scholarly journals Comparative resistance of the 20S and 26S proteasome to oxidative stress

1998 ◽  
Vol 335 (3) ◽  
pp. 637-642 ◽  
Author(s):  
Thomas REINHECKEL ◽  
Nicolle SITTE ◽  
Oliver ULLRICH ◽  
Ulrike KUCKELKORN ◽  
Kelvin J. A. DAVIES ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Mammalian Cells ◽  
K562 Cells ◽  
Enzymic Activity ◽  
26S Proteasome ◽  
Proteolytic Degradation ◽  
20S Proteasome ◽  
Independent Manner ◽  
H2o2 Treatment ◽  
Fluorogenic Peptide

Oxidatively modified ferritin is selectively recognized and degraded by the 20S proteasome. Concentrations of hydrogen peroxide (H2O2) higher than 10 µmol/mg of protein are able to prevent proteolytic degradation. Exposure of the protease to high amounts of oxidants (H2O2, peroxynitrite and hypochlorite) inhibits the enzymic activity of the 20S proteasome towards the fluorogenic peptide succinyl-leucine-leucine-valine-tyrosine-methylcoumarylamide (Suc-LLVY-MCA), as well as the proteolytic degradation of normal and oxidant-treated ferritin. Fifty per cent inhibition of the degradation of the protein substrates was achieved using 40 µmol of H2O2/mg of proteasome. No change in the composition of the enzyme was revealed by electrophoretic analysis up to concentrations of 120 µmol of H2O2/mg of proteasome. In further experiments, it was found that the 26S proteasome, the ATP- and ubiquitin-dependent form of the proteasomal system, is much more susceptible to oxidative stress. Whereas degradation of the fluorogenic peptide, Suc-LLVY-MCA, by the 20S proteasome was inhibited by 50% with 12 µmol of H2O2/mg, 3 µmol of H2O2/mg was enough to inhibit ATP-stimulated degradation by the 26S proteasome by 50%. This loss in activity could be followed by the loss of band intensity in the non-denaturing gel. Therefore we concluded that the 20S proteasome was more resistant to oxidative stress than the ATP- and ubiquitin-dependent 26S proteasome. Furthermore, we investigated the activity of both proteases in K562 cells after H2O2 treatment. Lysates from K562 cells are able to degrade oxidized ferritin at a higher rate than non-oxidized ferritin, in an ATP-independent manner. This effect could be followed even after treatment of the cells with H2O2 up to a concentration of 2 mM. The lactacystin-sensitive ATP-stimulated degradation of the fluorogenic peptide Suc-LLVY-MCA declined, after treatment of the cells with 1 mM H2O2, to the same level as that obtained without ATP stimulation. Therefore, we conclude that the regulation of the 20 S proteasome by various regulators takes place during oxidative stress. This provides further evidence for the role of the 20S proteasome in the secondary antioxidative defences of mammalian cells.

scholarly journals 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

2004 ◽  
Vol 378 (1) ◽  
pp. 177-184 ◽  
Author(s):  
Suchira BOSE ◽  
Fiona L. L. STRATFORD ◽  
Kerry I. BROADFOOT ◽  
Grant G. F. MASON ◽  
A. Jennifer RIVETT
Keyword(s):  
Mammalian Cells ◽  
Substantial Effect ◽  
26S Proteasome ◽  
20S Proteasome ◽  
Phosphorylation Sites ◽  
Animal Cells ◽  
Catalytic Subunits ◽  
Kinase Ck2 ◽  
Γ Interferon

In animal cells there are several regulatory complexes which interact with 20S proteasomes and give rise to functionally distinct proteasome complexes. γ-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 (α7) and C9 (α3). 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 γ-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 γ-interferon treatment results from the destabilization that occurs after dephosphorylation of the C8 subunit.

scholarly journals Ubiquitin-independent protein degradation in proteasomes

2018 ◽  
Vol 64 (2) ◽  
pp. 134-148 ◽  
Author(s):  
O.A. Buneeva ◽  
A.E. Medvedev
Keyword(s):  
Protein Degradation ◽  
Mammalian Cells ◽  
Intrinsically Disordered Proteins ◽  
Amino Acid Sequences ◽  
Disordered Proteins ◽  
20S Proteasome ◽  
Independent Manner ◽  
Intrinsically Disordered ◽  
Intrinsically Disordered Regions ◽  
Independent Protein

