1
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PKR Protects the Major Catalytic Subunit of PKA Cpk1 from FgBlm10-Mediated Proteasome Degradation in Fusarium graminearum. Int J Mol Sci 2022; 23:ijms231810208. [PMID: 36142119 PMCID: PMC9499325 DOI: 10.3390/ijms231810208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 08/31/2022] [Accepted: 09/02/2022] [Indexed: 11/17/2022] Open
Abstract
For optimal proteolytic function, the proteasome core (CP or 20S) must associate with activators. The cAMP-PKA pathway is reported to affect the activity of the proteasome in humans. However, the relationship between the proteasome and PKA is not well characterized. Our results showed that the major catalytic subunit Cpk1 was degraded without the protection of Pkr. Eleven (out of 67) pkr suppressors had FgBlm10 C-terminal truncation, one suppressor had an amino acid change mutation in the PRE6 ortholog (FGRRES_07282), and one in the PRE5 ortholog (FGRRES_05222). These mutations rescued the defects in growth and conidial morphology, Cpk1 stability, and PKA activities in the pkr mutant. The interaction of FgBlm10 with FgPre5 and FgPre6 were detected by co-immunoprecipitation, and the essential elements for their interaction were characterized, including the FgBlm10 C-terminus, amino acid D82 of FgPre6 and K62 of FgPre5. Additional FgBlm10-interacting proteins were identified in the wild type and pkr mutant, suggesting that PKA regulates the preference of FgBlm10-mediated proteasome assembly. In addition, PKA indirectly affected the phosphorylation of FgBlm10, and its localization in the nucleus. The truncation of the FgBlm10 C terminus also enhanced nuclear import and bleomycin resistance, suggesting its role in proteasome assembly at DNA damage sites. Collectively, our data demonstrated that regulation between PKA and proteasome degradation is critical for the vegetative growth of F. graminearum.
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2
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Yazgili AS, Ebstein F, Meiners S. The Proteasome Activator PA200/PSME4: An Emerging New Player in Health and Disease. Biomolecules 2022; 12:biom12081150. [PMID: 36009043 PMCID: PMC9406137 DOI: 10.3390/biom12081150] [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: 07/16/2022] [Revised: 08/17/2022] [Accepted: 08/18/2022] [Indexed: 11/24/2022] Open
Abstract
Proteasomes comprise a family of proteasomal complexes essential for maintaining protein homeostasis. Accordingly, proteasomes represent promising therapeutic targets in multiple human diseases. Several proteasome inhibitors are approved for treating hematological cancers. However, their side effects impede their efficacy and broader therapeutic applications. Therefore, understanding the biology of the different proteasome complexes present in the cell is crucial for developing tailor-made inhibitors against specific proteasome complexes. Here, we will discuss the structure, biology, and function of the alternative Proteasome Activator 200 (PA200), also known as PSME4, and summarize the current evidence for its dysregulation in different human diseases. We hereby aim to stimulate research on this enigmatic proteasome regulator that has the potential to serve as a therapeutic target in cancer.
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Affiliation(s)
- Ayse Seda Yazgili
- Comprehensive Pneumology Center (CPC), Helmholtz Center Munich, Max-Lebsche Platz 31, 81377 Munich, Germany
| | - Frédéric Ebstein
- Institut für Medizinische Biochemie und Molekularbiologie (IMBM), Universitätsmedizin Greifswald, Ferdinand-Sauerbruch-Straße, Klinikum DZ/7, 17475 Greifswald, Germany
| | - Silke Meiners
- Research Center Borstel/Leibniz Lung Center, Parkallee 1-40, 23845 Borstel, Germany
- Airway Research Center North (ARCN), German Center for Lung Research (DZL), 23845 Sülfeld, Germany
- Institute of Experimental Medicine, Christian-Albrechts University Kiel, 24118 Kiel, Germany
- Correspondence: ; Tel.: +49-4537-188-58
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3
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Enenkel C, Kang RW, Wilfling F, Ernst OP. Intracellular localization of the proteasome in response to stress conditions. J Biol Chem 2022; 298:102083. [PMID: 35636514 PMCID: PMC9218506 DOI: 10.1016/j.jbc.2022.102083] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 05/13/2022] [Accepted: 05/16/2022] [Indexed: 12/15/2022] Open
Abstract
The ubiquitin–proteasome system fulfills an essential role in regulating protein homeostasis by spatially and temporally controlling proteolysis in an ATP- and ubiquitin-dependent manner. However, the localization of proteasomes is highly variable under diverse cellular conditions. In yeast, newly synthesized proteasomes are primarily localized to the nucleus during cell proliferation. Yeast proteasomes are transported into the nucleus through the nuclear pore either as immature subcomplexes or as mature enzymes via adapter proteins Sts1 and Blm10, while in mammalian cells, postmitotic uptake of proteasomes into the nucleus is mediated by AKIRIN2, an adapter protein essentially required for nuclear protein degradation. Stressful growth conditions and the reversible halt of proliferation, that is quiescence, are associated with a decline in ATP and the reorganization of proteasome localization. Cellular stress leads to proteasome accumulation in membraneless granules either in the nucleus or in the cytoplasm. In quiescence, yeast proteasomes are sequestered in an ubiquitin-dependent manner into motile and reversible proteasome storage granules in the cytoplasm. In cancer cells, upon amino acid deprivation, heat shock, osmotic stress, oxidative stress, or the inhibition of either proteasome activity or nuclear export, reversible proteasome foci containing polyubiquitinated substrates are formed by liquid–liquid phase separation in the nucleus. In this review, we summarize recent literature revealing new links between nuclear transport, ubiquitin signaling, and the intracellular organization of proteasomes during cellular stress conditions.
