The regulator of ATPase of vacuoles and endosomes (RAVE) complex regulates organelle acidification by promoting V-ATPase assembly. This work demonstrates that RAVE is the first identified isoform-specific V-ATPase assembly factor required for control of vacuolar acidification. The regulator of ATPase of vacuoles and endosomes (RAVE) complex is implicated in vacuolar H+-translocating ATPase (V-ATPase) assembly and activity. In yeast, rav1∆ mutants exhibit a Vma− growth phenotype characteristic of loss of V-ATPase activity only at high temperature. Synthetic genetic analysis identified mutations that exhibit a full, temperature-independent Vma− growth defect when combined with the rav1∆ mutation. These include class E vps mutations, which compromise endosomal sorting. The synthetic Vma− growth defect could not be attributed to loss of vacuolar acidification in the double mutants, as there was no vacuolar acidification in the rav1∆ mutant. The yeast V-ATPase a subunit is present as two isoforms, Stv1p in Golgi and endosomes and Vph1p in vacuoles. Rav1p interacts directly with the N-terminal domain of Vph1p. STV1 overexpression suppressed the growth defects of both rav1∆ and rav1∆vph1∆, and allowed RAVE-independent assembly of active Stv1p-containing V-ATPases in vacuoles. Mutations causing synthetic genetic defects in combination with rav1∆ perturbed the normal localization of Stv1–green fluorescent protein. We propose that RAVE is necessary for assembly of Vph1-containing V-ATPase complexes but not Stv1-containing complexes. Synthetic Vma− phenotypes arise from defects in Vph1p-containing complexes caused by rav1∆, combined with defects in Stv1p-containing V-ATPases caused by the second mutation. Thus RAVE is the first isoform-specific V-ATPase assembly factor.
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Affiliation(s)
- Anne M Smardon
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210
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13
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Feng M, Fang Y, Han B, Zhang L, Lu X, Li J. Novel aspects of understanding molecular working mechanisms of salivary glands of worker honeybees (Apis mellifera) investigated by proteomics and phosphoproteomics. J Proteomics 2013; 87:1-15. [DOI: 10.1016/j.jprot.2013.05.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 05/12/2013] [Accepted: 05/13/2013] [Indexed: 01/23/2023]
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14
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Petzoldt AG, Gleixner EM, Fumagalli A, Vaccari T, Simons M. Elevated expression of the V-ATPase C subunit triggers JNK-dependent cell invasion and overgrowth in a Drosophila epithelium. Dis Model Mech 2013; 6:689-700. [PMID: 23335205 PMCID: PMC3634652 DOI: 10.1242/dmm.010660] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The C subunit of the vacuolar H+-ATPase or V-ATPase regulates the activity and assembly of the proton pump at cellular membranes. It has been shown to be strongly upregulated in oral squamous cell carcinoma, a highly metastatic epithelial cancer. In addition, increased V-ATPase activity appears to correlate with invasiveness of cancer cells, but the underlying mechanism is largely unknown. Using the Drosophila wing imaginal epithelium as an in vivo model system, we demonstrate that overexpression of Vha44, the Drosophila orthologue of the C subunit, causes a tumor-like tissue transformation in cells of the wing epithelium. Overexpressing cells are excluded from the epithelium and acquire invasive properties while displaying high apoptotic rates. Blocking apoptosis in these cells unmasks a strong proliferation stimulus, leading to overgrowth. Furthermore, we show that excess Vha44 greatly increases acidification of endocytic compartments and interferes with endosomal trafficking. As a result, cargoes such as GFP-Lamp1 and Notch accumulate in highly acidified enlarged endolysosomal compartments. Consistent with previous reports on the endocytic activation of Eiger/JNK signaling, we find that V-ATPase stimulation by Vha44 causes JNK signaling activation whereas downmodulation of JNK signaling rescues the invasive phenotypes. In summary, our in vivo-findings demonstrate that increased levels of V-ATPase C subunit induce a Eiger/JNK-dependent cell transformation within an epithelial organ that recapitulates early carcinoma stages.
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Affiliation(s)
- Astrid G Petzoldt
- Center for Systems Biology (ZBSA), University of Freiburg, Habsburgerstr. 49, 79104 Freiburg, Germany
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15
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Xu Y, Parmar A, Roux E, Balbis A, Dumas V, Chevalier S, Posner BI. Epidermal growth factor-induced vacuolar (H+)-atpase assembly: a role in signaling via mTORC1 activation. J Biol Chem 2012; 287:26409-22. [PMID: 22689575 DOI: 10.1074/jbc.m112.352229] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Using proteomics and immunofluorescence, we demonstrated epidermal growth factor (EGF) induced recruitment of extrinsic V(1) subunits of the vacuolar (H(+))-ATPase (V-ATPase) to rat liver endosomes. This was accompanied by reduced vacuolar pH. Bafilomycin, an inhibitor of V-ATPase, inhibited EGF-stimulated DNA synthesis and mammalian target of rapamycin complex 1 (mTORC1) activation as indicated by a decrease in eukaryotic initiation factor 4E-binding 1 (4E-BP1) phosphorylation and p70 ribosomal S6 protein kinase (p70S6K) phosphorylation and kinase activity. There was no corresponding inhibition of EGF-induced Akt and extracellular signal-regulated kinase (Erk) activation. Chloroquine, a neutralizer of vacuolar pH, mimicked bafilomycin effects. Bafilomycin did not inhibit the association of mTORC1 with Raptor nor did it affect AMP-activated protein kinase activity. Rather, the intracellular concentrations of essential but not non-essential amino acids were decreased by bafilomycin in EGF-treated primary rat hepatocytes. Cycloheximide, a translation elongation inhibitor known to augment intracellular amino acid levels, prevented the effect of bafilomycin on amino acids levels and completely reversed its inhibition of EGF-induced mTORC1 activation. In vivo administration of EGF stimulated the recruitment of Ras homologue enriched in brain (Rheb) but not mammalian target of rapamycin (mTOR) to endosomes and lysosomes. This was inhibited by chloroquine treatment. Our results suggest a role for vacuolar acidification in EGF signaling to mTORC1.
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Affiliation(s)
- Yanqing Xu
- Polypeptide Hormone Laboratory, Faculty of Medicine, McGill University, Montreal, Quebec H3A 2B2, Canada
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16
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Giraudo M, Califano J, Hilliou F, Tran T, Taquet N, Feyereisen R, Le Goff G. Effects of hormone agonists on Sf9 cells, proliferation and cell cycle arrest. PLoS One 2011; 6:e25708. [PMID: 21991338 PMCID: PMC3185036 DOI: 10.1371/journal.pone.0025708] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Accepted: 09/08/2011] [Indexed: 12/19/2022] Open
Abstract
Methoxyfenozide and methoprene are two insecticides that mimic the action of the main hormones involved in the control of insect growth and development, 20-hydroxyecdysone and juvenile hormone. We investigated their effect on the Spodoptera frugiperda Sf9 cell line. Methoxyfenozide was more toxic than methoprene in cell viability tests and more potent in the inhibition of cellular proliferation. Cell growth arrest occurred in the G2/M phase after a methoprene treatment and more modestly in G1 after methoxyfenozide treatment. Microarray experiments and real-time quantitative PCR to follow the expression of nuclear receptors ultraspiracle and ecdysone receptor were performed to understand the molecular action of these hormone agonists. Twenty-six genes were differentially expressed after methoxyfenozide treatment and 55 genes after methoprene treatment with no gene in common between the two treatments. Our results suggest two different signalling pathways in Sf9 cells.
