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Zhu Y, Shigeyoshi K, Hayakawa Y, Fujiwara S, Kishida M, Ohki H, Horibe T, Shionyu M, Mizukami T, Hasegawa M. Acceleration of Protein Degradation by 20S Proteasome-Binding Peptides Generated by In Vitro Artificial Evolution. Int J Mol Sci 2023; 24:17486. [PMID: 38139315 PMCID: PMC10743564 DOI: 10.3390/ijms242417486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Revised: 12/05/2023] [Accepted: 12/11/2023] [Indexed: 12/24/2023] Open
Abstract
Although the 20S core particle (CP) of the proteasome is an important component of the 26S holoenzyme, the stand-alone 20S CP acts directly on intrinsically disordered and oxidized/damaged proteins to degrade them in a ubiquitin-independent manner. It has been postulated that some structural features of substrate proteins are recognized by the 20S CP to promote substrate uptake, but the mechanism of substrate recognition has not been fully elucidated. In this study, we screened peptides that bind to the 20S CP from a random eight-residue pool of amino acid sequences using complementary DNA display an in vitro molecular evolution technique. The identified 20S CP-binding amino acid sequence was chemically synthesized and its effects on the 20S CP were investigated. The 20S CP-binding peptide stimulated the proteolytic activity of the inactive form of 20S CP. The peptide bound directly to one of the α-subunits, opening a gate for substrate entry on the α-ring. Furthermore, the attachment of this peptide sequence to α-synuclein enhanced its degradation by the 20S CP in vitro. In addition to these results, docking simulations indicated that this peptide binds to the top surface of the α-ring. These peptides could function as a key to control the opening of the α-ring gate.
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Affiliation(s)
- Yunhao Zhu
- Graduate School of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura-cho, Nagahama 526-0829, Japan
| | - Kaishin Shigeyoshi
- Graduate School of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura-cho, Nagahama 526-0829, Japan
| | - Yumiko Hayakawa
- Graduate School of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura-cho, Nagahama 526-0829, Japan
| | - Sae Fujiwara
- Graduate School of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura-cho, Nagahama 526-0829, Japan
| | - Masamichi Kishida
- Modality Research Laboratories, Biologics Division, Daiichi Sankyo Co., Ltd., 1-2-58, Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan
| | - Hitoshi Ohki
- Modality Research Laboratories, Biologics Division, Daiichi Sankyo Co., Ltd., 1-2-58, Hiromachi, Shinagawa-ku, Tokyo 140-8710, Japan
| | - Tomohisa Horibe
- Graduate School of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura-cho, Nagahama 526-0829, Japan
| | - Masafumi Shionyu
- Graduate School of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura-cho, Nagahama 526-0829, Japan
| | - Tamio Mizukami
- Graduate School of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura-cho, Nagahama 526-0829, Japan
- Frontier Pharma Inc., 1281-8 Tamura, Nagahama 526-0829, Japan
| | - Makoto Hasegawa
- Graduate School of Bioscience, Nagahama Institute of Bio-Science and Technology, 1266 Tamura-cho, Nagahama 526-0829, Japan
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2
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Buneeva OA, Kopylov AT, Medvedev AE. Proteasome Interactome and Its Role in the Mechanisms of Brain Plasticity. BIOCHEMISTRY (MOSCOW) 2023; 88:319-336. [PMID: 37076280 DOI: 10.1134/s0006297923030033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/28/2023]
Abstract
Abstract
Proteasomes are highly conserved multienzyme complexes responsible for proteolytic degradation of the short-lived, regulatory, misfolded, and damaged proteins. They play an important role in the processes of brain plasticity, and decrease in their function is accompanied by the development of neurodegenerative pathology. Studies performed in different laboratories both on cultured mammalian and human cells and on preparations of the rat and rabbit brain cortex revealed a large number of proteasome-associated proteins. Since the identified proteins belong to certain metabolic pathways, multiple enrichment of the proteasome fraction with these proteins indicates their important role in proteasome functioning. Extrapolation of the experimental data, obtained on various biological objects, to the human brain suggests that the proteasome-associated proteins account for at least 28% of the human brain proteome. The proteasome interactome of the brain contains a large number of proteins involved in the assembly of these supramolecular complexes, regulation of their functioning, and intracellular localization, which could be changed under different conditions (for example, during oxidative stress) or in different phases of the cell cycle. In the context of molecular functions of the Gene Ontology (GO) Pathways, the proteins of the proteasome interactome mediate cross-talk between components of more than 30 metabolic pathways annotated in terms of GO. The main result of these interactions is binding of adenine and guanine nucleotides, crucial for realization of the nucleotide-dependent functions of the 26S and 20S proteasomes. Since the development of neurodegenerative pathology is often associated with regioselective decrease in the functional activity of proteasomes, a positive therapeutic effect would be obviously provided by the factors increasing proteasomal activity. In any case, pharmacological regulation of the brain proteasomes seems to be realized through the changes in composition and/or activity of the proteins associated with proteasomes (deubiquitinase, PKA, CaMKIIα, etc.).
