1
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Chen KL, Ven TN, Crane MM, Brunner MLC, Pun AK, Helget KL, Brower K, Chen DE, Doan H, Dillard-Telm JD, Huynh E, Feng YC, Yan Z, Golubeva A, Hsu RA, Knight R, Levin J, Mobasher V, Muir M, Omokehinde V, Screws C, Tunali E, Tran RK, Valdez L, Yang E, Kennedy SR, Herr AJ, Kaeberlein M, Wasko BM. Loss of vacuolar acidity results in iron-sulfur cluster defects and divergent homeostatic responses during aging in Saccharomyces cerevisiae. GeroScience 2020; 42:749-764. [PMID: 31975050 PMCID: PMC7205917 DOI: 10.1007/s11357-020-00159-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 01/14/2020] [Indexed: 01/31/2023] Open
Abstract
The loss of vacuolar/lysosomal acidity is an early event during aging that has been linked to mitochondrial dysfunction. However, it is unclear how loss of vacuolar acidity results in age-related dysfunction. Through unbiased genetic screens, we determined that increased iron uptake can suppress the mitochondrial respiratory deficiency phenotype of yeast vma mutants, which have lost vacuolar acidity due to genetic disruption of the vacuolar ATPase proton pump. Yeast vma mutants exhibited nuclear localization of Aft1, which turns on the iron regulon in response to iron-sulfur cluster (ISC) deficiency. This led us to find that loss of vacuolar acidity with age in wild-type yeast causes ISC defects and a DNA damage response. Using microfluidics to investigate aging at the single-cell level, we observe grossly divergent trajectories of iron homeostasis within an isogenic and environmentally homogeneous population. One subpopulation of cells fails to mount the expected compensatory iron regulon gene expression program, and suffers progressively severe ISC deficiency with little to no activation of the iron regulon. In contrast, other cells show robust iron regulon activity with limited ISC deficiency, which allows extended passage and survival through a period of genomic instability during aging. These divergent trajectories suggest that iron regulation and ISC homeostasis represent a possible target for aging interventions.
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Affiliation(s)
- Kenneth L Chen
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Toby N Ven
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Matthew M Crane
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | | | - Adrian K Pun
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Kathleen L Helget
- Department of Biology and Biotechnology, University of Houston-Clear Lake, Houston, TX, 77058, USA
| | - Katherine Brower
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Dexter E Chen
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Ha Doan
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | | | - Ellen Huynh
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Yen-Chi Feng
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Zili Yan
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Alexandra Golubeva
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Roy A Hsu
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Raheem Knight
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Jessie Levin
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Vesal Mobasher
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Michael Muir
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Victor Omokehinde
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Corey Screws
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Esin Tunali
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Rachael K Tran
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Luz Valdez
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Edward Yang
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Scott R Kennedy
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Alan J Herr
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Matt Kaeberlein
- Department of Pathology, University of Washington, Seattle, WA, 98195, USA
| | - Brian M Wasko
- Department of Biology and Biotechnology, University of Houston-Clear Lake, Houston, TX, 77058, USA.
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2
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Flinck M, Hagelund S, Gorbatenko A, Severin M, Pedraz-Cuesta E, Novak I, Stock C, Pedersen SF. The Vacuolar H + ATPase α3 Subunit Negatively Regulates Migration and Invasion of Human Pancreatic Ductal Adenocarcinoma Cells. Cells 2020; 9:E465. [PMID: 32085585 PMCID: PMC7072798 DOI: 10.3390/cells9020465] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 02/10/2020] [Accepted: 02/13/2020] [Indexed: 12/12/2022] Open
Abstract
Increased metabolic acid production and upregulation of net acid extrusion render pH homeostasis profoundly dysregulated in many cancers. Plasma membrane activity of vacuolar H+ ATPases (V-ATPases) has been implicated in acid extrusion and invasiveness of some cancers, yet often on the basis of unspecific inhibitors. Serving as a membrane anchor directing V-ATPase localization, the a subunit of the V0 domain of the V-ATPase (ATP6V0a1-4) is particularly interesting in this regard. Here, we map the regulation and roles of ATP6V0a3 in migration, invasion, and growth in pancreatic ductal adenocarcinoma (PDAC) cells. a3 mRNA and protein levels were upregulated in PDAC cell lines compared to non-cancer pancreatic epithelial cells. Under control conditions, a3 localization was mainly endo-/lysosomal, and its knockdown had no detectable effect on pHi regulation after acid loading. V-ATPase inhibition, but not a3 knockdown, increased HIF-1 expression and decreased proliferation and autophagic flux under both starved and non-starved conditions, and spheroid growth of PDAC cells was also unaffected by a3 knockdown. Strikingly, a3 knockdown increased migration and transwell invasion of Panc-1 and BxPC-3 PDAC cells, and increased gelatin degradation in BxPC-3 cells yet decreased it in Panc-1 cells. We conclude that in these PDAC cells, a3 is upregulated and negatively regulates migration and invasion, likely in part via effects on extracellular matrix degradation.
