1
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Fung C, Miles LB, Bryson-Richardson RJ, Bird PI. Manipulation of Proteostasis Networks in Transgenic ZAAT Zebrafish via CRISPR-Cas9 Gene Editing. Methods Mol Biol 2024; 2750:19-32. [PMID: 38108964 DOI: 10.1007/978-1-0716-3605-3_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
The CRISPR-Cas9 genome editing system is used to induce mutations in genes of interest resulting in the loss of functional protein. A transgenic zebrafish α1-antitrypsin deficiency (AATD) model displays an unusual phenotype, in that it lacks the hepatic accumulation of the misfolding Z α1-antitrypsin (ZAAT) evident in human and mouse models. Here we describe the application of the CRISPR-Cas9 system to generate mutant zebrafish with defects in key proteostasis networks likely to be involved in the hepatic processing of ZAAT in this model. We describe the targeting of the atf6a and man1b1 genes as examples.
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Affiliation(s)
- Connie Fung
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia.
| | - Lee B Miles
- School of Biological Sciences, Monash University, Clayton, VIC, Australia
| | | | - Phillip I Bird
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Clayton, VIC, Australia
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2
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Fung C, Wilding B, Schittenhelm RB, Bryson-Richardson RJ, Bird PI. Expression of the Z Variant of α1-Antitrypsin Suppresses Hepatic Cholesterol Biosynthesis in Transgenic Zebrafish. Int J Mol Sci 2023; 24:ijms24032475. [PMID: 36768797 PMCID: PMC9917206 DOI: 10.3390/ijms24032475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 01/20/2023] [Accepted: 01/21/2023] [Indexed: 01/31/2023] Open
Abstract
Individuals homozygous for the Pi*Z allele of SERPINA1 (ZAAT) are susceptible to lung disease due to insufficient α1-antitrypsin secretion into the circulation and may develop liver disease due to compromised protein folding that leads to inclusion body formation in the endoplasmic reticulum (ER) of hepatocytes. Transgenic zebrafish expressing human ZAAT show no signs of hepatic accumulation despite displaying serum insufficiency, suggesting the defect in ZAAT secretion occurs independently of its tendency to form inclusion bodies. In this study, proteomic, transcriptomic, and biochemical analysis provided evidence of suppressed Srebp2-mediated cholesterol biosynthesis in the liver of ZAAT-expressing zebrafish. To investigate the basis for this perturbation, CRISPR/Cas9 gene editing was used to manipulate ER protein quality control factors. Mutation of erlec1 resulted in a further suppression in the cholesterol biosynthesis pathway, confirming a role for this ER lectin in targeting misfolded ZAAT for ER-associated degradation (ERAD). Mutation of the two ER mannosidase homologs enhanced ZAAT secretion without inducing hepatic accumulation. These insights into hepatic ZAAT processing suggest potential therapeutic targets to improve secretion and alleviate serum insufficiency in this form of the α1-antitrypsin disease.
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Affiliation(s)
- Connie Fung
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne 3800, Australia
- Correspondence: (C.F.); (P.I.B.)
| | - Brendan Wilding
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne 3800, Australia
| | - Ralf B. Schittenhelm
- Monash Proteomics and Metabolomics Facility, Monash University, Melbourne 3800, Australia
| | | | - Phillip I. Bird
- Department of Biochemistry and Molecular Biology, Biomedicine Discovery Institute, Monash University, Melbourne 3800, Australia
- Correspondence: (C.F.); (P.I.B.)
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3
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Chambers JE, Zubkov N, Kubánková M, Nixon-Abell J, Mela I, Abreu S, Schwiening M, Lavarda G, López-Duarte I, Dickens JA, Torres T, Kaminski CF, Holt LJ, Avezov E, Huntington JA, George-Hyslop PS, Kuimova MK, Marciniak SJ. Z-α 1-antitrypsin polymers impose molecular filtration in the endoplasmic reticulum after undergoing phase transition to a solid state. SCIENCE ADVANCES 2022; 8:eabm2094. [PMID: 35394846 PMCID: PMC8993113 DOI: 10.1126/sciadv.abm2094] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2021] [Accepted: 02/16/2022] [Indexed: 05/06/2023]
Abstract
Misfolding of secretory proteins in the endoplasmic reticulum (ER) features in many human diseases. In α1-antitrypsin deficiency, the pathogenic Z variant aberrantly assembles into polymers in the hepatocyte ER, leading to cirrhosis. We show that α1-antitrypsin polymers undergo a liquid:solid phase transition, forming a protein matrix that retards mobility of ER proteins by size-dependent molecular filtration. The Z-α1-antitrypsin phase transition is promoted during ER stress by an ATF6-mediated unfolded protein response. Furthermore, the ER chaperone calreticulin promotes Z-α1-antitrypsin solidification and increases protein matrix stiffness. Single-particle tracking reveals that solidification initiates in cells with normal ER morphology, previously assumed to represent a healthy pool. We show that Z-α1-antitrypsin-induced hypersensitivity to ER stress can be explained by immobilization of ER chaperones within the polymer matrix. This previously unidentified mechanism of ER dysfunction provides a template for understanding a diverse group of related proteinopathies and identifies ER chaperones as potential therapeutic targets.
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Affiliation(s)
- Joseph E. Chambers
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
| | - Nikita Zubkov
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
| | - Markéta Kubánková
- Department of Chemistry, Imperial College London, Wood Lane, London W12 0BZ, UK
| | - Jonathon Nixon-Abell
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
| | - Ioanna Mela
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS, UK
| | - Susana Abreu
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
| | - Max Schwiening
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
| | - Giulia Lavarda
- Departamento de Química Orgánica and Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Madrid 28049, Spain
| | - Ismael López-Duarte
- Departamento de Química Orgánica and Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Madrid 28049, Spain
| | - Jennifer A. Dickens
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
| | - Tomás Torres
- Departamento de Química Orgánica and Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, Madrid 28049, Spain
- IMDEA Nanociencia, Campus de Cantoblanco, Madrid 28049, Spain
| | - Clemens F. Kaminski
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, Cambridge CB3 0AS, UK
| | - Liam J. Holt
- Institute for Systems Genetics, New York University Grossman School of Medicine, 435 E 30th St, New York, NY 10016, USA
| | - Edward Avezov
- Department of Clinical Neurosciences and UK Dementia Research Institute, University of Cambridge, Cambridge CB2 0AH, UK
| | - James A. Huntington
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
| | - Peter St George-Hyslop
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
- Department of Medicine (Neurology), Temerty Faculty of Medicine, University of Toronto, University Health Network, Toronto, ON M5T 0S8, Canada
- Taub Institute For Research on Alzheimer’s Disease and the Ageing Brain, Department of Neurology, Columbia University Irvine Medical Center, 630 West 1/68 Street, New York, NY 10032, USA
| | - Marina K. Kuimova
- Department of Chemistry, Imperial College London, Wood Lane, London W12 0BZ, UK
| | - Stefan J. Marciniak
- Cambridge Institute for Medical Research (CIMR), Department of Medicine, University of Cambridge, The Keith Peters Building, Hills Road, Cambridge CB2 0XY, UK
- Royal Papworth Hospital, Cambridge CB2 0AY, UK
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Watanabe K, Nakayama K, Ohta S, Matsumoto A, Tsuda H, Iwamoto S. ILDR2 stabilization is regulated by its interaction with GRP78. Sci Rep 2021; 11:8414. [PMID: 33863978 PMCID: PMC8052334 DOI: 10.1038/s41598-021-87884-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 04/06/2021] [Indexed: 12/13/2022] Open
Abstract
Ildr2 was initially identified as a genetic modifier of diabetes susceptibility in B6.DBA Lepob congenic mice, and was associated with decreased β-cell replication rates, reduced β-cell mass, and persistent mild hypoinsulinemic hyperglycemia. However, the molecular mechanisms of how the ILDR2 protein is involved in these effects are largely unknown. We sought to identify ILDR2-interacting proteins to further elucidate the molecular mechanisms underpinning ILDR2 function in pancreatic β-cells. Using TAP tag technology, we purified proteins interacting with ILDR2 in the pancreatic β-cell line MIN6, and identified the endoplasmic reticulum resident chaperones, GRP78 and PDIA1, as novel proteins interacting with ILDR2. We demonstrated that GRP78 interacted with ILDR2 and was possibly involved in ILDR2 stabilization by inhibiting ubiquitin–proteasome degradation. Additionally, adenoviral ILDR2 knockdown led to reduced glucose-responsive insulin secretion in MIN6 β-cells, suggesting ILDR2 may be implicated in a new pathway in hypoinsulinemic hyperglycemia. These data provide evidence for a novel association between GRP78 and ILDR2, and suggest GPR78-ILDR2 may a novel target for diabetic therapeutic modulation in decreased insulin secretion.
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Affiliation(s)
- Kazuhisa Watanabe
- Division of Human Genetics, Center for Molecular Medicine, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi, 329-0498, Japan.
| | - Kazuhiro Nakayama
- Laboratory of Evolutionary Anthropology, Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba, 277-8562, Japan
| | - Satoshi Ohta
- Division of Structural Biochemistry, Department of Biochemistry, School of Medicine, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi, 329-0498, Japan
| | - Ayumi Matsumoto
- Division of Human Genetics, Center for Molecular Medicine, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi, 329-0498, Japan
| | - Hidetoshi Tsuda
- Division of Human Genetics, Center for Molecular Medicine, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi, 329-0498, Japan
| | - Sadahiko Iwamoto
- Division of Human Genetics, Center for Molecular Medicine, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi, 329-0498, Japan
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Mohan HM, Yang B, Dean NA, Raghavan M. Calreticulin enhances the secretory trafficking of a misfolded α-1-antitrypsin. J Biol Chem 2020; 295:16754-16772. [PMID: 32978262 PMCID: PMC7864070 DOI: 10.1074/jbc.ra120.014372] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 09/12/2020] [Indexed: 01/24/2023] Open
Abstract
α1-antitrypsin (AAT) regulates the activity of multiple proteases in the lungs and liver. A mutant of AAT (E342K) called ATZ forms polymers that are present at only low levels in the serum and induce intracellular protein inclusions, causing lung emphysema and liver cirrhosis. An understanding of factors that can reduce the intracellular accumulation of ATZ is of great interest. We now show that calreticulin (CRT), an endoplasmic reticulum (ER) glycoprotein chaperone, promotes the secretory trafficking of ATZ, enhancing the media:cell ratio. This effect is more pronounced for ATZ than with AAT and is only partially dependent on the glycan-binding site of CRT, which is generally relevant to substrate recruitment and folding by CRT. The CRT-related chaperone calnexin does not enhance ATZ secretory trafficking, despite the higher cellular abundance of calnexin-ATZ complexes. CRT deficiency alters the distributions of ATZ-ER chaperone complexes, increasing ATZ-BiP binding and inclusion body formation and reducing ATZ interactions with components required for ER-Golgi trafficking, coincident with reduced levels of the protein transport protein Sec31A in CRT-deficient cells. These findings indicate a novel role for CRT in promoting the secretory trafficking of a protein that forms polymers and large intracellular inclusions. Inefficient secretory trafficking of ATZ in the absence of CRT is coincident with enhanced accumulation of ER-derived ATZ inclusion bodies. Further understanding of the factors that control the secretory trafficking of ATZ and their regulation by CRT could lead to new therapies for lung and liver diseases linked to AAT deficiency.
