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Vidal CM, Ouyang C, Qi Y, Mendez-Dorantes C, Coblentz A, Alva-Ornelas JA, Stark JM, Seewaldt VL, Ann DK. Arginine regulates HSPA5/BiP translation through ribosome pausing in triple-negative breast cancer cells. Br J Cancer 2023; 129:444-454. [PMID: 37386138 PMCID: PMC10403569 DOI: 10.1038/s41416-023-02322-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 05/17/2023] [Accepted: 06/12/2023] [Indexed: 07/01/2023] Open
Abstract
BACKGROUND Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer with a high mortality rate due to a lack of therapeutic targets. Many TNBC cells are reliant on extracellular arginine for survival and express high levels of binding immunoglobin protein (BiP), a marker of metastasis and endoplasmic reticulum (ER) stress response. METHODS In this study, the effect of arginine shortage on BiP expression in the TNBC cell line MDA-MB-231 was evaluated. Two stable cell lines were generated in MDA-MB-231 cells: the first expressed wild-type BiP, and the second expressed a mutated BiP free of the two arginine pause-site codons, CCU and CGU, termed G-BiP. RESULTS The results showed that arginine shortage induced a non-canonical ER stress response by inhibiting BiP translation via ribosome pausing. Overexpression of G-BiP in MDA-MB-231 cells promoted cell resistance to arginine shortage compared to cells overexpressing wild-type BiP. Additionally, limiting arginine led to decreased levels of the spliced XBP1 in the G-BiP overexpressing cells, potentially contributing to their improved survival compared to the parental WT BiP overexpressing cells. CONCLUSION In conclusion, these findings suggest that the downregulation of BiP disrupts proteostasis during arginine shortage-induced non-canonical ER stress and plays a key role in cell growth inhibition, indicating BiP as a target of codon-specific ribosome pausing upon arginine shortage.
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Affiliation(s)
- Christina M Vidal
- Department of Diabetes Complications and Metabolism, Arthur Riggs Diabetes & Metabolism Research Institute, Beckman Research Institute of City of Hope, Duarte, CA, 91010, USA
- Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute of City of Hope, Duarte, CA, 91010, USA
| | - Ching Ouyang
- Department of Computational and Quantitative Medicine, Beckman Research Institute of City of Hope, Duarte, CA, 91010, USA
| | - Yue Qi
- Department of Diabetes Complications and Metabolism, Arthur Riggs Diabetes & Metabolism Research Institute, Beckman Research Institute of City of Hope, Duarte, CA, 91010, USA
| | - Carlos Mendez-Dorantes
- Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute of City of Hope, Duarte, CA, 91010, USA
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, Duarte, CA, 91010, USA
| | - Alaysia Coblentz
- Department of Diabetes Complications and Metabolism, Arthur Riggs Diabetes & Metabolism Research Institute, Beckman Research Institute of City of Hope, Duarte, CA, 91010, USA
| | - Jackelyn A Alva-Ornelas
- Department of Population Sciences, Beckman Research Institute of City of Hope, Duarte, CA, 91010, USA
| | - Jeremy M Stark
- Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute of City of Hope, Duarte, CA, 91010, USA
- Department of Cancer Genetics and Epigenetics, Beckman Research Institute of City of Hope, Duarte, CA, 91010, USA
| | - Victoria L Seewaldt
- Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute of City of Hope, Duarte, CA, 91010, USA
- Department of Population Sciences, Beckman Research Institute of City of Hope, Duarte, CA, 91010, USA
| | - David K Ann
- Department of Diabetes Complications and Metabolism, Arthur Riggs Diabetes & Metabolism Research Institute, Beckman Research Institute of City of Hope, Duarte, CA, 91010, USA.
- Irell & Manella Graduate School of Biological Sciences, Beckman Research Institute of City of Hope, Duarte, CA, 91010, USA.
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Toral M, Jiménez R, Romero M, Robles-Vera I, Sánchez M, Salaices M, Sabio JM, Duarte J. Role of endoplasmic reticulum stress in the protective effects of PPARβ/δ activation on endothelial dysfunction induced by plasma from patients with lupus. Arthritis Res Ther 2017; 19:268. [PMID: 29208022 PMCID: PMC5717848 DOI: 10.1186/s13075-017-1478-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 11/20/2017] [Indexed: 01/01/2023] Open
Abstract
Background We tested whether GW0742, a peroxisome proliferator-activated receptor beta/delta (PPARβ/δ) agonist, improves endothelial dysfunction induced by plasma from patients with systemic lupus erythematosus (SLE) involving the inhibition of endoplasmic reticulum (ER) stress. Methods A total of 12 non-pregnant women with lupus and 5 non-pregnant healthy women (controls) participated in the study. Cytokines and double-stranded DNA autoantibodies (anti-dsDNA) were tested in plasma samples. Endothelial cells, isolated from human umbilical cord veins (HUVECs), were used to measure nitric oxide (NO), intracellular reactive oxygen species (ROS) production, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity, and ER stress markers. Results Interferon-γ, interleukin-6, and interleukin-12 levels were significantly increased in plasma from patients with SLE with active nephritis (AN), as compared to both patients with SLE with inactive nephritis (IN) and the control group. The NO production stimulated by both the calcium ionophore A23187 and insulin was significantly reduced in HUVECs incubated with plasma from patients with AN-SLE as compared with the control group. Plasma from patients with IN-SLE did not modify A23187-stimulated NO production. Increased ROS production and NADPH oxidase activity were found in HUVECs incubated with plasma from patients with AN-SLE, which were suppressed by the ER stress inhibitor 4-PBA and the NADPH oxidase inhibitors, apocynin and VAS2870. GW0742 incubation restored the impaired NO production, the increased ROS levels, and the increased ER stress markers induced by plasma from patients with AN-SLE. These protective effects were abolished by the PPARβ/δ antagonist GSK0660 and by silencing PPARβ/δ. Conclusions PPARβ/δ activation may be an important target to control endothelial dysfunction in patients with SLE.
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Affiliation(s)
- Marta Toral
- Department of Pharmacology, School of Pharmacy, University of Granada, 18071, Granada, Spain
| | - Rosario Jiménez
- Department of Pharmacology, School of Pharmacy, University of Granada, 18071, Granada, Spain.,Instituto de Investigación Biosanitaria de Granada, ibs.GRANADA, Granada, Spain.,CIBER of cardiovascular diseases (CIBERCV), Madrid, Spain
| | - Miguel Romero
- Department of Pharmacology, School of Pharmacy, University of Granada, 18071, Granada, Spain.,Instituto de Investigación Biosanitaria de Granada, ibs.GRANADA, Granada, Spain.,CIBER of cardiovascular diseases (CIBERCV), Madrid, Spain
| | - Iñaki Robles-Vera
- Department of Pharmacology, School of Pharmacy, University of Granada, 18071, Granada, Spain
| | - Manuel Sánchez
- Department of Pharmacology, School of Pharmacy, University of Granada, 18071, Granada, Spain.,Instituto de Investigación Biosanitaria de Granada, ibs.GRANADA, Granada, Spain
| | - Mercedes Salaices
- CIBER of cardiovascular diseases (CIBERCV), Madrid, Spain.,Department of Pharmacology, School of Medicine, Autonomous University of Madrid, Research Institute Universitary Hospital La Paz (IdiPAZ), 28029, Madrid, Spain
| | - José Mario Sabio
- Instituto de Investigación Biosanitaria de Granada, ibs.GRANADA, Granada, Spain.,Department of Internal Medicine, Virgen de las Nieves Universitary Hospital, Granada, Spain
| | - Juan Duarte
- Department of Pharmacology, School of Pharmacy, University of Granada, 18071, Granada, Spain. .,Instituto de Investigación Biosanitaria de Granada, ibs.GRANADA, Granada, Spain. .,CIBER of cardiovascular diseases (CIBERCV), Madrid, Spain.
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3
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Kizuka Y, Funayama S, Shogomori H, Nakano M, Nakajima K, Oka R, Kitazume S, Yamaguchi Y, Sano M, Korekane H, Hsu TL, Lee HY, Wong CH, Taniguchi N. High-Sensitivity and Low-Toxicity Fucose Probe for Glycan Imaging and Biomarker Discovery. Cell Chem Biol 2017; 23:782-792. [PMID: 27447047 DOI: 10.1016/j.chembiol.2016.06.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 06/13/2016] [Accepted: 06/14/2016] [Indexed: 01/13/2023]
Abstract
Fucose, a terminal sugar in glycoconjugates, critically regulates various physiological and pathological phenomena, including cancer development and inflammation. However, there are currently no probes for efficient labeling and detection of this sugar. We chemically synthesized a novel series of alkynyl-fucose analogs as probe candidates and found that 7-alkynyl-fucose gave the highest labeling efficiency and low cytotoxicity. Among the fucose analogs, 7-alkynyl-fucose was the best substrate against all five fucosyltransferases examined. We confirmed its conversion to the corresponding guanosine diphosphate derivative in cells and found that cellular glycoproteins were labeled much more efficiently with 7-alkynyl-fucose than with an existing probe. 7-Alkynyl-fucose was detected in the N-glycan core by mass spectrometry, and 7-alkynyl-fucose-modified proteins mostly disappeared in core-fucose-deficient mouse embryonic fibroblasts, suggesting that this analog mainly labeled core fucose in these cells. These results indicate that 7-alkynyl-fucose is a highly sensitive and powerful tool for basic glycobiology research and clinical application for biomarker discovery.
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Affiliation(s)
- Yasuhiko Kizuka
- Disease Glycomics Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center for Systems Chemical Biology, Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Sho Funayama
- Department of Disease Glycomics (Seikagaku Corporation), Research Institute for Microbial Diseases, Osaka University, Osaka 567-0047, Japan
| | - Hidehiko Shogomori
- Department of Disease Glycomics (Seikagaku Corporation), Research Institute for Microbial Diseases, Osaka University, Osaka 567-0047, Japan
| | - Miyako Nakano
- Graduate School of Advanced Sciences of Matter, Hiroshima University, Hiroshima 739-8530, Japan
| | - Kazuki Nakajima
- Department of Disease Glycomics (Seikagaku Corporation), Research Institute for Microbial Diseases, Osaka University, Osaka 567-0047, Japan; Molecular Membrane Neuroscience, Brain Science Institute, RIKEN, Saitama 351-0198, Japan
| | - Ritsuko Oka
- Disease Glycomics Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center for Systems Chemical Biology, Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Shinobu Kitazume
- Disease Glycomics Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center for Systems Chemical Biology, Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Yoshiki Yamaguchi
- Structural Glycobiology Team, Global Research Cluster, RIKEN, Saitama 351-0198, Japan
| | - Masahiro Sano
- Department of Disease Glycomics (Seikagaku Corporation), Research Institute for Microbial Diseases, Osaka University, Osaka 567-0047, Japan
| | - Hiroaki Korekane
- Department of Disease Glycomics (Seikagaku Corporation), Research Institute for Microbial Diseases, Osaka University, Osaka 567-0047, Japan
| | - Tsui-Ling Hsu
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Hsiu-Yu Lee
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Chi-Huey Wong
- Genomics Research Center, Academia Sinica, Taipei 115, Taiwan
| | - Naoyuki Taniguchi
- Disease Glycomics Team, Systems Glycobiology Research Group, RIKEN-Max Planck Joint Research Center for Systems Chemical Biology, Global Research Cluster, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan; Department of Disease Glycomics (Seikagaku Corporation), Research Institute for Microbial Diseases, Osaka University, Osaka 567-0047, Japan.
