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Kästle M, Grune T. Interactions of the Proteasomal System with Chaperones. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 109:113-60. [DOI: 10.1016/b978-0-12-397863-9.00004-3] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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102
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Grindel BJ, Rohe B, Safford SE, Bennett JJ, Farach-Carson MC. Tumor necrosis factor-α treatment of HepG2 cells mobilizes a cytoplasmic pool of ERp57/1,25D₃-MARRS to the nucleus. J Cell Biochem 2011; 112:2606-15. [PMID: 21598303 DOI: 10.1002/jcb.23187] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
ERp57/PDIA3/1,25-MARRS has diverse functions and multiple cellular locations in various cell types. While classically described as an endoplasmic reticulum (ER) resident protein, ERp57 has a nuclear location sequence (NLS) and can enter the nucleus from the cytosol to alter transcription of target genes. Dysregulation and variable expression of ERp57 is associated with a variety of cancers including hepatocellular carcinoma (HCC). We investigated the dynamic mobility of ERp57 in an HCC cell line, HepG2, to better understand the movement and function of the non-ER resident pool of ERp57. Subcellular fractionation indicated ERp57 is highly expressed in the ER with a smaller cytoplasmic pool in HepG2 cells. Utilizing an ERp57 green fluorescent protein fusion construct created with and without a secretory signal sequence, we found that cytoplasmic ERp57 translocated to the nucleus within 15 min after tumor necrosis factor-α (TNF-α) treatment. Protein kinase C activators including 1,25-dihydroxyvitamin D(3) and phorbol myristate acetate did not trigger nuclear translocation of ERp57, indicating translocation is PKC independent. To determine if an interaction between the rel homology binding domain in ERp57 and the nuclear factor-κB subunit, p65, occurred after TNF-α treatment and could account for nuclear movement, co-immunoprecipitation was performed under control and conditions that stabilized labile disulfide bonds. No support for a functional interaction between p65 and ERp57 after TNF-α treatment was found in either case. Immunostaining for both ERp57-GFP and p65 after TNF-α treatment indicated that nuclear translocation of these two proteins occurs independently in HepG2 cells.
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Affiliation(s)
- Brian J Grindel
- Department of Biochemistry and Cell Biology, Rice University, Houston, Texas 77005, USA
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103
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Christianson JC, Olzmann JA, Shaler TA, Sowa ME, Bennett EJ, Richter CM, Tyler RE, Greenblatt EJ, Harper JW, Kopito RR. Defining human ERAD networks through an integrative mapping strategy. Nat Cell Biol 2011; 14:93-105. [PMID: 22119785 PMCID: PMC3250479 DOI: 10.1038/ncb2383] [Citation(s) in RCA: 392] [Impact Index Per Article: 30.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Accepted: 10/21/2011] [Indexed: 12/31/2022]
Abstract
Proteins that fail to correctly fold or assemble into oligomeric complexes in the endoplasmic reticulum (ER) are degraded by a ubiquitin and proteasome dependent process known as ER-associated degradation (ERAD). Although many individual components of the ERAD system have been identified, how these proteins are organised into a functional network that coordinates recognition, ubiquitination, and dislocation of substrates across the ER membrane is not well understood. We have investigated the functional organisation of the mammalian ERAD system using a systems-level strategy that integrates proteomics, functional genomics, and the transcriptional response to ER stress. This analysis supports an adaptive organisation for the mammalian ERAD machinery and reveals a number of metazoan-specific genes not previously linked to ERAD.
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Affiliation(s)
- John C Christianson
- Department of Biology & Bio-X Program, Stanford University, Stanford, California 94305, USA
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104
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Yazaki M, Kashiwagi K, Aritake K, Urade Y, Fujimori K. Rapid degradation of cyclooxygenase-1 and hematopoietic prostaglandin D synthase through ubiquitin-proteasome system in response to intracellular calcium level. Mol Biol Cell 2011; 23:12-21. [PMID: 22049022 PMCID: PMC3248891 DOI: 10.1091/mbc.e11-07-0623] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cyclooxygenase (COX)-1 and hematopoietic prostaglandin (PG) D synthase (H-PGDS) proteins, which are both involved in the arachidonate cascade, were stable in human megakaryocytic MEG-01 cells. In contrast, once the intracellular calcium level was increased by treatment with a calcium ionophore, both protein levels rapidly decreased with a half-life of less than 30 and 120 min for COX-1 and H-PGDS, respectively. In the presence of a proteasome inhibitor, COX-1 and H-PGDS proteins accumulated within 10 and 30 min, respectively, and concurrently appeared as the high-molecular-mass ubiquitinated proteins within 30 and 60 min, respectively, after an increase in the intracellular calcium level. The ubiquitination of these proteins was also observed when ADP, instead of a calcium ionophore, was used as an inducer to elevate the intracellular calcium level. When the entry of calcium ion into the cells was inhibited by ethylene glycol tetraacetic acid (EGTA), the ubiquitination of COX-1 and H-PGDS was clearly suppressed; and the addition of CaCl(2) to the medium cleared the EGTA-mediated suppression of the ubiquitination. These results indicate that COX-1 and H-PGDS were rapidly ubiquitinated and degraded through the ubiquitin-proteasome system in response to the elevation of the intracellular calcium level.
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Affiliation(s)
- Misato Yazaki
- Laboratory of Biodefense and Regulation, Osaka University of Pharmaceutical Sciences, Takatsuki, Osaka, Japan
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105
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Abstract
The endoplasmic reticulum (ER) uses an elaborate surveillance system called the ER quality control (ERQC) system. The ERQC facilitates folding and modification of secretory and membrane proteins and eliminates terminally misfolded polypeptides through ER-associated degradation (ERAD) or autophagic degradation. This mechanism of ER protein surveillance is closely linked to redox and calcium homeostasis in the ER, whose balance is presumed to be regulated by a specific cellular compartment. The potential to modulate proteostasis and metabolism with chemical compounds or targeted siRNAs may offer an ideal option for the treatment of disease.