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Affiliation(s)
- Harihar Milaganur Mohan
- Department of Microbiology and Immunology, Michigan Medicine, University of Michigan, Ann Arbor, Michigan, 48109 USA
| | - Boning Yang
- Department of Microbiology and Immunology, Michigan Medicine, University of Michigan, Ann Arbor, Michigan, 48109 USA
| | - Nicole A Dean
- Department of Microbiology and Immunology, Michigan Medicine, University of Michigan, Ann Arbor, Michigan, 48109 USA
| | - Malini Raghavan
- Department of Microbiology and Immunology, Michigan Medicine, University of Michigan, Ann Arbor, Michigan, 48109 USA.
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6
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Abstract
Alpha1-antitrypsin deficiency (A1ATD) is an inherited cause of chronic liver disease. It is inherited in an autosomal codominant pattern with each inherited allele expressed in the formation of the final protein, which is primarily produced in hepatocytes. The disease usually occurs in pediatric and elderly populations. The disease occurs with the accumulation of abnormal protein polymers within hepatocytes that can induce liver injury and fibrosis. It is a commonly under-recognized and underdiagnosed condition. Patients diagnosed with the disease should be regularly monitored for the development of liver disease. Liver transplant is of proven benefit in A1ATD liver disease.
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Affiliation(s)
- Vignan Manne
- Sunrise Health Consortium GME, 2880 North Tenaya Way, Las Vegas, NV 89128, USA
| | - Kris V Kowdley
- 3216 Northeast 45th Place Suite 212, Seattle, WA 98105, USA.
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7
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Khodayari N, Oshins R, Alli AA, Tuna KM, Holliday LS, Krotova K, Brantly M. Modulation of calreticulin expression reveals a novel exosome-mediated mechanism of Z variant α 1-antitrypsin disposal. J Biol Chem 2019; 294:6240-6252. [PMID: 30833329 DOI: 10.1074/jbc.ra118.006142] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Revised: 02/26/2019] [Indexed: 01/08/2023] Open
Abstract
α1-Antitrypsin deficiency (AATD) is an inherited disease characterized by emphysema and liver disease. AATD is most often caused by a single amino acid substitution at position 342 in the mature protein, resulting in the Z mutation of the AAT gene (ZAAT). This substitution is associated with misfolding and accumulation of ZAAT in the endoplasmic reticulum (ER) of hepatocytes, causing a toxic gain of function. ERdj3 is an ER luminal DnaJ homologue, which, along with calreticulin, directly interacts with misfolded ZAAT. We hypothesize that depletion of each of these chaperones will change the fate of ZAAT polymers. Our study demonstrates that calreticulin modulation reveals a novel ZAAT degradation mechanism mediated by exosomes. Using human PiZZ hepatocytes and K42, a mouse calreticulin-deficient fibroblast cell line, our results show ERdj3 and calreticulin directly interact with ZAAT in PiZZ hepatocytes. Silencing calreticulin induces calcium independent ZAAT-ERdj3 secretion through the exosome pathway. This co-secretion decreases ZAAT aggregates within the ER of hepatocytes. We demonstrate that calreticulin has an inhibitory effect on exosome-mediated ZAAT-ERdj3 secretion. This is a novel ZAAT degradation process that involves a DnaJ homologue chaperone bound to ZAAT. In this context, calreticulin modulation may eliminate the toxic gain of function associated with aggregation of ZAAT in lung and liver, thus providing a potential new therapeutic approach to the treatment of AATD-related liver disease.
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Affiliation(s)
- Nazli Khodayari
- From the Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine
| | - Regina Oshins
- From the Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine
| | - Abdel A Alli
- the Department of Physiology and Functional Genomics, College of Medicine, and
| | - Kubra M Tuna
- the Department of Physiology and Functional Genomics, College of Medicine, and
| | - L Shannon Holliday
- the Department of Orthodontics, College of Dentistry, University of Florida, Gainesville, Florida 32610 and
| | - Karina Krotova
- the Hormel Institute, University of Minnesota, Austin, Minnesota 55912
| | - Mark Brantly
- From the Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine,
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8
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Abstract
Alpha-1 antitrypsin deficiency is predominantly caused by point mutations that alter the protein's folding. These mutations fall into two broad categories: those that destabilize the protein dramatically and lead to its post-translational degradation and those that affect protein structure more subtly to promote protein polymerization within the endoplasmic reticulum (ER). This distinction is important because it determines the cell's response to each mutant. The severely misfolded mutants trigger an unfolded protein response (UPR) that promotes improved protein folding but can kill the cell in the chronic setting. In contrast, mutations that permit polymer formation fail to activate the UPR but instead promote a nuclear factor-κB-mediated ER overload response. The ability of polymers to increase a cell's sensitivity to ER stress likely explains apparent inconsistencies in the alpha-1 antitrypsin-signaling literature that have linked polymers with the UPR. In this review we discuss the use of mutant serpins to dissect each signaling pathway.
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9
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Khodayari N, Marek G, Lu Y, Krotova K, Wang RL, Brantly M. Erdj3 Has an Essential Role for Z Variant Alpha-1-Antitrypsin Degradation. J Cell Biochem 2017; 118:3090-3101. [PMID: 28419579 PMCID: PMC5575529 DOI: 10.1002/jcb.26069] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 04/14/2017] [Indexed: 01/16/2023]
Abstract
Alpha‐1‐antitrypsin deficiency (AATD) is an inherited disease characterized by emphysema and liver disease. AATD is most often caused by a single amino acid substitution at amino acid 342 in the mature protein, resulting in the Z mutation of the alpha‐1‐antitrypsin gene (ZAAT). This substitution is associated with misfolding and accumulation of ZAAT in the endoplasmic reticulum (ER) of hepatocytes and monocytes, causing a toxic gain of function. Retained ZAAT is eliminated by ER‐associated degradation and autophagy. We hypothesized that alpha‐1‐antitrypsin (AAT)‐interacting proteins play critical roles in quality control of human AAT. Using co‐immunoprecipitation, we identified ERdj3, an ER‐resident Hsp40 family member, as a part of the AAT trafficking network. Depleting ERdj3 increased the rate of ZAAT degradation in hepatocytes by redirecting ZAAT to the ER calreticulin‐EDEM1 pathway, followed by autophagosome formation. In the Huh7.5 cell line, ZAAT ER clearance resulted from enhancing ERdj3‐mediated ZAAT degradation by silencing ERdj3 while simultaneously enhancing autophagy. In this context, ERdj3 suppression may eliminate the toxic gain of function associated with polymerization of ZAAT, thus providing a potential new therapeutic approach to the treatment of AATD‐related liver disease. J. Cell. Biochem. 118: 3090–3101, 2017. © 2017 The Authors. Journal of Cellular Biochemistry Published by Wiley Periodicals Inc.
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Affiliation(s)
- Nazli Khodayari
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Florida, Gainesville, Florida
| | - George Marek
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Florida, Gainesville, Florida
| | - Yuanqing Lu
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Florida, Gainesville, Florida
| | - Karina Krotova
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Florida, Gainesville, Florida
| | - Rejean Liqun Wang
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Florida, Gainesville, Florida
| | - Mark Brantly
- Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Florida, Gainesville, Florida
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Abstract
α1-Antitrypsin deficiency (A1ATD) is an inherited disorder caused by mutations in SERPINA1, leading to liver and lung disease. It is not a rare disorder but frequently goes underdiagnosed or misdiagnosed as asthma, chronic obstructive pulmonary disease (COPD) or cryptogenic liver disease. The most frequent disease-associated mutations include the S allele and the Z allele of SERPINA1, which lead to the accumulation of misfolded α1-antitrypsin in hepatocytes, endoplasmic reticulum stress, low circulating levels of α1-antitrypsin and liver disease. Currently, there is no cure for severe liver disease and the only management option is liver transplantation when liver failure is life-threatening. A1ATD-associated lung disease predominately occurs in adults and is caused principally by inadequate protease inhibition. Treatment of A1ATD-associated lung disease includes standard therapies that are also used for the treatment of COPD, in addition to the use of augmentation therapy (that is, infusions of human plasma-derived, purified α1-antitrypsin). New therapies that target the misfolded α1-antitrypsin or attempt to correct the underlying genetic mutation are currently under development.
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11
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Teckman JH, Mangalat N. Alpha-1 antitrypsin and liver disease: mechanisms of injury and novel interventions. Expert Rev Gastroenterol Hepatol 2015; 9:261-8. [PMID: 25066184 DOI: 10.1586/17474124.2014.943187] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
α-1-Antitrypsin (α1AT) is a serum glycoprotein synthesized in the liver. The majority of patients with α1AT deficiency liver disease are homozygous for the Z mutant of α1AT (called ZZ or 'PIZZ'). This mutant gene directs the synthesis of an abnormal protein which folds improperly during biogenesis. Most of these mutant Z protein molecules undergo proteolysis; however, some of the mutant protein accumulates in hepatocytes. Hepatocytes with the largest mutant protein burdens undergo apoptosis, causing compensatory hepatic proliferation. Cycles of hepatocyte injury, cell death and compensatory proliferation results in liver disease ranging from mild asymptomatic enzyme elevations to hepatic fibrosis, cirrhosis and hepatocellular carcinoma. There is a high variability in clinical disease presentation suggesting that environmental and genetic modifiers are important. Management of α1AT liver disease is based on standard supportive care and liver transplant. However, increased understanding of the cellular mechanisms of liver injury has led to new clinical trials.
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Affiliation(s)
- Jeffrey H Teckman
- St. Louis University School of Medicine, Cardinal Glennon Children's Medical Center, 1465 South Grand Blvd, St. Louis, MO 63104, USA
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12
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Abstract
Alpha-1-antitrypsin (a1AT) deficiency is a common, but under-diagnosed, genetic disease. In the classical form, patients are homozygous for the Z mutant of the a1AT gene (called ZZ or PIZZ), which occurs in 1 in 2,000-3,500 births. The mutant Z gene directs the synthesis of large quantities of the mutant Z protein in the liver, which folds abnormally during biogenesis and accumulates intracellularly, rather than being efficiently secreted. The accumulation mutant Z protein within hepatocytes causes liver injury, cirrhosis, and hepatocellular carcinoma via a cascade of chronic hepatocellular apoptosis, regeneration, and end organ injury. There is no specific treatment for a1AT-associated liver disease, other than standard supportive care and transplantation. There is high variability in the clinical manifestations among ZZ homozygous patients, suggesting a strong influence of genetic and environmental modifiers. New insights into the biological mechanisms of intracellular injury have led to new, rational therapeutic approaches.