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Tong J, Okutani F, Murata Y, Taniguchi M, Namba T, Wang YJ, Kaba H. Tunicamycin impairs olfactory learning and synaptic plasticity in the olfactory bulb. Neuroscience 2017; 344:371-379. [PMID: 28087337 DOI: 10.1016/j.neuroscience.2017.01.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 11/25/2016] [Accepted: 01/02/2017] [Indexed: 01/05/2023]
Abstract
Tunicamycin (TM) induces endoplasmic reticulum (ER) stress and inhibits N-glycosylation in cells. ER stress is associated with neuronal death in neurodegenerative disorders, such as Parkinson's disease and Alzheimer's disease, and most patients complain of the impairment of olfactory recognition. Here we examined the effects of TM on aversive olfactory learning and the underlying synaptic plasticity in the main olfactory bulb (MOB). Behavioral experiments demonstrated that the intrabulbar infusion of TM disabled aversive olfactory learning without affecting short-term memory. Histological analyses revealed that TM infusion upregulated C/EBP homologous protein (CHOP), a marker of ER stress, in the mitral and granule cell layers of MOB. Electrophysiological data indicated that TM inhibited tetanus-induced long-term potentiation (LTP) at the dendrodendritic excitatory synapse from mitral to granule cells. A low dose of TM (250nM) abolished the late phase of LTP, and a high dose (1μM) inhibited the early and late phases of LTP. Further, high-dose, but not low-dose, TM reduced the paired-pulse facilitation ratio, suggesting that the inhibitory effects of TM on LTP are partially mediated through the presynaptic machinery. Thus, our results support the hypothesis that TM-induced ER stress impairs olfactory learning by inhibiting synaptic plasticity via presynaptic and postsynaptic mechanisms in MOB.
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Affiliation(s)
- Jia Tong
- Department of Physiology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
| | - Fumino Okutani
- Department of Physiology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan; Department of Occupational Health, Kochi Medical School, Nankoku, Kochi 783-8505, Japan.
| | - Yoshihiro Murata
- Department of Physiology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
| | - Mutsuo Taniguchi
- Department of Physiology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
| | - Toshiharu Namba
- Department of Physiology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
| | - Yu-Jie Wang
- Department of Physiology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
| | - Hideto Kaba
- Department of Physiology, Kochi Medical School, Nankoku, Kochi 783-8505, Japan
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Haas MJ, Jafri M, Wehmeier KR, Onstead-Haas LM, Mooradian AD. Inhibition of endoplasmic reticulum stress and oxidative stress by vitamin D in endothelial cells. Free Radic Biol Med 2016; 99:1-10. [PMID: 27458123 DOI: 10.1016/j.freeradbiomed.2016.07.020] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Revised: 07/14/2016] [Accepted: 07/21/2016] [Indexed: 11/19/2022]
Abstract
Endoplasmic reticulum (ER) stress and oxidative stress promote endothelial dysfunction and atherosclerosis. Since vitamin D has been shown in several studies to lower the risk of cardiovascular disease, we examined the effects of vitamin D on ER stress and oxidative stress in endothelial cells. ER stress was measured using the placental secreted alkaline phosphatase assay and oxidative stress was measured by hydroethidine fluorescence. Expression of ER stress markers, including glucose-regulated protein 78, c-jun N-terminal kinase 1 phosphorylation, and eukaryotic initiation factor 2α phosphorylation, as well as X-box binding protein-1 splicing were measured in tunicamycin (TM)-treated human umbilical endothelial cells (HUVEC) treated with 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) and other vitamin D analogs. When TM and 1,25-(OH)2D3 were added simultaneously, 1,25-(OH)2D3 prevented ER stress. However, the effect was much stronger when cells were pre-treated with 1,25-(OH)2D3 for 24-h. However, ER stress was not inhibited by 25-OH vitamin D3 (25-OHD3) or the vitamin D analog EB1089. Both ZK191784 and the vitamin D metabolite 24,25-dihydroxyvitamin D3 were as effective as 1,25-(OH)2D3 in preventing ER stress. Similar effects were observed dextrose-induced stress. All of the compounds tested, except for 25-OHD3, inhibited dextrose-induced (27.5mM) oxidative stress and ER stress. Although TM with and without 1,25-(OH)2D3 had no effect on VDR expression, inhibition of VDR expression via siRNA prevented 1,25-(OH)2D3, ZK191784, EB1089, and 24,25-dihydroxyvitamin D3 from inhibiting dextrose-mediated SO generation. Furthermore, each vitamin D analog, with the exception of 25-OHD3, prevented dextrose-induced toxicity. These results suggest that vitamin D has a protective effect on vascular endothelial cells.
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Affiliation(s)
- Michael J Haas
- Department of Medicine, University of Florida College of Medicine, Jacksonville, FL, United States.
| | - Mohammad Jafri
- Department of Medicine, University of Florida College of Medicine, Jacksonville, FL, United States
| | - Kent R Wehmeier
- Department of Medicine, University of Florida College of Medicine, Jacksonville, FL, United States
| | - Luisa M Onstead-Haas
- Department of Medicine, University of Florida College of Medicine, Jacksonville, FL, United States
| | - Arshag D Mooradian
- Department of Medicine, University of Florida College of Medicine, Jacksonville, FL, United States
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Taylor DL, Brennan TM, Bridges CG, Kang MS, Tyms AS. Synergistic Inhibition of Human Immunodeficiency Virus Type 1 in vitro by 6-0-butanoylcastanospermine (MDL 28574) in Combination with Inhibitors of the Virus-Encoded Reverse Transcriptase and Proteinase. ACTA ACUST UNITED AC 2016. [DOI: 10.1177/095632029500600303] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The anti-human immunodeficiency virus type 1 (HIV-1) activity of the α-glucosidase 1 inhibitor 6-0-butanoylcastanospermine (MDL 28574) was assessed in combination with the 2′,3′-dideoxynucleoside analogues zidovudine (AZT), didanosine (ddl) and zalcitabine (ddC). MDL 28574 was also evaluated in combination with the non-nucleoside reverse transcriptase (RT) inhibitor nevirapine and the HIV proteinase inhibitor saquinavir (Ro-31-8959). Drug interactions were examined by the isobologram technique and by calculating combination indices (C.l.s). In all cases synergistic inhibition of HIV-1 replication was observed. In three-drug combinations, a marked synergistic antiviral effect was also observed, with C.I. values in the range 0.35-0.44 for MDL 28574 in combination with AZT and nevirapine, and in the range 0.34-0.67 for MDL 28574 in combination with AZT and saquinavir. Moreover, the combination of MDL 28574 with other drugs did not produce detrimental effects on cell division. MDL 28574 is currently in clinical trials and may have an important role in combination chemotherapy for HIV infections.
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Affiliation(s)
- D. L. Taylor
- MRC Collaborative Centre, 1-3 Burtonhole Lane, Mill Hill, London NW7 1AD, UK
| | - T. M. Brennan
- MRC Collaborative Centre, 1-3 Burtonhole Lane, Mill Hill, London NW7 1AD, UK
| | - C. G. Bridges
- MRC Collaborative Centre, 1-3 Burtonhole Lane, Mill Hill, London NW7 1AD, UK
| | - M. S. Kang
- Marion Merrell Dow Research Institute, Galbraith Road, Cincinnati, Ohio, USA
| | - A. S. Tyms
- MRC Collaborative Centre, 1-3 Burtonhole Lane, Mill Hill, London NW7 1AD, UK
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7
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The glutathione mimic ebselen inhibits oxidative stress but not endoplasmic reticulum stress in endothelial cells. Life Sci 2015; 134:9-15. [PMID: 26006036 DOI: 10.1016/j.lfs.2015.05.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 04/01/2015] [Accepted: 05/01/2015] [Indexed: 12/14/2022]
Abstract
AIMS Reactive oxygen species are associated with cardiovascular disease, diabetes, and atherosclerosis, yet the use of antioxidants in clinical trials has been ineffective at improving outcomes. In endothelial cells, high-dextrose-induced oxidative stress and endoplasmic reticulum stress promote endothelial dysfunction leading to the recruitment and activation of peripheral blood lymphocytes and the breakdown of barrier function. Ebselen, a glutathione peroxidase 1 (GPX1) mimic, has been shown to improve β-cell function in diabetes and prevent atherosclerosis. MAIN METHODS To determine if ebselen inhibits both oxidative stress and endoplasmic reticulum (ER) stress in endothelial cells, we examined its effects in human umbilical vein endothelial cells (HUVEC) and human coronary artery endothelial cells (HCAEC) with and without high-dextrose. Oxidative stress and ER stress were measured by 2-methyl-6-(4-methoxyphenyl)-3,7-dihydroimidazo[1,2-A]pyrazin-3-one hydrochloride chemiluminescence and ER stress alkaline phosphatase assays, respectively. GPX1 over-expression and knockdown were performed by transfecting cells with a GPX1 expression construct or a GPX1-specific siRNA, respectively. KEY FINDINGS Ebselen inhibited dextrose-induced oxidative stress but not ER stress in both HUVEC and HCAEC. Ebselen also had no effect on tunicamycin-induced ER stress in HCAEC. Furthermore, augmentation of GPX1 activity directly by sodium selenite supplementation or transfection of a GPX1 expression plasmid decreased dextrose-induced oxidative stress but not ER stress, while GPX1 knockout enhanced oxidative stress but had no effect on ER stress. SIGNIFICANCE These results suggest that ebselen targets only oxidative stress but not ER stress.
