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Li Y, Sun D, Yan X, Wang Z, Zhang X. In vitro Reconstitution Assays of Arabidopsis 20S Proteasome. Bio Protoc 2021; 11:e3967. [PMID: 33889661 DOI: 10.21769/bioprotoc.3967] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Revised: 01/22/2021] [Accepted: 01/26/2021] [Indexed: 11/02/2022] Open
Abstract
The majority of cellular proteins are degraded by the 26S proteasome in eukaryotes. However, intrinsically disordered proteins (IDPs), which contain large portions of unstructured regions and are inherently unstable, are degraded via the ubiquitin-independent 20S proteasome. Emerging evidence indicates that plant IDP homeostasis may also be controlled by the 20S proteasome. Relatively little is known about the specific functions of the 20S proteasome and the regulatory mechanisms of IDP degradation in plants compared to other species because there is a lack of systematic protocols for in vitro assembly of this complex to perform in vitro degradation assays. Here, we present a detailed protocol of in vitro reconstitution assay of the 20S proteasome in Arabidopsis by modifying previously reported methods. The main strategy to obtain the 20S core proteasome here is to strip away the 19S regulatory subunits from the 26S proteasome. The protocol has two major parts: 1) Affinity purification of 20S proteasomes from stable transgenic lines expressing epitope-tagged PAG1, an essential component of the 20S proteasome (Procedures A-D) and 2) an in vitro 20S proteasome degradation assay (Procedure E). We anticipate that these protocols will provide simple and effective approaches to study in vitro degradation by the 20S proteasome and advance the study of protein metabolism in plants.
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Affiliation(s)
- Yanjun Li
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, USA
| | - Di Sun
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, USA
| | - Xingxing Yan
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, USA
| | - Zhiye Wang
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, USA.,State Key Laboratory of Plant Physiology and Biochemistry, College of Life Sciences, Zhejiang University, Hangzhou, China
| | - Xiuren Zhang
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, USA
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González Y, Doens D, Cruz H, Santamaría R, Gutiérrez M, Llanes A, Fernández PL. A Marine Diterpenoid Modulates the Proteasome Activity in Murine Macrophages Stimulated with LPS. Biomolecules 2018; 8:E109. [PMID: 30301161 PMCID: PMC6315684 DOI: 10.3390/biom8040109] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 09/14/2018] [Accepted: 10/01/2018] [Indexed: 11/17/2022] Open
Abstract
The proteasome is an intracellular complex that degrades damaged or unfolded proteins and participates in the regulation of several processes. The immunoproteasome is a specialized form that is expressed in response to proinflammatory signals and is particularly abundant in immune cells. In a previous work, we found an anti-inflammatory effect in a diterpenoid extracted from the octocoral Pseudopterogorgia acerosa, here called compound 1. This compound prevented the degradation of inhibitor κB α (IκBα) and the subsequent activation of nuclear factor κB (NFκB), suggesting that this effect might be due to inhibition of the ubiquitin-proteasome system. Here we show that compound 1 inhibits the proteasomal chymotrypsin-like activity (CTL) of murine macrophages in the presence of lipopolysaccharide (LPS) but not in its absence. This effect might be due to the capacity of this compound to inhibit the activity of purified immunoproteasome. The compound inhibits the cell surface expression of major histocompatibility complex (MHC)-I molecules and the production of proinflammatory cytokines induced by LPS in vitro and in vivo, respectively. Molecular docking simulations predicted that compound 1 selectively binds to the catalytic site of immunoproteasome subunits β1i and β5i, which are responsible for the CTL activity. Taken together these findings suggest that the compound could be a selective inhibitor of the immunoproteasome, and hence could pave the way for its future evaluation as a candidate for the treatment of inflammatory disorders and autoimmune diseases.
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Affiliation(s)
- Yisett González
- Centro de Biología Celular y Molecular de Enfermedades, Instituto de Investigaciones Científicas y Servicios de Alta Tecnología (INDICASAT AIP),Edificio 219, Ciudad del Saber, 0801 Panamá, Panamá.
| | - Deborah Doens
- Centro de Biología Celular y Molecular de Enfermedades, Instituto de Investigaciones Científicas y Servicios de Alta Tecnología (INDICASAT AIP),Edificio 219, Ciudad del Saber, 0801 Panamá, Panamá.
| | - Héctor Cruz
- Centro de Biología Celular y Molecular de Enfermedades, Instituto de Investigaciones Científicas y Servicios de Alta Tecnología (INDICASAT AIP),Edificio 219, Ciudad del Saber, 0801 Panamá, Panamá.
- Facultad de Ciencias de la Salud Dr. William C. Gorgas, Universidad Latina de Panamá, 0801 Panamá, Panamá.
| | - Ricardo Santamaría
- Centro de Biodiversidad y Descubrimiento de Drogas, INDICASAT AIP, Edificio 219, Ciudad del Saber, 0801 Panamá, Panamá.
| | - Marcelino Gutiérrez
- Centro de Biodiversidad y Descubrimiento de Drogas, INDICASAT AIP, Edificio 219, Ciudad del Saber, 0801 Panamá, Panamá.
| | - Alejandro Llanes
- Centro de Biología Celular y Molecular de Enfermedades, Instituto de Investigaciones Científicas y Servicios de Alta Tecnología (INDICASAT AIP),Edificio 219, Ciudad del Saber, 0801 Panamá, Panamá.
| | - Patricia L Fernández
- Centro de Biología Celular y Molecular de Enfermedades, Instituto de Investigaciones Científicas y Servicios de Alta Tecnología (INDICASAT AIP),Edificio 219, Ciudad del Saber, 0801 Panamá, Panamá.
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Ramos de Carvalho JE, Verwoert MT, Vogels IM, Reits EA, Van Noorden CJ, Klaassen I, Schlingemann RO. Involvement of the ubiquitin-proteasome system in the expression of extracellular matrix genes in retinal pigment epithelial cells. Biochem Biophys Rep 2018; 13:83-92. [PMID: 29387813 PMCID: PMC5789218 DOI: 10.1016/j.bbrep.2018.01.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2016] [Revised: 01/08/2018] [Accepted: 01/09/2018] [Indexed: 01/06/2023] Open
Abstract
Emerging evidence suggests that dysfunction of the ubiquitin-proteasome system is involved in the pathogenesis of numerous senile degenerative diseases including retinal disorders. The aim of this study was to assess whether there is a link between proteasome regulation and retinal pigment epithelium (RPE)-mediated expression of extracellular matrix genes. For this purpose, human retinal pigment epithelial cells (ARPE-19) were treated with different concentrations of transforming growth factor-β (TGFβ), connective tissue growth factor (CTGF), interferon-γ (IFNγ) and the irreversible proteasome inhibitor epoxomicin. First, cytotoxicity and proliferation assays were carried out. The expression of proteasome-related genes and proteins was assessed and proteasome activity was determined. Then, expression of fibrosis-associated factors fibronectin (FN), fibronectin EDA domain (FN EDA), metalloproteinase-2 (MMP-2), tissue inhibitor of metalloproteinases-1 (TIMP-1) and peroxisome proliferator-associated receptor-γ (PPARγ) was assessed. The proteasome inhibitor epoxomicin strongly arrested cell cycle progression and down-regulated TGFβ gene expression, which in turn was shown to induce expression of pro-fibrogenic genes in ARPE-19 cells. Furthermore, epoxomicin induced a directional shift in the balance between MMP-2 and TIMP-1 and was associated with down-regulation of transcription of extracellular matrix genes FN and FN-EDA and up-regulation of the anti-fibrogenic factor PPARγ. In addition, both CTGF and TGFβ were shown to affect expression of proteasome-associated mRNA and protein levels. Our results suggest a link between proteasome activity and pro-fibrogenic mechanisms in the RPE, which could imply a role for proteasome-modulating agents in the treatment of retinal disorders characterized by RPE-mediated fibrogenic responses.
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Key Words
- AMD, age-related macular degeneration
- ARPE-19, human retinal pigment epithelial cells
- CNV, choroidal neovascularization
- CTGF
- CTGF, connective tissue growth factor
- ECM, extracellular matrix
- EMT, epithelial-mesenchymal transition
- Epoxomicin
- FN EDA, fibronectin EDA domain
- FN, fibronectin
- Fibrosis
- IFNγ, interferon-γ
- MMP-2, matrix metalloproteinase-2
- PPARγ
- PPARγ, peroxisome proliferator-associated receptor-γ
- Proteasome
- RPE
- RPE, retinal pigment epithelium
- Retina
- TGFβ
- TGFβ, transforming growth factor-β
- TIMP-1, tissue inhibitor of metalloproteinases-1
- UPS, ubiquitin-proteasome system
- nAMD, neovascular age-related macular degeneration
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Affiliation(s)
- J. Emanuel Ramos de Carvalho
- Ocular Angiogenesis Group, Departments of Ophthalmology and Medical Biology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Milan T. Verwoert
- Ocular Angiogenesis Group, Departments of Ophthalmology and Medical Biology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Ilse M.C. Vogels
- Ocular Angiogenesis Group, Departments of Ophthalmology and Medical Biology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Eric A. Reits
- Department of Medical Biology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Cornelis J.F. Van Noorden
- Ocular Angiogenesis Group, Departments of Ophthalmology and Medical Biology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
- Department of Medical Biology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Ingeborg Klaassen
- Ocular Angiogenesis Group, Departments of Ophthalmology and Medical Biology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Reinier O. Schlingemann
- Ocular Angiogenesis Group, Departments of Ophthalmology and Medical Biology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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Götze S, Saborowski R, Martínez-Cruz O, Muhlia-Almazán A, Sánchez-Paz A. Proteasome properties of hemocytes differ between the whiteleg shrimp Penaeus vannamei and the brown shrimp Crangon crangon (Crustacea, Decapoda). Cell Stress Chaperones 2017; 22:879-891. [PMID: 28646424 PMCID: PMC5655376 DOI: 10.1007/s12192-017-0819-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Revised: 06/02/2017] [Accepted: 06/07/2017] [Indexed: 10/19/2022] Open
Abstract
Crustaceans are intensively farmed in aquaculture facilities where they are vulnerable to parasites, bacteria, or viruses, often severely compromising the rearing success. The ubiquitin-proteasome system (UPS) is crucial for the maintenance of cellular integrity. Analogous to higher vertebrates, the UPS of crustaceans may also play an important role in stress resistance and pathogen defense. We studied the general properties of the proteasome system in the hemocytes of the whiteleg shrimp, Penaeus vannamei, and the European brown shrimp Crangon crangon. The 20S proteasome was the predominant proteasome population in the hemocytes of both species. The specific activities of the trypsin-like (Try-like), chymotrypsin-like (Chy-like), and caspase-like (Cas-like) enzymes of the shrimp proteasome differed between species. P. vannamei exhibited a higher ratio of Try-like to Chy-like activities and Cas-like to Chy-like activities than C. crangon. Notably, the Chy-like activity of P. vannamei showed substrate or product inhibition at concentrations of more than 25 mmol L-1. The K M values ranged from 0.072 mmol L-1 for the Try-like activity of P. vannamei to 0.309 mmol L-1 for the Cas-like activity of C. crangon. Inhibition of the proteasome of P. vannamei by proteasome inhibitors was stronger than in C. crangon. The pH profiles were similar in both species. The Try-like, Chy-like, and Cas-like sites showed the highest activities between pH 7.5 and 8.5. The proteasomes of both species were sensitive against repeated freezing and thawing losing ~80-90% of activity. This study forms the basis for future investigations on the shrimp response against infectious diseases, and the role of the UPS therein.