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Affiliation(s)
- Jeffrey H Teckman
- St. Louis University School of Medicine, Cardinal Glennon Children's Medical Center, 1465 South Grand Blvd., St. Louis, MO, 63104, USA,
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13
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Dersh D, Jones SM, Eletto D, Christianson JC, Argon Y. OS-9 facilitates turnover of nonnative GRP94 marked by hyperglycosylation. Mol Biol Cell 2014; 25:2220-34. [PMID: 24899641 PMCID: PMC4116297 DOI: 10.1091/mbc.e14-03-0805] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
ER quality control factors GRP94 and OS-9 associate not for the disposal of ERAD substrates but
instead because OS-9 sequesters and degrades aberrant forms of GRP94, which are hyperglycosylated at
cryptic acceptor sites and have altered structure and activity. This highlights a novel mechanism of
quality control of an ER-resident chaperone. The tight coupling of protein folding pathways with disposal mechanisms promotes the efficacy of
protein production in the endoplasmic reticulum (ER). It has been hypothesized that the ER-resident
molecular chaperone glucose-regulated protein 94 (GRP94) is part of this quality control coupling
because it supports folding of select client proteins yet also robustly associates with the lectin
osteosarcoma amplified 9 (OS-9), a component involved in ER-associated degradation (ERAD). To
explore this possibility, we investigated potential functions for the GRP94/OS-9 complex in ER
quality control. Unexpectedly, GRP94 does not collaborate with OS-9 in ERAD of misfolded substrates,
nor is the chaperone required directly for OS-9 folding. Instead, OS-9 binds preferentially to a
subpopulation of GRP94 that is hyperglycosylated on cryptic N-linked glycan acceptor sites.
Hyperglycosylated GRP94 forms have nonnative conformations and are less active. As a result, these
species are degraded much faster than the major, monoglycosylated form of GRP94 in an
OS-9–mediated, ERAD-independent, lysosomal-like mechanism. This study therefore clarifies
the role of the GRP94/OS-9 complex and describes a novel pathway by which glycosylation of cryptic
acceptor sites influences the function and fate of an ER-resident chaperone.
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Affiliation(s)
- Devin Dersh
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA 19104Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Stephanie M Jones
- Ludwig Institute for Cancer Research, University of Oxford, Oxford OX3 7DQ, United Kingdom
| | - Davide Eletto
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA 19104
| | - John C Christianson
- Ludwig Institute for Cancer Research, University of Oxford, Oxford OX3 7DQ, United Kingdom
| | - Yair Argon
- Department of Pathology and Laboratory Medicine, The Children's Hospital of Philadelphia, Philadelphia, PA 19104Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
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14
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Ferris SP, Kodali VK, Kaufman RJ. Glycoprotein folding and quality-control mechanisms in protein-folding diseases. Dis Model Mech 2014; 7:331-41. [PMID: 24609034 PMCID: PMC3944493 DOI: 10.1242/dmm.014589] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Accepted: 01/14/2014] [Indexed: 12/31/2022] Open
Abstract
Biosynthesis of proteins--from translation to folding to export--encompasses a complex set of events that are exquisitely regulated and scrutinized to ensure the functional quality of the end products. Cells have evolved to capitalize on multiple post-translational modifications in addition to primary structure to indicate the folding status of nascent polypeptides to the chaperones and other proteins that assist in their folding and export. These modifications can also, in the case of irreversibly misfolded candidates, signal the need for dislocation and degradation. The current Review focuses on the glycoprotein quality-control (GQC) system that utilizes protein N-glycosylation and N-glycan trimming to direct nascent glycopolypeptides through the folding, export and dislocation pathways in the endoplasmic reticulum (ER). A diverse set of pathological conditions rooted in defective as well as over-vigilant ER quality-control systems have been identified, underlining its importance in human health and disease. We describe the GQC pathways and highlight disease and animal models that have been instrumental in clarifying our current understanding of these processes.
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Affiliation(s)
- Sean P. Ferris
- Department of Biological Chemistry and Medical Scientist Training Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - Vamsi K. Kodali
- Center for Neuroscience, Aging and Stem Cell Research, Sanford-Burnham Medical Research Institute, 10901 N. Torrey Pines Road, La Jolla, CA 92037, USA
| | - Randal J. Kaufman
- Center for Neuroscience, Aging and Stem Cell Research, Sanford-Burnham Medical Research Institute, 10901 N. Torrey Pines Road, La Jolla, CA 92037, USA
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15
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McCarthy C, Saldova R, O'Brien ME, Bergin DA, Carroll TP, Keenan J, Meleady P, Henry M, Clynes M, Rudd PM, Reeves EP, McElvaney NG. Increased outer arm and core fucose residues on the N-glycans of mutated alpha-1 antitrypsin protein from alpha-1 antitrypsin deficient individuals. J Proteome Res 2013; 13:596-605. [PMID: 24328305 DOI: 10.1021/pr400752t] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Alpha-1 antitrypsin (AAT) is the major physiological inhibitor of a range of serine proteases, and in the lung, it maintains a protease-antiprotease balance. AAT deficiency (AATD) is an autosomal co-dominant condition with the Z mutation being the most common cause. Individuals homozygous for Z (PiZZ) have low levels of circulating mutant Z-AAT protein leading to premature emphysematous lung disease. Extensive glycoanalysis has been performed on normal AAT (M-AAT) from healthy individuals and the importance of glycosylation in affecting the immune modulatory roles of AAT is documented. However, no glycoanalysis has been carried out on Z-AAT from deficient individuals to date. In this study, we investigate whether the glycans present on Z-AAT differ to those found on M-AAT from healthy controls. Plasma AAT was purified from 10 individuals: 5 AATD donors with the PiZZ phenotype and 5 PiMM healthy controls. Glycoanalysis was performed employing N-glycan release, exoglycosidase digestion and UPLC analysis. No difference in branched glycans was identified between AATD and healthy controls. However, a significant increase in both outer arm (α1-3) (p = 0.04) and core (α1-6) fucosylated glycans (p < 0.0001) was found on Z-AAT compared to M-AAT. This study has identified increased fucosylation on N-glycans of Z-AAT indicative of ongoing inflammation in AATD individuals with implications for early therapeutic intervention.
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Affiliation(s)
- Cormac McCarthy
- Respiratory Research Division, Royal College of Surgeons in Ireland , Beaumont Hospital, Dublin 9, Ireland
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16
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Strnad P, Nuraldeen R, Guldiken N, Hartmann D, Mahajan V, Denk H, Haybaeck J. Broad Spectrum of Hepatocyte Inclusions in Humans, Animals, and Experimental Models. Compr Physiol 2013; 3:1393-436. [DOI: 10.1002/cphy.c120032] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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17
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Marques PI, Ferreira Z, Martins M, Figueiredo J, Silva DI, Castro P, Morales-Hojas R, Simões-Correia J, Seixas S. SERPINA2 is a novel gene with a divergent function from SERPINA1. PLoS One 2013; 8:e66889. [PMID: 23826168 PMCID: PMC3691238 DOI: 10.1371/journal.pone.0066889] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2012] [Accepted: 05/11/2013] [Indexed: 11/23/2022] Open
Abstract
Serine protease inhibitors (SERPINs) are a superfamily of highly conserved proteins that play a key role in controlling the activity of proteases in diverse biological processes. The SERPIN cluster located at the 14q32.1 region includes the gene coding for SERPINA1, and a highly homologous sequence, SERPINA2, which was originally thought to be a pseudogene. We have previously shown that SERPINA2 is expressed in different tissues, namely leukocytes and testes, suggesting that it is a functional SERPIN. To investigate the function of SERPINA2, we used HeLa cells stably transduced with the different variants of SERPINA2 and SERPINA1 (M1, S and Z) and leukocytes as the in vivo model. We identified SERPINA2 as a 52 kDa intracellular glycoprotein, which is localized at the endoplasmic reticulum (ER), independently of the variant analyzed. SERPINA2 is not significantly regulated by proteasome, proposing that ER localization is not due to misfolding. Specific features of SERPINA2 include the absence of insoluble aggregates and the insignificant response to cell stress, suggesting that it is a non-polymerogenic protein with divergent activity of SERPINA1. Using phylogenetic analysis, we propose an origin of SERPINA2 in the crown of primates, and we unveiled the overall conservation of SERPINA2 and A1. Nonetheless, few SERPINA2 residues seem to have evolved faster, contributing to the emergence of a new advantageous function, possibly as a chymotrypsin-like SERPIN. Herein, we present evidences that SERPINA2 is an active gene, coding for an ER-resident protein, which may act as substrate or adjuvant of ER-chaperones.
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Affiliation(s)
- Patrícia Isabel Marques
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
- Institute of Biomedical Sciences Abel Salazar, University of Porto, Porto, Portugal
| | - Zélia Ferreira
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
- Department of Biology, Faculty of Sciences, University of Porto, Porto, Portugal
| | - Manuella Martins
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
| | - Joana Figueiredo
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
- Medical Faculty, University of Porto, Porto, Portugal
| | - Diana Isabel Silva
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
| | - Patrícia Castro
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
| | - Ramiro Morales-Hojas
- Molecular Evolution, Institute of Molecular and Cell Biology, University of Porto, Porto, Portugal
| | - Joana Simões-Correia
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
- Institute of Biomedical Research on Light and Image, Faculty of Medicine, University of Coimbra, Coimbra, Portugal
| | - Susana Seixas
- Institute of Molecular Pathology and Immunology of the University of Porto, Porto, Portugal
- * E-mail: (SS)
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18
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Teckman JH. Liver Disease in Alpha-1 Antitrypsin Deficiency: Current Understanding and Future Therapy. COPD 2013; 10 Suppl 1:35-43. [DOI: 10.3109/15412555.2013.765839] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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19
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Pan S, Cheng X, Sifers RN. Golgi-situated endoplasmic reticulum α-1, 2-mannosidase contributes to the retrieval of ERAD substrates through a direct interaction with γ-COP. Mol Biol Cell 2013; 24:1111-21. [PMID: 23427261 PMCID: PMC3623633 DOI: 10.1091/mbc.e12-12-0886] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Endoplasmic reticulum (ER) α-1, 2-mannosidase and γ-COP contribute to a Golgi-based quality control module that facilitates the retrieval of captured ER-associated protein degradation substrates back to the ER. Endoplasmic reticulum (ER) α-1, 2-mannosidase (ERManI) contributes to ER-associated protein degradation (ERAD) by initiating the formation of degradation signals on misfolded N-linked glycoproteins. Despite its inferred intracellular location, we recently discovered that the mammalian homologue is actually localized to the Golgi complex. In the present study, the functional role of Golgi-situated ERManI was investigated. Mass spectrometry analysis and coimmunoprecipitation (co-IP) identified a direct interaction between ERManI and γ-COP, the gamma subunit of coat protein complex I (COPI) that is responsible for Golgi-to-ER retrograde cargo transport. The functional relationship was validated by the requirement of both ERManI and γ-COP to support efficient intracellular clearance of the classical ERAD substrate, null Hong Kong (NHK). In addition, site-directed mutagenesis of suspected γ-COP–binding motifs in the cytoplasmic tail of ERManI was sufficient to disrupt the physical interaction and ablate NHK degradation. Moreover, a physical interaction between NHK, ERManI, and γ-COP was identified by co-IP and Western blotting. RNA interference–mediated knockdown of γ-COP enhanced the association between ERManI and NHK, while diminishing the efficiency of ERAD. Based on these findings, a model is proposed in which ERManI and γ-COP contribute to a Golgi-based quality control module that facilitates the retrieval of captured ERAD substrates back to the ER.