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Affiliation(s)
- Maeva Giraudo
- Institut National de la Recherche Agronomique, UMR 1301 Interactions Biotiques et Santé Végétale, Centre National de la Recherche Scientifique, UMR 6243, Université de Nice Sophia Antipolis, Sophia-Antipolis, France
- UMR 6023 CNRS-Université Blaise Pascal, Bât. Biologie A – Campus des Cézeaux, Aubière, France
| | - Jérôme Califano
- Institut National de la Recherche Agronomique, UMR 1301 Interactions Biotiques et Santé Végétale, Centre National de la Recherche Scientifique, UMR 6243, Université de Nice Sophia Antipolis, Sophia-Antipolis, France
- Département des affaires réglementaires, Grasse, France
| | - Frédérique Hilliou
- Institut National de la Recherche Agronomique, UMR 1301 Interactions Biotiques et Santé Végétale, Centre National de la Recherche Scientifique, UMR 6243, Université de Nice Sophia Antipolis, Sophia-Antipolis, France
| | - Trang Tran
- Institut National de la Recherche Agronomique, UMR 1301 Interactions Biotiques et Santé Végétale, Centre National de la Recherche Scientifique, UMR 6243, Université de Nice Sophia Antipolis, Sophia-Antipolis, France
- Lanaud Gestion-Pôle de Lanaud, Boisseuil, France
| | - Nathalie Taquet
- Institut National de la Recherche Agronomique, UMR 1301 Interactions Biotiques et Santé Végétale, Centre National de la Recherche Scientifique, UMR 6243, Université de Nice Sophia Antipolis, Sophia-Antipolis, France
- Bioimagerie, Villeneuve Loubet, France
| | - René Feyereisen
- Institut National de la Recherche Agronomique, UMR 1301 Interactions Biotiques et Santé Végétale, Centre National de la Recherche Scientifique, UMR 6243, Université de Nice Sophia Antipolis, Sophia-Antipolis, France
| | - Gaëlle Le Goff
- Institut National de la Recherche Agronomique, UMR 1301 Interactions Biotiques et Santé Végétale, Centre National de la Recherche Scientifique, UMR 6243, Université de Nice Sophia Antipolis, Sophia-Antipolis, France
- * E-mail:
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Merkulova M, Hurtado-Lorenzo A, Hosokawa H, Zhuang Z, Brown D, Ausiello DA, Marshansky V. Aldolase directly interacts with ARNO and modulates cell morphology and acidic vesicle distribution. Am J Physiol Cell Physiol 2011; 300:C1442-55. [PMID: 21307348 DOI: 10.1152/ajpcell.00076.2010] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Previously, we demonstrated that the vacuolar-type H(+)-ATPase (V-ATPase) a2-subunit functions as an endosomal pH sensor that interacts with the ADP-ribosylation factor (Arf) guanine nucleotide exchange factor, ARNO. In the present study, we showed that ARNO directly interacts not only with the a2-subunit but with all a-isoforms (a1-a4) of the V-ATPase, indicating a widespread regulatory interaction between V-ATPase and Arf GTPases. We then extended our search for other ARNO effectors that may modulate V-ATPase-dependent vesicular trafficking events and actin cytoskeleton remodeling. Pull-down experiments using cytosol of mouse proximal tubule cells (MTCs) showed that ARNO interacts with aldolase, but not with other enzymes of the glycolytic pathway. Direct interaction of aldolase with the pleckstrin homology domain of ARNO was revealed by pull-down assays using recombinant proteins, and surface plasmon resonance revealed their high avidity interaction with a dissociation constant: K(D) = 2.84 × 10(-10) M. MTC cell fractionation revealed that aldolase is also associated with membranes of early endosomes. Functionally, aldolase knockdown in HeLa cells produced striking morphological changes accompanied by long filamentous cell protrusions and acidic vesicle redistribution. However, the 50% knockdown we achieved did not modulate the acidification capacity of endosomal/lysosomal compartments. Finally, a combination of small interfering RNA knockdown and overexpression revealed that the expression of aldolase is inversely correlated with gelsolin levels in HeLa cells. In summary, we have shown that aldolase forms a complex with ARNO/Arf6 and the V-ATPase and that it may contribute to remodeling of the actin cytoskeleton and/or the trafficking and redistribution of V-ATPase-dependent acidic compartments via a combination of protein-protein interaction and gene expression mechanisms.
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Affiliation(s)
- Maria Merkulova
- Program in Membrane Biology and Nephrology Division, Center for Systems Biology, Simches Research Center, Massachusetts General Hospital, 185 Cambridge Street, Boston, MA 02114, USA
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18
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Zhang YQ, Gamarra S, Garcia-Effron G, Park S, Perlin DS, Rao R. Requirement for ergosterol in V-ATPase function underlies antifungal activity of azole drugs. PLoS Pathog 2010; 6:e1000939. [PMID: 20532216 PMCID: PMC2880581 DOI: 10.1371/journal.ppat.1000939] [Citation(s) in RCA: 145] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2010] [Accepted: 05/05/2010] [Indexed: 11/19/2022] Open
Abstract
Ergosterol is an important constituent of fungal membranes. Azoles inhibit ergosterol biosynthesis, although the cellular basis for their antifungal activity is not understood. We used multiple approaches to demonstrate a critical requirement for ergosterol in vacuolar H(+)-ATPase function, which is known to be essential for fungal virulence. Ergosterol biosynthesis mutants of S. cerevisiae failed to acidify the vacuole and exhibited multiple vma(-) phenotypes. Extraction of ergosterol from vacuolar membranes also inactivated V-ATPase without disrupting membrane association of its subdomains. In both S. cerevisiae and the fungal pathogen C. albicans, fluconazole impaired vacuolar acidification, whereas concomitant ergosterol feeding restored V-ATPase function and cell growth. Furthermore, fluconazole exacerbated cytosolic Ca(2+) and H(+) surges triggered by the antimicrobial agent amiodarone, and impaired Ca(2+) sequestration in purified vacuolar vesicles. These findings provide a mechanistic basis for the synergy between azoles and amiodarone observed in vitro. Moreover, we show the clinical potential of this synergy in treatment of systemic fungal infections using a murine model of Candidiasis. In summary, we demonstrate a new regulatory component in fungal V-ATPase function, a novel role for ergosterol in vacuolar ion homeostasis, a plausible cellular mechanism for azole toxicity in fungi, and preliminary in vivo evidence for synergism between two antifungal agents. New insights into the cellular basis of azole toxicity in fungi may broaden therapeutic regimens for patient populations afflicted with systemic fungal infections.
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Affiliation(s)
- Yong-Qiang Zhang
- The Johns Hopkins University School of Medicine of Baltimore, Maryland, United States of America
| | - Soledad Gamarra
- Public Health Research Institute, New Jersey Medical School-UMDNJ, Newark, New Jersey, United States of America
| | - Guillermo Garcia-Effron
- Public Health Research Institute, New Jersey Medical School-UMDNJ, Newark, New Jersey, United States of America
| | - Steven Park
- Public Health Research Institute, New Jersey Medical School-UMDNJ, Newark, New Jersey, United States of America
| | - David S. Perlin
- Public Health Research Institute, New Jersey Medical School-UMDNJ, Newark, New Jersey, United States of America
| | - Rajini Rao
- The Johns Hopkins University School of Medicine of Baltimore, Maryland, United States of America
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19
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Diakov TT, Kane PM. Regulation of vacuolar proton-translocating ATPase activity and assembly by extracellular pH. J Biol Chem 2010; 285:23771-8. [PMID: 20511227 DOI: 10.1074/jbc.m110.110122] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Vacuolar proton-translocating ATPases (V-ATPases) are responsible for organelle acidification in all eukaryotic cells. The yeast V-ATPase, known to be regulated by reversible disassembly in response to glucose deprivation, was recently reported to be regulated by extracellular pH as well (Padilla-López, S., and Pearce, D. A. (2006) J. Biol. Chem. 281, 10273-10280). Consistent with those results, we find 57% higher V-ATPase activity in vacuoles isolated after cell growth at extracellular pH of 7 than after growth at pH 5 in minimal medium. Remarkably, under these conditions, the V-ATPase also becomes largely insensitive to reversible disassembly, maintaining a low vacuolar pH and high levels of V(1) subunit assembly, ATPase activity, and proton pumping during glucose deprivation. Cytosolic pH is constant under these conditions, indicating that the lack of reversible disassembly is not a response to altered cytosolic pH. We propose that when alternative mechanisms of vacuolar acidification are not available, maintaining V-ATPase activity becomes a priority, and the pump is not down-regulated in response to energy limitation. These results also suggest that integrated pH and metabolic inputs determine the final assembly state and activity of the V-ATPase.
