1
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Zhao P, Wang C, Sun S, Wang X, Balch WE. Tracing genetic diversity captures the molecular basis of misfolding disease. Nat Commun 2024; 15:3333. [PMID: 38637533 PMCID: PMC11026414 DOI: 10.1038/s41467-024-47520-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Accepted: 04/04/2024] [Indexed: 04/20/2024] Open
Abstract
Genetic variation in human populations can result in the misfolding and aggregation of proteins, giving rise to systemic and neurodegenerative diseases that require management by proteostasis. Here, we define the role of GRP94, the endoplasmic reticulum Hsp90 chaperone paralog, in managing alpha-1-antitrypsin deficiency on a residue-by-residue basis using Gaussian process regression-based machine learning to profile the spatial covariance relationships that dictate protein folding arising from sequence variants in the population. Covariance analysis suggests a role for the ATPase activity of GRP94 in controlling the N- to C-terminal cooperative folding of alpha-1-antitrypsin responsible for the correction of liver aggregation and lung-disease phenotypes of alpha-1-antitrypsin deficiency. Gaussian process-based spatial covariance profiling provides a standard model built on covariant principles to evaluate the role of proteostasis components in guiding information flow from genome to proteome in response to genetic variation, potentially allowing us to intervene in the onset and progression of complex multi-system human diseases.
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Affiliation(s)
- Pei Zhao
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA
| | - Chao Wang
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA.
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory, Shenzhen, China.
| | - Shuhong Sun
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA
- Department of Nutrition and Food Hygiene, Center for Global Health, School of Public Health, Nanjing Medical University, Nanjing, China
- Institute for Brain Tumors, Collaborative Innovation Center for Cancer Personalized Medicine, and Center for Global Health, Nanjing Medical University, Nanjing, China
| | - Xi Wang
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - William E Balch
- Department of Molecular Medicine, Scripps Research, La Jolla, CA, USA.
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2
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Mann MJ, Melendez-Suchi C, Vorndran HE, Sukhoplyasova M, Flory AR, Irvine MC, Iyer AR, Guerriero CJ, Brodsky JL, Hendershot LM, Buck TM. Loss of Grp170 results in catastrophic disruption of endoplasmic reticulum function. Mol Biol Cell 2024; 35:ar59. [PMID: 38446639 PMCID: PMC11064666 DOI: 10.1091/mbc.e24-01-0012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 02/20/2024] [Accepted: 02/29/2024] [Indexed: 03/08/2024] Open
Abstract
GRP170 (Hyou1) is required for mouse embryonic development, and its ablation in kidney nephrons leads to renal failure. Unlike most chaperones, GRP170 is the lone member of its chaperone family in the ER lumen. However, the cellular requirement for GRP170, which both binds nonnative proteins and acts as nucleotide exchange factor for BiP, is poorly understood. Here, we report on the isolation of mouse embryonic fibroblasts obtained from mice in which LoxP sites were engineered in the Hyou1 loci (Hyou1LoxP/LoxP). A doxycycline-regulated Cre recombinase was stably introduced into these cells. Induction of Cre resulted in depletion of Grp170 protein which culminated in cell death. As Grp170 levels fell we observed a portion of BiP fractionating with insoluble material, increased binding of BiP to a client with a concomitant reduction in its turnover, and reduced solubility of an aggregation-prone BiP substrate. Consistent with disrupted BiP functions, we observed reactivation of BiP and induction of the unfolded protein response (UPR) in futile attempts to provide compensatory increases in ER chaperones and folding enzymes. Together, these results provide insights into the cellular consequences of controlled Grp170 loss and provide hypotheses as to why mutations in the Hyou1 locus are linked to human disease.
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Affiliation(s)
- Melissa J. Mann
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Chris Melendez-Suchi
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Hannah E. Vorndran
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Maria Sukhoplyasova
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Ashley R. Flory
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Mary Carson Irvine
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Anuradha R. Iyer
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | | | - Jeffrey L. Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Linda M. Hendershot
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Teresa M. Buck
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
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3
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Porter A, Vorndran HE, Marciszyn A, Mutchler SM, Subramanya AR, Kleyman TR, Hendershot LM, Brodsky JL, Buck TM. Excess dietary sodium partially restores salt and water homeostasis caused by loss of the endoplasmic reticulum molecular chaperone, GRP170, in the mouse nephron. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.13.575426. [PMID: 38260467 PMCID: PMC10802592 DOI: 10.1101/2024.01.13.575426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
The maintenance of fluid and electrolyte homeostasis by the kidney requires proper folding and trafficking of ion channels and transporters in kidney epithelia. Each of these processes requires a specific subset of a diverse class of proteins termed molecular chaperones. One such chaperone is GRP170, which is an Hsp70-like, endoplasmic reticulum (ER)-localized chaperone that plays roles in protein quality control and protein folding in the ER. We previously determined that loss of GRP170 in the mouse nephron leads to hypovolemia, electrolyte imbalance, and rapid weight loss. In addition, GRP170-deficient mice develop an AKI-like phenotype, typified by tubular injury, elevation of clinical kidney injury markers, and induction of the unfolded protein response (UPR). By using an inducible GRP170 knockout cellular model, we confirmed that GRP170 depletion induces the UPR, triggers an apoptotic response, and disrupts protein homeostasis. Based on these data, we hypothesized that UPR induction underlies hyponatremia and volume depletion in rodents, but that these and other phenotypes might be rectified by supplementation with high salt. To test this hypothesis, control and GRP170 tubule-specific knockout mice were provided with a diet containing 8% sodium chloride. We discovered that sodium supplementation improved electrolyte imbalance and reduced clinical kidney injury markers, but was unable to restore weight or tubule integrity. These results are consistent with UPR induction contributing to the kidney injury phenotype in the nephron-specific GR170 knockout model, and that the role of GRP170 in kidney epithelia is essential to both maintain electrolyte balance and cellular protein homeostasis.
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Affiliation(s)
- Aidan Porter
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA
- Division of Pediatric Nephrology, University of Pittsburgh, Pittsburgh, PA
| | - Hannah E. Vorndran
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA
| | - Allison Marciszyn
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA
| | - Stephanie M. Mutchler
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA
| | - Arohan R. Subramanya
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA
| | - Thomas R. Kleyman
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA
| | - Linda M. Hendershot
- Department of Tumor Cell Biology, St. Jude Children’s Research Hospital, Memphis, TN 30105
| | - Jeffrey L. Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA
| | - Teresa M. Buck
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA
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4
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Hendershot LM, Buck TM, Brodsky JL. The Essential Functions of Molecular Chaperones and Folding Enzymes in Maintaining Endoplasmic Reticulum Homeostasis. J Mol Biol 2023:168418. [PMID: 38143019 DOI: 10.1016/j.jmb.2023.168418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 12/18/2023] [Accepted: 12/19/2023] [Indexed: 12/26/2023]
Abstract
It has been estimated that up to one-third of the proteins encoded by the human genome enter the endoplasmic reticulum (ER) as extended polypeptide chains where they undergo covalent modifications, fold into their native structures, and assemble into oligomeric protein complexes. The fidelity of these processes is critical to support organellar, cellular, and organismal health, and is perhaps best underscored by the growing number of disease-causing mutations that reduce the fidelity of protein biogenesis in the ER. To meet demands encountered by the diverse protein clientele that mature in the ER, this organelle is populated with a cadre of molecular chaperones that prevent protein aggregation, facilitate protein disulfide isomerization, and lower the activation energy barrier of cis-trans prolyl isomerization. Components of the lectin (glycan-binding) chaperone system also reside within the ER and play numerous roles during protein biogenesis. In addition, the ER houses multiple homologs of select chaperones that can recognize and act upon diverse peptide signatures. Moreover, redundancy helps ensure that folding-compromised substrates are unable to overwhelm essential ER-resident chaperones and enzymes. In contrast, the ER in higher eukaryotic cells possesses a single member of the Hsp70, Hsp90, and Hsp110 chaperone families, even though several homologs of these molecules reside in the cytoplasm. In this review, we discuss specific functions of the many factors that maintain ER quality control, highlight some of their interactions, and describe the vulnerabilities that arise from the absence of multiple members of some chaperone families.
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Affiliation(s)
- Linda M Hendershot
- Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, United States.
| | - Teresa M Buck
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, United States
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, United States
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5
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Melnyk A, Lang S, Sicking M, Zimmermann R, Jung M. Co-chaperones of the Human Endoplasmic Reticulum: An Update. Subcell Biochem 2023; 101:247-291. [PMID: 36520310 DOI: 10.1007/978-3-031-14740-1_9] [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: 06/17/2023]
Abstract
In mammalian cells, the rough endoplasmic reticulum (ER) plays central roles in the biogenesis of extracellular plus organellar proteins and in various signal transduction pathways. For these reasons, the ER comprises molecular chaperones, which are involved in import, folding, assembly, export, plus degradation of polypeptides, and signal transduction components, such as calcium channels, calcium pumps, and UPR transducers plus adenine nucleotide carriers/exchangers in the ER membrane. The calcium- and ATP-dependent ER lumenal Hsp70, termed immunoglobulin heavy-chain-binding protein or BiP, is the central player in all these activities and involves up to nine different Hsp40-type co-chaperones, i.e., ER membrane integrated as well as ER lumenal J-domain proteins, termed ERj or ERdj proteins, two nucleotide exchange factors or NEFs (Grp170 and Sil1), and NEF-antagonists, such as MANF. Here we summarize the current knowledge on the ER-resident BiP/ERj chaperone network and focus on the interaction of BiP with the polypeptide-conducting and calcium-permeable Sec61 channel of the ER membrane as an example for BiP action and how its functional cycle is linked to ER protein import and various calcium-dependent signal transduction pathways.