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Affiliation(s)
- Cordula Enenkel
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
| | - Ryu Won Kang
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Florian Wilfling
- Mechanisms of Cellular Quality Control, Max-Planck-Institute of Biophysics, Frankfurt, Germany
| | - Oliver P Ernst
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada; Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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4
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Shmueli MD, Sheban D, Eisenberg-Lerner A, Merbl Y. Histone degradation by the proteasome regulates chromatin and cellular plasticity. FEBS J 2021; 289:3304-3316. [PMID: 33914417 PMCID: PMC9292675 DOI: 10.1111/febs.15903] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 04/07/2021] [Accepted: 04/26/2021] [Indexed: 11/27/2022]
Abstract
Histones constitute the primary protein building blocks of the chromatin and play key roles in the dynamic control of chromatin compaction and epigenetic regulation. Histones are regulated by intricate mechanisms that alter their functionality and stability, thereby expanding the regulation of chromatin‐transacting processes. As such, histone degradation is tightly regulated to provide spatiotemporal control of cellular histone abundance. While several mechanisms have been implicated in controlling histone stability, here, we discuss proteasome‐dependent degradation of histones and the protein modifications that are associated with it. We then highlight specific cellular and physiological states that are associated with altered histone degradation by cellular proteasomes.
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Affiliation(s)
- Merav D Shmueli
- Department of Immunology, Weizmann Institute of Science, Rehovot, Israel
| | - Daoud Sheban
- Department of Immunology, Weizmann Institute of Science, Rehovot, Israel
| | | | - Yifat Merbl
- Department of Immunology, Weizmann Institute of Science, Rehovot, Israel
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5
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Yuan Q, Zhang S, Li J, Xiao J, Li X, Yang J, Lu D, Wang Y. Comprehensive analysis of core genes and key pathways in Parkinson's disease. Am J Transl Res 2020; 12:5630-5639. [PMID: 33042444 PMCID: PMC7540129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Accepted: 07/25/2020] [Indexed: 06/11/2023]
Abstract
Parkinson's disease (PD) is a neurodegenerative disease that occurs mostly in middle-aged and older adults. Its main pathological feature is the progressive death of substantia nigra dopaminergic neurons. As the world's population ages, the number of PD patients is increasing. In this study, we explored the relationship between PD and the cell cycle. In this study, we collected two independent PD transcriptomic datasets, GSE54536 and GSE6613, from the Gene Expression Omnibus (GEO) database. Gene set enrichment analysis (GSEA) was used to identify dysregulated pathways in PD samples. Gene expression was verified by qPCR in PD patients. Nineteen pathways were negatively enriched in both the GSE54536 and GSE6613 datasets. Seven of these 19 pathways were cell cycle-related pathways, including the M/G1 transition, S phase, G1/S transition, mitotic G1-G1/S phases, CDT1 association with the CDC6 ORC origin complex, cell cycle checkpoints and synthesis of DNA. Next, we found that eight genes (PSMA4, PSMB1, PSMC5, PSMD11, MCM4, RPA1, POLE, and PSME4) were mainly enriched in the GSE54536 and GSE6613 datasets. In GSE54536, PSMA4, PSMB1, PSMC5, and PSME4 could significantly predict the occurrence of PD, whereas, in GSE6613, RPA1 and PSME4 could significantly predict the occurrence of PD. Only PSME4 showed significant results in both datasets. Finally, we assessed blood samples from PD patients and controls. Compared with the control samples, the PD samples had lower mRNA levels of PSME4. In summary,these findings can significantly enhance our understanding of the causes and potential molecular mechanisms of PD; the cell cycle signaling pathways and PSME4 may be therapeutic targets for PD.
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Affiliation(s)
- Qian Yuan
- Department of Neurology, Wuhan Wuchang Hospital, Wuchang Hospital Affiliated to Wuhan University of Science and TechnologyWuhan 430063, China
- Department of Neurology, The Second Affiliated Hospital of Zhengzhou UniversityZhengzhou 450014, China
| | - Simiao Zhang
- Department of Neurology, The Second Affiliated Hospital of Zhengzhou UniversityZhengzhou 450014, China
| | - Jingna Li
- Department of Neurology, The Second Affiliated Hospital of Zhengzhou UniversityZhengzhou 450014, China
| | - Jianhao Xiao
- Department of Neurology, Shanghai Pudong Hospital, Fudan University Pudong Medical CenterShanghai 201399, China
| | - Xiaodong Li
- Department of Neurology, Zhengzhou Central HospitalZhengzhou 450014, China
| | - Jingmin Yang
- NHC Key Laboratory of Birth Defects and Reproductive Health, Chongqing Population and Family Planning Science and Technology Research InstitueChongqing 400020, China
| | - Daru Lu
- NHC Key Laboratory of Birth Defects and Reproductive Health, Chongqing Population and Family Planning Science and Technology Research InstitueChongqing 400020, China
| | - Yunliang Wang
- Department of Neurology, The Second Affiliated Hospital of Zhengzhou UniversityZhengzhou 450014, China
- Department of Neurology, The 960th Hospital of Chinese PLAZibo 255300, China
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6
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Douida A, Batista F, Robaszkiewicz A, Boto P, Aladdin A, Szenykiv M, Czinege R, Virág L, Tar K. The proteasome activator PA200 regulates expression of genes involved in cell survival upon selective mitochondrial inhibition in neuroblastoma cells. J Cell Mol Med 2020; 24:6716-6730. [PMID: 32368861 PMCID: PMC7299700 DOI: 10.1111/jcmm.15323] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 01/15/2020] [Accepted: 04/08/2020] [Indexed: 12/22/2022] Open
Abstract
The conserved Blm10/PA200 activators bind to the proteasome core and facilitate peptide and protein turnover. Blm10/PA200 proteins enhance proteasome peptidase activity and accelerate the degradation of unstructured proteasome substrates. Our knowledge about the exact role of PA200 in diseased cells, however, is still limited. Here, we show that stable knockdown of PA200 leads to a significantly elevated number of cells in S phase after treatment with the ATP synthase inhibitor, oligomycin. However, following exposure to the complex I inhibitor rotenone, more PA200‐depleted cells were in sub‐G1 and G2/M phases indicative of apoptosis. Chromatin immunoprecipitation (ChIP) and ChIP‐seq data analysis of collected reads indicate PA200‐enriched regions in the genome of SH‐SY5Y. We found that PA200 protein peaks were in the vicinity of transcription start sites. Gene ontology annotation revealed that genes whose promoters were enriched upon anti‐PA200 ChIP contribute to the regulation of crucial intracellular processes, including proliferation, protein modifications and metabolism. Selective mitochondrial inhibitors induced PA200 redistribution in the genome, leading to protein withdrawal from some gene promoters and binding to others. Collectively, the results support a model in which PA200 potentially regulates cellular homeostasis at the transcriptional level, in addition to its described role as an alternative activator of the proteasome.