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Affiliation(s)
- Olga A Buneeva
- Institute of Biomedical Chemistry, Moscow, 119121, Russia
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3
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Buneeva OA, Kopylov AT, Medvedev AE. [The key role of the regulatory 19S subunit in changes in the brain proteasome subproteome induced by the neuroprotector isatin]. BIOMEDITSINSKAIA KHIMIIA 2022; 68:250-262. [PMID: 36005843 DOI: 10.18097/pbmc20226804250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Isatin (indole-2,3-dione) is an endogenous regulator exhibiting various effects mediated by numerous isatin-binding proteins localized in different compartments of cells of the brain and peripheral tissues. It attenuates manifestations of experimental parkinsonism induced by administration of the MPTP neurotoxin and reduces the movement disorders characteristic of this disease. The molecular mechanisms of the neuroprotective action of isatin include its direct interaction with proteasomes, intracellular supramolecular complexes responsible for the targeted elimination of proteins. Incubation of fractions of 26S and 20S rabbit brain proteasomes, containing the whole spectrum of proteasomal subunits, as well as a number of proteasome-associated proteins, with isatin (100 μM) had a significant impact on the profile of released proteins. In the case of 26S proteasomes containing, in addition to the core part (20S proteasome), 19S regulatory subparticles, incubation with isatin resulted in a more than threefold increase in the number of dissociated proteins. In the case of 20S proteasomes (containing only the 20S core particle), incubation with isatin resulted in a significant decrease in the number of dissociated proteins compared to the control. Our results indicate an important role of the regulatory 19S subunit components in the formation of the proteasome subproteome and the sensitivity of these supramolecular complexes to isatin.
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Affiliation(s)
- O A Buneeva
- Institute of Biomedical Chemistry, Moscow, Russia
| | - A T Kopylov
- Institute of Biomedical Chemistry, Moscow, Russia
| | - A E Medvedev
- Institute of Biomedical Chemistry, Moscow, Russia
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4
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Bikorimana JP, El-Hachem N, El-Kadiry AEH, Abusarah J, Salame N, Shammaa R, Rafei M. Thymoproteasome-Expressing Mesenchymal Stromal Cells Confer Protective Anti-Tumor Immunity via Cross-Priming of Endogenous Dendritic Cells. Front Immunol 2021; 11:596303. [PMID: 33542714 PMCID: PMC7853649 DOI: 10.3389/fimmu.2020.596303] [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: 08/19/2020] [Accepted: 12/14/2020] [Indexed: 12/01/2022] Open
Abstract
Proteasomes are complex macromolecular structures existing in various forms to regulate a myriad of cellular processes. Besides degrading unwanted or misfolded proteins (proteostasis), distinct immune functions were ascribed for the immunoproteasome and thymoproteasome (TPr) complexes. For instance, antigen degradation during ongoing immune responses mainly relies on immunoproteasome activity, whereas intrathymic CD8 T-cell development requires peptide generation by the TPr complex. Despite these substantial differences, the functional contribution of the TPr to peripheral T-cell immunity remains ill-defined. We herein explored whether the use of mesenchymal stromal cells (MSCs) engineered to exhibit altered proteasomal activity through de novo expression of the TPr complex can be exploited as a novel anti-cancer vaccine capable of triggering potent CD8 T-cell activation. Phenotypic and molecular characterization of MSC-TPr revealed a substantial decrease in MHCI (H2-Kb and H2-Dd) expression along with elevated secretion of various chemokines (CCL2, CCL9, CXCL1, LIX, and CX3CL1). In parallel, transcriptomic analysis pinpointed the limited ability of MSC-TPr to present endogenous antigens, which is consistent with their low expression levels of the peptide-loading proteins TAP, CALR, and PDAI3. Nevertheless, MSC-TPr cross-presented peptides derived from captured soluble proteins. When tested for their protective capacity, MSC-TPr triggered modest anti-tumoral responses despite efficient generation of effector memory CD4 and CD8 T cells. In contrast, clodronate administration prior to vaccination dramatically enhanced the MSC-TPr-induced anti-tumoral immunity clearly highlighting a refractory role mediated by phagocytic cells. Thus, our data elute to a DC cross-priming-dependant pathway in mediating the therapeutic effect of MSC-TPr.
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Affiliation(s)
- Jean-Pierre Bikorimana
- Department of Microbiology, Infectious Diseases and Immunology, Université de Montréal, Montreal, QC, Canada
| | - Nehme El-Hachem
- Centre Hospitalier Universitaire (CHU) Ste-Justine Research Center, Université de Montréal, Montreal, QC, Canada.,Genomics Institute of Precision Medicine, American University of Beirut, Beirut, Lebanon
| | | | - Jamilah Abusarah
- Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada
| | - Natasha Salame
- Department of Biomedical Sciences, Université de Montréal, Montreal, QC, Canada
| | - Riam Shammaa
- Department of Family and Community Medicine, University of Toronto, Toronto, ON, Canada.,Canadian Centers for Regenerative Therapy, Toronto, ON, Canada.,Intellistem Technologies Inc., Toronto, ON, Canada
| | - Moutih Rafei
- Department of Microbiology, Infectious Diseases and Immunology, Université de Montréal, Montreal, QC, Canada.,Department of Pharmacology and Physiology, Université de Montréal, Montreal, QC, Canada.,Department of Microbiology and Immunology, McGill University, Montreal, QC, Canada.,Molecular Biology Program, Université de Montréal, Montreal, QC, Canada
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5
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Wang Q, Conlon EG, Manley JL, Rio DC. Widespread intron retention impairs protein homeostasis in C9orf72 ALS brains. Genome Res 2020; 30:1705-1715. [PMID: 33055097 PMCID: PMC7706729 DOI: 10.1101/gr.265298.120] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 10/05/2020] [Indexed: 12/13/2022]
Abstract
The GGGGCC hexanucleotide expansion in C9orf72 (C9) is the most frequent known cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), yet a clear understanding of how C9 fits into the broader context of ALS/FTD pathology has remained lacking. The repetitive RNA derived from the C9 repeat is known to sequester hnRNPH, a splicing regulator, into insoluble aggregates, resulting in aberrant alternative splicing. Furthermore, hnRNPH insolubility and altered splicing of a robust set of targets have been observed to correlate in C9 and sporadic ALS/FTD patients alike, suggesting that changes along this axis are a core feature of disease pathogenesis. Here, we characterize previously uncategorized RNA splicing defects involving widespread intron retention affecting almost 2000 transcripts in C9ALS/FTD brains exhibiting a high amount of sequestered, insoluble hnRNPH. These intron retention events appear not to alter overall expression levels of the affected transcripts but rather the protein-coding regions. These retained introns affect transcripts in multiple cellular pathways predicted to be involved in C9 as well as sporadic ALS/FTD etiology, including the proteasomal and autophagy systems. The retained intron pre-mRNAs display a number of characteristics, including enrichment of hnRNPH-bound splicing enhancer motifs and a propensity for G-quadruplex (G-Q) formation, linking the defective splicing directly to high amounts of sequestered hnRNPH. Together, our results reveal previously undetected splicing defects in high insoluble hnRNPH-associated C9ALS brains, suggesting a feedback between effective RNA-binding protein dosage and protein quality control in C9, and perhaps all, ALS/FTD.
