1
|
Thomas T, Salcedo-Tacuma D, Smith DM. Structure, Function, and Allosteric Regulation of the 20S Proteasome by the 11S/PA28 Family of Proteasome Activators. Biomolecules 2023; 13:1326. [PMID: 37759726 PMCID: PMC10526260 DOI: 10.3390/biom13091326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 08/24/2023] [Accepted: 08/24/2023] [Indexed: 09/29/2023] Open
Abstract
The proteasome, a complex multi-catalytic protease machinery, orchestrates the protein degradation essential for maintaining cellular homeostasis, and its dysregulation also underlies many different types of diseases. Its function is regulated by many different mechanisms that encompass various factors such as proteasome activators (PAs), adaptor proteins, and post-translational modifications. This review highlights the unique characteristics of proteasomal regulation through the lens of a distinct family of regulators, the 11S, REGs, or PA26/PA28. This ATP-independent family, spanning from amoebas to mammals, exhibits a common architectural structure; yet, their cellular biology and criteria for protein degradation remain mostly elusive. We delve into their evolution and cellular biology, and contrast their structure and function comprehensively, emphasizing the unanswered questions regarding their regulatory mechanisms and broader roles in proteostasis. A deeper understanding of these processes will illuminate the roles of this regulatory family in biology and disease, thus contributing to the advancement of therapeutic strategies.
Collapse
Affiliation(s)
- Taylor Thomas
- Department of Biochemistry and Molecular Medicine, School of Medicine, West Virginia University, 64 Medical Center Drive, Morgantown, WV 26506, USA
| | - David Salcedo-Tacuma
- Department of Biochemistry and Molecular Medicine, School of Medicine, West Virginia University, 64 Medical Center Drive, Morgantown, WV 26506, USA
| | - David M. Smith
- Department of Biochemistry and Molecular Medicine, School of Medicine, West Virginia University, 64 Medical Center Drive, Morgantown, WV 26506, USA
- Department of Neuroscience, Rockefeller Neuroscience Institute, West Virginia University, Morgantown, WV 26506, USA
| |
Collapse
|
2
|
Kriachkov VA, Gotmanova NN, Tashlitsky VN, Bacheva AV. Brain-Derived 11S Regulator (PA28αβ) Promotes Proteasomal Hydrolysis of Elongated Oligoglutamine-Containing Peptides. Int J Mol Sci 2023; 24:13275. [PMID: 37686081 PMCID: PMC10487437 DOI: 10.3390/ijms241713275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Revised: 08/08/2023] [Accepted: 08/24/2023] [Indexed: 09/10/2023] Open
Abstract
Proteins with extended polyglutamine regions are associated with several neurodegenerative disorders, including Huntington's disease. Intracellular proteolytic processing of these proteins is not well understood. In particular, it is unclear whether long polyglutamine fragments resulting from the proteolysis of these proteins can be potentially cleaved by the proteasome. Here, we studied the susceptibility of the glutamine-glutamine bond to proteolysis by the proteasome using oligoglutamine-containing peptides with a fluorophore/quencher pair. We found that the addition of the 11S proteasomal regulator (also known as PA28) significantly accelerated the hydrolysis of oligoglutamine-containing peptides by the 20S proteasome. Unexpectedly, a similar effect was observed for the 26S proteasome in the presence of the 11S regulator. LC/MS data revealed that the hydrolysis of our peptides with both 20S and 26S proteasomes leads to N-terminal fragments containing two or three glutamine residues and that the hydrolysis site does not change after the addition of the 11S regulator. This was confirmed by the docking experiment, which shows that the preferred hydrolysis site is located after the second/third glutamine residue. Inhibitory analysis revealed that trypsin-like specificity is mainly responsible for the proteasomal hydrolysis of the glutamine-glutamine bond. Together, our results indicate that both 20S and 26S proteasomes are capable of degrading the N-terminal part of oligoglutamine fragments, while the 11S regulator significantly accelerates the hydrolysis without changing its specificity. This data suggests that proteasome activity may be enhanced in relation to polyglutamine substrates present in neurons in the early stages of polyglutamine disorders.
Collapse
Affiliation(s)
- Viacheslav A. Kriachkov
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Melbourne, VIC 3010, Australia;
| | - Natalia N. Gotmanova
- Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1, 119991 Moscow, Russia; (N.N.G.); (V.N.T.)
| | - Vadim N. Tashlitsky
- Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1, 119991 Moscow, Russia; (N.N.G.); (V.N.T.)
| | - Anna V. Bacheva
- Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1, 119991 Moscow, Russia; (N.N.G.); (V.N.T.)
