1
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Müller L, Hoppe T. UPS-dependent strategies of protein quality control degradation. Trends Biochem Sci 2024:S0968-0004(24)00149-X. [PMID: 38945729 DOI: 10.1016/j.tibs.2024.06.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Revised: 05/29/2024] [Accepted: 06/10/2024] [Indexed: 07/02/2024]
Abstract
The degradation of damaged proteins is critical for tissue integrity and organismal health because damaged proteins have a high propensity to form aggregates. E3 ubiquitin ligases are key regulators of protein quality control (PQC) and mediate the selective degradation of damaged proteins, a process termed 'PQC degradation' (PQCD). The degradation signals (degrons) that trigger PQCD are based on hydrophobic sites that are normally buried within the native protein structure. However, an open question is how PQCD-specialized E3 ligases distinguish between transiently misfolded proteins, which can be efficiently refolded, and permanently damaged proteins, which must be degraded. While significant progress has been made in characterizing degradation determinants, understanding the key regulatory signals of cellular and organismal PQCD pathways remains a challenge.
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Affiliation(s)
- Leonie Müller
- Institute for Genetics, University of Cologne, 50674 Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital of Cologne, 50931 Cologne, Germany
| | - Thorsten Hoppe
- Institute for Genetics, University of Cologne, 50674 Cologne, Germany; Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, 50931 Cologne, Germany; Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital of Cologne, 50931 Cologne, Germany.
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2
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Le LTHL, Park S, Lee JH, Kim YK, Lee MJ. N-recognins UBR1 and UBR2 as central ER stress sensors in mammals. Mol Cells 2024; 47:100001. [PMID: 38376480 PMCID: PMC10880078 DOI: 10.1016/j.mocell.2023.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 11/22/2023] [Accepted: 11/22/2023] [Indexed: 02/21/2024] Open
Abstract
In eukaryotes, a primary protein quality control (PQC) process involves the destruction of conformationally misfolded proteins through the ubiquitin-proteasome system. Because approximately one-third of eukaryotic proteomes fold and assemble within the endoplasmic reticulum (ER) before being sent to their destinations, the ER plays a crucial role in PQC. The specific functions and biochemical roles of several E3 ubiquitin ligases involved in ER-associated degradation in mammals, on the other hand, are mainly unknown. We identified 2 E3 ligases, ubiquitin protein ligase E3 component N-recognin 1 (UBR1) and ubiquitin protein ligase E3 component N-recognin 2 (UBR2), which are the key N-recognins in the N-degron pathway and participate in the ER stress response in mammalian cells by modulating their stability. Cells lacking UBR1 and UBR2 are hypersensitive to ER stress-induced apoptosis. Under normal circumstances, these proteins are polyubiquitinated through Lys48-specific linkages and are then degraded by the 26S proteasome. In contrast, when cells are subjected to ER stress, UBR1 and UBR2 exhibit greater stability, potentially as a cellular adaptive response to stressful conditions. Although the precise mechanisms underlying these findings require further investigation, our findings show that cytoplasmic UBR1 and UBR2 have anti-ER stress activities and contribute to global PQC in mammals. These data also reveal an additional level of complexity within the mammalian ER-associated degradation system, implicating potential involvement of the N-degron pathway.
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Affiliation(s)
- Ly Thi Huong Luu Le
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul 03080, Korea; Department of Biomedical Sciences, Seoul National University Graduate School, Seoul 03080, Korea
| | - Seoyoung Park
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul 03080, Korea; Inspharmtech Inc., Seoul 08511, Korea
| | - Jung Hoon Lee
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Yun Kyung Kim
- Center for Brain Disorders, Brain Science Institute, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea
| | - Min Jae Lee
- Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul 03080, Korea; Department of Biomedical Sciences, Seoul National University Graduate School, Seoul 03080, Korea; Ischemic/Hypoxic Disease Institute, Convergence Research Center for Dementia, Seoul National University College of Medicine, Seoul 03080, Korea.
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3
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Mehrtash AB, Hochstrasser M. Elements of the ERAD ubiquitin ligase Doa10 regulating sequential poly-ubiquitylation of its targets. iScience 2022; 25:105351. [PMID: 36325070 PMCID: PMC9619350 DOI: 10.1016/j.isci.2022.105351] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 08/16/2022] [Accepted: 10/11/2022] [Indexed: 11/29/2022] Open
Abstract
In ER-associated degradation (ERAD), misfolded ER proteins are degraded by the proteasome after undergoing ubiquitylation. Yeast Doa10 (human MARCHF6/TEB4) is a membrane-embedded E3 ubiquitin ligase that functions with E2s Ubc6 and Ubc7. Ubc6 attaches a single ubiquitin to substrates, which is extended by Ubc7 to form a polyubiquitin chain. We show the conserved C-terminal element (CTE) of Doa10 promotes E3-mediated Ubc6 activity. Doa10 substrates undergoing an alternative ubiquitylation mechanism are still degraded in CTE-mutant cells. Structure prediction by AlphaFold2 suggests the CTE binds near the catalytic RING-CH domain, implying a direct role in substrate ubiquitylation, and we confirm this interaction using intragenic suppression. Truncation analysis defines a minimal E2-binding region of Doa10; structural predictions suggest that Doa10 forms a retrotranslocation channel and that E2s bind within the cofactor-binding region defined here. These results provide mechanistic insight into how Doa10, and potentially other ligases, interact with their cofactors and mediate ERAD. The conserved Doa10 C-terminus promotes E3-mediated activity of Ubc6 The minimal E2-binding region of Doa10 includes TMs 1–9 The N- and C-terminus of Doa10 interact, likely forming an ERAD protein channel
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Affiliation(s)
- Adrian B. Mehrtash
- Department of Molecular, Cellular, & Developmental Biology, Yale University, New Haven, 06520 CT, USA
| | - Mark Hochstrasser
- Department of Molecular, Cellular, & Developmental Biology, Yale University, New Haven, 06520 CT, USA
- Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT 06520, USA
- Corresponding author
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4
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Nguyen KT, Ju S, Kim SY, Lee CS, Lee C, Hwang CS. N-Terminal Modifications of Ubiquitin via Methionine Excision, Deamination, and Arginylation Expand the Ubiquitin Code. Mol Cells 2022; 45:158-167. [PMID: 35253655 PMCID: PMC8926867 DOI: 10.14348/molcells.2022.2027] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 12/16/2021] [Accepted: 01/12/2022] [Indexed: 11/27/2022] Open
Abstract
Ubiquitin (Ub) is post-translationally modified by Ub itself or Ub-like proteins, phosphorylation, and acetylation, among others, which elicits a variety of Ub topologies and cellular functions. However, N-terminal (Nt) modifications of Ub remain unknown, except the linear head-to-tail ubiquitylation via Nt-Met. Here, using the yeast Saccharomyces cerevisiae and an Nt-arginylated Ub-specific antibody, we found that the detectable level of Ub undergoes Nt-Met excision, Nt-deamination, and Nt-arginylation. The resulting Nt-arginylated Ub and its conjugated proteins are upregulated in the stationary-growth phase or by oxidative stress. We further proved the existence of Nt-arginylated Ub in vivo and identified Nt-arginylated Ub-protein conjugates using stable isotope labeling by amino acids in cell culture (SILAC)-based tandem mass spectrometry. In silico structural modeling of Nt-arginylated Ub predicted that Nt-Arg flexibly protrudes from the surface of the Ub, thereby most likely providing a docking site for the factors that recognize it. Collectively, these results reveal unprecedented Nt-arginylated Ub and the pathway by which it is produced, which greatly expands the known complexity of the Ub code.