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Affiliation(s)
- Sandra Götze
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, PO Box 120161, 27515, Bremerhaven, Germany
| | - Reinhard Saborowski
- Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, PO Box 120161, 27515, Bremerhaven, Germany.
| | - Oliviert Martínez-Cruz
- Bioenergetics and Molecular Genetics Lab, Centro de Investigación en Alimentación y Desarrollo, A.C. (CIAD), Carretera a Ejido La Victoria Km 0.6, PO Box 1735, 83000, Hermosillo, Sonora, Mexico
| | - Adriana Muhlia-Almazán
- Bioenergetics and Molecular Genetics Lab, Centro de Investigación en Alimentación y Desarrollo, A.C. (CIAD), Carretera a Ejido La Victoria Km 0.6, PO Box 1735, 83000, Hermosillo, Sonora, Mexico
| | - Arturo Sánchez-Paz
- Laboratorio de Referencia, Análisis y Diagnóstico en Sanidad Acuícola, Centro de Investigaciones Biológicas del Noroeste (CIBNOR), Calle Hermosa, 101. Col. Los Angeles, 83106, Hermosillo, Sonora, Mexico.
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5
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New Insights into the Function of the Immunoproteasome in Immune and Nonimmune Cells. J Immunol Res 2015; 2015:541984. [PMID: 26636107 PMCID: PMC4617869 DOI: 10.1155/2015/541984] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 09/10/2015] [Indexed: 12/27/2022] Open
Abstract
The immunoproteasome is a highly efficient proteolytic machinery derived from the constitutive proteasome and is abundantly expressed in immune cells. The immunoproteasome plays a critical role in the immune system because it degrades intracellular proteins, for example, those of viral origin, into small proteins. They are further digested into short peptides to be presented by major histocompatibility complex (MHC) class I molecules. In addition, the immunoproteasome influences inflammatory disease pathogenesis through its ability to regulate T cell polarization. The immunoproteasome is also expressed in nonimmune cell types during inflammation or neoplastic transformation, supporting a role in the pathogenesis of autoimmune diseases and neoplasms. Following the success of inhibitors of the constitutive proteasome, which is now an established treatment modality for multiple myeloma, compounds that selectively inhibit the immunoproteasome are currently under active investigation. This paper will review the functions of the immunoproteasome, highlighting areas where novel pharmacological treatments that regulate immunoproteasome activity could be developed.
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Yuan F, Lu J, You P, Yang Z, Yang P, Ma Q, Tao T. Proteomic profiling of expression of proteasomal subunits from livers of mice treated with diethylnitrosamine. Proteomics 2012. [DOI: 10.1002/pmic.201200288] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Fuqiang Yuan
- School of Life Sciences; Xiamen University; Xiamen; Fujian; P. R. China
| | - Jia Lu
- School of Life Sciences; Xiamen University; Xiamen; Fujian; P. R. China
| | - Pan You
- School of Life Sciences; Xiamen University; Xiamen; Fujian; P. R. China
| | - Zengming Yang
- School of Life Sciences; Xiamen University; Xiamen; Fujian; P. R. China
| | - Pengyuan Yang
- Department of Chemistry and Institute of Biomedical Sciences; Fudan University; Shanghai; P. R. China
| | - Qiling Ma
- Department of Neurology; The First Hospital affiliated to Xiamen University; Xiamen; Fujian; China
| | - Tao Tao
- School of Life Sciences; Xiamen University; Xiamen; Fujian; P. R. China
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Abstract
The ubiquitin-proteasomal system is an essential element of the protein quality control machinery in cells. The central part of this system is the 20S proteasome. The proteasome is a barrel-shaped multienzyme complex, containing several active centers hidden at the inner surface of the hollow cylinder. So, the regulation of the substrate entry toward the inner proteasomal surface is a key control mechanism of the activity of this protease. This chapter outlines the knowledge on the structure of the subunits of the 20S proteasome, the binding and structure of some proteasomal regulators and inducible proteasomal subunits. Therefore, this chapter imparts the knowledge on proteasomal structure which is required for the understanding of the following chapters.
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Abstract
Malignant gliomas are the most destructive type of brain cancer. In order to gain a better understanding of the molecular mechanisms of glioma cell death and survival, we previously established an alkylating agent 1, 3-bis(2-chloroethyl)-1-nitrosourea (BCNU)-resistant variant of C6 rat glioma cells. Proteomic analysis indicated a significant down-regulation of integrin beta 3 (ITGB3) in the BCNU-resistant C6R cells. Re-expression of ITGB3 in C6R cells restored the BCNU sensitivity. In U87MG, U373MG, and T98G human glioma cells, there was a positive correlation between ITGB3 expression and the sensitivity to BCNU and etoposide, suggesting an important role of ITGB3 in glioma cell death. Over-expression of ITGB3 cDNA significantly increased the sensitivity of the human glioma cells to the anticancer drug-induced apoptosis. Nitric oxide showed an additive effect on the anticancer drug-induced glioma cell death by increasing ITGB3 expression. Subsequent dissection of signaling pathways indicated that extracellular signal-regulated kinase and unligated integrin-mediated cell death pathway may be involved in the pro-apoptotic role of ITGB3 in glioma cells. These results implicate ITGB3 in glioma cell death/survival and drug resistance.
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Affiliation(s)
- Jong-Heon Kim
- Department of Pharmacology, Brain Science and Engineering Institute, CMRI, Kyungpook National University School of Medicine, Daegu, Korea
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Zimmerman SW, Manandhar G, Yi YJ, Gupta SK, Sutovsky M, Odhiambo JF, Powell MD, Miller DJ, Sutovsky P. Sperm proteasomes degrade sperm receptor on the egg zona pellucida during mammalian fertilization. PLoS One 2011; 6:e17256. [PMID: 21383844 PMCID: PMC3044170 DOI: 10.1371/journal.pone.0017256] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Accepted: 01/27/2011] [Indexed: 12/24/2022] Open
Abstract
Despite decades of research, the mechanism by which the fertilizing spermatozoon penetrates the mammalian vitelline membrane, the zona pellucida (ZP) remains one of the unexplained fundamental events of human/mammalian development. Evidence has been accumulating in support of the 26S proteasome as a candidate for echinoderm, ascidian and mammalian egg coat lysin. Monitoring ZP protein degradation by sperm during fertilization is nearly impossible because those few spermatozoa that penetrate the ZP leave behind a virtually untraceable residue of degraded proteins. We have overcome this hurdle by designing an experimentally consistent in vitro system in which live boar spermatozoa are co-incubated with ZP-proteins (ZPP) solubilized from porcine oocytes. Using this assay, mimicking sperm-egg interactions, we demonstrate that the sperm-borne proteasomes can degrade the sperm receptor protein ZPC. Upon coincubation with motile spermatozoa, the solubilized ZPP, which appear to be ubiquitinated, adhered to sperm acrosomal caps and induced acrosomal exocytosis/formation of the acrosomal shroud. The degradation of the sperm receptor protein ZPC was assessed by Western blotting band-densitometry and proteomics. A nearly identical pattern of sperm receptor degradation, evident already within the first 5 min of coincubation, was observed when the spermatozoa were replaced with the isolated, enzymatically active, sperm-derived proteasomes. ZPC degradation was blocked by proteasomal inhibitors and accelerated by ubiquitin-aldehyde(UBAL), a modified ubiquitin protein that stimulates proteasomal proteolysis. Such a degradation pattern of ZPC is consistent with in vitro fertilization studies, in which proteasomal inhibitors completely blocked fertilization, and UBAL increased fertilization and polyspermy rates. Preincubation of intact zona-enclosed ova with isolated active sperm proteasomes caused digestion, abrasions and loosening of the exposed zonae, and significantly reduced the fertilization/polyspermy rates after IVF, accompanied by en-mass detachment of zona bound sperm. Thus, the sperm borne 26S proteasome is a candidate zona lysin in mammals. This new paradigm has implications for contraception and assisted reproductive technologies in humans, as well as animals.
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Affiliation(s)
- Shawn W. Zimmerman
- Division of Animal Science, and Departments of Obstetrics, Gynecology, and Women's Health, University of Missouri–Columbia, Columbia, Missouri, United States of America
| | - Gaurishankar Manandhar
- Division of Animal Science, and Departments of Obstetrics, Gynecology, and Women's Health, University of Missouri–Columbia, Columbia, Missouri, United States of America
| | - Young-Joo Yi
- Research Center for Transgenic Cloned Pigs, Chungnam National University, Daejeon, South Korea
| | - Satish K. Gupta
- Reproductive Cell Biology Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India
| | - Miriam Sutovsky
- Division of Animal Science, and Departments of Obstetrics, Gynecology, and Women's Health, University of Missouri–Columbia, Columbia, Missouri, United States of America
| | - John F. Odhiambo
- Division of Animal Science, and Departments of Obstetrics, Gynecology, and Women's Health, University of Missouri–Columbia, Columbia, Missouri, United States of America
| | - Michael D. Powell
- Morehouse School of Medicine, Morehouse Univeristy, Atlanta, Georgia, United States of America
| | - David J. Miller
- Department of Animal Sciences, University of Illinois at Urbana–Champaign, Urbana, Illinois, United States of America
| | - Peter Sutovsky
- Division of Animal Science, and Departments of Obstetrics, Gynecology, and Women's Health, University of Missouri–Columbia, Columbia, Missouri, United States of America
- * E-mail:
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Liggett A, Crawford L, Walker B, Morris T, Irvine A. Methods for measuring proteasome activity: Current limitations and future developments. Leuk Res 2010; 34:1403-9. [DOI: 10.1016/j.leukres.2010.07.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Revised: 06/10/2010] [Accepted: 07/03/2010] [Indexed: 10/19/2022]
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Li Y, Wang YS, Shen XF, Hui YN, Han J, Zhao W, Zhu J. Alterations of activity and intracellular distribution of the 20S proteasome in ageing retinal pigment epithelial cells. Exp Gerontol 2008; 43:1114-22. [PMID: 18817863 DOI: 10.1016/j.exger.2008.08.052] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2008] [Revised: 08/24/2008] [Accepted: 08/25/2008] [Indexed: 11/17/2022]
Abstract
Age-related macular degeneration (AMD) remains high incidence and accounts for a main cause of blindness in ageing people, but its mechanism is still poorly understood. Ageing and associated dysfunction of retinal pigment epithelial (RPE) cells were believed to be the pathological onset of AMD. 20S proteasome has been tightly correlated with cell ageing due to its fundamental role in maintaining cellular homeostasis, but its implication in the ageing process of human RPE cells was seldom concerned. This study aimed to demonstrate the interconnections between 20S proteasome and ageing RPE cells by characterizing age-dependent alterations of the 20S proteasome in primarily cultured human RPE cells. For this purpose, a replicative ageing RPE cell model was established and validated through testing the cell viability, beta-galactosidase activity and cellular autofluorescence. Decline in chymotrypsin-like, peptidylglutamyl-peptide hydrolase and trypsin-like activities of the 20S proteasome was detected in aged RPE cells through degradation of fluorogenic substrates. Immunofluorescence assay revealed that the 20S proteasome was concentrated in RPE nucleus, and redistributed partly to the peri-nuclear regions in old RPE passages. These age-dependent changes of the 20S complex were accompanied with a significantly increased fluorescent intensity of intracellular oxidized proteins. Further analysis of the proteasome-to-oxidized protein ratio indicated a preferred protection of the RPE nuclear proteins by the 20S proteasome, which also subsided remarkably as a function of the cell ageing. In conclusion, we demonstrated functional impairment and redistribution of the 20S proteasome with age in human RPE cells and supposed these alterations impactful on the process of RPE cell ageing and furthermore on the pathogenesis of AMD. Future researches on the mechanism of these alterations and the pathways to manipulate their effects are still strongly recommended.