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Affiliation(s)
- Mette Flinck
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, DK-2100 Copenhagen, Denmark; (M.F.); (S.H.); (M.S.); (E.P.-C.); (I.N.)
| | - Sofie Hagelund
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, DK-2100 Copenhagen, Denmark; (M.F.); (S.H.); (M.S.); (E.P.-C.); (I.N.)
| | - Andrej Gorbatenko
- Department of Pathology, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA;
| | - Marc Severin
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, DK-2100 Copenhagen, Denmark; (M.F.); (S.H.); (M.S.); (E.P.-C.); (I.N.)
| | - Elena Pedraz-Cuesta
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, DK-2100 Copenhagen, Denmark; (M.F.); (S.H.); (M.S.); (E.P.-C.); (I.N.)
| | - Ivana Novak
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, DK-2100 Copenhagen, Denmark; (M.F.); (S.H.); (M.S.); (E.P.-C.); (I.N.)
| | - Christian Stock
- Department of Gastroentero-, Hepato- and Endocrinology, Hannover Medical School, D-30625 Hannover, Germany;
| | - Stine Falsig Pedersen
- Section for Cell Biology and Physiology, Department of Biology, Faculty of Science, University of Copenhagen, DK-2100 Copenhagen, Denmark; (M.F.); (S.H.); (M.S.); (E.P.-C.); (I.N.)
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3
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PIN1 transcript variant 2 acts as a long non-coding RNA that controls the HIF-1-driven hypoxic response. Sci Rep 2019; 9:10599. [PMID: 31332228 PMCID: PMC6646326 DOI: 10.1038/s41598-019-47071-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2019] [Accepted: 07/10/2019] [Indexed: 02/08/2023] Open
Abstract
The transcription factor HIF-1 induces the expression of genes that are essential for cell survival and oxygen homeostasis in hypoxic conditions. The prolyl isomerase Pin1 plays a role in the regulation of HIF-1α. However, the mechanism by which Pin1 controls HIF-1α remains controversial. Surprisingly, we here show that a PIN1 transcript downregulates HIF-1α as a long non-coding RNA. Pin1-silencing siRNAs augmented the hypoxia-induced expression of HIF-1α, thereby upregulating the expression of HIF-1 target genes. However, the overexpression of Pin1 protein did not inhibit the hypoxic expression of HIF-1α. Pin1 restoration in Pin1-depleted cells also failed to reverse the induction of HIF-1α by Pin1 knockdown. Unexpectedly, HIF-1α was found to be induced by both siRNAs for PIN1 transcript variants 1/2 and that for PIN1 transcript variants 2/3, indicating that the PIN1 transcript variant 2 (PIN1-v2) is responsible for HIF-1α induction. Mechanistically, PIN1-v2, which is classified as a long non-coding RNA due to early termination of translation, was evaluated to inhibit the transcription of HIF1A gene. In conclusion, PIN1-v2 may function in balancing the HIF-1-driven gene expression under hypoxia.
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4
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Hayek SR, Rane HS, Parra KJ. Reciprocal Regulation of V-ATPase and Glycolytic Pathway Elements in Health and Disease. Front Physiol 2019; 10:127. [PMID: 30828305 PMCID: PMC6384264 DOI: 10.3389/fphys.2019.00127] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 01/31/2019] [Indexed: 12/24/2022] Open
Abstract
The ability of cells to adapt to fluctuations in glucose availability is crucial for their survival and involves the vacuolar proton-translocating ATPase (V-ATPase), a proton pump found in all eukaryotes. V-ATPase hydrolyzes ATP via its V1 domain and uses the energy released to transport protons across membranes via its Vo domain. This activity is critical for pH homeostasis and generation of a membrane potential that drives cellular metabolism. A number of stimuli have been reported to alter V-ATPase assembly in yeast and higher eukaryotes. Glucose flux is one of the strongest and best-characterized regulators of V-ATPase; this review highlights current models explaining how glycolysis and V-ATPase are coordinated in both the Saccharomyces cerevisiae model fungus and in mammalian systems. Glucose-dependent assembly and trafficking of V-ATPase, V-ATPase-dependent modulations in glycolysis, and the recent discovery that glucose signaling through V-ATPase acts as a molecular switch to dictate anabolic versus catabolic metabolism are discussed. Notably, metabolic plasticity and altered glycolytic flux are critical drivers of numerous human pathologies, and the expression and activity of V-ATPase is often altered in disease states or can be pharmacologically manipulated as treatment. This overview will specifically discuss connections between V-ATPase and glycolysis in cancer.
