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Cascio P. PA28γ: New Insights on an Ancient Proteasome Activator. Biomolecules 2021; 11:228. [PMID: 33562807 PMCID: PMC7915322 DOI: 10.3390/biom11020228] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Revised: 02/02/2021] [Accepted: 02/03/2021] [Indexed: 02/06/2023] Open
Abstract
PA28 (also known as 11S, REG or PSME) is a family of proteasome regulators whose members are widely present in many of the eukaryotic supergroups. In jawed vertebrates they are represented by three paralogs, PA28α, PA28β, and PA28γ, which assemble as heptameric hetero (PA28αβ) or homo (PA28γ) rings on one or both extremities of the 20S proteasome cylindrical structure. While they share high sequence and structural similarities, the three isoforms significantly differ in terms of their biochemical and biological properties. In fact, PA28α and PA28β seem to have appeared more recently and to have evolved very rapidly to perform new functions that are specifically aimed at optimizing the process of MHC class I antigen presentation. In line with this, PA28αβ favors release of peptide products by proteasomes and is particularly suited to support adaptive immune responses without, however, affecting hydrolysis rates of protein substrates. On the contrary, PA28γ seems to be a slow-evolving gene that is most similar to the common ancestor of the PA28 activators family, and very likely retains its original functions. Notably, PA28γ has a prevalent nuclear localization and is involved in the regulation of several essential cellular processes including cell growth and proliferation, apoptosis, chromatin structure and organization, and response to DNA damage. In striking contrast with the activity of PA28αβ, most of these diverse biological functions of PA28γ seem to depend on its ability to markedly enhance degradation rates of regulatory protein by 20S proteasome. The present review will focus on the molecular mechanisms and biochemical properties of PA28γ, which are likely to account for its various and complex biological functions and highlight the common features with the PA28αβ paralog.
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Affiliation(s)
- Paolo Cascio
- Department of Veterinary Sciences, University of Turin, Largo P. Braccini 2, 10095 Grugliasco, Italy
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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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Hemming ML, Lawlor MA, Andersen JL, Hagan T, Chipashvili O, Scott TG, Raut CP, Sicinska E, Armstrong SA, Demetri GD, Bradner JE, Ganz PA, Tomlinson G, Olopade OI, Couch FJ, Wang X, Lindor NM, Pankratz VS, Radice P, Manoukian S, Peissel B, Zaffaroni D, Barile M, Viel A, Allavena A, Dall'Olio V, Peterlongo P, Szabo CI, Zikan M, Claes K, Poppe B, Foretova L, Mai PL, Greene MH, Rennert G, Lejbkowicz F, Glendon G, Ozcelik H, Andrulis IL, Thomassen M, Gerdes AM, Sunde L, Cruger D, Birk Jensen U, Caligo M, Friedman E, Kaufman B, Laitman Y, Milgrom R, Dubrovsky M, Cohen S, Borg A, Jernström H, Lindblom A, Rantala J, Stenmark-Askmalm M, Melin B, Nathanson K, Domchek S, Jakubowska A, Lubinski J, Huzarski T, Osorio A, Lasa A, Durán M, Tejada MI, Godino J, Benitez J, Hamann U, Kriege M, Hoogerbrugge N, van der Luijt RB, van Asperen CJ, Devilee P, Meijers-Heijboer EJ, Blok MJ, Aalfs CM, Hogervorst F, Rookus M, Cook M, Oliver C, Frost D, Conroy D, Evans DG, Lalloo F, Pichert G, Davidson R, Cole T, Cook J, Paterson J, Hodgson S, Morrison PJ, Porteous ME, Walker L, Kennedy MJ, Dorkins H, Peock S, Godwin AK, Stoppa-Lyonnet D, de Pauw A, Mazoyer S, Bonadona V, Lasset C, Dreyfus H, Leroux D, Hardouin A, Berthet P, Faivre L, Loustalot C, Noguchi T, Sobol H, Rouleau E, Nogues C, Frénay M, Vénat-Bouvet L, Hopper JL, Daly MB, Terry MB, John EM, Buys SS, Yassin Y, Miron A, Goldgar D, Singer CF, Dressler AC, Gschwantler-Kaulich D, Pfeiler G, Hansen TVO, Jønson L, Agnarsson BA, Kirchhoff T, Offit K, Devlin V, Dutra-Clarke A, Piedmonte M, Rodriguez GC, Wakeley K, Boggess JF, Basil J, Schwartz PE, Blank SV, Toland AE, Montagna M, Casella C, Imyanitov E, Tihomirova L, Blanco I, Lazaro C, Ramus SJ, Sucheston L, Karlan BY, Gross J, Schmutzler R, Wappenschmidt B, Engel C, Meindl A, Lochmann M, Arnold N, Heidemann S, Varon-Mateeva R, Niederacher D, Sutter C, Deissler H, Gadzicki D, Preisler-Adams S, Kast K, Schönbuchner I, Caldes T, de la Hoya M, Aittomäki K, Nevanlinna H, Simard J, Spurdle AB, Holland H, Chen X, Platte R, Chenevix-Trench G, Easton DF. Enhancer Domains in Gastrointestinal Stromal Tumor Regulate KIT Expression and Are Targetable by BET Bromodomain Inhibition. Cancer Res 2019. [PMID: 18483246 DOI: 10.1158/0008-5472] [Citation(s) in RCA: 679] [Impact Index Per Article: 135.