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Affiliation(s)
- Kha The Nguyen
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Shinyeong Ju
- Center for Theragnosis, Korea Institute of Science and Technology, Seoul 02792, Korea
| | - Sang-Yoon Kim
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Chang-Seok Lee
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, Korea
| | - Cheolju Lee
- Center for Theragnosis, Korea Institute of Science and Technology, Seoul 02792, Korea
- Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Korea
| | - Cheol-Sang Hwang
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, Korea
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5
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Wang BB, Xu H, Isenmann S, Huang C, Elorza-Vidal X, Rychkov GY, Estévez R, Schittenhelm RB, Lukacs GL, Apaja PM. Ubr1-induced selective endophagy/autophagy protects against the endosomal and Ca 2+-induced proteostasis disease stress. Cell Mol Life Sci 2022; 79:167. [PMID: 35233680 PMCID: PMC8888484 DOI: 10.1007/s00018-022-04191-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 01/30/2022] [Accepted: 02/04/2022] [Indexed: 12/15/2022]
Abstract
The cellular defense mechanisms against cumulative endo-lysosomal stress remain incompletely understood. Here, we identify Ubr1 as a protein quality control (QC) E3 ubiquitin-ligase that counteracts proteostasis stresses by facilitating endosomal cargo-selective autophagy for lysosomal degradation. Astrocyte regulatory cluster membrane protein MLC1 mutations cause endosomal compartment stress by fusion and enlargement. Partial lysosomal clearance of mutant endosomal MLC1 is accomplished by the endosomal QC ubiquitin ligases, CHIP and Ubr1 via ESCRT-dependent route. As a consequence of the endosomal stress, a supportive QC mechanism, dependent on both Ubr1 and SQSTM1/p62 activities, targets ubiquitinated and arginylated MLC1 mutants for selective endosomal autophagy (endophagy). This QC pathway is also activated for arginylated Ubr1-SQSTM1/p62 autophagy cargoes during cytosolic Ca2+-assault. Conversely, the loss of Ubr1 and/or arginylation elicited endosomal compartment stress. These findings underscore the critical housekeeping role of Ubr1 and arginylation-dependent endophagy/autophagy during endo-lysosomal proteostasis perturbations and suggest a link of Ubr1 to Ca2+ homeostasis and proteins implicated in various diseases including cancers and brain disorders.
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Affiliation(s)
- Ben B Wang
- Lifelong Health, Organelle Proteostasis Diseases, South Australian Health and Medical Research Institute (SAHMRI), 5000 North Terrace, Adelaide, SA, 5000, Australia.,EMBL Australia, Adelaide, South Australia, 5000, Australia
| | - Haijin Xu
- Department of Physiology and Cell Information Systems, McGill University, 3655 Promenade Sir-William-Osler, Montréal, QC, H3G 1Y6, Canada
| | - Sandra Isenmann
- Lifelong Health, Organelle Proteostasis Diseases, South Australian Health and Medical Research Institute (SAHMRI), 5000 North Terrace, Adelaide, SA, 5000, Australia.,EMBL Australia, Adelaide, South Australia, 5000, Australia
| | - Cheng Huang
- Monash Biomedical Proteomics Facility, Department of Biochemistry, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, 3800, Australia
| | - Xabier Elorza-Vidal
- Unitat de Fisiologia, Departament de Ciències Fisiològiques, IDIBELL-Institute of Neurosciences, L'Hospitalet de Llobregat, Universitat de Barcelona, Barcelona, Spain.,Centro de Investigación en Red de Enfermedades Raras (CIBERER), ISCIII, Madrid, Spain
| | - Grigori Y Rychkov
- Lifelong Health, Organelle Proteostasis Diseases, South Australian Health and Medical Research Institute (SAHMRI), 5000 North Terrace, Adelaide, SA, 5000, Australia.,School of Medicine, University of Adelaide, Adelaide, SA, 5005, Australia
| | - Raúl Estévez
- Unitat de Fisiologia, Departament de Ciències Fisiològiques, IDIBELL-Institute of Neurosciences, L'Hospitalet de Llobregat, Universitat de Barcelona, Barcelona, Spain.,Centro de Investigación en Red de Enfermedades Raras (CIBERER), ISCIII, Madrid, Spain
| | - Ralf B Schittenhelm
- Monash Biomedical Proteomics Facility, Department of Biochemistry, Monash Biomedicine Discovery Institute, Monash University, Clayton, VIC, 3800, Australia
| | - Gergely L Lukacs
- Department of Physiology and Cell Information Systems, McGill University, 3655 Promenade Sir-William-Osler, Montréal, QC, H3G 1Y6, Canada. .,Department of Biochemistry, McGill University, Montréal, QC, H3G 1Y6, Canada.
| | - Pirjo M Apaja
- Lifelong Health, Organelle Proteostasis Diseases, South Australian Health and Medical Research Institute (SAHMRI), 5000 North Terrace, Adelaide, SA, 5000, Australia. .,EMBL Australia, Adelaide, South Australia, 5000, Australia. .,Department of Molecular and Biomedical Sciences, University of Adelaide, Adelaide, SA, 5005, Australia. .,College of Public Health and Medicine, Molecular Biosciences Theme, Flinders University, Bedford Park, SA, 5042, Australia.