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Affiliation(s)
- Summer R Hayek
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
| | - Hallie S Rane
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
| | - Karlett J Parra
- Department of Biochemistry and Molecular Biology, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
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5
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Tian R, Xu S, Chai S, Yin D, Zakon H, Yang G. Stronger selective constraint on downstream genes in the oxidative phosphorylation pathway of cetaceans. J Evol Biol 2017; 31:217-228. [PMID: 29172233 DOI: 10.1111/jeb.13213] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Revised: 11/11/2017] [Accepted: 11/18/2017] [Indexed: 02/05/2023]
Abstract
The oxidative phosphorylation (OXPHOS) pathway is an efficient way to produce energy via adenosine triphosphate (ATP), which is critical for sustaining an energy supply for cetaceans in a hypoxic environment. Several studies have shown that natural selection may shape the evolution of the genes involved in OXPHOS. However, how network architecture drives OXPHOS protein sequence evolution remains poorly explored. Here, we investigated the evolutionary patterns of genes in the OXPHOS pathway across six cetacean genomes within the framework of a functional network. Our results show a negative correlation between the strength of purifying selection and pathway position. This result indicates that downstream genes were subjected to stronger evolutionary constraints than upstream genes, which may be due to the dual function of ATP synthase in the OXPHOS pathway. Additionally, there was a positive correlation between codon usage bias and omega (ω = dN/dS) and a negative correlation with synonymous substitution rate (dS), indicating that the stronger selective constraint on genes (with less biased codon usage) along the OXPHOS pathway is attributable to an increase in the rate of synonymous substitution. Surprisingly, there was no significant correlation between protein-protein interactions and the evolutionary estimates, implying that highly connected enzymes may not always show greater evolutionary constraints. Compared with that observed for terrestrial mammals, we found that the signature of positive selection detected in five genes (ATP5J, LHPP, PPA1, UQCRC1 and UQCRQ) was cetacean-specific, reflecting the importance of OXPHOS for survival in hypoxic, aquatic environments.
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Affiliation(s)
- R Tian
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - S Xu
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - S Chai
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - D Yin
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
| | - H Zakon
- Department of Integrative Biology, The University of Texas, Austin, TX, USA.,Department of Neuroscience, The University of Texas, Austin, TX, USA
| | - G Yang
- Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing, China
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6
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Semenza GL. A compendium of proteins that interact with HIF-1α. Exp Cell Res 2017; 356:128-135. [PMID: 28336293 DOI: 10.1016/j.yexcr.2017.03.041] [Citation(s) in RCA: 84] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 03/18/2017] [Indexed: 12/23/2022]
Abstract
Hypoxia-inducible factor 1 (HIF-1) is the founding member of a family of transcription factors that function as master regulators of oxygen homeostasis. HIF-1 is composed of an O2-regulated HIF-1α subunit and a constitutively expressed HIF-1β subunit. This review provides a compendium of proteins that interact with the HIF-1α subunit, many of which regulate HIF-1 activity in either an O2-dependent or O2-independent manner.
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Affiliation(s)
- Gregg L Semenza
- Johns Hopkins University School of Medicine, 733 N. Broadway, Baltimore, MD 21205 USA.
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7
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Miles AL, Burr SP, Grice GL, Nathan JA. The vacuolar-ATPase complex and assembly factors, TMEM199 and CCDC115, control HIF1α prolyl hydroxylation by regulating cellular iron levels. eLife 2017; 6:e22693. [PMID: 28296633 PMCID: PMC5391204 DOI: 10.7554/elife.22693] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2016] [Accepted: 03/09/2017] [Indexed: 12/19/2022] Open
Abstract
Hypoxia Inducible transcription Factors (HIFs) are principally regulated by the 2-oxoglutarate and Iron(II) prolyl hydroxylase (PHD) enzymes, which hydroxylate the HIFα subunit, facilitating its proteasome-mediated degradation. Observations that HIFα hydroxylation can be impaired even when oxygen is sufficient emphasise the importance of understanding the complex nature of PHD regulation. Here, we use an unbiased genome-wide genetic screen in near-haploid human cells to uncover cellular processes that regulate HIF1α. We identify that genetic disruption of the Vacuolar H+ ATPase (V-ATPase), the key proton pump for endo-lysosomal acidification, and two previously uncharacterised V-ATPase assembly factors, TMEM199 and CCDC115, stabilise HIF1α in aerobic conditions. Rather than preventing the lysosomal degradation of HIF1α, disrupting the V-ATPase results in intracellular iron depletion, thereby impairing PHD activity and leading to HIF activation. Iron supplementation directly restores PHD catalytic activity following V-ATPase inhibition, revealing important links between the V-ATPase, iron metabolism and HIFs.
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Affiliation(s)
- Anna L Miles
- Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - Stephen P Burr
- Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - Guinevere L Grice
- Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
| | - James A Nathan
- Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom
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8
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Ng KR, Li JYZ, Gleadle JM. Human cytomegalovirus encoded microRNAs: hitting targets. Expert Rev Anti Infect Ther 2015; 13:1469-79. [PMID: 26509290 DOI: 10.1586/14787210.2015.1106939] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Human cytomegalovirus (HCMV) infection is of particular concern in immunodeficient individuals notably transplant recipients, leading to increased morbidity and mortality. HCMV is predicted to encode multiple microRNAs (miRNAs) and several have been characterized in vitro. Furthermore, these miRNAs have been shown to target human and viral mRNAs. Pathways involved in human cellular targets have key roles in vesicle trafficking, immune evasion and cell cycle control. This demonstration of viral miRNA targets provides novel insights into viral pathogenesis. This review details the evidence for the existence of HCMV-encoded miRNA and their targets. HCMV miRNA in blood and other tissues is a potential diagnostic tool and blocking the effects of specific HCMV-encoded miRNA with sequence specific antagomirs is a potential new therapy.