Proteasomes are large supramolecular protein complexes present in all prokaryotic and eukaryotic cells, where they perform targeted degradation of intracellular proteins. Until recently, it was generally accepted that prior proteolytic degradation in proteasomes the proteins had to be targeted by ubiquitination: the ATP-dependent addition of (typically four sequential) residues of the low-molecular ubiquitin protein, involving the ubiquitin-activating enzyme, ubiquitin-conjugating enzyme and ubiquitin ligase. The cytoplasm and nucleoplasm proteins labeled in this way are then digested in 26S proteasomes. However, in recent years it has become increasingly clear that using this route the cell eliminates only a part of unwanted proteins. Many proteins can be cleaved by the 20S proteasome in an ATP-independent manner and without previous ubiquitination. Ubiquitin-independent protein degradation in proteasomes is a relatively new area of studies of the role of the ubiquitin-proteasome system. However, recent data obtained in this direction already correct existing concepts about proteasomal degradation of proteins and its regulation. Ubiquitin-independent proteasome degradation needs the main structural precondition in proteins: the presence of unstructured regions in the amino acid sequences that provide interaction with the proteasome. Taking into consideration that in humans almost half of all genes encode proteins that contain a certain proportion of intrinsically disordered regions, it appears that the list of proteins undergoing ubiquitin-independent degradation will demonstrate further increase. Since 26S of proteasomes account for only 30% of the total proteasome content in mammalian cells, most of the proteasomes exist in the form of 20S complexes. The latter suggests that ubiquitin-independent proteolysis performed by the 20S proteasome is a natural process of removing damaged proteins from the cell and maintaining a constant level of intrinsically disordered proteins. In this case, the functional overload of proteasomes in aging and/or other types of pathological processes, if it is not accompanied by triggering more radical mechanisms for the elimination of damaged proteins, organelles and whole cells, has the most serious consequences for the whole organism.

Differential Impairment of 20S and 26S Proteasome Activities in Human Hematopoietic K562 Cells during Oxidative Stress

2000 ◽  
Vol 377 (1) ◽  
pp. 65-68 ◽  
Author(s):  
Thomas Reinheckel ◽  
Oliver Ullrich ◽  
Nicolle Sitte ◽  
Tilman Grune
Keyword(s):  
Oxidative Stress ◽  
K562 Cells ◽  
26S Proteasome

scholarly journals Subcellular localization of proteasomes and their regulatory complexes in mammalian cells

2000 ◽  
Vol 346 (1) ◽  
pp. 155-161 ◽  
Author(s):  
Paul BROOKS ◽  
Graciela FUERTES ◽  
Rachael Z. MURRAY ◽  
Suchira BOSE ◽  
Erwin KNECHT ◽  
...  
Keyword(s):  
Rat Liver ◽  
Subcellular Distribution ◽  
Mammalian Cells ◽  
Antigen Processing ◽  
Cultured Cells ◽  
26S Proteasome ◽  
Molecular Forms ◽  
20S Proteasome ◽  
Obvious Effect ◽  
Γ Interferon