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6
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Sherpa D, Chrustowicz J, Schulman BA. How the ends signal the end: Regulation by E3 ubiquitin ligases recognizing protein termini. Mol Cell 2022; 82:1424-1438. [PMID: 35247307 PMCID: PMC9098119 DOI: 10.1016/j.molcel.2022.02.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 01/18/2022] [Accepted: 02/01/2022] [Indexed: 12/31/2022]
Abstract
Specificity of eukaryotic protein degradation is determined by E3 ubiquitin ligases and their selective binding to protein motifs, termed "degrons," in substrates for ubiquitin-mediated proteolysis. From the discovery of the first substrate degron and the corresponding E3 to a flurry of recent studies enabled by modern systems and structural methods, it is clear that many regulatory pathways depend on E3s recognizing protein termini. Here, we review the structural basis for recognition of protein termini by E3s and how this recognition underlies biological regulation. Diverse E3s evolved to harness a substrate's N and/or C terminus (and often adjacent residues as well) in a sequence-specific manner. Regulation is achieved through selective activation of E3s and also through generation of degrons at ribosomes or by posttranslational means. Collectively, many E3 interactions with protein N and C termini enable intricate control of protein quality and responses to cellular signals.
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Affiliation(s)
- Dawafuti Sherpa
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Bavaria, Germany
| | - Jakub Chrustowicz
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Bavaria, Germany
| | - Brenda A Schulman
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, Martinsried, Bavaria, Germany.
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7
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Saada OA, Tsouris A, Large C, Friedrich A, Dunham MJ, Schacherer J. Phased polyploid genomes provide deeper insight into the multiple origins of domesticated Saccharomyces cerevisiae beer yeasts. Curr Biol 2022; 32:1350-1361.e3. [PMID: 35180385 DOI: 10.1016/j.cub.2022.01.068] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 12/02/2021] [Accepted: 01/21/2022] [Indexed: 10/19/2022]
Abstract
Yeasts, and in particular Saccharomyces cerevisiae, have been used for brewing beer for thousands of years. Population genomic surveys highlighted that beer yeasts are polyphyletic, with the emergence of different domesticated subpopulations characterized by high genetic diversity and ploidy level. However, the different origins of these subpopulations are still unclear as reconstruction of polyploid genomes is required. To gain better insight into the differential evolutionary trajectories, we sequenced the genomes of 35 Saccharomyces cerevisiae isolates coming from different beer-brewing clades, using a long-read sequencing strategy. By phasing the genomes and using a windowed approach, we identified three main beer subpopulations based on allelic content (European dominant, Asian dominant, and African beer). They were derived from different admixtures between populations and are characterized by distinctive genomic patterns. By comparing the fully phased genes, the most diverse in our dataset are enriched for functions relevant to the brewing environment such as carbon metabolism, oxidoreduction, and cell wall organization activity. Finally, independent domestication, evolution, and adaptation events across subpopulations were also highlighted by investigating specific genes previously linked to the brewing process. Altogether, our analysis based on phased polyploid genomes has led to new insight into the contrasting evolutionary history of beer isolates.
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Affiliation(s)
- Omar Abou Saada
- Université de Strasbourg, CNRS, GMGM UMR 7156, Strasbourg, France
| | - Andreas Tsouris
- Université de Strasbourg, CNRS, GMGM UMR 7156, Strasbourg, France
| | - Chris Large
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Anne Friedrich
- Université de Strasbourg, CNRS, GMGM UMR 7156, Strasbourg, France
| | - Maitreya J Dunham
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Joseph Schacherer
- Université de Strasbourg, CNRS, GMGM UMR 7156, Strasbourg, France; Institut Universitaire de France (IUF), Paris, France.
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8
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den Brave F, Gupta A, Becker T. Protein Quality Control at the Mitochondrial Surface. Front Cell Dev Biol 2021; 9:795685. [PMID: 34926473 PMCID: PMC8678412 DOI: 10.3389/fcell.2021.795685] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Accepted: 11/05/2021] [Indexed: 12/14/2022] Open
Abstract
Mitochondria contain two membranes, the outer and inner membrane. The outer membrane fulfills crucial functions for the communication of mitochondria with the cellular environment like exchange of lipids via organelle contact sites, the transport of metabolites and the formation of a signaling platform in apoptosis and innate immunity. The translocase of the outer membrane (TOM complex) forms the entry gate for the vast majority of precursor proteins that are produced on cytosolic ribosomes. Surveillance of the functionality of outer membrane proteins is critical for mitochondrial functions and biogenesis. Quality control mechanisms remove defective and mistargeted proteins from the outer membrane as well as precursor proteins that clog the TOM complex. Selective degradation of single proteins is also an important mode to regulate mitochondrial dynamics and initiation of mitophagy pathways. Whereas inner mitochondrial compartments are equipped with specific proteases, the ubiquitin-proteasome system is a central player in protein surveillance on the mitochondrial surface. In this review, we summarize our current knowledge about the molecular mechanisms that govern quality control of proteins at the outer mitochondrial membrane.
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Affiliation(s)
- Fabian den Brave
- Institute of Biochemistry and Molecular Biology, Faculty of Medicine, University of Bonn, Bonn, Germany
| | - Arushi Gupta
- Institute of Biochemistry and Molecular Biology, Faculty of Medicine, University of Bonn, Bonn, Germany
| | - Thomas Becker
- Institute of Biochemistry and Molecular Biology, Faculty of Medicine, University of Bonn, Bonn, Germany
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9
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Structural insights into Ubr1-mediated N-degron polyubiquitination. Nature 2021; 600:334-338. [PMID: 34789879 DOI: 10.1038/s41586-021-04097-8] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 10/06/2021] [Indexed: 11/09/2022]
Abstract
The N-degron pathway targets proteins that bear a destabilizing residue at the N terminus for proteasome-dependent degradation1. In yeast, Ubr1-a single-subunit E3 ligase-is responsible for the Arg/N-degron pathway2. How Ubr1 mediates the initiation of ubiquitination and the elongation of the ubiquitin chain in a linkage-specific manner through a single E2 ubiquitin-conjugating enzyme (Ubc2) remains unknown. Here we developed chemical strategies to mimic the reaction intermediates of the first and second ubiquitin transfer steps, and determined the cryo-electron microscopy structures of Ubr1 in complex with Ubc2, ubiquitin and two N-degron peptides, representing the initiation and elongation steps of ubiquitination. Key structural elements, including a Ubc2-binding region and an acceptor ubiquitin-binding loop on Ubr1, were identified and characterized. These structures provide mechanistic insights into the initiation and elongation of ubiquitination catalysed by Ubr1.