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Affiliation(s)
- Theodore T Diakov
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13219, USA
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20
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Wieczorek H, Beyenbach KW, Huss M, Vitavska O. Vacuolar-type proton pumps in insect epithelia. ACTA ACUST UNITED AC 2009; 212:1611-9. [PMID: 19448071 DOI: 10.1242/jeb.030007] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Active transepithelial cation transport in insects was initially discovered in Malpighian tubules, and was subsequently also found in other epithelia such as salivary glands, labial glands, midgut and sensory sensilla. Today it appears to be established that the cation pump is a two-component system of a H(+)-transporting V-ATPase and a cation/nH(+) antiporter. After tracing the discovery of the V-ATPase as the energizer of K(+)/nH(+) antiport in the larval midgut of the tobacco hornworm Manduca sexta we show that research on the tobacco hornworm V-ATPase delivered important findings that emerged to be of general significance for our knowledge of V-ATPases, which are ubiquitous and highly conserved proton pumps. We then discuss the V-ATPase in Malpighian tubules of the fruitfly Drosophila melanogaster where the potential of post-genomic biology has been impressively illustrated. Finally we review an integrated physiological approach in Malpighian tubules of the yellow fever mosquito Aedes aegypti which shows that the V-ATPase delivers the energy for both transcellular and paracellular ion transport.
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Affiliation(s)
- Helmut Wieczorek
- Department of Biology/Chemistry, University of Osnabrück, 49069 Osnabrück, Germany.
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21
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Diepholz M, Venzke D, Prinz S, Batisse C, Flörchinger B, Rössle M, Svergun DI, Böttcher B, Féthière J. A Different Conformation for EGC Stator Subcomplex in Solution and in the Assembled Yeast V-ATPase: Possible Implications for Regulatory Disassembly. Structure 2008; 16:1789-98. [DOI: 10.1016/j.str.2008.09.010] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2008] [Revised: 09/17/2008] [Accepted: 09/18/2008] [Indexed: 11/29/2022]
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22
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The yeast lysosome-like vacuole: endpoint and crossroads. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2008; 1793:650-63. [PMID: 18786576 DOI: 10.1016/j.bbamcr.2008.08.003] [Citation(s) in RCA: 293] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2008] [Revised: 08/01/2008] [Accepted: 08/06/2008] [Indexed: 12/21/2022]
Abstract
Fungal vacuoles are acidic organelles with degradative and storage capabilities that have many similarities to mammalian lysosomes and plant vacuoles. In the past several years, well-developed genetic, genomic, biochemical and cell biological tools in S. cerevisiae have provided fresh insights into vacuolar protein sorting, organelle acidification, ion homeostasis, autophagy, and stress-related functions of the vacuole, and these insights have often found parallels in mammalian lysosomes. This review provides a broad overview of the defining features and functions of S. cerevisiae vacuoles and compares these features to mammalian lysosomes. Recent research challenges the traditional view of vacuoles and lysosomes as simply the terminal compartment of biosynthetic and endocytic pathways (i.e. the "garbage dump" of the cell), and suggests instead that these compartments are unexpectedly dynamic and highly regulated.
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23
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Martínez-Muñoz GA, Kane P. Vacuolar and plasma membrane proton pumps collaborate to achieve cytosolic pH homeostasis in yeast. J Biol Chem 2008; 283:20309-19. [PMID: 18502746 DOI: 10.1074/jbc.m710470200] [Citation(s) in RCA: 209] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vacuolar proton-translocating ATPases (V-ATPases) play a central role in organelle acidification in all eukaryotic cells. To address the role of the yeast V-ATPase in vacuolar and cytosolic pH homeostasis, ratiometric pH-sensitive fluorophores specific for the vacuole or cytosol were introduced into wild-type cells and vma mutants, which lack V-ATPase subunits. Transiently glucose-deprived wild-type cells respond to glucose addition with vacuolar acidification and cytosolic alkalinization, and subsequent addition of K(+) ion increases the pH of both the vacuole and cytosol. In contrast, glucose addition results in an increase in vacuolar pH in both vma mutants and wild-type cells treated with the V-ATPase inhibitor concanamycin A. Cytosolic pH homeostasis is also significantly perturbed in the vma mutants. Even at extracellular pH 5, conditions optimal for their growth, cytosolic pH was much lower, and response to glucose was smaller in the mutants. In plasma membrane fractions from the vma mutants, activity of the plasma membrane proton pump, Pma1p, was 65-75% lower than in fractions from wild-type cells. Immunofluorescence microscopy confirmed decreased levels of plasma membrane Pma1p and increased Pma1p at the vacuole and other compartments in the mutants. Pma1p was not mislocalized in concanamycin-treated cells, but a significant reduction in cytosolic pH under all conditions was still observed. We propose that short-term, V-ATPase activity is essential for both vacuolar acidification in response to glucose metabolism and for efficient cytosolic pH homeostasis, and long-term, V-ATPases are important for stable localization of Pma1p at the plasma membrane.
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Affiliation(s)
- Gloria A Martínez-Muñoz
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA.
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24
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Voss M, Vitavska O, Walz B, Wieczorek H, Baumann O. Stimulus-induced phosphorylation of vacuolar H(+)-ATPase by protein kinase A. J Biol Chem 2007; 282:33735-33742. [PMID: 17872947 DOI: 10.1074/jbc.m703368200] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Eukaryotic vacuolar-type H(+)-ATPases (V-ATPases) are regulated by the reversible disassembly of the active V(1)V(0) holoenzyme into a cytosolic V(1) complex and a membrane-bound V(0) complex. The signaling cascades that trigger these events in response to changing cellular conditions are largely unknown. We report that the V(1) subunit C of the tobacco hornworm Manduca sexta interacts with protein kinase A and is the only V-ATPase subunit that is phosphorylated by protein kinase A. Subunit C can be phosphorylated as single polypeptide as well as a part of the V(1) complex but not as a part of the V(1)V(0) holoenzyme. Both the phosphorylated and the unphosphorylated form of subunit C are able to reassociate with the V(1) complex from which subunit C had been removed before. Using salivary glands of the blowfly Calliphora vicina in which V-ATPase reassembly and activity is regulated by the neurohormone serotonin via protein kinase A, we show that the membrane-permeable cAMP analog 8-(4-chlorophenylthio)adenosine-3',5'-cyclic monophosphate (8-CPT-cAMP) causes phosphorylation of subunit C in a tissue homogenate and that phosphorylation is reduced by incubation with antibodies against subunit C. Similarly, incubation of intact salivary glands with 8-CPT-cAMP or serotonin leads to the phosphorylation of subunit C, but this is abolished by H-89, an inhibitor of protein kinase A. These data suggest that subunit C binds to and serves as a substrate for protein kinase A and that this phosphorylation may be a regulatory switch for the formation of the active V(1)V(0) holoenzyme.
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Affiliation(s)
- Martin Voss
- Institut für Biochemie und Biologie, Zoophysiologie, Universität Potsdam, Karl-Liebknecht-Strasse 24/25, D-14476 Potsdam, Germany
| | - Olga Vitavska
- Fachbereich Biologie und Chemie, Tierphysiologie, Universität Osnabrück, Barbarastrasse 11, D-49076 Osnabrück, Germany
| | - Bernd Walz
- Institut für Biochemie und Biologie, Zoophysiologie, Universität Potsdam, Karl-Liebknecht-Strasse 24/25, D-14476 Potsdam, Germany
| | - Helmut Wieczorek
- Fachbereich Biologie und Chemie, Tierphysiologie, Universität Osnabrück, Barbarastrasse 11, D-49076 Osnabrück, Germany
| | - Otto Baumann
- Institut für Biochemie und Biologie, Zoophysiologie, Universität Potsdam, Karl-Liebknecht-Strasse 24/25, D-14476 Potsdam, Germany.