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Affiliation(s)
- Qingqing Wang
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA.,California Institute for Quantitative Biosciences, University of California, Berkeley, California 94720, USA
| | - Erin G Conlon
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - James L Manley
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
| | - Donald C Rio
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720, USA.,California Institute for Quantitative Biosciences, University of California, Berkeley, California 94720, USA
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6
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Blount JR, Johnson SL, Libohova K, Todi SV, Tsou WL. Degron capability of the hydrophobic C-terminus of the polyglutamine disease protein, ataxin-3. J Neurosci Res 2020; 98:2096-2108. [PMID: 32643791 DOI: 10.1002/jnr.24684] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Revised: 05/27/2020] [Accepted: 06/08/2020] [Indexed: 11/12/2022]
Abstract
Ataxin-3 is a deubiquitinase and polyglutamine disease protein whose cellular properties and functions are not entirely understood. Mutations in ataxin-3 cause spinocerebellar ataxia type 3 (SCA3), a neurodegenerative disorder that is a member of the polyglutamine family of diseases. Two major isoforms arise from alternative splicing of ATXN3 and are differently toxic in vivo as a result of faster proteasomal degradation of one isoform compared to the other. The isoforms vary only at their C-termini, suggesting that the hydrophobic C-terminus of the more quickly degraded form of ataxin-3 (here referred to as isoform 2) functions as a degron-that is, a peptide sequence that expedites the degradation of its host protein. We explored this notion in this study and present evidence that: (a) the C-terminus of ataxin-3 isoform 2 signals its degradation in a proteasome-dependent manner, (b) this effect from the C-terminus of isoform 2 does not require the ubiquitination of ataxin-3, and (c) the isolated C-terminus of isoform 2 can enhance the degradation of an unrelated protein. According to our data, the C-terminus of ataxin-3 isoform 2 is a degron, increasing overall understanding of the cellular properties of the SCA3 protein.
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Affiliation(s)
- Jessica R Blount
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Sean L Johnson
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Kozeta Libohova
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Sokol V Todi
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA.,Department of Neurology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Wei-Ling Tsou
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA
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7
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Olshina MA, Arkind G, Kumar Deshmukh F, Fainer I, Taranavsky M, Hayat D, Ben-Dor S, Ben-Nissan G, Sharon M. Regulation of the 20S Proteasome by a Novel Family of Inhibitory Proteins. Antioxid Redox Signal 2020; 32:636-655. [PMID: 31903784 DOI: 10.1089/ars.2019.7816] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Aims: The protein degradation machinery plays a critical role in the maintenance of cellular homeostasis, preventing the accumulation of damaged or misfolded proteins and controlling the levels of regulatory proteins. The 20S proteasome degradation machinery, which predominates during oxidative stress, is able to cleave any protein with a partially unfolded region, however, uncontrolled degradation of the myriad of potential substrates is improbable. This study aimed to identify and characterize the regulatory mechanism that controls 20S proteasome-mediated degradation. Results: Using a bioinformatic screen based on known 20S proteasome regulators, we have discovered a novel family of 20S proteasome regulators, named catalytic core regulators (CCRs). These regulators share structural and sequence similarities, and coordinate the function of the 20S proteasome by affecting the degradation of substrates. The CCRs are involved in the oxidative stress response via Nrf2, organizing into a feed-forward loop regulatory circuit, with some members stabilizing Nrf2, others being induced by Nrf2, and all of them inhibiting the 20S proteasome. Innovation and Conclusion: These data uncover a new family of regulatory proteins that utilize a fine-tuned mechanism to carefully modulate the activity of the 20S proteasome, in particular under conditions of oxidative stress, ensuring its proper functioning by controlling the degradative flux.
