1
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Gilda JE, Nahar A, Kasiviswanathan D, Tropp N, Gilinski T, Lahav T, Alexandrovich D, Mandel-Gutfreund Y, Park S, Shemer S. Proteasome gene expression is controlled by coordinated functions of multiple transcription factors. J Cell Biol 2024; 223:e202402046. [PMID: 38767572 PMCID: PMC11104393 DOI: 10.1083/jcb.202402046] [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: 02/06/2024] [Revised: 04/14/2024] [Accepted: 04/16/2024] [Indexed: 05/22/2024] Open
Abstract
Proteasome activity is crucial for cellular integrity, but how tissues adjust proteasome content in response to catabolic stimuli is uncertain. Here, we demonstrate that transcriptional coordination by multiple transcription factors is required to increase proteasome content and activate proteolysis in catabolic states. Using denervated mouse muscle as a model system for accelerated proteolysis in vivo, we reveal that a two-phase transcriptional program activates genes encoding proteasome subunits and assembly chaperones to boost an increase in proteasome content. Initially, gene induction is necessary to maintain basal proteasome levels, and in a more delayed phase (7-10 days after denervation), it stimulates proteasome assembly to meet cellular demand for excessive proteolysis. Intriguingly, the transcription factors PAX4 and α-PALNRF-1 control the expression of proteasome among other genes in a combinatorial manner, driving cellular adaptation to muscle denervation. Consequently, PAX4 and α-PALNRF-1 represent new therapeutic targets to inhibit proteolysis in catabolic diseases (e.g., type-2 diabetes, cancer).
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Affiliation(s)
| | | | | | - Nadav Tropp
- Faculty of Biology, Technion Institute of Technology, Haifa, Israel
| | - Tamar Gilinski
- Faculty of Biology, Technion Institute of Technology, Haifa, Israel
| | - Tamar Lahav
- Faculty of Biology, Technion Institute of Technology, Haifa, Israel
| | | | | | | | - Shenhav Shemer
- Faculty of Biology, Technion Institute of Technology, Haifa, Israel
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2
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Galka D, Ali TT, Bast A, Niederleithinger M, Gerhardt E, Motosugi R, Sakata E, Knop M, Outeiro TF, Popova B, Braus GH. Inhibition of 26S proteasome activity by α-synuclein is mediated by the proteasomal chaperone Rpn14/PAAF1. Aging Cell 2024; 23:e14128. [PMID: 38415292 PMCID: PMC11113265 DOI: 10.1111/acel.14128] [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: 09/28/2023] [Revised: 02/01/2024] [Accepted: 02/11/2024] [Indexed: 02/29/2024] Open
Abstract
Parkinson's disease (PD) is characterized by aggregation of α-synuclein (α-syn) into protein inclusions in degenerating brains. Increasing amounts of aggregated α-syn species indicate significant perturbation of cellular proteostasis. Altered proteostasis depends on α-syn protein levels and the impact of α-syn on other components of the proteostasis network. Budding yeast Saccharomyces cerevisiae was used as eukaryotic reference organism to study the consequences of α-syn expression on protein dynamics. To address this, we investigated the impact of overexpression of α-syn and S129A variant on the abundance and stability of most yeast proteins using a genome-wide yeast library and a tandem fluorescent protein timer (tFT) reporter as a measure for protein stability. This revealed that the stability of in total 377 cellular proteins was altered by α-syn expression, and that the impact on protein stability was significantly enhanced by phosphorylation at Ser129 (pS129). The proteasome assembly chaperone Rpn14 was identified as one of the top candidates for increased protein stability by expression of pS129 α-syn. Elevated levels of Rpn14 enhanced the growth inhibition by α-syn and the accumulation of ubiquitin conjugates in the cell. We found that Rpn14 interacts physically with α-syn and stabilizes pS129 α-syn. The expression of α-syn along with elevated levels of Rpn14 or its human counterpart PAAF1 reduced the proteasome activity in yeast and in human cells, supporting that pS129 α-syn negatively affects the 26S proteasome through Rpn14. This comprehensive study into the alternations of protein homeostasis highlights the critical role of the Rpn14/PAAF1 in α-syn-mediated proteasome dysfunction.
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Affiliation(s)
- Dajana Galka
- Department of Molecular Microbiology and Genetics, Institute for Microbiology and GeneticsUniversity of GöttingenGöttingenGermany
| | - Tariq T. Ali
- Department of Molecular Microbiology and Genetics, Institute for Microbiology and GeneticsUniversity of GöttingenGöttingenGermany
| | - Alexander Bast
- Department of Molecular Microbiology and Genetics, Institute for Microbiology and GeneticsUniversity of GöttingenGöttingenGermany
| | - Marie Niederleithinger
- Department of Molecular Microbiology and Genetics, Institute for Microbiology and GeneticsUniversity of GöttingenGöttingenGermany
| | - Ellen Gerhardt
- Department of Experimental Neurodegeneration, Center for Biostructural Imaging of NeurodegenerationUniversity Medical Center GöttingenGöttingenGermany
| | - Ryo Motosugi
- Institute for Auditory NeuroscienceUniversity Medical Center GöttingenGöttingenGermany
- Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells (MBExC)University of GöttingenGöttingenGermany
| | - Eri Sakata
- Institute for Auditory NeuroscienceUniversity Medical Center GöttingenGöttingenGermany
- Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells (MBExC)University of GöttingenGöttingenGermany
| | - Michael Knop
- Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ‐ZMBH AllianceHeidelberg UniversityHeidelbergGermany
| | - Tiago F. Outeiro
- Department of Experimental Neurodegeneration, Center for Biostructural Imaging of NeurodegenerationUniversity Medical Center GöttingenGöttingenGermany
- Translational and Clinical Research Institute, Faculty of Medical SciencesNewcastle UniversityNewcastle Upon TyneUK
- Max Planck Institute for Multidisciplinary SciencesGöttingenGermany
- Scientific employee with an honorary contract at Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE)GöttingenGermany
| | - Blagovesta Popova
- Department of Molecular Microbiology and Genetics, Institute for Microbiology and GeneticsUniversity of GöttingenGöttingenGermany
| | - Gerhard H. Braus
- Department of Molecular Microbiology and Genetics, Institute for Microbiology and GeneticsUniversity of GöttingenGöttingenGermany
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3
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Bhattarai D, Lee SO, MacMillan-Crow LA, Parajuli N. Normal Proteasome Function Is Needed to Prevent Kidney Graft Injury during Cold Storage Followed by Transplantation. Int J Mol Sci 2024; 25:2147. [PMID: 38396827 PMCID: PMC10888692 DOI: 10.3390/ijms25042147] [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: 01/08/2024] [Revised: 02/02/2024] [Accepted: 02/07/2024] [Indexed: 02/25/2024] Open
Abstract
Kidney transplantation is the preferred treatment for end-stage kidney disease (ESKD). However, there is a shortage of transplantable kidneys, and donor organs can be damaged by necessary cold storage (CS). Although CS improves the viability of kidneys from deceased donors, prolonged CS negatively affects transplantation outcomes. Previously, we reported that renal proteasome function decreased after rat kidneys underwent CS followed by transplantation (CS + Tx). Here, we investigated the mechanism underlying proteasome dysfunction and the role of the proteasome in kidney graft outcome using a rat model of CS + Tx. We found that the key proteasome subunits β5, α3, and Rpt6 are modified, and proteasome assembly is impaired. Specifically, we detected the modification and aggregation of Rpt6 after CS + Tx, and Rpt6 modification was reversed when renal extracts were treated with protein phosphatases. CS + Tx kidneys also displayed increased levels of nitrotyrosine, an indicator of peroxynitrite (a reactive oxygen species, ROS), compared to sham. Because the Rpt6 subunit appeared to aggregate, we investigated the effect of CS + Tx-mediated ROS (peroxynitrite) generation on renal proteasome assembly and function. We treated NRK cells with exogenous peroxynitrite and evaluated PAC1 (proteasome assembly chaperone), Rpt6, and β5. Peroxynitrite induced a dose-dependent decrease in PAC1 and β5, but Rpt6 was not affected (protein level or modification). Finally, serum creatinine increased when we inhibited the proteasome in transplanted donor rat kidneys (without CS), recapitulating the effects of CS + Tx. These findings underscore the effects of CS + Tx on renal proteasome subunit dysregulation and also highlight the significance of proteasome activity in maintaining graft function following CS + Tx.
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Affiliation(s)
- Dinesh Bhattarai
- Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Seong-Ok Lee
- Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Lee Ann MacMillan-Crow
- Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Nirmala Parajuli
- Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
- Division of Nephrology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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4
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Betancourt D, Lawal T, Tomko RJ. Wiggle and Shake: Managing and Exploiting Conformational Dynamics during Proteasome Biogenesis. Biomolecules 2023; 13:1223. [PMID: 37627288 PMCID: PMC10452565 DOI: 10.3390/biom13081223] [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: 07/04/2023] [Revised: 08/01/2023] [Accepted: 08/03/2023] [Indexed: 08/27/2023] Open
Abstract
The 26S proteasome is the largest and most complicated protease known, and changes to proteasome assembly or function contribute to numerous human diseases. Assembly of the 26S proteasome from its ~66 individual polypeptide subunits is a highly orchestrated process requiring the concerted actions of both intrinsic elements of proteasome subunits, as well as assistance by extrinsic, dedicated proteasome assembly chaperones. With the advent of near-atomic resolution cryo-electron microscopy, it has become evident that the proteasome is a highly dynamic machine, undergoing numerous conformational changes in response to ligand binding and during the proteolytic cycle. In contrast, an appreciation of the role of conformational dynamics during the biogenesis of the proteasome has only recently begun to emerge. Herein, we review our current knowledge of proteasome assembly, with a particular focus on how conformational dynamics guide particular proteasome biogenesis events. Furthermore, we highlight key emerging questions in this rapidly expanding area.
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Affiliation(s)
| | | | - Robert J. Tomko
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL 32306, USA; (D.B.); (T.L.)
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5
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Papendorf JJ, Ebstein F, Alehashemi S, Piotto DGP, Kozlova A, Terreri MT, Shcherbina A, Rastegar A, Rodrigues M, Pereira R, Park S, Lin B, Uss K, Möller S, da Silva Pina AF, Sztajnbok F, Torreggiani S, Niemela J, Stoddard J, Rosenzweig SD, Oler AJ, McNinch C, de Guzman MM, Fonseca A, Micheloni N, Fraga MM, Perazzio SF, Goldbach-Mansky R, de Jesus AA, Krüger E. Identification of eight novel proteasome variants in five unrelated cases of proteasome-associated autoinflammatory syndromes (PRAAS). Front Immunol 2023; 14:1190104. [PMID: 37600812 PMCID: PMC10436547 DOI: 10.3389/fimmu.2023.1190104] [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: 03/20/2023] [Accepted: 06/12/2023] [Indexed: 08/22/2023] Open
Abstract
Mutations in genes coding for proteasome subunits and/or proteasome assembly helpers typically cause recurring autoinflammation referred to as chronic atypical neutrophilic dermatosis with lipodystrophy and elevated temperatures (CANDLE) or proteasome-associated autoinflammatory syndrome (PRAAS). Patients with CANDLE/PRAAS present with mostly chronically elevated type I interferon scores that emerge as a consequence of increased proteotoxic stress by mechanisms that are not fully understood. Here, we report on five unrelated patients with CANDLE/PRAAS carrying novel inherited proteasome missense and/or nonsense variants. Four patients were compound heterozygous for novel pathogenic variants in the known CANDLE/PRAAS associated genes, PSMB8 and PSMB10, whereas one patient showed additive loss-of-function mutations in PSMB8. Variants in two previously not associated proteasome genes, PSMA5 and PSMC5, were found in a patient who also carried the PSMB8 founder mutation, p.T75M. All newly identified mutations substantially impact the steady-state expression of the affected proteasome subunits and/or their incorporation into mature 26S proteasomes. Our observations expand the spectrum of PRAAS-associated genetic variants and improve a molecular diagnosis and genetic counseling of patients with sterile autoinflammation.