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Forbes K, Shah VK, Siddals K, Gibson JM, Aplin JD, Westwood M. Statins inhibit insulin-like growth factor action in first trimester placenta by altering insulin-like growth factor 1 receptor glycosylation. Mol Hum Reprod 2014; 21:105-14. [PMID: 25304981 PMCID: PMC4275043 DOI: 10.1093/molehr/gau093] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The rapid rise in obesity, metabolic syndrome and type 2 diabetes is one of the major healthcare problems of the Western world. Affected individuals are often treated with statins (3-hydroxy-3-methylglutaryl co-enzyme A [HMG CoA] reductase inhibitors) to reduce circulating cholesterol levels and the risk of developing cardiovascular disease; given the evolving demographic profile of these conditions, such drugs are increasingly prescribed to women of reproductive age. We have previously shown that exposure of placental tissue to statins inhibits the action of insulin-like growth factors (IGF)-I and -II which are key regulators of trophoblast proliferation and placental development. N-linked glycans in the IGF receptor, IGF1R, influence its presentation at the cell surface. This study aimed to determine whether statins, which are known to affect N-glycosylation, modulate IGF1R function in placenta. Treatment of first trimester villous tissue explants with statins (pravastatin or cerivastatin) or inhibitors of N-glycosylation (tunicamycin, deoxymannojirimycin or castanospermine) altered receptor distribution in trophoblast and attenuated proliferation induced by IGF-I or IGF-II (Ki67; P < 0.05, n = 5). Decreased binding of Phaseolus vulgaris lectin and phytohaemagglutinin to IGF1R immunoprecipitated from treated explants demonstrated reduced levels of complex N-linked glycans. Co-incubation of tissue explants with statins and farnesyl pyrophosphate (which increases the supply of dolichol intermediates), prevented statin-mediated disruption of IGF1R localization and reversed the negative effect on IGF-mediated trophoblast proliferation. These data suggest that statins attenuate IGF actions in the placenta by inhibiting N-linked glycosylation and subsequent expression of mature IGF1R at the placental cell surface.
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Affiliation(s)
- Karen Forbes
- Maternal and Fetal Health Research Centre, University of Manchester, Manchester Academic Health Sciences Centre, Manchester M13 9WL, UK Maternal and Fetal Health Research Centre, St. Mary's Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester M13 9WL, UK
| | - Vinit K Shah
- Maternal and Fetal Health Research Centre, University of Manchester, Manchester Academic Health Sciences Centre, Manchester M13 9WL, UK Maternal and Fetal Health Research Centre, St. Mary's Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester M13 9WL, UK
| | - Kirk Siddals
- Centre for Imaging Sciences, Institute of Population Health, University of Manchester, Manchester Academic Health Sciences Centre, Manchester M13 9PY, UK
| | - J Martin Gibson
- Centre for Imaging Sciences, Institute of Population Health, University of Manchester, Manchester Academic Health Sciences Centre, Manchester M13 9PY, UK
| | - John D Aplin
- Maternal and Fetal Health Research Centre, University of Manchester, Manchester Academic Health Sciences Centre, Manchester M13 9WL, UK Maternal and Fetal Health Research Centre, St. Mary's Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester M13 9WL, UK
| | - Melissa Westwood
- Maternal and Fetal Health Research Centre, University of Manchester, Manchester Academic Health Sciences Centre, Manchester M13 9WL, UK Maternal and Fetal Health Research Centre, St. Mary's Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester M13 9WL, UK
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Park EC, Kim SI, Hong Y, Hwang JW, Cho GS, Cha HN, Han JK, Yun CH, Park SY, Jang IS, Lee ZW, Choi JS, Kim S, Kim GH. Inhibition of CYP4A reduces hepatic endoplasmic reticulum stress and features of diabetes in mice. Gastroenterology 2014; 147:860-9. [PMID: 24983671 DOI: 10.1053/j.gastro.2014.06.039] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 06/20/2014] [Accepted: 06/24/2014] [Indexed: 01/12/2023]
Abstract
BACKGROUND & AIMS Endoplasmic reticulum (ER) stress is implicated in the development of type 2 diabetes mellitus. ER stress activates the unfolded protein response pathway, which contributes to apoptosis and insulin resistance. We investigated the roles of cytochrome P450 4A (CYP4A) in the regulation of hepatic ER stress, insulin resistance, and the development of diabetes in mice. METHODS We used mass spectrometry to compare levels of CYP450 proteins in livers from C57BL/6J and C57BL/KsJ-db/db (db/db) mice; findings were confirmed by immunoblot and real-time PCR analyses. To create a model of diet-induced diabetes, C57BL/6J mice were placed on high-fat diets. Mice were given intraperitoneal injections of an inhibitor (HET0016) or an inducer (clofibrate) of CYP4A, or tail injections of small hairpin RNAs against CYP4A messenger RNA; liver tissues were collected and analyzed for ER stress, insulin resistance, and apoptosis. The effect of HET0016 and CYP4A knockdown also were analyzed in HepG2 cells. RESULTS Levels of the CYP4A isoforms were highly up-regulated in livers of db/db mice compared with C57BL/6J mice. Inhibition of CYP4A in db/db and mice on high-fat diets reduced features of diabetes such as insulin hypersecretion, hepatic steatosis, and increased glucose tolerance. CYP4A inhibition reduced levels of ER stress, insulin resistance, and apoptosis in the livers of diabetic mice; it also restored hepatic functions. Inversely, induction of CYP4A accelerated ER stress, insulin resistance, and apoptosis in livers of db/db mice. CONCLUSIONS CYP4A proteins are up-regulated in livers of mice with genetically induced and diet-induced diabetes. Inhibition of CYP4A in mice reduces hepatic ER stress, apoptosis, insulin resistance, and steatosis. Strategies to reduce levels or activity of CYP4A proteins in liver might be developed for treatment of patients with type 2 diabetes.
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Affiliation(s)
| | - Seung Il Kim
- Division of Life Science, Korea Basic Science Institute, Daejeon, Republic of Korea
| | - Yeonhee Hong
- Division of Life Science, Korea Basic Science Institute, Daejeon, Republic of Korea
| | - Jeong Won Hwang
- Division of Life Science, Korea Basic Science Institute, Daejeon, Republic of Korea
| | - Gun-Sik Cho
- Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk, Republic of Korea
| | - Hye-Na Cha
- Department of Physiology, College of Medicine, Yeungnam University, Daegu, Republic of Korea
| | - Jin-Kwan Han
- Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang, Kyungbuk, Republic of Korea
| | - Chul-Ho Yun
- School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea
| | - So-Young Park
- Department of Physiology, College of Medicine, Yeungnam University, Daegu, Republic of Korea
| | - Ik-Soon Jang
- Division of Life Science, Korea Basic Science Institute, Daejeon, Republic of Korea
| | - Zee-Won Lee
- Division of Life Science, Korea Basic Science Institute, Daejeon, Republic of Korea
| | - Jong-Soon Choi
- Division of Life Science, Korea Basic Science Institute, Daejeon, Republic of Korea; Graduate School of Analytical Science and Technology, Chungnam National University, Daejeon, Republic of Korea
| | | | - Gun-Hwa Kim
- Division of Life Science, Korea Basic Science Institute, Daejeon, Republic of Korea; Department of Functional Genomics, University of Science and Technology, Daejeon, Republic of Korea.
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10
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Sousa CA, Rodríguez-Borges JE, Garcia-Mera X. Synthesis and N-functionalization of isoxazolidines: a new approach to nucleoside analogues. Tetrahedron Lett 2014. [DOI: 10.1016/j.tetlet.2014.06.076] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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11
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Chesnokov V, Gong B, Sun C, Itakura K. Anti-cancer activity of glucosamine through inhibition of N-linked glycosylation. Cancer Cell Int 2014; 14:45. [PMID: 24932134 PMCID: PMC4057579 DOI: 10.1186/1475-2867-14-45] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Accepted: 05/13/2014] [Indexed: 12/19/2022] Open
Abstract
BACKGROUND We have reported that the glucosamine suppressed the proliferation of the human prostate carcinoma cell line DU145 through inhibition of STAT3 signaling. DU145 cells autonomously express IL-6 and the IL-6/STAT3 signaling is activated. IL-6 receptor subunits are subject to N-glycosylation, a posttranslational modification which is important for protein stability and function. We speculated that the inhibition of STAT3 phosphorylation by glucosamine might be a functional consequence of the reduced N-glycosylation of gp130. METHODS The human prostate cancer cell lines DU145 and PC-3 and human melanoma cell line A2058 were used in this study. Glucosamine effects on N-glycosylation of glycoproteins were determined by Western blot analysis. IL-6 binding to DU145 cells was analyzed by flow cytometry. The cell proliferation suppression was investigated by colorimetric Janus green staining method. RESULTS In DU145 cells glucosamine reduced the N-glycosylation of gp130, decreased IL-6 binding to cells and impaired the phosphorylation of JAK2, SHP2 and STAT3. Glucosamine acts in a very similar manner to tunicamycin, an inhibitor of protein N-glycosylation. Glucosamine-mediated inhibition of N-glycosylation was neither protein- nor cell-specific. Sensitivity of DU145, A2058 and PC-3 cells to glucosamine-induced inhibition of N-glycosylation were well correlated to glucosamine cytotoxicity in these cells. CONCLUSION Our results suggested that the glucosamine-induced global inhibition of protein N-glycosylation might be the basic mechanism underlying its multiple biochemical and cellular effects.
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Affiliation(s)
- Viktor Chesnokov
- Department of Molecular and Cellular Biology, Beckman Research Institute of City of Hope National Medical Center, 1500 East Duarte Road, Duarte, California 91010, USA
| | - Beata Gong
- Department of Molecular and Cellular Biology, Beckman Research Institute of City of Hope National Medical Center, 1500 East Duarte Road, Duarte, California 91010, USA
| | - Chao Sun
- Department of Molecular and Cellular Biology, Beckman Research Institute of City of Hope National Medical Center, 1500 East Duarte Road, Duarte, California 91010, USA
| | - Keiichi Itakura
- Department of Molecular and Cellular Biology, Beckman Research Institute of City of Hope National Medical Center, 1500 East Duarte Road, Duarte, California 91010, USA
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12
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Abstract
Control and modulation of electrical signaling is vital to normal physiology, particularly in neurons, cardiac myocytes, and skeletal muscle. The orchestrated activities of variable sets of ion channels and transporters, including voltage-gated ion channels (VGICs), are responsible for initiation, conduction, and termination of the action potential (AP) in excitable cells. Slight changes in VGIC activity can lead to severe pathologies including arrhythmias, epilepsies, and paralyses, while normal excitability depends on the precise tuning of the AP waveform. VGICs are heavily posttranslationally modified, with upward of 30% of the mature channel mass consisting of N- and O-glycans. These glycans are terminated typically by negatively charged sialic acid residues that modulate voltage-dependent channel gating directly. The data indicate that sialic acids alter VGIC activity in isoform-specific manners, dependent in part, on the number/location of channel sialic acids attached to the pore-forming alpha and/or auxiliary subunits that often act through saturating electrostatic mechanisms. Additionally, cell-specific regulation of sialylation can affect VGIC gating distinctly. Thus, channel sialylation is likely regulated through two mechanisms that together contribute to a dynamic spectrum of possible gating motifs: a subunit-specific mechanism and regulated (aberrant) changes in the ability of the cell to glycosylate. Recent studies showed that neuronal and cardiac excitability is modulated through regulated changes in voltage-gated Na(+) channel sialylation, suggesting that both mechanisms of differential VGIC sialylation contribute to electrical signaling in the brain and heart. Together, the data provide insight into an important and novel paradigm involved in the control and modulation of electrical signaling.