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10
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Chrustowicz J, Sherpa D, Teyra J, Loke MS, Popowicz GM, Basquin J, Sattler M, Prabu JR, Sidhu SS, Schulman BA. Multifaceted N-Degron Recognition and Ubiquitylation by GID/CTLH E3 Ligases. J Mol Biol 2021; 434:167347. [PMID: 34767800 DOI: 10.1016/j.jmb.2021.167347] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 11/02/2021] [Accepted: 11/02/2021] [Indexed: 12/22/2022]
Abstract
N-degron E3 ubiquitin ligases recognize specific residues at the N-termini of substrates. Although molecular details of N-degron recognition are known for several E3 ligases, the range of N-terminal motifs that can bind a given E3 substrate binding domain remains unclear. Here, we discovered capacity of Gid4 and Gid10 substrate receptor subunits of yeast "GID"/human "CTLH" multiprotein E3 ligases to tightly bind a wide range of N-terminal residues whose recognition is determined in part by the downstream sequence context. Screening of phage displaying peptide libraries with exposed N-termini identified novel consensus motifs with non-Pro N-terminal residues binding Gid4 or Gid10 with high affinity. Structural data reveal that conformations of flexible loops in Gid4 and Gid10 complement sequences and folds of interacting peptides. Together with analysis of endogenous substrate degrons, the data show that degron identity, substrate domains harboring targeted lysines, and varying E3 ligase higher-order assemblies combinatorially determine efficiency of ubiquitylation and degradation.
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Affiliation(s)
- Jakub Chrustowicz
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany. https://twitter.com/chrustowicz_j
| | - Dawafuti Sherpa
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany. https://twitter.com/dawafutisherpa
| | - Joan Teyra
- The Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Mun Siong Loke
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Grzegorz M Popowicz
- Helmholtz Zentrum München, Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany; Bavarian NMR Center, Department of Chemistry, Technical University of Munich, Germany
| | - Jerome Basquin
- Department of Structural Cell Biology, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
| | - Michael Sattler
- Helmholtz Zentrum München, Ingolstädter Landstrasse 1, 85764 Neuherberg, Germany; Bavarian NMR Center, Department of Chemistry, Technical University of Munich, Germany
| | - J Rajan Prabu
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany. https://twitter.com/rajanprabu
| | - Sachdev S Sidhu
- The Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada; Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada
| | - Brenda A Schulman
- Department of Molecular Machines and Signaling, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany.
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11
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Runnebohm AM, Evans MD, Richardson AE, Turk SM, Olesen JB, Smaldino PJ, Rubenstein EM. Loss of protein quality control gene UBR1 sensitizes Saccharomyces cerevisiae to the aminoglycoside hygromycin B. ACTA ACUST UNITED AC 2020; 6:76-83. [PMID: 33554225 DOI: 10.33043/ff.6.1.76-83] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Ubr1 is a conserved ubiquitin ligase involved in the degradation of aberrant proteins in eukaryotic cells. The human enzyme is found mutated in patients with Johanson-Blizzard syndrome. We hypothesized that Ubr1 is necessary for optimal cellular fitness in conditions associated with elevated abundance of aberrant and misfolded proteins. Indeed, we found that loss of Ubr1 in the model eukaryotic microorganism Saccharomyces cerevisiae strongly sensitizes cells to hygromycin B, which reduces translational fidelity by causing ribosome A site distortion. Our results are consistent with a prominent role for Ubr1 in protein quality control. We speculate that disease manifestations in patients with Johanson-Blizzard syndrome are linked, at least in part, to defects in protein quality control caused by loss of Ubr1 function.
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Affiliation(s)
- Avery M Runnebohm
- Ball State University, Department of Biology, Muncie, IN 47306.,These authors contributed equally to this work
| | - Melissa D Evans
- Ball State University, Department of Biology, Muncie, IN 47306.,These authors contributed equally to this work
| | | | - Samantha M Turk
- Ball State University, Department of Biology, Muncie, IN 47306
| | - James B Olesen
- Ball State University, Department of Biology, Muncie, IN 47306
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12
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Aggresomal sequestration and STUB1-mediated ubiquitylation during mammalian proteaphagy of inhibited proteasomes. Proc Natl Acad Sci U S A 2020; 117:19190-19200. [PMID: 32723828 PMCID: PMC7430983 DOI: 10.1073/pnas.1920327117] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The ubiquitin–proteasome system and autophagy are two major intracellular proteolytic pathways, and both remove misfolded and proteotoxic proteins from eukaryotic cells. This study describes the detailed regulatory pathway of proteasome degradation by autophagy for its own quality control. We discovered that a portion of inhibited proteasomes is actively sequestered into the aggresome, an insoluble fraction of the mammalian cell. The aggresome functions as a triage point for proteasome recovery and autophagic degradation. This mainly distinguishes proteasome quality control in mammals from that in other organisms. STUB1/CHIP E3 Ub ligase has a critical role in targeting inhibited proteasomes into the aggresome. These results provide strong insights into protein catabolism in various pathological conditions originating from impaired proteasomes. The 26S proteasome, a self-compartmentalized protease complex, plays a crucial role in protein quality control. Multiple levels of regulatory systems modulate proteasomal activity for substrate hydrolysis. However, the destruction mechanism of mammalian proteasomes is poorly understood. We found that inhibited proteasomes are sequestered into the insoluble aggresome via HDAC6- and dynein-mediated transport. These proteasomes colocalized with the autophagic receptor SQSTM1 and cleared through selective macroautophagy, linking aggresomal segregation to autophagic degradation. This proteaphagic pathway was counterbalanced with the recovery of proteasomal activity and was critical for reducing cellular proteasomal stress. Changes in associated proteins and polyubiquitylation on inhibited 26S proteasomes participated in the targeting mechanism to the aggresome and autophagosome. The STUB1 E3 Ub ligase specifically ubiquitylated purified human proteasomes in vitro, mainly via Lys63-linked chains. Genetic and chemical inhibition of STUB1 activity significantly impaired proteasome processing and reduced resistance to proteasomal stress. These data demonstrate that aggresomal sequestration is the crucial upstream event for proteasome quality control and overall protein homeostasis in mammals.