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Gastrointestinal stromal tumor (GIST) is a mesenchymal neoplasm characterized by activating mutations in the related receptor tyrosine kinases KIT and PDGFRA. GIST relies on expression of these unamplified receptor tyrosine kinase (RTK) genes through a large enhancer domain, resulting in high expression levels of the oncogene required for tumor growth. Although kinase inhibition is an effective therapy for many patients with GIST, disease progression from kinase-resistant mutations is common and no other effective classes of systemic therapy exist. In this study, we identify regulatory regions of the KIT enhancer essential for KIT gene expression and GIST cell viability. Given the dependence of GIST upon enhancer-driven expression of RTKs, we hypothesized that the enhancer domains could be therapeutically targeted by a BET bromodomain inhibitor (BBI). Treatment of GIST cells with BBIs led to cell-cycle arrest, apoptosis, and cell death, with unique sensitivity in GIST cells arising from attenuation of the KIT enhancer domain and reduced KIT gene expression. BBI treatment in KIT-dependent GIST cells produced genome-wide changes in the H3K27ac enhancer landscape and gene expression program, which was also seen with direct KIT inhibition using a tyrosine kinase inhibitor (TKI). Combination treatment with BBI and TKI led to superior cytotoxic effects in vitro and in vivo, with BBI preventing tumor growth in TKI-resistant xenografts. Resistance to select BBI in GIST was attributable to drug efflux pumps. These results define a therapeutic vulnerability and clinical strategy for targeting oncogenic kinase dependency in GIST. SIGNIFICANCE: Expression and activity of mutant KIT is essential for driving the majority of GIST neoplasms, which can be therapeutically targeted using BET bromodomain inhibitors.
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Affiliation(s)
- Matthew L Hemming
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts. .,Center for Sarcoma and Bone Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - Matthew A Lawlor
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Jessica L Andersen
- Center for Sarcoma and Bone Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - Timothy Hagan
- Department of Oncologic Pathology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - Otari Chipashvili
- Department of Oncologic Pathology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - Thomas G Scott
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
| | - Chandrajit P Raut
- Department of Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts
| | - Ewa Sicinska
- Department of Oncologic Pathology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - Scott A Armstrong
- Department of Pediatric Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts
| | - George D Demetri
- Center for Sarcoma and Bone Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts.,Ludwig Center at Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts
| | - James E Bradner
- Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, Massachusetts
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Rut W, Poręba M, Kasperkiewicz P, Snipas SJ, Drąg M. Selective Substrates and Activity-Based Probes for Imaging of the Human Constitutive 20S Proteasome in Cells and Blood Samples. J Med Chem 2018; 61:5222-5234. [DOI: 10.1021/acs.jmedchem.8b00026] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Wioletta Rut
- Department of Bioorganic Chemistry, Faculty of Chemistry, Wroclaw University of Science and Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw, Poland
| | - Marcin Poręba
- Department of Bioorganic Chemistry, Faculty of Chemistry, Wroclaw University of Science and Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw, Poland
- Program in Cell Death and Survival Networks, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California 92037, United States
| | - Paulina Kasperkiewicz
- Department of Bioorganic Chemistry, Faculty of Chemistry, Wroclaw University of Science and Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw, Poland