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Affiliation(s)
- Andrew R Ednie
- Programs in Cardiovascular Research and Neuroscience, Department of Molecular Pharmacology & Physiology, College of Medicine, University of South Florida, Tampa, Florida, USA
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13
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Lu Y, Qian L, Zhang Q, Chen B, Gui L, Huang D, Chen G, Chen L. Palmitate induces apoptosis in mouse aortic endothelial cells and endothelial dysfunction in mice fed high-calorie and high-cholesterol diets. Life Sci 2013; 92:1165-73. [PMID: 23680379 DOI: 10.1016/j.lfs.2013.05.002] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 03/30/2013] [Accepted: 05/01/2013] [Indexed: 12/13/2022]
Abstract
AIMS Obesity is associated with hypertriglyceridemia and elevated circulating free fatty acids (FFA), resulting in endothelial dysfunction. Endoplasmic reticulum (ER) stress has been implicated in many of these processes. To determine if ER stress participates in palmitate-induced apoptosis, we investigated the effects of diet-induced obesity and palmitate on mouse aortic endothelial cells (MAEC) in vivo and in vitro. MAIN METHODS Male C57BL/6 mice were fed standard chow diets (SCD) or high-calorie and high-cholesterol diets (HCD) for 3 months. Insulin resistance was detected, and the serum, including proinflammatory indices and markers of endothelial function, was also analyzed. The ultrastructure and apoptosis of the endothelial cells in the thoracic aorta were observed. The primary MAEC were separated and treated with palmitate at different concentrations or different times respectively to observe any changes in cellular proliferation, intracellular reactive oxygen species (ROS) levels and apoptosis. Finally, the ER stress markers C/EBP homologous protein (CHOP) and glucose-regulated protein 78 (GRP78) were analyzed. KEY FINDINGS HCD-fed obese mice became inflammation-activated and insulin-resistant. Swollen mitochondria, expanded ER and apoptosis in the endothelial cells of the thoracic aorta were observed in HCD-fed mice. Palmitate inhibited cell proliferation, increased production of ROS and induced apoptosis in MAEC. CHOP was overexpressed and shifted into the nucleus (mainly), while the expression of GRP78 was upregulated in the palmitate-treated MAEC. SIGNIFICANCE Our results indicate that diet-induced obesity results in endothelial dysfunction in vivo, and that oxidative and ER stress may be involved in apoptosis induced by the palmitate in vitro.
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MESH Headings
- Animals
- Aorta, Thoracic/drug effects
- Aorta, Thoracic/metabolism
- Aorta, Thoracic/pathology
- Apoptosis/drug effects
- Apoptosis/physiology
- Cells, Cultured
- Cholesterol, Dietary/adverse effects
- Cholesterol, Dietary/metabolism
- Endoplasmic Reticulum Chaperone BiP
- Endothelial Cells/drug effects
- Endothelial Cells/metabolism
- Endothelial Cells/pathology
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/pathology
- Endothelium, Vascular/physiopathology
- Energy Intake/physiology
- Male
- Mice
- Mice, Inbred C57BL
- Obesity/metabolism
- Obesity/pathology
- Palmitic Acid/toxicity
- Random Allocation
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Affiliation(s)
- Yunxia Lu
- Department of Biochemistry and Molecular Biology, Anhui Medical University, Hefei, Anhui 230032, PR China.
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14
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Naem E, Haas MJ, Wong NCW, Mooradian AD. Endoplasmic reticulum stress in HepG2 cells inhibits apolipoprotein A-I secretion. Life Sci 2012; 92:72-80. [PMID: 23154241 DOI: 10.1016/j.lfs.2012.11.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Revised: 10/03/2012] [Accepted: 10/30/2012] [Indexed: 10/27/2022]
Abstract
AIMS Endoplasmic reticulum (ER) stress modulates gene expression and has been implicated in causing dyslipidemias. To determine if ER stress may contribute to hypoalphalipoproteinemia through suppression of apo A-I gene expression, human hepatoma cell line Hep G2 was treated with ER stress inducers and the changes in apo A-I gene expression were compared to albumin gene expression. MAIN METHODS HepG2 cells were treated with tunicamycin (TM) and thapsigargin (TG), two potent inducers of ER stress, and apo A-I and albumin protein levels, mRNA levels, and promoter activity were measured. ER stress was measured using the ER stress-responsive alkaline phosphatase assay and by Western blot quantitation of ER stress markers such as glucose-regulated protein-78 (GRP-78), phosphorylated Jun N-terminal kinase (phospho-JNK), total JNK, phosphorylated eukaryotic initiation factor 2 alpha (phospho eIF2α), and total eIF2α. KEY FINDINGS TM and TG induced ER stress in HepG2 cells and reduced apo A-I and albumin secretion in a dose-dependent manner. Intracellular albumin levels increased in cells treated with TM and TG while intracellular apo A-I levels decreased. Albumin mRNA and albumin gene promoter activity were reduced in proportion to the decrease in albumin secreted while changes in the apo A-I mRNA levels and promoter activity were modest and did not account for the reduction in apo A-I secretion. SIGNIFICANCE These results indicate that apo A-I secretion is inhibited by ER stress possibly by affecting cellular degradation pathways. However, ER stress does not affect apo A-I secretion by regulating gene expression.
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Affiliation(s)
- Emad Naem
- The Department of Medicine, Division of Endocrinology, Diabetes, and Metabolism, University of Florida, Jacksonville College of Medicine, Jacksonville, FL 32209, USA
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15
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Sousa CA, Rizzo-Aguiar F, Vale MLC, García-Mera X, Caamaño O, Rodríguez-Borges JE. A route to selective functionalization of polyhydroxypyrrolidines. Tetrahedron Lett 2012. [DOI: 10.1016/j.tetlet.2011.12.037] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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16
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Siddals KW, Allen J, Sinha S, Canfield AE, Kalra PA, Gibson JM. Apposite insulin-like growth factor (IGF) receptor glycosylation is critical to the maintenance of vascular smooth muscle phenotype in the presence of factors promoting osteogenic differentiation and mineralization. J Biol Chem 2011; 286:16623-30. [PMID: 21454560 PMCID: PMC3089505 DOI: 10.1074/jbc.m110.202929] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Revised: 03/15/2011] [Indexed: 11/06/2022] Open
Abstract
Vascular calcification is strongly linked with increased morbidity and mortality from cardiovascular disease. Vascular calcification is an active cell-mediated process that involves the differentiation of vascular smooth muscle cells (VSMCs) to an osteoblast-like phenotype. Several inhibitors of this process have been identified, including insulin-like growth factor-I (IGF-I). In this study, we examined the role of the IGF receptor (IGFR) and the importance of IGFR glycosylation in the maintenance of the VSMC phenotype in the face of factors known to promote osteogenic conversion. IGF-I (25 ng/ml) significantly protected VSMCs from β-glycerophosphate-induced osteogenic differentiation (p < 0.005) and mineral deposition (p < 0.01). Mevalonic acid depletion (induced by 100 nm cerivastatin) significantly inhibited these IGF protective effects (p < 0.01). Mevalonic acid depletion impaired IGFR processing, decreased the expression of mature IGFRs at the cell surface, and inhibited the downstream activation of Akt and MAPK. Inhibitors of N-linked glycosylation (tunicamycin, deoxymannojirimycin, and deoxynojirimycin) also markedly attenuated the inhibitory effect of IGF-I on β-glycerophosphate-induced mineralization (p < 0.05) and activation of Akt and MAPK. These results demonstrate that alterations in the glycosylation of the IGFR disrupt the ability of IGF-I to protect against the osteogenic differentiation and mineralization of VSMCs by several interrelated mechanisms: decreased IGFR processing, reduced IGFR cell-surface expression, and reduced downstream signaling via the Akt and MAPK pathways. IGF-I thus occupies a critical position in the maintenance of normal VSMC phenotype and protection from factors known to stimulate vascular calcification.
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Affiliation(s)
- Kirk W Siddals
- Imaging, Genomics, and Proteomics Group, School of Cancer and Enabling Sciences, University of Manchester, Oxford Road, Manchester M13 9PY, United Kingdom.
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17
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Macedo CSD, Schwarz RT, Todeschini AR, Previato JO, Mendonça-Previato L. Overlooked post-translational modifications of proteins in Plasmodium falciparum: N- and O-glycosylation - A Review. Mem Inst Oswaldo Cruz 2010; 105:949-56. [DOI: 10.1590/s0074-02762010000800001] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2010] [Accepted: 11/16/2010] [Indexed: 11/22/2022] Open
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18
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Chandra S, Ruhela D, Deb A, Vishwakarma RA. Glycobiology of theLeishmaniaparasite and emerging targets for antileishmanial drug discovery. Expert Opin Ther Targets 2010; 14:739-57. [DOI: 10.1517/14728222.2010.495125] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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19
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Yoon MJ, Kim EH, Lim JH, Kwon TK, Choi KS. Superoxide anion and proteasomal dysfunction contribute to curcumin-induced paraptosis of malignant breast cancer cells. Free Radic Biol Med 2010; 48:713-26. [PMID: 20036734 DOI: 10.1016/j.freeradbiomed.2009.12.016] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2009] [Revised: 11/07/2009] [Accepted: 12/17/2009] [Indexed: 12/15/2022]
Abstract
Curcumin is considered a pharmacologically safe agent that may be useful in cancer chemoprevention and therapy. Here, we show for the first time that curcumin effectively induces paraptosis in malignant breast cancer cell lines, including MDA-MB-435S, MDA-MB-231, and Hs578T cells, by promoting vacuolation that results from swelling and fusion of mitochondria and/or the endoplasmic reticulum (ER). Inhibition of protein synthesis by cycloheximide blocked curcumin-induced vacuolation and subsequent cell death, indicating that protein synthesis is required for this process. The levels of AIP-1/Alix protein, a known inhibitor protein of paraptosis, were progressively downregulated in curcumin-treated malignant breast cancer cells, and AIP-1/Alix overexpression attenuated curcumin-induced death in these cells. ERK2 and JNK activation were positively associated with curcumin-induced cell death. Mitochondrial superoxide was shown to act as a critical early signal in curcumin-induced paraptosis, whereas proteasomal dysfunction was mainly responsible for the paraptotic changes associated with ER dilation. Notably, curcumin-induced paraptotic events were not observed in normal breast cells, including mammary epithelial cells and MCF-10A cells. Taken together, our findings on curcumin-induced paraptosis may provide novel insights into the mechanisms underlying the selective anti-cancer effects of curcumin against malignant cancer cells.