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Affiliation(s)
- Abdennour Douida
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,University of Debrecen, Doctoral School of Molecular Medicine, Debrecen, Hungary
| | - Frank Batista
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Agnieszka Robaszkiewicz
- Department of General Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Lodz, Poland
| | - Pal Boto
- Stem Cell Differentiation Laboratory, Department of Biochemistry and Molecular Biology, University of Debrecen, Debrecen, Hungary
| | - Azzam Aladdin
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,University of Debrecen, Doctoral School of Molecular Medicine, Debrecen, Hungary
| | - Mónika Szenykiv
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Rita Czinege
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - László Virág
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Krisztina Tar
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
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7
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Wang X, Meul T, Meiners S. Exploring the proteasome system: A novel concept of proteasome inhibition and regulation. Pharmacol Ther 2020; 211:107526. [PMID: 32173559 DOI: 10.1016/j.pharmthera.2020.107526] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 03/08/2020] [Indexed: 12/13/2022]
Abstract
The proteasome is a well-identified therapeutic target for cancer treatment. It acts as the main protein degradation system in the cell and degrades key mediators of cell growth, survival and function. The term "proteasome" embraces a whole family of distinct complexes, which share a common proteolytic core, the 20S proteasome, but differ by their attached proteasome activators. Each of these proteasome complexes plays specific roles in the control of cellular function. In addition, distinct proteasome interacting proteins regulate proteasome activity in subcellular compartments and in response to cellular signals. Proteasome activators and regulators may thus serve as building blocks to fine-tune proteasome function in the cell according to cellular needs. Inhibitors of the proteasome, e.g. the FDA approved drugs Velcade™, Kyprolis™, Ninlaro™, inactivate the catalytic 20S core and effectively block protein degradation of all proteasome complexes in the cell resulting in inhibition of cell growth and induction of apoptosis. Efficacy of these inhibitors, however, is hampered by their pronounced cytotoxic side-effects as well as by the emerging development of resistance to catalytic proteasome inhibitors. Targeted inhibition of distinct buiding blocks of the proteasome system, i.e. proteasome activators or regulators, represents an alternative strategy to overcome these limitations. In this review, we stress the importance of the diversity of the proteasome complexes constituting an entire proteasome system. Our building block concept provides a rationale for the defined targeting of distinct proteasome super-complexes in disease. We thereby aim to stimulate the development of innovative therapeutic approaches beyond broad catalytic proteasome inhibition.
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Affiliation(s)
- Xinyuan Wang
- Comprehensive Pneumology Center (CPC), University Hospital of the Ludwig-Maximilians-University (LMU) and Helmholtz Zentrum München, German Center for Lung Research (DZL), 81377 Munich, Germany
| | - Thomas Meul
- Comprehensive Pneumology Center (CPC), University Hospital of the Ludwig-Maximilians-University (LMU) and Helmholtz Zentrum München, German Center for Lung Research (DZL), 81377 Munich, Germany
| | - Silke Meiners
- Comprehensive Pneumology Center (CPC), University Hospital of the Ludwig-Maximilians-University (LMU) and Helmholtz Zentrum München, German Center for Lung Research (DZL), 81377 Munich, Germany.
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8
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Farooqi K, Ghazvini M, Pride LD, Mazzella L, White D, Pramanik A, Bargonetti J, Moore CW. A Protein in the Yeast Saccharomyces cerevisiae Presents DNA Binding Homology to the p53 Checkpoint Protein and Tumor Suppressor. Biomolecules 2020; 10:E417. [PMID: 32156076 PMCID: PMC7175211 DOI: 10.3390/biom10030417] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 02/28/2020] [Accepted: 03/04/2020] [Indexed: 02/07/2023] Open
Abstract
Saccharomyces cerevisiae does not contain a p53 homolog. Utilizing this yeast as an in vivo test tube model, our aim was to investigate if a yeast protein would show p53 DNA binding homology. Electrophoretic mobility shift analyses revealed the formation of specific DNA-protein complexes consisting of S. cerevisiae nuclear protein(s) and oligonucleotides containing p53 DNA binding sites. A S. cerevisiae p53 binding site factor (Scp53BSF) bound to a p53 synthetic DNA-consensus sequence (SCS) and a p53 binding-site sequence from the MDM2 oncogene. The complexes were of comparable size. Like mammalian p53, the affinity of Scp53BSF for the SCS oligonucleotide was higher than for the MDM2 oligonucleotide. Binding of Scp53BSF to the SCS and MDM2 oligonucleotides was strongly competed by unlabeled oligonucleotides containing mammalian p53 sites, but very little by a mutated site oligonucleotide. Importantly, Scp53BSF-DNA binding activity was significantly induced in extracts from cells with DNA damage. This resulted in dose-dependent coordinated activation of transcription when using p53-binding site reporter constructs. An ancient p53-like DNA binding protein may have been found, and activation of DNA-associated factors to p53 response elements may have functions not yet determined.