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Affiliation(s)
- Maya A Olshina
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Galina Arkind
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | | | - Irit Fainer
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Mark Taranavsky
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Daniel Hayat
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Shifra Ben-Dor
- Bioinformatics and Biological Computing Unit, Weizmann Institute of Science, Rehovot, Israel
| | - Gili Ben-Nissan
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Michal Sharon
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
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8
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Buneeva OA, Gnedenko OV, Medvedeva MV, Zgoda VG, Ivanov AS, Medvedev AE. [A biosensor study of protein interaction with the 20S proteasome core particle]. BIOMEDITSINSKAIA KHIMIIA 2019; 65:306-310. [PMID: 31436171 DOI: 10.18097/pbmc20196504306] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
It becomes increasingly clear that ubiquitination of cellular proteins is not an indispensable prerequisite of their degradation in proteasomes. There are a number of proteins to be eliminated which are not pre-ubiquitinated for their recognition by regulatory subcomplex of 26S proteasome, but which directly interact with the 20S proteasome core particle (20S proteasome). The obligatory precondition for such interaction consists in existence of disordered (hydrophobic) fragments in the target protein. In this study we have investigated the interaction of a number of multifunctional (moonlighting) proteins (glyceraldehyde-3-phosphate dehydrogenase (GAPDH), aldolase, pyruvate kinase) and neurodegeneration-related proteins (a-synuclein, myelin basic protein) with 20S proteasome immobilized on the SPR-biosensor chip and stabilized by means of a bifunctional agent dimethyl pimelimidate (in order to prevent possible dissociation of this subcomplex). Only two of all investigated proteins (aldolase and pyruvate kinase) interacted with the immobilized 20S proteasome (Kd of 8.17´10-7 M and 5.56´10-7 M, respectively). In addition to earlier detected GAPDH ubiquitination, mass spectrometric analysis of the studied proteins revealed the presence of the ubiquitin signature (Lys-e-Gly-Gly) only in aldolase. Oxidation of aldolase and pyruvate kinase, which promotes elimination of proteins via their direct interaction with 20S proteasome, caused a 2-3-fold decrease in their Kd values as comparison with this parameter obtained for the intact proteins. The results of this study provide further evidence for direct interaction of both ubiquitinated proteins (aldolase), and non-ubiquitinated proteins (pyruvate kinase) with the 20S proteasome core particle (20S proteasome). The effectiveness of this interaction is basically equal for the ubiquitinated proteins and non-ubiquitinated proteins.
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Affiliation(s)
- O A Buneeva
- Institute of Biomedical Chemistry, Moscow, Russia
| | - O V Gnedenko
- Institute of Biomedical Chemistry, Moscow, Russia
| | - M V Medvedeva
- Moscow State University, Biological Faculty, Moscow, Russia
| | - V G Zgoda
- Institute of Biomedical Chemistry, Moscow, Russia
| | - A S Ivanov
- Institute of Biomedical Chemistry, Moscow, Russia
| | - A E Medvedev
- Institute of Biomedical Chemistry, Moscow, Russia
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9
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The PSMA8 subunit of the spermatoproteasome is essential for proper meiotic exit and mouse fertility. PLoS Genet 2019; 15:e1008316. [PMID: 31437213 PMCID: PMC6726247 DOI: 10.1371/journal.pgen.1008316] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Revised: 09/04/2019] [Accepted: 07/17/2019] [Indexed: 01/01/2023] Open
Abstract
The ubiquitin proteasome system regulates meiotic recombination in yeast through its association with the synaptonemal complex, a ‘zipper’-like structure that holds homologous chromosome pairs in synapsis during meiotic prophase I. In mammals, the proteasome activator subunit PA200 targets acetylated histones for degradation during somatic DNA double strand break repair and during histone replacement during spermiogenesis. We investigated the role of the testis-specific proteasomal subunit α4s (PSMA8) during spermatogenesis, and found that PSMA8 was localized to and dependent on the central region of the synaptonemal complex. Accordingly, synapsis-deficient mice show delocalization of PSMA8. Moreover, though Psma8-deficient mice are proficient in meiotic homologous recombination, there are alterations in the proteostasis of several key meiotic players that, in addition to the known substrate acetylated histones, have been shown by a proteomic approach to interact with PSMA8, such as SYCP3, SYCP1, CDK1 and TRIP13. These alterations lead to an accumulation of spermatocytes in metaphase I and II which either enter massively into apoptosis or give rise to a low number of aberrant round spermatids that apoptose before histone replacement takes place. Proteins within the cells that are unnecessary or damaged are degraded by a large protein complex named the proteasome. The proteins to be degraded are marked by a small protein called ubiquitin. The addition of a small modification (acetyl group) to some proteins also promotes their degradation by the proteasome. Proteasomal degradation of proteins is an essential mechanism for many developmental programs including gametogenesis, a process whereby a diploid cell produces a haploid cell or gamete (sperm or egg). The mechanism by which this genome reduction occurs is called meiosis. Here, we report the study of a protein, named PSMA8 that is specific for the testis proteasome in vertebrates. Using the mouse as a model, we show that loss of PSMA8 leads to infertility in males. By co-immunoprecipitation-coupled mass spectroscopy we identified a large list of novel PSMA8 interacting proteins. We focused our functional analysis on several key meiotic proteins which were accumulated such as SYCP3, SYCP1, CDK1 and TRIP13 in addition to the known substrate of the spermatoproteasome, the acetylated histones. We suggest that the altered accumulation of these important proteins causes a disequilibrium of the meiotic division that produces apoptotic spermatocytes in metaphase I and II and also early spermatids that die soon after reaching this stage.