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Affiliation(s)
- Kiat Rui Ng
- a School of Medicine , Flinders University , Adelaide , Australia
| | - Jordan Y Z Li
- a School of Medicine , Flinders University , Adelaide , Australia.,b Department of Renal Medicine , Flinders Medical Centre , Adelaide , Australia.,c Department of General Medicine , Flinders Medical Centre , Adelaide , Australia
| | - Jonathan M Gleadle
- a School of Medicine , Flinders University , Adelaide , Australia.,b Department of Renal Medicine , Flinders Medical Centre , Adelaide , Australia
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9
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Jin HO, Hong SE, Kim CS, Park JA, Kim JH, Kim JY, Kim B, Chang YH, Hong SI, Hong YJ, Park IC, Lee JK. Combined effects of EGFR tyrosine kinase inhibitors and vATPase inhibitors in NSCLC cells. Toxicol Appl Pharmacol 2015; 287:17-25. [DOI: 10.1016/j.taap.2015.05.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 04/09/2015] [Accepted: 05/01/2015] [Indexed: 02/04/2023]
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10
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Mangieri LR, Mader BJ, Thomas CE, Taylor CA, Luker AM, Tse TE, Huisingh C, Shacka JJ. ATP6V0C knockdown in neuroblastoma cells alters autophagy-lysosome pathway function and metabolism of proteins that accumulate in neurodegenerative disease. PLoS One 2014; 9:e93257. [PMID: 24695574 PMCID: PMC3973706 DOI: 10.1371/journal.pone.0093257] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 02/22/2014] [Indexed: 02/06/2023] Open
Abstract
ATP6V0C is the bafilomycin A1-binding subunit of vacuolar ATPase, an enzyme complex that critically regulates vesicular acidification. We and others have shown previously that bafilomycin A1 regulates cell viability, autophagic flux and metabolism of proteins that accumulate in neurodegenerative disease. To determine the importance of ATP6V0C for autophagy-lysosome pathway function, SH-SY5Y human neuroblastoma cells differentiated to a neuronal phenotype were nucleofected with non-target or ATP6V0C siRNA and following recovery were treated with either vehicle or bafilomycin A1 (0.3-100 nM) for 48 h. ATP6V0C knockdown was validated by quantitative RT-PCR and by a significant decrease in Lysostracker Red staining. ATP6V0C knockdown significantly increased basal levels of microtubule-associated protein light chain 3-II (LC3-II), α-synuclein high molecular weight species and APP C-terminal fragments, and inhibited autophagic flux. Enhanced LC3 and LAMP-1 co-localization following knockdown suggests that autophagic flux was inhibited in part due to lysosomal degradation and not by a block in vesicular fusion. Knockdown of ATP6V0C also sensitized cells to the accumulation of autophagy substrates and a reduction in neurite length following treatment with 1 nM bafilomycin A1, a concentration that did not produce such alterations in non-target control cells. Reduced neurite length and the percentage of propidium iodide-positive dead cells were also significantly greater following treatment with 3 nM bafilomycin A1. Together these results indicate a role for ATP6V0C in maintaining constitutive and stress-induced ALP function, in particular the metabolism of substrates that accumulate in age-related neurodegenerative disease and may contribute to disease pathogenesis.
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Affiliation(s)
- Leandra R. Mangieri
- Department Pathology, Neuropathology Division, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Burton J. Mader
- Department Pathology, Neuropathology Division, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Birmingham Veterans Administration Medical Center, Birmingham, Alabama, United States of America
| | - Cailin E. Thomas
- Department Pathology, Neuropathology Division, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Charles A. Taylor
- Department Pathology, Neuropathology Division, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Austin M. Luker
- Department Pathology, Neuropathology Division, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Tonia E. Tse
- Department Pathology, Neuropathology Division, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Carrie Huisingh
- Department Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - John J. Shacka
- Department Pathology, Neuropathology Division, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- Department Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
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11
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Systematic microRNA analysis identifies ATP6V0C as an essential host factor for human cytomegalovirus replication. PLoS Pathog 2013; 9:e1003820. [PMID: 24385903 PMCID: PMC3873435 DOI: 10.1371/journal.ppat.1003820] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 10/21/2013] [Indexed: 11/19/2022] Open
Abstract
Recent advances in microRNA target identification have greatly increased the number of putative targets of viral microRNAs. However, it is still unclear whether all targets identified are biologically relevant. Here, we use a combined approach of RISC immunoprecipitation and focused siRNA screening to identify targets of HCMV encoded human cytomegalovirus that play an important role in the biology of the virus. Using both a laboratory and clinical strain of human cytomegalovirus, we identify over 200 putative targets of human cytomegalovirus microRNAs following infection of fibroblast cells. By comparing RISC-IP profiles of miRNA knockout viruses, we have resolved specific interactions between human cytomegalovirus miRNAs and the top candidate target transcripts and validated regulation by western blot analysis and luciferase assay. Crucially we demonstrate that miRNA target genes play important roles in the biology of human cytomegalovirus as siRNA knockdown results in marked effects on virus replication. The most striking phenotype followed knockdown of the top target ATP6V0C, which is required for endosomal acidification. siRNA knockdown of ATP6V0C resulted in almost complete loss of infectious virus production, suggesting that an HCMV microRNA targets a crucial cellular factor required for virus replication. This study greatly increases the number of identified targets of human cytomegalovirus microRNAs and demonstrates the effective use of combined miRNA target identification and focused siRNA screening for identifying novel host virus interactions. Human cytomegalovirus is a prevalent pathogen. Like other herpesviruses, human cytomegalovirus expresses small regulatory RNAs called microRNAs. The focus of this study was to understand the role of these RNAs in the context of viral infection and to use this information to identify novel host factors involved in human cytomegalovirus biology. We used a biochemical approach that allowed us to systematically identify cellular genes targeted by virus microRNAs. Because the virus targets these genes, it is reasonable to propose that these genes play an important role during infection. We confirmed this hypothesis using a second screen in which we knocked down expression of a number of the identified targets of the virus microRNAs. Knock down of one of the targets, a cellular factor called ATP6V0C, resulted in an almost complete block in production of infectious virus. These data suggest that endosomal acidification is crucial to HCMV replication, and the virus targets this process by microRNA regulation.