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Affiliation(s)
- Armin Melnyk
- Medical Biochemistry & Molecular Biology, Saarland University, Homburg, Germany
| | - Sven Lang
- Medical Biochemistry & Molecular Biology, Saarland University, Homburg, Germany
| | - Mark Sicking
- Medical Biochemistry & Molecular Biology, Saarland University, Homburg, Germany
| | - Richard Zimmermann
- Medical Biochemistry & Molecular Biology, Saarland University, Homburg, Germany.
| | - Martin Jung
- Medical Biochemistry & Molecular Biology, Saarland University, Homburg, Germany
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6
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Pranke IM, Chevalier B, Premchandar A, Baatallah N, Tomaszewski KF, Bitam S, Tondelier D, Golec A, Stolk J, Lukacs GL, Hiemstra PS, Dadlez M, Lomas DA, Irving JA, Delaunay-Moisan A, van Anken E, Hinzpeter A, Sermet-Gaudelus I, Edelman A. Keratin 8 is a scaffolding and regulatory protein of ERAD complexes. Cell Mol Life Sci 2022; 79:503. [PMID: 36045259 DOI: 10.1007/s00018-022-04528-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 08/08/2022] [Accepted: 08/12/2022] [Indexed: 11/03/2022]
Abstract
Early recognition and enhanced degradation of misfolded proteins by the endoplasmic reticulum (ER) quality control and ER-associated degradation (ERAD) cause defective protein secretion and membrane targeting, as exemplified for Z-alpha-1-antitrypsin (Z-A1AT), responsible for alpha-1-antitrypsin deficiency (A1ATD) and F508del-CFTR (cystic fibrosis transmembrane conductance regulator) responsible for cystic fibrosis (CF). Prompted by our previous observation that decreasing Keratin 8 (K8) expression increased trafficking of F508del-CFTR to the plasma membrane, we investigated whether K8 impacts trafficking of soluble misfolded Z-A1AT protein. The subsequent goal of this study was to elucidate the mechanism underlying the K8-dependent regulation of protein trafficking, focusing on the ERAD pathway. The results show that diminishing K8 concentration in HeLa cells enhances secretion of both Z-A1AT and wild-type (WT) A1AT with a 13-fold and fourfold increase, respectively. K8 down-regulation triggers ER failure and cellular apoptosis when ER stress is jointly elicited by conditional expression of the µs heavy chains, as previously shown for Hrd1 knock-out. Simultaneous K8 silencing and Hrd1 knock-out did not show any synergistic effect, consistent with K8 acting in the Hrd1-governed ERAD step. Fractionation and co-immunoprecipitation experiments reveal that K8 is recruited to ERAD complexes containing Derlin2, Sel1 and Hrd1 proteins upon expression of Z/WT-A1AT and F508del-CFTR. Treatment of the cells with c407, a small molecule inhibiting K8 interaction, decreases K8 and Derlin2 recruitment to high-order ERAD complexes. This was associated with increased Z-A1AT secretion in both HeLa and Z-homozygous A1ATD patients' respiratory cells. Overall, we provide evidence that K8 acts as an ERAD modulator. It may play a scaffolding protein role for early-stage ERAD complexes, regulating Hrd1-governed retrotranslocation initiation/ubiquitination processes. Targeting K8-containing ERAD complexes is an attractive strategy for the pharmacotherapy of A1ATD.
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Affiliation(s)
- Iwona Maria Pranke
- Inserm, U1151, CNRS UMR 8253, Université de Paris, 160 rue de Vaugirard, 75015, Paris, France.
| | - Benoit Chevalier
- Inserm, U1151, CNRS UMR 8253, Université de Paris, 160 rue de Vaugirard, 75015, Paris, France
| | - Aiswarya Premchandar
- Laboratory of Mass Spectrometry, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02106, Warsaw, Poland
| | - Nesrine Baatallah
- Inserm, U1151, CNRS UMR 8253, Université de Paris, 160 rue de Vaugirard, 75015, Paris, France
| | - Kamil F Tomaszewski
- Inserm, U1151, CNRS UMR 8253, Université de Paris, 160 rue de Vaugirard, 75015, Paris, France
| | - Sara Bitam
- Inserm, U1151, CNRS UMR 8253, Université de Paris, 160 rue de Vaugirard, 75015, Paris, France
| | - Danielle Tondelier
- Inserm, U1151, CNRS UMR 8253, Université de Paris, 160 rue de Vaugirard, 75015, Paris, France
| | - Anita Golec
- Inserm, U1151, CNRS UMR 8253, Université de Paris, 160 rue de Vaugirard, 75015, Paris, France
| | - Jan Stolk
- Department of Pulmonology, Leiden University Medical Center, Leiden, The Netherlands
| | - Gergely L Lukacs
- Department of Physiology, McGill University, Montréal, QC, Canada.,Department of Biochemistry, McGill University, Montréal, QC, Canada
| | - Pieter S Hiemstra
- Department of Pulmonology, Leiden University Medical Center, Leiden, The Netherlands
| | - Michal Dadlez
- Laboratory of Mass Spectrometry, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02106, Warsaw, Poland
| | - David A Lomas
- UCL Respiratory and the Institute of Structural and Molecular Biology, University College London, London, WC1E 6JF, UK
| | - James A Irving
- UCL Respiratory and the Institute of Structural and Molecular Biology, University College London, London, WC1E 6JF, UK
| | - Agnes Delaunay-Moisan
- Institute for Integrative Biology of the Cell (I2BC), Université Paris-Saclay, CEA, CNRS, Gif-sur-Yvette, France
| | - Eelco van Anken
- Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milan, Italy
| | - Alexandre Hinzpeter
- Inserm, U1151, CNRS UMR 8253, Université de Paris, 160 rue de Vaugirard, 75015, Paris, France
| | - Isabelle Sermet-Gaudelus
- Inserm, U1151, CNRS UMR 8253, Université de Paris, 160 rue de Vaugirard, 75015, Paris, France.,Cystic Fibrosis Center, Hôpital Necker Enfants Malades, Assistance Publique Hôpitaux de Paris, Paris, France
| | - Aleksander Edelman
- Inserm, U1151, CNRS UMR 8253, Université de Paris, 160 rue de Vaugirard, 75015, Paris, France.
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7
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Li H, Sun S. Protein Aggregation in the ER: Calm behind the Storm. Cells 2021; 10:cells10123337. [PMID: 34943844 PMCID: PMC8699410 DOI: 10.3390/cells10123337] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2021] [Revised: 11/19/2021] [Accepted: 11/22/2021] [Indexed: 02/06/2023] Open
Abstract
As one of the largest organelles in eukaryotic cells, the endoplasmic reticulum (ER) plays a vital role in the synthesis, folding, and assembly of secretory and membrane proteins. To maintain its homeostasis, the ER is equipped with an elaborate network of protein folding chaperones and multiple quality control pathways whose cooperative actions safeguard the fidelity of protein biogenesis. However, due to genetic abnormalities, the error-prone nature of protein folding and assembly, and/or defects or limited capacities of the protein quality control systems, nascent proteins may become misfolded and fail to exit the ER. If not cleared efficiently, the progressive accumulation of misfolded proteins within the ER may result in the formation of toxic protein aggregates, leading to the so-called “ER storage diseases”. In this review, we first summarize our current understanding of the protein folding and quality control networks in the ER, including chaperones, unfolded protein response (UPR), ER-associated protein degradation (ERAD), and ER-selective autophagy (ER-phagy). We then survey recent research progress on a few ER storage diseases, with a focus on the role of ER quality control in the disease etiology, followed by a discussion on outstanding questions and emerging concepts in the field.
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Affiliation(s)
- Haisen Li
- Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, MI 48201, USA;
| | - Shengyi Sun
- Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, MI 48201, USA;
- Department of Biochemistry, Microbiology and Immunology, Wayne State University School of Medicine, Detroit, MI 48201, USA
- Correspondence:
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8
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Lim J, Lee K, Im H. Reinforcement of the Unfolded Protein Response Mitigates Cytotoxicity Induced by Human Z‐Type α
1
‐Antitrypsin. B KOREAN CHEM SOC 2021. [DOI: 10.1002/bkcs.12289] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Jaeyeon Lim
- Department of Integrative Bioscience and Biotechnology Sejong University Seoul 05006 South Korea
| | - Kyunghee Lee
- Department of Chemistry Sejong University Seoul 05006 South Korea
| | - Hana Im
- Department of Integrative Bioscience and Biotechnology Sejong University Seoul 05006 South Korea
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9
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Karatas E, Raymond AA, Leon C, Dupuy JW, Di-Tommaso S, Senant N, Collardeau-Frachon S, Ruiz M, Lachaux A, Saltel F, Bouchecareilh M. Hepatocyte proteomes reveal the role of protein disulfide isomerase 4 in alpha 1-antitrypsin deficiency. JHEP Rep 2021; 3:100297. [PMID: 34151245 PMCID: PMC8192868 DOI: 10.1016/j.jhepr.2021.100297] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 04/06/2021] [Accepted: 04/09/2021] [Indexed: 11/25/2022] Open
Abstract
Background & Aims A single point mutation in the Z-variant of alpha 1-antitrypsin (Z-AAT) alone can lead to both a protein folding and trafficking defect, preventing its exit from the endoplasmic reticulum (ER), and the formation of aggregates that are retained as inclusions within the ER of hepatocytes. These defects result in a systemic AAT deficiency (AATD) that causes lung disease, whereas the ER-retained aggregates can induce severe liver injury in patients with ZZ-AATD. Unfortunately, therapeutic approaches are still limited and liver transplantation represents the only curative treatment option. To overcome this limitation, a better understanding of the molecular basis of ER aggregate formation could provide new strategies for therapeutic intervention. Methods Our functional and omics approaches here based on human hepatocytes from patients with ZZ-AATD have enabled the identification and characterisation of the role of the protein disulfide isomerase (PDI) A4/ERP72 in features of AATD-mediated liver disease. Results We report that 4 members of the PDI family (PDIA4, PDIA3, P4HB, and TXNDC5) are specifically upregulated in ZZ-AATD liver samples from adult patients. Furthermore, we show that only PDIA4 knockdown or alteration of its activity by cysteamine treatment can promote Z-AAT secretion and lead to a marked decrease in Z aggregates. Finally, detailed analysis of the Z-AAT interactome shows that PDIA4 silencing provides a more conducive environment for folding of the Z mutant, accompanied by reduction of Z-AAT-mediated oxidative stress, a feature of AATD-mediated liver disease. Conclusions PDIA4 is involved in AATD-mediated liver disease and thus represents a therapeutic target for inhibition by drugs such as cysteamine. PDI inhibition therefore represents a potential therapeutic approach for treatment of AATD. Lay summary Protein disulfide isomerase (PDI) family members, and particularly PDIA4, are upregulated and involved in alpha 1-antitrypsin deficiency (AATD)-mediated liver disease in adults. PDI inhibition upon cysteamine treatment leads to improvements in features of AATD and hence represents a therapeutic approach for treatment of AATD-mediated liver disease. PDIA4 is upregulated and involved in alpha 1-antitrypsin deficiency (AATD)-mediated liver disease in adults. Knockdown of PDIA4 by siRNA or inhibition upon cysteamine treatment leads to improvements in features of AATD. RNA interference against PDIA4 or cysteamine represent approaches for treatment of AATD-mediated liver disease.