- Program in Cell Death and Survival Networks, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California 92037, United States
| | - Scott J. Snipas
- Program in Cell Death and Survival Networks, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, California 92037, United States
| | - Marcin Drąg
- Department of Bioorganic Chemistry, Faculty of Chemistry, Wroclaw University of Science and Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw, Poland
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Huber EM, Groll M. The Mammalian Proteasome Activator PA28 Forms an Asymmetric α 4β 3 Complex. Structure 2017; 25:1473-1480.e3. [PMID: 28867616 DOI: 10.1016/j.str.2017.07.013] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 07/17/2017] [Accepted: 07/26/2017] [Indexed: 10/19/2022]
Abstract
The heptameric proteasome activator (PA) 28αβ is known to modulate class I antigen processing by docking onto 20S proteasome core particles (CPs). The exact stoichiometry and arrangement of its α and β subunits, however, is still controversial. Here we analyzed murine PA28 complexes regarding structure and assembly. Strikingly, PA28α, PA28β, and PA28αβ preparations form heptamers, but solely PA28α and PA28αβ associate with CPs. Co-expression of α and β yields one unique PA28αβ species with an unchangeable subunit composition. Structural data on PA28α, PA28β, and PA28αβ up to 2.9 Å resolution reveal a PA28α4β3 complex with an alternating subunit arrangement and a single α-α interface. Differential scanning fluorimetry experiments and activity assays classify PA28α4β3 as most stable and most active, indicating that this assembly might represent the physiologically relevant species. Together, our data resolve subunit composition and arrangement of PA28αβ and clarify how an asymmetric heptamer can be assembled from two highly homologous subunits.
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Affiliation(s)
- Eva M Huber
- Center for Integrated Protein Science, Department Chemie, Lehrstuhl für Biochemie, Technische Universität München, Lichtenbergstrasse 4, 85748 Garching, Germany.
| | - Michael Groll
- Center for Integrated Protein Science, Department Chemie, Lehrstuhl für Biochemie, Technische Universität München, Lichtenbergstrasse 4, 85748 Garching, Germany.
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Gaczynska M, Osmulski PA. Harnessing proteasome dynamics and allostery in drug design. Antioxid Redox Signal 2014; 21:2286-301. [PMID: 24410482 PMCID: PMC4241894 DOI: 10.1089/ars.2013.5816] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Accepted: 01/12/2014] [Indexed: 12/14/2022]
Abstract
SIGNIFICANCE The proteasome is the essential protease that is responsible for regulated cleavage of the bulk of intracellular proteins. Its central role in cellular physiology has been exploited in therapies against aggressive cancers where proteasome-specific competitive inhibitors that block proteasome active centers are very effectively used. However, drugs regulating this essential protease are likely to have broader clinical usefulness. The non-catalytic sites of the proteasome emerge as an attractive alternative target in search of highly specific and diverse proteasome regulators. RECENT ADVANCES Crystallographic models of the proteasome leave the false impression of fixed structures with minimal molecular dynamics lacking long-distance allosteric signaling. However, accumulating biochemical and structural observations strongly support the notion that the proteasome is regulated by precise allosteric interactions arising from protein dynamics, encouraging the active search for allosteric regulators. Here, we discuss properties of several promising compounds that affect substrate gating and processing in antechambers, and interactions of the catalytic core with regulatory proteins. CRITICAL ISSUES Given the structural complexity of proteasome assemblies, it is a painstaking process to better understand their allosteric regulation and molecular dynamics. Here, we discuss the challenges and achievements in this field. We place special emphasis on the role of atomic force microscopy imaging in probing the allostery and dynamics of the proteasome, and in dissecting the mechanisms involving small-molecule allosteric regulators. FUTURE DIRECTIONS New small-molecule allosteric regulators may become a next generation of drugs targeting the proteasome, which is critical to the development of new therapies in cancers and other diseases.