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Abstract
Intense interest in the 'Warburg effect' has been revived by the discovery that hypoxia-inducible factor 1 (HIF1) reprogrammes pyruvate oxidation to lactic acid conversion; lactic acid is the end product of fermentative glycolysis. The most aggressive and invasive cancers, which are often hypoxic, rely on exacerbated glycolysis to meet the increased demand for ATP and biosynthetic precursors and also rely on robust pH-regulating systems to combat the excessive generation of lactic and carbonic acids. In this Review, we present the key pH-regulating systems and synthesize recent advances in strategies that combine the disruption of pH control with bioenergetic mechanisms. We discuss the possibility of exploiting, in rapidly growing tumours, acute cell death by 'metabolic catastrophe'.
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Affiliation(s)
- Scott K Parks
- Institute for Research on Cancer and Aging of Nice (IRCAN), Equipe Labellisée LNCC, University of Nice-Sophia Antipolis, Centre National de la Recherche Scientifique, INSERM, Centre A. Lacassagne, Nice 06189, France
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13
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Inhibition of vacuolar H+ ATPase enhances sensitivity to tamoxifen via up-regulation of CHOP in breast cancer cells. Biochem Biophys Res Commun 2013; 437:463-8. [DOI: 10.1016/j.bbrc.2013.06.106] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Accepted: 06/27/2013] [Indexed: 10/26/2022]
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14
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Avnet S, Di Pompo G, Lemma S, Salerno M, Perut F, Bonuccelli G, Granchi D, Zini N, Baldini N. V-ATPase is a candidate therapeutic target for Ewing sarcoma. Biochim Biophys Acta Mol Basis Dis 2013; 1832:1105-16. [PMID: 23579072 DOI: 10.1016/j.bbadis.2013.04.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Revised: 03/29/2013] [Accepted: 04/02/2013] [Indexed: 11/29/2022]
Abstract
Suppression of oxidative phosphorylation combined with enhanced aerobic glycolysis and the resulting increased generation of protons are common features of several types of cancer. An efficient mechanism to escape cell death resulting from intracellular acidification is proton pump activation. In Ewing sarcoma (ES), although the tumor-associated chimeric gene EWS-FLI1 is known to induce the accumulation of hypoxia-induced transcription factor HIF-1α, derangements in metabolic pathways have been neglected so far as candidate pathogenetic mechanisms. In this paper, we observed that ES cells simultaneously activate mitochondrial respiration and high levels of glycolysis. Moreover, although the most effective detoxification mechanism of proton intracellular storage is lysosomal compartmentalization, ES cells show a poorly represented lysosomal compartment, but a high sensitivity to the anti-lysosomal agent bafilomycin A1, targeting the V-ATPase proton pump. We therefore investigated the role of V-ATPase in the acidification activity of ES cells. ES cells with the highest GAPDH and V-ATPase expression also showed the highest acidification rate. Moreover, the localization of V-ATPase was both on the vacuolar and the plasma membrane of all ES cell lines. The acidic extracellular pH that we reproduced in vitro promoted high invasion ability and clonogenic efficiency. Finally, targeting V-ATPase with siRNA and omeprazole treatments, we obtained a significant selective reduction of tumor cell number. In summary, glycolytic activity and activation of V-ATPase are crucial mechanisms of survival of ES cells and can be considered as promising selective targets for the treatment of this tumor.
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Affiliation(s)
- Sofia Avnet
- Laboratory for Orthopaedic Pathophysiology and Regenerative Medicine, Istituto Ortopedico Rizzoli, via di Barbiano 1/10, 40136, Bologna, Italy.