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Key Words
- AAT, alpha 1-antitrypsin
- AATD, alpha 1-antitrypsin deficiency
- Alpha 1-antitrypsin deficiency
- CF, cystic fibrosis
- CFTR, cystic fibrosis transmembrane conductance regulator
- Cysteamine
- ER, endoplasmic reticulum
- FFPE, formalin-fixed paraffin-embedded
- FKBP10, FK506-binding protein (FKBP) isoform 10
- HCC, hepatocellular carcinoma
- IHC, immunohistochemistry
- IP, immunoprecipitation
- Liver damage
- NHK, null Hong Kong variant of AAT
- P4HB, prolyl 4-hydroxylase subunit beta/PDIA1
- PDI, protein disulfide isomerase
- PDIA3, protein disulfide isomerase family A member 3/ERP57
- PDIA4
- PDIA4, protein disulfide isomerase family A member 4/ERP70/ERP72
- PDIi, PDI inhibitors
- Protein disulfide isomerase
- ROS, reactive oxygen species
- SURF4, proteins Surfeit 4
- Scr, scramble
- TRX, thioredoxin
- TXNDC5, thioredoxin domain containing 5/PDIA15
- Treatment
- WT, wild-type
- Z-AAT, alpha 1-antitrypsin Z variant
- ZZ, homozygosis for the Z mutant allele
- siRNA, small RNA interference
- ΔF508-CFTR, most common mutation of CFTR, which deletes phenylalanine508
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Affiliation(s)
- Esra Karatas
- University of Bordeaux, CNRS, INSERM, BaRITOn, U1053, Bordeaux, France
| | - Anne-Aurélie Raymond
- University of Bordeaux, CNRS, INSERM, BaRITOn, U1053, Bordeaux, France.,Oncoprot, University of Bordeaux, INSERM, TBM-Core, UMS 3427, US 5, Bordeaux, France
| | - Céline Leon
- University of Bordeaux, CNRS, INSERM, BaRITOn, U1053, Bordeaux, France
| | | | - Sylvaine Di-Tommaso
- Oncoprot, University of Bordeaux, INSERM, TBM-Core, UMS 3427, US 5, Bordeaux, France
| | - Nathalie Senant
- Plateforme d'histopathologie, TBM-Core US 005, Bordeaux, France
| | - Sophie Collardeau-Frachon
- Department of Pathology, Hôpital Femme Mère Enfant, Hospices Civils de Lyon, Lyon, France.,Hépatologie, Gastroentérologie et Nutrition pédiatriques, Centre de référence de l'atrésie des voies biliaires et cholestases génétiques, Hôpital Femme Mère Enfant, Hospices Civils de Lyon, Lyon, France.,Faculté de Médecine Lyon-Est, Université Claude Bernard Lyon 1, Lyon, France
| | - Mathias Ruiz
- Hépatologie, Gastroentérologie et Nutrition pédiatriques, Centre de référence de l'atrésie des voies biliaires et cholestases génétiques, Hôpital Femme Mère Enfant, Hospices Civils de Lyon, Lyon, France.,European Reference Network on Hepatological Diseases (ERN RARE-LIVER), Hamburg, Germany.,Faculté de Médecine Lyon-Est, Université Claude Bernard Lyon 1, Lyon, France
| | - Alain Lachaux
- Hépatologie, Gastroentérologie et Nutrition pédiatriques, Centre de référence de l'atrésie des voies biliaires et cholestases génétiques, Hôpital Femme Mère Enfant, Hospices Civils de Lyon, Lyon, France.,European Reference Network on Hepatological Diseases (ERN RARE-LIVER), Hamburg, Germany.,Faculté de Médecine Lyon-Est, Université Claude Bernard Lyon 1, Lyon, France
| | - Frédéric Saltel
- University of Bordeaux, CNRS, INSERM, BaRITOn, U1053, Bordeaux, France.,Oncoprot, University of Bordeaux, INSERM, TBM-Core, UMS 3427, US 5, Bordeaux, France
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10
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Finotti P, Pagetta A. A mutant α1antitrypsin in complex with heat shock proteins as the primary antigen in type 1 diabetes in silico investigation. Sci Rep 2021; 11:3002. [PMID: 33542414 PMCID: PMC7862655 DOI: 10.1038/s41598-021-82730-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 01/25/2021] [Indexed: 11/09/2022] Open
Abstract
Based on previous results demonstrating that complexes of a mutant α1-antitrypsin with the heat shock proteins (HSP)70 and glucose-regulated protein94 (Grp94) circulate in the blood of patients with type 1 diabetes, we raised the hypothesis that these complexes could represent the primary antigen capable of triggering the autoimmune reactions leading to overt diabetes. As a first approach to this issue, we searched whether A1AT and HSPs had a sequence similarity to major islet antigen proteins so as to identify among the similar sequences those with potential relevance for the pathogenesis of diabetes. A thorough in silico analysis was performed to establish the score of similarity of the human proteins: A1AT, pro-insulin (INS), GAD65, IAPP, IA-2, ICA69, Grp94, HSP70 and HSP60. The sequences of A1AT and HSPs with the highest score of similarity to the islet peptides reported in the literature as the main autoantigens in human diabetes were recorded. At variance with other HSPs, also including HSP90 and Grp78, Grp94 contained the highest number and the longest sequences with structural similarity to A1AT and to well-known immunogenic peptides/epitopes of INS, GAD65, and IA-2. The similarity of A1AT with Grp94 and that of Grp94 with INS also suggested a functional relationship among the proteins. Specific sequences were identified in A1AT, Grp94 and HSP70, with the highest score of cross-similarity to a pattern of eight different islet protein epitopes. The similarity also involved recently discovered autoantigens in type 1 diabetes such as a hybrid peptides of insulin and the defective ribosomal insulin gene product. The significant similarity displayed by specific sequences of Grp94 and A1AT to the islet peptides considered main antigens in human diabetes, is a strong indication for testing these sequences as new peptides of immunogenic relevance in diabetes.
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Affiliation(s)
- Paola Finotti
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Building "C", Largo E. Meneghetti, 2, 35131, Padua, Italy.
| | - Andrea Pagetta
- Department of Pharmaceutical and Pharmacological Sciences, University of Padua, Building "C", Largo E. Meneghetti, 2, 35131, Padua, Italy
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Poothong J, Jang I, Kaufman RJ. Defects in Protein Folding and/or Quality Control Cause Protein Aggregation in the Endoplasmic Reticulum. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 2021; 59:115-143. [PMID: 34050864 DOI: 10.1007/978-3-030-67696-4_6] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Protein aggregation is now a common hallmark of numerous human diseases, most of which involve cytosolic aggregates including Aβ (AD) and ⍺-synuclein (PD) in Alzheimer's disease and Parkinson's disease. However, it is also evident that protein aggregation can also occur in the lumen of the endoplasmic reticulum (ER) that leads to specific diseases due to loss of protein function or detrimental effects on the host cell, the former is inherited in a recessive manner where the latter are dominantly inherited. However, the mechanisms of protein aggregation, disaggregation and degradation in the ER are not well understood. Here we provide an overview of factors that cause protein aggregation in the ER and how the ER handles aggregated proteins. Protein aggregation in the ER can result from intrinsic properties of the protein (hydrophobic residues in the ER), oxidative stress or nutrient depletion. The ER has quality control mechanisms [chaperone functions, ER-associated protein degradation (ERAD) and autophagy] to ensure only correctly folded proteins exit the ER and enter the cis-Golgi compartment. Perturbation of protein folding in the ER activates the unfolded protein response (UPR) that evolved to increase ER protein folding capacity and efficiency and degrade misfolded proteins. Accumulation of misfolded proteins in the ER to a level that exceeds the ER-chaperone folding capacity is a major factor that exacerbates protein aggregation. The most significant ER resident protein that prevents protein aggregation in the ER is the heat shock protein 70 (HSP70) homologue, BiP/GRP78, which is a peptide-dependent ATPase that binds unfolded/misfolded proteins and releases them upon ATP binding. Since exogenous factors can also reduce protein misfolding and aggregation in the ER, such as chemical chaperones and antioxidants, these treatments have potential therapeutic benefit for ER protein aggregation-associated diseases.
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Affiliation(s)
- Juthakorn Poothong
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA
| | - Insook Jang
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA
| | - Randal J Kaufman
- Degenerative Diseases Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA.
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12
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Attanasio S, Ferriero R, Gernoux G, De Cegli R, Carissimo A, Nusco E, Campione S, Teckman J, Mueller C, Piccolo P, Brunetti-Pierri N. CHOP and c-JUN up-regulate the mutant Z α 1-antitrypsin, exacerbating its aggregation and liver proteotoxicity. J Biol Chem 2020; 295:13213-13223. [PMID: 32723872 DOI: 10.1074/jbc.ra120.014307] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2020] [Revised: 07/23/2020] [Indexed: 12/16/2022] Open
Abstract
α1-Antitrypsin (AAT) encoded by the SERPINA1 gene is an acute-phase protein synthesized in the liver and secreted into the circulation. Its primary role is to protect lung tissue by inhibiting neutrophil elastase. The Z allele of SERPINA1 encodes a mutant AAT, named ATZ, that changes the protein structure and leads to its misfolding and polymerization, which cause endoplasmic reticulum (ER) stress and liver disease through a gain-of-function toxic mechanism. Hepatic retention of ATZ results in deficiency of one of the most important circulating proteinase inhibitors and predisposes to early-onset emphysema through a loss-of-function mechanism. The pathogenetic mechanisms underlying the liver disease are not completely understood. C/EBP-homologous protein (CHOP), a transcription factor induced by ER stress, was found among the most up-regulated genes in livers of PiZ mice that express ATZ and in human livers of patients homozygous for the Z allele. Compared with controls, juvenile PiZ/Chop -/- mice showed reduced hepatic ATZ and a transcriptional response indicative of decreased ER stress by RNA-Seq analysis. Livers of PiZ/Chop -/- mice also showed reduced SERPINA1 mRNA levels. By chromatin immunoprecipitations and luciferase reporter-based transfection assays, CHOP was found to up-regulate SERPINA1 cooperating with c-JUN, which was previously shown to up-regulate SERPINA1, thus aggravating hepatic accumulation of ATZ. Increased CHOP levels were detected in diseased livers of children homozygous for the Z allele. In summary, CHOP and c-JUN up-regulate SERPINA1 transcription and play an important role in hepatic disease by increasing the burden of proteotoxic ATZ, particularly in the pediatric population.
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Affiliation(s)
| | - Rosa Ferriero
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy
| | - Gwladys Gernoux
- Department of Molecular, Cell, and Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | | | - Annamaria Carissimo
- Institute for Applied Mathematics "Mauro Picone" National Research Council, Naples, Italy
| | - Edoardo Nusco
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy
| | | | - Jeffrey Teckman
- St. Louis University School of Medicine, St. Louis, Missouri, USA
| | - Christian Mueller
- Department of Molecular, Cell, and Cancer Biology, University of Massachusetts Medical School, Worcester, Massachusetts, USA; Horae Gene Therapy Center, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Pasquale Piccolo
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy; Department of Translational Medicine, Federico II University, Naples, Italy.
| | - Nicola Brunetti-Pierri
- Telethon Institute of Genetics and Medicine, Pozzuoli, Italy; Department of Translational Medicine, Federico II University, Naples, Italy.
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Yadav K, Yadav A, Vashistha P, Pandey VP, Dwivedi UN. Protein Misfolding Diseases and Therapeutic Approaches. Curr Protein Pept Sci 2020; 20:1226-1245. [PMID: 31187709 DOI: 10.2174/1389203720666190610092840] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2019] [Revised: 02/01/2019] [Accepted: 02/24/2019] [Indexed: 12/12/2022]
Abstract
Protein folding is the process by which a polypeptide chain acquires its functional, native 3D structure. Protein misfolding, on the other hand, is a process in which protein fails to fold into its native functional conformation. This misfolding of proteins may lead to precipitation of a number of serious diseases such as Cystic Fibrosis (CF), Alzheimer's Disease (AD), Parkinson's Disease (PD), and Amyotrophic Lateral Sclerosis (ALS) etc. Protein Quality-control (PQC) systems, consisting of molecular chaperones, proteases and regulatory factors, help in protein folding and prevent its aggregation. At the same time, PQC systems also do sorting and removal of improperly folded polypeptides. Among the major types of PQC systems involved in protein homeostasis are cytosolic, Endoplasmic Reticulum (ER) and mitochondrial ones. The cytosol PQC system includes a large number of component chaperones, such as Nascent-polypeptide-associated Complex (NAC), Hsp40, Hsp70, prefoldin and T Complex Protein-1 (TCP-1) Ring Complex (TRiC). Protein misfolding diseases caused due to defective cytosolic PQC system include diseases involving keratin/collagen proteins, cardiomyopathies, phenylketonuria, PD and ALS. The components of PQC system of Endoplasmic Reticulum (ER) include Binding immunoglobulin Protein (BiP), Calnexin (CNX), Calreticulin (CRT), Glucose-regulated Protein GRP94, the thiol-disulphide oxidoreductases, Protein Disulphide Isomerase (PDI) and ERp57. ER-linked misfolding diseases include CF and Familial Neurohypophyseal Diabetes Insipidus (FNDI). The components of mitochondrial PQC system include mitochondrial chaperones such as the Hsp70, the Hsp60/Hsp10 and a set of proteases having AAA+ domains similar to the proteasome that are situated in the matrix or the inner membrane. Protein misfolding diseases caused due to defective mitochondrial PQC system include medium-chain acyl-CoA dehydrogenase (MCAD)/Short-chain Acyl-CoA Dehydrogenase (SCAD) deficiency diseases, hereditary spastic paraplegia. Among therapeutic approaches towards the treatment of various protein misfolding diseases, chaperones have been suggested as potential therapeutic molecules for target based treatment. Chaperones have been advantageous because of their efficient entry and distribution inside the cells, including specific cellular compartments, in therapeutic concentrations. Based on the chemical nature of the chaperones used for therapeutic purposes, molecular, chemical and pharmacological classes of chaperones have been discussed.