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Affiliation(s)
- Shujuan Pan
- Department of Pathology, Baylor College of Medicine, Houston, TX 77030, USA
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20
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Bouchecareilh M, Hutt DM, Szajner P, Flotte TR, Balch WE. Histone deacetylase inhibitor (HDACi) suberoylanilide hydroxamic acid (SAHA)-mediated correction of α1-antitrypsin deficiency. J Biol Chem 2012; 287:38265-78. [PMID: 22995909 PMCID: PMC3488095 DOI: 10.1074/jbc.m112.404707] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Revised: 09/12/2012] [Indexed: 02/06/2023] Open
Abstract
α1-Antitrypsin (α1AT) deficiency (α1ATD) is a consequence of defective folding, trafficking, and secretion of α1AT in response to a defect in its interaction with the endoplasmic reticulum proteostasis machineries. The most common and severe form of α1ATD is caused by the Z-variant and is characterized by the accumulation of α1AT polymers in the endoplasmic reticulum of the liver leading to a severe reduction (>85%) of α1AT in the serum and its anti-protease activity in the lung. In this organ α1AT is critical for ensuring tissue integrity by inhibiting neutrophil elastase, a protease that degrades elastin. Given the limited therapeutic options in α1ATD, a more detailed understanding of the folding and trafficking biology governing α1AT biogenesis and its response to small molecule regulators is required. Herein we report the correction of Z-α1AT secretion in response to treatment with the histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA), acting in part through HDAC7 silencing and involving a calnexin-sensitive mechanism. SAHA-mediated correction restores Z-α1AT secretion and serpin activity to a level 50% that observed for wild-type α1AT. These data suggest that HDAC activity can influence Z-α1AT protein traffic and that SAHA may represent a potential therapeutic approach for α1ATD and other protein misfolding diseases.
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Affiliation(s)
| | | | | | - Terence R. Flotte
- the Department of Pediatrics and Gene Therapy Center UMass Medical School, Worcester, Massachusetts 01655
| | - William E. Balch
- From the Department of Cell Biology
- The Skaggs Institute for Chemical Biology
- Department of Chemical Physiology, and
- the Institute for Childhood and Neglected Diseases, The Scripps Research Institute, La Jolla, California 92037 and
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21
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The endosomal protein-sorting receptor sortilin has a role in trafficking α-1 antitrypsin. Genetics 2012; 192:889-903. [PMID: 22923381 DOI: 10.1534/genetics.112.143487] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Up to 1 in 3000 individuals in the United States have α-1 antitrypsin deficiency, and the most common cause of this disease is homozygosity for the antitrypsin-Z variant (ATZ). ATZ is inefficiently secreted, resulting in protein deficiency in the lungs and toxic polymer accumulation in the liver. However, only a subset of patients suffer from liver disease, suggesting that genetic factors predispose individuals to liver disease. To identify candidate factors, we developed a yeast ATZ expression system that recapitulates key features of the disease-causing protein. We then adapted this system to screen the yeast deletion mutant collection to identify conserved genes that affect ATZ secretion and thus may modify the risk for developing liver disease. The results of the screen and associated assays indicate that ATZ is degraded in the vacuole after being routed from the Golgi. In fact, one of the strongest hits from our screen was Vps10, which can serve as a receptor for the delivery of aberrant proteins to the vacuole. Because genome-wide association studies implicate the human Vps10 homolog, sortilin, in cardiovascular disease, and because hepatic cell lines that stably express wild-type or mutant sortilin were recently established, we examined whether ATZ levels and secretion are affected by sortilin. As hypothesized, sortilin function impacts the levels of secreted ATZ in mammalian cells. This study represents the first genome-wide screen for factors that modulate ATZ secretion and has led to the identification of a gene that may modify disease severity or presentation in individuals with ATZ-associated liver disease.
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22
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Guerriero CJ, Brodsky JL. The delicate balance between secreted protein folding and endoplasmic reticulum-associated degradation in human physiology. Physiol Rev 2012; 92:537-76. [PMID: 22535891 DOI: 10.1152/physrev.00027.2011] [Citation(s) in RCA: 308] [Impact Index Per Article: 25.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Protein folding is a complex, error-prone process that often results in an irreparable protein by-product. These by-products can be recognized by cellular quality control machineries and targeted for proteasome-dependent degradation. The folding of proteins in the secretory pathway adds another layer to the protein folding "problem," as the endoplasmic reticulum maintains a unique chemical environment within the cell. In fact, a growing number of diseases are attributed to defects in secretory protein folding, and many of these by-products are targeted for a process known as endoplasmic reticulum-associated degradation (ERAD). Since its discovery, research on the mechanisms underlying the ERAD pathway has provided new insights into how ERAD contributes to human health during both normal and diseases states. Links between ERAD and disease are evidenced from the loss of protein function as a result of degradation, chronic cellular stress when ERAD fails to keep up with misfolded protein production, and the ability of some pathogens to coopt the ERAD pathway. The growing number of ERAD substrates has also illuminated the differences in the machineries used to recognize and degrade a vast array of potential clients for this pathway. Despite all that is known about ERAD, many questions remain, and new paradigms will likely emerge. Clearly, the key to successful disease treatment lies within defining the molecular details of the ERAD pathway and in understanding how this conserved pathway selects and degrades an innumerable cast of substrates.
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Affiliation(s)
- Christopher J Guerriero
- Department of Biological Sciences, University of Pittsburgh, A320 Langley Hall, Pittsburgh, PA 15260, USA
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23
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Mallinger A, Wen HM, Dankle GM, Glenn KA. Using a ubiquitin ligase as an unfolded protein sensor. Biochem Biophys Res Commun 2011; 418:44-8. [PMID: 22227190 DOI: 10.1016/j.bbrc.2011.12.109] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 12/21/2011] [Indexed: 11/26/2022]
Abstract
A significant fraction of all proteins are misfolded and must be degraded. The ubiquitin-proteasome pathway provides an essential protein quality control function necessary for normal cellular homeostasis. Substrate specificity is mediated by proteins called ubiquitin ligases. In the endoplasmic reticulum (ER) a specialized pathway, the endoplasmic reticulum associated degradation (ERAD) pathway provides means to eliminate misfolded proteins from the ER. One marker used by the ER to identify misfolded glycoproteins is the presence of a high-mannose (Man5-8GlcNAc2) glycan. Recently, FBXO2 was shown to bind high mannose glycans and participate in ERAD. Using glycan arrays, immobilized glycoprotein pulldowns, and glycan competition assays we demonstrate that FBXO2 preferentially binds unfolded glycoproteins. Using recombinant, bacterially expressed GST-FBXO2 as an unfolded protein sensor we demonstrate it can be used to monitor increases in misfolded glycoproteins after physiological or pharmaceutical stressors.
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Affiliation(s)
- Adam Mallinger
- Kansas City University of Medicine and Biosciences, Kansas City, MO 64106, USA
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24
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Pan S, Wang S, Utama B, Huang L, Blok N, Estes MK, Moremen KW, Sifers RN. Golgi localization of ERManI defines spatial separation of the mammalian glycoprotein quality control system. Mol Biol Cell 2011; 22:2810-22. [PMID: 21697506 PMCID: PMC3154878 DOI: 10.1091/mbc.e11-02-0118] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The current study provides mechanistic insight into the overlapping dynamics by which glycoprotein folding and quality control use distinct intracellular compartments as part of the proteostasis network in mammalian cells. The Golgi complex has been implicated as a possible component of endoplasmic reticulum (ER) glycoprotein quality control, although the elucidation of its exact role is lacking. ERManI, a putative ER resident mannosidase, plays a rate-limiting role in generating a signal that targets misfolded N-linked glycoproteins for ER-associated degradation (ERAD). Herein we demonstrate that the endogenous human homologue predominantly resides in the Golgi complex, where it is subjected to O-glycosylation. To distinguish the intracellular site where the glycoprotein ERAD signal is generated, a COPI-binding motif was appended to the N terminus of the recombinant protein to facilitate its retrograde translocation back to the ER. Partial redistribution of the modified ERManI was observed along with an accelerated rate at which N-linked glycans of misfolded α1-antitrypsin variant NHK were trimmed. Despite these observations, the rate of NHK degradation was not accelerated, implicating the Golgi complex as the site for glycoprotein ERAD substrate tagging. Taken together, these data provide a potential mechanistic explanation for the spatial separation by which glycoprotein quality control components operate in mammalian cells.
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Affiliation(s)
- Shujuan Pan
- Departments of Pathology & Immunology, Baylor College of Medicine, Houston, TX 77030, USA
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25
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Perlmutter DH. Alpha-1-antitrypsin deficiency: importance of proteasomal and autophagic degradative pathways in disposal of liver disease-associated protein aggregates. Annu Rev Med 2011; 62:333-45. [PMID: 20707674 DOI: 10.1146/annurev-med-042409-151920] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Alpha-1-antitrypsin (AT) deficiency is the most common genetic cause of liver disease in children. The primary pathological issue is a point mutation that renders an abundant hepatic secretory glycoprotein prone to altered folding and a tendency to polymerize and aggregate. However, the expression of serious liver damage among homozygotes is dependent on genetic and/or environmental modifiers. Several studies have validated the concept that endogenous hepatic pathways for disposal of aggregation-prone proteins, including the proteasomal and autophagic degradative pathways, could play a key role in the variation in hepatic damage and be the target of the modifiers. Exciting recent results have shown that a drug that enhances autophagy can reduce the hepatic load of aggregated protein and reverse fibrosis in a mouse model of this disease.
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Affiliation(s)
- David H Perlmutter
- Department of Pediatrics, Cell Biology and Physiology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, Pennsylvania 15217, USA.