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13
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Recognition of nonproline N-terminal residues by the Pro/N-degron pathway. Proc Natl Acad Sci U S A 2020; 117:14158-14167. [PMID: 32513738 DOI: 10.1073/pnas.2007085117] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Eukaryotic N-degron pathways are proteolytic systems whose unifying feature is their ability to recognize proteins containing N-terminal (Nt) degradation signals called N-degrons, and to target these proteins for degradation by the 26S proteasome or autophagy. GID4, a subunit of the GID ubiquitin ligase, is the main recognition component of the proline (Pro)/N-degron pathway. GID4 targets proteins through their Nt-Pro residue or a Pro at position 2, in the presence of specific downstream sequence motifs. Here we show that human GID4 can also recognize hydrophobic Nt-residues other than Pro. One example is the sequence Nt-IGLW, bearing Nt-Ile. Nt-IGLW binds to wild-type human GID4 with a K d of 16 μM, whereas the otherwise identical Nt-Pro-bearing sequence PGLW binds to GID4 more tightly, with a K d of 1.9 μM. Despite this difference in affinities of GID4 for Nt-IGLW vs. Nt-PGLW, we found that the GID4-mediated Pro/N-degron pathway of the yeast Saccharomyces cerevisiae can target an Nt-IGLW-bearing protein for rapid degradation. We solved crystal structures of human GID4 bound to a peptide bearing Nt-Ile or Nt-Val. We also altered specific residues of human GID4 and measured the affinities of resulting mutant GID4s for Nt-IGLW and Nt-PGLW, thereby determining relative contributions of specific GID4 residues to the GID4-mediated recognition of Nt-Pro vs. Nt-residues other than Pro. These and related results advance the understanding of targeting by the Pro/N-degron pathway and greatly expand the substrate recognition range of the GID ubiquitin ligase in both human and yeast cells.
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14
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Richards KA, Rubenstein EM. Endoplasmic reticulum stress-regulated degradation of a translocon-associated protein is independent of integrated stress response transcription factor Gcn4p. MICROPUBLICATION BIOLOGY 2020; 2020:10.17912/micropub.biology.000239. [PMID: 32550483 PMCID: PMC7252232 DOI: 10.17912/micropub.biology.000239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Kyle A Richards
- Ball State University, Department of Biology, Muncie, IN 47306
| | - Eric M Rubenstein
- Ball State University, Department of Biology, Muncie, IN 47306,
Correspondence to: Eric M Rubenstein ()
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15
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Telini BDP, Menoncin M, Bonatto D. Does Inter-Organellar Proteostasis Impact Yeast Quality and Performance During Beer Fermentation? Front Genet 2020; 11:2. [PMID: 32076433 PMCID: PMC7006503 DOI: 10.3389/fgene.2020.00002] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 01/06/2020] [Indexed: 02/02/2023] Open
Abstract
During beer production, yeast generate ethanol that is exported to the extracellular environment where it accumulates. Depending on the initial carbohydrate concentration in the wort, the amount of yeast biomass inoculated, the fermentation temperature, and the yeast attenuation capacity, a high concentration of ethanol can be achieved in beer. The increase in ethanol concentration as a consequence of the fermentation of high gravity (HG) or very high gravity (VHG) worts promotes deleterious pleiotropic effects on the yeast cells. Moderate concentrations of ethanol (5% v/v) change the enzymatic kinetics of proteins and affect biological processes, such as the cell cycle and metabolism, impacting the reuse of yeast for subsequent fermentation. However, high concentrations of ethanol (> 5% v/v) dramatically alter protein structure, leading to unfolded proteins as well as amorphous protein aggregates. It is noteworthy that the effects of elevated ethanol concentrations generated during beer fermentation resemble those of heat shock stress, with similar responses observed in both situations, such as the activation of proteostasis and protein quality control mechanisms in different cell compartments, including endoplasmic reticulum (ER), mitochondria, and cytosol. Despite the extensive published molecular and biochemical data regarding the roles of proteostasis in different organelles of yeast cells, little is known about how this mechanism impacts beer fermentation and how different proteostasis mechanisms found in ER, mitochondria, and cytosol communicate with each other during ethanol/fermentative stress. Supporting this integrative view, transcriptome data analysis was applied using publicly available information for a lager yeast strain grown under beer production conditions. The transcriptome data indicated upregulation of genes that encode chaperones, co-chaperones, unfolded protein response elements in ER and mitochondria, ubiquitin ligases, proteasome components, N-glycosylation quality control pathway proteins, and components of processing bodies (p-bodies) and stress granules (SGs) during lager beer fermentation. Thus, the main purpose of this hypothesis and theory manuscript is to provide a concise picture of how inter-organellar proteostasis mechanisms are connected with one another and with biological processes that may modulate the viability and/or vitality of yeast populations during HG/VHG beer fermentation and serial repitching.