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25
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Clare DK, Orlova EV, Finbow MA, Harrison MA, Findlay JBC, Saibil HR. An expanded and flexible form of the vacuolar ATPase membrane sector. Structure 2006; 14:1149-56. [PMID: 16843896 DOI: 10.1016/j.str.2006.05.014] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Revised: 04/28/2006] [Accepted: 05/02/2006] [Indexed: 11/20/2022]
Abstract
The vacuolar ATPase integral membrane c-ring from Nephrops norvegicus occurs in paired complexes in a double membrane. Using cryo-electron microscopy and single particle image processing of 2D crystals, we have obtained a projection structure of the c-ring of N. norvegicus. The c-ring was found to be very flexible, most likely as a result of an expanded conformation of the c subunits. This structure may support a role for the vacuolar ATPase c-rings in membrane fusion.
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Affiliation(s)
- Daniel K Clare
- School of Crystallography, Birkbeck College, University of London, Malet Street, London WC1E 7HX, United Kingdom
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26
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Ohira M, Smardon AM, Charsky CMH, Liu J, Tarsio M, Kane PM. The E and G Subunits of the Yeast V-ATPase Interact Tightly and Are Both Present at More Than One Copy per V1 Complex. J Biol Chem 2006; 281:22752-60. [PMID: 16774922 DOI: 10.1074/jbc.m601441200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The E and G subunits of the yeast V-ATPase are believed to be part of the peripheral or stator stalk(s) responsible for physically and functionally linking the peripheral V1 sector, responsible for ATP hydrolysis, to the membrane V0 sector, containing the proton pore. The E and G subunits interact tightly and specifically, both on a far Western blot of yeast vacuolar proteins and in the yeast two-hybrid assay. Amino acids 13-79 of the E subunit are critical for the E-G two-hybrid interaction. Different tagged versions of the G subunit were expressed in a diploid cell, and affinity purification of cytosolic V1 sectors via a FLAG-tagged G subunit resulted in copurification of a Myc-tagged G subunit, implying more than one G subunit was present in each V1 complex. Similarly, hemagglutinin-tagged E subunit was able to affinity-purify V1 sectors containing an untagged version of the E subunit from heterozygous diploid cells, suggesting that more than one E subunit is present. Overexpression of the subunit G results in a destabilization of subunit E similar to that seen in the complete absence of subunit G (Tomashek, J. J., Graham, L. A., Hutchins, M. U., Stevens, T. H., and Klionsky, D. J. (1997) J. Biol. Chem. 272, 26787-26793). These results are consistent with recent models showing at least two peripheral stalks connecting the V1 and V0 sectors of the V-ATPase and would allow both stalks to be based on an EG dimer.
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Affiliation(s)
- Masashi Ohira
- Department of Biochemistry and Molecular Biology, State University of New York Upstate Medical University, Syracuse, New York 13210, USA
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27
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Abstract
All eukaryotic cells contain multiple acidic organelles, and V-ATPases are central players in organelle acidification. Not only is the structure of V-ATPases highly conserved among eukaryotes, but there are also many regulatory mechanisms that are similar between fungi and higher eukaryotes. These mechanisms allow cells both to regulate the pHs of different compartments and to respond to changing extracellular conditions. The Saccharomyces cerevisiae V-ATPase has emerged as an important model for V-ATPase structure and function in all eukaryotic cells. This review discusses current knowledge of the structure, function, and regulation of the V-ATPase in S. cerevisiae and also examines the relationship between biosynthesis and transport of V-ATPase and compartment-specific regulation of acidification.
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Affiliation(s)
- Patricia M Kane
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 East Adams St., Syracuse, NY 13210, USA.
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28
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Dettmer J, Hong-Hermesdorf A, Stierhof YD, Schumacher K. Vacuolar H+-ATPase activity is required for endocytic and secretory trafficking in Arabidopsis. THE PLANT CELL 2006; 18:715-30. [PMID: 16461582 PMCID: PMC1383645 DOI: 10.1105/tpc.105.037978] [Citation(s) in RCA: 678] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
In eukaryotic cells, compartments of the highly dynamic endomembrane system are acidified to varying degrees by the activity of vacuolar H(+)-ATPases (V-ATPases). In the Arabidopsis thaliana genome, most V-ATPase subunits are encoded by small gene families, thus offering potential for a multitude of enzyme complexes with different kinetic properties and localizations. We have determined the subcellular localization of the three Arabidopsis isoforms of the membrane-integral V-ATPase subunit VHA-a. Colocalization experiments as well as immunogold labeling showed that VHA-a1 is preferentially found in the trans-Golgi network (TGN), the main sorting compartment of the secretory pathway. Uptake experiments with the endocytic tracer FM4-64 revealed rapid colocalization with VHA-a1, indicating that the TGN may act as an early endosomal compartment. Concanamycin A, a specific V-ATPase inhibitor, blocks the endocytic transport of FM4-64 to the tonoplast, causes the accumulation of FM4-64 together with newly synthesized plasma membrane proteins, and interferes with the formation of brefeldin A compartments. Furthermore, nascent cell plates are rapidly stained by FM4-64, indicating that endocytosed material is redirected into the secretory flow after reaching the TGN. Together, our results suggest the convergence of the early endocytic and secretory trafficking pathways in the TGN.
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Affiliation(s)
- Jan Dettmer
- Center for Plant Molecular Biology-Plant Physiology, Universität Tübingen, 72076 Tübingen, Germany
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29
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Dames P, Zimmermann B, Schmidt R, Rein J, Voss M, Schewe B, Walz B, Baumann O. cAMP regulates plasma membrane vacuolar-type H+-ATPase assembly and activity in blowfly salivary glands. Proc Natl Acad Sci U S A 2006; 103:3926-31. [PMID: 16537461 PMCID: PMC1450166 DOI: 10.1073/pnas.0600011103] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Reversible assembly of the V0V1 holoenzyme from V0 and V1 subcomplexes is a widely used mechanism for regulation of vacuolar-type H+-ATPases (V-ATPases) in animal cells. In the blowfly (Calliphora vicina) salivary gland, V-ATPase is located in the apical membrane of the secretory cells and energizes the secretion of a KCl-rich saliva in response to the hormone serotonin. We have examined whether the cAMP pathway, known to be activated by serotonin, controls V-ATPase assembly and activity. Fluorescence measurements of pH changes at the luminal surface of isolated glands demonstrate that cAMP, Sp-adenosine-3',5'-cyclic monophosphorothioate, or forskolin, similar to serotonin, cause V-ATPase-dependent luminal acidification. In addition, V-ATPase-dependent ATP hydrolysis increases upon treatment with these agents. Immunofluorescence microscopy and pelleting assays have demonstrated further that V1 components become translocated from the cytoplasm to the apical membrane and V-ATPase holoenzymes are assembled at the apical membrane during conditions that increase intracellular cAMP. Because these actions occur without a change in cytosolic Ca2+, our findings suggest that the cAMP pathway mediates the reversible assembly and activation of V-ATPase molecules at the apical membrane upon hormonal stimulus.