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Affiliation(s)
- Kanwal Farooqi
- Department of Molecular, Cellular and Biomedical Studies, City University of New York School of Medicine and B.S.-M.D. Program, Harris Hall, 160 Convent Avenue, New York, NY 10031, USA; (K.F.); (M.G.); (L.D.P.); (L.M.); (A.P.)
| | - Marjan Ghazvini
- Department of Molecular, Cellular and Biomedical Studies, City University of New York School of Medicine and B.S.-M.D. Program, Harris Hall, 160 Convent Avenue, New York, NY 10031, USA; (K.F.); (M.G.); (L.D.P.); (L.M.); (A.P.)
| | - Leah D. Pride
- Department of Molecular, Cellular and Biomedical Studies, City University of New York School of Medicine and B.S.-M.D. Program, Harris Hall, 160 Convent Avenue, New York, NY 10031, USA; (K.F.); (M.G.); (L.D.P.); (L.M.); (A.P.)
- City University of New York Graduate Center, Programs in Biochemistry and Biology, 365 Fifth Ave, New York, NY 10016, USA; (D.W.); (J.B.)
| | - Louis Mazzella
- Department of Molecular, Cellular and Biomedical Studies, City University of New York School of Medicine and B.S.-M.D. Program, Harris Hall, 160 Convent Avenue, New York, NY 10031, USA; (K.F.); (M.G.); (L.D.P.); (L.M.); (A.P.)
| | - David White
- City University of New York Graduate Center, Programs in Biochemistry and Biology, 365 Fifth Ave, New York, NY 10016, USA; (D.W.); (J.B.)
- Department of Biology, Hunter College, City University of New York, 695 Park Avenue, New York, NY 10021, USA
| | - Ajay Pramanik
- Department of Molecular, Cellular and Biomedical Studies, City University of New York School of Medicine and B.S.-M.D. Program, Harris Hall, 160 Convent Avenue, New York, NY 10031, USA; (K.F.); (M.G.); (L.D.P.); (L.M.); (A.P.)
| | - Jill Bargonetti
- City University of New York Graduate Center, Programs in Biochemistry and Biology, 365 Fifth Ave, New York, NY 10016, USA; (D.W.); (J.B.)
- Department of Biology, Hunter College, City University of New York, 695 Park Avenue, New York, NY 10021, USA
| | - Carol Wood Moore
- Department of Molecular, Cellular and Biomedical Studies, City University of New York School of Medicine and B.S.-M.D. Program, Harris Hall, 160 Convent Avenue, New York, NY 10031, USA; (K.F.); (M.G.); (L.D.P.); (L.M.); (A.P.)
- City University of New York Graduate Center, Programs in Biochemistry and Biology, 365 Fifth Ave, New York, NY 10016, USA; (D.W.); (J.B.)
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Coux O, Zieba BA, Meiners S. The Proteasome System in Health and Disease. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1233:55-100. [DOI: 10.1007/978-3-030-38266-7_3] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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10
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Wendler P, Enenkel C. Nuclear Transport of Yeast Proteasomes. Front Mol Biosci 2019; 6:34. [PMID: 31157235 PMCID: PMC6532418 DOI: 10.3389/fmolb.2019.00034] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2019] [Accepted: 04/26/2019] [Indexed: 11/13/2022] Open
Abstract
Proteasomes are key proteases in regulating protein homeostasis. Their holo-enzymes are composed of 40 different subunits which are arranged in a proteolytic core (CP) flanked by one to two regulatory particles (RP). Proteasomal proteolysis is essential for the degradation of proteins which control time-sensitive processes like cell cycle progression and stress response. In dividing yeast and human cells, proteasomes are primarily nuclear suggesting that proteasomal proteolysis is mainly required in the nucleus during cell proliferation. In yeast, which have a closed mitosis, proteasomes are imported into the nucleus as immature precursors via the classical import pathway. During quiescence, the reversible absence of proliferation induced by nutrient depletion or growth factor deprivation, proteasomes move from the nucleus into the cytoplasm. In the cytoplasm of quiescent yeast, proteasomes are dissociated into CP and RP and stored in membrane-less cytoplasmic foci, named proteasome storage granules (PSGs). With the resumption of growth, PSGs clear and mature proteasomes are transported into the nucleus by Blm10, a conserved 240 kDa protein and proteasome-intrinsic import receptor. How proteasomes are exported from the nucleus into the cytoplasm is unknown.
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Affiliation(s)
- Petra Wendler
- Institut für Biochemie und Biologie, Universität Potsdam, Potsdam, Germany
| | - Cordula Enenkel
- Department of Biochemistry, University of Toronto, Toronto, ON, Canada
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Herbert S, Brion A, Arbona JM, Lelek M, Veillet A, Lelandais B, Parmar J, Fernández FG, Almayrac E, Khalil Y, Birgy E, Fabre E, Zimmer C. Chromatin stiffening underlies enhanced locus mobility after DNA damage in budding yeast. EMBO J 2017; 36:2595-2608. [PMID: 28694242 PMCID: PMC5579376 DOI: 10.15252/embj.201695842] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 05/15/2017] [Accepted: 05/18/2017] [Indexed: 12/31/2022] Open
Abstract
DNA double-strand breaks (DSBs) induce a cellular response that involves histone modifications and chromatin remodeling at the damaged site and increases chromosome dynamics both locally at the damaged site and globally in the nucleus. In parallel, it has become clear that the spatial organization and dynamics of chromosomes can be largely explained by the statistical properties of tethered, but randomly moving, polymer chains, characterized mainly by their rigidity and compaction. How these properties of chromatin are affected during DNA damage remains, however, unclear. Here, we use live cell microscopy to track chromatin loci and measure distances between loci on yeast chromosome IV in thousands of cells, in the presence or absence of genotoxic stress. We confirm that DSBs result in enhanced chromatin subdiffusion and show that intrachromosomal distances increase with DNA damage all along the chromosome. Our data can be explained by an increase in chromatin rigidity, but not by chromatin decondensation or centromeric untethering only. We provide evidence that chromatin stiffening is mediated in part by histone H2A phosphorylation. Our results support a genome-wide stiffening of the chromatin fiber as a consequence of DNA damage and as a novel mechanism underlying increased chromatin mobility.