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Affiliation(s)
- Kusum Yadav
- Department of Biochemistry, University of Lucknow, Lucknow, U.P, India
| | - Anurag Yadav
- Department of Microbiology, College of Basic Sciences and Humanities, Sardar Krushinagar Dantiwada Agricultural University, Banaskantha, Gujarat, India
| | | | - Veda P Pandey
- Department of Biochemistry, University of Lucknow, Lucknow, U.P, India
| | - Upendra N Dwivedi
- Department of Biochemistry, University of Lucknow, Lucknow, U.P, India.,Institute for Development of Advanced Computing, ONGC Centre for Advanced Studies, University of Lucknow, Lucknow, U.P., India
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Pye A, Turner AM. Experimental and investigational drugs for the treatment of alpha-1 antitrypsin deficiency. Expert Opin Investig Drugs 2019; 28:891-902. [PMID: 31550938 DOI: 10.1080/13543784.2019.1672656] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Introduction: Alpha-1 antitrypsin deficiency (AATD) is most often associated with chronic lung disease, early onset emphysema, and liver disease. The standard of care in lung disease due to AATD is alpha-1 antitrypsin augmentation but there are several new and emerging treatment options under investigation for both lung and liver manifestations. Areas covered: We review therapeutic approaches to lung and liver disease in alpha-1 antitrypsin deficiency (AATD) and the agents in clinical development according to their mode of action. The focus is on products in clinical trials, but data from pre-clinical studies are described where relevant, particularly where progression to trials appears likely. Expert opinion: Clinical trials directed at lung and liver disease separately are now taking place. Multimodality treatment may be the future, but this could be limited by treatment costs. The next 5-10 years may reveal new guidance on when to use therapeutics for slowing disease progression with personalized treatment regimes coming to the forefront.
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Affiliation(s)
- Anita Pye
- Institute of Applied Health Research, University of Birmingham , Birmingham , UK
| | - Alice M Turner
- Institute of Applied Health Research, University of Birmingham , Birmingham , UK
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15
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Segeritz CP, Rashid ST, de Brito MC, Serra MP, Ordonez A, Morell CM, Kaserman JE, Madrigal P, Hannan NRF, Gatto L, Tan L, Wilson AA, Lilley K, Marciniak SJ, Gooptu B, Lomas DA, Vallier L. hiPSC hepatocyte model demonstrates the role of unfolded protein response and inflammatory networks in α 1-antitrypsin deficiency. J Hepatol 2018; 69:851-860. [PMID: 29879455 PMCID: PMC6562205 DOI: 10.1016/j.jhep.2018.05.028] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 04/25/2018] [Accepted: 05/17/2018] [Indexed: 02/02/2023]
Abstract
BACKGROUND & AIMS α1-Antitrypsin deficiency (A1ATD) is an autosomal recessive disorder caused by mutations in the SERPINA1 gene. Individuals with the Z variant (Gly342Lys) retain polymerised protein in the endoplasmic reticulum (ER) of their hepatocytes, predisposing them to liver disease. The concomitant lack of circulating A1AT also causes lung emphysema. Greater insight into the mechanisms that link protein misfolding to liver injury will facilitate the design of novel therapies. METHODS Human-induced pluripotent stem cell (hiPSC)-derived hepatocytes provide a novel approach to interrogate the molecular mechanisms of A1ATD because of their patient-specific genetic architecture and reflection of human physiology. To that end, we utilised patient-specific hiPSC hepatocyte-like cells (ZZ-HLCs) derived from an A1ATD (ZZ) patient, which faithfully recapitulated key aspects of the disease at the molecular and cellular level. Subsequent functional and "omics" comparisons of these cells with their genetically corrected isogenic-line (RR-HLCs) and primary hepatocytes/human tissue enabled identification of new molecular markers and disease signatures. RESULTS Our studies showed that abnormal A1AT polymer processing (immobilised ER components, reduced luminal protein mobility and disrupted ER cisternae) occurred heterogeneously within hepatocyte populations and was associated with disrupted mitochondrial structure, presence of the oncogenic protein AKR1B10 and two upregulated molecular clusters centred on members of inflammatory (IL-18 and Caspase-4) and unfolded protein response (Calnexin and Calreticulin) pathways. These results were validated in a second patient-specific hiPSC line. CONCLUSIONS Our data identified novel pathways that potentially link the expression of Z A1AT polymers to liver disease. These findings could help pave the way towards identification of new therapeutic targets for the treatment of A1ATD. LAY SUMMARY This study compared the gene expression and protein profiles of healthy liver cells and those affected by the inherited disease α1-antitrypsin deficiency. This approach identified specific factors primarily present in diseased samples which could provide new targets for drug development. This study also demonstrates the interest of using hepatic cells generated from human-induced pluripotent stem cells to model liver disease in vitro for uncovering new mechanisms with clinical relevance.
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Affiliation(s)
- Charis-Patricia Segeritz
- Wellcome Trust and MRC Cambridge Stem Cell Institute, Department of Surgery, University of Cambridge, UK; Cambridge Institute for Medical Research, University of Cambridge, UK
| | - Sheikh Tamir Rashid
- Wellcome Trust and MRC Cambridge Stem Cell Institute, Department of Surgery, University of Cambridge, UK; Cambridge Institute for Medical Research, University of Cambridge, UK; Centre for Stem Cells and Regenerative Medicine & Institute for Liver Studies, King's College London, UK.
| | - Miguel Cardoso de Brito
- Wellcome Trust and MRC Cambridge Stem Cell Institute, Department of Surgery, University of Cambridge, UK
| | - Maria Paola Serra
- Centre for Stem Cells and Regenerative Medicine & Institute for Liver Studies, King's College London, UK
| | - Adriana Ordonez
- Cambridge Institute for Medical Research, University of Cambridge, UK
| | - Carola Maria Morell
- Wellcome Trust and MRC Cambridge Stem Cell Institute, Department of Surgery, University of Cambridge, UK
| | - Joseph E Kaserman
- Center for Regenerative Medicine (CReM) of Boston University and Boston Medical Center, Boston, MA 02118, USA
| | - Pedro Madrigal
- Wellcome Trust and MRC Cambridge Stem Cell Institute, Department of Surgery, University of Cambridge, UK
| | - Nicholas R F Hannan
- Wellcome Trust and MRC Cambridge Stem Cell Institute, Department of Surgery, University of Cambridge, UK
| | - Laurent Gatto
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Building O, Downing Site, Cambridge CB2 1QW, UK
| | - Lu Tan
- Cambridge Institute for Medical Research, University of Cambridge, UK
| | - Andrew A Wilson
- Center for Regenerative Medicine (CReM) of Boston University and Boston Medical Center, Boston, MA 02118, USA
| | - Kathryn Lilley
- Cambridge Centre for Proteomics, Department of Biochemistry, University of Cambridge, Building O, Downing Site, Cambridge CB2 1QW, UK
| | | | - Bibek Gooptu
- NIHR Leicester BRC-Respiratory and Leicester Institute of Structural & Chemical Biology, University of Leicester, UK; ISMB/Birkbeck & UCL, University of London, UK; Division of Asthma, Allergy and Lung Biology, King's College London, UK
| | | | - Ludovic Vallier
- Wellcome Trust and MRC Cambridge Stem Cell Institute, Department of Surgery, University of Cambridge, UK; Wellcome Trust Sanger Institute, Genome Campus Hinxton, UK.
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16
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Hoter A, El-Sabban ME, Naim HY. The HSP90 Family: Structure, Regulation, Function, and Implications in Health and Disease. Int J Mol Sci 2018; 19:E2560. [PMID: 30158430 PMCID: PMC6164434 DOI: 10.3390/ijms19092560] [Citation(s) in RCA: 331] [Impact Index Per Article: 55.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 08/23/2018] [Accepted: 08/27/2018] [Indexed: 12/22/2022] Open
Abstract
The mammalian HSP90 family of proteins is a cluster of highly conserved molecules that are involved in myriad cellular processes. Their distribution in various cellular compartments underlines their essential roles in cellular homeostasis. HSP90 and its co-chaperones orchestrate crucial physiological processes such as cell survival, cell cycle control, hormone signaling, and apoptosis. Conversely, HSP90, and its secreted forms, contribute to the development and progress of serious pathologies, including cancer and neurodegenerative diseases. Therefore, targeting HSP90 is an attractive strategy for the treatment of neoplasms and other diseases. This manuscript will review the general structure, regulation and function of HSP90 family and their potential role in pathophysiology.
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Affiliation(s)
- Abdullah Hoter
- Department of Biochemistry and Chemistry of Nutrition, Faculty of Veterinary Medicine, Cairo University, Giza 12211, Egypt.
- Department of Physiological Chemistry, University of Veterinary Medicine Hannover, Hannover 30559, Germany.
| | - Marwan E El-Sabban
- Department of Anatomy, Cell Biology and Physiological Sciences, Faculty of Medicine, American University of Beirut, Beirut, Lebanon.
| | - Hassan Y Naim
- Department of Physiological Chemistry, University of Veterinary Medicine Hannover, Hannover 30559, Germany.
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Pan J, Cao D, Gong J. The endoplasmic reticulum co-chaperone ERdj3/DNAJB11 promotes hepatocellular carcinoma progression through suppressing AATZ degradation. Future Oncol 2018; 14:3001-3013. [PMID: 29992839 DOI: 10.2217/fon-2018-0401] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
AIM The co-chaperone ERdj3/DNAJB11 is involved in the endoplasmic reticulum stress response observed in cancer cells. We hypothesized that ERdj3 functions as a hepatocellular carcinoma (HCC) oncogene by inhibiting AATZ degradation. MATERIALS & METHODS ERdj3 and AATZ expressions were analyzed in 84 HCC patients. Cell proliferation, epithelial-mesenchymal transition marker expression, migration and invasiveness were assessed in HepG2 and Huh-7 cells. A murine xenograft tumor model was constructed. RESULTS ERdj3 is upregulated in HCC tumors and cell lines. Tumor ERdj3 levels are positively associated with cirrhosis, enhanced HCC status, inferior survival outcomes and AATZ levels. ERdj3 suppresses AATZ degradation. ERdj3 overexpression enhances proliferation, epithelial-mesenchymal transition marker expression, migration, invasiveness and xenograft tumor growth in an AATZ-dependent manner. CONCLUSION ERdj3 enhances HCC progression through suppressing AATZ degradation.