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106
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Jung C, Lee GJ, Jang M, Lee M, Lee J, Kang H, Sohn EJ, Hwang I. Identification of sorting motifs of AtβFruct4 for trafficking from the ER to the vacuole through the Golgi and PVC. Traffic 2011; 12:1774-92. [PMID: 21899678 DOI: 10.1111/j.1600-0854.2011.01276.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Although much is known about the molecular mechanisms involved in transporting soluble proteins to the central vacuole, the mechanisms governing the trafficking of membrane proteins remain largely unknown. In this study, we investigated the mechanism involved in targeting the membrane protein, AtβFructosidase 4 (AtβFruct4), to the central vacuole in protoplasts. AtβFruct4 as a green fluorescent protein (GFP) fusion protein was transported as a membrane protein during transit from the endoplasmic reticulum (ER) through the Golgi apparatus and the prevacuolar compartment (PVC). The N-terminal cytosolic domain of AtβFruct4 was sufficient for transport from the ER to the central vacuole and contained sequence motifs required for trafficking. The sequence motifs, LL and PI, were found to be critical for ER exit, while the EEE and LCPYTRL sequence motifs played roles in trafficking primarily from the trans Golgi network (TGN) to the PVC and from the PVC to the central vacuole, respectively. In addition, actin filaments and AtRabF2a, a Rab GTPase, played critical roles in vacuolar trafficking at the TGN and PVC, respectively. On the basis of these results, we propose that the vacuolar trafficking of AtβFruct4 depends on multiple sequence motifs located at the N-terminal cytoplasmic domain that function as exit and/or sorting signals in different stages during the trafficking process.
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Affiliation(s)
- Chanjin Jung
- Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea
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107
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Hu H, Eggers K, Chen W, Garshasbi M, Motazacker MM, Wrogemann K, Kahrizi K, Tzschach A, Hosseini M, Bahman I, Hucho T, Mühlenhoff M, Gerardy-Schahn R, Najmabadi H, Ropers HH, Kuss AW. ST3GAL3 mutations impair the development of higher cognitive functions. Am J Hum Genet 2011; 89:407-14. [PMID: 21907012 DOI: 10.1016/j.ajhg.2011.08.008] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Revised: 08/02/2011] [Accepted: 08/17/2011] [Indexed: 12/17/2022] Open
Abstract
The genetic variants leading to impairment of intellectual performance are highly diverse and are still poorly understood. ST3GAL3 encodes the Golgi enzyme β-galactoside-α2,3-sialyltransferase-III that in humans predominantly forms the sialyl Lewis a epitope on proteins. ST3GAL3 resides on chromosome 1 within the MRT4 locus previously identified to associate with nonsyndromic autosomal recessive intellectual disability. We searched for the disease-causing mutations in the MRT4 family and a second independent consanguineous Iranian family by using a combination of chromosome sorting and next-generation sequencing. Two different missense changes in ST3GAL3 cosegregate with the disease but were absent in more than 1000 control chromosomes. In cellular and biochemical test systems, these mutations were shown to cause ER retention of the Golgi enzyme and drastically impair ST3Gal-III functionality. Our data provide conclusive evidence that glycotopes formed by ST3Gal-III are prerequisite for attaining and/or maintaining higher cognitive functions.
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Affiliation(s)
- Hao Hu
- Department for Human Molecular Genetics, Max-Planck Institute for Molecular Genetics, Berlin, Germany
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108
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The KDEL receptor induces autophagy to promote the clearance of neurodegenerative disease-related proteins. Neuroscience 2011; 190:43-55. [DOI: 10.1016/j.neuroscience.2011.06.008] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Revised: 05/10/2011] [Accepted: 06/01/2011] [Indexed: 12/14/2022]
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109
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Expression of endoplasmic reticulum stress-related factors in the retinas of diabetic rats. EXPERIMENTAL DIABETES RESEARCH 2011; 2012:743780. [PMID: 21904541 PMCID: PMC3166715 DOI: 10.1155/2012/743780] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 06/18/2011] [Accepted: 06/20/2011] [Indexed: 11/17/2022]
Abstract
Recent reports show that ER stress plays an important role in diabetic retinopathy (DR), but ER stress is a complicated process involving a network of signaling pathways and hundreds of factors, What factors involved in DR are not yet understood. We selected 89 ER stress factors from more than 200, A rat diabetes model was established by intraperitoneal injection of streptozotocin (STZ). The expression of 89 ER stress-related factors was found in the retinas of diabetic rats, at both 1- and 3-months after development of diabetes, by quantitative real-time polymerase chain reaction arrays. There were significant changes in expression levels of 13 and 12 ER stress-related factors in the diabetic rat retinas in the first and third month after the development of diabetes, Based on the array results, homocysteine- inducible, endoplasmic reticulum stress-inducible, ubiquitin-like domain member 1(HERP), and synoviolin(HRD1) were studied further by immunofluorescence and Western blot. Immunofluorescence and Western blot analyses showed that the expression of HERP was reduced in the retinas of diabetic rats in first and third month. The expression of Hrd1 did not change significantly in the retinas of diabetic rats in the first month but was reduced in the third month.
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110
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Scruggs SB, Ping P, Zong C. Heterogeneous cardiac proteasomes: mandated by diverse substrates? Physiology (Bethesda) 2011; 26:106-14. [PMID: 21487029 DOI: 10.1152/physiol.00039.2010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Proteasome biology has taken central stage in cardiac physiology and pathophysiology. The molecular heterogeneity of proteasome subpopulations supports the specificity of proteasome function to degrade diverse substrate repertoires. Unveiling the dynamics of proteasome function should inspire new therapeutic strategies for combating cardiac disease.