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Affiliation(s)
- Sébastien Herbert
- Unité Imagerie et Modélisation, Institut Pasteur, Paris, France
- CNRS UMR 3691, C3BI, USR 3756 IP CNRS, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Alice Brion
- Equipe Biologie et Dynamique des Chromosomes, Institut Universitaire d'Hématologie, Hôpital St. Louis, Paris, France
- CNRS UMR 7212, INSERM U944, IUH, Université Paris Diderot Sorbonne Paris Cité, Paris, France
| | - Jean-Michel Arbona
- Unité Imagerie et Modélisation, Institut Pasteur, Paris, France
- CNRS UMR 3691, C3BI, USR 3756 IP CNRS, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Mickaël Lelek
- Unité Imagerie et Modélisation, Institut Pasteur, Paris, France
- CNRS UMR 3691, C3BI, USR 3756 IP CNRS, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Adeline Veillet
- Equipe Biologie et Dynamique des Chromosomes, Institut Universitaire d'Hématologie, Hôpital St. Louis, Paris, France
- CNRS UMR 7212, INSERM U944, IUH, Université Paris Diderot Sorbonne Paris Cité, Paris, France
| | - Benoît Lelandais
- Unité Imagerie et Modélisation, Institut Pasteur, Paris, France
- CNRS UMR 3691, C3BI, USR 3756 IP CNRS, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Jyotsana Parmar
- Unité Imagerie et Modélisation, Institut Pasteur, Paris, France
- CNRS UMR 3691, C3BI, USR 3756 IP CNRS, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Fabiola García Fernández
- Equipe Biologie et Dynamique des Chromosomes, Institut Universitaire d'Hématologie, Hôpital St. Louis, Paris, France
- CNRS UMR 7212, INSERM U944, IUH, Université Paris Diderot Sorbonne Paris Cité, Paris, France
| | - Etienne Almayrac
- Equipe Biologie et Dynamique des Chromosomes, Institut Universitaire d'Hématologie, Hôpital St. Louis, Paris, France
- CNRS UMR 7212, INSERM U944, IUH, Université Paris Diderot Sorbonne Paris Cité, Paris, France
| | - Yasmine Khalil
- Equipe Biologie et Dynamique des Chromosomes, Institut Universitaire d'Hématologie, Hôpital St. Louis, Paris, France
- CNRS UMR 7212, INSERM U944, IUH, Université Paris Diderot Sorbonne Paris Cité, Paris, France
| | - Eleonore Birgy
- Equipe Biologie et Dynamique des Chromosomes, Institut Universitaire d'Hématologie, Hôpital St. Louis, Paris, France
- CNRS UMR 7212, INSERM U944, IUH, Université Paris Diderot Sorbonne Paris Cité, Paris, France
| | - Emmanuelle Fabre
- Equipe Biologie et Dynamique des Chromosomes, Institut Universitaire d'Hématologie, Hôpital St. Louis, Paris, France
- CNRS UMR 7212, INSERM U944, IUH, Université Paris Diderot Sorbonne Paris Cité, Paris, France
| | - Christophe Zimmer
- Unité Imagerie et Modélisation, Institut Pasteur, Paris, France
- CNRS UMR 3691, C3BI, USR 3756 IP CNRS, Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
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12
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Enenkel C. The paradox of proteasome granules. Curr Genet 2017; 64:137-140. [PMID: 28835998 DOI: 10.1007/s00294-017-0739-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2017] [Revised: 08/15/2017] [Accepted: 08/17/2017] [Indexed: 01/22/2023]
Abstract
Profound knowledge is available for the structure, function and regulation of proteasomes, the key proteases for ubiquitin-dependent protein degradation in dividing cells. Far less understood are proteasome structure and function in quiescence, the resting phase of our body's cells, as in yeast cells grown to stationary phase. In quiescent yeast proteasomes exit the nucleus and accumulate in cytoplasmic protein droplets, called proteasome storage granules (PSG). PSG-like structures also exist in non-dividing mammalian cells suggesting that the mechanism underlying PSG organization is conserved from yeast to human. The PSG has physiological significance as it protects yeast cells against stress and confers fitness during aging. The molecular architecture of PSG remains an enigma, since PSG freely move as spherical units without being surrounded by membranes through the cytoplasm. They rapidly resolve with the resumption of cell proliferation and proteasomes reenter the nucleus. Our systems biology and biochemical data revealed that PSG are mainly composed of proteasomes and free ubiquitin. Often intrinsically disordered proteins undergo liquid phase separations, allowing soluble proteins to condense into protein droplets in an aqueous solution. The question is which proteins and factors nucleate PSG formation, since proteasomes composed of folded subunits are able to degrade intrinsically disordered proteins.
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Affiliation(s)
- Cordula Enenkel
- Department of Biochemistry, University of Toronto, 661 University Avenue, MaRS2 1511, Toronto, ON, M5G 1M1, Canada.