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Affiliation(s)
- Jonas Johannes Papendorf
- Institut für Medizinische Biochemie und Molekularbiologie (IMBM), Universitätsmedizin Greifswald, Greifswald, Germany
| | - Frédéric Ebstein
- Institut für Medizinische Biochemie und Molekularbiologie (IMBM), Universitätsmedizin Greifswald, Greifswald, Germany
| | - Sara Alehashemi
- Translational Autoinflammatory Diseases Section (TADS), Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Daniela Gerent Petry Piotto
- Division of Pediatric Rheumatology, Department of Pediatrics, Universidade Federal de São Paulo (Unifesp), São Paulo, Brazil
| | - Anna Kozlova
- Department of Immunology, D.Rogachev National Medical and Research Center for Pediatric Hematology, Oncology, and Immunology, Moscow, Russia
| | - Maria Teresa Terreri
- Division of Pediatric Rheumatology, Department of Pediatrics, Universidade Federal de São Paulo (Unifesp), São Paulo, Brazil
| | - Anna Shcherbina
- Department of Immunology, D.Rogachev National Medical and Research Center for Pediatric Hematology, Oncology, and Immunology, Moscow, Russia
| | - Andre Rastegar
- Translational Autoinflammatory Diseases Section (TADS), Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Marta Rodrigues
- Division of Pediatric Rheumatology, Department of Pediatrics, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
| | - Renan Pereira
- Department of Pediatrics, Universidade Federal de Ciencias da Saude de Porto Alegre, Porto Alegre, Brazil
| | - Sophia Park
- Translational Autoinflammatory Diseases Section (TADS), Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Bin Lin
- Translational Autoinflammatory Diseases Section (TADS), Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Kat Uss
- Translational Autoinflammatory Diseases Section (TADS), Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Sophie Möller
- Institut für Medizinische Biochemie und Molekularbiologie (IMBM), Universitätsmedizin Greifswald, Greifswald, Germany
| | - Ana Flávia da Silva Pina
- Division of Pediatric Rheumatology, Department of Pediatrics, Universidade Federal de São Paulo (Unifesp), São Paulo, Brazil
| | - Flavio Sztajnbok
- Division of Pediatric Rheumatology, Department of Pediatrics, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
| | - Sofia Torreggiani
- Translational Autoinflammatory Diseases Section (TADS), Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Julie Niemela
- Immunology Service, Department of Laboratory Medicine, Clinical Center, National Institutes of Health, Bethesda, MD, United States
| | - Jennifer Stoddard
- Immunology Service, Department of Laboratory Medicine, Clinical Center, National Institutes of Health, Bethesda, MD, United States
| | - Sergio D. Rosenzweig
- Immunology Service, Department of Laboratory Medicine, Clinical Center, National Institutes of Health, Bethesda, MD, United States
| | - Andrew J. Oler
- Bioinformatics and Computational Biosciences Branch, Office of Cyber Infrastructure and Computational Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Colton McNinch
- Bioinformatics and Computational Biosciences Branch, Office of Cyber Infrastructure and Computational Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Marietta M. de Guzman
- Section of Pediatric Rheumatology, Texas Children’s Hospital, Baylor College of Medicine, Houston, TX, United States
| | - Adriana Fonseca
- Division of Pediatric Rheumatology, Department of Pediatrics, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil
| | - Nicole Micheloni
- Division of Pediatric Rheumatology, Department of Pediatrics, Universidade Federal de São Paulo (Unifesp), São Paulo, Brazil
| | - Melissa Mariti Fraga
- Division of Pediatric Rheumatology, Department of Pediatrics, Universidade Federal de São Paulo (Unifesp), São Paulo, Brazil
| | - Sandro Félix Perazzio
- Division of Rheumatology – Department of Medicine, Universidade Federal de São Paulo (Unifesp), Sao Paulo, Brazil
| | - Raphaela Goldbach-Mansky
- Translational Autoinflammatory Diseases Section (TADS), Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Adriana A. de Jesus
- Translational Autoinflammatory Diseases Section (TADS), Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Elke Krüger
- Institut für Medizinische Biochemie und Molekularbiologie (IMBM), Universitätsmedizin Greifswald, Greifswald, Germany
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6
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Collins MA, Avery R, Albert FW. Substrate-specific effects of natural genetic variation on proteasome activity. PLoS Genet 2023; 19:e1010734. [PMID: 37126494 PMCID: PMC10174532 DOI: 10.1371/journal.pgen.1010734] [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: 06/14/2022] [Revised: 05/11/2023] [Accepted: 04/04/2023] [Indexed: 05/02/2023] Open
Abstract
Protein degradation is an essential biological process that regulates protein abundance and removes misfolded and damaged proteins from cells. In eukaryotes, most protein degradation occurs through the stepwise actions of two functionally distinct entities, the ubiquitin system and the proteasome. Ubiquitin system enzymes attach ubiquitin to cellular proteins, targeting them for degradation. The proteasome then selectively binds and degrades ubiquitinated substrate proteins. Genetic variation in ubiquitin system genes creates heritable differences in the degradation of their substrates. However, the challenges of measuring the degradative activity of the proteasome independently of the ubiquitin system in large samples have limited our understanding of genetic influences on the proteasome. Here, using the yeast Saccharomyces cerevisiae, we built and characterized reporters that provide high-throughput, ubiquitin system-independent measurements of proteasome activity. Using single-cell measurements of proteasome activity from millions of genetically diverse yeast cells, we mapped 15 loci across the genome that influence proteasomal protein degradation. Twelve of these 15 loci exerted specific effects on the degradation of two distinct proteasome substrates, revealing a high degree of substrate-specificity in the genetics of proteasome activity. Using CRISPR-Cas9-based allelic engineering, we resolved a locus to a causal variant in the promoter of RPT6, a gene that encodes a subunit of the proteasome's 19S regulatory particle. The variant increases RPT6 expression, which we show results in increased proteasome activity. Our results reveal the complex genetic architecture of proteasome activity and suggest that genetic influences on the proteasome may be an important source of variation in the many cellular and organismal traits shaped by protein degradation.
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Affiliation(s)
- Mahlon A. Collins
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Randi Avery
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Frank W. Albert
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota, United States of America
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7
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Sekaran S, Park S. The penultimate step of proteasomal ATPase assembly is mediated by a switch dependent on the chaperone Nas2. J Biol Chem 2023; 299:102870. [PMID: 36621624 PMCID: PMC9922823 DOI: 10.1016/j.jbc.2023.102870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 12/21/2022] [Accepted: 12/28/2022] [Indexed: 01/07/2023] Open
Abstract
The proteasome holoenzyme is a complex molecular machine that degrades most proteins. In the proteasome holoenzyme, six distinct ATPase subunits (Rpt1 through Rpt6) enable protein degradation by injecting protein substrates into it. Individual Rpt subunits assemble into a heterohexameric "Rpt ring" in a stepwise manner, by binding to their cognate chaperones. Completion of the heterohexameric Rpt ring correlates with release of a specific chaperone, Nas2; however, it is unclear whether and how this event may ensure proper Rpt ring assembly. Here, we examined the action of Nas2 by capturing the poorly characterized penultimate step of heterohexameric Rpt ring assembly. For this, we used a heterologous Escherichia coli system coexpressing all Rpt subunits and assembly chaperones as well as Saccharomyces cerevisiae to track Nas2 actions during endogenous Rpt ring assembly. We show that Nas2 uses steric hindrance to block premature progression of the penultimate step into the final step of Rpt ring assembly. Importantly, Nas2 can activate an assembly checkpoint via its steric activity, when the last ATPase subunit, Rpt1, cannot be added in a timely manner. This checkpoint can be relieved via Nas2 release, when Nas2 recognizes proper addition of Rpt1 to one side of its cognate Rpt5, and ATP hydrolysis by Rpt4 on the other side of Rpt5, allowing completion of Rpt ring assembly. Our findings reveal dual criteria for Nas2 release, as a mechanism to ensure both the composition and functional competence of a newly assembled proteasomal ATPase, to generate the proteasome holoenzyme.
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Affiliation(s)
- Suganya Sekaran
- Department of Molecular Cellular and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, USA
| | - Soyeon Park
- Department of Molecular Cellular and Developmental Biology, University of Colorado Boulder, Boulder, Colorado, USA.
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8
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Warnock JL, Jobin GW, Kumar S, Tomko RJ. Assembly chaperone Nas6 selectively destabilizes 26S proteasomes with defective regulatory particle-core particle interfaces. J Biol Chem 2023; 299:102894. [PMID: 36634850 PMCID: PMC9943895 DOI: 10.1016/j.jbc.2023.102894] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2022] [Revised: 12/22/2022] [Accepted: 12/28/2022] [Indexed: 01/11/2023] Open
Abstract
The 26S proteasome is a 66-subunit-chambered protease present in all eukaryotes that maintains organismal health by degrading unneeded or defective proteins. Defects in proteasome function or assembly are known to contribute to the development of various cancers, neurodegeneration, and diabetes. During proteasome biogenesis, a family of evolutionarily conserved chaperones assembles a hexameric ring of AAA+ family ATPase subunits contained within the proteasomal regulatory particle (RP) and guide their docking onto the surface of the proteolytic core particle (CP). This RP-CP interaction couples the substrate capture and unfolding process to proteolysis. We previously reported a mutation in the proteasome that promoted dissociation of the RP and CP by one of these chaperones, Nas6. However, the nature of the signal for Nas6-dependent proteasome disassembly and the generality of this postassembly proteasome quality control function for Nas6 remain unknown. Here, we use structure-guided mutagenesis and in vitro proteasome disassembly assays to demonstrate that Nas6 more broadly destabilizes 26S proteasomes with a defective RP-CP interface. We show that Nas6 can promote dissociation of mature proteasomes into RP and CP in cells harboring defects on either side of the RP-CP interface. This function is unique to Nas6 and independent from other known RP assembly chaperones. Further biochemical experiments suggest that Nas6 may exploit a weakened RP-CP interface to dissociate the RP from the CP. We propose that this postassembly role of Nas6 may fulfill a quality control function in cells by promoting the recycling of functional subcomplexes contained within defective proteasomes.
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9
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Nahar A, Sokolova V, Sekaran S, Orth JD, Park S. Assembly checkpoint of the proteasome regulatory particle is activated by coordinated actions of proteasomal ATPase chaperones. Cell Rep 2022; 39:110918. [PMID: 35675778 PMCID: PMC9214829 DOI: 10.1016/j.celrep.2022.110918] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Revised: 03/14/2022] [Accepted: 05/12/2022] [Indexed: 11/26/2022] Open
Abstract
The proteasome holoenzyme regulates the cellular proteome via degrading most proteins. In its 19-subunit regulatory particle (RP), a heterohexameric ATPase enables protein degradation by injecting protein substrates into the core peptidase. RP assembly utilizes “checkpoints,” where multiple dedicated chaperones bind to specific ATPase subunits and control the addition of other subunits. Here, we find that the RP assembly checkpoint relies on two common features of the chaperones. Individual chaperones can distinguish an RP, in which their cognate ATPase persists in the ATP-bound state. Chaperones then together modulate ATPase activity to facilitate RP subunit rearrangements for switching to an active, substrate-processing state in the resulting proteasome holoenzyme. Thus, chaperones may sense ATP binding and hydrolysis as a readout for the quality of the RP complex to generate a functional proteasome holoenzyme. Our findings provide a basis to potentially exploit the assembly checkpoints in situations with known deregulation of proteasomal ATPase chaperones. Nahar et al. report that cells build functional proteasomes by utilizing an assembly checkpoint, which is activated by a common feature of multiple dedicated chaperones; they can distinguish the nucleotide state of proteasomal ATPases and help facilitate proper subunit rearrangement to ensure efficient protein degradation by the proteasome.
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Affiliation(s)
- Asrafun Nahar
- Department of Molecular, Cellular and Developmental Biology, University of Colorado Boulder, 1945 Colorado Avenue, Boulder, CO 80309, USA
| | - Vladyslava Sokolova
- Department of Molecular, Cellular and Developmental Biology, University of Colorado Boulder, 1945 Colorado Avenue, Boulder, CO 80309, USA
| | - Suganya Sekaran
- Department of Molecular, Cellular and Developmental Biology, University of Colorado Boulder, 1945 Colorado Avenue, Boulder, CO 80309, USA
| | - James D Orth
- Department of Molecular, Cellular and Developmental Biology, University of Colorado Boulder, 1945 Colorado Avenue, Boulder, CO 80309, USA
| | - Soyeon Park
- Department of Molecular, Cellular and Developmental Biology, University of Colorado Boulder, 1945 Colorado Avenue, Boulder, CO 80309, USA.