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Affiliation(s)
- Mi Jin Yoon
- Department of Molecular Science & Technology, Institute for Medical Sciences, Ajou University School of Medicine, Suwon, 443-749, Korea
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20
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Rasmussen CE, de la Cruz BJ, Ghahramani Z, Wild DL. Modeling and visualizing uncertainty in gene expression clusters using dirichlet process mixtures. IEEE/ACM TRANSACTIONS ON COMPUTATIONAL BIOLOGY AND BIOINFORMATICS 2009; 6:615-628. [PMID: 19875860 DOI: 10.1109/tcbb.2007.70269] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Although the use of clustering methods has rapidly become one of the standard computational approaches in the literature of microarray gene expression data, little attention has been paid to uncertainty in the results obtained. Dirichlet process mixture (DPM) models provide a nonparametric Bayesian alternative to the bootstrap approach to modeling uncertainty in gene expression clustering. Most previously published applications of Bayesian model-based clustering methods have been to short time series data. In this paper, we present a case study of the application of nonparametric Bayesian clustering methods to the clustering of high-dimensional nontime series gene expression data using full Gaussian covariances. We use the probability that two genes belong to the same cluster in a DPM model as a measure of the similarity of these gene expression profiles. Conversely, this probability can be used to define a dissimilarity measure, which, for the purposes of visualization, can be input to one of the standard linkage algorithms used for hierarchical clustering. Biologically plausible results are obtained from the Rosetta compendium of expression profiles which extend previously published cluster analyses of this data.
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Affiliation(s)
- Carl Edward Rasmussen
- Department of Engineering, University of Cambridge, Trumpington Street, Cambridge, CB2 1PZ, UK.
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21
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Xu Q, Cheng HW, He HQ, Liu ZR, He M, Yang HT, Zhou ZL, Ji YH. Deglycosylation altered the gating properties of rNav1.3: glycosylation/deglycosylation homeostasis probably complicates the functional regulation of voltage-gated sodium channel. Neurosci Bull 2009; 24:283-7. [PMID: 18839021 DOI: 10.1007/s12264-008-0524-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
OBJECTIVE To examine the effect of deglycosylation on gating properties of rNav1.3. METHODS rNav1.3 was expressed in Xenopus oocyte, with glycosylation inhibition by using tunicamycin. Two-electrode voltage clamp was employed to record the whole-cell sodium current and data were analyzed by Origin software. Those of glycosylated rNav1.3 were kept as control. RESULTS Compared with glycosylated ones, the steady-state activation curve of deglycosylated rNav1.3 was positively shifted by about 10 mV, while inactivation curve was negatively shifted by about 8 mV. CONCLUSION Glycosylation altered the gating properties of rNav1.3 and contributed to the functional diversity.
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Affiliation(s)
- Qing Xu
- School of Life Science, Shanghai University, Shanghai 200444, China
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22
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Doddi VR, Kokatla HP, Pal APJ, Basak RK, Vankar YD. Synthesis of Hybrids of D-Glucose and D-Galactose with Pyrrolidine-Based Iminosugars as Glycosidase Inhibitors. European J Org Chem 2008. [DOI: 10.1002/ejoc.200800770] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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23
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Markkanen PMH, Petäjä-Repo UE. N-glycan-mediated quality control in the endoplasmic reticulum is required for the expression of correctly folded delta-opioid receptors at the cell surface. J Biol Chem 2008; 283:29086-98. [PMID: 18703511 DOI: 10.1074/jbc.m801880200] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A great majority of G protein-coupled receptors are modified by N-glycosylation, but the functional significance of this modification for receptor folding and intracellular transport has remained elusive. Here we studied these phenomena by mutating the two N-terminal N-glycosylation sites (Asn(18) and Asn(33)) of the human delta-opioid receptor, and expressing the mutants from the same chromosomal integration site in stably transfected inducible HEK293 cells. Both N-glycosylation sites were used, and their abolishment decreased the steady-state level of receptors at the cell surface. However, pulse-chase labeling, cell surface biotinylation, and immunofluorescence microscopy revealed that this was not because of intracellular accumulation. Instead, the non-N-glycosylated receptors were exported from the endoplasmic reticulum with enhanced kinetics. The results also revealed differences in the significance of the individual N-glycans, as the one attached to Asn(33) was found to be more important for endoplasmic reticulum retention of the receptor. The non-N-glycosylated receptors did not show gross functional impairment, but flow cytometry revealed that a fraction of them was incapable of ligand binding at the cell surface. In addition, the receptors that were devoid of N-glycans showed accelerated turnover and internalization and were targeted for lysosomal degradation. The results accentuate the importance of protein conformation-based screening before export from the endoplasmic reticulum, and demonstrate how the system is compromised when N-glycosylation is disrupted. We conclude that N-glycosylation of the delta-opioid receptor is needed to maintain the expression of fully functional and stable receptor molecules at the cell surface.
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Affiliation(s)
- Piia M H Markkanen
- Department of Anatomy and Cell Biology, Institute of Biomedicine, University of Oulu, FI-90014, Oulu, Finland
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24
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Abstract
Treatment of cells with inhibitors of the enzymes that synthesize N-linked oligosaccharide chains results in production of glycoproteins containing missing or altered chains. This approach is useful for examining potential functional role(s) of this class of oligosaccharides on specific proteins or intact cells. This unit describes the use of inhibitors to prevent N-linked glycosylation of proteins in cultured cells. First, the optimal concentration of inhibitor for the experiment (i.e., highest nontoxic concentration) is determined by monitoring [(35)S]methionine incorporation as a measure of protein biosynthesis. The ability of the inhibitor to hinder oligosaccharide processing is then determined by analyzing cells labeled with [(3)H]mannose using TCA precipitation or endo H digestion. Further suggestions are given on how to use methods for identifying a specific glycoprotein (if available) to measure the effect of the inhibitor on its N-linked oligosaccharide chains. A Support Protocol details a method for concentrating proteins by acetone precipitation.
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Affiliation(s)
- L D Powell
- University of California San Diego, La Jolla, California, USA
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25
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Abstract
Treatment of cells with inhibitors of the enzymes that synthesize N-linked oligosaccharide chains results in production of glycoproteins containing missing or altered chains. This approach is useful for examining potential functional role(s) of this class of oligosaccharides on specific proteins or intact cells. This unit describes the use of inhibitors to prevent N-linked glycosylation of proteins in cultured cells. First, the optimal concentration of inhibitor for the experiment (i.e., highest nontoxic concentration) is determined by monitoring [35S]methionine incorporation as a measure of protein biosynthesis. The inhibitor's ability to inhibit oligosaccharide processing is then determined by analyzing cells labeled with [(H)H]mannose using TCA precipitation or endo H digestion (UNIT 13). Further suggestions are given on how to use methods for identifying a specific glycoprotein (if available) to measure the effect of the inhibitor on its N-linked oligosaccharide chains. A support protocol details a method for concentrating proteins by acetone precipitation.
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Affiliation(s)
- L D Powell
- University of California San Diego, La Jolla, California, USA
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26
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Hsieh YH, Su IJ, Wang HC, Tsai JH, Huang YJ, Chang WW, Lai MD, Lei HY, Huang W. Hepatitis B virus pre-S2 mutant surface antigen induces degradation of cyclin-dependent kinase inhibitor p27Kip1 through c-Jun activation domain-binding protein 1. Mol Cancer Res 2007; 5:1063-72. [PMID: 17951406 DOI: 10.1158/1541-7786.mcr-07-0098] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The hepatitis B virus (HBV) large surface antigen (LHBS) mutant with deletion at the pre-S(2) region accumulates in endoplasmic reticulum (ER) and is associated with HBV-induced hepatocellular carcinogenesis. In this study, we found that the pre-S(2) LHBS mutant directly interacts with the Jun activation domain-binding protein 1 (JAB1). Association of pre-S(2) LHBS with JAB1 dissociated JAB1 from the JAB1/IRE1 complex in ER. The free (active) JAB1 then translocated into cell nuclei and rendered the Cdk inhibitor p27(Kip1) to cytosolic proteasome for degradation. The pre-S(2) LHBS mutant induced hyperphosphorylation of tumor suppressor retinoblastoma (RB) via cyclin-dependent kinase 2 (Cdk2), a downstream molecule regulated by p27(Kip1). This effect is independent of the ER stress signaling pathway. The transgenic mice carrying the pre-S(2) mutant LHBS gene also exhibited Cdk2 activation, p27(Kip1) degradation, as well as RB hyperphosphorylation. The mouse hepatocytes exhibited morphologic abnormalities such as chromatin condensation, multinucleation, and dysplasia of hepatocytes. In summary, the pre-S(2) LHBS mutant causes p27(Kip1) degradation through direct interaction with JAB1. The pre-S(2) mutant LHBS is suggested to be a potential oncoprotein for HBV-related hepatocellular carcinoma.