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Liu J, Zhu C, Ning G, Yang L, Cao Y, Huang S, Wang Q. Chemokine signaling links cell-cycle progression and cilia formation for left-right symmetry breaking. PLoS Biol 2019; 17:e3000203. [PMID: 31430272 PMCID: PMC6716676 DOI: 10.1371/journal.pbio.3000203] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 08/30/2019] [Accepted: 08/06/2019] [Indexed: 11/19/2022] Open
Abstract
Zebrafish dorsal forerunner cells (DFCs) undergo vigorous proliferation during epiboly and then exit the cell cycle to generate Kupffer's vesicle (KV), a ciliated organ necessary for establishing left-right (L-R) asymmetry. DFC proliferation defects are often accompanied by impaired cilia elongation in KV, but the functional and molecular interaction between cell-cycle progression and cilia formation remains unknown. Here, we show that chemokine receptor Cxcr4a is required for L-R laterality by controlling DFC proliferation and KV ciliogenesis. Functional analysis revealed that Cxcr4a accelerates G1/S transition in DFCs and stabilizes forkhead box j1a (Foxj1a), a master regulator of motile cilia, by stimulating Cyclin D1 expression through extracellular regulated MAP kinase (ERK) 1/2 signaling. Mechanistically, Cyclin D1-cyclin-dependent kinase (CDK) 4/6 drives G1/S transition during DFC proliferation and phosphorylates Foxj1a, thereby disrupting its association with proteasome 26S subunit, non-ATPase 4b (Psmd4b), a 19S regulatory subunit. This prevents the ubiquitin (Ub)-independent proteasomal degradation of Foxj1a. Our study uncovers a role for Cxcr4 signaling in L-R patterning and provides fundamental insights into the molecular linkage between cell-cycle progression and ciliogenesis.
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Affiliation(s)
- Jingwen Liu
- School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Chengke Zhu
- Key Laboratory of Freshwater Fish Reproduction and Development, Ministry of Education, Key Laboratory of Aquatics Science of Chongqing, College of Animal Science in Rongchang Campus, Southwest University, Chongqing, China
| | - Guozhu Ning
- State Key Laboratory of Membrane Biology, Institute of Zoology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, China
| | - Liping Yang
- State Key Laboratory of Membrane Biology, Institute of Zoology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, China
| | - Yu Cao
- State Key Laboratory of Membrane Biology, Institute of Zoology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, China
| | - Sizhou Huang
- Development and Regeneration Key Laboratory of Sichuan Province, Department of Anatomy and Histology and Embryology, Chengdu Medical College, Chengdu, China
- * E-mail: (SH); (QW)
| | - Qiang Wang
- State Key Laboratory of Membrane Biology, Institute of Zoology, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing, China
- Institute for Stem Cell and Regeneration, Chinese Academy of Sciences, Beijing, China
- * E-mail: (SH); (QW)
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11
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Kravchuk OI, Lyupina YV, Erokhov PA, Finoshin AD, Adameyko KI, Mishyna MY, Moiseenko AV, Sokolova OS, Orlova OV, Beljelarskaya SN, Serebryakova MV, Indeykina MI, Bugrova AE, Kononikhin AS, Mikhailov VS. Characterization of the 20S proteasome of the lepidopteran, Spodoptera frugiperda. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2019; 1867:840-853. [PMID: 31228587 DOI: 10.1016/j.bbapap.2019.06.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 06/05/2019] [Accepted: 06/17/2019] [Indexed: 02/08/2023]
Abstract
Multiple complexes of 20S proteasomes with accessory factors play an essential role in proteolysis in eukaryotic cells. In this report, several forms of 20S proteasomes from extracts of Spodoptera frugiperda (Sf9) cells were separated using electrophoresis in a native polyacrylamide gel and examined for proteolytic activity in the gel and by Western blotting. Distinct proteasome bands isolated from the gel were subjected to liquid chromatography-tandem mass spectrometry and identified as free core particles (CP) and complexes of CP with one or two dimers of assembly chaperones PAC1-PAC2 and activators PA28γ or PA200. In contrast to the activators PA28γ and PA200 that regulate the access of protein substrates to the internal proteolytic chamber of CP in an ATP-independent manner, the 19S regulatory particle (RP) in 26S proteasomes performs stepwise substrate unfolding and opens the chamber gate in an ATP-dependent manner. Electron microscopic analysis suggested that spontaneous dissociation of RP in isolated 26S proteasomes leaves CPs with different gate sizes related presumably to different stages in the gate opening. The primary structure of 20S proteasome subunits in Sf9 cells was determined by a search of databases and by sequencing. The protein sequences were confirmed by mass spectrometry and verified by 2D gel electrophoresis. The relative rates of sequence divergence in the evolution of 20S proteasome subunits, the assembly chaperones and activators were determined by using bioinformatics. The data confirmed the conservation of regular CP subunits and PA28γ, a more accelerated evolution of PAC2 and PA200, and especially high divergence rates of PAC1.