| |
Collapse
|
3
|
Frayssinhes JYA, Cerruti F, Laulin J, Cattaneo A, Bachi A, Apcher S, Coux O, Cascio P. PA28γ-20S proteasome is a proteolytic complex committed to degrade unfolded proteins. Cell Mol Life Sci 2021; 79:45. [PMID: 34913092 PMCID: PMC11071804 DOI: 10.1007/s00018-021-04045-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 11/15/2021] [Accepted: 11/17/2021] [Indexed: 02/07/2023]
Abstract
PA28γ is a nuclear activator of the 20S proteasome that, unlike the 19S regulatory particle, stimulates hydrolysis of several substrates in an ATP- and ubiquitin-independent manner and whose exact biological functions and molecular mechanism of action still remain elusive. In an effort to shed light on these important issues, we investigated the stimulatory effect of PA28γ on the hydrolysis of different fluorogenic peptides and folded or denatured full-length proteins by the 20S proteasome. Importantly, PA28γ was found to dramatically enhance breakdown rates by 20S proteasomes of several naturally or artificially unstructured proteins, but not of their native, folded counterparts. Furthermore, these data were corroborated by experiments in cell lines with a nucleus-tagged myelin basic protein. Finally, mass spectrometry analysis of the products generated during proteasomal degradation of two proteins demonstrated that PA28γ does not increase, but rather decreases, the variability of peptides that are potentially suitable for MHC class I antigen presentation. These unexpected findings indicate that global stimulation of the degradation of unfolded proteins may represent a more general feature of PA28γ and suggests that this proteasomal activator might play a broader role in the pathway of protein degradation than previously believed.
Collapse
Affiliation(s)
| | - Fulvia Cerruti
- Department of Veterinary Sciences, University of Turin, Largo P. Braccini 2, 10095, Grugliasco, Turin, Italy
| | - Justine Laulin
- Université Paris-Saclay, Institut Gustave Roussy, Inserm, Immunologie Des Tumeurs et Immunothérapie, Villejuif, France
| | | | - Angela Bachi
- The FIRC Institute of Molecular Oncology (IFOM), 20139, Milan, Italy
| | - Sebastien Apcher
- Université Paris-Saclay, Institut Gustave Roussy, Inserm, Immunologie Des Tumeurs et Immunothérapie, Villejuif, France
| | - Olivier Coux
- Centre de Recherche de Biologie Cellulaire de Montpellier (CRBM), CNRS UMR 5237, Université de Montpellier, 1919 Route de Mende, 34293, Montpellier, France
| | - Paolo Cascio
- Department of Veterinary Sciences, University of Turin, Largo P. Braccini 2, 10095, Grugliasco, Turin, Italy.
| |
Collapse
|
4
|
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: 680] [Impact Index Per Article: 136.0] [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.
Collapse
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
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
5
|
Adelöf J, Andersson M, Porritt M, Petersen A, Zetterberg M, Wiseman J, Hernebring M. PA28αβ overexpression enhances learning and memory of female mice without inducing 20S proteasome activity. BMC Neurosci 2018; 19:70. [PMID: 30400847 PMCID: PMC6218978 DOI: 10.1186/s12868-018-0468-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2018] [Accepted: 10/27/2018] [Indexed: 11/16/2022] Open
Abstract
Background The proteasome system plays an important role in synaptic plasticity. Induction and maintenance of long term potentiation is directly dependent on selective targeting of proteins for proteasomal degradation. The 20S proteasome activator PA28αβ activates hydrolysis of small nonubiquitinated peptides and possesses protective functions upon oxidative stress and proteinopathy. The effect of PA28αβ activity on behavior and memory function is, however, not known. We generated a mouse model that overexpresses PA28α (PA28αOE) to understand PA28αβ function during healthy adult homeostasis via assessment of physiological and behavioral profiles, focusing on female mice. Results PA28α and PA28β protein levels were markedly increased in all PA28αOE tissues analyzed. PA28αOE displayed reduced depressive-like behavior in the forced swim test and improved memory/learning function assessed by intersession habituation in activity box and shuttle box passive avoidance test, with no significant differences in anxiety or general locomotor activity. Nor were there any differences found when compared to WT for body composition or immuno-profile. The cognitive effects of PA28αOE were female specific, but could not be explained by alterations in estrogen serum levels or hippocampal regulation of estrogen receptor β. Further, there were no differences in hippocampal protein expression of neuronal or synaptic markers between PA28αOE and WT. Biochemical analysis of hippocampal extracts demonstrated that PA28α overexpression did not increase PA28–20S peptidase activity or decrease K48-polyubiquitin levels. Instead, PA28αOE exhibited elevated efficiency in preventing aggregation in the hippocampus. Conclusions This study reveals, for the first time, a connection between PA28αβ and neuronal function. We found that PA28α overexpressing female mice displayed reduced depressive-like behavior and enhanced learning and memory. Since the positive effects of PA28α overexpression arose without an activation of 20S proteasome capacity, they are likely independent of PA28αβ’s role as a 20S proteasome activator and instead depend on a recognized chaperone-like function. These findings suggest that proteostasis in synaptic plasticity is more diverse than previously reported, and demonstrates a novel function of PA28αβ in the brain. Electronic supplementary material The online version of this article (10.1186/s12868-018-0468-2) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Julia Adelöf
- Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden.,IMED Biotech Unit, Discovery Biology, Discovery Sciences, AstraZeneca, Gothenburg, Sweden
| | - My Andersson
- Department of Clinical Sciences, Epilepsy Centre, Lund University, Lund, Sweden
| | - Michelle Porritt
- IMED Biotech Unit, Discovery Biology, Discovery Sciences, AstraZeneca, Gothenburg, Sweden
| | - Anne Petersen
- Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Madeleine Zetterberg
- Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - John Wiseman
- IMED Biotech Unit, Discovery Biology, Discovery Sciences, AstraZeneca, Gothenburg, Sweden
| | - Malin Hernebring
- Department of Clinical Neuroscience, Institute of Neuroscience and Physiology, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden. .,IMED Biotech Unit, Discovery Biology, Discovery Sciences, AstraZeneca, Gothenburg, Sweden.