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10
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Padovani C, Jevtić P, Rapé M. Quality control of protein complex composition. Mol Cell 2022; 82:1439-1450. [PMID: 35316660 DOI: 10.1016/j.molcel.2022.02.029] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 01/26/2022] [Accepted: 02/21/2022] [Indexed: 12/13/2022]
Abstract
Eukaryotic cells possess hundreds of protein complexes that contain multiple subunits and must be formed at the correct time and place during development. Despite specific assembly pathways, cells frequently encounter complexes with missing or aberrant subunits that can disrupt important signaling events. Cells, therefore, employ several ubiquitin-dependent quality control pathways that can prevent, correct, or degrade flawed complexes. In this review, we will discuss our emerging understanding of such quality control of protein complex composition.
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Affiliation(s)
- Chris Padovani
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720, USA
| | - Predrag Jevtić
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720, USA; Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA 94720, USA
| | - Michael Rapé
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA 94720, USA; Howard Hughes Medical Institute, University of California at Berkeley, Berkeley, CA 94720, USA; California Institute for Quantitative Biosciences (QB3), University of California at Berkeley, Berkeley, CA 94720, USA.
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11
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Zavodszky E, Peak-Chew SY, Juszkiewicz S, Narvaez AJ, Hegde RS. Identification of a quality-control factor that monitors failures during proteasome assembly. Science 2021; 373:998-1004. [PMID: 34446601 PMCID: PMC7611656 DOI: 10.1126/science.abc6500] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2020] [Revised: 06/22/2021] [Accepted: 07/15/2021] [Indexed: 12/11/2022]
Abstract
In eukaryotic cells, half of all proteins function as subunits within multiprotein complexes. Imbalanced synthesis of subunits leads to unassembled intermediates that must be degraded to minimize cellular toxicity. Here, we found that excess PSMC5, a subunit of the proteasome base, was targeted for degradation by the HERC1 ubiquitin ligase in mammalian cells. HERC1 identified unassembled PSMC5 by its cognate assembly chaperone PAAF1. Because PAAF1 only dissociates after assembly, HERC1 could also engage later assembly intermediates such as the PSMC4-PSMC5-PAAF1 complex. A missense mutant of HERC1 that causes neurodegeneration in mice was impaired in the recognition and ubiquitination of the PSMC5-PAAF1 complex. Thus, proteasome assembly factors can serve as adaptors for ubiquitin ligases to facilitate elimination of unassembled intermediates and maintain protein homeostasis.
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12
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The parkinsonism-associated protein FBXO7 cooperates with the BAG6 complex in proteasome function and controls the subcellular localization of the complex. Biochem J 2021; 478:2179-2199. [PMID: 34060591 DOI: 10.1042/bcj20201000] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 05/28/2021] [Accepted: 05/28/2021] [Indexed: 11/17/2022]
Abstract
The regulation of proteasome activity is essential to cellular homeostasis and defects have been implicated in various disorders including Parkinson disease. The F-box protein FBXO7 has been implicated in early-onset parkinsonism and has previously been shown to have a regulatory role in proteasome activity and assembly. Here, we report the association of the E3 ubiquitin ligase FBXO7-SCF (SKP1, cullin-1, F-box protein) with the BAG6 complex, consisting of the subunits BAG6, GET4 and UBL4A. We identify the subunit GET4 as a direct interactor of FBXO7 and we show that the subunits GET4 and UBL4A are required for proper proteasome activity. Our findings demonstrate reduced binding of FBXO7 variants to GET4 and that FBXO7 variants bring about reduced proteasome activity. In addition, we find that GET4 is a non-proteolytic substrate of FBXO7, that binding of GET4 to BAG6 is enhanced in the presence of active FBXO7-SCF and that the cytoplasmic localization of the BAG6 complex is dependent on the E3 ubiquitin ligase activity. Taken together, our study shows that the parkinsonism-associated FBXO7 cooperates with the BAG6 complex in proteasome function and determines the subcellular localization of this complex.
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13
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Chen L, Zhang Y, Shu X, Chen Q, Wei T, Wang H, Wang X, Wu Q, Zhang X, Liu X, Zheng S, Huang L, Xiao J, Jiang C, Yang B, Wang Z, Guo X. Proteasome regulation by reversible tyrosine phosphorylation at the membrane. Oncogene 2021; 40:1942-1956. [PMID: 33603165 PMCID: PMC7990385 DOI: 10.1038/s41388-021-01674-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Revised: 12/21/2020] [Accepted: 01/21/2021] [Indexed: 01/30/2023]
Abstract
Reversible phosphorylation has emerged as an important mechanism for regulating 26S proteasome function in health and disease. Over 100 phospho-tyrosine sites of the human proteasome have been detected, and yet their function and regulation remain poorly understood. Here we show that the 19S subunit Rpt2 is phosphorylated at Tyr439, a strictly conserved residue within the C-terminal HbYX motif of Rpt2 that is essential for 26S proteasome assembly. Unexpectedly, we found that Y439 phosphorylation depends on Rpt2 membrane localization mediated by its N-myristoylation. Multiple receptors tyrosine kinases can trigger Rpt2-Y439 phosphorylation by activating Src, a N-myristoylated tyrosine kinase. Src directly phosphorylates Rpt2-Y439 in vitro and negatively regulates 26S proteasome activity at cellular membranes, which can be reversed by the membrane-associated isoform of protein tyrosine phosphatase nonreceptor type 2 (PTPN2). In H1975 lung cancer cells with activated Src, blocking Rpt2-Y439 phosphorylation by the Y439F mutation conferred partial resistance to the Src inhibitor saracatinib both in vitro and in a mouse xenograft tumor model, and caused significant changes of cellular responses to saracatinib at the proteome level. Our study has defined a novel mechanism involved in the spatial regulation of proteasome function and provided new insights into tyrosine kinase inhibitor-based anticancer therapies.
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Affiliation(s)
- Lu Chen
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Yanan Zhang
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Xin Shu
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Qiong Chen
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Tiantian Wei
- Academy for Advanced Interdisciplinary Studies, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
| | - Heman Wang
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Xiaorong Wang
- Departments of Physiology and Biophysics and of Developmental and Cell Biology, University of California, Irvine, CA, USA
| | - Qirou Wu
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Xiaomei Zhang
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Xiaoyan Liu
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Suya Zheng
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Lan Huang
- Departments of Physiology and Biophysics and of Developmental and Cell Biology, University of California, Irvine, CA, USA
| | - Junyu Xiao
- Academy for Advanced Interdisciplinary Studies, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China
| | - Chao Jiang
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Bing Yang
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China
| | - Zhiping Wang
- Center for Neuroscience and Department of Neurology of Second Affiliated Hospital, NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University School of Medicine, Hangzhou, China.
| | - Xing Guo
- Zhejiang Provincial Key Laboratory for Cancer Molecular Cell Biology, Life Sciences Institute, Zhejiang University, Hangzhou, China.
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14
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Abstract
The 26S proteasome is the most complex ATP-dependent protease machinery, of ~2.5 MDa mass, ubiquitously found in all eukaryotes. It selectively degrades ubiquitin-conjugated proteins and plays fundamentally indispensable roles in regulating almost all major aspects of cellular activities. To serve as the sole terminal "processor" for myriad ubiquitylation pathways, the proteasome evolved exceptional adaptability in dynamically organizing a large network of proteins, including ubiquitin receptors, shuttle factors, deubiquitinases, AAA-ATPase unfoldases, and ubiquitin ligases, to enable substrate selectivity and processing efficiency and to achieve regulation precision of a vast diversity of substrates. The inner working of the 26S proteasome is among the most sophisticated, enigmatic mechanisms of enzyme machinery in eukaryotic cells. Recent breakthroughs in three-dimensional atomic-level visualization of the 26S proteasome dynamics during polyubiquitylated substrate degradation elucidated an extensively detailed picture of its functional mechanisms, owing to progressive methodological advances associated with cryogenic electron microscopy (cryo-EM). Multiple sites of ubiquitin binding in the proteasome revealed a canonical mode of ubiquitin-dependent substrate engagement. The proteasome conformation in the act of substrate deubiquitylation provided insights into how the deubiquitylating activity of RPN11 is enhanced in the holoenzyme and is coupled to substrate translocation. Intriguingly, three principal modes of coordinated ATP hydrolysis in the heterohexameric AAA-ATPase motor were discovered to regulate intermediate functional steps of the proteasome, including ubiquitin-substrate engagement, deubiquitylation, initiation of substrate translocation and processive substrate degradation. The atomic dissection of the innermost working of the 26S proteasome opens up a new era in our understanding of the ubiquitin-proteasome system and has far-reaching implications in health and disease.
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Affiliation(s)
- Youdong Mao
- Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, 02215, Massachusetts, USA. .,School of Physics, Center for Quantitative Biology, Peking University, Beijing, 100871, China.
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15
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Proteasome Subunits Involved in Neurodegenerative Diseases. Arch Med Res 2020; 52:1-14. [PMID: 32962866 DOI: 10.1016/j.arcmed.2020.09.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2020] [Revised: 07/25/2020] [Accepted: 09/04/2020] [Indexed: 12/29/2022]
Abstract
The ubiquitin-proteasome system is the major pathway for the maintenance of protein homeostasis. Its inhibition causes accumulation of ubiquitinated proteins; this accumulation has been associated with several of the most common neurodegenerative diseases. Several genetic factors have been identified for most neurodegenerative diseases, however, most cases are considered idiopathic, thus making the study of the mechanisms of protein accumulation a relevant field of research. It is often mentioned that the biggest risk factor for neurodegenerative diseases is aging, and several groups have reported an age-related alteration of the expression of some of the 26S proteasome subunits and a reduction of its activity. Proteasome subunits interact with proteins that are known to accumulate in neurodegenerative diseases such as α-synuclein in Parkinson's, tau in Alzheimer's, and huntingtin in Huntington's diseases. These interactions have been explored for several years, but only until recently, we are beginning to understand them. In this review, we discuss the known interactions, the underlying patterns, and the phenotypes associated with the 26S proteasome subunits in the etiology and progression of neurodegenerative diseases where there is evidence of proteasome involvement. Special emphasis is made in reviewing proteasome subunits that interact with proteins known to have an age-related altered expression or to be involved in neurodegenerative diseases to explore key effectors that may trigger or augment their progression. Interestingly, while the causes of age-related reduction of some of the proteasome subunits are not known, there are specific relationships between the observed neurodegenerative disease and the affected proteasome subunits.
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16
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An Allosteric Interaction Network Promotes Conformation State-Dependent Eviction of the Nas6 Assembly Chaperone from Nascent 26S Proteasomes. Cell Rep 2020; 26:483-495.e5. [PMID: 30625330 PMCID: PMC6344052 DOI: 10.1016/j.celrep.2018.12.042] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 11/15/2018] [Accepted: 12/11/2018] [Indexed: 12/04/2022] Open
Abstract
The 26S proteasome is the central ATP-dependent protease in eukaryotes and is essential for organismal health. Proteasome assembly is mediated by several dedicated, evolutionarily conserved chaperone proteins. These chaperones associate transiently with assembly intermediates but are absent from mature proteasomes. Chaperone eviction upon completion of proteasome assembly is necessary for normal proteasome function, but how they are released remains unresolved. Here, we demonstrate that the Nas6 assembly chaperone, homolog of the human oncogene gankyrin, is evicted from nascent proteasomes during completion of assembly via a conformation-specific allosteric interaction of the Rpn5 subunit with the proteasomal ATPase ring. Subsequent ATP binding by the ATPase subunit Rpt3 promotes conformational remodeling of the ATPase ring that evicts Nas6 from the nascent proteasome. Our study demonstrates how assembly-coupled allosteric signals promote chaperone eviction and provides a framework for understanding the eviction of other chaperones from this bio-medically important molecular machine. Nemec et al. report how the evolutionarily conserved Nas6 assembly chaperone is evicted from nascent 26S proteasomes. Nucleotide binding events within the nascent proteasome trigger formation of conformation-specific intersubunit contacts that expel Nas6. This mechanism may serve a quality control function by blocking formation of 26S proteasomes from defective components.