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Affiliation(s)
- Sarah B Scruggs
- Departments of Physiology and Medicine, Division of Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, California, USA
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111
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Araki K, Nagata K. Functional in vitro analysis of the ERO1 protein and protein-disulfide isomerase pathway. J Biol Chem 2011; 286:32705-12. [PMID: 21757736 DOI: 10.1074/jbc.m111.227181] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Oxidative protein folding in the endoplasmic reticulum is supported by efficient electron relays driven by enzymatic reactions centering on the ERO1-protein-disulfide isomerase (PDI) pathway. A controlled in vitro oxygen consumption assay was carried out to analyze the ERO1-PDI reaction. The results showed the pH-dependent oxidation of PDI by ERO1α. Among several possible disulfide bonds regulating ERO1α activity, Cys(94)-Cys(131) and Cys(99)-Cys(104) disulfide bonds are dominant regulators by excluding the involvement of the Cys(85)-Cys(391) disulfide in the regulation. The fine-tuned species specificity of the ERO1-PDI pathway was demonstrated by functional in vitro complementation assays using yeast and mammalian oxidoreductases. Finally, the results provide experimental evidence for the intramolecular electron transfer from the a domain to the a' domain within PDI during its oxidation by ERO1α.
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Affiliation(s)
- Kazutaka Araki
- Department of Molecular and Cellular Biology, Institute for Frontier Medical Sciences, Kyoto University, Kyoto 606-8507, Japan
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112
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Greiner M, Kreutzer B, Lang S, Jung V, Cavalié A, Unteregger G, Zimmermann R, Wullich B. Sec62 protein level is crucial for the ER stress tolerance of prostate cancer. Prostate 2011; 71:1074-83. [PMID: 21557272 DOI: 10.1002/pros.21324] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2010] [Accepted: 11/22/2010] [Indexed: 11/10/2022]
Abstract
BACKGROUND We previously reported that over-expression of the SEC62 gene is a widespread phenomenon in prostate cancer. Since the use of endoplasmic reticulum (ER) stress-inducing substances such as thapsigargin in prostate cancer therapy is widely discussed in the literature, we investigated the influence of Sec62 protein content on the cellular response to these drugs. METHODS Growth effects were analyzed by real-time cell analysis and viability tests in DU145-cells representing an increased SEC62 expression or PC3- and LNCaP-cells representing a similar SEC62 expression compared to non-tumor cells. Ca(2+) -imaging in an established HeLa-system with fluorescent dye was used to study molecular effects of Sec62 depletion. RESULTS We found a lower propensity toward apoptotic cell death after thapsigargin treatment for DU145 cells compared to PC3 or LNCaP and siRNA-mediated silencing of SEC62 resulted in a reduced viability of thapsigargin-treated PC3 cells, indicating that Sec62 functions in cellular stress response. Measurement of cytosolic [Ca(2+) ] demonstrated the influence of Sec62 on the cellular response to thapsigargin on a molecular level. Using real-time cell analysis, we observed the loss of androgen stimulation of LNCaP cells in the presence of thapsigargin, and an additional negative effect on cell growth of Sec62 depletion. Also, for PC3- and DU145-cells Sec62 depletion inhibited growth after thapsigargin treatment. CONCLUSIONS Our data indicate a crucial function of Sec62 in the response to thapsigargin-induced ER stress. This will be of great significance on the background of elevated Sec62 protein levels in prostate cancer cells when treatment with thapsigargin analogs is considered.
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Affiliation(s)
- Markus Greiner
- Department of Medical Biochemistry and Molecular Biology, Saarland University, Homburg/Saar, Germany.
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113
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Bravo R, Vicencio JM, Parra V, Troncoso R, Munoz JP, Bui M, Quiroga C, Rodriguez AE, Verdejo HE, Ferreira J, Iglewski M, Chiong M, Simmen T, Zorzano A, Hill JA, Rothermel BA, Szabadkai G, Lavandero S. Increased ER-mitochondrial coupling promotes mitochondrial respiration and bioenergetics during early phases of ER stress. J Cell Sci 2011; 124:2143-52. [PMID: 21628424 PMCID: PMC3113668 DOI: 10.1242/jcs.080762] [Citation(s) in RCA: 432] [Impact Index Per Article: 33.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/02/2011] [Indexed: 01/02/2023] Open
Abstract
Increasing evidence indicates that endoplasmic reticulum (ER) stress activates the adaptive unfolded protein response (UPR), but that beyond a certain degree of ER damage, this response triggers apoptotic pathways. The general mechanisms of the UPR and its apoptotic pathways are well characterized. However, the metabolic events that occur during the adaptive phase of ER stress, before the cell death response, remain unknown. Here, we show that, during the onset of ER stress, the reticular and mitochondrial networks are redistributed towards the perinuclear area and their points of connection are increased in a microtubule-dependent fashion. A localized increase in mitochondrial transmembrane potential is observed only in redistributed mitochondria, whereas mitochondria that remain in other subcellular zones display no significant changes. Spatial re-organization of these organelles correlates with an increase in ATP levels, oxygen consumption, reductive power and increased mitochondrial Ca²⁺ uptake. Accordingly, uncoupling of the organelles or blocking Ca²⁺ transfer impaired the metabolic response, rendering cells more vulnerable to ER stress. Overall, these data indicate that ER stress induces an early increase in mitochondrial metabolism that depends crucially upon organelle coupling and Ca²⁺ transfer, which, by enhancing cellular bioenergetics, establishes the metabolic basis for the adaptation to this response.