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Affiliation(s)
- Junjiang Pan
- Department of Hepatobiliary Surgery, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, PR China
| | - Ding Cao
- Department of Hepatobiliary Surgery, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, PR China
| | - Jianping Gong
- Department of Hepatobiliary Surgery, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, PR China
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18
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Vincenz-Donnelly L, Holthusen H, Körner R, Hansen EC, Presto J, Johansson J, Sawarkar R, Hartl FU, Hipp MS. High capacity of the endoplasmic reticulum to prevent secretion and aggregation of amyloidogenic proteins. EMBO J 2018; 37:337-350. [PMID: 29247078 PMCID: PMC5793802 DOI: 10.15252/embj.201695841] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 10/19/2017] [Accepted: 10/25/2017] [Indexed: 01/09/2023] Open
Abstract
Protein aggregation is associated with neurodegeneration and various other pathologies. How specific cellular environments modulate the aggregation of disease proteins is not well understood. Here, we investigated how the endoplasmic reticulum (ER) quality control system handles β-sheet proteins that were designed de novo to form amyloid-like fibrils. While these proteins undergo toxic aggregation in the cytosol, we find that targeting them to the ER (ER-β) strongly reduces their toxicity. ER-β is retained within the ER in a soluble, polymeric state, despite reaching very high concentrations exceeding those of ER-resident molecular chaperones. ER-β is not removed by ER-associated degradation (ERAD) but interferes with ERAD of other proteins. These findings demonstrate a remarkable capacity of the ER to prevent the formation of insoluble β-aggregates and the secretion of potentially toxic protein species. Our results also suggest a generic mechanism by which proteins with exposed β-sheet structure in the ER interfere with proteostasis.
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Affiliation(s)
- Lisa Vincenz-Donnelly
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Martinsried, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Hauke Holthusen
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Roman Körner
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Martinsried, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Erik C Hansen
- Max Planck Institute of Immunobiology and Epigenetics, Freiburg, Germany
| | - Jenny Presto
- Division of Neurogeriatrics, Department of Neurobiology, Care Sciences and Society (NVS), Centre for Alzheimer Research, Karolinska Institutet, Huddinge, Sweden
| | - Jan Johansson
- Division of Neurogeriatrics, Department of Neurobiology, Care Sciences and Society (NVS), Centre for Alzheimer Research, Karolinska Institutet, Huddinge, Sweden
| | - Ritwick Sawarkar
- Max Planck Institute of Immunobiology and Epigenetics, Freiburg, Germany
| | - F Ulrich Hartl
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Martinsried, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
| | - Mark S Hipp
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Martinsried, Germany
- Munich Cluster for Systems Neurology (SyNergy), Munich, Germany
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Synthetic Cannabinoid Abuse and a Rare Alpha-1-Antitrypsin Mutant Causing Acute Fulminant Hepatitis: A Case Report and Review of the Literature. Case Reports Hepatol 2018; 2017:9627452. [PMID: 29333304 PMCID: PMC5733121 DOI: 10.1155/2017/9627452] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Revised: 05/25/2017] [Accepted: 06/18/2017] [Indexed: 11/17/2022] Open
Abstract
Synthetic cannabinoids (SCs) abuse is on the rise because they are easily obtained over the counter; they are potent psychoactive compounds and routine drug testing does not detect them. As their abuse is on the rise, so are their detrimental side effects; however, the occurrence of acute hepatitis due to SCs abuse has been reported only once before. In this case, testing revealed that the patient was also heterozygous for alpha-1-antitrypsin (A-1-AT) with the phenotype of PI⁎EM. This mutant phenotype has never been reported as a cause of A-1-AT disease and the abuse of SCs in a patient with this phenotype has also never been reported. This case illustrates the possible need to expand routine drug testing for SCs and consider A-1-AT phenotyping in certain clinical scenarios.
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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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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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Joly P, Vignaud H, Di Martino J, Ruiz M, Garin R, Restier L, Belmalih A, Marchal C, Cullin C, Arveiler B, Fergelot P, Gitler AD, Lachaux A, Couthouis J, Bouchecareilh M. ERAD defects and the HFE-H63D variant are associated with increased risk of liver damages in Alpha 1-Antitrypsin Deficiency. PLoS One 2017; 12:e0179369. [PMID: 28617828 PMCID: PMC5472284 DOI: 10.1371/journal.pone.0179369] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 05/30/2017] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The most common and severe disease causing allele of Alpha 1-Antitrypsin Deficiency (1ATD) is Z-1AT. This protein aggregates in the endoplasmic reticulum, which is the main cause of liver disease in childhood. Based on recent evidences and on the frequency of liver disease occurrence in Z-1AT patients, it seems that liver disease progression is linked to still unknown genetic factors. METHODS We used an innovative approach combining yeast genetic screens with next generation exome sequencing to identify and functionally characterize the genes involved in 1ATD associated liver disease. RESULTS Using yeast genetic screens, we identified HRD1, an Endoplasmic Reticulum Associated Degradation (ERAD) associated protein, as an inducer of Z-mediated toxicity. Whole exome sequencing of 1ATD patients resulted in the identification of two variants associated with liver damages in Z-1AT homozygous cases: HFE H63D and HERPUD1 R50H. Functional characterization in Z-1AT model cell lines demonstrated that impairment of the ERAD machinery combined with the HFE H63D variant expression decreased both cell proliferation and cell viability, while Unfolded Protein Response (UPR)-mediated cell death was hyperstimulated. CONCLUSION This powerful experimental pipeline allowed us to identify and functionally validate two genes involved in Z-1AT-mediated severe liver toxicity. This pilot study moves forward our understanding on genetic modifiers involved in 1ATD and highlights the UPR pathway as a target for the treatment of liver diseases associated with 1ATD. Finally, these findings support a larger scale screening for HERPUD1 R50H and HFE H63D variants in the sub-group of 1ATD patients developing significant chronic hepatic injuries (hepatomegaly, chronic cholestasis, elevated liver enzymes) and at risk developing liver cirrhosis.
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Affiliation(s)
- Philippe Joly
- University Lyon - University Claude Bernard Lyon 1 - EA 7424 – Inter-university Laboratory of Human Movement Science, Villeurbanne, France
- Laboratoire de Biochimie et biologie moléculaire Grand-Est, Hôpital Edouard Herriot, Hospices Civils de Lyon, Lyon, France
| | - Hélène Vignaud
- CNRS, University Bordeaux, UMR5095 Institut de Biochimie et Génétique Cellulaires, Bordeaux, France
| | - Julie Di Martino
- CNRS, University Bordeaux, UMR5095 Institut de Biochimie et Génétique Cellulaires, Bordeaux, France
- INSERM, University Bordeaux, UMR1053 Bordeaux Research In Translational Oncology, BaRITOn, Bordeaux, France
| | - Mathias Ruiz
- Department of Paediatric Gastroenterology, Hepatology and Nutrition, Children's Hospital of Lyon, Lyon, France
| | - Roman Garin
- Department of Paediatric Gastroenterology, Hepatology and Nutrition, Children's Hospital of Lyon, Lyon, France
| | - Lioara Restier
- Department of Paediatric Gastroenterology, Hepatology and Nutrition, Children's Hospital of Lyon, Lyon, France
| | - Abdelouahed Belmalih
- Department of Paediatric Gastroenterology, Hepatology and Nutrition, Children's Hospital of Lyon, Lyon, France
| | - Christelle Marchal
- CNRS, University Bordeaux, UMR5095 Institut de Biochimie et Génétique Cellulaires, Bordeaux, France
| | - Christophe Cullin
- CNRS, University Bordeaux, UMR5095 Institut de Biochimie et Génétique Cellulaires, Bordeaux, France
| | - Benoit Arveiler
- University Bordeaux, INSERM U1211, Laboratoire Maladies Rares, Génétique et Métabolisme (MRGM), Bordeaux, France
| | - Patricia Fergelot
- University Bordeaux, INSERM U1211, Laboratoire Maladies Rares, Génétique et Métabolisme (MRGM), Bordeaux, France
| | - Aaron D. Gitler
- Department of Genetics, Stanford University School of Medicine, Stanford, California, United States of America
| | - Alain Lachaux
- Department of Paediatric Gastroenterology, Hepatology and Nutrition, Children's Hospital of Lyon, Lyon, France
| | - Julien Couthouis
- Department of Genetics, Stanford University School of Medicine, Stanford, California, United States of America
| | - Marion Bouchecareilh
- CNRS, University Bordeaux, UMR5095 Institut de Biochimie et Génétique Cellulaires, Bordeaux, France
- INSERM, University Bordeaux, UMR1053 Bordeaux Research In Translational Oncology, BaRITOn, Bordeaux, France
- * E-mail:
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23
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Buck TM, Jordahl AS, Yates ME, Preston GM, Cook E, Kleyman TR, Brodsky JL. Interactions between intersubunit transmembrane domains regulate the chaperone-dependent degradation of an oligomeric membrane protein. Biochem J 2017; 474:357-376. [PMID: 27903760 PMCID: PMC5423784 DOI: 10.1042/bcj20160760] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Revised: 11/28/2016] [Accepted: 11/30/2016] [Indexed: 12/22/2022]
Abstract
In the kidney, the epithelial sodium channel (ENaC) regulates blood pressure through control of sodium and volume homeostasis, and in the lung, ENaC regulates the volume of airway and alveolar fluids. ENaC is a heterotrimer of homologous α-, β- and γ-subunits, and assembles in the endoplasmic reticulum (ER) before it traffics to and functions at the plasma membrane. Improperly folded or orphaned ENaC subunits are subject to ER quality control and targeted for ER-associated degradation (ERAD). We previously established that a conserved, ER lumenal, molecular chaperone, Lhs1/GRP170, selects αENaC, but not β- or γ-ENaC, for degradation when the ENaC subunits were individually expressed. We now find that when all three subunits are co-expressed, Lhs1-facilitated ERAD was blocked. To determine which domain-domain interactions between the ENaC subunits are critical for chaperone-dependent quality control, we employed a yeast model and expressed chimeric α/βENaC constructs in the context of the ENaC heterotrimer. We discovered that the βENaC transmembrane domain was sufficient to prevent the Lhs1-dependent degradation of the α-subunit in the context of the ENaC heterotrimer. Our work also found that Lhs1 delivers αENaC for proteasome-mediated degradation after the protein has become polyubiquitinated. These data indicate that the Lhs1 chaperone selectively recognizes an immature form of αENaC, one which has failed to correctly assemble with the other channel subunits via its transmembrane domain.