| |
Collapse
|
6
|
The sheep conceptus modulates proteome profiles in caruncular endometrium during early pregnancy. Anim Reprod Sci 2016; 175:48-56. [DOI: 10.1016/j.anireprosci.2016.11.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Revised: 09/29/2016] [Accepted: 11/01/2016] [Indexed: 01/08/2023]
|
7
|
Kasthuri SR, Umasuthan N, Whang I, Kim E, Park HC, Lee J. Genomic structural characterization and transcriptional expression analysis of proteasome activator PA28α and PA28β subunits from Oplegnathus fasciatus. FISH & SHELLFISH IMMUNOLOGY 2013; 35:1224-1234. [PMID: 23916540 DOI: 10.1016/j.fsi.2013.07.040] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 07/19/2013] [Accepted: 07/25/2013] [Indexed: 06/02/2023]
Abstract
Proteasomes are multicatalytic subunit complexes involved in the degradation of cytosolic proteins and antigen presentation. In this study, we have characterized the alpha and beta subunits of proteasome activator complex from rock bream at the molecular level. RbPA28α and RbPA28β possessed the characteristic features of the subunits identified from mammals and teleosts. The RbPA28α and RbPA28β proteasome subunits contained a proline-rich motif (Region A), subunit-specific insert in the region corresponding to the KEKE motif of the known PA28α (Region B), conserved activation loop (Region C), a potential protein kinase C recognition site (Region D) and a highly homologous C-terminal region (Region E) among all three PA28 subunits. Multiple sequence alignment and pairwise alignment revealed that RbPA28α and RbPA28β proteins shared high homology with the teleosts and mammals. RbPA28α and RbPA28β genome possessed 11 exons interrupted by 10 introns. In silico promoter analysis of RbPA28α and RbPA28β revealed various transcription factor-binding sites displaying their regulation under various stress conditions. Tissue distribution profiling showed a higher expression in blood and gills. Transcriptional expression analysis of RbPA28α and RbPA28β showed up-regulation in the immune tissues following LPS and poly I:C challenges, providing further evidence for the immunological role of RbPA28α and RbPA28β.
Collapse
Affiliation(s)
- Saranya Revathy Kasthuri
- Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea
| | | | | | | | | | | |
Collapse
|
8
|
Elnakady YA, Rohde M, Sasse F, Backes C, Keller A, Lenhof HP, Weissman KJ, Müller R. Evidence for the mode of action of the highly cytotoxic Streptomyces polyketide kendomycin. Chembiochem 2007; 8:1261-72. [PMID: 17592829 DOI: 10.1002/cbic.200700050] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The macrocyclic polyketide kendomycin exhibits antiosteoporotic and antibacterial activity, as well as strong cytotoxicity against multiple human tumor cell lines. Despite the promise of this compound in several therapeutic areas, the cellular target(s) of kendomycin have not been identified to date. We have used a number of approaches, including microscopy, proteomics, and bioinformatics, to investigate the mode of action of kendomycin in mammalian cell cultures. In response to kendomycin treatment, human U-937 tumor cells exhibit depolarization of the mitochondrial membrane, caspase 3 activation, and DNA laddering, consistent with induction of the intrinsic apoptotic pathway. To elucidate possible apoptotic triggers, DIGE and MALDI-TOF were used to identify proteins that are differently regulated in U-937 cells relative to controls. Statistical analysis of the proteomics data by the new web-based application GeneTrail highlighted several significant changes in protein expression, most notably among proteasomal regulatory subunits. Overall, the profile of altered expression closely matches that observed with other tumor cell lines in response to proteasome inhibition. Direct assay in vitro further shows that kendomycin inhibits the chymotrypsin-like activity of the rabbit reticulocyte proteasome, with comparable efficacy to the established inhibitor MG-132. We have also demonstrated that ubiquitinylated proteins accumulate in kendomycin-treated U-937 cells, while vacuolization of the endoplasmic reticulum and mitochondrial swelling are induced in a second cell line derived from kangaroo rat epithelial (PtK(2)) cells, phenotypes classically associated with inhibition of the proteasome. This study therefore provides evidence that kendomycin mediates its cytotoxic effects, at least in part, through proteasome inhibition.