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Affiliation(s)
- Roberto Bravo
- FONDAP Center for Molecular Studies of the Cell, Faculty of Chemical and Pharmaceutical Sciences and Faculty of Medicine, University of Chile, Santiago 8380492, Chile
| | - Jose Miguel Vicencio
- FONDAP Center for Molecular Studies of the Cell, Faculty of Chemical and Pharmaceutical Sciences and Faculty of Medicine, University of Chile, Santiago 8380492, Chile
- Department of Cell and Developmental Biology and Consortium for Mitochondrial Research, University College London, London WC1E 6BT, UK
| | - Valentina Parra
- FONDAP Center for Molecular Studies of the Cell, Faculty of Chemical and Pharmaceutical Sciences and Faculty of Medicine, University of Chile, Santiago 8380492, Chile
| | - Rodrigo Troncoso
- FONDAP Center for Molecular Studies of the Cell, Faculty of Chemical and Pharmaceutical Sciences and Faculty of Medicine, University of Chile, Santiago 8380492, Chile
| | - Juan Pablo Munoz
- Institute for Research in Biomedicine (IRB Barcelona) and Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Barcelona 08028, Spain
| | - Michael Bui
- Department of Cell Biology, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Clara Quiroga
- FONDAP Center for Molecular Studies of the Cell, Faculty of Chemical and Pharmaceutical Sciences and Faculty of Medicine, University of Chile, Santiago 8380492, Chile
| | - Andrea E. Rodriguez
- FONDAP Center for Molecular Studies of the Cell, Faculty of Chemical and Pharmaceutical Sciences and Faculty of Medicine, University of Chile, Santiago 8380492, Chile
| | - Hugo E. Verdejo
- FONDAP Center for Molecular Studies of the Cell, Faculty of Chemical and Pharmaceutical Sciences and Faculty of Medicine, University of Chile, Santiago 8380492, Chile
- Department of Cardiovascular Diseases, Faculty of Medicine, P. Catholic University of Chile, Santiago, Chile
| | - Jorge Ferreira
- Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Santiago 8380492, Chile
| | - Myriam Iglewski
- Department of Internal Medicine (Cardiology), University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Mario Chiong
- FONDAP Center for Molecular Studies of the Cell, Faculty of Chemical and Pharmaceutical Sciences and Faculty of Medicine, University of Chile, Santiago 8380492, Chile
| | - Thomas Simmen
- Department of Cell Biology, University of Alberta, Edmonton, AB T6G 2H7, Canada
| | - Antonio Zorzano
- Institute for Research in Biomedicine (IRB Barcelona) and Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Barcelona 08028, Spain
| | - Joseph A. Hill
- Department of Internal Medicine (Cardiology), University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Beverly A. Rothermel
- Department of Internal Medicine (Cardiology), University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Gyorgy Szabadkai
- Department of Cell and Developmental Biology and Consortium for Mitochondrial Research, University College London, London WC1E 6BT, UK
| | - Sergio Lavandero
- FONDAP Center for Molecular Studies of the Cell, Faculty of Chemical and Pharmaceutical Sciences and Faculty of Medicine, University of Chile, Santiago 8380492, Chile
- Institute of Biomedical Sciences, Faculty of Medicine, University of Chile, Santiago 8380492, Chile
- Department of Internal Medicine (Cardiology), University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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114
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Prediction of amyloid aggregation in vivo. EMBO Rep 2011; 12:657-63. [PMID: 21681200 DOI: 10.1038/embor.2011.116] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Accepted: 05/26/2011] [Indexed: 12/14/2022] Open
Abstract
Many human diseases owe their pathology, to some degree, to the erroneous conversion of proteins from their soluble state into fibrillar, β-structured aggregates, often referred to as amyloid fibrils. Neurodegenerative diseases, such as Alzheimer and spongiform encephalopathies, as well as type 2 diabetes and both localized and systemic amyloidosis, are among the conditions that are associated with the formation of amyloid fibrils. Several mathematical tools can rationalize and even predict important parameters of amyloid fibril formation. It is not clear, however, whether such algorithms have predictive powers for in vivo systems, in which protein aggregation is affected by the presence of other biological factors. In this review, we briefly describe the existing algorithms and use them to predict the effects of mutations on the aggregation of specific proteins, for which in vivo experimental data are available. The comparison between the theoretical predictions and the experimental data obtained in vivo is shown for each algorithm and experimental data set, and statistically significant correlations are found in most cases.
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115
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Brodsky JL, Skach WR. Protein folding and quality control in the endoplasmic reticulum: Recent lessons from yeast and mammalian cell systems. Curr Opin Cell Biol 2011; 23:464-75. [PMID: 21664808 DOI: 10.1016/j.ceb.2011.05.004] [Citation(s) in RCA: 181] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Revised: 04/29/2011] [Accepted: 05/17/2011] [Indexed: 12/16/2022]
Abstract
The evolution of eukaryotes was accompanied by an increased need for intracellular communication and cellular specialization. Thus, a more complex collection of secreted and membrane proteins had to be synthesized, modified, and folded. The endoplasmic reticulum (ER) thereby became equipped with devoted enzymes and associated factors that both catalyze the production of secreted proteins and remove damaged proteins. A means to modify ER function to accommodate and destroy misfolded proteins also evolved. Not surprisingly, a growing number of human diseases are linked to various facets of ER function. Each of these topics will be discussed in this article, with an emphasis on recent reports in the literature that employed diverse models.