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26
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Bouchecareilh M, Balch WE. Proteostasis: a new therapeutic paradigm for pulmonary disease. PROCEEDINGS OF THE AMERICAN THORACIC SOCIETY 2011; 8:189-95. [PMID: 21543800 PMCID: PMC3131838 DOI: 10.1513/pats.201008-055ms] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Accepted: 02/01/2011] [Indexed: 01/10/2023]
Abstract
Among lung pathologies, α1AT, chronic obstructive pulmonary disease (COPD), emphysema, and asthma are diseases triggered by local environmental stress in the airway that we refer to herein collectively as airway stress diseases (ASDs). A deficiency of α-1-antitrypsin (α1AT) is an inherited genetic disorder that is a consequence of the misfolding of α1AT during protein synthesis in liver hepatocytes, reducing secretion to the plasma and delivery to the lung. Deficiency of α1AT in the lung triggers a similar pathological phenotype to other ASDs. Moreover, the loss of α1AT in the lung is a well-known environmental risk factor for COPD/emphysema. To date there are no effective therapeutic approaches to address ASDs, which reflects a general lack of understanding of their cellular basis. Herein, we propose that ASDs are disorders of proteostasis. That is, they are initiated and propagated by a common theme-a challenge to protein folding capacity maintained by the proteostasis network (PN) (see Balch et al., Science 2008;319:916-919). The PN is a network of chaperones and degradative components that generates and manages protein folding pathways responsible for normal human physiology. In ASD, we suggest that the PN system fails to respond to the increased burden of unfolded proteins due to genetic and environmental stresses, thus triggering pulmonary pathophysiology. We introduce the enabling concept of proteostasis regulators (PRs), small molecules that regulate signaling pathways that control the composition and activity of PN components, as a new and general approach for therapeutic management of ASDs.
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Affiliation(s)
- Marion Bouchecareilh
- Department of Cell Biology, The Skaggs Institute for Chemical Biology, Department of Chemical Physiology and the Institute for Childhood and Neglected Diseases, The Scripps Research Institute, La Jolla, California
| | - William E. Balch
- Department of Cell Biology, The Skaggs Institute for Chemical Biology, Department of Chemical Physiology and the Institute for Childhood and Neglected Diseases, The Scripps Research Institute, La Jolla, California
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27
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Mechanisms underlying the cellular clearance of antitrypsin Z: lessons from yeast expression systems. Ann Am Thorac Soc 2011; 7:363-7. [PMID: 21030514 DOI: 10.1513/pats.201001-007aw] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The most frequent cause of α(1)-antitrypsin (here referred to as AT) deficiency is homozygosity for the AT-Z allele, which encodes AT-Z. Such individuals are at increased risk for liver disease due to the accumulation of aggregation-prone AT-Z in the endoplasmic reticulum of hepatocytes. However, the penetrance and severity of liver dysfunction in AT deficiency is variable, indicating that unknown genetic and environmental factors contribute to its occurrence. There is evidence that the rate of AT-Z degradation may be one such contributing factor. Through the use of several AT-Z model systems, it is now becoming appreciated that AT-Z can be degraded through at least two independent pathways. One model system that has contributed significantly to our understanding of the AT-Z disposal pathway is the yeast, Saccharomyces cerevisiae.
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28
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Perlmutter DH, Silverman GA. Hepatic fibrosis and carcinogenesis in α1-antitrypsin deficiency: a prototype for chronic tissue damage in gain-of-function disorders. Cold Spring Harb Perspect Biol 2011; 3:cshperspect.a005801. [PMID: 21421920 DOI: 10.1101/cshperspect.a005801] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
In α1-antitrypsin (AT) deficiency, a point mutation renders a hepatic secretory glycoprotein prone to misfolding and polymerization. The mutant protein accumulates in the endoplasmic reticulum of liver cells and causes hepatic fibrosis and hepatocellular carcinoma by a gain-of-function mechanism. Genetic and/or environmental modifiers determine whether an affected homozygote is susceptible to hepatic fibrosis/carcinoma. Two types of proteostasis mechanisms for such modifiers have been postulated: variation in the function of intracellular degradative mechanisms and/or variation in the signal transduction pathways that are activated to protect the cell from protein mislocalization and/or aggregation. In recent studies we found that carbamazepine, a drug that has been used safely as an anticonvulsant and mood stabilizer, reduces the hepatic load of mutant AT and hepatic fibrosis in a mouse model by enhancing autophagic disposal of this mutant protein. These results provide evidence that pharmacological manipulation of endogenous proteostasis mechanisms is an appealing strategy for chemoprophylaxis in disorders involving gain-of-function mechanisms.
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Affiliation(s)
- David H Perlmutter
- Department of Pediatrics, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh and Magee-Womens Hospital of UPMC, Pennsylvania 15224, USA.
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29
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Pan S, Iannotti MJ, Sifers RN. Analysis of serpin secretion, misfolding, and surveillance in the endoplasmic reticulum. Methods Enzymol 2011; 499:1-16. [PMID: 21683246 DOI: 10.1016/b978-0-12-386471-0.00001-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Biological checkpoints are known to function in the cellular nucleus to monitor the integrity of inherited genetic information. It is now understood that posttranslational checkpoint systems operate in numerous biosynthetic compartments where they orchestrate the surveillance of encoded protein structures. This is particularly true for the serpins where opposing, but complementary, systems operate in the early secretory pathway to initially facilitate protein folding and then selectively target the misfolded proteins for proteolytic elimination. A current challenge is to elucidate how this posttranslational checkpoint can modify the severity of numerous loss-of-function and gain-of-toxic-function diseases, some of which are caused by mutant serpins. This chapter provides a description of the experimental methodology by which the fate of a newly synthesized serpin is monitored, and how the processing of asparagine-linked oligosaccharides helps to facilitate both the protein folding and disposal events.
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Affiliation(s)
- Shujuan Pan
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, Texas, USA
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30
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Kelly E, Greene CM, Carroll TP, McElvaney NG, O’Neill SJ. Alpha-1 antitrypsin deficiency. ACTA ACUST UNITED AC 2011. [DOI: 10.1016/j.rmedc.2011.04.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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31
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Sifers RN. Intracellular processing of alpha1-antitrypsin. PROCEEDINGS OF THE AMERICAN THORACIC SOCIETY 2010; 7:376-80. [PMID: 21030516 PMCID: PMC3136957 DOI: 10.1513/pats.201001-011aw] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Accepted: 07/12/2010] [Indexed: 11/20/2022]
Abstract
α(1)-Antitrypsin (AAT) secreted from hepatocytes is an inhibitor of neutrophil elastase. Its normal circulating concentration functions to maintain the elasticity of the lung by preventing the hydrolytic destruction of elastin fibers. Severely diminished circulating concentrations of AAT, resulting from the impaired secretion of genetic variants that exhibit distinct polypeptide folding defects, can function as an etiologic agent for the development of chronic obstructive pulmonary disease. In addition, the inappropriate accumulation of structurally aberrant AAT within the hepatocyte endoplasmic reticulum can contribute to the etiology of liver disease. This article focuses on the discovery and characterization of a biosynthetic quality control system that contributes to the secretion of AAT by first facilitating its proper structural maturation, and then by orchestrating the selective elimination of those molecules that fail to attain structural maturation. Mechanistic elucidation of these interconnected quality control events recently led to the identification of an underlying genetic modifier capable of accelerating the onset of end-stage liver disease by impairing the efficiency of an initial step in the protein disposal process.
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Affiliation(s)
- Richard N Sifers
- Department of Pathology & Immunology, Baylor College of Medicine, One Baylor Plaza, T228, Mailstop BCM-315, Houston, TX 77030-3498, USA.
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32
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Rashid ST, Corbineau S, Hannan N, Marciniak SJ, Miranda E, Alexander G, Huang-Doran I, Griffin J, Ahrlund-Richter L, Skepper J, Semple R, Weber A, Lomas DA, Vallier L. Modeling inherited metabolic disorders of the liver using human induced pluripotent stem cells. J Clin Invest 2010; 120:3127-36. [PMID: 20739751 PMCID: PMC2929734 DOI: 10.1172/jci43122] [Citation(s) in RCA: 484] [Impact Index Per Article: 34.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Accepted: 07/14/2010] [Indexed: 12/18/2022] Open
Abstract
Human induced pluripotent stem (iPS) cells hold great promise for advancements in developmental biology, cell-based therapy, and modeling of human disease. Here, we examined the use of human iPS cells for modeling inherited metabolic disorders of the liver. Dermal fibroblasts from patients with various inherited metabolic diseases of the liver were used to generate a library of patient-specific human iPS cell lines. Each line was differentiated into hepatocytes using what we believe to be a novel 3-step differentiation protocol in chemically defined conditions. The resulting cells exhibited properties of mature hepatocytes, such as albumin secretion and cytochrome P450 metabolism. Moreover, cells generated from patients with 3 of the inherited metabolic conditions studied in further detail (alpha1-antitrypsin deficiency, familial hypercholesterolemia, and glycogen storage disease type 1a) were found to recapitulate key pathological features of the diseases affecting the patients from which they were derived, such as aggregation of misfolded alpha1-antitrypsin in the endoplasmic reticulum, deficient LDL receptor-mediated cholesterol uptake, and elevated lipid and glycogen accumulation. Therefore, we report a simple and effective platform for hepatocyte generation from patient-specific human iPS cells. These patient-derived hepatocytes demonstrate that it is possible to model diseases whose phenotypes are caused by pathological dysregulation of key processes within adult cells.
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Affiliation(s)
- S. Tamir Rashid
- Laboratory for Regenerative Medicine and
Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
INSERM U972, University Paris-Sud, IFR 69, Hôpital du Kremlin-Bicêtre, Le Kremlin-Bicêtre, France.
Department of Cell Biology and Development, Universita’ “La Sapienza,” Rome, Italy.
Department of Medicine, School of Clinical Medicine, and
University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom.
Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Department of Physiology, Development and Neuroscience, Multi-Imaging Centre School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Sebastien Corbineau
- Laboratory for Regenerative Medicine and
Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
INSERM U972, University Paris-Sud, IFR 69, Hôpital du Kremlin-Bicêtre, Le Kremlin-Bicêtre, France.
Department of Cell Biology and Development, Universita’ “La Sapienza,” Rome, Italy.
Department of Medicine, School of Clinical Medicine, and
University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom.
Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Department of Physiology, Development and Neuroscience, Multi-Imaging Centre School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Nick Hannan
- Laboratory for Regenerative Medicine and
Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
INSERM U972, University Paris-Sud, IFR 69, Hôpital du Kremlin-Bicêtre, Le Kremlin-Bicêtre, France.
Department of Cell Biology and Development, Universita’ “La Sapienza,” Rome, Italy.
Department of Medicine, School of Clinical Medicine, and
University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom.
Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Department of Physiology, Development and Neuroscience, Multi-Imaging Centre School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Stefan J. Marciniak
- Laboratory for Regenerative Medicine and
Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
INSERM U972, University Paris-Sud, IFR 69, Hôpital du Kremlin-Bicêtre, Le Kremlin-Bicêtre, France.
Department of Cell Biology and Development, Universita’ “La Sapienza,” Rome, Italy.
Department of Medicine, School of Clinical Medicine, and
University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom.
Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Department of Physiology, Development and Neuroscience, Multi-Imaging Centre School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Elena Miranda
- Laboratory for Regenerative Medicine and
Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
INSERM U972, University Paris-Sud, IFR 69, Hôpital du Kremlin-Bicêtre, Le Kremlin-Bicêtre, France.