Collapse
Affiliation(s)
- Yasser A Elnakady
- Department of Pharmaceutical Biotechnology, Saarland University, P.O. Box 151150, 66041 Saarbrücken, Germany
| | | | | | | | | | | | | | | |
Collapse
|
9
|
Ward NE, Pellis NR, Risin SA, Risin D. Gene expression alterations in activated human T-cells induced by modeled microgravity. J Cell Biochem 2006; 99:1187-202. [PMID: 16795038 DOI: 10.1002/jcb.20988] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Studies conducted in real Space and in ground-based microgravity analog systems (MAS) have demonstrated changes in numerous lymphocyte functions. In this investigation we explored whether the observed functional changes in lymphocytes in MAS are associated with changes in gene expression. NASA-developed Rotating Wall Vessel (RWV) bioreactor was utilized as a MAS. Activated T lymphocytes were obtained by adding 100 ng/ml of anti-CD3 and 100 U/ml of IL-2 in RPMI medium to blood donor mononuclear cells for 4 days. After that the cells were washed and additionally cultured for up to 2 weeks with media (RPMI, 10% FBS and 100 U/ml IL-2) replacement every 3-4 days. Flow cytometry analysis had proven that activated T lymphocytes were the only cells remaining in culture by that time. They were split into two portions, cultured for additional 24 h in either static or simulated microgravity conditions, and used for RNA extraction. The gene expression was assessed by Affymetrix GeneChip Human U133A array allowing screening for expression of 18,400 genes. About 4-8% of tested genes responded to MG by more than a 1.5-fold change in expression; however, reproducible changes were observed only in 89 genes. Ten of these genes were upregulated and 79 were downregulated. These genes were categorized by associated pathways and viewed graphically through histogram analysis. Separate histograms of each pathway were then constructed representing individual gene expression fold changes. Possible functional consequences of the identified reproducible gene expression changes are discussed.
Collapse
|
10
|
Nickell S, Mihalache O, Beck F, Hegerl R, Korinek A, Baumeister W. Structural analysis of the 26S proteasome by cryoelectron tomography. Biochem Biophys Res Commun 2006; 353:115-20. [PMID: 17173858 DOI: 10.1016/j.bbrc.2006.11.141] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2006] [Accepted: 11/27/2006] [Indexed: 11/15/2022]
Abstract
The 26S proteasome is the key enzyme of intracellular protein degradation in eukaryotic cells. It is a multisubunit complex of 2.5 MDa confining the proteolytic action to an inner compartment with tightly controlled access. Structural studies of this intriguing molecular machine have been hampered by its intrinsic instability and its dynamics. Here we have used an unconventional approach to obtain a three-dimensional structure of the holocomplex uncompromised by preparation-induced alterations and unbiased by any starting model. We have performed a tomographic reconstruction, followed by averaging over approx. 150 individual reconstructions, of Drosophila 26S proteasomes suspended in a thin layer of amorphous ice.