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Affiliation(s)
- Maria Gaczynska
- Department of Molecular Medicine, Institute of Biotechnology, University of Texas Health Science Center at San Antonio , San Antonio, Texas
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Cascio P. PA28αβ: the enigmatic magic ring of the proteasome? Biomolecules 2014; 4:566-84. [PMID: 24970231 PMCID: PMC4101498 DOI: 10.3390/biom4020566] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Revised: 05/15/2014] [Accepted: 06/08/2014] [Indexed: 11/16/2022] Open
Abstract
PA28αβ is a γ-interferon-induced 11S complex that associates with the ends of the 20S proteasome and stimulates in vitro breakdown of small peptide substrates, but not proteins or ubiquitin-conjugated proteins. In cells, PA28 also exists in larger complexes along with the 19S particle, which allows ATP-dependent degradation of proteins; although in vivo a large fraction of PA28 is present as PA28αβ-20S particles whose exact biological functions are largely unknown. Although several lines of evidence strongly indicate that PA28αβ plays a role in MHC class I antigen presentation, the exact molecular mechanisms of this activity are still poorly understood. Herein, we review current knowledge about the biochemical and biological properties of PA28αβ and discuss recent findings concerning its role in modifying the spectrum of proteasome's peptide products, which are important to better understand the molecular mechanisms and biological consequences of PA28αβ activity.
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Affiliation(s)
- Paolo Cascio
- Department of Veterinary Sciences, University of Turin, Grugliasco 10095, Italy.
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8
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Li X, Thompson D, Kumar B, DeMartino GN. Molecular and cellular roles of PI31 (PSMF1) protein in regulation of proteasome function. J Biol Chem 2014; 289:17392-405. [PMID: 24770418 DOI: 10.1074/jbc.m114.561183] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We investigated molecular features and cellular roles of PI31 (PSMF1) on regulation of proteasome function. PI31 has a C-terminal HbYX (where Hb is a hydrophobic amino acid, Y is tyrosine, and X is any amino acid) motif characteristic of several proteasome activators. Peptides corresponding to the PI31 C terminus also bind to and activate the 20 S proteasome in an HbYX-dependent manner, but intact PI31protein inhibits in vitro 20 S activity. Binding to and inhibition of the proteasome by PI31 are conferred by the HbYX-containing proline-rich C-terminal domain but do not require HbYX residues. Thus, multiple regions of PI31 bind independently to the proteasome and collectively determine effects on activity. PI31 blocks the ATP-dependent in vitro assembly of 26 S proteasome from 20 S proteasome and PA700 subcomplexes but has no effect on in vitro activity of the intact 26 S proteasome. To determine the physiologic significance of these in vitro effects, we assessed multiple aspects of cellular proteasome content and function after altering PI31 levels. We detected no change in overall cellular proteasome content or function when PI31 levels were either increased by moderate ectopic overexpression or decreased by RNA interference (RNAi). We also failed to identify a role of PI31 ADP-ribosylation as a mechanism for regulation of overall 26 S proteasome content and function, as recently proposed. Thus, despite its in vitro effects on various proteasome activities and its structural relationship to established proteasome regulators, cellular roles and mechanisms of PI31 in regulation of proteasome function remain unclear and require future definition.
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Affiliation(s)
- Xiaohua Li
- From the Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - David Thompson
- From the Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - Brajesh Kumar
- From the Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
| | - George N DeMartino
- From the Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390
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Raule M, Cerruti F, Benaroudj N, Migotti R, Kikuchi J, Bachi A, Navon A, Dittmar G, Cascio P. PA28αβ reduces size and increases hydrophilicity of 20S immunoproteasome peptide products. ACTA ACUST UNITED AC 2014; 21:470-480. [PMID: 24631123 DOI: 10.1016/j.chembiol.2014.02.006] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Revised: 12/20/2013] [Accepted: 02/03/2014] [Indexed: 11/25/2022]
Abstract
The specific roles that immunoproteasome variants play in MHC class I antigen presentation are unknown at present. To investigate the biochemical properties of different immunoproteasome forms and unveil the molecular mechanisms of PA28 activity, we performed in vitro degradation of full-length proteins by 20S, 26S, and PA28αβ-20S immunoproteasomes and analyzed the spectrum of peptides released. Notably, PA28αβ-20S immunoproteasomes hydrolyze proteins at the same low rates as 20S alone, which is in line with PA28, neither stimulating nor preventing entry of unfolded polypeptides into the core particle. Most importantly, binding of PA28αβ to 20S greatly reduces the size of proteasomal products and favors the release of specific, more hydrophilic, longer peptides. Hence, PA28αβ may either allosterically modify proteasome active sites or act as a selective "smart" sieve that controls the efflux of products from the 20S proteolytic chamber.