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17
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Kwon D, Kim SM, Correia MA. Cytochrome P450 endoplasmic reticulum-associated degradation (ERAD): therapeutic and pathophysiological implications. Acta Pharm Sin B 2020; 10:42-60. [PMID: 31993306 PMCID: PMC6976991 DOI: 10.1016/j.apsb.2019.11.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 10/30/2019] [Accepted: 10/31/2019] [Indexed: 02/07/2023] Open
Abstract
The hepatic endoplasmic reticulum (ER)-anchored cytochromes P450 (P450s) are mixed-function oxidases engaged in the biotransformation of physiologically relevant endobiotics as well as of myriad xenobiotics of therapeutic and environmental relevance. P450 ER-content and hence function is regulated by their coordinated hemoprotein syntheses and proteolytic turnover. Such P450 proteolytic turnover occurs through a process known as ER-associated degradation (ERAD) that involves ubiquitin-dependent proteasomal degradation (UPD) and/or autophagic-lysosomal degradation (ALD). Herein, on the basis of available literature reports and our own recent findings of in vitro as well as in vivo experimental studies, we discuss the therapeutic and pathophysiological implications of altered P450 ERAD and its plausible clinical relevance. We specifically (i) describe the P450 ERAD-machinery and how it may be repurposed for the generation of antigenic P450 peptides involved in P450 autoantibody pathogenesis in drug-induced acute hypersensitivity reactions and liver injury, or viral hepatitis; (ii) discuss the relevance of accelerated or disrupted P450-ERAD to the pharmacological and/or toxicological effects of clinically relevant P450 drug substrates; and (iii) detail the pathophysiological consequences of disrupted P450 ERAD, contributing to non-alcoholic fatty liver disease (NAFLD)/non-alcoholic steatohepatitis (NASH) under certain synergistic cellular conditions.
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Key Words
- 3MA, 3-methyladenine
- AAA, ATPases associated with various cellular activities
- ACC1, acetyl-CoA carboxylase 1
- ACC2, acetyl-CoA carboxylase 2
- ACHE, acetylcholinesterase
- ACOX1, acyl-CoA oxidase 1
- ALD, autophagic-lysosomal degradation
- AMPK1
- AP-1, activator protein 1
- ASK1, apoptosis signal-regulating kinase
- ATF2, activating transcription factor 2
- AdipoR1, gene of adiponectin receptor 1
- Atg14, autophagy-related 14
- CBZ, carbamazepine
- CHIP E3 ubiquitin ligase
- CHIP, carboxy-terminus of Hsc70-interacting protein
- Cytochromes P450
- Endoplasmic reticulum-associated degradation
- FOXO, forkhead box O
- Fas, fatty acid synthase
- GAPDH, glyceraldehyde 3-phosphate dehydrogenase
- INH, isoniazid
- IRS1, insulin receptor substrate 1
- Il-1β, interleukin 1 β
- Il-6, interleukin 6
- Insig1, insulin-induced gene 1
- JNK1
- Lpl, lipoprotein lipase
- Mcp1, chemokine (C–C motif) ligand 1
- Non-alcoholic fatty liver disease
- Non-alcoholic steatohepatitis
- Pgc1, peroxisome proliferator-activated receptor coactivator 1
- SREBP1c, sterol regulatory element binding transcription factor 1c
- Scd1, stearoyl-coenzyme A desaturase
- Tnf, tumor necrosis factor
- UPD, ubiquitin (Ub)-dependent proteasomal degradation
- Ub, ubiquitin
- gp78/AMFR E3 ubiquitin ligase
- gp78/AMFR, autocrine motility factor receptor
- shRNAi, shRNA interference
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18
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Reversible phosphorylation of Rpn1 regulates 26S proteasome assembly and function. Proc Natl Acad Sci U S A 2019; 117:328-336. [PMID: 31843888 DOI: 10.1073/pnas.1912531117] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The fundamental importance of the 26S proteasome in health and disease suggests that its function must be finely controlled, and yet our knowledge about proteasome regulation remains limited. Posttranslational modifications, especially phosphorylation, of proteasome subunits have been shown to impact proteasome function through different mechanisms, although the vast majority of proteasome phosphorylation events have not been studied. Here, we have characterized 1 of the most frequently detected proteasome phosphosites, namely Ser361 of Rpn1, a base subunit of the 19S regulatory particle. Using a variety of approaches including CRISPR/Cas9-mediated gene editing and quantitative mass spectrometry, we found that loss of Rpn1-S361 phosphorylation reduces proteasome activity, impairs cell proliferation, and causes oxidative stress as well as mitochondrial dysfunction. A screen of the human kinome identified several kinases including PIM1/2/3 that catalyze S361 phosphorylation, while its level is reversibly controlled by the proteasome-resident phosphatase, UBLCP1. Mechanistically, Rpn1-S361 phosphorylation is required for proper assembly of the 26S proteasome, and we have utilized a genetic code expansion system to directly demonstrate that S361-phosphorylated Rpn1 more readily forms a precursor complex with Rpt2, 1 of the first steps of 19S base assembly. These findings have revealed a prevalent and biologically important mechanism governing proteasome formation and function.
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19
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Eisele MR, Reed RG, Rudack T, Schweitzer A, Beck F, Nagy I, Pfeifer G, Plitzko JM, Baumeister W, Tomko RJ, Sakata E. Expanded Coverage of the 26S Proteasome Conformational Landscape Reveals Mechanisms of Peptidase Gating. Cell Rep 2019; 24:1301-1315.e5. [PMID: 30067984 PMCID: PMC6140342 DOI: 10.1016/j.celrep.2018.07.004] [Citation(s) in RCA: 88] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 06/08/2018] [Accepted: 07/02/2018] [Indexed: 12/31/2022] Open
Abstract
The proteasome is the central protease for intracellular protein breakdown. Coordinated binding and hydrolysis of ATP by the six proteasomal ATPase subunits induces conformational changes that drive the unfolding and translocation of substrates into the proteolytic 20S core particle for degradation. Here, we combine genetic and biochemical approaches with cryo-electron microscopy and integrative modeling to dissect the relationship between individual nucleotide binding events and proteasome conformational dynamics. We demonstrate unique impacts of ATP binding by individual ATPases on the proteasome conformational distribution and report two conformational states of the proteasome suggestive of a rotary ATP hydrolysis mechanism. These structures, coupled with functional analyses, reveal key roles for the ATPases Rpt1 and Rpt6 in gating substrate entry into the core particle. This deepened knowledge of proteasome conformational dynamics reveals key elements of intersubunit communication within the proteasome and clarifies the regulation of substrate entry into the proteolytic chamber.
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Affiliation(s)
- Markus R Eisele
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Randi G Reed
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL 32306-4300, USA
| | - Till Rudack
- Department of Biophysics, Ruhr University Bochum, 44801 Bochum, Germany
| | - Andreas Schweitzer
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Florian Beck
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Istvan Nagy
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Günter Pfeifer
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Jürgen M Plitzko
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Wolfgang Baumeister
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
| | - Robert J Tomko
- Department of Biomedical Sciences, Florida State University College of Medicine, Tallahassee, FL 32306-4300, USA.
| | - Eri Sakata
- Department of Molecular Structural Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
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20
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Abstract
The proteasome degrades most cellular proteins in a controlled and tightly regulated manner and thereby controls many processes, including cell cycle, transcription, signalling, trafficking and protein quality control. Proteasomal degradation is vital in all cells and organisms, and dysfunction or failure of proteasomal degradation is associated with diverse human diseases, including cancer and neurodegeneration. Target selection is an important and well-established way to control protein degradation. In addition, mounting evidence indicates that cells adjust proteasome-mediated degradation to their needs by regulating proteasome abundance through the coordinated expression of proteasome subunits and assembly chaperones. Central to the regulation of proteasome assembly is TOR complex 1 (TORC1), which is the master regulator of cell growth and stress. This Review discusses how proteasome assembly and the regulation of proteasomal degradation are integrated with cellular physiology, including the interplay between the proteasome and autophagy pathways. Understanding these mechanisms has potential implications for disease therapy, as the misregulation of proteasome function contributes to human diseases such as cancer and neurodegeneration.
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21
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Marshall RS, Vierstra RD. Dynamic Regulation of the 26S Proteasome: From Synthesis to Degradation. Front Mol Biosci 2019; 6:40. [PMID: 31231659 PMCID: PMC6568242 DOI: 10.3389/fmolb.2019.00040] [Citation(s) in RCA: 143] [Impact Index Per Article: 28.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Accepted: 05/09/2019] [Indexed: 01/12/2023] Open
Abstract
All eukaryotes rely on selective proteolysis to control the abundance of key regulatory proteins and maintain a healthy and properly functioning proteome. Most of this turnover is catalyzed by the 26S proteasome, an intricate, multi-subunit proteolytic machine. Proteasomes recognize and degrade proteins first marked with one or more chains of poly-ubiquitin, the addition of which is actuated by hundreds of ligases that individually identify appropriate substrates for ubiquitylation. Subsequent proteasomal digestion is essential and influences a myriad of cellular processes in species as diverse as plants, fungi and humans. Importantly, dysfunction of 26S proteasomes is associated with numerous human pathologies and profoundly impacts crop performance, thus making an understanding of proteasome dynamics critically relevant to almost all facets of human health and nutrition. Given this widespread significance, it is not surprising that sophisticated mechanisms have evolved to tightly regulate 26S proteasome assembly, abundance and activity in response to demand, organismal development and stress. These include controls on transcription and chaperone-mediated assembly, influences on proteasome localization and activity by an assortment of binding proteins and post-translational modifications, and ultimately the removal of excess or damaged particles via autophagy. Intriguingly, the autophagic clearance of damaged 26S proteasomes first involves their modification with ubiquitin, thus connecting ubiquitylation and autophagy as key regulatory events in proteasome quality control. This turnover is also influenced by two distinct biomolecular condensates that coalesce in the cytoplasm, one attracting damaged proteasomes for autophagy, and the other reversibly storing proteasomes during carbon starvation to protect them from autophagic clearance. In this review, we describe the current state of knowledge regarding the dynamic regulation of 26S proteasomes at all stages of their life cycle, illustrating how protein degradation through this proteolytic machine is tightly controlled to ensure optimal growth, development and longevity.
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Affiliation(s)
- Richard S Marshall
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
| | - Richard D Vierstra
- Department of Biology, Washington University in St. Louis, St. Louis, MO, United States
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22
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Nahar A, Fu X, Polovin G, Orth JD, Park S. Two alternative mechanisms regulate the onset of chaperone-mediated assembly of the proteasomal ATPases. J Biol Chem 2019; 294:6562-6577. [PMID: 30814255 DOI: 10.1074/jbc.ra118.006298] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 01/23/2019] [Indexed: 01/03/2023] Open
Abstract
The proteasome holoenzyme is a molecular machine that degrades most proteins in eukaryotes. In the holoenzyme, its heterohexameric ATPase injects protein substrates into the proteolytic core particle, where degradation occurs. The heterohexameric ATPase, referred to as 'Rpt ring', assembles through six ATPase subunits (Rpt1-Rpt6) individually binding to specific chaperones (Rpn14, Nas6, Nas2, and Hsm3). Here, our findings suggest that the onset of Rpt ring assembly can be regulated by two alternative mechanisms. Excess Rpt subunits relative to their chaperones are sequestered into multiple puncta specifically during early-stage Rpt ring assembly. Sequestration occurs during stressed conditions, for example heat, which transcriptionally induce Rpt subunits. When the free Rpt pool is limited experimentally, Rpt subunits are competent for proteasome assembly even without their cognate chaperones. These data suggest that sequestration may regulate amounts of individual Rpt subunits relative to their chaperones, allowing for proper onset of Rpt ring assembly. Indeed, Rpt subunits in the puncta can later resume their assembly into the proteasome. Intriguingly, when proteasome assembly resumes in stressed cells or is ongoing in unstressed cells, excess Rpt subunits are recognized by an alternative mechanism-degradation by the proteasome holoenzyme itself. Rpt subunits undergo proteasome assembly until the holoenzyme complex is generated at a sufficient level. The fully-formed holoenzyme can then degrade any remaining excess Rpt subunits, thereby regulating its own Rpt ring assembly. These two alternative mechanisms, degradation and sequestration of Rpt subunits, may help control the onset of chaperone-mediated Rpt ring assembly, thereby promoting proper proteasome holoenzyme formation.