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15
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Bafilomycin A1 activates HIF-dependent signalling in human colon cancer cells via mitochondrial uncoupling. Biosci Rep 2013; 32:587-95. [PMID: 22943412 PMCID: PMC3497721 DOI: 10.1042/bsr20120085] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Mitochondrial uncoupling is implicated in many patho(physiological) states. Using confocal live cell imaging and an optical O2 sensing technique, we show that moderate uncoupling of the mitochondria with plecomacrolide Baf (bafilomycin A1) causes partial depolarization of the mitochondria and deep sustained deoxygenation of human colon cancer HCT116 cells subjected to 6% atmospheric O2. A decrease in iO2 (intracellular O2) to 0–10 μM, induced by Baf, is sufficient for stabilization of HIFs (hypoxia inducible factors) HIF-1α and HIF-2α, coupled with an increased expression of target genes including GLUT1 (glucose transporter 1), HIF PHD2 (prolyl hydroxylase domain 2) and CAIX (carbonic anhydrase IX). Under the same hypoxic conditions, treatment with Baf causes neither decrease in iO2 nor HIF-α stabilization in the low-respiring HCT116 cells deficient in COX (cytochrome c-oxidase). Both cell types display equal capacities for HIF-α stabilization by hypoxia mimetics DMOG (dimethyloxalylglycine) and CoCl2, thus suggesting that the effect of Baf under hypoxia is driven mainly by mitochondrial respiration. Altogether, by activating HIF signalling under moderate hypoxia, mitochondrial uncoupling can play an important regulatory role in colon cancer metabolism and modulate adaptation of cancer cells to natural hypoxic environments.
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16
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von Schwarzenberg K, Wiedmann RM, Oak P, Schulz S, Zischka H, Wanner G, Efferth T, Trauner D, Vollmar AM. Mode of cell death induction by pharmacological vacuolar H+-ATPase (V-ATPase) inhibition. J Biol Chem 2012; 288:1385-96. [PMID: 23168408 DOI: 10.1074/jbc.m112.412007] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The vacuolar H(+)-ATPase (V-ATPase), a multisubunit proton pump, has come into focus as an attractive target in cancer invasion. However, little is known about the role of V-ATPase in cell death, and especially the underlying mechanisms remain mostly unknown. We used the myxobacterial macrolide archazolid B, a potent inhibitor of the V-ATPase, as an experimental drug as well as a chemical tool to decipher V-ATPase-related cell death signaling. We found that archazolid induced apoptosis in highly invasive tumor cells at nanomolar concentrations which was executed by the mitochondrial pathway. Prior to apoptosis induction archazolid led to the activation of a cellular stress response including activation of the hypoxia-inducible factor-1α (HIF1α) and autophagy. Autophagy, which was demonstrated by degradation of p62 or fusion of autophagosomes with lysosomes, was induced at low concentrations of archazolid that not yet increase pH in lysosomes. HIF1α was induced due to energy stress shown by a decline of the ATP level and followed by a shutdown of energy-consuming processes. As silencing HIF1α increases apoptosis, the cellular stress response was suggested to be a survival mechanism. We conclude that archazolid leads to energy stress which activates adaptive mechanisms like autophagy mediated by HIF1α and finally leads to apoptosis. We propose V-ATPase as a promising drugable target in cancer therapy caught up at the interplay of apoptosis, autophagy, and cellular/metabolic stress.
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Affiliation(s)
- Karin von Schwarzenberg
- Department of Pharmacy, Pharmaceutical Biology, Ludwig-Maximilians-University, 81377 Munich, Germany.
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17
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Haines BA, Davis DA, Zykovich A, Peng B, Rao R, Mooney SD, Jin K, Greenberg DA. Comparative protein interactomics of neuroglobin and myoglobin. J Neurochem 2012; 123:192-8. [PMID: 22816983 DOI: 10.1111/j.1471-4159.2012.07881.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Neuroglobin is a hypoxia-inducible O(2)-binding protein with neuroprotective effects in cell and animal models of stroke and Alzheimer's disease. The mechanism underlying neuroglobin's cytoprotective action is unknown, although several possibilities have been proposed, including anti-oxidative and anti-apoptotic effects. We used affinity purification-mass spectrometry methods to identify neuroglobin-interacting proteins in normoxic and hypoxic murine neuronal (HN33) cell lysates, and to compare these interactions with those of a structurally and functionally related protein, myoglobin. We report that the protein interactomes of neuroglobin and myoglobin overlap substantially and are modified by hypoxia. In addition, neuroglobin-interacting proteins include partners consistent with both anti-oxidative and anti-apoptotic functions, as well as with a relationship to several neurodegenerative diseases.