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Affiliation(s)
- Mary Raule
- Department of Veterinary Sciences, University of Turin, 10095 Grugliasco, Italy
| | - Fulvia Cerruti
- Department of Veterinary Sciences, University of Turin, 10095 Grugliasco, Italy
| | - Nadia Benaroudj
- Unité Biologie des Spirochètes, Institut Pasteur, 75015 Paris, France
| | - Rebekka Migotti
- Mass Spectrometry Core Unit, Max-Delbrück Center for Molecular Medicine, 13125 Berlin, Germany
| | - Julia Kikuchi
- Mass Spectrometry Core Unit, Max-Delbrück Center for Molecular Medicine, 13125 Berlin, Germany
| | - Angela Bachi
- IFOM, FIRC Institute of Molecular Oncology, 20139 Milan, Italy
| | - Ami Navon
- Department of Biological Regulation, The Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Gunnar Dittmar
- Mass Spectrometry Core Unit, Max-Delbrück Center for Molecular Medicine, 13125 Berlin, Germany
| | - Paolo Cascio
- Department of Veterinary Sciences, University of Turin, 10095 Grugliasco, Italy.
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10
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Burns KE, McAllister FE, Schwerdtfeger C, Mintseris J, Cerda-Maira F, Noens EE, Wilmanns M, Hubbard SR, Melandri F, Ovaa H, Gygi SP, Darwin KH. Mycobacterium tuberculosis prokaryotic ubiquitin-like protein-deconjugating enzyme is an unusual aspartate amidase. J Biol Chem 2012; 287:37522-9. [PMID: 22942282 DOI: 10.1074/jbc.m112.384784] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Deamidase of Pup (Dop), the prokaryotic ubiquitin-like protein (Pup)-deconjugating enzyme, is critical for the full virulence of Mycobacterium tuberculosis and is unique to bacteria, providing an ideal target for the development of selective chemotherapies. We used a combination of genetics and chemical biology to characterize the mechanism of depupylation. We identified an aspartate as a potential nucleophile in the active site of Dop, suggesting a novel protease activity to target for inhibitor development.
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Affiliation(s)
- Kristin E Burns
- Department of Microbiology, New York University, New York, New York 10016, USA
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11
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The role of the proteasome in the generation of MHC class I ligands and immune responses. Cell Mol Life Sci 2011; 68:1491-502. [PMID: 21387144 PMCID: PMC3071949 DOI: 10.1007/s00018-011-0657-y] [Citation(s) in RCA: 186] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2011] [Revised: 02/17/2011] [Accepted: 02/18/2011] [Indexed: 02/07/2023]
Abstract
The ubiquitin–proteasome system (UPS) degrades intracellular proteins into peptide fragments that can be presented by major histocompatibility complex (MHC) class I molecules. While the UPS is functional in all mammalian cells, its subunit composition differs depending on cell type and stimuli received. Thus, cells of the hematopoietic lineage and cells exposed to (pro)inflammatory cytokines express three proteasome immunosubunits, which form the catalytic centers of immunoproteasomes, and the proteasome activator PA28. Cortical thymic epithelial cells express a thymus-specific proteasome subunit that induces the assembly of thymoproteasomes. We here review new developments regarding the role of these different proteasome components in MHC class I antigen processing, T cell repertoire selection and CD8 T cell responses. We further discuss recently discovered functions of proteasomes in peptide splicing, lymphocyte survival and the regulation of cytokine production and inflammatory responses.
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12
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Abstract
The 2004 Nobel Prize in chemistry for the discovery of protein ubiquitination has led to the recognition of cellular proteolysis as a central area of research in biology. Eukaryotic proteins targeted for degradation by this pathway are first 'tagged' by multimers of a protein known as ubiquitin and are later proteolyzed by a giant enzyme known as the proteasome. This article recounts the key observations that led to the discovery of ubiquitin-proteasome system (UPS). In addition, different aspects of proteasome biology are highlighted. Finally, some key roles of the UPS in different areas of biology and the use of inhibitors of this pathway as possible drug targets are discussed.
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Affiliation(s)
- Dipankar Nandi
- Department of Biochemistry, Indian Institute of Science, Bangalore.