Department of Cell Biology and Development, Universita’ “La Sapienza,” Rome, Italy.
Department of Medicine, School of Clinical Medicine, and
University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom.
Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Department of Physiology, Development and Neuroscience, Multi-Imaging Centre School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Graeme Alexander
- Laboratory for Regenerative Medicine and
Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
INSERM U972, University Paris-Sud, IFR 69, Hôpital du Kremlin-Bicêtre, Le Kremlin-Bicêtre, France.
Department of Cell Biology and Development, Universita’ “La Sapienza,” Rome, Italy.
Department of Medicine, School of Clinical Medicine, and
University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom.
Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Department of Physiology, Development and Neuroscience, Multi-Imaging Centre School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Isabel Huang-Doran
- Laboratory for Regenerative Medicine and
Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
INSERM U972, University Paris-Sud, IFR 69, Hôpital du Kremlin-Bicêtre, Le Kremlin-Bicêtre, France.
Department of Cell Biology and Development, Universita’ “La Sapienza,” Rome, Italy.
Department of Medicine, School of Clinical Medicine, and
University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom.
Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Department of Physiology, Development and Neuroscience, Multi-Imaging Centre School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Julian Griffin
- Laboratory for Regenerative Medicine and
Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
INSERM U972, University Paris-Sud, IFR 69, Hôpital du Kremlin-Bicêtre, Le Kremlin-Bicêtre, France.
Department of Cell Biology and Development, Universita’ “La Sapienza,” Rome, Italy.
Department of Medicine, School of Clinical Medicine, and
University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom.
Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Department of Physiology, Development and Neuroscience, Multi-Imaging Centre School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Lars Ahrlund-Richter
- Laboratory for Regenerative Medicine and
Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
INSERM U972, University Paris-Sud, IFR 69, Hôpital du Kremlin-Bicêtre, Le Kremlin-Bicêtre, France.
Department of Cell Biology and Development, Universita’ “La Sapienza,” Rome, Italy.
Department of Medicine, School of Clinical Medicine, and
University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom.
Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Department of Physiology, Development and Neuroscience, Multi-Imaging Centre School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Jeremy Skepper
- Laboratory for Regenerative Medicine and
Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
INSERM U972, University Paris-Sud, IFR 69, Hôpital du Kremlin-Bicêtre, Le Kremlin-Bicêtre, France.
Department of Cell Biology and Development, Universita’ “La Sapienza,” Rome, Italy.
Department of Medicine, School of Clinical Medicine, and
University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom.
Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Department of Physiology, Development and Neuroscience, Multi-Imaging Centre School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Robert Semple
- Laboratory for Regenerative Medicine and
Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
INSERM U972, University Paris-Sud, IFR 69, Hôpital du Kremlin-Bicêtre, Le Kremlin-Bicêtre, France.
Department of Cell Biology and Development, Universita’ “La Sapienza,” Rome, Italy.
Department of Medicine, School of Clinical Medicine, and
University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom.
Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Department of Physiology, Development and Neuroscience, Multi-Imaging Centre School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Anne Weber
- Laboratory for Regenerative Medicine and
Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
INSERM U972, University Paris-Sud, IFR 69, Hôpital du Kremlin-Bicêtre, Le Kremlin-Bicêtre, France.
Department of Cell Biology and Development, Universita’ “La Sapienza,” Rome, Italy.
Department of Medicine, School of Clinical Medicine, and
University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom.
Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Department of Physiology, Development and Neuroscience, Multi-Imaging Centre School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom
| | - David A. Lomas
- Laboratory for Regenerative Medicine and
Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
INSERM U972, University Paris-Sud, IFR 69, Hôpital du Kremlin-Bicêtre, Le Kremlin-Bicêtre, France.
Department of Cell Biology and Development, Universita’ “La Sapienza,” Rome, Italy.
Department of Medicine, School of Clinical Medicine, and
University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom.
Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Department of Physiology, Development and Neuroscience, Multi-Imaging Centre School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom
| | - Ludovic Vallier
- Laboratory for Regenerative Medicine and
Department of Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
INSERM U972, University Paris-Sud, IFR 69, Hôpital du Kremlin-Bicêtre, Le Kremlin-Bicêtre, France.
Department of Cell Biology and Development, Universita’ “La Sapienza,” Rome, Italy.
Department of Medicine, School of Clinical Medicine, and
University of Cambridge Metabolic Research Laboratories, Institute of Metabolic Science, University of Cambridge, Cambridge, United Kingdom.
Department of Woman and Child Health, Karolinska Institutet, Stockholm, Sweden.
Department of Physiology, Development and Neuroscience, Multi-Imaging Centre School of Biological Sciences, University of Cambridge, Cambridge, United Kingdom
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Kelly E, Greene CM, Carroll TP, McElvaney NG, O'Neill SJ. Alpha-1 antitrypsin deficiency. Respir Med 2010; 104:763-72. [PMID: 20303723 DOI: 10.1016/j.rmed.2010.01.016] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Revised: 01/22/2010] [Accepted: 01/24/2010] [Indexed: 02/06/2023]
Abstract
OBJECTIVE To review the topic of alpha-1 antitrypsin (AAT) deficiency. METHOD Narrative literature review. RESULTS Much work has been carried out on this condition with many questions being answered but still further questions remain. DISCUSSION AND CONCLUSIONS AAT deficiency is an autosomal co-dominantly inherited disease which affects the lungs and liver predominantly. The clinical manifestations, prevalence, genetics, molecular pathophysiology, screening and treatment recommendations are summarised in this review.
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Affiliation(s)
- Emer Kelly
- Department of Respiratory Research, Royal College of Surgeons in Ireland, Beaumont Hospital, Education Research Building, Beaumont Road, Dublin, Ireland.
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34
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Geslain R, Cubells L, Bori-Sanz T, Alvarez-Medina R, Rossell D, Martí E, Ribas de Pouplana L. Chimeric tRNAs as tools to induce proteome damage and identify components of stress responses. Nucleic Acids Res 2009; 38:e30. [PMID: 20007146 PMCID: PMC2836549 DOI: 10.1093/nar/gkp1083] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Misfolded proteins are caused by genomic mutations, aberrant splicing events, translation errors or environmental factors. The accumulation of misfolded proteins is a phenomenon connected to several human disorders, and is managed by stress responses specific to the cellular compartments being affected. In wild-type cells these mechanisms of stress response can be experimentally induced by expressing recombinant misfolded proteins or by incubating cells with large concentrations of amino acid analogues. Here, we report a novel approach for the induction of stress responses to protein aggregation. Our method is based on engineered transfer RNAs that can be expressed in cells or tissues, where they actively integrate in the translation machinery causing general proteome substitutions. This strategy allows for the introduction of mutations of increasing severity randomly in the proteome, without exposing cells to unnatural compounds. Here, we show that this approach can be used for the differential activation of the stress response in the Endoplasmic Reticulum (ER). As an example of the applications of this method, we have applied it to the identification of human microRNAs activated or repressed during unfolded protein stress.
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Affiliation(s)
- Renaud Geslain
- Institute for Research in Biomedicine, Omnia Molecular, Barcelona Science Park, Instituto de Biología Molecular de Barcelona, CSIC, Parc Cientific de Barcelona, c/Baldiri Reixac 15-21, Barcelona 08028, Spain
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35
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Cameron PH, Chevet E, Pluquet O, Thomas DY, Bergeron JJM. Calnexin phosphorylation attenuates the release of partially misfolded alpha1-antitrypsin to the secretory pathway. J Biol Chem 2009; 284:34570-9. [PMID: 19815548 DOI: 10.1074/jbc.m109.053165] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Calnexin is a type I integral membrane phosphoprotein resident of the endoplasmic reticulum. Its intraluminal domain has been deduced to function as a lectin chaperone coordinating the timing of folding of newly synthesized N-linked glycoproteins of the secretory pathway. Its C-terminal cytosolic oriented extension has an ERK1 phosphorylation site at Ser(563) affecting calnexin association with the translocon. Here we find an additional function for calnexin phosphorylation at Ser(563) in endoplasmic reticulum quality control. A low dose of the misfolding agent l-azetidine 2-carboxylic acid slows glycoprotein maturation and diminishes the extent and rate of secretion of newly synthesized secretory alpha1-antitrypsin. Under these conditions the phosphorylation of calnexin is enhanced at Ser(563). Inhibition of this phosphorylation by the MEK1 inhibitor PD98059 enhanced the extent and rate of alpha1-antitrypsin secretion comparable with that achieved by inhibiting alpha-mannosidase activity with kifunensine. This is the first report in which the phosphorylation of calnexin is linked to the efficiency of secretion of a cargo glycoprotein.
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Affiliation(s)
- Pamela H Cameron
- Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec H3A 2B2, Canada
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36
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Termine DJ, Moremen KW, Sifers RN. The mammalian UPR boosts glycoprotein ERAD by suppressing the proteolytic downregulation of ER mannosidase I. J Cell Sci 2009; 122:976-84. [PMID: 19258393 DOI: 10.1242/jcs.037291] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The secretory pathway provides a physical route through which only correctly folded gene products are delivered to the eukaryotic cell surface. The efficiency of endoplasmic reticulum (ER)-associated degradation (ERAD), which orchestrates the clearance of structurally aberrant proteins under basal conditions, is boosted by the unfolded protein response (UPR) as one of several means to relieve ER stress. However, the underlying mechanism that links the two systems in higher eukaryotes has remained elusive. Herein, the results of transient expression, RNAi-mediated knockdown and functional studies demonstrate that the transcriptional elevation of EDEM1 boosts the efficiency of glycoprotein ERAD through the formation of a complex that suppresses the proteolytic downregulation of ER mannosidase I (ERManI). The results of site-directed mutagenesis indicate that this capacity does not require that EDEM1 possess inherent mannosidase activity. A model is proposed in which ERManI, by functioning as a downstream effector target of EDEM1, represents a checkpoint activation paradigm by which the mammalian UPR coordinates the boosting of ERAD.
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Affiliation(s)
- Daniel J Termine
- Department of Pathology, Baylor College of Medicine, Houston, TX 77030, USA
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37
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Schachter H. The functions of paucimannose N-glycans in Caenorhabditis elegans. TRENDS GLYCOSCI GLYC 2009. [DOI: 10.4052/tigg.21.131] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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38
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Perlmutter DH. Autophagic disposal of the aggregation-prone protein that causes liver inflammation and carcinogenesis in alpha-1-antitrypsin deficiency. Cell Death Differ 2008; 16:39-45. [PMID: 18617899 DOI: 10.1038/cdd.2008.103] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Alpha-1-antitrypsin (AT) deficiency is a relatively common autosomal co-dominant disorder, which causes chronic lung and liver disease. A point mutation renders aggregation-prone properties on a hepatic secretory protein in such a way that the mutant protein is retained in the endoplasmic reticulum of hepatocytes rather than secreted into the blood and body fluids where it ordinarily functions as an inhibitor of neutrophil proteases. A loss-of-function mechanism allows neutrophil proteases to degrade the connective tissue matrix of the lung causing chronic emphysema. Accumulation of aggregated mutant AT in the endoplasmic reticulum of hepatocytes causes liver inflammation and carcinogenesis by a gain-of-toxic function mechanism. However, genetic epidemiology studies indicate that many, if not the majority of, affected homozygotes are protected from liver disease by unlinked genetic and/or environmental modifiers. Studies performed over the last several years have demonstrated the importance of autophagy in disposal of mutant, aggregated AT and raise the possibility that predisposition to, or protection from, liver injury and carcinogenesis is determined by the balance of de novo biogenesis of the mutant AT molecule and its autophagic disposal.