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Affiliation(s)
- Teresa M Buck
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Alexa S Jordahl
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Megan E Yates
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - G Michael Preston
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Emily Cook
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Thomas R Kleyman
- Department of Medicine, Renal-Electrolyte Division, University of Pittsburgh, Pittsburgh, PA, U.S.A
| | - Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, U.S.A
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24
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Dickens JA, Ordóñez A, Chambers JE, Beckett AJ, Patel V, Malzer E, Dominicus CS, Bradley J, Peden AA, Prior IA, Lomas DA, Marciniak SJ. The endoplasmic reticulum remains functionally connected by vesicular transport after its fragmentation in cells expressing Z-α1-antitrypsin. FASEB J 2016; 30:4083-4097. [PMID: 27601439 PMCID: PMC5102109 DOI: 10.1096/fj.201600430r] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Accepted: 08/15/2016] [Indexed: 12/20/2022]
Abstract
α1-Antitrypsin is a serine protease inhibitor produced in the liver that is responsible for the regulation of pulmonary inflammation. The commonest pathogenic gene mutation yields Z-α1-antitrypsin, which has a propensity to self-associate forming polymers that become trapped in inclusions of endoplasmic reticulum (ER). It is unclear whether these inclusions are connected to the main ER network in Z-α1-antitrypsin-expressing cells. Using live cell imaging, we found that despite inclusions containing an immobile matrix of polymeric α1-antitrypsin, small ER resident proteins can diffuse freely within them. Inclusions have many features to suggest they represent fragmented ER, and some are physically separated from the tubular ER network, yet we observed cargo to be transported between them in a cytosol-dependent fashion that is sensitive to N-ethylmaleimide and dependent on Sar1 and sec22B. We conclude that protein recycling occurs between ER inclusions despite their physical separation.-Dickens, J. A., Ordóñez, A., Chambers, J. E., Beckett, A. J., Patel, V., Malzer, E., Dominicus, C. S., Bradley, J., Peden, A. A., Prior, I. A., Lomas, D. A., Marciniak, S. J. The endoplasmic reticulum remains functionally connected by vesicular transport after its fragmentation in cells expressing Z-α1-antitrypsin.
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Affiliation(s)
- Jennifer A Dickens
- Cambridge Institute for Medical Research, Cambridge, United Kingdom
- Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Adriana Ordóñez
- Cambridge Institute for Medical Research, Cambridge, United Kingdom
| | - Joseph E Chambers
- Cambridge Institute for Medical Research, Cambridge, United Kingdom
- Department of Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Alison J Beckett
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Vruti Patel
- Cambridge Institute for Medical Research, Cambridge, United Kingdom
| | - Elke Malzer
- Cambridge Institute for Medical Research, Cambridge, United Kingdom
| | - Caia S Dominicus
- Cambridge Institute for Medical Research, Cambridge, United Kingdom
| | - Jayson Bradley
- Cambridge Institute for Medical Research, Cambridge, United Kingdom
| | - Andrew A Peden
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Ian A Prior
- Institute of Translational Medicine, University of Liverpool, Liverpool, United Kingdom; and
| | - David A Lomas
- UCL Respiratory, University College London, London, United Kingdom
| | - Stefan J Marciniak
- Cambridge Institute for Medical Research, Cambridge, United Kingdom;
- Department of Medicine, University of Cambridge, Cambridge, United Kingdom
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25
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Perlmutter DH. α1-antitrypsin Deficiency: A Misfolded Secretory Protein Variant with Unique Effects on the Endoplasmic Reticulum. ENDOPLASMIC RETICULUM STRESS IN DISEASES 2016; 3:63-72. [PMID: 28217691 PMCID: PMC5310618 DOI: 10.1515/ersc-2016-0004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
In the classical form of α1-antitrypsin deficiency (ATD) a point mutation leads to accumulation of a misfolded secretory glycoprotein in the endoplasmic reticulum (ER) of liver cells and so ATD has come to be considered a prototypical ER storage disease. It is associated with two major types of clinical disorders, chronic obstructive pulmonary disease (COPD) by loss-of-function mechanisms and hepatic cirrhosis and carcinogenesis by gain-of-function mechanisms. The lung disease predominantly results from proteolytic damage to the pulmonary connective tissue matrix because of reduced levels of protease inhibitor activity of α1-anitrypsin (AT) in the circulating blood and body fluids. Cigarette smoking is a powerful disease-promoting modifier but other modifiers are known to exist because variation in the lung disease phenotype is still found in smoking and non-smoking homozygotes. The liver disease is highly likely to be caused by the proteotoxic effects of intracellular misfolded protein accumulation and a high degree of variation in the hepatic phenotype among affected homozygotes has been hypothetically attributed to genetic and environmental modifiers that alter proteostasis responses. Liver biopsies of homozygotes show intrahepatocytic inclusions with dilation and expansion of the ER and recent studies of iPS-derived hepatocyte-like cells from individuals with ATD indicate that the changes in the ER directly vary with the hepatic phenotype i.e there is much lesser alteration in the ER in cells derived from homozygotes that do not have clinically significant liver disease. From a signaling perspective, studies in mammalian cell line and animal models expressing the classical α1-antitrypsin Z variant (ATZ) have found that ER signaling is perturbed in a relatively unique way with powerful activation of autophagy and the NFκB pathway but relatively limited, if any, UPR signaling. It is still not known how much these unique structural and functional changes and the variation among affected homozygotes relate to the tendency of this variant to polymerize and aggregate and/or to the repertoire of proteostasis mechanisms that are activated.
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Affiliation(s)
- David H Perlmutter
- Corresponding author: David H Perlmutter, School of Medicine, Washington University in St Louis, 660 South Euclid Boulevard, St Louis, Missouri 63130, 314-362-6827,
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26
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Kandregula CAB, Smilin Bell Aseervatham G, Bentley GT, Kandasamy R. Alpha-1 antitrypsin: Associated diseases and therapeutic uses. Clin Chim Acta 2016; 459:109-116. [PMID: 27259467 DOI: 10.1016/j.cca.2016.05.028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 05/27/2016] [Accepted: 05/30/2016] [Indexed: 11/30/2022]
Affiliation(s)
- Chaya A Babu Kandregula
- Laboratory of Pulmonary Medicine, National Facility for Drug Development for Academia, Pharmaceutical & Allied Industries, Department of Pharmaceutical Technology, Centre for Excellence in Nanobio Translational REsearch (CENTRE), Anna University - BIT Campus, Tiruchirappalli, Tamil Nadu 620024, India
| | - G Smilin Bell Aseervatham
- Laboratory of Pulmonary Medicine, National Facility for Drug Development for Academia, Pharmaceutical & Allied Industries, Department of Pharmaceutical Technology, Centre for Excellence in Nanobio Translational REsearch (CENTRE), Anna University - BIT Campus, Tiruchirappalli, Tamil Nadu 620024, India
| | - Gary T Bentley
- Department of Internal Medicine, Morsani College of Medicine, Tampa, FL 33612, USA
| | - Ruckmani Kandasamy
- Laboratory of Pulmonary Medicine, National Facility for Drug Development for Academia, Pharmaceutical & Allied Industries, Department of Pharmaceutical Technology, Centre for Excellence in Nanobio Translational REsearch (CENTRE), Anna University - BIT Campus, Tiruchirappalli, Tamil Nadu 620024, India.
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27
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Abstract
Alpha-1 antitrypsin deficiency is the leading cause of childhood liver failure and one of the most common lethal genetic diseases. The disease-causing mutant A1AT-Z fails to fold correctly and accumulates in the endoplasmic reticulum (ER) of the liver, resulting in hepatic fibrosis and hepatocellular carcinoma in a subset of patients. Furthermore, A1AT-Z sequestration in hepatocytes leads to a reduction in A1AT secretion into the serum, causing panacinar emphysema in adults. The purpose of this work was to elucidate the details by which A1AT-Z is degraded in hepatic cell lines. We identified the ubiquitin ligase FBG1, which has been previously shown to degrade proteins by both the ubiquitin proteasome pathway and autophagy, as being key to A1AT-Z degradation. Using chemical and genetic approaches we show that FBG1 degrades A1AT-Z through both the ubiquitin proteasome system and autophagy. Overexpression of FBG1 decreases the half-life of A1AT-Z and knocking down FBG1 in a hepatic cell line, and in mice results in an increase in ATAT. Finally, we show that FBG1 degrades A1AT-Z through a Beclin1-dependent arm of autophagy. In our model, FBG1 acts as a safety ubiquitin ligase, whose function is to re-ubiquitinate ER proteins that have previously undergone de-ubiquitination to ensure they are degraded.
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28
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Behnke J, Feige MJ, Hendershot LM. BiP and its nucleotide exchange factors Grp170 and Sil1: mechanisms of action and biological functions. J Mol Biol 2015; 427:1589-608. [PMID: 25698114 DOI: 10.1016/j.jmb.2015.02.011] [Citation(s) in RCA: 135] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2014] [Revised: 02/10/2015] [Accepted: 02/10/2015] [Indexed: 12/26/2022]
Abstract
BiP (immunoglobulin heavy-chain binding protein) is the endoplasmic reticulum (ER) orthologue of the Hsp70 family of molecular chaperones and is intricately involved in most functions of this organelle through its interactions with a variety of substrates and regulatory proteins. Like all Hsp70 family members, the ability of BiP to bind and release unfolded proteins is tightly regulated by a cycle of ATP binding, hydrolysis, and nucleotide exchange. As a characteristic of the Hsp70 family, multiple DnaJ-like co-factors can target substrates to BiP and stimulate its ATPase activity to stabilize the binding of BiP to substrates. However, only in the past decade have nucleotide exchange factors for BiP been identified, which has shed light not only on the mechanism of BiP-assisted folding in the ER but also on Hsp70 family members that reside throughout the cell. We will review the current understanding of the ATPase cycle of BiP in the unique environment of the ER and how it is regulated by the nucleotide exchange factors, Grp170 (glucose-regulated protein of 170kDa) and Sil1, both of which perform unanticipated roles in various biological functions and disease states.
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Affiliation(s)
- Julia Behnke
- Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Matthias J Feige
- Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA
| | - Linda M Hendershot
- Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
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29
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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: 32] [Impact Index Per Article: 3.6] [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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30
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Abstract
Alpha-1-antitrypsin (α1AT) deficiency is a genetic disorder that manifests as pulmonary emphysema and liver cirrhosis. α1AT deficiency is the most common genetic cause of liver disease in children and also an underappreciated cause of liver disease in adults. The prevalence in the general population in Western Europe is approximately 1 in 2,000. The most common and severe deficiency allele is the Z variant (two alleles mutated). This variant is characterized by the accumulation of Z-α1AT polymers in the endoplasmic reticulum of hepatocytes leading to cell death and to a severe reduction of α1AT in the serum. The latter results in a loss of its antiprotease activity and its ability to protect lung tissue. Thus far, there are only very limited therapeutic options in α1AT deficiency. A more detailed understanding of the biology governing α1AT biogenesis is required in order to identify new pharmacological agents and biomarkers. This review will present current knowledge on α1AT deficiency and focus on recent discoveries and new strategies in the treatment of this disease.
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Affiliation(s)
- Marion Bouchecareilh
- Institut de biochimie et génétique cellulaires, CNRS UMR 5095, université de Bordeaux, 1, rue Camille Saint-Saëns, 33077 Bordeaux, France
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31
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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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32
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Turner AM. Alpha-1 antitrypsin deficiency: new developments in augmentation and other therapies. BioDrugs 2014; 27:547-58. [PMID: 23771682 DOI: 10.1007/s40259-013-0042-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Alpha 1 antitrypsin deficiency (AATD) is a rare cause of chronic obstructive pulmonary disease. The lung disease is thought to be caused primarily by a lack of effective protection against the harmful effects of neutrophil elastase due to the low AAT levels in the lung. Patients may also develop liver disease due to polymerisation of AAT within hepatocytes. Consequently there has been much research over the years into AAT augmentation therapy in patients with lung disease, initially intravenously, and more recently in inhaled forms. This review article will discuss the role of augmentation therapy in AATD and the current status of recombinant AAT. The potential for other therapeutic strategies, such as blocking polymer formation, enhancing autophagy, gene therapy and stem cell-based treatment, will also be discussed more briefly.