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Affiliation(s)
- Yi-Hsuan Hsieh
- Department of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan
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27
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Deniaud A, Sharaf el dein O, Maillier E, Poncet D, Kroemer G, Lemaire C, Brenner C. Endoplasmic reticulum stress induces calcium-dependent permeability transition, mitochondrial outer membrane permeabilization and apoptosis. Oncogene 2007; 27:285-99. [PMID: 17700538 DOI: 10.1038/sj.onc.1210638] [Citation(s) in RCA: 443] [Impact Index Per Article: 26.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The accumulation of Ca2+ in the mitochondrial matrix can stimulate oxidative phosphorylation, but can also, at high Ca2+ concentrations, transmit and amplify an apoptotic signal. Here, we characterized the capacity of physiological stimuli (for example, histamine and inositol-1,4,5-triphosphate) and inducers of endoplasmic reticulum (ER) stress (for example, A23187, thapsigargin and tunicamycin) to release Ca2+ from ER stores, induce mitochondrial Ca2+ accumulation, and trigger cell death in human cervix and colon carcinoma cell lines. Sustained Ca2+ accumulation in the mitochondrial matrix induced by ER stress triggered signs of proapoptotic mitochondrial alteration, namely permeability transition, dissipation of the electrochemical potential, matrix swelling, relocalization of Bax to mitochondria and the release of cytochrome c and apoptosis-inducing factor from mitochondria. In contrast, rapid and transient accumulation of Ca2+ induced by physiological stimuli failed to promote mitochondrial permeability transition and to affect cell viability. The specificity of this apoptosis pathway was validated in cells using a panel of pharmacological agents that chelate Ca2+ (BAPTA-AM) or inhibit inositol-1,4,5-trisphosphate receptor (IP(3)R; 2-aminoethoxydiphenyl borate), voltage-dependent anion channel (VDAC) (4,4'-diisothiocyanatostilbene-2,2'-disulfonate, NADH), the permeability transition pore (cyclosporin A and bongkrekic acid), caspases (z-VAD-fmk) and protein synthesis (cycloheximide). Finally, we designed an original cell-free system in which we confronted purified mitochondria and ER vesicles, and identified IP(3)R, VDAC and the permeability transition pore as key proteins in the ER-triggered proapoptotic mitochondrial membrane permeabilization process.
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Affiliation(s)
- A Deniaud
- Université de Versailles/SQY, CNRS UMR 8159, 45, Versailles, France
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28
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Free RB, Hazelwood LA, Cabrera DM, Spalding HN, Namkung Y, Rankin ML, Sibley DR. D1 and D2 dopamine receptor expression is regulated by direct interaction with the chaperone protein calnexin. J Biol Chem 2007; 282:21285-300. [PMID: 17395585 DOI: 10.1074/jbc.m701555200] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
As for all proteins, G protein-coupled receptors (GPCRs) undergo synthesis and maturation within the endoplasmic reticulum (ER). The mechanisms involved in the biogenesis and trafficking of GPCRs from the ER to the cell surface are poorly understood, but they may involve interactions with other proteins. We have now identified the ER chaperone protein calnexin as an interacting protein for both D(1) and D(2) dopamine receptors. These protein-protein interactions were confirmed using Western blot analysis and co-immunoprecipitation experiments. To determine the influence of calnexin on receptor expression, we conducted assays in HEK293T cells using a variety of calnexin-modifying conditions. Inhibition of glycosylation either through receptor mutations or treatments with glycosylation inhibitors partially blocks the interactions with calnexin with a resulting decrease in cell surface receptor expression. Confocal fluorescence microscopy reveals the accumulation of D(1)-green fluorescent protein and D(2)-yellow fluorescent protein receptors within internal stores following treatment with calnexin inhibitors. Overexpression of calnexin also results in a marked decrease in both D(1) and D(2) receptor expression. This is likely because of an increase in ER retention because confocal microscopy revealed intracellular clustering of dopamine receptors that were co-localized with an ER marker protein. Additionally, we show that calnexin interacts with the receptors via two distinct mechanisms, glycan-dependent and glycan-independent, which may underlie the multiple effects (ER retention and surface trafficking) of calnexin on receptor expression. Our data suggest that optimal receptor-calnexin interactions critically regulate D(1) and D(2) receptor trafficking and expression at the cell surface, a mechanism likely to be of importance for many GPCRs.
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Affiliation(s)
- R Benjamin Free
- Molecular Neuropharmacology Section, NINDS, National Institutes of Health, Bethesda, Maryland 20892-9405, USA
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Lipton HL, Kumar ASM, Hertzler S, Reddi HV. Differential usage of carbohydrate co-receptors influences cellular tropism of Theiler's murine encephalomyelitis virus infection of the central nervous system. Glycoconj J 2006; 23:39-49. [PMID: 16575521 DOI: 10.1007/s10719-006-5436-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Theiler's murine encephalomyelitis viruses (TMEV) are ubiquitous pathogens of mice, producing either rapidly fatal encephalitis (high-neurovirulence strains) or persistent central nervous system infection and inflammatory demyelination (low-neurovirulence strains). Although a protein entry receptor has not yet been identified, carbohydrate co-receptors that effect docking and concentration of the virus on the cell surface are known for both TMEV neurovirulence groups. Low-neurovirulence TMEV use alpha2,3-linked N-acetylneuramic acid (sialic acid) on an N-linked glycoprotein, whereas high-neurovirulence TMEV use the proteoglycan heparan sulfate (HS) as a co-receptor. While the binding of low-neurovirulence TMEV to sialic acid can be inhibited completely, only a third of the binding of high-neurovirulence TMEV to HS is inhibitable, suggesting that high-neurovirulence strains use another co-receptor or bind directly to the putative protein entry receptor. Four amino acids on the surface (VP2 puff B) of low-neurovirulence strains make contact with sialic acid through non-covalent hydrogen bonds. Since these virus residues are conserved in all TMEV strains, the capsid conformation of this region is probably responsible for sialic acid binding. A persistence determinant that maps within the virus coat using recombinant TMEV is also conformational in nature. Low-neurovirulence virus variants that do not bind to sialic acid fail to persist in the central nervous system of mice, indicating a role for sialic acid binding in TMEV persistence. Analysis of high-neurovirulence variants that do not bind HS demonstrates that HS co-receptor usage influences neuronal tropism in brain, whereas, the HS co-receptor use is not required for the infection of spinal cord anterior horn cells associated with poliomyelitis.
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Affiliation(s)
- Howard L Lipton
- Department of Neurology and Microbiology-Immunology, University of Illinois at Chicago, Chicago, IL 60612-7344, USA
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Alves MJ, García-Mera X, Vale MLC, Santos TP, Aguiar FR, Rodríguez-Borges JE. Stereoselective synthesis of polyhydroxylated pyrrolidines: a route to novel 3,5-bis(hydroxymethyl)pyrrolidines from 2-azabicyclo[2.2.1]hept-5-enes. Tetrahedron Lett 2006. [DOI: 10.1016/j.tetlet.2006.08.077] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Dugan AS, Eash S, Atwood WJ. An N-linked glycoprotein with alpha(2,3)-linked sialic acid is a receptor for BK virus. J Virol 2006; 79:14442-5. [PMID: 16254379 PMCID: PMC1280228 DOI: 10.1128/jvi.79.22.14442-14445.2005] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
BK virus (BKV) is a common human polyomavirus infecting >80% of the population worldwide. Infection with BKV is asymptomatic, but reactivation in renal transplant recipients can lead to polyomavirus-associated nephropathy. In this report, we show that enzymatic removal of alpha(2,3)-linked sialic acid from cells inhibited BKV infection. Reconstitution of asialo cells with alpha(2,3)-specific sialyltransferase restored susceptibility to infection. Inhibition of N-linked glycosylation with tunicamycin reduced infection, but inhibition of O-linked glycosylation did not. An O-linked-specific alpha(2,3)-sialyltransferase was unable to restore infection in asialo cells. Taken together, these data indicate that an N-linked glycoprotein containing alpha(2,3)-linked sialic acid is a critical component of the cellular receptor for BKV.
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Affiliation(s)
- Aisling S Dugan
- Graduate Program in Pathobiology, Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02903, USA
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Fuchs W, Wiesner D, Veits J, Teifke JP, Mettenleiter TC. In vitro and in vivo relevance of infectious laryngotracheitis virus gJ proteins that are expressed from spliced and nonspliced mRNAs. J Virol 2005; 79:705-16. [PMID: 15613298 PMCID: PMC538576 DOI: 10.1128/jvi.79.2.705-716.2005] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The positional homologue in the infectious laryngotracheitis virus (ILTV) genome of the glycoprotein gJ gene of herpes simplex virus and the gp2 gene of equine herpesvirus 1 is expressed into four proteins of 85, 115, 160, and 200 kDa (J. Veits, B. Kollner, J. P. Teifke, H. Granzow, T. C. Mettenleiter, and W. Fuchs, Avian Dis. 47:330-342, 2003). RNA analyses revealed that these proteins are expressed from two different late (gamma2) transcripts, an unspliced 5.5-kb and a spliced 4.3-kb mRNA that are translated into proteins of 985 and 611 amino acids, respectively. ILTV gJ is incorporated into virions and is modified by N- and O-linked glycosylation. After cotransfection of chicken cells with genomic DNA of a pathogenic ILTV strain and transfer plasmids, gJ-negative ILTV mutants could be isolated. In vitro growth studies demonstrated that deletion of the gJ gene has only minor effects on direct cell-to-cell spread as measured by plaque size. However, progeny virus titers of ILTV-DeltagJ were significantly reduced in comparison to those of the parental virus and a gJ rescue mutant. After experimental infection of chickens the gJ rescue mutant, like wild-type ILTV, caused severe disease and considerable mortality, whereas ILTV-DeltagJ was significantly attenuated. All immunized animals were protected against subsequent challenge infection with virulent ILTV. In sera collected after immunization with the gJ-rescue mutant or with wild-type ILTV, gJ-specific antibodies were detectable by immunofluorescence on cells that had been transfected with a gJ expression plasmid. As expected, no gJ-specific antibodies were found in sera obtained from chickens immunized with ILTV-DeltagJ. Thus, gJ deletion mutants of ILTV might be usable as attenuated live-virus vaccines. Furthermore, the gJ gene might constitute a reliable marker for serological discrimination between vaccinated and field virus-infected chickens.
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Affiliation(s)
- Walter Fuchs
- Institute of Molecular Biology, Friedrich-Loeffler-Institut, Boddenblick 5A, 17493 Greifswald-Insel Riems, Germany
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Abstract
Chemical genetics is a research approach that uses small molecules as probes to study protein functions in cells or whole organisms. Here, I review the parallels between classical genetic and chemical-genetic approaches and discuss the merits of small molecules to dissect dynamic cellular processes. I then consider the pros and cons of different screening approaches and specify strategies aimed at identifying and validating cellular target proteins. Finally, I highlight the impact of chemical genetics on our current understanding of cell biology and its potential for the future.
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Affiliation(s)
- Thomas U Mayer
- Max Planck Institute of Biochemistry, Department of Cell Biology, Am Klopfersitz 18a, D-82152 Martinsried, Germany.