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Affiliation(s)
- Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
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116
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Shim S, Lee W, Chung H, Jung YK. Amyloid β-induced FOXRED2 mediates neuronal cell death via inhibition of proteasome activity. Cell Mol Life Sci 2011; 68:2115-27. [PMID: 20972601 PMCID: PMC11115111 DOI: 10.1007/s00018-010-0561-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2010] [Revised: 09/16/2010] [Accepted: 10/05/2010] [Indexed: 01/03/2023]
Abstract
Proteasome inhibition has been regarded as one of the mediators of Aβ neurotoxicity. In this study, we found that FOXRED2, a novel endoplasmic reticulum (ER) residential protein, is highly up-regulated by Aβ in rat cortical neurons and SH-SY5Y cells. Over-expression of FOXRED2 inhibits proteasome activity in the microsomal fractions containing ER and interferes with proteasome assembly, as evidenced by gel filtration and native gel electrophoresis analysis. In contrast, reduced expression of FOXRED2 rescues Aβ-induced inhibition of proteasome activity. FOXRED2 is an unstable protein with two degradation boxes and one KEN box, and its N-terminal oxidoreductase domain is required for proteasome inhibition. Ectopic expression of FOXRED2 induces ER stress-mediated cell death via caspase-12, which is inhibited by Salubrinal. Further, down-regulation of FOXRED2 expression attenuates Aβ-induced cell death and the ER stress response. These results suggest that up-regulated FOXRED2 inhibits proteasome activity by interfering with 26S proteasome assembly to contribute to Aβ neurotoxicity via an ER stress response.
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Affiliation(s)
- SangMi Shim
- Creative Research Initiative (CRI)–Acceleration Research Laboratory, School of Biological Science/Bio-MAX Institute, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul, 151-742 Korea
| | - WonJae Lee
- Creative Research Initiative (CRI)–Acceleration Research Laboratory, School of Biological Science/Bio-MAX Institute, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul, 151-742 Korea
| | - HaeWon Chung
- Creative Research Initiative (CRI)–Acceleration Research Laboratory, School of Biological Science/Bio-MAX Institute, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul, 151-742 Korea
| | - Yong-Keun Jung
- Creative Research Initiative (CRI)–Acceleration Research Laboratory, School of Biological Science/Bio-MAX Institute, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul, 151-742 Korea
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117
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Hsieh MT, Chen RH. Cdc48 and cofactors Npl4-Ufd1 are important for G1 progression during heat stress by maintaining cell wall integrity in Saccharomyces cerevisiae. PLoS One 2011; 6:e18988. [PMID: 21526151 PMCID: PMC3079750 DOI: 10.1371/journal.pone.0018988] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Accepted: 03/25/2011] [Indexed: 11/30/2022] Open
Abstract
The ubiquitin-selective chaperone Cdc48, a member of the AAA (ATPase Associated with various cellular Activities) ATPase superfamily, is involved in many processes, including endoplasmic reticulum-associated degradation (ERAD), ubiquitin- and proteasome-mediated protein degradation, and mitosis. Although Cdc48 was originally isolated as a cell cycle mutant in the budding yeast Saccharomyces cerevisiae, its cell cycle functions have not been well appreciated. We found that temperature-sensitive cdc48-3 mutant is largely arrested at mitosis at 37°C, whereas the mutant is also delayed in G1 progression at 38.5°C. Reporter assays show that the promoter activity of G1 cyclin CLN1, but not CLN2, is reduced in cdc48-3 at 38.5°C. The cofactor npl4-1 and ufd1-2 mutants also exhibit G1 delay and reduced CLN1 promoter activity at 38.5°C, suggesting that Npl4-Ufd1 complex mediates the function of Cdc48 at G1. The G1 delay of cdc48-3 at 38.5°C is a consequence of cell wall defect that over-activates Mpk1, a MAPK family member important for cell wall integrity in response to stress conditions including heat shock. cdc48-3 is hypersensitive to cell wall perturbing agents and is synthetic-sick with mutations in the cell wall integrity signaling pathway. Our results suggest that the cell wall defect in cdc48-3 is exacerbated by heat shock, which sustains Mpk1 activity to block G1 progression. Thus, Cdc48-Npl4-Ufd1 is important for the maintenance of cell wall integrity in order for normal cell growth and division.
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Affiliation(s)
- Meng-Ti Hsieh
- Molecular Cell Biology, Taiwan International Graduate Program, Institute of Molecular Biology, Academia Sinica, and Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan
| | - Rey-Huei Chen
- Molecular Cell Biology, Taiwan International Graduate Program, Institute of Molecular Biology, Academia Sinica, and Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
- * E-mail:
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Shen M, Siu S, Byrd S, Edelmann KH, Patel N, Ketchem RR, Mehlin C, Arnett HA, Hasegawa H. Diverse functions of reactive cysteines facilitate unique biosynthetic processes of aggregate-prone interleukin-31. Exp Cell Res 2011; 317:976-93. [DOI: 10.1016/j.yexcr.2010.12.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 12/10/2010] [Accepted: 12/13/2010] [Indexed: 10/18/2022]
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119
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Li X, Zhang K, Li Z. Unfolded protein response in cancer: the physician's perspective. J Hematol Oncol 2011; 4:8. [PMID: 21345215 PMCID: PMC3060154 DOI: 10.1186/1756-8722-4-8] [Citation(s) in RCA: 135] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Accepted: 02/23/2011] [Indexed: 11/10/2022] Open
Abstract
The unfolded protein response (UPR) is a cascade of intracellular stress signaling events in response to an accumulation of unfolded or misfolded proteins in the lumen of the endoplasmic reticulum (ER). Cancer cells are often exposed to hypoxia, nutrient starvation, oxidative stress and other metabolic dysregulation that cause ER stress and activation of the UPR. Depending on the duration and degree of ER stress, the UPR can provide either survival signals by activating adaptive and antiapoptotic pathways, or death signals by inducing cell death programs. Sustained induction or repression of UPR pharmacologically may thus have beneficial and therapeutic effects against cancer. In this review, we discuss the basic mechanisms of UPR and highlight the importance of UPR in cancer biology. We also update the UPR-targeted cancer therapeutics currently in clinical trials.