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Affiliation(s)
- Oksana I Kravchuk
- N.K. Koltzov Institute of Developmental Biology, Russian Academy of Sciences, 26 Vavilova str., Moscow 119334, Russia
| | - Yulia V Lyupina
- N.K. Koltzov Institute of Developmental Biology, Russian Academy of Sciences, 26 Vavilova str., Moscow 119334, Russia
| | - Pavel A Erokhov
- N.K. Koltzov Institute of Developmental Biology, Russian Academy of Sciences, 26 Vavilova str., Moscow 119334, Russia
| | - Alexander D Finoshin
- N.K. Koltzov Institute of Developmental Biology, Russian Academy of Sciences, 26 Vavilova str., Moscow 119334, Russia
| | - Kim I Adameyko
- N.K. Koltzov Institute of Developmental Biology, Russian Academy of Sciences, 26 Vavilova str., Moscow 119334, Russia
| | - Maryia Yu Mishyna
- M.V. Lomonosov Moscow State University, Faculty of Biology, 1-12 Leninskie Gory, Moscow 119991, Russia
| | - Andrey V Moiseenko
- M.V. Lomonosov Moscow State University, Faculty of Biology, 1-12 Leninskie Gory, Moscow 119991, Russia
| | - Olga S Sokolova
- M.V. Lomonosov Moscow State University, Faculty of Biology, 1-12 Leninskie Gory, Moscow 119991, Russia
| | - Olga V Orlova
- V.A. Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 32 Vavilova str., Moscow 119334, Russia
| | - Svetlana N Beljelarskaya
- V.A. Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, 32 Vavilova str., Moscow 119334, Russia
| | - Marina V Serebryakova
- A.N. Belozersky Institute of Physico-Chemical Biology MSU, 1c40 Leniniskie Gory, Moscow 119234, Russia
| | - Maria I Indeykina
- N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, 4 Kosygina str., Moscow 119334, Russia
| | - Anna E Bugrova
- N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, 4 Kosygina str., Moscow 119334, Russia
| | - Alexey S Kononikhin
- N.M. Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, 4 Kosygina str., Moscow 119334, Russia; Skolkovo Institute of Science and Technology, 3 Ulitsa Nobelya, Moscow region, Skolkovo 121205, Russia
| | - Victor S Mikhailov
- N.K. Koltzov Institute of Developmental Biology, Russian Academy of Sciences, 26 Vavilova str., Moscow 119334, Russia.
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12
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Buneeva OA, Medvedev AE. [Ubiquitin-independent protein degradation in proteasomes]. BIOMEDIT︠S︡INSKAI︠A︡ KHIMII︠A︡ 2019; 64:134-148. [PMID: 29723144 DOI: 10.18097/pbmc20186402134] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Proteasomes are large supramolecular protein complexes present in all prokaryotic and eukaryotic cells, where they perform targeted degradation of intracellular proteins. Until recently, it was generally accepted that prior proteolytic degradation in proteasomes the proteins had to be targeted by ubiquitination: the ATP-dependent addition of (typically four sequential) residues of the low-molecular ubiquitin protein, involving the ubiquitin-activating enzyme, ubiquitin-conjugating enzyme and ubiquitin ligase. The cytoplasm and nucleoplasm proteins labeled in this way are then digested in 26S proteasomes. However, in recent years it has become increasingly clear that using this route the cell eliminates only a part of unwanted proteins. Many proteins can be cleaved by the 20S proteasome in an ATP-independent manner and without previous ubiquitination. Ubiquitin-independent protein degradation in proteasomes is a relatively new area of studies of the role of the ubiquitin-proteasome system. However, recent data obtained in this direction already correct existing concepts about proteasomal degradation of proteins and its regulation. Ubiquitin-independent proteasome degradation needs the main structural precondition in proteins: the presence of unstructured regions in the amino acid sequences that provide interaction with the proteasome. Taking into consideration that in humans almost half of all genes encode proteins that contain a certain proportion of intrinsically disordered regions, it appears that the list of proteins undergoing ubiquitin-independent degradation will demonstrate further increase. Since 26S of proteasomes account for only 30% of the total proteasome content in mammalian cells, most of the proteasomes exist in the form of 20S complexes. The latter suggests that ubiquitin-independent proteolysis performed by the 20S proteasome is a natural process of removing damaged proteins from the cell and maintaining a constant level of intrinsically disordered proteins. In this case, the functional overload of proteasomes in aging and/or other types of pathological processes, if it is not accompanied by triggering more radical mechanisms for the elimination of damaged proteins, organelles and whole cells, has the most serious consequences for the whole organism.
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Affiliation(s)
- O A Buneeva
- Institute of Biomedical Chemistry, Moscow, Russia
| | - A E Medvedev
- Institute of Biomedical Chemistry, Moscow, Russia
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Giżyńska M, Witkowska J, Karpowicz P, Rostankowski R, Chocron ES, Pickering AM, Osmulski P, Gaczynska M, Jankowska E. Proline- and Arginine-Rich Peptides as Flexible Allosteric Modulators of Human Proteasome Activity. J Med Chem 2018; 62:359-370. [PMID: 30452262 PMCID: PMC6796967 DOI: 10.1021/acs.jmedchem.8b01025] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
![]()
Proline-
and arginine-rich peptide PR11 is an allosteric inhibitor
of 20S proteasome. We modified its sequence inter alia by introducing
HbYX, RYX, or RHbX C-terminal extensions (Hb, hydrophobic moiety;
R, arginine; Y, tyrosine; X, any residue). Consequently, we were able
to improve inhibitory potency or to convert inhibitors into strong
activators: the former with an aromatic penultimate Hb residue and
the latter with the HbYX motif. The PR peptide activator stimulated
20S proteasome in vitro to efficiently degrade protein substrates,
such as α-synuclein and enolase, but also activated proteasome
in cultured fibroblasts. The positive and negative PR modulators differently
influenced the proteasome conformational dynamics and affected opening
of the substrate entry pore. The resolved crystal structure showed
PR inhibitor bound far from the active sites, at the proteasome outer
face, in the pocket used by natural activators. Our studies indicate
the opportunity to tune proteasome activity by allosteric regulators
based on PR peptide scaffold.