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de Macedo CS, Shams-Eldin H, Smith TK, Schwarz RT, Azzouz N. Inhibitors of glycosyl-phosphatidylinositol anchor biosynthesis. Biochimie 2003; 85:465-72. [PMID: 12770785 DOI: 10.1016/s0300-9084(03)00065-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Glycosyl-phosphatidylinositol (GPI) is a complex glycolipid structure that acts as a membrane anchor for many cell-surface proteins of eukaryotes. GPI-anchored proteins are particularly abundant in protozoa such as Trypanosoma brucei, Leishmania major, Plasmodium falciparum and Toxoplasma gondii, and represent the major carbohydrate modification of many cell-surface parasite proteins. Although the GPI core glycan is conserved in all organisms, many differences in additional modifications to GPI structures and biosynthetic pathways have been reported. Therefore, the characteristics of GPI biosynthesis are currently being explored for the development of parasite-specific inhibitors. In vitro and in vivo studies using sugars and substrate analogues as well as natural compounds have shown that it is possible to interfere with GPI biosynthesis at different steps in a species-specific manner. Here we review the recent and promising progress in the field of GPI inhibition.
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Affiliation(s)
- Cristiana Santos de Macedo
- Institut für Virologie, Zentrum für Hygiene und Med. Mikrobiologie, Philipps-Universität Marburg, Germany
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Shah AH, Lipton HL. Low-neurovirulence Theiler's viruses use sialic acid moieties on N-linked oligosaccharide structures for attachment. Virology 2002; 304:443-50. [PMID: 12504583 DOI: 10.1006/viro.2002.1735] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Low-neurovirulence BeAn and DA Theiler's murine encephalomyelitis viruses (TMEV) cause persistent infection in the central nervous system (CNS) of susceptible mouse strains, leading to an inflammatory demyelinating process. A role for a specific virus-cell receptor interaction has been posited to explain why only low- and not high-neurovirulence TMEV cause persistent CNS infections. Low- but not high-neurovirulence TMEV use sialic acid for attachment to mammalian cells, which may contribute to neurovirulence attenuation and viral persistence. Analysis of BeAn virus binding and infection in cells with altered (mutated) cell-surface expression of sialic acid containing glyconjugates indicated that both binding and infection are mediated entirely by N-linked glycoproteins. By contrast, GDVII virus binding and infection appears to be dependent only in part on N-linked glycoproteins and not on O-linked glycoproteins or glycolipids. These results indicate that low-neurovirulence BeAn virus uses a sialic acid moiety expressed on an N-linked carbohydrate of a glycoprotein that serves as the protein entry receptor.
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Affiliation(s)
- Ankur H Shah
- Department of Neurology, Evanston Hospital, Evanston/Chicago, IL 60201, USA
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Abstract
High-throughput screening of small molecules is used extensively in pharmaceutical settings for the purpose of drug discovery. In the case of antimicrobials, this involves the identification of small molecules that are significantly more toxic to the microbe than to the host. Only a small percentage of the small molecules identified in these screens have been studied in sufficient detail to explain the molecular basis of their antimicrobial effect. Rarer still are small molecule screens undertaken with the explicit goal of learning more about the biology of a particular microbe or the mechanism of its interaction with its host. Recent technological advances in small molecule synthesis and high-throughput screening have made such mechanism-directed small molecule approaches a powerful and accessible experimental option. In this article, we provide an overview of the methods and technical requirements and we discuss the potential of small molecule approaches to address important and often otherwise experimentally intractable problems in cellular microbiology.
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Affiliation(s)
- Gary E Ward
- Department of Microbiology and Molecular Genetics, University of Vermont, Burlington, Vermont 05405, USA.
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Nykänen MJ, Raudaskoski M, Nevalainen H, Mikkonen A. Maturation of barley cysteine endopeptidase expressed in Trichoderma reesei is distorted by incomplete processing. Can J Microbiol 2002; 48:138-50. [PMID: 11958567 DOI: 10.1139/w01-144] [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: 11/22/2022]
Abstract
Maturation of barley cysteine endopeptidase B (EPB) in Trichoderma reesei was studied with metabolic in hibitors, Western blotting, and immuno microscopy. The inactive 42-kDa recombinant EPB proprotein, first detected in apical cells, was sequentially processed in a time-dependent manner to a secreted polypeptide of 38.5 kDa, and thereafter, to polypeptides of 37.5, 35.5, and 32 kDa exhibiting enzyme activity both in the hyphae and culture medium. The sizes of the different forms of recombinant EPB were in accordance with molecular masses calculated from the deduced amino acid sequence, assuming cleavage at four putative Kex2p sites present in the 42-kDa proprotein. Both the liquid and the zymogram in-gel activity assays indicated that the 32-kDa enzyme produced in T. reesei in vivo was 2 kDa larger and four times less active than the endogenous EPB. Brefeldin A treatment prevented the last Kex2p processing step of EPB from a 35.5- to a 32-kDa protein. This coincided with a significant increase in the immuno-gold label for EPB and in modified Golgi-like bodies, which suggests that the processing step probably took place in medial Golgi. A 30.5-kDa EPB polypeptide was observed when glycosylation was inhibited by tunicamycin (TM) or when deglycosylation was carried out enzymatically. Deglycosylation increased the enzyme activity twofold, which was also indicated by an increased fluorescence by TM treatment in the zymogram in-gel activity assay. Simultaneous incubation with TM and monensin produced a peptide of 31.5 kDa. Therefore, monensin may inhibit the final processing step of an unglycosylated EPB by an unknown protease in the fungus. In any case, the final recombinant EPB product in Trichoderma differs from the mature endogenous 30-kDa enzyme produced in barley.
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Affiliation(s)
- Marko J Nykänen
- Department of Biological and Environmental Science, University of Jyväskylä, Finland
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Santos de Macedo C, Gerold P, Jung N, Azzouz N, Kimmel J, Schwarz RT. Inhibition of glycosyl-phosphatidylinositol biosynthesis in Plasmodium falciparum by C-2 substituted mannose analogues. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:6221-8. [PMID: 11733018 DOI: 10.1046/j.0014-2956.2001.02571.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Mannose analogues (2-deoxy-D-glucose, 2-deoxy-2-fluoro-D-glucose and 2-amino-2-deoxy-D-mannose) have been used to study glycosylphosphatidylinositol (GPtdIns) biosynthesis and GPtdIns protein anchoring in protozoal and mammalian systems. The effects of these analogues on GPtdIns biosynthesis and GPtdIns-protein anchoring of the human malaria parasite Plasmodium falciparum were evaluated in this study. At lower concentrations of 2-deoxy-D-glucose and 2-deoxy-2-fluoro-D glucose (0.2 and 0.1 mm, respectively), GPtdIns biosynthesis is inhibited without significant effects on total protein biosynthesis. At higher concentrations of 2-deoxy-D-glucose and 2-deoxy-2-fluoro-D-glucose (1.5 and 0.8 mm, respectively), the incorporation of [3H]glucosamine into glycolipids was inhibited by 90%, and the attachment of GPtdIns anchor to merozoite surface protein-1 (MSP-1) was prevented. However, at these concentrations, both sugar analogues inhibit MSP-1 synthesis and total protein biosynthesis. In contrast to 2-deoxy-2-fluoro-D-glucose and 2-amino-2-deoxy-D-mannose (mannosamine), the formation of new glycolipids was observed only in the presence of tritiated or nonradiolabelled 2-deoxy-D-glucose. Mannosamine inhibits GPtdIns biosynthesis at a concentration of 5 mm, but neither an accumulation of aberrant intermediates nor significant inhibition of total protein biosynthesis was observed in the presence of this analogue. Furthermore, the [3H]mannosamine-labelled glycolipid spectrum resembled the one described for [3H]glucosamine labelling. Total hydrolysis of mannosamine labelled glycolipids showed that half of the tritiated mannosamine incorporated into glycolipids was converted to glucosamine. This high rate of conversion led us to suggest that no actual inhibition from GPtdIns biosynthesis is achieved with the treatment with mannosamine, which is different to what has been observed for mammalian cells and other parasitic protozoa.
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Affiliation(s)
- C Santos de Macedo
- Med. Zentrum für Hygiene und Medizinische Mikrobiologie, Philipps-Universität Marburg, Marburg, Germany
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Chen Y, Segarini P, Raoufi F, Bradham D, Leask A. Connective tissue growth factor is secreted through the Golgi and is degraded in the endosome. Exp Cell Res 2001; 271:109-17. [PMID: 11697887 DOI: 10.1006/excr.2001.5364] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Connective tissue growth factor (CTGF) is a cysteine-rich heparin-binding polypeptide that promotes proliferation, collagen synthesis, and chemotaxis in mesanchymal cells. When coinjected subcutaneously with transforming growth factor beta (TGFbeta), CTGF promotes sustained fibrosis in rats. However, little is known about the cell biology and structure/functional relationship of CTGF. In particular, no detailed characterization of the subcellular localization of CTGF has occurred, nor have sequences been identified within this protein required for this localization. In this report, using immunofluorescence and Western blot analysis, we show that CTGF is localized to the Golgi apparatus both in dermal fibroblasts and activated hepatic stellate cells. Using these methods, no CTGF was detected in endosomal, plasma membrane, cytosolic or nuclear fractions. Addition of brefeldin A, a drug that disrupts the Golgi, blocks the secretion of CTGF. We further show that the amino-terminal 37 amino acids of CTGF are sufficient to localize a heterologous protein (red fluorescent protein, RFP) to the Golgi. Although within this region of human CTGF is a N-glycosylation site, tunicamycin, which blocks N-linked glycosylation, has no significant effect on CTGF secretion. Surprisingly, mutation of a single amino acid residue, CYS-34, to alanine prevents localization of a CTGF-RFP fusion protein to the Golgi. These results are the first proof that endogenous CTGF is localized to the Golgi apparatus. Furthermore, using exogenously added (125)I-labeled CTGF, we show that CTGF is internalized and rapidly degraded in the endosome. That is, CTGF is quantitatively secreted through the golgi and is degraded in the endosome.