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Affiliation(s)
- Yue Li
- Department of Ophthalmology, Xijing Hospital, The Fourth Military Medical University and Eye Institute of PLA, Chang-le Road 17, Xi'an, Shaanxi 710032, China
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Ho YK, Bargagna-Mohan P, Wehenkel M, Mohan R, Kim KB. LMP2-specific inhibitors: chemical genetic tools for proteasome biology. ACTA ACUST UNITED AC 2007; 14:419-30. [PMID: 17462577 PMCID: PMC5541682 DOI: 10.1016/j.chembiol.2007.03.008] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2006] [Revised: 02/09/2007] [Accepted: 03/01/2007] [Indexed: 11/16/2022]
Abstract
The immunoproteasome, having been linked to neurodegenerative diseases and hematological cancers, has been shown to play an important role in MHC class I antigen presentation. However, its other pathophysiological functions are still not very well understood. This can be attributed mainly to a lack of appropriate molecular probes that can selectively modulate the immunoproteasome catalytic subunits. Herein, we report the development of molecular probes that selectively inhibit the major catalytic subunit, LMP2, of the immunoproteasome. We show that these compounds irreversibly modify the LMP2 subunit with high specificity. Importantly, LMP2-rich cancer cells compared to LMP2-deficient cancer cells are more sensitive to growth inhibition by the LMP2-specific inhibitor, implicating an important role of LMP2 in regulating cell growth of malignant tumors that highly express LMP2.
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Affiliation(s)
- Yik Khuan Ho
- Department of Pharmaceutical Sciences, University of Kentucky, Lexington, KY 40536, USA
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Kapphahn RJ, Bigelow EJ, Ferrington DA. Age-dependent inhibition of proteasome chymotrypsin-like activity in the retina. Exp Eye Res 2007; 84:646-54. [PMID: 17258201 PMCID: PMC1900430 DOI: 10.1016/j.exer.2006.12.002] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2006] [Revised: 11/30/2006] [Accepted: 12/01/2006] [Indexed: 11/28/2022]
Abstract
The proteasome plays a fundamental role in processes essential for cell viability. A loss in proteasome function has been associated with aging, as well as a number of age-related diseases. Defining the mechanism(s) behind this loss in function will add important information regarding the molecular basis for aging. In the current study, we performed an age-based comparison of proteasome function and composition of subunits and regulatory proteins in the neural retina and retinal pigment epithelium (RPE) in Fischer 344 rats. In the RPE, there was no age-dependent difference in activity, subunit composition, or content of proteasome regulators, PA28 and PA700. In contrast, the aged neural retina demonstrated a significant reduction in the chymotrypsin-like activity and decreased degradation of both casein and casein modified by 4-hydroxynonenal. This loss in function could not be explained by differences in subunit composition, content of PA28 and PA700, or reversible modification of cysteine residues. To begin investigating the molecular basis for the age-associated decrement in proteasome function, we modified the cysteine residues in proteasome from young rats with the sulfhydryl-reactive chemical N-ethylmaleimide. We observed inhibition of the chymotrypsin-like activity and decreased degradation of casein that was comparable to that seen in aged retinas. Thus, chemical modification of cysteine provides an in vitro method that partially recapitulates aging proteasome. Further studies are required to confirm irreversible modification of functionally significant cysteine as a potential mechanism behind the age-related loss in proteasome function.
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Affiliation(s)
| | - Erin J. Bigelow
- Department of Ophthalmology, University of Minnesota, Minneapolis, MN 55455
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Prévotat L, Filomenko R, Solary E, Jeannin JF, Bettaieb A. Nitric oxide-induced down-regulation of beta-catenin in colon cancer cells by a proteasome-independent specific pathway. Gastroenterology 2006; 131:1142-52. [PMID: 17030184 DOI: 10.1053/j.gastro.2006.07.017] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2005] [Accepted: 06/21/2006] [Indexed: 12/06/2022]
Abstract
BACKGROUND & AIMS We have previously reported that nitric oxide could induce the death of colon cancer cells. Because an inappropriate activation of beta-catenin has been associated with intestinal cell malignant transformation, we explored whether nitric oxide could affect beta-catenin expression and function. METHODS Human colon cancer cell lines were treated with the nitric oxide donor glyceryl trinitrate (GTN) before analyzing beta-catenin expression by immunofluorescence, immunoblotting, and immunoprecipitation methods and its transcriptional activity using a luciferase reporter gene driven by a T-cell factor-responsive promotor. RESULTS GTN induces beta-catenin degradation and down-regulates its transcriptional activity in colon cancer cells. This effect is preceded by GTN-induced tyrosine nitration of beta-catenin, together with its dephosphorylation on serine 33, 37, and 45 and threonine 41. GTN-induced beta-catenin degradation involves proteases that are sensitive to a broad-spectrum caspase inhibitor, z-VAD-fmk, and to serine protease inhibitors N-tosyl-L-phenylalaline chloromethyl ketone (TPCK) and [4-(2-aminoethyl)-benzenesulfonylfluoride] (AEBSF), whereas the ubiquitin/proteasome pathway is not involved. Interestingly, only TPCK and AEBSF restore beta-catenin transcriptional activity and preserve beta-catenin nuclear localization in GTN-treated colon cancer cells. CONCLUSIONS Exposure of colon cancer cells to nitric oxide unraveled a so-far-unidentified mechanism of beta-catenin regulation. The protein is nitrated and dephosphorylated, and its transcriptional activity is reduced through degradation by a TPCK and AEBSF-sensitive protease.
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Affiliation(s)
- Laurent Prévotat
- Laboratoire d'Immunologie et Immunothérapie des Cancers, EPHE/INSERM U517, IFR100, Faculty of Medicine, 7 bd. Jeanne d'Arc, 21079 Dijon, France
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15
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Parcellier A, Brunet M, Schmitt E, Col E, Didelot C, Hammann A, Nakayama K, Nakayama KI, Khochbin S, Solary E, Garrido C. HSP27 favors ubiquitination and proteasomal degradation of p27
Kip1
and helps S‐phase re‐entry in stressed cells. FASEB J 2006; 20:1179-81. [PMID: 16641199 DOI: 10.1096/fj.05-4184fje] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Stress-inducible HSP27 protects cells from death through various mechanisms. We have recently demonstrated that HSP27 can also enhance the degradation of some proteins through the proteasomal pathway. Here, we show that one of these proteins is the cyclin-dependent kinase (Cdk) inhibitor p27Kip1. The ubiquitination and degradation of this protein that favors progression through the cell cycle was previously shown to involve either a Skp2-dependent mechanism,i.e., at the S-/G2-transition, or a KPC (Kip1 ubiquitination-promoting complex)-dependent mechanism, i.e.,at the G0/G1 transition. In this work, we demonstrate that, in response to serum depletion, p27Kip1 cellular content first increases then progressively decreases as cells begin to die. In this stressful condition, HSP27favors p27Kip1 ubiquitination and degradation by the proteasome. A similar observation was made in response to stress induced by the NO donor glyceryl trinitrate (GTN). HSP27-mediated ubiquitination ofp27Kip1 does not require its phosphorylation on Thr187 or Ser-10, nor does it depend on the SCFSkp2 ubiquitin ligase E3 complex. It facilitates the G1/S transition,which suggests that, in stressful conditions, HSP27might render quiescent cells competent to re-enter the cell cycle.
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16
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Löscher M, Fortschegger K, Ritter G, Wostry M, Voglauer R, Schmid J, Watters S, Rivett A, Ajuh P, Lamond A, Katinger H, Grillari J. Interaction of U-box E3 ligase SNEV with PSMB4, the beta7 subunit of the 20 S proteasome. Biochem J 2005; 388:593-603. [PMID: 15660529 PMCID: PMC1138967 DOI: 10.1042/bj20041517] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Recognition of specific substrates for degradation by the ubiquitin-proteasome pathway is ensured by a cascade of ubiquitin transferases E1, E2 and E3. The mechanism by which the target proteins are transported to the proteasome is not clear, but two yeast E3s and one mammalian E3 ligase seem to be involved in the delivery of targets to the proteasome, by escorting them and by binding to the 19 S regulatory particle of the proteasome. In the present study, we show that SNEV (senescence evasion factor), a protein with in vitro E3 ligase activity, which is also involved in DNA repair and splicing, associates with the proteasome by directly binding to the beta7 subunit of the 20 S proteasome. Upon inhibition of proteasome activity, SNEV does not accumulate within the cells although its co-localization with the proteasome increases significantly. Since immunofluorescence microscopy also shows increased co-localization of SNEV with ubiquitin after proteasome inhibition, without SNEV being ubiquitinated by itself, we suggest that SNEV shows E3 ligase activity not only in vitro but also in vivo and escorts its substrate to the proteasome. Since the yeast homologue of SNEV, Prp19, also interacts with the yeast beta7 subunit of the proteasome, this mechanism seems to be conserved during evolution. Therefore these results support the hypothesis that E3 ligases might generally be involved in substrate transport to the proteasome. Additionally, our results provide the first evidence for a physical link between components of the ubiquitin-proteasome system and the spliceosome.