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Affiliation(s)
- Bryan A Haines
- Buck Institute for Research on Aging, Novato, CA 94945, USA
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18
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Porporato PE, Dhup S, Dadhich RK, Copetti T, Sonveaux P. Anticancer targets in the glycolytic metabolism of tumors: a comprehensive review. Front Pharmacol 2011; 2:49. [PMID: 21904528 PMCID: PMC3161244 DOI: 10.3389/fphar.2011.00049] [Citation(s) in RCA: 332] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Accepted: 08/05/2011] [Indexed: 12/21/2022] Open
Abstract
CANCER IS A METABOLIC DISEASE AND THE SOLUTION OF TWO METABOLIC EQUATIONS: to produce energy with limited resources and to fulfill the biosynthetic needs of proliferating cells. Both equations are solved when glycolysis is uncoupled from oxidative phosphorylation in the tricarboxylic acid cycle, a process known as the glycolytic switch. This review addresses in a comprehensive manner the main molecular events accounting for high-rate glycolysis in cancer. It starts from modulation of the Pasteur Effect allowing short-term adaptation to hypoxia, highlights the key role exerted by the hypoxia-inducible transcription factor HIF-1 in long-term adaptation to hypoxia, and summarizes the current knowledge concerning the necessary involvement of aerobic glycolysis (the Warburg effect) in cancer cell proliferation. Based on the many observations positioning glycolysis as a central player in malignancy, the most advanced anticancer treatments targeting tumor glycolysis are briefly reviewed.
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Affiliation(s)
- Paolo E Porporato
- Pole of Pharmacology and Therapeutics, Institute of Experimental and Clinical Research, University of Louvain Medical School Brussels, Belgium
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19
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Semenza GL. Oxygen homeostasis. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2011; 2:336-361. [PMID: 20836033 DOI: 10.1002/wsbm.69] [Citation(s) in RCA: 257] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Metazoan life is dependent upon the utilization of O(2) for essential metabolic processes and oxygen homeostasis is an organizing principle for understanding metazoan evolution, ontology, physiology, and pathology. Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that is expressed by all metazoan species and functions as a master regulator of oxygen homeostasis. Recent studies have elucidated complex mechanisms by which HIF-1 activity is regulated and by which HIF-1 regulates gene expression, with profound consequences for prenatal development, postnatal physiology, and disease pathogenesis.
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Affiliation(s)
- Gregg L Semenza
- Vascular Program, Institute for Cell Engineering, The Johns Hopkins University School of Medicine, Baltimore, MA 21205, USA.,Departments of Pediatrics, Medicine, Oncology, Radiation Oncology, and Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, MA 21205, USA.,McKusick-Nathans Institute of Genetic Medicine, The Johns Hopkins University School of Medicine, Baltimore, MA 21205, USA
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Parks SK, Chiche J, Pouyssegur J. pH control mechanisms of tumor survival and growth. J Cell Physiol 2011; 226:299-308. [PMID: 20857482 DOI: 10.1002/jcp.22400] [Citation(s) in RCA: 268] [Impact Index Per Article: 19.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A distinguishing phenotype of solid tumors is the presence of an alkaline cellular feature despite the surrounding acidic microenvironment. This phenotypic characteristic of tumors, originally described by Otto Warburg, arises due to alterations in metabolism of solid tumors. Hypoxic regions of solid tumors develop due to poor vascularization and in turn regulate the expression of numerous genes via the transcription factor HIF-1. Ultimately, the tumor microenvironment directs the development of tumor cells adapted to survive in an acidic surrounding where normal cells perish. The provision of unique pH characteristics in tumor cells provides a defining trait that has led to the pursuit of treatments that target metabolism, hypoxia, and pH-related mechanisms to selectively kill cancer cells. Numerous studies over the past decade involving the cancer-specific carbonic anhydrase IX have re-kindled an interest in pH disruption-based therapies. Although an acidification of the intracellular compartment is established as a means to induce normal cell death, the defining role of acid-base disturbances in tumor physiology and survival remains unclear. The aim of this review is to summarize recent data relating to the specific role of pH regulation in tumor cell survival. We focus on membrane transport and enzyme studies in an attempt to elucidate their respective functions regarding tumor cell pH regulation. These data are discussed in the context of future directions for the field of tumor cell acid-base-related research.
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Affiliation(s)
- Scott K Parks
- Institute of Developmental Biology and Cancer Research, CNRS UMR 6543, University of Nice, Centre A. Lacassagne, Nice, France.
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21
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Zhdanov AV, Dmitriev RI, Papkovsky DB. Bafilomycin A1 activates respiration of neuronal cells via uncoupling associated with flickering depolarization of mitochondria. Cell Mol Life Sci 2010; 68:903-17. [PMID: 20820851 PMCID: PMC3037485 DOI: 10.1007/s00018-010-0502-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2010] [Revised: 07/08/2010] [Accepted: 08/06/2010] [Indexed: 10/27/2022]
Abstract
Bafilomycin A1 (Baf) induces an elevation of cytosolic Ca(2+) and acidification in neuronal cells via inhibition of the V-ATPase. Also, Baf uncouples mitochondria in differentiated PC12 ((d)PC12), (d)SH-SY5Y cells and cerebellar granule neurons, and markedly elevates their respiration. This respiratory response in (d)PC12 is accompanied by morphological changes in the mitochondria and decreases the mitochondrial pH, Ca(2+) and ΔΨm. The response to Baf is regulated by cytosolic Ca(2+) fluxes from the endoplasmic reticulum. Inhibition of permeability transition pore opening increases the depolarizing effect of Baf on the ΔΨm. Baf induces stochastic flickering of the ΔΨm with a period of 20 ± 10 s. Under conditions of suppressed ATP production by glycolysis, oxidative phosphorylation impaired by Baf does not provide cells with sufficient ATP levels. Cells treated with Baf become more susceptible to excitation with KCl. Such mitochondrial uncoupling may play a role in a number of (patho)physiological conditions induced by Baf.