Collapse
Affiliation(s)
- Stephan Nickell
- Max-Planck-Institute of Biochemistry, Department of Structural Biology, Am Klopferspitz 18, D-82152 Martinsried, Germany
| | | | | | | | | | | |
Collapse
|
11
|
Liu G, Zheng W, Chen X. Molecular cloning of proteasome activator PA28-beta subunit of large yellow croaker (Pseudosciana crocea) and its coordinated up-regulation with MHC class I alpha-chain and beta 2-microglobulin in poly I:C-treated fish. Mol Immunol 2006; 44:1190-7. [PMID: 16901544 DOI: 10.1016/j.molimm.2006.06.024] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2006] [Accepted: 06/20/2006] [Indexed: 10/24/2022]
Abstract
Antigenic peptides presented on MHC class I molecules to cytotoxic T-cells are generated in the cytosol by the 20S proteasome. Two activators PA28-alpha and PA28-beta, which are inducible by interferon-gamma (IFN-gamma), activate the latent 20S proteasome, thus playing an important role in the processing of MHC class I antigen. Molecular properties and function in the MHC class I antigen processing of PA28 have been well studied and documented in mammals while little is known in fish. In the present study, we reported the cloning of a PA28-beta gene homologue from the spleen of large yellow croaker (Pseudosciana crocea), an economically important marine fish (LycPA28-beta). The full-length cDNA of LycPA28-beta is 1133 nucleotides (nt) encoding a protein of 245 amino acids (aa), with a putative molecular weight of 27.7 kDa. The deduced protein shares 76, 69, 61, 60, 59, 57 and 57% sequence identity to sequences found in zebrafish, flounder, pig, rat, mouse, cattle and human, respectively. The deduced LycPA28-beta contains a PA28-beta subunit-specific insert in the region corresponding to the KEKE motif of the known PA28-alpha (Region B), a conserved activation loop (Region C) and a highly homologous C-terminal region among all three PA28 subunits (Region E), and a characteristic proline-rich motif (Region A) and a potential protein kinase C recognition site (Region D). Western blot analysis of various tissues indicated that LycPA28-beta was constitutively expressed in kidney, liver, spleen and intestine, and weakly expressed in muscle tissue, but not detected in gills, heart and brain. The LycPA28-beta expression was significantly up-regulated in kidney, liver, spleen, intestine and muscle tissues, and also induced in gills after 72 h of treatment with a viral micmic, polyinosinic polycytidynic acid (poly I:C). The transcriptional analysis of LycPA28-beta and MHC class I alpha-chain (alpha-chain) and beta(2)-microglobulin (beta(2)m) in spleens of poly I:C-induced large yellow croaker was further performed by RT-PCR. The results showed that the expression of LycPA28-beta and class I alpha-chain and beta(2)m genes was coordinately up-regulated by poly I:C, suggesting that induction of the MHC class I antigen processing and presentation pathway may be required for the antiviral immune response triggered poly I:C in large yellow croaker.
Collapse
Affiliation(s)
- Guozhu Liu
- Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, 178 Daxue Road, Xiamen 361005, PR China
| | | | | |
Collapse
|
12
|
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.
Collapse
Affiliation(s)
- Dipankar Nandi
- Department of Biochemistry, Indian Institute of Science, Bangalore.
| | | | | | | |
Collapse
|
13
|
Masters EI, Pratt G, Förster A, Hill CP. Purification and Analysis of Recombinant 11S Activators of the 20S Proteasome: Trypanosoma brucei PA26 and Human PA28α, PA28β, and PA28γ. Methods Enzymol 2005; 398:306-21. [PMID: 16275338 DOI: 10.1016/s0076-6879(05)98025-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Proteasomes perform the bulk of nonlysosomal degradation of aberrant, damaged, misfolded, and naturally short-lived regulatory proteins in eukaryotic cells. They are approximately 700-kDa assemblies whose hollow architecture sequesters the proteolytic sites inside a central chamber, thereby ensuring that the activity of isolated proteasomes is repressed. In vivo, proteasomes are activated by protein complexes, including the 11S activators (PA28 and PA26), which bind to one or both ends of the barrel-shaped structure. This chapter describes protocols for the purification of recombinant 11S regulators, characterization of their ability to stimulate proteasome activity, and crystallization of proteasome complexes.
Collapse
Affiliation(s)
- Eugene I Masters
- Department of Biology, University of Utah, Salt Lake City, UT 84103, USA
| | | | | | | |
Collapse
|
14
|
Hoang T, Fenne IS, Cook C, Børud B, Bakke M, Lien EA, Mellgren G. cAMP-dependent protein kinase regulates ubiquitin-proteasome-mediated degradation and subcellular localization of the nuclear receptor coactivator GRIP1. J Biol Chem 2004; 279:49120-30. [PMID: 15347661 DOI: 10.1074/jbc.m409746200] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Nuclear receptors and their coactivators are key regulators of numerous physiological functions. GRIP1 (glucocorticoid receptor-interacting protein) is a member of the steroid receptor coactivator family. Here, we show that GRIP1 is regulated by cAMP-dependent protein kinase (PKA) that induces its degradation through the ubiquitin-proteasome pathway. GRIP1 was down-regulated in transiently transfected COS-1 cells after treatment with 8-para-chlorophenylthio-cAMP or forskolin and 3-isobutyl-1-methylxanthine and in adrenocortical Y1 cells after incubation with adrenocorticotropic hormone. Pulse-chase experiments with transiently transfected COS-1 cells demonstrated that the half-life of GRIP1 was markedly reduced in cells overexpressing the PKA catalytic subunit, suggesting that activation of PKA increases the turnover of GRIP1 protein. The proteasome inhibitors MG132 and lactacystin abolished the PKA-mediated degradation of GRIP1. Using ts20 cells, a temperature-sensitive cell line that contains a thermolabile ubiquitin-activating E1 enzyme, it was confirmed that PKA-mediated degradation of GRIP1 is dependent upon the ubiquitin-proteasome pathway. Coimmunoprecipitation studies of COS-1 cells transfected with expression vectors encoding GRIP1 and ubiquitin using anti-GRIP1 and anti-ubiquitin antibodies showed that the ubiquitination of GRIP1 was increased by overexpression of PKA. Finally, we show that PKA regulates the intracellular distribution pattern of green fluorescent protein-GRIP1 and stimulates recruitment of GRIP1 to subnuclear foci that are colocalized with the proteasome. Taken together, these data demonstrate that GRIP1 is ubiquitinated and degraded through activation of the PKA pathway. This may represent a novel regulatory mechanism whereby hormones down-regulate a nuclear receptor coactivator.