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Affiliation(s)
- Bianca de Paula Telini
- Brewing Yeast Research Group, Centro de Biotecnologia da UFRGS, Departamento de Biologia Molecular e Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
| | - Marcelo Menoncin
- Brewing Yeast Research Group, Centro de Biotecnologia da UFRGS, Departamento de Biologia Molecular e Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
| | - Diego Bonatto
- Brewing Yeast Research Group, Centro de Biotecnologia da UFRGS, Departamento de Biologia Molecular e Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil
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16
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Interconversion between Anticipatory and Active GID E3 Ubiquitin Ligase Conformations via Metabolically Driven Substrate Receptor Assembly. Mol Cell 2020; 77:150-163.e9. [DOI: 10.1016/j.molcel.2019.10.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 09/04/2019] [Accepted: 10/08/2019] [Indexed: 12/20/2022]
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17
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Schäfer JA, Schessner JP, Bircham PW, Tsuji T, Funaya C, Pajonk O, Schaeff K, Ruffini G, Papagiannidis D, Knop M, Fujimoto T, Schuck S. ESCRT machinery mediates selective microautophagy of endoplasmic reticulum in yeast. EMBO J 2019; 39:e102586. [PMID: 31802527 PMCID: PMC6960443 DOI: 10.15252/embj.2019102586] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2019] [Revised: 10/30/2019] [Accepted: 11/11/2019] [Indexed: 01/14/2023] Open
Abstract
ER‐phagy, the selective autophagy of endoplasmic reticulum (ER), safeguards organelle homeostasis by eliminating misfolded proteins and regulating ER size. ER‐phagy can occur by macroautophagic and microautophagic mechanisms. While dedicated machinery for macro‐ER‐phagy has been discovered, the molecules and mechanisms mediating micro‐ER‐phagy remain unknown. Here, we first show that micro‐ER‐phagy in yeast involves the conversion of stacked cisternal ER into multilamellar ER whorls during microautophagic uptake into lysosomes. Second, we identify the conserved Nem1‐Spo7 phosphatase complex and the ESCRT machinery as key components for micro‐ER‐phagy. Third, we demonstrate that macro‐ and micro‐ER‐phagy are parallel pathways with distinct molecular requirements. Finally, we provide evidence that the ESCRT machinery directly functions in scission of the lysosomal membrane to complete the microautophagic uptake of ER. These findings establish a framework for a mechanistic understanding of micro‐ER‐phagy and, thus, a comprehensive appreciation of the role of autophagy in ER homeostasis.
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Affiliation(s)
- Jasmin A Schäfer
- DKFZ-ZMBH Alliance and CellNetworks Cluster of Excellence, Center for Molecular Biology of Heidelberg University (ZMBH), Heidelberg, Germany
| | - Julia P Schessner
- DKFZ-ZMBH Alliance and CellNetworks Cluster of Excellence, Center for Molecular Biology of Heidelberg University (ZMBH), Heidelberg, Germany
| | - Peter W Bircham
- DKFZ-ZMBH Alliance and CellNetworks Cluster of Excellence, Center for Molecular Biology of Heidelberg University (ZMBH), Heidelberg, Germany
| | - Takuma Tsuji
- Research Institute for Diseases of Old Age, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Charlotta Funaya
- Electron Microscopy Core Facility, Heidelberg University, Heidelberg, Germany
| | - Oliver Pajonk
- DKFZ-ZMBH Alliance and CellNetworks Cluster of Excellence, Center for Molecular Biology of Heidelberg University (ZMBH), Heidelberg, Germany
| | - Katharina Schaeff
- DKFZ-ZMBH Alliance and CellNetworks Cluster of Excellence, Center for Molecular Biology of Heidelberg University (ZMBH), Heidelberg, Germany
| | - Giulia Ruffini
- DKFZ-ZMBH Alliance and CellNetworks Cluster of Excellence, Center for Molecular Biology of Heidelberg University (ZMBH), Heidelberg, Germany
| | - Dimitrios Papagiannidis
- DKFZ-ZMBH Alliance and CellNetworks Cluster of Excellence, Center for Molecular Biology of Heidelberg University (ZMBH), Heidelberg, Germany
| | - Michael Knop
- DKFZ-ZMBH Alliance and CellNetworks Cluster of Excellence, Center for Molecular Biology of Heidelberg University (ZMBH), Heidelberg, Germany
| | - Toyoshi Fujimoto
- Research Institute for Diseases of Old Age, Juntendo University Graduate School of Medicine, Tokyo, Japan
| | - Sebastian Schuck
- DKFZ-ZMBH Alliance and CellNetworks Cluster of Excellence, Center for Molecular Biology of Heidelberg University (ZMBH), Heidelberg, Germany
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18
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Buchanan BW, Mehrtash AB, Broshar CL, Runnebohm AM, Snow BJ, Scanameo LN, Hochstrasser M, Rubenstein EM. Endoplasmic reticulum stress differentially inhibits endoplasmic reticulum and inner nuclear membrane protein quality control degradation pathways. J Biol Chem 2019; 294:19814-19830. [PMID: 31723032 DOI: 10.1074/jbc.ra119.010295] [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: 07/22/2019] [Revised: 11/04/2019] [Indexed: 12/29/2022] Open
Abstract
Endoplasmic reticulum (ER) stress occurs when the abundance of unfolded proteins in the ER exceeds the capacity of the folding machinery. Despite the expanding cadre of characterized cellular adaptations to ER stress, knowledge of the effects of ER stress on cellular physiology remains incomplete. We investigated the impact of ER stress on ER and inner nuclear membrane protein quality control mechanisms in Saccharomyces cerevisiae. We analyzed the turnover of substrates of four ubiquitin ligases (Doa10, Rkr1/Ltn1, Hrd1, and the Asi complex) and the metalloprotease Ste24 in induced models of ER stress. ER stress did not substantially impact Doa10 or Rkr1 substrates. However, Hrd1-mediated destruction of a protein that aberrantly engages the translocon (Deg1-Sec62) and substrates with luminal degradation signals was markedly impaired by ER stress; by contrast, Hrd1-dependent degradation of proteins with intramembrane degrons was largely unperturbed by ER stress. ER stress impaired the degradation of one of two Asi substrates analyzed and caused a translocon-clogging Ste24 substrate to accumulate in a form consistent with persistent translocon occupation. Degradation of Deg1-Sec62 in the absence of stress and stabilization during ER stress were independent of four ER stress-sensing pathways. Our results indicate ER stress differentially impacts degradation of protein quality control substrates, including those mediated by the same ubiquitin ligase. These observations suggest the existence of additional regulatory mechanisms dictating substrate selection during ER stress.