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13
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Förster A, Masters EI, Whitby FG, Robinson H, Hill CP. The 1.9 A structure of a proteasome-11S activator complex and implications for proteasome-PAN/PA700 interactions. Mol Cell 2005; 18:589-99. [PMID: 15916965 DOI: 10.1016/j.molcel.2005.04.016] [Citation(s) in RCA: 182] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2005] [Revised: 04/18/2005] [Accepted: 04/26/2005] [Indexed: 10/25/2022]
Abstract
Proteasomes are cylindrical structures that function in multiple cellular processes by degrading a wide variety of cytosolic and nuclear proteins. Substrate access and product release from the enclosed catalytic chamber occurs through axial pores that are opened by activator complexes. Here, we report high-resolution structures of wild-type and mutant archaeal proteasomes bound to the activator PA26. These structures support the proposal that an ordered open conformation is required for proteolysis and that its formation can be triggered by outward displacement of surrounding residues. The structures and associated biochemical assays reveal the mechanism of binding, which involves an interaction between the PA26 C terminus and a conserved lysine. Surprisingly, biochemical observations implicate an equivalent interaction for the unrelated ATP-dependent activators PAN and PA700.
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Affiliation(s)
- Andreas Förster
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, Utah 84132, USA
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14
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Gao X, Li J, Pratt G, Wilk S, Rechsteiner M. Purification procedures determine the proteasome activation properties of REGγ (PA28γ). Arch Biochem Biophys 2004; 425:158-64. [PMID: 15111123 DOI: 10.1016/j.abb.2004.03.021] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2003] [Revised: 03/11/2004] [Indexed: 10/26/2022]
Abstract
The proteasome activation properties of recombinant REG gamma molecules depend on purification procedures. Prior to ammonium sulfate precipitation recombinant REG gamma activates the trypsin-like catalytic subunit of the proteasome; afterwards it activates all three catalytic subunits. The expanded activation specificity is accompanied by reduced stability of the REG gamma heptamer providing support for the idea that a "tight" REG gamma heptamer suppresses the proteasome's chymotrypsin-like and postglutamyl-preferring active sites. In an attempt to determine whether REG gamma synthesized in mammalian cells also exhibits restricted activation properties, extracts were prepared from several mammalian organs and cell lines. Surprisingly, endogenous REG gamma was found to be largely monomeric. In an alternate approach, COS7 cells were cotransfected with plasmids expressing FLAG-REG gamma and REG gamma. The expressed FLAG-REG gamma molecules were shown to form oligomers with untagged REG gamma subunits, and the mixed oligomers preferentially activated the proteasome's trypsin-like subunit. Thus, REG gamma molecules synthesized in mammalian cells also exhibit restricted activation properties.
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Affiliation(s)
- Xiaolin Gao
- Department of Biochemistry, University of Utah School of Medicine, 50 N Medical Drive, Salt Lake City, UT 84132, USA
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15
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Förster A, Whitby FG, Hill CP. The pore of activated 20S proteasomes has an ordered 7-fold symmetric conformation. EMBO J 2003; 22:4356-64. [PMID: 12941688 PMCID: PMC202378 DOI: 10.1093/emboj/cdg436] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The 20S proteasome is a large multisubunit assembly that performs most of the intracellular non-lysosomal proteolysis of eukaryotes. Substrates access the proteasome active sites, which are sequestered in the interior of the barrel-shaped structure, through pores that are opened by binding of activator complexes. The crystal structure of yeast proteasome in complex with an 11S activator suggested that activation results from disordering of the proteasome gate residues. Here we report further analysis of this structure, which demonstrates that, in contrast to earlier models, the activated proteasome adopts an ordered 7-fold symmetric pore conformation that is stabilized by interactions formed by a cluster of highly conserved proteasome residues (Tyr8, Asp9, Pro17 and Tyr26). One non-canonical cluster, which appears to be mandated by the requirement that eukaryotic proteasomes also form an ordered closed conformation, explains all deviations from perfect conservation of these residues. We also demonstrate the importance of these conserved residues for proteolysis by an archaeal proteasome. Evolutionary considerations suggest that other activators might induce the same open proteasome conformation as seen with the 11S activator.