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Affiliation(s)
- Petra Dames
- *Institut für Biochemie und Biologie, Universität Potsdam, D-14415 Potsdam, Germany; and
| | - Bernhard Zimmermann
- *Institut für Biochemie und Biologie, Universität Potsdam, D-14415 Potsdam, Germany; and
- Advanced Imaging Microscopy, Carl Zeiss Jena, D-07745 Jena, Germany
| | - Ruth Schmidt
- *Institut für Biochemie und Biologie, Universität Potsdam, D-14415 Potsdam, Germany; and
| | - Julia Rein
- *Institut für Biochemie und Biologie, Universität Potsdam, D-14415 Potsdam, Germany; and
| | - Martin Voss
- *Institut für Biochemie und Biologie, Universität Potsdam, D-14415 Potsdam, Germany; and
| | - Bettina Schewe
- *Institut für Biochemie und Biologie, Universität Potsdam, D-14415 Potsdam, Germany; and
| | - Bernd Walz
- *Institut für Biochemie und Biologie, Universität Potsdam, D-14415 Potsdam, Germany; and
| | - Otto Baumann
- *Institut für Biochemie und Biologie, Universität Potsdam, D-14415 Potsdam, Germany; and
- To whom correspondence should be addressed. E-mail:
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30
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Ryu J, Kim H, Lee SK, Chang EJ, Kim HJ, Kim HH. Proteomic identification of the TRAF6 regulation of vacuolar ATPase for osteoclast function. Proteomics 2006; 5:4152-60. [PMID: 16196101 DOI: 10.1002/pmic.200402035] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Osteoclasts are cells specialized for bone resorption. For osteoclast activation, tumor necrosis factor receptor-associated factor 6 (TRAF6) plays a pivotal role. To find new molecules that bind TRAF6 and have a function in osteoclast activation, we employed a proteomic approach. TRAF6-binding proteins were purified from osteoclast cell lysates by affinity chromatography and their identity was disclosed by MS. The identified proteins included several heat shock proteins, actin and actin-binding proteins, and vacuolar ATPase (V-ATPase). V-ATPase, documented for a great increase in expression during osteoclast differentiation, is an important enzyme for osteoclast function; it transports proton to resorption lacunae for hydroxyapatite dissolution. The binding of V-ATPase with TRAF6 was confirmed both in vitro by GST pull-down assays and in osteoclasts by co-immunoprecipitation and confocal microscopy experiments. In addition, the V-ATPase activity associated with TRAF6 increased in osteoclasts stimulated with receptor activator of nuclear factor kappaB ligand (RANKL). Furthermore, a dominant-negative form of TRAF6 abrogated the RANKL stimulation of V-ATPase activity. Our study identified V-ATPase as a TRAF6-binding protein using a proteomics strategy and proved a direct link between these two important molecules for osteoclast function.
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Affiliation(s)
- Jiyoon Ryu
- Department of Cell and Developmental Biology, Dental Research Institute, College of Dentistry, Seoul National University, Seoul, Korea
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31
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Abstract
The yeast V-ATPase has emerged as an excellent model for other eukaryotic V-ATPases. In this review, recent biochemical and genomic studies of the yeast V-ATPase are described, with a focus on: 1) the role of V(1) subunit H in coupling ATP hydrolysis and proton pumping and 2) identification of the full set of yeast haploid deletion mutants that exhibit the pH and calcium-sensitive growth characteristic of loss of V-ATPase activity. The combination of "close-up" biochemical views of V-ATPase structure and mechanism and "geomic" views of its functional reach promises to provide new insights into the physiological of V-ATPases.
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Affiliation(s)
- Patricia M Kane
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 East Adams St., Syracuse, New York 13210, USA.
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32
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Abstract
The conversion of exogenous and endogenous proteins into immunogenic peptides recognized by T lymphocytes involves a series of proteolytic and other enzymatic events culminating in the formation of peptides bound to MHC class I or class II molecules. Although the biochemistry of these events has been studied in detail, only in the past few years has similar information begun to emerge describing the cellular context in which these events take place. This review thus concentrates on the properties of antigen-presenting cells, especially those aspects of their overall organization, regulation, and intracellular transport that both facilitate and modulate the processing of protein antigens. Emphasis is placed on dendritic cells and the specializations that help account for their marked efficiency at antigen processing and presentation both in vitro and, importantly, in vivo. How dendritic cells handle antigens is likely to be as important a determinant of immunogenicity and tolerance as is the nature of the antigens themselves.
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Affiliation(s)
- E Sergio Trombetta
- Department of Cell Biology and Section of Immunobiology, Ludwig Institute for Cancer Research, Yale University School of Medicine, New Haven, Connecticut 06520-8002, USA.
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33
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Sautin YY, Lu M, Gaugler A, Zhang L, Gluck SL. Phosphatidylinositol 3-kinase-mediated effects of glucose on vacuolar H+-ATPase assembly, translocation, and acidification of intracellular compartments in renal epithelial cells. Mol Cell Biol 2005; 25:575-89. [PMID: 15632060 PMCID: PMC543406 DOI: 10.1128/mcb.25.2.575-589.2005] [Citation(s) in RCA: 170] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vacuolar H+-ATPases (V-ATPases) are a family of ATP-driven proton pumps. They maintain pH gradients between intracellular compartments and are required for proton secretion out of the cytoplasm. Mechanisms of extrinsic control of V-ATPase are poorly understood. Previous studies showed that glucose is an important regulator of V-ATPase assembly in Saccharomyces cerevisiae. Human V-ATPase directly interacts with aldolase, providing a coupling mechanism for glucose metabolism and V-ATPase function. Here we show that glucose is a crucial regulator of V-ATPase in renal epithelial cells and that the effect of glucose is mediated by phosphatidylinositol 3-kinase (PI3K). Glucose stimulates V-ATPase-dependent acidification of the intracellular compartments in human proximal tubular cells HK-2 and porcine renal epithelial cells LLC-PK1. Glucose induces rapid ATP-independent assembly of the V1 and Vo domains of V-ATPase and extensive translocation of the V-ATPase V1 and Vo domains between different membrane pools and between membranes and the cytoplasm. In HK-2 cells, glucose stimulates polarized translocation of V-ATPase to the apical plasma membrane. The effects of glucose on V-ATPase trafficking and assembly can be abolished by pretreatment with the PI3K inhibitor LY294002 and can be reproduced in glucose-deprived cells by adenoviral expression of the constitutively active catalytic subunit p110alpha of PI3K. Taken together these data provide evidence that, in renal epithelial cells, glucose plays an important role in the control of V-ATPase-dependent acidification of intracellular compartments and V-ATPase assembly and trafficking and that the effects of glucose are mediated by PI3K-dependent signaling.
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Affiliation(s)
- Yuri Y Sautin
- Department of Medicine, Division of Nephrology, Box 100224, University of Florida, 1600 SW Archer Rd., Gainesville, FL 32610-0224, USA.
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34
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Coskun U, Rizzo VF, Koch MHJ, Grüber G. Ligand-dependent structural changes in the V(1) ATPase from Manduca sexta. J Bioenerg Biomembr 2005; 36:249-56. [PMID: 15337855 DOI: 10.1023/b:jobb.0000031976.44466.6e] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The response of V(1) ATPase of the tobacco hornworm Manduca sexta to Mg(2+) and nucleotide binding in the presence of the enhancer methanol has been studied by CuCl(2)-induced disulfide formation, fluorescence spectroscopy, and small-angle X-ray scattering. When the V(1) complex was supplemented with CuCl(2) nucleotide-dependence of A-B-E and A-B-E-D cross-linking products was observed in absence of nucleotides and presence of MgADP+Pi but not when MgAMP.PNP or MgADP were added. A zero-length cross-linking product of subunits D and E was formed, supporting their close proximity in the V(1) complex. The catalytic subunit A was reacted with N-4[4-[7-(dimethylamino)-4-methyl]coumarin-3-yl]maleimide (CM) and spectral shifts and changes in fluorescence intensity were detected upon addition of MgAMP.PNP, -ATP, -ADP+Pi, or -ADP. Differences in the fluorescence emission of these nucleotide-binding states were monitored using the intrinsic tryptophan fluorescence. The structural composition of the V(1) ATPase from M. sexta and conformational alterations in this enzyme due to Mg(2+) and nucleotide binding are discussed on the basis of these and previous observations.
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Affiliation(s)
- Unal Coskun
- Universität des Saarlandes, Fachrichtung 2.5 - Biophysik, D-66421 Homburg, Germany
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35
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Vitavska O, Merzendorfer H, Wieczorek H. The V-ATPase Subunit C Binds to Polymeric F-actin as Well as to Monomeric G-actin and Induces Cross-linking of Actin Filaments. J Biol Chem 2005; 280:1070-6. [PMID: 15525650 DOI: 10.1074/jbc.m406797200] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Previously, we have shown that the V-ATPase holoenzyme as well as the V1 complex isolated from the midgut of the tobacco hornworm (Manduca sexta) exhibits the ability of binding to actin filaments via the V1 subunits B and C (Vitavska, O., Wieczorek, H., and Merzendorfer,H. (2003) J. Biol. Chem. 278, 18499-18505). Since the recombinant subunit C not only enhances actin binding of the V1 complex but also can bind separately to F-actin, we analyzed the interaction of recombinant subunit C with actin. We demonstrate that it binds not only to F-actin but also to monomeric G-actin. With dissociation constants of approximately 50 nm, the interaction exhibits a high affinity, and no difference could be observed between binding to ATP-G-actin or ADP-G-actin, respectively. Unlike other proteins such as members of the ADF/cofilin family, which also bind to G- as well as to F-actin, subunit C does not destabilize actin filaments. On the contrary, under conditions where the disassembly of F-actin into G-actin usually occurred, subunit C stabilized F-actin. In addition, it increased the initial rate of actin polymerization in a concentration-dependent manner and was shown to cross-link actin filaments to bundles of varying thickness. Apparently bundling is enabled by the existence of at least two actin-binding sites present in the N- and in the C-terminal halves of subunits C, respectively. Since subunit C has the possibility to dimerize or even to oligomerize, spacing between actin filaments could be variable in size.