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Affiliation(s)
- Asrafun Nahar
- From the Department of Molecular, Cellular and Developmental Biology, University of Colorado Boulder, Boulder, Colorado 80309
| | - Xinyi Fu
- From the Department of Molecular, Cellular and Developmental Biology, University of Colorado Boulder, Boulder, Colorado 80309
| | - George Polovin
- From the Department of Molecular, Cellular and Developmental Biology, University of Colorado Boulder, Boulder, Colorado 80309
| | - James D Orth
- From the Department of Molecular, Cellular and Developmental Biology, University of Colorado Boulder, Boulder, Colorado 80309
| | - Soyeon Park
- From the Department of Molecular, Cellular and Developmental Biology, University of Colorado Boulder, Boulder, Colorado 80309
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23
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Ubiquitin-dependent switch during assembly of the proteasomal ATPases mediated by Not4 ubiquitin ligase. Proc Natl Acad Sci U S A 2018; 115:13246-13251. [PMID: 30530678 DOI: 10.1073/pnas.1805353115] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In the proteasome holoenzyme, the hexameric ATPases (Rpt1-Rpt6) enable degradation of ubiquitinated proteins by unfolding and translocating them into the proteolytic core particle. During early-stage proteasome assembly, individual Rpt proteins assemble into the hexameric "Rpt ring" through binding to their cognate chaperones: Nas2, Hsm3, Nas6, and Rpn14. Here, we show that Rpt ring assembly employs a specific ubiquitination-mediated control. An E3 ligase, Not4, selectively ubiquitinates Rpt5 during Rpt ring assembly. To access Rpt5, Not4 competes with Nas2 until the penultimate step and then with Hsm3 at the final step of Rpt ring completion. Using the known Rpt-chaperone cocrystal structures, we show that Not4-mediated ubiquitination sites in Rpt5 are obstructed by Nas2 and Hsm3. Thus, Not4 can distinguish a Rpt ring that matures without these chaperones, based on its accessibility to Rpt5. Rpt5 ubiquitination does not destabilize the ring but hinders incorporation of incoming subunits-Rpn1 ubiquitin receptor and Ubp6 deubiquitinase-thereby blocking progression of proteasome assembly and ubiquitin regeneration from proteasome substrates. Our findings reveal an assembly checkpoint where Not4 monitors chaperone actions during hexameric ATPase ring assembly, thereby ensuring the accuracy of proteasome holoenzyme maturation.
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24
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Zhu Y, Wang WL, Yu D, Ouyang Q, Lu Y, Mao Y. Structural mechanism for nucleotide-driven remodeling of the AAA-ATPase unfoldase in the activated human 26S proteasome. Nat Commun 2018; 9:1360. [PMID: 29636472 PMCID: PMC5893597 DOI: 10.1038/s41467-018-03785-w] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2017] [Accepted: 03/12/2018] [Indexed: 01/08/2023] Open
Abstract
The proteasome is a sophisticated ATP-dependent molecular machine responsible for protein degradation in all known eukaryotic cells. It remains elusive how conformational changes of the AAA-ATPase unfoldase in the regulatory particle (RP) control the gating of the substrate–translocation channel leading to the proteolytic chamber of the core particle (CP). Here we report three alternative states of the ATP-γ-S-bound human proteasome, in which the CP gates are asymmetrically open, visualized by cryo-EM at near-atomic resolutions. At least four nucleotides are bound to the AAA-ATPase ring in these open-gate states. Variation in nucleotide binding gives rise to an axial movement of the pore loops narrowing the substrate-translation channel, which exhibit remarkable structural transitions between the spiral-staircase and saddle-shaped-circle topologies. Gate opening in the CP is thus regulated by nucleotide-driven conformational changes of the AAA-ATPase unfoldase. These findings demonstrate an elegant mechanism of allosteric coordination among sub-machines within the human proteasome holoenzyme. The 26S proteasome consists of a core particle that is capped at each side by a regulatory particle. Here the authors present cryo-EM structures of the activated human 26S proteasome holoenzyme in three alternative open-gate states, which provides mechanistic insights into gate opening and dynamic remodeling of the substrate–translocation pathway.
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Affiliation(s)
- Yanan Zhu
- Center for Quantitative Biology, Peking University, Beijing, 100871, China.,State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Institute of Condensed Matter and Material Physics, School of Physics, Peking University, Beijing, 100871, China
| | - Wei Li Wang
- Intel Parallel Computing Center for Structural Biology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA.,Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, 02115, USA
| | - Daqi Yu
- State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Institute of Condensed Matter and Material Physics, School of Physics, Peking University, Beijing, 100871, China
| | - Qi Ouyang
- Center for Quantitative Biology, Peking University, Beijing, 100871, China.,State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Institute of Condensed Matter and Material Physics, School of Physics, Peking University, Beijing, 100871, China
| | - Ying Lu
- Department of Systems Biology, Harvard Medical School, Boston, MA, 02115, USA.
| | - Youdong Mao
- Center for Quantitative Biology, Peking University, Beijing, 100871, China. .,State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Institute of Condensed Matter and Material Physics, School of Physics, Peking University, Beijing, 100871, China. .,Intel Parallel Computing Center for Structural Biology, Dana-Farber Cancer Institute, Boston, MA, 02215, USA. .,Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA, 02115, USA.
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25
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Chen Y, Zhang Y, Guo X. Proteasome dysregulation in human cancer: implications for clinical therapies. Cancer Metastasis Rev 2018; 36:703-716. [PMID: 29039081 DOI: 10.1007/s10555-017-9704-y] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Cancer cells show heightened dependency on the proteasome for their survival, growth, and spread. Proteasome dysregulation is therefore commonly selected in favor of the development of many types of cancer. The vast abnormalities in a cancer cell, on top of the complexity of the proteasome itself, have enabled a plethora of mechanisms gearing the proteasome to the oncogenic process. Here, we use selected examples to highlight some general mechanisms underlying proteasome dysregulation in cancer, including copy number variations, transcriptional control, epigenetic regulation, and post-translational modifications. Research in this field has greatly advanced our understanding of proteasome regulation and will shed new light on proteasome-based combination therapies for cancer treatment.
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Affiliation(s)
- Yulin Chen
- Life Sciences Institute of Zhejiang University, 866 Yuhangtang Rd, Hangzhou, 310058, China
| | - Yanan Zhang
- Life Sciences Institute of Zhejiang University, 866 Yuhangtang Rd, Hangzhou, 310058, China
| | - Xing Guo
- Life Sciences Institute of Zhejiang University, 866 Yuhangtang Rd, Hangzhou, 310058, China.
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26
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Abstract
Proteasomes are complex molecular machines that consist of 66 subunits. The assembly of these complexes is highly coordinated in a process that requires at least ten proteasome-specific molecular chaperones. One of the challenges in studying assembly intermediates is their relatively low abundance as compared to the proteasome holoenzyme. Therefore, superior separating techniques are crucial for analyses of proteasomal complexes in general and studies in the assembly in particular. For this reason, native gel analyses have been abundantly used in studying proteasomes, as they provide a high resolution. Native gels are very versatile and can be used in various combinatorial approaches. In this chapter, we outline two approaches to prepare samples for native gels. The first is a yeast cryogrinding method and the second a core particle (CP)-base reconstitution approach. We describe the native gel electrophoresis, as well as various downstream analyses, including 2D native-SDS-PAGE. These techniques and approaches can all be used, often in parallel, to gain a variety of information about activity and composition of the complexes separated by native gel. The potential combined approaches are discussed in this review.
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27
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Two Distinct Regulatory Mechanisms of Transcriptional Initiation in Response to Nutrient Signaling. Genetics 2017; 208:191-205. [PMID: 29141908 DOI: 10.1534/genetics.117.300518] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 10/26/2017] [Indexed: 12/19/2022] Open
Abstract
SAGA (Spt-Ada-Gcn5-Acetyltransferase) and TFIID (transcription factor IID) have been previously shown to facilitate the formation of the PIC (pre-initiation complex) at the promoters of two distinct sets of genes. Here, we demonstrate that TFIID and SAGA differentially participate in the stimulation of PIC formation (and hence transcriptional initiation) at the promoter of PHO84, a gene for the high-affinity inorganic phosphate (Pi) transporter for crucial cellular functions, in response to nutrient signaling. We show that transcriptional initiation of PHO84 occurs predominantly in a TFIID-dependent manner in the absence of Pi in the growth medium. Such TFIID dependency is mediated via the NuA4 (nucleosome acetyltransferase of H4) histone acetyltransferase (HAT). Intriguingly, transcriptional initiation of PHO84 also occurs in the presence of Pi in the growth medium, predominantly via the SAGA complex, but independently of NuA4 HAT. Thus, Pi in the growth medium switches transcriptional initiation of PHO84 from NuA4-TFIID to SAGA dependency. Further, we find that both NuA4-TFIID- and SAGA-dependent transcriptional initiations of PHO84 are facilitated by the 19S proteasome subcomplex or regulatory particle (RP) via enhanced recruitment of the coactivators SAGA and NuA4 HAT, which promote TFIID-independent and -dependent PIC formation for transcriptional initiation, respectively. NuA4 HAT does not regulate activator binding to PHO84, but rather facilitates PIC formation for transcriptional initiation in the absence of Pi in the growth medium. On the other hand, SAGA promotes activator recruitment to PHO84 for transcriptional initiation in the growth medium containing Pi. Collectively, our results demonstrate two distinct stimulatory pathways for PIC formation (and hence transcriptional initiation) at PHO84 by TFIID, SAGA, NuA4, and 19S RP in the presence and absence of an essential nutrient, Pi, in the growth media, thus providing new regulatory mechanisms of transcriptional initiation in response to nutrient signaling.
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28
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Ferdoush J, Karmakar S, Barman P, Kaja A, Uprety B, Batra SK, Bhaumik SR. Ubiquitin–Proteasome System Regulation of an Evolutionarily Conserved RNA Polymerase II-Associated Factor 1 Involved in Pancreatic Oncogenesis. Biochemistry 2017; 56:6083-6086. [PMID: 29023102 DOI: 10.1021/acs.biochem.7b00865] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The evolutionarily conserved RNA polymerase II-associated factor 1 (Paf1) from yeast to humans regulates transcription and associated processes, and thus, malfunctions and/or misregulations of Paf1 are associated with cellular pathologies. Indeed, Paf1 (also known as PD2 or pancreatic differentiation 2) is found to be upregulated in poorly differentiated cancer cells, and such upregulation is involved in cellular transformation or oncogenesis. However, the basis for Paf1 upregulation in these cells remains largely unknown. In light of this, we have tested here the idea that the ubiquitin-proteasome system (UPS) regulates the cellular abundance of Paf1. In this direction, we analyzed the role of UPS in regulation of Paf1's abundance in yeast. We find that Paf1 undergoes ubiquitylation and is degraded by the 26S proteasome in yeast, thus deciphering UPS regulation of an evolutionarily conserved factor, Paf1, involved in various cellular processes at the crossroads of the cancer networks. Likewise, Paf1 undergoes proteasomal degradation in well-differentiated, but not poorly differentiated, pancreatic cancer cells, hence pointing to the UPS in upregulation of Paf1 in poorly differentiated cancers. Collectively, our results reveal UPS regulation of Paf1 and suggest downregulation of UPS in elevating Paf1's abundance in poorly differentiated cancers.