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Affiliation(s)
- Marlies Löscher
- *Institute of Applied Microbiology, University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Klaus Fortschegger
- *Institute of Applied Microbiology, University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Gustav Ritter
- *Institute of Applied Microbiology, University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Martina Wostry
- *Institute of Applied Microbiology, University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Regina Voglauer
- *Institute of Applied Microbiology, University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Johannes A. Schmid
- †Department of Vascular Biology and Thrombosis Research, University of Vienna, Brunnerstrasse 59, A-1235 Vienna, Austria
| | - Steven Watters
- ‡The Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, U.K
| | - A. Jennifer Rivett
- ‡The Department of Biochemistry, School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, U.K
| | - Paul Ajuh
- §Division of Gene Regulation and Expression, Wellcome Trust Biocentre, University of Dundee, Dow Street, Dundee DD1 5EH, U.K
| | - Angus I. Lamond
- §Division of Gene Regulation and Expression, Wellcome Trust Biocentre, University of Dundee, Dow Street, Dundee DD1 5EH, U.K
| | - Hermann Katinger
- *Institute of Applied Microbiology, University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
| | - Johannes Grillari
- *Institute of Applied Microbiology, University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
- ∥BMT Biomolecular Therapeutics, Brunnerstrasse 59, Vienna, Austria
- To whom correspondence should be addressed, at Muthgasse 18, A-1190, Vienna, Austria (email )
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17
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Ferrington DA, Husom AD, Thompson LV. Altered proteasome structure, function, and oxidation in aged muscle. FASEB J 2005; 19:644-6. [PMID: 15677694 DOI: 10.1096/fj.04-2578fje] [Citation(s) in RCA: 184] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The proteasome is the main protease for degrading oxidized proteins. We asked whether altered proteasome function contributes to the accumulation of oxidized muscle proteins with aging. Proteasome structure, function, and oxidation state were compared in young and aged F344BN rat fast-twitch skeletal muscle. In proteasome-enriched homogenates from aged muscle, we observed a two- to threefold increase in content of the 20S proteasome that was due to a corresponding increase in immunoproteasome. Content of the regulatory proteins, PA700 and PA28, relative to the 20S were reduced 75% with aging. Upon addition of exogenous PA700, there was a twofold increase in peptide hydrolysis in aged muscle, suggesting the endogenous content of PA700 is inadequate for complete activation of the 20S. Measures of catalytic activity showed a 50% reduction in specific activity for proteasome-enriched homogenates with aging. With purification of the 20S, proteasome specific activity was equivalent between ages, indicating that endogenous regulators inhibit proteasome in aged muscle. Significantly less degradation of oxidized calmodulin by the 20S from aged muscle was observed. Partial rescue of activity for aged 20S by DTT implies oxidation of functionally significant cysteines. These results demonstrate significant age-related changes in proteasome structure, function, and oxidation state that could inhibit removal of oxidized proteins.
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Affiliation(s)
- Deborah A Ferrington
- Department of Ophthalmology, 380 Lions Research Bldg., 2001 6th Street SE, University of Minnesota, Minneapolis, MN 55455, USA.
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18
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Luciani F, Keşmir C, Mishto M, Or-Guil M, de Boer RJ. A mathematical model of protein degradation by the proteasome. Biophys J 2005; 88:2422-32. [PMID: 15665121 PMCID: PMC1305341 DOI: 10.1529/biophysj.104.049221] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The proteasome is the major protease for intracellular protein degradation. The influx rate of protein substrates and the exit rate of the fragments/products are regulated by the size of the axial channels. Opening the channels is known to increase the overall degradation rate and to change the length distribution of fragments. We develop a mathematical model with a flux that depends on the gate size and a phenomenological cleavage mechanism. The model has Michaelis-Menten kinetics with a V(max) that is inversely related to the length of the substrate, as observed in the in vitro experiments. We study the distribution of fragment lengths assuming that proteasomal cleavage takes place at a preferred distance from the ends of a protein fragment, and find multipeaked fragment length distributions similar to those found experimentally. Opening the gates in the model increases the degradation rate, increases the average length of the fragments, and increases the peak in the distribution around a length of 8-10 amino acids. This behavior is also observed in immunoproteasomes equipped with PA28. Finally, we study the effect of re-entry of processed fragments in the degradation kinetics and conclude that re-entry is only expected to affect the cleavage dynamics when short fragments enter the proteasome much faster than the original substrate. In summary, the model proposed in this study captures the known characteristics of proteasomal degradation, and can therefore help to quantify MHC class I antigen processing and presentation.
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Affiliation(s)
- Fabio Luciani
- Institute for Theoretical Biology, Humboldt University-Berlin, Berlin, Germany
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19
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Hoyt MA, Zhang M, Coffino P. Probing the ubiquitin/proteasome system with ornithine decarboxylase, a ubiquitin-independent substrate. Methods Enzymol 2005; 398:399-413. [PMID: 16275346 DOI: 10.1016/s0076-6879(05)98033-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Ornithine decarboxylase (ODC) is an unusual proteasome substrate-ubiquitin conjugation plays no part in its turnover. It can therefore be used as a probe to distinguish proteasome-mediated actions that do or do not depend on the activity of the ubiquitin system. A 37 residue region of ODC suffices for proteasome interactions, and within this sequence functionally critical residues have been identified. Because no posttranslational modifications are required for substrate preparation, ODC and derived constructs can be readily generated as substrates for either in vitro or in vivo studies. This chapter describes methodologies that allow the use of ODC as a reporter to examine the ubiquitin-proteasome system, both in reconstituted in vitro systems and in living cells.
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Affiliation(s)
- Martin A Hoyt
- Department of Microbiology and Immunology, University of California-San Francisco, San Francisco, CA 94143-0414, USA
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20
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Hearn AR, de Haan L, Pemberton AJ, Hirst TR, Rivett AJ. Trafficking of exogenous peptides into proteasome-dependent major histocompatibility complex class I pathway following enterotoxin B subunit-mediated delivery. J Biol Chem 2004; 279:51315-22. [PMID: 15342647 DOI: 10.1074/jbc.m408279200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The B-subunit component of Escherichia coli heat-labile enterotoxin (EtxB), which binds to cell surface GM1 ganglioside receptors, was recently shown to be a highly effective vehicle for delivery of conjugated peptides into the major histocompatibility complex (MHC) class I pathway. In this study we have investigated the pathway of epitope delivery. The peptides used contained the epitope either located at the C terminus or with a C-terminal extension. Pretreatment of cells with cholesterol-disrupting agents blocked transport of EtxB conjugates to the Golgi/endoplasmic reticulum, but did not affect EtxB-mediated MHC class I presentation. Under these conditions, EtxB conjugates entered EEA1-positive early endosomes where peptides were cleaved and translocated into the cytosol. Endosome acidification was required for epitope presentation. Purified 20 S immunoproteasomes were able to generate the epitope from peptides in vitro, but 26 S proteasomes were not. Only presentation from the C-terminal extended peptide was proteasome-dependent in cells, and this was found to be significantly slower than presentation from peptides with the epitope at the C terminus. These results implicate the proteasome in the generation of the correct C terminus of the epitope and are consistent with proteasome-independent N-terminal trimming. Epitope presentation was blocked in a TAP-deficient cell line, providing further evidence that conjugated peptides enter the cytosol as well as demonstrating a requirement for the peptide transporter. Our findings demonstrate the utility of EtxB-mediated peptide delivery for rapid and efficient loading of MHC class I epitopes in several different cell types. Conjugated peptides are released from early endosomes into the cytosol where they gain access to proteasomes and TAP in the "classical" pathway of class I presentation.
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Affiliation(s)
- Arron R Hearn
- Department of Biochemistry , School of Medical Sciences, University of Bristol, University Walk, Bristol BS8 1TD, United Kingdom
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21
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Bose S, Stratford FLL, Broadfoot KI, Mason GGF, Rivett AJ. Phosphorylation of 20S proteasome alpha subunit C8 (alpha7) stabilizes the 26S proteasome and plays a role in the regulation of proteasome complexes by gamma-interferon. Biochem J 2004; 378:177-84. [PMID: 14583091 PMCID: PMC1223927 DOI: 10.1042/bj20031122] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2003] [Revised: 10/21/2003] [Accepted: 10/29/2003] [Indexed: 11/17/2022]
Abstract
In animal cells there are several regulatory complexes which interact with 20S proteasomes and give rise to functionally distinct proteasome complexes. gamma-Interferon upregulates three immuno beta catalytic subunits of the 20S proteasome and the PA28 regulator, and decreases the level of 26S proteasomes. It also decreases the level of phosphorylation of two proteasome alpha subunits, C8 (alpha7) and C9 (alpha3). In the present study we have investigated the role of phosphorylation of C8 by protein kinase CK2 in the formation and stability of 26S proteasomes. An epitope-tagged C8 subunit expressed in mammalian cells was efficiently incorporated into both 20S proteasomes and 26S proteasomes. Investigation of mutants of C8 at the two known CK2 phosphorylation sites demonstrated that these are the two phosphorylation sites of C8 in animal cells. Although phosphorylation of C8 was not absolutely essential for the formation of 26S proteasomes, it did have a substantial effect on their stability. Also, when cells were treated with gamma-interferon, there was a marked decrease in phosphorylation of C8, a decrease in the level of 26S proteasomes, and an increase in immunoproteasomes and PA28 complexes. These results suggest that the down-regulation of 26S proteasomes after gamma-interferon treatment results from the destabilization that occurs after dephosphorylation of the C8 subunit.
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Affiliation(s)
- Suchira Bose
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
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22
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Husom AD, Peters EA, Kolling EA, Fugere NA, Thompson LV, Ferrington DA. Altered proteasome function and subunit composition in aged muscle. Arch Biochem Biophys 2004; 421:67-76. [PMID: 14678786 DOI: 10.1016/j.abb.2003.10.010] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Myofibrillar protein degradation is mediated through the ubiquitin-proteasome pathway. To investigate if altered proteasome activity plays a role in age-related muscle atrophy, we examined muscle size and proteasome function in young and aged F344BN rats. Significant age-related muscle atrophy was confirmed by the 38% decrease in cross-sectional area of type 1 fibers in soleus muscle. Determination of proteasome function showed hydrolysis of fluorogenic peptides was equivalent between ages. However, when accounting for the 3-fold increase in content of the 20S catalytic core in aged muscle, the lower specific activity suggests a functional loss in individual proteins with aging. Comparing the composition of the catalytic beta-subunits showed an age-related 4-fold increase in the cytokine-inducible subunits, LMP2 and LMP7. Additionally, the content of the activating complexes, PA28 and PA700, relative to the 20S proteasome was reduced 50%. These results suggest significant alterations in the intrinsic activity, the percentage of immunoproteasome, and the regulation of the 20S proteasome by PA28 and PA700 in aged muscle.