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Affiliation(s)
- Alexander V Zhdanov
- Biochemistry Department, University College Cork, Cavanagh Pharmacy Building, College Road, Cork, Republic of Ireland.
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Pivtoraiko VN, Harrington AJ, Mader BJ, Luker AM, Caldwell GA, Caldwell KA, Roth KA, Shacka JJ. Low-dose bafilomycin attenuates neuronal cell death associated with autophagy-lysosome pathway dysfunction. J Neurochem 2010; 114:1193-204. [PMID: 20534000 PMCID: PMC2910188 DOI: 10.1111/j.1471-4159.2010.06838.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have shown previously that the plecomacrolide antibiotics bafilomycin A1 and B1 significantly attenuate cerebellar granule neuron death resulting from agents that disrupt lysosome function. To further characterize bafilomycin-mediated cytoprotection, we examined its ability to attenuate the death of naïve and differentiated neuronal SH-SY5Y human neuroblastoma cells from agents that induce lysosome dysfunction in vitro, and from in vivo dopaminergic neuron death in C. elegans. Low-dose bafilomycin significantly attenuated SH-SY5Y cell death resulting from treatment with chloroquine, hydroxychloroquine amodiaquine and staurosporine. Bafilomycin also attenuated the chloroquine-induced reduction in processing of cathepsin D, the principal lysosomal aspartic acid protease, to its mature 'active' form. Chloroquine induced autophagic vacuole accumulation and inhibited autophagic flux, effects that were attenuated upon treatment with bafilomycin and were associated with a significant decrease in chloroquine-induced accumulation of detergent-insoluble alpha-synuclein oligomers. In addition, bafilomycin significantly and dose-dependently attenuated dopaminergic neuron death in C. elegans resulting from in vivo over-expression of human wild-type alpha-synuclein. Together, our findings suggest that low-dose bafilomycin is cytoprotective in part through its maintenance of the autophagy-lysosome pathway, and underscores its therapeutic potential for treating Parkinson's disease and other neurodegenerative diseases that exhibit disruption of protein degradation pathways and accumulation of toxic protein species.
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Affiliation(s)
- Violetta N. Pivtoraiko
- Department of Pathology, Neuropathology Division, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Adam J. Harrington
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL
| | - Burton J. Mader
- Department of Pathology, Neuropathology Division, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Austin M. Luker
- Department of Pathology, Neuropathology Division, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Guy A. Caldwell
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL
- Departments of Neurobiology and Neurology, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Kim A. Caldwell
- Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL
- Departments of Neurobiology and Neurology, University of Alabama at Birmingham, Birmingham, AL 35294
| | - Kevin A. Roth
- Department of Pathology, Neuropathology Division, University of Alabama at Birmingham, Birmingham, AL 35294
| | - John J. Shacka
- Department of Pathology, Neuropathology Division, University of Alabama at Birmingham, Birmingham, AL 35294
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Park SE, Park JW, Cho YS, Ryu JH, Paick JS, Chun YS. HIF-1alpha promotes survival of prostate cells at a high zinc environment. Prostate 2007; 67:1514-23. [PMID: 17683079 DOI: 10.1002/pros.20641] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND The prostate contains extremely high concentrations of zinc, which may be required for male reproduction. Although zinc is essential for many cellular functions, excessive zinc induces cellular toxicity in general. However, despite exposure to high zinc environment, prostate cells survive and proliferate. Thus, the aim of this study was to identify the intrinsic molecular species that endow prostate cells with the ability to overcome zinc toxicity. METHODS Immunohistochemistry, histofluorescent zinc staining, Western blot, in vitro binding assay, immunoprecipitation, caspase activity assay, and proteasome activity assay. RESULTS In rat and human prostates, HIF-1alpha was found to be robustly expressed in epithelial layers containing high zinc levels. Moreover, in cultured prostate cells, HIF-1alpha expression was zinc-dependently induced even under normoxic conditions. Mechanistically, zinc ions inhibited HIF-1-prolyl hydroxylase (PHD) activity, and therefore blocked von Hippel-Lindau tumor suppressor protein (pVHL) binding to HIF-1alpha in vivo and in vitro. The HIF-1alpha stabilization was mediated by oxidative stress induced by zinc ion. Even when prostate cells were treated with high concentrations of zinc ion for extended times, only 10% of cells showed apoptotic death. However, this population of apoptotic cells was increased threefold after HIF-1alpha was knocked-down by siRNA. CONCLUSION These results suggest that HIF-1alpha functions as an intrinsic defense molecule that enables prostate cells to survive in a zinc-rich environment.
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Affiliation(s)
- Sook-Eun Park
- Cancer Research Institute, Seoul National University College of Medicine, 28 Yongon-dong, Chongno-gu, Seoul, Korea
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