Proteasomes can exist in several different molecular forms in mammalian cells. The core 20S proteasome, containing the proteolytic sites, binds regulatory complexes at the ends of its cylindrical structure. Together with two 19S ATPase regulatory complexes it forms the 26S proteasome, which is involved in ubiquitin-dependent proteolysis. The 20S proteasome can also bind 11S regulatory complexes (REG, PA28) which play a role in antigen processing, as do the three variable γ-interferon-inducible catalytic β-subunits (e.g. LMP7). In the present study, we have investigated the subcellular distribution of the different forms of proteasomes using subunit specific antibodies. Both 20S proteasomes and their 19S regulatory complexes are found in nuclear, cytosolic and microsomal preparations isolated from rat liver. LMP7 was enriched approximately two-fold compared with core α-type proteasome subunits in the microsomal preparations. 20S proteasomes were more abundant than 26S proteasomes, both in liver and cultured cell lines. Interestingly, some significant differences were observed in the distribution of different subunits of the 19S regulatory complexes. S12, and to a lesser extent p45, were found to be relatively enriched in nuclear fractions from rat liver, and immunofluorescent labelling of cultured cells with anti-p45 antibodies showed stronger labelling in the nucleus than in the cytoplasm. The REG was found to be localized predominantly in the cytoplasm. Three- to six-fold increases in the level of REG were observed following γ-interferon treatment of cultured cells but γ-interferon had no obvious effect on its subcellular distribution. These results demonstrate that different regulatory complexes and subpopulations of proteasomes have different distributions within mammalian cells and, therefore, that the distribution is more complex than has been reported for yeast proteasomes.

scholarly journals Lipid disequilibrium disrupts ER proteostasis by impairing ERAD substrate glycan trimming and dislocation

2017 ◽  
Vol 28 (2) ◽  
pp. 270-284 ◽  
Author(s):  
Milton To ◽  
Clark W. H. Peterson ◽  
Melissa A. Roberts ◽  
Jessica L. Counihan ◽  
Tiffany T. Wu ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Mammalian Cells ◽  
26S Proteasome ◽  
Unfolded Protein ◽  
Acid Analogue ◽  
Triacsin C ◽  
Chain Acyl ◽  
Dependent Cell ◽  
Outstanding Question ◽  
The Unfolded Protein Response

The endoplasmic reticulum (ER) mediates the folding, maturation, and deployment of the secretory proteome. Proteins that fail to achieve their native conformation are retained in the ER and targeted for clearance by ER-associated degradation (ERAD), a sophisticated process that mediates the ubiquitin-dependent delivery of substrates to the 26S proteasome for proteolysis. Recent findings indicate that inhibition of long-chain acyl-CoA synthetases with triacsin C, a fatty acid analogue, impairs lipid droplet (LD) biogenesis and ERAD, suggesting a role for LDs in ERAD. However, whether LDs are involved in the ERAD process remains an outstanding question. Using chemical and genetic approaches to disrupt diacylglycerol acyltransferase (DGAT)–dependent LD biogenesis, we provide evidence that LDs are dispensable for ERAD in mammalian cells. Instead, our results suggest that triacsin C causes global alterations in the cellular lipid landscape that disrupt ER proteostasis by interfering with the glycan trimming and dislocation steps of ERAD. Prolonged triacsin C treatment activates both the IRE1 and PERK branches of the unfolded protein response and ultimately leads to IRE1-dependent cell death. These findings identify an intimate relationship between fatty acid metabolism and ER proteostasis that influences cell viability.

scholarly journals Cellular Immune Response Induced by DNA Immunization of Mice with Drug Resistant Integrases of HIV-1 Clade A Offers Partial Protection against Growth and Metastatic Activity of Integrase-Expressing Adenocarcinoma Cells

2021 ◽  
Vol 9 (6) ◽  
pp. 1219
Author(s):  
Maria Isaguliants ◽  
Olga Krotova ◽  
Stefan Petkov ◽  
Juris Jansons ◽  
Ekaterina Bayurova ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
T Cell ◽  
Cell Response ◽  
Mammalian Cells ◽  
Metastatic Potential ◽  
T Cell Response ◽  
Dna Immunization ◽  
Drug Resistant ◽  
Metastatic Activity ◽  
Hiv 1