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Affiliation(s)
- Aimee D Husom
- Department of Physical Medicine and Rehabilitation, University of Minnesota, Minneapolis, MN 55455, USA
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23
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Fuertes G, Martín De Llano JJ, Villarroya A, Rivett AJ, Knecht E. Changes in the proteolytic activities of proteasomes and lysosomes in human fibroblasts produced by serum withdrawal, amino-acid deprivation and confluent conditions. Biochem J 2003; 375:75-86. [PMID: 12841850 PMCID: PMC1223664 DOI: 10.1042/bj20030282] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2003] [Revised: 06/23/2003] [Accepted: 07/04/2003] [Indexed: 11/17/2022]
Abstract
The contribution of the main proteolytic pathways to the degradation of long-lived proteins in human fibroblasts grown under different conditions was investigated. The effects of various commonly used pharmacological inhibitors of protein degradation were first analysed in detail. By choosing specific inhibitors of lysosomes and proteasomes, it was observed that together both pathways accounted for 80% or more of the degradation of cell proteins. With lysosomal inhibitors, it was found that serum withdrawal or amino-acid deprivation strongly stimulated macroautophagy but not other lysosomal pathways, whereas confluent conditions had no effect on macroautophagy and slightly activated other lysosomal pathways. Prolonged (24 h) serum starvation of confluent cultures strongly decreased the macroautophagic pathway, whereas the activity of other lysosomal pathways increased. These changes correlated with electron microscopic observations and morphometric measurements of lysosomes. With proteasomal inhibitors, it was found that, in exponentially growing cells in the absence of serum, activity of the ubiquitin-proteasome pathway increases, whereas under confluent conditions the contribution (in percentage) of proteasomes to degradation decreases, especially in cells deprived of amino acids. Interestingly, in confluent cells, the levels of two components of the 19 S regulatory complex and those of an interchangeable beta-subunit decreased. This was associated with a marked increase in the levels of components of PA28-immunoproteasomes. Thus confluent conditions affect proteasomes in a way that resembles treatment with interferon-gamma. Altogether, these results show that the activity of the various proteolytic pathways depends on the growth conditions of cells and will be useful for investigation of the specific signals that control their activity.
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Affiliation(s)
- Graciela Fuertes
- Instituto de Investigaciones Citológicas, Fundación Valenciana de Investigaciones Biomédicas, Amadeo de Saboya 4, 46010-Valencia, Spain
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24
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Bess KL, Swingler TE, Rivett AJ, Gaston K, Jayaraman PS. The transcriptional repressor protein PRH interacts with the proteasome. Biochem J 2003; 374:667-75. [PMID: 12826010 PMCID: PMC1223646 DOI: 10.1042/bj20030769] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2003] [Accepted: 06/25/2003] [Indexed: 02/07/2023]
Abstract
PRH (proline-rich homeodomain protein)/Hex is important in the control of cell proliferation and differentiation. We have shown previously that PRH contains two domains that can bring about transcriptional repression independently; the PRH homeodomain represses transcription by binding to TATA box sequences, whereas the proline-rich N-terminal domain can repress transcription by interacting with members of the Groucho/TLE (transducin-like enhancer of split) family of co-repressor proteins. The proteasome is a multi-subunit protein complex involved in the processing and degradation of proteins. Some proteasome subunits have been suggested to play a role in the regulation of transcription. In the present study, we show that PRH interacts with the HC8 subunit of the proteasome in the context of both 20 and 26 S proteasomes. Moreover, we show that PRH is associated with the proteasome in haematopoietic cells and that the proline-rich PRH N-terminal domain is responsible for this interaction. Whereas PRH can be cleaved by the proteasome, it does not appear to be degraded rapidly in vitro or in vivo, and the proteolytic activity of the proteasome is not required for transcriptional repression by PRH. However, proteasomal digestion of PRH can liberate truncated PRH proteins that retain the ability to bind to DNA. We discuss these findings in terms of the biological role of PRH in gene regulation and the control of cell proliferation.
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Affiliation(s)
- Kirstin L Bess
- Department of Biochemistry, University of Bristol, University Walk, Bristol BS81TD, UK
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25
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Parcellier A, Schmitt E, Gurbuxani S, Seigneurin-Berny D, Pance A, Chantôme A, Plenchette S, Khochbin S, Solary E, Garrido C. HSP27 is a ubiquitin-binding protein involved in I-kappaBalpha proteasomal degradation. Mol Cell Biol 2003; 23:5790-802. [PMID: 12897149 PMCID: PMC166315 DOI: 10.1128/mcb.23.16.5790-5802.2003] [Citation(s) in RCA: 260] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
HSP27 is an ATP-independent chaperone that confers protection against apoptosis through various mechanisms, including a direct interaction with cytochrome c. Here we show that HSP27 overexpression in various cell types enhances the degradation of ubiquitinated proteins by the 26S proteasome in response to stressful stimuli, such as etoposide or tumor necrosis factor alpha (TNF-alpha). We demonstrate that HSP27 binds to polyubiquitin chains and to the 26S proteasome in vitro and in vivo. The ubiquitin-proteasome pathway is involved in the activation of transcription factor NF-kappaB by degrading its main inhibitor, I-kappaBalpha. HSP27 overexpression increases NF-kappaB nuclear relocalization, DNA binding, and transcriptional activity induced by etoposide, TNF-alpha, and interleukin 1beta. HSP27 does not affect I-kappaBalpha phosphorylation but enhances the degradation of phosphorylated I-kappaBalpha by the proteasome. The interaction of HSP27 with the 26S proteasome is required to activate the proteasome and the degradation of phosphorylated I-kappaBalpha. A protein complex that includes HSP27, phosphorylated I-kappaBalpha, and the 26S proteasome is formed. Based on these observations, we propose that HSP27, under stress conditions, favors the degradation of ubiquitinated proteins, such as phosphorylated I-kappaBalpha. This novel function of HSP27 would account for its antiapoptotic properties through the enhancement of NF-kappaB activity.
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26
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Zhang M, Pickart CM, Coffino P. Determinants of proteasome recognition of ornithine decarboxylase, a ubiquitin-independent substrate. EMBO J 2003; 22:1488-96. [PMID: 12660156 PMCID: PMC152902 DOI: 10.1093/emboj/cdg158] [Citation(s) in RCA: 162] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Ornithine decarboxylase (ODC) is regulated by its metabolic products through a feedback loop that employs a second protein, antizyme 1 (AZ1). AZ1 accelerates the degradation of ODC by the proteasome. We used purified components to study the structural elements required for proteasomal recognition of this ubiquitin-independent substrate. Our results demonstrate that AZ1 acts on ODC to enhance the association of ODC with the proteasome, not the rate of its processing. Substrate-linked or free polyubiquitin chains compete for AZ1-stimulated degradation of ODC. ODC-AZ1 is therefore recognized by the same element(s) in the proteasome that mediate recognition of polyubiquitin chains. The 37 C-terminal amino acids of ODC harbor an AZ1-modulated recognition determinant. Within the ODC C terminus, three subsites are functionally distinguishable. The five terminal amino acids (ARINV, residues 457-461) collaborate with residue C441 to constitute one recognition element, and AZ1 collaborates with additional constituents of the ODC C terminus to generate a second recognition element.
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Affiliation(s)
- Mingsheng Zhang
- Department of Microbiology and Immunology, University of California, San Francisco, CA 94143, USA
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27
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Kirkpatrick DS, Dale KV, Catania JM, Gandolfi AJ. Low-level arsenite causes accumulation of ubiquitinated proteins in rabbit renal cortical slices and HEK293 cells. Toxicol Appl Pharmacol 2003; 186:101-9. [PMID: 12639501 DOI: 10.1016/s0041-008x(02)00019-4] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Arsenic is a known human carcinogen that affects a variety of processes within the cell. In this study, the effects of environmentally relevant As(III) exposures on the ubiquitin (Ub)-proteasome pathway have been investigated. Low-level As(III) exposure (0.5 - 10 microM) causes an accumulation of high-molecular-weight ubiquitin protein conjugates in both precision-cut rabbit renal-cortical slices and human embryonic kidney (HEK) 293 cells. The As(III) doses that induced these molecular changes were subcytotoxic in both model systems. Doses of 10 microM As(III) decreased cellular activity of the 20S proteasome by 40 and 15% in slices and HEK293 cells, respectively. As(III) did not cause any notable difference in Ub-conjugating activity of rabbit renal slices or HEK293 cells. Since ubiquitination plays such a vital role in maintaining cellular homeostasis, this noticeable perturbation of cellular ubiquitination is likely to have a multitude of signaling effects within the cells and may contribute to the pathogenesis of low-level arsenic.
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Affiliation(s)
- D S Kirkpatrick
- Department of Pharmacology and Toxicology, University of Arizona, Tuscon, AZ 85721, USA
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28
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Rivett AJ, Bose S, Pemberton AJ, Brooks P, Onion D, Shirley D, Stratford FLL, Forti K. Assays of proteasome activity in relation to aging. Exp Gerontol 2002; 37:1217-22. [PMID: 12470834 DOI: 10.1016/s0531-5565(02)00127-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Proteasomes play a major role in intracellular protein turnover. They exist in cells in several different molecular forms including 20S proteasomes, 26S proteasomes and PA28-20S proteasome complexes. In this study we have compared the properties of these purified proteasome complexes to try to design assays that will distinguish between the different complexes (26S proteasome, 20S proteasome, PA28-20S proteasome) in cell extracts. Although the different purified complexes were found to have differences in stability, and in their sensitivity to low concentrations of SDS and salt, the results suggest that it is not straightforward to assay selectively for each type of complex in cell extracts. The relative contribution of different proteasome complexes varies in different cell types and there may be other proteases present which hydrolyse the chosen substrate. Proteasome assays carried out under defined conditions allow comparisons of activity in cell extracts as a function of age, but separation by gel filtration on a Superose 6 column was found to be a useful method for determining the level of different proteasome related complexes.
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Affiliation(s)
- A Jennifer Rivett
- Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK.
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29
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Louie JL, Kapphahn RJ, Ferrington DA. Proteasome Function and Protein Oxidation in the Aged Retina. Exp Eye Res 2002. [DOI: 10.1006/exer.2002.2022] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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30
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Abstract
As the dominant protease dedicated to protein turnover, the proteasome shapes the cellular protein repertoire. Our knowledge of proteasome regulation and activity has improved considerably over the past decade. Novel inhibitors, in particular, have helped to advance our understanding of proteasome biology. They range from small peptide-based structures that can be modified to vary target specificity, to large macromolecular inhibitors that include proteins. While these reagents have played an important role in establishing our current knowledge of the proteasome's catalytic mechanism, many questions remain. Rapid advances in the synthesis and identification of new classes of proteasome inhibitors over the last 10 years serve as a positive indicator that many of these questions will soon be resolved. The future lies in designing compounds that can function as drugs to target processes involved in disease progression. It may only be a short while before the products of such research have safe application in a practical setting. Structural and combinatorial chemistry approaches are powerful techniques that will bring us closer to these goals.