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Affiliation(s)
- Jannatul Ferdoush
- Department
of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901, United States
| | - Saswati Karmakar
- Department
of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska 68198, United States
| | - Priyanka Barman
- Department
of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901, United States
| | - Amala Kaja
- Department
of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901, United States
| | - Bhawana Uprety
- Department
of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901, United States
| | - Surinder K. Batra
- Department
of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska 68198, United States
| | - Sukesh R. Bhaumik
- Department
of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901, United States
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29
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Lu Y, Wu J, Dong Y, Chen S, Sun S, Ma YB, Ouyang Q, Finley D, Kirschner MW, Mao Y. Conformational Landscape of the p28-Bound Human Proteasome Regulatory Particle. Mol Cell 2017; 67:322-333.e6. [PMID: 28689658 PMCID: PMC5580496 DOI: 10.1016/j.molcel.2017.06.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 04/14/2017] [Accepted: 06/07/2017] [Indexed: 10/19/2022]
Abstract
The proteasome holoenzyme is activated by its regulatory particle (RP) consisting of two subcomplexes, the lid and the base. A key event in base assembly is the formation of a heterohexameric ring of AAA-ATPases, which is guided by at least four RP assembly chaperones in mammals: PAAF1, p28/gankyrin, p27/PSMD9, and S5b. Using cryogenic electron microscopy, we analyzed the non-AAA structure of the p28-bound human RP at 4.5 Å resolution and determined seven distinct conformations of the Rpn1-p28-AAA subcomplex within the p28-bound RP at subnanometer resolutions. Remarkably, the p28-bound AAA ring does not form a channel in the free RP and spontaneously samples multiple "open" and "closed" topologies at the Rpt2-Rpt6 and Rpt3-Rpt4 interfaces. Our analysis suggests that p28 assists the proteolytic core particle to select a specific conformation of the ATPase ring for RP engagement and is released in a shoehorn-like fashion in the last step of the chaperone-mediated proteasome assembly.
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Affiliation(s)
- Ying Lu
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Jiayi Wu
- State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Institute of Condensed Matter Physics, School of Physics, Center for Quantitative Biology, Peking University, Beijing 100871, China
| | - Yuanchen Dong
- Intel Parallel Computing Center for Structural Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Shuobing Chen
- State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Institute of Condensed Matter Physics, School of Physics, Center for Quantitative Biology, Peking University, Beijing 100871, China
| | - Shuangwu Sun
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Yong-Bei Ma
- State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Institute of Condensed Matter Physics, School of Physics, Center for Quantitative Biology, Peking University, Beijing 100871, China
| | - Qi Ouyang
- State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Institute of Condensed Matter Physics, School of Physics, Center for Quantitative Biology, Peking University, Beijing 100871, China; Peking-Tsinghua Joint Center for Life Science, Peking University, Beijing 100871, China
| | - Daniel Finley
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Marc W Kirschner
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.
| | - Youdong Mao
- State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Institute of Condensed Matter Physics, School of Physics, Center for Quantitative Biology, Peking University, Beijing 100871, China; Intel Parallel Computing Center for Structural Biology, Dana-Farber Cancer Institute, Boston, MA 02215, USA; Department of Cancer Immunology and Virology, Dana-Farber Cancer Institute, Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA.
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30
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Marquez-Lona EM, Torres-Machorro AL, Gonzales FR, Pillus L, Patrick GN. Phosphorylation of the 19S regulatory particle ATPase subunit, Rpt6, modifies susceptibility to proteotoxic stress and protein aggregation. PLoS One 2017; 12:e0179893. [PMID: 28662109 PMCID: PMC5491056 DOI: 10.1371/journal.pone.0179893] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Accepted: 06/06/2017] [Indexed: 12/22/2022] Open
Abstract
The ubiquitin proteasome system (UPS) is a highly conserved and tightly regulated biochemical pathway that degrades the majority of proteins in eukaryotic cells. Importantly, the UPS is responsible for counteracting altered protein homeostasis induced by a variety of proteotoxic stresses. We previously reported that Rpt6, the ATPase subunit of the 19S regulatory particle (RP) of the 26S proteasome, is phosphorylated in mammalian neurons at serine 120 in response to neuronal activity. Furthermore, we found that Rpt6 S120 phosphorylation, which regulates the activity and distribution of proteasomes in neurons, is relevant for proteasome-dependent synaptic remodeling and function. To better understand the role of proteasome phosphorylation, we have constructed models of altered Rpt6 phosphorylation in S. cerevisiae by introducing chromosomal point mutations that prevent or mimic phosphorylation at the conserved serine (S119). We find that mutants which prevent Rpt6 phosphorylation at this site (rpt6-S119A), had increased susceptibility to proteotoxic stress, displayed abnormal morphology and had reduced proteasome activity. Since impaired proteasome function has been linked to the aggregation of toxic proteins including the Huntington's disease (HD) related huntingtin (Htt) protein with expanded polyglutamine repeats, we evaluated the extent of Htt aggregation in our phospho-dead (rpt6-S119A) and phospho-mimetic (rpt6-S119D) mutants. We showed Htt103Q aggregate size to be significantly larger in rpt6-S119A mutants compared to wild-type or rpt6-S119D strains. Furthermore, we observed that phosphorylation of endogenous Rpt6 at S119 is increased in response to various stress conditions. Together, these data suggest that Rpt6 phosphorylation at S119 may play an important function in proteasome-dependent relief of proteotoxic stress that can be critical in protein aggregation pathologies.
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Affiliation(s)
- Esther Magdalena Marquez-Lona
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Ana Lilia Torres-Machorro
- Section of Molecular Biology and UCSD Moores Cancer Center, Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Frankie R. Gonzales
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Lorraine Pillus
- Section of Molecular Biology and UCSD Moores Cancer Center, Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Gentry N. Patrick
- Section of Neurobiology, Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
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31
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Budenholzer L, Cheng CL, Li Y, Hochstrasser M. Proteasome Structure and Assembly. J Mol Biol 2017; 429:3500-3524. [PMID: 28583440 DOI: 10.1016/j.jmb.2017.05.027] [Citation(s) in RCA: 234] [Impact Index Per Article: 33.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 05/22/2017] [Accepted: 05/30/2017] [Indexed: 10/19/2022]
Abstract
The eukaryotic 26S proteasome is a large multisubunit complex that degrades the majority of proteins in the cell under normal conditions. The 26S proteasome can be divided into two subcomplexes: the 19S regulatory particle and the 20S core particle. Most substrates are first covalently modified by ubiquitin, which then directs them to the proteasome. The function of the regulatory particle is to recognize, unfold, deubiquitylate, and translocate substrates into the core particle, which contains the proteolytic sites of the proteasome. Given the abundance and subunit complexity of the proteasome, the assembly of this ~2.5MDa complex must be carefully orchestrated to ensure its correct formation. In recent years, significant progress has been made in the understanding of proteasome assembly, structure, and function. Technical advances in cryo-electron microscopy have resulted in a series of atomic cryo-electron microscopy structures of both human and yeast 26S proteasomes. These structures have illuminated new intricacies and dynamics of the proteasome. In this review, we focus on the mechanisms of proteasome assembly, particularly in light of recent structural information.
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Affiliation(s)
- Lauren Budenholzer
- Department of Molecular Biophysics & Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06520, USA
| | - Chin Leng Cheng
- Department of Molecular Biophysics & Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06520, USA
| | - Yanjie Li
- Department of Molecular Biophysics & Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06520, USA
| | - Mark Hochstrasser
- Department of Molecular Biophysics & Biochemistry, Yale University, 266 Whitney Avenue, New Haven, CT 06520, USA.
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32
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PA28 modulates antigen processing and viral replication during coxsackievirus B3 infection. PLoS One 2017; 12:e0173259. [PMID: 28278207 PMCID: PMC5344377 DOI: 10.1371/journal.pone.0173259] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 02/17/2017] [Indexed: 11/19/2022] Open
Abstract
The function of the proteasome is modulated at the level of subunit expression and by association with its regulatory complexes. During coxsackievirus B3 (CVB3) myocarditis, IFN-induced formation of immunoproteasomes (ip) is known to be critical for regulating immune modulating molecules. The function of the IFN-γ-inducible proteasome regulator subunits PA28 α and β, however, in this context was unknown. During viral myocarditis, we found an increased abundance of PA28β subunits in heart tissue. PA28α/β exists in PA28-20S-PA28 and PA700-20S-PA28 hybrid proteasome complexes in cells both with either predominant ip and standard proteasome (sp) expression. Being in line with reduced proteasome activity in PA28α/β-deficient cells, we observed increased levels of oxidized and poly-ubiquitinated proteins upon TLR3-activation in these cells. Moreover, PA28α/β is capable to interfere directly with viral replication of CVB3 and facilitates the generation of CVB3-derived MHC class I epitopes by the proteasome. In contrast to a distinct function of PA28α/β in vitro, gene ablation of PA28α/β in mice being on a genetic background with resistance towards the development of severe infection had no significant impact on disease progression. Other than reported for the ip, in this host PA28α/β is dispensable to meet the demand of increased peptide hydrolysis capacity by the proteasome during viral myocarditis.
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33
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Guo X, Huang X, Chen MJ. Reversible phosphorylation of the 26S proteasome. Protein Cell 2017; 8:255-272. [PMID: 28258412 PMCID: PMC5359188 DOI: 10.1007/s13238-017-0382-x] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 01/26/2017] [Indexed: 01/09/2023] Open
Abstract
The 26S proteasome at the center of the ubiquitin-proteasome system (UPS) is essential for virtually all cellular processes of eukaryotes. A common misconception about the proteasome is that, once made, it remains as a static and uniform complex with spontaneous and constitutive activity for protein degradation. Recent discoveries have provided compelling evidence to support the exact opposite insomuch as the 26S proteasome undergoes dynamic and reversible phosphorylation under a variety of physiopathological conditions. In this review, we summarize the history and current understanding of proteasome phosphorylation, and advocate the idea of targeting proteasome kinases/phosphatases as a new strategy for clinical interventions of several human diseases.
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Affiliation(s)
- Xing Guo
- The Life Sciences Institute of Zhejiang University, Hangzhou, 310058, China.
| | - Xiuliang Huang
- Ministry of Education Key Laboratory of Protein Science, School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Mark J Chen
- Department of Bioinformatics and Computational Biology, Genentech Inc., South San Francisco, CA, 94080, USA
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34
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Howell LA, Tomko RJ, Kusmierczyk AR. Putting it all together: intrinsic and extrinsic mechanisms governing proteasome biogenesis. ACTA ACUST UNITED AC 2017. [DOI: 10.1007/s11515-017-1439-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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35
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Nucleotide-dependent switch in proteasome assembly mediated by the Nas6 chaperone. Proc Natl Acad Sci U S A 2017; 114:1548-1553. [PMID: 28137839 DOI: 10.1073/pnas.1612922114] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The proteasome is assembled via the nine-subunit lid, nine-subunit base, and 28-subunit core particle (CP). Previous work has shown that the chaperones Rpn14, Nas6, Hsm3, and Nas2 each bind a specific ATPase subunit of the base and antagonize base-CP interaction. Here, we show that the Nas6 chaperone also obstructs base-lid association. Nas6 alternates between these two inhibitory modes according to the nucleotide state of the base. When ATP cannot be hydrolyzed, Nas6 interferes with base-lid, but not base-CP, association. In contrast, under conditions of ATP hydrolysis, Nas6 obstructs base-CP, but not base-lid, association. Modeling of Nas6 into cryoelectron microscopy structures of the proteasome suggests that Nas6 controls both base-lid affinity and base-CP affinity through steric hindrance; Nas6 clashes with the lid in the ATP-hydrolysis-blocked proteasome, but clashes instead with the CP in the ATP-hydrolysis-competent proteasome. Thus, Nas6 provides a dual mechanism to control assembly at both major interfaces of the proteasome.
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36
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Im E, Chung KC. Precise assembly and regulation of 26S proteasome and correlation between proteasome dysfunction and neurodegenerative diseases. BMB Rep 2017; 49:459-73. [PMID: 27312603 PMCID: PMC5227139 DOI: 10.5483/bmbrep.2016.49.9.094] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Indexed: 11/20/2022] Open
Abstract
Neurodegenerative diseases (NDs) often involve the formation of abnormal and toxic protein aggregates, which are thought to be the primary factor in ND occurrence and progression. Aged neurons exhibit marked increases in aggregated protein levels, which can lead to increased cell death in specific brain regions. As no specific drugs/therapies for treating the symptoms or/and progression of NDs are available, obtaining a complete understanding of the mechanism underlying the formation of protein aggregates is needed for designing a novel and efficient removal strategy. Intracellular proteolysis generally involves either the lysosomal or ubiquitin-proteasome system. In this review, we focus on the structure and assembly of the proteasome, proteasome-mediated protein degradation, and the multiple dynamic regulatory mechanisms governing proteasome activity. We also discuss the plausibility of the correlation between changes in proteasome activity and the occurrence of NDs. [BMB Reports 2016; 49(9): 459-473]
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Affiliation(s)
- Eunju Im
- Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, Korea
| | - Kwang Chul Chung
- Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, Seoul 03722, Korea
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37
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Abstract
Protein complexes form the critical foundation for a wide range of biological process, however understanding the intricate details of their activities is often challenging. In this review we describe how mass spectrometry plays a key role in the analysis of protein assemblies and the cellular pathways which they are involved in. Specifically, we discuss how the versatility of mass spectrometric approaches provides unprecedented information on multiple levels. We demonstrate this on the ubiquitin-proteasome proteolytic pathway, a process that is responsible for protein turnover. We follow the various steps of this degradation route and illustrate the different mass spectrometry workflows that were applied for elucidating molecular information. Overall, this review aims to stimulate the integrated use of multiple mass spectrometry approaches for analyzing complex biological systems.