Therapeutic DNA-vaccination against drug-resistant HIV-1 may hinder emergence and spread of drug-resistant HIV-1, allowing for longer successful antiretroviral treatment (ART) up-to relief of ART. We designed DNA-vaccines against drug-resistant HIV-1 based on consensus clade A integrase (IN) resistant to raltegravir: IN_in_r1 (L74M/E92Q/V151I/N155H/G163R) or IN_in_r2 (E138K/G140S/Q148K) carrying D64V abrogating IN activity. INs, overexpressed in mammalian cells from synthetic genes, were assessed for stability, route of proteolytic degradation, and ability to induce oxidative stress. Both were found safe in immunotoxicity tests in mice, with no inherent carcinogenicity: their expression did not enhance tumorigenic or metastatic potential of adenocarcinoma 4T1 cells. DNA-immunization of mice with INs induced potent multicytokine T-cell response mainly against aa 209–239, and moderate IgG response cross-recognizing diverse IN variants. DNA-immunization with IN_in_r1 protected 60% of mice from challenge with 4Tlluc2 cells expressing non-mutated IN, while DNA-immunization with IN_in_r2 protected only 20% of mice, although tumor cells expressed IN matching the immunogen. Tumor size inversely correlated with IN-specific IFN-γ/IL-2 T-cell response. IN-expressing tumors displayed compromised metastatic activity restricted to lungs with reduced metastases size. Protective potential of IN immunogens relied on their immunogenicity for CD8+ T-cells, dependent on proteasomal processing and low level of oxidative stress.

A manganese oxide nanozyme prevents the oxidative damage of biomolecules without affecting the endogenous antioxidant system

Nanoscale ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 3855-3863 ◽  
Author(s):  
Namrata Singh ◽  
Mohammed Azharuddin Savanur ◽  
Shubhi Srivastava ◽  
Patrick D'Silva ◽  
Govindasamy Mugesh
Keyword(s):  
Oxidative Stress ◽  
Oxidative Damage ◽  
Manganese Oxide ◽  
Antioxidant System ◽  
Mammalian Cells ◽  
Redox State ◽  
Stress Conditions ◽  
System P ◽  
Endogenous Antioxidant ◽  
Antioxidant Machinery

Multi-enzyme mimetic Mn3O4 nanoflowers (Mp) modulate the redox state of mammalian cells without altering the cellular antioxidant machinery under oxidative stress conditions.

Binding of aflatoxins to the 20S proteasome: effects on enzyme functionality and implications for oxidative stress and apoptosis

2007 ◽  
Vol 388 (1) ◽  
Author(s):  
Manila Amici ◽  
Valentina Cecarini ◽  
Assuntina Pettinari ◽  
Laura Bonfili ◽  
Mauro Angeletti ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
20S Proteasome ◽  
Enzyme Functionality

scholarly journals Assembly of the Drosophila 26 S proteasome is accompanied by extensive subunit rearrangements

2002 ◽  
Vol 365 (2) ◽  
pp. 527-536 ◽  
Author(s):  
Éva KURUCZ ◽  
István ANDÓ ◽  
Máté SÜMEGI ◽  
Harald HÖLZL ◽  
Barbara KAPELARI ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
26S Proteasome ◽  
Cross Linking ◽  
20S Proteasome ◽  
Electron Microscopic ◽  
Immunoblot Assay ◽  
Optimal Conformation ◽  
Regulatory Complex ◽  
Atpase Subunits ◽  
The Cross

The subunit contacts in the regulatory complex of the Drosophila 26 S proteasome were studied through the cross-linking of closely spaced subunits of the complex, and analysis of the cross-linking pattern in an immunoblot assay with the use of subunit-specific monoclonal antibodies. The cross-linking pattern of the purified 26 S proteasome exhibits significant differences as compared with that of the purified free regulatory complex. It is shown that the observed differences are due to extensive rearrangement of the subunit contacts accompanying the assembly of the 26 S proteasome from the regulatory complex and the 20S proteasome. Cross-linking studies and electron microscopic examinations revealed that these changes are reversible and follow the assembly or the disassembly of the 26 S proteasome. Although the majority of the changes observed in the subunit contacts affected the hexameric ring of the ATPase subunits, the alterations extended over the whole of the regulatory complex, affecting subunit contacts even in the lid subcomplex. Changes in the subunit contacts, similar to those in the regulatory complex, were detected in the 20S proteasome. These observations indicate that the assembly of the 26 S proteasome is not simply a passive docking of two rigid subcomplexes. In the course of the assembly, the interacting subcomplexes mutually rearrange their structures so as to create the optimal conformation required for the assembly and the proper functioning of the 26S proteasome.

Sign in / Sign up

Export Citation Format

Share Document