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Affiliation(s)
- D H Perlmutter
- Department of Pediatrics, Cell Biology and Physiology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, 3705 Fifth Avenue, Pittsburgh, PA 15213-2583, USA.
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39
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Endoplasmic reticulum chaperones are involved in the morphogenesis of rotavirus infectious particles. J Virol 2008; 82:5368-80. [PMID: 18385250 DOI: 10.1128/jvi.02751-07] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The final assembly of rotavirus particles takes place in the endoplasmic reticulum (ER). In this work, we evaluated by RNA interference the relevance to rotavirus assembly and infectivity of grp78, protein disulfide isomerase (PDI), grp94, calnexin, calreticulin, and ERp57, members of the two ER folding systems described herein. Silencing the expression of grp94 and Erp57 had no effect on rotavirus infectivity, while knocking down the expression of any of the other four chaperons caused a reduction in the yield of infectious virus of about 50%. In grp78-silenced cells, the maturation of the oligosaccharide chains of NSP4 was retarded. In cells with reduced levels of calnexin, the oxidative folding of VP7 was impaired and the trimming of NSP4 was accelerated, and in calreticulin-silenced cells, the formation of disulfide bonds of VP7 was also accelerated. The knockdown of PDI impaired the formation and/or rearrangement of the VP7 disulfide bonds. All these conditions also affected the correct assembly of virus particles, since compared with virions from control cells, they showed an altered susceptibility to EGTA and heat treatments, a decreased specific infectivity, and a diminished reactivity to VP7 with monoclonal antibody M60, which recognizes only this protein when its disulfide bonds have been correctly formed. In the case of grp78-silenced cells, the virus produced bound less efficiently to MA104 cells than virus obtained from control cells. All these results suggest that these chaperones are involved in the quality control of rotavirus morphogenesis. The complexity of the steps of rotavirus assembly that occur in the ER provide a useful model for studying the organization and operation of the complex network of chaperones involved in maintaining the quality control of this organelle.
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40
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Granell S, Baldini G, Mohammad S, Nicolin V, Narducci P, Storrie B, Baldini G. Sequestration of mutated alpha1-antitrypsin into inclusion bodies is a cell-protective mechanism to maintain endoplasmic reticulum function. Mol Biol Cell 2008; 19:572-86. [PMID: 18045994 PMCID: PMC2230602 DOI: 10.1091/mbc.e07-06-0587] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Revised: 10/18/2007] [Accepted: 11/16/2007] [Indexed: 12/21/2022] Open
Abstract
A variant alpha1-antitrypsin with E342K mutation has a high tendency to form intracellular polymers, and it is associated with liver disease. In the hepatocytes of individuals carrying the mutation, alpha1-antitrypsin localizes both to the endoplasmic reticulum (ER) and to membrane-surrounded inclusion bodies (IBs). It is unclear whether the IBs contribute to cell toxicity or whether they are protective to the cell. We found that in hepatoma cells, mutated alpha1-antitrypsin exited the ER and accumulated in IBs that were negative for autophagosomal and lysosomal markers, and contained several ER components, but not calnexin. Mutated alpha1-antitrypsin induced IBs also in neuroendocrine cells, showing that formation of these organelles is not cell type specific. In the presence of IBs, ER function was largely maintained. Increased levels of calnexin, but not of protein disulfide isomerase, inhibited formation of IBs and lead to retention of mutated alpha1-antitrypsin in the ER. In hepatoma cells, shift of mutated alpha1-antitrypsin localization to the ER by calnexin overexpression lead to cell shrinkage, ER stress, and impairment of the secretory pathway at the ER level. We conclude that segregation of mutated alpha1-antitrypsin from the ER to the IBs is a protective cell response to maintain a functional secretory pathway.
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Affiliation(s)
| | - Giovanna Baldini
- Dipartimento Universitario Clinico di Biomedicina, Universita' degli Studi di Trieste, Trieste I-34138, Italy
| | | | - Vanessa Nicolin
- Dipartimento Universitario Clinico di Biomedicina, Universita' degli Studi di Trieste, Trieste I-34138, Italy
| | - Paola Narducci
- Dipartimento Universitario Clinico di Biomedicina, Universita' degli Studi di Trieste, Trieste I-34138, Italy
| | - Brian Storrie
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR 72205; and
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Roth J, Yam GHF, Fan J, Hirano K, Gaplovska-Kysela K, Le Fourn V, Guhl B, Santimaria R, Torossi T, Ziak M, Zuber C. Protein quality control: the who's who, the where's and therapeutic escapes. Histochem Cell Biol 2008; 129:163-77. [PMID: 18075753 PMCID: PMC2228381 DOI: 10.1007/s00418-007-0366-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/28/2007] [Indexed: 01/01/2023]
Abstract
In cells the quality of newly synthesized proteins is monitored in regard to proper folding and correct assembly in the early secretory pathway, the cytosol and the nucleoplasm. Proteins recognized as non-native in the ER will be removed and degraded by a process termed ERAD. ERAD of aberrant proteins is accompanied by various changes of cellular organelles and results in protein folding diseases. This review focuses on how the immunocytochemical labeling and electron microscopic analyses have helped to disclose the in situ subcellular distribution pattern of some of the key machinery proteins of the cellular protein quality control, the organelle changes due to the presence of misfolded proteins, and the efficiency of synthetic chaperones to rescue disease-causing trafficking defects of aberrant proteins.
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Affiliation(s)
- Jürgen Roth
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Gary Hin-Fai Yam
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
- Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, University Eye Centre, Mongkok, Kowloon Hong Kong
| | - Jingyu Fan
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
- Department of Biophysics, Peking University Health Science Center, 100083 Beijing, P. R. China
| | - Kiyoko Hirano
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
- The Noguchi Institute, 1-8-1 Kaga, Itabashi, Tokyo 173-0003 Japan
| | - Katarina Gaplovska-Kysela
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Valerie Le Fourn
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Bruno Guhl
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Roger Santimaria
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Tania Torossi
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Martin Ziak
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
| | - Christian Zuber
- Division of Cell and Molecular Pathology, Department of Pathology, University of Zurich, 8091 Zurich, Switzerland
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42
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Glenn KA, Nelson RF, Wen HM, Mallinger AJ, Paulson HL. Diversity in tissue expression, substrate binding, and SCF complex formation for a lectin family of ubiquitin ligases. J Biol Chem 2008; 283:12717-29. [PMID: 18203720 DOI: 10.1074/jbc.m709508200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Post-translational modification of proteins regulates many cellular processes. Some modifications, including N-linked glycosylation, serve multiple functions. For example, the attachment of N-linked glycans to nascent proteins in the endoplasmic reticulum facilitates proper folding, whereas retention of high mannose glycans on misfolded glycoproteins serves as a signal for retrotranslocation and ubiquitin-mediated proteasomal degradation. Here we examine the substrate specificity of the only family of ubiquitin ligase subunits thought to target glycoproteins through their attached glycans. The five proteins comprising this FBA family (FBXO2, FBXO6, FBXO17, FBXO27, and FBXO44) contain a conserved G domain that mediates substrate binding. Using a variety of complementary approaches, including glycan arrays, we show that each family member has differing specificity for glycosylated substrates. Collectively, the F-box proteins in the FBA family bind high mannose and sulfated glycoproteins, with one FBA protein, FBX044, failing to bind any glycans on the tested arrays. Site-directed mutagenesis of two aromatic amino acids in the G domain demonstrated that the hydrophobic pocket created by these amino acids is necessary for high affinity glycan binding. All FBA proteins co-precipitated components of the canonical SCF complex (Skp1, Cullin1, and Rbx1), yet FBXO2 bound very little Cullin1, suggesting that FBXO2 may exist primarily as a heterodimer with Skp1. Using subunit-specific antibodies, we further demonstrate marked divergence in tissue distribution and developmental expression. These differences in substrate recognition, SCF complex formation, and tissue distribution suggest that FBA proteins play diverse roles in glycoprotein quality control.
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Affiliation(s)
- Kevin A Glenn
- Veterans Affairs Medical Center, Iowa City, Iowa 52242, USA.
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Calì T, Vanoni O, Molinari M. The endoplasmic reticulum crossroads for newly synthesized polypeptide chains. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2008; 83:135-79. [PMID: 19186254 DOI: 10.1016/s0079-6603(08)00604-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Tito Calì
- Institute for Research in Biomedicine, Bellizona, Switzerland
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44
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Hebert DN, Molinari M. In and out of the ER: protein folding, quality control, degradation, and related human diseases. Physiol Rev 2007; 87:1377-408. [PMID: 17928587 DOI: 10.1152/physrev.00050.2006] [Citation(s) in RCA: 486] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
A substantial fraction of eukaryotic gene products are synthesized by ribosomes attached at the cytosolic face of the endoplasmic reticulum (ER) membrane. These polypeptides enter cotranslationally in the ER lumen, which contains resident molecular chaperones and folding factors that assist their maturation. Native proteins are released from the ER lumen and are transported through the secretory pathway to their final intra- or extracellular destination. Folding-defective polypeptides are exported across the ER membrane into the cytosol and destroyed. Cellular and organismal homeostasis relies on a balanced activity of the ER folding, quality control, and degradation machineries as shown by the dozens of human diseases related to defective maturation or disposal of individual polypeptides generated in the ER.
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Affiliation(s)
- Daniel N Hebert
- Department of Biochemistry and Molecular Biology, Program in Molecular and Cellular Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA.
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Mallya M, Phillips RL, Saldanha SA, Gooptu B, Leigh Brown SC, Termine DJ, Shirvani AM, Wu Y, Sifers RN, Abagyan R, Lomas DA. Small molecules block the polymerization of Z alpha1-antitrypsin and increase the clearance of intracellular aggregates. J Med Chem 2007; 50:5357-63. [PMID: 17918823 PMCID: PMC2631427 DOI: 10.1021/jm070687z] [Citation(s) in RCA: 104] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The Z mutant of alpha1-antitrypsin (Glu342Lys) causes a domain swap and the formation of intrahepatic polymers that aggregate as inclusions and predispose the homozygote to cirrhosis. We have identified an allosteric cavity that is distinct from the interface involved in polymerization for rational structure-based drug design to block polymer formation. Virtual ligand screening was performed on 1.2 million small molecules and 6 compounds were identified that reduced polymer formation in vitro. Modeling the effects of ligand binding on the cavity and re-screening the library identified an additional 10 compounds that completely blocked polymerization. The best antagonists were effective at ratios of compound to Z alpha1-antitrypsin of 2.5:1 and reduced the intracellular accumulation of Z alpha1-antitrypsin by 70% in a cell model of disease. Identifying small molecules provides a novel therapy for the treatment of liver disease associated with the Z allele of alpha1-antitrypsin.