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38
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Boland K, Flanagan L, McCawley N, Pabari R, Kay EW, McNamara DA, Murray F, Byrne AT, Ramtoola Z, Concannon CG, Prehn JHM. Targeting the 19S proteasomal subunit, Rpt4, for the treatment of colon cancer. Eur J Pharmacol 2016; 780:53-64. [PMID: 26997367 DOI: 10.1016/j.ejphar.2016.03.031] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 03/15/2016] [Accepted: 03/16/2016] [Indexed: 11/20/2022]
Abstract
Deregulation of the ubiquitin-proteasome pathway has been frequently observed in a number of malignancies. Using quantitative Western blotting of normal and matched tumour tissue, we here identified a significant increase in the 19S proteasome subunit Rpt4 in response to chemoradiation in locally advanced rectal cancer patients with unfavourable outcome. We therefore explored the potential of Rpt4 reduction as a therapeutic strategy in colorectal cancer (CRC). Utilizing siRNA to down regulate Rpt4 expression, we show that silencing of Rpt4 reduced proteasomal activity and induced endoplasmic reticulum stress. Gene silencing of Rpt4 also inhibited cell proliferation, reduced clonogenic survival and induced apoptosis in HCT-116 colon cancer cells. We next developed a cell penetrating peptide-based nanoparticle delivery system to achieve in vivo gene silencing of Rpt4. Administration of Rpt4 siRNA nanoparticles reduced tumour growth and improved survival in a HCT-116 colon cancer xenograft tumour model in vivo. Collectively, our data suggest that inhibition of Rpt4 represents a novel strategy for the treatment of CRC.
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Affiliation(s)
- Karen Boland
- Centre for Systems Medicine and Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland; Department of Gastroenterology, Beaumont Hospital, Beaumont, Dublin 9, Ireland
| | - Lorna Flanagan
- Centre for Systems Medicine and Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland
| | - Niamh McCawley
- Centre for Systems Medicine and Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland; Department of Surgery, Beaumont Hospital, Beaumont, Dublin 9, Ireland
| | - Ritesh Pabari
- School of Pharmacy, Royal College of Surgeons in Ireland, York House, York Street, Dublin 2, Ireland
| | - Elaine W Kay
- Department of Pathology, Beaumont Hospital, Beaumont, Dublin 9, Ireland
| | | | - Frank Murray
- Department of Gastroenterology, Beaumont Hospital, Beaumont, Dublin 9, Ireland
| | - Annette T Byrne
- Centre for Systems Medicine and Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland
| | - Zebunnissa Ramtoola
- School of Pharmacy, Royal College of Surgeons in Ireland, York House, York Street, Dublin 2, Ireland
| | - Caoimhín G Concannon
- Centre for Systems Medicine and Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland
| | - Jochen H M Prehn
- Centre for Systems Medicine and Department of Physiology and Medical Physics, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland.
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39
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Proteasome Activation is Mediated via a Functional Switch of the Rpt6 C-terminal Tail Following Chaperone-dependent Assembly. Sci Rep 2015; 5:14909. [PMID: 26449534 PMCID: PMC4598862 DOI: 10.1038/srep14909] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Accepted: 09/11/2015] [Indexed: 11/18/2022] Open
Abstract
In the proteasome, the proteolytic 20S core particle (CP) associates with the 19S regulatory particle (RP) to degrade polyubiquitinated proteins. Six ATPases (Rpt1-Rpt6) of the RP form a hexameric Rpt ring and interact with the heptameric α ring (α1–α7) of the CP via the Rpt C-terminal tails individually binding to the α subunits. Importantly, the Rpt6 tail has been suggested to be crucial for RP assembly. Here, we show that the interaction of the CP and Rpt6 tail promotes a CP-Rpt3 tail interaction, and that they jointly mediate proteasome activation via opening the CP gate for substrate entry. The Rpt6 tail forms a novel relationship with the Nas6 chaperone, which binds to Rpt3 and regulates the CP-Rpt3 tail interaction, critically influencing cell growth and turnover of polyubiquitinated proteins. CP-Rpt6 tail binding promotes the release of Nas6 from the proteasome. Based on disulfide crosslinking that detects cognate α3-Rpt6 tail and α2-Rpt3 tail interactions in the proteasome, decreased α3-Rpt6 tail interaction facilitates robust α2-Rpt3 tail interaction that is also strongly ATP-dependent. Together, our data support the reported role of Rpt6 during proteasome assembly, and suggest that its function switches from anchoring for RP assembly into promoting Rpt3-dependent activation of the mature proteasome.
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40
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Alpha-ring Independent Assembly of the 20S Proteasome. Sci Rep 2015; 5:13130. [PMID: 26286114 PMCID: PMC4541365 DOI: 10.1038/srep13130] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 07/20/2015] [Indexed: 12/17/2022] Open
Abstract
Archaeal proteasomes share many features with their eukaryotic counterparts and serve as important models for assembly. Proteasomes are also found in certain bacterial lineages yet their assembly mechanism is thought to be fundamentally different. Here we investigate α-ring formation using recombinant proteasomes from the archaeon Methanococcus maripaludis. Through an engineered disulfide cross-linking strategy, we demonstrate that double α-rings are structurally analogous to half-proteasomes and can form independently of single α-rings. More importantly, via targeted mutagenesis, we show that single α-rings are not required for the efficient assembly of 20S proteasomes. Our data support updating the currently held "α-ring first" view of assembly, initially proposed in studies of archaeal proteasomes, and present a way to reconcile the seemingly separate bacterial assembly mechanism with the rest of the proteasome realm. We suggest that a common assembly network underpins the absolutely conserved architecture of proteasomes across all domains of life.
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41
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Abstract
The ubiquitin-proteasome system is the major degradation pathway for short-lived proteins in eukaryotic cells. Targets of the ubiquitin-proteasome-system are proteins regulating a broad range of cellular processes including cell cycle progression, gene expression, the quality control of proteostasis and the response to geno- and proteotoxic stress. Prior to degradation, the proteasomal substrate is marked with a poly-ubiquitin chain. The key protease of the ubiquitin system is the proteasome. In dividing cells, proteasomes exist as holo-enzymes composed of regulatory and core particles. The regulatory complex confers ubiquitin-recognition and ATP dependence on proteasomal protein degradation. The catalytic sites are located in the proteasome core particle. Proteasome holo-enzymes are predominantly nuclear suggesting a major requirement for proteasomal proteolysis in the nucleus. In cell cycle arrested mammalian or quiescent yeast cells, proteasomes deplete from the nucleus and accumulate in granules at the nuclear envelope (NE) / endoplasmic reticulum ( ER) membranes. In prolonged quiescence, proteasome granules drop off the nuclear envelopeNE / ER membranes and migrate as droplet-like entitiesstable organelles throughout the cytoplasm, as thoroughly investigated in yeast. When quiescence yeast cells are allowed to resume growth, proteasome granules clear and proteasomes are rapidly imported into the nucleus. Here, we summarize our knowledge about the enigmatic structure of proteasome storage granules and the trafficking of proteasomes and their substrates between the cyto- and nucleoplasm. Most of our current knowledge is based on studies in yeast. Their translation to mammalian cells promises to provide keen insight into protein degradation in non-dividing cells, which comprise the majority of our body’s cells.
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Affiliation(s)
- Maisha Chowdhury
- Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Cordula Enenkel
- Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada
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42
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Abstract
The ubiquitin-proteasome system is the major degradation pathway for short-lived proteins in eukaryotic cells. Targets of the ubiquitin-proteasome-system are proteins regulating a broad range of cellular processes including cell cycle progression, gene expression, the quality control of proteostasis and the response to geno- and proteotoxic stress. Prior to degradation, the proteasomal substrate is marked with a poly-ubiquitin chain. The key protease of the ubiquitin system is the proteasome. In dividing cells, proteasomes exist as holo-enzymes composed of regulatory and core particles. The regulatory complex confers ubiquitin-recognition and ATP dependence on proteasomal protein degradation. The catalytic sites are located in the proteasome core particle. Proteasome holo-enzymes are predominantly nuclear suggesting a major requirement for proteasomal proteolysis in the nucleus. In cell cycle arrested mammalian or quiescent yeast cells, proteasomes deplete from the nucleus and accumulate in granules at the nuclear envelope (NE) / endoplasmic reticulum ( ER) membranes. In prolonged quiescence, proteasome granules drop off the nuclear envelopeNE / ER membranes and migrate as droplet-like entitiesstable organelles throughout the cytoplasm, as thoroughly investigated in yeast. When quiescence yeast cells are allowed to resume growth, proteasome granules clear and proteasomes are rapidly imported into the nucleus. Here, we summarize our knowledge about the enigmatic structure of proteasome storage granules and the trafficking of proteasomes and their substrates between the cyto- and nucleoplasm. Most of our current knowledge is based on studies in yeast. Their translation to mammalian cells promises to provide keen insight into protein degradation in non-dividing cells, which comprise the majority of our body's cells.
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Affiliation(s)
- Maisha Chowdhury
- Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Cordula Enenkel
- Department of Biochemistry, University of Toronto, Toronto, ON, M5S 1A8, Canada
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43
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Wani PS, Rowland MA, Ondracek A, Deeds EJ, Roelofs J. Maturation of the proteasome core particle induces an affinity switch that controls regulatory particle association. Nat Commun 2015; 6:6384. [PMID: 25812915 PMCID: PMC4380239 DOI: 10.1038/ncomms7384] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 01/25/2015] [Indexed: 01/09/2023] Open
Abstract
Proteasome assembly is a complex process, requiring 66 subunits distributed over several subcomplexes to associate in a coordinated fashion. Ten proteasome-specific chaperones have been identified that assist in this process. For two of these, the Pba1-Pba2 dimer, it is well established that they only bind immature core particles (CP) in vivo. In contrast, the regulatory particle (RP) utilizes the same binding surface but only interacts with the mature CP in vivo. It is unclear how these binding events are regulated. Here, we show that Pba1-Pba2 binds tightly to immature CP, preventing RP binding. Changes in the CP that occur upon maturation significantly reduce its affinity for Pba1-Pba2, enabling the RP to displace the chaperone. Mathematical modeling indicates that this “affinity switch” mechanism has likely evolved to improve assembly efficiency by preventing the accumulation of stable, non-productive intermediates. Our work thus provides mechanistic insights into a crucial step in proteasome biogenesis.
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Affiliation(s)
- Prashant S Wani
- Graduate Biochemistry Group, Department of Biochemistry and Molecular Biophysics, Kansas State University, 336 Ackert Hall, Manhattan, Kansas 66506, USA
| | - Michael A Rowland
- Center for Computational Biology, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047, USA
| | - Alex Ondracek
- Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, 338 Ackert Hall, Manhattan, Kansas 66506, USA
| | - Eric J Deeds
- 1] Center for Computational Biology, University of Kansas, 2030 Becker Drive, Lawrence, Kansas 66047, USA [2] Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66047, USA [3] Santa Fe Institute, Santa Fe, New Mexico 87501, USA
| | - Jeroen Roelofs
- 1] Graduate Biochemistry Group, Department of Biochemistry and Molecular Biophysics, Kansas State University, 336 Ackert Hall, Manhattan, Kansas 66506, USA [2] Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, 338 Ackert Hall, Manhattan, Kansas 66506, USA
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Shirozu R, Yashiroda H, Murata S. Identification of minimum Rpn4-responsive elements in genes related to proteasome functions. FEBS Lett 2015; 589:933-40. [PMID: 25747386 DOI: 10.1016/j.febslet.2015.02.025] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 02/23/2015] [Accepted: 02/24/2015] [Indexed: 12/29/2022]
Abstract
The proteasome is an essential, 66-subunit protease that mediates ubiquitin-dependent proteolysis. The transcription factor Rpn4 regulates concerted expression of proteasome subunits to increase the proteasome by recognizing nonamer proteasome-associated control element (PACE) elements on the promoter regions. However, the genes for proteasome assembly chaperones and some of the subunits have no PACEs. Here we identified a minimal hexamer "PACE-core" sequence that responds to Rpn4. PACE-cores are found in many genes related to proteasome function including the assembly chaperones, but cannot substitute for PACE of the subunits. Our results add a new layer of complexity in transcriptional regulation of genes involved in protein degradation.