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Affiliation(s)
- M Bogyo
- Department of Biochemistry and Biophysics, University of California, San Francisco, 513 Parnassus Avenue, San Francisco, USA
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Maupin-Furlow JA, Kaczowka SJ, Ou MS, Wilson HL. Archaeal proteasomes: proteolytic nanocompartments of the cell. ADVANCES IN APPLIED MICROBIOLOGY 2002; 50:279-338. [PMID: 11677686 DOI: 10.1016/s0065-2164(01)50008-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- J A Maupin-Furlow
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida 32611-0700, USA
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32
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Faries PL, Rohan DI, Wyers MC, Marin ML, Hollier LH, Quist WC, LoGerfo FW. Relationship of the 20S proteasome and the proteasome activator PA28 to atherosclerosis and intimal hyperplasia in the human vascular system. Ann Vasc Surg 2001; 15:628-33. [PMID: 11769143 DOI: 10.1007/s10016-001-0055-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Down-regulation of the proteasome activator PA28 results in abnormal proteasome activation and has been implicated in the development of intimal hyperplasia (IH) in animal models. Demonstration of proteasome and PA28 expression has not yet been documented in the human vascular system. This study sought to define the distribution of the 20S proteasome and its activator PA28 in human vessels and determine the relationship between the expression of the proteasome and PA28 and the development of atherosclerosis and IH. Vascular biopsies were obtained from 70 patients at the time of surgery, were snap frozen and sectioned in 5-micron sections, and prepared using standard histological techniques. The immunoperoxidase technique was used to identify 20S proteasome and PA28 expression in diseased and normal human arteries and veins as well as in patent bypass grafts with and without IH. Expression was graded by a blinded pathologist (scale: 1-4). Repeat quantification of the immunopositive cells was also performed. Expression of 20S proteasome and PA28 was identified in all vascular tissues examined. The proteins were identified predominately within the cytoplasm of vascular smooth muscle cells and endothelial cells. PA28 was more intensely expressed in quiescent regions of the vessel wall as compared to areas undergoing active proliferation and remodeling. PA28-mediated activation of the proteasome may be necessary to maintain normal cellular homeostasis and prevent excessive cellular proliferation in the human vascular system. Abnormalities of proteasome activation may have a significant role in the development of atherosclerosis and IH.
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Affiliation(s)
- P L Faries
- Division of Vascular Surgery, Department of Surgery, Mount Sinai School of Medicine, Box 1259, 5 E. 98th Street, New York, NY 10029, USA.
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33
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Bose S, Brooks P, Mason GG, Rivett AJ. gamma-Interferon decreases the level of 26 S proteasomes and changes the pattern of phosphorylation. Biochem J 2001; 353:291-7. [PMID: 11139393 PMCID: PMC1221571 DOI: 10.1042/0264-6021:3530291] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
In mammalian cells proteasomes can be activated by two different types of regulatory complexes which bind to the ends of the proteasome cylinder. Addition of two 19 S (PA700; ATPase) complexes forms the 26 S proteasome, which is responsible for ATP-dependent non-lysosomal degradation of intracellular proteins, whereas 11 S complexes (PA28; REG) have been implicated in antigen processing. The PA28 complex is upregulated in response to gamma-interferon (gamma-IFN) as are three non-essential subunits of the 20 S proteasome. In the present study we have investigated the effects of gamma-IFN on the level of different proteasome complexes and on the phosphorylation of proteasome subunits. After treatment of cells with gamma-IFN, the level of 26 S proteasomes decreased and there was a concomitant increase in PA28-proteasome complexes. However, no free 19 S regulatory complexes were detected. The majority of the gamma-IFN-inducible proteasome subunits LMP2 and LMP7 were present in PA28-proteasome complexes, but these subunits were also found in 26 S proteasomes. The level of phosphorylation of both 20 S and 26 S proteasome subunits was found to decrease after gamma-IFN treatment of cells. The C8 alpha subunit showed more than a 50% decrease in phosphorylation, and the phosphorylation of C9 was only barely detectable after gamma-IFN treatment. These results suggest that association of regulatory components to 20 S proteasomes is regulated, and that phosphorylation of proteasome alpha subunits may be one mode of regulation.
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Affiliation(s)
- S Bose
- Department of Biochemistry, University of Bristol, School of Medical Sciences, Bristol BS8 1TD, U.K
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34
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Orlowski M, Wilk S. Catalytic activities of the 20 S proteasome, a multicatalytic proteinase complex. Arch Biochem Biophys 2000; 383:1-16. [PMID: 11097171 DOI: 10.1006/abbi.2000.2036] [Citation(s) in RCA: 230] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The proteasome, a multisubunit, multicatalytic proteinase complex, is attracting growing attention as the main intracellular, extralysosomal, proteolytic system involved in ubiquitin-(Ub) dependent and Ub-independent intracellular proteolysis. Its involvement in the mitotic cycle, and control of the half-life of most cellular proteins, functions absolutely necessary for cell growth and viability, make it an attractive target for researchers of intracellular metabolism and an important target for pharmacological intervention. The proteasome belongs to a new mechanistic class of proteases, the N-terminal nucleophile hydrolases, where the N-terminal threonine residue functions as the nucleophile. This minireview focuses on the three classical catalytic activities of the proteasome, designated chymotrypsin-like, trypsin-like, and peptidyl-glutamyl-peptide hydrolyzing in eukaryotes and also the activities of the more simple Archaebacteria and Eubacteria proteasomes. Other catalytic activities of the proteasome and their possible origin are also examined. The specificity of the catalytic components toward synthetic substrates, natural peptides, and proteins and their relationship to the catalytic centers are reviewed. Some unanswered questions and future research directions are suggested.
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Affiliation(s)
- M Orlowski
- Department of Pharmacology, Mount Sinai School of Medicine, New York, New York 10029, USA
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35
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Abstract
Proteasomes are multicatalytic proteinase complexes which play a central role in intracellular protein degradation. They catalyse key events in cell cycle regulation and in the activation of the transcription factor NFkappaB. Proteasome inhibitors have been useful for the characterization of proteasome catalytic components and in the elucidation of proteasome functions in animal cells. Potent small peptide inhibitors of proteasomes also represent a novel approach to the treatment of inflammatory diseases (which involve activation of NFkappaB) and cancer. Such compounds have recently been shown to be effective in a variety of animal models, and at least one is currently in use in clinical trials.
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Affiliation(s)
- A J Rivett
- Department of Biochemistry, University of Bristol, School of Medical Sciences, UK.
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36
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Dallaporta B, Pablo M, Maisse C, Daugas E, Loeffler M, Zamzami N, Kroemer G. Proteasome activation as a critical event of thymocyte apoptosis. Cell Death Differ 2000; 7:368-73. [PMID: 10773821 DOI: 10.1038/sj.cdd.4400661] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Caspase activation may occur in a direct fashion as a result of CD95 death receptor crosslinking (exogenous pathway) or may be triggered indirectly, via a Bcl-2 inhibitable mitochondrial permeabilization event (endogenous pathway). Thymocyte apoptosis is generally accompanied by proteasome activation. If death is induced by DNA damage, inactivation of p53, overexpression of a Bcl-2 transgene, inhibition of protein synthesis, and antioxidants (N-acetylcyteine, catalase) prevent proteasome activation. Glucocorticoid-induced proteasome activation follows a similar pattern of inhibition except for p53. Caspase inhibition fails to affect proteasome activation induced by topoisomerase inhibition or glucocorticoid receptor ligation. In contrast, caspase activation (but not p53 knockout or Bcl-2 overexpression) does interfere with proteasome activation induced by CD95. Specific inhibition of proteasomes with lactacystin or MG123 blocks caspase activation at a pre-mitochondrial level if thymocyte apoptosis is induced by DNA damage or glucocorticoids. In strict contrast, proteasome inhibition has no inhibitory effect on the mitochondrial and nuclear phases of apoptosis induced via CD95. Thus, proteasome activation is a critical event of thymocyte apoptosis stimulated via the endogenous pathway yet dispensable for CD95-triggered death.
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Affiliation(s)
- B Dallaporta
- Centre National de la Recherche Scientifique, ERS1984, 19 rue Guy Môquet, F-94801 Villejuif, France
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37
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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.
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38
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Cardozo C, Michaud C, Orlowski M. Components of the bovine pituitary multicatalytic proteinase complex (proteasome) cleaving bonds after hydrophobic residues. Biochemistry 1999; 38:9768-77. [PMID: 10423257 DOI: 10.1021/bi990735k] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two catalytic components of the multicatalytic proteinase complex (MPC, proteasome) designated as chymotrypsin-like (ChT-L) and branched chain amino acid preferring (BrAAP) cleave bonds after hydrophobic amino acids. The possible involvement of the ChT-L and peptidylglutamyl-peptide hydrolyzing (PGPH) activities in the cleavage of bonds attributed to the BrAAP component was examined. Several inhibitors of the ChT-L activity containing a phenylalaninal group did not affect the BrAAP activity at concentrations that were more than 150 times higher than their K(i) values for the ChT-L activity. Concentrations of lactacystin that inactivated more than 90% of the ChT-L activity had no effect on the BrAAP activity. Concentrations of 3,4-dichloroisocoumarin (DCI) that inactivated the ChT-L activity activated by up to 10-fold the BrAAP activity toward synthetic substrates and by more than 2-fold the degradation of the insulin B chain in a reaction not inhibited by Z-LGF-CHO, a selective inhibitor of the ChT-L activity. These findings are incompatible with any significant involvement of the ChT-L activity in the cleavage of BrAAP substrates. Both the native and DCI-treated MPC cleaved the insulin B chain mainly after acidic residues in a reaction inhibited by Z-GPFL-CHO, an inhibitor of the BrAAP and PGPH activities. DCI exposure did not result in acylation of the N-terminal threonine in the active site of the Y subunit. These results suggest involvement of the PGPH activity in the cleavage of BrAAP substrates, but this conclusion is incompatible with DCI activation of the BrAAP activity and inactivation of the PGPH activity, and with the finding that proteins inhibiting the PGPH activity had no effect on the BrAAP activity. Rationalization of these contradictions is discussed.
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Affiliation(s)
- C Cardozo
- Department of Pharmacology, Mount Sinai School of Medicine of the City University of New York 10029, USA.
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Gardrat F, Fraigneau B, Montel V, Raymond J, Azanza JL. Effect of high hydrostatic pressures on 20S proteasome activity. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 262:900-6. [PMID: 10411654 DOI: 10.1046/j.1432-1327.1999.00470.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The 20S proteasome is the catalytic core of the ubiquitin proteolytic pathway, which is implicated in many cellular processes. The cylindrical structure of this complex consists of four stacked rings of seven subunits each. The central cavity is formed by two beta catalytic subunit rings in which protein substrates are progressively degraded. The 20S proteasome is isolated in a latent form which can be activated in vitro by various chemical and physical treatments. In this study, the effects of high hydrostatic pressures on 20S proteasome enzymatic activity were investigated. When proteasomes were subjected to increasing hydrostatic pressures, a progressive loss of peptidase activities was observed between 75 and 150 MPa. The inactivation also occurred when proteasomes were pressurized in the presence of synthetic peptide substrates; this may be the result of the dissociation of the 20S particle into its subunits under pressure, as was shown by PAGE. Pressurized proteasomes also lost their caseinolytic activity. In contrast, in the presence of casein, the pressure-induced inactivation and the dissociation of the 20S particles were prevented. In addition, in comparison to that observed at atmospheric pressure, their caseinolytic activity was increased under pressure. Following depressurization, the caseinolytic activity returned to basal levels but was further enhanced following an additional pressurization treatment. Thus, the structure of the 20S particle exhibits a certain degree of plasticity. This pressure-induced activation of the 20S proteasome is discussed in relation to its hollow structure, its currently accepted proteolytic mechanism and the general effect of high pressures on the biochemical reactions and structures of biopolymers.