Collapse
Affiliation(s)
- Tuyen Hoang
- Hormone Laboratory, Section of Endocrinology, Institute of Medicine, Division of Anatomy and Cell Biology, Department of Biomedicine, University of Bergen and Haukeland University Hospital, Bergen N-5021, Norway
| | | | | | | | | | | | | |
Collapse
|
15
|
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?
Collapse
Affiliation(s)
- C P Hill
- Biochemistry Department, University of Utah Medical School, 50 N Medical Drive, Salt Lake City, UT 84132, USA
| | | | | |
Collapse
|
16
|
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.
Collapse
Affiliation(s)
- J Li
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84132-0001, USA
| | | | | | | | | | | | | | | |
Collapse
|
17
|
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.
Collapse
Affiliation(s)
- J Li
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City 84132-0001, USA
| | | |
Collapse
|
18
|
Stohwasser R, Salzmann U, Giesebrecht J, Kloetzel PM, Holzhütter HG. Kinetic evidences for facilitation of peptide channelling by the proteasome activator PA28. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:6221-30. [PMID: 11012676 DOI: 10.1046/j.1432-1327.2000.01706.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The activation kinetics of constitutive and IFNgamma-stimulated 20S proteasomes obtained with homomeric (recPA28alpha, recPA28beta) and heteromeric (recPA28alphabeta) forms of recombinant 11S regulator PA28 was analysed by means of kinetic modelling. The activation curves obtained with increasing concentrations of the individual PA28 subunits (RecP28alpha/RecP28beta/RecP28alpha + RecP28beta) exhibit biphasic characteristics which can be attributed to a low-level activation by PA28 monomers and full proteasome activation by assembled activator complexes. The dissociation constants do not reveal significant differences between the constitutive and the immunoproteasome. Intriguingly, the affinity of the proteasome towards the recPA28alphabeta complex is about two orders of magnitude higher than towards the homomeric PA28alpha and PA28beta complexes. Striking similarities can been revealed in the way how PA28 mediates the kinetics of latent proteasomes with respect to three different fluorogenic peptides probing the chymotrypsin-like, trypsin-like and peptidylglutamyl-peptide hydrolyzing like activity: (a) positive cooperativity disappears as indicated by a lack of sigmoid initial parts of the kinetic curves, (b) substrate affinity is increased, whereby (c), the maximal activity remains virtually constant. As these kinetic features are independent of the peptide substrates, we conclude that PA28 exerts its activating influence on the proteasome by enhancing the uptake (and release) of shorter peptides.
Collapse
Affiliation(s)
- R Stohwasser
- Deutsches Institut für Ernährungsforschung, Abt. Präventiv-Medizinische Lebensmittelforschung, Bergholz-Rehbrücke, Bundesrepublik Deutschland.
| | | | | | | | | |
Collapse
|
19
|
Schwarz K, van Den Broek M, Kostka S, Kraft R, Soza A, Schmidtke G, Kloetzel PM, Groettrup M. Overexpression of the proteasome subunits LMP2, LMP7, and MECL-1, but not PA28 alpha/beta, enhances the presentation of an immunodominant lymphocytic choriomeningitis virus T cell epitope. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 165:768-78. [PMID: 10878350 DOI: 10.4049/jimmunol.165.2.768] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The proteasome is a large protease complex that generates most of the peptide ligands of MHC class I molecules either in their final form or in the form of N-terminally extended precursors. Upon the stimulation of cells with IFN-gamma, three constitutively expressed subunits of the 20S proteasome are replaced by the inducible subunits LMP2 (low-molecular mass polypeptide 2), LMP7, and MECL-1 (multicatalytic endopeptidase complex-like-1) to form so-called immunoproteasomes. We show in this study that overexpression of these three subunits in triple transfectants led to a marked enhancement in the H-2Ld-restricted presentation of the immunodominant nonameric epitope NP118, which is derived from the nucleoprotein (NP) of lymphocytic choriomeningitis virus. Overexpression of the alpha and beta subunits of the IFN-gamma-inducible proteasome regulator PA28, in contrast, did not have a comparable effect. In vitro, immunoproteasomes as compared with constitutive proteasomes generated higher amounts of 11- and 12-mer fragments containing the NP118 epitope. These are likely to be cytosolic precursors of NP118, as a proline anchor residue in the second position of NP118 may interfere with TAP-mediated transport of the nonameric epitope itself. In conclusion, we provide evidence that up-regulation of the three inducible subunits, LMP2, LMP7, and MECL-1, can result in a marked improvement of Ag presentation and that, depending on the epitope, PA28 and immunoproteasomes may differentially affect Ag processing.