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Affiliation(s)
- Meera Mallya
- Department of Medicine, University of Cambridge, Cambridge Institute for Medical Research, Wellcome Trust/MRC building, Cambridge CB2 2XY, UK
| | - Russell L. Phillips
- Department of Medicine, University of Cambridge, Cambridge Institute for Medical Research, Wellcome Trust/MRC building, Cambridge CB2 2XY, UK
| | - S. Adrian Saldanha
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
| | - Bibek Gooptu
- Department of Medicine, University of Cambridge, Cambridge Institute for Medical Research, Wellcome Trust/MRC building, Cambridge CB2 2XY, UK
| | - Sarah C. Leigh Brown
- Department of Medicine, University of Cambridge, Cambridge Institute for Medical Research, Wellcome Trust/MRC building, Cambridge CB2 2XY, UK
| | - Daniel J. Termine
- Departments of Pathology, Molecular & Cellular Biology, and Molecular Physiology & Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
| | - Arash M. Shirvani
- Departments of Pathology, Molecular & Cellular Biology, and Molecular Physiology & Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
| | - Ying Wu
- Departments of Pathology, Molecular & Cellular Biology, and Molecular Physiology & Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
| | - Richard N. Sifers
- Departments of Pathology, Molecular & Cellular Biology, and Molecular Physiology & Biophysics, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
| | - Ruben Abagyan
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA
| | - David A Lomas
- Department of Medicine, University of Cambridge, Cambridge Institute for Medical Research, Wellcome Trust/MRC building, Cambridge CB2 2XY, UK
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46
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Soldà T, Galli C, Kaufman RJ, Molinari M. Substrate-specific requirements for UGT1-dependent release from calnexin. Mol Cell 2007; 27:238-249. [PMID: 17643373 DOI: 10.1016/j.molcel.2007.05.032] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2007] [Revised: 04/19/2007] [Accepted: 05/31/2007] [Indexed: 11/16/2022]
Abstract
Newly synthesized glycoproteins displaying monoglucosylated N-glycans bind to the endoplasmic reticulum (ER) chaperone calnexin, and their maturation is catalyzed by the calnexin-associated oxidoreductase ERp57. Folding substrates are eventually released from calnexin, and terminal glucoses are removed from N-glycans. The UDP-glucose:glycoprotein glucosyltransferase (UGT1, UGGT, GT) monitors the folding state of polypeptides released from calnexin and adds back a glucose residue on N-glycans of nonnative polypeptides, thereby prolonging retention in the calnexin chaperone system for additional folding attempts. Here we show that for certain newly synthesized glycoproteins UGT1 deletion has no effect on binding to calnexin. These proteins must normally complete their folding program in one binding event. Other proteins normally undergo multiple binding events, and UGT1 deletion results in their premature release from calnexin. For other proteins, UGT1 deletion substantially delays release from calnexin, unexpectedly showing that UGT1 activity might be required for a structural maturation needed for substrate dissociation from calnexin and export from the ER.
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Affiliation(s)
- Tatiana Soldà
- Institute for Research in Biomedicine, CH-6500 Bellinzona, Switzerland
| | - Carmela Galli
- Institute for Research in Biomedicine, CH-6500 Bellinzona, Switzerland
| | - Randal J Kaufman
- Howard Hughes Medical Institute, University of Michigan Medical Center, Ann Arbor, MI 48109, USA; Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, MI 48109, USA
| | - Maurizio Molinari
- Institute for Research in Biomedicine, CH-6500 Bellinzona, Switzerland.
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47
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Scott CM, Kruse KB, Schmidt BZ, Perlmutter DH, McCracken AA, Brodsky JL. ADD66, a gene involved in the endoplasmic reticulum-associated degradation of alpha-1-antitrypsin-Z in yeast, facilitates proteasome activity and assembly. Mol Biol Cell 2007; 18:3776-87. [PMID: 17634286 PMCID: PMC1995736 DOI: 10.1091/mbc.e07-01-0034] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Antitrypsin deficiency is a primary cause of juvenile liver disease, and it arises from expression of the "Z" variant of the alpha-1 protease inhibitor (A1Pi). Whereas A1Pi is secreted from the liver, A1PiZ is retrotranslocated from the endoplasmic reticulum (ER) and degraded by the proteasome, an event that may offset liver damage. To better define the mechanism of A1PiZ degradation, a yeast expression system was developed previously, and a gene, ADD66, was identified that facilitates A1PiZ turnover. We report here that ADD66 encodes an approximately 30-kDa soluble, cytosolic protein and that the chymotrypsin-like activity of the proteasome is reduced in add66Delta mutants. This reduction in activity may arise from the accumulation of 20S proteasome assembly intermediates or from qualitative differences in assembled proteasomes. Add66p also seems to be a proteasome substrate. Consistent with its role in ER-associated degradation (ERAD), synthetic interactions are observed between the genes encoding Add66p and Ire1p, a transducer of the unfolded protein response, and yeast deleted for both ADD66 and/or IRE1 accumulate polyubiquitinated proteins. These data identify Add66p as a proteasome assembly chaperone (PAC), and they provide the first link between PAC activity and ERAD.
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Affiliation(s)
- Craig M. Scott
- *Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | | | - Béla Z. Schmidt
- Department of Pediatrics, Cell Biology, and Physiology, Children's Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213
| | - David H. Perlmutter
- Department of Pediatrics, Cell Biology, and Physiology, Children's Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213
| | | | - Jeffrey L. Brodsky
- *Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
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48
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Abstract
The endoplasmic reticulum (ER) is the site of folding for proteins that are resident in the ER or that are destined for the Golgi, endosomes, lysosomes, the plasma membrane, or secretion. Cotranslational addition of preassembled glucose(3)-mannose(9)-N-acetylglucosamine(2) core oligosaccharides (N-glycosylation) is a common event for polypeptides synthesized in this compartment. Protein-bound oligosaccharides are exposed to several ER glycanases that sequentially remove terminal glucose or mannose residues. Their activity must be tightly regulated because the N-glycan composition determines whether the associated protein is subjected to folding attempts in the ER lumen or whether it is retrotranslocated into the cytosol and degraded.
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Affiliation(s)
- Maurizio Molinari
- Institute for Research in Biomedicine, Via V. Vela 6, CH-6500 Bellinzona, Switzerland.
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49
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Wu Y, Termine DJ, Swulius MT, Moremen KW, Sifers RN. Human endoplasmic reticulum mannosidase I is subject to regulated proteolysis. J Biol Chem 2007; 282:4841-4849. [PMID: 17166854 PMCID: PMC3969733 DOI: 10.1074/jbc.m607156200] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the early secretory pathway, opportunistic cleavage of asparagine-linked oligosaccharides by endoplasmic reticulum (ER) mannosidase I targets misfolded glycoproteins for dislocation into the cytosol and destruction by 26 S proteasomes. The low basal concentration of the glycosidase is believed to coordinate the glycan cleavage with prolonged conformation-based ER retention, ensuring that terminally misfolded glycoproteins are preferentially targeted for destruction. Herein the intracellular fate of human ER mannosidase I was monitored to determine whether a post-translational process might contribute to the regulation of its intracellular concentration. The transiently expressed recombinant human glycosidase was subject to rapid intracellular turnover in mouse hepatoma cells, as was the endogenous mouse ortholog. Incubation with either chloroquine or leupeptin, but not lactacystin, led to intracellular stabilization, implicating the involvement of lysosomal acid hydrolases. Inhibition of protein synthesis with cycloheximide led to intracellular depletion of the glycosidase and concomitant ablation of asparagine-linked glycoprotein degradation, confirming the physiologic relevance of the destabilization process. Metabolic incorporation of radiolabeled phosphate, detection by anti-phosphoserine antiserum, and the stabilizing effect of general serine kinase inhibition implied that ER mannosidase I is subjected to regulated proteolysis. Stabilization in response to genetically engineered removal of the amino-terminal cytoplasmic tail, a postulated regulatory domain, and colocalization of green fluorescent protein fusion proteins with Lamp1 provided two additional lines of evidence to support the hypothesis. A model is proposed in which proteolytically driven checkpoint control of ER mannosidase I contributes to the establishment of an equitable glycoprotein quality control standard by which the efficiency of asparagine-linked glycoprotein conformational maturation is measured.
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Affiliation(s)
- Ying Wu
- Departments of Pathology, Molecular and Cellular Biology, Molecular Physiology, and Biophysics, Baylor College of Medicine, Houston, Texas 77030 and the
| | - Daniel J Termine
- Departments of Pathology, Molecular and Cellular Biology, Molecular Physiology, and Biophysics, Baylor College of Medicine, Houston, Texas 77030 and the
| | - Matthew T Swulius
- Departments of Pathology, Molecular and Cellular Biology, Molecular Physiology, and Biophysics, Baylor College of Medicine, Houston, Texas 77030 and the
| | - Kelley W Moremen
- Department of Biochemistry and Molecular Biology and Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602
| | - Richard N Sifers
- Departments of Pathology, Molecular and Cellular Biology, Molecular Physiology, and Biophysics, Baylor College of Medicine, Houston, Texas 77030 and the.
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50
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Abstract
Glycosylation of asparagine residues in Asn-x-Ser/Thr motifs is a common covalent modification of proteins in the lumen of the endoplasmic reticulum (ER). By substantially contributing to the overall hydrophilicity of the polypeptide, pre-assembled core glycans inhibit possible aggregation caused by the inevitable exposure of hydrophobic patches on the as yet unstructured chains. Thereafter, N-glycans are modified by ER-resident enzymes glucosidase I (GI), glucosidase II (GII), UDP-glucose:glycoprotein glucosyltransferase (UGT) and mannosidase(s) and become functional appendices that determine the fate of the associated polypeptide. Recent work has improved our understanding of how the removal of terminal glucose residues from N-glycans allows newly synthesized proteins to access the calnexin chaperone system; how substrate retention in this specialized chaperone system is regulated by de-/re-glucosylation cycles catalyzed by GII and UGT1; and how acceleration of N-glycan dismantling upon induction of EDEM variants promotes ER-associated degradation (ERAD) under conditions of ER stress. In particular, characterization of cells lacking certain ER chaperones has revealed important new information on the mechanisms regulating protein folding and quality control. Tight regulation of N-glycan modifications is crucial to maintain protein quality control, to ensure the synthesis of functional polypeptides and to avoid constipation of the ER with folding-defective polypeptides.
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Affiliation(s)
- Lloyd W Ruddock
- Biocenter Oulu and Department of Biochemistry, University of Oulu, FIN-90014 Oulu, Finland
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