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Affiliation(s)
- Y Chen
- FibroGen, Inc., 225 Gateway Boulevard, South San Francisco, California 94080, USA
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Verhoeven AJ, Neve BP, Jansen H. Secretion and apparent activation of human hepatic lipase requires proper oligosaccharide processing in the endoplasmic reticulum. Biochem J 1999; 337 ( Pt 1):133-40. [PMID: 9854035 PMCID: PMC1219946] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Human hepatic lipase (HL) is a glycoprotein with four N-linked oligosaccharide side chains. The importance of glycosylation for the secretion of catalytically active HL was studied in HepG2 cells by using inhibitors of intracellular trafficking, N-glycosylation and oligosaccharide processing. Secretion of HL was inhibited by carbonyl cyanide m-chlorophenylhydrazone (CCCP), monensin, brefeldin A (BFA), tunicamycin, castanospermine and N-methyldeoxynojirimycin, but not by 1-deoxymannojirimycin. Secretion of alpha1-antitrypsin, an unrelated N-glycoprotein, was also inhibited by monensin, BFA and tunicamycin, but not by CCCP, castanospermine or N-methyldeoxynojirimycin. Intracellular HL activity decreased with CCCP, tunicamycin, castanospermine and N-methyldeoxynojirimycin, but increased with monensin and BFA. In the absence of protein synthesis de novo, HL activity secreted into the medium was 7.8+/-2.1-fold higher (mean+/-S.D., n=7) than the simultaneous fall in intracellular HL activity. In cells pretreated with monensin or BFA, this factor decreased to 1.3+/-0.5, indicating that the apparent increase in HL activity had already occurred within these cells. After chromatography on Sepharose-heparin, the specific triacylglycerol hydrolase activity of secreted HL was only 1.7+/-0. 3-fold higher than that of intracellular HL, indicating that the secretion-coupled increase in HL activity is only partly explained by true activation. We conclude that oligosaccharide processing by glucosidases in the endoplasmic reticulum is necessary for the transport of newly synthesized human HL, but not alpha1-antitrypsin, to the Golgi, where the catalytic activity of HL is unmasked.
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Affiliation(s)
- A J Verhoeven
- Department of Biochemistry, Cardiovascular Research Institute (COEUR), Erasmus University Rotterdam, P.O. Box 1738, 3000 DR Rotterdam, The
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Tönjes RR, Limbach C, Löwer R, Kurth R. Expression of human endogenous retrovirus type K envelope glycoprotein in insect and mammalian cells. J Virol 1997; 71:2747-56. [PMID: 9060628 PMCID: PMC191397 DOI: 10.1128/jvi.71.4.2747-2756.1997] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The human endogenous retrovirus type K (HERV-K) family codes for the human teratocarcinoma-derived retrovirus (HTDV) particles. The existence of the envelope protein (ENV) of HERV-K encoded by the subgenomic env mRNA has not yet been demonstrated. To study the genetic requirements for successful expression of ENV, we have constructed a series of recombinant HERV-K env expression vectors for infection and transfection experiments in insect cells and mammalian cells, respectively. Six baculovirus constructs bearing full-length or truncated HERV-K env with or without homologous or heterologous signal peptides were used for infections of insect cells. All recombinant baculoviruses yielded ENV proteins with the expected molecular masses. The full-length 80- to 90-kDa HERV-K ENV protein including the cORF leader sequence was glycosylated in insect cells. In addition, the 14-kDa cORF protein was expressed due to splicing of the full-length env mRNA. The ENV precursor protein is not cleaved to the surface (SU) and transmembrane (TM) glycoproteins; it does not appear on the surface of infected insect cells and is not secreted into the medium. For ENV expression in COS cells, plasmid vectors harboring the cytomegalovirus immediate-early promoter/intron A element and the tissue plasminogen activator (t-PA) signal peptide or the homologous HERV-K signal peptide upstream of the env gene were employed. Glycosylated and uncleaved ENV was expressed as in GH teratocarcinoma cells but at higher levels. The heterologous t-PA signal sequence was instrumental for expression of HERV-K ENV on the cell surface. Hence, we have shown for the first time that the HERV-K env gene has the potential to be expressed as a full-length envelope protein with appropriate glycosylation. In addition, our data provide explanations for the lack of infectivity of HERV-K/HTDV particles.
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Hiss D, Gabriels G, Jacobs P, Folb P. Tunicamycin potentiates drug cytotoxicity and vincristine retention in multidrug resistant cell lines. Eur J Cancer 1996; 32A:2164-72. [PMID: 9014761 DOI: 10.1016/s0959-8049(96)00262-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Tunicamycin (TM), an inhibitor of glycoprotein processing, was investigated for its potential to reverse the multiple drug resistance (MDR) phenotype. When TM was added in vitro to drug-resistant NIH-3T3-MDR and KB-8-5-11 cells, they developed an increased sensitivity to doxorubicin, epirubicin, vincristine and colchicine. Similarly, the sensitivity of NIH-3T3-MDR cells to cisplatin was also enhanced by TM. In the presence of TM, drug-sensitive NIH-3T3-parental cells exhibited greater susceptibility to the toxic effects of doxorubicin, epirubicin, vincristine (marginally significant), and colchicine, but not to cisplatin. Tunicamycin-treated drug-sensitive KB-3-1 cells showed an increased response to vincristine, but not to the other anticancer drugs. Pretreatment with TM inhibited glycoprotein synthesis in all the cell lines. Neither prior exposure to, nor co-incubation with TM, influenced the uptake of vincristine (VCR) in the various cell lines. However, NIH-3T3-MDR cells accumulated less VCR than their drug-sensitive controls and also exhibited reduced efflux of the drug when treated with TM. There were no significant differences in the levels of intracellular VCR uptake between drug-sensitive KB-3-1 and KB-8-5-11 cells. Tunicamycin increased intracellular VCR retention in KB-8-5-11 and NIH-3T3-MDR cells, but not in NIH-3T3-parental cells. However, drug-sensitive KB-3-1 cells expressed reduced VCR retention in response to TM exposure, indicating that correlations between VCR toxicity and its retention in the presence of TM should be made with caution. The results suggest that the enhancement of intracellular VCR retention in MDR cells lines caused by TM is likely to be the result of inhibition of VCR efflux. Inhibition of glycoprotein synthesis during TM exposure may account for the changes in VCR efflux and retention observed in the MDR cell lines. The enhancement of cisplatin cytotoxicity in NIH-3T3-MDR cells after exposure to TM is an interesting observation, since it is generally believed that agents which modify the MDR phenotype do not show a sensitising effect to cisplatin. These findings may have applications in the reversal of drug resistance.
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Affiliation(s)
- D Hiss
- Department of Pharmacology, University of Cape Town, Medical School, South Africa
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Chapter 5 Biosynthesis 7. How Can N-Linked Glycosylation and Processing Inhibitors be Used to Study Carbohydrate Synthesis and Function. ACTA ACUST UNITED AC 1995. [DOI: 10.1016/s0167-7306(08)60599-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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Powell LD, Paneerselvam K, Vij R, Diaz S, Manzi A, Buist N, Freeze H, Varki A. Carbohydrate-deficient glycoprotein syndrome: not an N-linked oligosaccharide processing defect, but an abnormality in lipid-linked oligosaccharide biosynthesis? J Clin Invest 1994; 94:1901-9. [PMID: 7962535 PMCID: PMC294598 DOI: 10.1172/jci117540] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The carbohydrate-deficient glycoprotein syndrome (CDGS) is a developmental disease associated with an abnormally high isoelectric point of serum transferrin. Carbohydrate analyses of this glycoprotein initially suggested a defect in N-linked oligosaccharide processing, although more recent studies indicate a defect in the attachment of these sugar chains to the protein. We studied both serum glycoproteins and fibroblast-derived [2-3H]mannose-labeled oligosaccharides from CDGS patients and normal controls. While there was a decrease in the glycosylation of serum glycoproteins of affected individuals, differences were not seen in either monosaccharide composition or oligosaccharide structures. The lectin-binding profiles of glycopeptides from [2-3H]-mannose-labeled fibroblasts were likewise indistinguishable. However, the incorporation of [2-3H]mannose into both glycoproteins and the dolichol-linked oligosaccharide precursor was significantly reduced. Thus, at least in some patients, CDGS is not due to a defect in processing of N-linked oligosaccharides, but rather to defective synthesis and transfer of nascent dolichol-linked oligosaccharide precursors. This abnormality could result in both a failure to glycosylate some sites on some proteins, as well as secondary abnormalities in overall glycoprotein processing and/or function.
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Affiliation(s)
- L D Powell
- Glycobiology Program, University of California at San Diego Cancer Center, La Jolla 92093
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47
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Taylor DL, Kang MS, Brennan TM, Bridges CG, Sunkara PS, Tyms AS. Inhibition of alpha-glucosidase I of the glycoprotein-processing enzymes by 6-O-butanoyl castanospermine (MDL 28,574) and its consequences in human immunodeficiency virus-infected T cells. Antimicrob Agents Chemother 1994; 38:1780-7. [PMID: 7986008 PMCID: PMC284636 DOI: 10.1128/aac.38.8.1780] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The 6-O-butanoyl derivative of castanospermine (MDL 28,574) was previously shown to be approximately 30-fold more potent than the naturally occurring molecule at inhibiting the replication of human immunodeficiency virus (HIV) (D. L. Taylor, P. S. Sunkara, P. S. Liu, M. S. Kang, T. L. Bowlin, and A. S. Tyms, AIDS 5:693-698, 1991). We now report that consistent with its improved anti-HIV activity, MDL 28,574 is more effective (50% inhibitory concentration [IC50], 20 microM) than the parent molecule (IC50, 254 microM) at causing the accumulation of glucosylated oligosaccharides in HIV-infected cells by inhibition of glycoprotein processing. These were predominantly of the glucose 3 type, as determined by P4 Bio-Gel analysis after digestion with purified alpha-glucosidase I, indicating that, intracellularly, this enzyme is the major target for inhibition. MDL 28,574, however, was less active (IC50, 1.27 microM) than castanospermine (IC50, 0.12 microM) against the mutual target enzyme, cellular alpha-glucosidase I, in a cell-free assay system. The increased effects of MDL 28,574 against alpha-glucosidase I in cell culture were attributed to the improved cellular uptake of the more lipophilic derivative. Inhibition of this enzyme activity in HIV-infected H9 cells impaired viral glycoprotein processing and resulted in the expression of abnormally configured gp120. This did not affect virus production, but the virions had decreased infectivity which was partially related to a reduced ability to bind to CD4+ T cells.
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Affiliation(s)
- D L Taylor
- Marion Merrell Dow Research Institute Laboratories, Medical Research Council Collaborative Centre, London, United Kingdom
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Bile salt-dependent lipase biosynthesis in rat pancreatic AR 4-2 J cells. Essential requirement of N-linked oligosaccharide for secretion and expression of a fully active enzyme. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)74454-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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49
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Schwarz RT, Tomavo S. The current status of the glycobiology of Toxoplasma gondii: glycosylphosphatidylinositols, N- and O-linked glycans. RESEARCH IN IMMUNOLOGY 1993; 144:24-31. [PMID: 8451515 DOI: 10.1016/s0923-2494(05)80092-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- R T Schwarz
- Zentrum für Hygiene und Medizinische Mikrobiologie, Philipps-Universität Marburg, Germany
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