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13
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Gu ZC, Wu E, Sailer C, Jando J, Styles E, Eisenkolb I, Kuschel M, Bitschar K, Wang X, Huang L, Vissa A, Yip CM, Yedidi RS, Friesen H, Enenkel C. Ubiquitin orchestrates proteasome dynamics between proliferation and quiescence in yeast. Mol Biol Cell 2017; 28:2479-2491. [PMID: 28768827 PMCID: PMC5597321 DOI: 10.1091/mbc.e17-03-0162] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 06/16/2017] [Accepted: 07/24/2017] [Indexed: 12/14/2022] Open
Abstract
Proteasomes are key protease complexes responsible for protein degradation, and their localization changes with the growth conditions. This work in yeast shows that proteasomes exit the nucleus with the transition from proliferation to quiescence. Ubiquitin is a key player in proteasome dynamics and cytoplasmic proteasome granule formation. Proteasomes are essential for protein degradation in proliferating cells. Little is known about proteasome functions in quiescent cells. In nondividing yeast, a eukaryotic model of quiescence, proteasomes are depleted from the nucleus and accumulate in motile cytosolic granules termed proteasome storage granules (PSGs). PSGs enhance resistance to genotoxic stress and confer fitness during aging. Upon exit from quiescence PSGs dissolve, and proteasomes are rapidly delivered into the nucleus. To identify key players in PSG organization, we performed high-throughput imaging of green fluorescent protein (GFP)-labeled proteasomes in the yeast null-mutant collection. Mutants with reduced levels of ubiquitin are impaired in PSG formation. Colocalization studies of PSGs with proteins of the yeast GFP collection, mass spectrometry, and direct stochastic optical reconstitution microscopy of cross-linked PSGs revealed that PSGs are densely packed with proteasomes and contain ubiquitin but no polyubiquitin chains. Our results provide insight into proteasome dynamics between proliferating and quiescent yeast in response to cellular requirements for ubiquitin-dependent degradation.
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Affiliation(s)
- Zhu Chao Gu
- Department of Biochemistry, University of Toronto, Toronto, ON M5G 1M1, Canada
| | - Edwin Wu
- Department of Biochemistry, University of Toronto, Toronto, ON M5G 1M1, Canada
| | - Carolin Sailer
- Department of Biochemistry, University of Toronto, Toronto, ON M5G 1M1, Canada
| | - Julia Jando
- Department of Biochemistry, University of Toronto, Toronto, ON M5G 1M1, Canada
| | - Erin Styles
- Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Ina Eisenkolb
- Department of Biochemistry, University of Toronto, Toronto, ON M5G 1M1, Canada
| | - Maike Kuschel
- Department of Biochemistry, University of Toronto, Toronto, ON M5G 1M1, Canada
| | - Katharina Bitschar
- Department of Biochemistry, University of Toronto, Toronto, ON M5G 1M1, Canada
| | - Xiaorong Wang
- Department of Physics and Biophysics, University of California, Irvine, Irvine, CA 92697
| | - Lan Huang
- Department of Physics and Biophysics, University of California, Irvine, Irvine, CA 92697
| | - Adriano Vissa
- Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Christopher M Yip
- Department of Biochemistry, University of Toronto, Toronto, ON M5G 1M1, Canada.,Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Ravikiran S Yedidi
- Department of Biochemistry, University of Toronto, Toronto, ON M5G 1M1, Canada
| | - Helena Friesen
- Donnelly Centre, University of Toronto, Toronto, ON M5S 3E1, Canada
| | - Cordula Enenkel
- Department of Biochemistry, University of Toronto, Toronto, ON M5G 1M1, Canada
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Yedidi RS, Fatehi AK, Enenkel C. Proteasome dynamics between proliferation and quiescence stages of Saccharomyces cerevisiae. Crit Rev Biochem Mol Biol 2016; 51:497-512. [PMID: 27677933 DOI: 10.1080/10409238.2016.1230087] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The ubiquitin-proteasome system (UPS) plays a critical role in cellular protein homeostasis and is required for the turnover of short-lived and unwanted proteins, which are targeted by poly-ubiquitination for degradation. Proteasome is the key protease of UPS and consists of multiple subunits, which are organized into a catalytic core particle (CP) and a regulatory particle (RP). In Saccharomyces cerevisiae, proteasome holo-enzymes are engaged in degrading poly-ubiquitinated substrates and are mostly localized in the nucleus during cell proliferation. While in quiescence, the RP and CP are sequestered into motile and reversible storage granules in the cytoplasm, called proteasome storage granules (PSGs). The reversible nature of PSGs allows the proteasomes to be transported back into the nucleus upon exit from quiescence. Nuclear import of RP and CP through nuclear pores occurs via the canonical pathway that includes the importin-αβ heterodimer and takes advantage of the Ran-GTP gradient across the nuclear membrane. Dependent on the growth stage, either inactive precursor complexes or mature holo-enzymes are imported into the nucleus. The present review discusses the dynamics of proteasomes including their assembly, nucleo-cytoplasmic transport during proliferation and the sequestration of proteasomes into PSGs during quiescence. [Formula: see text].
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Affiliation(s)
| | | | - Cordula Enenkel
- a Department of Biochemistry , University of Toronto , Toronto , Canada
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15
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Abstract
“Big Data” has surpassed “systems biology” and “omics” as the hottest buzzword in the biological sciences, but is there any substance behind the hype? Certainly, we have learned about various aspects of cell and molecular biology from the many individual high-throughput data sets that have been published in the past 15–20 years. These data, although useful as individual data sets, can provide much more knowledge when interrogated with Big Data approaches, such as applying integrative methods that leverage the heterogeneous data compendia in their entirety. Here we discuss the benefits and challenges of such Big Data approaches in biology and how cell and molecular biologists can best take advantage of them.