Collapse
Affiliation(s)
- K Schwarz
- Research Department, Cantonal Hospital St. Gall, St. Gallen, Switzerland
| | | | | | | | | | | | | | | |
Collapse
|
20
|
Li J, Gao X, Joss L, Rechsteiner M. The proteasome activator 11 S REG or PA28: chimeras implicate carboxyl-terminal sequences in oligomerization and proteasome binding but not in the activation of specific proteasome catalytic subunits. J Mol Biol 2000; 299:641-54. [PMID: 10835274 DOI: 10.1006/jmbi.2000.3800] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The REG homologs, alpha, beta and gamma, activate mammalian proteasomes in distinct ways. REGalpha and REGbeta activate the trypsin-like, chymotrypsin-like and peptidylglutamyl-preferring active sites, whereas REGgamma only activates the proteasome's trypsin-like subunit. The three REG homologs differ in carboxyl-terminal sequences that are located next to activation loops on their proteasome binding surface. To assess the importance of these carboxyl-terminal sequences in the activation of specific proteasome beta catalytic subunits, we characterized chimeras in which 8 or 12 residues were exchanged among the three proteins. Like the wild-type molecule, REGalpha chimeras activated all three proteasome catalytic subunits regardless of the carboxyl-terminal sequence. However, REGalpha-beta chimeras activated the proteasome at lower concentrations than wild-type REGalpha and higher levels of REGalpha-gamma chimeras were needed for maximal activation because exchanged carboxyl-terminal sequences can stabilize (REGalpha-beta) or destabilize (REGalpha-gamma) the REGalpha heptamer. REGgamma chimeras were equivalent to REGgamma in their activation properties, but they bound the proteasome less tightly than the wild-type molecule. REGbeta chimeras also bound the proteasome more weakly than wild-type REGbeta and were virtually unable to activate it. Our findings demonstrate that the carboxyl-terminal sequences of REG subunits can affect heptamer stability and proteasome affinity, but they do not determine which proteasome beta subunits become activated.
Collapse
Affiliation(s)
- J Li
- Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT, 84132, USA
| | | | | | | |
Collapse
|
21
|
Abstract
There are two immune responses in vertebrates: humoral immunity is mediated by circulating antibodies, whereas cytotoxic T lymphocytes (CTL) confer cellular immunity. CTL lyse infected cells upon recognition of cell-surface MHC Class I molecules complexed with foreign peptides. The displayed peptides are produced in the cytosol by degradation of host proteins or proteins from intracellular pathogens that might be present. Proteasomes are cylindrical multisubunit proteases that generate many of the peptides eventually transferred to the cell surface for immune surveillance. In mammalian proteasomes, six active sites face a central chamber. As this chamber is sealed off from the enzyme's surface, there must be mechanisms to promote entry of substrates. Two protein complexes have been found to bind the ends of the proteasome and activate it. One of the activators is the 19 S regulatory complex of the 26 S proteasome; the other activator is '11 S REG' [Dubiel, Pratt, Ferrell and Rechsteiner (1992) J. Biol. Chem. 267, 22369-22377] or 'PA28' [Ma, Slaughter and DeMartino (1992) J. Biol. Chem. 267, 10515-10523]. During the past 7 years, our understanding of the structure of REG molecules has increased significantly, but much less is known about their biological functions. There are three REG subunits, namely alpha, beta and gamma. Recombinant REGalpha forms a ring-shaped heptamer of known crystal structure. 11 S REG is a heteroheptamer of alpha and beta subunits. REGgamma is also presumably a heptameric ring, and it is found in the nuclei of the nematode work Caenorhabditis elegans and higher organisms, where it may couple proteasomes to other nuclear components. REGalpha and REGbeta, which are abundant in vertebrate immune tissues, are located mostly in the cytoplasm. Synthesis of REG alpha and beta subunits is induced by interferon-gamma, and this has led to the prevalent hypothesis that REG alpha/beta hetero-oligomers play an important role in Class I antigen presentation. In the present review we focus on the structural properties of REG molecules and on the evidence that REGalpha/beta functions in the Class I immune response.