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Affiliation(s)
- Małgorzata Giżyńska
- Department of Biomedical Chemistry, Faculty of Chemistry , University of Gdansk , Wita Stwosza 63 , 80-308 Gdansk , Poland
| | - Julia Witkowska
- Department of Biomedical Chemistry, Faculty of Chemistry , University of Gdansk , Wita Stwosza 63 , 80-308 Gdansk , Poland
| | - Przemysław Karpowicz
- Department of Biomedical Chemistry, Faculty of Chemistry , University of Gdansk , Wita Stwosza 63 , 80-308 Gdansk , Poland
| | - Rafał Rostankowski
- Department of Biomedical Chemistry, Faculty of Chemistry , University of Gdansk , Wita Stwosza 63 , 80-308 Gdansk , Poland
| | - Estrella S Chocron
- Department of Molecular Medicine, The Barshop Institute for Longevity and Aging Studies , University of Texas Health Science Center , 15355 Lambda Drive , San Antonio , Texas 78245 , United States
| | - Andrew M Pickering
- Department of Molecular Medicine, The Barshop Institute for Longevity and Aging Studies , University of Texas Health Science Center , 15355 Lambda Drive , San Antonio , Texas 78245 , United States
| | - Pawel Osmulski
- Department of Molecular Medicine, Institute of Biotechnology , University of Texas Health Science Center , 15355 Lambda Drive , San Antonio , Texas 78245 , United States
| | - Maria Gaczynska
- Department of Molecular Medicine, Institute of Biotechnology , University of Texas Health Science Center , 15355 Lambda Drive , San Antonio , Texas 78245 , United States
| | - Elżbieta Jankowska
- Department of Biomedical Chemistry, Faculty of Chemistry , University of Gdansk , Wita Stwosza 63 , 80-308 Gdansk , Poland
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Buneeva OA, Medvedev AE. Ubiquitin-Independent Degradation of Proteins in Proteasomes. BIOCHEMISTRY (MOSCOW), SUPPLEMENT SERIES B: BIOMEDICAL CHEMISTRY 2018. [DOI: 10.1134/s1990750818030022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Lysine-Less Variants of Spinal Muscular Atrophy SMN and SMNΔ7 Proteins Are Degraded by the Proteasome Pathway. Int J Mol Sci 2017; 18:ijms18122667. [PMID: 29292768 PMCID: PMC5751269 DOI: 10.3390/ijms18122667] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Revised: 11/30/2017] [Accepted: 12/04/2017] [Indexed: 11/17/2022] Open
Abstract
Spinal muscular atrophy is due to mutations affecting the SMN1 gene coding for the full-length protein (survival motor neuron; SMN) and the SMN2 gene that preferentially generates an exon 7-deleted protein (SMNΔ7) by alternative splicing. To study SMN and SMNΔ7 degradation in the cell, we have used tagged versions at the N- (Flag) or C-terminus (V5) of both proteins. Transfection of those constructs into HeLa cells and treatment with cycloheximide showed that those protein constructs were degraded. Proteasomal degradation usually requires prior lysine ubiquitylation. Surprisingly, lysine-less variants of both proteins tagged either at N- (Flag) or C-terminus (V5) were also degraded. The degradation of the endogenous SMN protein, and the protein constructs mentioned above, was mediated by the proteasome, as it was blocked by lactacystin, a specific and irreversible proteasomal inhibitor. The results obtained allowed us to conclude that SMN and SMNΔ7 proteasomal degradation did not absolutely require internal ubiquitylation nor N-terminal ubiquitylation (prevented by N-terminal tagging). While the above conclusions are firmly supported by the experimental data presented, we discuss and justify the need of deep proteomic techniques for the study of SMN complex components (orphan and bound) turn-over to understand the physiological relevant mechanisms of degradation of SMN and SMNΔ7 in the cell.
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The ER retention protein RER1 promotes alpha-synuclein degradation via the proteasome. PLoS One 2017; 12:e0184262. [PMID: 28877262 PMCID: PMC5587320 DOI: 10.1371/journal.pone.0184262] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 08/21/2017] [Indexed: 11/19/2022] Open
Abstract
Abnormal accumulation of α-synuclein (αSyn) has been linked to endoplasmic-reticulum (ER) stress, defective intracellular protein/vesicle trafficking, and cytotoxicity. Targeting factors involved in ER-related protein processing and trafficking may, therefore, be a key to modulating αSyn levels and associated toxicity. Recently retention in endoplasmic reticulum 1 (RER1) has been identified as an important ER retrieval/retention factor for Alzheimer's disease proteins and negatively regulates amyloid-β peptide levels. Here, we hypothesized that RER1 might also play an important role in retention/retrieval of αSyn and mediate levels. We expressed RER1 and a C-terminal mutant RER1Δ25, which lacks the ER retention/retrieval function, in HEK293 and H4 neuroglioma cells. RER1 overexpression significantly decreased levels of both wild type and A30P, A53T, and E46K disease causal mutants of αSyn, whereas the RER1Δ25 mutant had a significantly attenuated effect on αSyn. RER1 effects were specific to αSyn and had little to no effect on either βSyn or the Δ71-82 αSyn mutant, which both lack the NAC domain sequence critical for synuclein fibrillization. Tests with proteasomal and macroautophagy inhibitors further demonstrate that RER1 effects on αSyn are primarily mediated through the ubiquitin-proteasome system. RER1 also appears to interact with the ubiquitin ligase NEDD4. RER1 in human diseased brain tissues co-localizes with αSyn-positive Lewy bodies. Together, these findings provide evidence that RER1 is a novel and potential important mediator of elevated αSyn levels. Further investigation of the mechanism of RER1 and downstream effectors on αSyn may yield novel therapeutic targets for modulation in Parkinson disease and related synucleinopathies.