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Affiliation(s)
- Kara Dolinski
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08540
| | - Olga G Troyanskaya
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08540 Department of Computer Science, Princeton University, Princeton, NJ 08540 Simons Center for Data Analysis, Simons Foundation, New York, NY 10010
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16
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Rao G, Croft B, Teng C, Awasthi V. Ubiquitin-Proteasome System in Neurodegenerative Disorders. JOURNAL OF DRUG METABOLISM & TOXICOLOGY 2015; 6:187. [PMID: 30761219 PMCID: PMC6370320 DOI: 10.4172/2157-7609.1000187] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cellular proteostasis is a highly dynamic process and is primarily carried out by the degradation tools of ubiquitin-proteasome system (UPS). Abnormalities in UPS function result in the accumulation of damaged or misfolded proteins which can form intra- and extracellular aggregated proteinaceous deposits leading to cellular dysfunction and/or death. Deposition of abnormal protein aggregates and the cellular inability to clear them have been implicated in the pathogenesis of a number of neurodegenerative disorders such as Alzheimer's and Parkinson's. Contrary to the upregulation of proteasome function in oncogenesis and the use of proteasome inhibition as a therapeutic strategy, activation of proteasome function would serve therapeutic objectives of treatment of neurodegenerative diseases. This review describes the current understanding of the role of the proteasome in neurodegenerative disorders and potential utility of proteasomal modulation therein.
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Affiliation(s)
- Geeta Rao
- Department of Pharmaceutical Sciences, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
| | - Brandon Croft
- Department of Pharmaceutical Sciences, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
| | - Chengwen Teng
- Department of Pharmaceutical Sciences, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
| | - Vibhudutta Awasthi
- Department of Pharmaceutical Sciences, University of Oklahoma Health Science Center, Oklahoma City, OK, USA
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17
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Burcoglu J, Zhao L, Enenkel C. Nuclear Import of Yeast Proteasomes. Cells 2015; 4:387-405. [PMID: 26262643 PMCID: PMC4588042 DOI: 10.3390/cells4030387] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2015] [Accepted: 06/28/2015] [Indexed: 01/16/2023] Open
Abstract
Proteasomes are highly conserved protease complexes responsible for the degradation of aberrant and short-lived proteins. In highly proliferating yeast and mammalian cells, proteasomes are predominantly nuclear. During quiescence and cell cycle arrest, proteasomes accumulate in granules in close proximity to the nuclear envelope/ER. With prolonged quiescence in yeast, these proteasome granules pinch off as membraneless organelles, and migrate as stable entities through the cytoplasm. Upon exit from quiescence, the proteasome granules clear and the proteasomes are rapidly transported into the nucleus, a process reflecting the dynamic nature of these multisubunit complexes. Due to the scarcity of studies on the nuclear transport of mammalian proteasomes, we summarised the current knowledge on the nuclear import of yeast proteasomes. This pathway uses canonical nuclear localisation signals within proteasomal subunits and Srp1/Kap95, and the canonical import receptor, named importin/karyopherin αβ. Blm10, a conserved 240 kDa protein, which is structurally related to Kap95, provides an alternative import pathway. Two models exist upon which either inactive precursor complexes or active holo-enzymes serve as the import cargo. Here, we reconcile both models and suggest that the import of inactive precursor complexes predominates in dividing cells, while the import of mature enzymes mainly occurs upon exit from quiescence.
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Affiliation(s)
- Julianne Burcoglu
- Biochemistry Department, University of Toronto, Toronto, ON M5S 1A8, Canada.
| | - Liang Zhao
- Biochemistry Department, University of Toronto, Toronto, ON M5S 1A8, Canada.
| | - Cordula Enenkel
- Biochemistry Department, University of Toronto, Toronto, ON M5S 1A8, Canada.
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18
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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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19
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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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20
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Abstract
All living organisms require protein degradation to terminate biological processes and remove damaged proteins. One such machine is the 20S proteasome, a specialized barrel-shaped and compartmentalized multicatalytic protease. The activity of the 20S proteasome generally requires the binding of regulators/proteasome activators (PAs), which control the entrance of substrates. These include the PA700 (19S complex), which assembles with the 20S and forms the 26S proteasome and allows the efficient degradation of proteins usually labeled by ubiquitin tags, PA200 and PA28, which are involved in proteolysis through ubiquitin-independent mechanisms and PI31, which was initially identified as a 20S inhibitor in vitro. Unlike 20S proteasome, shown to be present in all Eukaryotes and Archaea, the evolutionary history of PAs remained fragmentary. Here, we made a comprehensive survey and phylogenetic analyses of the four types of regulators in 17 clades covering most of the eukaryotic supergroups. We found remarkable conservation of each PA700 subunit in all eukaryotes, indicating that the current complex PA700 structure was already set up in the last eukaryotic common ancestor (LECA). Also present in LECA, PA200, PA28, and PI31 showed a more contrasted evolutionary picture, because many lineages have subsequently lost one or two of them. The paramount conservation of PA700 composition in all eukaryotes and the dynamic evolution of PA200, PA28, and PI31 are discussed in the light of current knowledge on their physiological roles.