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Affiliation(s)
- Bryce W Buchanan
- Department of Biology, Ball State University, Muncie, Indiana 47306
| | - Adrian B Mehrtash
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520
| | | | | | - Brian J Snow
- Department of Biology, Ball State University, Muncie, Indiana 47306
| | - Laura N Scanameo
- Department of Biology, Ball State University, Muncie, Indiana 47306
| | - Mark Hochstrasser
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520.,Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520
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19
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Kampinga HH, Mayer MP, Mogk A. Protein quality control: from mechanism to disease : EMBO Workshop, Costa de la Calma (Mallorca), Spain, April 28 - May 03, 2019. Cell Stress Chaperones 2019; 24:1013-1026. [PMID: 31713048 PMCID: PMC6882752 DOI: 10.1007/s12192-019-01040-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/26/2019] [Indexed: 12/11/2022] Open
Abstract
The cellular protein quality control machinery with its central constituents of chaperones and proteases is vital to maintain protein homeostasis under physiological conditions and to protect against acute stress conditions. Imbalances in protein homeostasis also are keys to a plethora of genetic and acquired, often age-related, diseases as well as aging in general. At the EMBO Workshop, speakers covered all major aspects of cellular protein quality control, from basic mechanisms at the molecular, cellular, and organismal level to medical translation. In this report, the highlights of the meeting will be summarized.
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Affiliation(s)
- Harm H Kampinga
- Department of Biomedical Science of Cells & Systems, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
| | - Matthias P Mayer
- Center for Molecular Biology (ZMBH), University of Heidelberg, Im Neuenheimer Feld 282, 69120, Heidelberg, Germany.
| | - Axel Mogk
- Center for Molecular Biology (ZMBH), University of Heidelberg, Im Neuenheimer Feld 282, 69120, Heidelberg, Germany.
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20
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Melnykov A, Chen SJ, Varshavsky A. Gid10 as an alternative N-recognin of the Pro/N-degron pathway. Proc Natl Acad Sci U S A 2019; 116:15914-15923. [PMID: 31337681 PMCID: PMC6689949 DOI: 10.1073/pnas.1908304116] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
In eukaryotes, N-degron pathways (formerly "N-end rule pathways") comprise a set of proteolytic systems whose unifying feature is their ability to recognize proteins containing N-terminal degradation signals called N-degrons, thereby causing degradation of these proteins by the 26S proteasome or autophagy. Gid4, a subunit of the GID ubiquitin ligase in the yeast Saccharomyces cerevisiae, is the recognition component (N-recognin) of the GID-mediated Pro/N-degron pathway. Gid4 targets proteins by recognizing their N-terminal Pro residues or a Pro at position 2, in the presence of distinct adjoining sequence motifs. Under conditions of low or absent glucose, cells make it through gluconeogenesis. When S. cerevisiae grows on a nonfermentable carbon source, its gluconeogenic enzymes Fbp1, Icl1, Mdh2, and Pck1 are expressed and long-lived. Transition to a medium containing glucose inhibits the synthesis of these enzymes and induces their degradation by the Gid4-dependent Pro/N-degron pathway. While studying yeast Gid4, we identified a similar but uncharacterized yeast protein (YGR066C), which we named Gid10. A screen for N-terminal peptide sequences that can bind to Gid10 showed that substrate specificities of Gid10 and Gid4 overlap but are not identical. Gid10 is not expressed under usual (unstressful) growth conditions, but is induced upon starvation or osmotic stresses. Using protein binding analyses and degradation assays with substrates of GID, we show that Gid10 can function as a specific N-recognin of the Pro/N-degron pathway.
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Affiliation(s)
- Artem Melnykov
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125
| | - Shun-Jia Chen
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125
| | - Alexander Varshavsky
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125
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21
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Tran A. The N-end rule pathway and Ubr1 enforce protein compartmentalization via P2-encoded cellular location signals. J Cell Sci 2019; 132:jcs.231662. [PMID: 30940687 DOI: 10.1242/jcs.231662] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 03/22/2019] [Indexed: 12/24/2022] Open
Abstract
The Arg/N-end rule pathway and Ubr1, a ubiquitin E3 ligase conserved from yeast to humans, is involved in the degradation of misfolded proteins in the cytosol. However, the root physiological purpose of this activity is not completely understood. Through a systematic examination of single-residue P2-position mutants of misfolded proteins, and global and targeted bioinformatic analyses of the Saccharomyces cerevisiae proteome, it was determined that Ubr1 preferentially targets mistranslocated secretory and mitochondrial proteins in the cytosol. Degradation by Ubr1 is dependent on the recognition of cellular location signals that are naturally embedded into the second amino acid residue of most proteins. This P2-encoded location signaling mechanism may shed light on how Ubr1 and the N-end rule pathway are involved in neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. A corollary to this discovery is that the N-end rule pathway enforces the compartmentalization of secretory and mitochondrial proteins by degrading those that fail to reach their intended subcellular locations. The N-end rule pathway is therefore likely to have been critical to the evolution of endosymbiotic relationships that paved the way for advanced eukaryotic cellular life. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Anthony Tran
- National University of Singapore, Department of Biological Sciences, Singapore 117604
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22
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Schmidt RM, Schessner JP, Borner GH, Schuck S. The proteasome biogenesis regulator Rpn4 cooperates with the unfolded protein response to promote ER stress resistance. eLife 2019; 8:43244. [PMID: 30865586 PMCID: PMC6415940 DOI: 10.7554/elife.43244] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 02/27/2019] [Indexed: 12/27/2022] Open
Abstract
Misfolded proteins in the endoplasmic reticulum (ER) activate the unfolded protein response (UPR), which enhances protein folding to restore homeostasis. Additional pathways respond to ER stress, but how they help counteract protein misfolding is incompletely understood. Here, we develop a titratable system for the induction of ER stress in yeast to enable a genetic screen for factors that augment stress resistance independently of the UPR. We identify the proteasome biogenesis regulator Rpn4 and show that it cooperates with the UPR. Rpn4 abundance increases during ER stress, first by a post-transcriptional, then by a transcriptional mechanism. Induction of RPN4 transcription is triggered by cytosolic mislocalization of secretory proteins, is mediated by multiple signaling pathways and accelerates clearance of misfolded proteins from the cytosol. Thus, Rpn4 and the UPR are complementary elements of a modular cross-compartment response to ER stress.