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Affiliation(s)
- Andreas Förster
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
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16
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Huang X, Seifert U, Salzmann U, Henklein P, Preissner R, Henke W, Sijts AJ, Kloetzel PM, Dubiel W. The RTP site shared by the HIV-1 Tat protein and the 11S regulator subunit alpha is crucial for their effects on proteasome function including antigen processing. J Mol Biol 2002; 323:771-82. [PMID: 12419264 DOI: 10.1016/s0022-2836(02)00998-1] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The human immunodeficiency virus-1 Tat protein inhibits the peptidase activity of the 20S proteasome and competes with the 11S regulator/PA28 for binding to the 20S proteasome. Structural comparison revealed a common site in the Tat protein and the 11S regulator alpha-subunit (REGalpha) called the REG/Tat-proteasome-binding (RTP) site. Kinetic assays found amino acid residues Lys51, Arg52 and Asp67 forming the RTP site of Tat to be responsible for the effects on proteasomes in vitro. The RTP site identified in REGalpha consists of the residues Glu235, Lys236 and Lys239. Mutation of the REGalpha amino acid residues Glu235 and Lys236 to Ala resulted in an REGalpha mutant that lost the ability to activate the 20S proteasome even though it still forms complexes with REGbeta and binds to the 20S proteasome. The REGalpha RTP site is needed to enhance the presentation of a cytomegalovirus pp89 protein-derived epitope by MHC class I molecules in mouse fibroblasts. Cell experiments demonstrate that the Tat amino acid residues 37-72 are necessary for the interaction of the viral protein with proteasomes in vivo. Full-length Tat and the Tat peptide 37-72 suppressed 11S regulator-mediated presentation of the pp89 epitope. In contrast, the Tat peptide 37-72 with mutations of amino acid residues Lys51, Arg52 and Asp67 to Ala was not able to reduce antigen presentation.
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Affiliation(s)
- Xiaohua Huang
- Division of Molecular Biology, Department of Surgery, Medical Faculty Charité, Humboldt University, Monbijoustr. 2A, Berlin, Germany
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17
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Abstract
Although substantial progress has been made in understanding the biochemical properties of 11S regulators since their discovery in 1992, we still only have a rudimentary understanding of their biological role. As discussed above, we have proposed a model in which the alpha/beta complex promotes the production of antigenic peptides by opening the exit port of the 20S proteasome (Whitby et al. 2000). There are other possibilities, however, that are not exclusive of the exit port hypothesis. For example the alpha/beta complex may promote assembly of immunoproteasome as suggested by Preckel et al. 1999, or it may function as a docking module and conduit for the delivery of peptides to the ER lumen (Realini et al. 1994b). There are also unanswered structural and mechanistic questions. Higher resolution data are needed to discern important structural details of the PA26/20S proteasome complex. The models for binding and activation that are suggested from the structural data have to be tested by mutagenesis and biochemical analysis. What is the role of homolog-specific inserts? Will cognate regulator/proteasome complexes show conformational changes that are not apparent in the currently available crystal structures, including perhaps signs of allosteric communication between the regulator and the proteasome active sites?
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Affiliation(s)
- C P Hill
- Biochemistry Department, University of Utah Medical School, 50 N Medical Drive, Salt Lake City, UT 84132, USA
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18
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Li J, Gao X, Ortega J, Nazif T, Joss L, Bogyo M, Steven AC, Rechsteiner M. Lysine 188 substitutions convert the pattern of proteasome activation by REGgamma to that of REGs alpha and beta. EMBO J 2001; 20:3359-69. [PMID: 11432824 PMCID: PMC125523 DOI: 10.1093/emboj/20.13.3359] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
11S REGs (PA28s) are multimeric rings that bind proteasomes and stimulate peptide hydrolysis. Whereas REGalpha activates proteasomal hydrolysis of peptides with hydrophobic, acidic or basic residues in the P1 position, REGgamma only activates cleavage after basic residues. We have isolated REGgamma mutants capable of activating the hydrolysis of fluorogenic peptides diagnostic for all three active proteasome beta subunits. The most robust REGgamma specificity mutants involve substitution of Glu or Asp for Lys188. REGgamma(K188E/D) variants are virtually identical to REGalpha in proteasome activation but assemble into less stable heptamers/hexamers. Based on the REGalpha crystal structure, Lys188 of REGgamma faces the aqueous channel through the heptamer, raising the possibility that REG channels function as substrate-selective gates. However, covalent modification of proteasome chymotrypsin-like subunits by 125I-YL3-VS demonstrates that REGgamma(K188E)'s activation of all three proteasome active sites is not due to relaxed gating. We propose that decreased stability of REGgamma(K188E) heptamers allows them to change conformation upon proteasome binding, thus relieving inhibition of the CT and PGPH sites normally imposed by the wild-type REGgamma molecule.