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Affiliation(s)
- Olga Vitavska
- Department of Biology/Chemistry, Division of Animal Physiology, University of Osnabrück, 49069 Osnabrück, Germany
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36
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Abstract
Vacuolar H(+)-ATPases are ubiquitous multisubunit complexes mediating the ATP-dependent transport of protons. In addition to their role in acidifying the lumen of various intracellular organelles, vacuolar H(+)-ATPases fulfill special tasks in the kidney. Vacuolar H(+)-ATPases are expressed in the plasma membrane in the kidney almost along the entire length of the nephron with apical and/or basolateral localization patterns. In the proximal tubule, a high number of vacuolar H(+)-ATPases are also found in endosomes, which are acidified by the pump. In addition, vacuolar H(+)-ATPases contribute to proximal tubular bicarbonate reabsorption. The importance in final urinary acidification along the collecting system is highlighted by monogenic defects in two subunits (ATP6V0A4, ATP6V1B1) of the vacuolar H(+)-ATPase in patients with distal renal tubular acidosis. The activity of vacuolar H(+)-ATPases is tightly regulated by a variety of factors such as the acid-base or electrolyte status. This regulation is at least in part mediated by various hormones and protein-protein interactions between regulatory proteins and multiple subunits of the pump.
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Affiliation(s)
- Carsten A Wagner
- Institute of Physiology, Univ. of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
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37
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Abstract
The yeast vacuolar proton-translocating ATPase (V-ATPase) is an excellent model for V-ATPases in all eukaryotic cells. Activity of the yeast V-ATPase is reversibly down-regulated by disassembly of the peripheral (V1) sector, which contains the ATP-binding sites, from the membrane (V0) sector, which contains the proton pore. A similar regulatory mechanism has been found in Manduca sexta and is believed to operate in other eukaryotes. We are interested in the mechanism of reversible disassembly and its implications for V-ATPase structure. In this review, we focus on (1) characterization of the yeast V-ATPase stalk subunits, which form the interface between V1 and V0, (2) potential mechanisms of silencing ATP hydrolytic activity in disassembled V1 sectors, and (3) the structure and function of RAVE, a recently discovered complex that regulates V-ATPase assembly.
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Affiliation(s)
- Patricia M Kane
- Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, New York 13210, USA.
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38
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Morel N, Dedieu JC, Philippe JM. Specific sorting of the a1 isoform of the V-H+ATPase a subunit to nerve terminals where it associates with both synaptic vesicles and the presynaptic plasma membrane. J Cell Sci 2004; 116:4751-62. [PMID: 14600261 DOI: 10.1242/jcs.00791] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vacuolar H+ATPase (V-ATPase) accumulates protons inside various intracellular organelles, generating the electrochemical proton gradient required for many vital cellular processes. V-ATPase is a complex enzyme with many subunits that are organized into two domains. The membrane domain that translocates protons contains a proteolipid oligomer of several c subunits and a 100 kDa a subunit. Several a-subunit isoforms have been described that are important for tissue specificity and targeting to different membrane compartments, and could also result in the generation of V-ATPases with different functional properties. In the present report, we have cloned the Torpedo marmorata a1 isoform. This isoform was found to be addressed specifically to nerve endings, whereas VATPases in the neuron cell bodies contain a different a-subunit isoform. In nerve terminals, the V-ATPase membrane domain is present not only in synaptic vesicles but also in the presynaptic plasma membrane, where its density could reach 200 molecules microm(-2). This V-ATPase interacts with VAMP-2 and with the SNARE complexes involved in synaptic vesicle docking and exocytosis.
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Affiliation(s)
- Nicolas Morel
- Laboratoire de Neurobiologie Cellulaire et Moléculaire, CNRS, 91198 Gif sur Yvette, France.
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39
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Cvejic S, Zhu Z, Felice SJ, Berman Y, Huang XY. The endogenous ligand Stunted of the GPCR Methuselah extends lifespan in Drosophila. Nat Cell Biol 2004; 6:540-6. [PMID: 15133470 DOI: 10.1038/ncb1133] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2004] [Accepted: 04/13/2004] [Indexed: 11/08/2022]
Abstract
Many extracellular signals are transmitted to the interior of the cell by receptors with seven membrane-spanning helices that trigger their effects by means of heterotrimeric guanine-nucleotide-binding regulatory proteins (G proteins). These G-protein-coupled receptors (GPCRs) control various physiological functions in evolution from pheromone-induced mating in yeast to cognition in humans. The potential role of the G-protein signalling system in the control of animal ageing has been highlighted by the genetic revelation that mutation of a GPCR encoded by methuselah extends the lifespan of adult Drosophila flies. How methuselah functions in controlling ageing is not clear. A first essential step towards the understanding of methuselah function is to determine the ligands of Methuselah. Here we report the identification and characterization of two endogenous peptide ligands of Methuselah, designated Stunted A and B. Flies with mutations in the gene encoding these ligands show an increase in lifespan and resistance to oxidative stress. We conclude that the Stunted-Methuselah system is involved in the control of animal ageing.
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Affiliation(s)
- Svetlana Cvejic
- Department of Physiology, Cornell University Weill Medical College, New York, New York 10021, USA
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40
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Abstract
Acidification of some organelles, including the Golgi complex, lysosomes, secretory granules, and synaptic vesicles, is important for many of their biochemical functions. In addition, acidic pH in some compartments is also required for the efficient sorting and trafficking of proteins and lipids along the biosynthetic and endocytic pathways. Despite considerable study, however, our understanding of how pH modulates membrane traffic remains limited. In large part, this is due to the diversity of methods to perturb and monitor pH, as well as to the difficulties in isolating individual transport steps within the complex pathways of membrane traffic. This review summarizes old and recent evidence for the role of acidification at various steps of biosynthetic and endocytic transport in mammalian cells. We describe the mechanisms by which organelle pH is regulated and maintained, as well as how organelle pH is monitored and quantitated. General principles that emerge from these studies as well as future directions of interest are discussed.
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Affiliation(s)
- Ora A Weisz
- Renal-Electrolyte Division, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA
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41
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Xie XS, Padron D, Liao X, Wang J, Roth MG, De Brabander JK. Salicylihalamide A inhibits the V0 sector of the V-ATPase through a mechanism distinct from bafilomycin A1. J Biol Chem 2004; 279:19755-63. [PMID: 14998996 DOI: 10.1074/jbc.m313796200] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The newly identified specific V-ATPase inhibitor, salicylihalamide A, is distinct from any previously identified V-ATPase inhibitors in that it inhibits only mammalian V-ATPases, but not those from yeast or other fungi (Boyd, M. R., Farina, C., Belfiore, P., Gagliardi, S., Kim, J. W., Hayakawa, Y., Beutler, J. A., McKee, T. C., Bowman, B. J., and Bowman, E. J. (2001) J. Pharmacol. Exp. Ther. 297, 114-120). In addition, salicylihalamide A does not compete with concanamycin or bafilomycin for binding to V-ATPase, indicating that it has a different binding site from those classic V-ATPase inhibitors (Huss, M., Ingenhorst, G., Konig, S., Gassel, M., Drose, S., Zeeck, A., Altendorf, K., and Wieczorek, H. (2002) J. Biol. Chem. 277, 40544-40548). By using purified bovine brain V-pump and its dissociated V(1) and V(0) sectors, we identified the recognition and binding site for salicylihalamide to be within the V(0) domain. Salicylihalamide does not inhibit the ATP hydrolysis activity of the dissociated V(1)-ATPase but inhibits the ATPase activity of the holoenzyme by inhibiting the V(0) domain. Salicylihalamide causes a dramatic redistribution of cytosolic V(1) from soluble to membrane-associated form, a change not observed in cells treated with either bafilomycin or NH(4)Cl. By synthesizing and characterizing a series of salicylihalamide derivatives, we investigated the structural determinants of salicylihalamide inhibition in terms of potency and reversibility, and used this information to suggest a possible binding mechanism.