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Affiliation(s)
- F Gardrat
- Laboratoire de Biochimie et Technologie des Aliments (ISTAB), Talence, France
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40
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Loidl G, Groll M, Musiol HJ, Ditzel L, Huber R, Moroder L. Bifunctional inhibitors of the trypsin-like activity of eukaryotic proteasomes. CHEMISTRY & BIOLOGY 1999; 6:197-204. [PMID: 10099130 DOI: 10.1016/s1074-5521(99)80036-2] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND The 20S proteasome is a multicatalytic protease complex that exhibits trypsin-like, chymotrypsin-like and post-glutamyl-peptide hydrolytic activities associated with the active sites of the beta2, beta5 and beta1 subunits, respectively. Modulation of these activities using inhibitors is essential for a better understanding of the proteasome's mechanism of action. Although there are highly selective inhibitors of the proteasome's chymotryptic activity, inhibitors of similar specificity have not yet been identified for the other activities. RESULTS The X-ray structure of the yeast proteasome reveals that the sidechain of Cys118 of the beta3 subunit protrudes into the S3 subsite of the beta2 active site. The location of this residue was exploited for the rational design of bidentated inhibitors containing a maleinimide moiety at the P3 position for covalent linkage to the thiol group and a carboxy-terminal aldehyde group for hemiacetal formation with the Thr1 hydroxyl group of the active site. Structure-based modelling was used to determine the optimal spacing of the maleinimide group from the P2-P1 dipeptide aldehydes and the specificity of the S1 subsite was exploited to limit the inhibitory activity to the beta2 active site. X-ray crystallographic analysis of a yeast proteasome-inhibitor adduct confirmed the expected irreversible binding of the inhibitor to the P3 subsite. CONCLUSIONS Maleoyl-beta-alanyl-valyl-arginal is a new type of inhibitor that is highly selective for the trypsin-like activity of eukaryotic proteasomes. Despite the reactivity of the maleinimide group towards thiols, and therefore the limited use of this inhibitor for in vitro studies, it might represent an interesting new biochemical tool.
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Affiliation(s)
- G Loidl
- Max-Planck-Institut für Biochemie, 82152 Martinsried, Germany
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41
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Conconi M, Djavadi-Ohaniance L, Uerkvitz W, Hendil KB, Friguet B. Conformational changes in the 20S proteasome upon macromolecular ligand binding analyzed with monoclonal antibodies. Arch Biochem Biophys 1999; 362:325-8. [PMID: 9989942 DOI: 10.1006/abbi.1998.1037] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Proteasomes interact with a variety of macromolecular ligands that modulate their ability to degrade peptide and protein substrates. The effector PA28 increases the peptidase activities of proteasomes whereas HSP90 and alpha-crystallin inhibit a peptide-hydrolyzing activity. Four monoclonal antibodies were used as probes to detect conformational changes of proteasome subunits. Conformational changes in alpha- or beta-subunits were found upon binding PA28, HSP90, alpha-crystallin, and the substrate casein but not with the peptide substrate analogs calpain inhibitor 1 (Ac-Leu-Leu-norleucinal), calpain inhibitor 2 (Ac-Leu-Leu-methioninal), or MG 132 (N-Cbz-Leu-Leu-leucinal).
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Affiliation(s)
- M Conconi
- Unité de Biochimie Cellulaire, Institut Pasteur, 28 rue du Dr. Roux, Paris, 75724, France
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Grand RJ, Turnell AS, Mason GG, Wang W, Milner AE, Mymryk JS, Rookes SM, Rivett AJ, Gallimore PH. Adenovirus early region 1A protein binds to mammalian SUG1-a regulatory component of the proteasome. Oncogene 1999; 18:449-58. [PMID: 9927201 DOI: 10.1038/sj.onc.1202304] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Adenovirus early region 1A (Ad E1A) is a multifunctional protein which is essential for adenovirus-mediated transformation and oncogenesis. Whilst E1A is generally considered to exert its influence on recipient cells through regulation of transcription it also increases the level of cellular p53 by increasing the protein half-life. With this in view, we have investigated the relationship of Ad E1A to the proteasome, which is normally responsible for degradation of p53. Here we have shown that both Ad5 and Ad12 E1A 12S and 13S proteins can be co-immunoprecipitated with proteasomes and that the larger Ad12 E1A protein binds strongly to at least three components of the 26S but not 20S proteasome. One of these interacting species has been identified as mammalian SUGI, a proteasome regulatory component which also plays a role in the cell as a mediator of transcription. In vitro assays have demonstrated a direct interaction between Ad12 E1A 13S protein and mouse SUGI. Following infection of human cells with Ad5 wt and Ad5 mutants with lesions in the E1A gene it has been shown that human SUG1 can be co-immunoprecipitated with full-length E1A and with E1A carrying a deletion in conserved region 1 which is the region considered to be responsible for increased expression of p53. We have concluded therefore that Ad EIA binds strongly to SUGI but that this interaction is not responsible for inhibition of proteasome activity. This is consistent with the observation that purified Ad12 E1A inhibits the activity of the purified 20S but not 26S proteasomes. We have also demonstrated that SUGI can be co-immunoprecipitated with SV40 T and therefore we suggest that this may represent a common interaction of transforming proteins of DNA tumour viruses.
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Affiliation(s)
- R J Grand
- CRC Institute for Cancer Studies, University of Birmingham, Edgbaston, UK
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Samy TS, Schwacha MG, Chung CS, Cioffi WG, Bland KI, Chaudry IH. Proteasome participates in the alteration of signal transduction in T and B lymphocytes following trauma-hemorrhage. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1453:92-104. [PMID: 9989249 DOI: 10.1016/s0925-4439(98)00089-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Proteasomes are essential components of the cellular protein degradation machinery. They are nonlysosomal and their participation is critical for (1) the removal of short lived proteins involved in metabolic regulation and cell proliferation, (2) the control of the activities of regulators involved in gene transcription, such as nuclear factor-kappa B (NF-kappa B) and signal transducer and activator of transcription (STAT1), and (3) processing of antigenic peptides for MHC class I presentation. Trauma-hemorrhage induces profound immunosuppression which is characterized by reduced splenocyte proliferation, interleukin (IL)-2 and interferon (IFN)-gamma productive capacity, increased activation of transcription factors NF-kappa B and STAT1 in splenic T lymphocytes, reduced macrophage antigen presentation capacity and inordinate release of proinflammatory cytokines, such as IL-6 and tumor necrosis factor-alpha. Furthermore, it appears that the activity of several regulatory proteins involved in immune function is altered by trauma-hemorrhage. Since proteasomes are involved in regulation and removal of regulatory proteins, we hypothesized that trauma-hemorrhage alters proteasomal activity in splenic lymphocytes. The data showed that activities of 26s proteasome from CD3+CD4+ and CD3+CD8+ splenic T lymphocytes were enhanced following trauma-hemorrhage which was associated with increased expression of NF-kappa B and STAT1. On the other hand, trauma-hemorrhage attenuated the activity of 26s proteasome from splenic B lymphocytes which was restored upon IFN-gamma stimulation and correlated with increased expression of NF-kappa B. These studies indicate a potential role for proteasomes in the regulation of signal transduction in splenic T and B lymphocytes following trauma-hemorrhage, and also suggest them as potential therapeutic targets for attenuation of immune suppression associated with this form of injury.
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Affiliation(s)
- T S Samy
- Department of Surgery, Brown University School of Medicine, Providence, RI, USA
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Nussbaum AK, Dick TP, Keilholz W, Schirle M, Stevanović S, Dietz K, Heinemeyer W, Groll M, Wolf DH, Huber R, Rammensee HG, Schild H. Cleavage motifs of the yeast 20S proteasome beta subunits deduced from digests of enolase 1. Proc Natl Acad Sci U S A 1998; 95:12504-9. [PMID: 9770515 PMCID: PMC22860 DOI: 10.1073/pnas.95.21.12504] [Citation(s) in RCA: 229] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The 436-amino acid protein enolase 1 from yeast was degraded in vitro by purified wild-type and mutant yeast 20S proteasome particles. Analysis of the cleavage products at different times revealed a processive degradation mechanism and a length distribution of fragments ranging from 3 to 25 amino acids with an average length of 7 to 8 amino acids. Surprisingly, the average fragment length was very similar between wild-type and mutant 20S proteasomes with reduced numbers of active sites. This implies that the fragment length is not influenced by the distance between the active sites, as previously postulated. A detailed analysis of the cleavages also allowed the identification of certain amino acid characteristics in positions flanking the cleavage site that guide the selection of the P1 residues by the three active beta subunits. Because yeast and mammalian proteasomes are highly homologous, similar cleavage motifs might be used by mammalian proteasomes. Therefore, our data provide a basis for predicting proteasomal degradation products from which peptides are sampled by major histocompatibility complex class I molecules for presentation to cytotoxic T cells.
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Affiliation(s)
- A K Nussbaum
- Institut für Zellbiologie, Abteilung Immunologie, Universität Tübingen, Auf der Morgenstelle 15, D-72076 Tübingen, Germany
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45
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Dick TP, Nussbaum AK, Deeg M, Heinemeyer W, Groll M, Schirle M, Keilholz W, Stevanović S, Wolf DH, Huber R, Rammensee HG, Schild H. Contribution of proteasomal beta-subunits to the cleavage of peptide substrates analyzed with yeast mutants. J Biol Chem 1998; 273:25637-46. [PMID: 9748229 DOI: 10.1074/jbc.273.40.25637] [Citation(s) in RCA: 214] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Proteasomes generate peptides that can be presented by major histocompatibility complex (MHC) class I molecules in vertebrate cells. Using yeast 20 S proteasomes carrying different inactivated beta-subunits, we investigated the specificities and contributions of the different beta-subunits to the degradation of polypeptide substrates containing MHC class I ligands and addressed the question of additional proteolytically active sites apart from the active beta-subunits. We found a clear correlation between the contribution of the different subunits to the cleavage of fluorogenic and long peptide substrates, with beta5/Pre2 cleaving after hydrophobic, beta2/Pup1 after basic, and beta1/Pre3 after acidic residues, but with the exception that beta2/Pup1 and beta1/Pre3 can also cleave after some hydrophobic residues. All proteolytic activities including the "branched chain amino acid-preferring" component are associated with beta5/Pre2, beta1/Pre3, or beta2/Pup1, arguing against additional proteolytic sites. Because of the high homology between yeast and mammalian 20 S proteasomes in sequence and subunit topology and the conservation of cleavage specificity between mammalian and yeast proteasomes, our results can be expected to also describe most of the proteolytic activity of mammalian 20 S proteasomes leading to the generation of MHC class I ligands.