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Affiliation(s)
- Alice M Turner
- QEHB Research Labs, University of Birmingham, Mindelsohn Way, Birmingham, B15 2WB, UK,
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33
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O'Reilly LP, Long OS, Cobanoglu MC, Benson JA, Luke CJ, Miedel MT, Hale P, Perlmutter DH, Bahar I, Silverman GA, Pak SC. A genome-wide RNAi screen identifies potential drug targets in a C. elegans model of α1-antitrypsin deficiency. Hum Mol Genet 2014; 23:5123-32. [PMID: 24838285 DOI: 10.1093/hmg/ddu236] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
α1-Antitrypsin deficiency (ATD) is a common genetic disorder that can lead to end-stage liver and lung disease. Although liver transplantation remains the only therapy currently available, manipulation of the proteostasis network (PN) by small molecule therapeutics offers great promise. To accelerate the drug-discovery process for this disease, we first developed a semi-automated high-throughput/content-genome-wide RNAi screen to identify PN modifiers affecting the accumulation of the α1-antitrypsin Z mutant (ATZ) in a Caenorhabditis elegans model of ATD. We identified 104 PN modifiers, and these genes were used in a computational strategy to identify human ortholog-ligand pairs. Based on rigorous selection criteria, we identified four FDA-approved drugs directed against four different PN targets that decreased the accumulation of ATZ in C. elegans. We also tested one of the compounds in a mammalian cell line with similar results. This methodology also proved useful in confirming drug targets in vivo, and predicting the success of combination therapy. We propose that small animal models of genetic disorders combined with genome-wide RNAi screening and computational methods can be used to rapidly, economically and strategically prime the preclinical discovery pipeline for rare and neglected diseases with limited therapeutic options.
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Affiliation(s)
| | | | - Murat C Cobanoglu
- Department of Computational and Systems Biology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC and Magee-Womens Hospital Research Institute, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | | | | | | | | | | | - Ivet Bahar
- Department of Computational and Systems Biology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC and Magee-Womens Hospital Research Institute, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
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34
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Long OS, Benson JA, Kwak JH, Luke CJ, Gosai SJ, O'Reilly LP, Wang Y, Li J, Vetica AC, Miedel MT, Stolz DB, Watkins SC, Züchner S, Perlmutter DH, Silverman GA, Pak SC. A C. elegans model of human α1-antitrypsin deficiency links components of the RNAi pathway to misfolded protein turnover. Hum Mol Genet 2014; 23:5109-22. [PMID: 24838286 DOI: 10.1093/hmg/ddu235] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The accumulation of serpin oligomers and polymers within the endoplasmic reticulum (ER) causes cellular injury in patients with the classical form α1-antitrypsin deficiency (ATD). To better understand the cellular and molecular genetic aspects of this disorder, we generated transgenic C. elegans strains expressing either the wild-type (ATM) or Z mutant form (ATZ) of the human serpin fused to GFP. Animals secreted ATM, but retained polymerized ATZ within dilated ER cisternae. These latter animals also showed slow growth, smaller brood sizes and decreased longevity; phenotypes observed in ATD patients or transgenic mouse lines expressing ATZ. Similar to mammalian models, ATZ was disposed of by autophagy and ER-associated degradation pathways. Mutant strains defective in insulin signaling (daf-2) also showed a marked decrease in ATZ accumulation. Enhanced ATZ turnover was associated with the activity of two proteins central to systemic/exogenous (exo)-RNAi pathway: the dsRNA importer, SID-1 and the argonaute, RDE-1. Animals with enhanced exo-RNAi activity (rrf-3 mutant) phenocopied the insulin signaling mutants and also showed increased ATZ turnover. Taken together, these studies allude to the existence of a novel proteostasis pathway that mechanistically links misfolded protein turnover to components of the systemic RNAi machinery.
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Affiliation(s)
- Olivia S Long
- Departments of Pediatrics, Cell Biology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC and Magee Womens Hospital Research Institute, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Joshua A Benson
- Departments of Pediatrics, Cell Biology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC and Magee Womens Hospital Research Institute, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Joon Hyeok Kwak
- Departments of Pediatrics, Cell Biology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC and Magee Womens Hospital Research Institute, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Cliff J Luke
- Departments of Pediatrics, Cell Biology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC and Magee Womens Hospital Research Institute, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Sager J Gosai
- Departments of Pediatrics, Cell Biology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC and Magee Womens Hospital Research Institute, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Linda P O'Reilly
- Departments of Pediatrics, Cell Biology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC and Magee Womens Hospital Research Institute, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Yan Wang
- Departments of Pediatrics, Cell Biology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC and Magee Womens Hospital Research Institute, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Jie Li
- Departments of Pediatrics, Cell Biology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC and Magee Womens Hospital Research Institute, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Anne C Vetica
- Departments of Pediatrics, Cell Biology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC and Magee Womens Hospital Research Institute, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Mark T Miedel
- Departments of Pediatrics, Cell Biology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC and Magee Womens Hospital Research Institute, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Donna B Stolz
- Center for Biologic Imaging, University of Pittsburgh School of Medicine, 3500 Terrace Street, S233 BST, Pittsburgh, PA 15261, USA
| | - Simon C Watkins
- Center for Biologic Imaging, University of Pittsburgh School of Medicine, 3500 Terrace Street, S233 BST, Pittsburgh, PA 15261, USA
| | - Stephan Züchner
- Department of Human Genetics and Hussman Institute for Human Genomics, University of Miami Miller School of Medicine, 1501 NW 10th Avenue, Miami, FL 33136, USA
| | - David H Perlmutter
- Departments of Pediatrics, Cell Biology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC and Magee Womens Hospital Research Institute, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Gary A Silverman
- Departments of Pediatrics, Cell Biology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC and Magee Womens Hospital Research Institute, 4401 Penn Avenue, Pittsburgh, PA 15224, USA
| | - Stephen C Pak
- Departments of Pediatrics, Cell Biology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC and Magee Womens Hospital Research Institute, 4401 Penn Avenue, Pittsburgh, PA 15224, USA,
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Li J, Pak SC, O’Reilly LP, Benson JA, Wang Y, Hidvegi T, Hale P, Dippold C, Ewing M, Silverman GA, Perlmutter DH. Fluphenazine reduces proteotoxicity in C. elegans and mammalian models of alpha-1-antitrypsin deficiency. PLoS One 2014; 9:e87260. [PMID: 24498058 PMCID: PMC3909079 DOI: 10.1371/journal.pone.0087260] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Accepted: 12/27/2013] [Indexed: 12/15/2022] Open
Abstract
The classical form of α1-antitrypsin deficiency (ATD) is associated with hepatic fibrosis and hepatocellular carcinoma. It is caused by the proteotoxic effect of a mutant secretory protein that aberrantly accumulates in the endoplasmic reticulum of liver cells. Recently we developed a model of this deficiency in C. Elegans and adapted it for high-content drug screening using an automated, image-based array scanning. Screening of the Library of Pharmacologically Active Compounds identified fluphenazine (Flu) among several other compounds as a drug which reduced intracellular accumulation of mutant α1-antitrypsin Z (ATZ). Because it is representative of the phenothiazine drug class that appears to have autophagy enhancer properties in addition to mood stabilizing activity, and can be relatively easily re-purposed, we further investigated its effects on mutant ATZ. The results indicate that Flu reverses the phenotypic effects of ATZ accumulation in the C. elegans model of ATD at doses which increase the number of autophagosomes in vivo. Furthermore, in nanomolar concentrations, Flu enhances the rate of intracellular degradation of ATZ and reduces the cellular ATZ load in mammalian cell line models. In the PiZ mouse model Flu reduces the accumulation of ATZ in the liver and mediates a decrease in hepatic fibrosis. These results show that Flu can reduce the proteotoxicity of ATZ accumulation in vivo and, because it has been used safely in humans, this drug can be moved rapidly into trials for liver disease due to ATD. The results also provide further validation for drug discovery using C. elegans models that can be adapted to high-content drug screening platforms and used together with mammalian cell line and animal models.
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Affiliation(s)
- Jie Li
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Children’s Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
| | - Stephen C. Pak
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Children’s Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
| | - Linda P. O’Reilly
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Children’s Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
| | - Joshua A. Benson
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Children’s Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
| | - Yan Wang
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Children’s Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
| | - Tunda Hidvegi
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Children’s Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
| | - Pamela Hale
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Children’s Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
| | - Christine Dippold
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Children’s Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
| | - Michael Ewing
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Children’s Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
| | - Gary A. Silverman
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Children’s Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
| | - David H. Perlmutter
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Children’s Hospital of Pittsburgh of University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States of America
- * E-mail:
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Behnke J, Hendershot LM. The large Hsp70 Grp170 binds to unfolded protein substrates in vivo with a regulation distinct from conventional Hsp70s. J Biol Chem 2013; 289:2899-907. [PMID: 24327659 DOI: 10.1074/jbc.m113.507491] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The Hsp70 superfamily is a ubiquitous chaperone class that includes conventional and large Hsp70s. BiP is the only conventional Hsp70 in the endoplasmic reticulum (ER) whose functions include: assisting protein folding, targeting misfolded proteins for degradation, and regulating the transducers of the unfolded protein response. The ER also possesses a single large Hsp70, the glucose-regulated protein of 170 kDa (Grp170). Like BiP it is an essential protein, but its cellular functions are not well understood. Here we show that Grp170 can bind directly to a variety of incompletely folded protein substrates in the ER, and as expected for a bona fide chaperone, it does not interact with folded secretory proteins. Our data demonstrate that Grp170 and BiP associate with similar molecular forms of two substrate proteins, but while BiP is released from unfolded substrates in the presence of ATP, Grp170 remains bound. In comparison to conventional Hsp70s, the large Hsp70s possess two unique structural features: an extended C-terminal α-helical domain and an unstructured loop in the putative substrate binding domain with an unknown function. We find that in the absence of the α-helical domain the interaction of Grp170 with substrates is reduced. In striking contrast, deletion of the unstructured loop results in increased binding to substrates, suggesting the presence of unique intramolecular mechanisms of control for the chaperone functions of large Hsp70s.
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Affiliation(s)
- Julia Behnke
- From the Department of Tumor Cell Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105
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Gidalevitz T, Stevens F, Argon Y. Orchestration of secretory protein folding by ER chaperones. BIOCHIMICA ET BIOPHYSICA ACTA 2013; 1833:2410-24. [PMID: 23507200 PMCID: PMC3729627 DOI: 10.1016/j.bbamcr.2013.03.007] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 02/27/2013] [Accepted: 03/01/2013] [Indexed: 02/06/2023]
Abstract
The endoplasmic reticulum is a major compartment of protein biogenesis in the cell, dedicated to production of secretory, membrane and organelle proteins. The secretome has distinct structural and post-translational characteristics, since folding in the ER occurs in an environment that is distinct in terms of its ionic composition, dynamics and requirements for quality control. The folding machinery in the ER therefore includes chaperones and folding enzymes that introduce, monitor and react to disulfide bonds, glycans, and fluctuations of luminal calcium. We describe the major chaperone networks in the lumen and discuss how they have distinct modes of operation that enable cells to accomplish highly efficient production of the secretome. This article is part of a Special Issue entitled: Functional and structural diversity of endoplasmic reticulum.