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Affiliation(s)
- Rolf M Schmidt
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance and CellNetworks Cluster of Excellence, Heidelberg, Germany
| | - Julia P Schessner
- Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Georg Hh Borner
- Department of Proteomics and Signal Transduction, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Sebastian Schuck
- Center for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance and CellNetworks Cluster of Excellence, Heidelberg, Germany
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23
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Abstract
This perspective is partly review and partly proposal. N-degrons and C-degrons are degradation signals whose main determinants are, respectively, the N-terminal and C-terminal residues of cellular proteins. N-degrons and C-degrons include, to varying extents, adjoining sequence motifs, and also internal lysine residues that function as polyubiquitylation sites. Discovered in 1986, N-degrons were the first degradation signals in short-lived proteins. A particularly large set of C-degrons was discovered in 2018. We describe multifunctional proteolytic systems that target N-degrons and C-degrons. We also propose to denote these systems as "N-degron pathways" and "C-degron pathways." The former notation replaces the earlier name "N-end rule pathways." The term "N-end rule" was introduced 33 years ago, when only some N-terminal residues were thought to be destabilizing. However, studies over the last three decades have shown that all 20 amino acids of the genetic code can act, in cognate sequence contexts, as destabilizing N-terminal residues. Advantages of the proposed terms include their brevity and semantic uniformity for N-degrons and C-degrons. In addition to being topologically analogous, N-degrons and C-degrons are related functionally. A proteolytic cleavage of a subunit in a multisubunit complex can create, at the same time, an N-degron (in a C-terminal fragment) and a spatially adjacent C-degron (in an N-terminal fragment). Consequently, both fragments of a subunit can be selectively destroyed through attacks by the N-degron and C-degron pathways.
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24
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Patir-Nebioglu MG, Andrés Z, Krebs M, Fink F, Drzewicka K, Stankovic-Valentin N, Segami S, Schuck S, Büttner M, Hell R, Maeshima M, Melchior F, Schumacher K. Pyrophosphate modulates plant stress responses via SUMOylation. eLife 2019; 8:44213. [PMID: 30785397 PMCID: PMC6382351 DOI: 10.7554/elife.44213] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 02/05/2019] [Indexed: 01/11/2023] Open
Abstract
Pyrophosphate (PPi), a byproduct of macromolecule biosynthesis is maintained at low levels by soluble inorganic pyrophosphatases (sPPase) found in all eukaryotes. In plants, H+-pumping pyrophosphatases (H+-PPase) convert the substantial energy present in PPi into an electrochemical gradient. We show here, that both cold- and heat stress sensitivity of fugu5 mutants lacking the major H+-PPase isoform AVP1 is correlated with reduced SUMOylation. In addition, we show that increased PPi concentrations interfere with SUMOylation in yeast and we provide evidence that SUMO activating E1-enzymes are inhibited by micromolar concentrations of PPi in a non-competitive manner. Taken together, our results do not only provide a mechanistic explanation for the beneficial effects of AVP1 overexpression in plants but they also highlight PPi as an important integrator of metabolism and stress tolerance.
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Affiliation(s)
- M Görkem Patir-Nebioglu
- Department Cell Biology, Centre for Organismal Studies (COS), Heidelberg University, Heidelberg, Germany
| | - Zaida Andrés
- Department Cell Biology, Centre for Organismal Studies (COS), Heidelberg University, Heidelberg, Germany
| | - Melanie Krebs
- Department Cell Biology, Centre for Organismal Studies (COS), Heidelberg University, Heidelberg, Germany
| | - Fabian Fink
- Department Cell Biology, Centre for Organismal Studies (COS), Heidelberg University, Heidelberg, Germany
| | - Katarzyna Drzewicka
- Center for Molecular Biology of Heidelberg University (ZMBH) and DKFZ - ZMBH Alliance, Heidelberg, Germany
| | - Nicolas Stankovic-Valentin
- Center for Molecular Biology of Heidelberg University (ZMBH) and DKFZ - ZMBH Alliance, Heidelberg, Germany
| | - Shoji Segami
- Laboratory of Cell Dynamics, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Sebastian Schuck
- Center for Molecular Biology of Heidelberg University (ZMBH) and DKFZ - ZMBH Alliance, Heidelberg, Germany
| | - Michael Büttner
- Metabolomics Core Technology Platform, Centre for Organismal Studies (COS), Heidelberg University, Heidelberg, Germany
| | - Rüdiger Hell
- Metabolomics Core Technology Platform, Centre for Organismal Studies (COS), Heidelberg University, Heidelberg, Germany
| | - Masayoshi Maeshima
- Laboratory of Cell Dynamics, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Frauke Melchior
- Center for Molecular Biology of Heidelberg University (ZMBH) and DKFZ - ZMBH Alliance, Heidelberg, Germany
| | - Karin Schumacher
- Department Cell Biology, Centre for Organismal Studies (COS), Heidelberg University, Heidelberg, Germany
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25
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From Precise Slicing to General SHREDding: The Ubiquitin Ligase Ubr1 Roqs as a Multipurpose Protein Terminator. Mol Cell 2019; 70:989-990. [PMID: 29932909 DOI: 10.1016/j.molcel.2018.06.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
In the current issue of Molecular Cell, Szoradi et al. (2018) present compelling data demonstrating how the newly identified SHRED pathway in yeast selectively shifts the E3 ligase Ubr1 specificity from N-end rule substrates to misfolded proteins in cells under proteostatic stress.
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26
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Clausen L, Abildgaard AB, Gersing SK, Stein A, Lindorff-Larsen K, Hartmann-Petersen R. Protein stability and degradation in health and disease. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2018; 114:61-83. [PMID: 30635086 DOI: 10.1016/bs.apcsb.2018.09.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The cellular proteome performs highly varied functions to sustain life. Since most of these functions require proteins to fold properly, they can be impaired by mutations that affect protein structure, leading to diseases such as Alzheimer's disease, cystic fibrosis, and Lynch syndrome. The cell has evolved an intricate protein quality control (PQC) system that includes degradation pathways and a multitude of molecular chaperones and co-chaperones, all working together to catalyze the refolding or removal of aberrant proteins. Thus, the PQC system limits the harmful consequences of dysfunctional proteins, including those arising from disease-causing mutations. This complex system is still not fully understood. In particular the structural and sequence motifs that, when exposed, trigger degradation of misfolded proteins are currently under investigation. Moreover, several attempts are being made to activate or inhibit parts of the PQC system as a treatment for diseases. Here, we briefly review the present knowledge on the PQC system and list current strategies that are employed to exploit the system in disease treatment.
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Affiliation(s)
- Lene Clausen
- The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Amanda B Abildgaard
- The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Sarah K Gersing
- The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Amelie Stein
- The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Kresten Lindorff-Larsen
- The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
| | - Rasmus Hartmann-Petersen
- The Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
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