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Affiliation(s)
- Ryohei Shirozu
- Laboratory of Protein Metabolism, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
| | - Hideki Yashiroda
- Laboratory of Protein Metabolism, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan
| | - Shigeo Murata
- Laboratory of Protein Metabolism, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo 113-0033, Japan.
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45
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Base-CP proteasome can serve as a platform for stepwise lid formation. Biosci Rep 2015; 35:BSR20140173. [PMID: 26182356 PMCID: PMC4438304 DOI: 10.1042/bsr20140173] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Accepted: 01/26/2015] [Indexed: 12/14/2022] Open
Abstract
26S proteasome, a major regulatory protease in eukaryotes, consists of a 20S proteolytic core particle (CP) capped by a 19S regulatory particle (RP). The 19S RP is divisible into base and lid sub-complexes. Even within the lid, subunits have been demarcated into two modules: module 1 (Rpn5, Rpn6, Rpn8, Rpn9 and Rpn11), which interacts with both CP and base sub-complexes and module 2 (Rpn3, Rpn7, Rpn12 and Rpn15) that is attached mainly to module 1. We now show that suppression of RPN11 expression halted lid assembly yet enabled the base and 20S CP to pre-assemble and form a base-CP. A key role for Regulatory particle non-ATPase 11 (Rpn11) in bridging lid module 1 and module 2 subunits together is inferred from observing defective proteasomes in rpn11–m1, a mutant expressing a truncated form of Rpn11 and displaying mitochondrial phenotypes. An incomplete lid made up of five module 1 subunits attached to base-CP was identified in proteasomes isolated from this mutant. Re-introducing the C-terminal portion of Rpn11 enabled recruitment of missing module 2 subunits. In vitro, module 1 was reconstituted stepwise, initiated by Rpn11–Rpn8 heterodimerization. Upon recruitment of Rpn6, the module 1 intermediate was competent to lock into base-CP and reconstitute an incomplete 26S proteasome. Thus, base-CP can serve as a platform for gradual incorporation of lid, along a proteasome assembly pathway. Identification of proteasome intermediates and reconstitution of minimal functional units should clarify aspects of the inner workings of this machine and how multiple catalytic processes are synchronized within the 26S proteasome holoenzymes. Defective proteasome 19S regulatory particles (RPs) were identified in rpn11f–m1, a proteasomal mutant with mitochondrial phenotypes. The Rpn11 subunit initiates assembly of a five-subunit lid module competent to integrate into pre-assembled base-20S core particle (CP), with subsequent recruitment of remaining lid subunits.
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46
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Gu ZC, Enenkel C. Proteasome assembly. Cell Mol Life Sci 2014; 71:4729-45. [PMID: 25107634 PMCID: PMC11113775 DOI: 10.1007/s00018-014-1699-8] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Revised: 07/30/2014] [Accepted: 07/31/2014] [Indexed: 10/24/2022]
Abstract
In eukaryotic cells, proteasomes are highly conserved protease complexes and eliminate unwanted proteins which are marked by poly-ubiquitin chains for degradation. The 26S proteasome consists of the proteolytic core particle, the 20S proteasome, and the 19S regulatory particle, which are composed of 14 and 19 different subunits, respectively. Proteasomes are the second-most abundant protein complexes and are continuously assembled from inactive precursor complexes in proliferating cells. The modular concept of proteasome assembly was recognized in prokaryotic ancestors and applies to eukaryotic successors. The efficiency and fidelity of eukaryotic proteasome assembly is achieved by several proteasome-dedicated chaperones that initiate subunit incorporation and control the quality of proteasome assemblies by transiently interacting with proteasome precursors. It is important to understand the mechanism of proteasome assembly as the proteasome has key functions in the turnover of short-lived proteins regulating diverse biological processes.
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Affiliation(s)
- Zhu Chao Gu
- Department of Biochemistry, University of Toronto, Medical Sciences Building, 1 King’s College Circle, Toronto, ON M5S 1A8 Canada
| | - Cordula Enenkel
- Department of Biochemistry, University of Toronto, Medical Sciences Building, 1 King’s College Circle, Toronto, ON M5S 1A8 Canada
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47
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Wang Y, Sun H, Du W, Blanzieri E, Viero G, Xu Y, Liang Y. Identification of essential proteins based on ranking edge-weights in protein-protein interaction networks. PLoS One 2014; 9:e108716. [PMID: 25268881 PMCID: PMC4182551 DOI: 10.1371/journal.pone.0108716] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 09/03/2014] [Indexed: 12/02/2022] Open
Abstract
Essential proteins are those that are indispensable to cellular survival and development. Existing methods for essential protein identification generally rely on knock-out experiments and/or the relative density of their interactions (edges) with other proteins in a Protein-Protein Interaction (PPI) network. Here, we present a computational method, called EW, to first rank protein-protein interactions in terms of their Edge Weights, and then identify sub-PPI-networks consisting of only the highly-ranked edges and predict their proteins as essential proteins. We have applied this method to publicly-available PPI data on Saccharomyces cerevisiae (Yeast) and Escherichia coli (E. coli) for essential protein identification, and demonstrated that EW achieves better performance than the state-of-the-art methods in terms of the precision-recall and Jackknife measures. The highly-ranked protein-protein interactions by our prediction tend to be biologically significant in both the Yeast and E. coli PPI networks. Further analyses on systematically perturbed Yeast and E. coli PPI networks through randomly deleting edges demonstrate that the proposed method is robust and the top-ranked edges tend to be more associated with known essential proteins than the lowly-ranked edges.
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Affiliation(s)
- Yan Wang
- Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, College of Computer Science and Technology, Jilin University, Changchun, China
- Department of Information and Communication Technology, University of Trento, Povo, Italy
- Computational Systems Biology Lab, Department of Biochemistry and Molecular Biology and Institute of Bioinformatics, University of Georgia, Athens, GA, United States of America
| | - Huiyan Sun
- Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, College of Computer Science and Technology, Jilin University, Changchun, China
| | - Wei Du
- Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, College of Computer Science and Technology, Jilin University, Changchun, China
| | - Enrico Blanzieri
- Department of Information and Communication Technology, University of Trento, Povo, Italy
- * E-mail: (YCL); (EB)
| | - Gabriella Viero
- Institute of Biophysics, National Research Council, University of Trento, Povo, Italy
| | - Ying Xu
- Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, College of Computer Science and Technology, Jilin University, Changchun, China
- Computational Systems Biology Lab, Department of Biochemistry and Molecular Biology and Institute of Bioinformatics, University of Georgia, Athens, GA, United States of America
| | - Yanchun Liang
- Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education, College of Computer Science and Technology, Jilin University, Changchun, China
- * E-mail: (YCL); (EB)
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48
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Lu X, Li X, Guo K, Wang J, Huang M, Wang JL, Xie TZ, Moorefield CN, Cheng SZD, Wesdemiotis C, Newkome GR. One ligand in dual roles: self-assembly of a bis-rhomboidal-shaped, three-dimensional molecular wheel. Chemistry 2014; 20:13094-8. [PMID: 25155653 DOI: 10.1002/chem.201404358] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Indexed: 12/22/2022]
Abstract
A facile high yield, self-assembly process that leads to a terpyridine-based, three-dimensional, bis-rhomboidal-shaped, molecular wheel is reported. The desired coordination-driven supramolecular wheel involves eight structurally distorted tristerpyridine (tpy) ligands possessing a 60° angle between the adjacent tpy units and twelve Zn(2+) ions. The tpy ligand plays dual roles in the self-assembly process: two are staggered at 180° to create the internal hub, while six produce the external rim. The wheel can be readily generated by mixing the tpy ligand and Zn(2+) in a stoichiometric ratio of 2:3; full characterization is provided by ESI-MS, NMR spectroscopy, and TEM imaging.
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Affiliation(s)
- Xiaocun Lu
- Department of Polymer Science, Department of Chemistry, The University of Akron, 302 Buchtel Common, Akron, OH 44325 (USA) http://www.dendrimers.com
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49
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Abstract
The 26S proteasome is responsible for most regulated protein turnover and for the degradation of aberrant proteins in eukaryotes. The assembly of this ~2.5 MDa multicatalytic protease requires several dedicated chaperones and, once assembled, substrate selectivity is mediated by ubiquitin conjugation. After modification with ubiquitin, substrates are escorted to the proteasome by myriad factors, including Cdc48 (cell-division cycle 48). Cdc48 also associates with numerous cofactors, but, to date, it is unclear whether each cofactor facilitates proteasome delivery. We discovered that yeast lacking a conserved Cdc48 cofactor, Vms1 [VCP (valosin-containing protein)/Cdc48-associated mitochondrial stress-responsive], accumulate proteasome-targeted ubiquitinated proteins. Vms1 mutant cells also contain elevated levels of unassembled 20S proteasome core particles and select 19S cap subunits. In addition, we found that the ability of Vms1 to support 26S proteasome assembly requires Cdc48 interaction, and that the loss of Vms1 reduced 26S proteasome levels and cell viability after prolonged culture in the stationary phase. The results of the present study highlight an unexpected link between the Cdc48-Vms1 complex and the preservation of proteasome architecture, and indicate how perturbed proteasome assembly affects the turnover of ubiquitinated proteins and maintains viability in aging cells.
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50
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Pack CG, Yukii H, Toh-e A, Kudo T, Tsuchiya H, Kaiho A, Sakata E, Murata S, Yokosawa H, Sako Y, Baumeister W, Tanaka K, Saeki Y. Quantitative live-cell imaging reveals spatio-temporal dynamics and cytoplasmic assembly of the 26S proteasome. Nat Commun 2014; 5:3396. [PMID: 24598877 DOI: 10.1038/ncomms4396] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Accepted: 02/06/2014] [Indexed: 01/15/2023] Open
Abstract
The 26S proteasome is a 2.5-MDa multisubunit protease complex that degrades polyubiquitylated proteins. Although its functions and structure have been extensively characterized, little is known about its dynamics in living cells. Here, we investigate the absolute concentration, spatio-temporal dynamics and complex formation of the proteasome in living cells using fluorescence correlation spectroscopy. We find that the 26S proteasome complex is highly mobile, and that almost all proteasome subunits throughout the cell are stably incorporated into 26S proteasomes. The interaction between 19S and 20S particles is stable even in an importin-α mutant, suggesting that the 26S proteasome is assembled in the cytoplasm. Furthermore, a genetically stabilized 26S proteasome mutant is able to enter the nucleus. These results suggest that the 26S proteasome completes its assembly process in the cytoplasm and translocates into the nucleus through the nuclear pore complex as a holoenzyme.
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Affiliation(s)
- Chan-Gi Pack
- Cellular Informatics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Haruka Yukii
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
| | - Akio Toh-e
- Medical Mycology Center, Chiba University, 1-8-1 Inohana, Chiba 260-8673, Japan
| | - Tai Kudo
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
| | - Hikaru Tsuchiya
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
| | - Ai Kaiho
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
| | - Eri Sakata
- Department of Molecular Structural Biology, Max-Planck-Institute of Biochemistry, 82152 Martinsried, Germany
| | - Shigeo Murata
- Laboratory of Protein Metabolism, Graduate School of Pharmaceutical Sciences, the University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Hideyoshi Yokosawa
- Department of Medicinal Biochemistry, School of Pharmacy, Aichi Gakuin University, 1-100 Kusumoto-cho, Chikusa-ku, Nagoya 464-8650, Japan
| | - Yasushi Sako
- Cellular Informatics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Wolfgang Baumeister
- Department of Molecular Structural Biology, Max-Planck-Institute of Biochemistry, 82152 Martinsried, Germany
| | - Keiji Tanaka
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
| | - Yasushi Saeki
- Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, Setagaya-ku, Tokyo 156-8506, Japan
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