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Affiliation(s)
- Tali Gidalevitz
- Department of Biology, Drexel University, Drexel University, 418 Papadakis Integrated Science Bldg, 3245 Chestnut Street, Philadelphia, PA 19104
| | | | - Yair Argon
- Division of Cell Pathology, Department of Pathology and Lab Medicine, The Children's Hospital of Philadelphia and the University of Pennsylvania, 3615 Civic Center Blvd., Philadelphia, PA 19104, USA, , Phone: 267-426-5131, Fax: 267-426-5165)
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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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Ferris SP, Jaber NS, Molinari M, Arvan P, Kaufman RJ. UDP-glucose:glycoprotein glucosyltransferase (UGGT1) promotes substrate solubility in the endoplasmic reticulum. Mol Biol Cell 2013; 24:2597-608. [PMID: 23864712 PMCID: PMC3756913 DOI: 10.1091/mbc.e13-02-0101] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The N-glycans promote solubility in the ER even for mutant glycoproteins, such as mutant α1-antitrypsin. This study shows that enzymatic monoglucosylation activity of the enzyme UGGT1 and lectin chaperone abundance are required for N-glycans to provide maximum solubility to the misfolded substrate. Protein folding in the endoplasmic reticulum (ER) is error prone, and ER quality control (ERQC) processes ensure that only correctly folded proteins are exported from the ER. Glycoproteins can be retained in the ER by ERQC, and this retention contributes to multiple human diseases, termed ER storage diseases. UDP-glucose:glycoprotein glucosyltransferase (UGGT1) acts as a central component of glycoprotein ERQC, monoglucosylating deglucosylated N-glycans of incompletely folded glycoproteins and promoting subsequent reassociation with the lectin-like chaperones calreticulin and calnexin. The extent to which UGGT1 influences glycoprotein folding, however, has only been investigated for a few selected substrates. Using mouse embryonic fibroblasts lacking UGGT1 or those with UGGT1 complementation, we investigated the effect of monoglucosylation on the soluble/insoluble distribution of two misfolded α1-antitrypsin (AAT) variants responsible for AAT deficiency disease: null Hong Kong (NHK) and Z allele. Whereas substrate solubility increases directly with the number of N-linked glycosylation sites, our results indicate that additional solubility is conferred by UGGT1 enzymatic activity. Monoglucosylation-dependent solubility decreases both BiP association with NHK and unfolded protein response activation, and the solubility increase is blocked in cells deficient for calreticulin. These results suggest that UGGT1-dependent monoglucosylation of N-linked glycoproteins promotes substrate solubility in the ER.
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Affiliation(s)
- Sean P Ferris
- Department of Biological Chemistry and Medical Scientist Training Program, University of Michigan Medical School, Ann Arbor, MI 48109-1621, USA
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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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Buck TM, Plavchak L, Roy A, Donnelly BF, Kashlan OB, Kleyman TR, Subramanya AR, Brodsky JL. The Lhs1/GRP170 chaperones facilitate the endoplasmic reticulum-associated degradation of the epithelial sodium channel. J Biol Chem 2013; 288:18366-80. [PMID: 23645669 DOI: 10.1074/jbc.m113.469882] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The epithelial sodium channel, ENaC, plays a critical role in maintaining salt and water homeostasis, and not surprisingly defects in ENaC function are associated with disease. Like many other membrane-spanning proteins, this trimeric protein complex folds and assembles inefficiently in the endoplasmic reticulum (ER), which results in a substantial percentage of the channel being targeted for ER-associated degradation (ERAD). Because the spectrum of factors that facilitates the degradation of ENaC is incomplete, we developed yeast expression systems for each ENaC subunit. We discovered that a conserved Hsp70-like chaperone, Lhs1, is required for maximal turnover of the ENaC α subunit. By expressing Lhs1 ATP binding mutants, we also found that the nucleotide exchange properties of this chaperone are dispensable for ENaC degradation. Consistent with the precipitation of an Lhs1-αENaC complex, Lhs1 holdase activity was instead most likely required to support the ERAD of αENaC. Moreover, a complex containing the mammalian Lhs1 homolog GRP170 and αENaC co-precipitated, and GRP170 also facilitated ENaC degradation in human, HEK293 cells, and in a Xenopus oocyte expression system. In both yeast and higher cell types, the effect of Lhs1 on the ERAD of αENaC was selective for the unglycosylated form of the protein. These data establish the first evidence that Lhs1/Grp170 chaperones can act as mediators of ERAD substrate selection.
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Affiliation(s)
- Teresa M Buck
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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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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43
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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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44
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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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45
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Zhu Y, Ren C, Wan X, Zhu Y, Zhu J, Zhou H, Zhang T. Gene expression of Hsp70, Hsp90 and Hsp110 families in normal palate and cleft palate during mouse embryogenesis. Toxicol Ind Health 2012; 29:915-30. [PMID: 22585935 DOI: 10.1177/0748233712446720] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Most previous studies focused on a small number of heat shock proteins (Hsps) and their relationships with embryogenesis, and the actual roles of these Hsps in normal and abnormal embryonic development remain unclear. It was found in the present systemic study that except for Grp170, whose expression was not detectable at GD18, all 19 Hsps of Hsp70, Hsp90 and Hsp110 families were expressed in the normal development of embryonic palate tissue in mice, but their expression patterns varied with different Hsps, presenting as a correlation with the developmental phases. In the treatment group by all-trans retinoic acid (atRA), the messenger RNA (mRNA) abundance of HspA1A, HspA1L, HspA8, HspA9, HspA12A, HspA12B, HspA13, HspA14, Hsp90AA1, Hsp90AB1, Grp94, Trap1, Hsp105, Hsp110 and Grp170 was higher in the palates at GD11 (the beginning of palate development), the mRNA abundance of HspA1A, HspA12A and HspA12B was higher at GD18 (before birth) and an mRNA expression peak of HspA1L, HspA8, HspA9, Hsp90AA1, Grp94, Hsp110 and Grp170 was observed at GD17. The mRNA abundance of most genes in atRA-induced cleft palates of the treatment group was different from that of the control group. Grp78, HspA14 and Hsp105 were closely associated with the normal palate development and cleft palate in mouse embryo, possibly as palate development-related genes. Except Grp170, the other genes may be closely associated with the development of mouse palates through participating in the stress response process and/or the antiapoptosis process.
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Affiliation(s)
- Yongfei Zhu
- 1School of Medicine, Hunan Normal University, Changsha, People's Republic of China
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46
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Zhu Y, Zhou H, Zhu Y, Wan X, Zhu J, Zhang T. Gene expression ofHsp70,Hsp90, andHsp110families in normal and abnormal embryonic development of mouse forelimbs. Drug Chem Toxicol 2011; 35:432-44. [DOI: 10.3109/01480545.2011.640683] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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47
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Yamasaki M, Sendall TJ, Pearce MC, Whisstock JC, Huntington JA. Molecular basis of α1-antitrypsin deficiency revealed by the structure of a domain-swapped trimer. EMBO Rep 2011; 12:1011-7. [PMID: 21909074 DOI: 10.1038/embor.2011.171] [Citation(s) in RCA: 127] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Revised: 07/20/2011] [Accepted: 07/22/2011] [Indexed: 11/09/2022] Open
Abstract
α(1)-Antitrypsin (α1AT) deficiency is a disease with multiple manifestations, including cirrhosis and emphysema, caused by the accumulation of stable polymers of mutant protein in the endoplasmic reticulum of hepatocytes. However, the molecular basis of misfolding and polymerization remain unknown. We produced and crystallized a trimeric form of α1AT that is recognized by an antibody specific for the pathological polymer. Unexpectedly, this structure reveals a polymeric linkage mediated by domain swapping the carboxy-terminal 34 residues. Disulphide-trapping and antibody-binding studies further demonstrate that runaway C-terminal domain swapping, rather than the s4A/s5A domain swap previously proposed, underlies polymerization of the common Z-mutant of α1AT in vivo.
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Affiliation(s)
- Masayuki Yamasaki
- Department of Haematology, Cambridge Institute for Medical Research, University of Cambridge, Wellcome Trust/MRC Building, Hills Road, Cambridge CB2 0XY, UK
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McLaughlin M, Vandenbroeck K. The endoplasmic reticulum protein folding factory and its chaperones: new targets for drug discovery? Br J Pharmacol 2011; 162:328-45. [PMID: 20942857 DOI: 10.1111/j.1476-5381.2010.01064.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Cytosolic heat shock proteins have received significant attention as emerging therapeutic targets. Much of this excitement has been triggered by the discovery that HSP90 plays a central role in the maintenance and stability of multifarious oncogenic membrane receptors and their resultant tyrosine kinase activity. Numerous studies have dealt with the effects of small molecules on chaperone- and stress-related pathways of the endoplasmic reticulum (ER). However, unlike cytosolic chaperones, relatively little emphasis has been placed upon translational avenues towards targeting of the ER for inhibition of folding/secretion of disease-promoting proteins. Here, we summarise existing small molecule inhibitors and potential future targets of ER chaperone-mediated inhibition. Client proteins of translational relevance in disease treatment are outlined, alongside putative future disease treatment modalities based on ER-centric targeted therapies. Particular attention is paid to cancer and autoimmune disorders via the effects of the GRP94 inhibitor geldanamycin and its population of client proteins, overloading of the unfolded protein response, and inhibition of members of the IL-12 family of cytokines by celecoxib and non-coxib analogues.
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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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50
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Abstract
OBJECTIVES Homozygous ZZ α-1-antitrypsin (a1AT) deficiency is a common genetic liver disease that causes liver injury and hepatocellular carcinoma (HCC). The a1AT mutant Z gene encodes a mutant protein that accumulates within hepatocytes leading to hepatocellular death and a hepatic regenerative response. However, the mechanisms linking hepatocellular injury to these responses are poorly understood. In this study, we examined liver injury and response in human liver and in transgenic mice for involvement of hepatic progenitor cells. METHODS Liver biopsy specimens of low-grade, early-stage human ZZ liver exhibiting minimal inflammation and minimal fibrosis (grade 1 and stage 1) were examined for hepatic progenitor cell (HPC) proliferation using immunoreactivity for cytokeratin-7 (CK-7). Transgenic mouse model liver and other selected human biopsies were also examined. RESULTS Increased CK-7-positive HPC proliferation was seen in human ZZ liver compared to normal liver, but was 5-fold less HPC proliferation than in grade- and stage-matched disease control hepatitis C-infected liver. Livers from PiZ mice, a model transgenic for the human a1AT mutant Z gene, which recapitulates the human injury, also showed HPC proliferation. Human ZZ liver and PiZ mice develop dysplasia in the liver and HCC. HCC in PiZ mice was also characterized by HPC proliferation. Progressive hepatic fibrosis with age in the PiZ mice is demonstrated for the first time in the present study. CONCLUSIONS Chronic injury in both ZZ human and PiZ mouse liver is associated with hepatic fibrosis and a unique magnitude of HPC proliferation within the hepatic proliferative response.
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