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Affiliation(s)
- Philippe Fort
- CNRS, CRBM, UMR5237, Montpellier, France Université de Montpellier, France
| | - Andrey V Kajava
- CNRS, CRBM, UMR5237, Montpellier, France Université de Montpellier, France Institut de Biologie Computationnelle, Montpellier, France
| | - Fredéric Delsuc
- Université de Montpellier, France CNRS, IRD, Institut des Sciences de l'Evolution, UMR 5554, Montpellier, France
| | - Olivier Coux
- CNRS, CRBM, UMR5237, Montpellier, France Université de Montpellier, France
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21
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Enenkel C. Nuclear transport of yeast proteasomes. Biomolecules 2014; 4:940-55. [PMID: 25333764 PMCID: PMC4279164 DOI: 10.3390/biom4040940] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2014] [Revised: 08/18/2014] [Accepted: 09/26/2014] [Indexed: 12/25/2022] Open
Abstract
Proteasomes are conserved protease complexes enriched in the nuclei of dividing yeast cells, a major site for protein degradation. If yeast cells do not proliferate and transit to quiescence, metabolic changes result in the dissociation of proteasomes into proteolytic core and regulatory complexes and their sequestration into motile cytosolic proteasome storage granuli. These granuli rapidly clear with the resumption of growth, releasing the stored proteasomes, which relocalize back to the nucleus to promote cell cycle progression. Here, I report on three models of how proteasomes are transported from the cytoplasm into the nucleus of yeast cells. The first model applies for dividing yeast and is based on the canonical pathway using classical nuclear localization sequences of proteasomal subcomplexes and the classical import receptor importin/karyopherin αβ. The second model applies for quiescent yeast cells, which resume growth and use Blm10, a HEAT-like repeat protein structurally related to karyopherin β, for nuclear import of proteasome core particles. In the third model, the fully-assembled proteasome is imported into the nucleus. Our still marginal knowledge about proteasome dynamics will inspire the discussion on how protein degradation by proteasomes may be regulated in different cellular compartments of dividing and quiescent eukaryotic cells.
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Affiliation(s)
- 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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22
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Schmidt M, Finley D. Regulation of proteasome activity in health and disease. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1843:13-25. [PMID: 23994620 DOI: 10.1016/j.bbamcr.2013.08.012] [Citation(s) in RCA: 318] [Impact Index Per Article: 28.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Revised: 08/05/2013] [Accepted: 08/07/2013] [Indexed: 12/13/2022]
Abstract
The ubiquitin-proteasome system (UPS) is the primary selective degradation system in the nuclei and cytoplasm of eukaryotic cells, required for the turnover of myriad soluble proteins. The hundreds of factors that comprise the UPS include an enzymatic cascade that tags proteins for degradation via the covalent attachment of a poly-ubiquitin chain, and a large multimeric enzyme that degrades ubiquitinated proteins, the proteasome. Protein degradation by the UPS regulates many pathways and is a crucial component of the cellular proteostasis network. Dysfunction of the ubiquitination machinery or the proteolytic activity of the proteasome is associated with numerous human diseases. In this review we discuss the contributions of the proteasome to human pathology, describe mechanisms that regulate the proteolytic capacity of the proteasome, and discuss strategies to modulate proteasome function as a therapeutic approach to ameliorate diseases associated with altered UPS function. This article is part of a Special Issue entitled: Ubiquitin-Proteasome System. Guest Editors: Thomas Sommer and Dieter H. Wolf.
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Affiliation(s)
- Marion Schmidt
- Albert Einstein College of Medicine, Department of Biochemistry, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
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Weberruss MH, Savulescu AF, Jando J, Bissinger T, Harel A, Glickman MH, Enenkel C. Blm10 facilitates nuclear import of proteasome core particles. EMBO J 2013; 32:2697-707. [PMID: 23982732 DOI: 10.1038/emboj.2013.192] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 08/02/2013] [Indexed: 01/12/2023] Open
Abstract
Short-lived proteins are degraded by proteasome complexes, which contain a proteolytic core particle (CP) but differ in the number of regulatory particles (RPs) and activators. A recently described member of conserved proteasome activators is Blm10. Blm10 contains 32 HEAT-like modules and is structurally related to the nuclear import receptor importin/karyopherin β. In proliferating yeast, RP-CP assemblies are primarily nuclear and promote cell division. During quiescence, RP-CP assemblies dissociate and CP and RP are sequestered into motile cytosolic proteasome storage granuli (PSG). Here, we show that CP sequestration into PSG depends on Blm10, whereas RP sequestration into PSG is independent of Blm10. PSG rapidly clear upon the resumption of cell proliferation and proteasomes are relocated into the nucleus. Thereby, Blm10 facilitates nuclear import of CP. Blm10-bound CP serves as an import receptor-cargo complex, as Blm10 mediates the interaction with FG-rich nucleoporins and is dissociated from the CP by Ran-GTP. Thus, Blm10 represents the first CP-dedicated nuclear import receptor in yeast.
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Affiliation(s)
- Marion H Weberruss
- 1] Department of Biochemistry, University of Toronto, One King's College Circle, Toronto, Ontario, Canada [2] Institute of Biochemistry, University of Stuttgart, Stuttgart, Germany
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The Not4 RING E3 Ligase: A Relevant Player in Cotranslational Quality Control. ISRN MOLECULAR BIOLOGY 2013; 2013:548359. [PMID: 27335678 PMCID: PMC4890865 DOI: 10.1155/2013/548359] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/04/2012] [Accepted: 11/21/2012] [Indexed: 12/02/2022]
Abstract
The Not4 RING E3 ligase is a subunit of the evolutionarily conserved Ccr4-Not complex. Originally identified in yeast by mutations that increase transcription, it was subsequently defined as an ubiquitin ligase. Substrates for this ligase were characterized in yeast and in metazoans. Interestingly, some substrates for this ligase are targeted for polyubiquitination and degradation, while others instead are stable monoubiquitinated proteins. The former are mostly involved in transcription, while the latter are a ribosomal protein and a ribosome-associated chaperone. Consistently, Not4 and all other subunits of the Ccr4-Not complex are present in translating ribosomes. An important function for Not4 in cotranslational quality control has emerged. In the absence of Not4, the total level of polysomes is reduced. In addition, translationally arrested polypeptides, aggregated proteins, and polyubiquitinated proteins accumulate. Its role in quality control is likely to be related on one hand to its importance for the functional assembly of the proteasome and on the other hand to its association with the RNA degradation machines. Not4 is in an ideal position to signal to degradation mRNAs whose translation has been aborted, and this defines Not4 as a key player in the quality control of newly synthesized proteins.
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