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Affiliation(s)
- J Li
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84132-0001, USA
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19
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Abstract
The proteasome activators known as 11S REG or PA28 were discovered about 10 years ago. They are homo- or heteroheptameric rings that bind to the ends of 20S proteasomes and activate cleavage of peptides but not folded proteins. In this article, we focus on structural features of three homologous REG subunits (termed alpha, beta, gamma) that contribute to their oligomerization, proteasome binding and proteasome activation. We review a number of published studies on the biochemical properties of REGs and present new results in which N-terminal sequences and sequences flanking REG activation loops have been exchanged between homologs. Characterization of these chimeras and previously constructed C-terminal chimeras reveal that N-terminal and loop flanking sequences affect oligomerization, whereas C-terminal sequences are essential for proteasome binding. None of these regions is responsible for the broad activation specificity of REGs alpha/beta versus the narrow specificity of REGgamma. Rather, mutation in a single residue lining the channel through the REGgamma heptamer changes the activation property of the gamma homolog to match that of REGs alpha and beta.
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Affiliation(s)
- J Li
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City 84132-0001, USA
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20
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Masson P, Andersson O, Petersen UM, Young P. Identification and characterization of a Drosophila nuclear proteasome regulator. A homolog of human 11 S REGgamma (PA28gamma ). J Biol Chem 2001; 276:1383-90. [PMID: 11027688 DOI: 10.1074/jbc.m007379200] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We report the cloning and characterization of a Drosophila proteasome 11 S REGgamma (PA28) homolog. The 28-kDa protein shows 47% identity to the human REGgamma and strongly enhances the trypsin-like activities of both Drosophila and mammalian 20 S proteasomes. Surprisingly, the Drosophila REG was found to inhibit the proteasome's chymotrypsin-like activity against the fluorogenic peptide succinyl-LLVY-7-amino-4-methylcoumarin. Immunocytological analysis reveals that the Drosophila REG is localized to the nucleus but is distributed throughout the cell when nuclear envelope breakdown occurs during mitosis. Through site-directed mutagenesis studies, we have identified a functional nuclear localization signal present in the homolog-specific insert region. The Drosophila PA28 NLS is similar to the oncogene c-Myc nuclear localization motif. Comparison between uninduced and innate immune induced Drosophila cells suggests that the REGgamma proteasome activator has a role independent of the invertebrate immune system. Our results support the idea that gamma class proteasome activators have an ancient conserved function within metazoans and were present prior to the emergence of the alpha and beta REG classes.
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Affiliation(s)
- P Masson
- Department of Molecular Biology, Stockholm University, S-10691 Stockholm, Sweden
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21
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Whitby FG, Masters EI, Kramer L, Knowlton JR, Yao Y, Wang CC, Hill CP. Structural basis for the activation of 20S proteasomes by 11S regulators. Nature 2000; 408:115-20. [PMID: 11081519 DOI: 10.1038/35040607] [Citation(s) in RCA: 378] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Most of the non-lysosomal proteolysis that occurs in eukaryotic cells is performed by a nonspecific and abundant barrel-shaped complex called the 20S proteasome. Substrates access the active sites, which are sequestered in an internal chamber, by traversing a narrow opening (alpha-annulus) that is blocked in the unliganded 20S proteasome by amino-terminal sequences of alpha-subunits. Peptide products probably exit the 20S proteasome through the same opening. 11S regulators (also called PA26 (ref. 4), PA28 (ref. 5) and REG) are heptamers that stimulate 20S proteasome peptidase activity in vitro and may facilitate product release in vivo. Here we report the co-crystal structure of yeast 20S proteasome with the 11S regulator from Trypanosoma brucei (PA26). PA26 carboxy-terminal tails provide binding affinity by inserting into pockets on the 20S proteasome, and PA26 activation loops induce conformational changes in alpha-subunits that open the gate separating the proteasome interior from the intracellular environment. The reduction in processivity expected for an open conformation of the exit gate may explain the role of 11S regulators in the production of ligands for major histocompatibility complex class I molecules.
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Affiliation(s)
- F G Whitby
- Biochemistry Department, University of Utah, Salt Lake City 84132, USA
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