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Affiliation(s)
- Xiao-Song Xie
- Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390, USA.
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42
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Lu M, Sautin YY, Holliday LS, Gluck SL. The glycolytic enzyme aldolase mediates assembly, expression, and activity of vacuolar H+-ATPase. J Biol Chem 2003; 279:8732-9. [PMID: 14672945 DOI: 10.1074/jbc.m303871200] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Vacuolar H(+)-ATPases (V-ATPases) are a family of highly conserved proton pumps that couple hydrolysis of cytosolic ATP to proton transport out of the cytosol. How ATP is supplied for V-ATPase-mediated hydrolysis and for coupling of proton transport is poorly understood. We have reported that the glycolytic enzyme aldolase physically associates with V-ATPase. Here we show that aldolase interacts with three different subunits of V-ATPase (subunits a, B, and E). The binding sites for the V-ATPase subunits on aldolase appear to be on distinct interfaces of the glycolytic enzyme. Aldolase deletion mutant cells were able to grow in medium buffered at pH 5.5 but not at pH 7.5, displaying a growth phenotype similar to that observed in V-ATPase subunit deletion mutants. Abnormalities in V-ATPase assembly and protein expression observed in aldolase deletion mutant cells could be fully rescued by aldolase complementation. The interaction between aldolase and V-ATPase increased dramatically in the presence of glucose, suggesting that aldolase may act as a glucose sensor for V-ATPase regulation. Taken together, these findings provide functional evidence that the ATP-generating glycolytic pathway is directly coupled to the ATP-hydrolyzing proton pump through physical interaction between aldolase and V-ATPase.
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Affiliation(s)
- Ming Lu
- Department of Medicine, University of California, San Francisco, California 94143, USA.
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43
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Pozidis C, Chalkiadaki A, Gomez-Serrano A, Stahlberg H, Brown I, Tampakaki AP, Lustig A, Sianidis G, Politou AS, Engel A, Panopoulos NJ, Mansfield J, Pugsley AP, Karamanou S, Economou A. Type III protein translocase: HrcN is a peripheral ATPase that is activated by oligomerization. J Biol Chem 2003; 278:25816-24. [PMID: 12734178 DOI: 10.1074/jbc.m301903200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Type III protein secretion (TTS) is catalyzed by translocases that span both membranes of Gram-negative bacteria. A hydrophilic TTS component homologous to F1/V1-ATPases is ubiquitous and essential for secretion. We show that hrcN encodes the putative TTS ATPase of Pseudomonas syringae pathovar phaseolicola and that HrcN is a peripheral protein that assembles in clusters at the membrane. A decahistidinyl HrcN derivative was overexpressed in Escherichia coli and purified to homogeneity in a folded state. Hydrodynamic analysis, cross-linking, and electron microscopy revealed four distinct HrcN forms: I, 48 kDa (monomer); II, approximately 300 kDa (putative hexamer); III, 575 kDa (dodecamer); and IV, approximately 3.5 MDa. Form III is the predominant form of HrcN at the membrane, and its ATPase activity is dramatically stimulated (>700-fold) over the basal activity of Form I. We propose that TTS ATPases catalyze protein translocation as activated homo-oligomers at the plasma membrane.
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Affiliation(s)
- Charalambos Pozidis
- Institute of Molecular Biology and Biotechnology, FORTH and Department of Biology, University of Crete, P.O. Box 1527, GR-711 10 Iraklio, Crete, Greece
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44
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Armbrüster A, Bailer SM, Koch MHJ, Godovac-Zimmermann J, Grüber G. Dimer formation of subunit G of the yeast V-ATPase. FEBS Lett 2003; 546:395-400. [PMID: 12832076 DOI: 10.1016/s0014-5793(03)00643-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The G subunit of the vacuolar ATPase (V-ATPase) is a component of the stalk connecting the V(1) and V(O) sectors of the enzyme and is essential for normal assembly and function. Subunit G (Vma10p) of the yeast V-ATPase was expressed in Escherichia coli as a soluble protein and was purified to homogeneity. The molecular mass of subunit G, determined by Native-polyacrylamide gel electrophoresis, gel filtration analysis and small-angle X-ray scattering, was approximately 28+/-2 kDa, indicating that this protein is dimeric. With a radius of gyration (R(g)) and a maximum size (D(max)) of 2.7+/-0.2 nm and 8.0+/-0.3 nm, respectively, the G-dimer is rather elongated. To understand which region of subunit G is required to mediate dimerization, a G(38-144) form (the carboxyl-terminus) was expressed and purified. G(38-144) is homogeneous, with a molecular mass of approximately 12+/-3 kDa, indicating a monomeric form in solution.
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Affiliation(s)
- Andrea Armbrüster
- Universität des Saarlandes, Fachrichtung 2.5 - Biophysik, D-66421 Homburg, Germany
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45
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Zhan H, Yokoyama K, Otani H, Tanigaki K, Shirota N, Takano S, Ohkuma S. Different roles of proteolipids and 70-kDa subunits of V-ATPase in growth and death of cultured human cells. Genes Cells 2003; 8:501-13. [PMID: 12786941 DOI: 10.1046/j.1365-2443.2003.00651.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND The vacuolar-type proton-translocating adenosine triphosphatase (V-ATPase) plays important roles in cell growth and tumour progression. V-ATPase is composed of two distinct structures, a hydrophilic catalytic cytosolic sector (V(1)) and a hydrophobic transmembrane sector (V(0)). The V(1) sector is composed of 5-8 different subunits with the structure A(3)B(3)C(1)D(1)E(1)F(1)G(1)H(1). The V0 sector is composed of 5 different subunits with the structure 1161381191166. The over-expression of 16-kDa proteolipid subunit of V-ATPase in the perinuclear region of the human adventitial fibroblasts promotes phenotypic modulation that contributes to neointimal formation and medial thickening. A relationship between oncogenicity and the expression of the 16-kDa proteolipid has also been suggested in human pancreatic carcinoma tissue. RESULTS We found that the mRNA levels of the 16-kDa proteolipid but not of the 70-kDa subunit of V-ATPase in human myofibroblasts were more abundant in serum-containing medium (MF(+) cells) than serum-free medium (MF(-) cells). In HeLa cells, the levels of mRNA and protein of the 16-kDa, 21-kDa or 70-kDa were clearly suppressed when the corresponding anti-sense oligonucleotides were administered to the culture medium. The growth rate and viability (mostly due to necrosis) of HeLa cells were reduced markedly by the 16-kDa and 21-kDa anti-sense, but little by the 70-kDa anti-sense, and not at all by any sense oligonucleotides. The localization of 16-kDa/21-kDa proteolipid subunits was different from that of the 70-kDa subunit in HeLa cells. CONCLUSION These results suggest that the 16-kDa and 21-kDa proteolipid subunits of the V0 sector play crucial roles in growth and death of cultured human cells. Our results may provide new insights into the mechanism and therapeutic implications for vessel wall hyperplasia and tumorigenesis.