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Affiliation(s)
- T P Dick
- Department of Immunology, Institute for Cell Biology, University of Tübingen, Auf der Morgenstelle 15, D-72076 Tübingen, Federal Republic of Germany
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46
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Mykles DL. Intracellular proteinases of invertebrates: calcium-dependent and proteasome/ubiquitin-dependent systems. INTERNATIONAL REVIEW OF CYTOLOGY 1998; 184:157-289. [PMID: 9697313 DOI: 10.1016/s0074-7696(08)62181-6] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Cytosolic proteinases carry out a variety of regulatory functions by controlling protein levels and/or activities within cells. Calcium-dependent and ubiquitin/proteasome-dependent pathways are common to all eukaryotes. The former pathway consists of a diverse group of Ca(2+)-dependent cysteine proteinases (CDPs; calpains in vertebrate tissues). The latter pathway is highly conserved and consists of ubiquitin, ubiquitin-conjugating enzymes, deubiquitinases, and the proteasome. This review summarizes the biochemical properties and genetics of invertebrate CDPs and proteasomes and their roles in programmed cell death, stress responses (heat shock and anoxia), skeletal muscle atrophy, gametogenesis and fertilization, development and pattern formation, cell-cell recognition, signal transduction and learning, and photoreceptor light adaptation. These pathways carry out bulk protein degradation in the programmed death of the intersegmental and flight muscles of insects and of individuals in a colonial ascidian; molt-induced atrophy of crustacean claw muscle; and responses of brine shrimp, mussels, and insects to environmental stress. Selective proteolysis occurs in response to specific signals, such as in modulating protein kinase A activity in sea hare and fruit fly associated with learning; gametogenesis, differentiation, and development in sponge, echinoderms, nematode, ascidian, and insects; and in light adaptation of photoreceptors in the eyes of squid, insects, and crustaceans. Proteolytic activities and specificities are regulated through proteinase gene expression (CDP isozymes and proteasomal subunits), allosteric regulators, and posttranslational modifications, as well as through specific targeting of protein substrates by a diverse assemblage of ubiquitin-conjugases and deubiquitinases. Thus, the regulation of intracellular proteolysis approaches the complexity and versatility of transcriptional and translational mechanisms.
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Affiliation(s)
- D L Mykles
- Department of Biology, Colorado State University, Fort Collins 80523, USA
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Conconi M, Petropoulos I, Emod I, Turlin E, Biville F, Friguet B. Protection from oxidative inactivation of the 20S proteasome by heat-shock protein 90. Biochem J 1998; 333 ( Pt 2):407-15. [PMID: 9657982 PMCID: PMC1219599 DOI: 10.1042/bj3330407] [Citation(s) in RCA: 105] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Heat-shock protein 90 (Hsp 90) has been implicated in both protection against oxidative inactivation and inhibition of the multicatalytic proteinase (MCP, also known as 20 S proteasome). We report here that the protective and inhibitory effects of Hsp 90 depend on the activation state of the proteasome. Hsp 90 (and also alpha-crystallin) inhibits the N-Cbz-Leu-Leu-Leu-MCA-hydrolysing activity (Cbz=benzyloxycarbonyl; MCA=7-amido-4-methylcoumarin) when the rat liver MCP is in its latent form, but no inhibitory effects are observed when the MCP is in its active form. Metal-catalysed oxidation of the active MCP inactivates the Ala-Ala-Phe-MCA-hydrolysing (chymotrypsin-like), N-Boc-Leu-Ser-Thr-Arg-MCA-hydrolysing (trypsin-like; Boc=t-butyloxycarbonyl), N-Cbz-Leu-Leu-Glu-beta-naphthylamine-hydrolysing (peptidylglutamyl-peptide hydrolase) and N-Cbz-Leu-Leu-Leu-MCA-hydrolysing activities, whereas these activities are actually increased when the MCP is in its latent form. Hsp 90 protects against oxidative inactivation of the trypsin-like and N-Cbz-Leu-Leu-Leu-MCA-hydrolysing activities of the MCP active form, and alpha-crystallin protects the trypsin-like activity. The specificity of the Hsp 90-mediated protection was assessed by a quantitative analysis of the two-dimensional electrophoretic pattern of MCP subunits before and after oxidation of the MCP, in the presence or absence of Hsp 90. Treatment of the FAO hepatoma cell line with iron and ascorbate was found to inactivate the MCP. Hsp 90 overexpression obtained by challenging the cells with iron was associated with a decreased susceptibility to oxidative inactivation of the MCP trypsin-like activity. Depletion of Hsp 90 by using antisense oligonucleotides resulted in an increased susceptibility to oxidative inactivation of the MCP trypsin-like activity, providing evidence for the physiological relevance of Hsp 90-mediated protection of the MCP.
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Affiliation(s)
- M Conconi
- Unité de Biochimie Cellulaire, Institut Pasteur, 28 rue du Dr. Roux, 75724 Paris Cedex 15, France
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Abstract
The 26S proteasome complex plays a major role in the non-lysosomal degradation of intracellular proteins. Purified 26S proteasomes give a pattern of more than 40 spots on 2D-PAGE gels. The positions of subunits have been identified by mass spectrometry of tryptic peptides and by immunoblotting with subunit-specific antipeptide antibodies. Two-dimensional polyacrylamide gel electrophoresis of proteasomes immunoprecipitated from [32P]phosphate-labelled human embryo lung L-132 cells revealed the presence of at least three major phosphorylated polypeptides among the regulatory subunits as well as the C8 and C9 components of the core 20S proteasome. Comparison with the positions of the regulatory polypeptides revealed a minor phosphorylated form to be S7 (MSS1). Antibodies against S4, S6 (TBP7) and S12 (MOV34) all cross-reacted at the position of major phosphorylated polypeptides suggesting that several of the ATPase subunits may be phosphorylated. The phosphorylation of S4 was confirmed by double immunoprecipitation experiments in which 26S proteasomes were immunoprecipitated as above and dissociated and then S4 was immunoprecipitated with subunit-specific antibodies. Antibodies against the non-ATPase subunit S10, which has been suggested by others to be phosphorylated, did not coincide with the position of a phosphorylated polypeptide. Some differences were observed in the 2D-PAGE pattern of proteasomes immunoprecipitated from cultured cells compared to purified rat liver 26S proteasomes suggesting possible differences in subunit compositions of 26S proteasomes.
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Affiliation(s)
- G G Mason
- Department of Biochemistry, School of Medical Sciences, University of Bristol, UK
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Hirsch T, Dallaporta B, Zamzami N, Susin SA, Ravagnan L, Marzo I, Brenner C, Kroemer G. Proteasome Activation Occurs at an Early, Premitochondrial Step of Thymocyte Apoptosis. THE JOURNAL OF IMMUNOLOGY 1998. [DOI: 10.4049/jimmunol.161.1.35] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
Proteasomes and mitochondrial membrane changes are involved in thymocyte apoptosis. The hierarchical relationship between protease activation and mitochondrial alterations has been elusive. Here we show that inhibition of proteasomes by two specific agents, lactacystin or MG132, prevents all manifestations of thymocyte apoptosis induced by the glucocorticoid receptor agonist dexamethasone or by the topoisomerase II inhibitor etoposide. Lactacystin and MG132 prevent the early disruption of the mitochondrial transmembrane potential (ΔΨm), which precedes caspase activation, exposure of phosphatidylserine, and nuclear DNA fragmentation. In contrast, stabilization of the ΔΨm using the permeability transition pore inhibitor bongkrekic acid or inhibition of caspases by N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone does not prevent the activation of proteasomes, as determined with the fluorogenic substrate N-succinyl-l-leucyl-l-leucyl-l-valyl-l-tyrosine-7-amido-4-methylcoumarin. Thus, proteasome activation occurs upstream from mitochondrial changes and caspase activation. Whereas the proteasome-specific agents lactacystin and MG132 truly maintain thymocyte viability, a number of protease inhibitors that inhibit nuclear DNA fragmentation (acetyl-Asp-Glu-Val-Asp-fluoromethylketone; N-Boc-Asp(OMe)-fluoromethylketone; N-tosyl-l-Phe-chloromethylketone) do not prevent the cytolysis induced by DEX or etoposide. These latter agents fail to interfere with the preapoptotic ΔΨm disruption. Altogether, our data indicate that different proteases may be involved in the pre- or postmitochondrial phase of apoptosis. Only those protease inhibitors that interrupt the apoptotic process at the premitochondrial stage can actually preserve cell viability.
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Affiliation(s)
- Tamara Hirsch
- Centre National de la Recherche Scientifique, Unité Propre de Recherche 420, Villejuif, France
| | - Bruno Dallaporta
- Centre National de la Recherche Scientifique, Unité Propre de Recherche 420, Villejuif, France
| | - Naoufal Zamzami
- Centre National de la Recherche Scientifique, Unité Propre de Recherche 420, Villejuif, France
| | - Santos A. Susin
- Centre National de la Recherche Scientifique, Unité Propre de Recherche 420, Villejuif, France
| | - Luigi Ravagnan
- Centre National de la Recherche Scientifique, Unité Propre de Recherche 420, Villejuif, France
| | - Isabel Marzo
- Centre National de la Recherche Scientifique, Unité Propre de Recherche 420, Villejuif, France
| | - Catherine Brenner
- Centre National de la Recherche Scientifique, Unité Propre de Recherche 420, Villejuif, France
| | - Guido Kroemer
- Centre National de la Recherche Scientifique, Unité Propre de Recherche 420, Villejuif, France
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Beyette J, Mason GG, Murray RZ, Cohen GM, Rivett AJ. Proteasome activities decrease during dexamethasone-induced apoptosis of thymocytes. Biochem J 1998; 332 ( Pt 2):315-20. [PMID: 9601058 PMCID: PMC1219484 DOI: 10.1042/bj3320315] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The induction of apoptosis in thymocytes by the glucocorticoid dexamethasone was used as a model system to investigate whether there are changes in 20 S and 26 S proteasome activities during apoptosis. We observed that thymocytes contain high concentrations of proteasomes and that following treatment with dexamethasone, cell extracts showed a decrease in proteasome chymotrypsin-like activity which correlated with the degree of apoptosis observed. The decrease in chymotrypsin-like activity of 20 S and 26S proteasomes was still apparent after these complexes had been partially purified from apoptotic thymocyte extracts and was therefore not due to competition resulting from a general increase in protein turnover. The trypsin-like and peptidylglutamylpeptide hydrolase activities of proteasome complexes were also observed to decrease during apoptosis, but these decreases were reversed by the inhibition of apoptosis by the caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone. However, the chymotrypsin-like activity of proteasomes decreased further in the presence of the apoptosis inhibitor. Val-Ala-Asp-fluoromethylketone was found to inhibit the chymotrypsin- and trypsin-like activity of 26 S proteasomes in vitro. The decrease in proteasome activities in apoptosis did not appear to be due to a decrease in the concentration of total cellular proteasomes. Thus, the early decreases in 20 S and 26 S proteasome activities during apoptosis appear to be due to a down-regulation of their proteolytic activities and not to a decrease in their protein concentration. These data suggest that proteasomes may be responsible, in thymocytes, for the turnover of a protein that functions as a positive regulator of apoptosis.
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Affiliation(s)
- J Beyette
- Department of Biochemistry, University of Leicester, Leicester LE1 7RH, U.K. and Department of Biochemistry, School of Medical Sciences, University of Bristol, Bristol BS8 1TD, UK
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