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Affiliation(s)
- Xuemei Li
- Lea’s Foundation Center for Hematologic Disorders and Neag Comprehensive Cancer Center, University of Connecticut School of Medicine, Farmington, CT 06030-1601, USA
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120
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Riemer J, Hansen HG, Appenzeller-Herzog C, Johansson L, Ellgaard L. Identification of the PDI-family member ERp90 as an interaction partner of ERFAD. PLoS One 2011; 6:e17037. [PMID: 21359175 PMCID: PMC3040216 DOI: 10.1371/journal.pone.0017037] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Accepted: 01/11/2011] [Indexed: 01/28/2023] Open
Abstract
In the endoplasmic reticulum (ER), members of the protein disulfide isomerase (PDI) family perform critical functions during protein maturation. Herein, we identify the previously uncharacterized PDI-family member ERp90. In cultured human cells, we find ERp90 to be a soluble ER-luminal glycoprotein that comprises five potential thioredoxin (Trx)-like domains. Mature ERp90 contains 10 cysteine residues, of which at least some form intramolecular disulfides. While none of the Trx domains contain a canonical Cys-Xaa-Xaa-Cys active-site motif, other conserved cysteines could endow the protein with redox activity. Importantly, we show that ERp90 co-immunoprecipitates with ERFAD, a flavoprotein involved in ER-associated degradation (ERAD), through what is most likely a direct interaction. We propose that the function of ERp90 is related to substrate recruitment or delivery to the ERAD retrotranslocation machinery by ERFAD.
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Affiliation(s)
- Jan Riemer
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Henning G. Hansen
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | | | - Linda Johansson
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Lars Ellgaard
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
- * E-mail:
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121
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Endoplasmic reticulum stress activates autophagy but not the proteasome in neuronal cells: implications for Alzheimer's disease. Cell Death Differ 2011; 18:1071-81. [PMID: 21252911 DOI: 10.1038/cdd.2010.176] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Protein folding stress in the endoplasmic reticulum (ER) may lead to activation of the unfolded protein response (UPR), aimed to restore cellular homeostasis via transcriptional and post-transcriptional mechanisms. ER stress is also reported to activate the ER overload response (EOR), which activates transcription via NF-κB. We previously demonstrated that UPR activation is an early event in pre-tangle neurons in Alzheimer's disease (AD) brain. Misfolded and unfolded proteins are degraded via the ubiquitin proteasome system (UPS) or autophagy. UPR activation is found in AD neurons displaying both early UPS pathology and autophagic pathology. Here we investigate whether activation of the UPR and/or EOR is employed to enhance the proteolytic capacity of neuronal cells. Expression of the immunoproteasome subunits β2i and β5i is increased in AD brain. However, expression of the proteasome subunits is not increased by the UPR or EOR. UPR activation does not relocalize the proteasome or increase overall proteasome activity. Therefore proteasomal degradation is not increased by ER stress. In contrast, UPR activation enhances autophagy and LC3 levels are increased in neurons displaying UPR activation in AD brain. Our data suggest that autophagy is the major degradational pathway following UPR activation in neuronal cells and indicate a connection between UPR activation and autophagic pathology in AD brain.
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122
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Richie DL, Feng X, Hartl L, Aimanianda V, Krishnan K, Powers-Fletcher MV, Watson DS, Galande AK, White SM, Willett T, Latgé JP, Rhodes JC, Askew DS. The virulence of the opportunistic fungal pathogen Aspergillus fumigatus requires cooperation between the endoplasmic reticulum-associated degradation pathway (ERAD) and the unfolded protein response (UPR). Virulence 2011; 2:12-21. [PMID: 21217201 DOI: 10.4161/viru.2.1.13345] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The filamentous fungal pathogen Aspergillus fumigatus secretes hydrolytic enzymes to acquire nutrients from host tissues. The production of these enzymes exerts stress on the endoplasmic reticulum (ER), which is alleviated by two stress responses: the unfolded protein response (UPR), which adjusts the protein folding capacity of the ER, and ER-associated degradation (ERAD), which disposes of proteins that fail to fold correctly. In this study, we examined the contribution of these integrated pathways to the growth and virulence of A. fumigatus, focusing on the ERAD protein DerA and the master regulator of the UPR, HacA. A ΔderA mutant grew normally and showed no increase in sensitivity to ER stress. However, expression of the UPR target gene bipA was constitutively elevated in this strain, suggesting that the UPR was compensating for the absence of DerA function. To test this, the UPR was disrupted by deleting the hacA gene. The combined loss of derA and hacA caused a more severe reduction in hyphal growth, antifungal drug resistance and protease secretion than the loss of either gene alone, suggesting that DerA and HacA cooperate to support these functions. Moreover, the ΔderA/ΔhacA mutant was avirulent in a mouse model of invasive aspergillosis, which contrasted the wild type virulence of ΔderA and the reduced virulence of the ΔhacA mutant. Taken together, these data demonstrate that DerA cooperates with the UPR to support the expression of virulence-related attributes of A. fumigatus.