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Affiliation(s)
- Hong Zhan
- Department of Dynamic Physiology, Graduate School of Natural Science and Technology, Ishikawa 920-0934, Japan
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46
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Saliba KJ, Allen RJW, Zissis S, Bray PG, Ward SA, Kirk K. Acidification of the malaria parasite's digestive vacuole by a H+-ATPase and a H+-pyrophosphatase. J Biol Chem 2003; 278:5605-12. [PMID: 12427765 DOI: 10.1074/jbc.m208648200] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
As it grows within the human erythrocyte, the malaria parasite, Plasmodium falciparum, ingests the erythrocyte cytosol, depositing it via an endocytotic feeding mechanism in the "digestive vacuole," a specialized acidic organelle. The digestive vacuole is the site of hemoglobin degradation, the storage site for hemozoin (an inert biocrystal of toxic heme), the site of action of many antimalarial drugs, and the site of proteins known to be involved in antimalarial drug resistance. The acidic pH of this organelle is thought to play a critical role in its various functions; however, the mechanisms by which the pH within the vacuole is maintained are not well understood. In this study, we have used a combination of techniques to demonstrate the presence on the P. falciparum digestive vacuole membrane of two discrete H(+) pumping mechanisms, both capable of acidifying the vacuole interior. One is a V-type H(+)-ATPase, sensitive to concanamycin A and bafilomycin A(1). The other is a H(+)-pyrophosphatase, which was inhibited by NaF and showed a partial dependence on K(+). The operation of the H(+)-pyrophosphatase was dependent on the presence of a Mg(2+)-pyrophosphate complex, and kinetic experiments gave results consistent with free pyrophosphate acting as an inhibitor of the protein. The presence of the combination of a H(+)-ATPase and a H(+)-pyrophosphatase on the P. falciparum digestive vacuole is similar to the situation in the acidic tonoplasts (vacuoles) of plant cells.
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Affiliation(s)
- Kevin J Saliba
- School of Biochemistry and Molecular Biology, Faculty of Science, Australian National University, Canberra, Australian Capital Territory 0200, Australia.
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47
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Scimeca JC, Quincey D, Parrinello H, Romatet D, Grosgeorge J, Gaudray P, Philip N, Fischer A, Carle GF. Novel mutations in the TCIRG1 gene encoding the a3 subunit of the vacuolar proton pump in patients affected by infantile malignant osteopetrosis. Hum Mutat 2003; 21:151-7. [PMID: 12552563 DOI: 10.1002/humu.10165] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Fifty percent of the infantile malignant osteopetrosis (IMO) cases reported in the literature present mutations in the TCIRG1 gene encoding the 116-kDa osteoclast specific subunit of the vacuolar proton ATPase (ATP6I). In this study, we identified four novel mutations in a series of six IMO patients. All of these mutations correspond to single nucleotide changes and affect splice acceptor or donor sites, resulting in aberrant transcription products. We report also a missense mutation, G405R, previously described in several Costa Rican patients. This independent finding suggests that the highly conserved residue at amino acid 405 plays a critical role in the a3 subunit function. Finally, the results of this study were used to provide a prenatal diagnosis to one of the families.
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MESH Headings
- Chromosomes, Human, Pair 11/genetics
- Female
- Genes, Recessive/genetics
- Genetic Markers/genetics
- Genotype
- Haplotypes/genetics
- Humans
- Infant
- Infant, Newborn
- Infant, Newborn, Diseases/diagnosis
- Infant, Newborn, Diseases/genetics
- Infant, Newborn, Diseases/mortality
- Male
- Mutation/genetics
- Organ Specificity/genetics
- Osteoclasts/classification
- Osteoclasts/metabolism
- Osteopetrosis/diagnosis
- Osteopetrosis/genetics
- Osteopetrosis/mortality
- Pedigree
- Prenatal Diagnosis
- Protein Subunits/genetics
- Vacuolar Proton-Translocating ATPases/genetics
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Affiliation(s)
- Jean-Claude Scimeca
- Instabilité et Altérations des Génomes, UMR6549 CNRS/UNSA, Faculté de Médecine de l'Université de Nice-Sophia Antipolis, Nice, France
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48
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Abstract
The activity of the vacuolar H(+)-ATPase has been characterized in isolated vacuoles of the yeast Saccharomyces cerevisiae by means of the patch-clamp technique. With cytosolic calcium at virtually zero (<10(-9) M), Mg-ATP induced a transient, bafilomycin A(1)-sensitive current corresponding to the flow of positive charges from the cytoplasmic surface to the vacuolar lumen. The Mg-ATP-dependent current reached its maximum amplitude (30+/-8 mA m(-2) with 5 mM Mg-ATP, n=34) within 15-20 s and declined slowly over a period of about 15-20 min even in the continuous presence of Mg-ATP. This decline of pumping activity was independent of the cytosolic KCl concentration, suggesting an inhibitory mechanism different from the high salt-induced dissociation of V(0) and V(1) reported for the V-ATPase of plants and fungi. Cytosolic ADP was found to modulate the pump activity since Mg-ATP-induced pump current was smaller if monitored in the presence of 5 mM ADP and addition of 5 mM ADP in the presence of 5 mM Mg-ATP reduced the pump current by more than 50%. Furthermore, reduction of the cytosolic ADP concentration by the ATP-regenerating system creatine phosphate/creatine kinase partially relieved the endogenous inhibition of the V-ATPase, confirming that interaction of cytosolic ADP with the V-ATPase is the reason for the transient nature of the pump current in yeast vacuoles.
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Affiliation(s)
- Carsten Kettner
- Botanisches Institut I, Universität Karlsruhe (TH), Kaiserstrasse 12, 76128 Karlsruhe, Germany.
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49
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Lu M, Vergara S, Zhang L, Holliday LS, Aris J, Gluck SL. The amino-terminal domain of the E subunit of vacuolar H(+)-ATPase (V-ATPase) interacts with the H subunit and is required for V-ATPase function. J Biol Chem 2002; 277:38409-15. [PMID: 12163484 DOI: 10.1074/jbc.m203521200] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Vacuolar H(+)-ATPases (V-ATPases) are highly conserved proton pumps that couple hydrolysis of cytosolic ATP to proton transport out of the cytosol. Although it is generally believed that V-ATPases transport protons by a rotary catalytic mechanism analogous to that used by F(1)F(0)-ATPases, the structure and subunit composition of the central or peripheral stalk of the multisubunit complex are not well understood. We searched for proteins that bind to the E subunit of V-ATPase using the yeast two-hybrid assay and identified the H subunit as an interacting partner. Physical association between the E and H subunits of V-ATPase was confirmed in vitro by precipitation assays. Deletion mapping analysis revealed that a 78-amino acid fragment at the amino terminus of the E subunit was sufficient for binding to the H subunit. Expression of the amino-terminal fragments of the E subunits from human and yeast as dominant-negative mutants resulted in dramatic decreases in bafilomycin A(1)-sensitive ATP hydrolysis and proton transport activities of V-ATPase. Our data demonstrate the physiological significance of the interaction between the E and H subunits of V-ATPase and extend previous studies on the arrangement of subunits on the peripheral stalk of V-ATPase.
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Affiliation(s)
- Ming Lu
- Department of Medicine University of Florida College of Medicine, Gainesville, Florida 32610, USA.
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50
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Geyer M, Fackler OT, Peterlin BM. Subunit H of the V-ATPase involved in endocytosis shows homology to beta-adaptins. Mol Biol Cell 2002; 13:2045-56. [PMID: 12058068 PMCID: PMC117623 DOI: 10.1091/mbc.02-02-0026] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The vacuolar ATPase (V-ATPase) is a multisubunit enzyme that facilitates the acidification of intracellular compartments in eukaryotic cells and plays an important role in receptor-mediated endocytosis, intracellular trafficking processes, and protein degradation. In this study we show that the C-terminal fragment of 350 residues of the regulatory subunit H (V1H) of the V-ATPase shares structural and functional homologies with the beta-chains of adaptor protein complexes. Moreover, the fragment is similar to a region in the beta-subunit of COPI coatomer complexes, which suggests the existence of a shared domain in these three different families of proteins. For beta-adaptins, this fragment binds to cytoplasmic di-leucine-based sorting motifs such as in HIV-1 Nef that mediate endocytic trafficking. Expression of this fragment in cells blocks the internalization of transmembrane proteins, which depend on di-leucine-based motifs, whereas mutation of the consensus sequence GEY only partly diminishes the recognition of the sorting motif. Based on recent structural analysis, our results suggest that the di-leucine-binding domain consists of a HEAT or ARM repeat protein fold.
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Affiliation(s)
- Matthias Geyer
- Howard Hughes Medical Institute, Department of Medicine, University of California at San Francisco, California 94143-0703, USA.
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