Collapse
|
22
|
Yao Y, Huang L, Krutchinsky A, Wong ML, Standing KG, Burlingame AL, Wang CC. Structural and functional characterizations of the proteasome-activating protein PA26 from Trypanosoma brucei. J Biol Chem 1999; 274:33921-30. [PMID: 10567354 DOI: 10.1074/jbc.274.48.33921] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The activated 20 S proteasome, which has been found only in mammalian cells, is composed of two heptamer rings of an activator protein on each end of the 20 S proteasome and is inducible by interferon-gamma. A 20 S proteasome has been recently identified in a protozoan pathogen Trypanosoma brucei, but there has been no experimental evidence yet for the presence of a 26 S proteasome. Instead, an activated form of 20 S proteasome was isolated from this organism, which has significantly enhanced peptidase activities. It consists of an additional activator protein with an estimated molecular mass of 26 kDa (PA26) (To, W. Y., and Wang, C. C. (1997) FEBS Lett. 404, 253-262). The profile and sequences of tryptic peptides from PA26 were determined by mass spectrometry; no matches were found in the data base. The peptide sequences were used in reverse transcriptase-polymerase chain reaction to isolate a full-length cDNA clone encoding PA26. The protein sequence thus derived from it indicates little sequence identity with those of mammalian activator proteins PA28 alpha, beta, or gamma. There is only a single copy of PA26 gene in T. brucei. Purified recombinant PA26 polymerizes spontaneously to form heptamer ring with an outer diameter of 8.5 nm. The ring binds and activates 20 S proteasomes from T. brucei as well as rat, whereas human PA28alpha can neither bind nor activate T. brucei 20 S proteasome. The former is thus apparently more ubiquitous than PA28 in its capability of binding to and activating 20 S proteasomes. Its presence in T. brucei may also suggest a more ancient origin of proteasome activator proteins and a much wider involvement in protein degradation among other eukaryotic organisms than was originally envisaged.
Collapse
MESH Headings
- Amino Acid Sequence
- Animals
- Blotting, Southern
- Cloning, Molecular
- Cysteine Endopeptidases/chemistry
- Cysteine Endopeptidases/genetics
- Cysteine Endopeptidases/metabolism
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- DNA, Protozoan/analysis
- DNA, Protozoan/genetics
- Electrophoresis, Gel, Two-Dimensional
- Electrophoresis, Polyacrylamide Gel
- Enzyme Activation
- Gene Dosage
- Histidine/genetics
- Immunoblotting
- Insect Proteins/chemistry
- Insect Proteins/genetics
- Insect Proteins/metabolism
- Mass Spectrometry/methods
- Molecular Sequence Data
- Multienzyme Complexes/chemistry
- Multienzyme Complexes/genetics
- Multienzyme Complexes/metabolism
- Proteasome Endopeptidase Complex
- Protein Conformation
- Protein Isoforms/genetics
- Protozoan Proteins
- Rats
- Recombinant Fusion Proteins/chemistry
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/ultrastructure
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Analysis, Protein
- Sequence Homology, Amino Acid
- Trypanosoma brucei brucei/chemistry
- Trypanosoma brucei brucei/enzymology
- Trypanosoma brucei brucei/genetics
Collapse
Affiliation(s)
- Y Yao
- Department of Pharmaceutical Chemistry, Howard Hughes Medical Institute, University of California, San Francisco, California 94143, USA
| | | | | | | | | | | | | |
Collapse
|
23
|
DeMartino GN, Slaughter CA. The proteasome, a novel protease regulated by multiple mechanisms. J Biol Chem 1999; 274:22123-6. [PMID: 10428771 DOI: 10.1074/jbc.274.32.22123] [Citation(s) in RCA: 419] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Affiliation(s)
- G N DeMartino
- Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA.
| | | |
Collapse
|
24
|
Zaiss DM, Kloetzel PM. A second gene encoding the mouse proteasome activator PA28beta subunit is part of a LINE1 element and is driven by a LINE1 promoter. J Mol Biol 1999; 287:829-35. [PMID: 10222192 DOI: 10.1006/jmbi.1999.2656] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The PMSE2 gene encodes the beta-subunit of the proteasome activator PA28 and, as shown by genomic Southern blot analysis, there probably exist four copies sharing sequence homology with PMSE2. Here, we report that in the mouse genome there exist two different chromosomal loci for PA28beta, both of which are transcribed and and which encode a functional PA28beta subunit. One of these represents the previously described PMSE2 gene possessing an intron-exon structure and a gamma interferon (IFNgamma)-inducible promoter. The second one, named PMSE2b, which we describe here, exhibits all the characteristics of an expressed retrotransposon. Our data show that the PA28beta retrotransposon is inserted into a transcriptional active LINE1 element and is driven by a LINE1 F-type monomer promoter as revealed by luciferase assays. The resulting PMSE2b mRNA encodes a protein which is indistinguishable from that encoded by the IFNgamma-inducible PMSE2 gene. Since PA28 plays an important role in major histocompatibility complex class I antigen presentation, the implications for the mouse immune system through a constitutively expressed PA28beta subunit and the biological relevance of this finding are discussed.
Collapse
Affiliation(s)
- D M Zaiss
- Institute of Biochemistry-Charité, Humboldt University Medical School, Humboldt University, Monbijoustrasse 2, Berlin, 10117, Germany
| | | |
Collapse
|