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Affiliation(s)
- Daryl L Richie
- Department of Pathology & Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, USA
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123
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Ninagawa S, Okada T, Takeda S, Mori K. SEL1L Is Required for Endoplasmic Reticulum-associated Degradation of Misfolded Luminal Proteins but not Transmembrane Proteins in Chicken DT40 Cell Line. Cell Struct Funct 2011; 36:187-95. [DOI: 10.1247/csf.11018] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Affiliation(s)
- Satoshi Ninagawa
- Department of Biophysics, Graduate School of Science, Kyoto University
| | - Tetsuya Okada
- Department of Biophysics, Graduate School of Science, Kyoto University
- CREST, Japan Science and Technology Corporation
| | - Shunichi Takeda
- Department of Radiation Genetics, Graduate School of Medicine, Kyoto University
- CREST, Japan Science and Technology Corporation
| | - Kazutoshi Mori
- Department of Biophysics, Graduate School of Science, Kyoto University
- CREST, Japan Science and Technology Corporation
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124
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125
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Carvalho NDSP, Arentshorst M, Weenink XO, Punt PJ, van den Hondel CAMJJ, Ram AFJ. Functional YFP-tagging of the essential GDP-mannose transporter reveals an important role for the secretion related small GTPase SrgC protein in maintenance of Golgi bodies in Aspergillus niger. Fungal Biol 2010; 115:253-64. [PMID: 21354532 DOI: 10.1016/j.funbio.2010.12.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 12/08/2010] [Accepted: 12/19/2010] [Indexed: 11/26/2022]
Abstract
The addition of mannose residues to glycoproteins and glycolipids in the Golgi is carried out by mannosyltransferases. Their activity depends on the presence of GDP-mannose in the lumen of the Golgi. The transport of GDP-mannose (mannosyl donor) into the Golgi requires a specific nucleotide sugar transport present in the Golgi membrane. Here, we report the identification and functional characterization of the putative GDP-mannose transporter in Aspergillus niger, encoded by the gmtA gene (An17g02140). The single GDP-mannose transporter was identified in the A. niger genome and deletion analysis showed that gmtA is an essential gene. The lethal phenotype of the gmtA could be fully complemented by expressing an YFP-GmtA fusion protein from the endogenous gmtA promoter. Fluorescence studies revealed that, as in other fungal species, GmtA localized as punctate dots throughout the hyphal cytoplasm, representing Golgi bodies or Golgi equivalents. SrgC encodes a member of the Rab6/Ypt6 subfamily of secretion-related GTPases and is predicted to be required for the Golgi to vacuole transport. Loss of function of the srgC gene in A. niger resulted in strongly reduced growth and the inability to form conidiospores at 37°C and higher. Furthermore, the srgC disruption in the A. niger strain expressing the functional YFP-GmtA fusion protein led to an apparent 'disappearance' of the Golgi-like structures. The analysis suggests that SrgC has an important role in maintaining the integrity of Golgi-like structures in A. niger.
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Affiliation(s)
- Neuza D S P Carvalho
- Department Molecular Microbiology and Biotechnology, Institute of Biology, Leiden University, Sylviusweg 72, Leiden, The Netherlands
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126
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The endoplasmic reticulum-associated degradation is necessary for plant salt tolerance. Cell Res 2010; 21:957-69. [PMID: 21187857 DOI: 10.1038/cr.2010.181] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Eukaryotic organisms have quality-control mechanisms that allow misfolded or unassembled proteins to be retained in the endoplasmic reticulum (ER) and subsequently degraded by ER-associated degradation (ERAD). The ERAD pathway is well studied in yeast and mammals; however, the biological functions of plant ERAD have not been reported. Through molecular and cellular biological approaches, we found that ERAD is necessary for plants to overcome salt stress. Upon salt treatment ubiquitinated proteins increased in plant cells, especially unfolded proteins that quickly accumulated in the ER and subsequently induced ER stress responses. Defect in HRD3A of the HRD1/HRD3 complex of the ERAD pathway resulted in alteration of the unfolded protein response (UPR), increased plant sensitivity to salt, and retention of ERAD substrates in plant cells. Furthermore, we demonstrated that Ca(2+) release from the ER is involved in the elevation of UPR and reactive oxygen species (ROS) participates the ERAD-related plant salt response pathway.
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127
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Kramer LB, Shim J, Previtera ML, Isack NR, Lee MC, Firestein BL, Rongo C. UEV-1 is an ubiquitin-conjugating enzyme variant that regulates glutamate receptor trafficking in C. elegans neurons. PLoS One 2010; 5:e14291. [PMID: 21179194 PMCID: PMC3001443 DOI: 10.1371/journal.pone.0014291] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Accepted: 11/18/2010] [Indexed: 11/18/2022] Open
Abstract
The regulation of AMPA-type glutamate receptor (AMPAR) membrane trafficking is a key mechanism by which neurons regulate synaptic strength and plasticity. AMPAR trafficking is modulated through a combination of receptor phosphorylation, ubiquitination, endocytosis, and recycling, yet the factors that mediate these processes are just beginning to be uncovered. Here we identify the ubiquitin-conjugating enzyme variant UEV-1 as a regulator of AMPAR trafficking in vivo. We identified mutations in uev-1 in a genetic screen for mutants with altered trafficking of the AMPAR subunit GLR-1 in C. elegans interneurons. Loss of uev-1 activity results in the accumulation of GLR-1 in elongated accretions in neuron cell bodies and along the ventral cord neurites. Mutants also have a corresponding behavioral defect--a decrease in spontaneous reversals in locomotion--consistent with diminished GLR-1 function. The localization of other synaptic proteins in uev-1-mutant interneurons appears normal, indicating that the GLR-1 trafficking defects are not due to gross deficiencies in synapse formation or overall protein trafficking. We provide evidence that GLR-1 accumulates at RAB-10-containing endosomes in uev-1 mutants, and that receptors arrive at these endosomes independent of clathrin-mediated endocytosis. UEV-1 homologs in other species bind to the ubiquitin-conjugating enzyme Ubc13 to create K63-linked polyubiquitin chains on substrate proteins. We find that whereas UEV-1 can interact with C. elegans UBC-13, global levels of K63-linked ubiquitination throughout nematodes appear to be unaffected in uev-1 mutants, even though UEV-1 is broadly expressed in most tissues. Nevertheless, ubc-13 mutants are similar in phenotype to uev-1 mutants, suggesting that the two proteins do work together to regulate GLR-1 trafficking. Our results suggest that UEV-1 could regulate a small subset of K63-linked ubiquitination events in nematodes, at least one of which is critical in regulating GLR-1 trafficking.