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Phosphorylation of the C-terminal tail of proteasome subunit α7 is required for binding of the proteasome quality control factor Ecm29. Sci Rep 2016; 6:27873. [PMID: 27302526 PMCID: PMC4908598 DOI: 10.1038/srep27873] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2015] [Accepted: 05/26/2016] [Indexed: 12/15/2022] Open
Abstract
The proteasome degrades many short-lived proteins that are labeled with an ubiquitin chain. The identification of phosphorylation sites on the proteasome subunits suggests that degradation of these substrates can also be regulated at the proteasome. In yeast and humans, the unstructured C-terminal region of α7 contains an acidic patch with serine residues that are phosphorylated. Although these were identified more than a decade ago, the molecular implications of α7 phosphorylation have remained unknown. Here, we showed that yeast Ecm29, a protein involved in proteasome quality control, requires the phosphorylated tail of α7 for its association with proteasomes. This is the first example of proteasome phosphorylation dependent binding of a proteasome regulatory factor. Ecm29 is known to inhibit proteasomes and is often found enriched on mutant proteasomes. We showed that the ability of Ecm29 to bind to mutant proteasomes requires the α7 tail binding site, besides a previously characterized Rpt5 binding site. The need for these two binding sites, which are on different proteasome subcomplexes, explains the specificity of Ecm29 for proteasome holoenzymes. We propose that alterations in the relative position of these two sites in different conformations of the proteasome provides Ecm29 the ability to preferentially bind specific proteasome conformations.
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Lyupina YV, Zatsepina OG, Serebryakova MV, Erokhov PA, Abaturova SB, Kravchuk OI, Orlova OV, Beljelarskaya SN, Lavrov AI, Sokolova OS, Mikhailov VS. Proteomics of the 26S proteasome in Spodoptera frugiperda cells infected with the nucleopolyhedrovirus, AcMNPV. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:738-746. [DOI: 10.1016/j.bbapap.2016.02.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 02/04/2016] [Accepted: 02/29/2016] [Indexed: 01/13/2023]
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Penela P. Chapter Three - Ubiquitination and Protein Turnover of G-Protein-Coupled Receptor Kinases in GPCR Signaling and Cellular Regulation. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2016; 141:85-140. [PMID: 27378756 DOI: 10.1016/bs.pmbts.2016.04.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
G-protein-coupled receptors (GPCRs) are responsible for regulating a wide variety of physiological processes, and distinct mechanisms for GPCR inactivation exist to guarantee correct receptor functionality. One of the widely used mechanisms is receptor phosphorylation by specific G-protein-coupled receptor kinases (GRKs), leading to uncoupling from G proteins (desensitization) and receptor internalization. GRKs and β-arrestins also participate in the assembly of receptor-associated multimolecular complexes, thus initiating alternative G-protein-independent signaling events. In addition, the abundant GRK2 kinase has diverse "effector" functions in cellular migration, proliferation, and metabolism homeostasis by means of the phosphorylation or interaction with non-GPCR partners. Altered expression of GRKs (particularly of GRK2 and GRK5) occurs during pathological conditions characterized by impaired GPCR signaling including inflammatory syndromes, cardiovascular disease, and tumor contexts. It is increasingly appreciated that different pathways governing GRK protein stability play a role in the modulation of kinase levels in normal and pathological conditions. Thus, enhanced GRK2 degradation by the proteasome pathway occurs upon GPCR stimulation, what allows cellular adaptation to chronic stimulation in a physiological setting. β-arrestins participate in this process by facilitating GRK2 phosphorylation by different kinases and by recruiting diverse E3 ubiquitin ligase to the receptor complex. Different proteolytic systems (ubiquitin-proteasome, calpains), chaperone activities and signaling pathways influence the stability of GRKs in different ways, thus endowing specificity to GPCR regulation as protein turnover of GRKs can be differentially affected. Therefore, modulation of protein stability of GRKs emerges as a versatile mechanism for feedback regulation of GPCR signaling and basic cellular processes.
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Affiliation(s)
- P Penela
- Department of Molecular Biology and Centre of Molecular Biology "Severo Ochoa" (CSIC-UAM), Madrid, Autonomous University of Madrid, Madrid, Spain; Spain Health Research Institute The Princesa, Madrid, Spain.
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Mammalian proteasome subtypes: Their diversity in structure and function. Arch Biochem Biophys 2015; 591:132-40. [PMID: 26724758 DOI: 10.1016/j.abb.2015.12.012] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 12/22/2015] [Indexed: 11/21/2022]
Abstract
The 20S proteasome is a multicatalytic proteinase catalysing the degradation of the majority of intracellular proteins. Thereby it is involved in almost all basic cellular processes, which is facilitated by its association with various regulator complexes so that it appears in different disguises like 26S proteasome, hybrid-proteasome and others. The 20S proteasome has a cylindrical structure built up by four stacked rings composed of α- and β-subunits. Since the three active site-containing β-subunits can all or in part be replaced by immuno-subunits, three main subpopulations exist, namely standard-, immuno- and intermediate-proteasomes. Due to posttranslational modifications or/and genetic variations all α- and β-subunits occur in multiple iso- or proteoforms. This leads to the fact that each of the three subpopulations is composed of a variety of 20S proteasome subtypes. This review summarizes the knowledge of proteasome subtypes in mammalian cells and tissues and their possible biological and medical relevancy.
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