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Affiliation(s)
- Lawrence B Kramer
- The Waksman Institute, Department of Genetics, Rutgers, The State University of New Jersey, Piscataway, New Jersey, United States of America
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128
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Tran JR, Tomsic LR, Brodsky JL. A Cdc48p-associated factor modulates endoplasmic reticulum-associated degradation, cell stress, and ubiquitinated protein homeostasis. J Biol Chem 2010; 286:5744-55. [PMID: 21148305 DOI: 10.1074/jbc.m110.179259] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The hexameric AAA-ATPase, Cdc48p, catalyzes an array of cellular activities, including endoplasmic reticulum (ER)-associated degradation (ERAD), ER/Golgi membrane dynamics, and DNA replication. Accumulating data suggest that unique Cdc48p partners, such as Npl4p-Ufd1p and Ubx1p/Shp1p (p47 in vertebrates), target Cdc48p for these diverse functions. Other Cdc48p-associated proteins have been identified, but the interplay among these factors and their activities is largely cryptic. We now report on a previously uncharacterized Cdc48p-associated protein, Ydr049p, also known as Vms1p, which binds Cdc48p at both the ER membrane and in the cytosol under non-stressed conditions. Loss of YDR049 modestly slows the degradation of the cystic fibrosis transmembrane conductance regulator but does not impede substrate ubiquitination, suggesting that Ydr049p acts at a postubiquitination step in the ERAD pathway. Consistent with Ydr049p playing a role in Cdc48p substrate release, ydr049 mutant cells accumulate Cdc48p-bound ubiquitinated proteins at the ER membrane. Moreover, YDR049 interacts with genes encoding select UBX (ubiquitin regulatory X) and UFD (ubiquitin fusion degradation) proteins, which are Cdc48p partners. Exacerbated growth defects are apparent in some of the mutant combinations, and synergistic effects on the degradation of cystic fibrosis transmembrane conductance regulator and CPY*, which is a soluble ERAD substrate, are evident in specific ydr049-ufd and -ubx mutants. These data suggest that Ydr049p acts in parallel with Cdc48p partners to modulate ERAD and other cellular activities.
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Affiliation(s)
- Joseph R Tran
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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129
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Kawaguchi S, Hsu CL, Ng DTW. Interplay of substrate retention and export signals in endoplasmic reticulum quality control. PLoS One 2010; 5:e15532. [PMID: 21151492 PMCID: PMC2991357 DOI: 10.1371/journal.pone.0015532] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Accepted: 10/05/2010] [Indexed: 11/19/2022] Open
Abstract
Background Endoplasmic reticulum (ER) quality control mechanisms are part of a comprehensive system to manage cell stress. The flux of molecules is monitored to retain folding intermediates and target misfolded molecules to ER-associated degradation (ERAD) pathways. The mechanisms of sorting remain unclear. While some proteins are retained statically, the classical model substrate CPY* is found in COPII transport vesicles, suggesting a retrieval mechanism for retention. However, its management can be even more dynamic. If ERAD is saturated under stress, excess CPY* traffics to the vacuole for degradation. These observations suggest that misfolded proteins might display different signals for their management. Methodology/Principal Findings Here, we report the existence of a functional ER exit signal in the pro-domain of CPY*. Compromising its integrity causes ER retention through exclusion from COPII vesicles. The signal co-exists with other signals used for retention and degradation. Physiologically, the export signal is important for stress tolerance. Disabling it converts a benign protein into one that is intrinsically cytotoxic. Conclusions/Significance These data reveal the remarkable interplay between opposing signals embedded within ERAD substrate molecules and the mechanisms that decipher them. Our findings demonstrate the diversity of mechanisms deployed for protein quality control and maintenance of protein homeostasis.
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Affiliation(s)
- Shinichi Kawaguchi
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore, Singapore
| | - Chia-Ling Hsu
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore, Singapore
| | - Davis T. W. Ng
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore, Singapore
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
- * E-mail:
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130
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Swennen D, Henry C, Beckerich JM. Folding proteome of Yarrowia lipolytica targeting with uracil permease mutants. J Proteome Res 2010; 9:6169-79. [PMID: 20949976 DOI: 10.1021/pr100340p] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The acquisition of the correct folding of membrane proteins is a crucial process that involves several steps from the recognition of nascent protein, its targeting to the endoplasmic reticulum membrane, its insertion, and its sorting to its final destination. Yarrowia lipolytica is a hemiascomycetous dimorphic yeast and an alternative eukaryotic yeast model with an efficient secretion pathway. To better understand the quality control of membrane proteins, we constructed a model system based on the uracil permease. Mutated forms of the permease were stabilized and retained in the cell and made the strains resistant to the 5-fluorouracil drug. To identify proteins involved in the quality control, we separated proteins extracted in nondenaturing conditions on blue native gels to keep proteins associated in complexes. Some gel fragments where the model protein was immunodetected were subjected to mass spectrometry analysis. The proteins identified gave a picture of the folding proteome, from the translocation across the endoplasmic reticulum membrane, the folding of the proteins, to the vesicle transport to Golgi or the degradation via the proteasome. For example, EMC complex, Gsf2p or Yet3p, chaperone membrane proteins of the endoplasmic reticulum were identified in the Y. lipolytica native proteome.
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Affiliation(s)
- Dominique Swennen
- INRA, UMR1319 Micalis, Domaine de Vilvert, F-78352 Jouy-en-Josas, France.
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131
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Abstract
Plant peroxisomes are extremely dynamic, moving and undergoing changes of shape in response to metabolic and environmental signals. Matrix proteins are imported via one of two import pathways, depending on the targeting signal within the protein. Each pathway has a specific receptor but utilizes common membrane-bound translocation machinery. Current models invoke receptor recycling, which may involve cycles of ubiquitination. Some components of the import machinery may also play a role in proteolytic turnover of matrix proteins, prompting parallels with the endoplasmic-reticulum-associated degradation pathway. Peroxisome membrane proteins, some of which are imported post-translationally, others of which may traffic to peroxisomes via the endoplasmic reticulum, use distinct proteinaceous machinery. The isolation of mutants defective in peroxisome biogenesis has served to emphasize the important role of peroxisomes at all stages of the plant life cycle.
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